JP2006003508A - Image forming apparatus - Google Patents

Abstract

An image forming apparatus using a secondary transfer simultaneous fixing device 9 is provided which has excellent fixing properties without impairing durability of an intermediate transfer belt 7.
After a toner image formed on an image carrier is primarily transferred onto an intermediate transfer belt, the toner image on the intermediate transfer belt is secondarily transferred onto a transfer material by a transfer and simultaneous fixing device. In the image forming apparatus for fixing at the same time, a heating / pressurizing means 8 for heating and pressurizing the transfer material P introduced into the simultaneous transfer fixing device 9 is disposed upstream of the simultaneous transfer fixing device 9. Image forming apparatus.
[Selection] Figure 1

Description

  The present invention relates to a copying machine, a printer, a fax machine, and the like, which primarily transfers a toner image formed on an image carrier using an electrophotographic method onto an intermediate transfer belt, and then simultaneously fixes the toner image to a transfer material from the intermediate transfer belt. The present invention relates to an image forming apparatus.

  Conventionally, in an image forming apparatus such as a copying machine, a printer, or a fax machine using an electrophotographic method, an electrostatic latent image is formed on a photosensitive member, and is developed with charged toner, and is then formed on an intermediate transfer belt. Multi-color toner images are electrostatically superimposed for primary transfer, and the toner images on the intermediate transfer belt are electrostatically transferred to a secondary transfer material such as paper, and then heated and pressed. An image forming method for fixing by this is widely used.

  However, in the image forming method as described above, it is difficult to ensure a uniform transfer electric field over the entire surface of the transfer material due to the electrical characteristics and surface properties of the transfer material, such as paper, and the electric power between the toners. There is also a problem of image degradation such as toner scattering.

  In order to solve the above problems, a multicolor toner image is electrostatically superimposed on the intermediate transfer belt, which has uniform electrical characteristics over the entire surface and has a smooth surface, and is primarily transferred, and then heat and pressure are applied. An image forming apparatus that forms a color image by performing secondary transfer onto a transfer material simultaneously with fixing (transfer simultaneous fixing device) has been proposed (Patent Document 1).

  By performing secondary transfer and fixing simultaneously with heat and pressure, the above-mentioned problem of image deterioration caused by electrostatic secondary transfer is less likely to occur, and the toner transfer efficiency is also improved, resulting in high quality. A color image can be obtained.

In addition, an intermediate transfer belt having an elastic layer has been proposed in order to improve transferability to a transfer material having a large surface unevenness.
JP-A-5-249795

  However, in the simultaneous transfer and fixing device for obtaining a high-quality color image, it is necessary to heat the intermediate transfer belt in addition to the transfer material and the toner image, so that the amount of heat required for fixing tends to increase. Since the elastic intermediate transfer belt having a thickness is larger than that of a resin belt that is generally used, the heat capacity is large and the tendency is remarkable. When the amount of heat necessary for fixing is insufficient, the image quality deteriorates due to poor fixing of the toner image to the transfer material, reduction in image gloss, and the like.

  As a method of increasing the amount of heat at the time of fixing, there is a method of widening the nip region with a rubber roller having a low hardness. In this case, the deformation of the rubber roller also causes distortion in the intermediate transfer belt, and the durability of the intermediate transfer belt is caused by the repetition. Will fall.

  As another method, there has been proposed a simultaneous transfer fixing device using a toner fusing unit for heating the toner on the intermediate transfer belt upstream of the simultaneous transfer fixing unit. The upper toner image must be non-contacted so as not to be disturbed, and the intermediate transfer belt is exposed to a high temperature in a wider area than the nip area of the rubber roller. Therefore, the durability of the intermediate transfer belt is significantly impaired due to thermal deterioration of the intermediate transfer belt, image failure at the electrostatic primary transfer portion due to resistance change, and destruction of the intermediate transfer belt due to a decrease in mechanical strength. End up.

  However, even if the heat amount of the fixing unit is increased by the above-described method, the fixing property may not be sufficiently ensured when continuously printing thick paper or embossed paper having a large unevenness on the surface.

