JP4735390B2 - Supercharged internal combustion engine with oxygen enrichment device - Google Patents

Description

  The present invention relates to an internal combustion engine including an EGR system and an oxygen enrichment device in an intake passage.

  In internal combustion engines mounted on automobiles, NOx regulation values have become stricter in recent years, and therefore, the application of EGR (exhaust gas recirculation) tends to be expanded to the entire operating range of internal combustion engines. In the current EGR system, In addition to the control of the valve, an intake throttle, a reed valve, an exhaust throttle, etc. are used to secure the necessary EGR amount.

  However, in an internal combustion engine with a supercharger, when the internal combustion engine is under a high load, the intake pressure becomes high and it becomes difficult to secure the EGR amount. Therefore, it is necessary to maintain the exhaust pressure higher than the intake pressure, and therefore the fuel consumption deteriorates. There is a problem of doing.

  Further, at the time of a light load during the internal combustion period, a high EGR rate is required for the application of PCI (Premixed Compression Ignition) combustion, etc., but if the EGR gas is not sufficiently cooled, the intake air temperature Increases and the intake air density decreases. Therefore, even if the amount of oxygen supplied into the cylinder (inside the cylinder) is reduced and the fuel injection amount is desired to be increased, the excess air ratio λ in the cylinder cannot be 1 or less. As a result, there is a problem that PCI combustion cannot be performed. On the other hand, if this large amount of EGR gas is to be cooled, a large-capacity EGR cooler is required, but there is a problem that the amount of heat exchange in the EGR cooler is limited and not practical.

On the other hand, instead of the EGR system, an oxygen enrichment device (or nitrogen enrichment device) is used to supply intake air (nitrogen enriched air) with a reduced oxygen concentration into the cylinder to lower the combustion temperature. Has been proposed (see, for example, Patent Document 1 and Patent Document 2).

  Also, the oxygen-enriched air generated in the oxygen enricher is supplied to the oxidation catalyst of the exhaust pipe via a bypass pipe that bypasses the internal combustion engine, and the SOF components of HC and PM (particulate matter) in the exhaust gas A system that promotes the oxidation of is also proposed (see, for example, Patent Document 3 and Patent Document 4).

However, in recent internal combustion engines, it has been required to apply EGR even in a full load operation state. When the EGR flow path is abolished and an oxygen enrichment device is used instead of the EGR system, Since a large amount of nitrogen-enriched air is required, in order to enrich oxygen and nitrogen in the air with an oxygen-enriched membrane, etc., it is necessary to pressurize a large amount of air, and this work amount reduces fuel consumption. There is a problem of getting worse.
Japanese Patent No. 2864896 (Third Example, FIG. 20) Japanese Patent No. 2535281 Japanese Utility Model Publication No. 5-87259 No. 7-3007

  The present invention has been made to solve the above-described problems, and its purpose is to suppress deterioration of fuel consumption in a full-load operation state with a simple configuration by using an EGR system and an oxygen enricher in combination. An object of the present invention is to provide a supercharged internal combustion engine equipped with an oxygen enrichment device that can reduce the combustion temperature and prevent the generation of NOx.

An internal combustion engine with a supercharger equipped with an oxygen enricher for achieving the above object comprises an EGR system and an exhaust gas purifying device carrying an oxidation catalyst in an exhaust passage, and the intake air and a low oxygen concentration gas In the internal combustion engine with a supercharger in which an oxygen enrichment device that divides into high-concentration oxygen gas is provided in the intake passage, and a compressor of the supercharger is provided in the intake passage upstream of the oxygen enrichment device, The low-concentration oxygen gas divided by the gasification device is supplied to the intake system passage, and the high-concentration oxygen gas divided by the oxygen enrichment device is supplied to either the exhaust passage or the intake system passage upstream of the exhaust gas purification device. Passage switching means for selectively supplying the high-concentration gas to the upstream exhaust passage of the exhaust gas purifying device when the opening speed of the accelerator opening is equal to or lower than a predetermined value. Supply Configured.

  The intake system passage may be a passage portion that guides intake air to an intake manifold such as an intake pipe or an intake manifold, and may be an inlet side of an intercooler or the like. The passage switching means can be constituted by a switching valve such as a three-way valve, but may be constituted by on-off valves respectively provided in two passages.

