JPH0934321A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To effectively cool a sheet material where an image is formed and recorded and stabilize the discharge conveyance and loading of the sheet material onto a tray by providing a means which blows air to both the surfaces of the sheet material where the image is formed and recorded. SOLUTION: On the conveyance-directional downstream side of a fixing unit 20, a heat discharge fan 30 as a 1st air blowing means which blows air to one surface of the sheet material S to cool it and an air suction fan 31 as a 2nd air blowing means which blows air to the other surface of the sheet material S to cool it are arranged opposite each other across a sheet material conveyance path. The air is blown to both the surfaces of the sheet material S, which is then cooled, so that the sheet material S is effectively cooled. Further, the heat discharge fan 30 is at higher temperature than the air suction fan 31. Namely, the air blown to the image surface of the sheet material S after fixation is higher in temperature than the air blown to the opposite side (reverse surface), so the shrinkage of the sheet material S caused by abrupt cooling of the image surface side can be minimized.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus such as a copying machine or a printer for recording and forming an image on a sheet material, and more particularly to a blower such as a fan for blowing air on the sheet material on which the image is recorded to cool it. And an image forming apparatus having means.

[0002]

2. Description of the Related Art Conventionally, electrophotographic recording systems have been widely used in image forming apparatuses such as copying machines and printers. This is because the latent image formed on the photoconductor drum is developed into a visible image, the visible image (toner image) is transferred to a sheet material by electrostatic force, and then the transferred image is fixed by heat. An image is recorded and formed on the sheet material. Further, a double-sided image forming apparatus capable of recording and forming an image on the other surface (rear surface) of a sheet material having an image recorded and formed on one surface by the same operation as described above, and further yellow, magenta, cyan, black, etc. A color image forming apparatus capable of recording and forming a full-color image by mixing the toners has also been proposed and implemented.

FIG. 4 shows a conventional example of an image forming apparatus using the electrophotographic system as described above. In this image forming apparatus, the toner image formed on the photosensitive drum 51 is transferred to the transfer device 52.
After being transferred to the sheet material by, the fixing device 53 applies heat and pressure to the sheet material to fix the toner image on the sheet material. After this fixing, the image (toner image) of the sheet material is taken in by the intake fan 54 that takes in outside air into the apparatus.
The outside air is blown directly onto the surface to cool the sheet material, and the discharge rollers 55 sequentially discharge the sheet material onto a tray 56 outside the apparatus.

[0004]

However, in the above-mentioned conventional image forming apparatus, since the sheet material immediately after the black and white image or the full color image having a large amount of toner is heat-fixed is high in temperature, the cooling effect by the intake fan is high. Is insufficient,
There is a risk that the image surface and the non-image surface of the sheet material may become dirty on the tray, or the sheet materials may stick to each other.

Further, since the outside air is directly applied to the image surface side of the sheet material, the toner on the surface is rapidly cooled and shrunk, and the sheet material discharged onto the tray is wound around the image surface side (hereinafter referred to as "curl"). There is a risk of increasing.

Further, since air is blown from above against the discharged sheet material, particularly in the case of a sheet material having a weak stiffness, the sheet material bends on the tray and stops in the middle, which causes conveyance failure. There was a risk of it.

Further, the air for cooling the sheet material flows to the fixing device through a guide member for guiding the sheet material,
There is a possibility that the temperature control or temperature distribution of the fixing device may be disturbed to cause image unevenness or defective fixing.

The present invention has been made to solve the above problems. An object of the present invention is to effectively cool a sheet material on which an image is recorded and to discharge and convey the sheet material. This is to stabilize the stackability of sheet materials on the tray.

[0009]

A typical structure of the present invention for achieving the above object is to provide an image forming apparatus for recording and forming an image on a sheet material, with a sheet material on which an image is formed being sandwiched therebetween. At a position facing each other, a first air blowing unit that applies air to one surface of the sheet material to cool it, and a second air blowing unit that applies air to the other surface of the sheet material to cool it are disposed. Characteristically, specifically, the first air blowing unit and the second air blowing unit are arranged on the downstream side of the fixing unit that heats and fixes the image transferred to the sheet material in the image forming unit on the sheet material. The first blowing means blows air on the image recording surface of the sheet material, and the second blowing means blows air on the surface opposite to the first blowing means to cool the sheet material. . According to this structure, since the air is blown to both sides of the sheet material on which the image is recorded and formed, the sheet material is effectively cooled, and the discharging and conveying of the sheet material and the stackability on the tray are stabilized. .

