JP2010112207A - Exhaust gas purifier - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method and a system for an exhaust gas purification which can obtain a heat insulation effect of a catalyst at vehicle deceleration and can also secure the power of an exhaust brake when exhaust braking is necessary, so that both a role of the heat insulation of the catalyst and the securement of the power of the exhaust brake can be achieved, in an exhaust gas purification system of an internal combustion engine. <P>SOLUTION: A first exhaust throttle valve 17 is arranged between a branch of a bypass passage 19 detouring around an exhaust gas purifier 10 and the exhaust gas purifier 10, or at the upstream side of the branch, and an exhaust brake valve 20 is arranged in the bypass passage 19. In the case of normal travel, most of exhaust gas G flows through the exhaust gas purifier 10. When the power of the exhaust gas brake is not required at the deceleration, the exhaust brake valve 20 is opened and most of the exhaust gas G flows through the bypass passage 19, and when the power of the exhaust gas brake is required at the deceleration, the exhaust brake valve 20 is closed and most of the exhaust gas G flows through the bypass passage 19. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention is an internal combustion engine mounted on a vehicle, and an exhaust gas purification method and exhaust capable of obtaining an excellent heat retention effect by closing the exhaust brake valve in order to prevent the catalyst of the exhaust gas purification device from cooling when the vehicle is decelerated. More particularly, the present invention relates to an exhaust gas purification method and an exhaust gas purification system that can devise the structure of an exhaust system to achieve both the warming of the catalyst during deceleration and the function of the exhaust brake.

  In an internal combustion engine such as a diesel engine mounted on a vehicle, an exhaust gas purification device carrying a NOx purification catalyst, an oxidation catalyst, or the like is provided in order to purify exhaust gas discharged from the internal combustion engine. These catalysts cannot exhibit sufficient purification performance unless the temperature is higher than the activation temperature (light-off temperature) of the catalyst. Therefore, during the operation of the internal combustion engine, it is necessary to prevent the catalyst temperature from decreasing when the exhaust gas temperature decreases, such as during idle operation or deceleration operation, in order to improve the exhaust gas purification performance.

  In order to prevent the catalyst from cooling down during idling or when the vehicle is decelerating when the exhaust temperature decreases, the target intake air amount is reduced to reduce the intake amount, and the exhaust brake valve (exhaust brake throttle) is closed. As a result, the amount of exhaust gas discharged from the exhaust passage into the outside air is reduced, and the amount of heat discharged from the catalyst into the outside air via the exhaust gas is reduced. Thereby, the heat retention effect excellent with respect to the catalyst is acquired.

  For example, an exhaust gas purifying device is provided in an exhaust passage of an internal combustion engine mounted on a vehicle, and the exhaust temperature raising means is operated even when the continuous regeneration type DPF is regenerated, even when a stop idle state is entered during automatic traveling regeneration. When the stop of the vehicle is detected during the operation, the operation of the exhaust temperature raising means is continued and the exhaust throttle valve (exhaust brake valve) is closed. An exhaust gas purification system control method and an exhaust gas purification system that can efficiently maintain the exhaust gas temperature by opening the throttle valve and continuing the exhaust gas temperature raising means have been proposed (for example, Patent Document 1). reference).

However, in this heat retention method in the stationary idling state, the target intake air amount is lowered, so it is effective when the exhaust brake is not operated at the time of vehicle deceleration, but the exhaust brake needs to be operated. In this case, the exhaust brake force as a function of the original exhaust brake decreases due to a decrease in the flow rate of the exhaust gas serving as an exhaust gas for the exhaust brake, and the required exhaust brake force may not be exhibited. . That is, if this heat retention method is used as it is, there is a problem that it is difficult to ensure both exhaust brake force and prevention of catalyst cooling.
JP 2005-282545 A

  The present invention has been made in view of the above situation, and an object of the present invention is to provide an exhaust gas purification system including an exhaust gas purification device in an exhaust passage of an internal combustion engine. Exhaust gas purification that can obtain a heat retaining effect and can also ensure the exhaust brake force by the exhaust brake when the exhaust brake force is required, and can achieve both the role of catalyst heat retention and the securing of the exhaust brake force It is to provide a method and an exhaust gas purification system.

