JP5195080B2 - Fixing apparatus and image forming apparatus - Google Patents

Description

  The present invention relates to a fixing device for an image forming apparatus using an electrophotographic method, and more particularly to a fixing device capable of preventing deformation such as curling of a transfer material and an image forming apparatus provided with the fixing device.

Conventionally, in an image forming apparatus using an electrophotographic system such as a copying machine, a printer, or a facsimile, the surface of the image carrier is uniformly charged by a charging device, and laser light or LED light is emitted based on image information. An electrostatic latent image is formed on the image carrier by exposure from an exposure apparatus such as the above. Then, the electrostatic latent image is visualized with toner of a developing device, and the toner image is transferred to a transfer material such as transfer paper through a transfer device. Thereafter, the toner image formed on the transfer material is conveyed to a fixing device, and is passed between a heating member and a pressure member to be heated and pressurized to fix the toner image on the transfer material. Yes.
In such a fixing apparatus, the transfer material that has passed through the pressure contact portion between the heating member and the pressure member is curled due to the shape of the pressure contact portion and the properties of the transfer material, and the paper is discharged in a curled shape. End up. As a result, problems such as a decrease in print quality and a tendency to cause clogging of the transfer material in the transport path after fixing are caused.
In order to prevent this, a device that corrects deformation in the path after fixing, for example, a correction device described in Patent Document 1 is generally employed. Also, depending on the material of the transfer material, there are some that try to suppress the curl deformation by lowering the heating temperature at the time of fixing from the standard, and in addition, multiple curl correction devices are installed to cope with the curled state due to the transfer material There are some (see, for example, Patent Document 2).
JP 2001-261111 A Patent 3049628

However, in the one described in Patent Document 1, the correction device is disposed at a position separated from the fixing device, and the curling deformation of the transfer material that occurs in the process of being fed out from the fixing device and conveyed is corrected. There is a problem that a large correction force must be applied to the curled transfer material, which not only increases the size of the correction device, but also makes the transfer material insufficiently corrected.
Further, in the case of the one described in Patent Document 2, as in the case of Patent Document 1, two correction devices for correcting the deformation of both surfaces of the transfer material are arranged at a position separated from the fixing device, so that the curl deformation occurs. A large correction force must be applied to the transfer material, and not only the individual correction devices are increased in size, but also a large number of parts are required, resulting in an increase in the size of the device and an increase in cost.
The present invention has been made in view of the above circumstances, and provides a fixing device capable of easily and reliably correcting a transfer material with a simple structure and an image forming apparatus including the same. Objective.

In order to solve the above problems, the invention described in claim 1 is a heating means for heating the surface of a transfer material having a toner image transferred to the surface, and a pressurizing means for pressing the transfer material against the heating means. In the fixing device that heats and presses the transfer material by the heating means and the pressurizing means, and fixes the toner image on the transfer material, the pressurizing means faces the heating means. An endless pressure belt that is stretched between a pressure roller that rotates and a support roller disposed on the downstream side in the conveyance direction of the transfer material, and the transfer material is placed on the support roller on the endless pressure belt. And a correction means for correcting the curl deformation of the transfer material by pressing to H1, the hardness of the endless pressure belt is H1, the hardness of the contact portion of the heating means with the transfer material is H2, and the transfer material of the correction means When the hardness of the contact part with H3 is H3, H2 <H1 < Characterized in that it is set to have a third relationship.
According to a second aspect of the present invention, in the fixing device according to the first aspect, the correction unit includes a pressing force control unit that controls a pressing force to the transfer material.
According to a third aspect of the present invention, in the fixing device according to the second aspect, the pressing force control means controls the pressing force to change in accordance with a material of the transfer material or an environmental condition of the fixing device. It is characterized by.
According to a fourth aspect of the present invention, there is provided the fixing device according to any one of the first to third aspects, wherein the charge applying means applies a charge for adsorbing the transfer material to the surface of the endless pressure belt. It is provided with.
According to a fifth aspect of the present invention, in the fixing device according to the fourth aspect, the charge applying unit changes the applied charge in accordance with a transfer condition when the toner image is transferred onto the transfer material. It is controlled.
According to a sixth aspect of the present invention, there is provided an image forming unit that supplies toner to an electrostatic latent image formed on an image carrier and converts the electrostatic latent image into a toner image, and the image forming unit. 6. An image forming apparatus comprising: a transfer unit that transfers a toner image onto the surface of a transfer material; and a fixing device that fixes the toner image transferred by the transfer unit onto the transfer material. A fixing device according to any one of the above.

