JP2007218247A - Exhaust emission control device for internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an exhaust emission control device for an internal combustion engine capable of improving exhaust emission when an engine is cool, from immediately after start of the internal combustion engine till before an exhaust emission catalyst temperature reaches a catalyst activation temperature. <P>SOLUTION: This exhaust emission control device is equipped with: an EGR device for recirculating exhaust gas discharged from an internal combustion main body, from an exhaust system further downstream than the exhaust emission catalyst to an intake system of the internal combustion engine; and an oxygen supplying means for supplying high concentration oxygen gas having a higher oxygen concentration than at least that of normal air into the exhaust gas recirculated into the intake system by the EGR system. Exhaust gas discharged from the internal combustion engine main body by the EGR device is recirculated in the intake system from immediately after start of the internal combustion engine until the temperature of the exhaust emission control catalyst reaches the catalyst activation temperature, and the high concentration oxygen gas is supplied to the exhaust gas recirculated in the intake system by the oxygen supplying means. CO and HC in the exhaust gas recirculated in the intake system are subjected to re-combustion and purified. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an exhaust gas purification device for an internal combustion engine that purifies harmful components contained in exhaust gas discharged from an internal combustion engine body, and in particular, an internal combustion engine having an exhaust gas recirculation device (hereinafter referred to as an EGR device). The present invention relates to an exhaust purification device.

  2. Description of the Related Art Conventionally, in an internal combustion engine for automobiles, an exhaust gas is exhausted into an exhaust system of the internal combustion engine in order to purify harmful components such as HC (hydrocarbon), CO (carbon monoxide), and NOx (nitrogen oxide) contained in the exhaust gas. An exhaust emission control device in which a purification catalyst is arranged is known.

  As an exhaust purification catalyst used in such an exhaust purification device, for example, a three-way catalyst is widely known. The three-way catalyst simultaneously promotes an oxidation reaction of HC and CO, which are incomplete combustion components, and a reduction reaction of NOx produced by a reaction between nitrogen in the air and unburned oxygen, and HC, CO And a function of reducing NOx emission to the outside.

  It is known that the purification performance of an exhaust purification catalyst represented by such a three-way catalyst generally depends greatly on the temperature of the exhaust purification catalyst in use. For example, when a noble metal catalyst is used as an exhaust purification catalyst, in order to effectively exhibit the purification performance of the catalyst, it is necessary to raise the catalyst temperature to a certain temperature, for example, about 250 ° C. or more. It is known that there is.

  Therefore, when the engine is cold from immediately after the start of the internal combustion engine until the exhaust purification catalyst is warmed up to a temperature at which the exhaust purification function can be effectively exhibited (hereinafter referred to as the catalyst activation temperature), the exhaust gas by the exhaust purification catalyst is exhausted. There is no expectation of purification of harmful components in it, and it is necessary to take some measures to suppress the deterioration of exhaust emissions.

  As one of the measures for improving exhaust emission when the engine is cold immediately after starting the internal combustion engine, it is known to optimize the arrangement position of the exhaust purification catalyst in the exhaust system of the internal combustion engine. Specifically, the exhaust purification catalyst is disposed as close as possible to the internal combustion engine body, that is, by shortening the exhaust path from the internal combustion engine body to the exhaust purification catalyst, The heat loss of the exhaust in the exhaust path is reduced, and the exhaust purification catalyst temperature can be quickly raised to the catalyst activation temperature by the exhaust heat, which makes it possible to reduce the exhaust emission when the engine is cold immediately after the internal combustion engine is started. It is intended to improve.

  Further, as one of the measures for improving the exhaust emission when the engine is cold immediately after the start of the internal combustion engine, the exhaust system of the internal combustion engine is separated from the main exhaust purification catalyst for purifying the exhaust during normal operation. It is known to provide an auxiliary exhaust purification catalyst for exhaust purification when the engine is cold. Specifically, the auxiliary exhaust purification catalyst is activated earlier than the main exhaust purification catalyst by selecting an auxiliary exhaust purification catalyst that has a smaller capacity and lower exhaust purification performance than the main exhaust purification catalyst. This makes it possible to improve exhaust emission when the engine is cold immediately after starting the internal combustion engine.

  Further, in the measures for arranging the auxiliary exhaust purification catalyst as described above in the exhaust system, from the viewpoint of improving cost and space, the exhaust gas is recirculated from the exhaust system to the intake system in the EGR passage. Proposals have also been made to dispose an auxiliary exhaust purification catalyst.

JP-A-8-254158 JP 2005-264821 A

  However, in order to improve the exhaust emission when the engine is cold immediately after the internal combustion engine is started, in the measure for shortening the exhaust path from the internal combustion engine body to the exhaust purification catalyst, the exhaust purification catalyst temperature is set when the engine is cold. Although it is possible to quickly raise the catalyst activation temperature, for example, when the internal combustion engine is in an operating state such as a high load region, the exhaust path from the internal combustion engine body to the exhaust purification catalyst is short. Therefore, it is considered that there is a problem that the exhaust purification catalyst is excessively heated beyond the allowable temperature to increase the risk of causing thermal degradation.

  Further, in order to improve the exhaust emission when the engine is cold immediately after the start of the internal combustion engine, the internal combustion engine exhaust system is separated from the main exhaust purification catalyst for exhaust purification during the normal operation, and the engine cold immediately after the start of the engine. In the measure to arrange the auxiliary exhaust purification catalyst for exhaust gas purification at the time, the auxiliary exhaust purification catalyst is selected by selecting an auxiliary exhaust purification catalyst having a capacity smaller than that of the main exhaust purification catalyst and smaller exhaust purification performance. Although it is possible to activate the catalyst earlier than the main exhaust purification catalyst, it is still impossible to suppress the deterioration of exhaust emission until the auxiliary exhaust purification catalyst reaches the catalyst activation temperature. I think there is.

  In the present invention, in view of the above problems, immediately after starting the internal combustion engine without being affected by the distance of the exhaust path from the main body of the internal combustion engine to the exhaust purification catalyst, and without requiring the use of an auxiliary exhaust purification catalyst. An exhaust purification device for an internal combustion engine capable of improving exhaust emission when the engine is cold before the exhaust purification catalyst temperature reaches the catalyst activation temperature, and in particular, recirculates exhaust from the exhaust system to the intake system An object of the present invention is to provide an exhaust emission control device applicable to an internal combustion engine having an EGR device.

  According to the first aspect of the present invention, in an exhaust gas purification apparatus for an internal combustion engine in which an exhaust gas purification catalyst for purifying harmful components in exhaust gas discharged from the internal combustion engine body is disposed in an exhaust system, the exhaust gas purification catalyst is more effective than the exhaust gas purification catalyst. An EGR device that recirculates exhaust discharged from the internal combustion engine body from the exhaust system downstream to the intake system of the internal combustion engine, and at least normal air in the exhaust gas recirculated to the intake system by the EGR device Oxygen supply means for supplying a high-concentration oxygen gas having an oxygen concentration higher than the oxygen concentration of the EGR until the temperature of the exhaust purification catalyst reaches the catalyst activation temperature immediately after the start of the internal combustion engine. The exhaust gas exhausted from the internal combustion engine body by the device is recirculated to the intake system, and the high concentration oxygen gas is supplied to the exhaust gas recirculated to the intake system by the oxygen supply means. The intake system is re-combust CO and HC in the exhaust gas is recycled to the purification, the exhaust purification system of an internal combustion engine, wherein is provided that.

  That is, according to the first aspect of the present invention, the exhaust gas exhausted from the internal combustion engine body by the EGR device is recirculated to the intake system immediately after the internal combustion engine is started until the temperature of the exhaust purification catalyst reaches the catalyst activation temperature. By supplying high-concentration oxygen gas into the exhaust gas recirculated to the intake system by the supply means, CO and HC in the exhaust gas recirculated to the intake system are recombusted and purified. It should be noted here that at least the oxygen concentration of the normal air is not supplied to re-burn the CO and HC in the exhaust gas recirculated to the intake system, rather than supplying fresh air or fresh air. A high concentration oxygen gas having a high oxygen concentration is supplied. The fresh air contains only about 21% oxygen, and when a large amount of exhaust gas is recirculated to the intake system, the proportion of fresh air in the total amount of gas drawn into the combustion chamber is limited to a small amount. For this reason, it is practically difficult to supply oxygen sufficient to re-combust CO and HC in a large amount of exhaust gas. In the present invention, in the exhaust gas recirculated to the intake system, by supplying a high-concentration oxygen gas having an oxygen concentration higher than at least the oxygen concentration in the fresh air, compared to the case of introducing fresh air, A larger amount of CO and HC in the exhaust gas can be reburned, and exhaust emission can be improved. The catalyst activation temperature of the exhaust purification catalyst is intended to mean a temperature at which the exhaust purification catalyst can effectively exhibit the purification function.

  According to a second aspect of the present invention, the oxygen supply means includes an oxygen cylinder filled with only oxygen gas, and an oxygen supply amount control valve that adjusts the supply amount of oxygen gas from the oxygen cylinder. An exhaust gas purification for an internal combustion engine according to claim 1 is provided.

  That is, in the second aspect of the invention, the oxygen supply means includes an oxygen cylinder filled with only oxygen gas, so that only oxygen gas is supplied into the exhaust gas recirculated to the intake system. As a result, a larger amount of CO and HC in the exhaust gas can be reburned, and exhaust emission can be improved.

  According to a third aspect of the present invention, the EGR device is a valve that is disposed in an exhaust system downstream of the exhaust purification catalyst and controls a ratio of exhaust gas recirculated to the intake system. 3. The exhaust gas purification apparatus for an internal combustion engine according to claim 1, further comprising a back pressure control valve that controls a back pressure of an exhaust system downstream of the catalyst within a predetermined range. 4. .

  That is, in the invention of claim 3, the EGR device is a valve that is disposed in the exhaust system downstream of the exhaust purification catalyst and controls the ratio of exhaust gas recirculated to the intake system, and the exhaust gas downstream of the exhaust purification catalyst. By having a back pressure control valve that controls the back pressure of the system within a predetermined range, if the ratio of exhaust gas recirculated to the intake system is 100%, almost the entire amount of exhaust immediately after starting the internal combustion engine is made into the intake system. Can be recycled. Further, when the exhaust gas is recirculated to the intake system by the EGR device, the back pressure of the exhaust system downstream from the exhaust purification catalyst immediately after the internal combustion engine is started until the exhaust purification catalyst temperature reaches the catalyst activation temperature. In addition, it is possible to control to a predetermined value that can maintain a state in which the back pressure is stable and that the exhaust amount blown back directly from the exhaust system to the internal combustion engine body does not become extremely large. it can. This makes it possible to bring the exhaust gas to the stable intake air recirculation immediately after the internal combustion engine is started until the exhaust purification catalyst reaches the catalyst activation temperature. Here, the back pressure means the pressure of the gas discharged after work, that is, combustion in the internal combustion engine, and the back pressure in the exhaust system downstream from the exhaust purification catalyst means combustion in the internal combustion engine. The pressure of the exhaust gas discharged after the exhaust gas is intended to be the pressure of the exhaust gas flowing through the exhaust system downstream of the exhaust purification catalyst.

