JP5106252B2 - Image forming apparatus - Google Patents

Description

  The present invention relates to an image forming apparatus such as a copying machine, a printer, a facsimile machine or a composite machine thereof, and more particularly, an electrophotographic system in which a recording material onto which a toner image is transferred is passed through a fixing device and the toner image is fixed on the recording material using heat. The present invention relates to an image forming apparatus.

2. Description of the Related Art Conventionally, in image forming apparatuses such as printers, copiers, and facsimiles, a fixing device that fixes an image by heating and melting a toner image formed on a recording material such as paper or film is used in the image forming apparatus. It is known.
Generally, a fixing device that fixes an electrophotographic image formed as a toner image on a recording material supplies electric power to a heater that is a fixing heat source to light a halogen lamp, an infrared lamp, etc., and a fixing roller, a fixing belt A fixing member such as the above is heated, and the toner image is heated and melted by this heat to fix it on the recording material.
In the fixing device, a sufficient amount of heat is applied to melt the toner image and fix it to the recording material in order to perform normal fixing within a range that does not cause hot offset contamination and does not cause fixing failure. There is a need. However, when fixing a recording material such as a recording material, the amount of heat given to the recording material differs between the front and back in the thickness direction of the recording material, so that the amount of evaporation of moisture contained in the recording material differs, and further, the thickness direction of the recording material It is known that a phenomenon occurs in which the recording material is bent due to a difference in shrinkage between the front and back surfaces of the recording material due to a process at a temperature reached by the front and back surfaces. When curling (hereinafter simply referred to as “curling”) occurs due to this phenomenon, it may hit the outer wall of the conveying path in the middle of the conveying path, or a paper jam due to improper conveyance of the recording material, or In addition, it has become a factor that causes a stack failure when discharged to a discharge tray or the like. In addition, this curl would impair user convenience.

For this reason, in order to suppress the curl amount, in the prior art, a technique for reducing the curl amount by passing the recording material through a roller pair called a decurler mechanism for correcting the curl has been known.
As a conventional technique, for example, in Patent Document 1, “In a decurling apparatus in which an elastic roller and a hollow cooling pipe roller are nipped on each other's outer peripheral surfaces and a recording material is passed through the nip portion, the cooling pipe roller is A decurling device for an image forming apparatus having an endothermic action for removing heat from the surface of a recording material is disclosed.
In Patent Document 2, “a decurling device that is provided at a subsequent stage of the fixing device and removes curl generated on the sheet by passing through the fixing device, and includes a hard roller having a hard peripheral surface, and the hard roller described above. A soft roller that is in pressure contact and whose peripheral surface is elastically deformed to form a predetermined nip pressure with the hard roller; and a nip pressure switching unit that switches the nip pressure between the hard roller and the soft roller; A decal device is disclosed.
In Patent Document 3, “a temperature sensor that detects environmental temperature, a humidity sensor that detects environmental humidity, and a downstream sensor that is installed downstream of the fixing unit and applies pressure to the recording material to correct the curling of the recording material. An image forming apparatus comprising: a curl correcting mechanism, wherein the pressure applied to the recording material by the curl correcting mechanism is changed in accordance with the temperature detected by the temperature sensor and the humidity detected by the humidity sensor. Yes.

Japanese Patent Laid-Open No. 04-029559 JP 2006-036489 A JP 2007-182306 A

  Recently, however, image forming apparatuses having a plurality of paper discharge units such as a plurality of paper discharge trays are increasing, and it is not possible to provide a decurling mechanism corresponding to the paper discharge unit or the recording material conveyance path. However, there is a problem that the structure of the image forming apparatus becomes complicated and it is difficult to reduce the cost.

  Accordingly, the present invention has been made in view of the above-described problems, and an object of the present invention is to fix a fixing device corresponding to a paper discharge unit in an image forming apparatus including a plurality of paper discharge units such as a paper discharge tray. It is an object of the present invention to provide an image forming apparatus that controls the curl amount of the recording material at the paper discharge unit by changing the conditions. Furthermore, it is an object of the present invention to provide a print and printed matter that are stable over a long period of time by preventing the stack failure and paper jam by appropriately controlling the curl amount.

