JP2006336547A - Egr device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To materialize high EGR rate without causing great deterioration of fuel economy. <P>SOLUTION: This device is provided with a low pressure loop 14 drawing part of exhaust gas 9 out from an exhaust passage in a downstream of a turbine 2b and re-circulating the same to an intake pipe 5 in an upstream of a compressor 2a, and a high pressure loop 15 drawing part of exhaust gas 9 out from an exhaust manifold 10 and re-circulating the same to a part in a neighborhood of an inlet of an intake manifold 10, EGR valves 19, 21 provided in the low pressure loop 14 and the high pressure loop 15 and adjusting recirculation quantity of exhaust gas 9, and a control device 23 controlling each EGR valves 19, 21 performing base exhaust gas recirculation at EGR rate which is in a level not generating black smoke at a time of acceleration by the low pressure loop 14 and performing additional exhaust gas recirculation to compensate insufficient EGR rate part by the high pressure loop and coping with avoidance of black smoke at a time of acceleration mainly by immediately reducing recirculation quantity of exhaust gas 9 in the high pressure loop 15 side. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an EGR device for an engine equipped with a turbocharger.

  2. Description of the Related Art Conventionally, in an automobile engine or the like, a part of exhaust gas is extracted from the exhaust side and returned to the intake side, and combustion of fuel in the engine is suppressed by the exhaust gas returned to the intake side so that the combustion temperature is increased. So-called exhaust gas recirculation (EGR) is performed in which the generation of NOx (nitrogen oxide) is reduced by lowering.

  In general, when this type of exhaust gas recirculation is performed, an EGR pipe is used between an appropriate position of the exhaust passage extending from the exhaust manifold to the exhaust pipe and an appropriate position of the intake passage extending from the intake pipe to the intake manifold. The exhaust gas is recirculated using the differential pressure between the intake side and the exhaust side through the EGR pipe.

  In addition, if the exhaust gas recirculated to the engine is cooled in the middle of the EGR pipe, the temperature of the exhaust gas is reduced and the volume of the exhaust gas is reduced, which effectively reduces the combustion temperature without significantly reducing the output of the engine. Since the generation of NOx can be reduced, a water-cooled EGR cooler is provided in the middle of an EGR pipe for recirculating exhaust gas to the engine.

Incidentally, as prior art document information disclosing a technology related to this type of exhaust gas recirculation, there is the following Patent Document 1 or the like.
JP 2004-270565 A

  However, if the engine is equipped with a turbocharger, the pressure difference from the exhaust side is reduced because the intake side is supercharged, making it difficult to achieve a high EGR rate. However, it is necessary to reduce the exhaust gas by using a turbocharger or by installing a throttle valve in the middle of the exhaust pipe, thereby increasing the pressure on the exhaust side and ensuring a pressure difference from the intake side. If the exhaust side is boosted to such a high pressure that it can overcome the turbocharger supercharging pressure in this way, the pumping loss on the engine side will increase, resulting in a significant deterioration in fuel consumption (exhaust gas with a variable nozzle turbocharger). If the engine is narrowed down, there is a problem that the fuel efficiency is deteriorated due to a decrease in turbine efficiency.

  The present invention has been made in view of the above-described circumstances, and an object thereof is to achieve a high NOGR reduction effect by realizing a high EGR rate without causing a significant deterioration in fuel consumption.

  The present invention extracts a part of the exhaust gas from the exhaust passage downstream of the turbine of the turbocharger and recirculates it to the intake passage upstream of the compressor of the turbocharger, and extracts a part of the exhaust gas from the exhaust manifold. A high pressure loop that recirculates near the inlet of the intake manifold, a recirculation amount adjusting means that adjusts the recirculation amount of exhaust gas provided in each of the low pressure loop and the high pressure loop, and black smoke during acceleration by the low pressure loop. The exhaust gas recirculation that is the base at the EGR rate that is suppressed to an extent that does not occur is performed, the additional exhaust gas recirculation is performed to supplement the insufficient EGR rate in the high-pressure loop, and black smoke avoidance during acceleration is mainly Control for controlling each of the recirculation amount adjusting means so as to cope with the problem by immediately reducing the recirculation amount of the exhaust gas on the high pressure loop side EGR apparatus being characterized in that a location, in which according to the.

