JP2016018080A - Image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To perform appropriate sheet ejection control in consideration of the amount of curl occurring to sheets in an image forming apparatus.SOLUTION: When a fullness detection sensor 53 has detected that sheets on a paper ejection tray 52 has reached the full capacity, if a humidity is equal to or less than a reference value (curl of the sheets is small), an image forming apparatus continues printing until the sheets reach the full capacity even after the detection of fullness. Meanwhile, when the fullness detection sensor 53 has detected that the sheets on the paper ejection tray 52 has reached the full capacity, if a humidity is more than the reference value (curl of the sheets is large), the image forming apparatus stops printing at the time of the detection of fullness.SELECTED DRAWING: Figure 3

Description

  The present invention relates to an image forming apparatus having a discharge paper full detection function.

  In recent years, an image forming apparatus generally has a plurality of functions such as a copy machine, a printer, and a fax machine as a multi-function machine. Of these functions, the printer and FAX functions are premised on performing printing processing in a situation where the user is not near the apparatus. However, when printing is performed under such circumstances, if printing is performed further (ie, the ejection of the next sheet) while the printed sheets are accumulated on the sheet discharge tray, the following problems may occur. May occur.

  For example, the contact of the next sheet occurs at the trailing edge of the paper accumulated on the paper discharge tray, and the paper accumulation on the paper discharge tray is disturbed, or the paper is dropped by being pushed by the next paper. There is a risk that. Furthermore, the discharge of the next sheet is hindered by the sheet on the sheet discharge tray, which may cause a jam due to a conveyance failure.

  For this reason, Patent Document 1 proposes a paper discharge device including a full detection sensor. In the paper discharge device of Patent Document 1, the height of the paper stored in the paper discharge tray is detected by a full detection sensor, and control is performed to stop printing based on the detection result. Specifically, after the full detection, the printing is continued for a predetermined number of sheets, and then the printing is stopped.

  Further, in Patent Document 1, when different sized papers are stacked on the paper discharge tray (when large sized paper is discharged on small sized paper), printing is stopped immediately after full detection. Performing control is also disclosed. This is because stacking small-sized paper and then ejecting larger paper results in poor stacking of the paper, causing the trailing edge of the large paper to float, making it difficult to eject further paper. is there.

JP 2007-62865 A

  In the paper discharge device disclosed in Japanese Patent Laid-Open No. 2004-086105, control for stopping printing is advanced in consideration of deterioration of stacking property when papers of different sizes are accumulated on the paper discharge tray.

  However, the stacking property may be deteriorated in addition to the case where sheets of different sizes are accumulated. For example, the stacking property of the paper on the tray is also deteriorated by curling of the discharged paper. In general, a sheet printed by an electrophotographic method is curled in the width direction (a direction orthogonal to the sheet conveyance direction). In addition, the amount of curling varies depending on the ambient environment (particularly humidity) during printing and the type of paper.

  However, there is no conventional paper discharge device that changes the print stop control timing depending on the presence or absence of the curl of the discharged paper, and it has not been possible to perform appropriate paper discharge control.

  The present invention has been made in view of the above problems, and an object thereof is to perform appropriate paper discharge control in consideration of the amount of curl generated on a paper.

  In order to solve the above problems, the present invention is an image forming apparatus including an image forming unit that prints on a sheet, and a sheet discharge unit that discharges a sheet printed by the image forming unit. When the amount of paper discharged to the paper discharge unit reaches a predetermined amount, the full detection unit for detecting the full state in the paper discharge unit, the humidity detection unit for detecting humidity, and the printing operation of the image forming unit are controlled. The predetermined amount detected by the full detection unit is smaller than the maximum accommodation amount in the paper discharge unit, the control unit, as a print stop control at the time of full detection, If the humidity detected by the humidity detection unit is below a reference value, printing continues until the maximum capacity of the paper discharge unit is reached even after the full detection by the full detection unit is detected by the humidity detection unit. The If the long humidity exceeds a reference value, it is characterized by performing control to stop the printing by the full state detection time.

  According to the above configuration, the curl amount of the discharged paper is determined using the humidity as a parameter. When the curl amount is small (when the humidity is low), the maximum accommodation amount in the paper discharge unit is reached even after full detection. Until then, printing can be continued. On the other hand, when the curl amount is large (when the humidity is high), printing is stopped when the fullness is detected. Thereby, even when the curl is large, it is possible to prevent a problem such as dropping of the paper loaded on the paper discharge unit, and when the curl is small, printing with priority on the printing efficiency can be performed. That is, appropriate paper discharge control can be performed in consideration of the curl amount generated on the paper.

