JP4178960B2 - Exhaust gas purification device for internal combustion engine - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an exhaust gas purification device for an internal combustion engine having an exhaust aftertreatment device such as a particulate filter with a catalyst in an exhaust passage, and more particularly to avoid catalyst poisoning by hydrocarbons supplied to the exhaust aftertreatment device. The present invention relates to an exhaust gas purification apparatus having means.
[0002]
[Prior art]
In recent years, as an environmental measure, an exhaust gas purification device that treats gas discharged from an internal combustion engine with a catalyst or a filter and suppresses the release of harmful components has become important. One example is an exhaust gas purification device that collects particulates (PM), which are particulate matter discharged from a diesel engine, with a diesel particulate filter (hereinafter referred to as DPF) installed in the middle of an exhaust pipe. DPM is regenerated by periodically removing the PM that has been burned off, enabling continuous use.
[0003]
The regeneration of the DPF is normally performed when the PM deposition amount calculated based on the differential pressure across the DPF becomes a predetermined amount or more. At the time of regeneration, for example, post-injection is performed to supply unburned hydrocarbon (HC) to the DPF, and the supplied HC is burned using an oxidation catalyst previously supported on the DPF. With this combustion heat, the DPF temperature can be raised to a temperature at which PM burns, for example, 600 ° C. or more.
[0004]
However, at this time, if the DPF temperature is low, the rate of the catalytic reaction becomes small. When a large amount of HC is supplied here, the supplied HC adheres to the surface of the catalyst, the diffusion of exhaust gas containing harmful components to the vicinity of the catalyst is inhibited, and the catalytic reaction is lowered. A poison problem arises. Here, since HC poisoning is caused by physical adsorption of HC to the catalyst, the catalytic activity can be recovered by promoting the detachment of the attached HC while keeping the DPF temperature high. For example, Patent Document 1 is cited as a conventional technique related to the recovery operation of HC poisoning of a catalyst using this.
[0005]
[Patent Document 1]
JP-A-11-257125 [0006]
Patent Document 1 includes a determination unit that calculates the amount of HC adsorbed on the catalyst in a system that purifies nitrogen oxide (NOx) using a catalyst and determines catalyst poisoning based on whether the amount of adsorption is greater than a predetermined value. In addition, it is described that, when it is determined that the catalyst is poisoned, the control for recovering the poisoning is performed. Specifically, the recovery operation is performed by closing the intake throttle valve and opening the exhaust gas recirculation valve (EGR valve) to prevent a decrease in the temperature of the catalyst. The catalyst temperature is raised by the heat of oxidation reaction. In this system, HC is added upstream of the catalyst for NOx reduction purification.
[0007]
[Problems to be solved by the invention]
That is, the method of Patent Document 1 allows catalyst poisoning by HC to occur, and measures are taken only after HC poisoning has occurred. However, once HC poisoning occurs, it takes time to recover, and there is a problem that harmful components cannot be purified by the catalyst until HC poisoning is recovered. In particular, in the DPF, when the front end surface of the DPF is exposed to high-temperature exhaust gas after being poisoned by HC, the adhering HC is carbonized, and in the worst case, the DPF inlet may be blocked. . And in order to remove carbonized HC, it is necessary to incinerate that part at a very high temperature (for example, 600 ° C. or more) for a long time, while the exhaust temperature occupying most of the actual running is low ( For example, it is difficult to maintain a high temperature for a long time in a traveling state, and thus there is a problem that the fuel consumption is greatly deteriorated.
[0008]
From such a situation, in the exhaust gas purification apparatus, it is a big problem to avoid HC poisoning itself, instead of taking measures only after HC poisoning occurs. In particular, in the DPF, since it is necessary to supply a large amount of HC by post injection or the like in order to burn the accumulated PM, HC poisoning is likely to occur. When HC poisoning occurs, the DPF temperature does not rise quickly, and PM is not burned well, so it is particularly important to avoid this.