  Thus, the exhaust gas recirculation as a base is performed on the low pressure loop side in this way, and the additional exhaust gas recirculation is performed on the high pressure loop side to supplement the insufficient EGR rate. Therefore, while using a low pressure loop and a high pressure loop in combination, a high EGR rate is achieved, while the amount of exhaust gas recirculation that must be shared on the high pressure loop side is less than in the case of using a high pressure loop alone. The exhaust gas recirculation of the amount that should be shared on the high-pressure loop side can be realized relatively easily without excessive exhaust gas reduction with a turbocharger of the type, resulting in an increase in pumping loss. The drastic deterioration of fuel consumption due to the above will be avoided in advance.

  Here, the low-pressure loop has not been used to recirculate the exhaust gas at a high EGR rate until λ (air) However, the EGR device according to the present invention regenerates the exhaust gas based on the low-pressure loop with the EGR rate suppressed to such a level that black smoke is not generated during acceleration. Since only the circulation is performed, the generation of black smoke is avoided by immediately reducing the recirculation amount of the exhaust gas on the high-pressure loop side during acceleration.

  That is, in the low-pressure loop, exhaust gas is returned to the intake passage upstream of the turbocharger compressor, but the route from here to the engine via the compressor, intercooler, and intake manifold is long, and the exhaust gas is exhausted to this long route. Since the intake air mixed with gas exists, when the fuel injection amount increases in response to accelerator depression during acceleration, even if the recirculation amount adjusting means of the low pressure loop is immediately closed, There is a drawback that the λ lowering state continues and black smoke is likely to be generated until all the intake air mixed with exhaust gas is used up.

  On the other hand, in the high-pressure loop, exhaust gas is returned near the inlet of the intake manifold, so the intake air mixed with the exhaust gas exists only in the intake manifold, and even if the fuel injection amount increases during acceleration, the high-pressure loop If the loop recirculation amount adjusting means is closed, the intake air mixed with the exhaust gas in the intake manifold will be used up soon and λ will be recovered early, so that it is easy to avoid the generation of black smoke during acceleration.

  Therefore, as in the EGR device of the present invention, the exhaust gas recirculation that is the base is performed by the low pressure loop at the EGR rate that is suppressed to the extent that black smoke is not generated during acceleration, and the insufficient EGR rate is supplemented by the high pressure loop. By implementing additional exhaust gas recirculation as much as possible, it is possible to recover λ early by immediately reducing the amount of exhaust gas recirculation on the high-pressure loop side during acceleration, thereby preventing the occurrence of black smoke. It is possible to avoid it.

  Further, in the present invention, the filter case interposed in the middle of the exhaust pipe and containing the particulate filter has a double shell structure, and the exhaust pipe from the filter case to the turbine of the turbocharger has a double pipe structure. A return flow path for returning a part of the exhaust gas that has passed through the particulate filter to the upstream side is formed in the outer layer portion of the filter case and the exhaust pipe, and the most upstream portion near the turbine of the return flow path and the turbocharger It is preferable that an EGR pipe is connected to the inlet of the compressor, and a low pressure loop is constituted by these return flow path and the EGR pipe.

  In this way, part of the exhaust gas that has passed through the particulate filter is folded back to the return flow path, flows through the filter case and the outer layer portion of the exhaust pipe, and enters the compressor inlet from the most upstream part of the return flow path through the EGR pipe. However, the exhaust gas that is recirculated here is at a low temperature and low pressure when it passes through the particulate filter in the middle of the exhaust pipe, and it is exposed to the outside air with a large surface area. Since it is cooled by heat dissipation while flowing through the outer layer portion of the exhaust pipe, it is further sent from here to the intercooler and air-cooled to sufficiently lower the temperature of the exhaust gas, and the exhaust gas is reduced using an EGR cooler or the like. The need for water cooling is eliminated, and the complexity of the water cooling system and the enlargement of the radiator and fan are avoided.

