JP2007023796A - Fuel injection device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fuel injection device capable of shortening an actual interval between a pre-injection and a post-injection. <P>SOLUTION: A controller for the fuel injection device gradually shortens a command interval between a pilot injection and a main injection during an injection period for one cycle for each injector when a learning condition (including an engine stable operation state) is satisfied. The shortest command interval when the actual injection amount injected from each injector rapidly increases or immediately before the rapid increase is obtained. As such, where the interval is very short, the rapid increase in the actual injection amount can be advantageously used for obtaining the command interval where the actual interval for each injector becomes the shortest. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a fuel injection device capable of performing a plurality of injections (for example, pilot injection and main injection) within an injection period of one cycle.

(Conventional technology)
In an internal combustion engine (hereinafter referred to as an engine) such as a diesel engine, the combustion of fuel injected during the ignition delay period during combustion is rapid and becomes diffusion combustion accompanied by local explosive combustion, resulting in combustion noise (diesel knock , Vibration), causing exhaust gas deterioration.
Therefore, pilot injection that injects a small amount of fuel prior to main injection is performed, premixed combustion is generated in the combustion chamber before main injection, and ignition delay is shortened to prevent explosive combustion. A technique for reducing combustion noise and exhaust gas deterioration is known (see, for example, Patent Document 1).
Pilot injection is an example of pre-injection, and main injection is an example of post-injection.

(Problems of conventional technology)
In recent years, a technique for shortening the time interval (hereinafter, interval) between pilot injection and main injection has been proposed with the aim of further reducing combustion noise and exhaust gas.
However, when the interval becomes extremely short, there is a characteristic that the actual injection amount increases rapidly.
The command interval at which the actual injection amount suddenly increases varies depending on the machine difference of the injector. That is, the command interval at which the actual injection amount increases rapidly varies as shown in FIG. 2B due to individual differences among injectors.
Thus, since the actual injection amount varies when the command interval is very short, if the command interval is extremely short, the injection accuracy deteriorates. Further, in a multi-cylinder engine having a plurality of cylinders, if the command interval is extremely short, the stability of engine rotation deteriorates due to variations in the actual injection amount.

For the above reasons, conventionally, in order to avoid the variation in the actual injection amount when the command interval is extremely short, as shown in FIG. 2B, the shortest command interval in which the injection variation does not occur for each injector. J.
That is, conventionally, since the shortest command interval J that secures a margin that does not cause the injection variation for each injector is set, the actual interval cannot be made the shortest practically.

On the other hand, it is conceivable to reduce the tolerance of the actual injection amount by reducing the tolerance of the injector to suppress the difference in machine difference, but the manufacturing cost of the injector increases due to the reduction of the tolerance. Further, even if the tolerance is reduced, even if the tolerance is reduced, machine difference variation occurs. Therefore, the shortest command interval J that secures a margin that does not cause injection variation remains unchanged, and the actual interval cannot be minimized. .
Japanese Patent Laid-Open No. 10-252476

  The present invention has been made in view of the above problems, and an object thereof is to provide a fuel injection device capable of minimizing an actual interval between pre-injection and post-injection.

[Means of claim 1]
When a learning condition including a stable engine operating condition is satisfied, the control device in the fuel injection device adopting the means of claim 1 performs the pre-injection in the injection period of one cycle and the pre-injection by the shortest command interval measuring unit. The command interval with the subsequent post-injection is gradually shortened, and the shortest command interval immediately before or when the actual injection amount injected from the injector suddenly increases is obtained.
The control device executes the injection control using the shortest command interval obtained by the shortest command interval measuring means when the engine operating state is a predetermined operating state.

Thus, since the shortest command interval is obtained by using the fact that the command interval at which the actual injection amount rapidly increases for each injector, the actual interval between the pre-injection and the post-injection can be minimized.
That is, since the shortest command interval that is shorter than the shortest command interval set in consideration of the variation for each injector can be set, the deterioration of combustion noise and exhaust gas can be further reduced.
Moreover, since it is not necessary to reduce the tolerance of the injector in order to realize the shortest actual interval, it is possible to suppress an increase in the manufacturing cost of the injector. Further, even if the injector changes with time due to wear or the like, the shortest command interval is obtained every time the learning condition is satisfied, so that high accuracy and reliability can be obtained over a long period of time.

