JP2010001875A - Exhaust emission control device and exhaust emission control method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To propose an exhaust emission control device and an exhaust emission control method, capable of miniaturizing a heat exchanger, capable of highly maintaining exhaust emission control performance by efficiently exchanging heat by this small heat exchanger, and capable of restraining an increase in a pressure loss of exhaust gas by the heat exchanger, in the exhaust emission control device having the heat exchanger for transmitting heat of downstream side exhaust gas of an exhaust gas processing unit heating in exhaust gas processing of an internal combustion engine to upstream side exhaust gas of this exhaust gas processing unit. <P>SOLUTION: This exhaust emission control device comprises an upstream side bypass passage 5 for bypassing a part of the upstream side exhaust gas G1 around the heat exchanger 2, a downstream side bypass passage 9 for bypassing a part of the downstream side exhaust gas G3 around the heat exchanger 2, an upstream side opening-closing valve 6 for opening and closing the upstream side bypass passage 5, a downstream side opening-closing valve 10 for opening and closing the downstream side bypass passage 9, and a valve control device for controlling opening-closing operation of the upstream side opening-closing valve 6 and the downstream side opening-closing valve 10. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an exhaust gas purifying apparatus and an exhaust gas purifying apparatus for transferring heat generated in an exhaust gas processing unit such as a catalyst disposed in an exhaust gas passage of an internal combustion engine or the like to an exhaust gas upstream of the exhaust gas processing unit. Regarding the method.

  In an internal combustion engine such as a diesel engine mounted on an automobile, an exhaust gas processing device such as a catalyst is being attached to an exhaust passage in order to comply with strict exhaust gas regulations. For example, an oxidation catalyst is arranged in front of a DPF with catalyst (DPD), and HC, CO, etc. in the exhaust gas are oxidized by the catalytic action of this oxidation catalyst, and the temperature of the exhaust gas is increased by this reaction heat, or Injecting fuel into the exhaust pipe and oxidizing the fuel in the exhaust pipe or with an oxidation catalyst to raise the temperature of the exhaust gas, thereby maintaining the temperature of the DPF with catalyst high, Attempts have been made to improve the purification rate of the DPF with catalyst.

  Since these catalytic reactions are strongly influenced by the temperature of the catalyst, it is important to maintain a temperature at which the catalyst operates with high efficiency. In particular, in a diesel engine, a plurality of exhaust gas processing units such as a DPF (diesel particulate filter), an oxidation catalyst (DOC), and a NOx reduction catalyst (DeNOx) are installed. The temperature decreases and it becomes difficult to maintain the temperature above the activation temperature.

  In general, in order to improve the purification rate of exhaust gas having a low exhaust gas temperature, a large amount of noble metal catalyst is used, but in this case, the cost becomes high. In addition, with a catalyst having a high purification rate at low temperatures, the purification rate at high temperatures deteriorates, so it is difficult to maintain a high purification rate in a wide temperature range. Further, if the temperature of the exhaust gas processing unit is maintained by raising the temperature of the exhaust gas by utilizing the heat generated by the fuel by injection in the exhaust pipe, post injection, or the like, there is a problem that fuel consumption deteriorates.

  As one of countermeasures against such a situation, downstream exhaust gas that has passed through an exhaust gas processing unit that generates heat when exhaust gas such as an oxidation catalyst passes, and upstream that flows into this exhaust gas processing unit catalyst A method has been proposed in which the exhaust gas processing unit is maintained at a high temperature by exchanging heat with the exhaust gas on the side, and the exhaust gas processing capacity of the exhaust gas processing unit is maintained at a high level. That is, when heat is generated during processing of the exhaust gas, the purification rate in the exhaust gas purification device can be maintained high by providing the exhaust gas purification device with a heat exchange function.

  As one of the related items, for example, in order to efficiently raise and keep the temperature of the catalyst, between the exhaust pipe on the exhaust upstream side of the PM filter and the exhaust pipe on the exhaust downstream side, An exhaust purification device for an internal combustion engine has been proposed that includes a heat exchanger that recovers and stores heat and stores the stored heat to exhaust gas upstream of the exhaust (for example, see Patent Document 1).