  Furthermore, since the exhaust gas recirculated to the compressor inlet is cleaner than the atmosphere that has been dust-removed through the particulate filter, the interior of the intercooler downstream of the compressor is contaminated by soot or the like in the exhaust gas. There is no worry, and exhaust gas is recirculated to the inlet of the compressor, which is the lowest pressure in the intake system, so that a sufficient differential pressure between the exhaust side and the intake side is ensured and exhaust gas is satisfactorily Will be recycled.

  At this time, most of the exhaust gas returned from the rear of the particulate filter to the compressor inlet is returned by the return flow path that forms the outer layer portion of the filter case and the exhaust pipe, so that it is close to the turbine of the return flow path. It is only necessary to connect a short EGR pipe between the most upstream part and the inlet of the compressor of the turbocharger, and the overall structure is compact, so that the layout of the EGR pipe is not troublesome.

  On the other hand, from the particulate filter side, the outer periphery is insulated and insulated by the exhaust gas flowing through the return flow path, making it difficult for heat to be taken away by the outside air. Since the temperature is raised, the temperature of the entire particulate filter is efficiently increased, the combustion of the collected particulates is promoted, and the reliable regeneration with little remaining particulates is performed.

  Further, in the present invention, a pressure sensor for detecting a pressure difference between two points sandwiched by the recirculation amount adjusting means as a throttle in each of the low pressure loop and the high pressure loop, and a temperature for detecting the exhaust temperature between the two points. Sensor, calculate the recirculation amount of exhaust gas by an indirect measurement method based on detection signals from these pressure sensors and temperature sensors, and adjust each recirculation amount based on the calculated recirculation amount of exhaust gas It is preferable to configure the control device so that the feedback control is applied to the means.

  In this way, since the exhaust gas recirculation amount is detected by a highly responsive pressure sensor or temperature sensor, the recirculation amount is instantly identified and good feedback control is realized. In addition, there is no risk of detection being inaccurate due to the influence of vortices as in the case of using an air flow meter, so accurate exhaust gas even during acceleration when vortices are likely to occur due to sudden changes in the exhaust flow rate. The amount of recirculation is detected.

  Further, in the present invention, it is preferable to provide an exhaust throttle means for blocking the flow of the exhaust gas immediately after the exhaust gas intake port of the low-pressure loop, and in this way, when idling or extremely light load, etc. In the condition where the pressure difference between the intake side and the exhaust side is insufficient, the exhaust gas flow is blocked by the exhaust throttle means to secure the pressure difference between the intake side and the exhaust side, and smoothly into the low-pressure loop. It is possible to facilitate the recirculation of exhaust gas.

  According to the EGR device of the present invention described above, various excellent effects as described below can be obtained.

  (I) According to the invention described in claim 1 of the present invention, the exhaust gas recirculation that serves as a base is performed at an EGR rate that is suppressed to the extent that black smoke is not generated at the time of acceleration by the low pressure loop, and the EGR is insufficient in the high pressure loop. By implementing additional exhaust gas recirculation to supplement the rate, it is possible to achieve a high EGR rate without causing a significant deterioration in fuel consumption, and to obtain a good NOx reduction effect, Even if the fuel injection amount increases in response to accelerator depression during acceleration, λ can be recovered quickly by immediately reducing the amount of exhaust gas recirculation on the high-pressure loop side, thereby avoiding the occurrence of black smoke. can do.

  (II) According to the invention described in claim 2 of the present invention, it is not necessary to cool the exhaust gas by using an EGR cooler or the like when configuring the low pressure loop, so that the water cooling system is complicated, the radiator and the fan. Can be avoided, and a long low-pressure loop can be realized without requiring a long EGR pipe.

  (III) According to the invention described in claim 2 of the present invention, the exhaust gas having passed through the particulate filter is allowed to flow through the return flow path, whereby the outer peripheral portion of the particulate filter is insulated and kept warm. Therefore, it is possible to efficiently raise the temperature of the entire particulate filter and promote the combustion of the collected particulate filter, and it is possible to more surely regenerate the particulate filter with less unburned residue.

  (IV) According to the invention described in claim 3 of the present invention, it is possible to instantaneously detect the recirculation amount of the exhaust gas with a highly responsive pressure sensor or temperature sensor, and to realize good feedback control, In addition, an accurate exhaust gas recirculation amount can be detected even during acceleration when vortices are likely to occur due to sudden changes in the exhaust flow rate.