The features of the present invention, which is a means for solving the above problems, are listed below.
An image forming apparatus according to the present invention includes a fixing device that thermally fixes a toner image on a recording material by a fixing member having a heat source and a pressure member that presses the fixing member, and a recording material on which the toner image is thermally fixed. In the image forming apparatus having the paper discharge unit, the fixing condition of the fixing device is set to a fixing member according to the paper discharge unit having a plurality of paper discharge units and stacking the recording material after heat fixing. by detecting the temperature difference between the pressure member, characterized in that to change.
Alternatively, the image forming apparatus of the present invention further includes a decurler mechanism that corrects the curl of the recording material between the fixing device and the paper discharge unit.
Alternatively, the image forming apparatus of the present invention further includes a paper discharge unit that discharges paper through the decurler mechanism, and a paper discharge unit that discharges paper without passing through the decurler mechanism. The fixing condition of the fixing device is changed according to the paper discharge unit.
Alternatively, the image forming apparatus of the present invention is further characterized in that the fixing condition of the fixing device is changed according to the shape of the discharge surface of the paper discharge unit.
Alternatively, the image forming apparatus of the present invention is further characterized in that the fixing condition changes a target control temperature of the fixing member.
Alternatively, the image forming apparatus of the present invention, further, the fixing condition, you and changes the target control temperature of the pressure member.

  In the image forming apparatus of the present invention, the curl amount can be appropriately controlled in accordance with a paper discharge tray such as a paper discharge unit at a paper discharge destination, so that stacking failure or paper jam does not occur, and convenience for the user is impaired. Printing becomes possible.

  The best mode for carrying out the present invention will be described below with reference to the drawings. Note that it is easy for a person skilled in the art to make other embodiments by changing or correcting the present invention within the scope of the claims, and these changes and modifications are included in the scope of the claims. The following description is an example of the best mode of the present invention, and does not limit the scope of the claims.

The best mode for carrying out the present invention will be described below with reference to the embodiments shown in the drawings.
FIG. 1 is a diagram showing an overall schematic configuration of an internal mechanism in an image forming apparatus of the present invention.
The image forming apparatus 1 employs an electrophotographic system, and includes an image reading device 2 installed on the main body of the image forming device 1 and a duplex unit 3 attached to the right side surface. A transfer device 50 using an intermediate transfer belt 52 is provided in the main body of the image forming apparatus 1. The transfer device 50 is provided so as to run around an endless intermediate transfer belt 52 almost horizontally by being wound around a plurality of rollers, and to run counterclockwise in FIG.
Under the transfer device 50, cyan, magenta, yellow, and black image forming devices 4c, 4m, 4y, and 4k are arranged in a tandem manner along the stretch direction of the intermediate transfer belt 52. In each of the image forming devices 4c, 4m, 4y, and 4k, a charging device 20, a developing device 30, a transfer device 50, a cleaning device 40, and the like are installed around a drum-shaped photosensitive member 10 that rotates clockwise in the drawing. To do. Further, an exposure device 70 is provided below the image forming devices 4c, 4m, 4y, and 4k.
Under the exposure device 70, a paper feeding device 80 is provided. In the paper feeding device 80, paper feeding cassettes 81 for storing the recording material P are provided in two stages in this example. Then, the upper right corner of each of the paper feed cassette 81, formed by the feed roller 82 put on the sheet conveying path 97 by feeding the recording material P as a recording material in the paper feed cassette 81 one by one is provided.