  In the image forming apparatus, the reference value is preferably a numerical value within a range of 65 to 80%, and more preferably a numerical value within a range of 70 to 75%.

  In the image forming apparatus, the humidity detector may detect the humidity in the image forming apparatus when the fullness is detected by the fullness detector.

  In the image forming apparatus, when a print job is requested, if there is already discharged paper in the paper discharge unit, the control unit accumulates the paper discharged in the paper discharge unit. When the humidity detected by the humidity detector is below a reference value, the number of accumulated sheets is calculated from the maximum number of sheets stored in the paper discharge unit. The remaining amount obtained by subtracting from the predetermined number of sheets is calculated as the number of printable sheets. If the number of ejected sheets is equal to or less than the number of printable sheets, the requested print job is all printed, and the number of ejected sheets is equal to the number of printable sheets. If it exceeds, the requested print job is printed up to the number of printable sheets. If the humidity detected by the humidity detector exceeds a reference value, the full detector is That until the full state detection can be configured to perform control to perform the printing of the print job.

  According to the above configuration, even when multiple jobs are requested (when there is already ejected paper in the paper ejection unit when a print job is requested), appropriate print control can be performed according to the curl amount of the paper. Printing efficiency can be improved.

  The image forming apparatus further includes a paper type detection unit that detects whether or not a paper type used for printing is a paper that is likely to be curled during printing, and the control unit includes the paper type The print stop control can be performed only when the detection unit detects that the paper is likely to be curled during printing.

  According to the above configuration, when a paper that is unlikely to curl is used, printing efficiency can be improved by continuing printing after full detection, regardless of the humidity at that time.

  The image forming apparatus according to the present invention determines the curl amount of the discharged paper using humidity as a parameter, and when the curl amount is small (when the humidity is low), the maximum storage capacity in the paper discharge unit is reached even after full detection. Printing is continued until it is done, and when the curl amount is large (when the humidity is high), printing is stopped when full is detected. Accordingly, there is an effect that appropriate paper discharge control can be performed in consideration of the curl amount generated on the paper.

FIG. 3 is a diagram illustrating a configuration of a paper discharge unit of an image forming apparatus to which the present invention is applied. 1 is an explanatory diagram showing a schematic configuration of an image forming apparatus to which the present invention is applied. 4A and 4B are diagrams illustrating a state in which sheets are stacked on a sheet discharge tray up to a full detection height. FIG. 5A illustrates a state in which sheets with a small curl amount are stacked, and FIG. It is a figure which shows a state. 3 is a flowchart illustrating print stop control after full detection in the first embodiment. 3 is a flowchart illustrating print stop control after full detection in the first embodiment. 10 is a flowchart illustrating print stop control after full detection in the second embodiment.

[Embodiment 1]
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

(Mechanism of image forming apparatus and paper discharge unit)
FIG. 2 is an explanatory diagram showing a schematic configuration of the image forming apparatus 1 to which the present invention is applied. The image forming apparatus 1 is roughly composed of a document reading unit 2, an image forming unit 3, a sheet conveying unit, and a sheet discharging unit.

  The document reading unit 2 emits light to the document and generates image data corresponding to the image of the document from the reflected light. The image forming unit 3 forms a visible image based on the image data generated by the document reading unit 2, and prints the visible image on a predetermined sheet. The paper transport unit supplies the paper to the image forming unit 3 and discharges the printed paper to the paper discharge tray.

  The document reading unit 2 has a document table 21 made of transparent glass on the upper surface. A scanner optical system is disposed below the document table 21. The scanner optical system includes an exposure lamp 22, a reflecting mirror 23, an imaging lens 24, and a photoelectric conversion element (CCD) 25. The exposure lamp 22 is a light source for irradiating the document placed on the document table 21 with light. The reflecting mirror 23 guides the reflected light from the document to the imaging lens 24 and the CCD 25 as indicated by a one-dot chain line in the drawing, for example. The CCD 25 receives the reflected light imaged by the imaging lens 24 and generates an electrical signal corresponding to the reflected light as an image signal.