  (V) According to the invention described in claim 4 of the present invention, the exhaust throttling means can be used even under conditions where the pressure difference between the intake side and the exhaust side is insufficient during idling or extremely light load. Thus, the flow of the exhaust gas is blocked and the pressure difference between the intake side and the exhaust side can be surely ensured, so that smooth exhaust gas recirculation to the low pressure loop can be promoted.

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

  1 and 2 show an example of an embodiment for carrying out the present invention. FIGS. 1 and 2 show an example of an embodiment for carrying out the present invention. In FIG. 1, 1 is a variable nozzle type turbocharger. 2 shows a diesel engine equipped with 2 (variable geometry turbocharger), and intake air 4 guided from an air cleaner 3 is sent to the compressor 2a of the turbocharger 2 through an intake pipe 5 and pressurized by the compressor 2a. The intake air 4 is sent to the intercooler 6 to be cooled, and the intake air 4 is further guided from the intercooler 6 to the intake manifold 7 so that each cylinder 8 of the diesel engine 1 (in the case of inline 6 cylinders in FIG. 1). It is distributed in the example).

  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 passes through the exhaust pipe 11. In the middle of the exhaust pipe 11, a catalyst regeneration type particulate filter 12 that integrally carries an oxidation catalyst is held by a filter case 13 and is provided. .

  In the diesel engine 1, a part of the exhaust gas 9 is extracted from the exhaust passage downstream of the turbine 2b of the turbocharger 2 and recirculated to the intake pipe 5 upstream of the compressor 2a of the turbocharger 2. A loop 14 and a high-pressure loop 15 that extracts a part of the exhaust gas 9 from the exhaust manifold 10 and recirculates in the vicinity of the inlet of the intake manifold 7 are provided.

  Here, in the example shown in FIG. 1, the filter case 13 has a double shell structure composed of an inner shell 13a and an outer shell 13b, and an exhaust pipe 11 extending from the filter case 13 to the turbine 2b of the turbocharger 2 is provided. The exhaust gas 9 having passed through the particulate filter 12 is returned to the upstream side between the double pipe structure a composed of the inner pipe 11a and the outer pipe 11b and the outer shell 13b and between the inner pipe 11a and the outer pipe 11b. The return passages 16 and 17 are formed, and the recirculation amount of the exhaust gas 9 is adjusted between the most upstream portion of the return passage 17 near the turbine 2b and the inlet of the compressor 2a of the turbocharger 2. Are connected by a relatively short EGR pipe 18 provided with an EGR valve 19 (recirculation amount adjusting means). The low-pressure loop 14 is adapted to be constituted by the 17 and EGR pipe 18.

  On the other hand, an EGR valve 21 (recirculation amount adjusting means) for adjusting the recirculation amount of the exhaust gas 9 is provided between one end portion of the exhaust manifold 10 in the arrangement direction of each cylinder and the vicinity of the inlet of the intake manifold 7. The high-pressure loop 15 is configured to be connected by an EGR pipe 20 provided so that a part of the exhaust gas 9 can be extracted from the exhaust manifold 10 by the EGR pipe 20 and guided to the vicinity of the inlet of the intake manifold 7. It has become.

  The EGR pipe 20 of the high-pressure loop 15 is equipped with an EGR cooler 22 for cooling the recirculated exhaust gas 9, and the EGR cooler 22 exchanges heat between the cooling water and the exhaust gas 9. Thus, by reducing the temperature of the exhaust gas 9 and reducing its volume, the combustion temperature can be lowered without reducing the output of the diesel engine 1 so much that the generation of NOx can be effectively reduced.

  The opening degree of each of the EGR valves 19 and 21 is controlled by opening degree command signals 19a and 21a from a control device 23 constituting an engine control computer (ECU: Electronic Control Unit). As for the control, the accelerator opening signal 24a from the accelerator sensor 24 (load sensor) that detects the accelerator opening as the load of the diesel engine 1 and the rotation speed from the rotation sensor 25 that detects the engine speed of the diesel engine 1 are controlled. Based on the signal 25a, it is executed as follows.

