JP2008216804A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To avoid remelting of developer on recording materials stacked after image formation, while maintaining the print productivity to the maximum in an image forming apparatus. <P>SOLUTION: In a copying machine 1, sheets of paper with toner images fixed on them are output via a paper ejection port (not shown) from the inside of the copying machine 1, and stacked onto a paper ejection tray 38. Additionally, in the copying machine 1, the temperature and the height of the stack of sheets of paper on the paper ejection tray 38 are detected. If the temperature of the stack of paper is equal to or above the predetermined temperature and the height of the stack of sheets of paper is equal to or greater than a predetermined height, the control of a printing operation is altered so as to reduce the number of prints produced per minute. Thereby, printing productivity can be decreased. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an image forming apparatus, and more particularly to an image forming apparatus for fixing an image formed by a developer formed on a recording material using a heat fixing device.

  In image forming apparatuses such as copiers, printers, and MFPs (Multi Function Peripheral) that are complex machines of these, after forming an electrostatic image of a developer such as toner on a recording material, heating and pressurizing processes are performed. An image is formed by melting and fixing the developer on the recording material. The recording material on which the image is formed is stacked on a certain place such as a paper discharge tray.

Various techniques have been disclosed for such image forming apparatuses.
For example, Japanese Patent Application Laid-Open No. 2006-23377 discloses a technique for controlling the amount of heat applied to a recording material in order to stably fix the recording agent on the recording material in view of the diversification of recording materials. It is disclosed.

Patent Document 2 (Japanese Patent Application Laid-Open No. 2003-302875) detects the temperature of a recording material stacked after image formation in order to avoid the developer peeling from the recording material stacked after image formation. A technique is disclosed in which when the detected temperature exceeds a predetermined value, the image forming operation is prohibited until the detected temperature becomes equal to or lower than the predetermined value.
JP 2006-23377 A JP 2003-302875 A

  Conventionally, the heat remaining in the recording material loaded after image formation causes the developer on the recording material to melt again and adhere to the adjacent recording material, and the adjacent recording materials stick together, There has been a problem that the developer is peeled off from the recording material.

  On the other hand, in an image forming apparatus, it is always required to quickly form an image with more recording materials, that is, to improve printing productivity. From this point of view, when applying the technique disclosed in Patent Document 2 including the configuration of temporarily prohibiting the image forming operation in solving the above-described problem, there is some problem with respect to print productivity. Consideration is considered necessary.

  The present invention has been conceived in view of such circumstances, and an object of the present invention is to re-melt the developer on the recording material loaded after the image formation while maintaining the maximum printing productivity in the image forming apparatus. It is to avoid.

  An image forming apparatus according to the present invention is an image forming apparatus that heat-fixes an image formed by a developer formed on a recording material by using a heat-fixing device. A paper discharge tray for stacking materials, a stack amount detection means for detecting the amount of paper stacked on the paper discharge tray, a temperature detection means for detecting the temperature of the paper stacked on the paper discharge tray, Based on one of the amount of paper detected by the stacking amount detection unit and the temperature of the paper detected by the temperature detection unit, either one remelts the developer in the recording material on the paper discharge tray. A determination unit that determines whether or not the value requires a process for avoiding; and an execution unit that executes the process when the determination unit determines that the process is necessary. It is characterized by.

  In the image forming apparatus according to the aspect of the invention, the stack amount detection unit is urged in a direction opposite to a direction in which recording materials are stacked on the discharge tray, and one end is stacked on the uppermost portion of the discharge tray. By optically detecting the lever in contact with the recording material and the state of the lever when the one end is in contact with the recording material stacked on the uppermost portion of the paper discharge tray, Preferably, the apparatus further comprises a height detecting means for detecting the height of the recording material stacked on the paper discharge tray, and the temperature detecting means is attached to the one end of the lever.

  In the image forming apparatus according to the aspect of the invention, when the recording material is discharged from the heat fixing device to the paper discharge tray, the stack amount detection unit connects the one end of the lever to the paper discharge tray. It is preferable to further include a retreating means for retreating from the path through which the water is discharged.

  In the image forming apparatus according to the aspect of the invention, it is preferable that the execution unit decreases the print productivity in the image forming apparatus by executing the processing.

