JP2009040597A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming apparatus capable of determining whether or not a paper sheet is curled, before an image is actually printed on the paper sheet. <P>SOLUTION: An automatic paper feeding cassette 5 stores printing medium. Carrying roller pairs 7a, 7b, 7c, 7d carry the printing medium. A control part 30 performs test carriage of the printing medium to the carrying roller pairs 7a, 7b, 7c, 7d when a predetermined condition is satisfied. A detection part 33 detects a curled state of the printing medium to which the test carriage was performed. A storage part 31 stores a detection result of the detection part 33. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an image forming apparatus, and more particularly to an image forming apparatus that forms a toner image by electrophotography.

  In recent years, the ratio of recycled paper used has increased, and the importance of print quality for recycled paper in image forming apparatuses has also increased. However, recycled paper tends to curl when it is discharged, which causes misalignment in the post-processing apparatus and poor placement in the tray.

  By the way, in the conventional image forming apparatus, it is left to the user to determine the occurrence of paper curl. For this reason, the user cannot determine whether or not curling has occurred on the paper until printing is actually performed on the paper.

As an invention for reducing the curl amount, a printing apparatus stacker described in Patent Document 1 and a curl correction apparatus described in Patent Document 2 have been proposed. In the stacker for a printing apparatus described in Patent Document 1, the curl amount is reduced by pushing down the curled paper with a paddle. Further, in the curl correction apparatus described in Patent Document 2, the direction in which the paper curls is detected, and the curl is corrected by being pinched by a belt.
JP-A-5-155516 JP-A-8-175732

  SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide an image forming apparatus that can determine whether or not curling occurs on a sheet before an image is actually printed on the sheet.

  The present invention includes a cassette for storing a print medium, a transport unit that transports the print medium, a control unit that causes the transport unit to test transport the print medium when a predetermined condition is satisfied, and the transport unit. Detecting means for detecting a curled state of the test transported print medium.

  According to the present invention, the control means can detect whether or not curling occurs on the print medium due to the test conveyance. Therefore, the image forming apparatus can notify the user that curling can occur before printing the image on the print medium. Further, the image forming apparatus can perform an operation of suppressing the occurrence of curling before printing an image on a print medium.

  In the present invention, the image forming apparatus further includes a fixing unit that is provided on a conveyance path formed by the conveyance unit and fixes a toner image on the print medium, and the detection unit is disposed at a subsequent stage of the fixing unit. May be.

  According to the present invention, since there is a high possibility that curling will occur in the print medium when passing through the fixing device, the detection means is arranged at the subsequent stage of the fixing device, so that the curling of the printing medium can be more reliably generated. It can be detected.

  In the present invention, there may be further provided a reverse conveying means for returning the print medium that has been test-conveyed by the conveying means to the cassette.

  According to the present invention, since the test transported print medium is returned to the cassette, the print medium used for the test transport can also be used for image printing. As a result, wasteful consumption of the print medium is suppressed.

  In the present invention, the predetermined condition may be either when the power is turned on or when the cassette is opened and closed.

  According to the present invention, the test transport is executed either when the power is turned on or when the cassette is opened and closed. In these cases, there is a high possibility that the print medium in the cassette is replaced. That is, in these cases, there is a high possibility that the orientation of the front and back of the print medium in the cassette will be changed, so that image formation is performed by detecting the occurrence of curl of the print medium by performing test conveyance. The apparatus can more reliably recognize the occurrence of curling before printing an image on a print medium.

  In the present invention, the control unit may cause the transport unit to transport the print medium based on a detection result by the detection unit when printing an image on the print medium.

  According to the present invention, since the transport unit transports the print medium based on the detection result, transport that suppresses the occurrence of curling is realized.

  In the present invention, the conveying means includes a reversing means for reversing the front and back of the print medium, and the control means uses the reversing means when the detection result indicates that the print medium is curled. The front and back of the print medium may be reversed.

  According to the present invention, when the detection result indicates that curling has occurred in the printing medium, the reversing means reverses the front and back of the printing medium, so that curling of the printing medium is suppressed.

  In the present invention, a notification means for notifying a user of the detection result by the detection means may be further provided.

  According to the present invention, since the notification means notifies the user of the detection result, the user can know the detection result before printing the image on the print medium. Therefore, when curl can occur in the print medium, the user can take measures such as turning the print medium in the cassette upside down and setting it again.

(First embodiment)
(Overall configuration of image forming apparatus)
First, an image forming apparatus according to a first embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a diagram showing a schematic configuration of the image forming apparatus 1. In the following, Y and y are yellow, M and m are magenta, C and c are cyan, and K and k are black.