  That is, in the control device 23, the opening degree of each EGR valve 19, 21 corresponding to the current operation state is instructed so that a high EGR rate is realized as a total in both the low pressure loop 14 and the high pressure loop 15. However, at this time, the exhaust gas recirculation as a base is performed by the low pressure loop 14 at an EGR rate (for example, about 10 to 15%) suppressed to a level that does not generate black smoke during acceleration, and the high pressure loop 14 15, additional exhaust gas recirculation is carried out to supplement the shortage EGR rate (about 10 to 20%). Moreover, for avoiding black smoke during acceleration, the acceleration sensor 24 Based on the accelerator opening signal 24a, the amount of recirculation of the exhaust gas 9 on the high-pressure loop 15 side can be mainly reduced by immediate reduction.

  Further, the EGR pipe 18 of the low-pressure loop 14 and the EGR pipe 20 of the high-pressure loop 15 are respectively provided with pressure sensors 26 and 27 for detecting a pressure difference between two points sandwiching the EGR valves 19 and 21 as throttles, Temperature sensors 28 and 29 for detecting the exhaust temperature between two points are provided, and an indirect measurement method is used based on the detection signals 26a, 27a, 28a and 29a from the pressure sensors 26 and 27 and the temperature sensors 28 and 29. The recirculation amount of the exhaust gas 9 is calculated, and feedback control is applied to the EGR valves 19 and 21 based on the calculated recirculation amount of the exhaust gas 9.

  That is, when the measured value of the recirculation amount of the exhaust gas 9 in each of the EGR pipes 18 and 20 has a large deviation more than a predetermined value with respect to the scheduled control value by the control device 23, the recirculation amount of the exhaust gas 9 is increased. The indicated values of the opening command signals 19a and 21a to the EGR valves 19 and 21 are corrected so that the actually measured values approach the control planned values.

  Incidentally, the differential pressure type flow rate measuring means as illustrated here is already well known, and the average flow velocity of the flow path is determined based on the fact that the square root of the pressure difference before and after the restriction provided in the middle of the flow path is proportional to the flow speed. The flow rate is calculated by multiplying this by a known channel cross-sectional area, and the exhaust temperature is used for temperature correction for setting the temperature at the time of measurement to the standard temperature.

  In the example shown here, a throttle valve 30 is provided at the outlet of the filter case 13 (immediately after the intake port for the exhaust gas 9 in the low-pressure loop) as an exhaust throttle means for blocking the flow of the exhaust gas 9. The flow of the exhaust gas 9 is blocked by the closing operation command signal 30a from the control device 23 under the condition that the pressure difference between the intake side and the exhaust side is insufficient during idling or extremely light load. To get.

  In the figure, reference numeral 31 denotes an exhaust brake, and the connection point between one end of the EGR pipe 18 in the low-pressure loop 14 and the most upstream part near the turbine 2b of the return flow path 17 is set immediately after the exhaust brake 31. The low-pressure loop 14 does not affect the effectiveness of the exhaust brake 31.

  Thus, if the EGR device is configured in this way, the exhaust gas recirculation as a base is performed on the low pressure loop 14 side, and an additional exhaust gas recirculation is performed on the high pressure loop 15 side to supplement the insufficient EGR rate. Since the low pressure loop 14 and the high pressure loop 15 are used together, a high EGR rate is realized. On the other hand, the recirculation amount of the exhaust gas 9 that must be shared on the high pressure loop 15 side is independent of the high pressure loop 15. The amount of exhaust gas that should be shared by the high-pressure loop 15 side can be realized relatively easily without using the variable nozzle type turbocharger 2 to restrict the exhaust gas 9 excessively. As a result, a significant deterioration in fuel consumption due to an increase in pumping loss is avoided.

  Here, the low-pressure loop 14 has not been employed so far to recirculate the exhaust gas 9 at a high EGR rate because when the accelerator is depressed by the driver during driving and the vehicle enters an acceleration state, λ This is because (the excess air ratio) suddenly decreased and black smoke was likely to be generated. In this embodiment, the exhaust gas that becomes the base by the low-pressure loop 14 at an EGR rate that is suppressed to the extent that black smoke is not generated during acceleration. Since only gas recirculation is performed, the generation of black smoke is avoided by immediately reducing the recirculation amount of the exhaust gas 9 on the high-pressure loop 15 side during acceleration.

