JP2008196383A - 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 continuing operation of the internal combustion engine in an optimal operating state for exhaust emission while matching output torque of the internal combustion engine to requested output torque while the temperature of an exhaust emission control catalyst reaches a catalyst activation temperature. <P>SOLUTION: This exhaust emission control device is equipped with: an exhaust recirculation passage for communicating an exhaust system and an intake system further downstream than the exhaust emission control catalyst with fluid; a catalyst warmup means for recirculating exhaust gas discharged from an internal combustion engine main body to the intake system via the exhaust emission recirculation passage when the temperature of the exhaust emission control catalyst should be raised to a predetermined temperature or higher, and warming up the exhaust emission control catalyst by using heat of burned gas discharged from the internal combustion main body; and a torque control means for applying driving torque or braking torque to the internal combustion engine during warmup of the exhaust emission control catalyst by the catalyst warmup means and matching the output torque of the internal combustion engine to the requested torque. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an exhaust gas purification apparatus for an internal combustion engine in which an exhaust gas purification catalyst that purifies harmful components contained in exhaust gas discharged from an internal combustion engine body is disposed in an exhaust system.

  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.

  For this reason, at the time of engine cold start 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 catalyst activation temperature), the exhaust purification catalyst Purification of harmful components in exhaust gas cannot be expected, and it is necessary to take some measures to suppress the deterioration of exhaust emission.

  For example, the intake system of the internal combustion engine and the exhaust system of the internal combustion engine downstream of the exhaust purification catalyst are connected by an exhaust recirculation passage (EGR passage), and a control valve (EGR valve) is disposed in the exhaust recirculation passage. The HC adsorption catalyst is disposed in the exhaust gas recirculation passage between the control valve and the exhaust passage, and when the exhaust purification catalyst is in an inactive state, the control valve is closed until the exhaust purification catalyst becomes active. There is known an exhaust purification device for an internal combustion engine in which exhaust gas is guided into an exhaust gas recirculation passage (see Patent Document 1).

  However, it takes a considerable amount of time to change the exhaust purification catalyst from the inactive state to the active state, and keeping the exhaust gas from being released into the atmosphere during this period results in an abnormally high engine back pressure. There is a risk of hindering the operation of the internal combustion engine.

JP 2004-251126 A

  By the way, as one of means for improving the exhaust emission at the time of engine cold start immediately after the start of the internal combustion engine, the internal combustion engine main body after the start of the internal combustion engine until the temperature of the exhaust purification catalyst reaches the catalyst activation temperature. By recirculating almost the entire amount of exhaust discharged from the engine to the intake system of the internal combustion engine, and re-burning CO (carbon monoxide) and HC (hydrocarbon) in the exhaust gas recirculated to the intake system, It is conceivable to improve the exhaust emission at the start of the engine.

  In addition, when almost the entire amount of exhaust discharged from the internal combustion engine body is recirculated to the intake system of the internal combustion engine from immediately after the start of the internal combustion engine until the temperature of the exhaust purification catalyst reaches the catalyst activation temperature, By configuring exhausted exhaust gas to pass through the exhaust purification catalyst and then recirculating it to the intake system, it is possible to use the heat of burned gas discharged from the engine body to warm up the exhaust purification catalyst. It is conceivable to further improve the exhaust emission at the time of engine cold start.

  Further, as described above, from the time immediately after the internal combustion engine is started until the temperature of the exhaust purification catalyst reaches the catalyst activation temperature, the exhaust system is discharged from the exhaust system downstream from the exhaust purification catalyst to the intake system of the internal combustion engine. In the case of recirculating substantially the entire amount of exhaust gas, the internal combustion engine from the exhaust system downstream of the exhaust purification catalyst to the intake system of the internal combustion engine immediately after the start of the internal combustion engine until the temperature of the exhaust purification catalyst reaches the catalyst activation temperature. Recycle the exhaust discharged from the engine body, reduce the generation of harmful components due to the combustion of fuel in the combustion chamber, and operate the internal combustion engine in an optimal operating condition for exhaust emission so that the exhaust purification catalyst can be quickly heated. If it can be operated, the exhaust emission at the time of cold engine start can be further improved.

  However, there may be a case where the internal combustion engine cannot be operated in an optimal operating state in terms of exhaust emission due to restrictions on the engine speed at the time of engine cold start and restrictions on the necessary minimum torque.

  Still, if the internal combustion engine is operated in an optimal operating state, for example, the output torque in the optimal operating state may exceed the required torque, and as a result, the engine speed may become excessively high. is there. This excessively high engine speed is perceived as noise by the vehicle occupant and may result in a loss of vehicle merchantability. Further, an excessively large output torque may cause a dangerous sudden start when shifting from the idle operation state to the traveling state. Further, when the internal combustion engine is operated in the optimal operating state, for example, the output torque in the optimal operating state may be lower than the required torque, and as a result, the balance with the engine friction is lost, and the engine Can bring

  In the present invention, in view of the above problems, the exhaust gas discharged from the internal combustion engine main body is recirculated from the exhaust system downstream of the exhaust purification catalyst to the intake system of the internal combustion engine until the temperature of the exhaust purification catalyst reaches the catalyst activation temperature. Optimum operation in terms of exhaust emission, while adjusting the output torque of the internal combustion engine to the required torque, reducing the generation of harmful components due to the combustion of fuel in the combustion chamber and allowing the exhaust purification catalyst to rise in temperature quickly It is an object of the present invention to provide an exhaust purification device for an internal combustion engine that can continue to operate the internal combustion engine in a state.

