JP2012047078A - Exhaust emission control device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an exhaust emission control device that properly controls an exhaust gas temperature of an exhaust gas discharged from an exhaust pipe and regeneration time of a DPF when the DPF is regenerated in an idle state of a diesel engine.SOLUTION: At the start of regeneration of a DPF 13, when determining that the diesel engine 30 is in the idle state, an ECU 20 calculates a range of the engine speed of the diesel engine 30 so that a discharged temperature is a target discharged temperature Tor lower and a floor temperature of the DPF 13 is a target floor temperature Tor higher. The ECU calculates the engine speed so as to minimize the regeneration time of the DPF 13 within the range, on the basis of a heat radiation mapping included in a memory 40, and controls the engine speed of the diesel engine 30 at the calculated engine speed.

Description

  The present invention relates to an exhaust gas purification device, and more particularly to an exhaust gas purification device for purifying exhaust gas discharged from a diesel engine.

  The exhaust gas discharged from the diesel engine contains particulate matter (PM) subject to regulation. As a method of removing PM from exhaust gas, a method of filtering by providing a diesel particulate filter (DPF) in an exhaust pipe is generally known (see, for example, Patent Document 1). PM accumulated in the DPF must be periodically burned and removed (DPF regeneration). For this regeneration, the DPF bed temperature needs to be approximately 600 ° C. or higher. The rise of the DPF bed temperature is performed, for example, by adding fuel to the exhaust gas and oxidizing the fuel with an oxidation catalyst provided on the upstream side of the DPF to raise the exhaust gas temperature. The amount of fuel added to the exhaust gas is determined by the exhaust gas flow rate and the amount of PM deposited.

JP 2006-291826 A

  When the DPF regeneration is performed when the diesel engine mounted on the vehicle is in an idle state, the exhaust gas flow rate is low compared to the traveling state even if fuel is added to the exhaust gas. It becomes difficult to make it. Therefore, when the DPF is regenerated, the exhaust gas flow rate is increased to increase the exhaust gas temperature by increasing the rotational speed of the diesel engine. However, as described above, it is possible to increase the temperature of the exhaust gas flowing into the oxidation catalyst and the DPF by increasing the rotation speed, but if the exhaust gas temperature is excessively raised in the idle state, the vehicle is stopped. It is not preferable because the object around the exhaust pipe is continuously affected by the high temperature exhaust gas. On the other hand, if the DPF is regenerated while the exhaust gas temperature is low, there is a problem that the regeneration time becomes long and the amount of fuel added increases, resulting in deterioration of fuel consumption.

  The present invention has been made to solve such a problem, and when the DPF is regenerated when the diesel engine is in an idle state, the exhaust temperature of the exhaust gas discharged from the exhaust pipe, the regeneration time of the DPF, An object of the present invention is to provide an exhaust gas purification device capable of appropriately controlling the exhaust gas.

An exhaust gas purifying apparatus according to the present invention is an exhaust gas purifying apparatus for purifying exhaust gas discharged from a diesel engine through an exhaust pipe, and includes a fuel addition means for adding fuel to the exhaust gas, and an oxidation catalyst provided in the exhaust pipe And a DPF provided in the exhaust pipe downstream of the oxidation catalyst, a target exhaust temperature that is the temperature of exhaust gas discharged from the exhaust pipe to the outside air, and a target for the DPF bed temperature during regeneration of the DPF When the control device determines that the diesel engine is in an idle state when the regeneration of the DPF is started, the exhaust temperature becomes equal to or lower than the target exhaust temperature. The range of the rotational speed of the diesel engine in which the floor temperature of the diesel engine is equal to or higher than the target floor temperature is calculated, and the rotational speed of the diesel engine is controlled within the calculated range. By such control, the discharge temperature is suppressed to the target temperature or less within a range where the regeneration time of the DPF does not become excessively long.
Distribution exhaust gas temperature detection means for detecting the exhaust gas temperature of the exhaust gas flowing through the exhaust pipe downstream of the DPF, intake air amount detection means for detecting the amount of air sucked into the diesel engine, and outside air temperature detection for detecting the outside air temperature And the control device comprises a DPF from an exhaust gas temperature detected by the circulating exhaust gas temperature detection means, an intake air amount detected by the intake air amount detection means, and an outside air temperature detected by the outside air temperature detection means. The control device may estimate the range of the rotational speed of the diesel engine from the exhaust gas temperature and the heat dissipation amount.
Within the range, the control device may calculate the rotational speed of the diesel engine based on the regeneration time of the DPF.
Within the range, the control device may calculate the rotational speed of the diesel engine based on the fuel consumption of the diesel engine. In this case, the rotational speed of the diesel engine may be determined by feedback control.