  Next, the image forming unit 3 and the sheet conveying unit will be described. The image forming unit 3 includes a photosensitive roller 31, a charging unit 32, an exposure unit (LSU) 33, a developing unit 34, a transfer unit 35, a fixing unit 36, and a cleaning unit 37.

  The photosensitive roller 31 is a drum-shaped roller, and a photosensitive layer is formed on the surface thereof. The charging unit 32 charges the surface of the photosensitive roller 31 to a predetermined potential. The exposure unit 33 forms an electrostatic latent image corresponding to the image signal of the document by scanning and exposing the surface of the charged photosensitive roller 31 with laser light. The developing unit 34 develops the electrostatic latent image formed on the surface of the photosensitive roller 31 with toner, and forms a toner image. The transfer unit 35 transfers the toner image on the photosensitive roller 31 to a sheet. The fixing unit 36 includes a pair of fixing rollers, and fixes the toner image by heating and pressurizing a sheet (sheet on which an unfixed toner image is transferred) passing between the nips of the roller pair. The cleaning unit 37 removes the toner remaining on the surface of the photosensitive roller 31 after the toner image is transferred to the paper.

The paper transport unit includes a main transport path 41, a sub transport path 42, a fixed paper feed cassette 43, a pickup roller 44, a registration roller 45, a paper discharge roller 46, a transport roller, and the like.
The main conveyance path 41 is a conveyance path through which paper to be printed passes, and along the main conveyance path 41, a registration roller 45, a transfer unit 35, and a fixing unit 36 are arranged. The sub-transport path 42 is a transport path for switching back the paper on which the first surface has been printed when performing double-sided printing, and guiding it to the upstream side of the registration roller 45 in the main transport path 41.

  The fixed paper feed cassette 43 stores paper before printing. The pickup roller 44 is a half-moon-shaped roller for ejecting sheets one by one from the fixed sheet feeding cassette 43. The registration roller 45 once holds the sheet conveyed through the main conveyance path 41 and then conveys the leading end of the sheet in accordance with the toner image on the photosensitive roller 31.

  The sheet on which the toner image has been transferred is discharged to the sheet discharge unit via the fixing unit 36 and the discharge roller 46. The paper discharge roller 46 is provided in the vicinity of the paper discharge port, and discharges the paper to the first paper discharge tray 51 or the second paper discharge tray 52. The paper discharge roller 46 has a function as a back surface printing mechanism together with the sub-transport path 42.

  That is, when performing double-sided printing, after printing on the first surface of the paper is completed and the trailing edge of the paper is discharged from the main transport path 41, the paper discharge roller 46 rotates in the reverse direction, Transport to the transport path 42. The sheet transported to the sub transport path 42 is transported again to the registration roller 45 by the transport roller, and printing is performed on the second surface (back surface).

(Configuration of paper discharge unit)
Next, the configuration and operation of the paper discharge unit according to the present embodiment will be described in detail. In this embodiment, the paper discharge unit has two discharge trays, the first discharge tray 51 and the second discharge tray 52, but the present invention is not limited to this. A single sheet discharge tray may be used. In the following description, a case where full detection is performed on the paper discharged to the second paper discharge tray 52 will be described. That is, as shown in FIG. 1, the fullness detection sensor 53 detects the height of the sheet discharged to the second discharge tray 52 (hereinafter simply referred to as the discharge tray 52), and this height is a predetermined amount. A full detection signal is output when the value reaches.

  FIG. 1 is a diagram illustrating the configuration of the paper discharge unit. Here, a state is shown in which discharged paper is accumulated on the paper discharge tray 52 and the fullness detection sensor 53 detects the height of the accumulated paper. The fullness detection sensor 53 is provided in the vicinity of the paper discharge roller 46 and detects that the upper end of the accumulated paper reaches the lower end portion of the paper discharge roller 46. Further, a paper detection sensor 54 that detects the presence or absence of paper on the tray is disposed in the paper discharge tray 52.

  The full detection sensor 53 can be configured by combining, for example, an actuator 53A that is displaced according to the sheet height and a photo interrupter 53B. The actuator 53A is arranged so that the tip thereof is in contact with the upper surface of the paper accumulated on the paper discharge tray 52, and rotates according to the height of the accumulated paper. The photo interrupter 53B is disposed near the rear end of the actuator 53A, and is turned on / off according to the rotation position of the actuator 53A (that is, the height of the paper accumulated on the paper discharge tray 52).