  In the image forming apparatus of the present invention, the storage means for storing the recording material, the image forming means for forming an image by the developer on the recording material, and the recording material on which the image by the developer is formed by the image forming means A fixing unit for heating and fixing; and a feeding unit for feeding the recording material stored in the storing unit in the order of the image forming unit, the heating fixing unit, and the paper discharge tray. It is preferable to reduce the speed at which the recording material is fed by the feeding means.

  The image forming apparatus of the present invention further includes a cooling unit that cools the recording material on which the image formed by the developer is heated and fixed by the heating and fixing unit, and the execution unit improves the cooling capacity of the cooling unit. It is preferable to execute the above process.

  In the image forming apparatus according to the aspect of the invention, it is preferable that the execution unit executes the process by causing the notification unit to perform a notification operation.

  In the image forming apparatus of the present invention, the image forming apparatus further includes a detecting unit that detects whether or not a recording material is stacked on the paper discharge tray, and the stacking amount detecting unit includes an image formed by a developer on the heat fixing unit. Counting means for counting the number of recording materials formed on the recording medium, and reset means for resetting the count value of the counting means when the detection means determines that no recording material is loaded on the paper discharge tray. Preferably, it is configured.

  According to the present invention, in the image forming apparatus, not only the temperature of the recording material stacked on the paper discharge tray but also the amount of the recording material is taken into consideration, and it is necessary to perform processing for avoiding remelting. Is judged.

  Therefore, the image forming apparatus avoids remelting when the recording material is loaded on the discharge tray in such a small amount that remelting occurs even if the recording material on the discharge tray is slightly hot. Therefore, it can be determined that no processing is required. That is, it is possible to minimize the execution of processing that lowers printing productivity.

  Further, the image forming apparatus requires processing for avoiding remelting if a large amount of recording materials are stacked on the paper discharge tray even if the recording material on the paper discharge tray is relatively low in temperature. It can also be judged. In other words, the image forming apparatus can execute the process even when the process for avoiding remelting is originally necessary but may be unnecessary.

  As described above, the image forming apparatus can execute the process for avoiding remelting without causing a decrease in printing productivity as much as possible and surely when necessary.

  Embodiments of the present invention will be described below with reference to the drawings. In the following description, the same parts and components are denoted by the same reference numerals. Their names and functions are also the same unless otherwise noted.

[First Embodiment]
FIG. 1 is a schematic cross-sectional view showing an outline of a hardware configuration of a copying machine 1 which is an example of an image forming apparatus according to a first embodiment of the present invention. The copier 1 is a tandem digital color copier, which sequentially superimposes four color toners of yellow (Y), magenta (M), cyan (C), and black (K) to form a color image. Form.

  Referring to FIG. 1, the copying machine 1 according to the present embodiment includes an image reading unit 10, a paper transport unit 20, an image forming unit 30, and a paper storage unit 40.

  The image reading unit 10 includes a loading table 3 for setting a document, a document table glass 11, a conveyance unit 2 that automatically conveys documents set on the loading table 3 one by one to the document table glass 11, And a discharge table 4 for discharging the read document. Further, the document reading unit 10 includes a scanner (not shown) (scanner 19 in FIG. 2 described later). The scanner moves in parallel with the platen glass 11 by a scan motor, an exposure lamp that irradiates the document, a reflection mirror that changes the direction of the reflected light from the document, a mirror that changes the optical path from the reflection mirror, and a lens that collects the reflected light A half-mirror that determines the color according to the wavelength of the reflected light, reflects or transmits the reflected light and guides the reflected light to the two photoelectric conversion elements, and a CCD (Charge Coupled Device) that generates an electrical signal according to the received reflected light ) And the like.

  The document transported by the transport unit 2 is set on the document table glass 11 and is exposed and scanned when the scanner moves in parallel with the document table glass 11. The reflected light from the document is converted into an electrical signal by the photoelectric conversion element and input to the image forming unit 30.

  The image forming unit 30 includes an intermediate transfer belt 31, developing units 21Y, 21M, 21C, and 21K (representing these as the developing unit 21), and transfer rollers 25Y, 25M, 25C, and 25K (representing these). A controller 100 including a transfer roller 25, a fixing device 36, a CPU (Central Processing Unit) (CPU 15 in FIG. 2 to be described later), a program executed by the controller 100, and data used for executing the program And the like, a memory 101 for storing the above, a fan 60, a jam processing sensor 61, a paper discharge sensor 62, and a tray sensor 63.

