JP2011012653A - Nitrogen enrichment gas supply device and nitrogen enrichment gas supply method of internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a nitrogen enrichment gas supply device and a nitrogen enrichment gas supply method of an internal combustion engine which can control the enlargement of the device.SOLUTION: The nitrogen enrichment gas supply device is provided with a nitrogen enrichment gas generating device 30, an induction passage 31, and a supply passage 36. The nitrogen enrichment gas generating device 30 increases the nitrogen concentration of exhaust based on the differences in the permeability of each gas with respect to a separating member 30a. The induction passage guides the exhaust from the exhaust passage 16 of the internal combustion engine 10 to the device 30, and the supply passage supplies the exhaust (nitrogen enrichment exhaust) in which the nitrogen concentration has been increased by the device to the intake passage 11 of the internal combustion engine 10. The nitrogen enrichment gas generating device 30 increases the nitrogen concentration of exhaust by separating carbon dioxide and water vapor from the exhaust.

Description

  The present invention relates to an apparatus and method for supplying a nitrogen-enriched gas having an increased nitrogen concentration to an internal combustion engine.

  In this type of apparatus, there is an apparatus that supplies intake air (nitrogen-enriched intake air) in which a part of oxygen in intake air is removed by a separation membrane to increase nitrogen concentration to an internal combustion engine (for example, Patent Documents 1 and 2). reference). Those described in Patent Documents 1 and 2 adjust the ratio of natural intake air and nitrogen-enriched intake air, and perform combustion in a state where oxygen and fuel in the intake air react without excess or deficiency. Yes. As a result, the intake air amount can be increased as compared with the case where the nitrogen-enriched intake air is not supplied, so that the pumping loss of the internal combustion engine can be reduced and the fuel consumption can be improved. In addition, since the fuel is burned in the state where there is no surplus oxygen, it is possible to suppress the generation of nitrogen oxides and to suppress the reduction of exhaust purification efficiency by the three-way catalyst.

JP 2004-190570 A JP 2004-245085 A

  By the way, the thing of patent document 1, 2 utilizes the permeability | transmittance difference of nitrogen and oxygen with respect to a separation membrane, when removing oxygen in intake air with a separation membrane. Here, regarding the permeability to the separation membrane, the difference between nitrogen and oxygen is smaller than the difference between nitrogen and substances other than oxygen. For this reason, in order to separate nitrogen and oxygen by the separation membrane, it is necessary to pressurize the intake air at a relatively high pressure. In the devices described in Patent Documents 1 and 2, the turbocharger compressor is connected to the intake air. Used for pressure. Accordingly, the devices described in Patent Documents 1 and 2 are unavoidably increased in size of the device, and still have room for improvement.

  The present invention has been made in view of such circumstances, and a main object of the present invention is to provide a nitrogen-enriched gas supply device and a nitrogen-enriched gas supply method for an internal combustion engine that can prevent the apparatus from becoming large. It is what.

  The present invention employs the following means in order to solve the above problems.

  According to the first aspect of the present invention, the nitrogen enrichment means for increasing the nitrogen concentration of the gas, the induction passage for inducing exhaust from the exhaust passage of the internal combustion engine to the nitrogen enrichment means, and the nitrogen enrichment means And a supply passage for supplying the raised exhaust gas to the intake passage of the engine.

  According to the above configuration, exhaust gas is guided from the exhaust passage of the internal combustion engine to the nitrogen enrichment means through the induction passage, and the nitrogen concentration of the exhaust is increased by the nitrogen enrichment means. Then, the exhaust gas (nitrogen-enriched exhaust gas) whose nitrogen concentration is increased by the nitrogen enriching means is supplied to the intake passage of the internal combustion engine through the supply passage.

  Here, in the exhaust gas generated by the combustion of the mixture of fuel and intake air in the internal combustion engine, the oxygen content is small compared to the intake air, but the carbon dioxide and water vapor contents are large. In addition, these gas components have different gas separation ratios with respect to the nitrogen-enriching means due to differences in gas properties, for example, the nitrogen-enriching means includes, for example, an oxygen-enriched membrane or a hollow fiber membrane. In some cases, carbon dioxide and water vapor have higher membrane permeability than oxygen or nitrogen. For this reason, gas separation can be performed easily and accurately when separating carbon dioxide and water vapor from exhaust gas, compared to when separating oxygen from intake air (natural intake air) consisting of the atmosphere. Therefore, according to this invention, it can suppress that a gas separation apparatus enlarges.

