JP2004340137A - 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 for eliminating harmful components stored in or collected by an exhaust emission control unit with high responsiveness and high precision. <P>SOLUTION: Temperature of exhaust to be discharged from a combustion chamber when storage type NOx catalyst (exhaust emission control unit) reaches prescribed high temperature T1 as target catalyst temperature is set as basic discharge temperature (B32). Difference between the prescribed high temperature T1 and temperature of storage type NOx catalyst detected by a second temperature sensor is added to the basic discharge temperature to set target discharge temperature of exhaust discharged from the combustion chamber (B34, B36, B38, and B40). Temperature control to the storage type NOx catalyst is conducted in such a way that the actual discharge temperature of exhaust discharged from the combustion chamber, and detected by a first temperature becomes the target discharge temperature (B42, B44, and B46). <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an exhaust gas purification device for an internal combustion engine, and more particularly to a technique for removing harmful components occluded or collected in an exhaust gas purification unit.

In recent years, a storage NOx catalyst capable of purifying NOx even in an oxygen-excess atmosphere has been developed and put into practical use as an exhaust purification unit.
The occlusion-type NOx catalyst, the oxygen excess state stores NOx in the exhaust gas in the (oxidative atmosphere), as the nitrate X-NO _3, N ₂ a suction built the NOx with CO (carbon monoxide) over state (reduction atmosphere) ( It is configured as a catalyst having a property of reducing to nitrogen (carbonate X-CO ₃ is generated at the same time). For example, when the storage NOx catalyst is provided in the exhaust passage of the internal combustion engine, a rich air-fuel ratio that controls the air-fuel ratio to a stoichiometric air-fuel ratio or a value close to the stoichiometric air-fuel ratio before the NOx storage amount of the storage NOx catalyst is saturated. The operation is periodically switched to the fuel ratio operation to generate a CO-rich reducing atmosphere, whereby the stored NOx is purified and reduced (NOx purge) to regenerate the storage-type NOx catalyst.

Incidentally, the fuel contains a toxic component S (sulfur) components (sulfur component), the S component reacts with oxygen SOx (sulfur oxides), and the SOx is sulfate X-SO ₄ Is stored in the storage type NOx catalyst instead of NOx (S poisoning).
It is known that the SOx thus occluded is released and removed (S purge) by setting the air-fuel ratio to a rich state and setting the storage NOx catalyst to a high temperature state. For example, the SOx occlusion amount is estimated. When it is determined that the estimated value has reached a predetermined amount, a technique for enriching the air-fuel ratio and performing additional injection of fuel in an expansion stroke or an exhaust stroke to raise the temperature of the exhaust gas to bring the catalyst to a high temperature state is known. (For example, see Patent Document 1).

When the internal combustion engine is a diesel engine, the exhaust gas contains particulate matter (hereinafter abbreviated as PM) as a harmful component depending on the operating condition, and the PM is collected as an exhaust gas purification unit. Diesel particulate filter (hereinafter abbreviated as DPF) has been developed and put into practical use.
Since the exhaust pressure of the DPF gradually increases due to the deposition of PM, the exhaust resistance increases, and the fuel efficiency deteriorates. Therefore, it is necessary to periodically perform forced regeneration for removing the deposited PM.

Therefore, for example, a technique of estimating the amount of trapped PM and determining that the estimated value has reached a predetermined amount, also performs additional injection to raise the temperature of the exhaust, set the DPF to a high temperature state, and burn and remove the PM. Are known.
JP 2002-213229 A

  By the way, in the technology disclosed in Patent Document 1, a diesel engine is used as an internal combustion engine. However, since a diesel engine has a large intake air amount and is basically operated at a lean air-fuel ratio, gasoline is not used. The exhaust temperature is lower than that of the engine as a whole, and there is a problem that it takes time to sufficiently raise the temperature of the storage NOx catalyst or the DPF when performing S purge or forcibly regenerating the DPF.

  Further, in the technique of performing the additional injection, the hydrocarbon (HC) component supplied to the exhaust passage is oxidized by an oxidation catalyst function of a storage NOx catalyst or an oxidation catalyst provided upstream of the DPF or a storage NOx catalyst. The temperature of the occluded NOx catalyst or DPF is raised by using the generated heat of oxidation. In such a temperature raising method using the heat of oxidation of the oxidation catalyst, the oxidation reaction requires a certain amount of time. There is a problem that it takes time to raise the temperature of the storage NOx catalyst and the DPF.

Further, when enriching the air-fuel ratio in a diesel engine, there is a problem that smoke (black smoke) is easily generated.
In order to control the storage type NOx catalyst or DPF to a high temperature state when performing the S purge or the forced regeneration of the DPF, for example, a temperature sensor is provided in the storage type NOx catalyst or DPF or in the vicinity thereof, and the storage type NOx catalyst or DPF is provided. There is a technique for performing feedback control of the exhaust gas temperature rise based on the temperature information. However, since the temperature sensor has a slow response, when a turbocharger is provided in the exhaust passage, or when the heat capacity of the exhaust passage is large, such as when the exhaust passage is long, or when there is a temperature decrease due to heat energy consumption of the exhaust gas. However, there is also a problem that the temperature is large, causing hunting and poor controllability. In other words, even when the temperature rise of the exhaust gas is started, the temperature of the storage NOx catalyst or DPF does not readily rise at first at first, and when the heat capacity of the exhaust passage is satisfied, the temperature of the storage NOx catalyst or DPF rises rapidly. There is a problem of getting started. This problem is the same when an oxidation catalyst or a DPF is disposed upstream of the storage NOx catalyst, and when an oxidation catalyst or a storage NOx catalyst is disposed upstream of the DPF. Further, when the temperature is rapidly increased in such a manner, the storage NOx catalyst, the DPF, and the turbocharger may be overheated and damaged.

In this case, if an attempt is made to raise the exhaust gas temperature so as not to cause hunting or overheat the occlusion type NOx catalyst, DPF or turbocharger, the control must be slow, and the occlusion type NOx catalyst or DPF is still required. It takes time to raise the temperature, which is not preferable.
The present invention has been made to solve such problems, and an object of the present invention is to provide an internal combustion engine capable of removing harmful components occluded or trapped in an exhaust gas purification unit with high responsiveness and high accuracy. It is an object of the present invention to provide an exhaust gas purifying apparatus.

  In order to achieve the above object, an exhaust gas purifying apparatus for an internal combustion engine according to claim 1 is provided in an exhaust system of the internal combustion engine and purifies exhaust gas, and an exhaust port of the internal combustion engine is provided in the exhaust system. A first temperature sensor for detecting the temperature of the exhaust gas discharged from the combustion chamber of the internal combustion engine, and a first temperature sensor for detecting the temperature of the exhaust gas discharged from the combustion chamber of the internal combustion engine; A second temperature sensor for detecting a temperature of exhaust gas flowing into the unit, a deposition amount detecting means for estimating or detecting a deposition amount of harmful components in exhaust gas occluded or collected by the exhaust gas purification unit, and the deposition amount When the accumulation amount of the harmful component estimated or detected by the detection means reaches a predetermined amount, the exhaust gas purification unit is adjusted to a predetermined high temperature by the heat of the exhaust gas discharged from the combustion chamber, and the temperature of the stack is reduced. Release control means for releasing and removing the harmful components, wherein the release control means is configured to control the exhaust gas purification unit based on temperature information from the first temperature sensor and temperature information from the second temperature sensor. Is adjusted to a predetermined high temperature.

  Also, in the exhaust gas purifying apparatus for an internal combustion engine according to claim 2, according to claim 1, the release control means is configured to control a temperature of exhaust gas to be discharged from the combustion chamber when the temperature of the exhaust gas purifying unit reaches the predetermined high temperature. A basic discharge temperature setting unit that sets the basic discharge temperature as a basic discharge temperature, and a basic discharge temperature set by the basic discharge temperature setting unit and a difference between the predetermined high temperature and a temperature detected by the second temperature sensor. Target discharge temperature setting means for setting a target discharge temperature of exhaust gas discharged from the combustion chamber, wherein a target discharge temperature set by the target discharge temperature setting means and a temperature detected by the first temperature sensor are determined. The temperature of the exhaust gas purification unit is adjusted based on the difference.

  According to a third aspect of the present invention, in the exhaust gas purifying apparatus for an internal combustion engine according to the first or second aspect, the internal combustion engine has a throttle valve for adjusting an intake air amount in an intake system, and the emission control means includes an exhaust air-fuel ratio. Is controlled at a stoichiometric air-fuel ratio or an air-fuel ratio near the stoichiometric air-fuel ratio to control the temperature of the exhaust purification unit to a predetermined high temperature by controlling the throttle valve.

