JP2009138720A - Multi-turbo system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a multi-turbo system capable of preventing the regeneration of a particulate filter from being obstructed. <P>SOLUTION: This multi-turbo system comprises large-sized and small-sized turbo-chargers 1, 2, and performs supercharging by selecting the optimum one or both the turbo-chargers according to the operating state of an engine 3. The inlet of each of turbines 1a, 2a is connected to an exhaust manifold 4 through a branched portion 21. A converged portion 5 for converging the exhaust gases 7 from outlets of the turbines and guiding the converged exhaust gas into an exhaust pipe 16 is connected also to the branched portion 21 through a bypass hole 19. An exhaust changeover valve 20 properly changeable between three normal positions for opening inlets of one or both of the outlets of the turbines 1a, 2a to the exhaust manifold 4 side and holding the bypass hole 19 in a closed state and a regenerative position for opening both inlets of the turbines 1a, 2a and the bypass hole 19 to the exhaust manifold 4 side is installed at the branched portion 21. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a multi-turbo system that performs optimum supercharging by appropriately using a large turbocharger and a small turbocharger.

  In recent years, two large turbochargers and small turbochargers have been installed, and the pressure ratio is uniformly high from light load to high load by switching between large turbocharger and small turbocharger according to engine operating conditions (load and rotation speed). A multi-turbo system that can achieve the above has begun to be applied to vehicles.

  FIG. 7 shows an example of a conventional multi-turbo system. In the example shown here, the inlets of the turbines 1 a and 2 a of the large turbocharger 1 and the small turbocharger 2 are connected to the exhaust manifold 4 of the engine 3. The outlets of the turbines 1a and 2a are adjusted by the exhaust gas switching valve 6 which is connected individually and is provided at the junction 5 at the outlet of the turbines 1a and 2a.

  That is, at light and medium loads, only the outlet of the turbine 2a of the small turbocharger 2 is opened by the exhaust switching valve 6 to close the outlet of the turbine 1a of the large turbocharger 1, and the exhaust gas 7 guided from the exhaust manifold 4 is small. Only the turbocharger 2 is driven to efficiently recover the exhaust energy.

  Further, when the load is high, the exhaust switching valve 6 is switched from the illustrated state to the opposite side so that only the outlet of the turbine 1a of the large turbocharger 1 is opened and the outlet of the turbine 2a of the small turbocharger 2 is closed. 4, only the large turbocharger 1 is driven by the exhaust gas 7 derived from the exhaust gas 7 to efficiently recover the exhaust energy.

  Further, during transition from a light / medium load to a high load, the exhaust switching valve 6 is switched from the illustrated state to the neutral position so that both the outlets of the turbines 1a and 2a are opened and the small turbocharger 2 and the large turbocharger are opened. The charger 1 is used in combination to prevent a temporary drop in the pressure ratio when switching between the two.

  On the other hand, the intake air 8 at the time of light / medium load is introduced into the compressor 2b of the small turbocharger 2 via the compressor 1b of the large turbocharger 1 that is not driven, and is then cooled by the intercooler 9. The intake manifold 10 is guided to the intake manifold 10, but at the time of transition or high load, the intake switching valve 11 opens and the intake air 8 boosted by the compressor 1b of the large turbocharger 1 bypasses the turbine 2a of the small turbocharger 2. The intake switching valve 11 is gradually opened during the transition.

  In FIG. 7, 12 is an EGR line for recirculating a part of the exhaust gas 7 extracted from the exhaust manifold 4 to the intake pipe 13, 14 is a water-cooled EGR cooler installed in the middle of the EGR line 12, and 15 Is an EGR valve that opens and closes the flow path of the EGR line 12, 16 is an exhaust pipe, 17 is a particulate filter provided in the middle of the exhaust pipe 16, and 18 is an oxidation catalyst provided in the preceding stage of the particulate filter 17. Respectively.