  The intermediate transfer belt 31 is suspended by a plurality of rollers 32, 33, and 34 so as not to be loosened, and these rollers rotate counterclockwise (in the direction of arrow A in FIG. 1) in FIG. It is an endless belt that rotates in the same direction.

  The developing device 21 is a developing device 21Y, 21M, corresponding to each color toner of yellow (Y), magenta (M), cyan (C), and black (K) arranged at a predetermined interval along the intermediate transfer belt 31. Including 21C and 21K. The transfer roller 25 includes transfer rollers 25 </ b> Y, 25 </ b> M, 25 </ b> C, and 25 </ b> K that are paired with the photoconductor included in each developing device 21 via the intermediate transfer belt 31.

  The fixing device 36 transfers and fixes the toner image transferred to the intermediate transfer belt 31 onto a sheet. Specifically, the fixing device 36 includes a fixing roller, a member such as a coil and a heat source for heating the fixing roller, and a pressure roller provided to face the fixing roller, and the sheet S on which the toner image is transferred. Is passed through the nip portion between the fixing roller and the pressure roller to heat and fix the toner image on the paper S.

  The developing devices 21Y, 21M, 21C, and 21K are configured so that cartridges that store toners corresponding to the respective colors can be mounted.

  The paper storage unit 40 includes a paper feed cassette 41 that stores the paper S that is a printing medium, and the paper transport unit 20 includes rollers 42, 43, 35, and 37 and a paper discharge tray 38. The rollers 42, 43, 35, and 37 are installed in the transport path of the paper S from the paper feed cassette 41 to the paper discharge tray 38. In addition, printed sheets are discharged and stacked on the discharge tray 38.

  The controller 100 reads out and executes a program from the memory 101 based on an instruction signal input from an operation panel (not shown) or the like, and controls the above-described units. Further, the controller 100 may be provided with a timer such as a timer, and execute the program when a predetermined time is measured. The controller 100 and the memory 101 may be provided in the image reading unit 10, the paper conveyance unit 20, or the like other than the image forming unit 30.

  By executing the program, the controller 100 performs predetermined image processing on the image signal input from the image reading unit 10 or an external device, and performs color conversion to each color of yellow, magenta, cyan, and black. Create a digital signal. The image color data for cyan, the image color data for magenta, the image color data for yellow, and the image color data for black created by the controller 100 for each color are the controller 100 to the exposure unit of the developing unit 21.

  The exposure device outputs a laser beam to the photoconductor based on the image data input from the controller 100, so that the surface of the uniformly charged photoconductor is exposed according to the image data, and the electrostatic latent image is generated. It is formed. A developing bias voltage is applied to the developing roller, and a potential difference is generated between the developing roller and the latent image potential of the photoreceptor. In this state, charged toner is supplied to form a toner image on the surface of the photoreceptor. The toner image formed on the surface of the photosensitive member is transferred to the intermediate transfer belt 31 as an image carrier by a constant voltage or constant current transfer roller 25. This is called primary transfer.

  The toner image primarily transferred to the intermediate transfer belt 31 is transferred onto the paper S conveyed from the paper feed cassette 41 by the roller 34. This is called secondary transfer. The toner image secondarily transferred to the paper is fixed on the paper by the fixing device 36 and is discharged to the paper discharge tray 38 as an electrophotographic image.

  On the downstream side of the fixing device 36, a jam processing sensor 61 for detecting the presence or absence of a jam of the paper S and a fan 60 for cooling the paper are provided. A paper discharge sensor 62 is provided at the paper discharge port (in the vicinity of the paper discharge tray 38) of the copying machine 1 to detect that the paper has passed through the paper discharge port. Further, the paper discharge tray 38 is provided with a tray sensor 63 that detects the presence or absence of paper on the paper discharge tray 38.

FIG. 2 is a control block diagram of the copying machine 1.
Referring to FIG. 2, in addition to the components described so far, the copying machine 1 includes a CPU (Central Processing Unit) 15 that controls the operation of the copying machine 1 as a whole, and a RAM (work area of the CPU 15). Random Access Memory) 16, communication unit 14, key operation unit 17, display 18, communication unit 14, scanner 19, transport motor 29, cam motor 51, temperature sensor 52, and media driver 41. Including.