  In the exhaust gas purifying apparatus for an internal combustion engine according to a fourth aspect, in the third aspect, the release control means includes a basic throttle position setting means for setting a basic throttle position of the throttle valve in accordance with an operation state of the internal combustion engine. And correcting the basic throttle position set by the basic throttle position setting means based on a difference between a target discharge temperature set by the target discharge temperature setting means and a temperature detected by the first temperature sensor. The temperature of the exhaust gas purification unit is adjusted.

According to a fifth aspect of the present invention, in the exhaust gas purifying apparatus for an internal combustion engine according to the third or fourth aspect, the internal combustion engine is a diesel engine, and the emission control means sets the exhaust air-fuel ratio at or near the stoichiometric air-fuel ratio. The fuel injection timing is retarded while controlling the air-fuel ratio.
Further, in the exhaust gas purifying apparatus for an internal combustion engine according to claim 6, in claim 1, the exhaust gas purifying unit is provided in an exhaust system of the internal combustion engine. A storage type NOx catalyst that stores NOx and reduces the stored NOx when in a stoichiometric air-fuel ratio operation or a rich air-fuel ratio operation state, and wherein the second temperature sensor is located near the storage-type NOx catalyst. The temperature of exhaust gas flowing into the storage NOx catalyst, and the accumulation amount detection means estimates or detects the amount of sulfur component in the exhaust gas occluded by the storage NOx catalyst. When the sulfur component accumulation amount estimated or detected by the sulfur component accumulation amount detection device reaches a predetermined amount, the release control unit causes the storage NOx catalyst to move forward. The temperature of the exhaust gas discharged from the combustion chamber is adjusted to a predetermined high temperature by heat, and then the exhaust air-fuel ratio is controlled to a stoichiometric air-fuel ratio or a rich air-fuel ratio, and the storage NOx catalyst is maintained at the predetermined high temperature. A sulfur component releasing unit configured to release the accumulated sulfur component, wherein the sulfur component releasing unit is configured to store the sulfur component based on temperature information from the first temperature sensor and temperature information from the second temperature sensor. The temperature of the type NOx catalyst is adjusted to a predetermined high temperature.

According to a seventh aspect of the present invention, in the exhaust gas purifying apparatus for an internal combustion engine according to the sixth aspect, the internal combustion engine has a throttle valve for adjusting an intake air amount in an intake system. The temperature of the NOx storage catalyst is adjusted to a predetermined high temperature by controlling the throttle valve while controlling the stoichiometric air-fuel ratio or the rich air-fuel ratio.
Further, in the exhaust gas purifying apparatus for an internal combustion engine according to claim 8, in claim 1, the exhaust gas purifying unit includes a filter provided in an exhaust system of the internal combustion engine, for collecting particulate matter in exhaust gas, The second temperature sensor is provided near the filter, and detects the temperature of exhaust gas flowing into the filter. The deposition amount detecting means detects a particulate matter in the exhaust gas collected by the filter. The particulate matter deposition amount detecting means for estimating or detecting the amount of deposited matter is provided, and the release control means is configured to calculate the amount of particulate matter estimated or detected by the particulate matter deposited amount detecting means. When a predetermined amount is reached, the temperature of the filter is adjusted to a predetermined high temperature by the heat of exhaust gas discharged from the combustion chamber. And a forced regeneration means for controlling the fuel ratio to an air-fuel ratio on the lean air-fuel ratio side of the stoichiometric air-fuel ratio, maintaining the filter at the predetermined high temperature, burning the deposited particulate matter, and regenerating the filter. The forcible regeneration means adjusts the temperature of the filter to a predetermined high temperature based on temperature information from the first temperature sensor and temperature information from the second temperature sensor.

According to a ninth aspect of the present invention, in the exhaust gas purifying apparatus for an internal combustion engine according to the eighth aspect, the internal combustion engine has a throttle valve for adjusting an intake air amount in an intake system. The temperature of the filter is adjusted to a predetermined high temperature by controlling the throttle valve while controlling the air-fuel ratio or the air-fuel ratio near the stoichiometric air-fuel ratio.
According to a tenth aspect of the present invention, in the eighth aspect, the air-fuel ratio on the lean air-fuel ratio side is equivalent to an excess air ratio of 1.3 to 1.5.

The exhaust gas purifying apparatus for an internal combustion engine according to claim 11 is characterized in that, in claims 1 to 10, the target exhaust temperature setting means sets the target exhaust temperature within a range equal to or lower than a predetermined heat-resistant temperature.
Further, in the exhaust gas purifying apparatus for an internal combustion engine according to claim 12, in the exhaust gas purifying apparatus according to claim 1, the exhaust system and the intake system of the internal combustion engine further include a turbocharger for supercharging intake air to the combustion chamber. A temperature sensor provided upstream of the turbocharger in the exhaust system, detects a temperature of exhaust gas discharged from the combustion chamber and flowing into the turbocharger, and the emission control unit performs the exhaust purification. Basic exhaust temperature setting means for setting, as a basic exhaust temperature, the temperature of exhaust gas discharged from the combustion chamber and flowing into the turbocharger when the unit has reached the predetermined high temperature, and set by the basic exhaust temperature setting means. Based on the basic discharge temperature and the difference between the predetermined high temperature and the temperature detected by the second temperature sensor. Target exhaust temperature setting means for setting a target exhaust temperature of the exhaust gas to be exhausted, wherein the target exhaust temperature is set based on a difference between a target exhaust temperature set by the target exhaust temperature setting means and a temperature detected by the first temperature sensor. It is characterized in that the temperature of the exhaust gas purification unit is adjusted.

According to a thirteenth aspect of the present invention, in the twelfth aspect, the target exhaust temperature setting means sets the target exhaust temperature in a range equal to or lower than a heat resistant temperature of the turbocharger or the exhaust purification unit. It is characterized by:
According to a fourteenth aspect of the present invention, in the first or second aspect, the internal combustion engine includes an EGR passage that connects an intake system and an exhaust system, and an EGR valve that opens and closes the EGR passage. The emission control means controls the exhaust air-fuel ratio to a stoichiometric air-fuel ratio or an air-fuel ratio near the stoichiometric air-fuel ratio and controls the opening and closing of the EGR valve to bring the exhaust purification unit to a predetermined high temperature. It is characterized by adjustment.

  According to a fifteenth aspect of the present invention, in the fourteenth aspect, the internal combustion engine has a throttle valve for adjusting an intake air amount in an intake system, and the release control means determines the exhaust air-fuel ratio theoretically. Controlling the air-fuel ratio or the air-fuel ratio near the stoichiometric air-fuel ratio, controlling the throttle valve to the throttle side by a predetermined amount, and controlling the EGR valve to open and close to adjust the temperature of the exhaust gas purification unit to a predetermined high temperature. It is characterized by.

  According to the exhaust gas purifying apparatus for an internal combustion engine of the first aspect of the present invention, when discharging and removing harmful components in the exhaust gas occluded or collected by the exhaust gas purifying unit, the exhaust gas purifying unit is discharged from the combustion chamber. The temperature is controlled to a predetermined high temperature based on the temperature information from the first temperature sensor for detecting the temperature of the exhaust gas and the temperature information from the second temperature sensor for detecting the temperature of the exhaust gas flowing into the exhaust gas purification unit. Therefore, for example, when trying to control the temperature of the exhaust gas purification unit only by the second temperature sensor that detects the temperature of the exhaust gas flowing into the exhaust gas purification unit, the response is slow, the heat capacity of the exhaust passage is large, or the heat energy of the exhaust gas is large. In the case where there is a temperature decrease due to consumption, hunting is greatly caused and controllability is poor. However, the temperature of the exhaust gas purification unit is detected by the second temperature sensor. While monitoring, the first temperature sensor also monitors the exhaust gas temperature near the exhaust port, thereby controlling the temperature of the exhaust gas discharged from the combustion chamber to an appropriate temperature without excess or shortage, and controlling the exhaust gas purification unit to a predetermined temperature. High temperature can be controlled. Thereby, the temperature controllability of the exhaust gas purification unit can be improved, and the removal of the harmful components occluded or trapped in the exhaust gas purification unit can be realized with high responsiveness and high accuracy.

  Further, according to the exhaust gas purifying apparatus for an internal combustion engine of the second aspect, the exhaust gas to be discharged from the combustion chamber when the exhaust gas purifying unit reaches a predetermined high temperature which is the target temperature of the exhaust gas purifying unit. Is set as the basic discharge temperature, and the target discharge temperature of the exhaust gas discharged from the combustion chamber is set based on the difference between the basic discharge temperature and the predetermined high temperature and the temperature detected by the second temperature sensor. The temperature is controlled so that the temperature detected by the first temperature sensor becomes the target discharge temperature, so that the temperature of the exhaust gas discharged from the combustion chamber is properly controlled to an appropriate temperature without excess or shortage. As a result, the exhaust gas purification unit can quickly reach a predetermined high temperature. Further, when the temperature of the exhaust gas purification unit approaches a predetermined high temperature, the target exhaust temperature also approaches the basic exhaust temperature, so that the temperature of exhaust gas finally discharged from the combustion chamber can be controlled appropriately toward the basic exhaust temperature, The temperature of the exhaust gas purification unit can be favorably converged to a predetermined high temperature without hunting. Thereby, the temperature controllability of the exhaust gas purification unit can be improved, and the removal of the harmful components occluded or collected in the exhaust gas purification unit can be realized with high responsiveness and high accuracy.

