JP2013194611A - Engine control device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an engine control device in which a rotating speed of a compressor can be estimated accurately according to a simple method regardless of the presence/absence and introduction quantity of an EGR gas.SOLUTION: An engine control device includes an acquisition means, a storage means and an estimation means. At a downstream side from a connecting part of an intake pipe 11 and EGR piping 13 and a compressor 16a, the acquisition means acquires an intake density correlation value correlated with an intake density within the intake pipe 11. The storage means stores a correlation between an intake density correlation value prepared beforehand and a rotating speed of the compressor 16a. The estimation means estimates the rotating speed of the compressor 16a on the basis of the intake density correlation value acquired by the acquisition means and the correlation stored in the storage means.

Description

  The present invention relates to an engine control device including a supercharger and an EGR device.

  The number of revolutions of the supercharger (the number of revolutions of the compressor) is an important index for the protection of the supercharger and the engine and the control of the engine. If the rotational speed of the compressor becomes too high, the turbocharger and the engine may be damaged, and therefore it is necessary to limit the rotational speed of the compressor. Further, since the rotation speed of the compressor is an index indicating the supercharging state of the gas, the rotation speed of the compressor may be used for engine control.

  Therefore, it is desirable to accurately acquire the rotation speed of the compressor. However, it is not preferable to provide a dedicated rotation sensor for detecting the rotation speed of the compressor because the cost increases.

  Therefore, in Patent Document 1, the temporary compressor rotational speed in the steady state is calculated from the intake air amount-supercharging pressure-compressor rotational speed steady relationship, the supercharging pressure acquisition value, and the in-cylinder intake air amount, and further, the temporary compressor rotational speed is calculated. The number of rotations of the compressor in the actual operating state is estimated by correcting the number.

  Further, in Patent Document 2, the compressor rotational speed is calculated from the correlation between the air density introduced into the compressor and the compressor rotational speed and the acquired air density. Further, the compressor rotational speed is calculated from the correlation between the intake pressure ratio (supercharging pressure / atmospheric pressure) and the compressor rotational speed and the acquired intake pressure ratio.

Japanese Patent No. 4671068 JP 2011-185263 A

  However, in the case of Patent Document 1, introduction of EGR gas is not considered. When EGR gas is introduced, a deviation occurs in the correlation between the supercharging pressure, the intake air amount, and the compressor rotational speed. Therefore, when the compressor is installed in an engine that uses EGR gas, the rotational speed estimation method of Patent Document 1 is not suitable for estimating the rotational speed of the compressor.

  On the other hand, in the case of Patent Document 2, the correlation data between the air density and the compressor rotational speed or the correlation data between the intake pressure ratio and the compressor rotational speed for each of the operation of the EGR device and the non-operation of the EGR device. Are switched and used in accordance with the state of use of the EGR gas. Therefore, there is a possibility that the collection of correlation data becomes complicated. Furthermore, when the amount of EGR gas changes, there is a possibility that it cannot be estimated accurately.

  The present invention has been made in view of the above circumstances. An object of the present invention is to provide an engine control device capable of accurately estimating the rotation speed of a compressor by a simple method regardless of the presence or absence and the introduction amount of EGR gas.

  In order to solve the above-mentioned problem, the invention according to claim 1 is a supercharger including a compressor installed in an intake pipe of an engine and a turbine arranged in an exhaust pipe of the engine, the intake pipe, and the exhaust. An engine control device for controlling an engine, comprising an EGR device including an EGR pipe connected to a pipe and recirculating a part of the exhaust gas in the exhaust pipe to the intake pipe as EGR gas, An acquisition means for acquiring an intake density correlation value correlated with the density of the intake air in the intake pipe downstream of the connection portion with the EGR pipe and the compressor, the intake density correlation value created in advance and the compressor Based on the storage means storing the correlation with the rotational speed, the intake density correlation value acquired by the acquisition means, and the correlation stored in the storage means. There are, and a estimation unit that estimates a rotation speed of the compressor.

  According to the first aspect of the present invention, when the EGR device is operated, intake air in which air compressed by the compressor and EGR gas recirculated from the exhaust pipe to the intake pipe is mixed is supplied to the engine. Further, when the EGR device is not operated, the air compressed by the compressor is supplied to the engine as intake air.