  In particular, when the nitrogen-enriching means includes an oxygen-enriched membrane or a hollow fiber membrane, the gas separation efficiency of the nitrogen-enriching means depends on the temperature of the gas to be separated, and the higher the gas temperature, the higher the nitrogen concentration It is considered that the separation efficiency at the time of increasing is increased. For this reason, when nitrogen-enriched gas is generated using high-temperature exhaust gas, the separation efficiency can be improved as compared with the case where nitrogen-enriched gas is generated using natural air intake at room temperature. The effect of reducing the size can be suitably obtained.

  The nitrogen-enriching means includes, for example, a structure that increases the nitrogen concentration of the gas based on the difference in permeability of each gas with respect to the separation member, and the gas enrichment based on the difference in adsorbability of each gas with respect to the separation member. Including those having a structure for increasing the nitrogen concentration.

  In an internal combustion engine, when combustion is performed in a state where oxygen and fuel in the intake air react without excess or deficiency, the exhaust mainly contains nitrogen, carbon dioxide, and water vapor.

  Therefore, as in the invention according to claim 2, in the invention according to claim 1, the nitrogen enriching means increases the nitrogen concentration of the exhaust gas by separating carbon dioxide and water vapor from the exhaust gas. By adopting the above, the nitrogen concentration in the exhaust can be made higher.

  Here, the thermal efficiency of the internal combustion engine increases as the specific heat ratio of the working fluid (the ratio between the constant pressure specific heat and the constant volume specific heat) increases. And since nitrogen has a larger specific heat ratio than carbon dioxide and water vapor, the specific heat ratio of the exhaust gas can be increased by separating carbon dioxide and water vapor from the exhaust gas. As a result, the thermal efficiency of the internal combustion engine can be improved as compared with the case where exhaust gas whose nitrogen concentration is not increased is supplied to the internal combustion engine.

  Here, the gas separation by the nitrogen enrichment means increases the gas separation ability by changing the pressure inside the nitrogen enrichment means or at least one of the gas introduction side and the gas delivery side in the nitrogen enrichment means. be able to. However, when separating the oxygen and nitrogen in the intake air, the difference in the separation ratio between the two is not so large. Therefore, in order to increase the gas separation efficiency, it is necessary to use a large pressure device such as a turbocharger compressor. . For this reason, there is a concern about an increase in size of the apparatus.

  On the other hand, as described above, when carbon dioxide and water vapor are separated from exhaust gas, gas separation can be easily and accurately performed as compared with the case where oxygen is separated from natural intake air. Further, when the nitrogen-enriched gas is generated using the high-temperature exhaust gas, the separation efficiency by the nitrogen-enriching means can be improved as compared with the case where the nitrogen-enriched gas is generated using the normal temperature intake air.

  Therefore, as in the invention according to claim 3, the invention according to claim 1 or 2 also includes a pump that pressurizes the exhaust gas in the guide passage and sends it to the nitrogen-enriching means. Gas separation can be performed with high efficiency. That is, in the present invention, the pressurizing device for pressurizing the gas can be downsized as compared with the case where a compressor of a turbocharger or the like is used.

  According to a fourth aspect of the present invention, in the third aspect of the present invention, the pump is a pump capable of adjusting the flow rate of the exhaust gas, and is delivered by the pump based on the operating state of the engine. Since the control means for controlling the flow rate of the exhaust gas is provided, the flow rate of the exhaust gas sent to the nitrogen enrichment means by using a pump for pressurizing the exhaust gas, and consequently the nitrogen rich gas supplied to the intake passage of the engine The flow rate of the activated exhaust can be controlled according to the operating state of the engine.

  Alternatively, in the invention according to claim 3, the pump is configured as a pump that sends exhaust gas at a predetermined flow rate, and is based on a throttle valve that adjusts the flow rate of the exhaust gas supplied to the intake passage and the operating state of the internal combustion engine. And a control means for controlling the opening of the throttle valve. According to this configuration, it is possible to control the flow rate of the nitrogen-enriched exhaust gas supplied to the intake passage of the engine according to the operating state of the engine while employing a simple pump that cannot adjust the flow rate of the exhaust gas.

  According to a fifth aspect of the present invention, in the invention according to any one of the first to fourth aspects, a flow rate adjustment valve is provided for adjusting a flow rate of the exhaust gas supplied to the intake passage. According to this structure, even if it is a structure which does not have a pump etc. which can adjust the flow volume of exhaust_gas | exhaustion, the flow volume of the exhaust_gas | exhaustion supplied to an intake passage can be adjusted, and simplification of an apparatus can be achieved.

