JP2013142377A - Exhaust emission control device for engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an exhaust emission control device for an engine, which is capable of activating an HC adsorption catalyst for a relatively short period of time while suppressing desorption of HC.SOLUTION: First temperature raising control for raising the temperature of the HC adsorption catalyst at a set temperature raising rate is executed until the temperature of the HC adsorption catalyst reaches a predetermined temperature equal to or lower than a transition temperature. When the temperature of the HC adsorption catalyst becomes higher than the predetermined temperature, a second temperature raising control for raising the temperature of the HC adsorption catalyst while changing the temperature raising rate according to the adsorption amount of HC to the HC adsorption catalyst is executed.

Description

  The present invention relates to an exhaust emission control device for an engine, and more particularly, to a technique for activating an exhaust purification catalyst by raising an exhaust gas temperature.

  Exhaust components such as carbon monoxide (CO), hydrocarbons (HC), nitrogen oxides (NOx), and particulate matter (PM) in exhaust gas emitted from engines mounted on automobiles It is included. For this reason, an exhaust gas purification device including a three-way catalyst, an oxidation catalyst, or the like for decomposing (reducing or the like) the above substances is provided in the exhaust passage of the engine. Although these three-way catalysts and oxidation catalysts have high hydrocarbon (HC) purification efficiency, noble metals constituting the catalyst are difficult to exhibit catalytic performance below the oxidation activation temperature.

  Therefore, a catalyst with an HC adsorption function that adsorbs HC on zeolite, etc. in the operating range that does not reach the oxidation activation temperature, and desorbs and oxidizes and removes HC adsorbed on zeolite, etc. in the operating range after noble metal activity is adopted. However, there are some that ensure HC purification performance by adding this to the exhaust layout.

  However, even with a catalyst having an HC adsorption function, there is a risk that the amount of HC desorbed will increase if the temperature is excessively raised with a relatively large amount of hydrocarbon adsorbed by the catalyst. is there. For this reason, there is one in which the catalyst is activated early while suppressing the amount of HC desorption by lowering the rate of temperature rise as the amount of adsorbed hydrocarbon adsorbed by the catalyst increases ( For example, see Patent Document 1).

Japanese Patent No. 4595926

  When the temperature of an HC adsorption catalyst having an HC adsorption function is raised by such temperature rise control, the amount of HC desorption can be suppressed, but the time for raising the HC adsorption catalyst to a desired temperature becomes longer. .

  The present invention has been made in view of such circumstances, and provides an engine exhaust purification device that can activate an HC adsorption catalyst in a relatively short time while suppressing the amount of HC desorption. Objective.

  A first aspect of the present invention that solves the above-described problem is an HC adsorption catalyst that is provided in an exhaust passage of an engine and has a function of adsorbing and desorbing hydrocarbons contained in the exhaust, and the temperature of the HC adsorption catalyst. A catalyst temperature detecting means for detecting, an adsorption amount calculating means for calculating the adsorption amount of hydrocarbons on the HC adsorption catalyst, and a temperature rise control for raising the temperature of the HC adsorption catalyst to an oxidation activation temperature at a predetermined timing are executed. Temperature increase control execution means, the temperature increase control execution means, as the temperature increase control, until the temperature of the HC adsorption catalyst detected by the catalyst temperature detection means reaches a predetermined temperature below the transition temperature Performs a first temperature increase control for increasing the temperature of the HC adsorption catalyst at a preset temperature increase rate, and when the temperature of the HC adsorption catalyst becomes higher than the predetermined temperature, the adsorption amount calculating means Calculation In the exhaust purification apparatus for an engine and executes the second heating control for raising the temperature of the HC adsorption catalyst while changing the heating rate depending on the amount of adsorption was.

  In the first aspect, since the temperature of the HC adsorption catalyst can be increased at an appropriate temperature increase rate corresponding to the total amount of HC adsorption, the temperature of the HC adsorption catalyst can be increased well while suppressing the amount of HC desorption. Can do.

  According to a second aspect of the present invention, in the engine exhaust gas purification apparatus according to the first aspect, the temperature increase control execution means controls the temperature increase rate of the HC adsorption catalyst during the execution of the second temperature increase control. The engine exhaust gas purification apparatus is characterized in that the engine temperature is changed within a range equal to or lower than the set temperature increase rate.

  In the second aspect, it is possible to rapidly raise the temperature of the HC adsorption catalyst while more reliably suppressing the amount of HC desorption from the HC adsorption catalyst.

