JP2012225282A - Internal combustion engine and egr method of internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an internal combustion engine which reserves a mixture gas in a gas storage vessel, the mixture gas being prepared by mixing a part of exhaust gas with fresh air by using a gas compression device, and which temporarily supplies the mixture gas into a cylinder through a stored gas supply passage during a transition operation where the load is rapidly increased, and to provide an EGR (Exhaust Gas Recirculation) method of the internal combustion engine, the internal combustion engine and the EGR method enabling a part of the mixture gas to be prevented from leaking to an exhaust gas passage even when such a problem arises that an EGR valve disposed in an EGR passage is not completely closed.SOLUTION: The internal combustion engine is configured: to connect a stored gas supply passage and an intake passage via a flow passage switching device; to arrange the flow passage switching device disposed downstream from an EGR merging portion that is a merging portion of the EGR passage and the intake passage; and to provide a flow passage switching device that selects the stored gas supply passage or a passage upstream of the intake passage while a passage downstream of the intake passage is kept open.

Description

  The present invention relates to an internal combustion engine and an EGR method for an internal combustion engine that can increase the EGR rate by supplying mixed gas stored in a gas storage container into a cylinder during a transition period of the internal combustion engine.

  In EGR (exhaust gas recirculation) for reducing NOx (nitrogen oxide) in exhaust gas of an internal combustion engine such as a diesel engine, there are a high pressure EGR method and a low pressure EGR method in an internal combustion engine equipped with a supercharging system. In this high pressure EGR system, for example, as shown in FIG. 6, in an internal combustion engine 1X equipped with a high pressure EGR system, an EGR passage 17 is provided closer to the engine body 11 than the turbo-type supercharger 14, and the engine body The EGR gas Ge is recirculated from the 11 exhaust manifolds 11 b to the intake manifold 11 a via the EGR passage 17. In the low pressure EGR system, for example, as shown in FIG. 7, in the internal combustion engine 1Y provided with the low pressure EGR system, an EGR passage 17 is provided on the opposite side of the engine body 11 from the turbo-type supercharger 14. The EGR gas Ge is recirculated from the downstream side of the turbine 14b to the upstream side of the compressor 14a via the EGR passage 17.

  In any of these EGR systems, the MAF control system is generally used to control the amount of EGR gas. In this MAF control method, if the amount of fresh air (air amount) sucked into the cylinder of the engine without EGR is Mo and the amount of fresh air sucked into the cylinder by performing EGR is Me, it is recirculated. Since the EGR gas amount Megr is Megr = Mo−Me, the EGR gas amount Megr is controlled by controlling the fresh air amount Me based on the valve opening degree of the EGR valve 21 based on this.

  That is, based on the data map of the fresh air amount Me created by setting the fresh air amount Me for each engine operating state in advance using the engine rotational speed Ne and the fuel load Q as parameters, The target fresh air amount Met is calculated from the rotational speed Ne and the fuel load Q, and the actual fresh air amount Me is controlled to become the target fresh air amount Met, thereby controlling the EGR gas amount Megr. Yes.

  However, when a turbocharger is used, the exhaust gas energy (enthalpy) is used for supercharging, so it is impossible to eliminate the response delay (turbo lag) of the turbocharger. The MAF control method has the following problems due to the turbo lag. In a transient operation state in which the load increases rapidly due to the turbo lag, the supercharging pressure does not increase to the pressure set during steady operation, so the intake air amount of the engine decreases. In other words, even an engine with a turbo-type supercharger has the same intake air amount as a non-supercharged engine.

  Therefore, the target EGR amount set under the steady operation condition cannot be achieved, and as shown in FIG. 8, the NOx emission amount increases when performing a rapid transient operation. Further, in order to limit the amount of soot generated, smoke limit control is performed in which the amount of fuel input is suppressed within a region where the soot does not increase when the supercharging pressure does not rise above a certain level. As a result, as shown in FIGS. 9 and 10, there is a problem that the fuel injection amount Q and the air amount (Mo, Me) are both suppressed as indicated by dotted lines, and the power during acceleration is suppressed. For this reason, during transient operation in which the load increases rapidly during acceleration or the like, an increase in NOx emissions and a deterioration in fuel consumption occur.

