JP6805948B2 - Exhaust purification device - Google Patents

Description

The present invention relates to a configuration of an exhaust purification device that purifies exhaust gas emitted from a diesel engine.

In order to purify the exhaust gas of a diesel engine or the like, for example, a filter such as a DPF (Diesel particulate filter) or a reduction catalyst such as an SCR (Selective Catalytic Reduction) catalyst is provided as an exhaust purification device in the exhaust passage. For example, in an SCR catalyst, exhaust gas is purified by reducing nitrogen oxides (hereinafter, also referred to as “NOx”) with urea water supplied from the upstream side. In such a case, it is necessary to raise the temperature of the SCR catalyst to a predetermined temperature or higher in order to appropriately cause a reduction reaction. Further, in the DPF, the exhaust gas is purified by collecting particulate matter in the exhaust gas. If the filter is clogged with the collected particulate matter, the purification performance will deteriorate. Therefore, it is necessary to raise the DPF to a predetermined temperature or higher in order to burn the deposited particulate matter and regenerate the DPF.

Such a plurality of types of catalysts are provided at predetermined positions on the exhaust gas path. For example, Japanese Patent Application Laid-Open No. 2009-150279 discloses a configuration of an exhaust purification device in which a DPF is provided on the upstream side of an exhaust passage with respect to an SCR catalyst.

JP-A-2009-150279

However, in the exhaust purification device having the above-described configuration, the temperature of the exhaust gas is radiated and lowered toward the downstream side of the exhaust passage 42. Therefore, depending on the position where the DPF or SCR catalyst is provided, it is necessary to separately provide a catalyst for rapidly raising the temperature for each DPF or SCR catalyst in order to make the purification performance function. As a result, the manufacturing cost of the exhaust gas purification device may increase due to the increase in the number of catalysts mounted.

The present invention has been made to solve the above-mentioned problems, and an object of the present invention is to provide an exhaust gas purification device that appropriately generates purification performance while suppressing an increase in the number of catalysts mounted. ..

The exhaust purification device according to a certain aspect of the present invention supplies an exhaust passage connected to an engine and flowing exhaust gas, a filter for collecting particulate matter contained in the exhaust gas, and a reducing agent in the exhaust passage. It is an exhaust gas purification device provided with a supply device and a reduction catalyst provided at a position downstream of the supply device and purifying nitrogen oxides using a reducing agent. The exhaust passage merges with the first branch passage, the second branch passage, the third branch passage, and the upstream passage upstream of the branch position, which branches from a predetermined branch position and merges at a predetermined merging position. Includes downstream passages downstream of the location. A reduction catalyst is provided in the first branch passage. A filter is provided in the third branch passage. At the branch position, the exhaust purification device blocks the upstream passage from the first branch passage and the second branch passage, communicates the upstream passage with the third branch passage, and connects the first branch passage and the second branch passage. The first state, which communicates with the upstream passage, the second branch passage, and the third branch passage are blocked, the upstream passage and the first branch passage are communicated with each other, and the second branch passage and the third branch passage are separated. The downstream passage, the second branch passage, and the third branch passage are blocked from each other at the confluence position with the first switching valve that can switch to any of the second states of communication, and the downstream passage and the first branch. The third state, which communicates with the passage and connects the second branch passage and the third branch passage, and the downstream passage, the first branch passage, and the second branch passage are blocked, and the downstream passage and the third branch passage are separated. Further, a second switching valve capable of switching to any one of the fourth state of communicating and communicating the first branch passage and the second branch passage is provided.