  According to the present invention, when the regeneration of the DPF is started, when the diesel engine is in an idle state, the range of the rotational speed of the diesel engine in which the exhaust temperature is equal to or lower than the target exhaust temperature is calculated, and the rotational speed of the diesel engine is calculated. By controlling the value within the range, the exhaust temperature can be kept below the target exhaust temperature within a range where the regeneration time of the DPF does not become excessively long. Therefore, the exhaust temperature of the exhaust gas discharged from the exhaust pipe and the regeneration time of the DPF Can be controlled appropriately.

1 is a schematic configuration diagram of a diesel engine equipped with an exhaust gas purifying apparatus according to Embodiment 1 of the present invention. 2 is a heat dissipation map incorporated in the exhaust gas purifying apparatus according to Embodiment 1. 4 is a graph for explaining a control operation of the rotational speed of a diesel engine in the exhaust gas purifying apparatus according to Embodiment 1; 6 is a graph for explaining a change in fuel consumption in an exhaust gas purification apparatus according to Embodiment 2.

Embodiments of the present invention will be described below with reference to the accompanying drawings.
Embodiment 1 FIG.
FIG. 1 shows a schematic configuration diagram of a diesel engine equipped with an exhaust gas purifying apparatus according to Embodiment 1 of the present invention. An intake manifold 3 and an exhaust manifold 4 are connected to the cylinder head 1 of the in-line four-cylinder diesel engine 30. Each of the four cylinders 2 is provided with an injection 9 for injecting fuel (light oil) into the cylinder 2. Each injection 9 is connected to a common common rail 8. One end of the fuel passage 5 is connected to the common rail 8, and the other end of the fuel passage 5 is connected to the fuel supply pump 6. The common rail 8 is supplied with a high-pressure fuel from the fuel supply pump 6 so that a high-pressure fuel with a predetermined pressure is always maintained therein. One end of a fuel passage 7 is connected to the fuel supply pump 6, and the other end of the fuel passage 7 is connected to a fuel tank (not shown). A desired amount of fuel is injected from the injection 9 into the cylinder 2 using the pressure of the high-pressure fuel in the common rail 8.

An intake pipe 14 is connected to the intake manifold 3. The intake pipe 14 is provided with an intake air temperature sensor 15 for detecting the temperature of air flowing through the intake pipe 14 and an air flow sensor 16 for detecting the amount of air flowing through the intake pipe 14. Here, since the air flowing through the intake pipe 14 is air (outside air) sucked from the outside of the diesel engine 30, the intake air temperature sensor 15 detects the outside air temperature for detecting the outside air temperature t ₀ (° C.). The air flow sensor 16 constitutes intake air amount detection means for detecting the intake air amount m (g / sec) sucked into the diesel engine 30.

An exhaust pipe 11 through which exhaust gas flows is connected to the exhaust manifold 4. Further, the exhaust manifold 4 is provided with a fuel addition valve 10 which is a fuel addition means for adding fuel to the exhaust gas. The fuel addition valve 10 communicates with the fuel supply pump 6 through the fuel passage 17 and supplies fuel having a pressure lower than the pressure in the common rail 8. The exhaust pipe 11 is provided with an oxidation catalyst 12 and a DPF 13 from upstream to downstream. Temperature sensors 23 and 24 for detecting the temperature of the flowing exhaust gas are provided between the oxidation catalyst 12 and the DPF 13 and immediately downstream of the DPF 13, respectively. Here, the temperature sensor 24 constitutes a distribution exhaust gas temperature detection means for detecting the exhaust gas temperature t ₁ (° C.) of the exhaust gas flowing through the exhaust pipe 11 on the downstream side of the DPF 13. The DPF 13 is provided with a differential pressure sensor 25 for detecting a differential pressure p (Pa) before and after the DPF 13.