  According to the fourth aspect of the present invention, the exhaust emission control device further includes engine stall determination means for determining whether or not the internal combustion engine is in a state where there is a risk of engine stall. 4. The internal combustion engine according to claim 3, wherein when it is determined that the internal combustion engine is at risk of being stalled, the ratio of exhaust gas recirculated to the intake system by the back pressure control valve is reduced. An exhaust emission control device for an engine is provided.

  That is, in the invention of claim 4, when it is determined by the engine stall determination means that there is a risk of the engine being stalled, the ratio of the exhaust gas recirculated to the intake system by the back pressure control valve is reduced, Avoid the danger of the internal combustion engine stalling. In this exhaust purification system, even if a large amount of exhaust gas is recirculated to the intake system, it is possible to avoid engine stall by providing oxygen supply means that can supply oxygen gas sufficient to re-combust even a large amount of exhaust gas. However, by providing the engine stall determination means, it is possible to avoid engine stall more reliably.

  According to the invention described in claim 5, the engine stall determination means includes engine speed detection means for detecting engine speed, and a combustion pressure sensor for detecting pressure in the combustion chamber of the internal combustion engine body. At least of the fluctuation state of the engine speed detected by the engine speed detecting means and the pressure value in the combustion chamber detected by the combustion pressure sensor when the exhaust gas is recirculated to the intake system by the EGR device. 5. The exhaust gas purification apparatus for an internal combustion engine according to claim 4, wherein whether or not the internal combustion engine is in a state where there is a risk of being stalled is determined based on one.

  That is, in the invention of claim 5, the engine stall determination means has an engine speed detection means and a combustion pressure sensor, and is based on at least one of the fluctuation state of the engine speed and the pressure value in the combustion chamber. It is determined whether or not there is a risk of being stalled.

  According to a sixth aspect of the present invention, the internal combustion engine includes a fuel injection device that directly injects fuel into a combustion chamber of the internal combustion engine body, and an ignition device that generates sparks in the combustion chamber, The oxygen supply means is configured to directly supply high-concentration oxygen gas into the combustion chamber. During the compression stroke of the internal combustion engine, the fuel and the high-concentration oxygen gas are fed into the combustion chamber by the fuel injection device and the oxygen supply means. 2. The exhaust gas purification apparatus for an internal combustion engine according to claim 1, wherein a spark is generated in the combustion chamber by the ignition device.

  That is, in the invention of claim 6, the oxygen supply means is arranged so as to be able to directly supply high-concentration oxygen gas into the combustion chamber. Compared to the case where oxygen as well as fuel can be concentrated in the vicinity of the spark plug and the oxygen supply means is configured to supply high-concentration oxygen gas to the intake system. It enables stratified combustion which can bring about stable combustion with a small amount of fuel.

According to the invention described in claim 7, the EGR device includes an intercooler that cools the exhaust gas recirculated to the intake system by the EGR device and liquefies the H ₂ O component in the exhaust gas, and the liquefaction by the intercooler. An exhaust purification device for an internal combustion engine according to claim 1, further comprising an H ₂ O removal tank for storing and removing the H ₂ O component.

That is, in the invention of claim 7, the EGR device includes the intercooler and the H ₂ O removal tank, so that H ₂ O in the exhaust gas recirculated to the intake system is liquefied before the exhaust gas is introduced into the intake system. Thus, the amount of exhaust gas introduced into the intake system can be reduced. As a result, when the high concentration oxygen gas addition amount by the oxygen supply means is determined depending on the exhaust amount introduced into the intake system, it is possible to reduce the high concentration oxygen gas addition amount by the oxygen supply means. Become.

  According to an eighth aspect of the present invention, the oxygen supply means supplies a predetermined amount of high-concentration oxygen gas to the intake system according to the required torque after the temperature of the exhaust purification catalyst reaches the catalyst activation temperature. The exhaust emission control device for an internal combustion engine according to claim 3, wherein the exhaust gas purification device is provided.

  That is, in the invention of claim 8, after the temperature of the exhaust purification catalyst reaches the catalyst activation temperature, for example, even when a high torque that cannot be provided only by oxygen in the air is required, By supplying a predetermined amount of high-concentration oxygen gas by the supply means, it is possible to make up for the insufficient amount of oxygen and to bring about the required torque.

  According to a ninth aspect of the present invention, the EGR device has carbon dioxide storage means for storing by absorbing or adsorbing carbon dioxide in exhaust gas recirculated to the intake system by the EGR device. An exhaust emission control device for an internal combustion engine according to claim 1 is provided.

  That is, according to the ninth aspect of the present invention, by having the carbon dioxide storage means, it is possible to store by absorbing or adsorbing carbon dioxide in the exhaust gas recirculated to the intake system. Thereby, when the high concentration oxygen gas supply amount by the oxygen supply means is determined depending on the exhaust amount introduced into the intake system, the high concentration oxygen gas supply amount by the oxygen supply means can be reduced.

  According to the invention described in claim 10, the EGR device has an exhaust gas recirculation passage that fluidly communicates the intake system and the exhaust system downstream of the exhaust purification catalyst. The exhaust gas flowing out from the exhaust gas purification catalyst is circulated around the exhaust gas purification catalyst immediately after the internal combustion engine is started and until the temperature of the exhaust gas purification catalyst reaches the catalyst activation temperature, and then guided to the exhaust gas recirculation passage. The exhaust gas purification apparatus for an internal combustion engine according to claim 1, further comprising exhaust gas bypassing means.

  That is, in the invention of claim 10, by having the exhaust bypass means, the heat of the exhaust is utilized until the temperature of the exhaust purification catalyst reaches the catalyst activation temperature, compared with the case where there is no exhaust bypass means. The exhaust purification catalyst can be warmed up efficiently, while the temperature of the recirculated gas can be lowered by removing heat from the exhaust when warming up the exhaust purification catalyst.

According to the invention described in claim 11, the oxygen component and hydrogen component by electrolysis of the H _{2 O} component is an H _{2 O} component is liquefied stored in the H _{2 O} removal tank is removed by the intercooler And a water electrolysis unit that supplies the generated oxygen component to the oxygen supply unit and supplies the generated hydrogen component to the intake system. An exhaust emission control device for an internal combustion engine is provided.

  That is, in the invention of claim 11, the oxygen component generated by the water electrolysis means can be supplied to the oxygen supply means to supplement the oxygen component, and the oxygen consumption can be reduced. Further, the hydrogen component generated by the water electrolysis means can be supplied to the intake system, and the combustion in the combustion chamber can be improved.

  According to a twelfth aspect of the present invention, the oxygen supply means is pre-pressurized and compressed with oxygen filtration means for generating high-concentration oxygen gas from air in the atmosphere and supplying the high-concentration oxygen gas to the intake system. An oxygen tank for storing the high-concentration oxygen gas and supplying the high-concentration oxygen gas to the intake system, and the oxygen filtering means as a supply source of the high-concentration oxygen gas to the intake system based on the temperature of the exhaust purification catalyst 2. The exhaust gas purification apparatus for an internal combustion engine according to claim 1, further comprising a switching unit that selects one of the oxygen tank and the oxygen tank.

  That is, in the invention of claim 12, by having two high-concentration oxygen gas supply sources of the oxygen filtering means and the oxygen tank, compared with those having only one of the oxygen filtering means and the oxygen tank, A large amount of high-concentration oxygen gas can be supplied to the intake system over a long period of time without requiring a replenishment operation, and the high-concentration oxygen gas can be supplied to the intake system more reliably.

  According to the invention described in each claim, the exhaust gas exhausted from the internal combustion engine body by the EGR device is recirculated to the intake system from immediately after the start of the internal combustion engine until the temperature of the exhaust purification catalyst reaches the catalyst activation temperature. By supplying a high-concentration oxygen gas having an oxygen concentration at least higher than the oxygen concentration in the fresh air into the exhaust gas recirculated to the intake system, it is more than in the case of introducing fresh air. The amount of CO and HC in the exhaust gas can be reburned and purified, and it becomes possible to improve the exhaust emission from immediately after the internal combustion engine is started until the temperature of the exhaust purification catalyst reaches the catalyst activation temperature. Has a common effect.

Hereinafter, embodiments of an exhaust emission control device according to the present invention will be described with reference to the accompanying drawings.
FIG. 1 is a diagram showing a schematic configuration of a first embodiment of an exhaust gas purification apparatus for an internal combustion engine according to the present invention. In FIG. 1, 1 is an internal combustion engine body, 2 is a combustion chamber, 3 is an ignition device, 4 is a fuel injection device, 5 is an oxygen supply device, 6 is an exhaust system, 7 is a three-way catalyst, 8 is an A / F sensor, 9 is a back pressure sensor, 10 is an EGR device, 11 is an exhaust gas recirculation passage, 12 is an exhaust gas recirculation control valve, 13 is an intercooler, 14 is an H ₂ O removal tank, 15 is a back pressure control valve, and 16 is an intake system. , 17 is a surge tank, 18 is an air flow meter, 19 is a throttle valve, 20 is an intake pressure sensor, 21 is an engine speed detecting means, 22 is an accelerator opening detecting means, 23 is a catalyst temperature detecting means, and 24 is a combustion pressure sensor. , 25 indicate electronic control units (hereinafter referred to as ECUs). In FIG. 6 to FIG. 9 to be described later, the same components are denoted by the same numbers.

  In the combustion chamber 2 of the internal combustion engine body 1, an ignition device 3, a fuel injection device 4, a combustion pressure sensor 24, and an oxygen supply device 5 are disposed. The ignition device 3 plays a role of making sparks fly between the spark plug gaps in a timely manner in order to surely ignite the air-fuel mixture in the combustion chamber 2, and the ignition timing is controlled by an ECU 25 described later. The The fuel injection device 4 performs electronic control on the timing of fuel injection and the like, and injects the fuel into the combustion chamber 2 with an electromagnetic injection nozzle. Specifically, the ECU 25 (to be described later) sets an optimum fuel injection amount. The fuel is calculated and injected with an electromagnetic injection nozzle at a predetermined pressure. The combustion pressure sensor 24 serves to detect the pressure in the combustion chamber 2. In the present embodiment, a gasoline internal combustion engine is assumed. However, the exhaust purification apparatus can also be applied to a diesel internal combustion engine. In the case of a diesel internal combustion engine, the ignition device 3 is usually not included.

