JP2009161347A - Image forming device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To enhance an ability to correct curl of a recording material, enhancing an ability to cool the recording material. <P>SOLUTION: This image forming unit forms a toner image corresponding to image data by using a toner, and transfers the formed toner image from an intermediate transfer belt to a paper sheet. A fixing part fixes the toner image to the paper sheet by heating and pressing the paper sheet. A cooling device has a contact surface curved in a direction opposite to the curl direction of the paper sheet, and cools the paper sheet, to which the toner image is fixed by the fixing part, by bringing the paper sheet in contact with the contact surface. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an image forming apparatus.

A technique for correcting paper curl in an image forming apparatus is known. The curling of the paper means that the paper is curved in the transport direction and is also called a curl. Regarding the technology for correcting the curl of the paper, for example, Patent Document 1 discloses a fixing unit that heats and fixes toner on a recording material, and a curl correcting unit that is provided downstream of the fixing unit and corrects the curling of the recording material. An image forming apparatus including a cooling unit that is provided downstream of the curl correcting unit and cools the recording material and a humidifying unit that supplies moisture to the recording material on which toner is fixed by the fixing unit is disclosed. Patent Document 2 discloses an electrophotographic apparatus that suppresses curling of a sheet by bending the sheet in a direction opposite to a curved sheet conveyance path. Patent Document 3 discloses an image forming unit that forms a toner image on a recording sheet, a fixing unit that heat-fixes the recording sheet, a heat sink that has a planar area for cooling the fixed recording sheet, and a cooling unit. There is disclosed an image forming apparatus that includes a pressing member that presses a storage sheet against a flat area and corrects curl with respect to a curled recording sheet.
JP 2007-119109 A Japanese Patent No. 3904401 JP 2004-203527 A

  It is an object of the present invention to provide a technique for improving the ability to correct the curl of a recording material while improving the ability to cool the recording material.

  In order to solve the above-described problems, the first configuration of the present invention includes an image forming unit that forms an image on a recording material, and heat and pressure applied to the recording material on which an image is formed by the image forming unit. A fixing unit that fixes the image on the recording material; a first belt member that conveys the recording material on which the image is fixed by the fixing unit; and an inner periphery of the first belt member, and the fixing unit The recording material on which the image is fixed by the first belt member in a region including the curved portion. And a pressing member that presses the recording material conveyed by the first belt member against the curved portion side of the cooling body.

The second configuration of the present invention is characterized in that the curved portion is provided on the upstream side of the cooling body in the conveyance direction of the recording material.
The third configuration of the present invention is characterized in that the curved portion is continuous to the downstream side in the conveyance direction of the recording material, and the curvature on the downstream side of the curved portion is smaller than the curvature on the upstream side.
The fourth configuration of the present invention is characterized in that the cooling body has a planar area downstream of the curved portion in the recording material conveyance direction.

According to a fifth configuration of the present invention, the image forming unit is a unit that forms an image using a color material, and the amount of the color material of the image formed by the image forming unit or the image is transferred. Information acquisition means for acquiring information representing the thickness of the recording material to be adjusted, and adjusting the pressing force with which the pressing member presses the recording material against the curved portion side according to the information acquired by the information acquisition means And control means for controlling to do so.
According to a sixth configuration of the present invention, there are a plurality of the pressing members, and the control means presses the recording material conveyed by the first belt member against the curved portion side with different magnitudes of force. It is characterized by controlling as follows.

According to a seventh configuration of the present invention, there are a plurality of the pressing members, and the pressing member disposed on the upstream side in the recording material transport direction is disposed on the downstream side in the recording material transport direction. The pressing force of the recording material conveyed by the first belt member against the curved portion is larger than that of the pressing member.
The eighth configuration of the present invention is characterized in that the pressing member has a second belt member disposed on an inner peripheral surface thereof.

The invention according to claim 1 can improve the curling correction ability of the recording material while improving the cooling ability of the recording material as compared with the case where the cooling body is not curved.
The invention according to claim 2 can perform the curl correction of the recording material at a temperature at which the curl is easily corrected as compared with the case where this configuration is not provided.
The invention according to claim 3 can reduce the load on the recording material while maintaining the adhesion between the recording material and the belt and between the belt and the cooling body.
The invention according to claim 4 can make the recording material flat.
According to the fifth aspect of the present invention, the curling of the recording material can be corrected with a correction force corresponding to the curling amount of the recording material.
The invention according to claim 6 can reduce the load on the recording material while performing the curl correction of the recording material at a temperature at which the curl is easily corrected.
The invention according to claim 7 can reduce the load on the recording material while performing the curl correction of the recording material at a temperature at which the curl is easily corrected.
The invention according to claim 8 can convey the recording material in a stable state as compared with the case where this configuration is not provided.

