JP2011001944A - Exhaust gas circulation apparatus of internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an exhaust gas recirculation apparatus of an internal combustion engine capable of suppressing generation of deposits even if an amount of exhaust gas recirculation is increased.SOLUTION: A control device 100 repeatedly performs, by changing over switching valves 41, 42, 43: operations in a first mode in which exhaust gas is circulated into a first adsorber 11 in which carbon dioxide in the exhaust gas is adsorbed to an adsorbent, and carbon dioxide desorbed from an adsorbent in a second adsorber 12 is returned into an intake pipe 3; and operations in a second mode in which carbon dioxide desorbed from the adsorbent in the first adsorber 11 is returned into the intake pipe 3, and exhaust gas is circulated into the second adsorber 12 in which carbon dioxide in the exhaust gas is adsorbed to the adsorbent.

Description

  The present invention relates to an exhaust gas recirculation device that recirculates a part of engine exhaust gas from an exhaust system to an intake system.

  Conventionally, a part of the exhaust gas of the engine is taken out from the exhaust passage and recirculated to the intake passage again. By increasing the concentration of inert components in the air-fuel mixture and decreasing the oxygen concentration, the nitrogen oxide is reduced. There is known an exhaust gas recirculation device that suppresses the generation of (see, for example, Patent Document 1).

JP 2004-278351 A

  However, in the exhaust gas recirculation device of the above prior art, if the exhaust gas recirculation amount is increased in order to obtain a sufficient suppression effect of nitrogen oxide generation, soot and unburned components contained in the exhaust gas However, since a large amount is returned to the intake side, there is a problem that a large amount of deposit is generated in the intake passage. If the deposit amount increases in the intake passage, it becomes difficult to obtain a desired intake amount, and problems such as an increase in harmful substances in the exhaust gas occur.

  The present invention has been made in view of the above points, and an object of the present invention is to provide an exhaust gas recirculation device capable of suppressing the generation of deposits even when the exhaust gas recirculation amount is increased.

In order to achieve the above object, in the invention described in claim 1,
It is characterized by comprising separation and recirculation means for selectively separating carbon dioxide from the exhaust gas flowing through the exhaust passage of the internal combustion engine and returning the separated carbon dioxide to the intake passage of the internal combustion engine.

  According to this, the carbon dioxide in the exhaust gas can be selectively refluxed to the intake passage by the separation reflux means. Therefore, even if the exhaust gas recirculation amount is increased, the generation of deposits can be suppressed.

  In the invention according to claim 2, the separation and reflux means includes a carbon dioxide separator provided in the exhaust passage and including a carbon dioxide separation membrane that selectively permeates and separates carbon dioxide in the exhaust gas. It is characterized by that.

  According to this, carbon dioxide in the exhaust gas can be easily separated by the carbon dioxide separation membrane in the carbon dioxide separator provided in the exhaust passage and can be returned to the intake passage. Therefore, even if the exhaust gas recirculation amount is increased, the generation of deposits can be easily suppressed.

  The invention according to claim 3 is characterized in that the carbon dioxide separation membrane comprises a cardo type polyimide polymer membrane. According to this, it is easy to separate carbon dioxide from the exhaust gas.

  The invention according to claim 4 is characterized in that the carbon dioxide separation membrane is a hollow fiber membrane. According to this, carbon dioxide can be separated outside the hollow fiber membrane by circulating the exhaust gas inside the hollow fiber membrane.

In the invention according to claim 5,
The separation reflux means is
A first adsorber that is provided in an exhaust passage of the internal combustion engine, and includes a first adsorbent that adsorbs carbon dioxide when the atmosphere is equal to or higher than a predetermined pressure and desorbs carbon dioxide when the atmosphere is lower than the predetermined pressure;
A second adsorber that is provided in the exhaust passage and contains a second adsorbent that adsorbs carbon dioxide when the atmosphere is equal to or higher than a predetermined pressure and desorbs carbon dioxide when the atmosphere is lower than the predetermined pressure;
A first mode that permits the flow of exhaust gas to the first adsorber and prohibits the flow of exhaust gas to the second adsorber, and prohibits the flow of exhaust gas to the first adsorber and the second adsorber Mode switching means for switching to a second mode that permits the flow of exhaust gas to
The mode switching means is
In the case of the first mode, the inside of the first adsorber is set to a predetermined pressure or higher, exhaust gas that has passed through the first adsorber is discharged to the outside through the exhaust passage, and the inside of the second adsorber is set to a predetermined pressure. Less than that, the carbon dioxide desorbed from the second adsorbent is recirculated to the intake passage of the internal combustion engine,
In the case of the second mode, the inside of the first adsorber is made less than a predetermined pressure, the carbon dioxide desorbed from the first adsorbent is recirculated to the intake passage, and the inside of the second adsorber is made a predetermined pressure or more, The exhaust gas that has passed through the second adsorber is discharged to the outside through the exhaust passage.

  According to this, when the mode switching means switches between the first mode and the second mode, the exhaust gas is exhausted by the adsorbent of one of the first adsorber and the second adsorber whose internal pressure is equal to or higher than a predetermined pressure. Carbon dioxide can be adsorbed from the gas, and the carbon dioxide can be desorbed from the adsorbent of the other adsorber whose internal pressure is less than a predetermined pressure and can be returned to the intake passage. Therefore, carbon dioxide in the exhaust gas can be selectively recirculated to the intake passage. In this way, even if the exhaust gas recirculation amount is increased, the generation of deposits can be suppressed.

