JP2001122498A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image forming device equipped with an enhanced aligning performance for sheet material on a sheet discharging tray by reducing a curl (warp) of each sheet discharged onto the discharge tray. SOLUTION: A sheet material S having passed between a photosensitive drum 7 and a transcription roller 10 and undergone a transcription of a toner image is passed through a fixing nip of a fixing device 15 so that a heat fixation process is executed. The sheet material S passes a curl correcting device 25 and is discharged onto a sheet discharge tray 34 by either of the face-up paper discharge and face-down discharge. The sheet discharging part is finished with a plurality of optical range sensors 35a, 35b, 35c. The sensors 35a and 35b, one of them not being illustrated, measure the distances to the surfaces at the sides of sheet in its width direction. The sensor 35c measures the distance to the surface of the central part of sheet across the width positioned ahead of the other sensors 35a and 35b. A CPU 50 judges the curled condition of the sheet S on the basis of the distances measured by the sensors 35a, 35b, 35c and in accordance with the determined curled condition, controls a solenoid 26a of a flapper 26 to select the pas (to bend upward or downward) in the curl correcting device 25, and also controls a motor 25m which changes the amount of bending.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a printer, a copying machine, and a printer for forming an image on sheet materials fed one by one.
The present invention relates to an image forming apparatus such as a facsimile.

[0002]

2. Description of the Related Art FIG. 11 shows an overall configuration of a conventional image forming apparatus (laser beam printer).

Here, the configuration of the image forming apparatus will be briefly described.

The image forming apparatus includes a plurality of paper cassettes 1 and
2, and any one of them is selected by the operator. Then, the sheet material S is fed from the selected sheet feeding cassette.

[0005] The sheet materials S stacked and stored in the sheet cassettes 1 and 2 are sequentially sent out from the uppermost sheet material by a feed roller 3 rotating in a counterclockwise direction when a sheet feed command is issued.

The sheet material S sent out of the cassette is separated one by one by a separating / feeding roller pair 4 and fed directly or via a conveying roller pair 5 to a registration roller pair 6 in a rotation stopped state. You.

The sheet material S that has reached the registration roller pair 6
Stops moving when a predetermined amount of loop is formed by the leading edge of the sheet material abutting the nip of the registration roller pair 6. By the formation of this loop, the skew state of the sheet material S is corrected.

The sheet material S whose skew state has been corrected is transferred by a registration roller pair 6 which starts rotating at a predetermined timing between a photosensitive drum 7 rotating clockwise and a transfer roller 10. Is sent to And
The toner image on the photosensitive drum 7 is transferred to the sheet material S passing through the transfer unit by the transfer roller 10.

The image formation on the photosensitive drum 7 is performed simultaneously with the start of sheet feeding. First, the laser scanner 12 emits a laser beam L based on information sent from a host computer (not shown). This laser light L irradiates the surface of the photosensitive drum 7 via the reflection mirror 13. As a result, an electrostatic latent image is formed on the photosensitive drum 7 uniformly charged by the primary charger 8. Then, this electrostatic latent image is developed by the toner developing device 9. The toner adhered on the photosensitive drum 7 after the transfer of the toner image is removed by the removing member 11.

The sheet material S on which the toner image has been transferred after passing through the transfer section is sent to a fixing device (thermal fixing means) 15 by a conveyor belt 14, where it is heated and pressed. As a result, the toner image in the unfixed state is fixed on the sheet material S.

The fixing device 15 includes a fixing roller 15a for heating.
And a pressure roller 15b for pressing. The pressing roller 15b is configured to be able to contact and separate from the fixing roller 15a whose position is fixed, and is urged via a lever member 15f that is rotatable up and down around a support shaft 15e. By the fixing roller 15a.
The sheet material S passes between the fixing roller 15a and the pressure roller 15b (nip) and is heated and pressed.

The sheet material S which has passed through the fixing device 15 and has been subjected to the fixing process is discharged to the outside of the image forming apparatus main body 100A. In the case of the present image forming apparatus, a face-up paper sheet is discharged with the image face upward. And face-down paper discharge, which discharges paper with the image side facing down, can be selected. This is selected by the operator.