  According to the third aspect of the present invention, the throttle valve is controlled while controlling the exhaust air-fuel ratio to a stoichiometric air-fuel ratio or an air-fuel ratio near the stoichiometric air-fuel ratio. Since the temperature of the exhaust gas purification unit is adjusted to a predetermined high temperature, it is possible to suppress an increase in NOx, HC, CO, and the like in the exhaust gas, and based on the proportional relationship between the amount of intake air and the temperature of the exhaust gas purification unit, purify the exhaust gas temperature and thus the exhaust gas The temperature of the unit can be easily controlled (see FIG. 4).

According to a fourth aspect of the present invention, there is provided an exhaust purification system for an internal combustion engine, wherein the basic throttle position is corrected based on a difference between a target exhaust temperature and a temperature detected by a first temperature sensor. Since the temperature of the unit is adjusted, the exhaust gas temperature and thus the temperature of the exhaust gas purifying unit can be easily controlled only by correcting the basic throttle position.
According to a fifth aspect of the present invention, the internal combustion engine is a diesel engine and the exhaust air-fuel ratio is controlled to a stoichiometric air-fuel ratio or an air-fuel ratio near the stoichiometric air-fuel ratio. Since the fuel injection timing is retarded while increasing the amount of NOx, HC, CO and the like in the exhaust gas, the temperature controllability of the exhaust gas purification unit can be improved while preventing the generation of smoke.

Further, according to the exhaust gas purifying apparatus for an internal combustion engine of claim 6, in claim 1, the exhaust gas purifying unit is a storage type NOx catalyst for storing NOx in exhaust gas. Thus, the temperature controllability of the storage NOx catalyst can be improved, and the S purge can be realized with high responsiveness and high accuracy.
According to the exhaust gas purifying apparatus for an internal combustion engine of claim 7, the storage NOx catalyst is controlled to a predetermined value by controlling the throttle valve while controlling the exhaust air-fuel ratio to the stoichiometric air-fuel ratio or the rich air-fuel ratio. Since the temperature is adjusted to a high temperature, the exhaust gas temperature and thus the temperature of the storage NOx catalyst can be easily controlled based on the proportional relationship between the amount of intake air and the temperature of the storage NOx catalyst (see FIG. 4). In addition, if the exhaust air-fuel ratio is set to the rich air-fuel ratio, the S purge can be started early during the temperature rise of the storage NOx catalyst.

According to the exhaust gas purifying apparatus for an internal combustion engine of claim 8, the exhaust gas purifying unit in claim 1 is a filter for collecting particulate matter in the exhaust gas. The temperature controllability of the filter can be improved, and forced regeneration can be realized with high responsiveness and high accuracy.
According to the ninth aspect of the present invention, the filter is controlled by controlling the throttle valve while controlling the exhaust air-fuel ratio to the stoichiometric air-fuel ratio or an air-fuel ratio near the stoichiometric air-fuel ratio. Since the temperature is adjusted to a predetermined high temperature, it is possible to easily control the exhaust gas temperature and hence the filter temperature based on the proportional relationship between the intake air amount and the filter temperature while suppressing an increase in NOx or HC, CO, etc. in the exhaust gas. (See FIG. 4).

  Further, according to the exhaust gas purifying apparatus for an internal combustion engine of the tenth aspect, in the eighth aspect, the air-fuel ratio on the lean air-fuel ratio side corresponds to the excess air ratio of 1.3 to 1.5. In addition, it is possible to eliminate oxygen deficiency while minimizing a decrease in the exhaust gas temperature due to an increase in the intake air amount and a decrease in the temperature of the filter as much as possible, thereby favorably promoting the combustion of the particulate matter.

According to the exhaust gas purifying apparatus for an internal combustion engine of the eleventh aspect, since the target exhaust temperature is set in a range below the predetermined heat resistant temperature in the first to tenth aspects, the target exhaust temperature is set in the range below the predetermined heat resistant temperature. The temperature controllability of the exhaust gas purification unit can be improved while preventing the exhaust system members such as the exhaust gas purification unit from being damaged by overheating.
Further, according to the exhaust gas purification apparatus for an internal combustion engine of the twelfth aspect, even in the case of the first aspect, even if the exhaust system has a turbocharger having a particularly large heat capacity, the temperature of the exhaust gas purification unit is controlled by the second temperature sensor. While monitoring, the first temperature sensor also monitors the exhaust gas temperature upstream of the turbocharger, thereby controlling the temperature of the exhaust gas discharged from the combustion chamber and flowing into the turbocharger to an appropriate temperature without excess or shortage, thereby purifying the exhaust gas. The unit can be controlled at a predetermined high temperature. Thereby, regardless of the presence of the turbocharger, the temperature controllability of the exhaust gas purification unit can be improved, and the removal of the harmful components occluded or collected in the exhaust gas purification unit can be realized with high responsiveness and high accuracy.

  According to the thirteenth aspect of the present invention, the target exhaust temperature is set in a range below the allowable temperature limit of the turbocharger or the exhaust purification unit. The temperature can be clipped within the following range, and the temperature controllability of the exhaust gas purification unit can be improved while preventing the turbocharger and the exhaust gas purification unit from being damaged by overheating.

Further, according to the exhaust gas purifying apparatus for an internal combustion engine of claim 14, the exhaust gas purifying unit is controlled to open and close by adjusting the temperature of the exhaust gas purifying unit to a predetermined high temperature, thereby reducing pumping loss. However, it is possible to effectively increase the exhaust gas temperature and, consequently, the temperature of the exhaust gas purification unit.
According to a fifteenth aspect of the present invention, in the fourteenth aspect, the temperature of the exhaust purification unit is adjusted to a predetermined high temperature by controlling the throttle valve to the throttle side by a predetermined amount and controlling the opening and closing of the EGR valve. Therefore, it is possible to more effectively increase the exhaust gas temperature, and thus the temperature of the exhaust gas purification unit, while reducing the pumping loss.

Hereinafter, an embodiment of an exhaust gas purifying apparatus for an internal combustion engine according to the present invention will be described with reference to the drawings.
First, a first embodiment will be described.
Referring to FIG. 1, there is shown a schematic configuration diagram of an exhaust gas purification apparatus for an internal combustion engine according to a first embodiment of the present invention, which will be described below with reference to FIG.

Here, an in-line four-cylinder diesel engine (hereinafter simply referred to as engine) is employed as the engine 1.
The fuel supply system of the engine 1 includes, for example, a common rail system. In this system, an injector (fuel injection nozzle) 2 is provided for each cylinder, and these injectors 2 are connected to a common rail (not shown). . Each injector 2 is connected to an electronic control unit (ECU) 40, and opens and closes valves based on a fuel injection command from the ECU 40, and can inject fuel in the common rail into each combustion chamber at a desired timing at a high pressure. It is. That is, the injector 2 is capable of freely performing initial injection (pilot injection), additional injection, suspension of fuel injection, and the like, in addition to main injection for main combustion. The common rail system is known, and the details of the configuration of the common rail system will not be described herein.

  An intake port that communicates with a combustion chamber 3 of each cylinder of the engine 1 via an intake valve is connected to an intake pipe 6 via an intake manifold 4, and a turbocharger (supercharger) 8 is connected to the intake pipe 6. An air cleaner 9 is provided via a pump 8a. An electromagnetic throttle valve 5 for adjusting the amount of intake air is connected downstream of the turbocharger 8 of the intake pipe 6 with respect to the intake air, and an intake air amount is provided between the air cleaner 9 and the turbocharger 8. An air flow sensor (AFS) 7 for detecting is provided.

On the other hand, an exhaust port communicating with the combustion chamber 3 of each cylinder of the engine 1 via an exhaust valve is connected to an exhaust pipe 12 via an exhaust manifold 10. The exhaust pipe 12 is connected to a turbine 8 b of a turbocharger 8. Is interposed.
An EGR passage 14 extends from the exhaust manifold 10, and the end of the EGR passage 14 is connected to the intake manifold 6. The EGR passage 14 is provided with an electromagnetic EGR valve 16.

