JP2007119109A - Image forming device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To maintain the flat paper state by performing correction of curl generated on a recording material and preventing regeneration of the curl. <P>SOLUTION: When a user sets a document image on an image reading part 3 and instructs reading, an image formation part 5 transfers a toner image on the paper 10 conveyed from a paper feeding part 4. Nextly, a fixing device 14 applies heat to the paper 10 and fixes a toner. At this time, a moisture content possessed by the paper 10 is evaporated and a pulp fiber forming the paper is condensed to sometimes generate the curl. Water vapor injected by a moistening part 20 from a gap of the paper conveying belt 22 is fed to the paper 10 and the pulp fiber forming the paper is stretched to turn to the flexible state in which correction of the curl is easily performed. The paper 10 in the flexible state is curved in a direction opposite to a curl direction by a first decurler 30 or a second decurler and is corrected to the flat state and after it is brought into contact with a surface of a cooling part 40 to be cooled, it is delivered from a delivery tray 7 while maintaining the flat state. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an image forming apparatus that forms an image by fixing toner on a sheet.

  In a general image forming apparatus using toner, the toner is fixed by applying heat and pressure to the paper on which the toner is adhered. This paper is formed of pulp fibers, and the pulp fibers have the property that when the moisture evaporates by heating, the fibers condense, and conversely, when the moisture is added, the fibers elongate. For this reason, when heat is applied to the paper for fixing, the moisture evaporates and the pulp fibers condense, and the paper may curl.

Here, there is a difference in the type and structure of the pulp fibers constituting the paper and the amount of water held between the front surface and the back surface of the paper. For this reason, the expansion ratio of the pulp fiber differs between the front surface and the back surface of the paper. Further, the expansion / contraction rate varies depending on the bonding material and the coating material due to toner adhesion. For this reason, the curl of the paper is pulled to the surface having a large expansion / contraction rate due to the difference in expansion / contraction rate between the front surface and the back surface, and the curl is generated in either the mountain shape or the valley shape. For example, if toner adheres to the surface of the paper, it is pulled by the condensation of the toner, and the paper curls in a mountain shape. Similarly, even when the toner adheres to the surface of the paper, the paper curls in a valley shape if the contraction force of the pulp fibers on the back surface is stronger than the contraction force of the toner. Due to the curling of the paper, problems such as paper jams inside the image forming apparatus and irregular papers occur. In order to solve this problem, a technique for flattening the paper by pressing the paper curled using a roll, a belt or the like in the direction opposite to the curl has been developed. (For example, Patent Document 1, Patent Document 2, Patent Document 3, Patent Document 4)
JP 2000-229758 A JP-A-5-162916 Japanese Patent Laid-Open No. 5-221574 Japanese Patent No. 3440111

  However, in the technique disclosed in the above-mentioned patent document, the curl correction is performed in a state where the pulp fiber is condensed, so that there is a problem that the curl once corrected is pulled by the condensed pulp fiber and the curl is generated again. . SUMMARY An advantage of some aspects of the invention is that it provides an image forming apparatus including a curl correcting unit that does not cause curling again after curl correction.

In order to solve the above-mentioned problems, the present invention forms an image of a toner according to image data, transfers an image formed on the recording material, and heats the toner transferred by the image forming unit. Fixing means for fixing to the recording material; a curling correction means for correcting curling of the recording material; provided on the downstream side of the fixing means; provided downstream of the curling correction means; There is provided an image forming apparatus comprising a cooling unit for cooling and a humidifying unit for supplying moisture to the recording material on which toner is fixed by the fixing unit.
As a result, even if the recording material curls in the fixing unit used in image formation, the curl correction that prevents the curl from recurring can be performed using the curl correcting unit, the cooling unit, and the humidifying unit.

  In a preferred aspect of the present invention, the humidifying means is provided on the upstream side of the curl correcting means. As a result, curl correction can be performed on a sheet of paper that is flexible due to elongation of the pulp fibers by humidification of the humidifying means, so that more effective curl correction can be performed.

  In a further preferred aspect, the curl correcting means includes a first rotating roll formed of an elastic material and a second rotating roll formed of a hard material, and the second rotating roll is the first rotating roll. The first rotating roll and the shaft are parallel to each other, the outer peripheral surface of the first rotating roll is pressurized to a curved state, and the recording material conveyed by being humidified by the humidifying means is rotated in the first and second rotations. Transports between rolls. Thus, curl correction can be performed regardless of whether the paper curl is a mountain-shaped curl or a valley-shaped curl.

