JP2005344617A - Diesel engine exhaust purification system - Google Patents

Abstract

An exhaust purification device for a diesel engine is provided that improves fuel efficiency when regenerating the NOx catalyst device by regenerating the NOx catalyst device by utilizing the opportunity to regenerate the DPF.
In an exhaust emission control device for a diesel engine, an intake air amount is decreased based on a detected operating state, fuel is injected after combustion, and the collected particulates are combusted to cause DPF (filter). Is regenerated (S10 to S16), and when the filter is regenerated, a reducing agent is supplied so that the detected oxygen concentration decreases, and poisonous substances (SOx) in the exhaust adhering to the LNC (NOx catalyst device) are removed Reduction and removal are performed (S18 to S20).
[Selection] Figure 2

Description

  The present invention relates to an exhaust emission control device for a diesel engine, and more specifically to an apparatus for regeneration processing such as a DPF (diesel particulate filter) constituting the exhaust emission purification device for a diesel engine.

  The exhaust system of the diesel engine is provided with a filter (DPF) that collects solid particulates (particulates) such as unburned HC (hydrocarbon) in the exhaust gas, and NOx (nitrogen oxides) in the exhaust gas (exhaust). ) A NOx catalyst device that absorbs the components is arranged. When fine particles collected in the DPF adhere and accumulate, clogging occurs, so it is necessary to regenerate the DPF by burning it, and even if the SOx (sulfur oxide) adheres to the NOx catalyst device, As a result, the NOx purification performance decreases. Therefore, the DPF or NOx catalyst device needs to be periodically removed and regenerated.

With regard to this point, in the technology described in Patent Document 1 below, an oxidation catalyst device, a DPF, and a NOx catalyst device are arranged in series from the upstream side in the exhaust gas flow in the exhaust system of the diesel engine, The structure which provides the addition apparatus which injects the additive (light oil) for reduce | restoring NOx in exhaust gas between DPF and NOx catalyst apparatus is proposed. Accordingly, the NO ₂ to oxidize NOx in the exhaust gas in the oxidation catalyst device, together with its NO ₂ and with the microparticles are reacted deposited in the DPF to play DPF, in a subsequent stage of the NOx catalyst device, did not react by reducing the _{N 2} or NO by additives NO _2, thereby reducing the NOx such as NO _2.

Further, the technique described in Patent Document 2 adjusts the EGR and the intake air throttle so that the excess air ratio becomes a value of 1.0 to 1.5, and light oil (hydrocarbon) according to the amount of residual oxygen in the exhaust gas. As a reducing agent, the catalyst temperature is raised by actively causing an oxidation reaction with the light oil mixed in the NOx catalyst device, and the SOx (poisoning) adhering to the catalyst device in the resulting high temperature reducing atmosphere We propose a technology to regenerate the catalyst device from poisoning by reducing and removing the substance.
JP 2000-199423 A JP 2000-018024 A

  However, in the technique described in Patent Document 1, since the air flow rate is not reduced, the reducing agent necessary for operating the excess air ratio to the reducing atmosphere, that is, the use of light oil that is the fuel of the diesel engine is used. There is a problem that the amount of fuel increases, and the fuel efficiency decreases in the regeneration of the DPF.

  In the technique described in Patent Document 2, the EGR and the intake air throttle are adjusted so that the excess air ratio becomes a value of up to about 1.5, and the light oil (hydrocarbon) according to the amount of residual oxygen in the exhaust gas. ) Is mixed as a reducing agent, and the catalyst temperature is raised to a reproducible temperature by actively causing an oxidation reaction with the mixed light oil. However, a considerable amount of light oil is required to raise the temperature to that temperature. Therefore, there was room for improvement in terms of fuel efficiency.

  Accordingly, the object of the present invention is to solve the above-mentioned problems and to regenerate the NOx catalyst device by utilizing the opportunity to regenerate the DPF, thereby improving the fuel efficiency in the regeneration of the NOx catalyst device. It is to provide a purification device.

  In order to solve the above-mentioned object, the diesel engine according to claim 1 is provided with a filter that collects particulates in exhaust gas and a NOx catalyst device that is disposed downstream of the filter and removes NOx components in the exhaust gas. In the engine exhaust gas purification apparatus, an intake throttle device that is provided in an intake passage of the diesel engine and reduces an intake air amount of the intake passage, and is provided between the filter and the NOx catalyst device, and a reducing agent is added to the exhaust gas. A reducing agent supply device to be supplied; filter regeneration means for performing filter regeneration for eliminating particulate clogged by the filter by collecting particulates collected by the filter; and operating the reducing agent supply device during filter regeneration. Simultaneous reduction of supplying a reducing agent to the NOx catalyst device and simultaneously performing regeneration of the filter and regeneration of SOx poisoning of the NOx catalyst device It was composed as and means.