  It is known that there is a correlation between the intake pressure (supercharging pressure) and the rotation speed of the compressor. However, the correlation between the intake pressure and the rotational speed of the compressor differs between when the EGR device is operating and when the EGR device is not operating. The present inventor has found that the cause of the difference in correlation between when the EGR device is operated and when the EGR device is not operated is a change in intake air temperature due to the introduction of EGR gas. Furthermore, the present inventor has determined whether or not there is EGR gas between the intake air density correlation value (a value having a correlation with the intake air density) considering the change in intake air temperature due to the introduction of EGR gas, and the rotation speed of the compressor, and It was found that there was a strong correlation regardless of the amount introduced. That is, the present inventors have found that the compressor rotational speed can be accurately estimated by using the correlation between the intake density correlation value prepared in advance and the compressor rotational speed.

  According to the above configuration, the rotational speed of the compressor is estimated based on the intake air density correlation value acquired by the acquisition means and the correlation between the intake air density correlation value created in advance and the rotational speed of the compressor. Therefore, regardless of the presence or absence of EGR gas and the introduction amount, the rotation speed of the compressor can be accurately estimated by a simple method.

The block diagram of an engine system. The figure which shows the relationship between the intake pressure and the rotation speed of the compressor (without EGR). The figure which shows the relationship between intake pressure and the rotation speed of a compressor. The figure which shows the relationship between an intake density correlation value and the rotation speed of a compressor. The flowchart which shows the process sequence which protects a supercharger. The flowchart which shows the subroutine which estimates the rotation speed of a compressor. The modification of an EGR apparatus.

  Hereinafter, an embodiment embodied in a diesel engine will be described with reference to the drawings. First, the configuration of the engine system will be described with reference to FIG.

  The engine 10 includes an intake pipe 11, a combustion chamber 15 connected to the intake pipe 11, an exhaust pipe 12 connected to the combustion chamber 15, and a fuel injection valve 14 provided so as to protrude into the combustion chamber 15. It has. The air sucked into the intake pipe 11 flows into the combustion chamber 15 through the intake pipe 11 and is compressed in the combustion chamber 15 to become a high temperature. When fuel is injected from the fuel injection valve 14 into the combustion chamber 15 filled with high-temperature intake air, the fuel self-ignites and burns. Exhaust gas generated at this time is discharged to the outside of the engine 10 through the exhaust pipe 12. The fuel injection valve 14 is operated by an ECU 30 (an electronic control device) described later according to the operating state of the engine 10. Thereby, the fuel injection amount is controlled.

  A supercharger 16 is provided from the intake pipe 11 to the exhaust pipe 12. The supercharger 16 includes a compressor 16 a installed in the intake pipe 11 and a turbine 16 b installed in the exhaust pipe 12. The turbine 16b is driven by exhaust flow velocity energy. The compressor 16a is driven coaxially with the turbine 16b and compresses the sucked air. Thereby, the air flowing into the combustion chamber 15 is supercharged, and the charging efficiency is improved. When the supercharger 16 is a variable nozzle supercharger, the nozzle is operated by the ECU 30 according to the operating state of the engine 10.

  In the intake pipe 11, an intercooler 17 is installed downstream of the compressor 16 a, and a throttle valve 25 is installed downstream of the intercooler 17. The intercooler 17 cools the air compressed by the compressor 16a to reduce the volume. Thereby, the charging efficiency of the air flowing into the combustion chamber 15 is further improved. The throttle valve 25 is opened and closed according to the operating state of the engine 10 and adjusts the flow rate of air flowing into the combustion chamber 15.

  The exhaust pipe 12 is provided with a purification device 18 for purifying exhaust gas downstream of the turbine 16b. Examples of the purification device 18 include a DPF (Diesel Particulate Filter) for collecting PM (particulate matter) in the exhaust, a NOx catalyst for purifying NOx (nitrogen oxide) in the exhaust, and HC in the exhaust. There are oxidation catalysts for purifying (hydrocarbon) and CO (carbon monoxide).

  The engine 10 includes an EGR device 20 that includes an EGR pipe 13 and an EGR valve 19. The EGR device 20 recirculates a part of the exhaust gas in the exhaust pipe 12 as EGR gas to the intake pipe 11 through the EGR pipe 13. Thereby, the combustion temperature of the combustion chamber 15 is suppressed and generation | occurrence | production of NOx is reduced.