  According to the present invention, the pressure means provided with the endless pressure belt stretched between the pressure roller facing the heating means and the support roller disposed on the downstream side in the conveyance direction of the transfer material is used. A correction means for correcting the curl deformation of the transfer material by pressing the transfer material against the endless pressure belt on the support roller, the hardness of the endless pressure belt is H1, and the transfer material of the heating means When the hardness of the abutting portion is H2, and the hardness of the abutting portion with the transfer material of the correcting means is H3, by setting to have a relationship of H2 <H1 <H3, the structure is simple, It is possible to provide a fixing device capable of easily and surely correcting a transfer material and an image forming apparatus including the same.

As a result of studying the correction of curl deformation of the transfer material generated by being heated by the fixing device, the inventor has corrected the curl deformation by heating and applying the transfer material having a toner image on the surface thereof by the fixing device. It was determined that it is effective to apply a correction force to correct the curl deformation to the surface of the transfer material at the initial stage of the fixing process in which preheating by the fixing device remains when the pressure is applied. Based on this investigation, as a result of further investigation, as a pressure unit of the fixing device, a pressure roller that applies a pressing force to the heating unit, and a support roller disposed on the downstream side in the conveyance direction of the transfer material, A structure in which an endless pressure belt is stretched between the supporting roller and a correcting means for correcting the curl deformation by pressing the surface of the transfer material on the supporting roller is effective. I found out.
Further, in the fixing device having such a structure, the hardness of the endless pressure belt is H1, the hardness of the contact portion of the heating means with the transfer material is H2, and the contact portion of the correction means with the transfer material is When the hardness is set to H3, it is found that if the relationship of H2 <H1 <H3 is set, the curl deformation of the transfer material can be corrected easily and reliably, and the present invention is completed. It came. Hereinafter, the present invention will be described based on embodiments.

FIG. 1 is a diagram showing a schematic configuration of a color image forming apparatus according to an embodiment of the present invention.
The image forming apparatus according to this embodiment includes image forming units 1Y, 1M, 1C, and 1B that form yellow (Y), magenta (M), cyan (C), and black (B) toner images. As shown in FIG. 1, the image forming units 1Y, 1M, 1C, and 1B are stretched around support rollers 21, 22, and 14, and one of these support rollers 21, 22, and 14, for example, the support roller 14 The endless intermediate transfer belt 2 that is transported in the direction of the arrow A by the rotational driving force is juxtaposed along the transport direction to constitute a tandem color image forming unit.
The image forming units 1Y, 1M, 1C, and 1B have drum-shaped photoreceptors 3Y, 3M, 3C, and 3B that are image carriers that rotate in the directions of arrows, respectively. A charging device 4 for uniformly charging the surfaces of the photoreceptors 3Y, 3M, 3C, and 3B around 3C and 3B, and yellow (Y), magenta (M), cyan (C), and black (B). Developing devices 7Y, 7M, 7C, and 7B that store toner and supply toners of the respective colors to the respective photoreceptors 3Y, 3M, 3C, and 3B are provided. Also, above the photoconductors 3Y, 3M, 3C, and 3B, writing based on image information of yellow (Y), magenta (M), cyan (C), and black (B) transmitted from a scanner or a printer or the like. An exposure apparatus that outputs a laser beam in accordance with the dent image signal and irradiates the photosensitive members 3Y, 3M, 3C, and 3B with laser light through optical systems of rotating polygon mirrors 6Y, 6M, 6C, and 6B. 5Y, 5M, 5C, and 5B are provided.

A case where a color image is printed by this image forming apparatus will be described.
First, the surfaces of the rotating photoreceptors 3Y, 3M, 3C, and 3B are uniformly charged by the respective charging devices 4. The surfaces of the photoreceptors 3Y, 3M, 3C, and 3B that are charged in this way are irradiated with laser light based on the respective color images from the exposure devices 5Y, 5M, 5C, and 5B, and static images corresponding to the respective colors. An electrostatic latent image is formed. In this case, the polygon mirrors 6Y, 6M, 6C, and 6B can perform main scanning on the photosensitive member by being driven to rotate at a constant high speed by a motor. The electrostatic latent image is written by applying a position signal of a pixel unit to be recorded by the control device to the writing LD so that the pixel position is synchronized with the rotational position of the polygon mirror, and the density of the pixel as the image density. The image data of yellow (Y), magenta (M), cyan (C), and black (B), which are the primary colors of the toner after data processing, is performed by turning on / off the laser light in accordance with the write signal. Yes.
In this way, the toner of each color is supplied from the developing devices 7Y, 7M, 7C, and 7B to the electrostatic latent images formed on the surfaces of the photoreceptors 3Y, 3M, 3C, and 3B, and electrostatic The latent image is converted into a toner image. In this embodiment, a reversal development method using negatively charged toner is employed.