The sheet conveyance path 97 is formed on the right side in the main body of the image forming apparatus 1 from below to above. As the paper discharge unit, an in-body discharge unit 91 serving as a first paper discharge unit and a second bin serving as a second paper discharge unit are formed between the image forming apparatus 1 and the image reading device 2 on the upper side. Two paper discharge units 92 are provided. In addition, although not shown, a multi-bin paper discharge unit having a sorter function may be provided.
In the paper conveyance path 97, a registration roller 84, a secondary transfer roller 53, a fixing device 60, a paper discharge device 90 including a pair of paper discharge rollers, and the like are provided in order so as to face the intermediate transfer belt 52. Upstream of the secondary transfer roller 53, a sheet feeding path for re-feeding from the duplex unit 3 or for manually feeding the recording material P from the manual sheet feeder 86 across the duplex unit 3 to the sheet transport path 97. 99 is provided. Further, a refeed conveyance path 98 to the duplex unit 3 is branched downstream of the fixing device 60.
Then, when making a copy, the original image is read by the image reading device 2 and written by the exposure device 13, and each color toner image is formed on each image carrier of each image forming device 4c, 4m, 4y, 4k. Then, the toner image is sequentially transferred by the primary transfer rollers 51c, 51m, 51y , and 51k to form a color image on the intermediate transfer belt 52.

On the other hand, one of the paper feed rollers 82 is selectively rotated to feed the recording material P from the corresponding paper feed cassette 81 and put it into the paper transport path 97, or manually feed paper from the manual paper feeder 36 into the paper feed path 99. Put in. Then, the sheet is conveyed by the registration roller 84 through the sheet conveyance path 97 and sent to the secondary transfer position in a timely manner, and the color image formed on the intermediate transfer belt 52 is transferred to the recording material P by the secondary transfer roller 53. .
After the image is transferred, the recording material P is fixed by the fixing device 60 and then discharged to the paper discharge device 90 by the paper discharge roller and stacked.
When an image is also formed on the back surface of the recording material P, it is placed in the refeed conveyance path 98, reversed by the duplex unit 3, and then fed again through the feed path 99, and separately formed on the intermediate transfer belt 52. After the image is secondarily transferred to the recording material P, it is fixed again by the fixing device 60 and discharged to the paper discharge device 90 and stacked. The user can arbitrarily select and discharge the plurality of paper discharge units 91 and 92 of the paper discharge device 90 according to the printed matter.

FIG. 2 is a diagram showing a configuration of an embodiment of a fixing device used in the image forming apparatus of the present invention. In this example, a fixing belt 63 that is wound around a plurality of support rollers (in the example shown, two support rollers 61 and 64) is used as a fixing member. The fixing roller 61 is supported by the pressure roller 62 with the fixing belt 63 interposed therebetween to form a fixing nip portion 66 between the pressure roller 62 and the fixing belt 63, and a recording material is formed in the fixing nip portion 66. The toner image on the image surface is fixed to the recording material P through P. In this example, a pressure heat source 62 a is also provided inside the pressure roller 62.
In this example, the pressurizing heat source 62a is used with a built-in heater such as a halogen heater or a carbon heater, but is not limited to the heater, and a heat source that generates heat using electromagnetic induction is provided outside the heating roller 64. You may make it use. In this example, as the temperature detection means 65, the fixing belt 63 is provided with a temperature detection means 65 a that detects the temperature of the fixing belt 63 in close proximity, and the temperature of the fixing belt 63 is measured. Further, the pressure roller 62 is provided with a temperature detecting means 65b for detecting the temperature of the pressure roller 62 in close proximity to measure the temperature of the pressure roller 62 .
Temperature control is performed based on the information of the temperature detection means 65a so that the temperature of the fixing belt 63 becomes a target control temperature designated in advance.
Similarly, the control of the heat source of the pressure roller 62 is controlled based on the information of the temperature detection means 65b so that the temperature of the pressure roller 62 becomes the target control temperature designated in advance.
In this example, the heating heat sources 62a and 64a perform temperature control both in the standby state in which the fixing drive is stopped and during printing in which the fixing drive is rotating, but the pressure heat source 62a performs temperature control only in the standby state. Suppose that no power is supplied to the heat source during printing.