[Constitution]
FIG. 1 is a diagram illustrating a configuration of an image forming apparatus 1 according to the present embodiment. As shown in the figure, the image forming apparatus 1 includes a control unit 11, a paper storage unit 12, image forming units 13Y, 13M, 13C, and 13K, a touch panel 14, a fixing unit 15, a cooling device 16, and the like. And a main memory unit 17. Note that the symbols Y, M, C, and K indicate configurations corresponding to yellow, magenta, cyan, and black toners, respectively. The paper storage unit 12 stores paper cut into a predetermined size such as A3 or A4. The sheets stored in the sheet storage unit 12 are taken out one by one in accordance with an instruction from the control unit 11 and conveyed to the secondary transfer roll 42 via the sheet conveyance path. The touch panel 14 is a display operation unit that displays an image according to the control of the control unit 11 and supplies an operation signal according to a user operation to the control unit 11. The main storage unit 17 includes, for example, a hard disk and stores a processing program executed by the control unit 11.

  FIG. 2 is a block diagram illustrating an internal configuration of the control unit 11 according to the present embodiment. As shown in FIG. 2, when performing each process, the control unit 11 includes a CPU (Central Processing Unit) 111 that executes digital arithmetic processing according to a predetermined processing program, a RAM used as a working memory for the CPU 111, and the like. (Random Access Memory) 112, ROM (Read Only Memory) 113 in which processing programs executed by the CPU 111 are stored, EEPROM as an example of a storage means that can be rewritten and can retain data even when power supply is interrupted (Electronically Erasable and Programmable Read Only Memory) 114, control input / output of signals to / from the control target unit 116 such as the fixing unit 15 and the cooling device 16 connected to the control unit 11, the main storage unit 17, and the touch panel 14. The interface unit 115 is provided. Then, the CPU 111 of the control unit 11 reads a program for realizing each function from the main storage unit 17 into the RAM 112 and performs various processes. As described above, the main storage unit 17 stores a processing program to be executed by the control unit 11. When the CPU 111 operates the image forming apparatus 1, the processing program is read. Image formation is executed by the control unit 11.

  In the configuration shown in FIG. 1, the image forming units 13Y, 13M, 13C, and 13K as image forming units each include a photosensitive drum, a charging unit, an exposure unit, a developing unit, a primary transfer roll, and a cleaning member. Thus, toner images of each color corresponding to the image data are formed using the corresponding color toner, and transferred onto the intermediate transfer belt 41 in an overlapping manner. The intermediate transfer belt 41 is rotated in the direction A in the drawing by a driving roll (not shown). When the toner images are transferred in an overlapping manner by the image forming units 13Y, 13M, 13C, and 13K, the toner images are transferred to the intermediate transfer belt 41. It is conveyed to the position of the next transfer roll 42 and the opposing roll 43. The secondary transfer roll 42 transfers the toner image on the intermediate transfer belt 41 to the paper conveyed from the paper storage unit 12 by the potential difference with the intermediate transfer belt 41. The facing roll 43 is provided to face the secondary transfer roll with the intermediate transfer belt 41 interposed therebetween. The image data supplied to the image forming units 13Y, 13M, 13C, and 13K may represent an original image read by an image reading device (not shown) or transmitted from a computer device (not shown). It may be generated based on the received data.

  The fixing unit 15 in this configuration includes a heating roll 51 and a pressure roll 52, and applies heat and pressure to the paper conveyed from the secondary transfer roll 42 to fix the toner image on the paper. The heating roll 51 has a heat source such as a halogen lamp inside, and heats the temperature of the paper surface to, for example, about 100 degrees. The toner image formed on the paper surface by this heating is in a molten state. The pressure roll 52 is pressed against the heating roll 51 and applies pressure to the sheet passing between the heating roll 51 and the pressure roll 52. Further, a peeling member 53 made of metal or resin is provided near the surface of the heating roll 51. The paper that has undergone the fixing process by applying heat and pressure by the heating roll 51 and the pressure roll 52 is peeled off from the heating roll 51 by the peeling member 53 and conveyed to the cooling device 16 by the conveyance belt 54. It has become.

  The cooling device 16 in this configuration is a cooling unit for cooling the sheet heated by the fixing unit 15. FIG. 3 is a diagram illustrating a detailed configuration of the cooling device 16 as an example. As shown in the figure, the cooling device 16 includes a plurality of first transport rollers 61, a first transport belt 62, a plurality of second transport rollers 63, a second transport belt 64, and a plurality of pressure rollers 65. And a heat sink 66.