Incidentally, as prior art document information related to this type of multi-turbo system, there is the following Patent Document 1 by the same applicant as the present invention.
JP 2006-226156 A

  However, in such a conventional multi-turbo system, at least one of the large turbocharger 1 and the small turbocharger 2 must be passed through to collect exhaust energy and then be led downstream. Since the optimum one or both of the large turbocharger 1 and the small turbocharger 2 are selected and the exhaust energy is efficiently recovered, the temperature of the exhaust gas 7 sent to the exhaust pipe 16 from the multi-turbo system. When the particulate filter 17 for collecting particulates is provided in the middle of the exhaust pipe 16 as shown in the figure, it is difficult to regenerate the particulate filter 17. There was a problem.

  That is, in order to actively incinerate the particulates in the particulate filter 17 and regenerate the particulate filter 17, fuel is added to the exhaust gas 7 by post injection on the engine 3 side, and the addition It is necessary to oxidize the fuel with the oxidation catalyst 18 in the preceding stage of the particulate filter 17 and to incinerate the particulates by raising the catalyst bed temperature of the particulate filter 17 immediately after the exhaust gas 7 is heated by the reaction heat. However, if the exhaust energy is efficiently recovered by the multi-turbo system on the upstream side and the exhaust temperature is lowered, the catalyst bed temperature of the particulate filter 17 is difficult to rise, and the regeneration of the particulate filter 17 is hindered. There was a fear of coming.

  The present invention has been made in view of the above circumstances, and an object thereof is to provide a multi-turbo system that does not hinder the regeneration of the particulate filter.

  In the present invention, two large turbochargers and two small turbochargers are mounted, and supercharging is performed by selecting one or both of the large turbocharger and the small turbocharger according to the operating state of the engine. In the multi-turbo system, the inlet of each turbine of the large turbocharger and the small turbocharger is connected to the exhaust manifold of the engine via a single branch point, and the exhaust gas from the outlet of each turbine is joined. A junction point leading to the exhaust pipe is connected to the branch point via a bypass port, and one or both inlets of each turbine are opened to the exhaust manifold side to keep the bypass port closed. One normal position and both inlets and bypass ports of each turbine are all on the exhaust manifold side One of the playback position as appropriate to the exhaust switching valve may switch the to opened is characterized in that provided in the bifurcation.

  Thus, in this way, only the small turbocharger turbine inlet is opened to the exhaust manifold side by the exhaust switching valve during light and medium loads, and the large turbocharger turbine inlet is blocked and led from the exhaust manifold. Only the small turbocharger is driven by exhaust gas to efficiently collect exhaust energy, and at the time of high load, only the turbine inlet of the large turbocharger is opened by the exhaust switching valve to block the turbine inlet of the small turbocharger, Exhaust gas can be efficiently recovered by driving only the large turbocharger with the exhaust gas introduced from the exhaust manifold.

  Furthermore, at the time of transition from light / medium load to high load, both the inlet of each turbine is opened by the exhaust switching valve and the bypass port is kept closed, and a small turbocharger and a large turbocharger are used in combination. It is possible to prevent a temporary drop in the pressure ratio when switching between the two.

  In addition, when the particulate filter installed in the middle of the exhaust pipe is regenerated, if both the inlet and bypass ports of each turbine are opened to the exhaust manifold side by the exhaust switching valve, the hot exhaust gas immediately after leaving the engine will be exhausted. Since it flows preferentially to the bypass port with the least resistance and is directly led to the exhaust pipe without passing through any of the turbines, the exhaust gas remains in the high temperature state before the exhaust energy is recovered and enters the particulate filter. Thus, the particulate filter can be regenerated satisfactorily.

  At this time, it is not necessary to take heat away from each turbine by passing through each turbine, to guide exhaust gas through an extremely short path from the exhaust manifold to the exhaust pipe, and to pass only one exhaust switching valve. In other words, the fact that the flow path switching structure itself does not have to be deprived of much heat contributes to the prevention of a decrease in the exhaust temperature.