  The image forming apparatus 1 is a color printer that synthesizes four-color images using a tandem method. The image forming apparatus 1 includes image forming stations 2Y, 2M, 2C, and 2K, an automatic paper feed cassette 5, a pair of conveying rollers 7a, 7b, 7c, and 7d, a paper discharge unit 9, a transfer belt 10, a driving roller 11, and a driven roller. 12, a fixing device 15, a discharge roller pair 17, an optical scanning device 20, a reverse conveyance unit 21, a reversing unit 22, a control unit 30, a storage unit 31, a touch panel 32, and a detection unit 33.

  The image forming stations 2Y, 2M, 2C, and 2K are disposed immediately below the transfer belt 10, and are respectively photosensitive drums 3Y, 3M, 3C, and 3K, developing units 4Y, 4M, 4C, and 4K, chargers (not shown), and residual units. Including toner cleaner. Note that the image forming station 2K for forming a black image is configured in a large size so that a frequently used monochrome image can be formed at high speed.

  The optical scanning device 20 is disposed immediately below the image forming stations 2Y, 2M, 2C, and 2K. Based on the image data of Y, M, C, and K, the beams By, Bm, Bc, and Bk are applied to the photosensitive drums 3 respectively. Irradiate. Thereby, an electrostatic latent image is formed on the peripheral surface of each photosensitive drum 3. This electrostatic latent image is visualized with toner. Such an electrophotographic process is well known and will not be described.

  The transfer belt 10 is stretched endlessly around the driving roller 11 and the driven roller 12 and is rotated in the direction of the arrow X. On the surface of the transfer belt 10, the toner images of the respective colors formed on the respective photosensitive drums 3 are sequentially primary transferred and synthesized.

  The automatic paper feed cassette 5 stores print media such as recycled paper, and feeds paper one by one at a predetermined timing. The conveyance roller pairs 7a, 7b, 7c, and 7d form a conveyance path R and serve as conveyance means for conveying the fed print medium.

  The secondary transfer position 13 and the fixing device 15 are provided on the transport path R. At the secondary transfer position 13, the composite toner image is secondarily transferred from the transfer belt 10 to the print medium. The fixing device 15 heats and fixes the toner image on the print medium. The discharge roller pair 17 discharges the print medium on which the toner image is fixed onto the paper discharge unit 9.

  On the other hand, during duplex printing, the discharge roller pair 17 conveys the print medium to the outside of the image forming apparatus 1 and switches it back. The reverse conveying unit 21 returns the switched back print medium to the secondary transfer position 13. At the secondary transfer position 13, the toner image is secondarily transferred to the back surface of the print medium. The discharge roller pair 17 discharges the print medium onto the paper discharge unit 9.

  The control unit 30 is constituted by a CPU, for example, and controls the entire image forming apparatus 1. The storage unit 31 is composed of, for example, a hard disk, and stores image data and various data. The touch panel 32 serves as an input unit that receives user input and also serves as a notification unit that displays various images and notifies the user of information.

  By the way, when the print medium is recycled paper and the print medium is set in the automatic paper feed cassette 5 with the front and back sides being opposite to the original directions, the print medium is connected to the fixing device 15. When it passes, it curls. Therefore, the control unit 30 detects whether or not curl has occurred by performing test conveyance. The test conveyance means that the print medium is conveyed on the conveyance path R by the conveyance roller pairs 7a, 7b, 7c, and 7d without printing an image. This test conveyance is executed under predetermined conditions such as when the power is turned on or when the automatic paper feeding cassette 5 is opened and closed. This is because the orientation of the front and back of the print medium set in the automatic paper feed cassette 5 may be changed under these predetermined conditions.

  Therefore, the detection unit 33 is provided at the subsequent stage of the fixing device 15 and determines whether or not curling has occurred in the print medium that has been test-conveyed along the conveyance path R by the conveyance roller pairs 7a, 7b, 7c, and 7d (curl state). ) As a detecting means for detecting. The detection result by the detection unit 33 is stored in the storage unit 31. Details of the configuration of the detection unit 33 will be described below with reference to FIG. FIG. 2 is a configuration diagram of the detection unit 33. More specifically, FIG. 2A is a side view of the detection unit 33, and FIG. 2B is a view of the detection unit 33 viewed from the direction of the arrow α.

