JP5577077B2 - Fixing control device and image forming apparatus - Google Patents

Description

  The present invention relates to a fixing control device and an image forming apparatus that supply power intermittently from an AC power source to a fixing heater to control the temperature of a fixing roller.

  2. Description of the Related Art Conventionally, an image forming apparatus such as a copying machine includes a fixing device that forms an image by fixing toner transferred onto a sheet to the sheet. In a fixing control device that controls the temperature of such a fixing device, a CPU (Central Processing Unit) is configured to supply and stop power to the fixing heater for the triac based on a temperature signal input from a temperature sensor that detects the temperature of the fixing roller. However, there is a problem that the fixing roller becomes abnormally hot due to a software runaway in the CPU, a temperature sensor failure, a triac failure, etc., and the fixing roller is damaged.

  Various apparatuses and methods have been proposed for the above problems. For example, Patent Document 1 describes a temperature control device that configures a watchdog circuit using a zero-cross signal and maintains an OFF state of a fixing heater when a CPU abnormality is detected. Further, Patent Document 2 describes an image forming apparatus that forcibly turns off the triac from a partial pressure value generated from a temperature sensor and a resistor, in addition to the method described in Patent Document 1. Further, Patent Documents 3 to 5 describe devices that stop energization of the fixing heater by forcibly turning off the relay when abnormal heating of the fixing heater is confirmed by a temperature abnormality monitoring circuit.

JP 2009-042594 A JP 2009-128406 A Japanese Patent Laid-Open No. 10-307514 JP 2002-2222017 A JP 2008-170656 A

  In the case of the devices described in Patent Documents 1 to 5, a zero cross generation circuit is provided on the primary side of the triac, and an abnormality has occurred using the zero cross signal output from the zero cross generation circuit without the triac on / off relationship. Judgment whether or not. Therefore, it is impossible to correctly determine whether the triac is operating normally from the zero cross signal, which is inappropriate for detecting the triac abnormality.

  SUMMARY An advantage of some aspects of the invention is that it provides a fixing control device and an image forming apparatus that accurately detect breakage of components constituting the fixing control device, including a triac. Is.

Fixing control device according to the present invention, an AC power source for supplying an AC voltage to the fixing heater, interposed between the AC power supply and the fixing heater, a gate terminal of the second triac control signal is input, the From the second triac control signal input to the gate terminal, a triac that performs energization / cutoff between the fixing heater and the AC power source, a temperature control unit that outputs the first triac control signal, and the temperature control unit the output first triac control signal is input, a photocoupler that outputs the second triac control signal to the gate terminal, and a signal generating means for generating a zero-cross signal from the AC voltage the triac is output, based on the first triac control signal and the zero-crossing signal, whether the triac is operating normally Determining, based on the first triac control signal and the second triac control signal, and a determination means for determining whether the photocoupler is operating normally.
The present invention includes the following first to fifth inventions.
A fixing control device according to a first aspect of the present invention is an AC power source that supplies an AC voltage to a load, and a first switching unit that is interposed between the load and the AC power source and performs energization / cutoff between the load and the AC power source. And a control means for outputting a control signal for controlling energization / cutoff operation performed by the first switching means, and interposed between the control means and the first switching means, and between the control means and the first switching means. A second switching means for energizing / cutting off, a signal generating means for generating a zero-cross signal from the AC voltage output from the first switching means, a zero-cross signal output from the signal generating means, and the second switching means Determining means for determining whether or not the first switching means is operating normally based on the output control signal.

  Conventionally, since the signal generating means is provided on the input side of the first switching means, the zero cross signal is output without the on / off relationship of the first switching means. That is, it cannot be determined from the zero cross signal whether the first switching means is operating normally, and is inappropriate for detecting an abnormality in the first switching means.

  Therefore, by providing the signal generating means on the output side of the first switching means as described above, the zero cross signal should be output in conjunction with the on / off of the first switching means. That is, by comparing this zero-cross signal with the control signal that instructs energization / cutoff of the first switching means, the determination means can accurately determine whether or not the first switching means is operating normally.

A second invention is the fixing control device according to the first invention , wherein the judging means further takes in a control signal outputted by the control means, and the control signal outputted by the control means and the zero cross signal. Whether or not the first switching means is operating normally. Based on the control signal output from the control means and the control signal output from the second switching means, the second switching means is normal. It is determined whether or not it is operating.