In the case of face-up discharge, the flapper 16
Has been switched to the position shown by the broken line, and the path to the face-up paper discharge tray 21 has been opened. The sheet material S on which the fixing process has been performed is conveyed by the conveying roller pair 15c and the discharge roller pair 20 and
Is discharged on top.

In the case of face-down discharge, the flapper 16
Has been switched to the position shown by the solid line, and the path to the face-down paper discharge tray 19 has been opened. The sheet material S on which the fixing process has been performed is conveyed by the pair of conveying rollers 15c and 17 and the pair of discharge rollers 18 and discharged onto the face-down discharge tray 19.

By the way, the sheet material discharged from the image forming apparatus often has an upward or downward curl (warpage), which causes a deterioration of the sheet alignment in the image forming apparatus. For example, the sheet material is curled when passing through the heat fixing unit, and curled when passing through a curved path. This curl depends on the fixing conditions (temperature and pressure) in the heat fixing unit, the material of the sheet material, the stitching direction of the fiber, the storage conditions, the use environment, and the like, and is affected by the curvature of the curved path, and various forms. Make

FIGS. 12 to 17 show various examples of curls on the sheet material discharged from the image forming apparatus.

The sheet material S-1 shown in FIG. 12 has an upward curl that is curved in the longitudinal direction. The sheet material S-2 in FIG. 13 has an upward curl diagonally curved. The sheet material S-3 in FIG. 14 has an upward curl curved in the width direction. Sheet material S-4 in FIG.
Has a diagonally curved downward curl. The sheet material S-5 in FIG. 16 has a downward curl that is curved in the longitudinal direction. The sheet material S-6 in FIG. 17 has a downward curl curved in the width direction.

A conventional image forming apparatus main body 1 shown in FIG.
In 00B, a measure (curling reduction) is taken to improve the alignment of the sheet material S discharged onto the face-down discharge tray 19.

In the image forming apparatus 100B, the face-down sheet material S that has passed through the fixing device 15 passes through the curl correction device 22 and is discharged onto the discharge tray 19. Since the sheet material S passing through the curved reversal path has a downward curl, the curl correction device 22 bends the sheet material S upward to reduce the curl.
The curl correction device 22 includes a large-diameter correction roller 22a and two correction rollers 22b and 22c that are in pressure contact with the roller. In this case, the amount of bending in the curl correction device 22 is fixed to an amount determined in design.

In the case of the image forming apparatus main body 100B, a paper discharge tray 21 on which a sheet material S for face-up paper discharge is stacked.
And the sheet discharge tray 19 for stacking the sheet material S for face-down sheet discharge, the curl straightening device having a constant bending amount is provided to improve the alignment of the sheet material S on each tray 19 and 21. It is easy to do. this is,
This is because the curl on the sheet material S for face-up discharge has a similar tendency, and the curl on the sheet material S for face-down discharge has a similar tendency.

[0021]

In recent years, in an image forming apparatus, a face-up sheet material and a face-down sheet material are discharged onto the same discharge stacking means, or one sheet is discharged. An increase in the amount that can be stacked on the paper stacking means has been required.

However, in order to satisfy such demands, it is necessary to reduce curls in various forms (for example, the forms shown in FIGS. 12 to 17) attached to the sheet material to further improve the sheet discharge alignment. was there.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned circumstances, and an image forming apparatus capable of reducing curl of various forms on a sheet material and improving alignment of paper ejection. The purpose is to provide.

[0024]

According to the present invention, an image is formed on a sheet material fed one by one, and the sheet material on which the image has been formed is discharged and stacked. The present invention relates to an image forming apparatus that discharges the image to the upper side.

According to the present invention, in order to achieve the above object, a sheet material bending means for bending a sheet material on which an image has been formed, and a sheet material discharged on the sheet discharge stacking means are provided. It is characterized by having a warp detecting means for detecting a warped state and a control means for controlling the sheet material bending means in accordance with the warped state detected by the warp detecting means.

For example, the sheet material bending means can perform upward bending and downward bending, and the upward bending and the downward bending can be selected by switching paths. The control means selects one of the upward bending and the downward bending according to the direction of the warpage of the sheet material. The sheet material bending means can change the amount of bending, and the control means changes the amount of bending in accordance with the amount of warpage of the sheet material.