  The plurality of first transport rolls 61 are rolls that support the first transport belt 62, and at least one of the first transport rolls 61 is rotated by a drive unit (not shown). The first conveyor belt 62 is a first endless belt member that is stretched over a plurality of first conveyor rolls 61, and moves around in the direction of arrow B in the drawing according to the rotation of the first conveyor roll 61. The surface of the first conveying belt 62 is smooth, and the toner image that has been in a molten state on the sheet before contacting the first conveying belt comes into contact with the first conveying belt and becomes highly glossy.

  The second transport roll 63 is a roll that supports the second transport belt 64. The second conveyor belt 64 is a second endless belt member that is stretched around the plurality of second conveyor rolls 63 and the pressure rolls 65, and moves around with the first conveyor belt 62. The sheet on which the toner image is fixed by the fixing unit 15 described above is conveyed between the first conveying belt 62 and the second conveying belt 64 and is sandwiched between the first conveying belt 62 and the second conveying belt 64. In this state, the paper is transported in the paper transport direction C in the drawing according to these circular movements.

  The pressure roll 65 is a rotatable roll-shaped member, and is provided on the inner peripheral side of the second transport belt 64 at a position along the inner peripheral surface. The rotation shafts of these pressure rolls 65 are pushed from the inner peripheral side of the second conveyor belt 64 to the outer peripheral side by an elastic member 67 such as a spring. Since the pressure roll 65 is in contact with the inner peripheral surface of the second conveyor belt 64, the second conveyor belt is pressed from the inner circumference side to the first conveyor belt 62 and the heat sink 66 side with a predetermined pressure.

  The heat sink 66 is a cooling body that cools the first transport belt 62, and is provided on the inner peripheral side of the first transport belt 62 so as to be in contact with the inner peripheral surface thereof. The heat sink 66 includes a base portion 662 that is in contact with the inner peripheral surface of the first transport belt 62, a large number of fins 661 provided substantially perpendicular to the longitudinal direction of the base portion 662, and a case portion 663 that covers the base portion 662 and the fins 661. And two rotating fans 664 provided in the opening of the image forming apparatus 1, and a motor (not shown) as a drive source for rotating these rotating fans 664. The base 662 and the fins 661 are made of aluminum having good thermal conductivity. The base 662 absorbs heat transmitted from the paper via the first conveying belt 62, and the fins 661 cool the heat. 16 is released into the air. The surface area in contact with the air is increased by the fins 661, and the absorbed heat is diffused into the air. The heated air in the cooling device 16 is discharged to the outside of the image forming apparatus 1 by a rotating fan 664 that rotates. In this way, the cooling device 16 takes heat from the sheet and cools the sheet.

  Here, the shape of the heat sink 66 will be described in detail. In the heat sink 66, the contact surface 662a with the first conveyor belt 62 is curved so that the second conveyor belt 64 side is convex. That is, the heat sink 66 has a curved portion that is curved so that the second conveyor belt 64 side is convex. This curving direction is a direction opposite to the curling direction of the curl of the paper conveyed to the cooling device 16. The curved shape of the contact surface 662a is such that the curvature gradually decreases from the upstream side to the downstream side in the paper conveyance direction C.

  FIG. 4 is an enlarged view of only the contact surface 662a. As shown in the figure, the curvature radius R1 of the contact surface 662a at, for example, the position D1 is smaller than the curvature radius R2 at, for example, the position D2 on the downstream side in the paper conveyance direction C when viewed from the position D1. That is, the curvature of the contact surface 662a at the position D1 (upstream side in the paper transport direction C) is larger than the curvature at the position D2 (downstream side of the paper transport direction C). In this relationship of curvature, not only the position D1 and the position D2 but also the curvature continuously changes so that the curvature gradually decreases from the upstream side to the downstream side in the paper conveyance direction C.

[Operation]
Next, the operation of the image forming apparatus 1 will be described. First, the toner images formed by the image forming units 13Y, 13M, 13C, and 13K described above are transferred from the intermediate transfer belt 41 to a sheet. The sheet on which the toner image has been transferred is conveyed to the fixing unit 15, applied with heat and pressure, and then peeled off from the heating roll 51 by the peeling member 53. When the paper is peeled from the heating roll 51, the paper curls so that the surface on which the toner image is formed becomes convex. In the following description, the curl in which the surface on which the toner image is formed is convex is referred to as “down curl”.