  According to a sixth aspect of the invention, there is provided the concentration control valve according to any one of the first to fifth aspects, wherein the concentration control valve adjusts a nitrogen concentration of the exhaust gas supplied to the intake passage. According to this configuration, the nitrogen concentration of the exhaust gas supplied to the intake passage can be adjusted.

  The invention described in claim 7 includes the steps of inducing exhaust from the exhaust passage of the internal combustion engine to the nitrogen enrichment means, the step of increasing the nitrogen concentration of the exhaust by the nitrogen enrichment means, and the nitrogen enrichment means by the nitrogen enrichment means. And supplying the exhaust gas whose concentration has been increased to the intake passage of the engine.

  According to the said process, it can suppress that the apparatus which isolate | separates gas similarly to the invention of Claim 1 enlarges.

  The invention according to claim 8 is the invention according to claim 7, wherein the nitrogen enriching means includes a step of increasing the nitrogen concentration of the exhaust gas by separating carbon dioxide and water vapor from the exhaust gas. Similarly to the second aspect of the invention, the nitrogen concentration of the exhaust gas can be made higher and the thermal efficiency of the internal combustion engine can be improved.

The schematic diagram which shows the outline | summary of a nitrogen enriched gas supply apparatus. The figure which shows the permeability | transmittance of each gas component with respect to a gas separation membrane. The flowchart which shows the process sequence of nitrogen-rich exhaust gas supply control. The schematic diagram which shows the outline | summary of the nitrogen-rich gas supply apparatus of other embodiment.

  Hereinafter, an embodiment will be described with reference to the drawings.

  This embodiment is a nitrogen-enriched exhaust gas supply device that guides exhaust gas from an internal combustion engine mounted on a vehicle to a nitrogen-enriched gas generation device, increases the nitrogen concentration, and supplies the exhaust gas to the intake passage of the internal combustion engine. It has become.

  As shown in FIG. 1, an internal combustion engine 10 is connected to an intake passage 11 that supplies intake air to its combustion chamber. The internal combustion engine 10 employs a gasoline engine in which a mixture of gasoline as fuel and intake air is ignited by a spark plug and burned. The intake passage 11 is provided with a throttle valve 12 that adjusts the flow rate of intake air. The throttle valve 12 is driven by a throttle actuator 13. The actuator 13 includes an electric motor, a gear, and the like, and is driven based on a drive signal from an ECU (electronic control unit) 20. Then, the opening degree of the throttle valve 12 is controlled through the driving of the actuator 13 by the ECU 20.

  Connected to the internal combustion engine 10 is an exhaust passage 16 for discharging exhaust gas generated by combustion of the air-fuel mixture. The exhaust passage 16 is provided with a purification device 17 that purifies the exhaust. The purification device 17 is composed of a three-way catalyst that reduces carbon monoxide, hydrocarbons, and nitrogen oxides in the exhaust gas.

  The exhaust passage 16 is connected to a guide passage 31 that guides part of the exhaust to the nitrogen-enriched gas generator 30. The guide passage 31 is connected to a portion of the exhaust passage 16 on the downstream side of the exhaust with respect to the purification device 17. For this reason, the exhaust gas purified by the purification device 17, that is, the exhaust gas in which carbon monoxide, hydrocarbons and nitrogen oxides are purified into carbon dioxide, water vapor and nitrogen is introduced into the guide passage 31. Further, in the internal combustion engine 10, when combustion is performed in a state where oxygen and fuel in the intake air react without excess or deficiency, the fuel is completely burned and generation of nitrogen oxides is suppressed. The exhaust mainly contains nitrogen, carbon dioxide and water vapor. In other words, in that case, the oxygen in the exhaust gas is relatively low.

  The induction passage 31 is provided with a pump 32 that pressurizes exhaust gas and sends it to the nitrogen-enriched gas generation device 30. The pump 32 is an electric pump that can adjust the flow rate of exhaust gas to be sent out, and is driven based on a drive signal from the ECU 20. The pump 32 employs a pump that has a lower ability to pressurize the gas than a compressor of a turbocharger, that is, a pump that pressurizes the gas at a relatively low pressure. For this reason, the apparatus which pressurizes gas can be reduced in size. Then, the flow rate of the exhaust gas delivered by the pump 32 is controlled through the driving of the pump 32 by the ECU 20.