For example, the warp detecting means detects a warp state of the sheet material at a plurality of positions in the width direction and a plurality of positions in the longitudinal direction of the sheet material. One or a plurality of optical distance measuring sensors for measuring the distance to the sheet material surface are used for the warp detecting means.

Further, the present invention is characterized in that a heat fixing means for performing a fixing process on a sheet material on which an image has been formed is provided upstream of the sheet material bending means.

Further, the present invention has a heat fixing means for performing a fixing process on a sheet material on which an image has been formed,
The heat fixing unit also serves as the sheet material bending unit.

For example, the thermal fixing means includes a fixing roller for heating and a pressure roller for pressurizing the fixing roller, and a fixing nip pressure between the fixing roller and the pressure roller is changed. It is possible. The controller changes the fixing nip pressure according to the amount of warpage of the sheet material.

Further, the present invention is characterized in that a face-up sheet material and a face-down sheet material are discharged onto one discharge stacking means.

[0032]

Embodiments of the present invention will be described below with reference to the drawings.

<First Embodiment> FIG. 1 shows a first embodiment of the present invention.
FIG. 2 is a cross-sectional view illustrating an overall configuration of the image forming apparatus according to the first embodiment, and FIG. 2 is a front view of the image forming apparatus as viewed from a sheet discharge side.

The present image forming apparatus includes an image forming apparatus main body 10.
0C and a post-processing apparatus main body 200A connected to the image forming apparatus main body 100C.

The basic structure of the image forming apparatus main body 100C is not different from the structure of the image forming apparatus main body 100A in FIG. In the case of the image forming apparatus main body 100C here, the sheet material S that has passed through the fixing device 15 and has undergone the fixing process is guided into the post-processing apparatus main body 200A. This point is structurally different.

Here, the post-processing apparatus main body 200A will be described in detail. The post-processing apparatus main body 200A has a function of correcting the curl attached to the sheet material S that has been subjected to the fixing process, a function of discharging the sheet material S face-up and face-down, and It has a loading function.

The sheet material S that has been subjected to the fixing process is guided into the post-processing apparatus main body 200A from the inlet 23. The sheet material S guided into the post-processing apparatus main body 200A passes through a curl correcting device (sheet material bending means) 25. During this passage, the curl attached by the fixing device 15 is corrected. Here, the configuration of the curl correction device 25 will be described.

The curl correcting device 25 is configured around a large-diameter correcting roller 25a disposed at the center of the path 24. First correction rollers 25b and 25c are arranged at the 11 o'clock and 1 o'clock positions on the outer circumference of the correction roller 25a, and the second correction roller 25 is positioned at the 7 o'clock and 5 o'clock positions.
d and 25e are arranged.

The first straightening rollers 25b and 25c pass 24
Are integrated with each other by a member that forms a part of. Second
The correction rollers 25d and 25e are integrated by a member forming a part of the path 24.

The first correction rollers 25b and 25c are pressed against the correction roller 25a by a pressing spring 25f attached to a horizontal pedestal member 25h. The second correction rollers 25d and 25e are fixed to a correction roller 25a by a pressing spring 25g attached to a horizontal pedestal member 25i.
Is pressed.

The pedestal members 25h and 25i are screwed into a ball screw 25j installed in a vertical state, and move up and down when the ball screw 25j is rotated. When the pedestal members 25h and 25i are moved in the vertical direction in this manner, the force for pressing the first correction rollers 25b and 25c and the second correction rollers 25d and 25e can be changed. For example, when the ball screw 25j is rotated clockwise, the pressing force of the first straightening rollers 25b and 25c is increased, and when the ball screw 25j is rotated counterclockwise, the pressing force of the second straightening rollers 25d and 25e is increased. Enhanced. The ball screw 25j rotates clockwise or counterclockwise by driving a pressure adjusting motor 25m connected via gears 25k and 25l. The motor 25m is controlled by the CPU 50.