In this way, for example, when the first switching valve is set to the first state and the second switching valve is set to the third state, the exhaust gas from the upstream passage passes through the filter of the third branch passage from the branch position. , It flows into the second branch passage at the confluence position, passes through the reduction catalyst of the second branch passage to the first branch passage at the branch position, and then flows into the downstream passage at the confluence position. On the other hand, for example, when the first switching valve is set to the second state and the second switching valve is set to the fourth state, the exhaust gas from the upstream passage joins after passing through the reduction catalyst of the first branch passage from the branch position. It flows into the second branch passage at the position, passes through the filter of the second branch passage to the third branch passage at the branch position, and then flows into the downstream passage at the confluence position. In this way, by switching the states of the first switching valve and the second switching valve, the positional relationship between the upstream and downstream of the filter and the reduction catalyst can be changed in the exhaust gas flow path. Therefore, for example, the temperature can be raised quickly by changing the position where the temperature rise is required for the regeneration of the filter, the generation of purification performance, or the like to a position where the exhaust temperature is higher. Therefore, it is not necessary to separately provide a catalyst for raising the temperature for each filter or reduction catalyst. Therefore, it is possible to provide an exhaust gas purification device that appropriately generates the purification performance of the catalyst while suppressing an increase in the number of mounted catalysts.

Preferably, the exhaust gas purification device further includes a control device that controls the state of the first switching valve and the state of the second switching valve. The control device controls the state of the first switching valve so as to be in the first state and controls the state of the second switching valve so as to be in the third state when the filter is regenerated. The control device controls the state of the first switching valve so as to be in the second state and controls the state of the second switching valve so as to be in the fourth state when the filter is not regenerated.

In this way, for example, when the heat source for raising the temperature is arranged upstream of the exhaust passage, the position of the filter in the exhaust gas flow path should be upstream of the reduction catalyst when the filter is regenerated. Can be done. Therefore, the temperature of the filter can be rapidly raised to regenerate the filter. Further, when the filter is not regenerated, the position of the reduction catalyst can be located upstream of the filter in the exhaust gas flow path. Therefore, the purification performance for reducing the nitrogen oxides by rapidly raising the temperature of the reduction catalyst can be appropriately generated.

More preferably, when switching the first switching valve and the second switching valve, the control device switches the second switching valve after the switching of the first switching valve is completed.

In this way, by switching the second switching valve after the switching of the first switching valve is completed, the exhaust gas in the upstream passage is suppressed from flowing to the downstream passage via the second branch passage. Can be done.

According to the present invention, it is possible to provide an exhaust gas purification device that appropriately generates the purification performance of the catalyst while suppressing an increase in the number of mounted catalysts.

It is a figure which shows the structure of the exhaust gas purification apparatus. It is a figure for demonstrating the switching of the state of the 1st switching valve and the 2nd switching valve. It is a figure for demonstrating the relationship between a catalyst temperature and purification performance. It is a flowchart which shows the content of the control process executed by a control device. It is a figure for demonstrating the operation of the exhaust gas purification apparatus at the time of DPF non-regeneration. It is a figure for demonstrating the operation of the exhaust gas purification apparatus at the time of DPF regeneration.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. The same or corresponding parts in the drawings are designated by the same reference numerals, and the description thereof will not be repeated.

FIG. 1 is a diagram showing a configuration of an exhaust gas purification device 1 according to the present embodiment. The exhaust purification device 1 purifies the exhaust gas discharged from the engine 10.

The engine 10 is, for example, an internal combustion engine such as a diesel engine. During operation, the engine 10 burns a mixture of air and fuel in the cylinder to rotate the output shaft by a piston and a crank mechanism. The air-fuel mixture in the cylinder is discharged to the outside of the cylinder as exhaust gas after combustion.

An exhaust manifold 12 and a turbocharger 20 are provided on the exhaust side of the engine 10. The exhaust manifold 12 has branch pipes branched by the number corresponding to the number of cylinders, and each branch pipe is connected to each cylinder of the engine 10. One end of the first passage 14 is connected to the portion where the branch pipes of the exhaust manifold 12 are integrated into one. The other end of the first passage 14 is connected to the exhaust gas inlet of the turbine 28 of the turbocharger 20.