  In double-sided printing, the temperature of the transfer material on the second side is high, so fixing can be done with less heat compared to the first side, but fixing is required to ensure the fixability of the first side. The portion is controlled at a higher temperature, which is not preferable in terms of durability of the intermediate transfer belt.

  The present invention has been made in view of the above-described problems, and an object of the present invention is to provide an image forming apparatus having excellent fixability without impairing durability of an intermediate transfer belt in an image forming method using a simultaneous transfer fixing apparatus. It is what.

  A typical configuration of the image forming apparatus according to the present invention for achieving the above-described object is that the toner image formed on the image carrier is primarily transferred onto the intermediate transfer belt, and then the toner on the intermediate transfer belt. In an image forming apparatus in which an image is secondarily transferred onto a transfer material by a simultaneous transfer fixing device and fixed at the same time, heating and pressurizing the transfer material introduced into the simultaneous transfer fixing device on the upstream side of the simultaneous transfer fixing device. An image forming apparatus characterized in that means is arranged.

  That is, the transfer material is preheated (preheated) by a hot press action by a heating and pressurizing means, and the surface is smoothed and introduced into the simultaneous transfer fixing device. As a result, even when an elastic intermediate transfer belt having a large heat capacity is used, it is possible to achieve the same fixing performance as that without the heating and pressing means by reducing the temperature of the simultaneous transfer fixing device. Thermal deterioration is reduced and durability is improved. Further, when the temperature of the simultaneous transfer and fixing device is the same as that without the heating and pressing means, the fixing property and the image gloss are improved. An image having excellent fixability can be formed without impairing the durability of the intermediate transfer belt.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  FIG. 1 shows a longitudinal sectional view of an example of an image forming apparatus according to the present invention.

  The image forming apparatus shown in the figure is a four-color full-color image forming apparatus in which four image forming units Y, M, C, and K are arranged along the moving direction of an intermediate transfer belt 7 as an intermediate transfer member. The toner image formed on the intermediate transfer belt 7 is transferred and fixed simultaneously at the secondary transfer portion T2.

  The image forming apparatus shown in the figure includes four image forming units that form toner images of different colors, that is, image forming units Y and Y that respectively form a yellow toner image, a magenta toner image, a cyan toner image, and a black toner image. It has M, C, and K. These image forming units Y, M, C, and K have substantially the same electrophotographic process configuration and operation except that the toner is different.

As the yellow, magenta, cyan, and black toners, those using known materials and pigments can be used. The amount of toner applied on the intermediate transfer belt 7 is 0.4 mg / cm ² to 4 depending on the pigment content of each toner. Image forming conditions can be set in the range of 0.7 mg / cm ² . In the present embodiment, a two-component negatively charged toner having an average toner particle size of 6 μm is used, and the applied toner amount is set to 0.5 mg / cm ² for each color.

  In each of the image forming units Y, M, C, and K, 1 is a drum-type electrophotographic photosensitive member (hereinafter referred to as a photosensitive member) as an image carrier, and is driven in a direction indicated by an arrow (clockwise) by a driving unit (not shown). ). The photoconductor 1 is provided with a photoconductive layer on a conductive base layer, and an organic photoconductor (OPC), an amorphous silicon photoconductor, a selenium photoconductor, or the like is used. In this embodiment, an organic photoreceptor drum (OPC) is used.

  A charging unit 2 uniformly charges the surface of the photoreceptor 1 to a predetermined polarity and potential. As the charging means, a scorotron charger, a charging roller, a magnetic brush charger, or the like can be used. In this embodiment, a scorotron charger is used to charge the photosensitive member 1 to a predetermined negative polarity potential.

  Reference numeral 3 denotes exposure means (laser scanner, LED array, etc.), which is arranged downstream of the charging means 2 in the rotation direction of the photosensitive member 1. The surface of the photoreceptor 1 uniformly charged by the charging unit 2 is optically scanned by the exposure unit 3 based on the image information, thereby forming an electrostatic latent image.

