JP2020172343A - Sheet conveying device and image forming device - Google Patents

Abstract

To provide a sheet conveying device capable of preventing deflection of a sheet caused in skew correction from being buckled to cause defects such as folds and wrinkles.SOLUTION: In the sheet conveying device, an amount of sheets pushed into a pair of resist rollers is reduced when a skew amount detected at skew detecting parts exceeds a predetermined value, whereby deflection of the sheet is reduced to prevent defects such as folds and wrinkles.SELECTED DRAWING: Figure 3

Description

The present invention relates to a sheet transfer device and an image forming device including the same.

Conventionally, in an image forming apparatus such as a printer or a copier, a sheet fed from a sheet loading unit such as a paper cassette or a manual feed tray may be transported at an oblique angle (hereinafter referred to as skew). In the sheet transfer device, the sheet tip is abutted against the resist roller that has stopped rotating during the transfer, and the sheet is further pushed by the upstream transfer roller to correct the skew along the resist roller. There is.

Patent Document 1 proposes the following sheet transfer device. A plurality of sheets loaded on the sheet loading section are separated and fed one by one, and the skewed sheet is attached to the nip portion of the resist roller to correct the skew. A sensor for sheet detection is provided at a substantially central position in the axial direction of the resist roller on the upstream side in the transport direction of the resist roller. Then, by continuously pressing the tip of the sheet against the nip of the resist roller until the sensor detects the sheet, it is possible to correct more accurately and by the optimum amount according to the amount of skew of each sheet. is there.

Japanese Unexamined Patent Publication No. 9-77309

The user may set it roughly on the seat loading section. In this case, the fed sheet will be slanted more than expected and will hit the resist roller.

In the sheet transport device of Patent Document 1, the amount of pushing into the resist roller is increased in order to correct even a sheet that is greatly skewed. As described above, when the sheet is abutted against the resist roller in order to correct the greatly skewed sheet, the sheet is twisted and bent. As a result, when the sheet transfer by the resist roller is started after that, the bent portion of the sheet buckles, which may cause defects such as creases and wrinkles of the sheet. Since the sheet is not kept in a normal state, it may lead to sheet clogging in the device in some cases.

Therefore, the present invention has been made in view of such a current situation, and provides a sheet transport device capable of preventing defects such as creases and wrinkles of the sheet even when a sheet having a large skew is fed. The purpose is to do that.

The sheet transporting device of the present invention includes a stopping means for stopping the tip of the sheet when the tip of the sheet comes into contact with the sheet, and a transporting means which is arranged upstream of the stopping means in the transporting direction and transports the sheet toward the stopping means. When the detection unit detects that the tilt amount of the sheet is equal to or less than a predetermined value, the transporting means presses the tip of the sheet in contact with the sheet. When the sheet is conveyed by the first pushing amount while the stopping means is stopped and the detection unit detects that the amount of inclination of the sheet exceeds the predetermined value, the conveying means is used. With the tip of the sheet in contact with the stopping means stopped by the stopping means, the sheet is conveyed by a second pushing amount smaller than the first pushing amount.

According to the present invention, defects such as creases and wrinkles can be prevented.

The cross-sectional view which shows typically the image forming apparatus which concerns on this embodiment. The explanatory view which shows the operation of the sheet transfer apparatus in a normal state which concerns on this embodiment. The explanatory view which shows the operation of the sheet transfer apparatus at the time of a large skew which concerns on this embodiment. Block Diagram. A flowchart showing the procedure of skew correction. The perspective view which shows the operation of the sheet transfer apparatus at the time of a large skew which concerns on another embodiment. Flowchart in another embodiment. The figure which shows the modification.

Hereinafter, the image forming apparatus according to the embodiment of the present invention will be described with reference to the drawings.

<About the image forming device>
An embodiment of a sheet transfer device according to the present invention and an image forming device including the same will be specifically described with reference to the drawings.

First, an embodiment of the image forming apparatus according to the present invention will be described.

FIG. 1 is a schematic front view of a main body of a color image forming apparatus using an electrophotographic method. The image forming apparatus 100 is an intermediate transfer tandem type image forming apparatus in which image forming portions of four colors of yellow (Y), magenta (M), cyan (C), and black (Bk) are arranged side by side on the intermediate transfer belt 2. Is.