  The EGR pipe 13 branches from an upstream portion of the exhaust pipe 12 relative to the turbine 16 b and is connected to the intake pipe 11 at a downstream portion of the intake pipe 11 relative to the throttle valve 25. Therefore, the exhaust gas upstream of the turbine 16b in the exhaust pipe 12 is introduced into the intake pipe 11 (high pressure EGR). At that time, it is possible to assist the introduction of EGR gas by controlling the throttle valve 25 to the closed side in the intake pipe 11.

  The EGR valve 19 is attached to the EGR pipe 13 and opens and closes the flow path of the EGR pipe 13. As a result, the flow area of the EGR pipe 13 is adjusted, and the amount of EGR gas introduced is adjusted. When the EGR device 20 is in operation, an amount of EGR gas corresponding to the opening of the EGR valve 19 is introduced. On the other hand, when the EGR device 20 is not in operation, the EGR valve 19 is fully closed, and the amount of EGR gas introduced is zero. The opening and closing of the EGR valve 19 is operated by the ECU 30 according to the operating state of the engine 10.

  The EGR device 20 may include an EGR cooler (not shown). When the EGR cooler is installed in the EGR pipe 13, the EGR gas is cooled by the EGR cooler and the volume is reduced. Thereby, the charging efficiency of the intake air flowing into the combustion chamber 15 is improved.

  When the EGR device 20 is in operation, a mixture of air that has passed through the throttle valve 25 and EGR gas that is recirculated through the EGR pipe 13 is filled into the combustion chamber 15 as intake air. On the other hand, when the EGR device 20 is not in operation, the air that has passed through the throttle valve 25 is filled into the combustion chamber 15 as intake air. A pressure sensor 21 and a temperature sensor 22 that detect the state of the intake air are provided in the intake pipe 11 on the downstream side of the compressor 16 a and the connection portion between the intake pipe 11 and the EGR pipe 13. The pressure sensor 21 and the temperature sensor 22 measure the pressure and temperature of the intake air, respectively. In the present embodiment, the pressure sensor 21 and the temperature sensor 22 are included in the acquisition unit.

  Further, the engine 10 detects the operation amount of the accelerator pedal 32 by the driver or the crank sensor 23 that detects the rotation speed of the crankshaft 31 that is the output shaft of the engine 10 as a sensor that detects the operating state of the engine 10. An accelerator sensor 24 and the like are provided. In the present embodiment, the crank sensor 23 corresponds to detection means.

  The detection values of the various sensors are input to the ECU 30. The ECU 30 is mainly configured by a microcomputer including a CPU (central processing unit), a ROM, and a RAM (storage device), and executes various control programs stored in the ROM. Further, the ECU 30 operates the EGR valve 19 and the fuel injection valve 14 based on detection values of various sensors. In the present embodiment, the ECU 30 corresponds to an engine control device, storage means, and estimation means.

  Next, estimation of the rotation speed Ncmp of the compressor 16a will be described. FIG. 2 shows the relationship between the intake pressure (supercharging pressure) and the rotation speed Ncmp of the compressor 16a per minute when no EGR gas is introduced. Each point in the figure is obtained by changing the rotational speed Ne of the engine 10 per minute to 1000 rpm, 1500 rpm, 2000 rpm, 2500 rpm, and 3000 rpm, and obtaining the relationship between the intake pressure and the rotational speed Ncmp of the compressor 16a. . As shown in the drawing, each point is on one curve for each rotation speed Ne of the engine 10. That is, at each rotation speed Ne of the engine 10, there is a correlation between the intake pressure and the rotation speed Ncmp of the compressor 16a.

  FIG. 3 shows the relationship between the intake pressure and the rotational speed Ncmp of the compressor 16a when the rotational speed Ne of the engine 10 is 2000 rpm and EGR gas is introduced and when EGR gas is not introduced. When no EGR gas is introduced, a correlation similar to that in FIG. 2 is observed between the intake pressure and the rotation speed Ncmp of the compressor 16a. On the other hand, even when EGR gas is introduced, there is a correlation between the intake pressure and the rotation speed Ncmp of the compressor 16a. However, the curve indicating the correlation in the presence of EGR gas is deviated from the curve indicating the correlation in the absence of EGR gas. Furthermore, this deviation increases as the amount of EGR gas introduced increases. That is, the correlation between the intake pressure and the rotation speed Ncmp of the compressor 16a varies depending on the presence / absence of the EGR gas and the introduction amount.

