JP2004251230A - Activity determining device for oxidation catalyst for engine and exhaust emission control device of engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To precisely detect the activity degree of an oxidation catalyst arranged in an exhaust passage of an engine. <P>SOLUTION: An oxidation catalyst 28a and a filter 28b for catching exhaust minute particles in its downstream are arranged in the exhaust passage 26 of the engine 1. An ECU 40 controls an injector 5 so as to perform expansion process injection F1 as additional fuel injection to supply unburned fuel to the oxidation catalyst 28a. The injection time and the injection amount of the expansion process injection F1 at this time are set based on the activation rate of the oxidation catalyst 28a. The activation rate is inferred based on the exhaust gas flow rate of exhaust gas passing through the oxidation catalyst 28a, the temperature of exhaust gas flowing into the oxidation catalyst 28a, and the injection time and the injection amount of the expansion process injection F1 injected immediately before it. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a device for determining the activity of an oxidation catalyst for an engine disposed in an exhaust passage of an engine, and a device for purifying exhaust gas of an engine.
[0002]
[Prior art]
Generally, an oxidation catalyst having an oxidation function is arranged in an exhaust passage of an engine, and purifies HC (hydrocarbon) and CO (carbon monoxide) in exhaust gas by a catalytic reaction.
Further, since the oxidation catalyst has a property of generating reaction heat by a catalytic reaction, the oxidation catalyst is also used for raising the temperature of exhaust gas.
For example, a small oxidation catalyst is placed immediately downstream of the exhaust manifold of the engine, and a normal three-way catalyst is placed further downstream, so that a large amount of unburned fuel is supplied to the oxidation catalyst during cold start of the engine. By doing so, the oxidation catalyst is activated at an early stage, and the reaction heat of the oxidation catalyst generated thereby is used to activate the downstream three-way catalyst at an early stage.
[0003]
Also, for example, by disposing a ceramic particulate filter that captures fine particles while passing exhaust gas in the exhaust passage of a diesel engine or a direct injection gasoline engine capable of performing lean burn, the exhaust gas discharged from the engine is exhausted. It captures carbon particles and the like contained therein. In this case, by arranging an oxidation catalyst upstream of the particulate filter and supplying unburned fuel from upstream of the oxidation catalyst, the temperature of the particulate filter is raised by utilizing the reaction heat of the catalyst of the oxidation catalyst. A technique for regenerating the trapping ability of a particulate filter by burning out and removing the fine particles trapped thereby is also known.
Incidentally, as a method of supplying the unburned fuel to the oxidation catalyst, in a so-called direct injection engine in which a fuel injection valve is arranged so as to be directed into a combustion chamber of the engine and fuel is directly injected from the fuel injection valve into the combustion chamber, There is also known a method of supplying unburned fuel by controlling the fuel injection timing and injection amount.
[0004]
Incidentally, it is known that the oxidation catalyst shows a catalytic reaction when the active state of the oxidation catalyst is high, but does not show a catalytic reaction when the active state is low. Therefore, for example, in the technique using the reaction heat of the oxidation catalyst as described above, even if the unburned fuel is supplied when the active state is low, the catalyst reaction hardly occurs, so that the reaction heat of the catalyst is generated. Is not promoted, and the effect of raising the temperature of the exhaust gas is hardly obtained.
Therefore, it is necessary to determine the activity of the catalytic reaction and adjust the operation of the engine according to the activity.
[0005]
For example, as a method for determining the activity of a catalyst, Patent Document 1 listed below discloses a temperature of a catalyst carrier detected by a temperature sensor directly attached to the catalyst carrier, and a degree of deterioration of the catalyst obtained from a temperature history of such a catalyst temperature. There is disclosed a technique of determining the activity based on the above, or determining the activity from a change in the HC concentration between the upstream and downstream of the catalyst.
Further, according to this document, the catalyst activity is determined by such a method, and when the activity is low, the temperature of the EGR gas (exhaust gas recirculation gas) is adjusted so as to increase the temperature of the exhaust gas from the engine. It also discloses the technology to do so.
[0006]
[Patent Document 1]
JP 2001-280123 A
[0007]
[Problems to be solved by the invention]
However, as a result of the research by the inventors of the present invention, the activity of the oxidation catalyst is determined by the catalyst temperature and the degree of deterioration of the catalyst as described in Patent Document 1, and the HC concentration change between upstream and downstream of the oxidation catalyst. It was impossible to judge with higher accuracy, and it was found that the activity of the oxidation catalyst was significantly related to other factors other than these.
The inventors have found that one such other factor is the exhaust gas flow rate passing through the catalyst. Also, in this case, it is necessary to determine the activity of the catalyst with higher accuracy, instead of determining the activity of the catalyst solely based on the exhaust gas flow rate alone, in consideration of the catalyst temperature. I found it.
It has also been found that, in a so-called direct injection engine, the other factors mentioned above are the injection amount and the injection timing of the fuel injected from the fuel injection valve for supplying unburned fuel. In a direct injection engine, fuel is supplied directly into the combustion chamber to supply unburned fuel to the oxidation catalyst, and the amount of unburned fuel and the amount of unburned fuel are controlled by controlling the amount and timing of fuel injection. It is found that the unburned fuel supplied to the oxidation catalyst has a great influence on the activity of the oxidation catalyst.
However, conventionally, when determining the activity of the oxidation catalyst, when the unburned fuel is supplied to the oxidation catalyst from the flow rate of the exhaust gas passing through the oxidation catalyst or from the fuel injection valve of the direct injection engine as described above. The determination based on the fuel injection amount and the injection timing was not known at all, and it was impossible to determine the activity with high accuracy.
[0008]
The present invention has been made in view of the above problems, and has as its object to determine the activity of an oxidation catalyst based on the flow velocity of exhaust gas passing through the oxidation catalyst, or to determine the fuel efficiency of a direct injection engine. When supplying unburned fuel to the oxidation catalyst from the injection valve, the activity of the oxidation catalyst is determined based on the fuel injection amount and the injection timing injected from the fuel injection valve. To do.
[0009]
[Means for Solving the Problems]
In order to achieve the above object, according to the first aspect of the present invention, an oxidation catalyst having an oxidation function is disposed in an exhaust passage of an engine, and the activity of the oxidation catalyst is determined. In the oxidation catalyst activity determination device, temperature detection means for detecting a temperature related to the catalyst temperature on the upstream side of the oxidation catalyst, and exhaust flow velocity estimation means for estimating the exhaust gas flow velocity of the exhaust gas passing through the oxidation catalyst A determination means for determining the activity of the oxidation catalyst based on the detected temperature and the estimated exhaust gas flow velocity.