<Image formation process>
The image forming apparatus 100 includes four process cartridges Pa to Pd for forming a toner image. These process cartridges use different Y, M, C, and Bk toners, but other than that, they have the same configuration. However, the number of colors is not limited to four, and the order of the colors is not limited to this. Taking the process cartridge Pa that forms the Y toner image as an example, the surface of the photoconductor 6a that is rotationally driven clockwise in FIG. 1 is exposed and scanned by the exposure apparatus 7a that is driven based on the signal of the image information. An electrostatic latent image is formed. This electrostatic latent image is developed as a toner image in the process cartridge Pa. After that, a predetermined pressing force and a primary transfer bias are applied by the primary transfer device T1a, and a toner image is formed on the intermediate transfer belt 2. Similarly, in the other image forming portions Pb to Pd, the toner image is formed on the intermediate transfer belt 2.

The intermediate transfer belt 2 is installed on an intermediate transfer belt frame (not shown) and includes four primary transfer bias rollers 5a to 5d, a transfer cleaning device 4, and the like. The intermediate transfer belt 2 is stretched by a secondary transfer inner roller 1, a tension roller 3, and a secondary transfer upstream roller 8 that also drive and transmit to the intermediate transfer belt 2, and is conveyed and driven counterclockwise in the drawing. It is a belt. The primary transfer bias rollers 5a to 5d form a primary transfer nip by sandwiching the intermediate transfer belt 2 between the photoconductors 6a to 6d. The image-creating process is performed at the timing of superimposing on the toner image of the upstream color primary-transferred on the intermediate transfer belt 2 by sequentially passing through the primary transfer nip along with the transport drive of the intermediate transfer belt 2. Then, a four-color toner image is formed on the intermediate transfer belt 2 and conveyed to the secondary transfer unit T2.

<Sheet transfer process>
Below the image forming apparatus 100, a feeding apparatus 20 in which the sheet S is loaded and stored is provided. The pick roller 11 is rotatably supported so as to be able to come into contact with the top sheet S in the feed tray 10 on which the sheet is placed in the loaded state. The seat S is fed by rotationally driving the pick roller 11 by a driving means (not shown). The sheet S is fed to the resist front roller pair 12 constituting the skew correction unit 21, and the sheet S is fed by the resist front roller pair 12 and the registration roller pair 13 as the correction unit (hereinafter referred to as a resist roller pair). Skew is corrected. The sheet whose skew is corrected is conveyed to the secondary transfer unit T2 by the resist roller pair 13. In the secondary transfer unit T2, a nip is formed so that the opposing secondary transfer inner roller 1 and the secondary transfer outer roller 14 sandwich the intermediate transfer belt 2 in between. By applying a predetermined pressing force and a secondary transfer bias, the four-color toner image formed on the intermediate transfer belt 2 is secondarily transferred onto the sheet S to form a toner image.

<Process after secondary transcription>
The sheet S after the secondary transfer is conveyed to the fixing device 15. The fixing device 15 includes a heater as a heat source (not shown), and when the sheet S passes between the opposing rollers, a predetermined heat and pressure are applied to fix the toner image on the sheet S. The sheet S on which the toner image is fixed is discharged to the outside of the machine by the discharge roller 16. A discharge tray 17 is provided at the tip of the discharge roller 16, and the sheets S discharged to the outside of the machine by the discharge roller 16 are sequentially loaded on the discharge tray 17.

<About the skew correction section>
Next, the configuration of one embodiment of the skew correction unit will be described with reference to FIGS. 2, 3, 4, and 5.

The skew correction unit includes a pre-resist roller pair 12, a skew detection means 22, and a resist roller pair 13. The pre-resist roller pair 12 receives and conveys the sheet S fed from the feed tray 10. The skew detecting means 22 detects the amount of skew of the sheet S conveyed by the resist front roller pair 12 as the conveying means. The resist roller pair 13 corrects the skew of the sheet S conveyed from the resist pre-resist roller pair 12 and conveys the sheet S to the secondary transfer unit T2. The skew detecting means 22 as a detection unit detects the skew amount of the sheet upstream of the resist roller pair 13 in the transport direction. The pre-resist motor M2 rotationally drives the pre-resist roller pair 12. The resist motor M1 rotationally drives the resist roller pair 13.