  FIG. 5 is a diagram illustrating a state in which the down-curled paper P passes through the cooling device 16. The sheet P on which the toner image T is fixed by the fixing unit 15 is between the first conveyance belt 62 and the second conveyance belt 64 by the conveyance belt 54 with the toner image T on the first conveyance belt 62 side. Be transported. When the paper P enters between the first transport belt 62 and the second transport belt 64, the paper P is pressed against the first transport belt 62 by the second transport belt 64. At this time, the toner image T is still in a fluid state because the toner image T is not sufficiently cooled after being melted by the heating of the fixing unit 15. Therefore, when the paper P is pressed against the first conveying belt 62, the surface on which the toner image T is formed is brought into close contact with the surface of the first conveying belt 62, and the surface of the toner image T becomes smooth. Then, the sheet P moves in the sheet conveying direction C in the drawing as the first conveying belt 62 rotates in a state where the surface on which the toner image T is formed is in close contact with the surface of the first conveying belt 62. To go.

  When the sheet P moves to a position facing the heat sink 66, the paper P is pressed against the heat sink 66 by the pressure rolls 65, so that the sheet P fits the first transport belt 62 curved along the contact surface 662 a of the heat sink 66. Can be brought into close contact with. As described above, the contact surface 662a is curved so that the second conveying belt 64 side is convex, and therefore, the contact surface 662a is curved in the direction opposite to the curling direction of the down-curled paper P. Accordingly, the paper P that is in close contact with the first conveying belt 62 that is curved along the contact surface 662a is curved in a direction opposite to the curl direction of the down curl. At this time, the sheet P is cooled by the heat sink 66 via the first conveying belt 62 in a state where the sheet P is curved in the direction opposite to the curl direction of the down curl. After the heated object is suddenly cooled, it works to maintain its shape when it is in the cooled state. In the case of this paper P as well, the original down curl shape and the opposite direction are curved. This cancels out the effect that is caused and corrects the down curl so that it is flatter than before cooling.

  Furthermore, as described above, the contact surface 662a is curved so that the curvature gradually decreases from the upstream side to the downstream side in the paper conveyance direction C. Accordingly, the sheet P is strongly curved in the direction opposite to the curl direction of the down curl on the upstream side in the sheet conveyance direction C, and gradually becomes flat as it moves downstream. That is, the sheet P heated by the fixing unit 15 is not sufficiently cooled by the heat sink 66, and the curl is strongly corrected while the curl correction effect is maintained at a high temperature. In the vicinity of the outlet, the sheet is further cooled in a flat state in which the curl has been corrected, and after the cooling by the cooling device 16, the flat shape is obtained.

  In this way, the sheet P that has been sufficiently cooled while being brought into contact with the curved portion curved in the direction opposite to the curl direction is conveyed to the downstream end in the sheet conveyance direction C of the first conveyance belt 62, and then the first It is peeled off from the conveyor belt 62. At this time, the temperature of the paper P is cooled from about 100 degrees when heated by the fixing unit 15 to about 72 degrees, and the toner image T on the paper P is placed on the smooth surface of the first transport belt 62. Solidified along. Therefore, the paper P peeled from the first conveying belt 62 is in a flat state in which the toner image T is a glossy image and the down curl is corrected. In this way, the paper P that has been cooled and corrected for down curl by the cooling device 16 is transported to the discharge port by the paper transport path and discharged from the discharge port.

  In addition, when the molten toner image T is cooled from the molten state to the solidified state, unevenness in the cooling state may appear as unevenness in the toner image T. The first conveying belt 62 that is in contact with the paper P on which the toner image T that has passed through the fixing unit 15 and is still in a high temperature and melted state is cooled by the heat sink 66 and the temperature is prevented from rising rapidly. Yes. As a result, temperature unevenness of the first conveying belt 62 is suppressed, so that the melted toner image T can be prevented from coming into contact with uneven temperature, and occurrence of unevenness in the toner image T is suppressed. be able to. Further, since the heat sink 66 is curved in a convex shape, the degree of adhesion between the heat sink 66 and the first conveyor belt 62 is improved as compared with a state where both the heat sink 66 and the first conveyor belt 62 are flat. The heat exchange rate is also improved. In addition, since the heat sink 66 is curved, the conveyance path becomes longer than when the heat sink 66 is not curved. As a result, the path (distance) in which the sheet is in contact with the heat sink 66 via the first transport belt 62 becomes longer, and the heat exchange rate is increased. In addition, in general, when the hair is cooled while being cooled from a high temperature, the curling is performed well, and the paper P is also subjected to curl correction when being cooled from the high temperature. The curl correction power can be increased. If the other conditions are the same, the greater the curvature, the greater the curl correction force and the greater the load on the paper. Conversely, the smaller the curvature, the smaller the curl correction force and the greater the load on the paper. Get smaller. When the load on the paper is large, for example, when there is a difference in speed between the first conveyance belt 62 and the second conveyance belt 64, a conveyance abnormality called a jam occurs, or the toner image T is disturbed. There is a risk of doing. In the above-described embodiment, the contact surface 662a is curved so that the curvature gradually decreases from the upstream side to the downstream side in the paper conveyance direction C, so that the burden on the paper can be reduced.