The turbocharger 20 includes a compressor 26 and a turbine 28. One end of the first intake passage 22 is connected to the inlet of the intake air in the compressor 26. An air cleaner (not shown) or the like is provided at the other end of the first intake passage 22. One end of a second intake passage 24 connected to an intercooler (not shown) is connected to the intake air outlet of the compressor 26. A compressor blade (not shown) is rotatably provided in the compressor 26, and rotates integrally with the turbine blade (not shown) in the turbine 28. One end of the second passage 30 is connected to the exhaust gas outlet of the turbine 28 of the turbocharger 20.

The exhaust gas discharged to the outside of the cylinder flows into the turbine 28 via the exhaust manifold 12 and the first passage 14, and flows into the second passage 30 after applying a force for rotating the turbine blades. The rotation of the turbine blades causes the compressor blades to rotate and supercharge. An exhaust gas purification device 1 is connected to the other end of the second passage 30.

The exhaust gas purification device 1 includes an oxidation catalyst 40, an exhaust passage 42, an SCR catalyst 50, a first pressure sensor 64, a second pressure sensor 66, a first switching valve 80, a second switching valve 90, and urea. It includes a water injection device 110 and a urea water tank 112.

The exhaust passage 42 branches from a predetermined branch position and joins at a predetermined merging position. The first branch passage 44, the second branch passage 46, the third branch passage 48, and the upper distribution upstream of the branch position. It includes a road 52 and a downstream passage 54 downstream from the confluence position. The urea water injection device 110 and the SCR catalyst 50 are provided in the first branch passage 44. The SCR catalyst 50 is arranged at a position downstream of the urea water injection device 110 in the exhaust gas flow path. Further, a DPF 60 is provided in the third branch passage 48.

FIG. 2 is a diagram for explaining the switching of the states of the first switching valve 80 and the second switching valve 90.

As shown in FIG. 2, the first switching valve 80 has a first state (see the first switching valve 80 shown by the solid line in FIG. 2) and a second state (the first switching valve 80 shown by the broken line in FIG. 2). It is provided so that it can be switched to either of the above states (see). Specifically, in the first state, at the branch position, the first switching valve 80 shuts off the upstream passage 52, the first branch passage 44, and the second branch passage 46, and the upstream passage 52 and the third branch. It is in a state of communicating with the passage 48 and communicating with the first branch passage 44 and the second branch passage 46. In the second state, at the branch position, the first switching valve 80 shuts off the upstream passage 52, the second branch passage 46, and the third branch passage 48, and communicates the upstream passage 52 with the first branch passage 44. However, the second branch passage 46 and the third branch passage 48 are in a state of communicating with each other.

Further, the second switching valve 90 is in a third state (see the second switching valve 90 shown by the solid line in FIG. 2) and a fourth state (see the second switching valve 90 shown by the broken line in FIG. 2). It is provided so that it can be switched to any of the above states. Specifically, in the third state, at the merging position, the second switching valve 90 shuts off the downstream passage 54, the second branch passage 46, and the third branch passage 48, and the downstream passage 54 and the first branch passage 44. Is in a state of communicating with the second branch passage 46 and the third branch passage 48. In the fourth state, at the merging position, the second switching valve 90 shuts off the downstream passage 54 from the first branch passage 44 and the second branch passage 46, and communicates the downstream passage 54 with the third branch passage 48. It is a state in which the first branch passage 44 and the second branch passage 46 are communicated with each other.

Returning to FIG. 1, the constituent members of the oxidation catalyst 40 are coated with an oxidation catalyst made of a noble metal such as platinum, and the gas components (NOx, carbon oxide (COx) or unburned hydrocarbons) of the passing exhaust gas are coated. Oxidizes hydrogen (unburned HC, etc.). Further, the oxidation catalyst 40 oxidizes the fuel supplied by post-injection in the engine 10 or addition from a fuel addition device (not shown). Oxidation heat is generated by the oxidation reaction of this fuel.