  An exhaust gas purification method for achieving the above object includes an exhaust gas purification device in an exhaust passage of an internal combustion engine, a bypass passage that bypasses the exhaust gas purification device, and a branch portion of the bypass passage. In the exhaust gas purification method of the exhaust gas purification system in which the first exhaust throttle valve is disposed between the exhaust gas purification device or upstream of the branch part and the exhaust brake valve is disposed in the bypass passage, When the valve is operated so that most of the exhaust gas flows through the gas gas purification device and no exhaust brake force is required during deceleration, the exhaust brake valve is opened and most of the exhaust gas is bypassed by the bypass. When the valve is operated to flow through the passage and exhaust brake force is required at the time of deceleration, the exhaust brake valve is closed and most of the exhaust gas is bypassed. A method characterized by a valve operated to flow the road.

  According to this method, in normal running, most of the exhaust gas is purified by passing through the exhaust gas purification device having the exhaust throttle valve. When decelerating, the exhaust gas does not pass through the exhaust gas purification device, but flows through the bypass side where the exhaust brake valve is located.However, when decelerating, the fuel is not injected, so the combustion gas is not discharged. Does not occur. Further, since the exhaust throttle valve is closed on the exhaust gas purification device side and the exhaust gas does not flow, a catalyst heat retention effect can be obtained. Further, when the exhaust brake force is not required at the time of deceleration, the exhaust brake valve is opened in the bypass passage, so that the exhaust brake force is not generated and the drivability (riding comfort) is hardly affected. On the other hand, when the exhaust brake force is required during deceleration, the exhaust brake force can be obtained because the exhaust brake valve is closed.

  The exhaust throttle valve is usually used to close the exhaust passage and lower the exhaust gas flow rate to raise the catalyst temperature, and the exhaust brake valve closes the exhaust passage and increases the pumping loss when the vehicle decelerates. Is used to increase the exhaust brake force.

  In the above exhaust gas purification method, the exhaust gas purification device further includes a filter device that collects particulate matter in the exhaust gas, and a second exhaust throttle valve is provided in the exhaust passage after joining the bypass passage. In the exhaust gas purification system arranged and configured, when the idling operation is performed and the filter device is regenerated, the second exhaust throttle valve is fully closed and the exhaust gas flows on the exhaust gas purification device side. Operate the valve.

  According to this method, the exhaust gas flows on the exhaust gas purification device side, but the second exhaust throttle valve after joining the exhaust passage is closed, so the flow rate of the exhaust gas passing through the filter device is necessary for regeneration of the filter device. Therefore, when the filter device is regenerated, the temperature of the exhaust gas can be increased efficiently so that the particulate matter collected in the filter device can be burned and removed, and the filter device can be regenerated efficiently.

  An exhaust gas purification system for achieving the above object includes an exhaust gas purification device in an exhaust passage of an internal combustion engine, a bypass passage that bypasses the exhaust gas purification device, and a branch of the bypass passage. In an exhaust gas purification system in which a first exhaust throttle valve is disposed between a part and the exhaust gas purification device or upstream of the branch part, and an exhaust brake valve is disposed in the bypass passage, in the case of normal running, the exhaust gas Is operated so that most of the exhaust gas flows through the exhaust gas purification device, and when the exhaust brake force is not required at the time of deceleration, the exhaust brake valve is opened and most of the exhaust gas flows through the bypass passage. If the exhaust brake force is required at the time of deceleration, the exhaust brake valve is closed and most of the exhaust gas passes through the bypass passage. Configured with a control device for a valve operating to flow.