[0009]
The object of the present invention is to avoid the HC poisoning of the catalyst carried on the exhaust aftertreatment device itself in the exhaust gas purification device of the internal combustion engine, thereby eliminating the need for the recovery operation of the catalyst activity, and the PM in the meantime. The purpose is to prevent the deterioration of the combustion performance and the purification performance of harmful components, or to prevent problems such as carbonization of adhering HC, to maintain the catalyst performance for a long time, and to realize a highly reliable device.
[0010]
[Means for Solving the Problems]
In order to solve the above problems, the exhaust gas purifying apparatus for an internal combustion engine according to claim 1, a DPF carrying an oxidation catalyst disposed in an exhaust passage of an internal combustion engine, a temperature detecting means for detecting the temperature of the DPF, the to regenerate the DPF, post-injection, the HC supply means for supplying hydrocarbon to the DPF by either or a combination of operations increase the retard and EGR quantity of the fuel injection timing, HC supplied to the DPF the amount, the HC amount detecting means for calculating the sum of the HC amount caused by unburned HC amount and the HC supply means for generating on the basis of the combustion in the internal combustion engine, the temperature of the DPF detected by the temperature detecting means HC subjected to corresponding determines the upper limit value of the supply can be the amount of HC to the DPF, HC amount calculated by the HC amount detection means for controlling said HC supply means so as not to exceed the upper limit And a quantity control means, the HC amount detecting means, the amount of HC by the HC supply means, due to the operation of the HC supply means and the amount of HC is actually supplied to the DPF, the HC supply means The basic HC amount corresponding to the operation amount is calculated by subtracting the amount burned in the cylinder of the internal combustion engine, and the HC supply amount control means determines the upper limit value of the HC amount as the temperature of the DPF, the DPF It is determined based on the relationship of the amount of HC that does not cause HC poisoning when it is supplied .
[0011]
The present inventors have, as the temperature of the DPF is focused on the point that greatly affects the HC poisoning, determines the upper limit of which can be supplied HC amount according to the temperature of the DPF, detected by the HC amount detecting means It has been found that HC poisoning can be prevented by controlling the HC supply means based on the amount of HC to be supplied and limiting the amount of HC to be supplied to the upper limit value or less. In this way, since HC poisoning of the catalyst itself can be avoided, the recovery operation of the catalyst activity becomes unnecessary, and problems such as deterioration in purification performance during the recovery operation or carbonization of the attached HC are prevented. Therefore, a highly reliable apparatus with excellent catalyst performance can be realized.
Specifically, the amount of HC supplied to the DPF can be easily controlled by employing any one or combination of post-injection, retarding of fuel injection timing and increasing EGR amount as the HC supply means. Therefore, the control by the HC supply amount control means can be easily performed. Further, the hydrocarbons flowing into the DPF include hydrocarbons generated by combustion of the internal combustion engine in addition to the hydrocarbons supplied from the HC supply means, and the combined amount of these is the amount of HC supplied. By comparing with the upper limit value, more accurate control is possible.
[0013]
According to a second aspect of the present invention, the HC amount detection means calculates the amount of combustion in the cylinder of the internal combustion engine among the basic HC amounts according to the operation amount of the HC supply means based on the operating conditions of the internal combustion engine. ,
The HC supply amount control means determines whether or not the HC amount hydrocarbon amount calculated by the HC amount detection means is less than or equal to the upper limit value, and if a negative determination is made, becomes less than or equal to the upper limit value. Until then, the HC amount by the HC supply means is corrected to decrease.
[0014]
4. The configuration according to claim 3 , wherein the HC amount detection means calculates the basic HC amount according to the operation amount of the HC supply means and the HC amount of the unburned portion generated based on the combustion of the internal combustion engine as an operating condition of the internal combustion engine. Calculate based on
[0015]
According to a fourth aspect of the present invention, the temperature detecting means detects an exhaust temperature upstream of the DPF . Specifically, since the temperature of the exhaust gas flowing into the DPF greatly affects whether or not HC poisoning occurs, the upper limit value of the amount of HC that can be supplied is determined based on the exhaust gas temperature upstream of the DPF. By doing so, HC poisoning and reduction in purification performance can be avoided more effectively.