  The oxygen supply device 5 serves as oxygen supply means for supplying high-concentration oxygen gas having an oxygen concentration higher than at least normal oxygen concentration in exhaust gas recirculated to the intake system by the EGR device 10 described later. It plays a role.

  The main object of the present invention is to return almost all the exhaust gas in the exhaust system downstream from the exhaust purification catalyst to the intake system when the engine is cold and the purification performance of the exhaust purification catalyst cannot be expected immediately after the internal combustion engine is started. By supplying a high-concentration oxygen gas inside, CO and HC, which are harmful components in the exhaust, are reburned, and exhaust emission is improved.

  As one of the measures for supplying oxygen into the exhaust gas so as to re-combust CO and HC in the exhaust gas recirculated to the intake system, fresh air, that is, new air is supplied to the intake system by controlling a throttle valve 19 described later. Can be considered.

  However, when a large amount of exhaust gas is recirculated to the intake system, the proportion of fresh air in the total amount of gas introduced into the combustion chamber 2 is limited to a small amount, and only about 21% oxygen is contained in the fresh air. Since it is not contained, it is practically difficult to supply sufficient oxygen in the exhaust gas to reburn CO and HC in a large amount of exhaust gas.

  Therefore, in the exhaust gas purification apparatus of the present invention, oxygen for reburning CO and HC in the exhaust gas recirculated to the intake system is at least a high concentration oxygen having an oxygen concentration higher than the oxygen concentration in fresh air. By supplying with the oxygen supply device 5 that can supply gas, CO and HC in a larger amount of exhaust gas can be reburned compared with the case of introducing fresh air, and exhaust emission is improved. Make it possible.

  Various configurations are assumed for the configuration of the oxygen supply device 5, but when a large amount of exhaust gas is recirculated to the intake system, a larger amount of CO and HC in the exhaust gas is recombusted. The oxygen supply device 5 is optimally configured so as to be able to directly supply only oxygen gas. In this embodiment, for example, an oxygen cylinder containing only compressed and compressed oxygen gas, and an oxygen cylinder from the oxygen cylinder And an oxygen supply amount control valve for controlling the supply amount of the oxygen gas. As another configuration of the oxygen supply device 5, for example, a high-concentration oxygen gas generation device that provides a high-concentration oxygen gas exceeding the oxygen concentration of normal air may be used instead of an oxygen cylinder.

  As for the arrangement of the oxygen supply device 5, basically, a large amount of exhaust gas is recirculated to the intake system as long as it is configured and arranged to supply high-concentration oxygen gas into the exhaust gas recirculated to the intake system. When circulated, a larger amount of CO and HC in the exhaust can be reburned and may be placed in any position.

  In this embodiment, the oxygen supply device 5 occupies a large proportion of the combustion chamber 2 in the compression stroke of the internal combustion engine by arranging the oxygen supply device 5 so that the high-concentration oxygen gas can be directly supplied into the combustion chamber 2. Compared to the case where oxygen as well as fuel can be concentrated in the vicinity of the spark plug in the recirculated exhaust, and the oxygen supply device 5 is configured to supply high-concentration oxygen gas to the intake system. Thus, it is possible to realize stratified combustion that can be burned with a smaller amount of fuel, and to achieve further improvement in fuel consumption.

A three-way catalyst 7 is disposed in the exhaust system of the internal combustion engine body 1 as an exhaust purification catalyst for purifying harmful components in the exhaust. The three-way catalyst 7 plays a role of purifying HC, CO and NOx, which are harmful components in the exhaust gas, with maximum efficiency when the atmosphere of the three-way catalyst 7 has a stoichiometric air-fuel ratio. When the three-way catalyst atmosphere has a stoichiometric air-fuel ratio, oxidation of HC and CO in the exhaust gas and reduction of NOx are simultaneously performed, and these harmful components in the exhaust gas are harmless with CO ₂ (carbon dioxide), H ₂ O ( Water) and N ₂ (nitrogen). In the present embodiment, the exhaust purification catalyst that is disposed in the exhaust system of the internal combustion engine body 1 and purifies the harmful components in the exhaust gas is the three-way catalyst 7. However, the harmful components in the exhaust gas are removed by catalytic reaction. Any exhaust purification catalyst that can be purified can be applied to the present invention. For example, a selective oxidation catalyst for purifying HC is also applicable to the exhaust purification apparatus of the present invention.

  An air-fuel ratio sensor 8 (hereinafter referred to as an A / F sensor) is disposed in the exhaust system between the internal combustion engine body 1 and the three-way catalyst 7. The A / F sensor 8 serves to detect the air-fuel ratio of exhaust flowing through the exhaust system between the internal combustion engine body 1 and the three-way catalyst 7 and the air-fuel ratio of exhaust flowing into the three-way catalyst 7. The sensor has an output characteristic substantially proportional to the air-fuel ratio of the exhaust gas.

The EGR device 10 functions to recirculate the exhaust gas discharged from the internal combustion engine body 1 from the exhaust system downstream of the three-way catalyst 7 to the intake system of the internal combustion engine. The EGR device 10 includes an exhaust gas recirculation passage 11 that fluidly communicates an exhaust system downstream of the three-way catalyst 7 and an intake system. The exhaust gas recirculation passage 11 includes an exhaust gas that flows through the exhaust gas recirculation passage 11. An exhaust gas recirculation amount control valve 12 for controlling the flow rate (hereinafter referred to as EGR gas), an intercooler 13 for cooling the EGR gas, and a liquid produced by cooling H ₂ O in the EGR gas. An H ₂ O removal tank 14 for storing and removing H ₂ O (water) is provided. The exhaust gas recirculation passage 11 is not formed so as to fluidly communicate the exhaust system upstream of the three-way catalyst 7 and the intake system, but it connects the exhaust system and intake system downstream of the three-way catalyst 7. By being formed so as to be in fluid communication, the three-way catalyst temperature can be quickly raised to the catalyst activation temperature by the heat of the exhaust gas discharged from the internal combustion engine body 1.

  The EGR device 10 further includes a back pressure sensor 9 and a back pressure control valve 15 disposed in the exhaust system downstream of the three-way catalyst 7. The back pressure sensor 9 serves to detect the back pressure of the exhaust system downstream of the three-way catalyst 7. Here, the back pressure means the pressure of the gas discharged after work, that is, combustion in the internal combustion engine, and the back pressure in the exhaust system downstream from the exhaust purification catalyst means combustion in the internal combustion engine. The pressure of the exhaust gas discharged after the exhaust gas is intended to be the pressure of the exhaust gas flowing through the exhaust system downstream of the exhaust purification catalyst. The back pressure control valve 15 controls the back pressure within a predetermined range based on the detection information from the back pressure sensor 9, and the intake system via the exhaust gas recirculation passage 11 of the EGR device 10. It plays a role in controlling the ratio of exhaust gas recirculated. In the present embodiment, the back pressure sensor 9 is disposed between the three-way catalyst 7 and the place where the exhaust gas recirculation passage 11 branches from the exhaust system downstream of the three-way catalyst 7. Further, the back pressure control valve 15 is disposed in the exhaust system downstream of the location where the exhaust gas recirculation passage 11 branches from the exhaust system downstream of the three-way catalyst 7.

  The intake system of the internal combustion engine has a throttle valve 19 whose throttle valve opening is electronically controlled, an air flow meter 18 that measures the intake air flow rate adjusted by the throttle valve 19, and the accuracy of the air flow meter 18 is adversely affected. A surge tank 17 that prevents intake pulsation and intake interference to be applied, and an intake pressure sensor 20 that detects the intake pressure of the internal combustion engine are arranged. The air flow meter 18 plays the role of measuring the amount of air introduced into the internal combustion engine body 1 based on the flow rate of air flowing through the air flow meter 18. The air flow meter 18 has a built-in potentiometer and the like. An output signal of an analog voltage proportional to is generated.

  The engine speed detecting means 21 serves to detect the speed of the internal combustion engine, and specifically includes a rotational speed sensor that detects the speed of the output shaft of the internal combustion engine. The rotational speed of the internal combustion engine is detected by a rotational speed sensor. The accelerator opening detection means 22 plays a role of detecting the accelerator opening during operation of the internal combustion engine.

  The catalyst temperature detecting means 23 has a function of estimating the three-way catalyst temperature. The three-way catalyst temperature is estimated based on, for example, temperature information detected by an exhaust temperature sensor arranged on the upstream side of the three-way catalyst 7 near the internal combustion engine body 1 or on the downstream side far from the internal combustion engine body 1. In this case, the catalyst temperature detecting means 23 is configured with an exhaust temperature sensor as a main element. However, for example, there is a slight gap between the three-way catalyst 7 and the exhaust gas temperature sensor, and parameters such as a rotational load, an air-fuel ratio, a heat transfer coefficient, and a catalytic reaction speed are used to estimate a temperature gradient in the gap. Thus, each element for detecting these pieces of information is also a constituent element of the catalyst temperature detecting means 23.

  The ECU 25 includes a CPU (Central Processing Unit), a RAM (Random Access Memory), a ROM (Read Only Memory), and a known digital computer in which input / output ports are connected by a bidirectional bus, and exchanges signals with various sensors and driving devices. Parameters necessary for control such as the rotational speed and intake air amount of the internal combustion engine, and based on the calculated parameters, the operation of the internal combustion engine such as combustion air-fuel ratio control, fuel injection amount control, ignition timing control, etc. It plays the role of performing various controls.

  The ECU 25 is connected to an air flow meter 18 and a throttle valve 19, so that detection information from the air flow meter 18 can be taken into the ECU 25, and the throttle valve opening degree of the throttle valve 19 can be controlled by a signal from the ECU 25. It is configured to be able to. The ECU 25 is connected with an A / F sensor 8, a back pressure sensor 9, an intake pressure sensor 20, an engine speed detection means 21, an accelerator opening detection means 22, a catalyst temperature detection means 23, and a combustion pressure sensor 24. The detection information from these sensors and means can be taken into the ECU 25. Further, the ECU 25 is connected to the ignition device 3, the fuel injection device 4, the oxygen supply device 5, the back pressure control valve 15, and the exhaust gas recirculation amount control valve 12, and is based on the detection information from the various sensors and means. In accordance with a signal from the ECU 25, the ignition control by the ignition device 3, the fuel injection control by the fuel injection device 4, the oxygen gas supply amount control by the oxygen gas supply device 5, the back pressure by the back pressure control valve 15 and the EGR device The exhaust gas recirculation ratio is controlled to 10 and the EGR gas amount introduced into the intake system by the exhaust gas recirculation amount control valve 12 can be controlled.