  In the invention described in claim 6, the first adsorbent and the second adsorbent are both made of amorphous aluminum silicate having an imogolite structure. According to this, since the predetermined pressure for switching between adsorption of carbon dioxide to the adsorbent and desorption of carbon dioxide from the adsorbent can be made close to atmospheric pressure, the first mode and the second mode can be changed. It is easy to switch.

  Further, in the invention according to claim 7, the mode switching means performs the next mode switching when the accumulated value of the physical quantity related to the operation state of the internal combustion engine after the mode switching becomes a predetermined value or more. It is said. This makes it possible to estimate the amount of carbon dioxide recirculation after mode switching from the physical quantity related to the operating state of the internal combustion engine, and to switch the adsorber that is the recirculation source of carbon dioxide. It is possible to return to the passage.

  In the invention according to claim 8, the mode switching means has variable throttle means for restricting the exhaust passage on the downstream side of the first adsorber and the second adsorber in the exhaust passage, and the operating state of the internal combustion engine. On the basis of the above, the throttle state of the variable throttle means is changed, and the inside of the first adsorber or the second adsorber is set to a predetermined pressure or higher. According to this, among the first adsorber and the second adsorber, the inside of the adsorber that adsorbs carbon dioxide can be reliably raised to a predetermined pressure or higher.

  In the invention according to claim 9, a supercharger for increasing the intake pressure is provided in the intake passage, and the carbon dioxide desorbed from the first adsorbent and the second adsorbent is taken into the intake passage. It is characterized by returning to the upstream side of the supercharger in the passage. In this way, carbon dioxide is selectively recirculated to the intake passage and is unlikely to adversely affect the supercharger. Therefore, it is possible to recirculate upstream of the supercharger, such as the supercharging pressure and the operating load state of the internal combustion engine. Regardless of this, it is possible to return to the intake passage.

  Further, the invention described in claim 10 is characterized in that the intake passage is provided with an intercooler for cooling the intake air downstream of the supercharger. Thus, since carbon dioxide is selectively recirculated to the intake passage and the intercooler is hardly adversely affected, the intake air mixed with the recirculated carbon dioxide can be cooled by the intercooler.

  Further, as in the invention described in claim 11, the separation and recirculation means can recirculate the carbon dioxide separated from the exhaust gas into the intake passage through which the air whose air-fuel ratio is approximately the stoichiometric air-fuel ratio flows. Accordingly, a three-way catalyst can be disposed in the exhaust passage.

It is a schematic block diagram which shows the engine 2 which is an internal combustion engine equipped with the exhaust-gas recirculation apparatus 1 in 1st Embodiment to which this invention is applied. 1 is a schematic configuration diagram of an exhaust gas recirculation device 1. FIG. It is operation | movement explanatory drawing of the exhaust-gas recirculation apparatus 1, and has shown the 1st mode. It is operation | movement explanatory drawing of the exhaust-gas recirculation apparatus 1, and has shown 2nd mode. It is a schematic block diagram which shows the engine 2 which is an internal combustion engine equipped with the exhaust-gas recirculation apparatus 1 in 2nd Embodiment. It is a schematic block diagram which shows the engine 2 which is an internal combustion engine equipped with the exhaust-gas recirculation apparatus 201 in 3rd Embodiment. 1 is a schematic configuration diagram of an exhaust gas recirculation device 201. FIG. It is a schematic block diagram which shows the engine 2 which is an internal combustion engine equipped with the exhaust-gas recirculation apparatus 201 in 4th Embodiment. It is a schematic block diagram of the internal combustion engine equipped with the exhaust gas recirculation device 1 in another embodiment. It is a schematic block diagram of the internal combustion engine equipped with the exhaust gas recirculation device of the comparative example.

  A plurality of modes for carrying out the present invention will be described below with reference to the drawings. In each embodiment, parts corresponding to the matters described in the preceding embodiment may be denoted by the same reference numerals, and redundant description may be omitted. In the case where only a part of the configuration is described in each embodiment, the other parts of the configuration are the same as those described previously. In addition to the combination of parts specifically described in each embodiment, the embodiments may be partially combined as long as the combination is not particularly troublesome.

(First embodiment)
FIG. 1 is a schematic configuration diagram showing an engine 2 that is an internal combustion engine equipped with an exhaust gas recirculation device 1 according to a first embodiment to which the present invention is applied, and FIG. 2 is an outline of the exhaust gas recirculation device 1. It is a block diagram.

  As shown in FIG. 1, the exhaust gas recirculation device 1 of the present embodiment is mounted on, for example, a vehicle diesel engine 2 and includes an adsorption / desorption unit 10, an EGR pipe 30, and an EGR valve 33. is doing.

  The adsorption / desorption unit 10 is provided in the exhaust pipe 4 of the engine 2, selectively adsorbs carbon dioxide from the exhaust gas of the engine 2 flowing through the exhaust passage in the exhaust pipe 4, and desorbs the adsorbed carbon dioxide. Can be done. The EGR pipe (exhaust gas recirculation passage pipe) 30 recirculates the carbon dioxide desorbed by the adsorption / desorption unit 10 to the downstream side of the intake filter (air cleaner) 5 in the intake passage in the intake pipe 3 of the engine 2. The EGR valve 33 provided at the downstream end of the EGR pipe 30 adjusts the recirculation amount of the exhaust gas (carbon dioxide in the present embodiment) into the intake pipe 3.