  For example, when the height of the paper accumulated on the paper discharge tray 52 is less than a predetermined accumulation height A, the photo interrupter 53B is turned off (or on), and when the height is greater than or equal to the accumulation height A, the photo interrupter. 53B is turned on (or off). Thereby, it is possible to detect that the height of the paper accumulated on the paper discharge tray 52 has reached the predetermined accumulation height A by switching the photo interrupter 53B on and off. In this case, the accumulation height A is set as the full detection height. However, in the present invention, the configuration of the fullness detection sensor 53 is not limited to this, and can be realized by other sheet detection methods such as a reflection type photosensor, a combination of a microswitch and an actuator, or the like. .

  In the paper discharge unit according to the present embodiment, the accumulation height A, which is a full detection location, is set to be lower than the upper limit accumulation height in the discharge tray 52. Therefore, usually, a certain amount of printing (paper discharge) is possible even after full detection. In the present embodiment, even after full detection, printing (paper discharge) in an amount corresponding to the deposition height B is possible.

  FIGS. 3A and 3B are views showing a state in which sheets are stacked on the discharge tray 52 up to the full detection height, and FIG. FIG. 3B shows a state in which sheets with a large curl amount are accumulated. 3A and 3B are views seen from the front end side of the paper in the paper transport direction.

  As shown in FIGS. 3A and 3B, the actuator 53A in the fullness detection sensor 53 detects the height of the substantially central portion in the sheet width direction with respect to the stacked sheets. As shown in FIG. 3A, when the curl amount of the discharged paper is small (normal time), when the full detection height is reached at the center in the paper width direction, the paper height at both ends is also the full detection height. Is almost equal to That is, when the paper curl amount is small, printing (paper discharge) of an amount corresponding to the accumulation height B is possible even after full detection.

  On the other hand, as shown in FIG. 3B, when the curl amount of the discharged paper is large, the paper floats at both ends even if the full detection height is at the center in the paper width direction, and the paper height is near the discharge port. May have reached. As described above, when the amount of curl of the paper is large, if printing is performed even after the fullness is detected, the top surface hits due to excessive loading of the paper on the paper discharge tray 52 near the end in the paper width direction. There is a risk that extrusion may occur due to the contact of the next sheet to the trailing edge of the sheet.

(Print stop control after full detection)
In the image forming apparatus 1 according to the present embodiment, the humidity during the printing operation is measured in order to avoid the above-described trouble (fault caused by further printing after detection of fullness) when the curl amount of the discharged paper is large. However, the print stop control is varied according to the humidity. Here, the curl amount of the paper is generally large when the humidity is high and small when the humidity is low. For this reason, the image forming apparatus according to the present embodiment determines the curl amount of the discharged paper using humidity as a parameter.

  For this reason, the image forming apparatus 1 includes a humidity sensor 61 (see FIG. 2) for measuring humidity. Although the arrangement location of the humidity sensor 61 is not particularly limited, it is preferable to arrange the humidity sensor 61 in the vicinity of the fixed paper feed cassette 43 in which the paper before printing is accommodated. This is because the amount of curl generated on the printed paper varies depending on the moisture absorption amount of the paper, and it is considered appropriate to measure the humidity at the location where the paper before printing is stored for a long time. An output signal (humidity detection value) of the humidity sensor 61 is input to a control unit (not shown).

  A detection signal from the full detection sensor 53 is also input to the control unit. Based on this detection signal, the control unit can determine that the height of the paper accumulated on the paper discharge tray 52 has reached the full detection height. The control unit is configured by a CPU and a memory mounted on a control board in the image forming apparatus 1.

  Hereinafter, a control example in the case of performing the print stop control after full detection will be described with reference to the flowcharts of FIGS.

  First, when the image forming apparatus 1 receives a print job request (Yes in ST1), the control unit obtains the number of discharged sheets discharged in the print job (ST2). The number of discharged sheets is included in the print job data.

  Next, the control unit compares the humidity detection value obtained by the humidity sensor 61 with a preset reference value (70% here) (ST3). This reference value is set in advance and stored in the memory of the control unit. If the detected humidity value is equal to or lower than the reference value (Yes in ST3), the process proceeds to ST4. If the detected humidity value exceeds the reference value (No in ST3), the process proceeds to ST6.