  The key operation unit 17 and the display 18 are provided on the front surface of the copying machine 1 main body, and receive information input by a user operation. The display 18 displays information. The display 18 may be configured to function as a touch panel.

  The communication unit 14 is connected to a network or an external device, and transmits / receives print data. The media drive 41 can read and write information on a recording medium 400 that can be attached to and detached from the copying machine 1. The content stored in the memory 101 may be recorded on the recording medium 400. Then, the CPU 15 may be configured to execute a program recorded on the recording medium 400 using data recorded on the recording medium 400.

  The transport motor 29 is a motor for driving a roller provided in the paper transport unit 20.

  The cam motor 51, the temperature sensor 52, and the lever position sensor 53 relate to a lever that is provided in the paper discharge tray 38 and suppresses the paper on the paper discharge tray 38. Here, the lever will be described. This will be described with reference to FIGS. 3 (A) and 3 (B).

  3A and 3B show a state in which the sheets S are stacked on the sheet discharge tray 38. FIG.

  In the copying machine 1, the sheet on which the toner image is fixed as described above is discharged from the inside of the main body of the copying machine 1 through a discharge port (not shown) and stacked on the discharge tray 38. The copying machine 1 is provided with a lever 380 at such a paper discharge port.

  The lever 380 can be rotated about the fulcrum 380A in the direction indicated by the arrow R1 in FIG. 3A and the arrow R3 in FIG. 3B. The lever 380 is biased in the direction of the arrow R5 by the spring 381.

  A cam 383 is provided in a portion adjacent to the lower side of the fulcrum 380A of the lever 380. The cam 383 is attached to the shaft 383A and is driven in the direction indicated by the arrow R2 in FIG. 3A and the arrow R4 in FIG. 3B by being driven by the cam motor 51 (FIG. 2).

  The cam 383 comes into contact with the lower end of the lever 380 when rotated in the direction of the arrow R2 in FIG. As a result, the lever 380 rotates from the state shown in FIG. 3A in the R1 direction around the fulcrum 380A to the state shown in FIG. 3B. Further, the cam 383 rotates in the direction of arrow R4 in FIG. 3B, so that the contact between the cam 383 and the lever 380 is released. Accordingly, the lever 380 rotates from the state shown in FIG. 3B in the R3 direction around the fulcrum 380A to the state shown in FIG. 3A.

  A temperature sensor 52 made of a thermistor or the like is attached to a portion of the lever 380 that contacts the paper. In the copying machine 1, when the lever 380 is in contact with the sheet as shown in FIG. 3A, the temperature of the sheet on the sheet discharge tray 38 can be detected.

  FIG. 3A shows a state in which the lever 380 holds the paper stacked on the top of the paper discharge tray 38 from above. Hereinafter, the fact that the lever 380 is in this state is referred to as the detection position.

  FIG. 3B shows a state in which the lever 380 is retracted from the path of the sheet sent to the paper discharge tray 38. Hereinafter, the lever 380 being in this state is referred to as being in the retracted position.

  Note that the detailed position of the lever 380 at the detection position varies depending on the amount (height) of sheets stacked on the paper discharge tray 38, as shown in FIGS. 4A and 4B, for example. . Specifically, in the state shown in FIG. 4B, the height of the sheets stacked on the paper discharge tray 38 is higher than the state shown in FIG. Due to the difference in the stacking height of the sheets, the rotation angle of the lever 380 with the temperature sensor 52 in contact with the uppermost portion of the stacked sheets varies with the fulcrum 380A as an axis.

  The lever position sensor 53 (FIG. 2) is constituted by, for example, an optical sensor having an optical axis in a direction intersecting the paper surface of FIGS. 3 and 4, and detects the height of the lever 380 based on a mode in which the lever 380 shields light. To do. The CPU 15 calculates the height of the paper stacked on the paper discharge tray 380 based on the detected height of the lever 380. Note that the relationship between the height of the lever 380 and the height of the paper stacked on the paper discharge tray 380 is stored in the memory 101 as a table or a function.

  The CPU 15 controls the driving of the lever 380 in synchronism with the timing of paper conveyance during image formation (printing operation) on the paper. Here, the content of the process (lever drive process) executed in the case of such control will be described with reference to FIG. 5 which is a flowchart of the process.