The operational effects of the exhaust gas purification apparatus for an internal combustion engine of the embodiment shown in FIG. 1 having the above-described components will be described below.
FIG. 2 is a flowchart showing an embodiment of a control routine of an exhaust purification process executed when the engine is cold immediately after starting, which is executed in the internal combustion engine shown in FIG. 1 to which the exhaust purification apparatus is applied.

In the control routine shown in FIG. 2, by the EGR device 10 and the oxygen supply device 5 from immediately after the start of the internal combustion engine until the temperature of the three-way catalyst 7 (hereinafter referred to as catalyst) reaches the catalyst activation temperature at which the purification function can be exhibited. In performing the purification process of CO and HC in the exhaust, in order to provide an exhaust flow that recirculates all the exhaust discharged from the internal combustion engine body 1 to the intake system immediately after the start of the internal combustion engine, Before the engine is started, the back pressure control valve 15 is fully closed. When the internal combustion engine is started, it is determined whether or not the catalyst temperature has reached the catalyst activation temperature. If it is determined that the catalyst temperature has not reached the catalyst activation temperature, the EGR device 10 and the oxygen supply device 5 are determined. The exhaust gas purification process for CO and HC in the exhaust gas is started. When the exhaust gas purification process is started, first, a fluctuation state of the engine speed and a pressure in the combustion chamber are detected, and whether or not the internal combustion engine is in a state that may cause an engine stall (internal combustion engine operation stop). Monitoring starts. Here, when it is estimated that the internal combustion engine is in a state that may cause engine stall, control for opening the back pressure control bubble 15 by a certain amount is executed in order to avoid engine stall. Next, it is determined whether or not the back pressure of the exhaust system downstream of the catalyst 7 is within the range of the back pressure control target predetermined value, and it is determined that the back pressure is not within the range of the back pressure control target predetermined value. Then, the back pressure control valve 15 controls the back pressure to be within the range of the back pressure control target predetermined value. Next, the required torque amount is calculated from the accelerator opening, the required gas amount introduced into the combustion chamber 2 is calculated from the required torque amount, and the exhaust recirculation amount control valve 12 is opened based on the required gas amount. The degree is controlled and the exhaust gas is recirculated to the intake system. At this time, when the exhaust amount that can be recirculated to the intake system is insufficient with respect to the required gas amount, the amount of the shortage is controlled by controlling the throttle valve 19 to satisfy the required gas amount. Introduce a fresh air. Then, in the compression stroke of the internal combustion engine, a required amount of oxygen gas is supplied into the combustion chamber 2 by the oxygen supply device 5 according to the amount of EGR gas recirculated to the intake system, and according to the required gas amount. By injecting a required amount of fuel by the fuel injection device 4 and causing ignition by the ignition device 3, CO and HC, which are harmful components in the exhaust gas recirculated to the intake system, can be reburned and purified, It is possible to improve exhaust emission.
Details of each step will be described below.

  First, in step 101, it is determined whether or not the internal combustion engine is in an operating state. If it is determined that the internal combustion engine is not in an operating state, in step 102, whether or not there is a start request to the internal combustion engine. It is confirmed. Specifically, these determinations are determined or confirmed by the ECU 25 based on detection information from the engine speed detecting means 21 and the air flow meter 18. When the start request to the internal combustion engine is confirmed in step 102, the process proceeds to the subsequent step 103 and step 104.

  In step 103 and step 104, the back pressure control valve 15 is fully closed by a signal from the ECU 25, and then the internal combustion engine is started. Before the internal combustion engine is started, the back pressure control valve 15 is controlled to be fully closed, so that almost all the exhaust discharged from the internal combustion engine body 1 immediately after the start of the internal combustion engine is recirculated to the intake system. It is possible to provide an exhaust flow. When the back pressure control valve 15 is fully closed and the internal combustion engine is started, the routine proceeds to the subsequent step 105.

  In step 105, it is determined whether or not the catalyst temperature has reached the catalyst activation temperature, that is, the temperature at which the catalyst 7 can perform the purification function. Specifically, the ECU 25 determines whether or not the catalyst temperature has reached the catalyst activation temperature based on detection information from the catalyst temperature detection means 23, and determines that the catalyst temperature has not reached the catalyst activation temperature. If YES, go to step 106.

  In step 106, a determination is made whether the internal combustion engine is in a state that can cause an engine stall. If a large amount of EGR gas is recirculated to the intake system and introduced into the combustion chamber 2 in a state where the engine speed is not stable or the combustion pressure value is not sufficient, the combustion becomes unstable and the engine torque decreases. Can cause engine stalls. The exhaust gas purification apparatus according to the present invention includes an oxygen supply device 5 that can supply oxygen gas sufficient to re-burn even a large amount of EGR gas even if a large amount of EGR gas is recirculated to the intake system. Although it is considered that the engine stall can be avoided, a means for selectively determining whether or not the internal combustion engine may cause engine stall may be provided in order to achieve more reliable engine stall avoidance. In the present embodiment, the engine speed detection means 21, the combustion pressure sensor 24, and the ECU 25 constitute an engine stall determination means so that the engine speed (NE) fluctuates or the pressure in the combustion chamber 2 of the internal combustion engine body 1 is increased. Therefore, the ECU 25 can determine whether or not the internal combustion engine is in a state in which engine stall is likely to occur, so that it is possible to more reliably realize engine stall avoidance.

  If it is determined in step 106 that the internal combustion engine is in a state that may cause engine stall, the routine proceeds to step 107, where the ECU 25 opens the back pressure control valve 15 by a predetermined amount. As a result, the back pressure can be reduced, the amount of EGR gas recirculated to the intake system can be reduced, and the engine speed and the pressure in the combustion chamber can be quickly stabilized. After the back pressure control valve 15 is opened by a certain amount in step 107, the process returns to step 106, and it is determined again whether or not the internal combustion engine is likely to cause engine stall by the engine stall determination means. . The opening control of a certain step width of the back pressure control valve 15 in this step 107 is repeatedly executed until it is determined in step 106 that there is no possibility that the internal combustion engine will cause engine stall. Note that the step width of a certain amount of valve opening when the back pressure control valve 15 is controlled to open is appropriately determined in advance according to the design specifications of the internal combustion engine.

  If it is determined in step 106 that the internal combustion engine is in a state where there is no possibility of causing engine stall, the process proceeds to the subsequent step 108. In step 108, it is determined whether or not the back pressure of the exhaust system downstream from the catalyst 7 is within a predetermined target predetermined value range. Specifically, based on the detection information of the back pressure sensor 9 disposed in the exhaust system downstream of the catalyst 7, whether or not the back pressure is within a range of a predetermined target value determined in advance by the ECU 25. Is made. The target back pressure target value takes into account the stability of the back pressure when the EGR gas is recirculated to the intake system by the EGR device 10 and the exhaust amount directly blown back from the exhaust system into the combustion chamber. Determined.

  In order to improve exhaust emission from immediately after the internal combustion engine is started to when the catalyst 7 reaches the catalyst activation temperature, the exhaust gas is discharged from the internal combustion engine body 1 immediately after the internal combustion engine is started and until the catalyst 7 reaches the catalyst activation temperature. Most preferably, the target predetermined value of the back pressure is determined so that all of the exhausted exhaust gas can be recirculated as EGR gas to the intake system, and CO and HC in the exhaust gas can be reburned and purified.

However, in this exhaust purification device, as will be described in detail in step 111 described later, in order to re-combust CO and HC in the EGR gas recirculated to the intake system, the oxygen supply device 5 reduces the amount of EGR gas. In order to additionally supply oxygen gas equivalent to 21%, all of the exhaust discharged from the internal combustion engine body 1 through the period from immediately after the start of the internal combustion engine until the catalyst 7 reaches the catalyst activation temperature is recirculated as EGR gas to the intake system. In this case, every time EGR gas is recirculated to the intake system, the amount of EGR gas increases by about 21%. In the present embodiment, by providing the exhaust gas recirculation passage 11 with the intercooler 13 and the H ₂ O removal tank 14, H ₂ O in the EGR gas can be liquefied and removed, and the EGR gas can be removed from the exhaust gas recirculation passage. By reducing the amount of EGR gas while passing through 11, the increase in the amount of EGR gas caused by the addition of oxygen gas by the oxygen supply device 5 as described above can be suppressed. However, it is assumed that the H ₂ O component in the EGR gas is relatively small (about 10%), and the increase in the amount of EGR gas caused by the oxygen addition by the oxygen supply device 5 as described above is suppressed. Is not enough. This increases the back pressure, leading to an increase in the amount of exhaust gas blown back directly into the combustion chamber 2 from the exhaust system, making the back pressure unstable and preventing stable recirculation of EGR gas. In some cases, the internal combustion engine may be stalled (stopped).

  Therefore, in this exhaust purification apparatus, the target predetermined value of the back pressure is a value that can maintain a stable back pressure when EGR gas is recirculated to the intake system by the EGR apparatus 10. The exhaust amount directly blown back into the combustion chamber 2 from the exhaust system is set to a value that can be prevented from becoming extremely large, and is determined based on data obtained by an analysis or a test performed in advance. The Specifically, at least about 21% of the amount of EGR gas recirculated to the intake system is discharged to the exhaust system downstream of the back pressure control valve 15 without being recirculated to the EGR device 10. It is assumed that the target predetermined value of the back pressure is set to such a value. Thereby, it is possible to stabilize the recirculation of the EGR gas immediately after the internal combustion engine is started and until the catalyst 7 reaches the catalyst activation temperature, and it is possible to improve the exhaust emission.

  If it is determined in step 108 that the back pressure of the exhaust system downstream of the catalyst 7 is not within the range of the predetermined target value, the process proceeds to the subsequent step 109. In step 109, the back pressure is the target predetermined value. Controlled to be within the range of values. Specifically, the ECU 25 controls the valve opening / closing of the back pressure control valve 15 based on the detection information of the back pressure sensor 9, so that it is downstream from the back pressure control valve 15 without being recirculated to the EGR device 10. It is possible to control the amount of gas discharged to the exhaust system, and thereby control the back pressure within the range of the target predetermined value. After the back pressure control valve 15 is opened or closed by a certain amount in step 109, the process returns to step 108, and it is determined again whether or not the back pressure is within the range of a predetermined target value. The A certain amount of valve opening / closing control of the back pressure control valve 15 in this step 109 is repeatedly executed until it is determined in step 108 that the back pressure is within a predetermined target value range. Note that a certain amount of valve opening and closing when the back pressure control valve 15 is controlled to open and close is appropriately determined according to the design specifications of the internal combustion engine.