  Regarding the capacity of this heat exchanger, as shown in FIG. 11, the maximum flow rate of the exhaust gas and the heat exchange efficiency, as shown in FIG. There is a trade-off relationship that becomes smaller. When the engine is in an operating state where the frequency of low-load operation is high and the temperature of the exhaust gas is low, such as in the transient JE-05 mode exhaust gas test method, the heat generated by the heat exchanger Although exchange is useful, since the exhaust gas flow rate is small in such an operating state, it is necessary to make the heat exchanger as shown in FIG. 11A have a low exhaust gas flow rate and high heat exchange efficiency.

On the other hand, the operating state of the engine may be a high-load operation, and the exhaust gas flow rate increases in the high-load operation. Therefore, if the entire amount is passed through the heat exchanger, the heat exchanger becomes large. In such a large-capacity heat exchanger as shown in FIG. 11C, the heat exchange efficiency is remarkably lowered at low load operation where the flow rate of the exhaust gas is reduced. In addition, since the heat capacity of the exhaust gas purification system increases due to the increase in the size of the heat exchanger, there arises a problem that the warm-up property at the time of starting the engine deteriorates.
JP 2002-38935 A

  The present invention has been made in view of the above situation, and an object of the present invention is to reduce the heat of the exhaust gas downstream of the exhaust gas processing unit that generates heat during the exhaust gas processing of the internal combustion engine. In an exhaust gas purification apparatus equipped with a heat exchanger that transmits to upstream exhaust gas, the heat exchanger can be downsized, and heat exchange can be efficiently performed with this small heat exchanger to maintain high exhaust gas purification performance. A further object is to propose an exhaust gas purification device and an exhaust gas purification method capable of suppressing an increase in the pressure loss of the exhaust gas due to the heat exchanger.

  An exhaust gas purification apparatus for achieving the above object includes an exhaust gas processing unit that generates heat during exhaust gas processing of an internal combustion engine, and the heat of exhaust gas downstream of the exhaust gas processing unit In an exhaust gas purification apparatus having a heat exchanger that transmits heat to an exhaust gas upstream of an exhaust gas treatment unit, an upstream bypass passage that bypasses the heat exchanger for a part of the upstream exhaust gas, and a downstream A downstream bypass passage for bypassing part of the exhaust gas to the heat exchanger, an upstream opening / closing valve for opening / closing the upstream bypass passage, a downstream opening / closing valve for opening / closing the downstream bypass passage, and the upstream side A valve control device for controlling the opening / closing operation of the opening / closing valve and the downstream opening / closing valve is provided.

  According to this configuration, when the heat exchange is unnecessary, a part of the exhaust gas is bypassed in the upstream bypass passage, the downstream bypass passage, or the bypass passage on the same side, so that the capacity of the heat exchanger can be exchanged. Since the flow rate of the exhaust gas when necessary can be reduced to the minimum necessary flow rate, the capacity of the heat exchanger can be reduced and the size can be reduced.

  As a result, the temperature of the exhaust gas flowing into the exhaust gas treatment unit can be increased by efficiently exchanging heat with a small heat exchanger, and the exhaust gas treatment performance in the exhaust gas treatment unit can be maintained high, and the heat exchanger can be made compact. In spite of this, increase in the pressure loss of the exhaust gas due to the heat exchanger can be suppressed.

  In the exhaust gas purifying apparatus described above, when the operating region of the internal combustion engine is in a low exhaust gas temperature region, the valve control device causes the entire amount of the upstream exhaust gas and the downstream exhaust gas to flow through the heat exchanger. When the operating region of the internal combustion engine is not the low exhaust temperature region, control is performed to bypass part of the upstream side exhaust gas and / or part of the downstream side exhaust gas from the heat exchanger. Composed.

  The low exhaust temperature region referred to here is a temperature at which the temperature of the exhaust gas treatment unit is activated when the exhaust gas exiting the exhaust manifold of the internal combustion engine flows into the exhaust gas purification unit as it is (for example, an oxidation catalyst, This refers to an engine operating region that generates exhaust gas having an exhaust temperature that is lower than 150 ° C., and corresponds to low-load operation or low-speed operation. The exhaust temperature in this low exhaust temperature region (referred to here as the temperature of the exhaust gas immediately after the exhaust manifold) depends on the type of engine, the arrangement of the exhaust pipe and the exhaust gas processing unit, etc., but the exhaust temperature is 20 This is a case of about 150 ° C to 150 ° C.