  According to a third aspect of the present invention, in the engine exhaust gas purification apparatus according to the first or second aspect, the temperature increase control execution unit performs the adsorption amount calculation unit when executing the first temperature increase control. The engine exhaust gas purification apparatus is characterized in that the predetermined temperature is changed in accordance with the calculated adsorption amount.

  In the third aspect, a rapid increase in the amount of HC desorption can be effectively suppressed while rapidly raising the temperature of the HC adsorption catalyst.

  As described above, in the present invention, the first temperature increase control and the second temperature increase control are executed according to the temperature of the HC adsorption catalyst as the temperature increase control. Without increasing the amount, the HC adsorption catalyst can be rapidly heated to be activated.

1 is a schematic configuration diagram showing an engine including an exhaust purification device according to an embodiment of the present invention. It is a graph which shows the relationship between a catalyst temperature, an adsorption rate, and a desorption rate. It is a graph which shows the relationship between a catalyst temperature and HC desorption amount. It is a graph which shows the relationship between a catalyst temperature and HC desorption amount. It is a figure which shows an example of the map of the inflow HC amount prescribed | regulated by an engine speed and a torque. It is a graph which shows an example of the relationship between catalyst temperature and HC adsorption rate. It is a graph which shows an example of the relationship between total HC adsorption amount and HC adsorption rate. It is a graph which shows an example of the relationship between catalyst temperature and HC desorption rate. It is a graph which shows an example of the relationship between total HC adsorption amount and HC desorption rate. It is a flowchart which shows an example of the temperature rising control of HC adsorption catalyst.

  First, the overall configuration of the engine 10 including an exhaust emission control device according to an embodiment of the present invention will be described. An engine 10 illustrated in FIG. 1 is a diesel engine, and an engine body 11 includes a cylinder head 12 and a cylinder block 13. A piston 15 is accommodated in each cylinder bore 14 of the cylinder block 13. The piston 15 is connected to the crankshaft 17 via a connecting rod 16. A combustion chamber 18 is formed by the piston 15, the cylinder bore 14, and the cylinder head 12.

  An intake port 19 is formed in the cylinder head 12, and an intake pipe (intake passage) 21 including an intake manifold 20 is connected to the intake port 19. An intake valve 22 is provided in the intake port 19, and the intake port 19 is opened and closed by the intake valve 22. An exhaust port 23 is formed in the cylinder head 12, and an exhaust pipe (exhaust passage) 25 including an exhaust manifold 24 is connected to the exhaust port 23. An exhaust valve 26 is provided in the exhaust port 23, and the exhaust port 23 is opened and closed by the exhaust valve 26.

  A turbocharger 27 is provided in the middle of the intake pipe 21 and the exhaust pipe 25. An intercooler 28 is disposed in the intake pipe 21 on the downstream side of the turbocharger 27. The intake pipe 21 on the downstream side of the intercooler 28 is provided with a throttle valve 29 for opening and closing the intake pipe (intake passage) 21. An EGR pipe (EGR passage) 30 communicating with the exhaust pipe 25 upstream of the turbocharger 27 is connected to the intake pipe 21 downstream of the throttle valve 29. An EGR cooler 31 is provided in the EGR pipe 30, and an EGR valve 32 is provided in a connection portion between the EGR pipe 30 and the intake pipe 21.

  The cylinder head 12 is provided with a fuel injection valve 33 that directly injects fuel into the combustion chamber 18 of each cylinder. Fuel is supplied to the fuel injection valve 33 from the common rail 34. Fuel in a fuel tank (not shown) is supplied to the common rail 34 by a supply pump 35 at a predetermined pressure according to the rotational speed of the engine body 11. The fuel supplied to the common rail 34 is adjusted to a predetermined fuel pressure and supplied to the fuel injection valve 33.

  An exhaust pipe 25 on the downstream side of the turbocharger 27 includes an HC adsorption catalyst 51 constituting an exhaust purification device 50 according to the present embodiment, a diesel particulate filter (DPF: Diesel Particulate Filter: hereinafter referred to as DPF) 52, and Are provided in order from the upstream side.

  Exhaust temperature sensors 53A and 53B are provided in the vicinity of the inlets of the HC adsorption catalyst 51 and the DPF 52, respectively. Further, an air-fuel ratio sensor 54 for detecting the air-fuel ratio of the exhaust gas is provided in the vicinity of the outlet of the HC adsorption catalyst 51.

