JP2010255500A - Intake air composition variable internal combustion engine and method for controlling the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To make intake air composition appropriate according to an engine operation state. <P>SOLUTION: A gas separation device 24 is disposed at a downstream side of a catalyst 22 in an exhaust pipe 21, exhaust gas purified by a catalyst 22 is made to flow into a gas separation device 24, and nitrogen and a carbon dioxide are separated from the exhaust gas. The nitrogen and the carbon dioxide separate by the gas separation device 24 are introduced to an intake air passage of the engine 11 with its mix rate and/or mix quantity (intake system introduction quantity) which is changed according to an engine operation state. Consequently, the composition of intake air (concentration of the nitrogen and the carbon dioxide) can be changed to a composition suitable for the engine operation state according to the engine operation state, and theoretical thermal efficiency and actual efficiency are improved while reducing the occurrence of the knocking and the formation of NOx. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to an intake composition variable internal combustion engine having a function of changing the ratio (composition ratio) of carbon dioxide and nitrogen in intake air, and a control apparatus therefor.

As a conventional intake composition variable internal combustion engine, as described in Patent Document 1 (Japanese Patent Laid-Open No. 3-217649), the problem is to reduce NOx emission without increasing particulate emission. and those to the CO ₂ separation device for separating the carbon dioxide gas of the EGR gas to be recirculated to the intake side from the exhaust pipe is provided, the addition of carbon dioxide gas separated in the CO ₂ separation device to the intake of an internal combustion engine is there.

JP-A-3-217649

  In the technique of Patent Document 1 described above, the effect of reducing the combustion temperature (pressure) of the air-fuel mixture by reducing the combustion temperature (pressure) of the air-fuel mixture by adding carbon dioxide gas at high load can be expected, but carbon dioxide has a specific heat ratio κ of air. Therefore, if a large amount of carbon dioxide is added to the intake air at a low load, the specific heat ratio κ of the intake air is lowered, the theoretical thermal efficiency is lowered, and the fuel efficiency is lowered.

  Here, the theoretical thermal efficiency in the Otto cycle is expressed by the following equation, and it is understood that the specific heat ratio κ may be increased to increase the theoretical thermal efficiency.

  In general, as shown in FIG. 3, the exhaust gas of a vehicle fueled with gasoline contains 70% nitrogen and 12.5% carbon dioxide. As shown in FIG. 4, carbon dioxide has a large constant volume molar specific heat compared to air and nitrogen. Therefore, when reducing the combustion temperature of the air-fuel mixture and reducing NOx emissions, carbon dioxide should be added to the intake air. As shown in FIG. 5, carbon dioxide has a smaller specific heat ratio κ than air and nitrogen. Therefore, when carbon dioxide is added to the intake air, the specific heat ratio κ of the intake air decreases and the theoretical thermal efficiency decreases. .

  In order to increase the specific heat ratio κ of the intake air, nitrogen can be added to the intake air to increase the proportion of nitrogen in the intake air. On the other hand, if the specific heat ratio κ is large, the compression top dead center temperature on the Otto cycle Therefore, under conditions where knocking is likely to occur, such as when the load is high, it is necessary to retard the ignition timing, resulting in a decrease in actual efficiency. The compression top dead center temperature decreases as the constant volume specific heat (heat capacity) of the combustion gas increases. As shown in FIG. 4, in order to increase the constant volume specific heat, it is only necessary to add carbon dioxide to the intake air to increase the proportion of carbon dioxide in the intake air, thereby increasing the proportion of carbon dioxide. It is possible to suppress the occurrence of knock by reducing the compression top dead center temperature.

  Therefore, the problem to be solved by the present invention is to optimize the composition of the intake air in accordance with the operating state of the internal combustion engine, and to increase the theoretical thermal efficiency and the actual efficiency while reducing the generation of knocks and NOx. An object is to provide a variable composition internal combustion engine and a control device therefor.

  In order to solve the above-mentioned problem, an invention according to claim 1 is directed to an intake composition variable internal combustion engine having a function of changing a ratio of carbon dioxide and nitrogen in intake air. The gas separation means for separating the carbon dioxide and the carbon dioxide, and the mixing ratio and / or the mixing amount of nitrogen and carbon dioxide separated by the gas separation means according to the operating state of the internal combustion engine are changed and introduced into the intake passage of the internal combustion engine And a control means.