  Further, in the present invention, the exhaust switching valve adopts a type in which the flow path is switched using a butterfly valve, and a rotation range in which both inlets of each turbine can be opened to the exhaust manifold side to the butterfly valve. It is preferable that a shutter portion that partially closes the bypass port is provided.

  In this way, an exhaust switching valve that switches between three normal positions and one regeneration position does not require a particularly complicated flow path switching mechanism, and is relatively simple using a butterfly valve. And it becomes possible to comprise as a compact structure.

  Furthermore, in the present invention, it is preferable that an oxidation catalyst capable of oxidizing unburned fuel in the exhaust gas is built in the bypass port. It is possible to increase the catalytic activity by introducing exhaust gas having a small temperature drop due to the above to the oxidation catalyst and efficiently raising the temperature of the oxidation catalyst.

  According to the multi-turbo system 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, even if a multi-turbo system is adopted, the exhaust gas emitted from the engine is converted into the particulate filter while recovering the exhaust energy without being recovered. Therefore, the regeneration of the particulate filter can be favorably performed without any trouble.

  (II) According to the invention described in claim 2 of the present invention, an exhaust gas switching valve that switches between three normal positions and one regeneration position can be used as a butterfly valve without using a particularly complicated flow path switching mechanism. Therefore, it is possible to construct a relatively simple and compact structure using the above, and it is possible to realize a reduction in implementation cost and good mountability.

  (III) According to the invention described in claim 3 of the present invention, exhaust gas which has not yet undergone a temperature drop due to heat radiation from the pipe immediately after leaving the engine is introduced into the oxidation catalyst, and the oxidation catalyst is efficiently heated. Thus, the catalyst activity can be increased, so that the fuel filter can be effectively regenerated by starting fuel addition by post injection or the like on the engine side even under operating conditions where the exhaust temperature is lower than in the past.

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

  1 to 5 show an example of an embodiment for carrying out the present invention, and portions denoted by the same reference numerals as those in FIG. 7 represent the same items.

  As shown in FIG. 1, in the present embodiment, the inlets of the turbines 1 a and 2 a of the large turbocharger 1 and the small turbocharger 2 are connected to the exhaust manifold 4 of the engine 3 via a single branch point 21. At the same time, the joining location 5 that joins the exhaust gas 7 from the outlets of the turbines 1 a and 2 a and leads it to the exhaust pipe 16 is also connected to the branch location 21 via the bypass port 19.

  The branch portion 21 has three normal positions for opening one or both of the inlets of the turbines 1a and 2a with respect to the exhaust manifold 4 side and holding the bypass port 19 in the closed state. There is provided an exhaust switching valve 20 capable of appropriately switching between one regeneration position in which both the inlets of the turbines 1a and 2a and the bypass port 19 are opened to the exhaust manifold 4 side.

  That is, as shown in FIG. 2, the exhaust gas switching valve 20 has a butterfly valve 23 rotatably held via a rotary shaft 24 in a housing 22 connected to the inlets of the turbines 1a and 2a on both sides thereof. 2, only the inlet of the turbine 2a of the small turbocharger 2 is opened to the exhaust manifold 4 side at the rotation position indicated by the solid line in FIG. 2, and at the rotation position indicated by the chain line in FIG. Only the inlet of the turbine 1a of the large turbocharger 1 is opened to the exhaust manifold 4 side.

  Here, the bypass port 19 opened at a position facing the exhaust manifold 4 side of the housing 22 is formed by a one-dot chain line in FIG. 2 by a shutter portion 25 formed at one end of the butterfly valve 23 and extending in the rotation direction. The rotation position is set within a rotation range in which both inlets of the turbines 1a and 2a can be opened to the exhaust manifold 4 side.

  Further, the shutter 25 and the bypass port 19 are displaced so that the bypass port 19 is opened within a rotation range in which both inlets of the turbines 1a and 2a can be opened to the exhaust manifold 4 side. At the position (rotation position indicated by a two-dot chain line in FIG. 2), both the inlets of the turbines 1a and 2a and the bypass port 19 are all open to the exhaust manifold 4 side.