  If it is determined in step 108 that the back pressure is within the range of the predetermined target value, the process proceeds to the subsequent step 110. In step 110, the exhaust pressure is determined based on the detection information of the accelerator opening detection means 22. The valve opening of the recirculation amount control valve 12 and the valve opening of the throttle bubble 19 are appropriately controlled by the ECU 25, and gas is introduced into the combustion chamber 2.

  Specifically, first, detection information from the accelerator opening detection means 22 is taken into the ECU 25, and the ECU 25 calculates the necessary torque amount, and is necessary for realizing the necessary torque amount in the combustion chamber 2. The required amount of gas to be introduced into is calculated. In addition, when the exhaust gas recirculation amount control valve 12 is fully opened, the intake pressure detected from the intake pressure sensor 20, the back pressure detected from the back pressure sensor 9, and the flow of the exhaust gas recirculation passage 11 through which EGR gas flows. The amount of EGR gas that can be recirculated to the intake system from the road area or the like (hereinafter referred to as the total EGR gas amount) is calculated simultaneously by the ECU 25.

  This exhaust purification device recirculates the exhaust gas discharged from the internal combustion engine body 1 immediately after the start of the internal combustion engine until the catalyst 7 reaches the catalyst activation temperature as EGR gas to the intake system, and removes CO and HC in the EGR gas. The purpose is to improve exhaust emission by recombusting and purifying. To achieve this purpose, as much EGR gas as possible is introduced into the combustion chamber 2 and CO and HC in the EGR gas are recycled. It is preferably controlled to burn and purify.

  Therefore, in the present embodiment, when the total amount of EGR gas that can be recirculated to the intake system exceeds the required gas amount calculated based on the accelerator opening, that is, the required gas amount is satisfied only by the EGR gas. If it is possible, the ECU 25 controls the exhaust gas recirculation amount control valve 12 and the throttle valve 19 so that only the required amount of EGR gas is introduced into the combustion chamber 2. Also, when the total amount of EGR gas that can be recirculated to the intake system does not exceed the required amount of gas calculated based on the accelerator opening, that is, when the total amount of EGR gas is insufficient with respect to the required amount of gas In order to satisfy the required gas amount, the exhaust gas is recirculated so that all the EGR gas and the amount of fresh air that is insufficient with respect to the required gas amount are introduced into the combustion chamber 2. The ECU 25 controls the circulation amount control valve 12 and the throttle valve 19.

  In step 110, the valve opening of the exhaust gas recirculation amount control valve 12 and the valve opening of the throttle bubble 19 are controlled by the ECU 25 based on the detection information of the accelerator opening detection means 22, and gas is introduced into the combustion chamber 2. Then, the process proceeds to step 111. In step 111, a required amount of oxygen gas is supplied according to the amount of EGR gas recirculated to the intake system, and the required amount is determined according to the required amount of gas. By injecting this fuel and causing ignition, CO and HC, which are harmful components in the EGR gas recirculated to the intake system, are recombusted and purified.

  Specifically, in the compression stroke of the internal combustion engine, a required amount of oxygen gas is supplied into the combustion chamber 2 by the oxygen supply device 5 in accordance with the amount of EGR gas recirculated to the intake system, and the required gas amount. Accordingly, a required amount of fuel is injected by the fuel injection device 4 and ignition in the combustion chamber is brought about by the ignition device 3.

  Here, the required amount of oxygen gas supplied by the oxygen supply device 5 is intended to be the amount of oxygen gas required to burn the EGR gas recirculated to the intake system. In the present embodiment, EGR Assuming that no oxygen component is present in the gas, oxygen gas in an amount of about 21% with respect to the amount of EGR gas recirculated to the intake system is supplied into the combustion chamber 2 by the oxygen supply device. In addition, about the fresh air supplied in the combustion chamber 2 as needed, since about 21% of oxygen is contained in the fresh air, new oxygen is supplied to the fresh air by the oxygen supply device 5. There is no need to consider gas supply. The required amount of fuel injected by the fuel injection device 4 is intended to be the amount of fuel necessary to burn all the gas introduced into the combustion chamber 2, and fresh air is introduced into the combustion chamber as necessary. When the gas is introduced into the combustion chamber 2, the total amount of the gas introduced into the combustion chamber 2 is a combination of the EGR gas introduced into the combustion chamber 2, the fresh air, and the gas supplied by the oxygen supply device 5. It becomes gas.

  Since the EGR gas is a gas once burned, the EGR gas contains carbon dioxide, which has the effect of reducing the combustion speed, and when a large amount of EGR gas is introduced into the combustion chamber. The possibility of unstable combustion is high.

  Therefore, in the present embodiment, the oxygen supply device 5 is configured and arranged so that the high-concentration oxygen gas can be directly supplied into the combustion chamber 2, so that a large proportion of the combustion chamber 2 in the compression stroke of the internal combustion engine. When not only fuel but also oxygen gas can be concentrated in the vicinity of the spark plug with respect to the recirculated EGR gas that occupies the fuel, and the oxygen supply device 5 is configured to supply high-concentration oxygen gas to the intake system Compared to the above, it is possible to achieve stratified combustion that can bring about stable combustion with a smaller amount of fuel, and to achieve further improvement in fuel consumption.

  Furthermore, in the present embodiment, the optimal oxygen gas supply and fuel injection end timing that can bring about stable combustion with a smaller amount of fuel are determined based on data obtained from previously executed analysis or test. By mapping and storing the map in the memory of the ECU 25 and executing oxygen gas supply and fuel injection in the latter half of the compression stroke based on the map, stable combustion can be achieved with a smaller amount of fuel, and exhaust emission In addition, the fuel consumption can be further improved.

  FIG. 3 is a diagram showing an embodiment of a map of the optimal oxygen gas supply and fuel injection end timing created based on data obtained from analysis or tests executed in advance. In the present embodiment, the optimal oxygen gas supply and fuel injection end timing are controlled at the same time. In the map shown in FIG. 3, the optimal oxygen gas supply and fuel injection end timing is determined according to the engine speed and the engine load, and the pre-top dead center (BTDC) angle is shown as a parameter. In the oxygen gas supply control and the fuel injection control using this map, the engine speed and the engine load are specified by the ECU 25 based on detection information from the engine speed detection means 21, the accelerator opening degree detection means 22, and the like. An optimal oxygen gas supply and fuel injection end timing is calculated based on this map stored in the memory of the ECU 25, and the oxygen supply device is operated by the ECU 25 to satisfy the calculated optimal oxygen gas supply and fuel injection end timing. 5 and the fuel injection device 4 are controlled.

  Furthermore, in this embodiment, feedback control is performed so that the internal combustion engine is operated at the stoichiometric air-fuel ratio from immediately after the internal combustion engine is started until the catalyst temperature reaches the catalyst activation temperature. Specifically, the feedback control is based on the detection information of the A / F sensor 8 disposed in the exhaust system between the internal combustion engine body 1 and the catalyst 7 and the amount of oxygen gas supplied by the oxygen supply device 5 and the fuel. The fuel injection amount by the injection device 4 is appropriately feedback controlled by the ECU 25. As a result, CO and HC in the EGR gas can be recombusted in the combustion chamber 2 more reliably, and exhaust emission can be improved.

  The control routine from step 101 to step 111 described above is repeatedly executed immediately after the internal combustion engine is started until the catalyst temperature reaches the catalyst activation temperature. In step 105, the control routine is performed based on the detection information from the catalyst temperature detection means 23. When the ECU 25 confirms that the temperature has become equal to or higher than the catalyst activation temperature, the process proceeds to the subsequent steps 112 and 113, where the ECU 25 is controlled so that the back pressure control valve 15 is fully opened. After the temperature becomes equal to or higher than the catalyst activation temperature, it is possible to execute normal EGR control only by the valve control of the exhaust gas recirculation amount control valve 12.

  FIG. 4 is a flowchart showing an embodiment of a control routine of exhaust purification processing after catalyst warm-up, which is executed in the internal combustion engine shown in FIG. 1 to which the present exhaust purification device is applied.

  Without the back pressure control valve 15 disposed in the exhaust system downstream of the exhaust purification catalyst and controlling the ratio of exhaust gas recirculated to the intake system, the exhaust is made into the intake system only by the differential pressure between the intake system and the exhaust system. In an exhaust gas purification apparatus for an internal combustion engine having a recirculating EGR device, it is difficult to introduce a large amount of EGR gas into the combustion chamber because the negative pressure in the intake system decreases during high load operation. Further, in an internal combustion engine that does not have a supercharger, the amount of oxygen that can be supplied into the combustion chamber is small and the maximum torque that can be output is small compared to an internal combustion engine that has a supercharger. However, according to the exhaust purification device of the present invention in which the back pressure control valve 15 is provided and has the oxygen supply device 5, a large amount of EGR gas can be supplied into the combustion chamber even during high load operation, More oxygen can be supplied into the combustion chamber than when oxygen is supplied only by fresh air.

  In the control routine shown in FIG. 4, such characteristics are effectively utilized to improve fuel consumption and exhaust emission particularly after the catalyst is warmed up, that is, after the catalyst temperature exceeds the catalyst activation temperature. Control is performed to increase the output without providing it. The control similar to the control routine shown in FIG. 2 is executed for the control before the catalyst warms up, that is, immediately after the internal combustion engine is started and before the temperature of the catalyst 7 reaches the catalyst activation temperature.

Specifically, until the catalyst warms up, similar to the control routine shown in FIG. 2, substantially the entire amount of exhaust discharged from the rear of the exhaust system catalyst 7 is returned to the intake system, and the oxygen supply device Oxygen gas is added by 5 and CO and HC in the exhaust are reburned to improve exhaust emission. Then, after the catalyst is warmed up, the operating conditions are switched by the required torque. In this control routine, even after the catalyst is warmed up, in a torque region where the exhaust gas discharged from the internal combustion engine body 1 can be recirculated to the intake system and the required torque can be satisfied only with oxygen in the air. By introducing the EGR gas into the combustion chamber 2 by the back pressure control valve 15 in such a range that the combustion does not deteriorate, it becomes possible to improve the fuel consumption and the exhaust emission. Further, even after the catalyst is warmed up, even if a high torque that cannot be provided only by oxygen in the air is required, the introduction of the EGR gas into the combustion chamber 2 is stopped, and the oxygen supply device By supplying an insufficient amount of oxygen gas, the required torque can be provided.
Details of each step will be described below.