[0017]
DETAILED DESCRIPTION OF THE INVENTION
DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, a first embodiment of the invention will be described with reference to the drawings. FIG. 1 shows the overall configuration of an exhaust emission control device for a diesel engine. Between the exhaust pipes 2a and 2b, which are exhaust passages of the diesel engine 1, a diesel particulate having an oxidation catalyst supported on the surface as an exhaust aftertreatment device. A filter (hereinafter referred to as an oxidation catalyst-attached DPF) 3 is installed. The oxidation catalyst-attached DPF3 is formed, for example, by forming heat-resistant ceramics such as cordierite into a honeycomb structure and sealing a number of cells serving as gas flow paths so that the inlet side or the outlet side are staggered. An oxidation catalyst such as Pt is applied to the wall surface. The exhaust gas discharged from the engine 1 flows downstream while passing through the porous partition wall of the DPF 3 with an oxidation catalyst, and particulates (PM) are collected and gradually accumulated therebetween.
[0018]
Exhaust temperature sensors 41 and 42 are respectively installed in the upstream exhaust pipe 2a and the downstream exhaust pipe 2b of the oxidation catalyst-attached DPF 3. The exhaust temperature sensors 41 and 42 are connected to the ECU 6, detect the inlet gas temperature or the outlet gas temperature of the DPF 3 with an oxidation catalyst, and output it to the ECU 6. The upstream exhaust temperature sensor 41 is used as a temperature detection means for knowing the temperature of the oxidation catalyst-attached DPF 3 in the supply HC amount control described later. An air flow meter (intake air amount sensor) 43 is installed in the intake pipe 11 of the engine 1 to detect the intake air amount and output it to the ECU 6. The intake pipe 11 of the engine 1 communicates with the exhaust pipe 2a on the upstream side of the DPF 3 with the oxidation catalyst by an EGR passage 71 provided with the EGR valve 7. The driving of the EGR valve 7 is controlled by the ECU 6.
[0019]
The exhaust pipes 2a and 2b are connected to a differential pressure sensor 5 for detecting a differential pressure across the oxidation catalyst DPF 3 in order to know the amount of particulates collected by the oxidation catalyst DPF 3 (PM collection amount). Is done. One end side of the differential pressure sensor 5 is connected to the exhaust pipe 2a upstream of the DPF 3 with oxidation catalyst, and the other end side is connected to the exhaust pipe 2b downstream of the DPF 3 with oxidation catalyst via pressure introduction pipes 51 and 52, respectively. A signal corresponding to the differential pressure across the attached DPF 3 is output to the ECU 6. The ECU 6 calculates the PM accumulation amount from the differential pressure across the oxidation catalyst-attached DPF 3, and performs regeneration control of the oxidation catalyst-attached DPF 3 when the PM accumulation amount exceeds a predetermined amount.
[0020]
Various sensors such as an accelerator opening sensor 61 and a rotation speed sensor 62 are further connected to the ECU 6. The ECU 6 detects the operating state based on the detection signals from these sensors, calculates the optimal fuel injection amount, injection timing, injection pressure, etc. according to the operating state, and controls the fuel injection to the engine 1. Further, by adjusting the valve opening degree of the EGR valve 7, the exhaust amount (EGR amount) recirculated to the intake air is controlled.
[0021]
Here, the HC poisoning accompanying the regeneration of the oxidation catalyst-attached DPF 3 will be described. During regeneration of the DPF 3 with an oxidation catalyst, the ECU 6 performs an operation of supplying HC to the DPF 3 with an oxidation catalyst in order to burn the accumulated PM (HC supply means). The supplied HC is combusted by the oxidation catalyst supported on the surface of the cell wall of the DPF 3 with oxidation catalyst, and the DPF 3 with oxidation catalyst rises to a temperature at which the PM can be combusted by the combustion heat. Specifically, as the HC supply means, operations such as post injection, fuel injection timing retardation, EGR amount increase, intake throttle, etc. are performed, and two or more of these operations can be combined.