  As shown in FIG. 2, the adsorption / desorption unit 10 is interposed in the course of the exhaust pipe 4 of the engine 2, and an upstream exhaust pipe 20 and an upstream exhaust pipe 20 whose upstream ends are connected to the exhaust pipe 4. The first exhaust pipe 21 and the second exhaust pipe 22 branched into two on the downstream side, and the first and second exhaust pipes 21 and 22 merge into one on the downstream side, and the downstream end is connected to the exhaust pipe 4 again. A downstream exhaust pipe 23 is provided.

  The first exhaust pipe 21 is provided with the first adsorber 11 so that the exhaust gas flowing through the first exhaust pipe 21 can be passed through the first adsorber 11. On the other hand, the second adsorber 12 is provided in the second exhaust pipe 22, and the exhaust gas flowing through the second exhaust pipe 22 can be passed through the second adsorber 12. .

  At the branch point from the upstream exhaust pipe 20 to the first exhaust pipe 21 and the second exhaust pipe 22, the exhaust gas route circulated in the upstream exhaust pipe 20 is connected to the first exhaust pipe 21 side and the second exhaust pipe 22. For example, an electromagnetic switching valve 41, which is a flow path switching means for selectively switching between the two, is provided.

  Further, at the junction point from the first exhaust pipe 21 and the second exhaust pipe 22 to the downstream exhaust pipe 23, the path of the exhaust gas flowing into the downstream exhaust pipe 23 is connected to the first exhaust pipe 21 side and the second exhaust pipe 23 side. For example, an electromagnetic switching valve 42 which is a flow path switching means for selectively switching between the exhaust pipe 22 side is provided. In the downstream exhaust pipe 23 after the merging, for example, an electric variable throttle valve 44 that is a variable throttle means that throttles the exhaust passage in the downstream exhaust pipe 23 is disposed.

  A first EGR pipe 31 whose inside communicates with the inside of the first adsorber 11 is connected to the first adsorber 11, and a second EGR pipe 32 whose inside communicates with the inside of the second adsorber 12 is connected to the second adsorber 12. Is connected. At the junction where the downstream end of the first EGR pipe 31 and the downstream end of the second EGR pipe 32 join, the path of the exhaust gas flowing into the EGR pipe 30 is between the first EGR pipe 31 side and the second EGR pipe 32 side. For example, an electromagnetic switching valve 43, which is a flow path switching means for selectively switching, is provided.

The first adsorber 11 and the second adsorber 12 are both made of, for example, stainless steel having good corrosion resistance, and the first adsorbent is contained in the first adsorber 11 and the second adsorber 12 is contained therein. Contains a second adsorbent. In this embodiment, the first and second adsorbents are relatively inexpensive and relatively high (about 300 ° C.) made of amorphous aluminum silicate (SiO ₂ .Al ₂ O ₃ .2H ₂ O) having an imogolite structure. A) An inorganic carbon dioxide adsorbent having heat resistance is used.

  This adsorbent is a partially tubular aluminum silicate having an outer diameter of about 2.5 nm, an inner diameter of about 1 nm, and a length of several nanometers to several tens of nanometers in a so-called nanotube form. Carbon dioxide can be adsorbed by raising the pressure to a pressure slightly higher than atmospheric pressure, and carbon dioxide can be desorbed by returning the atmospheric pressure to atmospheric pressure. That is, the adsorption and desorption of carbon dioxide can be repeated by a so-called pressure swing adsorption method that swings both high and low pressures at a predetermined pressure near atmospheric pressure.

  The exhaust gas recirculation device 1 includes a control device 100 as control means. The control device 100 inputs information related to the operating state of the engine 2 and controls the switching valves 41, 42, 43 and the variable throttle valve 44 of the adsorption / desorption unit 10 based on this information. The information input to the control device 100 may be information from a sensor or the like (not shown) provided in the engine 2 or peripheral equipment of the engine 2, or information from an engine control device that controls the engine 2. Also good. The control device 100 may be a control device dedicated to the exhaust gas recirculation device 1 or may be a part of another control device such as an engine control device.

  Here, the adsorption / desorption unit 10, the EGR pipe 30 extending from the adsorption / desorption unit 10, the EGR valve 33, and the control device 100 constitute the exhaust gas recirculation device 1 in the present embodiment, and the switching valves 41, 42, 43, the variable throttle valve 44, and the control device 100 correspond to the mode switching means in the present invention. The exhaust gas recirculation device 1 selectively separates carbon dioxide from the exhaust gas flowing through the exhaust passage in the exhaust pipe 4 and recirculates the separated carbon dioxide to the intake passage in the intake pipe 3. Corresponds to separation and reflux means.

  Next, the operation of the exhaust gas recirculation device 1 will be described based on the above configuration.

  The control device 100 controls the switching valves 41, 42, 43 and the variable throttle valve 44 to switch between the first mode shown in FIG. 3 and the second mode shown in FIG.

  As shown in FIG. 3, in the first mode, the control device 100 sets the flow path of the switching valve 41 to the first exhaust pipe 21 side and also sets the flow path of the switching valve 42 to the first exhaust pipe 21 side. Further, the flow path of the switching valve 43 is on the second EGR pipe 32 side. In addition, the control device 100 sets the throttle state of the variable throttle valve 44 according to the operating state of the engine 2 to a predetermined pressure or more determined by the inside of the first adsorber 11 based on the adsorption / desorption equilibrium characteristics of the adsorbent. (Pressure value for adsorbing carbon dioxide).