  First, in step 211, the ECU 25 determines whether or not the catalyst temperature is equal to or higher than the catalyst activation temperature based on the detection information from the catalyst temperature detection means 23. Then, when it is confirmed that the catalyst temperature is equal to or higher than the catalyst activation temperature, the routine proceeds to the subsequent step 212.

  In step 212, the required torque and the required oxygen amount are calculated based on the accelerator opening. Specifically, detection information from the accelerator opening detection means 22 is taken into the ECU 25, a required torque corresponding to the accelerator opening is calculated, and introduced into the combustion chamber 2 necessary to realize the required torque. The required oxygen amount to be calculated is calculated. When these are calculated, the process proceeds to the following step 213.

  In step 213, whether or not the required oxygen amount calculated in step 212 can be covered only with oxygen in the air, that is, whether or not the required oxygen amount can be satisfied only by introducing fresh air through the throttle valve 19. Is determined by the ECU 25. FIG. 5 is a diagram showing an embodiment of a map for determining whether or not the required oxygen amount can be covered only with oxygen in the air based on the engine speed and the required torque. In the present embodiment, whether or not the required oxygen amount can be covered only with oxygen in the air based on the engine speed and the required torque is determined using the map shown in FIG. Specifically, when each of the engine speed and the required torque is in the region I shown in FIG. 5, it is determined that the required oxygen amount can be covered only with oxygen in the air, and when it is in the region II, it is necessary. It is determined that the amount of oxygen cannot be covered only with oxygen in the air. Note that the map shown in FIG. 5 is created in advance by test evaluation, analysis evaluation, or the like and stored in the memory of the ECU 25 or the like. If it is determined in step 213 that only the oxygen in the air can provide the amount of oxygen necessary to provide the required torque, the process proceeds to the subsequent step 214.

  In step 214, the ECU 25 calculates the opening degree of the throttle valve 19 that can secure the required oxygen amount calculated in step 212, and determines an EGR gas amount that is optimal from the viewpoint of fuel consumption. . In order to realize the EGR gas amount, the opening degree of the back pressure control valve 15 and the exhaust gas recirculation amount are based on the intake pressure detected from the intake pressure sensor 20 and the back pressure detected from the back pressure sensor 9. The opening degree of the control valve 12 is determined. Then, fresh air and EGR gas are introduced into the combustion chamber 2.

  In step 215 following step 214, it is determined whether or not the combustion in the combustion chamber has deteriorated due to the introduction of EGR gas. This determination is performed by the ECU 25 determining whether the combustion fluctuation in the combustion chamber 2 is larger than a predetermined value based on the detection value of the combustion pressure sensor 24.

  If it is determined in step 215 that the combustion in the combustion chamber 2 has deteriorated, the routine proceeds to step 216, where the ECU 25 closes the exhaust gas recirculation amount control valve 12 by a certain amount. As a result, the amount of EGR gas introduced into the combustion chamber 2 can be reduced, and the combustion in the combustion chamber 2 can be improved and stabilized. After the exhaust gas recirculation amount control valve 12 is closed by a certain amount in step 216, the process returns to step 215, and it is determined again whether or not the combustion in the combustion chamber 2 has deteriorated. The valve closing control of a certain step width in the exhaust gas recirculation amount control valve 12 in this step 216 is repeatedly executed until it is determined in step 215 that the combustion in the combustion chamber 2 has not deteriorated. Note that a certain amount of valve closing step width when the exhaust gas recirculation amount control valve 12 is controlled to close is appropriately determined in advance according to the design specifications of the internal combustion engine.

  If it is determined in step 215 that the combustion in combustion 2 has not deteriorated, the routine proceeds to step 217. In step 217, correction of the fuel injection amount is performed so that the internal combustion engine is operated at a desired air / fuel ratio, and in the present embodiment, the engine is operated at a theoretical air / fuel ratio. Specifically, the fuel injection amount by the fuel injection device 4 is feedback controlled by the ECU 25 based on detection information of the A / F sensor 8 disposed in the exhaust system between the internal combustion engine body 1 and the catalyst 7. Is executed.

  According to the control routine from step 212 to step 217 as described above, even after the catalyst is warmed up, the required torque is generated only by oxygen in the air while recirculating the exhaust discharged from the internal combustion engine body 1 to the intake system. In the torque range that can satisfy the conditions, it is possible to improve the fuel consumption and exhaust emission by introducing the EGR gas into the combustion chamber 2 by the back pressure control valve 15 in such a range that the combustion does not deteriorate. And

  Furthermore, in the control routine of the present embodiment, when it is determined in step 213 that the amount of oxygen necessary for providing the required torque calculated based on the accelerator opening cannot be covered only with oxygen in the air, Then, the process proceeds to step 218 and step 219, the exhaust gas recirculation amount control valve 12 is closed, the supply of EGR gas into the combustion chamber 2 is stopped, and the amount of oxygen necessary for providing the required torque is set in the combustion chamber 2. The oxygen supply device 5 supplies an oxygen gas that is insufficient with only oxygen in the air, and fuel injection is performed in an amount corresponding to the amount of oxygen supplied to the combustion chamber 2. As a result, even after the catalyst is warmed up, the required torque can be provided even when a high torque that cannot be provided only by oxygen in the air is set as the required torque.

  FIG. 6 is a diagram showing a schematic configuration of a second embodiment of the exhaust gas purification apparatus for an internal combustion engine according to the present invention. In the exhaust purification device of the second embodiment shown in FIG. 6, the carbon dioxide storage device 30 is disposed in the exhaust gas recirculation passage 11, and the oxygen supply device 5 supplies oxygen gas to the combustion chamber 2. The configuration is the same as that of the exhaust emission control device of the first embodiment shown in FIG. 1 except that it is configured to supply the intake system 16 instead of directly inside. As described above, with regard to the arrangement of the oxygen supply device 5, basically, a large amount of exhaust gas is supplied to the intake system as long as the oxygen gas can be supplied into the exhaust gas recirculated to the intake system. When recirculated, a larger amount of CO and HC in the exhaust can be reburned and may be placed in any position, as in the first embodiment shown in FIG. The oxygen supply device 5 may be configured and arranged so that oxygen gas can be directly supplied into the combustion chamber 2.

In the exhaust emission control device according to the present invention, as described above, the oxygen gas corresponding to about 21% of the EGR gas amount by the oxygen supply device 5 in order to re-combust CO and HC in the EGR gas recirculated to the intake system. Therefore, when exhaust gas discharged from the internal combustion engine body 1 is recirculated as EGR gas to the intake system immediately after the internal combustion engine is started and until the catalyst 7 reaches the catalyst activation temperature, Each time gas is recirculated to the intake system, the amount of EGR gas increases by about 21%. The exhaust gas recirculation passage 11 by providing the intercooler 13 and H ₂ O removal tank 14 can be removed by liquefying of H ₂ O in the EGR gas, the EGR gas is passing through the exhaust gas recirculation passage 11 By reducing the amount of EGR gas in the meantime, the increase in the amount of EGR gas caused by the addition of oxygen gas by the oxygen supply device 5 as described above can be suppressed. However, it is assumed that the H ₂ O component in the EGR gas is relatively small (about 10%), and the increase in the amount of EGR gas caused by the oxygen gas addition by the oxygen gas supply device 5 as described above is suppressed. Not enough to do that.

Therefore, in the second embodiment shown in FIG. 6, the carbon dioxide storage device 30 is added to the exhaust gas recirculation passage 11 in addition to the intercooler 13 and the H ₂ O removal tank 14 in order to further suppress the increase in the amount of EGR gas. Arrange. The carbon dioxide storage device 30 serves as a carbon dioxide storage means that absorbs or absorbs carbon dioxide in the exhaust gas recirculated to the intake system 16 by the EGR device 10.

In the present embodiment, a carbon dioxide storage device 30 having a carbon dioxide storage material such as lithium zirconate (Li ₂ ZrO ₃ ) as a constituent element is applied. It is known that lithium zirconate occludes carbon dioxide at low temperatures and releases carbon dioxide at high temperatures. Therefore, according to the carbon dioxide occlusion device 30 having a carbon dioxide occlusion material such as lithium zirconate (Li ₂ ZrO ₃ ) as a constituent element, when the exhaust temperature is low such as at the time of engine cold start, It is possible to occlude carbon dioxide considered to contain about 15%, and it is possible to suppress an increase in the amount of EGR gas caused by the additional supply of oxygen gas by the oxygen supply device 5. If the H ₂ O component and carbon dioxide in the exhaust gas can be completely removed or occluded, the amount of EGR gas basically does not increase even when oxygen gas is additionally supplied by the oxygen supply device 5. Therefore, the EGR gas can be recirculated while the back pressure control valve 15 and the throttle valve 19 are fully closed, and the exhaust emission can be further improved.

  FIG. 7 is a diagram showing a schematic configuration of a third embodiment of the exhaust gas purification apparatus for an internal combustion engine according to the present invention. In the exhaust purification device of the third embodiment shown in FIG. 7, the catalyst warm-up passage 40 and the catalyst warm-up passage switching valve 43 are disposed, and the oxygen supply device 5 is oxygenated. Except for being configured to supply gas to the intake system 16 rather than directly into the combustion chamber 2, it is the same as the configuration of the exhaust emission control device of the first embodiment shown in FIG. As described above, with regard to the arrangement of the oxygen supply device 5, basically, a large amount of exhaust gas is supplied to the intake system as long as the oxygen gas can be supplied into the exhaust gas recirculated to the intake system. When recirculated, a larger amount of CO and HC in the exhaust can be reburned and may be placed in any position, as in the first embodiment shown in FIG. The oxygen supply device 5 may be configured and arranged so that oxygen gas can be directly supplied into the combustion chamber 2.

Since the catalyst 7 and the exhaust passage on the upstream side of the catalyst 7 are usually exposed to the outside air, the exhaust may be cooled before reaching the catalyst 7. As a means for solving this problem, it is conceivable to warm the catalyst 7 and the exhaust passage upstream of the catalyst 7 by some method. However, when there is no heat source such as a special heater, only the heat of the exhaust is an effective heat source. On the other hand, when the temperature of the EGR gas is high, it is difficult to remove the H ₂ O component in the EGR gas, and the increase in the amount of EGR gas caused by the addition of oxygen gas by the oxygen supply device 5 is suppressed. The temperature is preferably low.