  In a further preferred aspect, the cooling means includes a roll that rotates in contact with the recording material being conveyed, and a cooling medium flow path into which the cooling medium is introduced into the roll. As a result, the cooled roll directly contacts the recording material, and cooling can be performed efficiently.

  According to the present invention, the paper whose curl has been corrected by the curl correcting means can maintain a flat paper state without recurring curl. As a result, it is possible to reduce the occurrence of problems such as paper jams inside the image forming apparatus and paper misalignment due to paper curl.

DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, embodiments of the invention will be described with reference to the drawings.
<Configuration of Embodiment>
FIG. 1 is a diagram illustrating a schematic configuration of the image forming apparatus 1. As shown in FIG. 1, an image forming apparatus 1 is roughly divided into a housing 2. An image reading unit 3 that optically reads a document image, a paper feeding unit 4 that supplies paper 10, and an image that forms an image. It has a forming unit 5, a curl correction unit 6, and a discharge tray 7 for discharging printed matter.

  The image forming unit 5 optically scans the photosensitive drum 11 with the original image read by the image reading unit 3, and the developing device 12 sequentially applies C (cyan), M (magenta), and Y (yellow) to the optically scanned image. , K (black) toner is attached to the photosensitive drum 11 and then attached to the paper 10 via the intermediate transfer member 13. The toner image generated as described above is fixed by the fixing device 14. The fixing device 14 is provided on the downstream side of the intermediate transfer member 13 and includes a heating roll 14a and a pressure roll 14b. The surface of the heating roll 14a is formed of a material (metal or the like) having high electrothermal conductivity, and heat generated from a high-temperature heater provided inside the heating roll 14a is transmitted to the surface, and the surface of the heating roll 14a receives toner. It is kept at a temperature that can be dissolved. The pressure roll 14b is provided in parallel with the heating roll 14a, and pressurizes the outer peripheral surface of the heating roll 14a with the paper 10 conveyed between the heating roll 14a and the pressure roll 14b interposed therebetween. The toner adhering to the toner 10 is fixed on the paper 10.

The sheet 10 on which the toner image is fixed by the fixing device 14 is unloaded from the fixing device 14 and conveyed by the sheet conveying belt 22. The sheet conveying belt 22 is an annular belt as illustrated, and conveys the sheet 10 in the right direction of the drawing by running in the clockwise direction of the drawing. The paper 10 transported by the transport belt 22 passes through the first decurler 30 and the second decurler 31 that correct curl, passes through the cooling unit 40, and is discharged to the discharge tray 7.
A humidifying unit 20 is provided on the downstream side of the fixing device 14 and below the sheet conveying belt 22. Here, FIG. 2 is a plan view of the paper conveying belt 22 and the humidifying unit 20.

As shown in FIG. 2, the sheet conveying belt 22 described above is stretched around two drive rollers, and a plurality of the sheet conveying belts 22 are provided at predetermined intervals in the width direction of the sheet conveying path.
A large number of injection holes 21 through which water vapor is ejected are provided on the upper surface of the humidifying unit 20. A water tank (not shown) in which water is stored is provided inside the housing of the humidifying unit 20. In this water tank, a vibrator (not shown) is arranged, and this vibrator vibrates at a high frequency (ultrasonic wave) enough to vaporize water. Therefore, when the vibrator vibrates, the water stored in the water tank is vaporized and ejected upward through the gap between the paper transport belts 22 and 22.

Next, the first decurler 30 and the second decurler 31 will be described in detail. Here, FIG. 3 is a side view showing a process from the sheet conveying belt 22 to the cooling unit 40.
The first decurler 30 corrects the curl of the paper 10 by sandwiching the paper 10 discharged from the paper transport belt 22, and is configured by a combination of two rolls. That is, the first hard roll 30a having a small diameter and hard and the first elastic roll 30b having a large diameter and elasticity are configured. The axis of the first hard roll 30a is provided in parallel with the axis of the first elastic roll 30b, and the outer peripheral surfaces of the first hard roll 30a and the first elastic roll 30b are in contact with each other. . The first hard roll 30a moves up and down according to the control of a control unit (not shown), and when it moves down, presses the circumferential surface of the first elastic roll 30b to be curved as shown.

  The second decurler 31 is provided on the downstream side of the first decurler 30 and is composed of a hard second hard roll 31a having a small diameter and a second elastic roll 31b having a large diameter and elasticity like the first decurler 30. However, the positions of the second hard roll 31 a and the second elastic roll 31 b are provided in the upside down direction with respect to the first decurler 30. The 2nd hard roll 31a drives up and down like the 1st hard roll 30a, and presses it so that the circumference surface of the 2nd elastic roll 31b may be curved.