On the other hand, primary transfer rollers 9a, 9b, 9c, and 9d disposed on the back side of the intermediate transfer belt 2 disposed below the photoreceptors 3Y, 3M, 3C, and 3B come into contact with the intermediate transfer belt 2. A primary bias is applied by power supplies 31a, 31b, 31c, and 31d connected to the primary transfer rollers 9a, 9b, 9c, and 9d, respectively. As a result, toner images of the respective colors on the photoreceptors 3Y, 3M, 3C, and 3B are electrostatically superimposed and transferred onto the intermediate transfer belt 2, and four color toner images are superimposed to form a color toner image. Is done.
The intermediate transfer belt 2 on which the color toner image is formed in this way is transferred to the secondary transfer roller 23 via the support roller 21. A transfer sheet P as a transfer material in a transfer sheet cassette (not shown) is fed to the secondary transfer roller 23 at a timing set at the same time, and once stopped at the registration roller 12, the transfer sheet P is transferred by the registration roller 12. Is sent to the secondary transfer roller 23 in accordance with the transfer timing of the color toner image from the intermediate transfer belt 2. Electric charges are supplied to the secondary transfer roller 23 by a power source 25, and the color toner image on the intermediate transfer belt 2 is collectively transferred onto the fed transfer paper P.
In this embodiment, as the photoreceptors 3Y, 3M, 3C, and 3B, drum-shaped cylinders having a diameter of 30 mm are coated with negatively chargeable OPC, and charging rollers are used for charging. Further, the developing devices 7Y, 7M, 7C, and 7B use a two-component developing system in which the carrier and the toner are stirred and charged. The toner is negatively charged and forms a toner image on the latent image portion exposed by the laser beam.

The primary transfer rollers 9a, 9b, 9c, and 9d are metal rods and are arranged so as to be shifted to the downstream side in the traveling direction of the intermediate transfer belt 2 from directly below the photoreceptors 3Y, 3M, 3C, and 3B. The rollers 9a, 9b, 9c, and 9d are connected to high-voltage power supplies 31a, 31b, 31c, and 31d through power supplies by feeding.
The intermediate transfer belt 2 has a two-layer structure of a base layer and a surface layer, and is formed with a total thickness of 150 μm. The surface layer is formed of a resin layer in which PTEF, which is a fluororesin with a good releasability and has a volume resistivity of about 1 × 10 ¹² Ω · cm with a thickness of about 10 μm, and the base layer preferably has a volume resistance of 1 × 10 ⁷ Ω · cm to 1 × 10 ⁹ Ω · cm NBR and EPDM rubber. By setting the volume resistance value of the base layer of the intermediate transfer belt 2 to a range of at least 10 ⁶ to 10 ¹¹ Ω · cm, image formation on the four photoconductors 3Y, 3M, 3C, and 3B is reliably transferred, In addition, the image formation on the transfer paper P can be performed so that there is no abnormal image.

The secondary transfer roller 23 is formed on a core metal having a diameter of 10 mm with a conductive rubber layer having a volume resistivity of 1 × 10 ⁸ Ω · cm, such as chloroprene rubber, urethane rubber, or elastomer resin. Is connected to a high-voltage power supply 25 through a power supply spring. In addition, the support roller 14 that is the opposite roller of the secondary transfer roller 23 is grounded. The secondary transfer roller 23 is rotated by applying pressure to the intermediate transfer belt 2 by a spring and further transmitting a driving force from a motor through a gear. The transferred transfer paper P is supplied with current from the power source to the secondary transfer roller 23 to transfer the color toner image on the intermediate transfer belt 2. The transfer paper P onto which the color toner image has been transferred and transferred by the secondary transfer roller 23 in this way is sent to the fixing device 8, and the color toner image transferred and transferred to the surface of the P is transferred as described later. The toner is fixed on the transfer paper P by being heated and pressurized by the transfer device 8.
In the image forming apparatus of the present embodiment, the intermediate transfer belt 2 is used for the toner image on the photoconductor, and the toner image on the photoconductor is transferred to the intermediate transfer belt by the primary transfer rollers 9a, 9b, 9c, 9d. After the transfer onto the transfer sheet 2, the toner image on the intermediate transfer belt 2 is transferred onto the transfer paper P by the secondary transfer roller 23. However, the toner image on the photosensitive member may be directly transferred onto the transfer paper P by transfer means such as a transfer roller without using the intermediate transfer belt 2.