  That is, in the low-pressure loop 14, the exhaust gas 9 is returned to the inlet of the compressor 2 a of the turbocharger 2, but the path from here to the diesel engine 1 through the compressor 2 a, the intercooler 6, and the intake manifold 7 is long. Since the intake air 4 mixed with the exhaust gas 9 is present in this long path, the EGR valve 19 of the low-pressure loop 14 is immediately closed when the fuel injection amount increases in response to the depression of the accelerator during acceleration. However, there is a drawback that the λ-decreasing state continues and black smoke is likely to be generated until all the intake air 4 mixed with the exhaust gas 9 in the long path is used up.

  In contrast, in the high-pressure loop 15, the exhaust gas 9 is returned near the inlet of the intake manifold 7, so that the intake air 4 mixed with the exhaust gas 9 exists only in the intake manifold 7, and the fuel injection amount during acceleration is high. If the EGR valve 21 of the high-pressure loop 15 is closed, the intake 4 mixed with the exhaust gas 9 in the intake manifold 7 will be used up soon and λ will recover quickly. There is an advantage that it is easy to avoid.

  Therefore, as in the EGR device of the present embodiment, the exhaust gas recirculation as a base is performed by the low-pressure loop 14 at an EGR rate that is suppressed to the extent that black smoke is not generated at the time of acceleration, and the high-pressure loop 15 corresponds to the insufficient EGR rate. If additional exhaust gas recirculation is carried out to supplement λ, it is possible to recover λ early by immediately reducing the recirculation amount of the exhaust gas 9 on the high-pressure loop 15 side during acceleration, so that black It is possible to avoid the generation of smoke.

  FIG. 2 is a time chart showing an example of control during acceleration by the control device 23. From the top, the accelerator opening, the engine speed (Ne), and the EGR rate (low pressure loop, high pressure loop, total of both loops) ) And fuel injection amount (q) and λ (excess air ratio) to the engine, respectively, and in the case illustrated here, a case of rapid acceleration in which the accelerator is stepped on deeply is shown.

That is, when the accelerator is stepped on deeply from the time point T ₀ by the driver, the fuel injection amount increases following the stepping, and the engine speed also increases rapidly. In the control device 23, sudden acceleration is recognized from a large change amount of the accelerator opening per unit time, the EGR valve 21 of the high pressure loop 15 is fully closed at once, and the exhaust gas recirculation by the high pressure loop 15 side is temporarily suspended. After that, the EGR valve 21 is gradually opened and the exhaust gas recirculation is gradually resumed, and the EGR valve 19 on the low-pressure loop 14 side is slightly narrowed as necessary. Control is performed as follows.

  As a result, if the EGR valve 21 of the high-pressure loop 15 is not closed, the change in λ at the lowermost stage in the figure should be greatly reduced as shown by the chain line curve, but the increase in the fuel injection amount necessary for the acceleration is increased. Is offset by the rapid decrease in the total EGR rate mainly due to the cut off of the exhaust gas recirculation of the high-pressure loop 15, so that it is possible to recover λ without reducing so much, and the drop is black. It will remain in the range where no smoke is generated (because the low pressure loop 14 side has an EGR rate which is suppressed to the extent that black smoke is not generated during acceleration).

  The time chart illustrated in FIG. 2 is a case of sudden acceleration, but in the case of slow acceleration where the accelerator is stepped a little shallower, the EGR valve 21 of the high-pressure loop 15 is narrowed to a fully closed state. Of course, there may be cases in which only the intermediate opening is narrowed down to an appropriate intermediate opening.

  Particularly in this embodiment, the filter case 13 that is interposed in the exhaust pipe 11 and accommodates the particulate filter 12 has a double-shell structure, and the exhaust from the filter case 13 to the turbine of the turbocharger 2. The pipe 11 has a double-pipe structure, the return passages 16 and 17 formed in the outer layers of the filter case 13 and the exhaust pipe 11, the most upstream portion of the return passages 16 and 17 near the turbine 2b, and the compressor 2a. Since the low-pressure loop 14 is configured by the relatively short EGR pipe 18 connected to the inlet, a part of the exhaust gas 9 that has passed through the particulate filter 12 is folded back to the return flow path 16, and the filter case 13 and the outer layer portion of the exhaust pipe 11, and the compressor from the most upstream part of the return flow path 17 through the EGR pipe 18 Tsu will be recycled to the inlet of the sub 2a.