  According to this configuration, by introducing the low oxygen concentration gas into the cylinder (inside the cylinder) through the intake system passage such as the intake manifold, it is possible to obtain the same effect as EGR and assist the EGR of the EGR system. . Therefore, at the time of a high load that requires a high EGR rate, EGR and the supply of the low oxygen concentration gas to the intake manifold can be used together, so that it is not necessary to increase the size of the EGR system, particularly the EGR cooler. Furthermore, when EGR is required, since the amount of EGR gas that recirculates from the exhaust to the intake can be reduced if the oxygen concentration of the fresh air is low, by supplying the low oxygen concentration gas, the air is supplied as it is. PCI (Premixed Compression Ignition) combustion can be applied in a wide range of operation.

  In this PCI combustion (premixed compression ignition combustion), premixing is actively introduced and the entire mixture is diluted to lower the combustion temperature, so that not only smoke but also NOx can be reduced. It is.

Further, in the internal combustion engine with a supercharger equipped with the above oxygen enrichment apparatus, the internal combustion engine is an internal combustion engine that performs premixed compression ignition combustion, and when the opening speed of the accelerator opening is larger than a predetermined value, Concentration gas is configured to be introduced to the intake manifold side. In other words, when shifting from light load operation to high load operation with a high EGR rate and a small injection amount by stepping on the accelerator, the response time of the intake of the turbocharger was temporarily delayed, which was temporarily commensurate with the fuel injection amount Since the amount of oxygen is insufficient, a high oxygen concentration gas is supplied to the intake manifold side only in this acceleration state.

  According to this configuration, when a large amount of oxygen is required in the cylinder such as shifting from PCI combustion to conventional combustion due to acceleration or the like, high oxygen concentration gas is supplied to the intake manifold side by switching the passage switching means. Since the oxygen concentration in the cylinder can be rapidly changed by supplying to the fuel cell, the driving performance (drivability) can be improved and the generation of NOx and smoke can be suppressed. Further, during normal operation, by introducing a high oxygen concentration gas into the oxidation catalyst, oxidation of HC, PM, etc. in the exhaust gas in the oxidation catalyst can be promoted. Therefore, the performance of the oxidation catalyst in the exhaust passage can be improved without sacrificing transient characteristics during acceleration.

  According to the internal combustion engine with a supercharger equipped with the oxygen enrichment apparatus according to the present invention, a low oxygen state in the cylinder is realized by a combination of EGR and supply of low oxygen concentration gas to the intake side with a simple configuration. This can improve the trade-off relationship between NOx and fuel consumption, and can reduce the combustion temperature and prevent the generation of NOx while minimizing the deterioration of fuel consumption under the full load operating condition.

  In addition, the high oxygen concentration gas generated by the oxygen enricher is introduced into the intake manifold during acceleration operation, so that the oxygen concentration in the cylinder can be changed quickly when a large amount of oxygen is required in the cylinder. The driving performance (drivability) can be improved, and the generation of NOx and smoke can be suppressed. Further, during normal operation, by introducing a high oxygen concentration gas directly into the oxidation catalyst, the oxidation of HC, PM, etc. in the exhaust gas in the oxidation catalyst can be promoted.

  Hereinafter, an internal combustion engine with a supercharger provided with an oxygen enrichment device according to an embodiment of the present invention will be described with reference to the drawings.

  The supercharged internal combustion engine 1 equipped with this oxygen enrichment device is a diesel engine with a turbocharger 3 and is configured as shown in FIGS. An intake pipe 2 of the internal combustion engine (engine) 1 is provided with a compressor 3 a of a supercharger (turbocharger) 3, an oxygen enricher 4, an intercooler 5, and an intake throttle valve 6. The intake pipe 2 is an intake manifold. 7 is connected.

  The oxygen enrichment device 4 includes an oxygen separation membrane (oxygen enrichment membrane) 4a that separates into a gas having a high oxygen concentration and a gas having a high nitrogen concentration. Although this oxygen separation membrane 4a is shown by slanting lines in the figure, it is actually formed of a polymer hollow fiber membrane. When air A pressurized by the compressor 3a is allowed to pass through, the oxygen separation membrane 4a passes through this membrane. The oxygen concentration of Ab increases, and the remaining gas Aa has a high nitrogen concentration and a low oxygen concentration.