  According to this configuration, when the operating state of the internal combustion engine that requires heat exchange between the downstream exhaust gas and the upstream exhaust gas is in the low exhaust temperature region, the amount of exhaust gas is relatively small. As a result, the entire amount of exhaust gas can be passed through a heat exchanger to efficiently exchange heat. In addition, when the operating state of the internal combustion engine is not in the low exhaust temperature region so that heat exchange between the downstream exhaust gas and the upstream exhaust gas is not necessary, the exhaust gas amount is relatively large. Therefore, by flowing a part of the exhaust gas around the heat exchanger, it is possible to suppress an increase in the pressure loss of the exhaust gas while keeping the capacity of the heat exchanger at the flow rate of the exhaust gas in the low exhaust temperature region. become.

  Therefore, the capacity and heat exchange efficiency of the heat exchanger should be optimized when heat exchange is required, that is, in the low exhaust temperature region. Easy to set. Even when the operating state of the internal combustion engine is not in the low exhaust temperature region, exhaust gas for the capacity of the heat exchanger flows through the heat exchanger without diverting the entire amount of exhaust gas, so the heat exchanger cools down. Can be prevented.

  In the above exhaust gas purification device, a part or all of the upstream bypass passage is provided around at least one of the heat exchanger or the exhaust gas treatment unit, or a part or all of the downstream bypass passage. Is provided around at least one of the heat exchanger or the exhaust gas treatment unit, or a part or all of the upstream bypass passage is at least one of the heat exchanger or the exhaust gas treatment unit. And a part or all of the downstream bypass passage is provided around the upstream bypass passage.

  According to these configurations, the heat exchanger and / or the exhaust gas treatment unit or both are disposed in an upstream bypass passage through which exhaust gas having a relatively low temperature but higher than the outside air temperature passes or a relatively high temperature exhaust gas. Since it is surrounded by the downstream bypass passage through which the gas passes or by both of the bypass passages, the heat release from the heat exchanger or the exhaust gas processing unit or both can be significantly reduced, and the heat retention can be improved.

  Therefore, even in a transient operation region where the frequency of low exhaust temperature operation is high, the heat exchanger can be kept warm, so that the exhaust gas treatment unit can be maintained at a high temperature. If the exhaust gas temperature is not in the low exhaust temperature region, the exhaust gas temperature is also high, so that high exhaust gas purification performance can be maintained even if the exhaust gas flows into the exhaust gas processing unit without sufficient heat exchange.

  An exhaust gas purification method for achieving the above object includes an exhaust gas processing unit that generates heat during exhaust gas processing of an internal combustion engine, and heat of the exhaust gas downstream of the exhaust gas processing unit. In the exhaust gas purification method using the exhaust gas purification device provided with the heat exchanger that transmits the exhaust gas to the exhaust gas upstream of the exhaust gas treatment unit, when the operating region of the internal combustion engine is a low exhaust temperature region, When the total amount of the upstream exhaust gas and the total amount of the downstream exhaust gas are allowed to flow through the heat exchanger, and the operating region of the internal combustion engine is not the low exhaust temperature region, a part of the upstream exhaust gas or the downstream A part of the exhaust gas on the side or both of them bypass the heat exchanger.

  According to this method, when the operating state of the internal combustion engine that requires heat exchange between the downstream exhaust gas and the upstream exhaust gas is in the low exhaust temperature region, the amount of exhaust gas is relatively small, When the operating state of the internal combustion engine in which the entire amount of exhaust gas can be passed through a heat exchanger to efficiently exchange heat and no heat exchange is required is not in the low exhaust temperature region, the amount of exhaust gas is relatively large, By bypassing the heat exchanger around the heat exchanger, it is possible to avoid an increase in exhaust gas pressure loss even when the capacity of the heat exchanger is kept at the flow rate of the exhaust gas in the low exhaust temperature region. .