A storage NOx catalyst 20 is interposed in the exhaust pipe 12. As described above, the storage NOx catalyst 20 temporarily stores NOx in an oxidizing atmosphere having an exhaust air-fuel ratio (exhaust λ) closer to a lean air-fuel ratio, and NOx in a reducing atmosphere mainly containing CO, which has an exhaust air-fuel ratio closer to a rich air-fuel ratio. Has a function of reducing to N ₂ (nitrogen) or the like. More specifically, the storage NOx catalyst 20 is configured as a catalyst having platinum (Pt), rhodium (Rh) or the like as a noble metal, and an alkali metal such as barium (Ba) or an alkaline earth metal as a storage material. Has been adopted. Note that the storage NOx catalyst 20 may also have an oxidation function or a three-way catalyst function.

  Further, a temperature sensor (a second sensor) that detects the temperature of exhaust gas discharged from the combustion chamber 3 and flowing into the turbocharger 8 is provided at a portion of the exhaust pipe 12 near the combustion chamber 3, for example, the exhaust port of the exhaust manifold 10 or any one of the cylinders. 1) is provided. Further, the storage NOx catalyst 20 of the exhaust pipe 12 is provided with a temperature sensor (second temperature sensor) 22 for detecting the inlet temperature of the storage NOx catalyst 20, and the exhaust gas is upstream of the storage NOx catalyst 20. On the side, an air-fuel ratio sensor (λ sensor) 19 for detecting an exhaust air-fuel ratio (exhaust λ) is provided. In the configuration of FIG. 1, the temperature sensor 18 is provided at, for example, the exhaust port, but is not limited to this. For example, any of the exhaust pipes 12 on the downstream side of the exhaust port and the upstream side of the turbocharger 8 is provided. You may make it provide in a part.

The ECU 40 is a control device for performing comprehensive control of the exhaust gas purification device for an internal combustion engine including the engine 1 according to the present invention.
On the input side of the ECU 40, various sensors are connected in addition to the air flow sensor 7, the temperature sensors 18, 22 and the air-fuel ratio sensor 19.
On the other hand, various devices such as the injector 2, the throttle valve 5, the EGR valve 16 and the like are connected to the output side of the ECU 40, and based on various input information, an air-fuel ratio (λ), a fuel injection amount, an intake air amount, and the like. Is set, the fuel injection amount command signal is supplied to the injector 2, the intake air amount command signal is supplied to the throttle valve 5, and other signals are output to various devices.

  By the way, as described above, the storage NOx catalyst 20 also stores SOx (harmful components) together with NOx (S poisoning), and this SOx lowers the NOx purification ability. When the amount of SOx stored in the fuel cell reaches a predetermined amount, release and removal of the SOx, that is, S purge is performed. Here, the amount of SOx stored in the storage NOx catalyst 20 is estimated based on, for example, the operation time of the engine 1 or the like, but may be detected by other methods (for example, sulfur component accumulation amount detection means, Accumulation amount detecting means).

In order to perform the S purge, it is necessary to set the storage NOx catalyst 20 in a reducing atmosphere and raise the temperature to a predetermined high temperature T1 (for example, 650 ° C.) as described above. The temperature controllability is improved, and the S purge is realized with high responsiveness and high accuracy.
Hereinafter, an S purge control method (sulfur component release means, release control means) according to the first embodiment of the present invention will be described in detail.

Referring to FIG. 2, there is shown a block diagram of λ control for bringing the storage NOx catalyst 20 into a reducing atmosphere. Referring to FIG. 3, temperature control for raising the temperature of the storage NOx catalyst 20 to a predetermined high temperature T1 is shown. A block diagram is shown and will be described below with reference to FIGS.
First, as shown in FIG. 2, in block B10, a target air-fuel ratio (target λ) of the exhaust air-fuel ratio (exhaust λ) is set in order to make the storage NOx catalyst 20 a reducing atmosphere. Here, the target air-fuel ratio (target λ) is, for example, a stoichiometric air-fuel ratio (λ = 1.0) in order to prevent an increase in NOx, HC, CO, and the like in the exhaust gas when the temperature of the storage NOx catalyst 20 is raised. Is done. It should be noted that the target λ may not necessarily be the stoichiometric air-fuel ratio (λ = 1.0), but may be an air-fuel ratio near the stoichiometric air-fuel ratio as long as NOx, HC, CO, etc. in the exhaust do not extremely increase. Is also good.

On the other hand, in block B12, the air flow sensor 7 detects the amount of intake air. Then, in block B14, the total fuel injection amount from the injector 2 is determined according to the intake air amount so that the actual exhaust air-fuel ratio (actual λ) becomes the target air-fuel ratio.
Here, a small amount of fuel is pilot-injected prior to the main injection in order to stabilize the combustion by the main injection (main injection) and thereby stabilize the engine torque. Set. Thus, in block B18, the difference between the total fuel injection amount and the pilot injection amount is obtained as the basic main injection amount. Note that the ratio between the pilot injection amount and the basic main injection amount may be appropriately set according to the operating state of the engine 1 while observing the stability of the engine torque.

  On the other hand, in the block B20, the actual exhaust λ, that is, the actual λ, is detected by the λ sensor 19, and in the block B22, the deviation between the target λ and the actual λ is detected. It is converted into a correction amount. Then, in block B24, the correction amount of the fuel injection amount is added to the basic main injection amount, and the main injection amount to be actually injected so that the exhaust λ becomes the target λ is determined.

As shown in FIG. 3, in block B30, the basic throttle position of the throttle valve 5 is set based on the accelerator operation amount of the driver and the engine rotation speed Ne (basic throttle position setting means).
In block B32, the exhaust gas to be discharged from the combustion chamber 3 of the engine 1 and flow into the turbocharger 8 when the storage NOx catalyst 20 reaches a predetermined high temperature T1 (for example, 650 ° C.) which is a target catalyst temperature. The temperature is set in advance as a basic discharge temperature based on experiments or the like (basic discharge temperature setting means).

  On the other hand, in block B36, the inlet temperature of the storage NOx catalyst 20, that is, the actual catalyst temperature is detected by the temperature sensor 22, and in block B38, the actual catalyst temperature and the target catalyst temperature in block B34, that is, the predetermined high temperature T1 are determined. A deviation is detected. Then, in block B40, a target discharge temperature of exhaust gas discharged from the combustion chamber 3 and flowing into the turbocharger 8 is set in consideration of the deviation in addition to the basic discharge temperature (target discharge temperature setting means).

  If the target discharge temperature is too high, the exhaust system members such as the turbocharger 8, the storage NOx catalyst 20, and other catalysts may be overheated. Clips are applied at temperature. That is, the target exhaust temperature is set in a range not higher than the allowable temperature limit of the exhaust system members such as the turbocharger 8 and the storage NOx catalyst 20. Thus, damage due to overheating of the turbocharger 8, the storage NOx catalyst 20, and the like is prevented.

In block B42, the temperature of the exhaust gas discharged from the combustion chamber 3 and flowing into the turbocharger 8, that is, the actual exhaust temperature, is detected by the temperature sensor 18, and in block B44, the deviation between the actual exhaust temperature and the target exhaust temperature is detected. Then, the deviation is converted into a correction amount of the throttle position of the throttle valve 5.
Referring to FIG. 4, for example, in a diesel engine, when the air-fuel ratio is constant (for example, the stoichiometric air-fuel ratio, that is, λ = 1.0), the catalyst temperature when the throttle position is changed and the intake air amount is changed is shown. Although shown as experimental data of the inventor, it has been confirmed that the intake air amount and the catalyst temperature have a proportional relationship under a constant air-fuel ratio. In other words, when the air-fuel ratio is constant, when the throttle position changes to the increasing side, the exhaust gas temperature rises accordingly, and the temperature of the storage NOx catalyst 20 rises.

Therefore, here, the deviation between the actual discharge temperature and the target discharge temperature is converted into an intake air amount, that is, a throttle position correction amount, based on the proportional relationship in FIG.
When the correction amount of the throttle position is obtained in this way, in block B46, the correction amount is added to the basic throttle position, and the target throttle position is set.
When the target throttle position is set, the throttle valve 5 is controlled toward the target throttle position, and the intake air amount changes. The change amount of the intake air amount is appropriately fed back to the λ control in FIG. , The exhaust λ is always controlled to the target λ.

The λ control and the temperature control are repeatedly performed in an integral manner, whereby the exhaust gas temperature rises toward the target exhaust gas temperature, and the temperature of the storage NOx catalyst 20 reaches a predetermined high temperature T1, which is the target catalyst temperature. Controlled.
When the temperature of the storage NOx catalyst 20 reaches a predetermined high temperature T1, which is the target DPF temperature, the exhaust air-fuel ratio (exhaust λ) is controlled to the stoichiometric air-fuel ratio (λ = 1.0). The release of the SOx stored in the fuel cell 20, that is, the reduction and removal of the SOx, is favorably promoted.