  As shown in FIG. 2, the detection unit 33 includes guides 35 and 36, detection plates 37 and 38, and sensors 39 and 40. The guides 35 and 36 are arranged substantially in parallel with each other, and are produced by bending a metal plate or the like, and play a role of regulating the traveling direction of the print medium. A part of the guides 35 and 36 bulge outward as shown in FIG. Further, as shown in FIG. 2B, a slit S is formed in the guide 35. Although not shown, the guide 36 is similarly formed with a slit S.

  The detection plates 37 and 38 are members provided so as to be rotatable outside the guides 35 and 36 in a plane perpendicular to the guides 35 and 36. The detection plates 37 and 38 are inserted through the slits S inside the swelled portions of the guides 35 and 36. The sensors 39 and 40 are provided at one end of the detection plates 37 and 38 and detect the state of the detection plates 37 and 38. More specifically, the light receiving portions of the sensors 39 and 40 are not shielded by the detection plates 37 and 38 when a part of the detection plates 37 and 38 is inside the bulged portion of the guides 35 and 36 as indicated by solid lines. . At this time, a high level signal is output from the sensors 39 and 40. On the other hand, the light receiving portions of the sensors 39, 40 are shielded from light by the detection plates 37, 38 when a part of the detection plates 37, 38 is outside the swollen portions of the guides 35, 36 as indicated by the dotted lines. At this time, low level signals are output from the sensors 39 and 40.

  In the detection unit 33 configured as described above, when the curled print medium passes, the print medium contacts either the detection plate 37 or the detection plate 38, and the detection plate 37 or the detection plate 38 is As indicated by the dotted line 2 (a), the light receiving portion of the sensor 39 or the sensor 40 is shielded from light. On the other hand, when a print medium without curling passes, the print medium does not come into contact with either the detection plate 37 or the detection plate 38, and the detection plate 37 or the detection plate 38 is indicated by a solid line in FIG. As shown, the light receiving portion of the sensor 39 or sensor 40 is not shielded. Based on the signals output from the sensors 39 and 40 at this time, the control unit 30 determines whether or not curling has occurred in the print medium. Above, description of the structure of the detection part 33 is complete | finished.

  The discharge roller pair 17 transports the print medium to the outside of the image forming apparatus 1 after the detection unit 33 detects the presence or absence of curling, and transports it to the reverse transport unit 21. The reverse conveyance unit 21 returns the print medium to the automatic paper feed cassette 5. Thereby, test conveyance is completed.

  Further, when image printing is executed in the image forming apparatus 1, the control unit 30 conveys the print medium based on the detection result stored in the storage unit 31, as a pair of conveyance rollers 7 a and 7 b. , 7c, 7d and the inverting unit 22 are executed. More specifically, when curling has occurred, the reversing unit 22 causes the reversing unit 22 to reverse the front and back of the print medium in accordance with instructions from the control unit 30. Thereafter, the conveyance roller pairs 7a, 7b, 7c, and 7d convey the print medium whose front and back are reversed. On the other hand, when no curling occurs, the reversing unit 22 does not operate, and the transport roller pairs 7a, 7b, 7c, and 7d transport the print medium. Below, the structure of the inversion part 22 is demonstrated.

  The reversing unit 22 constitutes a part of the conveying means, and includes reversing roller pairs 23a and 23b, a switching claw 24, and reversing paths R1, R2, and R3. The switching claw 24 plays a role of switching whether to output the print medium fed from the automatic paper feed cassette 5 to the transport path R or to the reverse path R1 according to an instruction from the control unit 30. The print medium output to the reverse path R1 is conveyed to the reverse path R3 by the reverse roller pair 23a. Thereby, the front and back of the print medium are reversed. Next, the reverse roller pair 23a rotates in the reverse direction and conveys the print medium to the upper reverse path R2. Thereafter, the reversing roller pair 23b conveys the printing medium whose front and back are reversed to the conveying path R.

(Operation of image forming apparatus)
The operation of the image forming apparatus 1 configured as described above will be described below with reference to the drawings. In the image forming apparatus 1, there are two types of operations, test conveyance and main printing. As described above, the test conveyance is an operation for determining whether or not curling occurs on the print medium. The main printing is an operation for printing an image on a printing medium in accordance with an instruction from a user or the like.

  First, test conveyance will be described with reference to the drawings. FIG. 3 is a flowchart showing processing performed by the control unit 30 during test conveyance.

  The control unit 30 determines whether or not the image forming apparatus 1 has just been turned on (step S1). If it is immediately after the power is turned on, the process proceeds to step S3. If not immediately after the power is turned on, the process proceeds to step S2.