An ECU 20 is provided as a control device. The ECU 20 includes a fuel supply pump 6, each injection 9, a fuel addition valve 10, an intake air temperature sensor 15, an air flow sensor 16, temperature sensors 23 and 24, and a differential pressure sensor. 25 is electrically connected. The ECU 20 includes an accelerator sensor 18 that detects the depression angle of the accelerator pedal 19 that is operated by the driver, a vehicle speed sensor 21 that detects the vehicle speed of a vehicle (not shown) on which the diesel engine 30 is mounted, and a crankshaft. A rotational speed sensor 22 that is disposed in the vicinity of the end portion 26 and detects the rotational speed of the diesel engine 30 is electrically connected. Further, the ECU 20 has a memory 40. The memory 40 includes a target exhaust temperature T ₁ (° C.) for the temperature of exhaust gas discharged from the exhaust pipe 11 to the outside air (hereinafter referred to as “exhaust temperature”), and a target bed temperature for the bed temperature when the DPF 13 is regenerated. T ₂ (° C.) and a reference differential pressure P ₀ (Pa) for the differential pressure before and after the DPF 13 are set. In the first embodiment, the target discharge temperature T _{1 is set} to 300 ° C., and the target bed temperature T _{2 is set} to 610 ° C.

The memory 40 further incorporates a heat release map for estimating the heat release amount ΔT radiated from the exhaust pipe 11 downstream of the DPF 13. Here, the heat release amount ΔT means a temperature that decreases before the exhaust gas immediately after flowing out of the DPF 13 is discharged from the exhaust pipe 11 to the outside air. An example of this heat dissipation map is shown in FIG. The heat release map is a matrix in which Δt (= t ₁ −t ₀ ) is taken in the vertical direction and the intake air amount m detected by the air flow sensor 16 is taken in the horizontal direction, and for each combination of Δt and m, A heat release amount ΔT is specified. Note that the intake air amount m is used here, because it is difficult to directly measure the flow rate of the high-temperature exhaust gas, so the intake air amount m correlated with the exhaust gas flow rate is used instead. . For example, when Δt = 550 ° C. and m = 30 g / sec, the heat release amount ΔT = 320 ° C. Therefore, if the exhaust gas temperature t ₁ is 580 ° C., the exhaust temperature is 260 ° C. (= 580 ° C. − 320 ° C.). Each numerical value in the heat dissipation map is a value obtained by experiment, simulation, or the like, and is a value depending on the specification of the diesel engine 30 or the like.

Next, the operation of the diesel engine provided with the exhaust gas purifying apparatus according to Embodiment 1 of the present invention will be described.
As shown in FIG. 1, when the diesel engine 30 starts, the fuel supply pump 6 supplies fuel from a fuel tank (not shown) to the common rail 8 via the fuel passages 7 and 5, and a predetermined high pressure is supplied into the common rail 8. Maintain fuel.

Further, when the diesel engine 30 is started, intake air is sucked into each cylinder 2 via the intake pipe 14 and the intake manifold 3. At this time, the temperature of the air sucked from the outside air and circulated through the intake pipe 14, that is, the outside air temperature t ₀ is detected by the intake air temperature sensor 15, and the intake pipe 14 is sucked and sucked from the outside air by the air flow sensor 16. The amount of air flowing, that is, the intake air amount m sucked into the diesel engine 30 is detected. The detected values for the outside air temperature t ₀ and the intake air amount m are transmitted to the ECU 20. In each cylinder 2, air is compressed by a piston (not shown) to become high temperature and pressure, and fuel is injected from each injection 9. Thereby, combustion occurs in each cylinder 2. Exhaust gas generated by combustion in each cylinder 2 is discharged from each cylinder 2, collected by the exhaust manifold 4, and flows through the exhaust pipe 11. The exhaust gas flowing through the exhaust pipe 11 passes through the oxidation catalyst 12 and then flows into the DPF 13. After the PM contained in the exhaust gas is captured by the DPF 13, the exhaust gas is discharged to the outside air.

As the amount of PM trapped in the DPF 13 increases, the differential pressure p detected by the differential pressure sensor 25 increases. ECU20 is, the differential pressure p is Once you become a standard differential pressure _{P 0} or more, it is determined that it is necessary to regenerate the DPF13. Before starting the regeneration of the DPF 13, the ECU 20 determines whether or not the vehicle on which the diesel engine 30 is mounted is in an idle state based on detection values of the accelerator sensor 18 and the vehicle speed sensor 21. When the detected value of the accelerator sensor 18 satisfies both the fact that the driver does not step on the accelerator and the detected value of the vehicle speed sensor 21 that the vehicle is stopped, the vehicle is in an idle state. Is determined.

