JP2010216279A - Fuel injection control device and accumulator fuel injection system using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fuel injection control device capable of detecting an injector having an excessive static leakage amount, and an accumulator fuel injection system using the same. <P>SOLUTION: The fuel injection control device employed for an accumulator fuel injection system determines whether the abnormality of a static leakage amount inside an injector exists by detecting the downtrend of a residual pressure in a common rail after engine stop and comparing the detected downtrend of residual pressure with a criterion. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a fuel injection control device used in an accumulator fuel injection system and an accumulator fuel injection system using the same.

  As such a fuel injection control device, Patent Document 1 discloses a device that detects fuel leakage abnormality in a plurality of injectors provided in an accumulator fuel injection system.

  In the control device of this Patent Document 1, after calculating the amount of dynamic leak of each injector from the amount of common rail pressure drop per unit time, and calculating the amount of change in leak by comparing with the initial amount of dynamic leak of each injector, A method of determining a leak abnormality by comparing the leak amount change value with a threshold value is employed.

Japanese Patent Application Laid-Open No. 2005-307885

  By the way, there are a dynamic leak and a static leak as a kind of fuel leak in the injector. The dynamic leak is a fuel leak that goes out from the injector to the fuel pipe on the low pressure side during fuel injection of the injector. On the other hand, the static leak is a fuel leak from a slight gap such as a sliding portion of the injector to the fuel pipe on the low pressure side, regardless of the fuel injection of the injector.

  Among these, the static leak is an increase in the amount of leak due to an increase in the above-described gap with time due to a distortion (a mounting distortion) caused by the mounting state of the injector. In addition, when fuel with poor fuel cleanliness (fuel containing foreign matter such as dust) is used, if the fuel is supplied to the injector in a state that contains foreign matter, the gap inside the injector increases due to this foreign matter. There is a concern that the amount of static leak increases.

  Here, in the past, the change in the dynamic leak amount had a greater effect on the engine performance than the change in the static leak amount, so an increase in the dynamic leak amount was regarded as a problem. Since the influence of this is small, the increase in the amount of static leak was not particularly regarded as a problem.

  However, if the amount of static leak increases and becomes excessive, the load on the pump that supplies fuel to the injector increases, resulting in a problem that fuel efficiency deteriorates. In addition, since the quality (degree of cleanliness) of fuel supplied by the region (country) is different recently, the amount of increase in static leaks is larger than the amount of increase assumed by the region. Was found to occur.

  Incidentally, the above-mentioned Patent Document 1 does not disclose a specific means for detecting an injector having an excessive static leak amount.

  An object of the present invention is to provide a fuel injection control device capable of detecting an injector having an excessive static leak amount and a pressure accumulation fuel injection system using the same.

  In order to achieve the above object, in the invention described in claim 1, detection means (S3 to S7, S3, S22, S23) for detecting a residual pressure drop tendency in the common rail (20) after the internal combustion engine is stopped, Comparing the detected residual pressure drop tendency with a predetermined determination criterion, the abnormality determination means (S9, S24) for determining whether or not the amount of static leak in the injector (40) is abnormal is provided. It is a feature.

  Here, when the internal combustion engine is stopped from the operating state, the fuel supply to the common rail is stopped, so that the pressure of the fuel remaining in the common rail, that is, the residual pressure is lowered. Since this residual pressure decreasing tendency is determined by the size of the gap inside the injector, as in the present invention, by comparing the residual pressure decreasing tendency in the common rail after the stop of the internal combustion engine with a criterion, An injector with an excessive amount can be detected.

  More specifically, the fuel pressure (P_act) in the common rail (20) after a predetermined time (Ts, Ta) has elapsed since the stop of the internal combustion engine by the detection means (S3 to S7). ) Is detected, and when the detected fuel pressure (P_act) is smaller than the determination reference value (Pth1) in the abnormality determination means (S9), it is determined that the amount of static leak in the injector (40) is abnormal. can do.

  Alternatively, as described in claim 3, the detection means (S3, S22, S23) uses the elapsed time from when the internal combustion engine stops until the fuel pressure in the common rail (20) reaches a predetermined pressure (Pth1). T_act) is detected, and when the elapsed time (T_act) detected by the abnormality determination means (S24) is shorter than the determination reference value (Ts, Ta), the static leak amount inside the injector (40) is abnormal. It can be determined that there is.

