JPH11167232A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent transfer paper from mutually blocking, in the case of discharging the transfer paper image side facing down on a paper discharging tray. SOLUTION: In this image forming device, the transfer paper is allowed to pass through a fixing device 10 in a state that the image is formed on the transfer paper rear side, and discharged on the paper discharging tray 12 by a paper discharging roller 11. In the vicinity on the downstream side of the paper discharging roller 11 below the transfer paper, a sucking fan unit 21 or a cooling blade is set as cooling means, and in the process that the transfer paper is discharged, the toner is rapidly cooled by the cooling means. Therefore, the mutual blocking of the transfer paper each other on the paper discharging tray 12 can be prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a transfer paper having an unfixed image formed on a lower surface thereof, which is passed through a fixing device to fix the unfixed image, and discharges the transfer paper from a discharge section to a discharge tray. More particularly, the present invention relates to a technique for preventing fusing (blocking) between transfer papers.

[0002]

2. Description of the Related Art An image forming apparatus such as a copying machine or a printer using an electrophotographic system transfers a toner image directly from a photoconductor or an intermediate transfer to a transfer sheet fed from a sheet feeding section. Indirectly transferred via the belt. The transfer paper to which the unfixed toner image has been transferred is directly conveyed to a fixing device, where the unfixed toner image is heated and fused on the transfer paper. Then, the transfer paper carrying the fixed toner image is discharged from a paper discharge unit onto a paper discharge tray and stacked. Alternatively, the sheet may be sent from the sheet discharging unit to the transfer sheet post-processing device and subjected to various post-processing.

By the way, generally, the transfer paper coming out of the transfer section is transported to a fixing device with an unfixed toner image placed on its upper surface, and further discharged in that state, that is, the toner image is left as it is on the upper surface side of the transfer paper. However, recently, for example, an image of a type that includes an intermediate transfer unit (intermediate transfer belt) as described later, transfers a toner image to a lower surface of a transfer sheet, and the transfer sheet is directly sent to a fixing device. Forming devices are also known.

[0004]

The transfer paper on which the above-mentioned unfixed image is formed on the lower surface is passed through a fixing device to fix the unfixed image, and the transfer paper is discharged from a discharge section to a discharge tray. In the image forming apparatus of the type, after the transfer process is completed, the image forming apparatus enters the fixing device, and when the fixed high-temperature transfer paper is stacked on the paper discharge tray, especially when the OHP sheet or the thick paper (basis weight 90 kg / cm ²⁾ Transfer paper) may be blocked due to insufficient cooling of the image of the transfer paper.

[0005] That is, if the image surface is on the lower side, when the transfer papers overlap, the toner layer is sandwiched between the two transfer papers, so that the cooling time is very short (because there is almost no natural heat radiation time). This causes blocking.

SUMMARY OF THE INVENTION It is an object of the present invention to prevent transfer papers from blocking each other in an image forming apparatus of a type in which transfer papers are discharged to a paper discharge tray while an image surface faces downward.

[0007]

According to a first aspect of the present invention, a transfer sheet having an unfixed image formed on a lower surface thereof is passed through a fixing device to fix the unfixed image, and An image forming apparatus that discharges transfer paper from a paper discharge unit to a paper discharge tray is characterized in that a cooling unit that cools the lower surface of the transfer paper is provided near the paper discharge tray.

[0008] In order to achieve the above object, a second aspect is provided.
The invention described in claim 1 is characterized in that, in the invention described in claim 1, the cooling means is installed at a position adjacent to a downstream side of a discharge roller constituting a discharge section.

In order to achieve the above object, a third aspect of the present invention is provided.
The invention described in claim 1 is characterized in that, in the invention described in claim 1, the cooling means includes a suction fan that takes in outside air and blows the outside air onto the lower surface of the transfer paper.

[0010] In order to achieve the above object, the present invention relates to claim 4.
The invention described in claim 1 is characterized in that, in the invention described in claim 1, the cooling means is constituted by a metal cooling plate having a radiation fin provided with a surface coating having high releasability. .

According to another aspect of the present invention, the above object is achieved.
The invention described in the first aspect is characterized in that the operation and non-operation of the cooling unit can be switched depending on the type of transfer paper.

According to the first aspect of the invention, since the cooling means for cooling the lower surface of the transfer paper is provided near the paper discharge tray, the high-temperature toner image on the lower surface of the transfer paper is quickly cooled, and blocking between the transfer papers is eliminated. .

According to the second aspect of the present invention, since the cooling means is installed at a position downstream of and adjacent to the paper discharge roller constituting the paper discharge unit, the lower surface of the transfer paper immediately after exiting the paper discharge unit is immediately cooled. You.

According to the third aspect of the present invention, the cooling means is provided with a suction fan which takes in outside air and blows the outside air onto the lower surface of the transfer paper. Cooled.