[0010]
Normally, the oxidation catalyst contains a catalyst metal, and the exhaust metal is oxidized by approaching or coming into contact with the catalyst metal and the exhaust material contained in the exhaust gas. The inventors have found that the activity of the oxidation catalyst is different between when the exhaust gas flow rate is high and when the exhaust gas flow rate is low, even when the environment surrounding the other oxidation catalyst is the same.
The reason for this is that when the exhaust gas flow rate is high, the contact time and approach time between the catalyst metal and the exhaust material are shortened, so that the oxidizing effect on the exhaust material such as HC and CO is suppressed, and as a result, It is considered that the oxidation of the oxidation catalyst as a whole is also suppressed and the activity decreases. On the other hand, when the exhaust gas flow rate is low, it is considered that the contact time or approach time between the catalyst metal and the exhaust material is relatively long, and the oxidizing action on the exhaust material is promoted, thereby improving the activity.
Therefore, in the first aspect of the present invention, the activity of the oxidation catalyst is determined based on the flow rate of the exhaust gas passing through the catalyst, whereby the activity can be determined with high accuracy. In addition, the determination is made in consideration of the temperature related to the catalyst temperature on the upstream side of the oxidation catalyst, and the activity can be more accurately determined.
[0011]
According to a second aspect of the present invention, in the first aspect, the engine supplies a fuel injection valve for directly injecting fuel into a combustion chamber, and supplies unburned fuel from the fuel injection valve to the oxidation catalyst. An injection control means for controlling an injection amount and an injection timing of fuel injected by the fuel injection valve based on an operation state of the engine; and the determination means further comprises: a fuel controlled by the injection control means. The activity of the oxidation catalyst is determined on the basis of the injection amount and the injection timing.
[0012]
A fuel injection valve for directly injecting fuel into the combustion chamber is provided. When the cylinder of the engine is in an expansion stroke or an exhaust stroke, for example, the fuel injection valve supplies unburned fuel to the oxidation catalyst in the exhaust passage from the fuel injection valve. In such a case, the supply state such as the supply amount of the unburned fuel is adjusted by controlling the fuel injection amount and the injection timing.
In this case, the larger the injection amount of the fuel injected for supplying the unburned fuel or the later the injection timing, the more the mixing property (vaporization and mixing properties) between the unburned fuel and the exhaust gas is suppressed. Due to this effect, even when the environment surrounding other oxidation catalysts is the same, when the injection amount is large and small, or when the injection timing is late (retard side) and early (advance side), The inventors have found that the activities of the respective oxidation catalysts as a whole are different from each other.
The reason for this is that, as the injection amount is larger or the injection timing is later, the miscibility of the unburned fuel is suppressed, the oxidation reaction of the catalyst in the entire oxidation catalyst is not actively performed, and the reaction heat is suppressed, Thus, as a result of the local suppression of the temperature rise inside the oxidation catalyst, it is considered that the activity of the oxidation catalyst as a whole increases slowly. On the other hand, as the injection amount is smaller or the injection timing is earlier, the miscibility of the unburned fuel is increased, the reaction with the oxidation catalyst is promoted, and the temperature inside the oxidation catalyst is raised as a whole. It is believed that the activity is increased quickly.
Therefore, in the invention according to claim 2, when controlling the injection amount and the injection timing of the fuel injected from the fuel injection valve to supply unburned fuel to the oxidation catalyst, the exhaust gas passing through the oxidation catalyst is controlled. The activity of the catalyst is determined based not only on the flow rate of the gas and the temperature related to the catalyst temperature on the upstream side of the oxidation catalyst but also on the basis of the injection amount and the injection timing. Therefore, even when unburned fuel is supplied from the fuel injection valve to the oxidation catalyst, the activity of the oxidation catalyst can be accurately determined.
[0013]
According to a third aspect of the present invention, in the second aspect, the engine includes an intake air amount detecting means for detecting an intake air amount flowing into the combustion chamber, and the exhaust flow velocity estimating means includes a detected intake air amount. And estimating the exhaust gas flow velocity based on the detected amount of fuel injected by the injection control means and the detected temperature.
With such a configuration, the exhaust gas flow velocity can be accurately estimated based on the intake air amount drawn into the combustion chamber, the fuel injection amount, and the temperature related to the detected catalyst temperature on the upstream side of the oxidation catalyst. In addition, the activity of the oxidation catalyst can be determined inexpensively and accurately without disposing a sensor for directly detecting the exhaust gas flow velocity in the exhaust passage. In addition, since the intake air amount is an actual measurement value detected by the intake amount detection means, the exhaust gas flow rate can be more accurately estimated, and the accuracy of the activity determination can be improved.
[0014]
According to a fourth aspect of the present invention, there is provided an oxidation catalyst disposed in an exhaust passage of an engine and having an oxidation function, a fuel injection valve for directly injecting fuel into a combustion chamber of the engine, and supplying unburned fuel to the oxidation catalyst. An injection control unit for controlling an injection amount and an injection timing of the fuel injected by the fuel injection valve based on an operation state of the engine; and an injection control unit for controlling the injection amount and the injection timing controlled by the injection control unit. Determining means for determining the activity of the oxidation catalyst.
[0015]
As described in claim 2, when unburned fuel is supplied to the oxidation catalyst in the exhaust passage from the fuel injection valve that directly injects fuel into the combustion chamber, the fuel is injected for supplying unburned fuel. The greater the fuel injection amount or the later the injection timing, the more the mixture of unburned fuel and exhaust gas is suppressed. As a result, even when the environment surrounding other oxidation catalysts is the same, the activity of the entire oxidation catalyst is different when the injection amount is large and small, or when the injection timing is late and early.
Therefore, in the invention according to claim 4, when controlling the injection amount and the injection timing of the fuel injected from the fuel injection valve in order to supply the unburned fuel to the oxidation catalyst, based on the injection amount and the injection timing, To determine the activity of the catalyst. Thus, even when unburned fuel is supplied from the fuel injection valve to the oxidation catalyst, the activity of the oxidation catalyst can be accurately determined.