  Further, since the residual pressure drop tendency varies depending on the fuel temperature, as in claim 4, the fuel temperature detection means (S4) for detecting the temperature of the fuel stored in the common rail (20) is provided, and the abnormality determination means comprises: The accuracy of abnormality determination can be increased by using the determination reference value according to claims 2 and 3 determined based on the detected temperature.

  According to a fifth aspect of the present invention, there is provided a fuel injection control device according to any one of the first to fourth aspects, a common rail (20) for storing high-pressure fuel, and a fuel stored in the common rail (20). An injector (40) that injects into the internal combustion engine, and a rail pressure sensor (22) that measures the pressure of the fuel stored in the common rail (20) and outputs the measurement result to the fuel injection control device. It is said. According to this, similarly to the first to fourth aspects of the invention, it is possible to detect an injector with excessive static leak.

  In addition, the code | symbol in the bracket | parenthesis of each means described in this column and the claim shows the correspondence with the specific means as described in embodiment mentioned later.

It is a mimetic diagram showing the whole pressure accumulation type fuel injection system composition in a 1st embodiment of the present invention. It is a flowchart of the abnormality determination process of the amount of static leaks which engine ECU50 in 1st Embodiment performs. It is a time chart for demonstrating the abnormality determination method of the amount of static leaks in 1st Embodiment. It is a flowchart of the abnormality determination process of the amount of static leaks which engine ECU50 in 2nd Embodiment performs. It is a time chart for demonstrating the abnormality determination method of the amount of static leaks in 2nd Embodiment.

(First embodiment)
In FIG. 1, the whole block diagram of the pressure accumulation type fuel injection system in this embodiment is shown. An accumulator fuel injection system 1 in FIG. 1 injects fuel into a diesel engine as an internal combustion engine, and includes a fuel supply pump 10, a common rail 20, an EDU 30, an injector 40, and an engine as a fuel injection control device. ECU50.

  The fuel supply pump 10 pumps high-pressure fuel to the common rail 20. Specifically, the fuel supply pump 10 is supplied from the feed pump 11 to the pump cylinder in response to a control signal input from the engine ECU 50 and a feed pump 11 that pumps fuel from the fuel tank 70 via the suction pipe 61. A suction metering valve 12 that adjusts the fuel flow rate, a plunger 13 that slides in a liquid-tight state inside the pump cylinder when the cam rotates together with a camshaft that is rotated by the engine, and a check valve 14 that prevents backflow of fuel. And.

  In such a fuel supply pump 10, the fuel pumped up from the fuel tank 70 by the feed pump 11 is adjusted by the suction metering valve 12 and sucked into a pump chamber (not shown). Further, the fuel in the pump chamber is pressurized by the plunger 13 sliding in the pump cylinder according to the rotation of the cam. When the pressurized fuel pressure exceeds the valve opening pressure of the check valve 14, the pressurized fuel is supplied to the common rail 20 via the supply pipe 62.

  Further, the fuel supply pump 10 is provided with a temperature sensor 15 so that the temperature of the fuel pumped up from the fuel tank 70 is detected, and a signal corresponding to the temperature is input to the engine ECU 50. In FIG. 1, the temperature sensor 15 is depicted in a block diagram, but is actually attached to the fuel supply pump 10.

  Then, excess fuel in the fuel supply pump 10 is returned to the fuel tank 70 via the fuel pipe 63. Further, the suction pipe 61 is provided with a fail filter 64 that filters the fuel sucked from the fuel tank 70 and removes foreign matters.

  The common rail 20 is a livestock pressure means for storing high-pressure fuel supplied from the fuel supply pump 10 while maintaining the target rail pressure. This target rail pressure is determined by the engine ECU 50 based on the operation state of the diesel engine such as an accelerator opening signal and an engine speed signal, for example.

  In addition, a pressure limiter 21 is attached to the common rail 20 to open the valve when the fuel pressure in the common rail 20 exceeds a predetermined upper limit value and to release the fuel pressure in the common rail 20. The fuel flowing out from the pressure limiter 21 is returned to the fuel tank 70 through the fuel pipe 63.