  On the other hand, in the case of using a mechanical supercharger that performs supercharging by directly driving the supercharger by an engine crankshaft or the like, the delay in the supercharging response can be eliminated, but the engine speed is determined. However, there is a problem that fuel efficiency deteriorates because the amount of supercharging is determined regardless of the amount of fuel and the amount of work required for driving is large.

  As a countermeasure, in recent years, an internal combustion engine 1Z having a storage gas supply system as shown in FIG. 11 has been studied, and in this storage gas supply system, a part Gp of the exhaust gas G discharged from the internal combustion engine 1Z. The mixed gas C mixed with air Aa is compressed by a positive displacement compressor (exhaust compressor) 25 to increase the pressure, and the increased mixed gas C is stored in a gas storage container (pressure container) 27 to release electromagnetic waves in a transient state. The valve 36 is opened and the mixed gas C is discharged to the intake passage 12 downstream of the intake valve (intake throttle) 35 via the pressure regulating valve 29, whereby the amount of intake air into the cylinder of the internal combustion engine 1Z is supercharged. There has been proposed a supercharging control device that increases the same level as an attached engine, reduces NOx by the effect of EGR, and solves the problem of turbo lag (see, for example, Patent Document 1).

  When this storage gas supply system is adopted, the supercharging pressure is increased by releasing the gas mixture C pressurized during the transition into the intake passage 12 of the engine 1Z, thereby increasing the amount of air into the cylinder. Can increase the amount of fuel. As a result, acceleration performance is improved and soot discharge can be suppressed. Further, since the supercharging pressure is higher than the internal pressure of the exhaust manifold 11b, the pumping loss of the internal combustion engine 1Z is reduced, and the fuel efficiency can be improved.

  However, this storage gas supply system also has the following problems. That is, when the EGR valve 21 is opened when performing EGR, the intake pressure is larger than the internal pressure of the exhaust manifold 11b, so that part of the pressurized mixed gas C in the intake passage 12 escapes to the exhaust manifold 11b side. End up. For this reason, this storage gas supply system incorporates a control for completely closing the EGR valve 21 when the mixed gas C is supplied. However, the EGR valve 21 is completely closed due to contamination of the valve seat or the inclusion of foreign matter such as carbon particles. It may not be. When this problem is encountered, a part of the mixed gas C in the intake passage 12 escapes to the exhaust manifold 11 b side through the exhaust passage 13.

  If a part of the mixed gas C in the intake passage 12 escapes to the exhaust manifold 11b side, the amount of intake air into the cylinder of the engine is reduced, and supercharging is not sufficiently performed. There is a limit and the power of acceleration cannot be drawn out sufficiently.

JP 2011-21558 A

  The present invention has been made in view of the above situation, and its purpose is to use a gas compression device to store a mixed gas obtained by mixing a part of exhaust gas and air in a gas storage container, and the load is rapidly increased. In an internal combustion engine that temporarily supplies mixed gas into a cylinder during an increasing transient operation to suppress NOx emission during the transient operation and improve acceleration performance, the EGR valve provided in the EGR passage is incompletely blocked. An internal combustion engine and an EGR method for an internal combustion engine that can prevent a part of a mixed gas supplied from a gas storage container from leaking into an exhaust system passage even if a malfunction such as poor sealing occurs in the EGR valve Is to provide.

  In order to achieve the above object, an internal combustion engine of the present invention comprises an EGR passage for recirculating a part of exhaust gas of the internal combustion engine into the cylinder, and a mixture in which a part of the exhaust gas of the internal combustion engine and air are mixed. An internal combustion engine comprising: a gas compression device that compresses gas; a gas storage container that stores a mixed gas compressed by the gas compression device; and a gas storage supply passage that connects the gas storage container and an intake system passage. The intake system passage and the gas storage supply passage are connected via a passage switching device, and the flow passage switching device is disposed downstream of an EGR merging portion that is a merging portion of the EGR passage and the intake system passage. And the flow path switching device is configured to switch between the stored gas supply passage side and the upstream side of the intake system passage while the downstream side of the intake system passage is open. The intake system passage includes not only the intake passage but also an intake manifold.