[Means of claim 2]
The control device in the fuel injection device adopting the means of claim 2 is for obtaining the shortest command interval for each injector in an engine having a plurality of cylinders.
Since the shortest command interval when the actual injection amount suddenly increases or immediately before the rapid increase is obtained for each injector, there is no problem that the actual injection amount varies from injector to injector even when the command interval is extremely short. For this reason, even in an engine having a plurality of cylinders, engine rotation does not become unstable.

[Means of claim 3]
When a learning condition including a stable engine operating condition is satisfied, the control device in the fuel injection device adopting the means of claim 3 performs the pre-injection in the injection period of one cycle and the subsequent to the pre-injection by the deviation measuring means. The command interval with injection is gradually shortened, and the deviation between the command interval when the actual injection amount injected from the injector increases rapidly and the reference interval given in advance is obtained.
The command interval correction means in the control device corrects the command interval based on the deviation obtained by the deviation measurement means.

Even if it is provided as in claim 3, it is possible to obtain the same effect as the "means of claim 1" described above.
Specifically, since the deviation with respect to the reference interval is obtained by utilizing the fact that the command interval at which the actual injection amount increases rapidly for each injector, the actual interval between the pre-injection and the post-injection can be minimized.
In other words, since the shortest command interval shorter than the shortest command interval set in consideration of the variation for each injector can be achieved, further reduction in combustion noise and exhaust gas can be realized.
Moreover, since it is not necessary to reduce the tolerance of the injector in order to realize the shortest actual interval, it is possible to suppress an increase in the manufacturing cost of the injector. Further, even if the injector changes with time due to wear or the like, the shortest command interval is obtained every time the learning condition is satisfied, so that high accuracy and reliability can be obtained over a long period of time.

[Means of claim 4]
The control device in the fuel injection device adopting the means of claim 4 obtains a deviation for each injector in an engine having a plurality of cylinders.
Since a deviation from the reference interval is obtained for each injector, there is no problem that the actual injection amount varies for each injector even in a place where the command interval is very short. For this reason, even in an engine having a plurality of cylinders, engine rotation does not become unstable.

[Means of claim 5]
In the fuel injection device employing the means of claim 5, the means for detecting a sudden increase in the actual injection amount injected from the injector is a sensor for detecting the operating state of the engine or the combustion state of the combustion chamber (for example, the engine speed). Sensor, in-cylinder pressure sensor, in-cylinder ion current sensor, engine vibration sensor, exhaust gas air-fuel ratio sensor, and the like.

The fuel injection apparatus of the best mode 1 is an injector that injects fuel into a combustion chamber of an engine, and a control capable of executing a plurality of injections in one cycle injection period by controlling injection start and injection stop of the injector. Device.
When the learning condition including the stable operation state of the engine is satisfied, the control device gradually shortens the command interval between the pre-injection in the one-cycle injection period and the post-injection following the pre-injection. Shortest command interval measuring means for obtaining the shortest command interval immediately before or when the actual injection amount to be injected rapidly increases.
The control device executes the injection control using the shortest command interval obtained by the shortest command interval measuring means when the engine operating state is a predetermined operating state.

The fuel injection device of the best mode 2 is an injector that injects fuel into a combustion chamber of an engine, and a control capable of executing a plurality of injections in one cycle injection period by controlling injection start and injection stop of the injector. Device.
When the learning condition including the stable operation state of the engine is satisfied, the control device gradually shortens the command interval between the pre-injection in the one-cycle injection period and the post-injection following the pre-injection. Deviation measuring means for obtaining a deviation between a command interval when the actual injection amount to be injected rapidly increases and a reference interval given in advance, and a command interval correction for correcting the command interval based on the deviation obtained by the deviation measuring means Means.

  Example 1 will be described with reference to the drawings. In the first embodiment, the “basic configuration of the common rail fuel injection device” will be described first, and then the “features of the first embodiment” according to the present invention will be described.