  Therefore, the capacity and heat exchange efficiency of the heat exchanger can be easily set by optimizing when heat exchange is required, and the heat exchanger can be downsized. Also, when purifying exhaust gas, if heat exchange is required, the exhaust gas can be purified with high exhaust gas purification performance by maintaining a high heat exchange rate, and if heat exchange is unnecessary, Pressure loss due to the heat exchanger can be reduced.

  Examples of the exhaust gas treatment unit include an oxidation catalyst device (DOC), a selective reduction catalyst device (SCR), a NOx storage reduction catalyst device (LNT) and other NOx reduction catalysts (DeNOx), and a catalyst-equipped filter device (CSF). The filter device (DPF) which does not carry a catalyst and the hydrocarbon storage catalyst device (HC trap) can be formed by one or several combinations.

  According to the exhaust gas purification device and the exhaust gas purification method of the present invention, when heat exchange is unnecessary, a part of the exhaust gas is bypassed in the upstream bypass passage or the downstream bypass passage or both bypass passages. The capacity of the exhaust gas flowing through the heat exchanger can be set to the minimum necessary capacity as the flow rate of the exhaust gas when heat exchange is necessary, and the size can be reduced.

  This makes it possible to efficiently exchange heat with a small heat exchanger and increase the temperature of the exhaust gas flowing into the exhaust gas treatment unit to maintain high exhaust gas treatment performance in the exhaust gas treatment unit. An increase in pressure loss can be suppressed. Moreover, since the increase in the heat capacity of the exhaust gas purification system can be suppressed with the downsizing of the heat exchanger, it is possible to suppress the deterioration of warm-up characteristics at the time of engine start.

  Hereinafter, an exhaust gas purification apparatus and an exhaust gas purification method according to an embodiment of the present invention will be described with reference to schematic perspective views of FIGS. 1 to 4 and schematic side sectional views of FIGS. 5 to 10. To do. In FIG. 1 to FIG. 4, the upstream side open / close valve 6 and the downstream side open / close valve 10 shown in FIG. 5 to FIG. 10 are omitted for easy understanding of the drawings. Moreover, the hatched part (hunting part) of FIGS. 1-4 has shown the entrance part and exit part of each apparatus or channel | path.

  As shown in FIGS. 1, 2, and 5, the exhaust gas purifying apparatus 1 of this embodiment generates heat in the passage of the exhaust gas G1 of the engine (internal combustion engine) during the heat exchanger 2 and the exhaust gas treatment. An exhaust gas processing unit 3 is provided. The heat exchanger 2 transfers the heat of the exhaust gas G3 downstream of the exhaust gas processing unit 3 to the exhaust gas G2 upstream of the exhaust gas processing unit 3. Thereby, the heat generated in the exhaust gas processing unit is recovered.

  The exhaust gas G1 flowing out from the engine passes through the low-temperature side passage of the heat exchanger 2 from the inlet-side passage 4 to become the exhaust gas G2 heated by heat exchange, and then the heated exhaust gas G2 is upstream. It flows into the exhaust gas processing unit 3 via the passage 7. The exhaust gas G3 further heated by the heat generated during processing in the exhaust gas processing unit 3 flows into the high temperature side passage of the heat exchanger 2 via the downstream side passage 8. The exhaust gas G4 cooled by heat exchange in the heat exchanger 2 is configured to flow out from the outlet side passage 11 of the exhaust gas purification device 1 to the exhaust passage (not shown) of the engine as the exhaust gas G5.

  The heat exchanger 2 may be a plate heat exchanger or a tube type heat exchanger having a high heat exchange rate. As a result, the exhaust gas G3 flowing out of the exhaust gas processing unit 3 having exothermic properties, such as a catalyst, flows again into the high-temperature side passage of the heat exchanger 2, and the exhaust gas G1 flowing into the exhaust gas purification device 1 is heated. Therefore, the temperature of the exhaust gas G2 at the inlet of the exhaust gas processing unit 3 can be increased. The capacity of the heat exchanger 2 is the flow rate of the exhaust gases G1 and G3 when the engine operating state is in the low exhaust temperature region.