  Referring to FIG. 5, first, in step SA10, CPU 15 energizes cam motor 51 so that lever 380 is set to the detection position, and proceeds to step SA20.

  Next, in step SA20, the CPU 15 determines whether or not a printing operation is instructed to the copying machine 1. The instruction of the printing operation to the copying machine 1 is that an operation for inputting such information to the key operation unit 17 is performed, or such information is input through the communication unit 14. Made. If the CPU 15 determines that there is an instruction for a printing operation, the process proceeds to step SA30.

  In step SA30, the CPU 15 determines whether or not the leading edge of the paper has passed the paper discharge roller 37 by checking the detection state of the paper discharge sensor 62. If it is determined that the paper has passed, the process proceeds to step SA40.

  In step SA40, the CPU 15 energizes the cam motor 51 to move the lever 380 to the retracted position, and proceeds to step SA50.

  In step SA50, the CPU 15 checks the detection state of the paper discharge sensor 62 to determine whether or not the trailing edge of the paper whose passage of the leading edge has been detected in step SA30 has passed the paper discharge roller 37. If it is determined, the process proceeds to step SA60.

  In step SA60, the CPU 15 energizes the cam motor 51 so that the lever 380 is set to the detection position, and proceeds to step SA70.

  In step SA70, the CPU 15 determines whether or not the printing operation whose instruction has been confirmed in step SA20 is completed. If it is determined that the printing operation is not yet completed, the process returns to step SA30. Terminate.

Next, sticking prevention processing executed in the copying machine 1 will be described.
In the copying machine 1, the paper loaded on the paper discharge tray 38 does not escape due to the heat applied when it passes through the fixing device 36 and is fixed on the paper by this heat. It is conceivable that the toner that has been melted again is pasted together on the paper discharge tray 38. In the copying machine 1, processing for preventing such sticking between sheets (sticking prevention processing) is executed in parallel with the printing operation and the like.

  The occurrence of sticking is considered to be related to the temperature of the paper on the paper discharge tray 38 and the height of the stacked paper (the amount of paper). Specifically, for example, as shown in FIG. 6, it is considered that sticking occurs when the temperature of the paper is high and the height at which the paper is stacked is high (corresponding to the sticking occurrence region). In the graph shown in FIG. 6, the vertical axis defines the temperature of the sheets stacked on the paper discharge tray 38, and the horizontal axis defines the height stacked.

FIG. 7 is a flowchart of the sticking prevention process.
In the sticking prevention process, the CPU 15 first checks in step SB10 the detection output of the temperature sensor 52 to determine whether or not the temperature of the paper stacked on the paper discharge tray 38 is equal to or higher than T1. If it is determined that it is equal to or greater than T1, the process proceeds to step SB20.

  In step SB20, the CPU 15 checks the detection output of the lever position sensor 53 to determine whether the height of the paper stacked on the paper discharge tray 38 is H1 or higher, and is H1 or higher. If determined, the process proceeds to step SB30.

  In step SB30, the CPU 15 changes the print productivity and advances the process to step SB40. Here, specifically, the control mode of the operations of the developing device 21 and the transport motor 29 is changed so that the number of printed sheets per minute is changed from P1 to P2 (P1> P2). The

  In step SB40, the CPU 15 determines whether or not the height of the paper stacked on the paper discharge tray 38 is less than H1, and if it is determined that the height is less than H1, the process proceeds to step SB50.

  In step SB50, the CPU 15 restores the print productivity changed in step SB40, that is, changes the number of printed sheets per minute from P2 to P1, and returns the process to step SB10.

  In the present embodiment described above, the copying machine 1 executes the sticking prevention process so that the paper on the paper discharge tray 38 has a temperature of T1 or higher and a stacked height of H1 or higher. In some cases, print productivity is reduced.

  Whether the sticking prevention process of the present embodiment is plotted in the sticking occurrence area when the paper temperature and the stack height are plotted in the graph of FIG. 6 instead of the process of step SB10 and step SB20. It may be configured such that the process proceeds to step SB30 on the condition that it is determined whether or not it is plotted in the sticking occurrence region.