  Reference numeral 4 denotes a developing unit, which is disposed on the downstream side of the exposure unit 3 in the rotation direction of the photoreceptor 1 and develops the electrostatic latent image on the photoreceptor 1 with toner. In the present embodiment, the electrostatic latent image on the photoreceptor 1 is developed as a toner image with negatively charged toner.

  Reference numeral 5 denotes an electrostatic primary transfer unit, which is disposed at a primary transfer position T1 at a position facing the photoreceptor 1 with the intermediate transfer belt 7 in between, and on the intermediate transfer belt 7 by a transfer electric field of the primary transfer unit 5. The toner image on the photoreceptor 1 is primarily transferred to the surface. As the primary transfer means, a scorotron transfer charger, a transfer roller, a transfer blade, a transfer brush, or the like can be used. In this embodiment, a scorotron transfer charger is used, and the toner image on the photoreceptor 1 is primarily transferred onto the intermediate transfer belt 7 by a positive transfer electric field.

  A photosensitive member cleaning unit 6 removes untransferred toner remaining on the intermediate transfer belt without being transferred by the primary transfer unit 5 from the surface of the photosensitive member.

  The above-described operation is performed in the four image forming units Y, M, C, and K, and the yellow toner image formed by the image forming unit Y and the magenta toner formed by the image forming unit M are formed on the intermediate transfer belt 7. The image, the cyan toner image formed by the image forming unit C, and the black toner image formed by the image forming unit K are primarily transferred in a superimposed manner in the primary transfer portion T1 of each image forming unit. As a result, an unfixed full-color toner image composed of superposed toner images of yellow, magenta, cyan and black is synthesized and formed on the intermediate transfer belt 7.

  The intermediate transfer belt 7 as an intermediate transfer member is driven in contact with the photosensitive member 1 of each color image forming unit Y, M, C, K. The intermediate transfer belt 7 is suspended by a driving roller 71, driven rollers 72 and 73, and an upper heating roller 91 of the simultaneous transfer fixing device 9, and is driven to rotate in the direction of arrow R.

  The intermediate transfer belt 7 is an elastic intermediate transfer belt made of a laminated structure material of a base layer (base film), an elastic layer, and a surface layer. For the base layer, heat-resistant resins such as polyester, fluororesin, polyphenylene sulfide, polyamideimide, polyimide, polyetherketone, and polycarbonate, metals such as aluminum and nickel, or composite materials thereof can be used.

  For the surface layer, a material having high releasability to toners such as PFA, PTFE and other fluororesins, fluororubber, silicone resin and silicone rubber, or a mixture of the above materials with polyurethane as a binder may be used. it can.

  For the elastic layer, an elastic material such as CR (chloroprene rubber), hydrin rubber, silicone rubber, fluorine rubber or the like can be used.

The electrical characteristics of the intermediate transfer belt 7 are preferably a volume resistivity of 10 ⁵ to 10 ¹³ Ω · cm, a surface resistivity of 10 ⁶ to 10 ¹⁴ Ω / □, and a volume resistivity of 10 ⁶ to 10 ¹⁰ Ω · cm. The surface resistivity is more preferably 10 ⁹ to 10 ¹³ Ω / □.

In this embodiment, the intermediate transfer belt 7 is made of polyimide having a base layer of 75 μm thickness, a surface layer of PFA having a thickness of 10 μm, and an intermediate elastic layer of silicone rubber having a thickness of 300 μm. Further, the electric resistance of each layer was adjusted by a known method, and the volume resistivity was 10 ⁹ Ω · cm and the surface resistivity was 10 ¹¹ Ω / □ as an intermediate transfer belt.

  Volume resistivity and surface resistivity are R8340A resistance measuring instruments manufactured by Advantest, using a probe with a main electrode outer diameter of 50 mm and a guard electrode of 70 mm in an environment of 23 ° C./50% RH with an applied voltage of 500 V and a charge time of 10 seconds. Measured under measurement conditions.