  In the exhaust gas purification apparatus for an internal combustion engine in the cited document 1, an EGR passage for recirculating exhaust gas from the exhaust system downstream of the exhaust purification catalyst to the intake system of the internal combustion engine is provided, and is discharged from the engine body. The configuration is such that the heat of the burned gas can be used to warm up the exhaust purification catalyst. However, in the exhaust gas purification apparatus for an internal combustion engine in the cited document 1, when at least the three-way catalyst is in an inactive state and the flow path switching valve is in the first state, the EGR valve is closed and the exhaust gas is returned to the intake system. It is described that the circulation is interrupted, and at the time of cold start of the engine, the exhaust gas exhausted from the internal combustion engine body is recirculated from the exhaust system downstream of the exhaust purification catalyst to the intake system of the internal combustion engine. Absent.

  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. Exhaust gas exhausted from the internal combustion engine body when the exhaust gas recirculation passage that fluidly communicates the exhaust system downstream and the intake system of the internal combustion engine and the temperature of the exhaust purification catalyst should be raised to a predetermined value or more Is recirculated to the intake system through the exhaust gas recirculation passage, and catalyst warm-up means for warming up the exhaust gas purification catalyst using heat of burned gas discharged from the internal combustion engine body, and the catalyst Torque control means for applying drive torque or braking torque to the internal combustion engine and causing the output torque of the internal combustion engine to match the required torque during warming-up of the exhaust purification catalyst by the warm-up means. When Exhaust gas purifying apparatus for an internal combustion engine is provided that.

  That is, according to the first aspect of the present invention, when the temperature of the exhaust gas recirculation passage communicating the exhaust system downstream of the exhaust purification catalyst and the intake system and the exhaust purification catalyst should be raised to a predetermined value or more, the internal combustion engine A catalyst warm-up means for recirculating the exhaust discharged from the engine body to the intake system through the exhaust gas recirculation passage, and warming the exhaust purification catalyst using the heat of the burned gas discharged from the engine body; Prepare. Thereby, exhaust gas discharged from the internal combustion engine body is recirculated to the intake system of the internal combustion engine, and CO (carbon monoxide) and HC (hydrocarbon) in the exhaust gas recirculated to the intake system can be recombusted. In addition, the heat of the burned gas discharged from the engine body can be used for warming up the exhaust purification catalyst, and it becomes possible to improve exhaust emission at the time of engine cold start.

  According to the first aspect of the present invention, during the warming-up of the exhaust purification catalyst by the catalyst warming-up means, a drive torque for adding a desired amount of torque to the output torque of the internal combustion engine, or a desired amount from the output torque of the internal combustion engine. And a torque control means for applying a braking torque for absorbing the torque to the internal combustion engine so that the output torque of the internal combustion engine matches the required torque. Thereby, when exhaust gas is recirculated, the output torque of the internal combustion engine is adjusted to the required torque, the generation of harmful components due to the combustion of fuel in the combustion chamber is reduced, and the exhaust purification catalyst can be quickly heated. The internal combustion engine can be continuously operated in an optimum operating state in terms of exhaust emission, and it is possible to quickly warm up the exhaust purification catalyst and further improve exhaust emission.

  According to a second aspect of the present invention, the torque control means has a function as a generator that converts mechanical energy into electrical energy, and a motor generator that has a function as an electric motor that converts electrical energy into mechanical energy. The exhaust purification device for an internal combustion engine according to claim 1, wherein a drive torque or a braking torque is applied to the internal combustion engine by the motor / generator.

  That is, in the invention of claim 2, the torque control means includes a motor / generator having a function as a generator and a function as an electric motor. Driving torque or braking torque can be applied.

  According to the third aspect of the present invention, motoring for driving the internal combustion engine by the motor / generator without performing combustion is performed before heating by the catalyst warming means, and heating is performed by the motoring. 3. The internal combustion engine according to claim 2, further comprising pre-warming means for allowing the exhausted gas to pass through the exhaust purification catalyst and then recirculate to the intake system through the exhaust gas recirculation passage. An exhaust emission control device is provided.

  That is, according to the third aspect of the present invention, the exhaust system preliminary warm-up including the exhaust purification catalyst by motoring without combustion is executed before the warm-up by the catalyst warm-up means. Specifically, the exhaust heat is increased by heat generated due to the work of the motor / generator for reciprocating the piston, and the exhaust system is preliminarily warmed up including the exhaust purification catalyst. According to this, it is possible to raise the temperature of the exhaust system including the exhaust purification catalyst to some extent before performing the warm-up by the catalyst warm-up means accompanied with combustion, and the exhaust purification at the time of executing the warm-up by the catalyst warm-up means The catalyst can be warmed up quickly, and the fuel is not consumed during the driving by the motoring, and the fuel consumption can be suppressed.

  According to a fourth aspect of the present invention, after the combustion of the internal combustion engine is stopped, motoring for driving the internal combustion engine by the motor / generator without performing combustion is performed, and the internal combustion engine body is driven by the motoring. The exhaust gas purification apparatus for an internal combustion engine according to claim 2, wherein the burned gas discharged from the exhaust gas is passed through the exhaust gas purification catalyst and then recirculated to the intake system via the exhaust gas recirculation passage. Is provided.