  If it is immediately after the power is turned on, the control unit 30 determines whether or not the automatic sheet cassette 5 has been opened and closed (step S2). If the automatic sheet cassette 5 has been opened and closed, the process proceeds to step S3. If the automatic sheet cassette 5 has not been opened / closed, this process ends. That is, the control unit 30 shifts to a print instruction standby state without performing test conveyance.

  In step S3, the control unit 30 feeds only one print medium to the automatic paper feed cassette 5 (step S3). Note that the number of print media fed in step S3 is not limited to one.

  When the print medium is fed, the control unit 30 rotates the pair of transport rollers 7a, 7b, 7c, and 7d to transport the print medium (step S4). At this time, the print medium passes through the secondary transfer position 13 and the fixing device 15. The secondary transfer of the toner image is not performed at the secondary transfer position 13. On the other hand, the fixing device 15 performs heating and pressure-bonding processing on the print medium. As a result, the print medium is recycled paper, and curling occurs depending on the direction in which the print medium is set in the automatic paper feed cassette 5.

  Next, the print medium passes through the detection unit 33. At this time, the control unit 30 detects the occurrence of curl based on the low level signal or the high level signal output from the detection unit 33 (step S5). When a low level signal is output, the control unit 30 determines that curl has occurred in the print medium. On the other hand, when a high level signal is output, the control unit 30 determines that no curling has occurred on the print medium. And the control part 30 memorize | stores the determination result in the memory | storage part 31 as a detection result (step S6).

  Finally, the control unit 30 drives the discharge roller pair 17 and the reverse conveyance unit 21 to return the print medium to the automatic paper feed cassette 5 (step S7). It should be noted that the orientation of the print medium when the print medium is returned in step S7 is the same as the orientation of the print medium when the print medium is fed in step S3. With the above operation, the test conveyance is completed.

  Next, the main printing will be described with reference to the drawings. FIG. 4 is a flowchart illustrating processing performed by the control unit 30 during the actual printing.

  The control unit 30 determines whether or not there is a print instruction from the user (step S11). The print instruction from the user is executed by the user operating the touch panel 32, for example. If there is a print instruction, the process proceeds to step S12. If there is no print instruction, this process repeats step S11, and the control unit 30 waits for a print instruction.

  When there is a print instruction, the control unit 30 refers to the detection result stored in the storage unit 31 and determines whether or not curling may occur on the print medium when the image is printed (step S12). If curl can occur, the process proceeds to step S13. If no curl occurs, the process proceeds to step S14.

  When curling can occur, the control unit 30 reverses the front and back of the print medium and transports the print medium to the reversing unit 22 and the transport roller pair 7a (step S13). More specifically, the control unit 30 controls the direction of the switching claw 24 so as to guide the print medium fed from the automatic paper feed cassette 5 to the reversing path R1. Then, the control unit 30 causes the reversing roller pair 23a to convey the print medium conveyed along the reversing path R1 to the lower reversing path R3. Thereafter, the control unit 30 reverses the rotation direction of the reversing roller pair 23a and rotates the reversing roller pair 23b to convey the print medium above the reversing paths R3 and R2. As a result, the print medium is transported to the transport path R with the front and back sides reversed. Thereafter, the process proceeds to step S15.

  When curl does not occur, the control unit 30 conveys the print medium to the conveyance roller pair 7a without reversing the front and back of the print medium (step S14). More specifically, the control unit 30 controls the direction of the switching claw 24 so as to guide the print medium fed from the automatic paper feed cassette 5 to the transport path R side. As a result, the print medium is transported to the transport path R. Thereafter, the process proceeds to step S15.

  In step S15, the control unit 30 prints an image on the print medium (step S15). More specifically, the control unit 30 causes the conveyance roller pairs 7b, 7c, and 7d to convey the print medium. At this time, the toner image is secondarily transferred to the printing medium at the secondary transfer position 13, and the toner image that has been secondarily transferred is fixed by the fixing device 15. Thereafter, the print medium on which the image is printed is discharged to the paper discharge unit 9 by the discharge roller pair 17. This is the end of the main printing. In the main printing, an image is printed on one print medium, but an image may be printed on a plurality of print media.

(effect)
According to the image forming apparatus 1 as described above, the control unit 30 detects the presence or absence of curling before the user issues a print instruction. When the curl can occur in the print medium, the control unit 30 automatically reverses the front and back of the print medium and prints an image. Therefore, in the image forming apparatus 1, it is possible to suppress the occurrence of curling on the print medium.