  According to this configuration, in the transient operation of the internal combustion engine, the flow path in which the intake system passage and the stored gas supply passage join downstream of the EGR valve and downstream of the EGR merging portion where the EGR passage joins the intake system passage. Since the switching device is arranged, the flow switching device prevents the mixed gas supplied from the gas storage container from leaking to the exhaust system passage via the EGR passage even if a malfunction such as a sealing failure occurs in the EGR valve. it can. Therefore, even if a malfunction occurs in which the EGR valve provided in the EGR passage is incompletely closed, the mixed gas supplied from the gas storage container can be efficiently supplied into the cylinder without passing through the exhaust system passage. .

  In the internal combustion engine, the flow path switching device is configured by a three-way switching valve, or the flow path switching device is provided with an intake valve provided in the intake system passage and an open / close valve provided in the stored gas supply passage. By configuring with, the flow path switching device can be configured relatively easily.

  An EGR method for an internal combustion engine for achieving the above object compresses and stores a mixed gas obtained by mixing a part of exhaust gas in an exhaust system passage of the internal combustion engine with air, and in EGR, When the engine is not in a transient operation, a part of the exhaust gas of the internal combustion engine is recirculated into the cylinder via the EGR passage, and when the engine is in a transient operation, the internal gas is temporarily supplied to the intake system passage. In the engine EGR method, when the internal combustion engine is in a transient operation, the EGR gas from the EGR passage and the fresh air from the intake system passage are blocked by a flow path switching device, and only the mixed gas is The method is characterized in that the gas is supplied to a downstream side of an EGR merging portion, which is a merging portion of an EGR passage and the intake system passage.

  According to this method, during the transient operation of the internal combustion engine, the EGR gas and the fresh air are blocked by the flow path switching device downstream of the EGR valve and downstream of the EGR merging portion where the EGR passage merges with the intake system passage. Since only the mixed gas supplied from the gas storage container is supplied, the mixed gas leaks to the exhaust system passage via the EGR passage by the flow path switching device even if the EGR valve has a malfunction such as poor sealing. Can be prevented. Therefore, even if a malfunction occurs in which the EGR valve provided in the EGR passage is incompletely closed, the mixed gas supplied from the gas storage container can be efficiently supplied into the cylinder without passing through the exhaust system passage. .

  In the above EGR method for an internal combustion engine, the EGR gas and fresh air are shut off and the mixed gas is supplied by the flow path switching device constituted by a three-way switching valve, or the EGR gas and fresh air are shut off. And a method of supplying the mixed gas by the flow path switching device configured by the intake valve provided in the intake system passage and the on-off valve provided in the storage gas supply passage, the flow path is relatively easy. A switching device can be configured.

  According to the internal combustion engine and the EGR method of the internal combustion engine according to the present invention, EGR shortage caused by turbo lag during transient operation such as rapid acceleration can be resolved, NOx emission during transient operation can be reduced, and acceleration performance can be reduced. In addition, it is possible to improve and reduce PM, and even if the EGR valve is not fully closed due to problems such as biting of foreign matter, the mixed gas supplied from the gas storage container can enter the exhaust system passage. It is possible to prevent escape, and it is possible to reliably avoid a decrease in acceleration performance due to the escape of the mixed gas to the exhaust system passage side.

It is a figure showing composition of an internal-combustion engine of a 1st embodiment concerning the present invention. It is a figure which shows the structure of the internal combustion engine of 2nd Embodiment which concerns on this invention. It is a figure for demonstrating the drive of the positive displacement compressor for stored gas. It is a figure which shows the structure of the flow-path switching apparatus comprised by the three-way switching valve in the state by which the intake line was connected. It is a figure which shows the structure of the flow-path switching apparatus comprised by the three-way switching valve in the state by which the stored gas supply line was connected. It is a figure which shows the structure of the internal combustion engine of a high pressure EGR system of a prior art. It is a figure which shows the structure of the low pressure EGR type internal combustion engine of a prior art. It is a figure which shows the relationship between the change of a vehicle speed, and instantaneous NOx discharge | emission amount. It is a figure which shows the characteristic of the fuel injection quantity in a full load, and the movement at the time of transition. It is a figure which shows the response delay of the turbo supercharger at the time of transition, and the relationship of EGR. It is a figure which shows the structure of the internal combustion engine of a prior art.

  Hereinafter, an internal combustion engine and an EGR method for an internal combustion engine according to embodiments of the present invention will be described with reference to the drawings.