  That is, in the invention of claim 4, the driving of the internal combustion engine with combustion is stopped in a state where the exhaust system including the exhaust purification catalyst has been heated to some extent by the driving of the internal combustion engine with combustion, and the internal combustion engine is driven by motoring. The burned gas discharged from the main body is passed through the exhaust purification catalyst and then recirculated to the intake system. Even when the driving of the internal combustion engine with combustion is stopped, the exhaust heat can be increased by the heat generated due to the work of the motor generator for reciprocating the piston, and the exhaust heat is discharged from the main body of the internal combustion engine. Since the burned burned gas is allowed to pass through the exhaust purification catalyst and then recirculated to the intake system via the exhaust recirculation passage, the temperature of the exhaust purification catalyst can be continuously increased. Since the ring is not accompanied by combustion, it is possible to suppress an excessive increase in back pressure and deterioration of exhaust emission.

  According to the fifth aspect of the present invention, the apparatus includes oxygen supply means for supplying high-concentration oxygen gas having an oxygen concentration higher than the oxygen concentration of air into the exhaust gas recirculated to the intake system. An exhaust emission control device for an internal combustion engine according to claim 1 is provided.

  That is, the invention of claim 5 is provided with an oxygen supply means for supplying a high-concentration oxygen gas having an oxygen concentration higher than at least the normal air oxygen concentration, so that fresh air, that is, new air is not supplied. The high-concentration oxygen gas having an oxygen concentration higher than that of at least normal air makes it possible to re-burn CO and HC in the exhaust gas recirculated to the intake system. 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 sufficient oxygen in the exhaust gas to reburn CO and HC in the large amount of recirculated exhaust gas. Therefore, in the invention of claim 5, when fresh air is introduced by supplying high-concentration oxygen gas having an oxygen concentration higher than the oxygen concentration in fresh air into the exhaust gas recirculated to the intake system. As compared with the above, CO and HC in a larger amount of exhaust gas can be reburned, and exhaust emission can be improved.

  According to the sixth aspect of the present invention, during the warm-up execution by the catalyst warm-up means, the torque control means generates a driving torque according to the increase in back pressure caused by the oxygen supply by the oxygen supply means. The exhaust gas purification apparatus for an internal combustion engine according to claim 5, wherein the exhaust gas purification apparatus is provided to the engine.

  When oxygen is supplied into the exhaust gas by the oxygen supply means, the combustion pressure rises, and the back pressure rises accordingly. And when the back pressure rises, in the configuration where the exhaust gas is recirculated to the intake system, the intake pressure rises and the in-cylinder inflow gas amount increases, the required compression force in the compression stroke increases, and a larger driving torque Is required. Therefore, in the invention of claim 6, the torque control means provides the internal combustion engine with a drive torque corresponding to the increase in the back pressure caused by the oxygen supply by the oxygen supply means, so that the required drive torque due to the increase in the back pressure can be reduced. It makes it possible to compensate for the increase.

  According to the seventh aspect of the present invention, when the torque fluctuation of the internal combustion engine becomes larger than a predetermined value during operation of the internal combustion engine after completion of warm-up by the catalyst warm-up means, the torque control means 2. The exhaust gas purification apparatus for an internal combustion engine according to claim 1, wherein a driving torque or a braking torque is applied to the internal combustion engine to control a torque fluctuation of the internal combustion engine to be within a predetermined value. Is done.

  That is, according to the seventh aspect of the present invention, during the operation of the internal combustion engine after the warm-up by the catalyst warm-up means, the torque control means controls the torque fluctuation of the internal combustion engine to be within a predetermined value, thereby allowing the catalyst warm-up. It is possible to improve the torque fluctuation of the internal combustion engine after the machine.

  According to the invention described in each claim, when it is necessary to raise the temperature of the exhaust purification catalyst to a predetermined value or more, such as when the engine is cold-started, the internal combustion is performed from the exhaust system downstream of the exhaust purification catalyst. Exhaust gas exhausted from the internal combustion engine body can be recirculated to the engine intake system, and when exhaust gas is recirculated, the output torque of the internal combustion engine is adjusted to the required output torque while The internal combustion engine can be continuously operated in an optimal operating state, and there is a common effect that the exhaust purification catalyst can be quickly warmed up and exhaust emission can be improved.

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 schematic configuration diagram of an entire exhaust gas purification apparatus for an internal combustion engine showing an embodiment of 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 is an electronic control unit (hereinafter referred to as ECU), 26 is a motor / generator, 27 is a motor / generator control unit, 28 is a battery, and 29 is an exhaust temperature sensor.

  In the combustion chamber 2 of the internal combustion engine body 1, an ignition device 3, a fuel injection device 4, and a combustion pressure sensor 24 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 plays a role of supplying high-concentration oxygen gas having an oxygen concentration higher than at least the oxygen concentration in the air into the exhaust gas recirculated to the intake system by the EGR device 10 described later.

  In the exhaust gas purification apparatus for an internal combustion engine of the present invention, at the time of engine cold start in which the purification performance of the exhaust gas purification catalyst cannot be expected immediately after the internal combustion engine is started, substantially the entire amount of exhaust gas in the exhaust system downstream from the exhaust gas purification catalyst is exhausted. Returning to step 3, the high-concentration oxygen gas is supplied into the exhaust gas, so that CO and HC, which are harmful components in the exhaust gas, are recombusted to improve exhaust emission.