  According to this configuration, the judging means takes in the control signal output from the control means and compares this control signal with the zero cross signal, so that it can accurately judge whether or not the first switching means is operating normally. Can do. Further, the judging means compares the control signal output from the control means with the control signal output from the second switching means, so that the damaged portion of which abnormality has occurred in either the first switching means or the second switching means is specified. be able to.

A third invention is the fixing control device of the first invention , wherein the third switching is interposed between the load and the first switching means, and performs energization / cutoff between the load and the first switching means. Means for outputting a cutoff signal to the third switching means when the judgment means judges that the first switching means is not operating normally, and the third switching means According to the cutoff signal, the load and the first switching means are shut off.

  According to this configuration, since the third switching means shuts off the load and the first switching means according to the shut-off signal output when the judging means judges that the first switching means is not operating normally, Abnormal heating of the load can be prevented.

A fourth invention is the fixing control device according to the second invention , wherein the third switching is interposed between the load and the first switching means, and performs energization / cutoff between the load and the first switching means. Means for outputting a cut-off signal to the third switching means when it is determined that the first switching means or the second switching means is not operating normally, The third switching means shuts off the load and the first switching means according to the cutoff signal.

  According to this configuration, the third switching means is connected between the load and the first switching means in accordance with a cutoff signal output when the judging means judges that the first switching means or the second switching means is not operating normally. Therefore, abnormal heating of the load can be prevented.

An image forming apparatus according to a fifth aspect of the present invention includes an image forming unit that includes a fixing roller and a fixing heater that heats the fixing roller, and fixes the toner formed on the sheet to the sheet to form an image . A fixing control device according to any one of the fourth aspect , wherein the fixing control device intermittently supplies an AC voltage from the AC power source to the fixing heater as the load to control the temperature of the fixing roller. To do.

According to this structure, there exists an effect of the 1st-4th invention .

  According to the present invention, by providing the signal generating means on the output side of the first switching means, the zero cross signal should be output in conjunction with the on / off of the first switching means. That is, by comparing this zero-cross signal with the control signal that instructs energization / cutoff of the first switching means, the determination means can accurately determine whether or not the first switching means is operating normally.

FIG. 2 is a side view schematically showing an internal configuration of the image forming apparatus. 1 is a block diagram illustrating an electrical configuration of an image forming apparatus. FIG. 3 is a block diagram illustrating an electrical configuration of the fixing control device according to the first embodiment. The flowchart which showed the flow of the abnormality determination process in 1st Embodiment. FIG. 9 is a block diagram illustrating an electrical configuration of a fixing control device according to a second embodiment. The flowchart which showed the flow of the abnormality determination process in 2nd Embodiment.

  Embodiments of an image forming apparatus according to the present invention will be described below with reference to the drawings.

[First Embodiment]
FIG. 1 is a side view schematically showing an internal configuration of an image forming apparatus 1 according to an embodiment of the present disclosure. The image forming apparatus 1 has functions such as a copy function, a printer function, a scanner function, and a facsimile function. The image forming apparatus 1 includes a main body 2, a stack tray 3 disposed on the left side of the main body 2, and a main body. 2 has a document reading unit 4 disposed above the document reading unit 4 and a document conveying unit 5 disposed above the document reading unit 4.

  An input operation unit 6 is provided on the front part of the image forming apparatus 1. The input operation unit 6 displays a start key 7 for a user to input a print execution instruction, a numeric keypad 8 for inputting the number of copies to be printed, operation guide information for various copying operations, and the like. A display unit 9 composed of a liquid crystal display or the like having a touch panel function for input, a reset key 10 for resetting setting contents set on the display unit 9, a stop key 11 for stopping an operation being executed, and a copy A function switching key 12 for switching between a function, a printer function, a scanner function, and a transmission function is provided.

  The document reading unit 4 includes a scanner unit 13 including a CCD (Charge Coupled Device) sensor and an exposure lamp, and a document table 14 and a document reading slit 15 made of a transparent member such as glass. The scanner unit 13 is configured to be movable by a drive unit (not shown). When reading a document placed on the document table 14, the scanner unit 13 is moved along the document surface at a position facing the document table 14, and the document image is displayed. Image data acquired while scanning is output to a control unit described later. Further, when reading a document fed by the document conveying unit 5, the document is moved to a position facing the document reading slit 15, and the document is synchronized with the document conveying operation by the document conveying unit 5 via the document reading slit 15. Are obtained and the image data is output to the control unit.