  Furthermore, a rail pressure sensor 22 is attached to the common rail 20, and a signal corresponding to the actual common rail pressure in the common rail 20 (hereinafter referred to as an actual rail pressure) is input to the engine ECU 50.

  The EDU 30 is a drive device that inputs an open / close signal for opening and closing the fuel injection valve of the injector 40 to the injector 40 based on a drive signal input from the engine ECU 50.

  The injector 40 is attached to a cylinder of the diesel engine, and injects fuel into the cylinder by opening and closing a fuel injection valve based on an open / close signal input from the EDU 30. In such an injector, the fuel inlet 41 into which the high-pressure fuel from the common rail 20 is introduced via the high-pressure pipe 65, and surplus fuel inside the injector 40 flows out toward the fuel tank 70 via the fuel pipe 63. And a fuel outlet 42.

  Although not shown, the injector 40 includes a nozzle portion (nozzle body and nozzle needle) for injecting fuel, an electromagnetic valve for controlling the injection amount, an orifice for controlling the injection rate, and a command piston, as is well known. ing.

  In FIG. 1, only one such injector 40 is shown. However, the injector 40 is provided in each cylinder according to the number of cylinders of the diesel engine, and is connected to each injector 40 via each high-pressure pipe 65. High pressure fuel is supplied.

  The engine ECU 50 includes a microcomputer including a CPU, ROM, EEPROM, RAM, and the like (not shown), and performs arithmetic processing according to a program stored in the microcomputer.

  Signals are input to the engine ECU 50 from sensors, and the engine ECU 50 performs fuel injection control and static leak amount abnormality determination processing based on these input signals and the like. Yes.

  Here, as the sensors, for example, in addition to the temperature sensor 15 and the rail pressure sensor 22 described above, an engine speed sensor 80 for detecting the engine speed provided in the diesel engine, an ignition (IG) switch 81, an accelerator. Examples include an accelerator opening sensor that detects the opening.

  As described above, the fuel injection control calculates the target rail pressure of the common rail 20 (command common rail pressure), the fuel injection amount (command injection amount) of the injector 40, the injection timing, and the like based on the operating state of the diesel engine. This is control for operating the fuel supply pump 10 and the injector 40 based on the calculation result.

  The static leak amount abnormality determination process is for confirming whether there is an injector with excessive static leak amount due to deterioration. When the static leak amount abnormality is determined, inform the driver, etc. It is executed to promote replacement of the injector and prevent deterioration of fuel consumption.

  Hereinafter, the static leak amount abnormality determination process will be described in detail.

  First, the abnormality determination of the static leak amount is performed by the following method. When the engine is stopped from the operating state, the fuel supply from the fuel supply pump 10 to the common rail 20 is stopped, so that the pressure (residual pressure) of the fuel remaining in the common rail 20 decreases with time. The drop in the residual pressure of the common rail 20 is caused by the fuel in the common rail 20 flowing out to the low-pressure side fuel pipe 63 through a gap formed in a sliding portion such as a nozzle needle or a command piston inside the injector 40. The tendency of the residual pressure to drop is determined by the size of the gap inside the injector 40.

  Accordingly, in the static leak amount abnormality determination process of the present invention, the tendency of the residual pressure of the common rail 20 to decrease immediately after the engine stops is detected, and the presence or absence of an abnormality in the static leak amount is determined based on this downward tendency. Whether there is an abnormality in the amount of static leak is determined by comparing the detected downward tendency with a downward tendency that is a predetermined criterion. In addition, since the viscosity of the fuel differs depending on the fuel temperature and the rate of decrease in the residual pressure is different, when this abnormality determination is performed, a decreasing tendency is set as a determination criterion according to the fuel temperature.

  Next, the static leak amount abnormality determination process will be described in detail with reference to FIGS. FIG. 2 shows a flowchart of the static leak amount abnormality determination process executed by the engine ECU 50, and FIG. 3 shows a time chart for explaining the static leak amount abnormality determination process.

  The static leak amount abnormality determination process shown in FIG. 2 is started from the time when the engine is started and the engine ECU 50 is started, and steps S1 and S2 are executed at a predetermined cycle until the process proceeds to step S3.

  In step S1, it is determined whether or not it is in an idle stable state. This determination is made based on, for example, a signal that is always input from the engine speed sensor 80, a command injection amount calculated by the fuel injection control by the engine ECU 50, and a command common rail pressure. It is determined whether the amount and common rail pressure are stable.