  Here, the low exhaust temperature region is a temperature at which the temperature of the exhaust gas treatment unit is activated when the exhaust gas exiting the exhaust manifold of the internal combustion engine flows into the exhaust gas purification unit as it is (for example, an oxidation catalyst). The engine operating region that generates exhaust gas having an exhaust temperature lower than 150 ° C. corresponds to low-load operation or low-speed operation. The exhaust temperature in this low exhaust temperature region (referred to here as the temperature of the exhaust gas immediately after the exhaust manifold) depends on the type of engine, the arrangement of the exhaust pipe and the exhaust gas processing unit 3, and the like. This is a case of about 20 ° C to 150 ° C.

  Further, in this embodiment, the exhaust gas treatment unit 3 includes a selective reduction catalyst device (SCR) 3a, a filter device (DPF) 3b that does not carry a catalyst, and an oxidation catalyst device (DOC) 3c. . The exhaust gas processing unit 3 is not limited to the illustrated apparatus, and heat is generated during the processing of the exhaust gas G2, and the temperature of the exhaust gas G3 flowing out is higher than the temperature of the inflowing exhaust gas G2. These three devices 3a, 3b, 3c, NOx reduction catalyst (DeNOx) such as NOx occlusion reduction type catalyst device (LNT), filter device with catalyst (CSF), hydrocarbon occlusion catalyst device It can be formed of one or a combination of several (HC traps). For example, in the case of an oxidation catalyst (DOC), CO and HC in the exhaust gases G1 and G2 can be oxidized. Therefore, this oxidation reaction heat increases the temperature of the exhaust gas G3, thereby improving the exhaust gas purification rate. Contribute.

  In the present invention, further, an upstream bypass passage 5 that bypasses part of the upstream exhaust gas G1 from the heat exchanger 2 and a downstream side that bypasses the heat exchanger 2 from a part of the downstream exhaust gas G3. The bypass passage 9, the upstream opening / closing valve 6 that opens / closes the upstream bypass passage 5, the downstream opening / closing valve 10 that opens / closes the downstream bypass passage 9, and the opening / closing operation of the upstream opening / closing valve 6 and the downstream opening / closing valve 10. A valve control device (not shown) for controlling is provided.

  This valve control device is incorporated in a control device called an ECU (engine control unit) that controls the overall operation of the engine, and switching between the heat exchanger 2 and the flow paths 5 and 9 to the outer periphery thereof is performed by an ECU or the like. Judging from the calculated flow rate of the exhaust gas G1, the opening / closing operation of the upstream opening / closing valve 6 and the downstream opening / closing valve 10 is performed. Further, in order to reduce the cost, the upstream side open / close valve 6 and the downstream side open / close valve 10 are constituted by reed valves, and a load such as a spring when closing the valve is determined and set in advance, and the exhaust gas G1, When the pressure of G3 exceeds a predetermined threshold value, the valve may be automatically opened by the pressures of the exhaust gases G1 and G3.

  In this embodiment, as shown in FIGS. 3 and 6, the upstream bypass passage 5 is disposed so as to surround the periphery of the heat exchanger 2. As shown in FIGS. 4 and 7, the downstream bypass passage 9 is disposed so as to surround the upstream bypass passage 5. According to this configuration, since the heat exchanger 2 is surrounded by both the bypass passages 5 and 9, it is possible to remarkably reduce the amount of heat released from the heat exchanger 2 and improve the heat retaining property. Therefore, the temperature of the exhaust gas processing unit 3 can be maintained at a high temperature even in an engine operating state such as a transient operating state where the frequency of the low exhaust temperature region is high.

  In this embodiment, the upstream bypass passage 5 is provided around the heat exchanger 2 and the downstream bypass passage 9 is provided around the upstream bypass passage 5. In some cases, a part or the whole is provided around the heat exchanger 2, or a part or the whole of the upstream bypass passage 5 is provided around the heat exchanger 2. In this case, the exhaust gas purification device 1 can be made smaller. Further, a part or all of the downstream bypass passage 9 may be provided around the heat exchanger 2 and a part or all of the upstream bypass passage 5 may be provided around the downstream bypass passage 9. In this case, the heat exchanger 2 is surrounded by the downstream bypass passage 9 having a high exhaust gas temperature and further surrounded by the upstream bypass passage 5 having a low exhaust gas temperature. In addition, regarding each of the bypass passages 5 and 9, these may be disposed not around the heat exchanger 2 but around the exhaust gas treatment unit 3, and both of the heat exchanger 2 and the exhaust gas treatment unit 3 may be arranged. You may arrange | position around.