  The exhaust gas 9 that is recirculated is originally at a low temperature and low pressure when it passes through the particulate filter 12 in the middle of the exhaust pipe 11, and is exposed to the outside air with a large surface area and the outer layer of the exhaust pipe 11. Since it is cooled by heat radiation while flowing through the part, it is further sent from here to the intercooler 6 and air-cooled, so that the temperature of the exhaust gas 9 is sufficiently lowered, and the exhaust gas 9 is water-cooled using an EGR cooler or the like. This eliminates the need for a complicated water cooling system and an increase in the size of the radiator and fan.

  Further, since the exhaust gas 9 recirculated to the inlet of the compressor 2a is cleaner than the air that has been dust-removed through the particulate filter 12, the intercooler downstream of the compressor 2a is caused by soot or the like in the exhaust gas 9. 6 and the exhaust gas 9 is recirculated to the inlet of the compressor 2a having the lowest pressure in the intake system, so that the differential pressure between the exhaust side and the intake side is sufficient. Therefore, the exhaust gas 9 is recirculated well.

  At this time, the exhaust gas 9 returned from the rear of the particulate filter 12 to the inlet of the compressor 2a is returned by the return flow passages 16 and 17 constituting the outer layer portion of the filter case 13 and the exhaust pipe 11 in most of the strokes. It is only necessary to connect the most upstream portion of the return flow passages 16, 17 near the turbine 2b and the inlet of the compressor 2a of the turbocharger 2 with a short EGR pipe 18, and the EGR pipe has a compact overall structure. No need to worry about 18 layouts.

  On the other hand, when viewed from the particulate filter 12 side, the outer peripheral portion is insulated and insulated by the exhaust gas 9 flowing through the return flow path 16 so that it is difficult for heat to be taken away by the outside air. Since the temperature of the difficult outer peripheral portion is increased, the entire particulate filter 12 is efficiently heated to promote the combustion of the collected particulates, and the reliable regeneration with little remaining particulates is performed. Become.

  Therefore, according to the above-described embodiment, the exhaust gas recirculation that serves as a base is performed at the EGR rate that is suppressed to the extent that black smoke is not generated during acceleration by the low-pressure loop 14, and the high-pressure loop 15 is to supplement the insufficient EGR rate. By implementing the additional exhaust gas recirculation, it is possible to achieve a high EGR rate without causing a significant deterioration in fuel consumption and to obtain a good NOx reduction effect, and to step on the accelerator during acceleration Even if the fuel injection amount increases promptly, it is possible to recover λ early by mainly reducing the recirculation amount of the exhaust gas 9 on the high pressure loop 15 side, thereby avoiding the occurrence of black smoke. .

  Further, since it is not necessary to cool the exhaust gas 9 with an EGR cooler or the like when configuring the low-pressure loop 14, it is possible to avoid the complexity of the water-cooling system and the enlargement of the radiator and the fan. A compact low-pressure loop 14 can be realized without requiring a long EGR pipe.

  Further, by flowing the exhaust gas 9 that has passed through the particulate filter 12 to the return flow path 16, the outer peripheral portion of the particulate filter 12 can be insulated and kept warm, so that the particulate filter 12 as a whole can be heated. The temperature of the particulate filter 12 can be efficiently increased to promote the combustion of the collected particulates, and the particulate filter 12 with less unburned particles can be reliably regenerated.

  Further, in this embodiment, the recirculation amount of the exhaust gas 9 in the low pressure loop 14 and the high pressure loop 15 is detected by the pressure sensors 26 and 27 and the temperature sensors 28 and 29 having high responsiveness. Since the circulation rate is specified instantly and good feedback control is realized, and there is no fear of inaccurate detection due to the influence of vortices as in the case of using an air flow meter, the exhaust flow rate Even during acceleration when vortices are likely to occur due to a sudden change, the accurate recirculation amount of the exhaust gas 9 can be detected.