  In ST4, the control unit determines whether or not the number of discharged sheets acquired in ST2 is equal to or less than the maximum capacity of the discharge tray 52. Here, the maximum capacity of the paper discharge tray 52 is the capacity corresponding to the stacking height (A + B) in FIG. This maximum capacity is set in advance and stored in the memory of the control unit. If the number of discharged sheets is equal to or less than the maximum capacity of the discharge tray 52 (Yes in ST4), the process proceeds to ST5, and if the number of discharged sheets exceeds the maximum capacity of the discharge tray 52 (No in ST4). The process proceeds to ST6.

  In ST5, the print continuation flag is turned on after full detection. In ST6, the print continuation flag after full detection is turned off. Here, the print continuation flag after full detection indicates whether or not printing can be continued after full detection. After the process of ST5 or ST6, the print job print process is started (ST7).

  If the print job is completed without detecting the full state of the paper discharge tray 52 after the print job is started (No in ST8, Yes in ST9), the control is ended. If the full state of the paper discharge tray 52 is detected (No in ST8) before the print job is completed (No in ST9), the process proceeds to ST10.

  In ST10, the control unit determines whether or not the print continuation flag after full detection is on. If it is on (Yes in ST10), the control unit continues printing (ST11). Here, when the print continuation flag after full detection is ON, the humidity detection value is equal to or less than the reference value, and the number of discharged sheets by the print job is equal to or less than the maximum capacity of the discharge tray 52. That is, the curl amount of the printed paper is small, and printing (paper discharge) of an amount corresponding to the stacking height B is possible even after the paper discharge tray 52 is fully detected. Further, even if printing is performed until the print job is completed, the number of discharged sheets does not exceed the maximum capacity of the discharge tray 52, so printing is continued even after full detection.

  After ST11, if the print job is completed without reaching the predetermined number of sheets after full detection (No in ST12, Yes in ST13), a warning for removing the paper from the discharge tray 52 is displayed (ST14). ). This warning display may be performed on a display unit provided on the operation panel of the image forming apparatus 1 or may be displayed on a screen of a personal computer or the like that has requested a print job. Thereafter, if the sheet is removed (Yes in ST15), the warning display is erased (ST16), and the control is terminated. Here, the removal of the sheet in ST15 can be detected by, for example, the sheet detection sensor 54.

  After ST11, before the print job is completed (No in ST13), if the number of printed sheets after full detection has reached a predetermined number (Yes in ST12), the process proceeds to ST17.

  In ST17, printing is stopped at that time, and a warning for removing the paper from the paper discharge tray 52 is displayed (ST18). Thereafter, if the sheet is removed (Yes in ST19), the warning display is deleted (ST20), and the control is terminated.

  If the print continuation flag after full detection is OFF in ST10 (No in ST10), the process proceeds to ST17 in order to stop printing at that time. Here, when the print continuation flag after full detection is off, the humidity detection value exceeds the reference value, or the number of sheets discharged by the print job exceeds the maximum capacity of the discharge tray 52. is there. If the humidity detection value exceeds the reference value, the amount of curl on the printed paper is large, and if the printing after full detection is continued, the above-described problems may occur, and printing is stopped at that point. Also, if the number of discharged sheets exceeds the maximum capacity of the paper discharge tray 52, printing cannot be performed until the job is completed even if printing is continued. It is set to control to emit.

  In the above description, the reference value used for the determination in ST3 is 70%, but the present invention is not limited to this. We investigated the relationship between humidity and curl amount for various copy papers sold and used in Japan and abroad, and found that many types of paper produce large curls at 70% to 75% humidity. It was issued. For this reason, it is preferable to set the reference value in a range of 65% to 80%, and more preferably in a range of 70% to 75%.

  In the above description, humidity detection is performed at the time when a print job is requested. However, the present invention is not limited to this, and humidity detection may be performed when the discharge tray 52 is full.

[Embodiment 2]
In the first embodiment, print stop control after full detection has been described assuming a single print job. However, in an actual image forming apparatus, a plurality of print jobs are generated. For this reason, printing of the next print job (hereinafter referred to as the next job) may be started in a state where the printed matter of the previous print job (hereinafter referred to as the previous job) remains on the paper discharge tray 52. In the second embodiment, the print stop control after full detection when a plurality of print jobs occur will be described with reference to the flowchart of FIG. The configuration of the image forming apparatus according to the second embodiment is the same as that of the image forming apparatus 1 according to the first embodiment, and thus detailed description thereof is omitted.