[0016]
According to a fifth aspect of the present invention, there is provided a purifying section which is disposed in an exhaust passage of an engine and has an oxidation catalyst for purifying exhaust gas contained in exhaust gas, and a temperature related to an upstream temperature of the purifying section. Temperature detection means for detecting the flow rate of exhaust gas, exhaust flow velocity estimating means for estimating the flow velocity of the exhaust gas passing through the purifying section, and the activity of the oxidation catalyst based on the detected temperature and the estimated exhaust gas flow velocity. Determination means, a fuel injection valve that injects fuel directly into the combustion chamber of the engine, and supplies unburned fuel to the purification unit based on the determined activity of the oxidation catalyst, and supplies the unburned fuel to the purification unit. An injection control means for controlling at least one of the injection amount and the injection timing of the fuel injected by the fuel injection valve so as to increase the temperature is provided.
[0017]
In the invention described in claim 5, the exhaust material refers to gases such as HC and CO in the exhaust gas, and carbon particles as one type of fine particles.
As described in claim 1 above, when the catalyst metal contained in the oxidation catalyst and the exhaust material contained in the exhaust gas approach or come into contact with each other, the exhaust material is oxidized. And the late time, the activity of the oxidation catalyst is different.
Therefore, in claim 5 according to the present invention, the activity of the oxidation catalyst is determined based on the flow velocity of the exhaust gas passing through the catalyst to determine the activity with high accuracy, and the activity determination is more accurately performed. It is possible to do.
Further, since the accurate activity is grasped in this manner and at least one of the fuel injection amount and the injection timing in the supply of the unburned fuel is controlled, for example, the activity of the oxidation catalyst is accurately determined. Due to the inability to perform the process, excessive unburned fuel is supplied to the current activation state of the oxidation catalyst, and the temperature of the purifying unit rises to an abnormal level, and the purifying unit is damaged. It is possible to appropriately raise the temperature of the purifying unit without causing a problem that the amount of fuel is too small to deteriorate the temperature raising performance of the purifying unit. As a result, the exhaust gas purification performance can be improved.
[0018]
According to a sixth aspect of the present invention, there is provided a purifying section which is disposed in an exhaust passage of an engine, has an oxidation catalyst, and purifies exhaust gas contained in exhaust gas, and a fuel for directly injecting fuel into a combustion chamber of the engine. An injection valve, injection control means for controlling an injection amount and an injection timing of fuel injected by the fuel injection valve so as to supply unburned fuel from the fuel injection valve to the purifying section, and the injection control Determining means for determining the activity of the oxidation catalyst based on the fuel injection amount and the injection timing controlled by the means; wherein the injection control means determines the activity of the oxidation catalyst determined by the determination means. According to the present invention, at least one of the fuel injection amount and the fuel injection timing is controlled.
[0019]
As described in the second and fourth aspects, when the unburned fuel is supplied to the oxidation catalyst in the exhaust passage from the fuel injection valve that directly injects the fuel into the combustion chamber, the unburned fuel is supplied. The greater the injection amount of the fuel to be injected or the later the injection timing, the more the mixing property between the unburned fuel and the exhaust gas is suppressed. As a result, the activity of the oxidation catalyst as a whole differs when the injection amount is large and small, or when the injection timing is late and early.
Therefore, in the invention according to claim 6 of the present invention, when controlling the injection amount and the injection timing of the fuel injected from the fuel injection valve to supply the unburned fuel to the oxidation catalyst, the injection amount and the injection timing are controlled. Since the activity of the catalyst is determined based on the injection timing, the activity of the oxidation catalyst immediately after the unburned fuel is supplied from the fuel injection valve to the oxidation catalyst can be accurately determined.
In this way, since the accurate activity is grasped and at least one of the fuel injection amount and the injection timing in the supply of unburned fuel is controlled, for example, it is possible to accurately determine the activity of the oxidation catalyst. Due to the inability to do so, excessive unburned fuel is supplied with respect to the current activation state of the oxidation catalyst, and the temperature of the purifying unit becomes abnormally high, causing damage to the purifying unit. It is possible to appropriately raise the temperature of the purification unit without causing a problem that the temperature rise performance of the purification unit is deteriorated due to too small amount. As a result, the exhaust gas purification performance can be improved.
[0020]
According to a seventh aspect of the present invention, in the fifth or sixth aspect, the purifying unit includes an oxidation catalyst and a particulate filter disposed downstream of the oxidation catalyst and capable of capturing exhaust particulates in exhaust gas. In addition, the injection control means supplies unburned fuel to the oxidation catalyst so that the temperature of the particulate filter becomes high enough to incinerate and remove trapped exhaust particulates. It is characterized in that at least one of the injection amount and the injection timing is controlled.
When an oxidation catalyst and a particulate filter are arranged in the exhaust passage, and the temperature of the downstream particulate filter is increased by increasing the temperature of the oxidation catalyst, in order to incinerate and remove exhaust particulates captured by the particulate filter. Requires a large amount of unburned fuel to be supplied to the oxidation catalyst. When supplying such a large amount of unburned fuel, if the control of the supply amount of unburned fuel is not performed accurately based on accurate determination of the activity of the oxidation catalyst, for example, excess unburned fuel may be supplied. As a result, the temperature of the purification unit becomes so high that the temperature of the purification unit becomes abnormally high and the purification unit is damaged, and the problem that the unburned fuel is too small and the temperature rise performance of the purification unit is deteriorated is more likely to occur. .
Therefore, in claim 7 of the present invention, when the unburned fuel is supplied to the oxidation catalyst, the temperature of the particulate filter is so high that the trapped exhaust particulates can be incinerated and removed. As described above, since at least one of the injection amount and the injection timing is controlled, the occurrence of the above-described inconvenience can be prevented, the temperature of the particulate filter can be raised accurately, and the exhaust particulates are incinerated and removed. The performance can be improved.
[0021]
BEST MODE FOR CARRYING OUT THE INVENTION
[0022]
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
(overall structure)
FIG. 1 shows an example of an exhaust gas purification device A for an engine according to an embodiment of the present invention, and 1 is a diesel engine mounted on a vehicle. The engine 1 has a plurality of cylinders (cylinders) 2, 2,... (Only one is shown), and a piston 3 is inserted into each of the cylinders 2 so as to be able to reciprocate. 2 has a combustion chamber 4 defined therein. An injector 5 (fuel injection valve) is provided on the ceiling of the combustion chamber 4, and high-pressure fuel is directly injected into the combustion chamber 4 from an injection port at the tip thereof.