  A nitrogen-enriched gas generating device 30 (nitrogen-enriching means) is connected downstream of the pump 32 in the induction passage 31, and exhaust gas pressurized by the pump 32 is introduced into the device 30 through the induction passage 31. The The device 30 increases the nitrogen concentration in the exhaust based on the difference in permeability of each gas with respect to the separation member 30a. Further, a supply passage 36 is connected to the device 30, and exhaust gas (nitrogen-enriched exhaust gas) whose nitrogen concentration has been increased by the device 30 is supplied to the intake passage 11 of the internal combustion engine 10 through the supply passage 36.

  Specifically, the separation member 30a of the apparatus 30 is configured by a bundle of hollow fiber-like polymer membranes (hollow fiber membranes) made of polyimide resin or the like, and each gas has a permeability to the hollow fiber membrane. Different. And while exhaust gas is introduced into the hollow part of the hollow fiber membrane and the exhaust gas flows through the hollow part of the hollow fiber membrane, gas having a smaller molecular diameter than nitrogen molecules, such as carbon dioxide and water vapor, rapidly passes through the hollow fiber membrane. To penetrate. For this reason, the exhaust with an increased nitrogen concentration flows out from the downstream end of the exhaust in the hollow fiber membrane. On the other hand, the gas which permeate | transmitted the hollow fiber membrane is discharged | emitted in air | atmosphere through the discharge passage 30b of the apparatus 30. FIG.

  The material and shape of the separation member 30a are not limited to the above, and other materials and shapes such as a flat plate-shaped separation membrane made of another resin can be used as appropriate. Specifically, an oxygen-enriched membrane (gas separation membrane) made of, for example, silicon having the property that gas molecules dissolve in the membrane, and the rate at which gas molecules dissolve, diffuse, and desorb in this oxygen-enriched membrane Separates carbon dioxide, water vapor and nitrogen by utilizing the difference between gas molecules. At this time, water vapor or carbon dioxide has a higher permeation rate with respect to the oxygen-enriched film than nitrogen or oxygen.

  Further, in the device 30, the nitrogen concentration (separation concentration) in the exhaust gas sent out from the device 30 varies depending on the pressure of the exhaust gas supplied to the device 30, and the higher the exhaust gas pressure, the higher the nitrogen concentration. Become. Conversely, when the separation efficiency of nitrogen separation is low, it is necessary to increase the pressure of the gas introduced into the apparatus 30 by a relatively large apparatus such as a turbocharger compressor. There is a concern about enlargement.

  Here, when performing gas separation by the separation member 30a, the present inventors mainly separate water vapor, carbon dioxide, and nitrogen contained in the exhaust gas rather than separating oxygen and nitrogen mainly contained in the intake air. We focused on the fact that it is easier and more accurate to separate the two. More specifically, the permeability to the separation member 30a is different between gas molecules, and attention has been paid to the fact that carbon dioxide and water vapor have higher membrane permeability than nitrogen and oxygen.

  FIG. 2 is a diagram showing the permeability of each gas component with respect to the gas separation membrane as an example representing the difference in membrane permeability between gases. In addition, in FIG. 2, membrane permeability is represented as a separation ratio of each gas component with respect to nitrogen, and it shows that permeability is higher with respect to a gas separation membrane than nitrogen, so that a separation ratio is large.

  In FIG. 2, the separation ratio of oxygen to nitrogen is 2.5, and the separation ratio is not so large. On the other hand, the separation ratio of carbon dioxide gas to nitrogen is 12.6, and the separation ratio of water vapor is 22. Carbon dioxide and water vapor have a larger separation ratio of nitrogen than oxygen. For this reason, it can be said that the separation of carbon dioxide and water vapor from the exhaust gas is easier to separate and the separation accuracy is higher than the separation of oxygen from the intake air (natural intake air) consisting of the atmosphere. Therefore, by using the gas introduced into the separation member 30a as exhaust, gas separation by the separation member 30a can be performed at a relatively low pressure. In other words, when the exhaust of the internal combustion engine 10 is used, it is less necessary to pressurize the gas to a high pressure in order to increase the nitrogen concentration of the gas.

  Therefore, in the present embodiment, a nitrogen-enriched gas is generated from the exhaust gas, and the generated nitrogen-enriched gas is supplied to the intake passage 11 of the internal combustion engine 10. Specifically, in the nitrogen-rich exhaust gas supply device of FIG. 1, the induction passage 31 that guides exhaust gas from the exhaust passage 16 of the internal combustion engine 10 to the nitrogen-rich gas generation device 30 and the nitrogen-rich gas generation device 30 A supply passage 36 for supplying exhaust gas to be supplied to the intake passage 11 is provided, so that nitrogen-enriched gas generated by using exhaust instead of intake air is supplied to the intake passage 11.