  In this configuration, the composition of the intake air (the composition of the nitrogen and carbon dioxide is changed by adding to the intake air by changing the mixing ratio and / or the mixing amount of nitrogen and carbon dioxide separated from the exhaust gas according to the operating state of the internal combustion engine. (Concentration) can be changed to a composition suitable for the operating state of the internal combustion engine, and the theoretical thermal efficiency and actual efficiency can be increased while reducing the occurrence of knocks and NOx.

  Specifically, as described in claim 2, it is preferable to introduce a gas having a higher nitrogen mixing ratio in a low load range and a higher carbon dioxide mixing ratio into the intake passage as the load becomes higher. In the low load range, the compression top dead center temperature is lower than in the high load range and knocking is less likely to occur. Therefore, in the low load range, the nitrogen mixing ratio is increased to increase the specific heat ratio κ of the intake air. The theoretical thermal efficiency can be increased. Further, by increasing the mixing ratio of carbon dioxide as the load becomes higher, and suppressing the increase in the compression top dead center temperature as the load becomes higher, the occurrence of knocking can be suppressed even in a high load range. Thereby, the theoretical thermal efficiency and the actual efficiency can be increased by increasing the mixing ratio of nitrogen within a range in which the occurrence of knocking can be suppressed.

  Further, as in claim 3, the mixing ratio and / or mixing amount of nitrogen and carbon dioxide may be changed based on the cooling water temperature or oil temperature of the internal combustion engine. In short, the lower the temperature of the internal combustion engine, the less likely knocking occurs. Therefore, the mixing ratio and / or mixing amount of nitrogen and carbon dioxide should be changed based on the cooling water temperature or oil temperature correlated with the temperature of the internal combustion engine. For example, the mixing ratio and / or mixing amount of nitrogen and carbon dioxide can be appropriately changed according to the temperature of the internal combustion engine.

  Specifically, as described in claim 4, it is preferable to increase the mixing ratio and / or mixing amount of nitrogen as the cooling water temperature or oil temperature of the internal combustion engine is lower. As the temperature of the internal combustion engine is lower, knocking is less likely to occur. Therefore, it is possible to increase the theoretical thermal efficiency by increasing the mixing ratio and / or amount of nitrogen in the low temperature range.

  Further, as in claim 5, the lower the rotational speed of the internal combustion engine, the higher the mixing ratio and / or the mixing amount of carbon dioxide. As the rotational speed of the internal combustion engine is lower, knocking is more likely to occur. Therefore, if the mixing ratio and / or amount of carbon dioxide is increased as the rotational speed of the internal combustion engine is lower, knocking occurs in the low rotational speed region. Can be suppressed.

  In the present invention, nitrogen and carbon dioxide may be separated from a part of the exhaust gas (for example, EGR gas). However, considering that the ratio of carbon dioxide in the exhaust gas is small, as in claim 6 In addition, all exhaust gas flowing through the exhaust passage is passed through the exhaust passage of the internal combustion engine, and during the passage, nitrogen and carbon dioxide are separated from the exhaust gas, and a mixed gas of nitrogen and carbon dioxide is taken into the intake air of the internal combustion engine. It is good also as a structure which provided the gas separation apparatus introduce | transduced into a channel | path. According to this configuration, it is possible to ensure the amount of carbon dioxide by flowing all the exhaust gas flowing through the exhaust passage to the gas separation device.

  In this case, as described in claim 7, it is preferable that the gas separation device is provided with a mixing adjusting means for changing the mixing ratio and / or mixing amount of the separated nitrogen and carbon dioxide and introducing them into the intake passage. In this way, it is possible to control to change the mixing ratio and / or the mixing amount of nitrogen and carbon dioxide according to the operating state of the internal combustion engine.

  Further, considering that particulates (particulate matter PM) are included in the exhaust gas, a gas separation device may be provided on the downstream side of the catalyst in the exhaust passage as in claim 8. . In this way, in the process of exhaust gas passing through the catalyst, the particulate matter in the exhaust gas is removed and then the exhaust gas flows into the gas separation device. It is possible to prevent the occurrence of problems such as the vent hole being clogged with particulates.