The urea water injection device 110 is controlled by a control signal from the control device 100, and is a reducing agent for urea in the exhaust gas flowing in the first branch passage 44 (that is, in the exhaust gas on the upstream side of the SCR catalyst 50). Spray water. Urea water is supplied to the urea water injection device 110 from a urea water tank 112 that stores urea water using a pump (not shown) or the like. The urea water injection device 110 is composed of, for example, an injection nozzle or the like, and injects urea water into the first branch passage 44.

The SCR catalyst 50 selectively reduces and purifies NOx contained in the exhaust gas using ammonia (NH ₃ ) generated from urea water by hydrolysis.

The DPF 60 is made of, for example, ceramic or stainless steel. The DPF 60 collects particulate matter from the passing exhaust gas while allowing the passing of the exhaust gas. An oxidation catalyst made of a noble metal such as platinum is applied to the DPF60. Therefore, the DPF 60 can also oxidize the gas component of the exhaust gas described above.

The control device 100 includes a CPU (Central Processing Unit) that performs various processes, memories such as ROM (Read Only Memory) and RAM (Random Access Memory) that store programs and data, and an external device of the control device 100. Includes input / output ports (neither shown) for exchanging information.

The control device 100 receives a signal from the device connected to the input port, and the device connected to the output port based on the received signal (for example, the first switching valve 80, the second switching valve 90, the urea water injection device). 110 etc.) to control the operation. For example, a first pressure sensor 64 and a second pressure sensor 66 are connected to the input port of the control device 100.

The first pressure sensor 64 detects the pressure P1 of the exhaust gas on the upstream side of the DPF 60. The first pressure sensor 64 outputs a signal indicating the detected exhaust gas pressure P1 on the upstream side of the DPF 60 to the control device 100.

The second pressure sensor 66 detects the pressure P2 of the exhaust gas on the downstream side of the DPF 60. The second pressure sensor 66 outputs a signal indicating the detected exhaust gas pressure P2 on the downstream side of the DPF 60 to the control device 100.

In addition, it is assumed that signals for the engine speed Ne and the accelerator opening degree Acc are input to the input port of the control device 100.

In the SCR catalyst 50 constituting the exhaust gas purification device 1 having the above configuration, the exhaust gas is purified by reducing NOx with urea water supplied from the upstream side. In such a case, it is necessary to raise the temperature of the SCR catalyst 50 to a predetermined temperature or higher in order to appropriately cause a reduction reaction.

FIG. 3 is a diagram for explaining the relationship between the catalyst temperature and the reduction rate. The vertical axis of FIG. 3 shows the reduction rate (purification rate) indicating the purification performance of the SCR catalyst 50. The horizontal axis of FIG. 3 indicates the catalyst temperature. As shown in FIG. 3, NOx can be reduced when the catalyst temperature becomes the threshold value A or higher. Then, when the catalyst temperature becomes the threshold value B (for example, about 200 ° C.) or higher, the reduction rate C at which an appropriate reduction reaction occurs is reached. Therefore, it is necessary to raise the temperature of the SCR catalyst 50 to the threshold value B or higher in order for the purification performance of the SCR catalyst 50 to function appropriately.

Further, in the DPF 60, the exhaust gas is purified by collecting particulate matter (hereinafter, may be referred to as PM (Particular Matter)) in the exhaust gas. Since the purification performance deteriorates when the filter portion of the DPF 60 is clogged with the collected particulate matter, the control device 100 executes a regeneration control for burning the accumulated particulate matter to regenerate the DPF 60. The control device 100 executes regeneration control when the accumulated amount of PM is equal to or greater than the threshold value. In order to execute the regeneration control, it is necessary to raise the DPF 60 to a temperature higher than a predetermined temperature suitable for regeneration.