Thus, the removal of the SOx stored in the storage NOx catalyst 20 is completed, and the NOx storage capacity of the storage NOx catalyst 20 recovers favorably. Actually, the time from when the temperature of the storage NOx catalyst 20 reaches the predetermined high temperature T1 to when the removal of SOx is completed is set in advance, and the S purge is performed over the set time.
As described above, in the S purge control according to the first embodiment of the present invention, the temperature of the exhaust gas discharged from the combustion chamber 3 and flowing into the turbocharger 8 when the storage NOx catalyst 20 reaches the predetermined high temperature T1 is determined. The temperature is set as the basic exhaust temperature, and the storage NOx catalyst 20 is further provided with a temperature sensor 22 for detecting the temperature of the storage NOx catalyst 20, and is discharged from the combustion chamber 3 into the exhaust manifold 10 or the exhaust port and flows into the turbocharger 8. A temperature sensor 18 for detecting the temperature of the exhaust gas to be exhausted is provided. The difference between the predetermined high temperature T1 which is the target catalyst temperature and the temperature detected by the temperature sensor 22 is added to the above-mentioned basic exhaust temperature, and the turbo exhausted from the combustion chamber 3 A target discharge temperature of exhaust gas flowing into the charger 8 is set, and temperature control is performed so that the temperature detected by the temperature sensor 18 becomes the target discharge temperature. It is way.

  Thus, in the S purge control according to the present invention, even if the heat capacity of the exhaust passage is large due to the presence of the turbocharger 8, the temperature of the exhaust gas discharged from the combustion chamber 3 and flowing into the turbocharger 8 can be adjusted to an appropriate level. It is possible to control the temperature of the storage NOx catalyst 20 to a predetermined high temperature T1 quickly by properly controlling the temperature to an appropriate temperature. If the λ control and the temperature control are repeatedly performed, the temperature of the storage NOx catalyst 20 approaches the predetermined high temperature T1, but if the temperature of the storage NOx catalyst 20 approaches the predetermined high temperature T1, the target emission is reduced. Since the temperature approaches the basic discharge temperature, the temperature of the exhaust gas finally discharged from the combustion chamber 3 and flowing into the turbocharger 8 can be favorably controlled toward the basic discharge temperature. The temperature can be favorably converged to the predetermined high temperature T1 without hunting. Therefore, by using the S purge control according to the present invention, the temperature controllability of the storage NOx catalyst 20 can be improved, and the S purge can be realized with high responsiveness and high accuracy.

Further, since the temperature of the storage NOx catalyst 20 can be controlled by controlling the throttle position of the throttle valve 5, the temperature of the storage NOx catalyst 20 can be easily controlled.
Incidentally, FIG. 4 also shows the degree of generation of smoke (black smoke) when the fuel injection timing of the injector 2 is changed to the retard side as experimental data of the inventor. As described above, it has been confirmed that when the air-fuel ratio is constant, the more the fuel injection timing is on the retard side, the more the generation of smoke is suppressed.

Therefore, in the S purge control according to the present invention, the λ control and the temperature control are performed, and the fuel injection timing is greatly retarded. According to the figure, when the air-fuel ratio is constant (for example, stoichiometric air-fuel ratio, that is, λ = 1.0), the fuel injection timing is preferably controlled to a retard side from 35 ° ATDC, for example, It is better to control to the retard side than ATDC.
Thus, in a diesel engine, when the exhaust air-fuel ratio is controlled to the stoichiometric air-fuel ratio or the rich air-fuel ratio, smoke is easily generated. However, while the generation of such smoke is prevented, the temperature control of the storage NOx catalyst 20 is performed. It is possible to improve the performance.

When performing the S purge, the EGR valve 16 is preferably set to a fully closed state. This prevents high-temperature exhaust gas from flowing into the intake system via the EGR passage 14, and prevents damage to the intake system members such as the EGR valve 16 due to overheating. This also suppresses the generation of smoke.
Referring to FIG. 5, the experimental results (engine torque, intake air amount, actual catalyst temperature, actual exhaust temperature, main injection amount, pilot injection amount, exhaust λ, degree of smoke generation) in the case where the above-mentioned S purge control is performed are time-dependent. Also shown in the chart, the actual catalyst temperature and the actual discharge temperature in the case where only the temperature sensor 22 is provided to detect the temperature of the storage type NOx catalyst 20 and control is performed without hunting are shown by broken lines in FIG. Although the actual catalyst temperature and the actual discharge temperature when the temperature control of the storage NOx catalyst 20 is performed by utilizing the catalytic reaction by the additional injection are shown by the dashed line, the S purge control according to the present invention is not performed. As shown in the figure, while maintaining the exhaust λ satisfactorily constant, the temperature sensor is controlled with a small degree of smoke generation with almost no fluctuation in engine torque. The temperature of the exhaust gas discharged from the combustion chamber 3 and flowing into the turbocharger 8, that is, the exhaust temperature is quickly increased and stored as compared with the case where only 2 is provided (broken line) or the case where the catalytic reaction is used (dashed line). The temperature of the type NOx catalyst 20, that is, the catalyst temperature can be quickly raised to a predetermined high temperature T1 (for example, 650 ° C.). The temperature of 20 can be favorably converged to a predetermined high temperature T1 without hunting.

Here, the target λ is set to the stoichiometric air-fuel ratio (λ = 1.0) from the time when the temperature of the exhaust gas rises until the end of the S purge. After setting the lean air-fuel ratio side to the fuel ratio, the target λ may be changed to the stoichiometric air-fuel ratio (λ = 1.0).
Further, in a range where HC, CO, etc. in the exhaust do not extremely increase, the target λ may be set to a rich air-fuel ratio side from the stoichiometric air-fuel ratio (λ = 1.0) from the start of the S purge control. Good.

Hereinafter, a modified example of the first embodiment will be described.
In the first embodiment, at the time of performing the S purge, the target λ is set to, for example, 1.0, and the target throttle position is controlled according to the block diagram of the temperature control shown in FIG. It is not limited. That is, at the time of performing the S purge, intake throttle means (for example, controlling the throttle valve 5 to a predetermined amount throttle side) for reducing the intake air amount to a constant intake amount without variably controlling the intake air amount is provided. The blocks B30 and B46 in FIG. 3 may be used as the basic pilot injection amount and the target pilot injection amount, respectively, and the exhaust gas temperature may be adjusted to a predetermined high temperature by controlling the fuel injection amount.

Next, a second embodiment will be described.
Referring to FIG. 6, there is shown a schematic configuration diagram of an exhaust gas purifying apparatus for an internal combustion engine according to a second embodiment of the present invention, and the second embodiment will be described below. 6 differs from FIG. 1 only in that no turbocharger 8 is interposed, the other configuration is the same as FIG. 1, and a block diagram of the S purge control is also shown in FIG. Since these are the same as 2 and 3, description of the configuration and the S purge control method is omitted here. However, since the turbocharger 8 is not interposed, the temperature sensor 18 is provided in the exhaust manifold 10 or the exhaust port. In a block B40 in FIG. Is set, and in block B42, the temperature of the exhaust gas discharged from the combustion chamber 3 is detected by the temperature sensor 18 as the actual discharge temperature.

  That is, in the S purge control according to the second embodiment of the present invention, the temperature of the exhaust gas to be discharged from the combustion chamber 3 when the storage NOx catalyst 20 has reached the predetermined high temperature T1, is set as the basic discharge temperature, Further, the storage NOx catalyst 20 is provided with a temperature sensor 22 for detecting the temperature of the storage NOx catalyst 20, and the exhaust manifold 10 or an exhaust port is provided with a temperature sensor 18 for detecting the temperature of exhaust gas discharged from the combustion chamber 3. The temperature difference between the predetermined high temperature T1 as the target catalyst temperature and the temperature detected by the temperature sensor 22 is set as a target discharge temperature of the exhaust gas discharged from the combustion chamber 3 in consideration of the basic discharge temperature. Is controlled so that the temperature detected by the above becomes the target discharge temperature.

  Thus, in the S purge control according to the second embodiment of the present invention, even if the exhaust pipe 12 is long and the temperature is reduced due to the exhaust heat energy consumption, the exhaust gas discharged from the combustion chamber 3 is reduced. The temperature of the NOx storage catalyst can be properly controlled to an appropriate temperature without excess or shortage so that the storage NOx catalyst 20 can quickly reach the predetermined high temperature T1, and the temperature of the storage NOx catalyst can be satisfactorily maintained at the predetermined high temperature T1 without hunting. It can be converged. Therefore, the temperature controllability of the storage NOx catalyst 20 can be improved, and S purge can be realized with high responsiveness and high accuracy.

Next, a third embodiment will be described.
Referring to FIG. 7, there is shown a schematic configuration diagram of an exhaust gas purifying apparatus for an internal combustion engine according to a third embodiment of the present invention, and the third embodiment will be described below. 7 is different from FIG. 6 only in that an oxidation catalyst 24 is provided on the upstream side of the storage NOx catalyst 20. Other configurations are the same as those in FIG. Since the control block diagram is the same as in FIGS. 2 and 3, the description of the configuration and the S purge control method is omitted here.