When the flapper 26 disposed immediately upstream of the straightening roller 25a is switched to the position shown by the broken line, the sheet material S guided into the post-processing apparatus main body 200A is brought into contact with the straightening roller 25a. One straightening roller 25b, 25c
And passes through a first straightening pass formed by At this time, the correction roller 25a is rotating counterclockwise. When the flapper 26 is switched to the position shown by the solid line,
It passes through a second straightening path formed by the straightening roller 25a and the second straightening rollers 25d and 25e. At this time, the correction roller 25a is rotating clockwise. Then, a downward bending is applied to the sheet material S passing through the first straightening pass, and an upward bending is applied to the sheet material S passing through the second straightening pass.

In the present image forming apparatus, the sheet material S stacked on a discharge tray (discharge stacking means) 34 described later is used.
State of curl attached to (curl direction, curl amount)
Is selected (either the first correction pass or the second correction pass), and the bending amount (the pressing force of the correction roller) is set.

For example, if the sheet material S has a small amount of upward curl, the sheet material S is bent downward through the first straightening pass. In this case, the first straightening rollers 25b, 2
The pressing force of 5c is set to a small value. Also, for example,
If the sheet material S has a large amount of downward curl, the sheet material S is bent upward through the second straightening pass. In this case, the pressing force of the second correction rollers 25d and 25e is set to be large. In this way, curling of the sheet material S is reduced.

The sheet material S having been subjected to the curl correction that has passed through the curl correction device 25 is discharged out of the post-processing apparatus main body 200A by either face-up discharge or face-down discharge.

In the case of face-up discharge, the flapper 28 installed at the most downstream portion of the path 24 is switched to the position shown by the solid line to open the face-up path 26. As a result, the sheet material S having been subjected to the curl correction is guided to the same path 26, and the conveying roller pair 30 and the discharge roller pair 33
And is discharged onto the discharge tray 34.

In the case of face-down discharge, the flapper 2
8, 29 are switched to the positions shown by broken lines to open a face-down path 27 for reversing the sheet material. As a result, the sheet material S having been subjected to the curl correction is guided to the same path 27, and is conveyed by a reversing roller (a roller whose outer periphery is partially cut) 31 and a roller 32 which rotate clockwise (forward). . Then, when the rear end of the sheet material S passes through the flapper 29, the reversing roller 31 temporarily stops, and the flapper 29 is switched to the position shown by the solid line. afterwards,
The reversing roller 31 rotates counterclockwise (reverse rotation) to send the sheet material S to the paper discharge port, and the sheet material S is discharged onto the discharge tray 34 by the discharge roller pair 33.

Next, the configuration of the paper discharge unit will be described. (See FIG. 1 and FIG. 2.) A plurality of optical distance measuring sensors (warpage) for detecting the curl state of the sheet material (top sheet material) S stacked on the sheet ejection tray 34 are provided at the sheet ejection section. Detection means) 35a, 35
b, 35c are installed. The sensors 35a and 35b measure the distance to the surface at both sides in the width direction of the sheet material S. The sensor 35c measures the distance to the front surface of the sheet material S at the center in the width direction in front of the sensors 35a and 35b.
The CPU 50 determines the curl state of the sheet material S based on the distances measured by the sensors 35a, 35b, 35c.

FIGS. 3 to 8 show the relationship between the distances when the sensors 35a, 35b and 35c measure the sheet material S having various forms of curls.

The sheet material S-1 in FIG. 3 has an upward curl that is curved in the longitudinal direction. In this case, the relationship between the distances La1, Lb1 measured by the sensors 35a, 35b and the distance Lc1 measured by the sensor 35c is La1, Lb1.
<Lc1.

The sheet material S-2 in FIG. 4 has an upward curl diagonally curved. In this case, the relationship between the distances La2, Lb2 measured by the sensors 35a, 35b and the distance Lc2 measured by the sensor 35c is La2, Lb2 <
Lc2.

The sheet material S-3 in FIG. 5 has an upward curl curved in the width direction. In this case, the relationship between the distances La3, Lb3 measured by the sensors 35a, 35b and the distance Lc3 measured by the sensor 35c is La3, Lb3 <
Lc3.