  According to this configuration, during normal travel, most of the exhaust gas is purified by passing through the exhaust gas purification device having the exhaust throttle valve. At the time of deceleration, the exhaust gas purification device side closes the exhaust throttle valve and the exhaust gas does not flow, so that a catalyst heat retention effect can be obtained. Further, when the exhaust brake force is not required at the time of deceleration, the exhaust brake valve is opened in the bypass passage, so that the exhaust brake force is not generated and the drivability (riding comfort) is hardly affected. On the other hand, when the exhaust brake force is required during deceleration, the exhaust brake force can be obtained because the exhaust brake valve is closed.

  In the above exhaust gas purification system, when both the first exhaust throttle valve and the exhaust brake valve are fully closed, the flow rate of the exhaust gas in the first exhaust throttle valve is the same as that of the exhaust gas in the exhaust brake valve. If it is formed so as to be smaller than the flow rate, when both the exhaust brake valve and the first exhaust throttle valve are fully closed during deceleration, most of the exhaust gas flows through the exhaust brake valve side, that is, the bypass side with little pressure loss. As a result, it becomes difficult for the exhaust gas to flow to the exhaust gas purification device side, so that a catalyst heat retaining effect can be obtained.

  Further, in the above exhaust gas system, the exhaust gas purification device further includes a filter device that collects particulate matter in the exhaust gas, and a second exhaust throttle is provided in the exhaust passage after merging with the bypass passage. When the control device is idling and the filter device is regenerated, the second exhaust throttle valve is fully closed and the exhaust gas flows through the exhaust gas purification device side. It is configured to perform control.

  According to this configuration, the exhaust gas flows on the exhaust gas purification device side. However, since the second exhaust throttle valve after joining the exhaust passage is closed, the flow rate of the exhaust gas passing through the filter device is necessary for the regeneration of the filter device. Therefore, when the filter device is regenerated, the temperature of the exhaust gas can be increased efficiently so that the particulate matter collected in the filter device can be burned and removed, and the filter device can be regenerated efficiently.

  This exhaust gas purification method and exhaust gas purification system includes an oxidation catalyst (DOC), a three-way catalyst (TWC), a lean NOx reduction catalyst (LNT) such as a NOx storage reduction catalyst, a selective reduction catalyst (SCR), and a catalyst. This is very effective for an exhaust gas purification system that requires heat retention during deceleration in an exhaust gas purification device such as a DPF (diesel particulate filter).

  According to the exhaust gas purification method and the exhaust gas purification system of the present invention, in the exhaust gas purification system provided with the exhaust gas purification device in the exhaust passage of the internal combustion engine, the heat retention effect of the catalyst of the exhaust gas purification device during vehicle deceleration can be achieved. When the exhaust brake force is required, the exhaust brake force by the exhaust brake can be ensured.

  Hereinafter, an exhaust gas purification method and an exhaust gas purification system according to embodiments of the present invention will be described with reference to the drawings. FIG. 1 shows a configuration of an exhaust gas purification system 1 according to a first embodiment of the present invention. The exhaust gas purification system 1 includes an exhaust gas purification device 18 in an exhaust passage 16 of an engine (internal combustion engine) 10.

  The engine 10 of the exhaust gas purification system 1 includes an intake air amount sensor 12 (MAF sensor), a compressor 13b of a turbocharger 13, an intercooler 14, and an intake valve (intake throttle) 15 in an intake passage 11 connected to an intake manifold 10a. It has. The intake valve 15 adjusts the flow rate of fresh air A drawn into the intake passage 11.

  Further, the exhaust passage 16 connected to the exhaust manifold 10b includes a turbine 13b of the turbocharger 13, a first exhaust throttle valve 17, and an exhaust gas purification device 18. A bypass passage 19 that bypasses the first exhaust throttle valve 17 and the exhaust gas purification device 18 is provided, and the bypass passage 19 joins the exhaust passage 16 upstream of a silencer (not shown). An exhaust brake valve 17 is disposed upstream of the silencer in the bypass passage 19.