  The document transport unit 5 includes a document placement unit 16 for placing a document, a document discharge unit 17 for discharging a document whose image has been read, and one document placed on the document placement unit 16. A document transport mechanism 18 including a paper feed roller, a transport roller (not shown), and the like for feeding the paper one by one to a position facing the document reading slit 15 and discharging it to the document discharge section 17 is provided.

  In addition, the document conveying section 5 is provided so as to be rotatable with respect to the main body section 2 so that the front side thereof can move upward. By moving the front side of the document conveying section 5 upward to open the upper surface of the document table 14, it is possible to place a read document, for example, a book in a spread state, on the upper surface of the document table 14.

  The main body 2 includes a plurality of paper feed cassettes 19, a paper feed roller 20 that feeds the paper from the paper feed cassette 19 one by one and transports it to the image forming unit 21, and an image on the paper transported from the paper feed cassette 19. And an image forming unit 21 for forming the image.

  The image forming unit 21 outputs a laser beam or the like based on the image data acquired by the scanner unit 13 to expose the photosensitive drum 22, and forms an electrostatic latent image on the surface of the photosensitive drum 22. A developing unit 24 that forms a toner image by attaching toner to the surface of the photosensitive drum 22 on which the electrostatic latent image is formed; a transfer unit 25 that transfers the toner image on the photosensitive drum 22 to a sheet; A fixing device 28 having a fixing roller 26 and a pressure roller 27 for fixing the toner image to the paper by heating the paper on which the toner image has been transferred, and a paper conveying path in the image forming unit 21. A pair of conveyance rollers 30 and 31 for conveying the stack tray 3 or the discharge tray 29 is provided.

  Further, the fixing device 28 includes a temperature sensor 41 that measures the temperature of the fixing roller 26. The temperature sensor 41 outputs the measured temperature to a control unit described later. Then, the control unit performs temperature control so that the fixing roller 26 maintains a predetermined temperature according to the measured temperature.

  When images are formed on both sides of a sheet, the image forming unit 21 forms an image on one side of the sheet, and then the sheet is nipped between the pair of conveying rollers 30 on the discharge tray 29 side. In this state, the conveyance roller pair 30 is reversed to switch back the sheet, and the sheet is sent to the sheet conveyance path 32 to be conveyed again to the upstream area of the image forming unit 21. The image forming unit 21 forms an image on the other surface. After that, the paper is discharged to the stack tray 3 or the discharge tray 29.

  FIG. 2 is a block diagram illustrating an electrical configuration of the image forming apparatus 1. The image forming apparatus 1 includes a control unit 71, a storage unit 72, a document transport unit 5, a scanner unit 13, an image memory 73, an image processing unit 74, an image forming unit 21, an input operation unit 6, and a network I / F unit 75. Configured. In addition, the same code | symbol is attached | subjected to the same component as demonstrated using FIG. 1, and description is abbreviate | omitted.

  The storage unit 72 stores programs, data, and the like for realizing various functions provided in the image forming apparatus 1. The image memory 73 temporarily stores image data acquired by the scanner unit 13 and image data transmitted from an external device via the network I / F unit 75. The image processing unit 74 performs image processing such as image correction and enlargement / reduction on the image data stored in the image memory 73.

  The image forming unit 21 forms an image on a sheet based on the image data acquired by the scanner unit 13, and includes a fixing control device 76 that controls the temperature of the fixing roller 26 of the fixing device 28. The fixing controller 76 will be described in detail later.

  The network I / F unit 75 is a communication interface circuit that communicates with an external device via a network such as a LAN (Local Area Network) or a WAN (Wide Area Network).

  The control unit 71 is configured by a CPU or the like, reads out a program stored in the storage unit 72, executes processing, outputs an instruction signal to each functional unit, transfers data, and the like, and controls the image forming apparatus 1 in an integrated manner. The temperature control unit 711 and the abnormality determination unit 712 are included.