According to the fourth aspect of the present invention, the cooling means is constituted by a metal cooling plate having radiating fins coated with a surface layer having high releasability. , The lower surface of the transfer paper is efficiently cooled by the radiation fins.

According to the fifth aspect of the present invention, the operation and non-operation of the cooling means can be switched depending on the type of the transfer paper, so that, for example, more fixing energy is required as compared with a normal transfer paper. It is possible to select such that cooling is performed for thick paper or OHP sheet, and not for other normal transfer paper.

[0017]

Embodiments of the present invention will be described below with reference to the accompanying drawings. FIG. 1 is a configuration diagram of an image forming apparatus on which the present invention is based. The image forming apparatus is a full-color laser printer. The laser printer includes a photosensitive belt 1 stretched between two pulleys, and an intermediate transfer unit 2 having an endless belt that comes into contact with the photosensitive belt 1. As the developing units, a black developing unit 3, Y (yellow), M (magenta), C
There is a (cyan) color developing unit 4. The color developing unit 4 is of a rotary type and contacts the photosensitive belt 1 in a switching manner.

At the bottom of the main body, there is a main body paper feeder 5, and at one side, there is a manual paper feeder 6. Both paper feeders 5, 6
A registration roller 7 is provided in the vicinity of the junction. A fixing device 10 having a fixing roller 8 and a pressure roller 9 is provided near the downstream side of the intermediate transfer unit 2. On the downstream side, there is a paper discharge roller 11 and further a paper discharge tray 12.

In the case of a monocolor image, the photosensitive belt 1
Is transferred to the intermediate transfer unit 2 once, and is transferred to transfer paper in the transfer section of the intermediate transfer unit 2. In the case of a full-color image, the image is transferred from the photoreceptor belt 1 four times to the intermediate transfer unit 2 for each color, and a superimposed full-color image is formed on the intermediate transfer unit 2.
Thereafter, the transfer paper is conveyed to a transfer section, where a full-color image is transferred. The transfer paper on which the image has been transferred is conveyed to the fixing device 10 with the unfixed image facing down, where the unfixed image is fixed. After that, the transfer paper is discharged onto the paper discharge tray 12 by the paper discharge roller 11.

FIG. 2 is an enlarged view of a main part of the image forming apparatus according to the first embodiment of the present invention, FIG. 3 is a diagram showing a state of transfer paper and toner discharged to a paper discharge tray, and FIG. FIG. 3 is a perspective view of the suction fan unit shown in FIG. 2. In FIG. 2, the transfer sheet P transfers the toner image to the lower surface of the transfer unit 13 of the intermediate transfer unit 2, and is conveyed to the fixing device 10 while being supported by the support 14. The intermediate transfer unit 2 after the transfer of the toner image is cleaned by the intermediate transfer belt cleaner 15.

A high-temperature toner (toner layer) T (see FIG. 3) after heating and melting is located at a position adjacent to the downstream side of the paper discharge roller 11 constituting the paper discharge part and below the transfer paper P. Suction fan unit 21 as cooling means for rapidly cooling
Is installed. As shown in FIG. 4, the suction fan unit 21 includes a suction fan 22 in the outside air intake portion, and forms a cooling air blowing opening 23. The outside air A is taken into the unit by the suction fan 22, and the cooling air B is blown from the cooling air blowing opening 23 toward the lower surface of the transfer paper P.

As shown in FIG. 3, the toner T formed on the lower surface of the transfer paper P is normally sandwiched between the two transfer papers P without sufficiently radiating heat naturally. By providing the suction fan unit 21 near the downstream side of the paper discharge roller 11, the toner T is quickly cooled, and blocking is prevented.

FIG. 5 is an enlarged view of a main part of an image forming apparatus showing a second embodiment of the present invention, and FIG. 6 is a perspective view of a cooling plate shown in FIG. In the second embodiment shown in FIG. 5, a cooling plate 31 constituting a cooling unit is provided in the vicinity of the discharge roller 11 and below the transfer sheet P. The cooling plate 31 is made of metal, and has a plurality of radiating fins 32 provided upright as shown in FIG. The surface of the radiation fin 32 (and other metal parts) is made of Teflon (PT
FE) The coating is applied, and the transfer paper P
, The heat of the high-temperature toner is removed and the toner can be rapidly cooled. Although not directly related to the present invention, FIG. 5 shows a rolling support member 21 and a fixed support member 22 on the downstream side of the transfer unit.

In the first embodiment shown in FIG. 2 and the second embodiment shown in FIG. 5, the cooling means is installed near the downstream side of the discharge roller 11 and below the transfer paper P. Other suitable places near the paper discharge tray 12 may be used. By the way, there are many types (basis weight) of the transfer paper P,
The transfer paper P having a normal basis weight (90 kg / cm ² or less) other than the thick paper receives little heat in the fixing device 10, so that it is not necessary to operate the cooling unit.