  The diesel engine exhaust gas purification apparatus according to claim 2 further includes an operation state detection means for detecting an operation state of the diesel engine, and an exhaust temperature detection means for detecting an exhaust temperature flowing into the NOx catalyst device. And a catalyst device upstream temperature control means for controlling the temperature so that the temperature upstream of the NOx catalyst device becomes a predetermined value based on the operation state detected by the operation state detection means.

  In the exhaust gas purification apparatus for a diesel engine according to a third aspect, the simultaneous regeneration means is configured to operate once every time the filter regeneration means operates n (n> 1) times.

  In claim 1, in an exhaust emission control device for a diesel engine, comprising: a filter that collects particulates in exhaust gas; and a NOx catalyst device that is disposed downstream of the filter and removes NOx components in exhaust gas. An intake throttle device that is provided in an intake passage of a diesel engine and reduces an intake amount of the intake passage; a reducing agent supply device that is provided between the filter and the NOx catalyst device and supplies a reducing agent to exhaust; Filter regeneration means for performing filter regeneration for burning particulates collected by the filter and eliminating clogging of the filter, and operating the reducing agent supply device during filter regeneration to apply a reducing agent to the NOx catalyst device And a simultaneous regeneration means for supplying and simultaneously performing the filter regeneration and the SOx poisoning regeneration of the NOx catalyst device That is, since the NOx catalyst device is regenerated in synchronization with the regeneration of the DPF, the high-temperature exhaust gas (exhaust gas) heated by the combustion in the DPF can be supplied to the NOx catalyst device and can be regenerated. Since the amount of reducing agent used such as fuel required to raise the temperature can be reduced, the NOx catalyst device can be regenerated while improving fuel efficiency.

  Further, in the reduction of SOx in the NOx catalyst device, if CO (carbon monoxide) and HC (hydrocarbon) are present, the reduction effect is improved even if the oxygen concentration is the same, but a large amount of CO ( Since carbon monoxide) and HC (hydrocarbon) can be supplied to the NOx catalyst device, the NOx catalyst device can be regenerated more effectively.

  At this time, by reducing the amount of intake air during the regeneration of the DPF, the minimum amount of oxygen necessary for the regeneration of the DPF is supplied, so that the oxygen concentration downstream of the DPF can be lowered and the CO and HC can be increased simultaneously. Can improve the reproduction efficiency.

  The diesel engine exhaust gas purification apparatus according to claim 2 further includes an operation state detection means for detecting an operation state of the diesel engine, and an exhaust temperature detection means for detecting an exhaust temperature flowing into the NOx catalyst device. And a catalyst device upstream temperature control means for controlling the temperature so that the temperature upstream of the NOx catalyst device becomes a predetermined value based on the operation state detected by the operation state detection means. In addition to the effects described above, the temperature of the NOx catalyst device can be reliably raised to the temperature required for regeneration.

  In the exhaust purification device for a diesel engine according to claim 3, since the regeneration of the NOx catalyst device is performed once every n (n> 1) times of regeneration of the filter, the NOx catalyst device When the regeneration of this is not required as frequently as the regeneration of the DPF, the regeneration can be optimally performed according to the regeneration frequency of the NOx catalyst device. Further, the amount of fuel used can be saved by simultaneously performing SOx regeneration and DPF regeneration of the NOx catalyst device only when necessary.

  The best mode for carrying out an exhaust emission control device for a diesel engine according to the present invention will be described below with reference to the accompanying drawings.

  FIG. 1 is a schematic view generally showing an exhaust emission control device for a diesel engine according to a first embodiment of the present invention.

  In FIG. 1, reference numeral 10 denotes a four-cylinder diesel engine (internal combustion engine; hereinafter referred to as “engine”). In the engine 10, air drawn from an air cleaner (not shown) flows through an intake pipe (intake passage) 12 and an intake manifold (not shown) branched therefrom, and an intake valve (not shown) of each cylinder is opened. At the same time, when the piston (not shown) descends, it is sucked into the combustion chamber (not shown). The sucked air is compressed and becomes hot when the piston moves up.