  Furthermore, when exhaust gas is used instead of intake air, the gas to be separated that passes through the permeable membrane has a high temperature due to the combustion of the air-fuel mixture. Here, as a property of the permeable membrane, it is considered that the higher the temperature of the gas introduced into the permeable membrane, the higher the efficiency in increasing the nitrogen concentration by the permeable membrane. For this reason, when high-temperature exhaust gas generated by combustion of the air-fuel mixture is introduced into the permeable membrane, the separation efficiency for increasing the nitrogen concentration is higher than when natural air intake at normal temperature is introduced into the permeable membrane. Get higher. Therefore, when supplying nitrogen-enriched gas to the intake passage 11 and using exhaust instead of intake, it is possible to employ a small electric pump as the pump 32, and the thickness of the permeable membrane used for gas separation. It is possible to reduce the thickness of the separation member 30a.

  Further, the thermal efficiency of the internal combustion engine 10 increases as the specific heat ratio κ (ratio between the constant pressure specific heat Cp and the constant volume specific heat Cv) of the working fluid increases. Specifically, the theoretical thermal efficiency η of the gasoline engine is expressed by the following equation. In the following equation, ε is a compression ratio, and κ = Cp / Cv.

η = 1− (1 / ε) ^κ−1

Here, nitrogen has a larger specific heat ratio κ than carbon dioxide and water vapor. Specifically, for example, when the gas temperature is 900 K, the specific heat ratio of carbon dioxide is κco ₂ = 1.19, and the specific heat ratio of water vapor is Whereas κh ₂ o = 1.26, the specific heat ratio of nitrogen is κn ₂ = 1.35. For this reason, when carbon dioxide and water vapor are separated from the exhaust gas, the specific heat ratio κ of the exhaust gas becomes larger than when gas separation is not performed. Therefore, when supplying the nitrogen-enriched exhaust gas in which the nitrogen concentration is increased by separating carbon dioxide and water vapor from the exhaust gas to the internal combustion engine 10, it is compared with the case where the exhaust gas without increasing the nitrogen concentration is supplied to the internal combustion engine 10 as it is. Thus, the thermal efficiency of the internal combustion engine 10 is improved.

  The supply passage 36 is connected to a portion of the intake passage 11 on the downstream side of the intake air from the throttle valve 12. The supply passage 36 is provided with a nitrogen-rich exhaust valve 37 (flow rate control valve) for adjusting the flow rate of the nitrogen-rich exhaust, and the nitrogen-rich exhaust valve 37 is driven by a valve actuator 38. The valve actuator 38 is configured by an electromagnetic solenoid or the like, and is driven based on a drive signal from the ECU 20. Then, the opening degree of the nitrogen-rich exhaust valve 37 is controlled through the driving of the valve actuator 38 by the ECU 20.

  The ECU 20 is a microcomputer that includes a CPU, a RAM, a ROM, an input / output interface, and the like. The ECU 20 includes an accelerator sensor 41 that detects the amount of depression of the accelerator pedal of the vehicle, a rotational speed sensor 42 that detects the rotational speed of the internal combustion engine 10, an intake flow sensor 43 that detects the flow rate of intake air in the intake passage 11, and the exhaust passage 16. , A detection signal from an oxygen concentration sensor 44 or the like that detects the oxygen concentration in the portion upstream of the exhaust gas from the purification device 17 is input. Then, the CPU of the ECU 20 sends out the fuel injection amount control of the internal combustion engine 10, the opening degree control of the throttle valve 12, and the pump 32 using a map, a program or the like stored in the ROM based on these detection signals. Exhaust flow control, opening control of the nitrogen-rich exhaust valve 37, and the like are executed.

  In the nitrogen-rich exhaust gas supply device having such a configuration, nitrogen-rich exhaust gas supply amount control for controlling the amount of nitrogen-rich exhaust gas supplied to the internal combustion engine 10 is executed by the processing procedure shown in the flowchart of FIG. This process is repeatedly executed by the ECU 20 with a predetermined cycle.