  As a result, the exhaust gas of the engine 2 sequentially flows through the upstream exhaust pipe 20, the first exhaust pipe 21, and the downstream exhaust pipe 23 and is discharged to the outside through the exhaust passage in the exhaust pipe 4. . Of the exhaust gas of the engine 2, carbon dioxide, which is an inert component, passes through the first adsorber 11 that has a pressure equal to or higher than the carbon dioxide adsorption pressure, and is incorporated in the first adsorbent. Exhaust gas other than inert components is exhausted to the outside.

  On the other hand, the upstream end of the second exhaust pipe 22 is closed by the switching valve 41, and the second adsorber 12 communicated with the intake pipe 3 via the second EGR pipe 32 and the EGR pipe 30 is connected to the intake pipe 3. The inside is made less than a predetermined pressure that is a carbon dioxide desorption pressure by the intake pressure that is a negative pressure. Accordingly, carbon dioxide is desorbed from the built-in second adsorbent, and the desorbed carbon dioxide is recirculated into the intake pipe 3 via the second EGR pipe 32 and the EGR pipe 30.

  When it is estimated that the controller 100 has set the first mode and desorption from the second adsorbent has progressed to reach a limit at which carbon dioxide can be stably refluxed, the first mode shown in FIG. The mode is switched from the mode to the second mode shown in FIG. The estimation as to whether or not carbon dioxide has reached the limit at which it can be recirculated is, for example, the cumulative value of the fuel injection amount to the engine 2 after setting the first mode, the cumulative value of the rotational speed of the engine 2, This is performed depending on whether or not any of the accumulated values of the accelerator opening has reached a predetermined value.

  That is, when the accumulated value of the physical quantity related to the operating state of the engine 2 after the mode switching becomes a predetermined value or more, the next mode switching is performed. This makes it possible to estimate the amount of carbon dioxide reflux after mode switching from the physical quantity related to the operating state of the engine 2 and to switch the adsorber that is the source of carbon dioxide reflux. It is possible to return to the intake passage in the pipe 3.

  As shown in FIG. 4, in the second mode, the control device 100 sets the flow path of the switching valve 41 to the second exhaust pipe 22 side and also sets the flow path of the switching valve 42 to the second exhaust pipe 22 side. In addition, the flow path of the switching valve 43 is the first EGR pipe 31 side. Further, the control device 100 sets the throttle state of the variable throttle valve 44 according to the operating state of the engine 2 so that the inside of the second adsorber 12 is equal to or higher than a predetermined pressure (pressure value at which the adsorbent adsorbs carbon dioxide). Adjust as follows.

  As a result, the exhaust gas of the engine 2 sequentially flows through the upstream exhaust pipe 20, the second exhaust pipe 22, and the downstream exhaust pipe 23 and is discharged to the outside through the exhaust passage in the exhaust pipe 4. . Among the exhaust gas of the engine 2, carbon dioxide, which is an inert component, passes through the second adsorber 12 in which the internal pressure is equal to or higher than a predetermined pressure that is carbon dioxide adsorption pressure. Exhaust gas other than inert components is exhausted to the outside.

  On the other hand, while the upstream end of the first exhaust pipe 21 is closed by the switching valve 41, the first adsorber 11 communicated with the intake pipe 3 through the first EGR pipe 31 and the EGR pipe 30 is provided in the intake pipe 3. The inside is made less than a predetermined pressure that is a carbon dioxide desorption pressure by the intake pressure that is a negative pressure. Accordingly, carbon dioxide is desorbed from the built-in first adsorbent, and the desorbed carbon dioxide is recirculated into the intake pipe 3 via the first EGR pipe 31 and the EGR pipe 30.

  When it is estimated that the controller 100 has set the second mode, the desorption from the first adsorbent in the first adsorber 11 has progressed, and has reached a limit at which carbon dioxide can be stably recirculated. Then, the mode is switched again from the second mode shown in FIG. 4 to the first mode shown in FIG. The estimation as to whether or not the carbon dioxide has reached the limit at which it can be stably recirculated is performed in the same manner as when the mode is switched from the first mode to the second mode. Then, the carbon dioxide is continuously returned to the intake passage in the intake pipe 3 by sequentially repeating the switching between the first mode and the second mode.

  Note that the mode switching timing between the first mode and the second mode is determined by the adsorbent regardless of indirect estimation that the accumulated value of the physical quantity related to the operating state of the engine 2 after the mode switching is equal to or greater than a predetermined value. It may be based on direct detection of the carbon dioxide adsorption weight.

  According to the configuration and operation described above, the control device 100 switches the switching valves 41, 42, and 43 to distribute the exhaust gas into the first adsorber 11 and to distribute the exhaust gas into the second adsorber 12. The first mode for prohibition and the second mode for prohibiting the flow of exhaust gas into the first adsorber 11 and flowing the exhaust gas into the second adsorber 12 are repeated.

  In the case of the first mode, the inside of the first adsorber 11 is adjusted by the variable throttle valve 44 so as to be equal to or higher than a predetermined pressure that is the carbon dioxide adsorption pressure, and carbon dioxide is selected from the exhaust gas passing through the first adsorber 11 Thus, the first adsorbent is adsorbed and components other than carbon dioxide are discharged to the outside through the exhaust passage. Further, the inside of the second adsorber 12 is set to be less than a predetermined pressure that is a carbon dioxide desorption pressure, and the carbon dioxide desorbed from the second adsorbent is returned to the intake passage in the intake pipe 3.