  That is, in the S purge control according to the third embodiment of the present invention, similarly to the case of the second embodiment, when the storage type NOx catalyst 20 has reached the predetermined high temperature T1, it should be discharged from the combustion chamber 3. The temperature of the exhaust gas is set as a basic exhaust temperature. Further, the storage NOx catalyst 20 is provided with a temperature sensor 22 for detecting the temperature of the storage NOx catalyst 20, and the exhaust gas is discharged from the combustion chamber 3 to the exhaust manifold 10 or the exhaust port. A temperature sensor 18 for detecting the temperature of the exhaust gas is provided. And the temperature is controlled so that the temperature detected by the temperature sensor 18 becomes the target discharge temperature.

  Thus, in the S purge control according to the third embodiment of the present invention, even if the heat capacity of the exhaust passage is large due to the presence of the oxidation catalyst 24, the temperature of the exhaust gas discharged from the combustion chamber 3 is not excessively and sufficiently. It is possible to control the temperature of the storage NOx catalyst 20 to the predetermined high temperature T1 promptly by properly controlling the temperature to an appropriate temperature, and to converge the temperature of the storage NOx catalyst to the predetermined high temperature T1 without hunting. Therefore, the temperature controllability of the storage NOx catalyst 20 can be improved, and S purge can be realized with high responsiveness and high accuracy.

Here, the oxidation catalyst 24 is provided on the upstream side of the storage type NOx catalyst 20. However, the same operation and effect as described above can be obtained even when a particulate filter as described later is arranged in place of the oxidation catalyst 24. It is what is done.
Next, a fourth embodiment will be described.
The fourth embodiment is different from the first embodiment shown in FIG. 1 in that a diesel particulate filter (hereinafter abbreviated as DPF) 20 'as shown in FIG. 8 is used in place of the storage NOx catalyst 20 of the first embodiment. The third embodiment is different from the first embodiment. Hereinafter, the description of the common parts with the first embodiment will be omitted, and only the different parts will be described.

  As described above, the exhaust contains particulate matter (harmful component, hereinafter abbreviated as PM) as a harmful component, and such PM is trapped by the DPF 20 '. Then, the DPF 20 ′ gradually increases the exhaust pressure due to the deposition of PM and increases the exhaust resistance, which in turn deteriorates fuel efficiency. Therefore, when the deposition amount of PM reaches a predetermined amount, the DPF 20 ′ removes the deposited PM. The combustion is removed and the DPF 20 'is forcibly regenerated (DPF forced regeneration).

As in the case of the SOx amount, the PM accumulation amount is estimated based on, for example, the operation time of the engine 1 or the like, but may be detected by another method (differential pressure across the DPF 20 ′) ( Particulate matter deposited amount detecting means, deposited amount detecting means).
In order to perform DPF forced regeneration, it is necessary to raise the temperature of the DPF 20 'to a predetermined high temperature T1' (for example, 650 to 700 ° C) as described above. Here, the temperature controllability of the DPF 20 'is improved. The DPF forced regeneration is realized with high responsiveness and high accuracy.

Hereinafter, the DPF forced regeneration control method (forcible regeneration means, release control means) according to the fourth embodiment of the present invention of the exhaust gas purification apparatus thus configured will be described in detail.
In the fourth embodiment, the block diagram of FIG. 2 is applied to the λ control until the predetermined high temperature T 1 ′ is reached, and the temperature control is replaced with the block diagram of FIG. 9 applies.

  As shown in FIG. 2, in block B10, a target air-fuel ratio (target λ) of the exhaust air-fuel ratio (exhaust λ) is set. Here, the target air-fuel ratio (target λ) is set to, for example, a stoichiometric air-fuel ratio (λ = 1.0) in order to prevent an increase in NOx, HC, CO, and the like in the exhaust gas when the temperature of the DPF 20 ′ rises. Note that the target λ does not necessarily have to be the stoichiometric air-fuel ratio (λ = 1.0), and the air-fuel ratio in the vicinity of the stoichiometric air-fuel ratio, that is, as long as NOx, HC, CO, and the like in the exhaust do not extremely increase. The air-fuel ratio on the rich side may be used, or the air-fuel ratio on the lean side may be used. Thereafter, through blocks B12 to B22, the main injection amount to be actually injected is determined in block B24 so that the exhaust λ becomes the target λ. However, blocks B12 to B24 are as described above, and description thereof will be omitted. .

  As shown in FIG. 9, in block B30, a basic throttle position of the throttle valve 5 is set (basic throttle position setting means). In block B32, when the DPF 20 'reaches a predetermined high temperature T1' (for example, 650 to 700 ° C.) which is the target catalyst temperature, the exhaust gas to be discharged from the combustion chamber 3 of the engine 1 and flow into the turbocharger 8 The temperature is set as a basic discharge temperature (basic discharge temperature setting means).

  On the other hand, in block B36 ', the inlet temperature of the DPF 20', that is, the actual DPF temperature, is detected by the temperature sensor 22, and in block B38, the actual DPF temperature and the target DPF temperature in the block B34 ', that is, the predetermined high temperature T1'. A deviation is detected. Then, in block B40, a target discharge temperature of exhaust gas discharged from the combustion chamber 3 and flowing into the turbocharger 8 is set in consideration of the deviation in addition to the basic discharge temperature (target discharge temperature setting means). As described above, the target discharge temperature is clipped at block B39 at the heat-resistant temperature of the exhaust system member.

  In block B42, the actual exhaust temperature exhausted from the combustion chamber 3 and flowing into the turbocharger 8 is detected by the temperature sensor 18, and in block B44, the deviation between the actual exhaust temperature and the target exhaust temperature is detected, and the deviation is further detected. Is converted into a correction amount of the throttle position of the throttle valve 5 based on the proportional relationship in FIG. Then, in block B46, the correction amount is added to the basic throttle position, and a target throttle position is set.

Also in this case, the amount of change in the intake air amount is appropriately fed back to the λ control in FIG. 2 described above, and the exhaust λ is controlled to always be the target λ. As a result, the exhaust gas temperature rises toward the target exhaust temperature, and the temperature of the DPF 20 'is controlled to a predetermined high temperature T1' which is the target DPF temperature.
When a predetermined time elapses after the temperature of the DPF 20 'has reached a predetermined high temperature T1', which is the target DPF temperature, the target λ is closer to the lean air-fuel ratio than the stoichiometric air-fuel ratio (λ = 1.0) (for example, 1.3). <Λ ≦ 1.5). When the target λ is changed to the lean air-fuel ratio side (for example, 1.3 <λ ≦ 1.5), a decrease in the exhaust gas temperature due to an increase in the intake air amount, that is, a decrease in the temperature of the DPF 20 ′ is prevented as much as possible. In addition, oxygen deficiency can be eliminated while PM combustion is favorably promoted.

  Thus, the combustion of the PM collected by the DPF 20 'is completed, the PM collected by the DPF 20' is removed, and the DPF 20 'is properly regenerated. In practice, the determination of the completion of PM combustion after the temperature of the DPF 20 'has reached the predetermined high temperature T1' is made based on the pressure difference across the DPF 20 'and information from a temperature sensor separately provided downstream of the DPF 20'. Is In addition, the time until the combustion of PM is completed may be set in advance according to the amount of accumulated PM collected by the DPF 20 ′ and the set temperature at the time of regeneration, and the DPF forced regeneration control may be performed over the set time. .

  As described above, in the DPF forced regeneration control according to the fourth embodiment of the present invention, when the DPF 20 'has reached the predetermined high temperature T1', the temperature of the exhaust gas discharged from the combustion chamber 3 and flowing into the turbocharger 8 is basically determined. The temperature is set as the exhaust temperature, and a temperature sensor 22 for detecting the temperature of the DPF 20 ′ is provided in the DPF 20 ′, and the temperature of the exhaust gas discharged from the combustion chamber 3 and flowing into the turbocharger 8 is detected in the exhaust manifold 10 or the exhaust port. A temperature sensor 18 is provided, and the exhaust gas discharged from the combustion chamber 3 and flows into the turbocharger 8 in consideration of the difference between the predetermined high temperature T1 'as the target DPF temperature and the temperature detected by the temperature sensor 22 in addition to the basic discharge temperature. Is set, and the temperature is controlled so that the temperature detected by the temperature sensor 18 becomes the target discharge temperature. To have.