  First, a target supply amount of nitrogen-rich exhaust is set based on the operating state of the internal combustion engine 10 (S11). Specifically, the target supply amount of the nitrogen-enriched exhaust gas is set by referring to a map stored in the ROM of the ECU 20 based on detection signals from the accelerator sensor 41 and the rotation speed sensor 42. This map defines the relationship between the amount of depression of the accelerator pedal as the load of the internal combustion engine 10, the rotational speed of the internal combustion engine 10, and the target supply amount of nitrogen-rich exhaust. The target supply amount of the nitrogen-enriched exhaust gas is specified to increase as the accelerator pedal depression amount increases and as the rotational speed of the internal combustion engine 10 increases.

  At the same time, the opening degree of the throttle valve 12 is controlled based on the operating state of the internal combustion engine 10 (S12). Specifically, the target opening of the throttle valve 12 is set based on detection signals from the accelerator sensor 41, the rotation speed sensor 42, the intake flow rate sensor 43, etc., and the opening of the throttle valve 12 is controlled to the target opening. Then, the throttle actuator 13 is driven.

  Subsequently, the driving of the pump 32 and the opening degree of the nitrogen-rich exhaust valve 37 are controlled based on the target supply amount of the nitrogen-rich exhaust (S13). Specifically, by controlling the driving of the pump 32, the flow rate of the exhaust gas sent from the pump 32 is controlled. That is, the pump 32 pressurizes and delivers the exhaust gas, and adjusts the flow rate of the exhaust gas to be delivered. Then, the nitrogen concentration of the exhaust is increased by the nitrogen-enriched gas generator 30, and the flow rate of the nitrogen-enriched exhaust is controlled through the opening degree control of the nitrogen-enriched exhaust valve 37. Note that the flow rate of the nitrogen-enriched exhaust gas supplied from the supply passage 36 to the intake passage 11 is affected by the pressure in the intake passage 11. The opening is controlled. As a result, a target supply amount of nitrogen-enriched exhaust gas is supplied from the supply passage 36 to the intake passage 11. Thus, this process is terminated.

  The embodiment described above has the following advantages.

  Exhaust gas is guided from the exhaust passage 16 of the internal combustion engine 10 to the nitrogen-enriched gas generating device 30 through the induction passage 31, and the nitrogen concentration of the exhaust gas is increased based on the difference in permeability of each gas with respect to the separation member 30a. Then, the exhaust gas (nitrogen-enriched exhaust gas) whose nitrogen concentration is increased by the device 30 is supplied to the intake passage 11 of the internal combustion engine 10 through the supply passage 36.

  Here, the exhaust gas generated by the combustion of the mixture of fuel and intake air in the internal combustion engine 10 contains nitrogen, carbon dioxide, and water vapor, and the permeability of the carbon dioxide and water vapor to the separation member 30a is oxygen permeation. Higher than sex. For this reason, gas separation by the separation member 30a can be performed at a low pressure when separating carbon dioxide and water vapor from the exhaust as compared to separating oxygen from intake air (natural intake air) consisting of the atmosphere. Further, the higher the temperature of the gas, the higher the efficiency in increasing the nitrogen concentration by the separation member 30a. For this reason, when producing | generating a nitrogen-enriched gas using high temperature exhaust_gas | exhaustion, efficiency can be improved rather than the case where producing | generating a nitrogen-enriched gas using normal temperature natural air intake. As a result, it is possible to suppress an increase in size of a device that pressurizes the gas or a device that separates the gas.

  In the internal combustion engine 10, when combustion is performed in a state in which oxygen and fuel in the intake air react without excess or deficiency, the exhaust mainly contains nitrogen, carbon dioxide, and water vapor.

  Therefore, since the nitrogen-enriched gas generating device 30 increases the nitrogen concentration of the exhaust gas by separating carbon dioxide and water vapor from the exhaust gas, the nitrogen concentration of the exhaust gas can be further increased. Here, the thermal efficiency η of the internal combustion engine 10 increases as the specific heat ratio κ (ratio between the constant pressure specific heat Cp and the constant volume specific heat Cv) of the working fluid increases. Since nitrogen has a larger specific heat ratio κ than carbon dioxide and water vapor, the specific heat ratio κ of the exhaust gas can be increased by separating carbon dioxide and water vapor from the exhaust gas. As a result, the thermal efficiency of the internal combustion engine 10 can be improved as compared with the case where exhaust gas whose nitrogen concentration is not increased is supplied to the internal combustion engine 10. In addition, it is not necessary to form a special combustion state such as lean combustion for increasing the specific heat ratio κ.