  In the second mode, the inside of the first adsorber 11 is made less than a predetermined pressure that is a carbon dioxide desorption pressure, and the carbon dioxide desorbed from the first adsorbent is returned to the intake passage in the intake pipe 3. Further, the inside of the second adsorber 12 is adjusted by the variable throttle valve 44 so as to be equal to or higher than a predetermined pressure which is the carbon dioxide adsorption pressure, and carbon dioxide is selectively emitted from the exhaust gas passing through the second adsorber 12. And the components other than carbon dioxide are discharged to the outside through the exhaust passage.

  As described above, by repeatedly switching between the first mode and the second mode, of the first adsorber 11 and the second adsorber 12, the adsorber having an internal pressure equal to or higher than a predetermined pressure that is a carbon dioxide adsorption pressure. Always adsorb carbon dioxide from the exhaust gas with the adsorbent of this type, desorb carbon dioxide from the adsorbent of the adsorber whose internal pressure is less than the predetermined pressure that is the carbon dioxide desorption pressure, and always return to the intake passage Can do. Therefore, the carbon dioxide in the exhaust gas can be selectively recovered and always returned to the intake passage. The exhaust gas recirculated into the intake pipe 3 is only carbon dioxide, soot and unburned components in the exhaust gas are not recirculated into the intake passage, and the exhaust gas recirculation amount increases according to the operating state of the engine 2 Also, the generation of deposits can be suppressed.

  In addition, as the first adsorbent incorporated in the first adsorber 11 and the second adsorbent incorporated in the second adsorber 12, both adopt amorphous aluminum silicate having an imogolite structure. Therefore, the pressure (carbon dioxide adsorption pressure and carbon dioxide desorption pressure) when performing adsorption and desorption of carbon dioxide by the pressure swing adsorption method can be set near atmospheric pressure, and the configuration of the exhaust gas recirculation device 1 is extremely simple. Can be

  Further, a variable throttle valve 44 is provided in the downstream exhaust passage 23, and the inside of the adsorber that allows the exhaust gas to pass through is adjusted by adjusting the throttle opening of the variable throttle valve 44 based on the operating state of the engine 2. The pressure is higher than a predetermined pressure at which carbon can be adsorbed. Therefore, the insides of the first adsorber 11 and the second adsorber 12 can be easily and stably raised to a predetermined pressure that is the carbon dioxide adsorption pressure.

  If the influence on the performance of the engine 2 can be allowed, a fixed throttle may be provided in the exhaust passage regardless of the variable throttle valve 44. Further, the variable throttle valve 44 can be eliminated if the inside of the adsorber through which the exhaust gas is allowed to pass by the positive pressure of the exhaust can be set to a predetermined pressure or higher capable of adsorbing carbon dioxide.

(Second Embodiment)
Next, a second embodiment will be described based on FIG.

  The second embodiment is an example in which the exhaust gas recirculation device 1 to which the present invention is applied is mounted on an engine including a supercharger and an intercooler. In addition, about the part similar to 1st Embodiment, the same code | symbol is attached | subjected and the description is abbreviate | omitted.

  As shown in FIG. 5, in this embodiment, a supercharger 6 that boosts the intake air and an intercooler 7 that cools the intake air whose pressure has been increased and its temperature has been increased by heat exchange are disposed in the intake pipe 3. In this example, as the supercharger 6, a turbocharger that rotates the exhaust turbine by the energy of the exhaust gas flowing in the exhaust pipe 4 and compresses the intake air by driving a coaxial compressor is used. Yes. A mechanical supercharger (so-called supercharger) may be employed as the supercharger.

  An exhaust gas recirculation device 1 similar to that of the first embodiment is mounted on such an engine 2 with a supercharger. As shown in FIG. 5, the adsorption / desorption unit 10 is provided on the downstream side of the supercharger 6 of the exhaust pipe 4 from the exhaust turbine, and the carbon dioxide in the exhaust gas is removed from the supercharger 6 via the EGR pipe 30. It recirculates in the intake pipe 3 upstream from the compressor.

  Even in such a configuration, carbon dioxide, which is an inert component in the exhaust gas, is selectively returned to the intake passage in the intake pipe 3, so that the compressor of the supercharger 6 and the intake passage in the intercooler 7 are used. It is possible to prevent deposits from being deposited.

When the exhaust gas recirculation device is mounted on a conventional engine with a supercharger, it is difficult to recirculate the exhaust gas unless it is an intake passage downstream of the compressor of the supercharger. In such a configuration, although when the boost pressure is low engine low load than the exhaust pressure can be refluxed exhaust gas easily boost pressure combustion temperature and NO _X are heavily infested with increased discharge There was a problem that the exhaust gas could not be recirculated at the time of high engine load higher than the atmospheric pressure.

  However, according to the present embodiment, carbon dioxide in the exhaust gas can be recirculated to the intake passage in the intake pipe 3 before pressure increase, so that recirculation can always be performed regardless of the operating load state of the engine 2.

  Conventionally, when the intercooler 7 is made of aluminum, corrosion occurs when a high-temperature exhaust gas is circulated. Therefore, an EGR cooler made of a material having corrosion resistance has to be installed. However, according to the present embodiment, only carbon dioxide, which is an inert component in the exhaust gas, is recirculated. Therefore, even if the intercooler 7 is made of aluminum, the occurrence of corrosion can be suppressed, and an EGR cooler is provided. There is no need.