  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 oxygen gas. However, the oxygen supply device 5 may have other configurations. For example, instead of an oxygen cylinder, a high-concentration oxygen gas generation device that generates oxygen gas exceeding the oxygen concentration of normal air may be used. .

  In addition, as for the arrangement of the oxygen supply device 5, if a high concentration oxygen gas can be supplied into the exhaust gas recirculated to the intake system, a large amount of exhaust gas is recirculated to the intake system. A larger amount of CO and HC in the exhaust can be reburned and may be placed in any position.

  In the present embodiment, the oxygen supply device 5 is configured and arranged so as to supply high-concentration oxygen gas to the intake system 16. However, the oxygen supply device 5 may be configured and arranged so that the high-concentration oxygen gas can be directly supplied into the combustion chamber 2. In the case where the oxygen supply device 5 is arranged so as to be able to directly supply high-concentration oxygen gas into the combustion chamber 2, the oxygen supply device 5 has been recirculated which accounts for a large proportion in the combustion chamber 2 during the compression stroke of the internal combustion engine. Compared to the case where the oxygen supply device 5 is configured to supply high-concentration oxygen gas to the intake system, not only fuel but also oxygen gas can be concentrated in the vicinity of the spark plug with respect to the exhaust gas. This makes it possible to perform stratified combustion that can be burned with this fuel, and to achieve further improvement in fuel efficiency.

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. This is brought about by cooling the exhaust gas recirculation amount control valve 12 for controlling the flow rate (hereinafter referred to as recirculation gas), the intercooler 13 for cooling the recirculation gas, and H ₂ O in the recirculation gas being cooled. And an H ₂ O removal tank 14 for storing and removing liquid H ₂ O (water). 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. Therefore, the EGR device 10 also serves as catalyst warm-up means.

  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 indicates the pressure of 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 is combusted in the internal combustion engine. This is the pressure of the exhaust gas discharged after the exhaust gas, and the pressure of the exhaust gas flowing in 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 the exhaust temperature sensor 29 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 the exhaust temperature sensor 29 as a main element. However, for example, there is a slight gap between the three-way catalyst 7 and the exhaust temperature sensor 29. In order to estimate a temperature gradient or the like at this gap, the rotational load, the air-fuel ratio, the heat transfer coefficient, the catalyst reaction rate, etc. Correction is performed using parameters, and each element for detecting each piece of information is also a component 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. In addition to calculating parameters necessary for control such as the engine speed and intake air amount, various parameters relating to the operation of the internal combustion engine such as combustion air-fuel ratio control, fuel injection amount control, and ignition timing control are calculated based on the calculated parameters. It plays the role of controlling.

  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 includes 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, a combustion pressure sensor 24, and an exhaust temperature sensor. 29 is connected, and each detection information from these sensors and means can be taken into the ECU 25. Further, the ECU 25 is connected to an ignition device 3, a fuel injection device 4, an oxygen supply device 5, a back pressure control valve 15, and an exhaust gas recirculation amount control valve 12, and detection information from the various sensors and means described above. On the basis of the 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 exhaust gas recirculation is controlled by the EGR device 10 and the recirculation gas amount introduced into the intake system by the exhaust gas recirculation amount control valve 12 can be controlled.

  The motor / generator 26 has a function as a generator that converts mechanical energy into electrical energy and a function as an electric motor that converts electrical energy into mechanical energy. In the present embodiment, the motor / generator 26 is mounted on the output shaft of the internal combustion engine and is connected to the motor / generator control device 27. The motor / generator control device 27 is connected to a battery 28 that generates a DC high voltage current. The motor / generator control device 27 is connected to the ECU 25, and the operation of the motor / generator 26 is controlled by the ECU 25.

  When the motor / generator 26 is driven as an electric motor, the DC high voltage of the battery 28 is converted into a three-phase AC by the motor / generator controller 27, and this three-phase AC is supplied to the motor / generator 26. The generated torque, that is, the driving torque of the motor / generator 26 is substantially proportional to the current value of the three-phase alternating current, and this current value is determined based on the required driving torque of the motor / generator 26.

  On the other hand, when the motor / generator 26 is driven by an external force, it can be operated as a generator, and the electric power generated at this time is regenerated in the battery 28. The regenerative braking torque can be applied to the internal combustion engine by causing the motor / generator to function as a generator. When the motor / generator 26 is operated as a generator, the motor / generator control device 27 controls the battery 28 to regenerate the electric power generated by the motor / generator 26.

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 a first embodiment of a control routine of an exhaust purification process executed in the internal combustion engine shown in FIG. 1 to which the present exhaust purification apparatus is applied.

In the control routine shown in FIG. 2, the EGR device 10 and the oxygen supply device 5 perform the period from immediately after the internal combustion engine is started 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. A purification process of CO and HC in the exhaust gas is executed. Further, the heat of the burned gas discharged from the engine body is used for warming up the catalyst 7 to promote warming up of the catalyst 7. Further, when the exhaust gas is recirculated until the temperature of the catalyst 7 reaches the catalyst activation temperature, generation of harmful components due to combustion of fuel in the combustion chamber while adjusting the output torque of the internal combustion engine to the required torque. Torque control by the motor / generator 26 is executed so that the internal combustion engine can continue to be operated in an optimum operating state in terms of exhaust emission so that the temperature of the catalyst can be increased quickly.
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, 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. Note that the target predetermined value of the back pressure takes into consideration the stability of the back pressure when the recirculated 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. To be 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 gas is recirculated as a recirculated gas to the intake system, and CO and HC in the exhaust can be reburned and purified.