The fixing roller 61 and the pressure roller 62 include an elastic layer made of a heat-resistant elastic material on the outer periphery of a metal cored bar. The thickness of the elastic layer is adjusted as appropriate. Further, a release layer made of a fluorine-based resin or the like is provided on the surface layer of the elastic layer in order to improve the release property of the transfer paper and toner. A halogen heater is disposed inside each of the core bars. The pressure roller 62 is pressed by a pressure member such as a spring (not shown) toward the fixing roller 61 with the fixing belt 63 interposed therebetween, and is fixed between the fixing roller 61 by deforming the elastic layer. A fixing nip 66 that can pressurize and heat the toner for a time is formed.
The fixing belt 63 is made of an endless belt-like substrate made of heat-resistant resin or metal. Examples of the material of the heat resistant resin include polyimide, polyamideimide, polyether ether ketone, and examples of the material of the metal belt include nickel, aluminum, and stainless steel. A resin and a multilayer may be formed. In particular, a belt obtained by electroforming nickel on a polyimide resin is preferable because it has strength and elasticity and is durable. The thickness is preferably 100 μm or less. Since the fixing belt 63 is in pressure contact with transfer paper and toner, a surface layer is formed of an elastic layer made of a high releasable silicone rubber and a resin having a high releasability. This surface layer is made of, for example, a silicone resin, a fluororesin, specifically, polytetrafluoroethylene (PTFE), tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (PFA), tetrafluoroethylene-hexafluoropropylene copolymer. Polymer resin such as coalescence (FEP) is used.
The heating roller 64 is a thin-walled roller of a hollow metal cylinder such as aluminum, carbon steel, and stainless steel, but the temperature distribution in the axial direction is achieved by using an aluminum cylinder having a thickness of 1 to 4 mm with good thermal conductivity. Can be reduced. Further, the surface of the heating roller 64 is subjected to an alumite treatment in order to prevent abrasion with the fixing belt 63.
As a matter of course, here, the fixing belt is described as the fixing member, but a fixing type fixing roller that does not use the fixing belt can be similarly applied.

The image forming apparatus of the present invention includes a plurality of paper discharge units 91 and 92. Here, as the paper discharge unit, an in-body paper discharge unit 91 and a 1-bin paper discharge unit 92 provided thereon are provided. The decurler mechanism 95 is provided on a conveyance path 97 that conveys the recording material P from the fixing device 60 to each paper discharge unit.
FIG. 3 is a diagram illustrating a configuration of an embodiment of the decurler mechanism.
The decurler mechanism 95 is provided on the upstream side in the discharge direction of the recording material P from the fixing device 60. In addition, since there are a plurality of paper discharge units, in the present invention, the in-body paper discharge unit 91 of the image forming apparatus 1 is provided on the paper conveyance path 97 for conveying and discharging the recording material P.
Here, the decurling mechanism 95 is formed by the backup rollers 951 and 952 and the conveying roller 953. In the decurling mechanism 95, a conveying roller 953 is disposed on the side where the sheet can be curved and corrected in the direction opposite to the direction in which the curling occurs on the side in contact with the toner image on the recording material P. The transport roller is formed of a good thermal conductor, and its surface is directly used for cooling the recording material P. Further, it is preferable to coat the surface with a resin having high releasability so that the toner is not offset. For this reason, the recording material P that has reached the decurling mechanism 95 is cooled when it comes into contact with the conveying roller 953, and the rigidity of the recording material P is increased, so that the original rigidity is restored.
The transport roller 953 is cooled by a fan (not shown) provided in the vicinity. Therefore, the bending rigidity of the recording material P, which has been lowered by being softened by the fixing device 60, can be restored by the temperature drop.