(Basic configuration of common rail fuel injection system)
The common rail fuel injection device shown in FIG. 3 is an injection system that injects fuel into a four-cylinder engine (for example, a diesel engine: not shown), and includes a common rail 1, an injector 2, a supply pump 3, a control device 4, and the like. ing. The control device 4 includes an ECU (engine control unit) and an EDU (drive unit). FIG. 3 shows an example in which the ECU and the EDU are mounted in one control device 4. May be installed separately.
The engine is provided with a plurality of cylinders that continuously perform the respective processes of suction, compression, explosion, and exhaust. In the first embodiment, a four-cylinder engine is shown as an example. It may be.

The common rail 1 is a pressure accumulating container for accumulating high pressure fuel supplied to the injector 2, and the high pressure fuel is supplied via a pump pipe (high pressure fuel flow path) 6 so that rail pressure corresponding to fuel injection pressure is continuously accumulated. And a plurality of injector pipes 7 for supplying high-pressure fuel to each injector 2.
A pressure limiter 10 is attached to a relief pipe 9 that returns fuel from the common rail 1 to the fuel tank 8. The pressure limiter 10 is a safety valve, and is opened when the actual rail pressure in the common rail 1 exceeds the limit set value, and suppresses the actual rail pressure of the common rail 1 below the limit set value.
The common rail 1 is attached with a pressure reducing valve 11 that opens when the actual rail pressure in the common rail 1 exceeds a predetermined valve opening pressure (target rail pressure) and flows the fuel in the common rail 1 to the low pressure side. Yes. The pressure reducing valve 11 may not be mounted.

  The injector 2 is mounted in each cylinder of the engine and supplies fuel into the combustion chamber of each cylinder. The injector 2 is connected to the downstream ends of a plurality of injector pipes 7 that branch from the common rail 1. High-pressure fuel accumulated in the common rail 1 is injected based on a given signal (injection command pulse).

The supply pump 3 is a fuel pump that pumps high-pressure fuel to the common rail 1, and feeds the fuel in the fuel tank 8 to the supply pump 3 through the fuel filter 8a and the fuel sucked up by the feed pump. A high-pressure pump that compresses to a high pressure and feeds it to the common rail 1 is mounted. The feed pump and the high-pressure pump are driven by a common camshaft. The camshaft is rotationally driven by the engine.
The supply pump 3 is equipped with an SCV (suction metering valve) 12 that adjusts the amount of fuel sucked into the high-pressure pump, and the SCV 12 is adjusted by the control device 4 so that the common rail 1 The actual rail pressure accumulated is adjusted.

(Description of the control device 4)
The control device 4 includes a CPU for performing control processing and arithmetic processing, a storage device (memory such as ROM, SRAM or EEPROM, RAM) for storing various programs and data, an input circuit, an output circuit, a power supply circuit, an injector drive circuit, and A microcomputer having a well-known structure configured to include functions such as a pump drive circuit is provided. Various arithmetic processes are performed on the basis of sensors signals (engine parameters: signals corresponding to the occupant's operating state, engine operating state, etc.) read into the control device 4.
The sensors connected to the control device 4 include an accelerator sensor 13 that detects the accelerator opening, a rotation speed sensor 14 that detects the engine speed, a water temperature sensor 15 that detects the engine coolant temperature, and the common rail 1. There are a rail pressure sensor 16 that detects the accumulated rail pressure, a fuel temperature sensor 17 that detects the temperature of the fuel supplied to the injector 2, and other sensors 18.

[Features of Example 1]
The fuel injection control according to the present invention will be described.
In order to prevent engine noise and engine vibration, exhaust gas purification, engine output and fuel consumption at a high level, the control device 4 performs an injection mode (single injection mode, Implement control to change the pilot injection mode.
In addition, the control device 4 also prevents the engine noise and the engine vibration, purifies the exhaust gas, and balances the engine output and the fuel consumption at a high level when executing the multi-injection such as the pilot injection mode. Accordingly, control is performed to change the interval between the pre-injection (for example, pilot injection) and the post-injection (for example, main injection) following the pre-injection.

(Basic description of pilot injection mode)
Next, control for minimizing the interval will be described by taking an interval between the pilot injection and the subsequent main injection as an example.
Here, the “pilot injection mode” is an injection mode in which “pilot injection → interval → main injection” is performed within an injection period of one cycle.
Specifically, as shown in the upper part of FIG. 2A, the control device 4 displays (1) a command pulse (ON) for opening the injector 2 when the injection start timing corresponding to the current operation state is reached. Output over the pilot command period TQp calculated according to the operating state, and (2) command pulse stop (OFF) for closing the injector 2 is performed over the command interval Tint calculated according to the current operating state. (3) A command pulse (ON) for opening the injector 2 again is output over the main command period TQm calculated according to the current operation state.
Thereby, the injection rate of the injector 2 changes as shown in the lower part of FIG. 2A, and the pilot injection mode is executed.