  Here, as described above, it is determined whether or not the engine is in the idling stable state in order to compare the residual pressure decrease tendency of the common rail 20 immediately after the engine stops with the reference residual pressure decrease tendency. This is because it is necessary that the pressure of the common rail 20 is always constant. In the idling stable state, as shown in FIG. 3, the common rail pressure is a target pressure value and is always a constant value.

  When the engine has stopped without proceeding to step S2, the abnormality determination process ends with the engine stopping.

  If it is determined in step S1 that the engine is in the idle stable state, it is determined in step S2 whether or not the ignition (IG) switch has been turned off. That is, based on the signal input from the IG switch 81, it is determined whether or not the engine has been stopped from the operating state.

  When it is determined that the engine has been stopped, the process proceeds to step S3, and measurement of the elapsed time from the time point when the IG switch 81 is turned off is started by the timer of the engine ECU 50. In step S3 and subsequent steps, processing is continued by receiving power supply from a battery or the like even after the engine is stopped.

  Further, in step S4, the fuel temperature is acquired by inputting a signal from the temperature sensor 15. This step S4 corresponds to the fuel temperature detecting means of the present invention.

  In step S5, the measurement time (predetermined time) Ts for measuring the actual rail pressure is determined as any one of Th, Ta, and Tc in FIG. 3, for example, according to the acquired fuel temperature. The measurement time Ts is an elapsed time from the time when the IG switch is turned off from on, and is a timing at which the actual rail pressure is measured. For example, if the fuel temperature is normal temperature, as will be described later, the determination criterion at normal temperature indicated by the thick line in FIG. 3 is used, so the measurement time Ts is determined to be Ta in FIG.

  In step S6, it is determined whether the measurement time of the timer has passed the predetermined time Ts. When the predetermined time Ts has elapsed, the process proceeds to step S7, and the actual rail pressure P_act at the predetermined time Ts is measured. For example, the actual rail pressure P_act when the time Ta has elapsed is measured. In the present embodiment, steps S <b> 3 to S <b> 7 correspond to detection means for detecting the residual pressure drop tendency in the common rail 20.

  In step S8, the actual rail pressure P_act is compared with a diagnosable pressure determination threshold value Pth2 (see FIG. 3) to determine whether the actual rail pressure P_act is greater than Pth2. This is because, when the actual rail pressure P_act is abnormally low, there is a possibility that the rail pressure sensor 22 has an abnormality such as a failure in addition to the excessive static leak amount. Do not judge abnormalities.

  Therefore, if the actual rail pressure P_act is greater than Pth2, it is determined that an abnormality can be determined and the process proceeds to step S9. On the other hand, if the actual rail pressure P_act is equal to or less than Pth2, it is determined that the abnormality cannot be determined, and the abnormality determination process for the static leak amount ends.

  In step S9, it is determined whether or not the actual rail pressure P_act is smaller than the abnormality determination pressure threshold value Pth1. This abnormality determination pressure threshold value Pth1 is the determination reference value of the present invention. Further, this step S9 corresponds to the abnormality determining means of the present invention.

  Here, the alternate long and short dash line curve in FIG. 3 shows the residual pressure drop tendency at the normal time, and the broken curve in FIG. 3 shows the residual pressure drop tendency at the abnormal time. When the residual pressure at the same elapsed time, for example, time Ta, is compared, the residual pressure at the same elapsed time is smaller than that at normal time in an abnormal time when the amount of static leak is excessive.

  Therefore, the lower limit value of the residual pressure at the predetermined time Ts when the static leak amount is normal is set to the abnormality determination pressure threshold value Pth1, and if the actual rail pressure P_act is smaller than Pth1, the static leak amount is It turns out that it is an excessive abnormal state.

  Therefore, for example, as shown in FIG. 3, if the actual rail pressure P_act is P2, since P_act <Pth1, the process proceeds to step S10, the static leak amount is determined to be abnormal, and the process proceeds to step S11. On the other hand, if the actual rail pressure P_act is P1, P_act> Pth1, and the static leak amount is normal, so the static leak amount abnormality determination process ends.