FIG. 1 is a schematic configuration diagram of an entire engine control system according to an embodiment of the present invention. FIG. 2 is a diagram illustrating a configuration example of the gas separation device. FIG. 3 is a diagram for explaining the composition of air (atmosphere) and exhaust gas. FIG. 4 is a diagram for explaining the relationship between the temperature of CO ₂ , air, N ₂ , O ₂ and Ar and the constant volume specific heat. FIG. 5 is a diagram for explaining the relationship between the temperature of CO ₂ , air, N ₂ , O ₂ , and Ar and the specific heat ratio. FIG. 6 is a flowchart showing the flow of processing of the intake composition variable control program. FIG. 7A is a diagram conceptually illustrating an example of the mixture ratio base value map, and FIG. 7B is a diagram conceptually illustrating an example of the N ₂ ratio multiplication coefficient map. FIG. 8A is a diagram conceptually showing an example of the introduction amount base value map, and FIG. 8B is a diagram conceptually showing an example of the introduction amount correction coefficient map. FIG. 9 is a time chart showing an execution example of the intake composition variable control.

Hereinafter, an embodiment embodying a mode for carrying out the present invention will be described.
First, a schematic configuration of the entire engine control system will be described with reference to FIG.
In an intake pipe 12 (intake passage) of an engine 11 that is an internal combustion engine, there are a throttle valve 13 that adjusts the amount of intake air and a throttle opening sensor 14 that detects the opening (throttle opening) of the throttle valve 13. Is provided. A surge tank 15 (intake passage) is provided downstream of the throttle valve 13, and an intake manifold 16 (intake passage) for introducing air into each cylinder of the engine 11 is provided in the surge tank 15. In the vicinity of the intake port of the intake manifold 16, a fuel injection valve 17 for injecting fuel toward the intake port is attached. A spark plug 18 is attached to each cylinder of the engine 11 for each cylinder, and the air-fuel mixture in the cylinder is ignited by the spark discharge of each spark plug 18.

  On the other hand, the exhaust pipe 21 (exhaust passage) of the engine 11 is provided with a catalyst 22 such as a three-way catalyst for purifying the exhaust gas, and the air / fuel ratio or rich / lean of the exhaust gas is provided upstream of the catalyst 22. An exhaust gas sensor 23 (such as an air-fuel ratio sensor or an oxygen sensor) for detection is provided.

Further, a gas separation device 24 is provided on the downstream side of the catalyst 22 in the exhaust pipe 21. As shown in FIG. 2, the gas separation device 24 is provided with a cylindrical gas separation membrane 26 (gas separation means) formed of a hollow fiber membrane made of, for example, polyimide resin in a casing 25, and flows in the exhaust pipe 21. All the exhaust gas flows into the tubular gas separation membrane 26. The gas separation membrane 26 is configured such that CO ₂ (carbon dioxide) is more permeable than N ₂ (nitrogen) in the exhaust gas.

The casing 25 of the gas separation device 24 is provided with a carbon dioxide passage 27 for taking out CO ₂ that has permeated through the gas separation membrane 26, and a nitrogen passage 28 for taking out N ₂ that flows without passing through the gas separation membrane 26. . The carbon dioxide passage 27 and the nitrogen passage 28 merge with the merged exhaust pipe 29 on the downstream side, and a mixing passage 30 for mixing CO ₂ and N ₂ is provided between the carbon dioxide passage 27 and the nitrogen passage 28. The mixing passage 30 is provided with a mixing ratio adjusting valve 31 for adjusting the mixing ratio of CO ₂ and N ₂ . This gas mixture mixing ratio of the opening adjustment by CO ₂ and N ₂ were adjusted mixing ratio adjustment valve 31, the downstream side of the intake passage (the surge tank 15 of the throttle valve 13 of the engine 11 through the EGR passage 32, an exhaust pipe 21 or any one of the intake manifolds 16). The combined exhaust pipe 29 is provided with an introduction amount adjusting valve 33, and the amount of mixed gas introduced into the intake side of the engine 11 through the EGR passage 32 by adjusting the exhaust pressure by adjusting the opening degree of the introduction amount adjusting valve 33. Configured to adjust. In this case, the mixing ratio adjusting valve 31 and the introduction amount adjusting valve 33 function as mixing adjusting means in the claims.

  In the configuration example of FIG. 2, the introduction amount adjustment valve 33 is provided in the merged exhaust pipe 29, but an introduction amount adjustment valve is provided in the EGR passage 32, and the opening side of the introduction amount adjustment valve adjusts the opening of the engine 11. The amount of the mixed gas introduced into may be adjusted.