(Background of Example 1)
In recent years, techniques for shortening the interval between pilot injection and main injection have been proposed with the aim of further reducing combustion noise and exhaust gas.
By the way, when the command interval becomes extremely short, there is a characteristic that the actual injection amount injected from the injector 2 increases rapidly, but the command interval at which the actual injection amount increases rapidly is as shown in FIG. It varies depending on the machine difference of the injector 2. Therefore, in the prior art, in order to avoid the variation in the actual injection amount when the command interval is extremely short, as shown in FIG. 2B, the shortest command interval where there is no injection variation for each injector 2. J was set.
As described above, in the prior art, since the shortest command interval J is set by securing a margin that does not cause an injection variation for each injector 2, the actual interval cannot be made substantially shortest.

(Configuration of Example 1)
In order to solve the above problems, the control device 4 of the first embodiment is provided with “shortest command interval measurement means” and “shortest command interval execution means”.
The “shortest command interval measuring means” is provided for each injector 2 when a learning condition (for example, every time the vehicle travel distance reaches a predetermined distance) including a stable operation state of the engine (for example, an idling state after completion of warm-up) is satisfied. In addition, a command interval between pilot injection (pre-injection) and main injection (post-injection) following the injection period in one cycle is set as a reference interval that is set in advance (for example, an interval in which a margin that does not cause injection variation is ensured: For example, learning is performed by gradually shortening from the conventional shortest command interval J), and measuring the shortest command intervals A1 to A4 for each injector 2 when the actual injection amount injected from each injector 2 suddenly increases or immediately before the rapid increase. Each shortest command interval A1 that is a program and measured for each injector 2 A4 is stored in the storage device.

In the first embodiment, an example in which a rotation speed sensor 14 that detects an engine rotation speed (an example of an engine operating state) is used as a means for detecting a sudden increase in the actual injection amount injected from the injector 2 is shown. .
The “shortest command interval execution means” uses the shortest command intervals A1 to A4 stored for each injector 2 when the engine is in a predetermined operation state (for example, when the engine load is small). It is an execution program which performs injection control of.

A control example of the “shortest command interval measuring means” will be described with reference to the flowchart of FIG.
If the control routine is entered during engine operation (start), it is first determined in steps S1 and S2 whether or not a learning condition is satisfied. Specifically, in step S1, when the vehicle travel distance reaches a predetermined distance, or when it is time to determine deterioration of the injector 2, the shortest command interval is determined to be the learning execution time. In step S2, it is determined whether or not the current engine operating state is stable by idling. If the determination result of step S2 is NO, the process returns to step S1.

  If the determination result in step S2 is YES, it is determined that the learning condition is satisfied, and the command interval of each injector 2 (specifically, the command interval of the injector 2 in which the shortening completion flag is not set) The time is gradually shortened (step S3). Note that the command interval when starting shortening is, for example, a preset reference interval.

Next, it is determined whether or not the engine rotational fluctuation has increased (step S4). In other words, it is determined whether or not there has been a sudden increase in the actual injection amount due to the shortening of the actual interval. If the determination result of step S4 is NO, the process returns to step S3.
If the decision result in the step S4 is YES, the shortening of the command interval of the injector 2 of the cylinder (#n cylinder in the figure in which the actual injection amount suddenly increased due to the shortening of the actual interval) whose engine rotational fluctuation has been increased is finished. At the same time (set a shortening completion flag), the command interval at that time (when the engine rotational fluctuation is increased) is temporarily stored in the cache or the like as the shortest command interval at that injector 2 (step S5).

Next, it is determined whether or not the shortening of the command interval of the injectors 2 for all the cylinders has been completed (that is, whether or not the shortening completion flag has been set for all the cylinders) (step S6). If the determination result in step S6 is NO, it is determined that there is a cylinder for which the measurement of the shortest command interval has not been completed, and the process returns to step S3.
If the decision result in the step S6 is YES, the shortest command intervals A1 to A4 for all the cylinders are stored in the storage device (step S7), and this control routine is ended (END).