[0022]
However, at this time, if the temperature of the oxidation catalyst-attached DPF 3 is low, there is a problem that HC poisoning occurs. HC poisoning means that the catalyst reaction rate is low because the catalyst temperature is low, and when a large amount of HC is supplied to the catalyst, the supplied HC adheres to the catalyst surface and closes to the catalyst (Pt, etc.) This refers to a phenomenon in which the catalytic reaction is lowered due to the inhibition of the diffusion of gas containing harmful components. Since this HC poisoning is caused by physical adsorption of HC on the catalyst, it can be reversibly recovered by reducing the amount of HC supplied and keeping the catalyst temperature high.
[0023]
Therefore, in the present invention, the ECU 6 determines the upper limit value of the amount of HC that can be supplied to the DPF 3 with oxidation catalyst according to the temperature of the DPF 3 with oxidation catalyst, so that the actually supplied HC amount is less than or equal to the upper limit value. The HC supply means is controlled (HC supply amount control means). FIG. 2 is based on an experiment conducted by the present inventors. Both the upstream exhaust temperature of the DPF 3 with an oxidation catalyst (DPF input gas temperature) and the amount of HC supplied to the DPF 3 with an oxidation catalyst (input gas HC amount) are both shown. In the figure taken on the axis, the region where HC poisoning occurs is shown. In FIG. 2, it was determined that HC poisoning occurred when the catalyst temperature change after HC supply (temperature increase rate per unit time) <predetermined value, and in other cases it was determined that there was no HC poisoning. This is because if there is no HC poisoning, the catalyst temperature rises quickly, and if there is HC poisoning, the rise in the catalyst temperature becomes small.
[0024]
As shown in the figure, the temperature of the exhaust gas containing HC supplied (inflowing) to the oxidation catalyst-attached DPF 3 greatly influences whether or not HC poisoning occurs, and the upstream exhaust temperature of the oxidation catalyst-attached DPF 3 is When the temperature is 250 ° C. or lower, the possibility of HC poisoning is extremely high. When the upstream exhaust temperature is 250 ° C. or higher, the higher the upstream exhaust temperature, the less likely HC poisoning occurs, and the upper limit value of the amount of HC that can be supplied to the HC poisoning increases. Therefore, specifically, the temperature of the oxidation catalyst-provided DPF 3 = the upstream exhaust temperature (the detected temperature of the exhaust temperature sensor 41), and the upper limit value of the HC amount at which HC poisoning does not occur is determined based on FIG. On the other hand, the amount of HC in the exhaust gas supplied to the oxidation catalyst-attached DPF 3 is detected (HC amount detection means), and the result is compared with the above upper limit value to determine whether HC poisoning occurs. At this time, the HC amount detection means calculates the amount of HC supplied to the oxidation catalyst-attached DPF 3 by the following equation.
Supply HC amount = (1) HC amount generated by engine combustion + (2) HC amount supplied by the HC supply means, that is, to be considered in the present invention (causing HC poisoning) The “supplied HC amount” is obtained by adding the HC amount generated by combustion of the engine and the HC amount supplied by the HC supply means such as post injection.
[0025]
More specifically,
(1) The amount of HC generated by engine combustion is obtained based on engine operating conditions (for example, engine speed and output torque).
For example, FIG. 3 is a diagram showing the amount of HC generated by engine combustion in a graph in which the engine speed and output torque are taken on both axes, and by storing this relationship in advance, the engine speed and output (1) The amount of HC due to engine combustion can be easily calculated from the torque.
[0026]
Also,
(2) The amount of HC supplied by the HC supply unit can be obtained based on the operation amount (for example, post injection amount) of the HC supply unit and the engine condition (for example, output torque).