  Based on this, in the third embodiment shown in FIG. 7, the exhaust gas flowing out from the catalyst 7 is circulated around the catalyst 7 from immediately after the start of the internal combustion engine until the catalyst temperature reaches the catalyst activation temperature. After that, exhaust bypass means for guiding the exhaust circulation passage 11 is provided. The exhaust bypass means includes a catalyst system warm-up passage 40 and a catalyst system warm-up passage switching valve 43. The catalyst system warm-up passage 40 serves to warm up the catalyst 7 and the exhaust passage upstream of the catalyst 7 when the engine is cold, and lowers the temperature of the EGR gas. It is configured to surround the exhaust passage on the upstream side. The catalyst system warm-up passage switching valve 43 is disposed in front of the intercooler 13 disposed in the exhaust gas recirculation passage 11 (that is, EGR gas is on the inflow side), and flows out from the catalyst 7 before the catalyst warm-up. It serves to guide the exhausted exhaust to the exhaust gas recirculation passage 11 via the catalyst warm-up passage 40.

  The arrows shown in the catalyst system warm-up passage 40 in FIG. 7 indicate the flow of exhaust when the back pressure control valve 15 and the catalyst system warm-up passage switching valve 43 are fully closed. As shown by the arrows in FIG. 7, the exhaust pressure flowing out from the catalyst 7 is not directly caused to flow into the intercooler 13 by fully closing the back pressure control valve 15 and the catalyst system warm-up passage switching valve 43. It is possible to flow into the intercooler 13 after passing through the forward path 41 and the return path 42 of the catalyst system warm-up path. As understood from FIG. 7, the catalyst system warm-up passage 40 is configured to surround the catalyst 7 and the exhaust passage upstream of the catalyst 7, and the exhaust gas is allowed to flow through the catalyst system warm-up passage 40. The catalyst 7 and the exhaust passage upstream of the catalyst 7 can be warmed up by the heat of the exhaust. Further, since the heat of the exhaust is taken away when the catalyst 7 and the exhaust passage on the upstream side of the catalyst 7 are warmed up, the temperature of the EGR gas flowing into the intercooler 13 can be lowered.

The control routine of the exhaust gas purification process that is executed in the internal combustion engine shown in FIG. 7 to which the present exhaust gas purification apparatus is applied and the engine is cold immediately after starting is the same as the control routine shown in FIG. 2 except for the following points. It is. That is, in step 105 of the control routine shown in FIG. 2, when it is determined that the catalyst temperature has not reached the catalyst activation temperature, the catalyst system warm-up passage switching valve 43 is fully closed, so that the heat of the exhaust The catalyst 7 and the exhaust passage upstream of the catalyst 7 can be warmed up, and the temperature of the EGR gas flowing into the intercooler 13 can be lowered. This makes it possible to improve the warm-up performance of the catalyst 7 and facilitate the removal of the H ₂ O component in the EGR gas by the H ₂ O removal tank 14 together with the effect of the intercooler 13. Is possible. When it is determined in step 105 of the control routine shown in FIG. 2 that the catalyst temperature has reached the catalyst activation temperature, the catalyst system warm-up passage switching valve 43 is fully opened.

  FIG. 8 is a diagram showing a schematic configuration of the fourth embodiment of the exhaust gas purification apparatus for an internal combustion engine according to the present invention. In the exhaust gas purification apparatus of the fourth embodiment shown in FIG. 8, a water electrolysis apparatus 50, an oxygen tank 51 and a hydrogen tank 52 are disposed, and the oxygen supply apparatus 5 burns oxygen gas. Except for being configured to supply the intake system 16 instead of directly into the chamber 2, it is the same as the configuration of the exhaust emission control device of the first embodiment shown in FIG. As described above, with regard to the arrangement of the oxygen supply device 5, basically, a large amount of exhaust gas is supplied to the intake system as long as the oxygen gas can be supplied into the exhaust gas recirculated to the intake system. When recirculated, a larger amount of CO and HC in the exhaust can be reburned and may be placed in any position, as in the first embodiment shown in FIG. The oxygen supply device 5 may be configured and arranged so that oxygen gas can be directly supplied into the combustion chamber 2.

  In the exhaust emission control device according to the present invention, as described above, CO and HC in the EGR gas recirculated to the intake system are reburned from immediately after the internal combustion engine is started until the catalyst temperature reaches the catalyst activation temperature. In order to achieve this, oxygen gas corresponding to about 21% of the EGR gas amount is additionally supplied by the oxygen supply device 5. Therefore, it is preferable that the oxygen supply device 5 is configured so as to supply more oxygen gas. In addition, when a large amount of EGR gas is introduced into the combustion chamber 2, the combustion rate tends to decrease due to the amount of carbon dioxide in the EGR gas and the combustion tends to become unstable. One means for improving this It is conceivable to improve combustion by supplying hydrogen gas to the intake system.

Based on this, in the fourth embodiment shown in FIG. 8, electrolysis of H _{2 O} component is stored in a H _{2 O} component is liquefied by the intercooler 13 in H _{2 O} removal tank 14 is removed Then, a water electrolysis means is provided that generates an oxygen component and a hydrogen component, supplies the generated oxygen component to the oxygen supply device 5, and supplies the generated hydrogen component to the intake system 16. The water electrolysis means includes a water electrolysis apparatus 50, an oxygen tank 51, and a hydrogen tank 52. The water electrolyzer 50 sucks the water stored in the H ₂ O tank 14, generates an oxygen component and a hydrogen component from the water by electrolysis, and generates the generated oxygen component to the oxygen tank 51 and also This serves to supply the hydrogen component to the hydrogen tank 52. The hydrogen tank 52 is configured to store the hydrogen component generated and supplied by the water electrolysis apparatus 50 and to supply the intake system 16 as hydrogen gas as necessary. The oxygen tank 51 is configured to store the oxygen component generated and supplied by the water electrolyzer 50 and to supply the intake system as oxygen gas as necessary. In the form, it is configured as one component of the oxygen supply device 5.

According to the exhaust gas purification apparatus of the fourth embodiment shown in FIG. 8 having the water electrolyzer 50, the oxygen tank 51, and the hydrogen tank 52 configured as described above, the catalyst temperature before the catalyst warms up, that is, immediately after the start of the internal combustion engine. Is stored in the H ₂ O removal tank 14 when most of the exhaust gas is recirculated to the intake system as EGR gas and CO and HC in the EGR gas are reburned until the catalyst reaches the catalyst activation temperature. Water can be electrolyzed by the water electrolyzer 50 to generate an oxygen component and a hydrogen component. And by supplying the produced | generated oxygen component to the oxygen tank 51, an oxygen component can be replenished and it becomes possible to aim at reduction of oxygen consumption. Further, the generated hydrogen component can be supplied to the intake system 16 via the hydrogen tank 52, and combustion in the combustion chamber 2 can be improved. The control routine of the exhaust gas purification process that is executed in the internal combustion engine shown in FIG. 8 to which the present exhaust gas purification apparatus is applied and the engine is cold immediately after the engine is started is the same as the control routine shown in FIG.

  FIG. 9 is a diagram showing a schematic configuration of a fifth embodiment of the exhaust gas purification apparatus for an internal combustion engine according to the present invention. In the exhaust emission control device of the fifth embodiment shown in FIG. 9, the oxygen filtering device 60, the oxygen tank 61, and the oxygen gas passage switching device 62 are disposed, and the oxygen supply device 5 is oxygen gas. 1 is the same as that of the exhaust emission control device of the first embodiment shown in FIG. 1 except that the exhaust gas is supplied to the intake system 16 instead of directly into the combustion chamber 2. As described above, with regard to the arrangement of the oxygen supply device 5, basically, a large amount of exhaust gas is supplied to the intake system as long as the oxygen gas can be supplied into the exhaust gas recirculated to the intake system. When recirculated, a larger amount of CO and HC in the exhaust can be reburned and may be placed in any position, as in the first embodiment shown in FIG. The oxygen supply device 5 may be configured and arranged so that oxygen gas can be directly supplied into the combustion chamber 2.

  As described above, in the exhaust purification catalyst device of the present invention having the back pressure control valve 15 and the oxygen supply device 5, immediately after the start of the internal combustion engine and before the catalyst warms up until the catalyst temperature reaches the catalyst activation temperature. Provides only oxygen in the air to reburn CO and HC in the EGR gas recirculated to the intake system, and after catalyst warm-up after the catalyst temperature exceeds the catalyst activation temperature When high torque that cannot be performed is required, oxygen gas may be supplied by the oxygen supply device 5 in order to provide the required torque. As described above, when oxygen supply by the oxygen supply device 5 is required both before and after catalyst warm-up, the amount of oxygen gas consumed is extremely large. Replenishment of oxygen gas is frequently required.

  Based on this, in the fifth embodiment shown in FIG. 9, the oxygen supply device 5 generates high-concentration oxygen gas from air in the atmosphere and supplies the high-concentration oxygen gas to the intake system 16. An oxygen filtering device 60 as a means, an oxygen tank 61 that stores high-pressure oxygen gas that has been pressurized and compressed in advance, and supplies the high-concentration oxygen gas to the intake system 16; As a high-concentration oxygen gas supply source, an oxygen gas passage switching device 62 serving as switching means for selecting either the oxygen filtering device 60 or the oxygen tank 61 is provided. In the present embodiment, the oxygen filtering device 60 has an oxygen filtering membrane, and plays a role of generating high-concentration oxygen gas from air in the atmosphere by the filtering membrane and supplying the high-concentration oxygen gas to the intake system 16. It is comprised as follows. In the present embodiment, the oxygen tank 61 is, for example, an oxygen cylinder filled with only pre-pressurized and compressed oxygen gas, and supplies the compressed and compressed oxygen gas to the intake system. It is structured to play a role. The oxygen filtering device 60 and the oxygen tank 61 may be configured to supply oxygen gas directly to the combustion chamber 2 without going through the intake system 16. The oxygen gas passage switching device 62 switches the supply source of oxygen gas to the intake system 16, that is, one of the oxygen filtration device 60 and the oxygen tank 61 as a supply source of oxygen gas to the intake system 16. It is comprised so that the role which selects may be played. In the present embodiment, the oxygen filtering device 60, the oxygen tank 61, and the oxygen gas passage switching device 62 are configured as one component of the oxygen supply device 5.