  By the way, in this embodiment, measurement time Ts is determined according to fuel temperature by step S5. This is because, as described above, the viscosity of the fuel varies depending on the fuel temperature, and the time for reaching the abnormality determination pressure threshold value Pth1 varies.

  Specifically, as shown in FIG. 3, when the fuel temperature is higher than room temperature, the determination criterion at high temperature is used, so the measurement time Ts is set to a time Th shorter than that at room temperature. On the other hand, at the low temperature when the fuel temperature is lower than the normal temperature, since the criterion for the low temperature is used, the measurement time Ts is set to a time Tc longer than the normal temperature. Thus, by determining the measurement time Ts of the actual rail pressure according to the fuel temperature, it is possible to improve the accuracy of the abnormality determination.

  Then, in step S11, the abnormality determination process is completed by storing the determination result.

  In the case where the result determined to be abnormal in step S11 is stored, for example, when the engine is started and the engine ECU 50 is started, a warning lamp installed in the meter is turned on, or a static leak occurs in the meter. The driver or vehicle mechanic is informed of the presence of the injector 40 having an abnormal static leak amount by displaying that the injector 40 having an abnormal amount exists or being stored as a diagnosis code.

  As described above, in the present embodiment, the actual rail pressure P_act after a lapse of a predetermined time from the engine stop is detected, and the detected actual rail pressure P_act is compared with the abnormality determination pressure threshold value Pth1 serving as a determination criterion. Whether or not there is an abnormality in the amount of static leak is determined. According to this, the presence or absence of an injector with an excessive static leak amount can be confirmed, and if there is an injector with an excessive static leak amount, the driver or vehicle mechanic is notified of this fact, prompting replacement of the injector, and fuel consumption. Can be prevented.

(Second Embodiment)
FIG. 4 shows a flowchart of a static leak amount abnormality determination process executed by the engine ECU 50 in this embodiment, and FIG. 5 shows a time chart for explaining a static leak amount abnormality determination method.

  In the first embodiment, the actual rail pressure P_act after the elapse of a predetermined time from the time when the engine is stopped is detected in order to detect the tendency of the remaining pressure of the common rail 20 to decrease immediately after the engine is stopped. In the embodiment, an elapsed time from when the engine is stopped until the residual pressure of the common rail 20 reaches the reference pressure Pth1 is detected.

  Specifically, the static leak amount abnormality determination process shown in FIG. 4 is executed. Steps S1 to S4 are the same as steps S1 to S4 in FIG. 2 described in the first embodiment.

  In step S21, a determination reference time Ts corresponding to the acquired fuel temperature T_fuel is determined. For example, one of Ta, Th, and Tc in FIG. 5 is selected as the determination reference time Ts.

  Next, in step S22, based on a signal that is constantly input from the rail pressure sensor 22, it is determined whether or not the actual rail pressure P_act has reached a predetermined pressure Pth1.

  When the actual rail pressure P_act reaches the predetermined pressure Pth1, the process proceeds to step S23, and the elapsed time T_act at that time is calculated. In the present embodiment, steps S3, S22, and S23 correspond to detection means for detecting the residual pressure drop tendency in the common rail 20 of the present invention.

  In step S24, it is determined whether the calculated elapsed time T_act is smaller than the determination reference time Ts. This determination reference time Ts is the determination reference value of the present invention, and this step S24 corresponds to the abnormality determination means of the present invention.

  Here, the alternate long and short dash line curve in FIG. 5 shows the residual pressure drop tendency at the normal time, and the broken curve in FIG. 5 shows the residual pressure drop tendency at the abnormal time. For example, when the elapsed time until reaching the same predetermined pressure Pth1 is compared, the elapsed time T2 at the time of abnormality when the amount of static leak becomes excessive is shorter than the elapsed time T1 at normal time. Therefore, for example, by setting the lower limit value of the elapsed time until the predetermined pressure Pth1 when the static leak amount is normal to the determination reference time Ts, the elapsed time T_act can be shorter than the determination reference time Ts. In this case, it can be seen that the static leak amount is an abnormal state.

  Therefore, for example, when the determination reference time Ts is determined to be the determination reference time Ta at normal temperature in step S21, as shown in FIG. 5, if the elapsed time T_act is T2, since T_act <Ts, the process proceeds to step S25. Then, it is determined that the amount of static leak is abnormal. In step S26, the fact is stored, and the abnormality determination process for the amount of static leak is terminated. On the other hand, if the elapsed time T_act is T1, T_act> Ts, and the static leak amount is normal, so the static leak amount abnormality determination process ends.