The sheet material S-4 in FIG. 6 has a downward curl diagonally curved. In this case, the relationship between the distances La4, Lb4 measured by the sensors 35a, 35b and the distance Lc4 measured by the sensor 35c is La4, Lb4>
Lc4.

The sheet material S-5 shown in FIG. 7 has a downward curl that is curved in the longitudinal direction. In this case, the relationship between the distances La5 and Lb5 measured by the sensors 35a and 35b and the distance Lc5 measured by the sensor 35c is La5 and Lb5.
> Lc5.

The sheet material S-6 in FIG. 8 has a downward curl curved in the width direction. In this case, the sensor 35
a, 35b measured by the distance La6, Lb6 and the sensor 35
The relationship of distance Lc6 measured by c is La6, Lb6> Lc
It becomes 6.

The CPU 50 determines whether the curl is upward or downward based on the relationship between the distance measured by the sensors 35a and 35b and the distance measured by the sensor 35c, and determines the amount of curl based on the difference between the two. judge.

When the sheet material S has a curl of a predetermined amount or more, the curl correction device 25 operates as follows.
Control.

That is, when the sheet material S discharged face-up has an upward curl and the sheet material S discharged face-down has a downward curl, the curl correcting device 25 Sheet material S
The solenoid 26a of the flapper 26 is controlled so that a downward bending is applied to the flapper. At the same time, the motor 25m is controlled to set the amount of bending.

In the case where the sheet material S discharged face-up has a downward curl and the sheet material discharged face-down has an upward curl, The solenoid 26a is controlled so that an upward bending is applied to the sheet material S. At the same time, the motor 25m is controlled to set the amount of bending.

<Second Embodiment> FIG. 9 shows a second embodiment of the present invention.
FIG. 1 is a cross-sectional view illustrating an overall configuration of an image forming apparatus (laser beam printer) according to an embodiment.

The present image forming apparatus comprises an image forming apparatus main body 10
0D and a post-processing apparatus main body 200B connected to the image forming apparatus main body 100D.

The image forming apparatus main body 100D is the same as the image forming apparatus main body 100C of FIG. 1 except for a part of the configuration. The post-processing apparatus main body 200B is different from the post-processing apparatus main body 200A in FIG.
Has been removed.

In this image forming apparatus, the fixing device 15 in the image forming apparatus main body 100D corrects the curl.

In the fixing device 15, the pressure roller 15b
The pressing spring 15g for pressing is mounted on a horizontal pedestal member 37a screwed to a ball screw 37b installed in a vertical state.

The ball screw 37b is connected to the gears 37c and 37d.
Is rotated clockwise or counterclockwise by the drive of the pressure adjusting motor 37e connected via the. The motor 37e is controlled by the CPU 50.

In such a configuration, for example, when the ball screw 37b is rotated clockwise, the pressure roller 15b
The pressing force of the pressing roller 15b is increased by rotating the pressing roller 15b counterclockwise. Thus, the fixing nip pressure between the fixing roller 15a and the pressure roller 15b can be changed.

In the present image forming apparatus, the discharge tray 3
The fixing nip pressure is changed according to the curl state of the sheet material S stacked on the sheet 4. For example, when the sheet material S has a predetermined amount of curl or more, the fixing nip pressure is reduced according to the curl amount.

However, if the fixing nip pressure is reduced, the fixability of the toner image may be affected. Therefore, in such a case, the CPU 50 changes the fixing temperature of the fixing roller 15a to deal with this. When the fixing nip pressure is low, the fixing property is improved by increasing the fixing temperature.

<Third Embodiment> FIG. 10 shows another configuration example of the post-processing apparatus main body 200B in the image forming apparatus of FIG. FIG. 10A is a sectional view, and FIG.
FIG. 4 is a front view as viewed from the paper discharge side.

Here, the post-processing apparatus main body 200B shown in FIG.
Only the points different from the above will be described.

In the case of the post-processing apparatus main body 200 C, the curl state of the sheet material S stacked on the sheet discharge tray 34 is measured by one optical distance measuring sensor 39.

The distance measuring sensor 39 installed at the center in the sheet width direction is rotatable about a shaft 39a by a motor 40 connected via a swing link 41.