  Reference numeral 8 denotes a heating and pressurizing unit, which is disposed upstream of the simultaneous transfer and fixing device 9 in the transfer material conveyance direction. The heating and pressing means 8 of this example is composed of a roller pair including an upper roller 81 and a lower roller 82 that are rotationally driven in the direction of the arrow. A nip N is formed by pressing the lower roller 82 against the upper roller 81 by a pressing mechanism 83.

  The heating and pressurizing unit 8 heats and pressurizes the transfer material P fed from a paper feeding unit (not shown) in the nip N and introduces it into the secondary transfer simultaneous fixing unit T2 of the simultaneous transfer fixing device 9.

  The heating and pressurizing means 8 is used to improve the fixing property of the toner image onto the transfer material P in the secondary transfer simultaneous fixing portion T2, and the temperature between the upper roller 81 and the lower roller 82, and between the upper roller 81 and the lower roller 82. Each pressure can be controlled.

  As the upper roller 81 and the lower roller 82, an elastic layer such as fluorine rubber or silicone rubber on a hollow metal roller, a fluorine resin such as PFA or PTFE having high releasability with respect to toner on the surface layer, fluorine rubber, or silicone resin In addition, a material obtained by laminating a material such as silicone rubber can be used, and a metal roller or a metal roller having a toner release layer laminated can be used. Heaters H1 and H2 are disposed inside the upper roller 81 and / or the lower roller 82.

  In this embodiment, the upper roller 81 and the lower roller 82 are rollers having an outer diameter of 30 mm, in which a silicone rubber having a hardness of 35 degrees is 0.5 mm on a hollow aluminum roller and a PFA of 50 μm is laminated on the surface layer. Further, halogen lamps H1 and H2 are arranged as heaters inside both the upper roller 81 and the lower roller 82.

  TH1 and TH2 are thermistors as roller surface temperature detecting means disposed on the upper roller 81 and the lower roller 82, respectively. The detected temperature information of the thermistors TH1 and TH2 is input to the control circuit (CPU) 100. Based on the detected temperature information that is input, the control circuit 100 includes a power supply circuit V1 for each of the halogen lamps H1 and H2 so that the roller surface temperatures of the upper roller 81 and the lower roller 82 are respectively maintained at predetermined management temperatures. Controls the output of V2. The control circuit 100 controls the pressure mechanism 83 based on predetermined control information to control the pressure between the upper roller 81 and the lower roller 82 to a predetermined management pressure.

  The simultaneous transfer fixing device 9 includes an upper heating roller 91 inside the intermediate transfer belt 7 and a lower heating roller 92 that is in pressure contact with the upper heating roller 91 with the intermediate transfer belt 7 interposed therebetween. . A nip between the intermediate transfer belt 7 and the lower heating roller 92 is a secondary transfer simultaneous fixing portion T2.

  As the upper heating roller 91 and the lower heating roller 92, an elastic layer such as fluorine rubber or silicone rubber on a hollow metal roller, a fluororesin such as PFA or PTFE having high releasability for toner on the surface layer, fluorine rubber, A material in which a material such as silicone resin or silicone rubber is laminated can be used, and a metal roller or a metal roller having a toner release layer laminated can be used.

  Further, heaters H3 and H4 are disposed inside the upper heating roller 91 and / or the lower heating roller 92, and the temperature is set and controlled so that the toner temperature becomes equal to or higher than the toner softening temperature in the secondary transfer simultaneous fixing region T2. The

  In this embodiment, the upper heating roller 91 and the lower heating roller 92 are rollers having an outer diameter of 50 mm in which a silicone rubber having a hardness of 25 degrees and a PFA of 50 μm are laminated on the surface layer on an aluminum hollow roller. In addition, halogen lamps H3 and H4 are arranged as heaters inside each.

  TH3 and TH4 are thermistors as roller surface temperature detecting means disposed on the upper heating roller 91 and the lower heating roller 92, respectively. The detected temperature information of the thermistors TH3 and TH4 is input to the control circuit (CPU) 100. The control circuit 100 supplies power to each of the halogen lamps H3 and H4 so that the roller surface temperatures of the upper heating roller 91 and the lower heating roller 92 are maintained at a predetermined management temperature even based on the detected temperature information input thereto. Control V3 and V4.