Then, the low concentration oxygen side (Aa side) of the oxygen enrichment device 4 is connected to the intake pipe 2 (intake system passage), and the high concentration oxygen side (Ab side) of the oxygen enrichment device 4 is switched to the first passage 15. Connected to the intake pipe 2 (intake system passage) via the second passage 16 via the valve (passage switching means) 18 and upstream of the exhaust gas purification device 10 carrying the oxidation catalyst via the third passage 17. The exhaust pipe (exhaust passage) 9 is connected. The switching valve 18 can be constituted by a switching valve such as a three-way valve, but in addition to this configuration, an opening / closing valve may be provided in each of the second passage 16 and the third passage 17. The second passage 16 may be introduced directly into the intake manifold 7, but as shown in FIG. 1, fresh air supplied into the cylinder is introduced into the intake manifold 7 via the intercooler 5 or the like. This is more preferable because the amount of air can be increased and the amount of fresh air can be easily adjusted by the intake throttle valve 6.

  An exhaust pipe 9 connected to the exhaust manifold 8 of the internal combustion engine 1 is provided with a turbine 3b of the supercharger 3, an exhaust gas purification device 10 carrying an oxidation catalyst, and a DPF device 11.

The exhaust gas purifying apparatus 10 carrying the oxidation catalyst has a catalyst coating layer of active aluminum oxide (Al ₂ O ₃ ), platinum (Pt), palladium on the surface of a support made of honeycomb cordierite or heat-resistant steel. It is formed by supporting a catalytically active component made of a noble metal such as (Pd) or rhodium (Rh). The exhaust gas purifying apparatus 10 oxidizes HC, CO, etc. in the inflowing exhaust gas to bring the exhaust gas into a low oxygen state and raise the exhaust temperature by combustion heat.

  The DPF device 11 is formed of a monolith honeycomb wall flow type filter or the like in which the inlets and outlets of the porous ceramic honeycomb channels are alternately plugged. PM (particulate matter) in the exhaust gas is collected by the porous ceramic wall surface.

  Further, an EGR pipe 12 that connects the exhaust manifold 8 to the intake manifold 7 is provided as an EGR system, and an EGR cooler 13 and an EGR valve 14 are provided in the EGR pipe 12.

  In the internal combustion engine 1, the air A is compressed and boosted by the compressor 3 a of the supercharger 3 of the intake pipe 2, cooled by the intercooler 5, and then the amount of the air A is adjusted by the intake throttle valve 6, and from the intake manifold 7. Enter the cylinder (inside the cylinder). The exhaust gas G generated in the cylinder exits from the exhaust manifold 8 to the exhaust pipe 9, drives the turbine 3b of the turbocharger 3, and then passes through the exhaust gas purification device 10 carrying the oxidation catalyst and the DPF device 11. As a result, the exhaust gas Gc is purified and discharged into the atmosphere through a silencer (not shown). Further, a part of the exhaust gas G exits from the exhaust manifold 8 as EGR gas Ge, passes through the EGR cooler 13 of the EGR pipe 12, is adjusted in amount by the EGR valve 14, and is recirculated to the intake manifold 7 side. The

  A control device (ECU: engine control unit) 20 that performs overall control of the operation of the internal combustion engine 1 and also performs recovery control of the purification capability of the DPF device 11 is provided. In addition to the input from the accelerator opening sensor 21, detection values from an excess air ratio sensor, a temperature sensor, a crank angle sensor, and the like, which are not shown, are input to the control device 20. A throttle valve 6, an EGR valve 14, a fuel injection valve (not shown) of a common rail electronic control fuel injection device for fuel injection, and the like are output.

  Next, a method for controlling the internal combustion engine 1 will be described. In this embodiment, the control of the switching valve 18 is incorporated in the control device 20 of the internal combustion engine 1 and is performed in parallel with the control of the EGR system.

  As shown in FIG. 3, the control of the switching valve 18 is called from the upper control flow when the operation of the internal combustion engine 1 is started, and the switching valve 18 is determined to be switched to. The flow returns to the upper control flow, is called again, and is shown as a flow that repeats until the operation of the internal combustion engine 1 is stopped.