However, in the exhaust purification device 1 having the above-described configuration, the temperature of the exhaust gas is radiated and lowered toward the downstream side of the exhaust passage 42. Therefore, depending on the position where the DPF 60, the SCR catalyst 50, or the like is provided, it is necessary to separately provide a catalyst for rapidly raising the temperature for each DPF 60 or SCR catalyst in order to make the purification performance function. As a result, the manufacturing cost of the exhaust gas purification device 1 may increase due to the increase in the number of catalysts mounted.

Therefore, in the present embodiment, the configuration of the exhaust gas purification device 1 shall be the configuration shown in FIG. In this way, by switching the states of the first switching valve 80 and the second switching valve 90, it is possible to change the upstream / downstream positional relationship between the DPF 60 and the SCR catalyst 50 in the exhaust gas flow path.

Further, in the present embodiment, the control device 100 controls the state of the first switching valve 80 so as to be in the first state and the second switching valve 90 so as to be in the third state when the DPF 60 is regenerated. The state shall be controlled. Further, the control device 100 controls the state of the first switching valve 80 so as to be in the second state and controls the state of the second switching valve 90 so as to be in the fourth state when the DPF 60 is not regenerated. And.

In this way, when the DPF 60 is regenerated, the position of the DPF 60 can be set upstream from the SCR catalyst 50 in the exhaust gas flow path. Therefore, since the position of the DPF 60 is close to the oxidation catalyst 40 which is the heat source for raising the temperature, the temperature of the DPF 60 can be rapidly raised to regenerate the DPF 60. Further, when the DPF 60 is not regenerated, the position of the SCR catalyst 50 can be set upstream from the DPF 60 in the exhaust gas flow path. Therefore, since the position of the SCR catalyst 50 is close to the oxidation catalyst 40, the purification performance for rapidly raising the temperature of the SCR catalyst 50 and reducing NOx can be appropriately generated.

Hereinafter, the control process executed by the control device 100 in the present embodiment will be described with reference to FIG. FIG. 4 is a flowchart showing the contents of the control process executed by the control device 100. The process shown in this flowchart is called and executed from the main routine (not shown) at predetermined control cycles. Each step included in these flowcharts is basically realized by software processing by the control device 100, but a part or all of them are realized by hardware (electric circuit) manufactured in the control device 100. You may.

In step 100 (hereinafter, step is referred to as S) 100, the control device 100 determines whether or not the DPF 60 is being regenerated. For example, when the accumulated amount of PM is equal to or more than the threshold value, the control device 100 determines that the DPF 60 is being regenerated. For example, when the differential pressure between the pressure P1 on the upstream side and the pressure P2 on the downstream side of the DPF 60 is equal to or greater than the threshold value, the control device 100 determines that the amount of PM deposited is equal to or greater than the threshold value. If it is determined that the DPF 60 is being regenerated (YES in S100), the process is transferred to S102.

At S102, the control device 100 switches the first switching valve 80 to the first state. In S104, the control device 100 switches the second switching valve 90 to the third state. For example, the control device 100 switches the second switching valve 90 to the third state after the switching of the first switching valve 80 is completed.

The timing for switching the second switching valve 90 to the third state is, for example, the exhaust gas flowing into the third branch passage 48 from the upstream passage 52 after the switching of the first switching valve 80 to the first state is started. It is desirable that the switching of the second switching valve 90 is completed by the time the second switching valve 90 is reached. In this way, the exhaust gas flowing from the upstream passage 52 into the third branch passage 48 can be circulated to both the SCR catalyst 50 and the DPF 60.

On the other hand, when it is determined that the DPF 60 is not being regenerated (that is, the DPF 60 is not being regenerated) (NO in S100), the control device 100 shifts the process to S106.

At S106, the control device 100 switches the first switching valve 80 to the second state. At S108, the control device 100 switches the second switching valve 90 to the fourth state. The control device 100, for example, switches the second switching valve 90 to the fourth state after the first switching valve 80 is switched to the second state.