(Second Embodiment)
Next, an image forming apparatus according to a second embodiment of the present invention will be described with reference to the drawings. The overall configuration of the image forming apparatus 1 is shown in FIG. 1 as with the image forming apparatus 1 of the first embodiment.

  The image forming apparatus 1 according to the present embodiment relates to the first embodiment in that when it is detected that curling has occurred during test conveyance, the fact is displayed on the touch panel 32 and notified. This is different from the image forming apparatus 1. Below, it demonstrates centering on this difference. Note that the overall configuration of the image forming apparatus 1 according to the present embodiment is the same as that of the image forming apparatus 1 according to the first embodiment, and a description thereof will be omitted.

  Hereinafter, the test conveyance of the image forming apparatus 1 will be described with reference to FIGS. 5 and 6. FIG. 5 is a flowchart showing processing performed by the control unit 30 during test conveyance. FIG. 6 is a diagram illustrating a detection result displayed on the touch panel 32.

  First, the operations performed by the control unit 30 in steps S1 to S5 are the same as those operations in the first embodiment, and thus description thereof is omitted.

  In step S21, the control unit 30 determines whether or not curling has occurred in the print medium (step S21). If curl has occurred, the process proceeds to step S22. If no curl has occurred, the process proceeds to step S6.

  If the curl has occurred, the control unit 30 causes the touch panel 32 to display a screen indicating that the curl has occurred as shown in FIG. 6 (step S22). Thereafter, the process proceeds to step S6. Since the processes performed after step S6 are the same as those in the first embodiment, the description thereof is omitted.

(effect)
According to the image forming apparatus 1 as described above, when curl occurs on the print medium, the fact is displayed on the touch panel 32, so that the user can curl the print medium before printing the image. You can know that there is a risk. Therefore, the user can suppress the occurrence of curling, for example, by inverting the front and back of the print medium in the automatic paper feed cassette 5. In the image forming apparatus 1 according to the present embodiment, the reversal of the front and back of the print medium that the image forming apparatus 1 according to the first embodiment is performing at the time of actual printing may be performed. It does not have to be.

  In the image forming apparatus 1 according to the first embodiment and the second embodiment, the table of the print medium is the upper surface of the print medium in the state set in the automatic paper feed cassette 5 of FIG. Here, the back of the printing medium refers to the lower surface in the state of being set in the automatic paper feeding cassette 5.

1 is a diagram illustrating a schematic configuration of an image forming apparatus according to the present invention. It is a block diagram of a detection part. 5 is a flowchart illustrating processing performed by a control unit during test conveyance in the image forming apparatus according to the first embodiment. It is the flowchart which showed the process which a control part performs at the time of this printing. 6 is a flowchart illustrating processing performed by a control unit during test conveyance in an image forming apparatus according to a second embodiment. It is the figure which showed the detection result displayed on a touch panel.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Image forming apparatus 5 Automatic paper feed cassette 7a, 7b, 7c, 7d Conveyance roller pair 15 Fixing device 17 Discharge roller pair 21 Reverse conveyance part 22 Inversion part 30 Control part 31 Storage part 32 Touch panel 33 Detection part R Conveyance path

Claims (7)

A cassette for storing print media;
Conveying means for conveying the print medium;
Control means for causing the transport means to test transport the print medium when a predetermined condition is satisfied;
Detecting means for detecting a curled state of the print medium that has been test-conveyed by the conveying means;
An image forming apparatus comprising: A fixing unit provided on a conveyance path formed by the conveyance unit and fixing a toner image on the print medium;
In addition,
The detecting means is disposed at a subsequent stage of the fixing means;
The image forming apparatus according to claim 1. Reverse conveying means for returning the print medium that has been test-conveyed by the conveying means to the cassette;
The image forming apparatus according to claim 1, further comprising: The predetermined condition is either when the power is turned on or when the cassette is opened and closed,
The image forming apparatus according to claim 1, wherein the image forming apparatus is an image forming apparatus. The control unit causes the conveyance unit to convey the print medium based on a detection result by the detection unit when printing an image on the print medium;
The image forming apparatus according to claim 1, wherein the image forming apparatus is an image forming apparatus. The conveying means is
Inversion means for inverting the front and back of the print medium,
Including
When the control means is the detection result indicating that the print medium is curled, the control means reverses the front and back of the print medium by the reversing means.
The image forming apparatus according to claim 5. A notification means for notifying a user of the detection result by the detection means;
The image forming apparatus according to claim 1, further comprising:

Images