  An intake throttle device 14 is disposed at an appropriate position of the intake pipe 12. The intake throttle device 14 includes a valve 14a and an actuator 14b such as an electric motor connected thereto. In the intake throttle device 14, when the actuator 14b is driven via a drive circuit (not shown), the valve 14a is driven in the closing direction accordingly to adjust the opening of the intake pipe 12 in the throttle direction, Reduce the amount of intake air that passes through.

  On the other hand, fuel (light oil) stored in a fuel tank (not shown) is supplied to an injector 16 disposed at a position facing the combustion chamber of each cylinder via a pump and a common rail (both not shown) and driven. When the injector 16 is driven (opened) through a circuit (not shown), it is injected into the combustion chamber and touches the intake air that has become highly compressed and heated to spontaneously ignite and burn. As a result, the piston is driven downward and then rises again, and when the exhaust valve (not shown) opens, exhaust gas (exhaust gas) is discharged to the exhaust system.

  In the exhaust system, an oxidation catalyst device (hereinafter referred to as “DOC”) 22 made of platinum or the like is disposed at an appropriate position of an exhaust pipe 20 connected to an exhaust manifold (not shown), and an exhaust gas is disposed downstream thereof. A filter (Diesel Particulate Filter, hereinafter referred to as “DPF”) 24 that collects solid particulates (particulates) of unburned HC (hydrocarbon) in the exhaust gas is disposed, and further downstream thereof is NOx (nitrogen oxide) in the exhaust gas. ) A NOx catalyst device (hereinafter referred to as “LNC”) 26 that absorbs components is disposed.

  The DPF 24 is formed of a ceramic honeycomb filter, and the upstream end is closed inside the exhaust gas passage, the downstream end is opened, the upstream end is opened, and the downstream end is The closed exhaust gas passages are alternately arranged, and a wall surface of the porous chamber is formed between adjacent passages. The LNC 26 includes a NOx catalyst device in which platinum or the like is supported on a carrier, or a selective reduction type NOx catalyst device in which iridium and an alkaline earth metal are supported on a carrier selected from metal carbide or metal nitride. Either of these is used.

  Further, a reducing agent supply device 30 that supplies a reducing agent to the exhaust gas flowing therethrough is disposed between the DPF 24 and the LNC 26. The reducing agent supply device 30 also has the same structure as the injector 16 described above, and is connected to a fuel tank through a fuel supply system, and when driven through a drive circuit (not shown), the pumped fuel (light oil) is supplied. Inject and supply to exhaust gas.

  In the exhaust system described above, when the exhaust gas is in an oxidizing atmosphere in the DOC 22, CO (carbon monoxide) and HC (hydrocarbon) are oxidized and removed and flow downstream, and the unburned HC (hydrocarbon) in the DPF 24. Solid particulates (particulates) such as are collected.

The exhaust gas then reaches the LNC 26, and the NOx (nitrogen oxide) component and SOx (sulfur oxide) in the exhaust gas are absorbed by the LNC 26 and then discharged outside the engine. Note that NOx and SOx absorbed by the LNC 26 are reduced and purified to S ₂ or N ₂ by a reducing action in a high-temperature reducing atmosphere, as will be described later.

  Further, an EGR pipe (EGR passage) 32 is provided between the exhaust pipe 20 and the intake pipe 12 to connect the exhaust system and the intake system, and an EGR valve 34 is provided in the EGR pipe 32, and the EGR pipe 32. Open and close. That is, when the EGR valve 34 is operated via a drive circuit (not shown), a part of the exhaust gas is recirculated from the EGR pipe 32 to the intake system.

  A crank angle sensor 36 comprising a plurality of sets of electromagnetic pickups is disposed near the crankshaft (not shown) of the engine 10 and outputs a cylinder discrimination signal and outputs a TDC signal at or near each TDC of the four cylinders. In addition, a crank angle signal is output for each predetermined crank angle.

  In addition, an accelerator opening sensor 44 is disposed in the vicinity of an accelerator pedal 42 disposed on the floor of a vehicle driver's seat (not shown), and outputs a signal corresponding to the accelerator opening (indicating engine load) AP. At the same time, a wheel speed sensor 46 is disposed at an appropriate position of the wheel (not shown), and outputs a signal for each rotation per predetermined angle of the wheel.