  Based on the measured temperature of the fixing roller 26 output from the temperature sensor 41, the temperature control unit 711 outputs a control signal to the fixing control device 76 so as to perform temperature control so that the fixing roller 26 maintains a predetermined temperature. To do. The abnormality determination unit 712 determines whether or not the components constituting the fixing control device 76 are operating normally based on the signal output from the fixing control device 76, and determines that the components are not operating normally. Outputs an instruction signal for stopping the heating of the fixing roller 26 to the fixing control device 76.

  FIG. 3 is a block diagram showing an electrical configuration of the fixing control device 76 in the present embodiment. The fixing control device 76 includes a photocoupler 81, a triac 82, a relay 83, a fixing heater 84, an AC power supply 85, a zero cross generation circuit 86 and an arithmetic circuit 87. As shown in the figure, the triac 82, the relay 83, and the fixing heater 84 are connected in series with an AC power supply 85.

  The temperature controller 711 of the controller 71 outputs a triac control signal S2 for the triac 82 in order to control the temperature of the fixing roller 26 based on the measured temperature S1 output from the temperature sensor 41. The triac control signal S2 enters the gate terminal of the triac 82 through the photocoupler 81 as the triac control signal S3. The triac 82 is turned on / off based on the triac control signal S3, whereby the fixing heater 84 and the AC power supply 85 are energized / interrupted, and the temperature of the fixing roller 84 is adjusted.

  The zero-cross generation circuit 86 takes in the AC voltage output from the triac 82 (AC voltage on the T2 side of the triac 82), and generates a zero-cross signal S4 that is a pulse signal having a predetermined width at the zero-cross point of the AC voltage. The result is output to the arithmetic circuit 87.

  The arithmetic circuit 87 takes in the zero cross signal S4 from the zero cross generation circuit 86 and the triac control signal S3 from the photocoupler 81 and outputs the operation result of the triac 82 to the abnormality determination unit 712 as the determination signal S5. When the abnormality determination unit 712 determines that the triac 82 is abnormal based on the determination signal S5, the abnormality determination unit 712 outputs a cutoff signal S6 to the relay 83 to cut off the AC voltage supplied from the AC power supply 85 to the triac 82.

  Note that the control unit 71 and the arithmetic circuit 87 in this embodiment correspond to determination means, but the arithmetic circuit 87 is omitted, and the control unit 71 directly takes in the zero cross signal S4 and the triac control signal S3. The abnormality of the triac 82 may be determined by comparing the two signals.

  The relay 83 is disposed between the fixing heater 84 and the triac 82, and energizes / cuts off the fixing heater 84 and the triac 82 in accordance with the cutoff signal S 6 output from the abnormality determination unit 712.

  Further, when the abnormality determination unit 712 determines that the triac 82 is abnormal based on the determination signal S5 from the arithmetic circuit 87, the abnormality determination unit 712 displays a message indicating that an abnormality has occurred in the fixing control device 76 on the display unit 9 or a warning sound. The occurrence of abnormality is notified to the user.

  FIG. 4 is a flowchart showing a flow of abnormality determination processing in the present embodiment. When the triac control signal S3 output from the photocoupler 81 is in the OFF state (step S11; OFF), and when the zero cross signal S4 is in the ON state (step S12; ON), the arithmetic circuit 87 indicates that the triac 82 is abnormal. A determination signal S5 is output. Similarly, when the triac control signal S3 is in the ON state (step S11; ON) and when the zero cross signal S4 is in the OFF state (step S13; OFF), the arithmetic circuit 87 indicates that the triac 82 is abnormal. The determination signal S5 is output.

  Abnormality determination unit 712 receives determination signal S5 indicating the occurrence of an abnormality, determines that an abnormality has occurred in triac 82 (step S14), and outputs cutoff signal S6 to relay 83 (step S15). . The relay 83 cuts off the AC voltage supplied from the fixing heater 84 to the triac 82 by the cut-off signal S6. Further, the abnormality determination unit 712 notifies the user of the occurrence of abnormality such as displaying a message indicating the occurrence of abnormality of the fixing control device 76 on the display unit 9 or generating a warning sound (step S16). The process ends.

  On the other hand, when the triac control signal S3 is in the OFF state (step S11; OFF), when the zero cross signal S4 is also in the OFF state (step S12; OFF), or when the triac control signal S3 is in the ON state (step S11; ON), when the zero cross signal S4 is also in the ON state (step S13; ON), the arithmetic circuit 87 outputs a determination signal S5 indicating the normal operation of the triac 82, and the control unit 71 shifts the processing to step S11.

