JP6470602B2 - Exhaust temperature raising device - Google Patents

Description

  The present invention relates to an exhaust gas temperature raising device.

  Particulate matter (particulate matter) discharged from a diesel engine is mainly composed of soot made of carbonaceous matter and SOF content (Soluble Organic Fraction) made of high-boiling hydrocarbon components. The composition contains a small amount of sulfate (mist-like sulfuric acid component). As a measure to reduce this type of particulates, a particulate filter is installed in the middle of the exhaust pipe through which the exhaust gas flows. It has been done 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. The outlet of the flow channel is sealed, and only the exhaust gas that has permeated through the porous thin wall that defines each flow channel is discharged downstream, and the particulates in the exhaust gas are porous. It is intended to be collected on the inner surface of the thin wall.

  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 particulates to self-combust, so an oxidation catalyst that uses Pt, Pd, etc. as an active species is integrated. It is made to carry.

  In this way, 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. In the region, the collected amount exceeds the treated amount of the particulates, so if the operation state at a low exhaust temperature continues, the particulate filter will not regenerate well and the particulate filter will be over-collected. There is a risk of falling into a state.

  Therefore, as shown in FIG. 2, a flow-through type oxidation catalyst 4 is separately provided in front of the particulate filter 3 installed in the middle of the exhaust pipe 2 of the diesel engine 1, and the accumulated amount of particulates has increased. Following the main injection of fuel performed in the vicinity of the compression top dead center in each cylinder 5 of the diesel engine 1, post injection is performed at a timing of non-ignition later than the compression top dead center, whereby fuel is injected into the exhaust gas 6. It is considered that the particulate filter 3 is forcibly regenerated by adding it.

  That is, according to this forced regeneration, the HC gas generated by fuel addition undergoes an oxidation reaction while passing through the preceding oxidation catalyst 4, and the particulate filter 3 immediately after the inflow of the exhaust gas 6 heated by the reaction heat. Thus, the catalyst bed temperature is raised and the particulates are burned out, and the particulate filter 3 is regenerated.

  As prior art document information related to the forced regeneration of such a particulate filter, there is the following Patent Document 1 by the same applicant as the present invention.

JP 2003-193824 A

  However, when the turbocharger 7 is mounted on the diesel engine 1, the exhaust gas 6 discharged from each cylinder 5 of the diesel engine 1 works in the turbine 7 a and then is guided to the particulate filter 3 through the exhaust pipe 2. Therefore, when the temperature reaches the particulate filter 3, the temperature is greatly lowered, and there is a problem that the forced regeneration of the particulate filter 3 cannot be performed efficiently.

  Especially in cases where the space for mounting the particulate filter 3 can be secured only at a position away from the diesel engine 1 depending on the vehicle type, the exhaust gas from the diesel engine 1 to the particulate filter 3 when the outside air temperature is low, such as in rainy weather or in winter. The exhaust gas temperature is lowered by the heat radiation from the exhaust pipe 2 while the gas is guided, and the operating region in which the particulate filter 3 can be forcibly regenerated may be narrower than usual.

  In the example shown in FIG. 2, the exhaust manifold 8 and the intake manifold 9 are connected by an EGR pipe 10, and a part of the exhaust gas 6 is extracted from the exhaust manifold 8, so that the EGR cooler 11 and the EGR valve 12. The EGR device 13 is provided so that it can be recirculated to the intake manifold 9 via the EGR valve, but in this case, the EGR valve prevents the added fuel from the post injection from flowing into the intake side in a large amount and causing HC polymerization or the like. 12 must be closed to stop the recirculation of the exhaust gas 6, but there is also a problem that the NOx reduction rate is greatly deteriorated while the recirculation of the exhaust gas 6 is stopped.

  2, reference numeral 7b denotes a compressor of the turbocharger 7, 14 denotes an air cleaner, and 15 denotes an intercooler for cooling the intake air 16 pressurized by the compressor 7b.

  The present invention has been made in view of the above circumstances, and it is possible to obtain a higher exhaust gas temperature raising performance than before, and when the EGR device is provided, the exhaust gas recirculation is not stopped even during the exhaust gas temperature raising. An object of the present invention is to provide an exhaust temperature raising device that can be used.