  In the exhaust system of the engine 10, a first wide area air-fuel ratio sensor 50 is disposed upstream of the DOC 22, and generates an output proportional to the oxygen concentration in the exhaust gas flowing through that portion. Further, a temperature sensor (exhaust temperature detection means) 52 is disposed downstream of the DOC 22 and upstream of the DPF 24, and generates an output proportional to the temperature of the exhaust gas flowing into the DPF, and at a downstream position of the reducing agent supply device 30. Is provided with a second wide-area air-fuel ratio sensor 54, which produces an output proportional to the oxygen concentration in the exhaust gas flowing through that portion.

  The output of the sensor group described above is sent to an ECU (electronic control unit) 60. The ECU 60 includes a microcomputer comprising a CPU, ROM, and RAM, an input / output circuit (not shown), a counter, and the like. The ECU 60 detects (calculates) the engine speed NE by counting the crank angle signal output from the crank angle sensor 36 with a counter among the outputs of the sensor group.

  The ECU 60 also counts the output of the wheel speed sensor 46 with a counter to detect the vehicle speed, and calculates the travel distance of the vehicle after the engine 10 is started. When the engine 10 is stopped, the ECU 60 updates the calculated travel distance by adding it to the cumulative value of the travel distance stored in the backup RAM (not shown), and calculates the cumulative value of the travel distance of the vehicle from a certain point in time. .

  Since this embodiment relates to an exhaust emission control device, illustration and description of other sensors used for normal control of the engine 10 are omitted for the sake of simplicity.

  Next, the operation of the exhaust emission control device for a diesel engine shown in FIG. 1 will be described.

  FIG. 2 is a flowchart showing the operation. This operation is a process performed by the CPU in the microcomputer of the ECU 60.

  In the following description, it is determined in S10 whether or not the regeneration time of the DPF 24 is reached. This is performed by comparing the integrated value of the travel distance of the vehicle with a predetermined value. That is, when the accumulated value of the travel distance of the vehicle exceeds a predetermined value, it is determined that the amount of collected particulates is excessive and it is in the regeneration period.

  Instead of this, when the pressure before and after the DPF 24 is detected and the difference between the detected pressures exceeds a predetermined value, the DPF 24 is clogged, that is, the amount of particulates is excessive and the regeneration time is reached. You may make it judge that there exists.

  When the result in S10 is negative, the subsequent processing is skipped, and when the result is affirmative, the process proceeds to S12, the regeneration timer (up counter) is started, the process proceeds to S14, and based on the exhaust gas temperature detected by the temperature sensor 52, The exhaust gas temperature flowing into the LNC 26 is predicted (detected).

  Next, in S16, based on the predicted (detected) exhaust gas temperature, the actuator of the intake throttle device 14 is based on the detected engine speed NE and the accelerator pedal opening AP so that the temperature of the LNC 26 becomes a predetermined regeneration temperature. 14b and the injector 16 are driven to execute control for reducing the intake air amount, and post injection (post Inj) control for injecting fuel in the exhaust stroke after combustion is executed.

  In the LNC 26, when HC such as light oil is supplied as a reducing agent in a high temperature reducing atmosphere, the attached SOx (sulfur oxide) is removed and regenerated by reducing it, In order to completely remove SOx in a reducing atmosphere, for example, a high temperature of 600 ° C. or higher is required.

  Therefore, in this embodiment, by reducing the intake air amount, the temperature drop due to the introduction of fresh air is suppressed as much as possible, and the post-injection is performed to supply unburned fuel to the DPF 24, which burns in the DPF 24. The temperature was raised.

  Specifically, the above control is performed so that the temperature of the exhaust gas flowing out from the DPF 24 reaches about 650 ° C. As a result, a large amount of CO and HC is generated from the DPF 24, mixed in the exhaust gas heated to 650 ° C., and sent to the subsequent LNC 26.

  Next, in S18, based on the output of the second wide area air-fuel ratio sensor 54, the reducing agent supply device 30 is operated so as to reduce the detected oxygen concentration, and fuel (light oil) is supplied as a reducing agent. Specifically, when the oxygen concentration of the exhaust gas upstream of the reducing agent supply device 30 is about 17: 1 at the air-fuel ratio, the oxygen concentration of the exhaust gas flowing into the LNC 26 is about 14: 1 at the air-fuel ratio. Inject fuel.