  As a result, in the DPF forced regeneration control according to the present invention, the temperature of exhaust gas discharged from the combustion chamber 3 and flowing into the turbocharger 8 is excessively or insufficiently increased even when the heat capacity of the exhaust passage is large due to the presence of the turbocharger 8. Therefore, the temperature of the DPF 20 'can be quickly controlled to a predetermined high temperature T1'. When the λ control and the temperature control are repeatedly performed, the temperature of the DPF 20 ′ approaches the predetermined high temperature T1 ′. However, when the temperature of the DPF 20 ′ approaches the predetermined high temperature T1 ′, the target discharge temperature becomes the basic discharge temperature. Since the temperature approaches the temperature, the temperature of the exhaust gas finally discharged from the combustion chamber 3 and flowing into the turbocharger 8 can be favorably controlled toward the basic discharge temperature, and the temperature of the DPF 20 'can be controlled to a predetermined value without hunting. It is possible to favorably converge on the high temperature T1 '. Therefore, by using the DPF forced regeneration control according to the present invention, the temperature controllability of the DPF 20 'can be improved, and the DPF forced regeneration can be realized with high responsiveness and high accuracy.

Further, since the temperature of the DPF 20 'can be controlled by controlling the throttle position of the throttle valve 5, the temperature of the DPF 20' can be easily controlled.
Also in the DPF forced regeneration control, based on FIG. 4, the λ control and the temperature control are performed, and the fuel injection timing is controlled, for example, to the retard side from 35 ° ATDC, preferably, to the retard side from 40 ° ATDC, for example. Is good. Thereby, it is possible to improve the temperature controllability of the DPF 20 ′ while preventing the generation of smoke.

Also in this case, it is preferable that the EGR valve 16 be fully closed. This prevents damage to the intake system members such as the EGR valve 16 due to overheating, and further suppresses the generation of smoke.
Referring to FIG. 10, the experimental results (the intake air amount, the actual DPF temperature, the actual exhaust temperature, the main injection amount, the pilot injection amount, and the exhaust λ) when the DPF forced regeneration control is performed are time charts as in FIG. In the same drawing, the actual DPF temperature and the actual discharge temperature when only the temperature sensor 22 is provided to detect the temperature of the DPF 20 ′ and control is performed without hunting are indicated by broken lines, and are added. The actual DPF temperature and the actual discharge temperature in the case where the temperature control of the DPF 20 ′ is performed by utilizing the catalytic reaction by injection are indicated by dashed lines, but the same is achieved by performing the DPF forced regeneration control according to the present invention. As shown in the figure, compared with the case where only the temperature sensor 22 is provided (dashed line) or the case where a catalytic reaction is utilized (dashed line), the turbo exhausted from the combustion chamber 3 while maintaining the exhaust gas λ in a good and constant state. The temperature of the exhaust gas flowing into the charger 8, that is, the exhaust temperature, can be quickly raised to raise the temperature of the DPF 20 ′, that is, the DPF temperature, to a predetermined high temperature T 1 ′ (for example, 650 to 700 ° C.). The temperature of the DPF 20 'can be satisfactorily converged to a predetermined high temperature T1' without hunting by properly controlling the discharge temperature toward the basic discharge temperature.

Hereinafter, a modified example of the fourth embodiment will be described.
In the fourth embodiment, when the forced regeneration control of the DPF 20 'is performed, the target λ is set to, for example, 1.0, and the target throttle position is controlled according to the temperature control block diagram shown in FIG. However, the present invention is not limited to this. That is, when the forced regeneration control of the DPF 20 'is performed, intake throttle means for reducing the intake air amount to a constant intake amount without variably controlling the intake air amount (for example, controlling the throttle valve 5 to a predetermined amount to the throttle side). ), The block B30 and the block B46 in FIG. 9 may be used as the basic pilot injection amount and the target pilot injection amount, respectively, and the exhaust gas temperature may be adjusted to a predetermined high temperature by controlling the fuel injection amount.

  Further, in the fourth embodiment, when the forced regeneration control of the DPF 20 'is performed, the target λ is set to, for example, 1.0, and the EGR valve 16 is fully closed to control the target throttle position. However, the present invention is not limited to this. That is, when the forced regeneration control of the DPF 20 'is performed, intake throttle means for reducing the intake air amount to a constant intake amount without variably controlling the intake air amount (for example, controlling the throttle valve 5 to a predetermined amount to the throttle side). The exhaust gas temperature may be adjusted to a predetermined high temperature by controlling the opening and closing of the EGR valve 16. When the opening and closing control of the EGR valve 16 is performed, the exhaust gas temperature may be adjusted to a predetermined high temperature by controlling the opening and closing of only the EGR valve 16 within a range where the EGR system is not damaged without providing the intake throttle means. . In this way, the pumping loss can be reduced, and the exhaust gas temperature and thus the temperature of the DPF 20 'can be effectively increased.

Next, a fifth embodiment will be described.
Although not shown in the fifth embodiment, the second embodiment is different from the fourth embodiment in that the storage type NOx catalyst 20 of the second embodiment shown in FIG. 6 is replaced with the DPF 20 'shown in FIG. It differs from the fourth embodiment in that the turbocharger 8 is not interposed.

  In the DPF forced regeneration control according to the fifth embodiment, the temperature of the exhaust gas discharged from the combustion chamber 3 exceeds the temperature even if the exhaust pipe 12 is long and there is a temperature decrease due to the exhaust heat energy consumption. It is possible to control the temperature of the DPF 20 'to the predetermined high temperature T1' quickly without any shortcomings, and to converge the temperature of the DPF 20 'to the predetermined high temperature T1' without hunting. Accordingly, the temperature controllability of the DPF 20 'can be improved, and the DPF forced regeneration can be realized with high responsiveness and high accuracy.

Next, a sixth embodiment will be described.
Although not shown in the sixth embodiment, similar to the fourth and fifth embodiments, the point that the storage type NOx catalyst 20 of the third embodiment shown in FIG. 7 is replaced with the DPF 20 ′ shown in FIG. The fifth embodiment is different from the fifth embodiment in that an oxidation catalyst 24 is provided upstream of the DPF 20 '.

  In the DPF forced regeneration control according to the sixth embodiment, even when the heat capacity of the exhaust passage is large due to the presence of the oxidation catalyst 24, the temperature of the exhaust gas discharged from the combustion chamber 3 is adjusted to an appropriate temperature without excess or shortage. It is possible to control the temperature of the DPF 20 'to the predetermined high temperature T1' promptly and to converge the temperature of the DPF 20 'to the predetermined high temperature T1' without hunting. Accordingly, the temperature controllability of the DPF 20 'can be improved, and the DPF forced regeneration can be realized with high responsiveness and high accuracy.

Here, the oxidation catalyst 24 is provided on the upstream side of the DPF 20 ′. However, the same operation and effect as described above can be obtained when a storage type NOx catalyst is provided instead of the oxidation catalyst 24.
The description of the embodiment of the exhaust gas purification apparatus according to the present invention is finished above, but the embodiment of the present invention is not limited to the above embodiment.

For example, in the above embodiment, the engine 1 is a common rail diesel engine, but the diesel engine may be of any type.
In addition, although a diesel engine is adopted as the engine 1, the engine 1 may be an intake pipe injection type or a cylinder injection type gasoline engine or the like, and the present invention can be applied favorably even in these cases. .

FIG. 1 is a schematic configuration diagram illustrating an exhaust gas purification device for an internal combustion engine according to a first embodiment using a storage-type NOx catalyst of the present invention. It is a block diagram of λ control at the time of S purge control. It is a block diagram of temperature control at the time of S purge control. For example, the experimental data shows the catalyst temperature (DPF temperature) when the intake air amount is changed in a diesel engine under the condition that the air-fuel ratio is constant (for example, the stoichiometric air-fuel ratio). FIG. 5 is a time chart showing experimental results (engine torque, intake air amount, actual catalyst temperature, actual exhaust temperature, main injection amount, pilot injection amount, exhaust λ, degree of smoke generation) when the S purge control according to the present invention is performed. is there. It is a schematic structure figure showing an exhaust gas purification device of an internal-combustion engine concerning a 2nd example using a storage type NOx catalyst of the present invention. FIG. 5 is a schematic configuration diagram showing an exhaust gas purification device for an internal combustion engine according to a third embodiment using the storage type NOx catalyst of the present invention. It is the schematic which shows the DPF of the exhaust gas purification device of the internal combustion engine which concerns on the 4th, 5th, and 6th Example using the DPF of this invention. It is a block diagram of temperature control at the time of DPF forced regeneration control. 5 is a time chart showing experimental results (intake air amount, actual DPF temperature, actual discharge temperature, main injection amount, pilot injection amount, exhaust λ) when DPF forced regeneration control according to the present invention is performed.