The timing for switching the second switching valve 90 to the fourth state is, for example, the exhaust gas flowing into the first branch passage 44 from the upstream passage 52 after the switching of the first switching valve 80 to the second state is started. It is desirable to set so that the switching of the second switching valve 90 is completed by the time the second switching valve 90 is reached. In this way, the exhaust gas flowing from the upstream passage 52 into the first branch passage 44 can be circulated to both the SCR catalyst 50 and the DPF 60.

The operation of the exhaust gas purification device 1 according to the present embodiment based on the above configuration and flowchart will be described with reference to FIGS. 5 and 6.

FIG. 5 is a diagram for explaining the operation of the exhaust gas purification device 1 when the DPF 60 is not regenerated. For example, when the differential pressure between the pressure P1 on the upstream side and the pressure P2 on the downstream side of the DPF60 is smaller than the threshold value, the amount of PM deposited is smaller than the threshold value, so that the DPF60 is not regenerated. Is determined (NO in S100). In this case, after the first switching valve 80 is switched to the second state (S106), the second switching valve 90 is switched to the fourth state (S108).

The exhaust gas discharged from the engine 10 flows to the oxidation catalyst 40 via the exhaust manifold 12, the first passage 14, the turbine 28, and the second passage 30. In the oxidation catalyst 40, the gas component contained in the exhaust gas is oxidized to generate heat of oxidation, and the temperature of the exhaust gas rises. As shown by the arrow in FIG. 5, the exhaust gas that has passed through the oxidation catalyst 40 flows into the first branch passage 44 after reaching the branch position from the upstream passage 52. The temperature of the SCR catalyst 50 is raised by the exhaust gas flowing into the first branch passage 44. When the temperature of the SCR catalyst 50 is raised, the exhaust gas temperature is raised by post-injection or fuel supply from the fuel addition device.

In the first branch passage 44, the urea water injected from the urea water injection device 110 is attached to the SCR catalyst 50. Ammonia (NH ₃ ) is produced by hydrolysis of the adhered urea water in the heated SCR catalyst 50, and NOx is purified by using the produced ammonia as a reducing agent. The exhaust gas that has passed through the SCR catalyst 50 flows into the second branch passage 46 at the confluence position. The exhaust gas that has flowed into the second branch passage 46 flows to the first switching valve 80 side. Then, at the branch position, the exhaust gas flows from the second branch passage 46 into the third branch passage 48. The exhaust gas that has flowed into the third branch passage 48 reaches the DPF 60. Since the oxidation catalyst is applied to the DPF 60, the ammonia slipped from the SCR catalyst 50 is removed by the oxidation reaction of the oxidation catalyst. The exhaust gas that has passed through the DPF 60 flows into the downstream passage 54 at the confluence position.

FIG. 6 is a diagram for explaining the operation of the exhaust gas purification device 1 during regeneration of the DPF 60. For example, when the differential pressure between the pressure P1 on the upstream side and the pressure P2 on the downstream side of the DPF60 is equal to or greater than the threshold value, the amount of PM deposited is equal to or greater than the threshold value, so that the DPF60 is being regenerated. It is determined (YES in S100). Therefore, after the first switching valve 80 is switched to the first state (S102), the second switching valve 90 is switched to the third state (S104).

As a result, the exhaust gas that has passed through the oxidation catalyst 40 flows into the third branch passage 48 after reaching the branch position from the upstream passage 52, as shown by the arrow in FIG. The temperature of the DPF 60 is raised by the exhaust gas flowing into the third branch passage 48. When the temperature of the DPF 60 is raised, the exhaust gas temperature is raised by the fuel supply from the fuel addition device in the post injection.