[0023]
On the other hand, the base end of the injector 5 for each cylinder 2 is connected to a common fuel distribution pipe 6 (common rail) by branch pipes 6a, 6a,. The common rail 6 is connected to a high-pressure supply pump 9 by a fuel supply pipe 8, and has a high-pressure state so that fuel supplied from the high-pressure supply pump 9 can be supplied to the injectors 5, 5,. A fuel pressure sensor 7 for detecting the internal fuel pressure (common rail pressure) is provided.
[0024]
The high-pressure supply pump 9 is connected to a fuel supply system (not shown), and is drivingly connected to a crankshaft 10 by a toothed belt or the like. The fuel supply to the common rail 6 is adjusted by returning the fuel to the fuel supply system via the common rail 6. The opening of the solenoid valve is controlled by an ECU 40 (described later) in accordance with the value detected by the fuel pressure sensor 7, so that the fuel pressure is controlled to a predetermined value corresponding to the operating state of the engine 1.
Although not shown, a valve operating mechanism that opens and closes an intake valve and an exhaust valve is disposed at an upper portion of the engine 1, while a rotation angle of the crankshaft 10 is detected at a lower portion of the engine 1. A crank angle sensor 11 and an engine water temperature sensor 13 for detecting a temperature of cooling water are provided. Although not shown in detail, the crank angle sensor 11 includes a plate to be detected provided at the end of the crankshaft and an electromagnetic pickup disposed so as to face the outer periphery thereof. A pulse signal is output each time the projections formed at equal intervals pass through.
[0025]
An intake passage 16 for supplying air (fresh air) filtered by an air cleaner 15 to the combustion chamber 4 of each cylinder 2 is connected to a side surface on one side (right side in the figure) of the engine 1. A surge tank 17 is provided at a downstream end of the intake passage 16. Each of the passages branched from the surge tank 17 communicates with the combustion chamber 4 of each cylinder 2 through an intake port. An intake pressure sensor 18 for detecting a pressure state of intake air is provided.
[0026]
A hot film type air flow sensor 19 for detecting a flow rate of air taken into the engine 1 from the outside and an intake air driven by a turbine 27 described later are arranged in the intake passage 16 in order from the upstream side to the downstream side. , An intercooler 21 for cooling the intake air compressed by the compressor 20, and an intake throttle valve 22 composed of a butterfly valve. The intake throttle valve 22 is set in an arbitrary state between a fully closed state and a fully opened state when the valve shaft is rotated by a stepping motor 23. Even when the intake throttle valve 22 is fully closed, the intake throttle valve 22 and the intake passage 16 are closed. It is configured such that a gap enough for air to flow is left between the peripheral wall and the peripheral wall.
[0027]
On the other hand, an exhaust passage 26 is connected to a side surface on the opposite side (left side in the figure) of the engine 1 so as to discharge combustion gas (exhaust gas) from the combustion chamber 4 of each cylinder 2. The upstream end of the exhaust passage 26 is an exhaust manifold that branches off for each cylinder 2 and communicates with the combustion chamber 4 through an exhaust port, and the exhaust passage 26 downstream of the exhaust manifold has an upstream side to a downstream side. , A linear O2 sensor 29 that detects the oxygen concentration in the exhaust, a turbine 27 that is rotated by receiving the exhaust flow, and an oxidation catalyst 28a that can oxidize harmful components (HC, CO, etc.) in the exhaust. A filter 28b, which can capture fine particles such as carbon discharged from the combustion chamber, is provided downstream of the filter 28b.
[0028]
The oxidation catalyst 28a is a general one in which a catalyst layer supporting a noble metal such as Pt is coated on the cell surface of a porous ceramic honeycomb carrier, and the catalyst components are particularly adjusted to have excellent oxidation performance. The filter 28b is made of porous ceramics, and is a general diesel particulate filter in which one of the cells adjacent to the honeycomb is plugged at the upstream end and the other cell is plugged at the downstream end. A catalyst layer supporting a noble metal such as Pt is coated on the cell surface. The temperature rise performance is improved by the reaction heat of the catalyst metal.
The filter 28b does not have to carry a catalyst metal. Conversely, the catalyst layer may contain an alkali metal or an alkaline earth metal in order to further combine the NOx absorption ability in addition to the noble metal in the catalyst layer. .
The oxidation catalyst 28a and the filter 28b are separated from each other and arranged upstream and downstream. The distance between the oxidation catalyst 28a and the filter 28b is determined by the temperature of the oxidation catalyst 28a. To the extent that it can be communicated to.
[0029]
The turbocharger 30 including the turbine 27 and the compressor 20 in the intake passage 16 is a variable turbocharger (hereinafter referred to as VGT) in which the cross-sectional area of the exhaust passage to the turbine 27 is changed by movable flaps 31, 31,. Are respectively connected to the diaphragm 32 via a link mechanism (not shown), and the magnitude of the negative pressure acting on the diaphragm 32 is controlled by a solenoid valve for controlling the negative pressure. The rotation position of the flaps 31, 31,... Is adjusted by the adjustment by 33.
[0030]
In the exhaust passage 26, an upstream end of an exhaust gas recirculation passage (hereinafter, referred to as an EGR passage) 34 for recirculating a part of the exhaust gas to the intake side so as to open toward a portion of the exhaust gas upstream of the turbine 27 is provided. It is connected. The downstream end of the EGR passage 34 is connected to the intake passage 16 between the intake throttle valve 22 and the surge tank 17, and a part of the exhaust gas extracted from the exhaust passage 26 is recirculated to the intake passage 16. I have. Further, an EGR cooler 37 for cooling the exhaust flowing through the inside of the EGR passage 34 and an exhaust gas recirculation amount control valve (hereinafter, referred to as an EGR valve) 35 whose opening can be adjusted are arranged in the middle of the EGR passage 34. The EGR valve 35 is of a negative pressure responsive type. Like the flaps 31, 31,... Of the VGT 30, the magnitude of the negative pressure applied to the diaphragm is adjusted by the electromagnetic valve 36, so that the EGR passage 34 The cross-sectional area is adjusted linearly to adjust the flow rate of the exhaust gas recirculated to the intake passage 16. Note that the EGR cooler 37 may not be provided.
[0031]
Each of the injectors 5, the high-pressure supply pump 9, the intake throttle valve 22, the VGT 30, the EGR valve 35, and the like are all operated upon receiving a control signal from a control unit (Electronic Control Unit: hereinafter referred to as ECU) 40. On the other hand, the ECU 40 receives output signals from the fuel pressure sensor 7, the crank angle sensor 11, the engine water temperature sensor 13, the intake pressure sensor 18, the air flow sensor 19, the linear O2 sensor 29, and the like. An output signal from an accelerator opening sensor 39 for detecting a pedal operation amount (accelerator opening) is input.