  Since the pump 32 for pressurizing the exhaust gas in the guide passage 31 and sending it to the nitrogen-enriched gas generating device 30 is provided, the pressurizing device for pressurizing the gas is downsized compared to the case of using a turbocharger compressor or the like. can do.

  The pump 32 is an electric pump capable of adjusting the flow rate of exhaust gas, and the ECU 20 uses the pump 32 for pressurizing the exhaust gas in order to control the flow rate of exhaust gas delivered by the pump 32 based on the operating state of the internal combustion engine 10. Then, the flow rate of the exhaust gas sent to the nitrogen-enriched gas generation device 30 and the flow rate of the nitrogen-rich exhaust gas supplied to the intake passage 11 of the internal combustion engine 10 are controlled according to the operating state of the internal combustion engine 10. Can do.

  Since carbon dioxide, water vapor, and nitrogen have a larger separation ratio difference (difference in membrane permeability) than oxygen and nitrogen, by separating carbon dioxide and water vapor from exhaust gas, air intake (natural intake) ), The separation accuracy can be improved, and as a result, the nitrogen concentration of the nitrogen-enriched gas can be increased.

  It is not limited to the said embodiment, For example, it can also implement as follows.

  In the above embodiment, the opening degree of the nitrogen-enriched exhaust valve 37 is controlled by the ECU 20, but an open / close valve is employed instead of the nitrogen-enriched exhaust valve 37 that can adjust the opening degree. The on-off valve can be switched between an open state and a closed state. Further, the nitrogen-rich exhaust valve 37 and the opening / closing valve can be omitted. Even in these cases, the flow rate of the nitrogen-rich exhaust gas supplied to the intake passage 11 can be controlled by controlling the flow rate of the exhaust gas sent out by the pump 32.

  In the above embodiment, an electric pump capable of adjusting the flow rate of exhaust gas is adopted as the pump 32, but a pump that sends exhaust gas at a predetermined flow rate can also be adopted. Even in this case, the nitrogen-rich exhaust valve 37 (flow rate control valve) that adjusts the flow rate of the exhaust gas supplied to the intake passage 11 and the nitrogen-rich exhaust valve 37 are opened based on the operating state of the internal combustion engine 10. And the ECU 20 that controls the degree of exhaust gas, the flow rate of the nitrogen-enriched exhaust gas that is supplied to the intake passage 11 of the internal combustion engine 10 is determined as the operating state of the internal combustion engine 10 while adopting a simple pump that cannot adjust the flow rate of the exhaust gas. Can be controlled according to.

  In the above embodiment, the exhaust gas is pressurized and delivered by the pump 32. However, if the pressure necessary to increase the nitrogen concentration in the exhaust gas introduced into the nitrogen-enriched gas generation device 30 can be secured, The pump 32 can be omitted. In that case, an exhaust throttle valve for adjusting the flow rate of exhaust gas is provided in the exhaust passage 16 on the downstream side of the connection portion of the induction passage 31 so that the pressure of the exhaust gas introduced into the nitrogen-enriched gas generating device 30 You may make it raise. Further, the pressure of the exhaust gas introduced into the device 30 is also increased by connecting a guide passage for guiding the exhaust gas to the nitrogen-enriched gas generation device 30 on the upstream side of the exhaust gas from the purification device 17 in the exhaust passage 16. be able to. On the other hand, when it is desired to increase the pressure of the exhaust gas introduced into the nitrogen-enriched gas generation device 30, a compressor having a higher ability to pressurize the exhaust gas than the pump 32 can be adopted.

  In addition to the configuration of the above-described embodiment, a recirculation passage that bypasses the nitrogen-enriched gas generation device 30 (nitrogen-enriching means) and recirculates the exhaust gas of the internal combustion engine 10 to the intake passage 11, and the supply passage 36 to the intake passage 11 The internal combustion engine 10 is provided with a switching valve (switching means) that switches between a state in which exhaust gas having a high nitrogen concentration is supplied to the exhaust gas and a state in which exhaust gas is supplied from the recirculation passage to the intake passage 11. Depending on the operation state, the state in which the nitrogen-enriched exhaust gas is supplied and the state in which the exhaust gas whose nitrogen concentration is not increased may be switched.