  Further, when both the first exhaust throttle valve 17 and the exhaust brake valve 20 are fully closed, the flow rate of the exhaust gas G in the first exhaust throttle valve 17 is smaller than the flow rate of the exhaust gas G in the exhaust brake valve 20. Formed as follows. A second exhaust throttle valve 21 is disposed in the downstream exhaust passage 16 where the bypass passage 19 has joined.

  The first and second exhaust throttle valves 17 and 21 and the exhaust brake valve 20 adjust the flow rate of the exhaust gas. Normally, the first and second exhaust throttle valves 17 and 21 are provided with the filter device 18b during idling. In this regeneration control, the exhaust passage 16 is closed to reduce the flow rate of the exhaust gas, thereby increasing the temperature of the exhaust gas and increasing the catalyst temperature. On the other hand, the exhaust brake valve 20 is used to increase the exhaust brake force by closing the exhaust passage 16 and increasing the pumping loss when the vehicle is decelerated.

  Further, the EGR passage 22 connecting the exhaust manifold 10b and the intake manifold 10a is provided with an EGR cooler 23 and an EGR valve 24. The EGR valve 24 adjusts the flow rate of the EGR gas Ge flowing through the EGR passage 22.

  The exhaust gas purification device 18 is composed of a catalyst device 18a and a filter device 18b. In order to maintain the purification performance of the exhaust gas G, the temperature of the supported catalyst is increased to a certain level equal to or higher than the catalyst activation temperature. It needs to be raised.

  The catalyst device 18a is configured by, for example, a three-way catalyst device (TWC), an oxidation catalyst device (DOC), a NOx storage reduction catalyst device (LNT), or a combination thereof. In the case of an oxidation catalyst device, an oxidation catalyst such as platinum is supported on a porous ceramic honeycomb structure carrier. This oxidation catalyst serves to oxidize HC and CO in the exhaust gas to purify the exhaust gas, and is supplied as a NOx reducing agent during NOx regeneration for restoring the NOx storage capacity of the NOx storage reduction catalyst 3 It functions to oxidize part of the HC and raise the temperature of the exhaust gas.

When the catalyst device 18a is a NOx occlusion reduction type catalyst device, the catalyst device 18a is formed by supporting an alkali metal or an alkaline earth metal together with a noble metal, and oxidizes NO in exhaust gas containing excess oxygen to form nitrate as a nitrate. It is adsorbed to NOx to purify NOx. The NOx occlusion reduction type catalyst stores NOx when the exhaust gas is lean air-fuel ratio, and releases the stored NOx when the exhaust gas is rich air-fuel ratio, and reduces the released NOx in a reducing atmosphere. Reduce.
The filter device 18b is composed of a DPF with a catalyst provided with a diesel particulate filter (DPF) for collecting particulate matter (PM) in the exhaust gas. The catalyst-attached DPF is formed of a monolith honeycomb wall flow type filter or the like in which the inlet and outlet of a porous ceramic honeycomb channel are alternately plugged. A catalyst such as platinum or cerium oxide is supported on the filter. By this DPF with catalyst, PM in the exhaust gas is collected by the porous ceramic wall.

  Further, in order to measure the temperature, NOx, oxygen concentration, etc. of the exhaust gas G, a temperature sensor (not shown) and a NOx and λ (excess air ratio) sensor (not shown) are provided in the exhaust passage 16 and the exhaust gas purification device 18. It is arranged. A control device (not shown) is provided that inputs measurement values of these sensors and data necessary for operation control of the engine 10 and performs engine operation state, exhaust gas purification control and regeneration control of the exhaust gas purification system 1. ing. This control device is a control device called an ECU (engine control unit). In the control related to the exhaust gas purification method of the present invention, the intake valve 15 is based on the data from the engine 10 and the detected value from the intake air amount sensor 12. The first exhaust throttle valve 17, the exhaust brake valve 20, the second exhaust throttle valve 21, and the EGR valve 24 are controlled.