The present invention is characterized by the configuration of the fixing device. Embodiments of a fixing device according to the present invention will be described in detail with reference to the drawings.
FIG. 2 is a diagram showing a schematic configuration of the fixing device according to the first embodiment of the present invention. As shown in FIG. 2, the fixing device 8 according to the first embodiment includes a heater 34 at the center as a heating unit that heats the toner image on the transfer paper P, and a heating roller 30 that is rotatably mounted. It has. Further, the pressure roller 38 is rotatably mounted as a pressure means so as to face the heating roller 30, and is arranged on the downstream side in the transfer direction B of the transfer paper P, and is stretched around a drive support roller 41 that is driven to rotate. The endless pressure belt 37 is provided.
The endless pressure belt 37 is transferred in the direction of arrow C by the rotational drive of the support drive roller 41. The pressure belt 37 is pressed toward the heating roller 30 by a spring member 45 that presses the bearing portions 38 b of the rotating shaft 38 a at both ends of the pressure roller 38.
Further, as shown in FIG. 2, on the driving support roller 41, correction is performed as a correction means for correcting the curl deformation of the transfer paper P by pressing the surface of the transfer paper P placed on the pressure belt 37. A roller 42 is rotatably mounted on the rotation shaft 42a. The transfer paper P on the pressure belt 37 is pressed toward the support drive roller 41 by the spring member 43 that is pressed by the bearing portions 42b of the rotating shaft 42a at both ends of the correction roller 42. Accordingly, the pressure belt 37 is transferred in the C direction along with the rotation of the drive support roller 41, the heating roller 30 and the correction roller 42 are rotated, and the transfer paper P having the toner image on the surface is heated by the heating roller 30. The toner of the toner image is melted and softened by the pressing force of the pressure roller 38, and the toner image is fixed and fixed on the transfer paper P.

In this way, when the toner image on the transfer paper P is fixed, the transfer paper P tends to be curled with the surface as a concave surface. In this embodiment, with respect to the curl deformation of the transfer paper P, the transfer paper P on the pressure belt 37 is also conveyed in the B direction along with the transfer of the pressure belt 37 in the C direction. The pressure belt 37 is pressed and clamped at the nip portion N2 between the roller 41 and the correction roller 42, and the curl deformation of the transfer paper P is corrected.
In this case, when the hardness of the contact portion 30a (the peripheral surface of the heating roller 30) that contacts the transfer paper P of the heating roller 30 is H2, H2 is a hardness specified by JIS-A of 20 to 50, Preferably it is set to 25-30. The heating roller 30 is configured by forming a resin layer 31 having heat resistance and good releasability on the peripheral surface of a pipe-shaped cored bar 32. A pipe 34 is provided with a heater 34.
Accordingly, the distal end of the separation claw 35 and the thermistor 36 are disposed on the peripheral surface 30 a of the resin layer 31. Further, an entrance guide 39 having a leading end directed to the nip portion N1 is disposed on the transfer paper P entrance side of the nip portion N1 between the heating roller 30 and the pressure roller 38. In the fixing apparatus according to the present embodiment, the transfer paper P having the transfer toner image on the surface is guided by the entrance guide 39 and passed between the heating roller 30 and the pressure belt 37 and the transfer toner image on the transfer paper P is heated. Fixes with pressure. At that time, the thermistor 36 detects the surface temperature of the heating roller 30, receives the detection signal, appropriately controls the heating temperature by a control unit (not shown), and turns on the heater 34 to keep the surface temperature of the heating roller 30 constant. It keeps in.