The air blown on the sheet material is characterized in that the temperature of the first blowing means is higher than that of the second blowing means. With this configuration, the wind applied to the image surface of the sheet material has a higher temperature than the wind applied to the opposite surface (back surface), so that the image surface of the sheet material cools and shrinks rapidly. Can be minimized, and thus the curl amount of the sheet material toward the image surface side can be reduced.

Further, in the region on the downstream side of the discharging means for discharging and conveying the sheet material onto the tray outside the apparatus, the force given to the sheet material by the first blowing means is larger than that of the second blowing means. Is characterized by. According to this configuration, the strength and flow of the wind with respect to the discharged and conveyed sheet material is such that the wind from the first blowing means flows toward the outside of the machine while pressing the sheet material from above (on the image surface side). The wind from the second blowing means faces the wind from above and flows toward the outside of the machine entrained below the sheet material (on the back surface side). The discharge and conveyance of the sheet material is stable, and the sheets are stacked on the tray with good consistency.

Further, in the sheet material conveying path between the fixing means for heating and fixing the image transferred by the image forming section on the sheet material and the sheet material cooling area by the first air blowing means and the second air blowing means, It is characterized in that a through roller pair having a nip extending longer than the maximum width of the usable sheet material is arranged. According to this structure, it is possible to prevent the wind that hits both sides of the sheet material and flows along the surfaces from reaching the fixing means by the through roller pair, so that stable image fixing can be performed.

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION An embodiment of an image forming apparatus to which the present invention is applied will be specifically described below with reference to the drawings. In this embodiment, a full-color copying machine is exemplified as the image forming apparatus. FIG. 1 is a schematic sectional view of the vicinity of a sheet material discharging portion in a full-color copying machine according to the present invention. FIG. 2 is a state diagram showing a discharged state of the sheet material blown by the blowing means according to the present invention. FIG. 3 is a sectional view of a full-color copying machine to which the present invention is applied.

As an order of description, the entire structure of the full-color copying machine will be described first with reference to FIG. 3, and then the structure of the blowing means for cooling the sheet material after fixing in the sheet material discharge portion will be described. 1 and FIG. 2 will be described.

In FIG. 3, reference numeral 1 is a copying machine main body, and an automatic document feeder 2 is supported on the upper part of the copying machine main body so as to be openable and closable. The automatic document feeder 2 automatically feeds the originals placed on the original table 2a one by one onto the platen glass 3 of the copying machine main body 1 or sets the originals set at a predetermined position on the platen glass 3. It is brought into close contact with the platen glass 3. Then, the image of the original set on the platen glass 3 as described above is read by the reader unit 4 including the CCD or the like provided in the copying machine main body 1. In the reader unit 4, 4a is a light source for irradiating a document with light, and 4b is a photoelectric conversion element such as a CCD that receives reflected light from the document and converts it into an electric signal, and 4c and 4d.
Is a mirror and a lens for guiding the reflected light from the original to the photoelectric conversion element 4b.

Further, the copying machine main body 1 is provided with an image forming section 5 in which image forming stations 5M, 5Y, 5C and 5B corresponding to respective colors of magenta, yellow, cyan and black are arranged in a line. . Each image forming station is configured by combining photoconductor drums 6a to 6d for each color, and chargers 7a to 7d, developing units 8a to 8d, cleaning units 9a to 9d, etc. as process means acting on the drums. ing. On the lower side of the image forming unit 5,
A belt transport unit 10 including transfer devices 10a to 10d for transferring an image (toner image) formed on each drum onto a sheet material S.
Are arranged. Further, on the upper side of the image forming section 5, there is arranged a laser unit 11 as an image writing device for separating the image information read by the reader section 4 into respective color components and exposing the respective drums.

A sheet material P is provided on the lower portion of the copying machine main body 1.
The cassettes 12 and 13 for accommodating and storing are stored in a pullable manner. Further, a manual feeding unit 14 is arranged on the left side of the copying machine main body 1, and a large-capacity feeding deck 15 is detachably attached to the lower part thereof. For feeding the sheet material S, the sheet size is set in advance or the document is pre-scanned and automatically selected, and
12, 13, the manual feeding unit 14, or the feeding deck 15 is appropriately fed by a pickup roller 16 and separated by a retard roller pair 17 into a plurality of conveying roller pairs.
The skew feeding is corrected by being abutted against the registration roller pair 19 which is stopped via a sheet feeding path composed of 18 and the like. Then, the sheet material S is sent to the image forming section 5 by the registration roller pair 19 at a timing.