  The arrangement position of the adsorption / desorption unit 10 is not limited to the downstream side of the turbocharger 6 and the exhaust turbine may be upstream of the exhaust turbine.

(Third embodiment)
Next, a third embodiment will be described based on FIG. 6 and FIG.

  FIG. 6 is a schematic configuration diagram showing an engine 2 that is an internal combustion engine equipped with an exhaust gas recirculation device 201 according to a third embodiment to which the present invention is applied, and FIG. 7 is an outline of the exhaust gas recirculation device 201. It is a block diagram. In addition, about the part similar to 1st Embodiment, the same code | symbol is attached | subjected and the description is abbreviate | omitted.

  As shown in FIG. 6, the exhaust gas recirculation device 201 of the present embodiment is mounted on, for example, a vehicle diesel engine 2, and includes a separation device 210 corresponding to a carbon dioxide separator, an EGR pipe 30, And an EGR valve 33.

  The separation device 210 is provided in the exhaust pipe 4 of the engine 2, and can selectively separate carbon dioxide from the exhaust gas of the engine 2 that flows through the exhaust passage in the exhaust pipe 4. The EGR pipe (exhaust gas recirculation passage pipe) 30 recirculates the carbon dioxide separated by the separation device 210 to the downstream side of the intake filter (air cleaner) 5 in the intake passage in the intake pipe 3 of the engine 2. The EGR valve 33 provided at the downstream end of the EGR pipe 30 adjusts the recirculation amount of the exhaust gas (carbon dioxide in the present embodiment) into the intake pipe 3.

  As shown in FIG. 7, the separation device 210 is interposed in the middle of the route of the exhaust pipe 4 of the engine 2, and a cylindrical container body in which connectors (connection parts) to the exhaust pipe 4 are disposed at both ends. 211 and a hollow fiber membrane 212 which is a carbon dioxide separation membrane provided in the cylindrical container body 211. In this embodiment, as the hollow fiber membrane 212, a tubular membrane having an inner diameter of about 200 μm made of a cardo type polyimide polymer membrane is used.

  A large number (for example, several tens of thousands) of hollow fiber membranes 212 are arranged in parallel inside the cylindrical container body 211 so as to extend in the axial direction of the cylindrical container body 211. The internal spaces of the multiple hollow fiber membranes 212 communicate with the exhaust passages in the exhaust pipe 4 at both ends, and the outer spaces of the hollow fiber membranes 212 in the cylindrical container body 211 are connected to the EGR pipe 30. Communicate.

  Here, the separation device 210, the EGR pipe 30 extending from the separation device 210, and the EGR valve 33 constitute the exhaust gas recirculation device 201 in the present embodiment. The exhaust gas recirculation device 201 selectively separates carbon dioxide from the exhaust gas flowing through the exhaust passage in the exhaust pipe 4 and recirculates the separated carbon dioxide to the intake passage in the intake pipe 3. Corresponds to separation and reflux means.

  Next, the operation of the exhaust gas recirculation device 201 will be described based on the above configuration.

  When the engine 2 is operated, the exhaust gas of the engine 2 flows into the hollow fiber membrane 212 of the separation device 210 from the upstream side portion (portion on the engine 2 side) of the exhaust pipe 4. When the exhaust gas flowing into the hollow fiber membrane 212 of the separation device 210 flows in the hollow fiber membrane 212 in the axial direction (right direction in FIG. 7), carbon dioxide, which is an inert component in the exhaust gas, is hollow. It passes through the thread membrane 212 and is separated outside the hollow fiber membrane 212.

  At this time, the pressure in the outer space of the hollow fiber membrane 212 in the separation vessel 210 cylindrical container body 211 communicating with the inside of the intake pipe 3 via the EGR pipe 30 is the inside of the hollow fiber membrane 212 communicating with the inside of the exhaust pipe 4. Since the pressure is lower than the space pressure, carbon dioxide is rapidly separated from the exhaust gas.

  Exhaust gas other than the inert component from which carbon dioxide has been separated flows out from the hollow fiber membrane 212 to the downstream side portion (exhaust port side portion) of the exhaust pipe 4 and is discharged to the outside through the exhaust pipe 4. . On the other hand, carbon dioxide separated from the exhaust gas by the hollow fiber membrane 212 is recirculated into the intake pipe 3 through the EGR pipe 30.

  According to the above-described configuration and operation, carbon dioxide in the exhaust gas can be selectively recovered by the hollow fiber membrane 212 of the separation device 210 and can always be returned to the intake passage. The exhaust gas recirculated into the intake pipe 3 is only carbon dioxide, soot and unburned components in the exhaust gas are not recirculated into the intake passage, and the exhaust gas recirculation amount increases according to the operating state of the engine 2 Also, the generation of deposits can be suppressed.

  Further, since a carbon dioxide separation membrane made of a cardo type polyimide polymer membrane is used for the separation device 210, it is easy to separate carbon dioxide in the exhaust gas. Further, since the carbon dioxide separation membrane is the hollow fiber membrane 212, carbon dioxide can be separated very easily by circulating exhaust gas having a higher pressure than the outside on the inside. Furthermore, since a large number of hollow fiber membranes 212 are employed, a relatively large membrane surface area can be secured, and carbon dioxide can be satisfactorily separated even when a large amount of exhaust gas is circulated.