The HC adsorption catalyst 51 has, for example, an adsorption layer and a noble metal catalyst layer on the surface of a honeycomb structure carrier made of a ceramic material. The adsorption layer is a layer containing various zeolites having a characteristic of adsorbing hydrocarbon (HC) contained in the exhaust gas. The noble metal catalyst layer is a layer containing activated alumina carrying a noble metal component such as platinum (Pt) or palladium (Pd) that improves the oxidation function. Moreover, you may mix not dividing into an adsorption layer and a noble metal catalyst layer. The HC adsorption catalyst 51 adsorbs HC when the catalyst temperature is low, and when the catalyst temperature rises to the oxidation activation temperature, the adsorbed hydrocarbon is desorbed and oxidized and removed by the noble metal catalyst layer. The oxidation activation temperature here is a temperature at which the noble metal catalyst layer is activated. In the HC adsorption catalyst 51, when exhaust gas flows in, nitrogen monoxide (NO) in the exhaust gas is oxidized and nitrogen dioxide (NO ₂ ) is generated.

The DPF 52 is, for example, a honeycomb structure filter formed of a ceramic material. PM trapped in the DPF 52 is oxidized (combusted) by NO ₂ in the exhaust gas and discharged as CO ₂ , and NO ₂ remaining in the DPF 52 is reduced to NO and discharged.

  The engine 10 includes an electronic control unit (ECU) 70. The ECU 70 includes an input / output device, a storage device that stores a control program, a control map, and the like, a central processing unit, timers, and counters. Yes. The ECU 70 performs comprehensive control of the engine 10 including the exhaust purification device 50 based on information from various sensors. Further, the ECU 70 also functions as a part of the exhaust purification device 50, and appropriately controls the fuel injection valve 33 and the like based on information from various sensors such as the exhaust temperature sensors 53A and 53B and the air-fuel ratio sensor 54.

  By the way, the HC adsorption catalyst 51 cannot oxidize and remove exhaust gas components unless the catalyst temperature rises to the oxidation activation temperature. In order not to cause such a problem, for example, temperature increase control for increasing the temperature of the HC adsorption catalyst 51 to the oxidation activation temperature is executed at a predetermined timing such as when the exhaust gas temperature is low. Thereby, the performance of the HC adsorption catalyst 51 is exhibited, and the exhaust gas component can be oxidized and removed.

  The ECU 70 constituting the exhaust purification device 50 according to the present embodiment includes a temperature rise control execution means 71 and an adsorption amount calculation means 72. The temperature increase control execution means 71 executes temperature increase control for increasing the temperature of the HC adsorption catalyst 51 to the oxidation activation temperature at a predetermined timing. The conditions for executing the temperature increase control may be appropriately determined in consideration of, for example, the driving state of the vehicle, the performance of the HC adsorption catalyst 51, the total HC adsorption amount, and the like.

  When the temperature increase control execution means 71 executes the temperature increase control, the temperature increase control execution means 71 controls the fuel injection valve 33 in accordance with the temperature of the HC adsorption catalyst 51 to increase the temperature of the exhaust gas passing through the HC adsorption catalyst 51. For example, the temperature of the exhaust gas can be increased by performing post injection with a retarded injection timing or an expansion stroke.

  The temperature of the HC adsorption catalyst 51 is detected by an exhaust temperature sensor (catalyst temperature detection means) 53A provided near the inlet of the HC adsorption catalyst 51 and an exhaust temperature sensor (catalyst temperature detection means) 53B provided near the outlet. The Of course, the method for detecting the temperature of the HC adsorption catalyst 51 is not particularly limited. Further, the temperature of the HC adsorption catalyst 51 may be estimated based on detection results of various sensors.

  Further, the temperature increase control execution means 71 performs first temperature increase control for increasing the temperature of the HC adsorption catalyst 51 at a preset temperature increase rate until the temperature of the HC adsorption catalyst 51 reaches a predetermined temperature equal to or lower than the transition temperature. Execute. Further, when the temperature of the HC adsorption catalyst 51 becomes higher than the predetermined temperature, the second temperature increase control for increasing the temperature of the HC adsorption catalyst 51 is executed while changing the temperature increase rate according to the total HC adsorption amount.