  According to the exhaust gas purification device of the fifth embodiment shown in FIG. 9 having the oxygen filtering device 60, the oxygen tank 61, and the oxygen gas passage switching device 62 configured as described above, either the oxygen filtering device 60 or the oxygen tank 61 is used. Compared to those having only one of them, more oxygen gas can be supplied over a long period of time without the need for replenishment, and more if necessary from before catalyst warm-up to after catalyst warm-up. It becomes possible to supply oxygen gas reliably.

  The control routine of the exhaust gas purification process executed in the internal combustion engine shown in FIG. 9 to which the present exhaust gas purification apparatus is applied, when the engine is cold immediately after starting, is the same as the control routine shown in FIG. 2 except for the following points. It is. That is, if it is determined in step 105 of the control routine shown in FIG. 2 that the catalyst temperature has not reached the activation temperature, oxygen gas is supplied from the oxygen tank 61 to the intake system 16 by the oxygen gas passage switching device 62. It is controlled so that When it is determined in step 105 of the control routine shown in FIG. 2 that the catalyst temperature has reached the activation temperature, oxygen gas is taken in from the oxygen filtering device 60 by the oxygen gas passage switching device 62 as necessary. It is controlled to be supplied to the system 16. Note that such control requires that a larger amount of oxygen gas be supplied, assuming that the oxygen gas concentration supplied from the oxygen tank 61 is higher than the oxygen gas concentration supplied from the oxygen filtration device 60. It is assumed that oxygen gas is supplied from the oxygen tank 61 before the possible catalyst warm-up. However, the present invention is not limited to this, and depending on the concentration of oxygen gas supplied from each of the oxygen filtering device 60 and the oxygen tank 61, the required amount of oxygen gas, and the like, the oxygen gas passage switching device 62 can appropriately The oxygen gas supply source may be switched. By having two oxygen gas supply sources of the oxygen filtration device 60 and the oxygen tank 61 in this way, more oxygen gas is replenished compared to one having only one of the oxygen filtration means and the oxygen tank. It can be supplied to the intake system over a long period of time without requiring work, and oxygen gas can be supplied to the intake system more reliably as needed from before the catalyst warms up to after the catalyst warms up. The control of the exhaust gas purification process after the catalyst warm-up after the oxygen gas passage switching device 62 is controlled so that oxygen gas is supplied from the oxygen filtering device 60 to the intake system is the control routine shown in FIG. It may be controlled as follows.

  As described above, according to the exhaust purification apparatus of the present invention, when the engine is cold and the purification performance of the exhaust purification catalyst is not expected immediately after starting the internal combustion engine, almost the entire exhaust gas in the exhaust system downstream of the exhaust purification catalyst is made into the intake system. The exhaust gas is re-combusted by supplying high-concentration oxygen gas having an oxygen concentration higher than at least normal oxygen concentration in the exhaust gas to re-burn CO and HC, which are harmful components in the exhaust gas, Can be improved. Further, for example, EGR gas can be supplied into the combustion chamber even during high-load operation, and more oxygen can be supplied into the combustion chamber than when oxygen is supplied only by fresh air. According to the exhaust emission control device of the present invention, after the catalyst is warmed up, that is, after the catalyst temperature exceeds the catalyst activation temperature, the back pressure control valve 15 and the oxygen supply device 5 are appropriately controlled as necessary. Further, it is possible to improve fuel efficiency and exhaust emission, and to achieve high output without providing a supercharger.

1 is a diagram showing a schematic configuration of a first embodiment of an exhaust gas purification apparatus for an internal combustion engine according to the present invention. It is a flowchart figure which shows one Embodiment of the control routine of the exhaust gas purification process in the time of engine cold immediately after a start performed by the internal combustion engine shown in FIG. 1 to which this exhaust gas purification apparatus is applied. It is a figure which shows one Embodiment of the map of the optimal end time of oxygen gas supply and fuel injection created based on the data obtained from the analysis, test, etc. which were performed previously. It is a flowchart figure which shows one Embodiment of the control routine of the exhaust gas purification process after the catalyst warming-up performed by the internal combustion engine shown in FIG. 1 to which this exhaust gas purification apparatus is applied. It is a figure which shows one Embodiment of the map which determines whether required oxygen amount can be covered only with oxygen in air based on an engine speed and request torque. It is a figure which shows schematic structure of 2nd embodiment of the exhaust gas purification device of the internal combustion engine which concerns on this invention. It is a figure which shows schematic structure of 3rd embodiment of the exhaust gas purification apparatus of the internal combustion engine which concerns on this invention. It is a figure which shows schematic structure of 4th embodiment of the exhaust gas purification device of the internal combustion engine which concerns on this invention. It is a figure which shows schematic structure of 5th embodiment of the exhaust gas purification apparatus of the internal combustion engine which concerns on this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Internal combustion engine body 2 Combustion chamber 3 Ignition device 4 Fuel injection device 5 Oxygen supply device 6 Exhaust system 7 Three-way catalyst 8 A / F sensor 9 Back pressure sensor 10 EGR device 11 Exhaust gas recirculation passage 12 Exhaust gas recirculation control valve 13 Intercooler 14 H ₂ O removal tank 15 Back pressure control valve 16 Intake system 17 Surge tank 18 Air flow meter 19 Throttle valve 20 Intake pressure sensor 21 Engine speed detection means 22 Accelerator opening degree detection means 23 Catalyst temperature detection means 24 Combustion pressure sensor 25 ECU

Claims (12)

In an exhaust gas purification apparatus for an internal combustion engine in which an exhaust gas purification catalyst for purifying harmful components in exhaust gas discharged from the internal combustion engine body is disposed in an exhaust system,
An EGR device that recirculates exhaust gas discharged from the internal combustion engine body from the exhaust system downstream of the exhaust purification catalyst to the intake system of the internal combustion engine;
Oxygen supply means for supplying high-concentration oxygen gas having an oxygen concentration at least higher than the oxygen concentration of normal air into the exhaust gas recirculated to the intake system by the EGR device;
Comprising
The exhaust gas exhausted from the internal combustion engine body by the EGR device is recirculated to the intake system from immediately after the internal combustion engine is started until the temperature of the exhaust purification catalyst reaches the catalyst activation temperature, and the oxygen supply means Supplying high-concentration oxygen gas into the exhaust gas recirculated to the intake system, and re-burning and purifying CO and HC in the exhaust gas recirculated to the intake system;
An exhaust emission control device for an internal combustion engine. The oxygen supply means includes an oxygen cylinder in which only oxygen gas is sealed, and an oxygen supply amount control valve that adjusts the supply amount of oxygen gas from the oxygen cylinder.
The exhaust emission control device for an internal combustion engine according to claim 1. The EGR device is a valve that is disposed in an exhaust system downstream of the exhaust purification catalyst and controls a ratio of exhaust gas recirculated to the intake system, and is configured to reduce a back pressure of the exhaust system downstream of the exhaust purification catalyst. Having a back pressure control valve to control within a predetermined range,
3. An exhaust emission control device for an internal combustion engine according to claim 1, wherein the exhaust gas purification device is an internal combustion engine.   The exhaust emission control device further includes an engine stall determination unit that determines whether or not the internal combustion engine is in a state where there is a danger of being stalled, and the engine stall risk is due to the engine stall determination unit. 4. The exhaust gas purification apparatus for an internal combustion engine according to claim 3, wherein when it is determined, the ratio of exhaust gas recirculated to the intake system by the back pressure control valve is reduced. The engine stall determination means includes engine speed detection means for detecting engine speed, and a combustion pressure sensor for detecting pressure in a combustion chamber of the internal combustion engine body.
At least of the fluctuation state of the engine speed detected by the engine speed detecting means and the pressure value in the combustion chamber detected by the combustion pressure sensor when the exhaust gas is recirculated to the intake system by the EGR device. Based on one, it is determined whether the internal combustion engine is in a state where there is a risk of stalling,
The exhaust emission control device for an internal combustion engine according to claim 4, wherein the exhaust gas purification device is an internal combustion engine. The internal combustion engine includes a fuel injection device that directly injects fuel into a combustion chamber of the internal combustion engine main body, and an ignition device that generates sparks in the combustion chamber,
The oxygen supply means is configured to directly supply high-concentration oxygen gas into the combustion chamber,
In the compression stroke of the internal combustion engine, fuel and high-concentration oxygen gas are supplied into the combustion chamber by the fuel injection device and the oxygen supply means, and sparks are generated in the combustion chamber by the ignition device.
The exhaust emission control device for an internal combustion engine according to claim 1. The EGR device includes a intercooler liquefying of H ₂ O component in the exhaust gas of the exhaust is cooled recirculated to the intake system by the EGR device, is removed and stored of H ₂ O component is liquefied by the intercooler An H ₂ O removal tank;
The exhaust emission control device for an internal combustion engine according to claim 1.   The oxygen supply means supplies a predetermined amount of high-concentration oxygen gas to the intake system according to a required torque after the temperature of the exhaust purification catalyst reaches the catalyst activation temperature. 3. An exhaust emission control device for an internal combustion engine according to 3.   2. The internal combustion engine according to claim 1, wherein the EGR device has carbon dioxide storage means for storing by absorbing or adsorbing carbon dioxide in exhaust gas recirculated to the intake system by the EGR device. Engine exhaust purification system. The EGR device has an exhaust gas recirculation passage that fluidly communicates the intake system and the exhaust system downstream of the exhaust purification catalyst,
The exhaust gas purification device circulates exhaust gas flowing out from the exhaust gas purification catalyst around the exhaust gas purification catalyst from immediately after the internal combustion engine is started until the temperature of the exhaust gas purification catalyst reaches a catalyst activation temperature. The exhaust gas purification device for an internal combustion engine according to claim 1, further comprising exhaust gas bypassing means for guiding the exhaust gas to the exhaust gas recirculation passage. Wherein of H _{2 O} component a H _{2 O} component is liquefied is stored removed the H _{2 O} removal tank by intercooler by electrolyzing to produce the oxygen component and hydrogen component, the generated oxygen component 8. The exhaust gas purification device for an internal combustion engine according to claim 7, further comprising a water electrolysis unit that supplies the generated hydrogen component to the intake system by supplying the oxygen supply unit to the oxygen supply unit.   The oxygen supply means generates high-concentration oxygen gas from air in the atmosphere and supplies the high-concentration oxygen gas to the intake system; and stores high-concentration oxygen gas that has been compressed and compressed in advance. An oxygen tank that supplies high-concentration oxygen gas to the intake system, and one of the oxygen filtering means and the oxygen tank as a supply source of high-concentration oxygen gas to the intake system based on the temperature of the exhaust purification catalyst 2. The exhaust gas purification apparatus for an internal combustion engine according to claim 1, further comprising switching means for selecting the engine.

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