[Modification]
The above is the description of the embodiment, but the contents of this embodiment can be modified as follows. Moreover, you may combine the following each aspect suitably.
(Modification 1)
In the embodiment described above, the contact surface 662a of the heat sink 66 is curved so that the curvature gradually decreases from the upstream side to the downstream side in the paper conveyance direction C. Thus, the entire contact surface of the heat sink 66 is not curved, but only the upstream side of the contact surface in the paper conveyance direction C is curved, and the downstream side of the paper conveyance direction C may be flat. . FIG. 6 is a view showing a heat sink 66 according to this modification, and FIG. 7 is an enlarged view of only the contact surface 665a of the heat sink 66. As shown in FIG. As shown in FIG. 7, the contact surface 665a of the heat sink 66 is curved in the upstream area E1 in the sheet conveying direction C so that the second conveying belt 64 side is convex like the above-described embodiment. However, in the area E2 on the downstream side in the sheet conveyance direction C, the area E2 is not curved and is flat. That is, a curved portion that is curved in a convex shape is disposed on the upstream side (region E1) of the heat sink 66 in the paper conveyance direction C, and a region downstream in the paper conveyance direction C from the position of the curved portion. E2 is not curved but is a flat planar region. In this case, the sheet is strongly corrected in the down curl while moving in the region E1, and is adjusted to a flat state while moving in the region E2.

(Modification 2)
In the above-described embodiment, the example of correcting the down-curled paper has been described, but the paper curl that can be corrected by the cooling device 16 is not limited to the down-curl. For example, when the paper is thin and the amount of toner in the toner image is large, the toner may be condensed by heating during fixing, and the paper may curl so that the surface on which the toner image is formed becomes concave. . This is called upper curl. FIG. 8 is a diagram showing a configuration of the cooling device 16 for correcting the upper curl. As shown in the figure, in the cooling device 16, the contact surface 666a of the heat sink 66 is curved so that the second conveying belt 64 side is concave. In this case, the sheet is bent in the direction opposite to the curl direction of the upper curl by being brought into close contact with the first conveying belt 62 that is curved along the contact surface 666a. Thereby, the upper curl of the paper is corrected.

(Modification 3)
In the above-described embodiment, an example in which only the downcurled paper is corrected has been described. However, both the downcurled paper and the upper curled paper may be corrected. In this case, a reverse conveyance path is provided between the fixing unit 15 and the cooling device 16. FIG. 9 is a diagram illustrating a configuration in which the reverse conveyance path 17 is provided. As shown in the figure, the reverse conveyance path 17 is provided with a path switching member 171 for switching the sheet conveyance path in accordance with an instruction from the control unit 11. In this case, the control unit 11 determines whether the sheet is an upper curl or a down curl, and causes the path switching member 171 to switch the sheet conveyance path according to the curl direction of the sheet.

  Here, a method for determining the curl direction of the paper will be described. When a user operates a display operation unit such as a touch panel to specify a paper type, the control unit 11 acquires the specified paper type. Each of the plurality of paper storage units 12 stores a single type of paper determined in advance. Therefore, the control unit 11 causes the paper to be conveyed from the paper storage unit 12 in which the designated type of paper is stored, and forms an image on the paper. Further, the control unit 11 acquires the paper type designated by the user, and specifies the thickness of the paper predetermined according to the paper type. The correspondence between the type of paper and its thickness is stored in the storage means in the control unit 11. Subsequently, the control unit 11 counts the number of colored pixels among the total number of pixels of the image data supplied from the image reading unit or the computer apparatus, and determines whether or not the number of colored pixels is equal to or greater than a threshold value. . This threshold value is also stored in the storage means in the control unit 11. When the number of colored pixels is equal to or larger than the threshold value, the control unit 11 determines that the toner amount of the toner image formed based on the image data is large. When the number is smaller than the threshold value, the control unit 11 forms based on the image data. It is determined that the toner amount of the toner image to be printed is small. Then, the control unit 11 determines whether the sheet is an upper curl or a down curl based on the sheet thickness and the toner amount determined as described above. For example, the control unit 11 determines that the paper is upper curled when the paper is thin and has a large amount of toner, and otherwise determines that the paper is down curled.