  First, when the image forming apparatus 1 receives a request for a print job (next job) (Yes in ST31), the control unit determines whether there is paper on the paper discharge tray 52 based on the output of the paper detection sensor 54. Is determined (ST32). If there is no paper on the paper discharge tray 52 (No in ST32), the process can be performed as a single print job. Therefore, the process proceeds to ST2 in the flow of FIG. 4, and the same process as in the first embodiment is performed.

  On the other hand, if there is paper on the paper discharge tray 52 (Yes in ST32), processing is required as a plurality of print jobs. In this case, the control unit obtains the number of sheets accumulated on the sheet discharge tray 52 and the number of sheets discharged in the next job (ST33, ST34). The number of accumulated sheets in ST33 can be obtained by adding the number of discharged sheets included in the print job data and storing it in the memory every time a print job occurs. The accumulated number of sheets acquired in ST33 is updated and stored every time a print job is generated while the paper detection sensor 54 detects the presence of paper, but the paper detection sensor 54 detects the absence of paper. At this point, it is reset to 0.

  Next, the control unit compares the humidity detection value obtained by the humidity sensor 61 with a preset reference value (70% here) (ST35). If the detected humidity value is equal to or lower than the reference value (Yes in ST35), the process proceeds to ST36.

  In ST36, the control unit subtracts the accumulated number from the predetermined number and calculates the remaining printable number. The predetermined number here is the number corresponding to the maximum capacity of the paper discharge tray 52 (that is, A + B in FIG. 1). Further, the control unit compares the number of printable sheets with the number of discharged sheets in the next job. If the number of discharged sheets is equal to or smaller than the number of printable sheets (Yes in ST37), all the next jobs are printed (ST38), and the number of discharged sheets can be printed. If the number exceeds the number (No in ST37), the next job is printed by the number of printable sheets (ST39).

  When printing in ST38 or ST39 is completed, it is checked whether or not the full state of the paper discharge tray 52 is detected (ST40). If full detection is not performed (No in ST40), the process returns to ST31 and waits for a request for the next print job. If full detection is detected (Yes in ST40), a warning for removing the paper from the paper discharge tray 52 is displayed (ST41). Thereafter, if the sheet is removed (Yes in ST42), the warning display is deleted (ST43), and the control is terminated.

  On the other hand, if the humidity detection value exceeds the reference value in ST35 (No in ST35), it is confirmed whether or not a full state is detected (ST44). If there is no full detection (No in ST44), printing of the next job is started (ST45).

  If the print job is completed without detecting fullness after the start of printing in ST45 (Yes in ST46), the process is terminated as it is. On the other hand, if full detection is detected before the end of the print job (No in ST46, Yes in ST44), printing is stopped at that time and a warning for removing the paper from the paper discharge tray 52 is displayed (ST47). Thereafter, if the sheet is removed (Yes in ST48), the warning display is deleted (ST49), and the control is terminated.

  As described above, in the control according to the second embodiment, when a plurality of jobs are requested (when there is already ejected paper on the paper ejection tray 52 when a print job is requested), the humidity is the reference value. If so, the next job is printed up to the maximum capacity in the paper discharge tray 52, and if the humidity exceeds the reference value, the next job is printed until full detection is detected. Thereby, even in the case of a plurality of jobs, appropriate print control according to the curl amount of the paper can be performed, and the print efficiency can be improved.

  In the control of the first and second embodiments, when printing is stopped in the middle of a print job and a warning is issued, the remaining printing operation may be resumed when the paper is removed from the paper discharge tray. .

[Embodiment 3]
In the first and second embodiments, the case has been described in which the print stop control after full detection is varied according to the humidity during printing. In the third embodiment, a case where print stop control after full detection is performed using not only humidity but also the type and temperature of paper will be described.

  The curl amount of the printed paper does not depend only on the humidity, but also varies depending on the type of paper. For example, curl is less likely to occur when the paper is thick than when it is thin. Alternatively, even when the paper is a paper that is difficult to absorb moisture (for example, OHP paper), curling is less likely to occur.