FIG. 4 shows a control block diagram. The CPU 24 as a control means controls the operation of each part of the skew correction unit 21 including the resist motor M1 and the pre-resist motor M2 based on the signal from the skew detection means 22. The CPU 24 is connected to an operation unit 23 configured so that the user can acquire information on the image forming apparatus, and controls the display of the operation unit 23. The CPU 24 executes the operation of the flowchart of FIG. 5 using the RAM as a working memory according to the program stored in the ROM.

FIG. 2 is an explanatory diagram for explaining the operation of skew correction in a normal time according to the present embodiment. 2 (a) to 2 (c) show the order in which the skew correction unit corrects the skew while conveying the sheet. Note that FIGS. 3 and 6 also show a process in which the skew correction unit corrects skew while transporting the sheet.

The pre-resist roller pair 12 is rotationally driven by the pre-resist motor M2 before receiving the sheet S fed from the feed tray 10. On the other hand, the resist roller pair 13 is in a state where the rotation is stopped. The amount of skew of the sheet S conveyed by the pre-resist roller pair 12 is detected by the skew detecting means 22. The skew amount described here may be any parameter as long as it can be quantitatively detected, such as the inclination angle of the tip end portion or the left and right end portions of the sheet S, and the positional difference between both ends on the tip end side of the sheet S. In the present embodiment, the skew detection means 22 includes a plurality of sheet detection sensors arranged side by side in parallel with the longitudinal direction (width direction orthogonal to the transport direction) of the resist roller pair 13. The inclination of the tip of the sheet S is detected by detecting the deviation of the ON timing of each sheet detection sensor. Next, the sheet is conveyed so that the tip end portion of the sheet S whose skew amount is detected abuts against the stopped resist roller pair 13. Even after the sheet S hits the resist roller pair 13, the pre-resist roller pair 12 continues to rotate and drive (oblique correction operation). By this operation, the tip end portion of the sheet S is pushed so as to follow the longitudinal direction of the resist roller pair 13, and the skew of the sheet S is corrected.

At this time, as shown in FIG. 2B, the sheet S is in a bent state between the resist front roller pair 12 and the resist roller pair 13. This is because the tip of the sheet S is stopped by the resist roller pair 13 as a stopping means with respect to the sheet S tilted at the position of the resist front roller pair 12, so that the sheet S is in a bent state. Because it becomes. Then, at the timing when the skew correction is completed, the resist roller pair 13 starts rotational driving, and the sheet S is conveyed to the secondary transfer unit T2. Ideally, the bending of the sheet S when the sheet S is conveyed by the resist roller pair 13 is held until the rear end portion of the sheet S passes through the resist front roller pair 12.

FIG. 2 shows a case where the skew amount is equal to or less than a predetermined threshold value A, and the skew amount is small and within the assumed range. It corresponds to the control in the order of S1, S2, S3, S4, S5, S7 shown in the flowchart of FIG. 5, and the first pushing amount a may be a constant value or may be changed depending on the conditions such as the paper type. You may. When the skew amount is not more than a predetermined value, the resist motor M1 is started to rotate the resist roller pair 13 after the sheet is conveyed by the first pushing amount a so that the sheet bends (S7 in FIG. 5). ). In the present embodiment, the resist motor M1 and the pre-resist motor M2 are driven to convey the sheet by the resist roller pair 13 and the resist pre-roller pair 12.

FIG. 3 is a perspective view showing an operation at the time of large skew (that is, when the sheet is greatly skewed). The basic operation for correcting the skew even at the time of large skew is the same as the content described with reference to FIG. Here, the skew detection means 22 detects that the skew amount exceeds a predetermined threshold value A, and shows a case where the skew amount is large and is out of the expected range. This corresponds to the control in the order of S1, S2, S3, S4, S6, and S7 shown in the flowchart of FIG. When the skew amount exceeds the threshold value A in this way, the tip portion of the sheet S abuts on the resist roller pair 13 and then is set as the second push amount b on the resist front roller pair 12. Here, the first and second push-in amounts are set to the pre-resist roller pair 12 so that the sheet is flexed while the rotation of the resist roller pair 13 is stopped after the tip of the sheet reaches the resist roller pair 13. Corresponds to the amount of sheet transported. In other words, the first and second push-in amounts are the amounts at which the pre-resist roller pair 12 feeds the sheet from the time when the tip of the sheet reaches the resist roller pair 13 until the resist roller pair 13 starts rotating. Here, the relationship between the first push-in amount a and the second push-in amount b is
b <a
Is a feature of this embodiment. When the skew amount threshold value A exceeds this, the seat S bends too much or the force transmitted to the seat S becomes too large in the diagonal direction, so that the seat S buckles and breaks into the seat S. It is desirable to set the value at the boundary where eyes and wrinkles occur. In such a case, by making the pushing amount (second pushing amount) b smaller than the normal value (first pushing amount) a, it is possible to reduce the bending of the sheet S and prevent the occurrence of creases and wrinkles. Will be. Here, the pushing amount b may be a constant value like the pushing amount a, or may be changed depending on conditions such as the paper type.