  As shown in FIG. 1, an engine (internal combustion engine) 1 according to a first embodiment of the present invention includes an intake passage 12 connected to an engine body 11, an intake manifold 11a, and an exhaust passage 13 connected to an exhaust manifold 11b. It is configured. The intake manifold 11a and the intake passage 12 form an intake system passage, and the exhaust manifold 11b and the exhaust passage 13 form an exhaust system passage.

  The intake passage 12 is provided with a compressor 14a of a turbocharger 14, and the exhaust passage 13 is provided with a turbine 14b of a turbocharger 14, a diesel particulate filter (DPF) device 15, and a NOx occlusion reduction type. A NOx purification catalyst 16 formed of a catalyst or the like is provided.

  Further, an EGR passage 17 is branched from the exhaust passage 13 on the upstream side of the turbine 14b, and merges with the intake passage 12 on the upstream side of the compressor 14a at the EGR merging portion 18. The EGR passage 17 is provided with a diesel particulate filter (DPF) device 19, an EGR cooler 20, and an EGR valve 21 from the upstream side.

  Further, an exhaust gas introduction passage 22 is provided so as to branch from the exhaust passage 13 on the downstream side of the NOx purification catalyst 16. The exhaust gas introduction passage 22 is provided with an EGR cooler 23 and a three-way valve 24, and the exhaust gas introduction passage 22 is formed by a mechanical positive displacement turbocharger (preferably a reciprocating type) or the like. It is connected to the. The gas compression device 25 is connected to a gas storage container 27 formed of a pressure container or the like by a compressed gas supply passage 26. The gas storage container 27 is connected to the intake passage 12 by a stored gas supply passage 28. The exhaust gas introduction passage 22, the compressed gas supply passage 26 and the stored gas supply passage 28 form a mixed gas system passage.

  As shown in FIG. 3, the gas compression device 25 transmits power from an axle 31 of a vehicle on which the engine 1 is mounted to a drive shaft of the gas compression device 25 via gears 32 and 33 and an electromagnetic clutch 34. When the electromagnetic clutch 34 is turned on and connected, the gas compression device 25 is driven, and the mixed gas C from the mixed gas system passages 22, 26, 28 is compressed and pressurized to be supplied to the gas storage container 27. And store. A pressure regulating valve 29 is disposed in the stored gas supply passage 28 to adjust the pressure of the mixed gas C supplied to the flow path switching device 30. At this time, it is preferable that the three-way valve 24 adjusts the amount of part Gp of the exhaust gas G and the amount of air Aa to keep the oxygen concentration in the mixed gas C stored in the gas storage container 27 substantially constant, Thereby, the control when performing EGR can be simplified.

  And in order to control said apparatus, the control apparatus 40 which controls the whole driving | operation of the engine 1 called an engine control unit (ECU) is provided, and the pressure in the gas storage container 27 and engine by this control apparatus 40 are provided. The rotational speed, the accelerator opening, and the like are detected, and the electromagnetic clutch 34 and the three-way valve 24 are controlled based on the detection result, and the amount (pressure) of the mixed gas C in the gas storage container 27, the exhaust gas Gp, and the air Aa The mixing ratio is adjusted and controlled.

  As shown in FIG. 1, when the gas storage device 27 is provided with an adjustment valve 27a for adjusting the maximum pressure inside the gas storage container 27 and the gas compression device 25 is driven, work always occurs. The adjustment valve 27a is adjusted as follows. 1 and 2, the regulating valve 27a is provided in the gas storage container 27, but the regulating valve 27a may be provided in the exhaust gas introduction passage 22 between the gas storage container 27 and the gas compression device 25.

  That is, the engine 1 compresses the EGR passage 17 for recirculating a part Ge of the exhaust gas G into the cylinder and the mixed gas C in which the part Gp of the exhaust gas G of the engine 1 and the air A are mixed. The compressor 25 includes a gas storage container 27 that stores the mixed gas C compressed by the gas compressor 25, and a gas storage supply passage 28 that connects the gas storage container 27 and the intake passage 12.

  The intake passage 12 and the stored gas supply passage 28 are connected via a flow path switching device 30. The flow path switching device 30 is disposed downstream of the EGR merging portion 18 that is a merging portion of the EGR passage 17 and the intake passage 12. The flow path switching device 30 is configured to switch between the stored gas supply passage 28 side and the upstream passage side of the intake passage 12 while the downstream passage side of the intake passage 12 is open.