[0032]
An exhaust gas temperature sensor 41 for estimating the temperature of the oxidation catalyst 28a or the temperature of the filter 28b is arranged upstream of the oxidation catalyst 28a. On the other hand, a filter upstream pressure sensor 42 for detecting an exhaust pressure on the upstream side of the filter 28b is disposed in the exhaust passage 26 on the upstream side of the filter 28b, preferably between the filter 28b and the oxidation catalyst 28a. A filter downstream pressure sensor 43 is disposed in the exhaust passage 26 on the downstream side. The output signal of the exhaust gas temperature sensor 41, the output signal of the filter upstream pressure sensor 42, and the output signal of the filter downstream pressure sensor 43 are further input to the ECU 40.
[0033]
(Fuel injection control)
Next, the fuel injection control according to the present embodiment will be described.
The ECU 40 calculates an accelerator opening amount (engine load) from a signal input from the input accelerator opening sensor 39, calculates an engine speed from a signal input from the crank angle sensor 11, and calculates these by an injection control unit. (Not shown) to control the main injection M and the expansion stroke injection F1 as an additional injection for regeneration of the filter 28b based on the engine load and the engine speed.
When the filter 28b is regenerated, the EGR valve 35 is closed by the ECU 40 so that the exhaust gas purification control by the additional injection can be executed accurately.
[0034]
As shown in S1 of FIG. 2, the main injection M is a fuel injection performed by the injector 5 near the top dead center of the compression stroke for each cylinder, and the fuel injected by this injection raises the piston position and burns. Since the indoor pressure is injected at an extremely high pressure, self-ignition is performed and main combustion is performed. The injection amount of the main injection M is set in advance based on a torque (required torque) corresponding to the output so that a required output by an occupant or the like is obtained. S1 in FIG. 2 is a timing chart illustrating an operation state of a needle valve (not shown) of the injector 5.
Specifically, the ECU 40 stores a main injection amount map (not shown) that is set so that the main injection amount is increased as the engine speed is higher and the accelerator opening is larger. A main injection timing map (not shown) in which the execution timing of the main injection M is set based on the rotation speed and the accelerator opening amount is stored, and the main injection amount and the injection are set based on the engine rotation speed and the accelerator opening amount. The time is set.
[0035]
The form of the main injection M is not limited to such a single injection, but may be a combination of a so-called pilot injection that is performed temporarily shortly before the compression stroke top dead center and a main injection near the compression stroke top dead center. Alternatively, the main injection M itself executed near the top dead center of the compression stroke may be divided into multiple injections with a small pause interval (about 1 ms or less).
[0036]
During operation of the diesel engine, fine particles are contained in the exhaust gas. Therefore, a filter 28b is disposed to capture the fine particles. By the way, in normal diesel combustion, the temperature is relatively low from 150 ° C. to 300 ° C., and at such a low temperature, the trapped fine particles are difficult to burn and burn. In general, it is necessary to maintain a high temperature of 500 ° C. or more for several minutes during incineration and removal of soot. Therefore, the oxidation catalyst 28a is arranged at a position near the exhaust gas upstream of the filter 28b, and the oxidation catalyst metal is applied to the filter 28b itself. ing. When the difference between the exhaust pressures of the upstream and downstream of the filter 28b is equal to or larger than a predetermined value, the amount of the fine particles captured by the filter 28b increases, and it is determined that the forcible removal of these fine particles is necessary. Therefore, additional injection different from the main injection is performed toward the oxidation catalyst 28a and the filter 28b to maintain the high temperature by fuel supply, and the filter 28b is regenerated. In order to perform incineration and removal of fine particles, it is necessary to continuously maintain a considerably high temperature. Therefore, in a low rotation or low load region, and a medium rotation and a medium load region, the additional injection amount is inevitably increased. It is set to be 1.5 to 4 times larger than the main injection amount.
[0037]
In the present embodiment, as the additional injection, the expansion stroke injection F1 is executed after the completion of the injection of the main injection M during the expansion stroke, as shown in S1 of FIG.
The injection timing of the expansion stroke injection F1 is advanced to the injection timing side of the main injection M to set the initial timing of the expansion stroke, or the injection timing of the main injection M is delayed with the injection timing of the expansion stroke injection F1 unchanged. When the angle is changed (when the period between the injection timing of the main injection M and the injection timing of the expansion stroke injection F1 is shortened), most of the injected fuel is affected by the main combustion caused by the main injection M. At the same time, the amount of unburned fuel supplied to the oxidation catalyst 28a decreases. However, the unburned fuel supplied at this time is due to the fuel injected at a high temperature and pressure in the combustion chamber, and therefore has a high mixing property with the exhaust gas. The activation rate of the catalyst can be improved. At this time, the temperature rise of the exhaust gas itself exhausted from the combustion chamber 4 and supplied to the oxidation catalyst 28a is also promoted.
[0038]
Conversely, when the injection timing of the expansion stroke injection F1 is retarded and set near the middle stage of the expansion stroke (when the period between the injection timing of the main injection M and the injection timing of the expansion stroke injection F1 is extended), Since the injected fuel is hardly burned by the main combustion, the supply amount of the unburned fuel to the oxidation catalyst 28a increases. Since the unburned fuel supplied at this time is derived from fuel injected at a low temperature and pressure in the combustion chamber, the mixing property is lower than when the expansion stroke injection F1 is injected at the beginning of the expansion stroke. Not, but relatively high.
At this time, the effect of increasing the temperature of the exhaust gas supplied to the oxidation catalyst 28a is suppressed. In this case, as described later, the unburned fuel having a high degree of miscibility is mixed with the oxidation catalyst 28a. Therefore, the activation rate of the oxidation catalyst 28a can be improved. Then, if the activation rate of the oxidation catalyst 28a becomes high, high reaction heat is generated by the unburned fuel attached to the oxidation catalyst 28a, and the temperature of the filter 28b downstream thereof is positively increased.
[0039]
Further, when the injection timing of the expansion stroke injection F1 is greatly retarded and set in the latter half of the expansion stroke, a large amount of unburned fuel having extremely low miscibility is supplied to the oxidation catalyst 28a, as will be described later. Even if a large amount of such unburned fuel adheres to the oxidation catalyst 28a, the activity of the oxidation catalyst 28a is improved temporarily but not so much. At this time, almost no increase in the temperature of the exhaust gas can be expected.