However, in this exhaust purification device, as will be described in detail in step 109 described later, the amount of recirculated gas is recirculated by the oxygen supply device 5 in order to reburn CO and HC in the recirculated gas recirculated to the intake system. In order to additionally supply about 21% of the oxygen gas, all of the exhaust gas discharged from the internal combustion engine body 1 through the period immediately after the internal combustion engine is started until the catalyst 7 reaches the catalyst activation temperature is recirculated as a recirculation gas to the intake system. When it is made to circulate, every time the recirculation gas is recirculated to the intake system, the recirculation gas amount 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 recirculation gas can be liquefied and removed, and the recirculation gas is exhausted and recirculated. By reducing the amount of recirculation gas while passing through the circulation passage 11, an increase in the amount of recirculation 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 recirculation gas is 10%, which is sufficient to suppress the increase in the recirculation gas amount caused by the oxygen addition by the oxygen gas supply device 5 as described above. I can not say. This increases the back pressure, leading to an increase in the amount of exhaust that is blown back directly into the combustion chamber 2 from the exhaust system, making the back pressure unstable and hindering stable recirculation of the recirculated gas. In this case, the internal combustion engine is stalled (stopped).

  Therefore, in the present exhaust purification apparatus, the target predetermined value of the back pressure can maintain a state in which the back pressure is stable when the recirculated gas is recirculated to the intake system by the EGR device 10. This value is a value that can prevent the exhaust amount directly blown back into the combustion chamber 2 from the exhaust system from becoming extremely large, and is determined based on data obtained by analysis or tests executed in advance. Is done. Specifically, at least about 21% of the recirculated gas amount 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 recirculated gas immediately after the internal combustion engine is started until the catalyst 7 reaches the catalyst activation temperature, and it is possible to improve the exhaust emission.

  If it is determined in step 106 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 107. In step 107, 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 107, the process returns to step 106, and it is again determined whether or not the back pressure is within a predetermined target predetermined value range. The A certain amount of valve opening / closing control of the back pressure control valve 15 in this step 107 is repeatedly executed until it is determined in step 106 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 106 that the back pressure is within the range of the predetermined target value, the process proceeds to the subsequent step 108.

  In step 108, first, based on the configuration of the internal combustion engine, etc., the optimum operating conditions in terms of exhaust emission such that the generation of harmful components due to the combustion of fuel in the combustion chamber of the internal combustion engine is small and the catalyst can be quickly heated, In the present embodiment, an optimal engine load is set. In this embodiment, the engine load is calculated based on the output torque or the engine speed and the amount of gas introduced into the combustion chamber. Also, torque that does not cause an engine stall at least, and that does not cause an excessive increase in the engine speed that is recognized as noise by the vehicle occupant and results in damage to the vehicle merchandise. Is set as the required torque. Note that when the accelerator pedal is depressed by the driver, the required torque is set based on the detection information of the accelerator opening detection means 22.

  Next, from the set optimum engine load and required torque, the recirculation gas amount introduced into the combustion chamber necessary for realizing the optimum engine load is calculated by the ECU 25 using a map or the like. In order to circulate the calculated amount of recirculated gas to the intake system, the opening degree of the exhaust gas recirculation amount control valve 12 is controlled based on the back pressure, the intake pipe negative pressure, etc., and the throttle valve 19 is fully closed. The If the calculated amount of recirculated gas is larger than the amount of gas that can actually be recirculated, a short amount of fresh air is introduced by controlling the throttle valve 19 to satisfy the required gas amount. The amount of gas that can be actually recirculated is the intake pressure detected from the intake pressure sensor 20, the back pressure detected from the back pressure sensor 9, and the recirculation gas when the exhaust recirculation amount control valve 12 is fully open. The ECU 25 calculates the flow area of the flowing exhaust gas recirculation passage 11 and the like.

  By the way, in order to reburn and purify CO and HC in the recirculated gas without introducing fresh air, oxygen supply and fuel injection in an amount corresponding to the amount of recirculated gas introduced into the combustion chamber are performed. In this case, the output torque of the internal combustion engine increases as the amount of recirculation gas introduced into the combustion chamber increases, and the engine speed increases as the output torque of the internal combustion engine increases. Therefore, when the calculated amount of recirculation gas introduced into the combustion chamber is large, the output torque may become higher than the required torque, and the engine speed may become excessively high. This excessively high engine speed is perceived as noise by the vehicle occupant and may result in a loss of vehicle merchantability. Further, an excessively large output torque may cause a dangerous sudden start when shifting from the idle operation state to the traveling state. Further, when the calculated amount of recirculation gas introduced into the combustion chamber is small, there is a possibility that a small output torque is not produced. For example, if the output torque is excessively lower than the required torque, the balance with the engine friction may be lost, resulting in engine stall. As described above, there may occur a case where the internal combustion engine cannot be operated in an optimum operating state in terms of exhaust emission due to the restriction on the engine speed at the time of cold start of the engine and the restriction such as the minimum necessary torque.