  For this reason, when a print job is requested, the type of the paper is determined, and if the paper easily causes curling, the control described in the first and second embodiments is performed, and curling is unlikely to occur. For paper, the above control can be prevented. In other words, when a sheet that does not easily curl is used, printing can be continued up to the maximum capacity of the discharge tray 52 even after full detection, regardless of the humidity at that time. Note that the paper type can be easily determined from the designation information of the paper feed cassette in the print job.

  In addition, the following control can be considered when printing stop control after full detection is performed using the humidity and temperature during printing. That is, even when the ambient temperature of the apparatus main body is low, the curling of the paper is difficult to occur. Therefore, when the ambient temperature is equal to or higher than the predetermined temperature, the control as described in the first and second embodiments is performed, and the ambient temperature is When the temperature is lower than the predetermined temperature, the above control can be avoided. That is, when the ambient temperature is lower than the predetermined temperature, printing may be continued up to the maximum capacity of the paper discharge tray 52 even after full detection, regardless of the humidity at that time. The ambient temperature can be easily measured by providing a temperature sensor inside the image forming apparatus.

  In this way, when paper that is unlikely to curl is used, or when the ambient temperature is low, printing efficiency can be improved by continuing printing after full detection, regardless of the humidity at that time. it can.

  In addition to the method described above, the predetermined number of sheets that can be printed after full detection can be changed according to the paper type and temperature. That is, it is conceivable to reduce the number of sheets that can be printed even after full detection is detected at a paper type and temperature at which paper curl is likely to occur, compared to a paper type and temperature at which paper curl is less likely to occur.

  The present invention is not limited to the above-described embodiments, and various modifications are possible within the scope shown in the claims, and embodiments obtained by appropriately combining technical means disclosed in different embodiments. Is also included in the technical scope of the present invention.

DESCRIPTION OF SYMBOLS 1 Image forming apparatus 2 Original reading part 3 Image forming part 46 Paper discharge roller 51 1st paper discharge tray 52 2nd paper discharge tray (paper discharge tray, paper discharge part)
53 Full detection sensor (full detection part)
54 Paper detection sensor 61 Humidity sensor (humidity detection unit)

Claims (6)

An image forming apparatus comprising: an image forming unit that prints on a sheet; and a sheet discharge unit that discharges a sheet printed by the image forming unit.
A full detection unit for detecting a full state in the paper discharge unit when the paper discharged to the paper discharge unit reaches a predetermined amount;
A humidity detector for detecting humidity;
A control unit for controlling the printing operation of the image forming unit,
The predetermined amount detected by the full detection unit is smaller than a maximum accommodation amount in the paper discharge unit,
If the humidity detected by the humidity detection unit is below a reference value, the control unit reaches the maximum capacity in the paper discharge unit even after the full detection by the full detection unit. The image forming apparatus is characterized in that the printing is continued until the printing is continued, and if the humidity detected by the humidity detection unit exceeds a reference value, the printing is stopped when the fullness is detected. The image forming apparatus according to claim 1,
The image forming apparatus according to claim 1, wherein the reference value is a numerical value within a range of 65 to 80%. The image forming apparatus according to claim 2,
The image forming apparatus according to claim 1, wherein the reference value is a numerical value within a range of 70 to 75%. The image forming apparatus according to any one of claims 1 to 3,
The image forming apparatus according to claim 1, wherein the humidity detecting unit detects humidity in the image forming apparatus when the fullness detecting unit detects fullness. The image forming apparatus according to any one of claims 1 to 4, wherein:
When there is already ejected paper in the paper ejecting section when requesting a print job,
The controller is
Acquire the number of sheets accumulated in the paper discharge unit and the number of discharges of the requested print job;
If the humidity detected by the humidity detector is below a reference value, the remaining number obtained by subtracting the number of accumulated sheets from the maximum number of sheets stored in the paper discharge unit from a predetermined number is calculated as the number of printable sheets, and the number of discharged sheets is If the number is less than the printable number, the requested print job is all printed. If the number of ejected sheets exceeds the printable number, the requested print job is reduced to the printable number. Let them print,
When the humidity detected by the humidity detection unit exceeds a reference value, control is performed to perform printing of the print job until full detection is detected by the full detection unit. . An image forming apparatus according to any one of claims 1 to 5,
Furthermore, it has a paper type detection unit that detects whether or not the paper type used for printing is a paper that is likely to curl during printing,
The image forming apparatus according to claim 1, wherein the control unit performs the print stop control only when the paper type detection unit detects that the paper is likely to be curled during printing.

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