The hardness specified by JIS-A is a hardness that measures the hardness of general rubber specified by JIS standard (JIS K6253). An indenter (called a push needle or indenter) is pushed into the surface of the object to be measured. It is a value of measurement using a spring type rubber hardness meter that measures the amount of deformation and digitizes it. In this embodiment, a heating roller is used as the heating means. However, the heating roller 30 is not limited to a roller body such as the heating roller 30 and may be an endless belt body or a pad-shaped body.
On the other hand, the pressure belt 37 is stretched around the inner periphery thereof by the pressure roller 38 and the drive support roller 41 as described above. The pressure roller 38 is supported at both ends of a rotary shaft 38a by a cubic bearing portion 38b. A biasing spring 45 is attached to the bearing portion 38b, and the pressure roller 38 and the pressure belt are supported by the biasing spring 45. 37 is pressed against the heating roller 30.
The hardness of the pressure belt 37 on the pressure roller 38 facing the heating roller 30 is H1. The hardness H1 of the contact portion of the pressure belt 37 with the heating roller 30 is larger than the hardness H2 of the heating roller 30, and by applying the contact pressure, the heating roller 30 bites into the heating roller 30 as shown in FIG. The contact area of the abutting portion (nip portion N1) becomes large and fixing is sufficiently performed. Further, the shape of the nip portion N1 follows the shape of the pressure belt 37 and the pressure roller 38, and the transfer paper P is also deformed to that shape. The pressure belt has a hardness H1 of 50 to 80 according to JIS-A. Preferably, 70-80 is desirable.

Further, the correction roller 42 is set to have a hardness of the contact portion 42c as H3 and larger than the hardness H1 of the pressure belt 37, for example, 70 to 100 according to JIS-A, and as shown in FIG. Encroach into the pressure belt 37. As the correction roller 42, a roller in which a correction layer 42c made of a rubber material, a metal, or the like is formed on a core metal constituting the rotating shaft 42a can be used. As described above, the relationship between the hardnesses of the respective members in pressure contact with the transfer paper P is adjusted and set so as to satisfy H2 <H1 <H3. As a result, the transfer paper P that has been curled and deformed in accordance with the shape of the pressure belt 37 and the pressure roller 38 at the portion with the heating roller 30 remains preheated from the heating roller 30 and the correction roller 42. Therefore, it is pressed in the opposite direction. As a result, the transfer paper P that has been curled at the nip N1 with the heating roller 30 is straightened and deformed by the straightening roller 42, and when it is discharged from the fixing device 8, the curled deformation is corrected.
Although the correction roller 42 is used as the correction unit of the fixing device 8 according to the first embodiment, the correction unit is not limited to the roller but may be a pad member.

Next, a fixing device according to a second embodiment of the present invention will be described with reference to FIG.
FIG. 3 is a diagram showing a schematic configuration of the fixing device according to the second embodiment of the present invention.
The fixing device 8 according to the second embodiment is different from the fixing device according to the first embodiment described above in that a pressing force urging unit for the correction roller 42 is provided. In the fixing device 8 according to the second embodiment, cam means 50 is used instead of the spring member 43 in the first embodiment as means for urging the transfer paper P with a pressing force.
That is, as shown in FIG. 3, a spring member (not shown) that presses upward (in a direction away from the drive support roller 41) is attached to the bearing portion 42 b of the correction roller 42, and comes into contact with the rotation shaft 42 a of the correction roller 42. A regulating member 52 that regulates the upward movement of the rotating shaft 42a is attached so as to be movable in the direction of arrow D. The restricting member 52 is attached so as to come into contact with the cam surface 51b of the rotating cam 51 that rotates in the arrow E direction around the rotating shaft 51a. Therefore, when the rotary cam 51 rotates in the direction of arrow E, the regulating member 52 moves in the vertical direction (D direction), and the pressing force of the correction roller 42 against the drive support roller 41 can be changed. Yes.
Further, the rotary cam 51 is configured so that a driving motor (not shown) that rotates and drives the rotary cam 51 is changed by the pressing force control means 53 according to the material such as the thickness and type of the transfer paper P. The rotation angle of 51 is controlled. Therefore, depending on the material or the like of the transfer paper P, it is possible to reliably correct the curl deformation by pressing the transfer paper P curled by the correction roller 42 with an appropriate pressing force.