  Further, immediately after the intake port of the exhaust gas 9 in the low-pressure loop 14, a throttle valve 30 is provided as an exhaust throttle means for blocking the flow of the exhaust gas 9, so that the intake side during idling, extremely light load, etc. Even under conditions where the pressure difference with the exhaust side is insufficient, the flow of the exhaust gas 9 can be blocked by the throttle valve 30 to ensure the pressure difference between the intake side and the exhaust side. Smooth recirculation of the exhaust gas 9 to the low-pressure loop 14 can be promoted.

  The EGR device of the present invention is not limited to the above-described embodiment. The configuration of the low-pressure loop is not limited to the illustrated example, and the recirculation amount adjusting means narrows down the exhaust gas recirculation amount. The mechanism is not necessarily limited to the valve type, and the exhaust throttling means is not limited to the valve type, and various modifications can be made without departing from the scope of the present invention. is there.

It is the schematic which shows an example of the form which implements this invention. It is the time chart which showed an example of the control at the time of acceleration by the control apparatus of FIG.

Explanation of symbols

2 Turbocharger 2a Compressor 2b Turbine 4 Intake 5 Intake pipe 7 Intake manifold 9 Exhaust gas 10 Exhaust manifold 11 Exhaust pipe 11a Inner pipe 11b Outer pipe 12 Particulate filter 13 Filter case 13a Inner shell 13b Outer shell 14 Low pressure loop 15 High pressure loop 16 Return Flow path 17 Return flow path 18 EGR pipe 19 EGR valve (recirculation amount adjusting means)
20 EGR pipe 21 EGR valve (recirculation amount adjusting means)
23 control device 24 accelerator sensor 26 pressure sensor 26a detection signal 27 pressure sensor 27a detection signal 28 temperature sensor 28a detection signal 29 temperature sensor 29a detection signal 30 throttle valve (exhaust throttle means)

Claims (4)

  A part of the exhaust gas is extracted from the exhaust passage downstream from the turbine of the turbocharger and recirculated to the intake passage upstream from the compressor of the turbocharger, and a part of the exhaust gas is extracted from the exhaust manifold. A high-pressure loop that recirculates in the vicinity of the inlet, a recirculation amount adjusting means that adjusts the recirculation amount of exhaust gas provided in each of the low-pressure loop and the high-pressure loop, and black smoke is not generated during acceleration by the low-pressure loop. The exhaust gas recirculation that is the base with the suppressed EGR rate is implemented, and additional exhaust gas recirculation is performed in the high-pressure loop to supplement the insufficient EGR rate, and black smoke avoidance during acceleration is mainly performed on the high-pressure loop side. And a control device for controlling each of the recirculation amount adjusting means so as to cope with it by immediately reducing the recirculation amount of the exhaust gas. EGR apparatus characterized by a.   The filter case that is inserted in the middle of the exhaust pipe and accommodates the particulate filter has a double shell structure, and the exhaust pipe that reaches the turbine of the turbocharger from the filter case has a double pipe structure. A return flow path for returning a part of the exhaust gas that has passed through the particulate filter to the upstream side is formed in the outer layer portion of the return flow path, and between the most upstream portion near the turbine of the return flow path and the inlet of the compressor of the turbocharger. The EGR device according to claim 1, wherein the EGR device is connected by an EGR pipe, and a low pressure loop is configured by the return flow path and the EGR pipe.   Each of the low-pressure loop and the high-pressure loop is equipped with a pressure sensor for detecting a pressure difference between two points sandwiched by a recirculation amount adjusting means as a throttle, and a temperature sensor for detecting an exhaust temperature between the two points. An exhaust gas recirculation amount is calculated by an indirect measurement method based on detection signals from the pressure sensor and the temperature sensor, and feedback control is applied to each of the recirculation amount adjustment means based on the calculated exhaust gas recirculation amount. The EGR apparatus according to claim 1, wherein a control apparatus is configured.   The EGR device according to claim 1, 2 or 3, further comprising an exhaust throttle means for blocking the flow of exhaust gas immediately after the exhaust gas intake port of the low-pressure loop.

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