When the vehicle is not in an idle state, the ECU 20 performs a regeneration process of the DPF 13 by a known technique. The ECU ₂₀ calculates a fuel addition amount at which the bed temperature of the DPF 13 becomes the target bed temperature T ₂ based on the detection values of the temperature sensors 23 and 24 and the detection value of the airflow sensor 16, and the fuel addition valve 10 Fuel is added to the exhaust gas in an added amount. The added fuel flows into the oxidation catalyst 12 together with the exhaust gas. As the fuel reacts with oxygen contained in the exhaust gas and is oxidized by the oxidation catalyst 12, the exhaust gas temperature rises due to the reaction heat. When the exhaust gas whose temperature has been raised by the reaction heat flows into the DPF 13, the bed temperature of the DPF 13 becomes the target bed temperature T ₂ , and the PM trapped in the DPF 13 is burned and removed from the DPF 13. When the ECU 20 determines that the PM trapped by the DPF 13 has been removed based on the detection value of the differential pressure sensor 25, the ECU 20 stops the fuel addition from the fuel addition valve 10 and ends the regeneration of the DPF 13.

On the other hand, when the vehicle is in an idle state, the ECU 20 performs a process for making the diesel engine 30 reproducible and a process for optimizing the regenerative state.
First, the rotational speed of the diesel engine 30 is increased to a predetermined rotational speed (idle up), and the exhaust gas flow rate and the intake air amount are increased. By this process, after increasing the exhaust gas flow rate, the addition of fuel from the fuel addition valve 10 starts, the bed temperature of the DPF 13, the target bed temperature T _2.
The ECU 20 calculates Δt from the detected values of the intake air temperature sensor 15 and the temperature sensor 24, and uses this Δt and the intake air amount m detected by the airflow sensor 16 to release the air based on the heat dissipation map shown in FIG. The amount of heat ΔT is estimated. For example, assuming that the outside air temperature t ₀ = 30 ° C., the exhaust gas temperature t ₁ = 580 ° C., and the intake air amount m = 30 g / sec, Δt = t ₁ −t ₀ = 550 ° C. Therefore, from the heat dissipation map, ΔT = 320 Estimated at ° C. Then, the exhaust temperature becomes 260 ° C. (= t ₁ −ΔT = 580 ° C.−320 ° C.), which is lower than the target exhaust temperature T ₁ = 300 ° C. set in the memory 40. Can be further shortened. Specifically, since the discharge temperature 260 ° C. is 40 ° C. lower than the target discharge temperature T ₁ = 300 ° C., the heat release amount ΔT can be reduced by 40 ° C., that is, the heat release amount ΔT can be 280 ° C. In the heat dissipation map, when Δt = 550 ° C., the intake air amount m at which ΔT = 280 ° C. is 40 g / sec. The ECU 20 calculates the rotational speed of the diesel engine 30 at which the intake air amount m = 40 g / sec. The calculated rotation speed is the rotation speed based on the time required for regeneration of the DPF 13, that is, the rotation speed at which the regeneration time of the DPF 13 is the shortest. The diesel engine 30, by controlling the number of rotation is calculated, under the condition that the discharge temperature becomes the target exhaust temperature T ₁ of less, the shortest reproduction time of DPF 13. The operation from the start of regeneration of the DPF 13 to the end of regeneration of the DPF 13 after calculating the amount of fuel added from the fuel addition valve 10 is the same as when the vehicle is not in an idle state.

Next, control of the rotational speed of the diesel engine 30 will be described. In the graph shown in FIG. 3, the horizontal axis represents the intake air amount (corresponding to the exhaust gas flow rate and the rotational speed of the diesel engine 30), and the vertical axis represents the bed temperature of the DPF 13. When the floor temperature of the DPF 13 is equal to or lower than a certain temperature t ′, the trapped PM is not burned (cannot be regenerated), so the region below the temperature t ′ is filled with diagonal lines. If the intake air amount m is less than a certain amount m ′, the exhaust gas flow rate decreases, and if fuel is added in this state, the added atmosphere temperature becomes low and the fuel does not react. That is, the added fuel takes the heat of the exhaust gas and vaporizes it. However, if the flow rate of the exhaust gas is small, the temperature drop of the exhaust gas becomes relatively large. When the temperature of the exhaust gas is lowered, the temperature of the oxidation catalyst 12 is also lowered. When the temperature of the oxidation catalyst 12 is lower than the activation temperature, the added fuel does not react with the catalyst. For this reason, even if fuel is added, PM is not burned and the DPF 13 cannot be regenerated. Therefore, a region below the intake air amount m ′ is shaded as a non-addable region. Further, in order to increase the bed temperature of the DPF 13 while keeping the discharge temperature constant, the heat release amount ΔT must be increased. Therefore, the intake air amount m must be decreased as the bed temperature increases. Therefore, the boundary line L ₀ for achieving the target bed temperature of the DPF 13 while keeping the temperature of the exhaust gas discharged from the exhaust pipe 11 constant is a straight line having a downward slope. Region of the upper than the boundary line L ₀ is because one of the bed temperature of the exhaust temperature or DPF13 is a region that can not achieve the target value, and fill the area with diagonal lines. In FIG. 3, the range of the number of revolutions controlled by the diesel engine 30 is calculated based on the region not shaded by the diagonal lines.