While the sheet material S sent to the image forming section 5 is conveyed by the belt conveying section 10, the images formed on the photosensitive drums of the respective image forming stations are successively superposed and transferred by a known image forming process. A multicolor image is formed. The sheet material P on which the multicolor image is formed is sent to the fixing device 20 by the belt conveying unit 10, and heat and pressure are applied to fix the transferred image.

When the sheet material S after the image fixing is switched in its conveying path by the flapper 21 and the image is formed on only one side, the sheet material S is discharged onto the discharge tray 23 outside the apparatus by the discharge roller pair 22 to perform double-sided image formation. Is guided to the reversing conveyance path 25 by the re-feeding roller pair 24, is reversed and conveyed by the reversing conveyance roller pair 26, and is accommodated in the intermediate tray 27 as the accommodating portion with the image surface facing upward.

Sheet materials S stacked on the intermediate tray 27
Are picked up by a pickup roller 28, separated and fed one by one by a retard roller pair 29, and fed to the image forming section 5 by the registration roller pair 19 at a predetermined timing. Then, the sheet material S is subjected to heat and pressure by the fixing device 20 after the images formed on the photoconductor drums of the respective image forming stations are successively transferred in the known image forming process in the same manner as the above-mentioned operation. Is applied to fix the image, and the image is discharged onto a discharge tray 23 outside the apparatus.

Here, the blowing means for cooling the sheet material P after the heat fixing by the fixing device 20 will be described with reference to FIGS. 1 and 2.

As shown in FIG. 1, on the downstream side of the fixing device 20 in the conveying direction, air is blown onto one surface of the sheet material S at a position substantially opposite to the sheet material conveying path to cool the sheet material S. An exhaust heat fan 30 as a first air blowing means and an intake fan 31 as a second air blowing means for applying air to the other surface of the sheet S to cool it are arranged.

Further, the fixing device 20 and the exhaust heat fan 30
A through roller pair 32 having a nip extending longer than the maximum width of the usable sheet material is disposed in the sheet material conveying path between the sheet material cooling region of the intake fan 31 and the sheet material cooling area. The through roller pair 32 in the present embodiment is a soft roller in which silicon rubber is arranged on the surface layer of a metal roller,
It has a nip of about 310 mm, which is longer in the thrust direction than the widest sheet material of about 305 mm used in this copier.

By the pair of through rollers 32, the heat exhaust fan 30
Also, the wind from the intake fan 31 can be prevented from reaching the fixing device 20, and since the temperature control or temperature distribution of the fixing device 20 is not unstable by the wind, stable image fixing can be achieved. Can be done.

The heat exhaust fan 30 is a stay of the copying machine body.
It is fixed to 33 through a vibration isolator 34, and the heat exhaust fan 30
The upper half area of the exhaust of the louver hole 35 of the exterior cover 35
It is blown out from the machine a, and the lower half area is the wind direction control plate.
36, the exterior cover 35 and the stay 32 are blown into the space between the pair of through rollers 32 and the exterior cover 35 from above as a duct. This wind is applied to the upper surface side (image surface side) of the sheet material S after heat fixing, and the sheet material S is cooled.

The intake fan 31 is a stay of the copying machine body.
It is fixed to 37, sucks the air outside the machine through the louver hole 35b of the exterior cover 35 and the dustproof filter 38, and between the exterior cover 35, the wind direction regulating plate 39, and the guide plate forming the reversing conveyance path 25,
The stay 37 serves as a duct and is blown into the space between the pair of through rollers 32 and the exterior cover 35 from below. This wind is applied to the lower surface side (back surface side) of the sheet material S after heat fixing, and the sheet material S is cooled.

The exhaust heat fan 30 and the intake fan 31 blow air on both sides of the sheet material S immediately after fixing, so that the sheet material S is effectively cooled. Therefore, it is possible to prevent the image surface and the non-image surface of the sheet material on the tray 23 from becoming dirty.