  With this configuration, the exhaust gas purification device 18 is provided in the exhaust passage 16 of the engine 10, and a bypass passage 19 that bypasses the exhaust gas purification device 18 is provided, and between the branch portion of the bypass passage 19 and the exhaust gas purification device. The exhaust throttle valve (exhaust throttle) 17 is disposed, and the exhaust brake valve (exhaust brake) 20 is disposed in the bypass passage 19.

  Next, the exhaust gas purification method of the present invention will be described. In this exhaust gas purification method, during normal running, the first exhaust throttle valve 17 is fully opened, the exhaust brake valve 20 is fully closed, and the second exhaust throttle valve 21 is fully opened. Most of the exhaust gas is allowed to flow through the exhaust gas purification device. As a result, most of the exhaust gas G is purified by passing through the exhaust gas purification device 18 having the first exhaust throttle valve 17. In addition, when there is a leak of the exhaust gas G from the exhaust brake valve 20, an additional valve that substantially completely shuts off the flow rate may be installed.

  Further, when exhaust braking force is not required when the vehicle is decelerated, that is, when the operation switch of the exhaust brake provided in the driver's seat is OFF, the first exhaust throttle valve 17 is fully closed and the exhaust brake The valve operation is performed so that the valve 20 is fully opened and the second exhaust throttle valve 21 is fully opened, so that most of the exhaust gas flows through the bypass passage.

  As a result, the exhaust gas G flows through the bypass side 19 with the exhaust brake valve 20 without passing through the exhaust gas purification device 18, but since no fuel is injected during deceleration, combustion gas is not discharged. The problem does not occur. Further, since the first exhaust throttle valve 17 is closed and the exhaust gas G does not flow on the exhaust gas purification device 18 side, a catalyst heat retention effect can be obtained. Further, since the exhaust brake valve 20 of the bypass passage 19 is opened, no exhaust brake force is generated and there is almost no influence on drivability (riding comfort).

  When the exhaust brake force is required at the time of deceleration, that is, when the exhaust brake operation switch provided in the driver's seat is ON, the first exhaust throttle valve 17 is fully closed and the exhaust brake valve 20 is fully closed and the second exhaust throttle valve 21 is fully opened so that most of the exhaust gas G flows through the bypass passage 19.

  The exhaust gas G does not pass through the exhaust gas purification device 18 and most of the exhaust gas G flows through the bypass side 19 with the exhaust brake valve 20 with a small pressure loss. However, since fuel is not injected during deceleration, the combustion gas is discharged. As a result, there is no problem in exhaust gas countermeasures. Further, since the first exhaust throttle valve 17 is closed and the exhaust gas G does not flow on the exhaust gas purification device 18 side, a catalyst heat retention effect can be obtained. Furthermore, since the exhaust brake valve 20 is closed, an exhaust brake force can be obtained.

  Further, during the idling operation and the regeneration control of the filter device 18b, the first exhaust throttle valve 17 is fully closed, the exhaust brake valve 20 is fully opened, and the second exhaust throttle valve 21 is fully closed. Then, the valve is operated so that the exhaust gas G flows through the exhaust gas purification device 18 side.

  As a result, the exhaust gas G flows on the exhaust gas purification device 19 side, but since the second exhaust throttle valve 21 after merging in the exhaust passage 16 is closed, the flow rate of the exhaust gas G passing through the filter device 18b is reduced. Can be reduced to the minimum flow rate required for regeneration of the filter device 18b, and the particulate matter (PM) collected in the filter device 18b can be burned and removed efficiently by efficiently raising the temperature of the exhaust gas G when the filter device 18b is regenerated. The filter device 18b can be regenerated.

  Next, an exhaust gas purification system 1 according to a second embodiment of the present invention as shown in FIG. 2 will be described. The exhaust gas purification system 1 includes an exhaust gas purification device 18A in an exhaust passage 16 of an engine (internal combustion engine) 10.