(Effect of Example 1)
As described above, the fuel injection device according to the first embodiment obtains the shortest command intervals A1 to A4 by using the fact that the command interval at which the actual injection amount rapidly increases for each injector 2, and therefore, between the pilot injection and the main injection. The actual interval can be minimized. That is, since it can be set to the shortest command intervals A1 to A4 shorter than the conventional shortest command interval J set in consideration of variation for each injector 2, further reduction in combustion noise and exhaust gas can be realized.

  Further, since it is not necessary to reduce the tolerance of the injector 2 in order to realize the shortest actual interval, it is possible to suppress an increase in manufacturing cost of the injector 2. Further, even if the injector 2 changes with time due to wear or the like, the shortest command intervals A1 to A4 are obtained every time the learning condition is satisfied, so that high accuracy and reliability can be obtained over a long period of time.

  Furthermore, since the shortest command intervals A1 to A4 are obtained for each injector 2 of a plurality of cylinders, there is no problem that the actual injection amount of each injector 2 varies even in an operation state in which the command interval is extremely short. For this reason, even with an engine having a plurality of cylinders, even if the interval between the cylinders is extremely short, the engine rotation does not become unstable.

A second embodiment will be described. Note that the same reference numerals as those in the first embodiment denote the same functions as those in the first embodiment.
The control device 4 of the first embodiment obtains the shortest command intervals A1 to A4 for each injector 2 by the “shortest command interval measuring means”, and “shortest command interval execution means” An example is shown in which the shortest command intervals A1 to A4 obtained in the “command interval measuring means” are used as they are.

On the other hand, the control device 4 of the second embodiment obtains the shortest command intervals A1 to A4 by the “deviation measuring means” and the “command interval correcting means”.
The “deviation measuring means” obtains the shortest command interval (command interval when the actual injection amount rapidly increases by gradually shortening the command interval) for each injector 2 (the same as the first embodiment up to here). The deviations B1 to B4 between the shortest command interval and a predetermined reference interval (for example, the conventional shortest command interval J or the machine difference median C in which a margin that does not cause injection variation is ensured) are obtained. A program to be stored in a storage device.

Two specific examples of the “deviation measuring means” will be described with reference to FIG.
(1) The first example of “deviation measuring means” obtains the shortest command intervals A1 to A4 for each injector 2 as shown in steps S1 to S6 of the first embodiment.
Next, in a step corresponding to step S7 of the first embodiment, as shown in FIG. 4A, the shortest command intervals A1 to A4 for each injector 2 and the machine difference median value C (reference interval) given in advance. Deviations B1 to B4 with respect to an example) and stored in a storage device.

(2) The second example of “deviation measuring means” obtains the shortest command intervals A1 to A4 for each injector 2 as shown in steps S1 to S6 of the first embodiment.
Next, in a step corresponding to step S7 in the first embodiment, as shown in FIG. 4B, the shortest command intervals A1 to A4 for each injector 2 and the shortest command interval J (reference interval of the reference interval) given in advance are set. Deviations B1 to B4 with respect to (example) are obtained and stored in the storage device.

  The “command interval correction means” is the deviation (that is, the deviation stored in the storage device) B1 obtained by the “deviation measurement means” when the engine operating state is in a predetermined operating state (for example, when the engine load is small). This is a program that executes each shortest command interval A1 to A4 by correcting the command interval based on ~ B4.

Even if it provides in this way, the same effect as Example 1 can be acquired.
Specifically, in order to obtain the deviations B1 to B4 with respect to the reference interval by using different command intervals at which the actual injection amount rapidly increases for each injector 2, the actual interval between the pilot injection and the main injection can be minimized. It becomes possible. That is, since the shortest command intervals A1 to A4 shorter than the conventional shortest command interval J set in consideration of the variation for each injector 2, the combustion noise and the deterioration of exhaust gas can be further reduced.
Further, since it is not necessary to reduce the tolerance of the injector 2 in order to realize the shortest actual interval, it is possible to suppress an increase in manufacturing cost of the injector 2. Moreover, even if a change with time due to wear or the like occurs in the injector 2, the deviations B1 to B4 are obtained every time the learning condition is satisfied, so that high accuracy and reliability can be obtained over a long period of time.