Further, the exhaust heat fan 30 and the intake fan 31
The wind applied to the sheet material S by the exhaust heat fan
The temperature of 30 is higher than that of the intake fan 31. That is, the temperature of the air sent from the exhaust heat fan 30 to the image surface side of the sheet material S is higher than the outside temperature (outside temperature because the heat in the apparatus generated by the rotation of the motor, the fixing heater, etc. is exhausted. The temperature is higher than that of the toner by about 8 to 20 ° C.), and is maintained in a temperature range lower than the glass transition point of the toner.

As a result, the temperature of the wind applied to the image surface of the sheet material S after fixing becomes higher than that of the air applied to the opposite surface (back surface) thereof, so that the image surface side of the sheet material S is Minimizes rapid cooling and shrinkage. Therefore, the curl amount of the sheet material S toward the image surface side becomes small.

Further, in the region on the downstream side of the discharge roller pair 22, the force of the wind applied to the sheet material S by the exhaust heat fan 30 is set to be larger than that of the intake fan 31. That is, when only the exhaust heat fan 30 is operated, the wind velocity component flowing from the top to the bottom of the wind is about 1.5.
In the range of up to 1.8 m / s, the discharge roller pair 22 is substantially uniform in the thrust direction. Further, the wind velocity component flowing from the bottom to the top when only the intake fan 31 is operated is about
Similarly, in the range of 0.6 to 0.8 m / s, the discharge roller pair 22 is substantially uniform in the thrust direction. The area of the sheet material S that receives the wind from above and below is substantially the same on the upper and lower surfaces.

As shown in FIG. 2, when the sheet material S after fixing is discharged to the outside of the machine by the discharge roller pair 22, the flow of wind when both the upper and lower fans 30 and 31 are operated is Flows out of the plane. That is, as shown by an arrow in FIG. 2A, the wind from above by the exhaust heat fan 30 flows toward the outside of the machine while pressing the sheet material S from above, and the wind from below by the intake fan 31 blows into the seat. The material is also caught under the material S and flows to the outside of the machine in a manner facing the wind from above. Further, as shown in FIG. 2B, when the trailing edge of the sheet material S separates from the nip of the discharge roller pair 22, the sheet material S
Is pressed onto the discharge tray 23 by the wind from above. By the flow and balance of the upper and lower winds, the discharge conveyance of the sheet material S is stabilized, and the sheet material S is stacked at a predetermined position on the discharge tray 23 with good consistency.

In the above-described embodiment, the exhaust heat fan for exhausting the heat in the apparatus is used as the first air blowing means, and the intake fan for taking the outside air into the apparatus is used as the second air blowing means. However, the present invention is not limited to this, and, for example, an air blowing unit that applies air to the sheet material to cool it may be provided separately from the exhaust heat fan and the intake fan. Further, the air blowing unit is not limited to the fan, and may be any unit that sends air to the sheet material to cool it.

Further, in the above-described embodiment, a full-color copying machine is illustrated as an image forming apparatus to which the present invention is applied, but the invention is not limited to this, and for example, a printer,
The same effect can be obtained by applying the present invention to another image forming apparatus such as a facsimile machine. Further, the recording system is not limited to the electrophotographic system, and other recording systems such as an inkjet system and a thermal transfer system may be used as long as they can promote fixation of ink or toner on the sheet material by blowing air. Good.

[0034]

As described above, according to the present invention,
Since air is blown to both sides of the sheet material by the first air blowing means and the second air blowing means, which are arranged at positions substantially opposite to each other with the sheet material on which the image is recorded formed therebetween, the sheet material is cooled. Cooling is effectively performed. Therefore, the discharged sheet materials can be stably conveyed without the sheet materials discharged onto the tray sticking to each other and the image surface and the non-image surface of the sheet material being contaminated. Further, it is possible to prevent the sheet material from getting stuck in the tray on the way and causing a jam, and the sheet material is stacked on the tray with good consistency.

Further, since the wind blown to the image surface of the sheet material by the first blowing means has a higher temperature than the wind blown to the opposite surface (back surface) by the second blowing means, the sheet material It is possible to minimize the rapid cooling and shrinkage of the image surface of. Therefore, the curl amount of the sheet material toward the image surface side is reduced, the sheet material can be stably discharged and conveyed, and the sheet material can be stacked on the tray with good consistency.

Further, since the exhaust heat means for exhausting the heat inside the apparatus is used as the first air blowing means and the intake means for taking the outside air into the apparatus is used as the second air blowing means, the temperature difference of the above-mentioned air is used. Can be easily set, and an increase in cost due to an increase in the number of parts can be prevented.