In the example in the first embodiment, the target bed temperature T ₂ = 610 ° C. is located above the temperature t ′ in FIG. The condition of the intake air amount m = 30 g / sec is located in the above region. In the first embodiment, the intake air amount m is increased to 40 g / sec so as to minimize the regeneration time of the DPF 13, but this operation is performed under the condition of the target bed temperature T ₂ = 610 ° C. in FIG. This corresponds to the movement to L ₀ (arrow A). The intake air amount at the position on the boundary line L ₀ corresponds to 40 g / sec. Under the condition of the target bed temperature T ₂ = 610 ° C., the range of the rotational speed that is controlled by the diesel engine 30 is a range in which the intake air amount m is larger than m ′ and 40 g / sec or less. If the target bed temperature T ₂ is changed (for example, T ₂ ′), the range that can be calculated is a horizontal range in which the intake air amount m is larger than m ′ and passes through the value of the target bed temperature T ₂ ′. The range is equal to or less than the air amount (m ″) at the intersection of the straight line parallel to the axis and the boundary line L ₀ .

Thus, when starting the reproduction of the DPF 13, when the diesel engine 30 is in an idle state, it calculates the range rotation speed of the diesel engine 30 exhaust temperature is less than the target discharge temperature T _1, the diesel engine 30 by controlling the rotational speed within its range, to the extent that the playback time of the DPF13 is not excessively long, since the discharge temperature is suppressed to less than the target discharge temperature T _1, the discharge temperature of the exhaust gas discharged from the exhaust pipe 11 And the regeneration time of the DPF 12 can be appropriately controlled.

Embodiment 2. FIG.
Next, an exhaust gas purification apparatus according to Embodiment 2 of the present invention will be described.
A diesel engine including the exhaust gas purifying apparatus according to the second embodiment, an operation of regenerating the DPF when the vehicle is not in an idle state, and an operation of regenerating the DPF when the vehicle is in an idle state, The operation for calculating the engine speed range is the same as in the first embodiment. Therefore, in Embodiment 2, the same reference numerals as those in FIG. 1 are used as the reference numerals indicating the respective components.
The exhaust gas purification apparatus according to Embodiment 2 of the present invention calculates the rotational speed at which the fuel efficiency of the diesel engine 30 is optimal within the rotational speed range, and calculates the rotational speed of the diesel engine 30 to the calculated rotational speed. It is something that controls to a number.

The fuel consumption when the DPF 13 is regenerated when the vehicle is in an idle state increases (1) the fuel required to maintain the normal idle state and (2) the exhaust gas flow rate (in other words, the intake air amount). In addition, the fuel required to increase the rotational speed from the rotational speed in the normal idle state, and (3) fuel added to the exhaust gas from the fuel addition valve 10 for regeneration of the DPF 13. When (2) is increased, the above (3) is also increased. However, since the reproduction speed increases (because the reproduction time is shortened), from the above (1) to (3) due to the balance with the reproduction speed. As shown in FIG. 4, it can be understood that the best exhaust gas flow rate, that is, the rotational speed of the diesel engine 30 exists in the obtained fuel efficiency. On this premise, in the second embodiment, the discharge temperature is less than the target discharge temperature T _1, and, within the scope bed temperature of the DPF13 is the rotational speed of the diesel engine 30 as a target bed temperature T _2, the fuel consumption is best It controls to the rotation speed which becomes.