  When the control flow of FIG. 3 starts, the speed V at which the accelerator opening is opened is calculated from the accelerator opening signal of the accelerator opening sensor 21 in step S11. Next, in step S12, it is compared with the accelerator opening threshold value Vc to determine whether or not the vehicle is in an accelerated state. This threshold value Vc is a threshold value of the opening speed of the accelerator opening for determining whether or not the vehicle is in an acceleration state, and is set in advance through experiments, calculations, or the like.

  If it is determined in step S12 that the speed V is equal to or lower than the threshold value Vc, it is determined that the vehicle is not in an acceleration state. In step S13, the switching valve 18 is switched as shown in FIG. 15 flows into the third passage 17 and is introduced to the upstream side of the exhaust gas purification apparatus 10 carrying the oxidation catalyst. Thus, in the non-accelerated state (normal operation state), the high oxygen concentration gas Ab is allowed to flow directly to the oxidation catalyst, so that HC (hydrocarbon), CO (carbon monoxide), PM (particulate matter) in the exhaust gas. Thus, the oxidation reaction in the oxidation catalyst can be promoted, and the performance of the oxidation catalyst in the exhaust passage can be improved.

If it is determined in step S12 that the velocity V is greater than the threshold value Vc, it is determined that the vehicle is in an accelerated state . In step S14, the switching valve 18 is switched as shown in FIG. 15 flows into the second passage 16 and is introduced into the intake pipe 2. That is, in the acceleration state, the high oxygen concentration gas Ab is caused to flow into the intake pipe 2 to be introduced to the intake manifold 7 side, thereby increasing the amount of oxygen in the cylinder.

  Thereby, it is possible to follow a sudden change in the intake composition during the transient operation. That is, as shown in FIG. 6, when the accelerator is opened to shift to a high load operation from a light load with a small fuel injection amount and a high EGR rate, the EGR rate is lowered and only in this acceleration state, A high oxygen concentration gas Ab having a high oxygen concentration is supplied to the intake pipe 2, and the in-cylinder oxygen concentration is increased so as to match the increase in the target injection amount. At this time of acceleration, in the internal combustion engine with a supercharger 1 of the prior art, since the response of intake air is delayed, the amount of oxygen corresponding to the fuel injection amount is insufficient and the transient performance deteriorates. In the supercharger-equipped internal combustion engine 1 equipped with the converter, the in-cylinder oxygen concentration can be increased in accordance with the increase in the target injection amount, so that the driving performance (drivability) and smoke can be improved.

  And after step S13 or step S14 is complete | finished, it returns and returns to a high-order control flow. Thereafter, the control valve 18 is started again from the upper control flow at the control interval of the switching valve 18 or the acceleration state determination interval. This is repeated until the operation of the internal combustion engine 1 is stopped.

  According to the supercharged internal combustion engine 1 equipped with the oxygen enrichment device having the above-described configuration, a molecular film (oxygen enriched film) 4a capable of separating oxygen and nitrogen in the air is connected to the intake pipe 2 downstream of the compressor 3a. The low oxygen concentration gas Aa generated in the oxygen-enriched film 4a is supplied to the intake manifold 7 side. As a result, the same NOx reduction effect as that of EGR can be obtained, and the in-cylinder can be reduced to a low oxygen concentration without excessive fuel consumption deterioration in the full load operation region. In particular, when a low oxygen amount condition is required in the cylinder, if the oxygen concentration of fresh air is low, the amount of EGR gas that recirculates from the exhaust to the intake can be reduced. Therefore, PCI can be used in a wider operating range than in the case of normal air. Combustion can be applied.

  In other words, high load operation of PCI combustion is limited by severe diesel knock, noise, and smoke. Further, when the EGR amount is large and the load is high, the intake air temperature rises, so that it is likely to be a severe diesel knock. If a low oxygen concentration can be achieved with a small amount of EGR gas, an increase in intake air temperature is suppressed. Thus, PCI combustion can be expanded.

  Therefore, according to the supercharger-equipped internal combustion engine 1, the PCI combustion region can be expanded and NOx can be reduced. Moreover, by using EGR and the low oxygen concentration gas Aa in combination, it is possible to reduce heat loss due to suppression of enlarging the EGR system and suppression of exhaust heat amount by the EGR cooler 13.