[Second Embodiment]
The image forming apparatus according to the present embodiment can have the same configuration as that of the image forming apparatus according to the first embodiment, and only the contents of the sticking prevention process are different. Therefore, the contents of the sticking prevention process in the copying machine 1 will be described using the copying machine 1 described above as the image forming apparatus of the present embodiment. FIG. 8 shows a flowchart of the sticking prevention process executed in the copying machine 1 of the present embodiment.

  Referring to FIG. 8, in the sticking prevention process of the present embodiment, CPU 15 first checks the detection output of temperature sensor 52 in step SC10, thereby detecting the temperature of the paper stacked on discharge tray 38. Is greater than or equal to T1, and if it is greater than or equal to T1, the process proceeds to step SC20.

  In step SC20, the CPU 15 checks the detection output of the lever position sensor 53 to determine whether or not the height of the paper stacked on the paper discharge tray 38 is H1 or higher, and is H1 or higher. If determined, the process proceeds to step SC30.

  In step SC30, the CPU 15 increases the driving voltage of the fan 60 from V1 to V2 (V1 <V2) to increase the air volume of the fan 60, and proceeds to step SC40.

  In step SC40, the CPU 15 determines whether or not the height of the paper stacked on the paper discharge tray 38 is less than H1, and proceeds to step SC50 when determining that it is less than H1.

  In step SC50, the CPU 15 restores the air volume of the fan 60 changed in step SC40, that is, changes the drive voltage of the fan 60 from V2 to V1, and returns the process to step SC10.

  In the present embodiment described above, the copying machine 1 executes the sticking prevention process so that the paper on the paper discharge tray 38 has a temperature of T1 or higher and a stacked height of H1 or higher. The air volume of the fan 60 is increased.

  Whether the sticking prevention process according to the present embodiment is plotted in the sticking occurrence area when the paper temperature and the stack height are plotted in the graph of FIG. 6 instead of the processes in steps SC10 and SC20. It may be configured such that the process proceeds to step SC30 on the condition that it is determined whether or not it is plotted in the pasting occurrence region.

[Third Embodiment]
The image forming apparatus according to the present embodiment can have the same configuration as that of the image forming apparatus according to the first embodiment, and only the contents of the sticking prevention process are different. Therefore, the contents of the sticking prevention process in the copying machine 1 will be described using the copying machine 1 described above as the image forming apparatus of the present embodiment. FIG. 9 shows a flowchart of the sticking prevention process executed in the copying machine 1 of the present embodiment.

  Referring to FIG. 9, in the sticking prevention process of the present embodiment, CPU 15 first checks the detection output of temperature sensor 52 in step SD10 to thereby detect the temperature of the paper stacked on discharge tray 38. Is greater than or equal to T1, and if it is greater than or equal to T1, the process proceeds to step SD20.

  In step SD20, the CPU 15 checks the detection output of the lever position sensor 53 to determine whether or not the height of the paper stacked on the paper discharge tray 38 is H1 or higher, and is H1 or higher. If determined, the process proceeds to step SD30.

  In step SD30, the CPU 15 displays a message prompting the removal of the paper on the paper discharge tray 38 on the display 18 and stops it if the printing operation is being executed, and proceeds to step SD40.

  In step SD40, the CPU 15 determines whether or not the height of the paper stacked on the paper discharge tray 38 is less than H1, and proceeds to step SD50 when determining that it is less than H1.

  In step SD50, the CPU 15 ends the display on the display 18 performed in step SD40, restarts the printing operation, and returns the process to step SD10.

  In the present embodiment described above, the copying machine 1 executes the sticking prevention process, whereby the temperature on the paper on the paper discharge tray 38 is T1 or higher and the stacked height is H1 or higher. If the printing operation is in progress, the printing operation is stopped, and a special message such as a message prompting the removal of the paper is displayed on the display 18.

  Whether the sticking prevention process of the present embodiment is plotted in the sticking occurrence area when the paper temperature and the stacking height are plotted in the graph of FIG. 6 instead of the process of step SD10 and step SD20. It may be configured such that the process proceeds to step SD30 on the condition that it is determined whether or not it is plotted in the sticking occurrence region.

[Fourth Embodiment]
The image forming apparatus according to the present embodiment can have the same configuration as that of the image forming apparatus according to the first embodiment, and only the contents of the sticking prevention process are different. Therefore, the contents of the sticking prevention process in the copying machine 1 will be described using the copying machine 1 described above as the image forming apparatus of the present embodiment.