(Fourth embodiment)
Next, a fourth embodiment will be described with reference to FIG.

  The fourth embodiment is an example in which an exhaust gas recirculation device 201 to which the present invention is applied is mounted on an engine including a supercharger and an intercooler. In addition, about the part similar to the 1st-3rd embodiment, the same code | symbol is attached | subjected and the description is abbreviate | omitted.

  As shown in FIG. 8, in this embodiment, a supercharger 6 that boosts the intake air and an intercooler 7 that cools the intake air whose pressure has been increased and its temperature has been increased by heat exchange are disposed in the intake pipe 3. In this example, as the supercharger 6, a turbocharger that rotates the exhaust turbine by the energy of the exhaust gas flowing in the exhaust pipe 4 and compresses the intake air by driving a coaxial compressor is used. Yes. A mechanical supercharger (so-called supercharger) may be employed as the supercharger.

  An exhaust gas recirculation device 201 similar to that of the third embodiment is attached to such an engine 2 with a supercharger. As shown in FIG. 8, the separation device 210 is provided downstream of the supercharger 6 exhaust turbine of the exhaust pipe 4 and compresses the carbon dioxide in the exhaust gas through the EGR pipe 30 by the supercharger 6. It recirculates in the intake pipe 3 upstream from the machine.

  Even in such a configuration, carbon dioxide, which is an inert component in the exhaust gas, is selectively returned to the intake passage in the intake pipe 3, so that the compressor of the supercharger 6 and the intake passage in the intercooler 7 are used. It is possible to prevent deposits from being deposited.

  Further, according to the present embodiment, as in the second embodiment, carbon dioxide in the exhaust gas can be recirculated to the intake passage in the intake pipe 3 before pressure increase, so that the engine 2 is always operated regardless of the operating load state. Reflux can be performed.

  Further, according to the present embodiment, as in the second embodiment, since only carbon dioxide, which is an inert component in the exhaust gas, is recirculated, the occurrence of corrosion can be suppressed even if the intercooler 7 is made of aluminum. This eliminates the need for an EGR cooler.

  The disposing position of the separation device 210 is not limited to the downstream side of the supercharger 6 and the exhaust turbine may be upstream of the exhaust turbine.

(Other embodiments)
The preferred embodiments of the present invention have been described above, but the present invention is not limited to the above-described embodiments, and various modifications can be made without departing from the spirit of the present invention.

  In the first and second embodiments, amorphous aluminum silicate having an imogolite structure is used as the first adsorbent in the first adsorber 11 and the second adsorbent in the second adsorber 12. However, the present invention is not limited to this, and any material having heat resistance and capable of adsorbing and desorbing carbon dioxide may be used. For example, ceramics made of zeolite, potassium carbonate or the like, porous metal complexes, etc. may be used.

  In the first and second embodiments, the adsorption / desorption unit 10 has two adsorbers, the first adsorber 11 and the second adsorber 12, but has three or more adsorbers. It doesn't matter. It is effective to apply the present invention to at least two adsorbers among three or more adsorbers.

  Moreover, in the said 3rd and 4th embodiment, although the cardo type polyimide polymer membrane was used as a carbon dioxide separation membrane of the separation apparatus 210, it is not limited to this, Carbon dioxide is extracted from exhaust gas. What is necessary is just to be separable. The carbon dioxide separation membrane may not be a hollow fiber membrane.

  The means for separating carbon dioxide from the exhaust gas is not limited to means using an adsorption / desorption method using an adsorbent and means using a membrane separation method, and may be a means using another separation method. It doesn't matter.

  Moreover, although each said embodiment demonstrated the case where the exhaust-gas recirculation apparatus 1,201 was mounted | worn with the diesel engine 2 for vehicles, an internal combustion engine is not limited to a diesel engine. For example, the internal combustion engine on which the exhaust gas recirculation devices 1 and 201 are mounted may be a gasoline direct injection engine or an internal combustion engine other than for a vehicle.

  In addition, although the description has been omitted in each of the above embodiments, if the exhaust gas recirculation devices 1 and 201 to which the present invention is applied are used, a three-way catalyst is employed for exhaust gas purification processing as shown in FIG. It becomes possible.

Conventionally, diesel engines and gasoline direct-injection engines have lean combustion with an air-fuel ratio of about 20 to 60, and the oxidation reaction of carbon monoxide and hydrocarbons and the reduction reaction of nitrogen oxides cannot be balanced and a three-way catalyst is used. It was difficult to use. Therefore, for example, as shown in FIG. 10, while a part of the exhaust gas is recirculated through the EGR pipe 130, the remainder of the exhaust gas is oxidized catalyst 108A, PM (particulate matter) that oxidizes carbon monoxide and hydrocarbons. ) Is captured, and thereafter, a urea-added NO _X selective reduction catalyst or NO _X storage reduction catalyst 108B is passed through to reduce nitrogen oxides.

  On the other hand, if the exhaust gas recirculation device 1 to which the present invention is applied is used, air in which the air-fuel ratio of the engine 2 is substantially the stoichiometric air-fuel ratio is circulated through the intake passage in the intake pipe 3 shown in FIG. The three-way catalyst 8 can be employed for the exhaust gas purification treatment by mixing the carbon dioxide that has been refluxed into the air. Therefore, the number of catalysts for exhaust gas purification treatment can be reduced. Although illustration is omitted, the same effect can be obtained by using the exhaust gas recirculation device 201 to which the present invention is applied.