In the above, the resist roller pair 13 has been illustrated as a stopping means for stopping the tip of the sheet. However, as a stopping means, a gate member that appears in the transport path and abuts the tip of the sheet may be provided. FIG. 8 shows a modified example in which the gate member 41 is provided. The gate member 41 can stop the tip of the sheet upstream of the nip of the roller pair 133 and is held rotatably. Then, the gate member 41 can be moved to the retracted position at the dotted line position by the solenoid 42. When the pre-resist roller pair 12 conveys the sheet by the amount of pushing while the tip of the sheet is stopped by the gate member 41, the sheet bends. Then, since the tip of the gate member 41 is aligned, the skew of the sheet is corrected. Here, the CPU controls the solenoid 42 so that the gate member 41 is moved to the retracted position when the pre-resist roller pair 12 conveys the sheet by the amount of pushing. Then, the sheet is nipped into the rotating roller pair 133, and the sheet is conveyed. As described above, the pushing amount of the pre-resist roller pair 12 for conveying the sheet is changed with the tip stopped by the gate member 41 based on the determination of whether or not the skewing amount is large. That is, when it is determined that the skew is large, the pushing amount is set to be small.

From here, another embodiment will be described with reference to FIGS. 6 and 7.

In another embodiment, the configuration is the same as that of the above-described embodiment, and the basic operation for correcting the skew is also the same as the content described in the above-described embodiment. Therefore, the differences from the above-described embodiment will be described in detail below.

When the skew detecting means 22 detects that the skew amount is equal to or less than the threshold value B, the operation when it is detected that the value exceeds the value B and is 4 will be described. When the amount of skew is equal to or less than the threshold value B, a correction operation is performed in which the pre-resist roller pair 12 conveys the sheet in a state where the tip of the sheet is brought into contact with the resist roller pair 13 and the tip of the sheet is stopped by the resist roller pair 13. Do.

Here, the threshold value B of the skew amount is a boundary that cannot prevent the occurrence of creases and wrinkles of the sheet S no matter how much the pushing amount to the resist roller pair 13 is reduced when the threshold value B is exceeded. It is desirable to set it as a value. If the sheet S is bent even a little in this state, there is a high possibility that folds and wrinkles of the sheet S will occur. When the amount of skew exceeds the threshold value B, the resist roller pair 13 starts rotating in a predetermined rotation direction before the tip portion of the sheet S hits the resist roller pair 13. The predetermined rotation direction here is a direction in which the sheet is conveyed in the conveying direction. Then, when the tip of the sheet reaches the resist roller pair 13, the resist roller pair 13 is rotated in a predetermined rotation direction. That is, the sheet is passed through the sheet without performing the operation of abutting the sheet against the resist roller pair 13 in order to form a deflection in the sheet. As a result, the bending of the sheet S is eliminated, and it is possible to prevent the occurrence of creases and wrinkles. This corresponds to the control in the order of S7, S8, S9, S10, S11, S13 in the flowchart shown in FIG.

In another embodiment as well, the CPU 24 executes the operation of the flowchart of FIG. 7 using the RAM as a working memory according to the program stored in the ROM.

In addition, also in this other embodiment, the modification using the gate member 41 of FIG. 8 can be applied. When it is detected that the skew is small, the gate member 41 stops the tip of the sheet. When it is detected that the skew is large, the gate member 41 conveys the sheet without stopping the tip of the sheet. That is, when it is determined that the skew is large, the tip of the sheet reaches the roller pair 133 while the gate member 41 is in the retracted position and the roller pair 133 is rotated. As a result, the sheet is conveyed without stopping the tip of the sheet.