  In the copying machine 1 of the present embodiment, the number of sheets on which a printing operation has been performed (hereinafter referred to as the number of printed sheets) is counted based on the detection output of the paper discharge sensor 62 and stored in the memory 101. . In the copying machine 1 of the present embodiment, the CPU 15 does not detect the output of the lever position sensor 53, but based on the number of printed sheets stored in the memory 101, the CPU 15 Get the height and execute the sticking prevention process. As a result, the copying machine 1 according to the present embodiment may not include the lever position sensor 53.

  In the copying machine 1 according to the present embodiment, a table and a function for converting the number of printed sheets into a stacking height of sheets on the sheet discharge tray 38 are stored in the memory 101.

  FIG. 10 shows a flowchart of the sticking prevention process executed in the copying machine 1 of the present embodiment.

  Referring to FIG. 10, in the sticking prevention process of the present embodiment, CPU 15 first determines in step SE10 whether or not the number of prints has reached the number for check, and if it has been determined, proceeds to step SE20. Proceed with the process.

  Here, the number of check sheets is the number of prints that triggers the CPU 15 to execute the processing after step SE20. For example, the number of prints may be set every predetermined number of sheets such as 100 sheets, 200 sheets, and 300 sheets, or 300 sheets. Up to 100 sheets may be set, and every 300 sheets or more may be set to 50 sheets. Information for specifying the number of check sheets is stored in the memory 101.

  In step SE20, the CPU 15 acquires the stacking height by converting the number of prints to the stacking height based on the above-described table and function, and proceeds to step SE30.

  In step SE30, the CPU 15 obtains the temperature of the paper on the paper discharge tray 38 by checking the detection output of the temperature sensor 52, and advances the process to step SE40.

  In step SE40, when the CPU 15 plots the stacking height and the sheet temperature acquired in step SE20 and step SE30 in the graph shown in FIG. If it is determined that there is, the process proceeds to step SE50, and if not, the process proceeds to step SE60.

  In step SE50, the CPU 15 changes the print productivity as in step SB40 (see FIG. 7), and advances the process to step SE60.

  In step SE60, the CPU 15 checks the detection output of the tray sensor 63 to determine whether or not all the sheets on the discharge tray 38 have been removed. If so, the process proceeds to step SE70. If not, the process returns to step SE10.

  In step SE70, the print sheet count value is reset, and the process returns to step SE10. If the print productivity is changed at step SE50, the CPU 15 restores the print productivity at step SE70.

  In the present embodiment described above, compared to the case where the sticking prevention process is executed based only on the temperature of the paper on the paper discharge tray 38, the temperature is plotted in the sticking occurrence region even at a temperature lower than H1 in step SE40. In the case of printing paper, the discharge productivity 38 is taken, and when the temperature H1 is exceeded, the print productivity drop is not taken unless plotting is performed in the sticking occurrence area. Depending on the state of the paper loaded in the printer, it is possible to take measures to reduce print productivity.

  In each of the embodiments described above, the sheet stacking amount is detected based on the height or number of sheets stacked. However, in the image forming apparatus according to the present invention, the sheet stacking on the sheet discharge tray is detected. The load amount of paper such as weight may be detected by other modes.

  Each embodiment disclosed this time must be considered as illustrative in all points and not restrictive. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims. Moreover, it is intended that the techniques shown in the respective embodiments are realized in combination as much as possible.

  That is, for example, the print productivity is changed in the sticking prevention process of the first embodiment, and the air volume of the fan 60 is changed in the same process of the second embodiment, but these changes are made at the same time. Also good. That is, when the temperature of the paper on the paper discharge tray 38 is T1 or higher and the height is H1 or higher, the print productivity may be changed and the air volume of the fan 60 may be changed.