However, when the decurler mechanism 95 is provided, the mechanism and structure of the image forming apparatus 1 are complicated, the efficiency in mechanical design is lowered, and it is difficult to reduce the cost. Therefore, as shown in FIG. 1, a first paper discharge unit 91 that discharges paper through the decurler mechanism and a second paper discharge unit 92 that discharges paper without passing through the decurler mechanism are provided. For example, convenience can be improved by discharging the copy image to the in-body discharge unit 91 and discharging the printer output image to the 1-bin discharge unit 92. In this example, the shapes (curvatures) of the discharge surfaces of the in-body discharge unit 91 and the 1-bin discharge unit 92 are the same.
By providing the decurler mechanism 95, even if the amount of curling of the recording material P (hereinafter simply referred to as “curling amount”) is increased by applying high heat and / or pressure to the recording material P, the curling is corrected. The curl amount can be reduced. For this reason, when forming a color image, a multilayer toner image must be fixed on the recording material P, and it is difficult to prevent the occurrence of curling because it is fixed at a high temperature and / or high pressure. It was. A decurling mechanism 95 is provided in the transport path 97 for performing such image formation.
On the other hand, in the image forming apparatus 1 with the facsimile mechanism, the facsimile can sufficiently transmit information even with a monochrome image. In this case, a substantially single layer toner image of black toner is fixed. Since it is not necessary to increase the temperature of the apparatus 60, the curling amount of the recording member P can be reduced. Therefore, even if the fixing conditions of the fixing device 60 are changed by the paper discharge units 91 and 92 by the conveyance path 97 having different arrangement of the decurling mechanism 95, the fixing without the hot offset or the fixing defect that causes the toner image to be easily peeled off. A possible image forming apparatus 1 can be provided.

FIG. 4 is data in which the curl amount due to the difference in the paper discharge unit is compared for each recording material. The data is the average value of the four corners of the recording material P immediately after 10 sheets are discharged to the in-body discharge unit 18 and the 1-bin discharge unit 38, respectively.
FIG. 5 is a diagram illustrating a position where the curl amount of the recording material is measured. The heights of the four corners of the recording material P immediately after paper discharge were measured.
It is the temperature of the fixing roller 61 that most affects the amount of curl in the fixing device 1. The fixing roller 61 that is in contact with the toner is in direct contact between the recording material P and the fixing roller 61 at the white background image portion. For this purpose, the amount of curl is increased by evaporating a large amount of moisture in the recording material P. The temperature setting of the fixing roller 61 at the time of fixing is 180 ° C., and all other fixing conditions are the same. The only difference is whether or not the decurler mechanism 95 is passed after fixing.
As is clear from FIG. 5, the curl at the time of discharging one bin without passing through the decurler mechanism 95 is larger than the curl at the time of discharging inside the cylinder that passes through the decurler mechanism 95 for correcting the curl, which is larger than the desired curl amount. It can be seen that the curl amount is reached.
As described above, the effect of the decurler mechanism 95 for correcting the curl is enormous, but it may not be used due to problems in the configuration of the image forming apparatus 1 and cost. For example, in this embodiment, the decurler mechanism 95 cannot be provided because the upper reading device 2 is arranged immediately above when discharging one bin. Therefore, in order to reduce the curl amount without using the decurler mechanism 95, the fixing condition is changed.

There are multiple causes for curling amplification during fixing, but the main causes are as follows.
(1) The temperature of the fixing belt 63 is high. (2) The temperature difference between the fixing belt 63 and the pressure roller 62 is large. FIG. 6 shows that one bin is discharged when the target control temperature of the fixing belt is 180 ° C. and 160 ° C. This is data comparing curl amounts immediately after 10 sheets are discharged to the paper section 92. (All other conditions are the same)
As can be seen from FIG. 6, the curling amount is reduced by lowering the temperature of the fixing belt 63, so that the curling amount can be reduced below the desired curling amount.
However, lowering the temperature of the fixing belt 63 may cause fixing failure and the like, and reducing the curl amount and securing the fixing performance are in a trade-off relationship. For this reason, there is a limit to lowering the temperature of the fixing belt 63.
Therefore, the above (2) was noted. Since the amount of water evaporation on the front and back of the recording material P greatly affects the curl amount, the temperature of the pressure roller 62 in the fixing device 1 is changed. In particular, the temperature of the pressure roller is brought close to the temperature of the fixing roller 61. Consider increasing the temperature of the pressure roller 62 in order to reduce the temperature difference between the fixing belt 63 and the pressure roller 62 during fixing.