  Conventionally, since the zero cross generation circuit is provided on the T1 side of the triac, the zero cross signal output from the zero cross generation circuit is output regardless of the ON / OFF relationship of the triac. That is, the zero cross signal cannot correctly determine whether or not the triac is operating normally, and is inappropriate for detecting a triac abnormality.

  Therefore, as described in the present embodiment, by providing the zero cross generation circuit 86 on the T2 side of the triac 82, the zero cross signal should be output in conjunction with the on / off of the triac 82. That is, when the arithmetic circuit 87 compares the zero cross signal and the triac control signal S3 and outputs the determination signal S5, the abnormality determination unit 712 uses the determination signal S5 to determine whether or not the triac 82 is operating normally. It can be judged accurately.

[Second Embodiment]
In the first embodiment, the arithmetic circuit 87 outputs a determination signal S5 indicating normality / abnormality of the triac 82 based on the triac control signal S3 and the zero cross signal S4 output from the photocoupler 81, and this determination signal S5 is used. The case where the abnormality determination unit 712 determines whether the triac 82 is normal or abnormal has been described. In the second embodiment, the arithmetic circuit 87 uses the triac control signal S2 output from the temperature control unit 711 in addition to the triac control signal S3 and the zero cross signal S4 to determine whether the triac 82 and the photocoupler 81 are normal or abnormal. A case where the signal S5 is output and the abnormality determination unit 712 determines whether the triac 82 and the photocoupler 81 are normal / abnormal using the determination signal S5 will be described. The internal configuration and electrical configuration of the image forming apparatus 1 in the second embodiment are the same as those shown in FIGS.

  FIG. 5 is a block diagram showing an electrical configuration of the fixing control device 76 in the present embodiment. Only the parts different from the fixing controller 76 in the first embodiment shown in FIG. 3 will be described below.

  The arithmetic circuit 87 receives the triac control signal S2 from the temperature control unit 711, the triac control signal S3 from the photocoupler 81, and the zero cross signal S4 from the zero cross generation circuit 86. The arithmetic circuit 87 compares the triac control signal S2 and the triac control signal S3, and outputs the operation result of the photocoupler 81 to the abnormality determination unit 712 as the determination signal S5. Further, the triac control signal S2 and the zero cross signal S4 are compared, and the operation result of the triac 82 is output to the abnormality determination unit 712 as the determination signal S5.

  When the abnormality determination unit 712 determines that the photocoupler 81 or the triac 82 is abnormal based on the determination signal S5, the abnormality determination unit 712 outputs a cutoff signal S6 to the relay 83, and generates an AC voltage supplied from the AC power supply 85 to the triac 82. Shut off.

  FIG. 6 is a flowchart showing the flow of the abnormality determination process in the present embodiment. When the triac control signal S2 output from the temperature controller 711 is in the OFF state (step S21; OFF), and when the triac control signal S3 is in the ON state (step S22; ON), the arithmetic circuit 87 is connected to the photocoupler 81. A determination signal S5 indicating the occurrence of abnormality is output. Similarly, when the triac control signal S2 is in the ON state (step S21; ON) and when the triac control signal S3 is in the OFF state (step S23; OFF), the arithmetic circuit 87 causes the photocoupler 81 to generate an abnormality. Is output.

  Abnormality determination unit 712 receives determination signal S5 indicating the occurrence of abnormality in photocoupler 81, determines that an abnormality has occurred in photocoupler 81 (step S24), and outputs cutoff signal S6 to relay 83. (Step S29). The relay 83 cuts off the AC voltage supplied from the fixing heater 84 to the triac 82 by the cut-off signal S6. Further, the abnormality determination unit 712 notifies the user of the occurrence of abnormality such as displaying a message indicating the occurrence of abnormality of the fixing control device 76 on the display unit 9 or generating a warning sound (step S30). The process ends.

  On the other hand, when the triac control signal S2 is OFF (step S21; OFF), when the triac control signal S3 is also OFF (step S22; OFF), or when the triac control signal S2 is ON (step S21). ON), when the triac control signal S3 is also in the ON state (step S23; ON), the arithmetic circuit 87 outputs a determination signal S5 indicating the normal operation of the photocoupler 81, and the control unit 71 advances the process to step S25. .