When the temperature of the DPF 60 rises due to the exhaust gas flowing into the third branch passage 48, the PM accumulated in the filter portion of the DPF 60 burns to regenerate the DPF 60. The exhaust gas that has passed through the DPF 60 flows into the second branch passage 46 at the confluence position. The exhaust gas that has flowed into the second branch passage 46 flows to the first switching valve 80 side. Then, at the branch position, the exhaust gas passes from the second branch passage 46 to the SCR catalyst 50 of the first branch passage 44.

The unburned HC contained in the exhaust gas before passing through the oxidation catalyst 40 is oxidized in the process of the exhaust gas flowing through the oxidation catalyst 40 and the DPF 60, so that the deterioration of the purification performance of the SCR catalyst 50 is suppressed. The exhaust gas that has passed through the SCR catalyst 50 flows to the downstream passage 54 at the confluence position.

As described above, according to the exhaust gas purification device according to the present embodiment, when the first switching valve 80 is set to the first state and the second switching valve 90 is set to the third state during the regeneration of the DPF 60, the upper distribution is performed. Exhaust gas from the road 52 flows into the second branch passage 46 at the confluence position after passing through the DPF 60 of the third branch passage 48 from the branch position, and flows from the second branch passage 46 to the first branch passage 44 at the branch position. After passing through the SCR catalyst 50, it flows into the downstream passage 54 at the confluence position. Further, when the DPF 60 is not regenerated, when the first switching valve 80 is set to the second state and the second switching valve 90 is set to the fourth state, the exhaust gas from the upstream passage 52 is sent from the branch position to the first branch passage. After passing through the SCR catalyst 50 of 44, it flows into the second branch passage 46 at the confluence position, passes from the second branch passage 46 to the DPF 60 of the third branch passage 48 at the branch position, and then enters the downstream passage 54 at the confluence position. Inflow. In this way, by switching the states of the first switching valve 80 and the second switching valve 90, the positional relationship between the upstream and downstream of the DPF 60 and the SCR catalyst 50 can be changed in the exhaust gas flow path. Therefore, for example, the one where the temperature rise is required for the regeneration of the filter or the generation of purification performance is moved to the upstream position where the exhaust temperature is higher (the position close to the oxidation catalyst 40 which is the heat source for the temperature rise). By doing so, the temperature can be raised quickly. Therefore, it is not necessary to separately provide a catalyst for raising the temperature for each SCR catalyst 50 or DPF 60. Therefore, it is possible to provide an exhaust gas purification device that appropriately generates the purification performance of the catalyst while suppressing an increase in the number of mounted catalysts. Further, since the exhaust gas always flows into the DPF 60 and the SCR catalyst 50 from the same direction, the collected PM can be prevented from flowing back in the DPF 60. Further, in the SCR catalyst 50, since the exhaust gas flows in from the same direction, it is not necessary to provide a plurality of urea water injection devices according to the inflow direction.

Further, by switching the second switching valve 90 after the switching of the first switching valve 80 is completed, the exhaust gas of the upstream passage 52 is suppressed from flowing to the downstream passage 54 via the second branch passage 46. can do.

Further, since it is not necessary to arrange the SCR catalyst 50 and the DPF 60 in the series direction, it is possible to prevent the length of the exhaust gas purification device 1 in the series direction from becoming long.

Further, since the oxidation catalyst is also applied to the DPF 60, the position of the DPF 60 becomes a position downstream of the position of the SCR catalyst 50 in the exhaust gas flow path when the DPF 60 is not regenerated, so that the position of the DPF 60 is lower than that of the SCR catalyst 50. The slipped NH ₃ can be removed. Therefore, it is not necessary to separately provide an oxidation catalyst for removing the slipped NH ₃ from the SCR catalyst 50, so that an increase in the number of mounted catalysts can be suppressed.

Further, when the DPF 60 is regenerated, the oxidation catalyst is also applied to the DPF 60, so that the unburned HC in the exhaust gas can be removed together with the oxidation catalyst 40, so that the deterioration of the purification performance of the SCR catalyst 50 can be suppressed. it can.