  The exhaust gas purifying device 18A of the second embodiment is a straight catalyst canning type in which the exhaust gas purifying device 18 of the first embodiment has a catalyst device 18a and a filter device 18b arranged in a straight line. On the other hand, it is different in that it is a folded catalyst canning type arranged in a U shape. By adopting this configuration, the bypass passage 19A of the second embodiment can be made significantly shorter than the bypass passage 19 of the first embodiment.

  The positional relationship among the first exhaust throttle valve 17A, the exhaust brake valve 20A, and the second exhaust throttle valve 21A of the second embodiment is the same as that of the first exhaust throttle valve 17, the exhaust brake valve 20, and the second embodiment. The positional relationship of the second exhaust throttle valve 21 is the same, and the exhaust gas purification method in the second embodiment is the same as the exhaust gas purification method in the first embodiment.

  Next, an exhaust gas purification system 1 according to a third embodiment of the present invention as shown in FIG. 3 will be described. The exhaust gas purification system 1 includes an exhaust gas purification device 18B in an exhaust passage 16 of an engine (internal combustion engine) 10.

  The exhaust gas purification device 18B of the third embodiment is the same as the exhaust gas purification device 18A of the second embodiment, but the first exhaust throttle valve 17B is branched between the exhaust passage 16 and the bypass passage 19B. In the first embodiment, the first exhaust throttle valve 17A is disposed between the branch portion of the bypass passage 19A and the exhaust gas purifying device 18A. Is different. With this configuration, the first exhaust throttle valve 17B can be easily arranged in the third embodiment.

  The positional relationship of the first exhaust throttle valve 17B of the third embodiment is the positional relationship of the first exhaust throttle valve 17 of the first embodiment, and the first exhaust throttle valve 17A of the second embodiment. Therefore, in the third embodiment, the valve operation for flowing the exhaust gas is different from those in the first and second embodiments.

  In the exhaust gas purification method of the third embodiment, in normal running, the first exhaust throttle valve 17B is fully closed, the exhaust brake valve 20B is fully opened, and the second exhaust throttle valve 21B is fully opened. The valve is operated so that most of the exhaust gas flows through the exhaust gas purification device.

  Further, when the exhaust braking force is not required at the time of deceleration of the vehicle, the valve operation for fully opening the first exhaust throttle valve 17B, fully opening the exhaust brake valve 20B, and fully opening the second exhaust throttle valve 21B is performed. As a result, most of the exhaust gas flows through the bypass passage. When exhaust braking force is required during deceleration, the first exhaust throttle valve 17 is fully opened, the exhaust brake valve 20 is fully closed, and the second exhaust throttle valve 21 is fully opened. Thus, most of the exhaust gas G flows through the bypass passage 19.

Further, during the idle operation and the regeneration control of the filter device 18b, the first exhaust throttle valve 17B is fully closed, the exhaust brake valve 20B is fully opened, and the second exhaust throttle valve 21B is fully closed. Then, the valve is operated so that the exhaust gas G flows through the exhaust gas purification device 18 side.
By these valve operations, the flow of the exhaust gas G of the first and second embodiments can be realized, so that the same effect as the exhaust gas purification method of the first and second embodiments can be obtained.

  According to the exhaust gas purification method and the exhaust gas purification system 1 configured as described above, during normal traveling, the valve is operated so that most of the exhaust gas G flows through the exhaust gas purification devices 18, 18A, 18A, and the speed is reduced. If the exhaust brake force is not needed at the time, the exhaust brake valve 20, 20A, 20B is opened, and the valve is operated so that most of the exhaust gas G flows through the bypass passage 19, and the exhaust brake force is reduced during deceleration. If necessary, the exhaust brake valves 20, 20 </ b> A, 20 </ b> B can be closed and the valve operation can be performed so that most of the exhaust gas G flows through the bypass passages 19, 19 </ b> A, 19 </ b> B.