  Therefore, in the present exhaust purification apparatus, the internal combustion engine is provided with a driving torque that adds a desired amount of torque to the output torque of the internal combustion engine or a braking torque that absorbs a desired amount of torque from the output torque of the internal combustion engine. The torque control means for matching the output torque of the engine with the required torque, in this embodiment, the motor / generator 26, makes it possible to request the output torque of the internal combustion engine without depending on the amount of recirculated gas introduced into the combustion chamber. It is possible to match the torque.

  Thereby, when exhaust gas is recirculated, the output torque of the internal combustion engine is adjusted to the required torque, the generation of harmful components due to the combustion of fuel in the combustion chamber is reduced, and the exhaust purification catalyst can be quickly heated. The internal combustion engine can be continuously operated in an optimum operating state in terms of exhaust emission, and it is possible to quickly warm up the exhaust purification catalyst and further improve exhaust emission.

  Based on this, in step 108, a desired braking torque amount or driving torque amount to be applied to the internal combustion engine by the motor / generator 26 is calculated based on the calculated recirculation gas amount and the set required torque. Is done. When the recirculation gas amount, the required torque amount, and the desired braking torque amount or driving torque amount to be applied to the internal combustion engine by the motor / generator 26 are calculated at step 108, the routine proceeds to the subsequent step 109.

  In step 109, supply of a required amount of oxygen gas and fuel injection are executed in accordance with the amount of recirculated gas introduced into the combustion chamber, and ignition is performed, whereby the recirculated gas in the recirculated gas is recirculated to the intake system. CO and HC, which are harmful components, are reburned and purified. Specifically, a required amount of oxygen gas is supplied by the oxygen supply device 5 in accordance with the amount of recirculation gas calculated in step 108, and a required amount of fuel is injected by the fuel injection device 4, and the ignition device 3 leads to ignition in the combustion chamber.

  Here, the necessary amount of oxygen supplied by the oxygen supply device 5 is intended to be the amount of oxygen necessary for burning the recirculated gas introduced into the combustion chamber. In this embodiment, the recirculated gas is used. Assuming that no oxygen component is present therein, the oxygen supply device 5 supplies about 21% of the oxygen gas with respect to the amount of recirculated gas introduced into the combustion chamber. 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 introduced into the combustion chamber 2, the total amount of the gas introduced into the combustion chamber 2 is the total amount of the recirculated gas introduced into the combustion chamber 2 and fresh air.

  Further, in step 109, when the calculated amount of exhaust gas is recirculated until the temperature of the catalyst reaches the catalyst activation temperature, combustion is performed while adjusting the output torque of the internal combustion engine to the required output torque. According to the motor / generator 26, which can keep the internal combustion engine operating in an optimal operating state in terms of exhaust emission so that the generation of harmful components due to combustion of fuel in the room is small and the exhaust purification catalyst can be quickly heated. Torque control is executed. Specifically, the motor / generator 26 is controlled so as to apply the desired braking torque amount or driving torque amount calculated in step 108 to the internal combustion engine.

  Further, in step 109, feedback control is performed so that the internal combustion engine is operated at a predetermined air-fuel ratio immediately after the internal combustion engine is started and 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 recirculation gas can be more reliably recombusted in the combustion chamber 2, and exhaust emission can be improved.

  During the warming-up, the motor / generator 26 may apply a driving torque to the internal combustion engine in accordance with the increase in the back pressure caused by the oxygen supply by the oxygen supply device 5.

  When oxygen is supplied into the exhaust gas by the oxygen supply device 5, the combustion pressure rises, and the back pressure rises accordingly. And when the back pressure rises, in the configuration where the exhaust gas is recirculated to the intake system, the intake pressure rises and the in-cylinder inflow gas amount increases, the required compression force in the compression stroke increases, and a larger driving torque Is required. In view of this, the motor / generator 26 applies a drive torque corresponding to the increase in the back pressure caused by the oxygen supply from the oxygen supply device 5 to compensate for the increase in the required drive torque due to the increase in the back pressure. It becomes possible.

  The control routine from step 101 to step 109 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, that is, when it is confirmed that the warm-up has been completed, the routine proceeds to the subsequent steps 110 and 111.

  In step 110 and step 111, a recirculation gas amount suitable for the current operation state is calculated, and the opening degree of the exhaust gas recirculation amount control valve 12 is controlled based on the calculated recirculation gas amount. EGR control is executed. At that time, the ECU 25 is controlled so that the back pressure control valve 15 is fully opened. The exhaust gas recirculation amount control valve 12 may be fully opened, and EGR control may be executed in which the opening degree of the back pressure control valve 15 is controlled based on the calculated recirculation gas amount.

  FIG. 3 is a flowchart showing a second embodiment of the control routine of the exhaust purification process executed in the internal combustion engine shown in FIG. 1 to which the present exhaust purification apparatus is applied.

In the control routine shown in FIG. 3, the internal combustion engine is started when there is a request for starting the internal combustion engine in the control routine of the first embodiment of the exhaust gas purification process at the time of cold engine start immediately after the start shown in FIG. Before performing the motoring, the motor / generator 26 drives the internal combustion engine without causing combustion. The gas heated by the motoring is passed through the catalyst 7 and then taken in through the exhaust gas recirculation passage 11. By recirculating to the system 16 and performing preliminary warm-up of the exhaust system including the catalyst 7, it is possible to further promote catalyst warm-up.
Details of each step will be described below.

  First, in step 201 and step 202, as in step 101 and step 102 of the control routine shown in FIG. 1, it is confirmed whether or not the internal combustion engine is in an operating state and whether or not there is a request for starting the internal combustion engine. . When the start request to the internal combustion engine is confirmed in step 202, the process proceeds to the subsequent step 203.