  A sensor 45 that can detect the curl direction by optically detecting the posture of the paper 10 is provided between the paper transport belt 22 and the first decurler 30. The sensor 45 may be any sensor as long as the posture of the paper 10 can be detected, and may be a mechanical sensor that contacts the paper 10 to detect the curl state (for example, Patent Document 2000- 229758, etc.). When the curl detected by the sensor 45 is a mountain-shaped curl (a shape in which the central portion in the sheet conveyance direction protrudes upward), the control unit described above moves the first hard roll 30a of the first decurler 30 downward. Drive (see FIGS. 3A to 3C). On the other hand, when the curl detected by the sensor 45 is a valley-shaped curl (a shape in which the front end portion and the rear end portion protrude upward in the sheet conveyance direction), the control unit (not shown) controls the second decurler 31. 2 The hard roll 31a is driven downward (see FIGS. 4A to 4C).

A cooling unit 40 is provided on the downstream side of the second decurler 31. The cooling unit 40 includes a first cooling roll 40a and a second cooling roll 40b. The axis of the first cooling roll 40a is provided in parallel to the axis of the second cooling roll 40b, and the outer circumferences of the first cooling roll 40a and the second cooling roll 40b are provided so as to be in contact with each other in the vertical direction. FIG. 5 is a cross-sectional view of the first and second cooling rolls 40a and 40b. As shown to Fig.5 (a), the flowing water channel 46 through which cooling water flows is provided in the inside of the 1st, 2nd cooling roll 40a, 40b. The flowing water channel 46 is in a state of being cooled by flowing water, whereby the heat generated by the first cooling roll 40 a and the second cooling roll 40 b is cooled by the flowing water channel 46.
In addition, as shown in FIG.5 (b), the 1st cooling roll 40a and the 2nd cooling roll 40b may be formed in hollow, and the fan 47 which sends in cooling air in it may be provided.

<Operation of Embodiment>
When the user sets an original image in the image reading unit 3 and instructs to read the image, the image reading unit 3 generates image data corresponding to the read image and supplies it to the image forming unit 5. As a result, the image forming unit 5 generates a toner image and transfers the toner image onto the paper 10 conveyed from the paper supply unit 4. The paper 10 to which the toner has been transferred is heated and pressurized by the fixing device 14, whereby the toner is fixed to the paper 10. At this time, the water content of the paper 10 is evaporated by heating.

Next, the sheet 10 that has been fixed is conveyed on the sheet conveying belt 22 and absorbs water vapor generated from the humidifying unit 20. As a result, moisture evaporated by heating during fixing is compensated. The posture of the sheet 10 conveyed on the sheet conveying belt 22 is detected by the sensor 45.
Here, when the occurrence of curling is not detected, the first hard roll 30a is not moved to the first elastic roll 30b side, and the second hard roll 31a is not moved to the second elastic roll 31b side. As a result, no deformation stress is applied to the paper 10 passing between these rolls, and the paper 10 passes as it is. That is, the first decurler 30 and the second decurler 31 do not perform curl correction processing.

On the other hand, when the sensor 45 detects a mountain-shaped curl with respect to the paper 10, the control unit drives the first hard roll 30 a of the first decurler 30 downward. As a result, the sheet 10 is pressed against the circumferential surface of the first elastic roll 30b by the first hard roll 30a of the first decurler 30 and is bent in the direction opposite to the curl direction to be corrected to be flat. After the curl-corrected paper 10 passes through the second decurler 31, it passes between the first cooling roll 40a and the second cooling roll 40b, and comes into contact with the surfaces of the first and second cooling rolls 40a and 40b. It is cooled and discharged from the discharge tray 7.
In this case, when the moisture is supplied by the humidifying unit 20, the pulp fibers of the paper 10 are stretched, and a flexible state in which the curl can be easily corrected is obtained. Moreover, since it cools with the 1st, 2nd cooling roll 40a, 40b, the flat state by which the curl was corrected is maintained.

Next, the curl correction operation when the sensor 45 described above detects that the curl direction of the paper 10 is valley-shaped will be described.
As shown in FIG. 4, when the sensor 45 detects that the curl direction of the paper 10 is valley-shaped and sends information to the control unit, the control unit drives the second hard roll 31 a of the second decurler 31 upward. The sheet 10 humidified by the humidifying unit 20 is pressed against the circumferential surface of the second elastic roll 31b by the second hard roll 31a of the second decurler 31, and is bent in the direction opposite to the curl direction to be corrected to be flat. The curled paper 10 passes between the first cooling roll 40a and the second cooling roll 40b and is cooled by contacting the surfaces of the first and second cooling rolls 40a and 40b, so that the paper 10 is in a flat state. It is discharged from the discharge tray 7 while being maintained. In this case as well, as described above, the paper 10 is in a flexible state in which curl correction can be easily performed and is cooled after the curl correction, so that the paper 10 remains flat and recurl is generated. Is prevented.