1 is a schematic cross-sectional view showing an outline of a hardware configuration of a copier that is a first embodiment of an image forming apparatus of the present invention. FIG. 2 is a control block diagram of the copying machine of FIG. 1. FIG. 2 is a diagram for explaining the operation of a lever provided in the vicinity of a paper discharge tray of the copying machine of FIG. 1. FIG. 4 is a diagram illustrating a change in position of the lever of FIG. 3 according to the amount of sheets stacked on a paper discharge tray. 2 is a flowchart of lever drive processing executed by the copier of FIG. FIG. 2 is a diagram schematically illustrating a relationship between a sheet temperature and a stack height in the sheet discharge tray of the copier of FIG. 1 and sheet pasting. 3 is a flowchart of sticking prevention processing executed by the copier of FIG. It is a flowchart of the sticking prevention process performed in the second embodiment of the image forming apparatus of the present invention. It is a flowchart of the sticking prevention process performed in 3rd Embodiment of the image forming apparatus of this invention. It is a flowchart of the sticking prevention process performed in 4th Embodiment of the image forming apparatus of this invention.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 Copy machine, 2 conveyance part, 3 loading stand, 4 discharge stand, 10 image reading part, 11 manuscript table glass, 14 communication part, 15 CPU, 16 RAM, 17 key operation part, 18 display, 19 scanner, 20 paper conveyance , 21, 21Y, 21M, 21C, 21K Developer, 25, 25Y, 25M, 25C, 25K Transfer roller, 29 Conveyor motor, 30 Image forming unit, 31 Intermediate transfer belt, 32-35, 37, 42, 43 Roller, 36 fixing device, 38 paper discharge tray, 40 paper storage unit, 51 cam motor, 52 temperature sensor, 60 fan, 61 jam processing sensor, 62 paper discharge sensor, 63 tray sensor, 100 controller, 101 memory, 380 lever, 381 Spring, 383 cam.

Claims (8)

An image forming apparatus that heats and fixes an image formed by a developer formed on a recording material by using a heat fixing device,
A paper discharge tray for stacking recording materials on which images of the developer are heat-fixed,
A load amount detecting means for detecting the amount of sheets stacked on the paper discharge tray;
Temperature detecting means for detecting the temperature of the paper stacked on the paper discharge tray;
Based on one of the amount of paper detected by the stacking amount detection unit and the temperature of the paper detected by the temperature detection unit, either one remelts the developer in the recording material on the paper discharge tray. A determination means for determining whether or not the value requires processing to avoid;
An image forming apparatus comprising: an execution unit that executes the process when the determination unit determines that the process is necessary. The load amount detecting means includes
A lever that is biased in a direction opposite to the direction in which the recording materials are stacked on the paper discharge tray, and has one end abutting on the recording material stacked on the top of the paper discharge tray;
By optically detecting the state of the lever when the one end is in contact with the recording material stacked on the uppermost portion of the paper discharge tray, the recording material stacked on the paper discharge tray is detected. A height detecting means for detecting the height,
The image forming apparatus according to claim 1, wherein the temperature detection unit is attached to the one end of the lever.   The stacking amount detecting means is a retracting means for retracting the one end of the lever from a path through which the recording material is discharged to the paper discharge tray when the recording material is discharged from the heat fixing device to the paper discharge tray. The image forming apparatus according to claim 2, further comprising:   The image forming apparatus according to claim 1, wherein the execution unit reduces print productivity in the image forming apparatus by executing the processing. Storage means for storing the recording material;
Image forming means for forming an image with a developer on the recording material;
A heating and fixing device for heating and fixing the recording material on which an image formed by the developer is formed by the image forming unit;
A feeding means for feeding the recording material accommodated in the accommodation means in the order of the image forming means, the heat fixing device, and the paper discharge tray;
The image forming apparatus according to claim 4, wherein the execution unit decreases a speed at which the recording material is fed by the feeding unit. A cooling means for cooling the recording material on which the image formed by the developer is heated and fixed by the heat fixing device;
The image forming apparatus according to claim 1, wherein the execution unit executes the processing by improving a cooling capacity of the cooling unit. An informing means for informing the information;
The image forming apparatus according to claim 1, wherein the execution unit executes the process by causing the notification unit to perform a notification operation. A detecting unit for detecting whether or not a recording material is stacked on the paper discharge tray;
The load amount detecting means includes
A counting means for measuring the number of recording materials on which an image formed by a developer is formed on the heat fixing device;
8. The apparatus according to claim 1, further comprising: a reset unit that resets a count value of the counting unit when the detection unit determines that no recording material is stacked on the paper discharge tray. The image forming apparatus described in 1.

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