Next, a fixing device according to a third embodiment of the present invention will be described with reference to FIG.
FIG. 4 is a diagram showing a schematic configuration of a fixing device according to the third embodiment of the present invention.
The fixing device 8 according to the third embodiment is different from the fixing device according to the first embodiment described above in that it includes a charge applying unit that applies a charge that attracts the transfer paper P to the pressure belt 37. Yes. In the fixing device 8 according to the second embodiment, the driving support roller 41 is formed of a conductive material such as metal, and a variable voltage is applied to the rotating shaft 41a from the power source 54 to In addition, the charge for sucking the transfer paper P can be charged.
As this voltage, for example, a voltage obtained by superimposing a negative voltage on an AC voltage can be used. As a result, the transfer paper P discharged from the heating roller 30 can be stably conveyed without being wrapped around the heating roller 30 and can be reliably conveyed to the correction roller 42.

Next, a fixing device according to a fourth embodiment of the present invention will be described with reference to FIG.
FIG. 5 is a diagram showing a schematic configuration of a fixing device according to the fourth embodiment of the present invention.
The fixing device 8 according to the fourth embodiment is an improvement of the fixing device according to the third embodiment described above. In the fixing device according to the above-described third embodiment, a variable voltage is applied to the pressure belt 37 from the power source 54 to be charged, and the transfer paper P is sucked to the pressure belt 37, thereby stably conveying the transfer paper P. It has become However, the transfer paper P is charged by the secondary transfer roller 23 when the toner image is transferred from the intermediate transfer belt 2.
In this case, since the transfer voltage changes depending on the front and back of the transfer paper P, the paper type, the size of the paper, etc., the charge amount of the transfer paper P varies. Therefore, in consideration of the charging by the secondary transfer roller 23, the intended purpose may not be achieved unless the pressure belt 37 is charged. Therefore, in the fourth embodiment, the voltage applied to the secondary transfer roller 23 is detected, and the voltage applied to the pressure belt 37 is detected by the CPU (computer processing unit) based on this voltage. By controlling, it is adjusted and controlled. By performing such control, the charge amount to the pressure belt is appropriately controlled, and the transfer of the transfer paper P can be reliably stabilized.

Next, a fixing device according to a fifth embodiment of the present invention will be described with reference to FIG.
FIG. 6 is a diagram showing a schematic configuration of a fixing device according to the fifth embodiment of the present invention.
The fixing device 8 according to the fifth embodiment is a combination of the pressing force urging means according to the second embodiment and the charge applying means according to the third embodiment. In the fixing device 8 according to the fifth embodiment, a sensor 56 that detects the thickness and charge amount of the transfer paper P is disposed between the fixing device 8 and the secondary transfer roller 23, and the sensor 56 detects the thickness. The material such as the thickness and type of the transfer paper P and the charge amount are detected, and based on these detection data, the pressing force of the correction roller 42 by the cam means 50 and the applied voltage to the pressure belt 37 are controlled by the control means 57. I try to control it. Therefore, it is possible to more reliably correct the curl deformation by applying a pressing force by the correction roller 42 and a voltage applied to the pressure belt 37 according to the material of the transfer paper P.
In the fifth embodiment, the material and the charge amount of the transfer paper P are detected as the sensor 56, but in addition to these detections, the environment such as the temperature and humidity around the fixing device 8 is detected. The conditions may be detected, and the pressing force of the correction roller 42 and the applied voltage of the pressure belt 37 may be controlled by the control unit 57 based on these environmental conditions.

Next, a fixing device according to a sixth embodiment of the present invention will be described with reference to FIGS.
FIG. 7 is a diagram showing a schematic configuration of a fixing device according to the second embodiment of the present invention. FIG. 8 is a graph showing the relationship between the heating temperature of the fixing device and the curl curvature of the transfer paper.
The fixing device 8 according to the sixth embodiment is different from the fixing device according to the fifth embodiment described above as a means for controlling the pressing force of the correction roller 42 and the applied voltage of the pressure belt 37 to be measured in advance. The CPU 55 uses the database 58 that stores curl curvature data obtained corresponding to the material of the paper P and the like.
The database 58 stores curl curvature data of the transfer paper P when the material of the transfer paper P and the heating temperature of the fixing device are changed as shown in FIG. Therefore, the heating temperature of the heating roller 30 detected by the thermistor 36 of the fixing device 8 and data such as the material of the transfer paper P from the sensor 56 are detected and the curl curvature stored in the database 58 is used. Thus, the pressing force of the correction roller 42 and the applied voltage of the pressure belt 37 can be controlled more appropriately.
In FIG. 8, the curve 1 is the curl curvature of the surface of the transfer paper type 1 having the toner image on the surface, the curve 2 is the curl curvature of the surface of the transfer paper type 2 having the toner image on the surface, and the curve 3 is the front and back. The curl curvature of transfer paper type 1 having toner images on both sides is shown.