The fixing device 1 often uses a fixing member having a low heat capacity such as the fixing belt 63 of this example from the viewpoint of shortening the warm-up time and saving energy, but the fixing nip portion 66 necessary for fixing is used. In order to secure this width, a member having a larger heat capacity than the fixing roller 61 is often used, such as providing a rubber layer for the pressure roller 62. For this reason, a temperature difference between the fixing roller 61 and the pressure roller 62 is likely to occur, which is a factor that increases the curl amount. Therefore, conversely, reducing the temperature difference between the fixing roller 61 and the pressure roller 62 can also reduce the curl amount.
FIG. 7 is a view showing a change in temperature of the pressure roller after the rotation is started when the fixing belt and the pressure roller are rotated in a state where the temperature of the fixing belt is kept constant at 180 ° C. However, the temperature of the pressure roller 62 before the start of rotation is 100 ° C. When the rotation starts, the pressure roller 62 receives an amount of heat from the fixing belt 63 and the temperature rises. The temperature difference between the fixing belt 63 and the pressure roller 62 before the start of rotation is 80 deg. However, the temperature difference becomes 50 deg after 30 s after the start of rotation. As described above, the temperature difference between the fixing belt 63 and the pressure roller 62 can be reduced by rotating the fixing belt 63 while keeping the temperature constant.
Hereinafter, the operation of raising the temperature of the pressure roller 62 by the rotational heating of the fixing belt 63 is referred to as a pre-rotation operation.

FIG. 8 shows data comparing curl amounts depending on the presence or absence of the pre-rotation operation. Immediately after 10 sheets are discharged to the 1-bin discharge unit 92 when printing is started after the pre-rotation operation is performed for 30 s after the printing command is received from the user, and when printing is started without performing the pre-rotation This compares the curl amount. The target control temperature of the fixing belt 63 is 180 ° C.
As can be seen from FIG. 8, the curl amount can be reduced without lowering the target control temperature of the fixing belt 63 by performing the pre-rotation operation and reducing the temperature difference between the fixing belt 63 and the pressure roller 62.
In this example, the curling amount is reduced by changing the duration of the pre-rotation operation. However, when the temperature of the pressure roller 62 reaches, for example, 130 ° C., the pre-rotation operation is terminated and printing is started. For example, the end timing of the pre-rotation operation may be associated with the temperature of the pressure roller 62.
In addition, when the pre-rotation end timing is determined by “continuation time” or “temperature of the pressure roller 62” as described above, a temperature difference between the fixing belt 63 and the pressure roller 62 is targeted depending on conditions such as environmental temperature. There are times when it does not pass. Therefore, using the information of the temperature detecting means 29 of the fixing belt 63 and the temperature detecting means 301 of the pressure roller 62, the pre-rotation is continued until the temperature difference between them becomes, for example, 30 deg, and then printing is started. In addition, the end timing of the pre-rotation operation may be determined from the temperature difference between the fixing belt 63 and the pressure roller 62.

As described above, the curl amount without passing through the decurler mechanism 95 is realized by (1) lowering the target control temperature of the fixing belt 63 and (2) reducing the temperature difference between the fixing belt 63 and the pressure roller 62. Can be reduced.
The information on where the recording material P is discharged is included in the print job and can be determined when a printing command is issued. Therefore, it is possible to easily change the fixing condition depending on the discharge destination. It is. As described above, according to the present invention, when the presence / absence of passage of the decurler mechanism 95 differs according to each of the plurality of paper discharge units 91 and 92, the fixing condition is changed based on the information of the paper discharge units 91 and 92. The curl amounts in the respective paper discharge units 91 and 92 can be appropriately controlled.