FIG. 4 shows the post-injection amount under each engine operating condition in the graph in which the engine speed and the output torque are taken on both axes. This is adapted in advance for each engine operating condition, and is the basic post injection amount in the present invention. However, since a part of the post-injected fuel burns in the cylinder, the post-injection amount is not equal to the HC amount supplied by the post-injection. Therefore, in the present invention, the amount of HC supplied by the HC supply means is calculated in consideration of this combustion amount. This will be described with reference to FIG.
[0027]
The amount of HC actually supplied to the DPF 3 with the oxidation catalyst due to the post injection varies depending on the engine output torque and the like as shown in FIG. This is because the amount of post-injected fuel that burns in the cylinder varies depending on the temperature inside the cylinder and the post-injection timing. Therefore, by using the relationship of FIG. 5, the amount of post-injection combusted in the cylinder is obtained, and (2) the amount of HC by the HC supply means (the amount of HC supplied to the DPF due to post-injection) It can be calculated as follows:
HC amount supplied to DPF due to post-injection = (basic post-injection amount [FIG. 4] —combustion in cylinder of post-injection amount [FIG. 5]) × constant (constant: injection amount is HC amount Constant to convert to
[0028]
The ECU 6 compares the supplied HC amount calculated by the HC amount detecting means in this way with the upper limit value of the HC amount at which HC poisoning does not occur. If the upper limit value is exceeded, there is a possibility that HC poisoning may occur. It is determined that there is, and the amount of HC supplied by the HC supply means such as post injection is corrected to decrease. Thereby, it is possible to avoid the occurrence of HC poisoning by controlling the supplied HC amount to be equal to or lower than the upper limit value.
[0029]
Note that the basic post-injection amount in FIG. 4 is obtained on the engine test bench when the temperature of the oxidation catalyst-attached DPF 3 is sufficiently stable. Usually, since it is desired to quickly raise the temperature of the oxidation catalyst-attached DPF 3 at the time of regeneration, the basic post injection amount is determined from the viewpoint of performing as much post injection as possible. For this reason, when actually mounted on a vehicle and operating, even if the engine operating conditions are the same, the temperature of the oxidation catalyst-attached DPF 3 does not match the temperature when the basic post-injection amount is obtained on the engine test bench Cases arise (especially immediately after start-up or early acceleration). The present invention avoids this, and corrects the amount of supplied HC to supply an appropriate amount of HC, thereby preventing HC poisoning.
[0030]
FIG. 6 is a flowchart showing an example of HC supply amount control by the ECU 6. First, in step 101, the ECU 6 determines whether an HC supply operation to the oxidation catalyst-attached DPF 3 by the HC supply means is being performed, in this case, a post injection execution condition. If an affirmative determination is made in step 101, the process proceeds to step 102, and the engine speed and the accelerator opening are read from the outputs of the accelerator opening sensor 61 and the rotation speed sensor 62. Further, the exhaust temperature upstream of the oxidation catalyst-attached DPF 3 is read from the output of the exhaust temperature sensor 41. If step 101 is negative, the process ends without executing post injection.
[0031]
Here, the post injection is executed to regenerate the DPF 3 with the oxidation catalyst by burning the PM when the amount of PM deposited on the oxidation catalyst-attached DPF 3 exceeds a predetermined amount. Specifically, after main fuel injection for engine operation (expansion process after top dead center), a small amount of fuel is additionally injected to generate unburned HC, which is supplied to the DPF 3 with an oxidation catalyst. The HC supplied to the oxidation catalyst-attached DPF 3 is burned by the catalyst on the oxidation catalyst-attached DPF 3, and the combustion heat causes the DPF to become high temperature (for example, 500 ° C. or more), so that the PM on the oxidation catalyst-attached DPF 3 burns. The same applies to operations such as retarding the fuel injection timing or increasing the EGR amount instead of post-injection.