  As described above, when it is determined that the sheet is down-curled, the control unit 11 causes the path switching member 171 to switch the sheet conveyance path to a path that does not convey the sheet to the reverse conveyance path 17 side. In this case, the sheet that has passed through the fixing unit 15 is directly conveyed to the cooling device 16 as in the above-described embodiment, and the down curl is corrected. On the other hand, when it is determined that the sheet becomes an upper curl, the control unit 11 causes the path switching member 171 to switch the sheet conveyance path to the path along which the sheet is conveyed to the reverse conveyance path 17. In this case, the paper that has passed through the fixing unit 15 is first transported to the reverse transport path 17 and is switched back there, so that the paper is transported to the cooling device 16 with the front and back surfaces reversed. Become. That is, the paper that has been the upper curl is conveyed to the cooling device 16 in the same state as that of the down curl. Thereby, the upper curl of the sheet is corrected in the same manner as in the above-described embodiment.

  In the above-described modification, it is determined whether the paper is an upper curl or a down curl based on the paper type and the toner amount specified by the user. Is not limited to this. For example, the curl direction of the paper may be determined using an optical sensor or the like. In this case, the optical sensor is provided above the sheet conveyance path on the downstream side of the fixing unit 15, for example. For example, when the time until the optical sensor receives the reflected light of the light emitted toward the paper is long at the front end of the paper, short at the center, and long at the rear end. Determines that the paper is down-curled. On the other hand, when the time until the optical sensor receives the reflected light of the light emitted toward the paper by the optical sensor is short at the front end of the paper, long at the center, and short at the rear end, It is determined that the paper is upper curl.

(Modification 4)
In the embodiment described above, the pressure roll 65 presses the second conveyor belt 64 against the heat sink 66 with a predetermined pressure, but this pressure may be changed according to the curl amount of the paper. In this case, the other end of the elastic member 67 that supports the rotating shaft of the pressure roll 65 at one end is in contact with a drive unit such as a solenoid, and the control unit 11 drives the drive unit to The second conveyor belt 64 is pressed against the heat sink 66 with a pressure corresponding to the curl amount of the sheet. In this case, the EEPROM 114 of the control unit 11 stores a pressure control table for controlling the pressure applied by the pressure roll 65. FIG. 10 is a diagram illustrating an example of the pressure control table L. As illustrated in FIG. As shown in the figure, in the pressure control table L, “toner amount”, “sheet thickness” of the toner image, and pressure are associated with each other. In the drawing, “strong” represents that the pressure to be pressed is large, “weak” represents that the pressure to be pressed is small, and “medium” represents that the pressure to be pressed is medium. In this pressure control table L, for example, when “toner amount” is “large” and “paper thickness” is “thin”, “strong” is specified as the pressure applied by the pressure roll 65. . This is because when the “toner amount” is “large” and the “paper thickness” is “thin”, the curl amount of the paper tends to increase. This is because the pressure of the pressure roll 55 needs to be increased. On the other hand, in this pressure control table L, when “toner amount” is “low” and “paper thickness” is “thick”, “weak” is specified as the pressure applied by the pressure roll 65. The This is because when the “toner amount” is “low” and the “paper thickness” is “thick”, the curl amount of the paper tends to decrease, so the pressure of the pressure roll 65 is reduced. However, this is because the curl is sufficiently corrected. In other cases, “medium” is specified as the pressure applied by the pressure roll 65.

  Next, the operation in this modification will be described. The control unit 11 specifies the thickness of the paper, determines the toner amount of the toner image, and information indicating the thickness of the paper and information indicating the toner amount of the toner image in the same manner as the third modification described above. And get. Subsequently, the control unit 11 refers to the pressure control table L stored in the memory, and specifies the pressure associated with the acquired information indicating the thickness of the paper and the information indicating the toner amount. For example, when the information that the paper is thin and the information that the toner amount is large are acquired, the pressure of “strong” that associates the paper thickness with “thin” and the toner amount “high” is specified. Is done. In this case, the control unit 11 performs control to drive the drive unit so as to apply a “strong” pressure to the pressure roll 65. In response to this driving, the pressure roll 65 presses the second conveyor belt 64 against the heat sink 66 with a “strong” pressure. As described above, the control unit 11 performs the control of pressing with an appropriate pressure corresponding to the curl amount, whereby the curl correction can be performed with a correction force corresponding to the curl amount of the paper. Therefore, excessive correction of curl with a strong correction force is prevented.