  First, in the same manner as in the first embodiment, the rotational speed of the diesel engine 30 is controlled to the rotational speed that minimizes the regeneration time of the DPF 13. Thereafter, the rotational speed of the diesel engine 30 is gradually decreased, the fuel consumption is calculated under each condition, and the rotational speed at which the fuel consumption is optimal is calculated (feedback control). Considering the relationship between the fuel efficiency and the exhaust gas flow rate shown in FIG. 4, when the fuel efficiency increases when the rotational speed of the diesel engine 30 is decreased, the rotational speed at which the regeneration time of the DPF 13 is the shortest is the best fuel efficiency. It is considered that the number of revolutions becomes.

  Thus, the exhaust temperature of the exhaust gas discharged from the exhaust pipe 11 and the regeneration time of the DPF 12 can be appropriately controlled while optimizing the fuel consumption. Note that the method of calculating the rotational speed at which the fuel efficiency is optimal is not limited to the feedback control described above, and a calculation formula is incorporated in the ECU 20 to calculate from various conditions, and a map or the like is incorporated in the memory 40. However, it may be calculated based on a map or the like.

  In Embodiments 1 and 2, the fuel addition valve 10 for directly adding fuel to the exhaust gas is used as the fuel addition means, but the present invention is not limited to this. As the post-injection, fuel may be added from the injection 9 to the cylinder 2. In this case, the fuel addition means is the injection 9.

  In the first and second embodiments, the diesel engine 30 is an in-line four-cylinder diesel engine. However, the present invention is not limited to this. The number of cylinders may be arbitrary, and is not limited to an in-line type, and may be a V-type or a horizontally opposed type.

  Each numerical value used in the first and second embodiments is merely an example for explaining the operation of the exhaust gas purifying apparatus, and changes depending on the specifications of the diesel engine, traveling conditions, and the like. In particular, the numerical values in the heat dissipation map shown in FIG. 2 are merely examples, and it is necessary to specify numerical values through experiments, simulations, and the like based on the specifications of the diesel engine, the environment of the area where the vehicle is traveling, and the like.

  9 Injection (fuel addition means), 10 Fuel addition valve (fuel addition means), 11 Exhaust pipe, 12 Oxidation catalyst, 13 DPF, 15 Intake air temperature sensor (outside air temperature detection means), 16 Air flow sensor (intake air amount detection means) , 20 ECU (control device), 24 temperature sensor (circulation exhaust gas temperature detection means), 30 diesel engine.

Claims (5)

An exhaust gas purification device for purifying exhaust gas discharged from a diesel engine through an exhaust pipe,
Fuel addition means for adding fuel to the exhaust gas;
An oxidation catalyst provided in the exhaust pipe;
A DPF provided in the exhaust pipe downstream of the oxidation catalyst;
A control device in which a target exhaust temperature for the exhaust temperature that is the temperature of exhaust gas discharged from the exhaust pipe to the outside air and a target bed temperature for the bed temperature of the DPF at the time of regeneration of the DPF are set,
When starting the regeneration of the DPF, the control device determines that the diesel engine is in an idle state, the exhaust temperature is equal to or lower than the target exhaust temperature, and the bed temperature of the DPF is the target floor. An exhaust gas purifying apparatus that calculates a range of the rotational speed of the diesel engine that is equal to or higher than a temperature and controls the rotational speed within the range. A circulating exhaust gas temperature detecting means for detecting an exhaust gas temperature of the exhaust gas flowing through the exhaust pipe on the downstream side of the DPF;
Intake air amount detection means for detecting the amount of air sucked into the diesel engine;
An outside air temperature detecting means for detecting the outside air temperature,
The control device includes the DPF from the exhaust gas temperature detected by the circulating exhaust gas temperature detection means, the intake air amount detected by the intake air amount detection means, and the outside air temperature detected by the outside air temperature detection means. A heat dissipation map that estimates the amount of heat released from the exhaust pipe on the downstream side of
The exhaust gas purification device according to claim 1, wherein the control device estimates the range from the exhaust gas temperature and the heat radiation amount.   The exhaust gas purification device according to claim 1 or 2, wherein the control device calculates a rotational speed of the diesel engine based on a regeneration time of the DPF within the range.   The exhaust gas purification device according to claim 1, wherein the control device calculates a rotational speed of the diesel engine based on a fuel consumption of the diesel engine within the range.   The exhaust gas purification device according to claim 4, wherein the rotational speed of the diesel engine is determined by feedback control.

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