Further, regarding the strength and flow of the wind to the discharged and conveyed sheet material, the wind from the first blowing means flows toward the outside of the machine while pressing the sheet material from above (image side), The wind from the second blower winds downward from the sheet material (on the rear surface side) in a form of facing the wind from above and flows toward the outside of the machine. Due to the vertical air flow and balance with respect to the sheet material, the discharge and conveyance of the sheet material is stable and the sheet material is stacked on the tray with good consistency.

Further, in the sheet material conveying path between the fixing means and the sheet material cooling area by the first air blowing means and the second air blowing means on the downstream side of the fixing means, it is longer than the maximum width of the usable sheet material. Since the through roller pair having the extended nip is arranged, it is possible to prevent the wind flowing along both surfaces of the sheet material from reaching the fixing means.
A stable image can be fixed.

[Brief description of drawings]

FIG. 1 is a schematic cross-sectional view of the vicinity of a sheet material discharging portion in a full-color copying machine according to the present invention.

FIG. 2 is a state diagram showing a discharge state of a sheet material which is blown with air from a blowing unit according to the present invention.

FIG. 3 is a sectional view of a full-color copying machine to which the present invention is applied.

FIG. 4 is a schematic view of a conventional black-and-white copying machine.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Copier main body 2 ... Automatic document feeder 2a ... Original placing table 3 ... Platen glass 4 ... Reader section 4a ... Light source 4b ... Photoelectric conversion element 4c ... Mirror 4d ... Lens
5 ... Image forming section 5M, 5Y, 5C, 5B ... Image forming station 6a-6d ... Photosensitive drum 7a-7d ...
Charging device 8a to 8d ... Developing device 9a to 9d ... Cleaning device 10a to 10d ... Transfer device 10 ... Belt transport unit 11 ... Laser unit 12, 13 ... Cassette 14 ... Manual feed unit
15 ... Feeding deck 16 ... Pickup roller 17 ... Retard roller pair 18 ... Conveying roller pair 19 ... Registration roller pair 20 ... Fixer 21 ... Flapper 22 ... Ejection roller pair 23 ... Ejection tray 24 ... Refeeding roller pair 25 ... Reverse Transport path 26 ...
Reverse transport roller pair 27 ... Intermediate tray 28 ... Pickup roller 29 ... Retard roller pair 30 ... Exhaust heat fan 31 ...
Intake fan 32 ... Through roller pair 33, 37 ... Stay 34 ...
Anti-vibration material 35 ... Exterior cover 35a, 35b ... Louver hole 3
6, 39 ... Wind direction control plate 38 ... Dust filter

Claims (7)

[Claims] 1. An image forming apparatus for recording and forming an image on a sheet material, wherein air is blown to one surface of the sheet material to cool the sheet material on which the image is formed at a position substantially opposite to each other. An image forming apparatus comprising: one air blowing unit; and a second air blowing unit that applies air to the other surface of the sheet material to cool the sheet material. 2. The first blowing unit and the second blowing unit are arranged downstream of a fixing unit that heats and fixes the image transferred to the sheet material in the image forming unit on the sheet material, The first blowing means blows air on the image recording surface of the sheet material, and the second blowing means blows air on the surface opposite to the first blowing means to cool the sheet material. 1
An image forming apparatus according to claim 1. 3. The image forming apparatus according to claim 1, wherein the wind blown on the sheet material has a higher temperature in the first blowing unit than in the second blowing unit. 4. The first air blowing means is an exhaust heat means for exhausting heat inside the apparatus, and the second air blowing means is an intake means for taking in outside air into the apparatus. Item 2. The image forming apparatus according to item 2. 5. The force of the wind applied to the sheet material by the first blower means is higher than that of the second blower means in the region on the downstream side of the discharge means for discharging and conveying the sheet material onto the tray outside the apparatus. The image forming apparatus according to claim 1, wherein the image forming apparatus is large. 6. A sheet material conveying path between a fixing means for heating and fixing the image transferred by the image forming section onto the sheet material, and a sheet material cooling area by the first air blowing means and the second air blowing means, The image forming apparatus according to claim 1, further comprising a pair of through rollers having a nip extending longer than a maximum width of a usable sheet material. 7. The image forming apparatus according to claim 1, wherein the image forming apparatus is a copying machine, a printer, or a facsimile machine.