  Therefore, in the exhaust gas purification system 1 provided with the exhaust gas purification devices 18, 18A, 18A in the exhaust passage 16 of the engine 10, the heat retention effect of the catalyst of the exhaust gas purification devices 18, 18A, 18A during vehicle deceleration can be obtained. In addition, when the exhaust brake force is required, the exhaust brake force by the exhaust brake can be secured.

It is a figure which shows the structure of the exhaust-gas purification system of 1st Embodiment which concerns on this invention. It is a figure which shows the structure of the circumference | surroundings of the exhaust-gas purification apparatus of 2nd Embodiment which concerns on this invention. It is a figure which shows the surrounding structure of the exhaust-gas purification apparatus of 3rd Embodiment which concerns on this invention.

Explanation of symbols

1 Exhaust gas purification system 10 Engine (internal combustion engine)
16 Exhaust passage 17, 17A, 17B First exhaust throttle valve 18, 18A, 18A Exhaust gas purification device 18a Catalyst device 18b Filter device 19, 19A, 19B Bypass passage 20, 20A, 20B Exhaust brake valve 21, 21A, 21B Second Exhaust throttle valve G Exhaust gas

Claims (5)

An exhaust gas purification device is provided in the exhaust passage of the internal combustion engine, and a bypass passage that bypasses the exhaust gas purification device is provided, and between the branch portion of the bypass passage and the exhaust gas purification device or upstream of the branch portion. In the exhaust gas purification method of the exhaust gas purification system, wherein the first exhaust throttle valve is an exhaust brake valve disposed in the bypass passage,
In the case of normal running, the valve is operated so that most of the exhaust gas flows through the gas purification device. When the exhaust brake force is not required during deceleration, the exhaust brake valve is opened and the exhaust gas is opened. When the valve is operated so that most of the exhaust gas flows through the bypass passage and exhaust brake force is required at the time of deceleration, the exhaust brake valve is closed and most of the exhaust gas flows through the bypass passage. An exhaust gas purification method characterized by operating a valve.   Further, the exhaust gas purification device includes a filter device that collects particulate matter in the exhaust gas, and an exhaust gas configured by arranging a second exhaust throttle valve in the exhaust passage after the bypass passage is joined. In the purification system, when the idling operation is performed and the filter device is regenerated, the second exhaust throttle valve is fully closed, and the valve operation is performed so that the exhaust gas flows through the exhaust gas purification device side. The exhaust gas purification method according to claim 1. An exhaust gas purification device is provided in the exhaust passage of the internal combustion engine, and a bypass passage that bypasses the exhaust gas purification device is provided, and between the branch portion of the bypass passage and the exhaust gas purification device or upstream of the branch portion. In the exhaust gas purification system in which the first exhaust throttle valve is provided with an exhaust brake valve in the bypass passage,
In the case of normal running, the valve is operated so that most of the exhaust gas flows through the exhaust gas purification device. When the exhaust brake force is not required at the time of deceleration, the exhaust brake valve is opened and the exhaust gas is opened. When the valve is operated so that most of the exhaust gas flows through the bypass passage and exhaust brake force is required at the time of deceleration, the exhaust brake valve is closed and most of the exhaust gas flows through the bypass passage. An exhaust gas purification system comprising a control device for operating a valve.   The exhaust gas flow rate in the first exhaust throttle valve is smaller than the exhaust gas flow rate in the exhaust brake valve when both the first exhaust throttle valve and the exhaust brake valve are fully closed. The exhaust gas purification system according to claim 3 or 4, characterized in that:   Furthermore, the exhaust gas purification device includes a filter device that collects particulate matter in the exhaust gas, and a second exhaust throttle valve is disposed in the exhaust passage after the bypass passage is joined, and the control device includes: 2. The control for performing valve operation so that the second exhaust throttle valve is fully closed and the exhaust gas flows through the exhaust gas purification device is performed during idle operation and regeneration of the filter device. The exhaust gas purification system according to 3 or 4.

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