  The flow path switching device 30 can be constituted by a three-way switching valve 30 as shown in FIGS. In addition, although not shown, the intake valve provided in the intake system passage 12 and the opening / closing valve provided in the stored gas supply passage 28 may be used. That is, in the case where the intake passage 12 is closed with an intake valve (intake throttle) or the like without using the three-way switching valve 30, an EGR merging portion 18 is provided upstream of the intake valve (not shown) to provide EGR gas. Ge is shut off in two stages by an EGR valve 21 and an intake valve (not shown).

  In the three-way switching valve 30 shown in FIGS. 4 and 5, the shutter 30c is moved by moving the rod 30b of the driving high-speed cylinder 30a by inserting the driving low-pressure air Ap and extracting the piston back surface air Ae. As shown in FIG. 4, the storage gas supply passage 28 side is closed to connect the upstream side 12a and the downstream side 12b of the intake passage 12, and as shown in FIG. 5, the upstream side 12a of the intake passage 12 is connected. The side is closed, and the stored gas supply passage 28 and the downstream side 12b of the intake passage 12 are communicated.

  Next, an engine (internal combustion engine) 1A according to a second embodiment of the present invention will be described. As shown in FIG. 2, in the engine 1A of the second embodiment, the EGR passage 17 branches from the exhaust passage 13 downstream of the NOx purification catalyst 16, and the exhaust gas introduction passage 22 branches from the EGR passage 17. The EGR passage 17 branches from the exhaust passage 13 upstream of the turbine 14 b of the turbocharger 14, and the exhaust gas introduction passage 22 branches from the exhaust passage 13 downstream of the NOx purification catalyst 15. This is different from the first embodiment. Other points are the same as in the first embodiment.

  That is, the exhaust gas Ge flowing into the EGR passage 17 is a part of the exhaust gas G before passing through the turbine 14b of the turbocharger 14 in the engine 1 of the first embodiment. On the other hand, in the engine 1A of the second embodiment, it is a part of the exhaust gas G after passing through the turbine 14b of the turbocharger 14. In other words, the engine 1 of the first embodiment employs the high pressure EGR method, and the engine 1A of the second embodiment employs the low pressure EGR method.

  Next, an EGR method for an internal combustion engine according to the present invention will be described. This EGR method for an internal combustion engine is a method that can be implemented by the internal combustion engine 1, 1 </ b> A or the like having the above-described configuration. This EGR method for an internal combustion engine compresses and stores a mixed gas C obtained by mixing a part Gp of the exhaust gas G in the exhaust passage (exhaust system passage) 13 of the engine (internal combustion engine) 1 and 1A with air Aa.

  At the same time, in the EGR, when the engine 1, 1A is not in a transient operation, a part Ge of the exhaust gas G of the engine 1, 1A is recirculated into the cylinder via the EGR passage 17, and the engine 1, 1A is in a transient state. During operation, the mixed gas C is temporarily supplied to the intake passage (intake system passage) 12.

  Further, when the engine 1, 1A is in a transient operation, the EGR gas Ge from the EGR passage 17 and the fresh air A from the intake passage 12 are shut off by the flow path switching device 30, and only the mixed gas C is removed from the EGR. The EGR merging portion, which is a merging portion between the passage 17 and the intake passage 12, is supplied downstream.

  In this EGR method for an internal combustion engine, the EGR gas Ge and the fresh air A are shut off and the mixed gas C is supplied by a flow path switching device 30 constituted by a three-way switching valve as shown in FIGS. Or an intake valve (not shown) provided in the intake passage (intake system passage) 12 and a storage gas supply passage 27 for shutting off the EGR gas Ge and fresh air A and supplying the mixed gas C. This is performed by the flow path switching device 30 constituted by a separate on-off valve (not shown).

  In these controls, the control device 40 is based on detected values such as engine rotational speed Ne, engine air amount (Mo, Me), engine fuel amount (fuel injection amount) Q, pressure inside the gas storage container 27, and the like. The pressure regulating valve 29, the EGR valve 21, and the flow path switching device 30 are controlled.