  The present invention is an engine exhaust temperature raising device equipped with a turbocharger and equipped with an after-treatment device in an exhaust pipe after the turbine of the turbocharger, wherein the exhaust manifold is placed at an appropriate position in the arrangement direction of each cylinder. The main manifold and the sub-manifold are divided through one on-off valve, the sub-manifold and the inlet side of the exhaust pipe after-treatment device are connected by a communication pipe through the second on-off valve, and the communication pipe Is equipped with an oxidation catalyst so that post-injection can be carried out only with a part of the cylinders corresponding to the sub-manifold.

  Thus, when raising the temperature of the exhaust gas led to the aftertreatment device, the first on-off valve is closed and the second on-off valve is opened, and post injection is carried out only with some cylinders corresponding to the sub manifold. The exhaust gas flows from the sub-manifold to the connecting pipe in a state of containing the HC gas generated from the added fuel by the post injection, and the HC gas in the exhaust gas passes through the oxidation catalyst installed in the connecting pipe. Since the oxidation reaction causes the temperature of the exhaust gas to be significantly increased by the reaction heat, the bed temperature of the aftertreatment device is raised by the inflow of the heated exhaust gas.

  At this time, the exhaust gas flowing directly from the sub-manifold to the inlet side of the aftertreatment device bypasses the turbine of the turbocharger and is guided without work, so that the temperature does not drop significantly from the high temperature state just exiting the engine. Introduced into the oxidation catalyst and further heated, the exhaust temperature can be raised to a higher temperature even in the same operating range as before, and the exhaust temperature raising performance is greatly improved. .

  When the exhaust manifold is divided into the main manifold and the sub manifold, if the sub manifold is set on the side close to the position of the post-processing device, the connecting pipe connecting the sub-manifold and the inlet side of the post-processing device. Can be made shorter than the length of the exhaust pipe from the turbine outlet to the entry side of the aftertreatment device, and the amount of heat radiation lost before reaching the aftertreatment device can also be reduced.

  Further, in the present invention, when the engine is equipped with an EGR device, the EGR device is preferably configured to extract a part of the exhaust gas from the main manifold and recirculate it to the intake side. .

  In this way, it is possible to recirculate only the exhaust gas not added with fuel in the main manifold to the intake side, and even if a part of the exhaust gas is recirculated to the intake side, the added fuel is returned to the intake side. Since there is no fear of causing a large amount of HC polymerization and the like, it is not necessary to stop the recirculation of the exhaust gas during the temperature rise of the exhaust.

  Further, in the present invention, a variable geometry turbocharger is adopted as the turbocharger, and the turbine capacity can be changed in response to the change in the amount of gas flowing into the turbine when the first on-off valve is closed. Preferably it is.

  That is, when the first on-off valve is closed and opened, the amount of gas flowing into the turbine changes even in the same operating range. If it is made to change, it will become possible to drive the turbine of a turbocharger efficiently.

  In the present invention, it is preferable that at least a particulate filter is provided as a post-processing device. In this way, when the particulate filter is forcibly regenerated, the temperature of the particulate filter is increased to a higher temperature than before. The exhaust gas can be heated and sent in, and the forced regeneration of the particulate filter can be performed efficiently and reliably.

  According to the exhaust temperature raising apparatus 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 from a part of the cylinders corresponding to the sub-manifold is used as the exhaust gas dedicated to fuel addition, and the exhaust gas bypasses the turbine of the turbocharger. By introducing it into the oxidation catalyst in a high temperature state, it can be led to the aftertreatment device after further heating, so that the exhaust temperature can be raised to a higher temperature even in the same operating range as before. It is possible to significantly improve the exhaust gas temperature raising performance than before.

  (II) According to the invention described in claim 2 of the present invention, since only the exhaust gas not added with fuel in the main manifold can be recirculated to the intake side, the exhaust gas is recirculated during the temperature rise of the exhaust gas. Therefore, it is possible to avoid the problem that the NOx reduction rate is greatly deteriorated during the temperature rise of the exhaust gas.

  (III) According to the invention described in claim 3 of the present invention, even if the amount of gas flowing into the turbine in the same operation region changes between when the first on-off valve is closed and when it is opened, this inflow The turbine can be efficiently driven by changing the turbine capacity in response to the change in the gas amount.