  At this time, oxygen in the exhaust gas flowing out from the DPF 24 is consumed by the combustion of the solid fine particles (PM), so that the amount of fuel necessary for the reducing atmosphere is small. If the oxygen concentration (air / fuel ratio) is the same, the greater the amount of CO and HC, the better the reduction efficiency. As described above, the exhaust gas flowing out from the DPF 24 contains a large amount of CO and HC. As a result, the amount of fuel required is further reduced.

  In the LNC 26, the SOx deposited and deposited in the high-temperature reducing atmosphere generated by the LNC 26 is reduced and removed by HC in the supplied fuel and CO and HC in the inflowing exhaust gas, and the LNC 26 is poisoned by SOx. Played from.

  Next, in S20, it is determined whether or not the value of the reproduction timer has exceeded a predetermined value (a predetermined time required for reproduction). As the predetermined value, a time required for both the DPF 24 and the LNC 26 to be regenerated is obtained and set in advance. When the result is negative, the process returns to S16. When the result is positive, since the regeneration of the DPF 24 and the LNC 26 is completed, the process ends and returns to normal exhaust gas purification control.

  In this embodiment, since the LNC 26 is regenerated in synchronism with the regeneration of the DPF 24 (in other words, at the same time), the high temperature exhaust gas heated by the combustion in the DPF 24 can be supplied to the LNC 26. The amount of fuel (reducing agent) used for raising the temperature to a recyclable temperature and reducing atmosphere can be reduced, and thus the LNC 26 can be regenerated while improving fuel efficiency.

  Furthermore, since a large amount of CO and HC generated when the DPF 24 is regenerated is supplied to the LNC 26, the LNC 26 can be regenerated more effectively.

  Further, the exhaust temperature flowing into the LNC 26 is predicted (estimated) based on the detected exhaust temperature, and the detected temperature is detected so that the temperature of the LNC 26 becomes a predetermined regeneration temperature based on the estimated catalyst inflow temperature. Since the intake throttle device 14 and the injector 16 are driven based on the engine speed NE and the accelerator opening AP (that is, the detected operating state), in addition to the above-described effects, the temperature of the LNC 26 is necessary for regeneration. The temperature can be reliably raised to the temperature.

  FIG. 3 is a flowchart showing the operation of the exhaust emission control device for a diesel engine according to the second embodiment of the present invention.

  The focus will be on differences from the first embodiment. In the diesel engine purification apparatus according to the second embodiment, the regeneration of the LNC 26 is performed n (n> 1) times of the DPF 24, for example, It was executed only once every 5 times.

  In the following description, first, in S100, it is determined whether or not the regeneration timing of the DPF 24 is in the same manner as in the first embodiment. When the result is negative, the subsequent processing is skipped, and when the result is affirmative, the process proceeds to S102. It is determined whether or not it is in the playback time. This is performed, for example, by detecting the NOx concentration in the exhaust gas using a NOx sensor downstream of the LNC 26 and determining a decrease in LNC reactivity based on the NOx concentration.

  When the result in S102 is affirmative, the process proceeds to S104 and subsequent steps, and the same simultaneous reproduction process as in the first embodiment is executed. On the other hand, when the result in S102 is negative, the program proceeds to S114 and subsequent steps, and only the regeneration of the DPF 24 is executed. Specifically, in S114, the second regeneration timer (up counter) is started, and then the process proceeds to S116, where post-injection (post-Inj) control for injecting fuel in the exhaust stroke after combustion is executed. That is, the DPF 24 is heated by burning the fuel from the post-injection in the DOC 22, and as a result, the solid fine particles (PM) in the DPF 24 are burned.

  Next, in S118, it is determined whether or not the value of the second regeneration timer has exceeded a second predetermined value (predetermined time required for regeneration of the DPF 24). As the second predetermined value, a time required for the DPF 24 to be regenerated is obtained and set in advance. When the result is negative in S118, the process returns to S116, and when the result is positive, the process is finished because the regeneration of the DPF 24 is completed, and the process returns to the normal exhaust gas purification control.

  In the second embodiment, when the regeneration timing of the DPF 24 and the regeneration timing of the LNC 26 do not match, only the regeneration processing of the DPF 24 is performed, and when they coincide, the regeneration processing of the DPF 24 and the regeneration processing of the LNC 26 are performed simultaneously.