  According to the above-described internal combustion engine 1, 1A and internal combustion engine EGR method, EGR deficiency due to turbo lag can be resolved during transient operation such as rapid acceleration, and NOx emissions during transient operation can be reduced and accelerated. The performance can be improved and the PM can be reduced. Furthermore, even if the EGR valve 21 has a problem such as a foreign matter bite and the EGR valve 21 is not fully closed, the mixed gas supplied from the gas storage container 27 C can be prevented from escaping into the exhaust system passages 11b and 13, and a decrease in acceleration performance due to the escape of the mixed gas C to the exhaust system passages 11b and 13 can be reliably avoided.

  The internal combustion engine and the EGR method of the internal combustion engine of the present invention can prevent the mixed gas supplied from the gas storage container even if a malfunction such as a sealing failure that causes the EGR valve provided in the EGR passage to be completely closed occurs. Since it is possible to prevent a part of the gas from leaking into the exhaust system passage, the gas compression device is used to store a mixed gas in which a part of the exhaust gas and fresh air are mixed in the gas storage container, and the load increases rapidly. It can be used in an internal combustion engine mounted on a truck, a bus, a passenger car, etc. that temporarily supplies mixed gas into a cylinder during transient operation to suppress NOx emission during transient operation and improve acceleration performance.

1, 1A engine (internal combustion engine)
11 Engine body 11a Intake manifold (intake system passage)
11b Exhaust manifold (exhaust system passage)
12 Intake passage (intake system passage)
13 Exhaust passage (exhaust system passage)
14 Turbo-type supercharger 14a Compressor 14b Turbine 15, 19 Diesel particulate filter (DPF) device 16 NOx purification catalyst 17 EGR passage 18 EGR merging section 20, 23 EGR cooler 21 EGR valve 22 Exhaust gas introduction passage 24 Three-way valve 25 Gas Compressor 26 Compressed gas supply passage 27 Storage gas container 28 Storage gas supply passage 30 Three-way switching valve (channel switching device)
31 Vehicle axle 34 Electromagnetic clutch 35 Intake valve (intake throttle)
40 Control device A Fresh air Aa Air C Mixed gas G Exhaust gas Ge EGR gas Gp Part of exhaust gas

Claims (6)

An EGR passage for recirculating a portion of the exhaust gas of the internal combustion engine into the cylinder;
A gas compression device for compressing a mixed gas in which a part of the exhaust gas of the internal combustion engine and air are mixed;
A gas storage container for storing the mixed gas compressed by the gas compression device;
In the internal combustion engine provided with a storage gas supply passage connecting the gas storage container and the intake system passage,
While connecting the intake system passage and the stored gas supply passage through a flow switching device,
The flow path switching device is disposed on the downstream side of an EGR merging portion that is a merging portion of the EGR passage and the intake system passage,
The flow path switching device is configured to switch between the stored gas supply passage side and the upstream side of the intake system passage while the downstream side of the intake system passage is open. Internal combustion engine.   2. The internal combustion engine according to claim 1, wherein the flow path switching device comprises a three-way switching valve.   2. The internal combustion engine according to claim 1, wherein the flow path switching device includes an intake valve provided in the intake system passage and an on-off valve provided in the stored gas supply passage. In the EGR, a part of the exhaust gas in the exhaust system passage of the internal combustion engine is compressed and stored, and in EGR, when the internal combustion engine is not in a transient operation, a part of the exhaust gas of the internal combustion engine is passed through the EGR passage. In an EGR method for an internal combustion engine that temporarily recirculates the mixed gas to an intake system passage when the internal combustion engine is in a transient operation through recirculation in a cylinder via
When the internal combustion engine is in a transient operation, the EGR gas from the EGR passage and the fresh air from the intake system passage are shut off by a flow path switching device, and only the mixed gas is sent to the EGR passage and the intake system. An EGR method for an internal combustion engine, characterized in that the EGR method supplies to the downstream side of an EGR junction that is a junction with a passage.   5. The EGR method for an internal combustion engine according to claim 4, wherein the EGR gas and fresh air are shut off and the mixed gas is supplied by the flow path switching device constituted by a three-way switching valve.   The EGR gas and fresh air are shut off and the mixed gas is supplied by the flow path switching device including an intake valve provided in the intake system passage and an on-off valve provided in the stored gas supply passage. The EGR method for an internal combustion engine according to claim 4.

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