  Here, the “transition temperature” refers to a temperature at which the rate at which HC is adsorbed on the HC adsorption catalyst 51 (adsorption rate) matches the rate at which HC is desorbed from the HC adsorption catalyst 51 (desorption rate). For example, as shown in FIG. 2, the adsorption rate gradually decreases as the temperature of the HC adsorption catalyst 51 (for example, the inlet temperature) increases. On the other hand, the desorption rate gradually increases as the temperature of the HC adsorption catalyst 51 increases. The inlet temperature T1 of the HC adsorption catalyst 51 in which the adsorption rate and the desorption rate coincide with each other is the “transition temperature”.

  Then, until the temperature of the HC adsorption catalyst 51 reaches a predetermined temperature equal to or lower than the transition temperature, the first temperature increase control for increasing the temperature of the HC adsorption catalyst 51 at a preset temperature increase rate is executed. The set temperature increase rate may be appropriately determined in consideration of various conditions such as the operating state of the engine 10 and fuel consumption, but is preferably set to a speed as fast as possible. Thereby, it is possible to rapidly raise the temperature of the HC adsorption catalyst 51 while suppressing the amount of HC desorption from the HC adsorption catalyst.

  Here, FIG. 3 shows that the temperature rising rate is constant (80 ° C./min), each HC adsorption catalyst having a different amount of HC (HC accumulation amount) already adsorbed in the adsorption layer is heated, 6 is a graph showing the results of examining changes in the amount of HC desorbed from each HC adsorption catalyst (HC desorption amount). As shown in FIG. 3, regardless of the HC accumulation amount, the HC desorption amount tends to decrease until the temperature of the HC adsorption catalyst reaches the vicinity of the transition temperature Ta, and the temperature of the HC adsorption catalyst decreases the transition temperature Ta. If it exceeds this value, the amount of HC desorption tends to increase. The increasing tendency of the HC desorption amount is more remarkable as the HC accumulation amount is larger.

  FIG. 4 is a graph showing the results of examining the change in the HC desorption amount when the HC adsorption catalyst is heated at a different temperature increase rate with the HC accumulation amount being constant (0.8 g). As shown in FIG. 4, regardless of the temperature increase rate, the HC desorption amount tends to decrease until the temperature of each HC adsorption catalyst reaches the vicinity of the transition temperature Ta. When the amount exceeds HC, the amount of HC desorption tends to increase. The increasing tendency of the HC desorption amount is more remarkable as the temperature increase rate is higher.

  As described above, when the temperature of the HC adsorption catalyst 51 is equal to or lower than the transition temperature, the HC desorption amount tends to decrease regardless of the HC accumulation amount and the temperature increase rate. That is, by performing the first temperature increase control, the HC adsorption catalyst 51 can be rapidly heated while suppressing the amount of HC desorption from the HC adsorption catalyst 51 as described above.

  Moreover, it is preferable that the upper limit of the temperature of the HC adsorption catalyst 51 on which the first temperature raising control is executed is the transition temperature. This is because the temperature of the HC adsorption catalyst 51 can be raised more rapidly. However, when the set temperature increase rate is relatively fast, the temperature of the HC adsorption catalyst 51 may rise and exceed the transition temperature even after the completion of the first temperature increase control. Therefore, in the present embodiment, the upper limit value of the catalyst temperature at which the first temperature increase control is executed is set from the transition temperature so that the temperature of the HC adsorption catalyst 51 does not exceed the transition temperature in consideration of the set temperature increase rate. Is set to a low predetermined temperature.

  Further, when the temperature of the HC adsorption catalyst 51 becomes higher than the predetermined temperature, the temperature increase control execution means 71 changes the temperature increase rate according to the adsorption amount calculated by the adsorption amount calculation means 72 and changes the HC adsorption catalyst 51. Second temperature increase control for increasing the temperature is executed.

  Here, the adsorption amount calculating means 72 calculates the adsorption amount of HC (total HC adsorption amount) to the HC adsorption catalyst 51. The total HC adsorption amount includes the amount of HC already accumulated in the HC adsorption catalyst 51 (HC accumulation amount), the amount of HC newly adsorbed on the HC adsorption catalyst 51 (HC adsorption amount), and the HC adsorption catalyst 51. From the desorption amount of HC desorbed from (HC desorption amount), the following equation (1) is obtained.

  Total HC adsorption amount = HC accumulation amount + HC adsorption amount-HC desorption amount (1)

  The total HC adsorption amount is obtained from the inflow HC amount, the first HC adsorption rate correction value, the second adsorption rate correction value, and the adsorption time. The inflow HC amount is the amount of HC flowing into the HC adsorption catalyst 51. The inflow HC amount defined by the engine speed and torque and, for example, the engine speed and torque as shown in FIG. And based on the map.