  During normal operation, the high oxygen concentration gas Ab generated in the oxygen-enriched film 4a can be supplied to the exhaust pipe 9, so that the oxidation of HC and CO in the post-treatment oxidation catalyst can be promoted. In particular, in the case of only the EGR system of the prior art, oxygen in the exhaust gas is insufficient in a large amount of EGR state, so the oxidation reaction in the oxidation catalyst does not progress so much and the oxidation catalyst does not warm, but by sending a high oxygen concentration gas Ab Even under such operating conditions, the temperature of the oxidation catalyst is maintained, and the exhaust gas purification rate at the oxidation catalyst can be improved by increasing the temperature. In addition, the regeneration reaction of oxidizing and removing PM deposited on the DPF device 11 by the high oxygen concentration gas Ab is also promoted.

  Further, when the EGR rate at the time of acceleration changes rapidly and a large amount of oxygen is required when shifting from PCI combustion to conventional diesel combustion, the high oxygen concentration gas Ab is supplied to the intake manifold 7 side. Thus, since the oxygen concentration in the cylinder can be changed quickly, the controllability of the intake composition can be improved, and NOx and smoke can be suppressed.

  Therefore, by reducing NOx and promoting oxidation of HC, CO, and PM, the burden of exhaust purification in the aftertreatment device can be reduced, and the exhaust gas purification device 10 carrying the oxidation catalyst can be downsized.

It is a figure which shows the structure of the internal combustion engine with a supercharger provided with the oxygen enrichment apparatus of embodiment which concerns on this invention. It is a figure which shows the structure of the periphery of an oxygen enrichment apparatus. It is a control flowchart figure which shows control of a switching valve. It is a block diagram of the periphery of the oxygen enrichment device showing the switching valve and the flow state when introducing a high oxygen concentration gas into the exhaust passage. It is a block diagram of the periphery of the oxygen enrichment apparatus which shows the switching valve and flow state when introducing a high oxygen concentration gas into the intake passage side. It is a schematic diagram showing a time series of EGR, target injection amount and in-cylinder oxygen concentration.

Explanation of symbols

1 Internal combustion engine (diesel engine)
2 Intake pipe (intake passage)
3 Supercharger (turbocharger)
3a Compressor 3b Turbine 4 Oxygen enrichment device 4a Oxygen enrichment membrane 5 Intercooler 7 Intake manifold 8 Exhaust manifold 9 Exhaust pipe (exhaust passage)
10 Exhaust gas purification device carrying oxidation catalyst 12 EGR pipe (EGR passage)
13 EGR cooler 14 EGR valve 15 1st passage 16 2nd passage 17 3rd passage 18 Switching valve (passage switching means)
20 Control device 21 Accelerator opening sensor A Air Aa Low oxygen concentration gas Ab High oxygen concentration gas G Exhaust gas Gc Purified exhaust gas Ge EGR gas V Accelerator opening speed Vc Accelerator opening threshold

Claims (2)

The exhaust gas purifying device having an EGR system and an exhaust passage carrying an oxidation catalyst, an oxygen enriching device for separating the intake air into a low oxygen concentration gas and a high concentration oxygen gas is provided in the intake passage, and the compressor of the supercharger is In the internal combustion engine with a supercharger provided in the intake passage on the upstream side of the oxygen enrichment device, the low concentration oxygen gas divided by the oxygen enrichment device is supplied to the intake system passage, and the oxygen enrichment device There is a passage switching means for selectively supplying the divided high-concentration oxygen gas to either the exhaust passage or the intake passage on the upstream side of the exhaust gas purification device, and the passage switching means opens the accelerator opening. An internal combustion engine with a supercharger equipped with an oxygen enrichment device, wherein a high oxygen concentration gas is supplied to an exhaust passage upstream of the exhaust gas purification device when the speed is equal to or less than a predetermined value . The internal combustion engine is an internal combustion engine that performs premixed compression ignition combustion, and the high oxygen concentration gas is introduced to the intake manifold side when the opening speed of the accelerator opening is larger than a predetermined value . An internal combustion engine with a supercharger equipped with an oxygen enrichment device.

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