  Further, the engine 11 is provided with a cooling water temperature sensor 34 for detecting the cooling water temperature and a crank angle sensor 35, and a crank angle and an engine rotation speed Ne are detected based on an output signal of the crank angle sensor 35.

  Outputs of these various sensors are input to an engine control circuit (hereinafter referred to as “ECU”) 36. The ECU 36 is mainly composed of a microcomputer, and executes various engine control programs stored in a built-in ROM (storage medium), so that the fuel injection amount of the fuel injection valve 17 and the like can be determined according to the engine operating state. The ignition timing of the spark plug 18 is controlled. Further, the ECU 36 executes an intake composition variable control program shown in FIG. 6 to be described later, thereby adjusting the opening degrees of the mixing ratio adjusting valve 31 and the introduction amount adjusting valve 33 in accordance with the engine operating state, so that the gas separation membrane The mixing ratio and / or the mixing amount of nitrogen and carbon dioxide separated in 26 are changed and introduced into the intake passage of the engine 11 so that the composition of the intake air (the concentration of nitrogen and carbon dioxide) becomes a composition suitable for the engine operating state. Change.

  The theoretical thermal efficiency in the Otto cycle is expressed by the following equation, and it is understood that the specific heat ratio κ may be increased in order to increase the theoretical thermal efficiency.

In general, as shown in FIG. 3, the exhaust gas of a vehicle fueled with gasoline contains 70% N ₂ and 12.5% CO ₂ . As shown in FIG. 4, CO ₂ has a constant volume specific heat larger than that of air or N ₂ , so when reducing the NOx emission amount by lowering the combustion temperature of the air-fuel mixture, add CO ₂ to the intake air. However, as shown in FIG. 5, since CO ₂ has a smaller specific heat ratio κ than air or N ₂ , when CO ₂ is added to the intake air, the specific heat ratio κ of the intake air decreases and the theoretical thermal efficiency decreases. .

In order to increase the specific heat ratio κ of the intake air, it is only necessary to add N ₂ to the intake air to increase the ratio of N ₂ in the intake air. On the other hand, if the specific heat ratio κ is large, compression top dead on the Otto cycle Since the point temperature becomes high, it is necessary to retard the ignition timing under conditions where knocking is likely to occur, such as when the load is high, and the actual efficiency decreases. The compression top dead center temperature decreases as the constant volume specific heat (heat capacity) of the combustion gas increases. As shown in FIG. 4, in order to increase the constant volume specific heat, it is only necessary to add CO ₂ to the intake air to increase the proportion of CO _{2 in} the intake air, thereby increasing the proportion of CO _2. It is possible to suppress the occurrence of knock by reducing the compression top dead center temperature.

In consideration of such characteristics, in the present embodiment, the N ₂ mixing ratio is increased in the low load region, and the gas with the CO ₂ mixing ratio increasing as the load becomes higher is introduced into the intake system of the engine 11. I have to. In the low load range, the compression top dead center temperature is lower than in the high load range, and knocking is less likely to occur. Therefore, in the low load range, increase the mixing ratio of N ₂ and increase the specific heat ratio κ of the intake air. Therefore, the theoretical thermal efficiency may be increased. Further, by increasing the mixing ratio of CO _{2 as} the load becomes higher, and suppressing the increase in the compression top dead center temperature as the load becomes higher, the occurrence of knocking can be suppressed even in the high load range. As a result, the theoretical thermal efficiency and actual efficiency can be increased by increasing the mixing ratio and mixing amount of N ₂ within a range in which the occurrence of knocking can be suppressed.

Further, since knocking is less likely to occur as the temperature of the engine 11 is lower, the mixing ratio of N ₂ and CO ₂ and the intake system introduction amount are changed based on the coolant temperature (or oil temperature) correlated with the temperature of the engine 11. By doing so, the mixing ratio of N ₂ and CO ₂ and the intake system introduction amount can be appropriately changed according to the temperature of the engine 11.

Specifically, so that increase the coolant temperature (or oil temperature) of the mixing ratio and mixing amount of low that N ₂ of the engine 11. As the temperature of the engine 11 is lower, knocking is less likely to occur. Therefore, it is possible to increase the theoretical thermal efficiency by increasing the mixing ratio and mixing amount of N _{2 in} the low temperature region.