  According to these configurations, at least one of the heat exchanger 2 and the exhaust gas treatment unit 3 is passed through the upstream bypass passage 5 through which the exhaust gas G1 having a relatively low temperature but higher than the outside air temperature passes, or Since it is surrounded by the downstream bypass passage 9 through which the relatively high-temperature exhaust gas G3 passes or by both bypass passages 5 and 9, the amount of heat released from at least one of the heat exchanger 2 or the exhaust gas treatment unit 3 is significantly reduced. And heat retention can be improved. That is, when the high temperature gas G3 flows through at least one outer peripheral portion of the contact heat exchanger 2 or the exhaust gas treatment unit 3, a heat retaining effect on at least one of the contact heat exchanger 2 or the exhaust gas treatment unit 3 can be expected. Accordingly, high heat exchange efficiency can be maintained, and the temperature of the exhaust gas G2 flowing into the exhaust gas processing unit 3 can be increased. Therefore, even in a transient operation state where the frequency of the low exhaust temperature region is high, the exhaust gas processing unit 3 The temperature can be maintained at a high temperature.

  In the case of the low exhaust temperature region, when both the upstream side open / close valve 6 and the downstream side open / close valve 10 are closed, the entire amount of the exhaust gas G1 passes through the heat exchanger 2 as shown in FIG. The exhaust gas G2 flows into the exhaust gas processing unit 3 via the upstream passage 7. Further, the exhaust gas G3 flowing out from the exhaust gas processing unit 3 passes through the heat exchanger 2 and the exhaust gas G4 after heat exchange flows out from the outlet side passage 11 to the exhaust passage (not shown) as the exhaust gas G5. To do.

  Further, when the upstream side opening / closing valve 6 is opened, as shown in FIG. 8, a part of the exhaust gas G1 flowing through the inlet side passage 4 passes through the upstream side bypass passage 5 and bypasses the heat exchanger 2. Then, it flows into the exhaust gas processing unit 3. On the other hand, when the downstream opening / closing valve 10 is opened, as shown in FIG. 9, a part of the exhaust gas G3 flowing through the downstream passage 8 passes through the downstream bypass passage 9 and bypasses the heat exchanger 2. And flows to the outlet side passage 11.

  Further, when both the upstream side opening / closing valve 6 and the downstream side opening / closing valve 10 are opened, a part of the exhaust gas G1 flowing through the inlet side passage 4 passes through the upstream side bypass passage 5 as shown in FIG. Then, bypassing the heat exchanger 2 and joining the exhaust gas G2 passing through the heat exchanger 2 and flowing into the exhaust gas processing unit 3, a part of the exhaust gas G3 flowing through the downstream passage 8 is The gas passes through the downstream bypass passage 9, bypasses the heat exchanger 2, merges with the exhaust gas G4 that has passed through the heat exchanger 2, and flows out from the outlet side passage 11 as exhaust gas G5.

  Next, an exhaust gas purification method in the exhaust gas purification apparatus 1 having the above configuration will be described. According to the exhaust gas purification method of the present invention, when the engine operating region is the low exhaust temperature region, the upstream side on-off valve 6 and the downstream side on-off valve 10 are closed, and the heat exchanger 2 is connected to the upstream side. The total amount of exhaust gas G1 and the total amount of exhaust gas G3 on the downstream side are allowed to flow into. Further, when the engine operating region is not the low exhaust temperature region, a part of the exhaust gas G1 on the upstream side, a part of the exhaust gas G3 on the downstream side, or both of the exhaust gases G1, G3, The heat exchanger 2 is bypassed.

  That is, when the engine operating region is in the low exhaust temperature region, the valve control device causes the heat exchanger 2 to flow the entire upstream exhaust gas G1 and the downstream exhaust gas G3 to the engine operating region. When the exhaust gas temperature is not in the low exhaust temperature region, control is performed to bypass part of the exhaust gas G1 on the upstream side, part of the exhaust gas G3 on the downstream side, or both of the exhaust gases G1, G3 from the heat exchanger 2. Configured.