Explanation of reference numerals

1 diesel engine (internal combustion engine)
2 Injector 5 Throttle valve 7 Air flow sensor (AFS)
8 Turbocharger 10 Exhaust manifold 12 Exhaust pipe 18 Temperature sensor (first temperature sensor)
19 Air-fuel ratio sensor (λ sensor)
20 Storage NOx catalyst 20 'Diesel particulate filter (DPF)
22 Temperature sensor (second temperature sensor)
24 oxidation catalyst 40 electronic control unit (ECU)

Claims (15)

An exhaust purification unit that is provided in an exhaust system of the internal combustion engine and purifies exhaust gas;
A first temperature sensor that is provided in the exhaust system near an exhaust port of the internal combustion engine and detects a temperature of exhaust gas discharged from a combustion chamber of the internal combustion engine;
A second temperature sensor that is provided in the exhaust system near the exhaust gas purification unit and detects a temperature of exhaust gas flowing into the exhaust gas purification unit;
Accumulation amount detection means for estimating or detecting the accumulation amount of harmful components in the exhaust gas occluded or collected in the exhaust gas purification unit,
When the accumulation amount of the harmful component estimated or detected by the accumulation amount detection means reaches a predetermined amount, the exhaust gas purifying unit is adjusted to a predetermined high temperature by the heat of the exhaust gas discharged from the combustion chamber, and the temperature of the exhaust gas purification unit is adjusted. Release control means for releasing and removing the harmful components,
The internal combustion engine, wherein the release control means adjusts the temperature of the exhaust gas purification unit to a predetermined high temperature based on temperature information from the first temperature sensor and temperature information from the second temperature sensor. Exhaust purification equipment. The release control means,
Basic exhaust temperature setting means for setting a temperature of exhaust gas to be discharged from the combustion chamber when the exhaust purification unit has reached the predetermined high temperature as a basic discharge temperature; and a basic discharge temperature setting means for setting the basic discharge temperature. Target discharge temperature setting means for setting a target discharge temperature of exhaust gas discharged from the combustion chamber based on a difference between the discharge temperature and the predetermined high temperature and a temperature detected by the second temperature sensor,
The temperature adjustment of the exhaust gas purification unit is performed based on a difference between a target exhaust temperature set by the target exhaust temperature setting means and a temperature detected by the first temperature sensor. Exhaust purification device for internal combustion engine. The internal combustion engine has a throttle valve for adjusting an intake air amount in an intake system,
The release control means controls the temperature of the exhaust gas purification unit to a predetermined high temperature by controlling the throttle valve while controlling the exhaust air-fuel ratio to a stoichiometric air-fuel ratio or an air-fuel ratio near the stoichiometric air-fuel ratio. The exhaust gas purifying apparatus for an internal combustion engine according to claim 1 or 2, wherein: The release control means,
Basic throttle position setting means for setting a basic throttle position of the throttle valve according to the operating state of the internal combustion engine,
By correcting a basic throttle position set by the basic throttle position setting means based on a difference between a target discharge temperature set by the target discharge temperature setting means and a temperature detected by the first temperature sensor, the exhaust gas is exhausted. The exhaust gas purifying apparatus for an internal combustion engine according to claim 3, wherein the temperature of the purifying unit is adjusted. The internal combustion engine is a diesel engine,
The exhaust gas of an internal combustion engine according to claim 3 or 4, wherein the release control means retards the fuel injection timing while controlling the exhaust air-fuel ratio to a stoichiometric air-fuel ratio or an air-fuel ratio near the stoichiometric air-fuel ratio. Purification device. The exhaust gas purification unit is provided in an exhaust system of the internal combustion engine, stores NOx in exhaust when the internal combustion engine is in a lean air-fuel ratio operation state, and stores the NOx in a stoichiometric air-fuel ratio operation state or a rich air-fuel ratio operation state. An occluded NOx catalyst for reducing occluded NOx,
The second temperature sensor is provided near the storage NOx catalyst, and detects the temperature of exhaust gas flowing into the storage NOx catalyst,
The accumulation amount detection unit is configured by a sulfur component accumulation amount detection unit that estimates or detects the accumulation amount of the sulfur component in the exhaust gas occluded by the occlusion type NOx catalyst,
When the amount of sulfur component estimated or detected by the sulfur component amount detection unit reaches a predetermined amount, the release control unit causes the storage NOx catalyst to perform a predetermined operation based on heat of exhaust gas exhausted from the combustion chamber. Temperature, and then control the exhaust air-fuel ratio to the stoichiometric air-fuel ratio or the rich air-fuel ratio, and maintain the storage NOx catalyst at the predetermined high temperature to release the accumulated sulfur component. Consisting of
The sulfur component releasing means adjusts the temperature of the NOx storage catalyst to a predetermined high temperature based on temperature information from the first temperature sensor and temperature information from the second temperature sensor. An exhaust gas purifying apparatus for an internal combustion engine according to claim 1. The internal combustion engine has a throttle valve for adjusting an intake air amount in an intake system,
The sulfur component releasing means controls the temperature of the storage NOx catalyst to a predetermined high temperature by controlling the throttle valve while controlling the exhaust air-fuel ratio to a stoichiometric air-fuel ratio or a rich air-fuel ratio. Item 7. An exhaust gas purification device for an internal combustion engine according to Item 6. The exhaust gas purification unit is provided in an exhaust system of the internal combustion engine, and includes a filter that collects particulate matter in exhaust gas,
The second temperature sensor is provided near the filter and detects a temperature of exhaust gas flowing into the filter.
The deposition amount detection means is constituted by a particulate matter deposition amount detection means for estimating or detecting the deposition amount of the particulate matter in the exhaust gas collected by the filter,
When the amount of particulate matter estimated or detected by the particulate matter accumulation amount detection means reaches a predetermined amount, the release control means causes the filter to emit heat from exhaust gas discharged from the combustion chamber. The temperature is adjusted to a predetermined high temperature, and thereafter, the exhaust air-fuel ratio is controlled to an air-fuel ratio on the lean air-fuel ratio side from the stoichiometric air-fuel ratio, and the filter is maintained at the predetermined high temperature to burn the deposited particulate matter. Consisting of forced regeneration means for regenerating the filter,
The temperature of the filter may be adjusted to a predetermined high temperature based on temperature information from the first temperature sensor and temperature information from the second temperature sensor. An exhaust gas purifying apparatus for an internal combustion engine according to claim 1. The internal combustion engine has a throttle valve for adjusting an intake air amount in an intake system,
The forced regeneration unit controls the temperature of the filter to a predetermined high temperature by controlling the throttle valve while controlling the exhaust air-fuel ratio to a stoichiometric air-fuel ratio or an air-fuel ratio near the stoichiometric air-fuel ratio, An exhaust gas purifying apparatus for an internal combustion engine according to claim 8.   The exhaust gas purification apparatus for an internal combustion engine according to claim 8, wherein the air-fuel ratio on the lean air-fuel ratio side is equivalent to an excess air ratio of 1.3 to 1.5.   The exhaust gas purifying apparatus for an internal combustion engine according to any one of claims 1 to 10, wherein the target discharge temperature setting means sets the target discharge temperature in a range equal to or lower than a predetermined heat-resistant temperature. The exhaust system and the intake system of the internal combustion engine have a turbocharger that performs intake supercharging to the combustion chamber,
The first temperature sensor is provided upstream of the turbocharger of the exhaust system, and detects a temperature of exhaust gas discharged from the combustion chamber and flowing into the turbocharger,
The release control means,
Basic exhaust temperature setting means for setting, as a basic exhaust temperature, the temperature of exhaust gas discharged from the combustion chamber and flowing into the turbocharger when the exhaust purification unit has reached the predetermined high temperature; and Setting a target discharge temperature of exhaust discharged from the combustion chamber and flowing into the turbocharger based on a basic discharge temperature set by the above and a difference between the predetermined high temperature and a temperature detected by the second temperature sensor. Discharge temperature setting means,
The temperature of the exhaust gas purification unit is adjusted based on a difference between a target exhaust temperature set by the target exhaust temperature setting means and a temperature detected by the first temperature sensor. Exhaust purification device for internal combustion engine.   The exhaust gas purifying apparatus for an internal combustion engine according to claim 12, wherein the target exhaust temperature setting means sets the target exhaust temperature within a range equal to or lower than a heat resistant temperature of the turbocharger or the exhaust gas purification unit. The internal combustion engine includes an EGR device including an EGR passage that communicates an intake system and an exhaust system, and an EGR valve that opens and closes the EGR passage.
The release control means controls the exhaust gas purification unit to a predetermined high temperature by controlling the exhaust air-fuel ratio to a stoichiometric air-fuel ratio or an air-fuel ratio near the stoichiometric air-fuel ratio and controlling the opening and closing of the EGR valve. The exhaust gas purifying apparatus for an internal combustion engine according to claim 1 or 2, wherein: The internal combustion engine has a throttle valve for adjusting an intake air amount in an intake system,
The release control means controls the exhaust air-fuel ratio to a stoichiometric air-fuel ratio or an air-fuel ratio in the vicinity of the stoichiometric air-fuel ratio, controls the throttle valve to a predetermined throttle side, and controls the opening and closing of the EGR valve to control the exhaust air-fuel ratio. The exhaust gas purifying apparatus for an internal combustion engine according to claim 14, wherein the temperature of the purifying unit is adjusted to a predetermined high temperature.

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