By the way, in both of the above-described embodiments, in the case of large skew, the amount of pushing into the resist roller pair 13 is reduced or the skew is not corrected, so that the function as the original skew correction unit functions. It will be in a lowered state. That is, since the skew of the sheet S cannot be corrected appropriately, the image secondarily transferred to the sheet S is tilted with respect to the sheet S. However, it is possible to provide an image forming apparatus suitable for a user who is concerned about wrinkles generated by a sheet. Further, in order to cope with the fact that the skew of the sheet S cannot be corrected satisfactorily, the following configuration may be made. That is, when the skew detecting means 22 detects the skew amount exceeding a predetermined threshold value A or the threshold value B, the sheet S on which the image is formed is discharged onto the discharge tray 17, and then continuously. Stop the transport operation of transporting the next sheet to be performed. Then, it is also good to display on the screen of the operation unit 23 operated by the user to urge the correction of the inclination of the sheet loaded on the feed tray 10. As a result, the user has an opportunity to redo the setting of the sheet on the mounting portion, and it is possible to prevent the subsequent skewing.

The skew detecting means 22 may be configured to be used for detecting the transport timing of the sheet S. That is, the CPU 24 determines the timing at which the tip of the sheet reaches the resist roller pair 13 based on the signal from the sensor of the skew detecting means 22. As a result, it is not necessary to prepare another detection means as a means for detecting the timing at which the sheet hits the resist roller pair 13, and it is possible to prevent the image forming apparatus from becoming complicated and large in size.

The present invention is not limited to the above-described embodiment. In addition, the effects described in the present embodiment merely list the most preferable effects arising from the present invention, and the effects according to the present invention are not limited to those described in the present embodiment. Although the present embodiment has been described using the electrophotographic image forming apparatus 100, the present invention is not limited thereto. For example, it can also be used in an inkjet image forming apparatus that forms an image on a sheet by ejecting an ink liquid from a nozzle.

100 Image forming device 10 Feed tray 12 Roller before resist 13 Resist roller vs 20 Sheet feeder 22 Skew detection means S sheet

Claims (8)

Stopping means that the tip of the sheet comes into contact and stops the tip of the sheet,
A transport means arranged upstream of the stop means and transporting the sheet toward the stop means, and a transport means.
When the detection unit has a detection unit for detecting the inclination of the sheet and the detection unit detects that the inclination amount of the sheet is equal to or less than a predetermined value, the conveying means stops the tip of the abutted sheet. With the means stopped, the sheet is conveyed by the first pushing amount, and the sheet is conveyed.
When the detection unit detects that the amount of inclination of the sheet exceeds the predetermined value, the transporting means is in a state where the stopping means stops the tip of the sheet in contact with the stopping means. A sheet transporting device for transporting the sheet by a second pushing amount smaller than the first pushing amount. Stopping means that the tip of the sheet comes into contact and stops the tip of the sheet,
A transport means arranged upstream of the stop means and transporting the sheet toward the stop means, and a transport means.
When the detection unit has a detection unit for detecting the inclination of the sheet and the detection unit detects that the amount of inclination of the sheet is equal to or less than a predetermined value, the tip of the sheet in contact with the stopping means is pressed by the stopping means. The transporting means performs an operation of transporting the sheet while the is stopped.
A sheet conveying device characterized in that the operation is not performed when the detection unit detects that the amount of inclination of the sheet exceeds the predetermined value. The sheet conveying device according to claim 1 or 2, wherein the detecting unit also serves as a sheet detecting means for detecting the timing at which the sheet hits the stopping means. The one according to any one of claims 1 to 3, wherein the detection unit includes a plurality of sensors arranged side by side in a direction orthogonal to the transport direction of the sheet, and detects the inclination of the tip of the sheet. Sheet transfer device. The sheet transport device according to any one of claims 1 to 4, wherein the stopping means is a pair of rollers. The sheet transport device according to any one of claims 1 to 4, wherein the stopping means is a gate member in which the tip of the sheet is in contact with and can move. The sheet transport device according to any one of claims 1 to 6,
An image forming unit that forms an image on a sheet conveyed by the sheet conveying device,
An image forming apparatus comprising. A tray on which a sheet to be fed toward the stopping means is placed,
It has an operation unit that allows the user to acquire information on the image forming apparatus.
The seventh aspect of claim 7, wherein when the amount of inclination of the sheet exceeds the predetermined value, the operation unit is made to display a prompt to correct the inclination of the sheet placed on the tray. Image forming device.

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