  The first adsorption rate correction value is for correcting the HC adsorption rate that changes according to the temperature of the HC adsorption catalyst 51. For example, as shown in FIG. 6, the HC adsorption rate tends to decrease as the temperature of the HC adsorption catalyst 51 increases. The first adsorption rate correction value is calculated based on the relationship between the temperature of the HC adsorption catalyst and the HC adsorption rate.

  The second adsorption rate correction value corrects the HC adsorption rate that changes according to the total HC adsorption amount. For example, as shown in FIG. 7, the HC adsorption rate tends to decrease as the total HC adsorption amount increases. The second adsorption rate correction value is calculated based on the relationship between the total HC adsorption amount and the HC adsorption rate.

  On the other hand, the HC desorption amount is obtained from the first desorption rate correction value, the second desorption rate correction value, the desorption time, and the HC accumulation amount. The first desorption rate correction value corrects the HC desorption rate that changes according to the temperature of the HC adsorption catalyst. For example, as shown in FIG. 8, the HC desorption rate tends to increase as the temperature of the HC adsorption catalyst 51 increases. The first desorption rate correction value is calculated based on the relationship between the temperature of the HC adsorption catalyst 51 and the HC desorption rate. The second desorption rate correction value corrects the HC desorption rate that changes according to the total HC adsorption amount. For example, as shown in FIG. 9, the HC desorption rate tends to increase as the total HC adsorption amount increases. The second adsorption rate correction value is calculated based on the relationship between the total HC adsorption amount and the HC desorption rate.

  As described above, the temperature increase control execution means 71 performs the HC adsorption while changing the temperature increase rate according to the total HC adsorption amount calculated by the adsorption amount calculation means 72 during the second temperature increase control. The temperature of the catalyst 51 is raised.

  As a result, the temperature of the HC adsorption catalyst 51 can be increased at an appropriate temperature increase rate corresponding to the total amount of HC adsorption, and thus the temperature of the HC adsorption catalyst 51 can be increased satisfactorily while suppressing the amount of HC desorption. .

  The range of the temperature increase rate of the HC adsorption catalyst 51 is not particularly limited, but is preferably a range equal to or lower than the set temperature increase rate in the first temperature increase control. That is, in the first temperature increase control, the temperature of the HC adsorption catalyst 51 is increased at the highest possible temperature increase rate, and in the second temperature increase control, the temperature increase rate is gradually decreased according to the total amount of HC adsorption. It is preferable to do. Thereby, it is possible to rapidly raise the temperature of the HC adsorption catalyst 51 while suppressing the amount of HC desorption from the HC adsorption catalyst 51.

  Hereinafter, with reference to the flowchart shown in FIG. 10, the temperature increase control of the HC adsorption catalyst 51 in the exhaust purification device 50 according to the present embodiment will be further described.

  As shown in FIG. 10, first, in step S1, it is determined whether or not various conditions (execution conditions) for executing the temperature increase control are satisfied. This execution condition is not particularly limited and may be appropriately determined as necessary. For example, the running condition of the vehicle, the total HC adsorption amount described above, and the like are included.

  If the execution condition is satisfied in step S1 (step S1: Yes), the process proceeds to step S2. If the execution condition is not satisfied (step S1: No), the process ends without executing the temperature increase control.

  In step S2, it is determined whether or not the temperature of the HC adsorption catalyst 51 (inlet temperature), that is, the temperature of the HC adsorption catalyst 51 detected by the exhaust temperature sensor 53A is higher than the transition temperature. When the temperature of the HC adsorption catalyst 51 is lower than the transition temperature (step S2: No), the process proceeds to step S3, and the first temperature increase control described above is executed. On the other hand, when the inlet temperature of the HC adsorption catalyst 51 is higher than the transition temperature (step S2: Yes), the process proceeds to step S4, and the second temperature increase control described above is executed. In the second temperature increase control, the total HC adsorption amount of the HC adsorption catalyst 51 is calculated (estimated) as described above, the temperature increase rate is appropriately changed based on the total HC adsorption amount, and the changed temperature increase rate Thus, the temperature of the HC adsorption catalyst 51 is raised.