On the other hand, thick paper (transfer paper having a basis weight of more than 90 kg / cm ² , OHP sheet) reduces the linear velocity passing through the fixing device 10 to give more fixing energy. That is, it is heating more. Therefore, the cooling means must be operated for these transfer papers P.
Therefore, it is determined that cooling is necessary only when there is a designation (cardboard mode, OHP mode) by the operation unit or by the personal computer or RIP (raster image processor / printer controller), and the cooling means is used. . This allows the cooling means to be used efficiently only when necessary.

FIG. 7 is a table showing the relationship between the type of transfer paper and the necessity of cooling the lower surface of the transfer paper. As shown in FIG. 7, the cooling means may be operated in the thick paper mode and the OHP mode. As described above, in the image forming apparatus according to the embodiment of the present invention, the transfer sheet passes through the fixing device 10 with the image formed on the lower surface of the transfer sheet, and is discharged to the discharge tray 12 by the discharge rollers 11. Is done. A suction fan unit 22 or a cooling plate 31 as a cooling means is installed near the downstream side of the paper discharge roller 11 and below the transfer paper, and the toner is rapidly discharged by the cooling means in the process of discharging the transfer paper. Is cooled. Therefore, it is possible to prevent the transfer papers from blocking on the paper output tray 12.

[0027]

According to the first aspect of the present invention, the cooling means for cooling the lower surface of the transfer paper is provided near the paper discharge tray.
The high-temperature toner image on the lower surface of the transfer paper is quickly cooled, and the blocking between the transfer papers can be eliminated.

According to the second aspect of the present invention, since the cooling means is provided at a position adjacent to the downstream side of the paper discharge roller constituting the paper discharge part, the lower surface of the transfer paper immediately after exiting from the paper discharge part is immediately placed. Can be cooled.

According to the third aspect of the present invention, the cooling means is provided with a suction fan that takes in outside air and blows the outside air onto the lower surface of the transfer paper. It can be cooled efficiently.

According to the fourth aspect of the present invention, the cooling means is constituted by a metal cooling plate having heat-dissipating fins provided with a surface coating having high releasability, and the lower surface of the transfer paper is formed by the cooling plate. When passing over the transfer paper, the lower surface of the transfer paper can be efficiently cooled by the radiation fins.

According to the fifth aspect of the present invention, the operation and non-operation of the cooling means can be switched depending on the type of the transfer paper, so that, for example, more fixing energy is required as compared with a normal transfer paper. It is possible to select such that cooling is performed on the thick paper or the OHP sheet, and cooling is not performed on the other normal transfer paper, thereby improving the usability.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of an image forming apparatus which is a premise of the present invention.

FIG. 2 is an enlarged view of a main part of the image forming apparatus according to the first embodiment of the present invention.

FIG. 3 is a diagram illustrating a state of transfer paper and toner discharged to a discharge tray.

FIG. 4 is a perspective view of the suction fan unit shown in FIG. 2;

FIG. 5 is an enlarged view of a main part of an image forming apparatus according to a second embodiment of the present invention.

FIG. 6 is a perspective view of the cooling plate shown in FIG.

FIG. 7 is a table showing the relationship between the type of transfer paper and the necessity of cooling the lower surface of the transfer paper.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 photoreceptor belt 2 intermediate transfer unit 3 black developing unit 4 color developing unit 5 main body feeder 6 manual feeder 7 registration roller 8 fixing roller 9 pressure roller 10 fixing device 11 discharge roller 12 discharge tray 13 transfer unit DESCRIPTION OF SYMBOLS 14 Support 15 Intermediate transfer belt cleaner 21 Suction fan unit 22 Suction fan 23 Cooling air blowing opening 31 Cooling plate 32 Radiation fin P Transfer paper T Toner (toner layer) A Outside air B Cooling air

Claims (5)

[Claims] An image forming apparatus of a type in which a transfer sheet having an unfixed image formed on a lower surface thereof is passed through a fixing device to fix the unfixed image, and the transfer sheet is discharged from a discharge section to a discharge tray. An image forming apparatus, comprising: a cooling unit that cools a lower surface of a transfer sheet near a discharge tray. 2. The image forming apparatus according to claim 1, wherein the cooling unit is installed at a position adjacent to a downstream side of a paper discharge roller constituting a paper discharge unit. 3. The image forming apparatus according to claim 1, wherein the cooling unit includes a suction fan that takes in outside air and blows the outside air onto a lower surface of the transfer sheet. 4. An image forming apparatus according to claim 1, wherein said cooling means is constituted by a metal cooling plate having heat radiation fins provided with a surface coating having high releasability. 5. The image forming apparatus according to claim 1, wherein the operation and non-operation of the cooling unit can be switched according to the type of transfer paper.