In the image forming apparatus 1 of the present invention, the fixing conditions of the fixing device 60 are changed according to the shape of the discharge surface of the paper discharge unit. FIG. 9 is a diagram showing an overall schematic configuration of the internal mechanism in the image forming apparatus of the present invention. This configuration is the same as that in FIG. 1 before image fixing.
The decurler mechanism 95 is not provided, and after image fixing, based on user selection information, the first discharge unit 91 of the in-body discharge unit or the second discharge unit 92 of the flat one-bin discharge unit. The paper is discharged to either of these. The discharge surfaces of the first and second paper discharge units 91 and 92 are usually curved, and can be converged at the same position when the recording material P discharged from the paper discharge rollers 91a and 92a is stacked. preferable.
However, in the curved first paper discharge unit 91, the recording material P discharged from the fixing device 60 is not cooled, and therefore remains at a high temperature. The amount of curl tends to increase due to the evaporation of the water inside.
However, when the number of output sheets is small, the user can easily collect them without converging at the same position. Therefore, the discharge surface of the second paper discharge unit 92 is linear and the inclination angle is low. Many. In this case, the high temperature recording material P discharged from the fixing device 60 tends to hardly increase the curl amount even if moisture inside the recording material P evaporates.
Accordingly, the curvature of the recording material P can be controlled by changing the fixing conditions of the fixing device 1 according to the curved state of the discharge surface, the overall inclination, and the like, in particular, the curved state of the discharge surface. In particular, it is preferable to fix the discharge portion 91 having a large curved shape and a discharge surface having a large inclination angle at a low fixing temperature under the condition that no fixing failure occurs.
Further, it is preferable to fix the discharge portion 92 having a small curved shape and a small inclination angle by increasing the fixing temperature condition. In this case, the image forming apparatus 1 can be reduced in size by not providing the decurler mechanism 95 even under fixing conditions where the curl amount increases.

  FIG. 10 shows data comparing curl amounts according to the shape of the paper discharge unit. To the first discharge portion 91 of the in-body discharge portion and the second discharge portion 92 of the flat one-bin discharge portion under the fixing conditions where the target control temperature of the fixing belt 63 is 180 ° C. and the pre-rotation operation is 0 s. The curl amount immediately after 10 sheets are discharged is shown. As described above, since the recording material P is not cooled immediately after being discharged, the curl ridge may be formed along the shape of the discharge surface in this way. Even in such a case, by setting the set temperature and pre-rotation operation time of the fixing belt 63 appropriately according to the paper discharge units 91 and 92, the curl amount can be set according to the paper discharge surfaces of the paper discharge units 91 and 92. It is possible to control appropriately.

Furthermore, in the image forming apparatus 1 of the present invention, three paper discharge units may be provided.
FIG. 11 is a diagram showing a schematic configuration of a part of the internal mechanism in the image forming apparatus of the present invention. The paper discharge device 90 includes a first paper discharge unit 91 having a decurler mechanism 95a, a second paper discharge unit 92 having a decurler mechanism 95b, and a third paper discharge unit 93 having no decurler mechanisms 95a and 95b. .
When a large amount of heat is lost, such as when printing a very large number of monochrome images continuously, or when printing a color image that needs to fix a large number of toner images, the fixing roller 61, Since fixing failure occurs unless the fixing belt 63 is heated to a certain level, a first paper discharge unit 91 including a decurler mechanism 95a for suppressing the generated curl is provided. In addition, when printing a large number of monochrome images, a second paper discharge unit 92 including a decurler mechanism 95b for suppressing curling generated to bring the fixing roller 61 and the fixing belt 63 to a standard temperature is provided. . In this case, since the fixing temperature is lower than when discharging to the first paper discharge unit 91, the decurler mechanism 95b also decurs with a weaker force than the decurler mechanism 95a.
Further, when only a small number of monochrome images are printed, the fixing roller 61 and the fixing belt 63 can be prevented from causing poor fixing at a certain high temperature, and curling is unlikely to occur. A paper portion 93 is provided. In this case, it is preferable not to provide the decurler mechanism 95 and to reduce the curvature of the paper discharge surface of the paper discharge unit 93.