  Normally, in order to simplify the valve opening / closing control, the upstream opening / closing valve 6 and the downstream opening / closing valve 10 are simultaneously operated by the valve control device. However, since the volume of the exhaust gas varies depending on the temperature of the exhaust gas, the upstream side open / close valve 6 and the downstream side open / close valve 10 may be individually controlled in accordance with the flow rate of the exhaust gas that can pass therethrough. Further, when the upstream side open / close valve 6 and the downstream side open / close valve 10 are formed by reed valves or the like and are automatically opened and closed by the pressures of the exhaust gases G1 and G3, that is, the valve control device is In the case of an elastic body such as a spring, it does not always open and close simultaneously.

  According to this method, when the operating state of the engine that requires heat exchange between the exhaust gas G3 on the downstream side and the exhaust gas G1 on the upstream side is in a low exhaust temperature region, that is, low rotation operation or low In the case of load operation or the like, since the flow rates of the exhaust gases G1 and G3 are relatively small, the entire amount of the exhaust gases G1 and G3 can be passed through the heat exchanger 2 to efficiently exchange heat. In addition, when the engine operating state that does not require heat exchange is not in the low exhaust temperature region, the flow rates of the exhaust gases G1 and G3 are relatively large, so that a part of the exhaust gases G1 and G3 is bypassed the heat exchanger 2. Therefore, even if the capacity of the heat exchanger 2 is kept in accordance with the flow rates of the exhaust gases G1 and G3 in the low exhaust temperature region, an increase in pressure loss of the exhaust gases G1 and G3 can be avoided. .

  According to the exhaust gas purification device 1 and the exhaust gas purification method described above, it is necessary to keep the temperature of the exhaust gas processing unit 3 at a high temperature, and heat is generated between the exhaust gases G2 and G3 in the operation region where the flow rate of the exhaust gas G1 is small. The exhaust gas purification device 1 is reduced in size and heat capacity is reduced. Further, when the exhaust gas temperature is high, the exhaust gas purification device 1 is made to flow by flowing a high-temperature gas through the heat exchanger 2 and its outer periphery. Keep temperature high.

  Accordingly, since the capacity and heat exchange efficiency of the heat exchanger 2 need only be optimized when heat exchange is required, the capacity and heat exchange efficiency of the heat exchanger can be easily set. The heat exchanger 2 can be reduced in size. In addition, when purifying the exhaust gas G3, if heat exchange is necessary, the exhaust gas G3 can be purified with high exhaust gas purification performance in the exhaust gas processing unit 3 while maintaining a high heat exchange rate. When heat exchange is unnecessary, the pressure loss due to the heat exchanger 2 can be reduced.

  As a result, the heat of the exhaust gas G2 flowing into the exhaust gas processing unit 3 by efficiently exchanging heat with the small heat exchanger 2 can be increased, and the exhaust gas processing performance in the exhaust gas processing unit 3 can be maintained high. An increase in the pressure loss of the exhaust gases G1 and G3 due to the exchanger 2 can be suppressed.

  If the exhaust gas G1, G3 is not in a low operating region where the flow rate is large, the temperature of the exhaust gas G1, G2 is also high, so even if the exhaust gas G1, G2 flows into the exhaust gas processing unit 3 without heat exchange, High exhaust gas purification performance can be maintained.

  In addition, the exhaust gas purification device 1 and the exhaust gas purification method described above, and the premixed compression ignition (PCI) combustion that can significantly reduce NOx and soot by thoroughly mixing fuel and air and then burning the mixture. By using in combination, relatively high concentrations of CO and HC are oxidized by the catalyst of the exhaust gas treatment unit 3, the temperature of the exhaust gas treatment unit 3 is maintained high, and the low-temperature activity for NOx and soot is increased. Since NOx, soot, etc. in the exhaust gas can be reduced in a wide operating range, the state of the exhaust gas discharged into the atmosphere can be made good while maintaining low fuel consumption.