Hereinafter, a modified example will be described.
In the above-described embodiment, the configuration of the exhaust gas purification device 1 has been described without particularly limiting the arrangement of the SCR catalyst 50 and the DPF 60. For example, the SCR catalyst 50 and the DPF 60 are housed in one housing. It may be arranged as follows. In this way, since the positions of the SCR catalyst 50 and the DPF 60 are close to each other, a heat receiving effect can be generated between the SCR catalyst 50 and the DPF 60, and a temperature drop can be suppressed.

In the above-described embodiment, it has been described that urea water is used as a reducing agent, but the reducing agent is not particularly limited to urea water, and may be, for example, ammonia water.

The above-mentioned modification may be carried out in whole or in combination.
It should be considered that the embodiments disclosed this time are exemplary in all respects and not restrictive. The scope of the present invention is shown not by the above description but by the scope of claims, and it is intended that all modifications within the meaning and scope equivalent to the scope of claims are included.

1 Exhaust purification device, 10 engine, 12 exhaust manifold, 14 1st passage, 20 turbocharger, 22 1st intake passage, 24 2nd intake passage, 26 compressor, 28 turbine, 30 2nd passage, 40 oxidation catalyst, 42 exhaust Passage, 44 1st branch passage, 46 2nd branch passage, 48 3rd branch passage, 50 SCR catalyst, 52 upstream passage, 54 downstream passage, 60 DPF, 64 1st pressure sensor, 66 2nd pressure sensor, 80th 1 switching valve, 90 2nd switching valve, 100 control device, 110 urea water injection device, 112 urea water tank.

Claims (3)

An exhaust passage connected to the engine and flowing through the exhaust gas, a filter for collecting particulate matter contained in the exhaust gas, a supply device for supplying a reducing agent into the exhaust passage, and a downstream of the supply device. An exhaust gas purification device provided at the position of the above and equipped with a reduction catalyst for purifying nitrogen oxides using the reducing agent.
The exhaust passage is a first branch passage, a second branch passage, a third branch passage, and an upstream passage upstream of the branch position, which branches from a predetermined branch position and merges at a predetermined merging position. , Including the downstream passage downstream from the confluence position,
The reduction catalyst is provided in the first branch passage.
The filter is provided in the third branch passage.
The exhaust gas purification device is
At the branch position, the upstream passage, the first branch passage, and the second branch passage are blocked, the upstream passage and the third branch passage are communicated with each other, and the first branch passage and the second branch passage are communicated with each other. The first state of communicating with the branch passage, the upstream passage, the second branch passage, and the third branch passage are blocked, and the upstream passage and the first branch passage are communicated with each other, and the second A first switching valve capable of switching to any one of the second states communicating the branch passage and the third branch passage, and
At the confluence position, the downstream passage, the second branch passage, and the third branch passage are blocked, the downstream passage and the first branch passage are communicated with each other, and the second branch passage and the third branch passage are communicated with each other. The downstream passage, the first branch passage, and the second branch passage are blocked from each other, and the downstream passage and the third branch passage are communicated with each other, and the first branch passage and the second branch passage are communicated with each other. An exhaust purification device further comprising a second switching valve capable of switching to any one of the fourth states communicating with the second branch passage. The exhaust gas purification device further includes a control device that controls the state of the first switching valve and the state of the second switching valve.
The control device is
When the filter is regenerated, the state of the first switching valve is controlled so as to be in the first state, and the state of the second switching valve is controlled so as to be in the third state.
According to claim 1, the state of the first switching valve is controlled so as to be in the second state when the filter is not regenerated, and the state of the second switching valve is controlled so as to be in the fourth state. The exhaust purification device described. 2. The control device switches the second switching valve after the switching of the first switching valve is completed when the switching of the first switching valve and the switching of the second switching valve are performed. Exhaust gas purification device described in.

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