The distance measuring sensor 39 is, as shown in FIG.
The distance measuring light is emitted from two places separated by an angle α to measure the distance at two places in the longitudinal direction of the sheet material S. Further, as shown in FIG. 7B, the distance measuring sensor 39 is rotated at an angle θ1 in the clockwise direction and at an angle θ2 in the clockwise direction and at an angle θ2 in the counterclockwise direction. The distance is measured at three positions in the width direction of the sheet material S with the position.

That is, the distance measuring sensor 39 measures the distance (Ld) at two positions in the longitudinal direction of the sheet material at the center position in the sheet material width direction.
1, Le1), and distance measurement (Ld2, Le) at two locations in the longitudinal direction of the sheet material at one position separated by a predetermined distance from the center position.
2) Then, distance measurement (Ld3, Le3) is performed at two positions in the longitudinal direction of the sheet material at the other position separated by a predetermined distance from the center position.
The curl state of the sheet material S can be determined from the distance measurement information at each of these positions.

In each of the first, second, and third embodiments, the image forming apparatus main body and the post-processing apparatus main body are configured separately, but may be integrated.

It goes without saying that the measuring method using the distance measuring sensor 39 in FIG. 10 can be applied to the post-processing apparatus main body 200A in FIG.

[0077]

As described above, in the image forming apparatus of the present invention, the state of warpage of the sheet material discharged onto the sheet discharging and stacking means is detected, and the sheet material bending means is operated in accordance with the warped state. Since the sheet is controlled to bend the sheet on which the image has been formed, it is possible to reduce the warpage of the surface of the sheet stacked on the sheet discharging stacking means. As a result, the alignment of the sheet material on the discharge stacking means is improved.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view (FIG. 1A) and a block diagram of a control system (FIG. 1B) showing the overall configuration of an image forming apparatus according to a first embodiment of the present invention.

FIG. 2 is a front view of the image forming apparatus of FIG. 1 as viewed from a sheet discharging side.

FIG. 3 is a cross-sectional view illustrating a state in which an optical distance measurement sensor is measuring a curl state of a sheet material stacked on a paper discharge tray.

FIG. 4 is a cross-sectional view showing a state in which an optical distance measuring sensor is measuring a curl state of a sheet material stacked on a paper discharge tray.

FIGS. 5A and 5B are a cross-sectional view (FIG. 5A) and a front view (FIG. 5B) showing how the optical distance measuring sensor measures the curl state of the sheet material stacked on the sheet discharge tray.

FIG. 6 is a cross-sectional view illustrating a state where an optical distance measuring sensor is measuring a curl state of a sheet material stacked on a sheet discharge tray.

FIG. 7 is a cross-sectional view illustrating a state where an optical distance measuring sensor is measuring a curl state of a sheet material stacked on a paper discharge tray.

FIG. 8 is a sectional view (FIG. 8A) and a front view (FIG. 8B) showing how the optical distance measuring sensor measures the curl state of the sheet material stacked on the sheet discharge tray.

FIG. 9 is a cross-sectional view (FIG. 9A) and a block diagram of a control system (FIG. 9B) showing the overall configuration of an image forming apparatus according to a second embodiment of the present invention.

10 is a cross-sectional view (FIG. 10A) showing another configuration example (third embodiment) of the post-processing apparatus main body in the image forming apparatus of FIG. ) Figure).

FIG. 11 is a cross-sectional view illustrating the configuration of an entire conventional image forming apparatus.

FIG. 12 is a cross-sectional view illustrating a curled state (upward curl) of a sheet material stacked on a sheet discharge tray.

FIG. 13 is a cross-sectional view illustrating a curled state (upward curl) of a sheet material stacked on a discharge tray.

FIG. 14 is a cross-sectional view ((a) view) and a front view ((b) view) showing a curled state (upward curl) of a sheet material stacked on a sheet discharge tray.

FIG. 15 is a cross-sectional view illustrating a curled state (curled downward) of a sheet material stacked on a sheet discharge tray.

FIG. 16 is a cross-sectional view illustrating a curled state (downward curl) of a sheet material stacked on a discharge tray.