  Thus, when the multi-turbo system is configured as described above, the butterfly valve of the exhaust gas switching valve 20 is rotated to the rotation position indicated by the solid line in FIG. Only the inlet of the turbine 2 a of the small turbocharger 2 is opened to the exhaust manifold 4 side to close the inlet of the turbine 1 a of the large turbocharger 1, and only the small turbocharger 2 is driven by the exhaust gas 7 guided from the exhaust manifold 4. Thus, exhaust energy can be recovered efficiently.

  At this time, the intake switching valve 11 is closed, and all of the intake air 8 is introduced into the compressor 2b of the small turbocharger 2 via the compressor 1b of the large turbocharger 1 which is not driven, and the intake air is taken in by the compressor 2b. After the pressure is raised, it is led to the intercooler 9, where it is cooled and then led to the intake manifold 10.

  Further, when the load is high, the butterfly valve 23 of the exhaust gas switching valve 20 is rotated to the rotation position indicated by the chain line in FIG. 2, thereby opening only the inlet of the turbine 1a of the large turbocharger 1 as shown in FIG. Thus, the inlet of the turbine 2a of the small turbocharger 2 is closed, and only the large turbocharger 1 can be driven by the exhaust gas 7 introduced from the exhaust manifold 4 to efficiently recover the exhaust energy.

  At this time, the intake switching valve 11 is kept open, and after the intake air 8 is introduced into the compressor 1b of the large turbocharger 1 to increase the pressure, the resistance is minimized without passing through the compressor 2b of the small turbocharger 2 that is not driven. It is led to the intercooler 9 through the intake switching valve 11 in the open state, and after cooling here, it is led to the intake manifold 10.

  Further, at the time of transition from light / medium load to high load, the butterfly valve 23 of the exhaust gas switching valve 20 is rotated to the rotation position indicated by the one-dot chain line in FIG. , 2a are both opened and the bypass port 19 is kept closed, and the small turbocharger 2 and the large turbocharger 1 are used together to prevent a temporary drop in the pressure ratio when switching between the two. It becomes possible. Note that the intake switching valve 11 is gradually opened as the load increases, thereby smoothly driving both the small turbocharger 2 and the large turbocharger 1.

  In addition, when the particulate filter 17 provided in the middle of the exhaust pipe 16 is regenerated, the butterfly valve 23 of the exhaust switching valve 20 is rotated to a rotational position indicated by a two-dot chain line in FIG. When both the inlets 2a and the bypass port 19 of 2a are opened to the exhaust manifold 4 side, the high-temperature exhaust gas 7 immediately after exiting the engine 3 is preferentially given to the bypass port 19 with the least resistance as shown in FIG. Since it flows in and is directly guided to the exhaust pipe 16 without passing through any of the turbines 1a and 2a, the exhaust gas 7 is guided to the particulate filter 17 in a high temperature state before the exhaust energy is recovered, The particulate filter 17 can be regenerated satisfactorily.

  At this time, the turbines 1a and 2a are not routed through the turbines 1a and 2a, and the exhaust gas 7 can be guided from the exhaust manifold 4 to the exhaust pipe 16 through an extremely short path. The fact that only one switch valve 20 needs to be passed and the flow path switching structure itself does not lose much heat also contributes to prevention of a decrease in exhaust temperature.

  Note that the active regeneration of the particulate filter 17 is performed under an operating condition at a low exhaust temperature at which spontaneous ignition of the collected particulates cannot be expected. At this time, the intake switching valve 11 is closed. Then, a route that preferentially guides intake air to the compressor 2b of the small turbocharger 2 is selected.

  As described above, according to the above-described embodiment, even when the multi-turbo system is employed, the exhaust gas 7 emitted from the engine 3 is guided to the particulate filter 17 in a high temperature state without collecting exhaust energy. Therefore, the regeneration of the particulate filter 17 can be carried out satisfactorily without any trouble.