  The present inventor investigated the cause of the change in correlation depending on the presence or absence of the EGR gas and the amount of introduction, and found that the change in the intake air temperature caused by the introduction of the EGR gas into the intake pipe 11 is the cause. Obtained. Further, the present inventor has a strong correlation between the intake density correlation value considering the change in the intake air temperature due to the introduction of the EGR gas and the rotation speed Ncmp of the compressor 16a regardless of the presence or absence of the EGR gas and the introduction amount. The knowledge that there is.

  FIG. 4 shows the relationship between the intake density correlation value and the rotational speed Ncmp of the compressor 16a. Each point is obtained by changing the rotational speed Ne of the engine 10 to 1500 rpm, 2000 rpm, and 2500 rpm, and obtaining the relationship between the intake density correlation value and the rotational speed Ncmp of the compressor 16a. When the rotational speed Ne of the engine 10 is set to 1500 rpm and 2500 rpm, the relationship between the intake density correlation value and the rotational speed Ncmp of the compressor 16a is obtained for the case where EGR gas is introduced and the case where no EGR gas is introduced. Yes. When the rotation speed Ne of the engine 10 was 2000 rpm, the EGR gas rate of intake air was changed in four ways by changing the nozzle opening of the variable nozzle supercharger, including the case where no EGR gas was introduced. In some cases, the relationship between the intake density correlation value and the rotational speed Ncmp of the compressor 16a is obtained.

  As shown in the figure, when the rotational speed Ne of the engine 10 is 1500 rpm, each point is substantially on one curve regardless of the presence or absence of EGR gas. Even when the rotational speed Ne of the engine 10 is 2500 rpm, it is on a curve different from 1500 rpm, but each point is on almost one curve regardless of the presence or absence of EGR gas. Further, when the rotational speed Ne of the engine 10 is 2000 rpm, it is on a curve different from 1500 rpm and 2500 rpm, but each point is on almost one curve regardless of the presence or absence of the EGR gas and the introduction amount. That is, at each rotation speed Ne of the engine 10, there is a strong correlation between the intake density correlation value and the rotation speed Ncmp of the compressor 16a regardless of the presence or absence and the introduction amount of EGR gas.

  Therefore, if the correlation between the intake density correlation value created in advance and the rotation speed Ncmp of the compressor 16a is used, the rotation speed Ncmp of the compressor 16a can be accurately estimated regardless of the presence or absence of the EGR gas and the introduction amount. Furthermore, if the correlation between the intake air density correlation value and the rotation speed Ncmp of the compressor 16a is created for each rotation speed Ne of the engine 10, the rotation speed Ncmp of the compressor 16a is estimated even if the rotation speed Ne of the engine 10 is changed. it can. The correlation created in advance is stored in the storage device of the ECU 30.

  Hereinafter, a processing procedure for estimating the rotation speed Ncmp of the compressor 16a and protecting the supercharger 16 based on the estimated rotation speed Ncmp will be described with reference to the flowcharts of FIGS. FIG. 5 is a main routine for executing processing for protecting the supercharger 16. This process is periodically and repeatedly executed by the ECU 30.

  First, in S1, an upper limit value Nlim of the rotation speed of the compressor 16a is determined. The upper limit value Nlim may be a maximum allowable value that does not cause the turbocharger 16 to fail.

  Next, in S2, a subroutine for estimating the rotation speed Ncmp of the compressor 16a is executed. FIG. 6 is a subroutine for estimating the rotation speed Ncmp of the compressor 16a. In this subroutine, first, the rotational speed Ne of the engine 10 is detected by the crank sensor 23 (S21).

  Subsequently, in the intake pipe 11, the intake pressure P of the intake air existing downstream of the connecting portion of the intake pipe 11 and the EGR pipe 13 and the compressor 16a is measured by the pressure sensor 21 (S22). Further, the intake air temperature T of the intake air existing in the same portion of the intake pipe 11 is measured by the temperature sensor 22 (S23). Then, the intake pressure P measured by the pressure sensor 21 is divided by the intake air temperature T measured by the temperature sensor 22 to calculate P / T. The calculated P / T is a value having a correlation with the density of the intake air, as can be seen from the gas state equation PV = nRT. The calculated P / T is set as an intake air density correlation value (S24).