  In step 203, it is determined by the ECU 25 based on the detection value from the exhaust temperature sensor 29 whether or not the exhaust temperature is less than a predetermined value. The predetermined value here is appropriately set in advance based on the configuration and design specifications of the internal combustion engine. If it is determined that the exhaust gas temperature is less than the predetermined value, the process proceeds to subsequent steps 204 and 205.

  In step 204 and step 205, motoring for driving the internal combustion engine by the motor / generator without combustion is performed, and the gas heated by the motoring is passed through the catalyst 7, and then the exhaust gas recirculation passage 11 is set. The exhaust system is recirculated to the intake system 16 and the exhaust system is preliminarily warmed up, and the catalyst warm-up is further promoted.

  First, in step 204, the back pressure control valve 15 and the throttle valve 19 are fully closed by a signal from the ECU 25, and the exhaust gas recirculation amount control valve 12 is slightly opened. In step 205, motoring for driving the internal combustion engine is executed by the motor / generator 26 without combustion.

  As a result, air existing between the throttle valve 19 and the back pressure control valve 15 is circulated between the intake system 16 and the exhaust system 6 via the exhaust recirculation passage 11 by motoring without exposing to the atmosphere. be able to. The piston is reciprocated by the motoring, and the temperature of the circulating air is gradually increased by the heat caused by the work of the motor / generator 26 to reciprocate the piston. As a result, the exhaust system 6 including the catalyst 7 can be preliminarily warmed up. Further, in this embodiment, the exhaust gas recirculation amount control valve 12 is slightly opened, the passage of the circulating air is narrowed, and the work of the motor / generator 26 when the piston is reciprocated is increased. It promotes the heat generated in the circulating air. This preliminary warm-up by motoring is repeatedly executed until the exhaust gas temperature becomes a predetermined value or higher. If it is determined in step 203 that the exhaust gas temperature is equal to or higher than the predetermined value, the process proceeds to the subsequent step 206, step 207 and step 208.

  If there is a request for starting the internal combustion engine and the exhaust gas temperature is equal to or higher than the predetermined value, the routine does not proceed to step 204 and step 205. Therefore, in step 206 and step 207, the back pressure control valve 15 is fully closed. If it is determined that the back pressure control valve 15 is not fully closed, the back pressure control valve 15 is fully closed, and the routine proceeds to step 208 where the internal combustion engine is started. .

  In Steps 209 to 215 after the start of the internal combustion engine following Step 208, the same control as Steps 105 to 111 of the control routine shown in FIG. 2 is executed, and detailed description thereof is omitted here. To do.

  In the control routine shown in FIG. 3, when the internal combustion engine is requested to start, preliminary warm-up is performed by motoring before starting the internal combustion engine. The control routine may be such that the exhaust system 6 including the catalyst 7 is heated to some extent by an operation involving combustion of the internal combustion engine. In this case, the warming up by motoring stops the operation involving combustion of the internal combustion engine while the exhaust system 6 including the catalyst 7 has been heated to some extent by the operation involving combustion of the internal combustion engine. The burned gas discharged from the engine body is passed through the catalyst 7 and then recirculated to the intake system 16. Even if the operation of the internal combustion engine with combustion is stopped, the exhaust heat can be increased from the motoring and the burned gas discharged from the internal combustion engine body is passed through the catalyst 7 and then passed through the exhaust gas recirculation passage 11. Since it can be recirculated to the intake system 16, the temperature of the catalyst 7 can be continuously increased. Further, since the motoring does not involve combustion, an excessive increase in back pressure and deterioration of exhaust emission can be suppressed. It becomes possible. FIG. 4 shows the time transition of the catalyst temperature and the warming by the motoring in the case where the warming up by the motoring is performed in a state where the exhaust system 6 including the catalyst 7 is heated to some extent by the operation accompanied by the combustion of the internal combustion engine. It is a figure which shows one Embodiment of an opportunity.

  FIG. 5 is a flowchart showing a third embodiment of the control routine of the exhaust purification process executed in the internal combustion engine shown in FIG. 1 to which the present exhaust purification apparatus is applied.

After the catalyst 7 has been warmed up, that is, after the catalyst temperature has become equal to or higher than the activation temperature, the internal combustion engine is brought into an optimum operating state in terms of fuel consumption, and a large amount in order to obtain an optimum operating state in terms of fuel consumption. When the recirculation gas is introduced into the combustion chamber, the recirculation gas contains a large amount of CO _2, so the combustion speed decreases and the combustion becomes unstable. Deterioration can be brought about.

Therefore, in the control routine shown in FIG. 5, after the warm-up of the catalyst 7 in the control routine of the first embodiment of the exhaust gas purification process at the time of engine cold start shown in FIG. 2, that is, the catalyst temperature becomes equal to or higher than the activation temperature. Later, the internal combustion engine is put into an optimum operating state in terms of fuel consumption, and a driving torque or a braking torque is applied to the internal combustion engine by the motor / generator 26 as necessary to reduce the torque fluctuation during the engine operation. This makes it possible to operate the internal combustion engine in an optimum driving state in terms of fuel consumption without deteriorating the performance.
Details of each step will be described below.