[0040]
In detail, the start timing of the injection of the expansion stroke injection F1 is between 0 ° and 130 ° after the top dead center of the compression stroke (ATDC) from the end of the injection of the main injection M, and more preferably about 10 ° to 100 ° at the ATDC. , A specific time of a predetermined allowable range period (not shown) set according to the operating state is set. The predetermined allowable range period is set in the advance range when the engine speed is low and the engine load is low, and is set in the retard range when the engine speed is high and the load is high. .
[0041]
(Activity determination control of oxidation catalyst)
Next, the activity determination control of the oxidation catalyst according to the present embodiment will be described.
The ECU 40 calculates the intake air amount from the signal input from the air flow sensor 19 and calculates the temperature of the exhaust gas upstream (immediately before the inlet) of the oxidation catalyst 28a from the signal input from the exhaust gas temperature sensor 41. When many particles are trapped by the filter 28b and the regeneration process of the filter 28b is being performed, first, the flow rate of the exhaust gas is estimated as follows. This is performed based on the detected intake air amount and exhaust gas temperature, and the injection amount of the expansion stroke injection F1, which is the above-described additional injection for supplying unburned fuel.
The reason is that the flow rate of the exhaust gas is determined by the amount of intake air supplied into the combustion chamber 4 and the amount of fuel injection. If the injection amount of the main injection M is further taken into consideration as the amount of fuel injection, the estimation accuracy becomes higher. Is improved.
[0042]
Next, the activation rate of the oxidation catalyst 28a (unit:%, based on the detected catalyst gas temperature To, which is the detected exhaust gas temperature upstream of the oxidation catalyst, and the exhaust gas flow rate obtained earlier). , And the activation rate of 50% means that the amount of exhausted material that has flowed out is reduced by half with respect to the amount of exhausted material that flows in).
[0043]
The exhaust gas flow rate of the exhaust gas passing through the oxidation catalyst and the activation rate of the oxidation catalyst 28a are closely related. Specifically, when the exhaust gas flow rate is high, the contact time and the approach time between the catalyst metal supported on the oxidation catalyst 28a and the exhaust material (for example, a reducing agent such as HC or CO) are shortened. It is considered that the oxidizing action of the catalyst is suppressed, and as a result, the oxidation of the oxidation catalyst as a whole is also suppressed, so that the activation rate decreases. On the other hand, when the exhaust gas flow rate is low, the contact time and the approach time between the catalyst metal and the exhaust material are relatively long, and the oxidizing action on the exhaust material is promoted, so that the activity is considered to be improved. In addition, it has been found that the higher the exhaust gas temperature, the higher the activity is. Therefore, in this embodiment, the exhaust gas flow rate and the exhaust gas temperature upstream of the oxidation catalyst 28a, that is, the actual measured value To of the catalyst temperature, are two. An original control map is provided, from which the activation rate of the oxidation catalyst 28a is determined.
[0044]
This map will be described with reference to FIG.
In the map, the activation rate is set on the horizontal axis, and the catalyst temperature To, which is the actual measurement value, is set on the vertical axis. If the exhaust gas flow rates are the same (for example, on the Ma line), as the catalyst temperature To rises, The activation rate is set to be high.
Even at the same catalyst temperature, the activation rate is set so as to decrease as the exhaust gas flow rate increases. For example, when the catalyst temperature is Tox, the activation rate at the time when the exhaust gas flow rate is low is AC3. When the catalyst temperature is high and the exhaust gas flow rate is medium at Mb at the same catalyst temperature, the activation rate is medium at AC2. At the same catalyst temperature and Mc at a high exhaust gas flow rate, the activation rate is a small value at AC1. become.
Ma, Mb, and Mc indicate reference lines on the map when the exhaust gas flow velocity is a specific value and the temperature correction amount described later is not corrected.
The format of the map is not limited to that shown in FIG.
[0045]
Next, a temperature correction amount for the above-described exhaust gas temperature will be described.
The temperature correction amount is determined based on the injection amount of the expansion stroke injection F1 for supplying unburned fuel and the injection timing.
This is because, as the injection amount of the expansion stroke injection F1 injected for supplying the unburned fuel is larger or the injection timing is later, the mixing property (vaporization and mixing) of the unburned fuel with the exhaust gas is suppressed. It is for the purpose. Under the influence, even when the environment surrounding the other oxidation catalyst is the same, when the injection amount is large and small, or when the injection timing is late (retard side) and early (advance side), respectively This results in different activities of the oxidation catalyst as a whole.
Specifically, the larger the injection amount of the expansion stroke injection F1 or the later the injection timing, the more the mixing property between the unburned fuel and the exhaust gas is suppressed, whereby the reaction between the oxidation catalyst and the unburned fuel is reduced. And the heat of reaction accompanying the oxidation reaction of the catalyst is suppressed. Thus, as a result of the local suppression of the temperature rise inside the oxidation catalyst, it is considered that the activity of the oxidation catalyst as a whole increases slowly.
On the other hand, as the injection amount of the expansion stroke injection F1 is smaller or the injection timing is earlier, the mixing property between the unburned fuel and the exhaust gas is increased, and the reaction between the oxidation catalyst and the unburned fuel is promoted, and the oxidation catalyst is accelerated. It is considered that the temperature of the entire inside is increased, and the activity of the oxidation catalyst as a whole is rapidly increased.
[0046]
Therefore, in the present embodiment, there is provided a binary control map of the injection timing and the injection amount in the expansion stroke injection F1, and based on the temperature correction amount determined by this map, the reference line on the map of FIG. The activation rate is obtained as described above by correcting Ma, Mb, Mc, and the like. As shown in FIG. 4, the map sets the injection timing on the horizontal axis and the injection amount on the vertical axis. As the injection timing is set to the retard side or the injection amount is larger, the temperature correction amount Tc Is set to be large.
When the temperature correction amount Tc is determined in this manner, the temperature correction amount Tc is uniformly added to the reference line in FIG. 3 to obtain a correction line (for example, Mbm). The activation rate will be determined based on the map.