1 is a perspective view schematically showing an external appearance of an exhaust gas purification apparatus according to an embodiment of the present invention. It is a perspective view which shows typically the structure of the heat exchanger of the exhaust gas purification apparatus of FIG. 1, and an exhaust gas processing unit. FIG. 2 is a perspective view schematically showing a configuration of an upstream bias passage of the exhaust gas purification device of FIG. 1. FIG. 2 is a perspective view schematically showing a configuration of a downstream side bias passage of the exhaust gas purification device of FIG. 1. 1 schematically shows a configuration of a heat exchanger and an exhaust gas processing unit of an exhaust gas purification apparatus according to an embodiment of the present invention, and a flow of exhaust gas when both an upstream side open / close valve and a downstream side open / close valve are closed. It is a sectional side view. FIG. 6 is a side sectional view schematically showing a configuration of an upstream bypass passage of the exhaust gas purification device of FIG. 5. FIG. 6 is a side sectional view schematically showing a configuration of a downstream bypass passage of the exhaust gas purification device of FIG. 5. FIG. 6 is a side sectional view schematically showing the flow of exhaust gas when the upstream on-off valve is opened and the downstream on-off valve is closed in the exhaust gas purification apparatus of FIG. 5. FIG. 6 is a side sectional view schematically showing the flow of exhaust gas when the upstream on-off valve is closed and the downstream on-off valve is opened in the exhaust gas purification apparatus of FIG. 5. FIG. 6 is a side sectional view schematically showing the flow of exhaust gas when both the upstream side opening / closing valve and the downstream side opening / closing valve are opened in the exhaust gas purification apparatus of FIG. 5. It is a figure which shows the relationship between the high temperature side flow volume and low temperature side temperature efficiency in a heat exchanger.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Exhaust gas purification apparatus 2 Heat exchanger 3 Exhaust gas processing unit 4 Inlet side passage 5 Upstream bypass passage 6 Upstream side on-off valve 7 Upstream side passage 8 Downstream side passage 9 Downstream side bypass passage 10 Downstream side on-off valve 11 Outlet side passage G1, G2, G3, G4, G5 Exhaust gas

Claims (5)

A heat exchanger that includes an exhaust gas processing unit that generates heat during exhaust gas processing of an internal combustion engine, and that transfers heat of exhaust gas downstream of the exhaust gas processing unit to exhaust gas upstream of the exhaust gas processing unit In an exhaust gas purifying apparatus comprising:
An upstream bypass passage that bypasses the heat exchanger for a part of the exhaust gas on the upstream side, a downstream bypass passage that bypasses the heat exchanger for a part of the exhaust gas on the downstream side, and the upstream bypass passage An upstream on-off valve that opens and closes, a downstream on-off valve that opens and closes the downstream bypass passage, and a valve control device that controls opening and closing operations of the upstream on-off valve and the downstream on-off valve Exhaust gas purification device.   When the operating range of the internal combustion engine is a low exhaust temperature range, the valve control device causes the entire amount of upstream exhaust gas and the entire amount of downstream exhaust gas to flow through the heat exchanger. 2. The control according to claim 1, wherein when the temperature is not in a low exhaust temperature range, control is performed to bypass part of the upstream side exhaust gas and / or part of the downstream side exhaust gas from the heat exchanger. Exhaust gas purification device.   A part or all of the upstream bypass passage is provided around at least one of the heat exchanger or the exhaust gas treatment unit, or a part or all of the downstream bypass passage is provided to the heat exchanger or the exhaust. The exhaust gas processing apparatus according to claim 1, wherein the exhaust gas processing apparatus is provided around at least one of the gas processing units.   A part or all of the upstream bypass passage is provided around at least one of the heat exchanger or the exhaust gas treatment unit, and a part or all of the downstream bypass passage is provided around the upstream bypass passage. The exhaust gas processing apparatus according to claim 1 or 2, wherein   A heat exchanger that includes an exhaust gas processing unit that generates heat during exhaust gas processing of an internal combustion engine, and that transfers heat of exhaust gas downstream of the exhaust gas processing unit to exhaust gas upstream of the exhaust gas processing unit In the exhaust gas purifying method using the exhaust gas purifying apparatus, the total amount of the upstream exhaust gas and the total amount of the downstream exhaust gas in the heat exchanger when the operating region of the internal combustion engine is the low exhaust temperature region When the operating region of the internal combustion engine is not the low exhaust temperature region, a part of the upstream exhaust gas or a part of the downstream exhaust gas or both of them are bypassed from the heat exchanger. Exhaust gas purification method.

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