  In the control routine shown in FIG. 5, the same control as in steps 101 to 109 of the control routine shown in FIG. 2 is executed for steps 301 to 309 before the catalyst temperature reaches the activation temperature. The detailed description of is omitted.

  If it is determined in step 305 that the catalyst temperature is equal to or higher than the activation temperature, the process proceeds to step 310 and step 311 to calculate and calculate the optimum recirculation gas amount in terms of fuel consumption in the current engine operating state. The opening degree of the back pressure control valve 15 and the exhaust gas recirculation amount control valve 12 is controlled by the ECU 25 so that an amount of the recirculated gas is introduced into the combustion chamber. At this time, the oxygen supply amount and the fuel injection amount are also calculated based on the calculated recirculation gas amount.

  When the opening degree of the back pressure control valve 15 and the exhaust gas recirculation amount control valve 12 is controlled by the ECU 25 in step 311, in next step 312, it is determined whether or not the torque fluctuation of the internal combustion engine exceeds a predetermined value. If it is determined by the ECU 25 and it is determined that the torque fluctuation value is larger than the predetermined value, the process proceeds to the next step 313, where torque fluctuation reduction control by the motor / generator 26 is executed. Specifically, the motor / generator 26 applies an appropriate driving torque or braking torque to the internal combustion engine to control the torque fluctuation value to fall within a predetermined value.

  As a result, even after a large amount of recirculated gas is introduced into the combustion chamber in order to bring the internal combustion engine into an optimum operating state in terms of fuel consumption after the catalyst temperature becomes equal to or higher than the activation temperature, the torque fluctuations It is possible to drive the internal combustion engine in an optimum driving state in terms of fuel efficiency while reducing the deterioration of drivability.

1 is a schematic configuration diagram of an entire exhaust gas purification apparatus for an internal combustion engine showing an embodiment of the present invention. It is a flowchart figure which shows 1st embodiment of the control routine of the exhaust gas purification process performed with the internal combustion engine shown in FIG. 1 to which this exhaust gas purification apparatus is applied. It is a flowchart figure which shows 2nd embodiment of the control routine of the exhaust gas purification process performed with the internal combustion engine shown in FIG. 1 to which this exhaust gas purification apparatus is applied. When the warming-up by motoring is performed in a state where the exhaust system including the exhaust purification catalyst has been heated to some extent by the operation accompanied by combustion of the internal combustion engine, the time transition of the catalyst temperature and the warming-up timing by motoring It is a figure which shows embodiment. It is a flowchart figure which shows 3rd embodiment of the control routine of the exhaust gas purification process performed with the internal combustion engine shown in FIG. 1 to which this exhaust gas purification apparatus is applied.

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
26 Motor / Generator 27 Motor / Generator Controller 28 Battery 29 Exhaust Temperature Sensor

Claims (7)

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 exhaust gas recirculation passage in fluid communication between the exhaust system downstream of the exhaust purification catalyst and the intake system of the internal combustion engine;
When the temperature of the exhaust purification catalyst is to be raised to a predetermined value or higher, the exhaust gas discharged from the internal combustion engine body is recirculated to the intake system via the exhaust gas recirculation passage, and is discharged from the internal combustion engine body. Catalyst warm-up means for warming up the exhaust purification catalyst using the heat of burned gas,
Torque control means for applying drive torque or braking torque to the internal combustion engine and matching the output torque of the internal combustion engine with the required torque during the warming-up of the exhaust purification catalyst by the catalyst warm-up means. An exhaust gas purification apparatus for an internal combustion engine characterized by the above.   The torque control means has a motor generator having a function as a generator that converts mechanical energy into electrical energy and a function as an electric motor that converts electrical energy into mechanical energy, and the internal combustion engine 2. The exhaust gas purification apparatus for an internal combustion engine according to claim 1, wherein driving torque or braking torque is applied to the engine.   Before performing warm-up by the catalyst warm-up means, motoring is performed to drive the internal combustion engine by the motor / generator without combustion, and gas heated by the motoring is passed through the exhaust purification catalyst. 3. The exhaust gas purification apparatus for an internal combustion engine according to claim 2, further comprising preliminary warm-up means for recirculating to the intake system through the exhaust gas recirculation passage.   After the combustion of the internal combustion engine is stopped, motoring for driving the internal combustion engine by the motor / generator without combustion is performed, and the exhaust purification of the burned gas discharged from the main body of the internal combustion engine is performed by the motoring. 3. The exhaust gas purification apparatus for an internal combustion engine according to claim 2, wherein the exhaust gas is recirculated to the intake system through the exhaust gas recirculation passage after passing through a catalyst.   2. The internal combustion engine according to claim 1, further comprising oxygen supply means for supplying high-concentration oxygen gas having an oxygen concentration higher than that of air into the exhaust gas recirculated to the intake system. Engine exhaust purification system.   The drive torque according to the increase in the back pressure caused by the oxygen supply by the oxygen supply means is applied to the internal combustion engine by the torque control means during the warm-up execution by the catalyst warm-up means. Item 6. An exhaust emission control device for an internal combustion engine according to Item 5.   During the operation of the internal combustion engine after completion of warm-up by the catalyst warm-up means, when torque fluctuation of the internal combustion engine becomes larger than a predetermined value, drive torque or braking torque is applied to the internal combustion engine by the torque control means. 2. The exhaust gas purification apparatus for an internal combustion engine according to claim 1, wherein the control is performed so that the torque fluctuation of the internal combustion engine is within a predetermined value.

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