  In addition to the configuration of the above embodiment or in place of the nitrogen enriched exhaust valve 37 of the above embodiment, for example, as shown in FIG. 4, the nitrogen enrichment in the nitrogen enriched gas generation device 30 or in the supply passage 36 A valve (concentration control valve) 39 for adjusting the nitrogen concentration of the nitrogen-enriched exhaust gas is provided on the downstream side of the gas generating device 30, and the valve opening degree is controlled by the ECU 20 so that the nitrogen-enriched gas generating device 30 delivers the valve. The nitrogen concentration of the nitrogen enriched exhaust is controlled. As a nitrogen concentration adjustment mechanism, for example, the valve opening is adjusted by the ECU 20 to change the exhaust residence time in the nitrogen-enriched gas generator 30. At this time, as the residence time of the exhaust gas becomes longer, the permeation amount of carbon dioxide and water vapor increases with respect to the permeation amount of nitrogen. As a result, the nitrogen concentration of the nitrogen-enriched exhaust gas sent from the nitrogen-enriched gas generation device 30 Will be higher. Therefore, in order to increase the nitrogen concentration in the nitrogen-enriched exhaust gas supplied to the intake passage 11, the drive of the valve 39 is controlled so that the valve opening is reduced.

  In the above embodiment, the separation member 30a of the nitrogen-enriched gas generating device 30 is configured by a hollow fiber membrane or an oxygen-enriched membrane, and exhaust gas separation is performed by utilizing the property that the membrane permeation speed differs between gas molecules. However, the exhaust gas separation method is not limited to this. For example, a PSA (Pressure Swing Adsorption) system is employed in which gas separation is performed using the property that the adsorption ability differs between gas molecules. In this case, the separation member 30a is made of a microporous material such as zeolite or activated carbon. In general, zeolite is capable of selectively adsorbing carbon dioxide more selectively than nitrogen molecules and oxygen molecules, so that carbon dioxide and nitrogen in the exhaust gas can be easily separated with high accuracy.

  In the above embodiment, a gasoline engine is employed as the internal combustion engine 10, but not limited to a gasoline engine, a diesel engine may be employed. In that case, the purification device 17 is configured by a DPF (diesel particulate filter), a NOx storage reduction catalyst, or the like. Even with such a configuration, it is possible to supply the internal combustion engine 10 with exhaust gas (nitrogen-enriched exhaust gas) in which the nitrogen concentration is increased by separating carbon dioxide and water vapor in the exhaust gas.

  DESCRIPTION OF SYMBOLS 10 ... Internal combustion engine, 11 ... Intake passage, 16 ... Exhaust passage, 30 ... Nitrogen-rich gas production | generation apparatus as a nitrogen enrichment means, 30a ... Separation member, 31 ... Induction passage, 36 ... Supply passage

Claims (8)

Nitrogen enrichment means for increasing the nitrogen concentration of the gas;
An induction passage for inducing exhaust from the exhaust passage of the internal combustion engine to the nitrogen enriching means;
A nitrogen-enriched gas supply apparatus for an internal combustion engine, comprising: a supply passage for supplying the exhaust gas whose nitrogen concentration is increased by the nitrogen-enriching means to an intake passage of the engine.   2. The nitrogen-enriched gas supply device for an internal combustion engine according to claim 1, wherein the nitrogen-enriching means increases the nitrogen concentration of the exhaust gas by separating carbon dioxide and water vapor from the exhaust gas.   3. The nitrogen-enriched gas supply device for an internal combustion engine according to claim 1, further comprising a pump that pressurizes the exhaust gas in the induction passage and sends the pressurized exhaust gas to the nitrogen-enriching unit. The pump is a pump capable of adjusting the flow rate of the exhaust,
4. The nitrogen-enriched gas supply device for an internal combustion engine according to claim 3, further comprising control means for controlling a flow rate of the exhaust gas sent by the pump based on an operating state of the engine.   The nitrogen-enriched gas supply device for an internal combustion engine according to any one of claims 1 to 4, further comprising a flow rate adjusting valve that adjusts a flow rate of the exhaust gas supplied to the intake passage.   The nitrogen-enriched gas supply device for an internal combustion engine according to any one of claims 1 to 5, further comprising a concentration control valve that adjusts a nitrogen concentration of the exhaust gas supplied to the intake passage. Inducing exhaust from the exhaust passage of the internal combustion engine to the nitrogen enrichment means;
Increasing the nitrogen concentration of the exhaust by the nitrogen enrichment means;
And supplying the exhaust gas whose nitrogen concentration has been increased by the nitrogen enriching means to the intake passage of the engine.   8. The nitrogen-enriched gas supply method for an internal combustion engine according to claim 7, wherein the nitrogen-enriching means increases the nitrogen concentration of the exhaust gas by separating carbon dioxide and water vapor from the exhaust gas.

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