  Further, particularly in this embodiment, it is not necessary to employ a particularly complicated flow path switching mechanism when configuring the exhaust gas switching valve 20 for switching between three normal positions and one regeneration position, and the butterfly valve 23 is used. Therefore, it can be configured as a relatively simple and compact structure, and the implementation cost can be reduced and good mountability can be realized.

  FIG. 6 shows another embodiment of the present invention. In the example shown here, unburned fuel in the exhaust gas 7 is connected to the bypass port 19 connecting the junction 5 and the branch 21. An oxidation catalyst 26 that can oxidize the gas is provided in the interior, and in this way, exhaust gas 7 is introduced into the oxidation catalyst 26 with little temperature drop due to pipe heat dissipation immediately after leaving the engine 3, Since the oxidation catalyst 26 can be efficiently heated to increase the catalyst activity, the particulate filter 17 is started by starting fuel addition by post-injection or the like on the engine 3 side even under operating conditions where the exhaust temperature is lower than before. Can be effectively reproduced.

  That is, the oxidation catalyst 18 that is generally provided in the front stage of the particulate filter 17 is far away from the engine 3, so that the exhaust temperature decreases due to pipe heat dissipation before reaching the oxidation catalyst 18. Therefore, there is an operation region in which fuel addition cannot be started because sufficient activity of the oxidation catalyst 18 cannot be obtained. However, if the exhaust gas 7 immediately after exiting the engine 3 can be introduced into the oxidation catalyst 26, this is the case. Therefore, the addition of fuel can be started from operating conditions where the exhaust temperature is lower than in the prior art.

  At this time, the oxidation catalyst 18 provided in the preceding stage of the particulate filter 17 can be omitted as appropriate according to the exhaust gas temperature raising effect of the oxidation catalyst 26, but is used together as shown here. You may do it.

  The multi-turbo system of the present invention is not limited to the above-described embodiment, and the configuration of the exhaust gas switching valve is not necessarily limited to the configuration shown in the drawings. In addition, the scope of the present invention is not deviated. Of course, various changes can be made.

It is the schematic which shows an example of the form which implements this invention in the state at the time of light and medium load. It is sectional drawing which shows the detail of the exhaust gas switching valve of FIG. It is the schematic which shows the state at the time of the high load of the multi-turbo system of FIG. It is the schematic which shows the state at the time of the transition of the multi-turbo system of FIG. It is the schematic which shows the state at the time of filter reproduction | regeneration of the multi-turbo system of FIG. It is the schematic which shows another form example of this invention. It is the schematic which shows a prior art example.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Large turbocharger 1a Turbine 2 Small turbocharger 2a Turbine 3 Engine 4 Exhaust manifold 5 Merge location 7 Exhaust gas 16 Exhaust pipe 19 Bypass port 20 Exhaust switching valve 21 Branch location 23 Butterfly valve 25 Shutter part 26 Oxidation catalyst

Claims (3)

  A multi-turbo system that has two large turbochargers and two small turbochargers, and performs supercharging by selecting one or both of the large turbocharger and the small turbocharger according to the operating state of the engine. In the above, the inlets of the turbines of the large turbocharger and the small turbocharger are connected to the exhaust manifold of the engine via a single branch point, and exhaust gases from the outlets of the turbines are merged and led to the exhaust pipe. Three normal positions for connecting a junction point to the branch point through a bypass port, and opening one or both inlets of each turbine to the exhaust manifold side to hold the bypass port closed. Open both inlets and bypass ports of each turbine to the exhaust manifold side. Multi turbo system, characterized in that the exhaust control valve may suitably switched and one reproduction position provided in the bifurcation.   The exhaust switching valve uses a butterfly valve to switch the flow path, and the bypass port is blocked by a part of the rotation range in which both inlets of each turbine can be opened to the exhaust manifold side. The multi-turbo system according to claim 1, further comprising a shutter unit configured to perform a shutter operation.   The multi-turbo system according to claim 1 or 2, wherein an oxidation catalyst capable of oxidizing unburned fuel in the exhaust gas is built in the bypass port.

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