  (IV) According to the invention described in claim 4 of the present invention, at the time of forced regeneration of the particulate filter, the exhaust gas can be heated and sent to the particulate filter to a higher temperature than before, The forced regeneration of the particulate filter can be performed efficiently and reliably.

It is the schematic which shows an example of the form which implements this invention. It is the schematic which shows a prior art example.

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

  FIG. 1 shows an example of an embodiment for carrying out the present invention, and parts denoted by the same reference numerals as those in FIG. 2 represent the same items.

  As shown in FIG. 1, in this embodiment, the exhaust manifold 8 is divided into a main manifold 8A and a sub-manifold 8B via an on-off valve 17 at an appropriate position in the direction in which the cylinders 5 are arranged, and an in-line 6-cylinder diesel engine is obtained. 5 cylinders in 1 (engine) correspond to the main manifold 8A, and only 1 cylinder corresponds to the sub manifold 8B.

  The sub-manifold 8B and the inlet side of the particulate filter 3 (post-treatment device) of the exhaust pipe 2 are connected by a communication pipe 19 via an on-off valve 18, and an oxidation catalyst is provided in the middle of the communication pipe 19. In addition, the exhaust pipe 2 is provided with only the particulate filter 3 by installing the oxidation catalyst 20 in the communication pipe 19.

  Further, a control device 21 is provided for controlling the fuel injection of the diesel engine 1 by a control signal 1x so that post injection is performed only by the cylinder 5 corresponding to the sub-manifold 8B. The opening / closing operation of the opening / closing valve 18 can also be controlled by the control signals 17x, 18x.

  Here, when the exhaust manifold 8 is divided into the main manifold 8A and the sub-manifold 8B, the sub-manifold 8B is set on the side close to the arrangement position of the particulate filter 3 so that the length of the connecting pipe 19 is as short as possible. It is.

  Further, the diesel engine 1 is equipped with an EGR device 13 including an EGR pipe 10, an EGR cooler 11, and an EGR valve 12. The EGR device 13 removes a part of the exhaust gas 6 from the main manifold 8A. It is configured to be extracted and recirculated to the intake manifold 9.

  The turbocharger 7 employs a conventionally known variable geometry turbocharger in which a nozzle portion on the turbine 7a side is annularly provided with a number of nozzle vanes capable of adjusting the angle so that the nozzle opening can be arbitrarily changed. Thus, when the on-off valve 17 is closed, the turbine capacity can be changed in response to a change in the amount of gas flowing into the turbine 7a.

  Thus, when the exhaust gas 6 guided to the particulate filter 3 is heated to forcibly regenerate the particulate filter 3, the on-off valve 17 is closed and the on-off valve 18 is opened, and the cylinder 5 corresponding to the sub-manifold 8B. When the post injection is performed alone, the exhaust gas 6 flows from the sub-manifold 8B to the communication pipe 19 in a state including the HC gas generated from the added fuel by the post injection, and the oxidation catalyst provided in the communication pipe 19 Since the HC gas in the exhaust gas 6 undergoes an oxidation reaction while passing through 20, and the temperature of the exhaust gas 6 is significantly increased by the reaction heat, the particulate filter 3 The catalyst bed temperature is raised, the particulates are burned out, and the particulate filter 3 is regenerated.

  At this time, the exhaust gas 6 that flows directly from the sub-manifold 8B to the inlet side of the particulate filter 3 bypasses the turbine 7a of the turbocharger 7 and is guided without work. It is introduced into the oxidation catalyst 20 without significantly lowering the temperature, and further heating is performed, so that the exhaust temperature can be raised to a higher temperature even in the same operation region as before, and the exhaust temperature raising performance is improved. It will be greatly improved.

  When the exhaust manifold 8 is divided into the main manifold 8A and the sub-manifold 8B, the sub-manifold 8B is set on the side close to the arrangement position of the particulate filter 3, so that the sub-manifold 8B and the particulate filter 3 are inserted. It is possible to make the connecting pipe 19 connecting the two sides shorter than the length of the exhaust pipe 2 from the outlet of the turbine 7 a to the inlet side of the particulate filter 3, and it is lost before reaching the particulate filter 3. It is also possible to reduce the heat radiation.