  Further, in S25, the correlation between the intake density correlation value P / T and the rotation speed Ncmp of the compressor 16a, which is created in advance for each rotation speed Ne of the engine 10, is read from the storage device of the ECU 30. Then, based on the detected rotation speed Ne of the engine 10, the acquired intake air density correlation value P / T, and the read correlation, the rotation speed Ncmp of the compressor 16a is estimated. Thereafter, the processing of this subroutine is terminated, and the process returns to S3 of the main subroutine.

  In S3, it is determined whether or not the estimated rotation speed Ncmp of the compressor 16a is larger than the upper limit value Nlim. When the rotation speed Ncmp of the compressor 16a is equal to or lower than the upper limit value Nlim (No), this process is terminated as it is. On the other hand, when the rotation speed Ncmp of the compressor 16a is larger than the upper limit value Nlim (Yes), the process proceeds to S4.

  In S4, the process which reduces the rotation speed Ncmp of the compressor 16a is performed, and the supercharger 16 is protected. Specific processing examples for reducing the rotational speed Ncmp of the compressor 16a include the following. When the supercharger 16 is a variable nozzle supercharger, the rotational speed Ncmp of the compressor 16a is lowered by opening the variable nozzle to reduce the flow velocity energy of the exhaust. When the supercharger 16 is not a variable nozzle supercharger, the fuel injection valve 14 is operated to limit the fuel injection amount and the output of the engine 10 is limited. Thereby, the rotation speed Ncmp of the compressor 16a is reduced.

  The present embodiment described above has the following effects.

  When the EGR device 20 is in operation, intake air in which air compressed by the compressor 16 a and EGR gas recirculated from the exhaust pipe 12 to the intake pipe 11 is mixed is supplied to the engine 10. Further, when the EGR device 20 is not operated, the air compressed by the compressor 16a is supplied to the engine 10 as intake air.

  Then, the pressure sensor 21 and the temperature sensor 22 obtain an intake density correlation value correlated with the intake density. Further, a correlation between the intake air density correlation value and the rotation speed Ncmp of the compressor 16 a is created in advance and stored in the storage device of the ECU 30. Therefore, the rotation speed Ncmp of the compressor 16a is estimated based on the intake air density correlation value and the correlation between the intake air density correlation value and the rotation speed Ncmp of the compressor 16a regardless of the presence or absence of the EGR gas and the introduction amount. That is, the rotational speed Ncmp of the compressor 16a can be accurately estimated by a simple method.

  Based on the rotation speed Ne of the engine 10 detected by the crank sensor 23, the acquired intake air density correlation value, and the correlation created for each rotation speed Ne of the engine 10, the rotation speed Ncmp of the compressor 16a Is estimated. Therefore, even if the rotation speed Ne of the engine 10 is changed, the rotation speed Ncmp of the compressor 16a can be estimated. The rotational speed Ne of the engine 10 is detected by a crank sensor 23 that is normally installed on the crankshaft 31 of the engine 10. Therefore, it is not necessary to newly provide a rotation sensor, and the cost is not increased.

  The intake density correlation value is calculated by dividing the intake pressure P measured by the pressure sensor 21 by the intake air temperature T measured by the temperature sensor 22. Therefore, since the intake density correlation value is a parameter that takes into account the temperature change due to the introduction of EGR gas, it has a strong correlation with the rotational speed Ncmp of the compressor 16a regardless of the presence or absence of the EGR gas and the introduction amount.

  The EGR pipe 13 is connected to a portion downstream of the throttle valve 25 provided downstream of the compressor 16 a in the intake pipe 11 and a portion upstream of the turbine 16 b of the exhaust pipe 12. Therefore, it is possible to assist the introduction of the EGR gas by controlling the throttle valve 25 to the closed side. Further, high-pressure EGR gas is introduced into the intake pipe 11 from a portion of the exhaust pipe 12 upstream of the turbine 16 b.

  Although the introduction of the high-pressure EGR gas has a large influence on the intake air temperature, the rotation speed Ncmp of the compressor 16a can be easily and accurately estimated from the correlation between the intake air density correlation value and the rotation speed Ncmp of the compressor 16a. Therefore, it can respond also to introduction of high-pressure EGR gas.