1 is a diagram illustrating an overall schematic configuration of an internal mechanism in an image forming apparatus of the present invention. 1 is a diagram illustrating a configuration of an embodiment of a fixing device used in an image forming apparatus of the present invention. It is a figure which shows the structure of one Embodiment of a decurler mechanism. This is data in which the curl amount due to the difference in the paper discharge unit is compared for each recording material. It is a figure which shows the position which measures the curl amount of a recording material. This is data comparing curl amounts immediately after 10 sheets are discharged to the 1-bin discharge unit 38 when the target control temperature of the fixing belt is 180 ° C. and 160 ° C. FIG. 6 is a diagram showing a change in temperature of the pressure roller after starting rotation when the fixing belt and the pressure roller are rotated in a state where the temperature of the fixing belt is kept constant at 180 ° C. This data compares the amount of curl with and without pre-rotation operation. 1 is a diagram illustrating an overall schematic configuration of an internal mechanism in an image forming apparatus of the present invention. This is data comparing curl amounts according to the shape of the paper discharge section. FIG. 2 is a diagram illustrating a schematic configuration of a part of an internal mechanism in the image forming apparatus of the present invention.

Explanation of symbols

First image forming apparatus 2 image reading winding device 3 duplex unit 4 imaging device 10 photoconductor 20 charging device 30 developing device 40 a cleaning device 50 transfer device 51 primary transfer rollers 52 intermediate transcription belt 53 secondary transfer roller 54 supporting rollers 60 fixing 61 fixing row La (supporting roller)
62 the pressure roller 62a heated heat source 63 fixing belt 64 heated low La (supporting roller)
64a heating heat source 65 temperature detector 66 fixing nip portion 70 exposure device 80 the sheet feeding apparatus 81 the paper feed cassette 82 sheet feeding roller 83 conveying roller pair 84 registration rollers 86 Bypass paper feeding device 90 sheet discharging device 91 first sheet discharge portion 91a discharge Paper roller 92 Second paper discharge unit 92a Paper discharge roller 93 Third paper discharge unit 93a Paper discharge roller 95 Decurler mechanism 951, 952 Backup roller 953 Transport roller 97 Paper transport path 98 Re-feed transport path 99 Paper feed path P Recording material

Claims (6)

A fixing device that thermally fixes a toner image on a recording material by a fixing member having a heat source and a pressure member that presses the fixing member;
In an image forming apparatus having a paper discharge unit for stacking a recording material on which a toner image is thermally fixed,
The image forming apparatus includes a plurality of paper discharge units, and the fixing conditions of the fixing device are determined according to the temperature of the fixing member and the pressure member according to the paper discharge unit on which the recording material after thermal fixing is stacked. an image forming apparatus characterized in that change by detecting the difference. The image forming apparatus according to claim 1.
The image forming apparatus includes a decurler mechanism that corrects a curl of a recording material between a fixing device and a paper discharge unit. The image forming apparatus according to claim 2.
The image forming apparatus includes a paper discharge unit that discharges paper through the decurler mechanism, and a paper discharge unit that discharges paper without passing through the decurler mechanism,
An image forming apparatus, wherein a fixing condition of the fixing device is changed according to each paper discharge unit. The image forming apparatus according to any one of claims 1 to 3,
The image forming apparatus, wherein the fixing condition of the fixing device is changed according to a shape of a discharge surface of a paper discharge unit. The image forming apparatus according to claim 1,
The image forming apparatus, wherein the fixing condition is to change a target control temperature of the fixing member. The image forming apparatus according to claim 1,
The image forming apparatus, wherein the fixing condition is to change a target control temperature of the pressure member.

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