  In each of the above embodiments, the adsorption / desorption unit 10 of the exhaust gas recirculation device 1 or the separation device 210 of the exhaust gas recirculation device 201 is provided in the course of the exhaust pipe 4, but PM in the exhaust gas has accumulated. Sometimes when the adsorption / desorption function of the adsorption / desorption unit 10 is lowered or when the separation function of the separation device 210 is lowered, the adsorption / desorption unit 10 or the separation device 210 is disposed downstream of the DPF 9 in the exhaust pipe 4. It is preferable to do. When the adsorption / desorption function of the adsorption / desorption unit 10 is not lowered due to PM accumulation or when the separation function of the separation device 210 is not lowered, the adsorption / desorption unit 10 or the separation device 210 is disposed in any of the exhaust paths. It is also possible.

1,201 Exhaust gas recirculation device (separation refluxing means)
2 Engine (Internal combustion engine)
DESCRIPTION OF SYMBOLS 3 Intake piping 4 Exhaust piping 6 Supercharger 7 Intercooler 10 Adsorption / desorption unit 11 1st adsorption device 12 2nd adsorption device 41 Switching valve (a part of mode switching means)
42 switching valve (part of mode switching means)
43 Switching valve (part of mode switching means)
44 Variable throttle valve (variable throttle means, part of mode switching means)
100 Control device (part of mode switching means)
210 Separator (carbon dioxide separator)
212 Hollow fiber membrane (carbon dioxide separation membrane)

Claims (11)

  Exhaust gas for an internal combustion engine, comprising separation and recirculation means for selectively separating carbon dioxide from exhaust gas flowing through an exhaust passage of the internal combustion engine and recirculating the separated carbon dioxide to the intake passage of the internal combustion engine Gas recirculation device. The separation reflux means includes
The exhaust of the internal combustion engine according to claim 1, further comprising a carbon dioxide separator provided in the exhaust passage and incorporating a carbon dioxide separation membrane that selectively permeates and separates carbon dioxide in the exhaust gas. Gas recirculation device.   The exhaust gas recirculation device for an internal combustion engine according to claim 2, wherein the carbon dioxide separation membrane is made of a cardo type polyimide polymer membrane.   The exhaust gas recirculation device for an internal combustion engine according to claim 2 or 3, wherein the carbon dioxide separation membrane is a hollow fiber membrane. The separation reflux means includes
A first adsorber that is provided in the exhaust passage and contains a first adsorbent that adsorbs carbon dioxide when the atmosphere is equal to or higher than a predetermined pressure and desorbs carbon dioxide when the atmosphere is lower than the predetermined pressure;
A second adsorber that is provided in the exhaust passage and contains a second adsorbent that adsorbs carbon dioxide when the atmosphere is equal to or higher than the predetermined pressure and desorbs carbon dioxide when the atmosphere is lower than the predetermined pressure;
A first mode that permits the flow of exhaust gas to the first adsorber and prohibits the flow of exhaust gas to the second adsorber; and prohibits the flow of exhaust gas to the first adsorber and Mode switching means for switching between a second mode for allowing the exhaust gas to flow to the second adsorber,
The mode switching means is
In the case of the first mode, the inside of the first adsorber is set to the predetermined pressure or more, and exhaust gas that has passed through the first adsorber is discharged to the outside through the exhaust passage, and the second adsorption is performed. The inside of the vessel is less than the predetermined pressure, the carbon dioxide desorbed from the second adsorbent is recirculated to the intake passage,
In the case of the second mode, the inside of the first adsorber is made less than the predetermined pressure, the carbon dioxide desorbed from the first adsorbent is returned to the intake passage, and the inside of the second adsorber 2. The exhaust gas recirculation device for an internal combustion engine according to claim 1, wherein the exhaust gas passing through the second adsorber is discharged to the outside through the exhaust passage when the pressure is equal to or higher than the predetermined pressure.   The exhaust gas recirculation device for an internal combustion engine according to claim 5, wherein both the first adsorbent and the second adsorbent are made of amorphous aluminum silicate having an imogolite structure.   The mode switching means performs the next mode switching when the accumulated value of the physical quantity related to the operation state of the internal combustion engine after the mode switching becomes a predetermined value or more. An exhaust gas recirculation device for an internal combustion engine according to claim 1.   The mode switching means has variable restricting means for restricting the exhaust passage on the downstream side of the first adsorber and the second adsorber in the exhaust passage, and is variable based on the operating state of the internal combustion engine. The internal combustion engine according to any one of claims 5 to 7, wherein the throttle state of the throttle means is changed so that the inside of the first adsorber or the second adsorber is equal to or higher than the predetermined pressure. Exhaust gas recirculation device. The intake passage is provided with a supercharger for increasing the intake pressure,
The internal combustion engine according to any one of claims 1 to 8, wherein the separation and recirculation means recirculates carbon dioxide separated from the exhaust gas to the upstream side of the supercharger in the intake passage. Exhaust gas recirculation device.   The exhaust gas recirculation device for an internal combustion engine according to claim 9, wherein an intercooler for cooling the intake air is provided in the intake passage downstream of the supercharger. The separation and recirculation means recirculates carbon dioxide separated from the exhaust gas into the intake passage through which air in which the air-fuel ratio of the internal combustion engine is substantially the stoichiometric air-fuel ratio flows.
The exhaust gas recirculation device for an internal combustion engine according to any one of claims 1 to 10, wherein a three-way catalyst is disposed in the exhaust passage.

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