<Modification>
As mentioned above, although embodiment of this invention was described, this invention is not limited to embodiment mentioned above, It can implement with another various form.
(1) In the embodiment described above, the humidifying unit 20 is provided on the upstream side of the first decurler 30, but may be provided on the downstream side of the first decurler 30 or on both the upstream side and the downstream side. Further, as shown in FIG. 6, the humidifying unit 20 is installed at a position where the curl correction processing by the first and second decurlers 30 and 31 and the humidification processing by the humidifying unit 20 can be performed simultaneously, and the curl correction processing and the humidification processing are performed simultaneously. It doesn't matter.

(2) In the above-described embodiment, the humidifying unit 20 has been described using an ultrasonic humidifier in which the vibrator emits high-frequency ultrasonic waves to vaporize water in the housing. The water supply may be performed using a device that rotates and blows water droplets, a device that blows air containing moisture with a fan, a means for supplying moisture by bringing a sponge containing moisture into contact with the paper 10, and the like.

(3) In the above-described embodiment, the curl correction processing is performed on the curled paper 10 using the first and second decurlers 30 and 31. For example, the top and bottom of the paper 10 are sandwiched between flat plate members. The curl may be corrected by correcting the curl by pressing, or by correcting the curl by pressing with a belt.

(4) In the above-described embodiment, the sheet 10 is cooled using the first and second cooling rolls 40a and 40b. However, as shown in FIG. You may cool by applying. In this case, the curl correction process and the cooling process are performed at almost the same position.

1 is a diagram showing a schematic configuration of an image forming apparatus to which an embodiment of the present invention is applied. FIG. 3 is a plan view showing a paper transport belt 22 and a humidifying unit 20 according to the same embodiment. It is a figure which shows the curl correction of the paper 10 curled into the mountain shape which concerns on the same embodiment. It is a figure which shows the curl correction of the paper 10 curled into the valley shape according to the embodiment. It is sectional drawing which shows the 1st, 2nd cooling roll 40a, 40b which concerns on the same embodiment. It is a figure which shows the example which performed the humidification process and the curl correction process which applied the modification of this invention simultaneously. It is a figure which shows the example which performed the curl correction process and the cooling process which applied the modification of this invention substantially simultaneously.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Image forming apparatus, 2 ... Housing | casing, 3 ... Image reading part, 4 ... Paper feed part, 5 ... Image forming part, 6 ... Curl correction part, 7 ... Discharge tray, 10 ... Paper, 11 ... Photoconductor drum, DESCRIPTION OF SYMBOLS 12 ... Developing device, 13 ... Intermediate transfer body, 14 ... Fixing device, 14a ... Heating roll, 14b ... Pressure roll, 20 ... Humidification part, 21 ... Injection hole, 22 ... Paper conveyance belt, 30 ... First decurler, 30a ... 1st hard roll, 30b ... 1st elastic roll, 31 ... 2nd decurler, 31a ... 2nd hard roll, 31b ... 2nd elastic roll, 40 ... Cooling part, 40a ... 1st cooling roll, 40b ... 2nd cooling Roll, 41 ... Blower, 45 ... Sensor, 46 ... Flow channel, 47 ... Fan.

Claims (4)

An image forming unit that forms a toner image according to image data and transfers the formed image to a recording material;
Fixing means for heating and fixing the toner transferred by the image forming means to the recording material;
A curl correction unit that is provided downstream of the fixing unit and corrects curling of the recording material;
A cooling means provided on the downstream side of the curl correction means for cooling the recording material;
An image forming apparatus comprising: a humidifying unit that supplies moisture to the recording material on which toner is fixed by the fixing unit. The humidifying means is
The image forming apparatus according to claim 1, wherein the image forming apparatus is provided upstream of the curl correction unit. The curl correcting means includes
A first rotating roll formed of an elastic material;
A second rotating roll formed of a hard material,
The second rotating roll pressurizes the first rotating roll in a state in which the axis of the first rotating roll is parallel to the curved surface of the first rotating roll, is humidified by the humidifying means, and is conveyed. The image forming apparatus according to claim 2, wherein the image forming apparatus is conveyed between the first and second rotating rolls. The cooling means is
A roll that rotates in contact with the recording material being conveyed;
The image forming apparatus according to claim 1, further comprising a cooling medium flow path for allowing a cooling medium to flow into the roll.

Images