  Even if it does in this way, the effect similar to 1st Embodiment is acquired.

(Other embodiments)
(1) About the order of each step shown by FIG. 2, 4 demonstrated in 1st, 2nd embodiment, you may change in the range which can be implemented not only in these.

  For example, in FIG. 2 and FIG. 4, steps S1 and S2 are processed in order. However, if it is possible to identify when the IG switch is turned from on to off in an idle stable state, the order of steps S1 and S2 is changed. It may be replaced. For example, after determining whether the IG switch is turned off from on, in the case of Yes, it may be determined whether the idle stable state was before the IG switch was turned off.

  (2) In the first embodiment described above, the selection candidates for determining the measurement time (predetermined time) Ts for measuring the actual rail pressure in accordance with the acquired fuel temperature in step S5 are Th in FIG. The number of Ta and Tc is three, but the number is not limited to three and may be changed to other numbers. Similarly, in the second embodiment, there are three selection candidates Ta, Th, and Tc in FIG. 5 when determining the determination reference time Ts according to the acquired fuel temperature in step S21. It may be changed to other numbers. In short, the number of determination criteria determined according to the fuel temperature can be arbitrarily set.

  (3) In the first embodiment, the actual rail pressure P_act after the elapse of a predetermined time from the stop of the engine is detected and compared with the determination reference value in order to determine the static leak amount abnormality. In the second embodiment, the elapsed time from when the engine is stopped until the residual pressure of the common rail 20 reaches the reference pressure Pth1 is detected and compared with the determination reference value. It is also possible to calculate the inclination (the amount of decrease in the residual pressure per unit time) like a character and compare it with the criterion value.

  (4) In each of the above-described embodiments, the present invention is applied to an accumulator fuel injection system that injects fuel into a diesel engine. However, an accumulator fuel injection that accumulates gasoline and directly injects gasoline fuel into an internal combustion engine. The present invention may be applied to a system.

1 Accumulated fuel injection system 20 Common rail 22 Rail pressure sensor 40 Injector 50 Engine ECU

Claims (5)

The injector (40) is used in an accumulator fuel injection system (1) including a common rail (20) for storing high-pressure fuel and an injector (40) for injecting fuel stored in the common rail (20) into an internal combustion engine. In the fuel injection control device for controlling the fuel injection by
Detecting means (S3 to S7, S3, S22, S23) for detecting a residual pressure drop tendency in the common rail (20) after the internal combustion engine is stopped;
An abnormality determining means (S9, S24) for determining whether or not the amount of static leak in the injector (40) is abnormal by comparing the detected tendency of decreasing the residual pressure with a predetermined criterion. A fuel injection control device. The detection means (S3 to S7) detects a fuel pressure (P_act) in the common rail (20) after a predetermined time (Ts, Ta) has elapsed since the stop of the internal combustion engine,
The abnormality determination means (S9) determines that the amount of static leak in the injector (40) is abnormal when the detected fuel pressure (P_act) is smaller than the determination reference value (Pth1). The fuel injection control device according to claim 1, wherein The detection means (S3, S22, S23) detects an elapsed time (T_act) from when the internal combustion engine stops until the fuel pressure in the common rail (20) reaches a predetermined pressure (Pth1),
The abnormality determination means (S24) determines that the amount of static leak in the injector (40) is abnormal when the detected elapsed time (T_act) is shorter than the determination reference value (Ts, Ta). The fuel injection control device according to claim 1, wherein Fuel temperature detection means (S4) for detecting the temperature of the fuel stored in the common rail (20),
The abnormality determination unit uses a value determined based on the temperature acquired by the fuel temperature detection unit (S4) as the determination reference value. The fuel injection control device described. The fuel injection control device according to any one of claims 1 to 4,
A common rail (20) for storing high-pressure fuel;
An injector (40) for injecting fuel stored in the common rail (20) into an internal combustion engine;
A pressure accumulation type fuel injection system comprising: a rail pressure sensor (22) that measures a pressure of fuel stored in the common rail (20) and outputs a measurement result to the fuel injection control device.

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