  In the intake pipe 11, an intercooler 17 is installed between the compressor 16 a and a connection portion between the intake pipe 11 and the EGR pipe 13. Therefore, the air compressed by the compressor 16a is cooled by the downstream intercooler 17, and the efficiency of charging the intake air into the combustion chamber 15 is improved. Moreover, since the intercooler 17 is installed upstream of the EGR pipe 13, there is no possibility that the intercooler 17 is corroded by the high-pressure EGR gas.

  Further, the present invention is not limited to the above-described embodiment, and can be implemented as follows, for example.

  The intake air density correlation value may be a value obtained by dividing the mass of intake air existing in a portion from the connection portion with the EGR pipe 13 to the connection portion with the combustion chamber 15 in the intake pipe 11 by the volume of that portion. In this case, the mass of the intake air can be calculated based on the detected value of the intake air flow rate. Further, the volume can be calculated in advance based on the design value of the engine 10 or the like.

  As shown in FIG. 7, the EGR pipe 13 is connected to the upstream portion of the compressor 16a in the intake pipe 11 and the downstream portion of the exhaust pipe 12 relative to the purification device 18 provided on the downstream side of the turbine 16b. It may be. Such an EGR device 20 recirculates a part of the exhaust gas existing in the low exhaust pressure portion of the exhaust pipe 12 to the low negative pressure portion of the intake pipe 11. Even in such a configuration, since the temperature of the intake air is affected by the introduction of the EGR gas, there is a benefit of obtaining the compressor rotation speed based on the intake air density correlation value.

  The storage means may be a portable medium such as an optical disk or an external storage device such as a hard disk.

  The engine 10 may be a gasoline engine or other engines.

  DESCRIPTION OF SYMBOLS 10 ... Engine, 11 ... Intake pipe, 12 ... Exhaust pipe, 13 ... EGR piping, 16 ... Supercharger, 16a ... Compressor, 16b ... Turbine, 20 ... EGR apparatus, 21 ... Pressure sensor, 22 ... Temperature sensor.

Claims (6)

A turbocharger (16) including a compressor (16a) installed in an intake pipe (11) of an engine (10) and a turbine (16b) arranged in the exhaust pipe (12) of the engine; and the intake pipe An engine control device for controlling an engine, including an EGR device (20) including an EGR pipe (13) connected to the exhaust pipe and recirculating a part of the exhaust gas in the exhaust pipe to the intake pipe as EGR gas (30)
An acquisition means for acquiring an intake density correlation value correlated with the density of the intake air in the intake pipe at the downstream of the compressor and the connection portion of the intake pipe and the EGR pipe;
Storage means for storing a correlation between the intake density correlation value created in advance and the rotation speed of the compressor;
Estimating means for estimating the rotational speed of the compressor based on the intake air density correlation value acquired by the acquiring means and the correlation stored in the storage means;
An engine control device comprising: A detecting means (23) for detecting the rotational speed of the engine;
The correlation is created for each engine speed,
The estimation means is based on the engine speed detected by the detection means, the intake density correlation value acquired by the acquisition means, and the correlation stored in the storage means. The engine control apparatus according to claim 1, wherein the engine speed is estimated. The acquisition means includes a pressure sensor (21) for measuring the intake pressure in the intake pipe and a temperature sensor for measuring the intake air temperature in the intake pipe, downstream of the connection portion between the intake pipe and the EGR pipe and the compressor. (22)
The engine control device according to claim 1, wherein the intake air density correlation value is calculated from an intake air pressure measured by the pressure sensor and an intake air temperature measured by the temperature sensor.   The engine control apparatus according to claim 3, wherein the intake air density correlation value is calculated by dividing the intake air pressure measured by the pressure sensor by the intake air temperature measured by the temperature sensor. The engine includes a throttle valve (25) downstream of the compressor in the intake pipe,
The engine control device according to any one of claims 1 to 4, wherein the EGR pipe is connected to a portion of the intake pipe downstream of the throttle valve and a portion of the exhaust pipe upstream of the turbine.   The engine control device according to claim 5, wherein an intercooler (17) is installed between the compressor and the connecting portion in the intake pipe.

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