  As described above, in the embodiment according to the present invention, the pressure belt 37 stretched between the drive support roller 41 and the pressure roller 38 is used, and the pressure belt is moved by the correction roller 42 at a position facing the drive support roller 41. 37, the curl deformation of the transfer paper P is corrected by pressing the transfer paper P on the sheet 37, so that the curl deformation of the transfer paper P can be appropriately corrected with a simple structure. Moreover, since the respective hardnesses are set so that the hardness relationship among the pressure belt 37, the heating roller 30, and the correction roller satisfies H2 <H1 <H3, the curl deformation of the transfer paper P is corrected appropriately and reliably. It becomes possible.

1 is a diagram illustrating a schematic configuration of a color image forming apparatus according to an embodiment of the present invention. 1 is a diagram illustrating a schematic configuration of a fixing device according to a first embodiment of the present invention. It is a figure which shows schematic structure of the fixing device which concerns on 2nd Embodiment by this invention. It is a figure which shows schematic structure of the fixing device which concerns on 3rd Embodiment by this invention. It is a figure which shows schematic structure of the fixing device which concerns on 4th Embodiment by this invention. It is a figure which shows schematic structure of the fixing device which concerns on 5th Embodiment by this invention. It is a figure which shows schematic structure of the fixing device which concerns on 6th Embodiment by this invention. FIG. 6 is a graph showing the relationship between the heating temperature of the fixing device and the curl curvature of the transfer paper.

Explanation of symbols

  1Y, 1M, 1C, 1B image forming unit, 2 intermediate transfer belt, 3Y, 3M, 3C, 3B photoconductor, 4 charging device, 5Y, 5M, 5C, 5B exposure device, 9a, 9b, 9c, 9d primary transfer Roller, 14, 21, 22 Support roller, 23 Secondary transfer roller, 25, 54 Power supply, 30 Heating roller, 34 Heating heater, 36 Thermistor, 37 Pressure belt, 38 Pressure roller, 38a Rotating shaft, 38b Bearing part, 41 Drive support roller, 41a Rotating shaft, 42 Correction roller, 42a Rotating shaft, 42b Bearing portion, 42c Correction layer, 43, 45 Spring member, 50 Cam means, 51 Restricting member, 52 Rotating cam, 53 Pressing force control means, 55 CPU, 56 sensors, 57 control means, 58 database

Claims (6)

A heating unit that heats the surface of the transfer material on which the toner image has been transferred; and a pressurizing unit that presses the transfer material against the heating unit. In the fixing device for fixing the toner image on the transfer material by heating and pressurizing the transfer material,
The pressure unit includes an endless pressure belt stretched between a pressure roller facing the heating unit and a support roller disposed on the downstream side in the conveyance direction of the transfer material,
A correction means for correcting the curl deformation of the transfer material by pressing the transfer material against the endless pressure belt on the support roller;
The hardness of the endless pressure belt on the pressure roller is H1 a , the hardness of the endless pressure belt on the support roller is H1b, and the hardness of the contact portion of the heating means with the transfer material is H2. The fixing device is set so as to have a relationship of H2 < H1a and H1b <H3 , where H3 is a hardness of a contact portion of the correcting means with the transfer material. The fixing device according to claim 1,
The fixing device, wherein the correction means includes a pressing force control unit that controls a pressing force with respect to the transfer material. The fixing device according to claim 2,
The fixing device, wherein the pressing force control unit controls the pressing force to change in accordance with a material of the transfer material or an environmental condition of the fixing device. The fixing device according to any one of claims 1 to 3,
A fixing device comprising charge applying means for applying a charge for adsorbing a transfer material to the surface of the endless pressure belt to the endless pressure belt. The fixing device according to claim 4.
The fixing device, wherein the charge applying unit is controlled to change the applied charge in accordance with a transfer condition when the toner image is transferred to the transfer material. Image forming means for supplying toner to the electrostatic latent image formed on the image carrier to convert the electrostatic latent image into a toner image, and transferring the toner image formed by the image forming means to the surface of the transfer material In an image forming apparatus comprising: a transfer unit; and a fixing device that fixes a toner image transferred by the transfer unit onto a transfer material.
The fixing device, an image forming apparatus which is a fixing device according to any one of claims 1 to 5.

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