[0047]
Specifically, when the estimated exhaust gas flow velocity is a predetermined value and the reference line Mb on the map is selected according to FIG. 3, the injection timing is advanced and the injection amount is small. When “0” is set as the temperature correction amount Tc, the reference line Mb is not changed. Therefore, if the actual measured value of the exhaust gas temperature is Tox at this time, the activation rate is AC2. However, when the injection timing is on the retard side and the injection amount is large, and a relatively large value “Tcx” is set as the temperature correction amount Tc based on FIG. 4, the reference line Mb on the map in FIG. The temperature is raised uniformly by Tcx (° C.), and the correction line Mbm is set. According to this correction line Mbm, if the actual measured value To of the exhaust gas temperature at this time is Tox, the activation rate becomes AC2m (<AC2).
Thus, the activation rate is set to be lower as the injection timing of the expansion stroke injection F1 is more retarded or the injection amount is larger, even if the measured value of the temperature of the exhaust gas flowing into the oxidation catalyst is the same.
[0048]
Next, a control flowchart for determining activation of the oxidation catalyst 28a in the present embodiment will be described with reference to FIG.
In FIG. 5, for example, after starting every predetermined time, in steps SA1 and SA2, the intake air amount is detected by the air flow sensor 19 and the exhaust gas temperature is detected by the exhaust gas temperature sensor 41, respectively. Next, at step SA3, the injection amount and the injection timing of the expansion stroke injection F1, which is injected immediately before the present time or a predetermined time earlier than the present time and affects the activity of the oxidation catalyst 28a at the present time, are stored. Read from the storage unit. Next, in step SA4, the exhaust gas flow velocity is estimated based on the detected intake air amount, the detected exhaust gas temperature, and the injection amount of the expansion stroke injection F1. At this time, the exhaust gas flow velocity may be estimated based on the main injection amount. Next, in step SA5, the temperature correction amount Tc is calculated from the injection amount and the injection timing of the expansion stroke injection F1 based on the above-described map in FIG. 4, and the process proceeds to step SA6. In step SA6, a reference line on the map in FIG. 3 is selected based on the estimated exhaust gas flow velocity, and the reference line is corrected as described above based on the temperature correction amount Tc, and a correction line is set. Next, in step SA7, the catalyst activation rate is determined from the measured exhaust gas temperature based on the correction line on the map in FIG.
[0049]
Next, a control flowchart of the injection control of the expansion stroke injection F1 will be described with reference to FIG.
In the control flowchart of FIG. 6, for example, after starting at every predetermined crank angle, the engine speed and engine load are detected in step SB1, and the process proceeds to step SB2. In step SB2, the oxidation catalyst 28a is detected by the exhaust gas temperature sensor 41. Detects upstream exhaust gas temperature. In step SB3, the amount of particulates captured by the filter 28b is estimated from the pressure difference between the pressures detected by the upstream pressure sensor 42 and the downstream pressure sensor 43. This is because it is estimated that the larger the differential pressure is, the larger the trapped amount of the fine particles is. In the next step SB4, when the estimated trapped amount of the fine particles is equal to or more than a predetermined value, the trapped fine particles are incinerated to filter 28b. Is determined to be necessary, and the flow advances to step SB5. On the other hand, if the trapping amount is equal to or smaller than the predetermined value in step SB4, it is determined that the particles are not accumulated enough to regenerate the filter 28b, and the process returns to step SB1. In step SB5, an injection timing and an injection amount are set based on an injection timing map (not shown) and an injection amount map (not shown) of the expansion stroke injection F1, and the process proceeds to step SB6.
[0050]
In the injection timing map and the injection amount map, the injection timing and the injection amount are set in accordance with the engine speed, the engine load, and the activation rate of the oxidation catalyst 28a obtained in FIG. Specifically, the injection timing is set to the retard side as the rotation speed increases, the load increases, and the activation degree of the oxidation catalyst 28a increases. The reason for this is that in such a state, the exhaust gas temperature is already high only by the combustion of the main injection. Therefore, it is better to increase the amount of the unburned fuel than to increase the temperature of the exhaust gas flowing into the oxidation catalyst 28a, and to increase the filter 28b. This is because the temperature can be increased.
The injection amount is set to decrease as the rotation speed increases, the load increases, and the activation rate of the oxidation catalyst 28a increases. This is because, in this state, the exhaust gas temperature is already high, and if the injection amount is increased more than necessary, the fuel efficiency deteriorates, or the filter 28b becomes abnormally hot due to the large supply of unburned fuel and melts, or This is to prevent a problem that the amount is excessive and a part of the fuel passes through the filter 28b and is released to the atmosphere without being purified to deteriorate the emission.
On the other hand, as the rotation speed decreases, the load decreases, and the activation degree of the oxidation catalyst 28a decreases, the injection timing is set to the advanced side. The reason for this is that, in such a state, the exhaust gas temperature is low only by the combustion of the main injection, and the exhaust gas temperature is increased in order to activate the oxidation catalyst 28a rather than to supply the unburned combustion to raise the temperature of the filter 28b. This is for increasing the temperature of the fuel cell and efficiently executing additional injection without additional injection of extra fuel.
In addition, the injection amount increases as the rotation speed decreases, the load decreases, and the activation degree of the oxidation catalyst 28a decreases. The purpose of this is also to efficiently increase the exhaust gas temperature by performing additional injection efficiently.
In step SB6, the expansion stroke injection F1 set in step SB5 is executed when the detected crank angle reaches the set injection timing, and the process returns to step SB1.
[0051]
According to such an embodiment, the activation rate of the oxidation catalyst 28a can be estimated with high accuracy, and the injection amount and the injection timing of the expansion stroke injection F1 are set based on such accurate activation rate. Since the injection is performed, it is possible to prevent the excessive supply and the insufficient supply of the unburned fuel to the oxidation catalyst 28a and appropriately and efficiently raise the temperature of the filter 28b. The performance of incineration removal is improved, and as a result, the regeneration performance of the filter 28b can be improved.
[0052]
(Other embodiments)
In the embodiment of the present invention, when the filter 28b is regenerated, the activation rate of the oxidation catalyst 28b is estimated as described above and the additional injection is controlled based on the estimation rate. The present invention is not limited to 28b, but may be an ordinary catalyst device such as a three-way catalyst, an HC trap catalyst, or a NOx trap catalyst, or may be an additional injection device for raising the temperature thereof. .
In this case, since these ordinary catalyst devices have an oxidation catalyst function by themselves, there is no need to provide an oxidation catalyst upstream of these catalyst devices.
[0053]
Further, in the embodiment of the present invention, the main injection M is executed near the top dead center of the compression stroke. However, the present invention is not limited to this. The fuel may be injected a plurality of times over the compression stroke from the beginning, or the fuel may not be injected near the top dead center of the compression stroke, but may be injected from the intake stroke on the more advanced side to the compression stroke. May be.