Further, the lower the engine speed Ne, the higher the CO ₂ mixing ratio and the mixing amount. As the engine speed Ne becomes lower, knocking is more likely to occur. Therefore, if the CO ₂ mixing ratio and amount are increased as the engine speed Ne becomes lower, the occurrence of knocking in the low speed region can be suppressed. Can do.

The intake composition variable control of the present embodiment described above is executed by the ECU 36 in the following manner according to the intake composition variable control program of FIG.
The intake composition variable control program of FIG. 6 is repeatedly executed at a predetermined cycle during engine operation, and serves as a control means in the claims. When this program is started, first, at step 101, the engine speed Ne, load, and cooling water temperature are read, and at the next step 102, the current engine speed is referred to with reference to the mixture ratio base value map of FIG. depending on the load and speed Ne to calculate the mixing ratio based values of N ₂ and CO _2, with reference to N ₂ ratio multiplication coefficient map of FIG. 7 (b), N ₂ ratio multiplied in accordance with the present cooling water temperature A coefficient is calculated, and the mixing ratio base value is multiplied by the N ₂ ratio multiplication coefficient to obtain the mixing ratio of N ₂ and CO ₂ .

Here, the mixing ratio base value map of FIG. 7A is set so that the mixing ratio of N ₂ is increased in the low load region, and the mixing ratio of CO ₂ is increased as the load becomes higher. Further, the N ₂ ratio multiplication coefficient map of FIG. 7B is set so that the N ₂ ratio multiplication coefficient is increased and the mixing ratio of N ₂ is increased as the cooling water temperature (or oil temperature) is lower. .

Thereafter, the process proceeds to step 103, and based on the mixing ratio of N ₂ and CO ₂ calculated in step 102, the opening of the mixing ratio adjusting valve 31 that realizes the mixing ratio is calculated by a map or the like.

  Thereafter, the process proceeds to step 104, where the introduction amount base value corresponding to the current engine speed Ne and the load is calculated with reference to the introduction amount base value map of FIG. 8A, and the introduction of FIG. Referring to the amount correction coefficient map, an introduction amount correction coefficient corresponding to the current cooling water temperature is calculated, and the introduction amount base value is multiplied by the introduction amount correction coefficient to obtain the intake system introduction amount.

  Here, the introduction amount base value map of FIG. 8A is set so that the introduction amount is reduced in the low load region and the introduction amount is increased as the load becomes higher. In addition, the introduction amount correction coefficient map in FIG. 8B is set so that the introduction amount correction coefficient is decreased and the intake system introduction amount is decreased as the coolant temperature (or oil temperature) is lower.

Thereafter, the process proceeds to step 105, and based on the intake system introduction amount calculated in step 104, the opening degree of the introduction amount adjusting valve 33 that realizes the intake system introduction amount is calculated by a map or the like. Then, in the next step 106, the opening of the mixing ratio adjusting valve 31 and the opening of the introduction amount adjusting valve 33 are driven to the opening calculated in steps 103 and 105, respectively. The calculated mixing ratio of N ₂ and CO ₂ and the intake system introduction amount are realized.

An execution example of the intake composition variable control of the present embodiment described above will be described with reference to FIG. In the example of FIG. 9, when the engine speed Ne increases, the load increases slightly later, and when the engine speed Ne decreases, the load decreases slightly later. Comparing low temperature and high temperature, under all operating conditions, the mixing ratio of N ₂ is higher at low temperatures than at high temperatures, while the mixing ratio of CO ₂ is lower at higher temperatures. More than. Further, the intake system introduction amount is higher at high temperatures than at low temperatures.

In both cases of low temperature and high temperature, when the load increases, the mixing ratio of N ₂ decreases, the mixing ratio of CO ₂ increases, and the intake system introduction amount increases. On the other hand, when the load decreases, the mixing ratio of N ₂ increases, the mixing ratio of CO ₂ decreases, and the intake system introduction amount decreases.

Further, in both cases of low temperature and high temperature, when the engine rotational speed Ne increases, the intake system introduction amount slightly increases. When the engine rotational speed Ne decreases, the mixing ratio of N ₂ decreases, and CO 2 The mixing ratio of ₂ increases and the intake system introduction amount increases.

  According to the present embodiment described above, the mixing ratio of nitrogen and carbon dioxide separated by the gas separation membrane 26 is adjusted by adjusting the opening degree of the mixing ratio adjusting valve 31 and the introduction amount adjusting valve 33 according to the engine operating state. Since the mixture amount is changed and introduced into the intake passage of the engine 11, the composition of the intake air (nitrogen and carbon dioxide concentrations) is changed to a composition suitable for the engine operation state according to the engine operation state. This makes it possible to increase the theoretical thermal efficiency and actual efficiency while suppressing the occurrence of knocks and NOx.