FIG. 17 is a cross-sectional view ((a) view) and a front view ((b) view) showing a curled state (downward curl) of a sheet material stacked on a discharge tray.

FIG. 18 is a cross-sectional view illustrating a configuration of a main part of another conventional image forming apparatus.

[Explanation of symbols]

15 Fixing Device (Heat Fixing Means, Sheet Material Bending Means) 15a Fixing Roller 15b Pressure Roller 25 Curling Correction Device (Sheet Material Bending Means) 26 Face-Up Path 27 Face-Down Path 34 Discharge Tray (Discharge Stacking Means) 35a, 35b, 35c, 39 Optical distance measuring sensor (warpage detecting means) 50 CPU (control means) S Sheet material

Continued on the front page (72) Inventor Masato Nonaka 5540-11 Sakate-cho, Mizukaido, Ibaraki Prefecture Within Canon Aptex Co., Ltd. (72) Inventor Makoto Izumi 3-30-2 Shimomaruko, Ota-ku, Tokyo Within Canon Inc. 72) Inventor Takashi Kuwata 3-30-2 Shimomaruko, Ota-ku, Tokyo Inside Canon Inc. (72) Inventor Osamu Sekiya 3-30-2 Shimomaruko 3-chome, Ota-ku, Tokyo Canon Inc. (72) Invention Person Minoru Kawanishi 3-30-2 Shimomaruko, Ota-ku, Tokyo Inside Canon Inc. (72) Inventor Yuzo Isoda 3-30-2 Shimomaruko, Ota-ku, Tokyo Inside Canon Inc. (72) Inventor Yasuhiro Uchida Tokyo 3-30-2 Shimomaruko, Ota-ku, Tokyo F-term (reference) in Canon Inc. 2H033 AA15 BB33 BB34 CA01 CA39 3F048 AA02 AA04 AA05 AB01 BA30 BB02 CA00 EA00 EB40 3F053 HA03 HA06 HB01 HB22 LA02 LA05 AC04 AC03 BA04 BB01 BG01 CA08 CA31

Claims (13)

[Claims] An image forming apparatus forms an image on a sheet material fed one by one, and discharges the sheet material on which the image has been formed onto discharge stacking means. Sheet material bending means for bending the sheet material; warp detecting means for detecting a warped state of the surface of the sheet material discharged onto the discharge stacking means; An image forming apparatus comprising: a control unit configured to control the sheet material bending unit. 2. The image forming apparatus according to claim 1, wherein the sheet material bending means can perform upward bending and downward bending. 3. The image forming apparatus according to claim 2, wherein the upward bending and the downward bending can be selected by switching a path. 4. The image forming apparatus according to claim 2, wherein the control unit selects one of the upward bending and the downward bending according to a warping direction of the sheet material. 5. The image forming apparatus according to claim 1, wherein the sheet material bending means can change a bending amount. 6. The image forming apparatus according to claim 5, wherein the control unit changes the bending amount according to a warpage amount of the sheet material. 7. The image forming apparatus according to claim 1, wherein the warp detecting unit detects a warp state of the sheet material at a plurality of positions in a width direction and a plurality of positions in a longitudinal direction of the sheet material. 8. The image forming apparatus according to claim 7, wherein one or a plurality of optical distance measuring sensors for measuring a distance to a sheet material surface are used as the warpage detecting means. 9. The image forming apparatus according to claim 1, further comprising a heat fixing unit configured to perform a fixing process on the sheet material on which an image has been formed, upstream of the sheet material bending unit. Image forming device. 10. A heat fixing device for performing a fixing process on a sheet material on which an image has been formed, wherein the heat fixing device also serves as the sheet material bending device. 2. The image forming apparatus according to 1. 11. The heat fixing means includes a fixing roller for heating and a pressing roller for pressing to press the fixing roller, and a fixing nip pressure between the fixing roller and the pressing roller is changed. 2. The method according to claim 1, wherein the function is enabled.
0. The image forming apparatus according to item 0. 12. The image forming apparatus according to claim 11, wherein the control unit changes the fixing nip pressure according to a warpage amount of the sheet material. 13. A face-up sheet material and a face-down sheet material are discharged onto one sheet stacking means. Image forming device.