Further, in the embodiment of the present invention, after determining the activation rate of the oxidation catalyst 28a, the injection amount and the injection timing of the expansion stroke injection F1 are controlled based on the determination, but only one of them is controlled. Is also good.
Further, in the embodiment of the present invention, the additional injection is performed only once in the expansion stroke injection F1. However, the injection may be performed once or a plurality of times from the expansion stroke to the exhaust stroke. .
Further, in the present embodiment, the exhaust gas temperature on the upstream side of the oxidation catalyst 28a is detected. However, the present invention is not limited to this, and the temperature of the oxidation catalyst is detected by a temperature sensor directly disposed on the upstream side of the oxidation catalyst 28a. Is also good.
Further, the engine 1 may be a direct injection gasoline engine.
[0054]
【The invention's effect】
As described above, in the present invention, the activity of the oxidation catalyst is determined based on the flow rate of the exhaust gas passing through the oxidation catalyst and the temperature related to the catalyst temperature on the upstream side of the oxidation catalyst. Thus, it is possible to determine with high accuracy.
Further, when supplying unburned fuel to the oxidation catalyst from the fuel injection valve of the direct injection engine, the activity of the oxidation catalyst is determined based on the fuel injection amount and the injection timing, so that the determination can be made with high accuracy. It is.
Further, in the case where unburned fuel is supplied from the fuel injection valve of the direct injection engine to the purifying unit including the oxidation catalyst, the temperature of the purifying unit is determined based on the activity of the oxidation catalyst accurately determined by such a method. Since the fuel injection amount or the injection timing is controlled so as to increase the temperature, the temperature of the purification unit can be appropriately increased without causing excessive supply or insufficient supply of the unburned fuel.
[Brief description of the drawings]
FIG. 1 is an overall configuration diagram showing an exhaust gas purification device for an engine according to an embodiment of the present invention.
FIG. 2 is an explanatory view schematically showing an injection operation by an injector 5.
FIG. 3 is an explanatory diagram showing a map for obtaining an activation rate.
FIG. 4 is an explanatory diagram showing a map for obtaining a temperature correction amount.
FIG. 5 is a flowchart showing a control procedure for determining the activity of the oxidation catalyst.
FIG. 6 is a flowchart showing a control procedure of additional injection control.
[Explanation of symbols]
2: Cylinder
4: Combustion chamber
5: Injector (fuel injection valve)
19: Air flow sensor (intake air amount detection means)
28a: oxidation catalyst (purification unit)
28b: Filter (purification unit)
41: Exhaust gas temperature sensor (temperature detecting means)
F1: Expansion stroke injection

Claims (7)

In an exhaust passage of an engine, an oxidation catalyst having an oxidation function is arranged, and an activity determination device for an oxidation catalyst for an engine that determines the activity of the oxidation catalyst includes:
Temperature detection means for detecting a temperature related to a catalyst temperature on the upstream side of the oxidation catalyst,
Exhaust flow velocity estimating means for estimating an exhaust gas velocity of the exhaust gas passing through the oxidation catalyst;
An activity determination device for an oxidation catalyst for an engine, comprising: determination means for determining the activity of the oxidation catalyst based on the detected temperature and the estimated exhaust gas flow velocity. The engine includes a fuel injection valve that injects fuel directly into the combustion chamber,
Injection control means for controlling an injection amount and an injection timing of fuel injected by the fuel injection valve based on an operation state of the engine such that unburned fuel is supplied from the fuel injection valve to the oxidation catalyst. Equipped,
2. The engine oxidation catalyst according to claim 1, wherein the determination unit further determines the activity of the oxidation catalyst based on a fuel injection amount and an injection timing controlled by the injection control unit. Activity determination device. The engine includes an intake air amount detection unit that detects an intake air amount flowing into the combustion chamber,
The exhaust gas flow rate estimating means estimates the exhaust gas flow rate based on the detected intake air amount, the amount of fuel injected by the injection control means, and the detected temperature. 3. The apparatus for determining the activity of an oxidation catalyst for an engine according to 2. An oxidation catalyst disposed in an exhaust passage of the engine and having an oxidation function;
A fuel injection valve that injects fuel directly into the combustion chamber of the engine;
Injection control means for controlling an injection amount and an injection timing of fuel injected by the fuel injection valve based on an operation state of the engine so as to supply unburned fuel to the oxidation catalyst;
A determination device for determining the activity of the oxidation catalyst based on the injection amount and the injection timing controlled by the injection control device. A purifying unit disposed in the exhaust passage of the engine and having an oxidation catalyst to purify exhaust substances contained in the exhaust gas;
Temperature detection means for detecting a temperature related to the upstream temperature of the purification unit,
Exhaust flow velocity estimating means for estimating the flow velocity of the exhaust gas passing through the purification unit;
Determining means for determining the activity of the oxidation catalyst based on the detected temperature and the estimated exhaust gas flow velocity,
A fuel injection valve that injects fuel directly into the combustion chamber of the engine;
Based on the determined activity of the oxidation catalyst, the amount and amount of fuel injected by the fuel injection valve so as to supply unburned fuel to the purifying unit and raise the temperature of the purifying unit. An exhaust emission control device for an engine, comprising: injection control means for controlling at least one of the timings. A purifying unit disposed in the exhaust passage of the engine and having an oxidation catalyst to purify exhaust substances contained in the exhaust gas;
A fuel injection valve that injects fuel directly into the combustion chamber of the engine;
Injection control means for controlling an injection amount and an injection timing of fuel injected by the fuel injection valve so as to supply unburned fuel from the fuel injection valve to the purification section;
Determining means for determining the activity of the oxidation catalyst based on the fuel injection amount and the injection timing controlled by the injection control means,
An exhaust gas purifying apparatus for an engine, wherein the injection control means controls at least one of a fuel injection amount and an injection timing according to the activity of the oxidation catalyst determined by the determination means. The purification unit includes an oxidation catalyst, and a particulate filter disposed downstream of the oxidation catalyst and capable of capturing exhaust particulates in exhaust gas.
The injection control means supplies the unburned fuel to the oxidation catalyst, so that the temperature of the particulate filter becomes high enough to incinerate and remove the trapped exhaust particulates. 7. The exhaust gas purifying apparatus for an engine according to claim 5, wherein at least one of the injection timings is controlled.

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