In addition, in this embodiment, considering that the ratio of CO _{2 in} the exhaust gas is small, a gas separation device 24 is provided in the exhaust pipe 21, and all the exhaust gas flowing in the exhaust pipe 21 is supplied to the gas separation device 24. since to flow, there is an advantage that tends to secure the amount of CO _2. However, the present invention may be configured such that a gas separation device is provided in the EGR passage for returning a part of the exhaust gas to the intake system.

  Further, in the present embodiment, since the gas separation device 24 is provided on the downstream side of the catalyst 22 in the exhaust pipe 21, the particulates in the exhaust gas are removed in the process of passing the exhaust gas. The exhaust gas flows into the gas separation device 24, and it is possible to prevent the occurrence of problems such as clogging of fine holes in the gas separation membrane 26 inside the gas separation device 24 with particulates.

  It should be noted that the present invention can be implemented with various modifications within a range not departing from the gist, such as appropriately changing the configuration of the gas separation device 24.

  DESCRIPTION OF SYMBOLS 11 ... Engine (internal combustion engine), 12 ... Intake pipe (intake passage), 15 ... Surge tank (intake passage), 16 ... Intake manifold (intake passage), 21 ... Exhaust pipe (exhaust passage), 22 ... Catalyst, 24 ... Gas separation device 26 ... Gas separation membrane (gas separation means) 27 ... Carbon dioxide passage 28 ... Nitrogen passage 29 ... Confluence exhaust pipe 30 ... Mixing passage 31 ... Mixing ratio adjusting valve (mixing adjusting means) 32 ... EGR passage, 33 ... Introduction amount adjusting valve (mixing adjusting means), 34 ... Cooling water temperature sensor, 35 ... Crank angle sensor, 36 ... ECU (control means)

Claims (8)

In the intake composition variable internal combustion engine having the function of changing the ratio of carbon dioxide and nitrogen in the intake air,
Gas separation means for separating nitrogen and carbon dioxide from at least part of the exhaust gas of the internal combustion engine;
Control means for introducing into the intake passage of the internal combustion engine by changing the mixing ratio and / or the mixing amount of nitrogen and carbon dioxide separated by the gas separation means in accordance with the operating state of the internal combustion engine. A control device for an intake composition variable internal combustion engine.   2. The intake composition variable according to claim 1, wherein the control means introduces into the intake passage a gas in which the mixing ratio of nitrogen is increased in a low load region and the mixing ratio of carbon dioxide is increased as the load becomes higher. Control device for internal combustion engine.   3. The intake composition variable internal combustion engine according to claim 1, wherein the control unit changes a mixing ratio and / or a mixing amount of nitrogen and carbon dioxide based on a cooling water temperature or an oil temperature of the internal combustion engine. Control device.   4. The control apparatus for an intake composition variable internal combustion engine according to claim 3, wherein the control means increases the mixing ratio and / or mixing amount of nitrogen as the cooling water temperature or oil temperature of the internal combustion engine is lower.   The control device for an intake air composition variable internal combustion engine according to any one of claims 1 to 4, wherein the control means increases the mixing ratio and / or the mixing amount of carbon dioxide as the rotational speed of the internal combustion engine is lower. . In the intake composition variable internal combustion engine having the function of changing the ratio of carbon dioxide and nitrogen in the intake air,
All exhaust gas flowing through the exhaust passage is passed through the exhaust passage of the internal combustion engine, and during the passage, nitrogen and carbon dioxide are separated from the exhaust gas, and a mixed gas of nitrogen and carbon dioxide is supplied to the intake passage of the internal combustion engine. An intake composition variable internal combustion engine comprising a gas separation device to be introduced.   7. The intake composition variable internal combustion engine according to claim 6, wherein the gas separation device has a mixing adjusting means for introducing into the intake passage by changing a mixing ratio and / or mixing amount of the separated nitrogen and carbon dioxide. . The exhaust passage is provided with a catalyst for purifying exhaust gas,
The intake composition variable internal combustion engine according to claim 6 or 7, wherein the gas separation device is provided downstream of the catalyst in the exhaust passage.

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