  Furthermore, since deviations B1 to B4 with respect to the reference interval are obtained for each injector 2 of a plurality of cylinders, there is no problem that the actual injection amount of each injector 2 varies even in an operation state in which the command interval is extremely short. For this reason, even with an engine having a plurality of cylinders, even if the interval between the cylinders is extremely short, the engine rotation does not become unstable.

[Modification]
In the above embodiment, the example in which the rotation speed sensor 14 for detecting the engine rotation speed is used as means for detecting a sudden increase in the actual injection amount injected from the injector 2 has been described. By detecting the operating state of the engine or the combustion state of the combustion chamber by other sensors such as an ion current sensor, an engine vibration sensor, and an exhaust gas air-fuel ratio sensor, the actual injection amount injected from the injector 2 increases rapidly. It may be detected. Of course, a combination of a plurality of sensors may be used to detect a sudden increase in the actual injection amount injected from the injector 2.

  In the above embodiment, the example in which the interval is shortened has been described by taking the pilot injection mode as an example. On the other hand, you may apply this invention as a means to shorten the interval between pre-injection in the injection form which performs multiple times of pre-injection (micro injection) before main injection. Or you may apply this invention as a means to shorten the interval of back-and-front injection in the injection form which divides substantially equal amount injection into multiple times.

  In the above embodiment, the present invention is applied to a common rail fuel injection device. However, the present invention may be applied to a fuel injection device that does not use a common rail. That is, for example, the present invention may be applied to a fuel injection device used for a gasoline engine other than a diesel engine.

It is a flowchart which shows the example of control of the shortest command interval measurement means (Example 1). FIG. 5 is an explanatory diagram of a pilot injection mode and a graph for explaining a characteristic that an actual injection amount increases rapidly when the command interval becomes extremely short (Example 1). 1 is a schematic view of a common rail fuel injection device (Example 1). FIG. FIG. 10 is a graph for explaining a characteristic that an actual injection amount suddenly increases when a command interval becomes extremely short (Example 2).

Explanation of symbols

2 Injector 4 Control device (including functions of shortest command interval measuring means, shortest command interval executing means, deviation measuring means, command interval correcting means)
14 Rotational speed sensor (means for detecting a sudden increase in the actual injection amount injected from the injector)

Claims (5)

A fuel injection device comprising an injector that injects fuel into a combustion chamber of an internal combustion engine, and a control device that can control injection start and injection stop of the injector and execute a plurality of injections in one injection period. And
The controller is
When the learning condition including the stable operation state of the internal combustion engine is satisfied, the command interval between the pre-injection in the one-cycle injection period and the post-injection following the pre-injection is gradually shortened and injected from the injector. A fuel injection device comprising shortest command interval measuring means for obtaining a shortest command interval immediately before or when the actual injection amount suddenly increases. The fuel injection device according to claim 1,
The internal combustion engine includes a plurality of cylinders, and the injector is provided for each of the plurality of cylinders.
The fuel injection device, wherein the control device obtains the shortest command interval for each injector. A fuel injection device comprising an injector that injects fuel into a combustion chamber of an internal combustion engine, and a control device that can control injection start and injection stop of the injector and execute a plurality of injections in one injection period. And
The controller is
When the learning condition including the stable operation state of the internal combustion engine is satisfied, the command interval between the pre-injection in the one-cycle injection period and the post-injection following the pre-injection is gradually shortened and injected from the injector. Deviation measuring means for obtaining a deviation between the command interval when the actual injection amount increases rapidly and a predetermined reference interval;
Command interval correcting means for correcting the command interval based on the deviation obtained by the deviation measuring means;
A fuel injection device comprising: The fuel injection device according to claim 3, wherein
The internal combustion engine includes a plurality of cylinders, and the injector is provided for each of the plurality of cylinders.
The said control apparatus calculates | requires the said deviation for every injector, The fuel-injection apparatus characterized by the above-mentioned. The fuel injection device according to claim 1, wherein:
The fuel injection device according to claim 1, wherein the means for detecting a sudden increase in the actual injection amount injected from the injector is a sensor for detecting an operating state of the internal combustion engine or a combustion state of the combustion chamber.

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