[0032]
At that time, whether or not the amount of PM deposited on the oxidation catalyst-attached DPF 3 has reached a predetermined amount is calculated, for example, from the differential pressure before and after the oxidation catalyst-attached DPF 3 detected by the differential pressure sensor 5, The determination is made by comparing with a predetermined amount determined in advance. This utilizes the fact that the differential pressure generated when a predetermined amount of exhaust gas passes through the oxidation catalyst-attached DPF 3 is correlated with the amount of PM deposited on the oxidation catalyst-attached DPF 3, and these relationships are obtained in advance through experiments or the like. . The amount of exhaust is calculated from, for example, the intake air amount detected by the air flow meter 43, the temperature before and after the oxidation catalyst-attached DPF 3 detected by the exhaust temperature sensors 41 and 42, the differential pressure detected by the differential pressure sensor 5, and the like.
[0033]
In step 103, the engine output torque calculated from the engine speed and the accelerator opening is used, and based on the relationship shown in FIG. 3 (preliminarily obtained through experiments or the like and stored in the ECU 6) The amount of HC discharged from the engine is calculated. Further, at step 104, the basic post-injection amount is determined based on FIG. 4 using the engine output torque calculated from the engine speed and the accelerator opening. This basic post injection amount is adapted in advance for each engine operating condition and stored in the ECU 6.
[0034]
In step 105, the basic post-injection amount determined in step 104 and the engine output torque calculated from the accelerator opening are used to obtain the post-injection amount combusted in the cylinder based on FIG. As shown in FIG. 5, as the output torque increases, the amount of fuel combusted in the cylinder increases. Therefore, the temperature in the cylinder becomes high, and the fuel combusted in the cylinder increases even if the post injection amount is the same.
[0035]
In step 106, the DPF supply HC amount is calculated. First, using the value determined in steps 104 and 105 for the amount of HC by post injection,
HC amount supplied to DPF due to post injection = (basic post injection amount [FIG. 4] −post injection amount combusted in cylinder [FIG. 5]) × constant, this value and step Using the value calculated in 103,
DPF supply HC amount = HC amount discharged from the engine + HC amount supplied to the DPF due to post injection The DPF supply HC amount is calculated.
[0036]
In step 107, the upper limit value of the DPF supply HC amount that does not cause HC poisoning corresponding to the current exhaust temperature is calculated from the exhaust temperature upstream of the oxidation catalyst-attached DPF 3 read in step 102 using the relationship of FIG. . In step 108, the upper limit value is compared with the DPF supply HC amount calculated in step 106 to determine whether the DPF supply HC amount is equal to or less than the upper limit value. If the DPF supply HC amount exceeds the upper limit value, the process proceeds to step 109, and the post injection amount is corrected to decrease until the DPF supply HC amount becomes the upper limit value. That is, a guard is applied so that the supplied HC amount does not exceed the upper limit value.
[0037]
Then, it progresses to step 110 and performs post injection based on a correction result. If the DPF supply HC amount is less than or equal to the upper limit value in step 108, the routine proceeds to step 110 and post injection is executed.
[0038]
FIG. 7 is a time chart showing the effect of the present invention. The solid line indicates the amount of HC supplied when the HC amount supplied to the DPF 3 with the oxidation catalyst is controlled based on the flowchart of FIG. 6 (the present invention). This is a case where control is not performed (conventional). Conventionally, even when the exhaust temperature upstream of the DPF 3 with an oxidation catalyst (DPF upstream temperature) is relatively low, a large amount of HC is supplied for PM combustion. The temperature of the attached DPF 3 does not increase easily. On the other hand, in the present invention, the amount of HC supplied to the DPF 3 with oxidation catalyst so as not to cause HC poisoning according to the exhaust temperature upstream of the DPF 3 with oxidation catalyst (HC amount by engine combustion + post injection, etc.) Since the HC amount is adjusted, the temperature of the oxidation catalyst-attached DPF 3 can be quickly raised. As a result, it is possible to effectively realize the combustion of PM on the DPF 3 with an oxidation catalyst or the purification of harmful components in the exhaust.
[0039]
As described above, according to the present invention, it is possible to prevent HC poisoning in advance to avoid a decrease in catalyst performance due to the adhesion of HC, and to accompany a recovery operation when HC poisoning has occurred. Deterioration of fuel consumption can be avoided.