  In this embodiment, when the diesel engine 1 is equipped with the EGR device 13, the EGR device 13 can extract a part of the exhaust gas 6 from the main manifold 8 </ b> A and recirculate it to the intake manifold 9. Therefore, only the exhaust gas 6 not added with fuel in the main manifold 8A can be recirculated to the intake side, and even if a part of the exhaust gas 6 is recirculated to the intake side, the added fuel Therefore, there is no need to stop the recirculation of the exhaust gas 6 during the temperature rise of the exhaust gas.

  Therefore, according to the above embodiment, the exhaust gas 6 from the cylinder 5 corresponding to the sub-manifold 8B is used as the exhaust gas 6 dedicated to fuel addition, and the exhaust gas 6 bypasses the turbine 7a of the turbocharger 7 and is in a high temperature state. By introducing it into the oxidation catalyst 20 as it is, it is possible to guide it to the particulate filter 3 after further heating, so that the exhaust temperature can be raised to a higher temperature even in the same operating region as before. The exhaust gas temperature raising performance can be greatly improved as compared with the past, and the exhaust gas 6 heated to a temperature higher than the conventional temperature is sent to the particulate filter 3 to forcibly regenerate the particulate filter 3. It can be performed efficiently and reliably.

  Further, since only the exhaust gas 6 not added with fuel in the main manifold 8A can be recirculated to the intake side, it is not necessary to take measures to stop the recirculation of the exhaust gas 6 during the temperature rise of the exhaust. It is possible to avoid the problem that the NOx reduction rate is greatly deteriorated during the temperature rise.

  Moreover, the amount of gas flowing into the turbine 7a changes even when the on-off valve 17 is closed and opened, but in this embodiment, variable geometry is used as the turbocharger 7. Since the turbocharger is adopted, even if the amount of inflow gas to the turbine 7a in the same operation region changes between when the on-off valve 17 is closed and when it is opened, the turbine responds to the change in the amount of inflow gas. The turbine 7a can be efficiently driven by changing the capacity.

  The exhaust temperature raising device of the present invention is not limited to the above-described embodiment. In the drawing, the post-processing device is a particulate filter, but the post-processing device reduces NOx. May be a selective reduction type catalyst or NOx occlusion reduction catalyst, etc., in which case it may be used for the purpose of raising the catalyst bed temperature to the active temperature in the operating region where the exhaust temperature is low, In the illustrated example, the case of an in-line 6-cylinder engine is illustrated in which 5 cylinders correspond to the main manifold and only 1 cylinder corresponds to the sub-manifold, but the engine type is limited to the in-line 6-cylinder engine. However, the number of cylinders allocated to the sub-manifold is not limited to one cylinder, and various modifications can be made without departing from the scope of the present invention. It is a matter of course.

1 Diesel engine (engine)
2 Exhaust pipe 3 Particulate filter (Post-processing device)
5 Cylinder 6 Exhaust Gas 7 Turbocharger 7a Turbine 8 Exhaust Manifold 8A Main Manifold 8B Sub Manifold 13 EGR Device 17 Open / Close Valve (First Open / Close Valve)
18 On-off valve (second on-off valve)
19 Connecting pipe 20 Oxidation catalyst

Claims (4)

  An exhaust temperature raising device for an engine equipped with a turbocharger and equipped with an after-treatment device in an exhaust pipe after the turbine of the turbocharger, wherein the exhaust manifold is arranged at a first position of the first on-off valve The main manifold and the sub-manifold are divided through a connection pipe, and the sub-manifold and the inlet side of the exhaust pipe after-treatment device are connected by a communication pipe through a second on-off valve, and an oxidation catalyst is connected to the communication pipe. An exhaust gas temperature raising apparatus that is equipped and configured to perform post-injection only with a part of cylinders corresponding to the sub-manifold.   The exhaust gas according to claim 1, wherein the engine is equipped with an EGR device, and the EGR device is configured to extract a part of the exhaust gas from the main manifold and to recirculate it to the intake side. Temperature rising device.   A variable geometry turbocharger is employed as the turbocharger, and the turbine capacity can be changed in response to a change in the amount of gas flowing into the turbine when the first on-off valve is closed. Item 3. The exhaust gas temperature raising device according to Item 1 or 2.   The exhaust temperature raising device according to claim 1, 2 or 3, wherein at least a particulate filter is provided as the aftertreatment device.

Images