  As described above, in the present invention, the first temperature increase control for increasing the temperature of the HC adsorption catalyst 51 at the set temperature increase rate is executed until the temperature of the HC adsorption catalyst 51 reaches a predetermined temperature equal to or lower than the transition temperature. did. When the temperature of the HC adsorption catalyst 51 is equal to or lower than the transition temperature, the HC desorption amount does not increase regardless of the total HC adsorption amount including the HC accumulation amount and the temperature increase rate. Therefore, by executing the first temperature increase control, the HC adsorption catalyst 51 can be rapidly heated without increasing the amount of HC desorption from the HC adsorption catalyst 51.

  As described above, the higher the total HC adsorption amount, the more the HC desorption amount increases after the transition temperature is exceeded. That is, the greater the total HC adsorption amount, the more likely the HC desorption amount to increase rapidly. For this reason, the predetermined temperature may be changed according to the adsorption amount calculated by the adsorption amount calculation unit 72 when the temperature increase control execution unit 71 executes the first temperature increase control. Specifically, the predetermined temperature may be lowered as the adsorption amount calculated by the adsorption amount calculation means 72 increases. Thereby, the rapid increase in the amount of HC desorption can be effectively suppressed while the temperature of the HC adsorption catalyst 51 is rapidly raised. For example, even when the temperature of the HC adsorption catalyst exceeds the transition temperature at the time of switching from the first temperature increase control to the second temperature increase control, a rapid increase in the amount of HC desorption is suppressed.

  Further, in the present invention, when the temperature of the HC adsorption catalyst 51 becomes higher than the predetermined temperature, the temperature of the HC adsorption catalyst 51 is increased while changing the temperature increase rate according to the adsorption amount calculated by the adsorption amount calculation means 72. The temperature increase control of 2 was executed. As a result, as described above, the HC adsorption catalyst 51 can be heated at an appropriate temperature increase rate corresponding to the total HC adsorption amount, and the HC adsorption catalyst 51 can be heated well while suppressing the HC desorption amount. be able to.

  Although the embodiment of the present invention has been described above, the present invention is not limited to this embodiment. The present invention can be modified as appropriate without departing from the spirit of the present invention.

  For example, although the diesel engine has been exemplified in the above-described embodiment, of course, the present invention can be applied to an engine other than the diesel engine.

DESCRIPTION OF SYMBOLS 10 Engine 11 Engine main body 12 Cylinder head 13 Cylinder block 14 Cylinder bore 15 Piston 16 Connecting rod 17 Crankshaft 18 Combustion chamber 19 Intake port 20 Intake manifold 21 Intake pipe 22 Intake valve 23 Exhaust port 24 Exhaust manifold 25 Exhaust pipe 26 Exhaust valve 27 Turbocharger 28 Intercooler 29 Throttle valve 30 EGR pipe 31 EGR cooler 32 EGR valve 33 Fuel injection valve 34 Common rail 35 Supply pump 50 Exhaust gas purification device 51 HC adsorption catalyst 52 DPF
53 Exhaust temperature sensor 54 Air-fuel ratio sensor 70 ECU
71 Temperature rise control execution means 72 Adsorption amount calculation means

Claims (3)

An HC adsorption catalyst provided in the exhaust passage of the engine and having a function of adsorbing and desorbing hydrocarbons contained in the exhaust;
Catalyst temperature detecting means for detecting the temperature of the HC adsorption catalyst;
An adsorption amount calculating means for calculating the amount of hydrocarbon adsorbed on the HC adsorption catalyst;
Temperature increase control execution means for executing temperature increase control for increasing the temperature of the HC adsorption catalyst to the oxidation activation temperature at a predetermined timing;
The temperature increase control execution means includes the temperature increase control as:
First temperature increase control for increasing the temperature of the HC adsorption catalyst at a preset temperature increase rate until the temperature of the HC adsorption catalyst detected by the catalyst temperature detection means reaches a predetermined temperature not higher than the transition temperature. Run
When the temperature of the HC adsorption catalyst becomes higher than the predetermined temperature, a second temperature increase control for increasing the temperature of the HC adsorption catalyst while changing the temperature increase rate according to the adsorption amount calculated by the adsorption amount calculating means. An exhaust emission control device for an engine characterized in that The exhaust emission control device for an engine according to claim 1,
The engine temperature control execution means changes the temperature increase rate of the HC adsorption catalyst within the range of the set temperature increase rate or less during execution of the second temperature increase control. . The engine exhaust gas purification apparatus according to claim 1 or 2,
The engine temperature purification control execution means changes the predetermined temperature according to the adsorption amount calculated by the adsorption amount calculation means when executing the first temperature increase control. apparatus.

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