[0041]
Note that when the upper limit value is calculated using the DPF upstream exhaust temperature, the DPF upstream exhaust temperature varies greatly depending on the operating conditions. Therefore, it is also possible to use an average value of a plurality of points sampled for stable detection. . In the above embodiment, the HC amount detection means calculates the DPF supply HC amount based on the engine operating conditions or the like, but an HC sensor is provided as the HC amount detection means to directly detect the HC amount. Is also possible. Further, without providing the HC amount detection means, it is possible for the HC supply amount control means to calculate the post injection amount so as not to exceed the upper limit value in consideration of HC poisoning in advance.
[Brief description of the drawings]
FIG. 1 is an overall configuration diagram of an exhaust emission control device showing a first embodiment of the present invention.
FIG. 2 is a diagram showing a region where HC poisoning occurs in a diagram in which the DPF upstream exhaust temperature and the DPF supply HC amount are taken on both axes.
FIG. 3 is a diagram showing the amount of HC generated by engine combustion in a graph in which engine speed and output torque are taken on both axes.
FIG. 4 is a diagram showing the post-injection amount under each engine operating condition in a graph in which the engine speed and output torque are taken on both axes.
FIG. 5 is a diagram showing the relationship between the amount of post-injection and post-injected fuel combusted in a cylinder, using engine output torque as a parameter.
FIG. 6 is a flowchart showing an example of control of the ECU according to the present invention.
FIG. 7 is a time chart showing the effect of the present invention.
[Explanation of symbols]
1 Diesel engine (internal combustion engine)
2a, 2b Exhaust passage 3 DPF with oxidation catalyst (exhaust aftertreatment device)
41, 42 Exhaust temperature sensor (temperature detection means)
43 Air Flow Meter 5 Differential Pressure Sensor 6 ECU (HC Supply Control Unit)
61 Rotational speed sensor 62 Accelerator opening sensor 7 EGR valve 71 EGR passage

Claims (4)

A DPF carrying an oxidation catalyst installed in an exhaust passage of an internal combustion engine, a temperature detecting means for detecting the temperature of the DPF, to regenerate the aforementioned DPF, post-injection, retarding the fuel injection timing and EGR amount HC supply means for supplying hydrocarbons to the DPF by any one or a combination of the operations of increasing the amount of HC, the amount of HC supplied to the DPF , the amount of unburned HC generated based on the combustion of the internal combustion engine, and the amount of HC HC amount detection means for calculating the sum of HC amounts by the HC supply means; and an upper limit value of the HC amount that can be supplied to the DPF according to the temperature of the DPF detected by the temperature detection means; HC supply amount control means for controlling the HC supply means so that the HC amount calculated by the detection means is not more than the upper limit value,
The HC amount detection means uses the HC amount by the HC supply means as the HC amount actually supplied to the DPF due to the operation of the HC supply means, and the basic HC according to the operation amount of the HC supply means calculated by subtracting the amount of combustion in a cylinder of an internal combustion engine of the amount,
The HC supply amount control means determines the upper limit value of the HC amount based on the relationship between the temperature of the DPF and the HC amount that does not cause HC poisoning when supplied to the DPF. An exhaust purification device for an internal combustion engine. The HC amount detection means calculates the amount of combustion in the cylinder of the internal combustion engine among the basic HC amounts according to the operation amount of the HC supply means, based on the operating conditions of the internal combustion engine,
The HC supply amount control means determines whether or not the HC amount calculated by the HC amount detection means is less than or equal to the upper limit value. The exhaust emission control device for an internal combustion engine according to claim 1, wherein the amount of HC by the HC supply means is corrected to decrease . The HC amount detection means calculates a basic HC amount according to an operation amount of the HC supply means and an unburned HC amount generated based on combustion of the internal combustion engine based on operating conditions of the internal combustion engine. 3. An exhaust emission control device for an internal combustion engine according to 2 . The exhaust emission control device for an internal combustion engine according to any one of claims 1 to 3, wherein the temperature of the DPF detected by the temperature detection means is an exhaust temperature upstream of the DPF .