  Next, when the triac control signal S2 is in the OFF state (step S25; OFF), and when the zero-cross signal S4 is in the ON state (step S26; ON), the arithmetic circuit 87 determines that the triac 82 is abnormal. S5 is output. Similarly, when the triac control signal S2 is in the ON state (step S25; ON) and when the zero cross signal S4 is in the OFF state (step S27; OFF), the arithmetic circuit 87 indicates that the triac 82 is abnormal. The determination signal S5 is output.

  Abnormality determination unit 712 receives determination signal S5 indicating the occurrence of abnormality, determines that an abnormality has occurred in triac 82 (step S28), and outputs cutoff signal S6 to relay 83 (step S29). . The relay 83 cuts off the AC voltage supplied from the fixing heater 84 to the triac 82 by the cut-off signal S6. Further, the abnormality determination unit 712 notifies the user of the occurrence of abnormality such as displaying a message indicating the occurrence of abnormality of the fixing control device 76 on the display unit 9 or generating a warning sound (step S30). The process ends.

  On the other hand, when the triac control signal S2 is in the OFF state (step S25; OFF), when the zero cross signal S4 is also in the OFF state (step S26; OFF), or when the triac control signal S2 is in the ON state (step S25; ON), when the zero cross signal S4 is also in the ON state (step S27; ON), the arithmetic circuit 87 outputs the determination signal S5 indicating the normal operation of the triac 82, and the control unit 71 shifts the processing to step S21.

  As described above, by providing the zero cross generation circuit 86 on the T2 side of the triac 82, the zero cross signal should be output in conjunction with the on / off of the triac 82. That is, when the arithmetic circuit 87 compares the zero cross signal and the triac control signal S3 and outputs the determination signal S5, the abnormality determination unit 712 uses the determination signal S5 to determine whether or not the triac 82 is operating normally. It can be judged accurately.

  Then, when the arithmetic circuit 87 compares the triac control signal S2 with the triac control signal S3 output from the photocoupler 81, the abnormality determination unit 712 can determine the operation of the photocoupler 81. By comparing the triac control signal S2 and the zero cross signal S4, the abnormality determination unit 712 can determine the operation of the triac 82. As described above, the abnormality determination unit 712 can identify a damaged portion where an abnormality has occurred in either the photocoupler 81 or the triac 82.

1 Image forming apparatus 21 Image forming unit (image forming means)
28 Fixing Device 71 Control Unit 711 Temperature Control Unit (Control Unit)
712 Abnormality determination unit (determination means)
76 Fixing control device 81 Photocoupler (second switching means)
82 Triac (first switching means)
83 Relay (third switching means)
84 Fixing heater (load)
85 AC power supply 86 Zero cross generation circuit (signal generation means)
87 Arithmetic circuit (Judgment means)

Claims (3)

An AC power supply for supplying an AC voltage to the fixing heater ;
The fixing heater and interposed between said AC power source, a gate terminal of the second triac control signal is input, by the second triac control signal input to the gate terminal, the AC power supply and the fixing heater A triac for energization / interruption between
A temperature control unit for outputting a first triac control signal;
A photocoupler that receives the first triac control signal output from the temperature control unit and outputs the second triac control signal to the gate terminal;
Signal generating means for generating a zero-cross signal from the AC voltage output by the triac ;
Based on the first triac control signal and the zero cross signal, it is determined whether or not the triac is operating normally, and based on the first triac control signal and the second triac control signal. Determining means for determining whether or not the photocoupler is operating normally;
A fixing control device. The fixing heater and interposed between said triac, further comprising a third switching means for performing energization / cutoff between the said fixing heater triac,
The determination means outputs a cutoff signal to the third switching means when it is determined that the TRIAC or the photocoupler is not operating normally, and the third switching means follows the cutoff signal. The fixing control device according to claim 1, wherein the fixing heater and the triac are interrupted. Having the fixing heater for heating the fixing roller and the fixing roller, an image forming means for forming an image of toner formed on the sheet by the fixing to the paper,
The fixing control device according to claim 1 or 2,
And the fixing control device intermittently supplies an AC voltage from the AC power source to the fixing heater to control the temperature of the fixing roller.

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