  That is, since the regeneration of the LNC is performed once every time the DPF 24 is regenerated n (n> 1) times, the regeneration of the LNC 26 is performed when the regeneration of the LNC 26 is not required as frequently as the regeneration of the DPF 24. Reproduction can be performed optimally according to the frequency. Further, the amount of fuel used can be saved by simultaneously performing SOx regeneration and DPF regeneration of the NOx catalyst device only when necessary.

  The remaining configuration and effects are not different from those of the first embodiment.

  As described above, in the first and second embodiments, the filter (DPF 24) that collects particulates in the exhaust, and the NOx catalyst device (LNC26) that is disposed downstream of the filter and removes NOx components in the exhaust. ), The intake throttle device 14 provided in the intake passage 12 of the diesel engine for reducing the intake amount of the intake passage, the filter (DPF 24), and the NOx catalyst device (LNC26). And a regenerator supply device 30 for supplying a reductant to the exhaust, and a filter that performs filter regeneration that burns particulates collected by the filter (DPF 24) and eliminates clogging of the filter Regenerating means (ECU 60, S10 to S16), and operating the reducing agent supply device 14 during filter regeneration It is configured to include a simultaneous regeneration means (ECU 60, S18, S20) that supplies a reducing agent to the NOx catalyst device (LNC26) and simultaneously performs regeneration of the filter (DPF24) and SOx poisoning regeneration of the NOx catalyst device. did.

  Further, an operating state detecting means (crank angle sensor 36, accelerator opening sensor 44) for detecting the operating state of the diesel engine, and an exhaust temperature detecting means (temperature) for detecting the exhaust temperature flowing into the NOx catalyst device (LNC 26). The upstream temperature of the catalyst device that controls the temperature so that the temperature upstream of the NOx catalyst device (LNC26) becomes a predetermined value based on the sensor 52, ECU 60, S14) and the operating state detected by the operating state detecting means. The control means (ECU 60, S16) is provided.

  In the second embodiment, the simultaneous regeneration means is configured to operate once every time the filter regeneration means operates n (n> 1) (S100, S102).

  Further, in the above description, the present invention has been described by taking the vehicle engine as an example. However, the present invention can also be applied to a marine propulsion engine engine such as an outboard motor having a crankshaft in a vertical direction. .

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic view showing an exhaust emission control device for a diesel engine according to a first embodiment of the present invention. It is a flowchart which shows operation | movement of the apparatus shown in FIG. FIG. 4 is a flow chart similar to FIG. 2 showing the operation of the exhaust purification device for a diesel engine according to the second embodiment of the present invention.

Explanation of symbols

10 Diesel engine (internal combustion engine)
12 Intake pipe (intake system)
14 Intake throttle device 16 Injector 20 Exhaust pipe (exhaust system)
22 Oxidation catalyst equipment (DOC)
24 Filter (DPF)
26 NOx catalyst device (LNC)
30 Reducing agent supply device 32 EGR pipe (EGR passage)
34 EGR valve 36 Crank angle sensor 44 Accelerator opening sensor 54 Second wide area air-fuel ratio sensor 60 ECU (electronic control unit)

Claims (3)

In a diesel engine exhaust gas purification apparatus comprising a filter that collects particulates in exhaust gas, and a NOx catalyst device that is disposed downstream of the filter and removes NOx components in exhaust gas,
a. An intake throttle device that is provided in an intake passage of the diesel engine and reduces an intake amount of the intake passage;
b. A reducing agent supply device that is provided between the filter and the NOx catalyst device and supplies a reducing agent to the exhaust;
c. Filter regeneration means for performing filter regeneration for burning particulates collected by the filter and eliminating clogging of the filter;
And d. Simultaneous regeneration means for operating the reducing agent supply device during filter regeneration to supply the reducing agent to the NOx catalyst device and simultaneously performing the filter regeneration and the SOx poisoning regeneration of the NOx catalyst device;
An exhaust emission control device for a diesel engine, comprising: further,
e. An operating state detecting means for detecting an operating state of the diesel engine;
f. Exhaust temperature detecting means for detecting the exhaust temperature flowing into the NOx catalyst device;
And g. Catalyst device upstream temperature control means for controlling the temperature so that the temperature upstream of the NOx catalyst device becomes a predetermined value based on the operation state detected by the operation state detection unit;
The exhaust emission control device for a diesel engine according to claim 1, comprising:   The exhaust purification device for a diesel engine according to claim 1 or 2, wherein the simultaneous regeneration means operates once every time the filter regeneration means operates n (n> 1) times.

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