  In the pressure control table L described above, “toner amount”, “paper thickness”, and pressure are associated with each other, but “toner amount” and pressure, or “paper thickness” and pressure only. May be associated with each other. In this case, when “toner amount” is “large” or “paper thickness” is “thin”, “strong” is specified as the pressure applied by the pressure roll 65, and “toner” When the “amount” is “small” or the “paper thickness” is “thick”, “weak” may be specified as the pressure applied by the pressure roll 65. This is because when the “toner amount” is “large” or when the “paper thickness” is “thin”, the curl amount tends to increase, and the “toner amount” is “low”. This is because the curl amount tends to decrease when the “paper thickness” is “thick”.

(Modification 5)
In the above-described embodiment, each pressure roll 65 presses the second conveyor belt 64 against the curved portion side of the heat sink 66 with a predetermined pressure, but this pressure is different for each pressure roll 65. It may be allowed. That is, each pressure roll 65 may press the sheet conveyed by the first conveyance belt 62 against the heat sink 66 side with different pressures. For example, the pressure of the pressure roll 65 disposed on the upstream side in the paper conveyance direction C is increased, and the pressure roll 65 disposed on the downstream side is weakened. In this case, the curl of the paper P is more strongly corrected on the upstream side in the paper transport direction C. Further, the pressure of the pressure roll 65 disposed on the upstream side in the paper conveyance direction C is weakened, the pressure of the pressure roll 65 disposed on the midstream side is increased, and the pressure of the pressure roll 65 disposed on the downstream side is increased. It may be weakened. In this case, the sheet P is different at each position of the curved portion such that the curl is corrected weakly on the upstream side in the sheet conveyance direction C, the curl is corrected strongly on the midstream side, and the curl is corrected weakly on the downstream side. The curl is corrected step by step by the correction force. Since the temperature of the sheet is high on the upstream side in the sheet conveyance direction C, if the sheet is strongly curved, the image on the sheet may be disturbed. However, the pressure of the pressure roll 65 disposed on the upstream side is weakened. Then, the disturbance can be suppressed, and if the pressure of the pressure roll 65 arranged on the middle stream side is increased, the curl correcting force is increased.

  In the above-described embodiment, since it is assumed that the sheet is cooled by the heat sink 66 to a sufficiently low temperature that makes it difficult to correct curl, the curl correction force is strong on the upstream side in the sheet conveyance direction C. The curl correction force is weakened on the upstream side in the paper conveyance direction C. On the other hand, the cooling power of the heat sink 66 is weaker than in the case of the embodiment, and even when the heat sink 66 is in a region on the downstream side in the transport direction of the heat sink 66, a temperature that can efficiently correct curl is held on the paper. May weaken the pressure of the pressure roll 65 disposed on the upstream side in the paper conveyance direction C and increase the pressure of the pressure roll 65 disposed on the downstream side. In this case, the curl of the paper P is gradually corrected from the upstream side to the downstream side in the paper transport direction C. If the paper is strongly curved, the toner image on the paper is disturbed by the curvature. As described above, if the curl is gradually corrected from the upstream side to the downstream side in the paper conveyance direction C as described above, the toner image is suddenly strong in a fluid state on the upstream side in the paper conveyance direction C. As compared with the case where pressure is applied, the disturbance of the toner image is suppressed.

(Modification 6)
In the above-described embodiment, the example of the peeling of the fixing unit 15 is given as an example of the factor that causes the paper to curl. For example, the paper may be curled due to the influence of heat from the fixing roller, the toner being pulled due to the condensation of the toner due to the difference in expansion ratio between the front surface and the back surface of the paper, the paper transport path itself being bent, etc. In addition, when a long sheet is wound and stored in the sheet storage unit, the sheet curls during the storing period. The cooling device 16 described above can correct the curl in the same manner as described above even if the paper curl has occurred for various reasons. Therefore, any cause of paper curl may be used.

(Modification 7)
In the above-described embodiment, the fixing unit 15 includes the heating roll 51 and the pressure roll 52, but the configuration of the fixing unit 15 is not limited thereto. For example, the fixing unit 15 may include a heating roll 51 and a pressure belt. This pressure belt is composed of a belt member and a pressure pad, and the pressure pad presses the belt member against the heating roll 51 side, whereby pressure is applied to the paper passing between the heating roll 51 and the pressure belt. It is supposed to add. In short, the fixing unit 15 only needs to apply heat and pressure to the paper on which the toner image has been transferred by the transfer unit 14 to fix the toner image on the paper.

(Modification 8)
In the above-described embodiment, the cooling device 16 is provided with the second conveyance belt 64 as a configuration for supporting the conveyed paper. However, this configuration is not limited to the belt shape, but a plate-shaped guide member or the like. There may be. If this guide member is formed of a relatively soft material, the sheet can be pressed against the curved portion 662 a side of the heat sink 66 by the pressure roll 65.

(Modification 9)
In the embodiment described above, the pressure roller 65 is provided in the cooling device 16 as a configuration for pressing the paper against the curved portion 662a side of the heat sink 66, but this configuration may not be a roll shape. In short, the cooling device 16 only needs to be provided with a pressing member that presses the paper against the heat sink 62 side.

(Modification 10)
In the above-described modification 4, the example in which the pressure control of the pressure roll 65 is changed depending on the thickness of the paper has been described, but the pressure control of the pressure roll 65 may be different between the coated paper and the non-coated paper. Good. Further, the object on which the toner image is formed is not limited to paper, but an image may be formed on a plastic card, for example, and fixed and cooled.

1 is a diagram illustrating a configuration of an image forming apparatus according to an exemplary embodiment. FIG. 2 is a block diagram illustrating an internal configuration of a control unit of the image forming apparatus. It is a figure which shows the detailed structure of the cooling device of the said image forming apparatus. It is the figure which expanded only the contact surface of the said cooling device. It is a figure which shows a mode that the paper curled down passes a cooling device. It is a figure which shows the heat sink which concerns on a modification. It is the figure which expanded only the contact surface of the heat sink. It is a figure which shows the structure of the cooling device for correcting the upper curl which concerns on a modification. It is a figure which shows the structure provided with the inversion conveyance path | route which concerns on a modification. It is a figure which shows an example of the pressure control table which concerns on a modification.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Image forming apparatus, 11 ... Control part, 12 ... Paper storage part, 13Y, 13M, 13C, 13K ... Image forming unit, 14 ... Touch panel, 15 ... Fixing part, 16 ... Cooling device, 41 ... Intermediate transfer belt, 42 ... secondary transfer roll, 43 ... opposite roll, 17 ... main storage device, 51 ... heating roll, 52 ... pressure roll, 53 ... peeling member, 54 ... conveying belt, 61 ... first conveying roll, 62 ... first conveying Belt, 63 ... second transport roll, 64 ... second transport belt, 65 ... pressure roll, 66 ... heat sink, 67 ... elastic member, 661 ... fin, 662,665-666 ... base, 662a, 665a-666a ... contact Surface, 663... Case portion, 664.

Claims (8)

Image forming means for forming an image on a recording material;
Fixing means for fixing the image to the recording material by applying heat and pressure to the recording material on which the image is formed by the image forming means;
A first belt member for conveying the recording material on which an image is fixed by the fixing unit;
A curved portion that is in contact with the inner periphery of the first belt member and is curved in a direction opposite to the curve in the conveyance direction of the recording material on which the image is fixed by the fixing unit, is conveyed by the first belt member. A cooling body that cools the recording material that is formed through the first belt member in a region including the curved portion;
An image forming apparatus comprising: a pressing member that presses the recording material conveyed by the first belt member against the curved portion side of the cooling body. The image forming apparatus according to claim 1, wherein the curved portion is provided on an upstream side of the cooling body in a conveyance direction of the recording material. The image forming apparatus according to claim 2, wherein the curved portion is continuous to the downstream side in the conveyance direction of the recording material, and the curvature on the downstream side of the curved portion is smaller than the curvature on the upstream side. The image forming apparatus according to claim 2, wherein the cooling body has a planar area downstream of the curved portion in the conveyance direction of the recording material. The image forming means is a means for forming an image using a color material,
Information acquisition means for acquiring information representing the amount of the color material of the image formed by the image forming means or the thickness of the recording material onto which the image is transferred;
2. A control unit that controls the pressing member to adjust a pressing force that presses the recording material against the curved portion side according to information acquired by the information acquisition unit. The image forming apparatus described The pressing member includes a plurality of pressing members, and the control means controls the pressing of the recording material conveyed by the first belt member to the bending portion side with different forces. Item 6. The image forming apparatus according to Item 5. There are a plurality of the pressing members, and the pressing member arranged on the upstream side in the conveyance direction of the recording material is more than the pressing member arranged on the downstream side in the conveyance direction of the recording material. The image forming apparatus according to claim 1, wherein a force for pressing the recording material conveyed by one belt member against the curved portion side is large. The image forming apparatus according to claim 1, wherein the pressing member includes a second belt member disposed on an inner peripheral surface thereof.

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