  The transfer material P is conveyed from the heating and pressurizing unit 8 to the secondary transfer simultaneous fixing unit T2 of the simultaneous transfer fixing device 9 in synchronization with the toner image on the intermediate transfer belt 7, and the toner image on the intermediate transfer belt 7 is transferred. Is secondarily transferred onto the transfer material P by heat and pressure, and simultaneously fixed.

  Reference numeral 10 denotes a cooling fan, which is disposed downstream of the secondary transfer simultaneous fixing unit T2 in the intermediate transfer belt moving direction and facing the front side of the intermediate transfer belt portion upstream of the driven roller 73 in the intermediate transfer belt moving direction. It is. The cooling fan 10 is a cooling device for cooling the transfer material, the toner image on the transfer material, and the intermediate transfer belt that have passed through the secondary transfer simultaneous fixing portion T2 in close contact with the surface of the intermediate transfer belt 7. The transfer material P that is in close contact with the surface of the intermediate transfer belt 7 and is cooled by the cooling fan 10 is conveyed as a full-color image formed product with the driven roller 73 as a separation roller, with this roller portion being curvature-separated from the surface of the intermediate transfer belt 7. The

  An intermediate transfer belt cleaning unit 11 removes transfer residual toner that is not transferred to the transfer material on the intermediate transfer belt. A cleaning roller, a cleaning blade, a cleaning web, or the like can be used. In this embodiment, a cleaning web device is used.

  A feature of the present invention resides in that, on the upstream side of the simultaneous transfer fixing device 9, a heating / pressurizing unit 8 for the transfer material for improving the fixability of the toner image onto the transfer material is arranged. That is, the transfer material P is pre-heated (pre-heated) by the hot press action by the heating and pressurizing means 8 and the surface is smoothed and introduced into the secondary transfer simultaneous fixing portion T2 of the simultaneous transfer fixing device 9. . As a result, it is possible to achieve fixing performance equivalent to the state in which the elastic intermediate transfer belt 7 having a large heat capacity is used and no heating and pressurizing means 8 is provided by reducing the temperature of the simultaneous transfer fixing device 9, and elasticity. The durability of the intermediate transfer belt 7 was improved. Further, when the temperature of the simultaneous transfer fixing device 9 is the same as that without the heating and pressing means 8, the fixing property and the image gloss are improved.

  In the image forming apparatus of Example 1, the control temperature of the roller 81 or / and 82 of the heating and pressing means 9 is controlled according to the heat capacity of the transfer material P used for the paper.

  When the image formation execution mode is the thick paper continuous printing mode with a large heat capacity, the control circuit 100 sets the management temperature of the roller 81 or / and 82 to compensate for the shortage of heat in the secondary transfer simultaneous fixing unit T2. By making the transfer material higher than the control temperature when thin paper with a small heat capacity is used, the fixing property of the thick paper can be reduced without increasing the temperature and pressure of the simultaneous transfer fixing device 9 and without reducing the productivity. It was possible to be equivalent.

  The type information of the transfer material P used for paper passing is automatically or manually input from the transfer material type information input unit 101 to the control circuit 100 by a transfer material type automatic detection unit (not shown).

  Control according to the transfer material heat capacity of the roller temperature of the heating and pressurizing means 9 is performed by storing appropriate management temperatures for various transfer materials such as plain paper, thick paper, and thin paper in the control circuit 100 in advance. This is done by causing the control circuit to determine appropriate switching according to the type information of the transfer material P and the image forming execution mode.

  FIG. 2 is a control flowchart performed by the control circuit 100 in the second embodiment.

  In the image forming apparatus of Example 1, the pressure applied between the rollers 81 and 82 of the pressure heating means 9 was controlled according to the surface roughness of the transfer material P used for the paper.

  The control circuit 100 controls the pressurizing mechanism 83 to control the rollers 81. The pressure applied between 82 is controlled to be larger by a predetermined value than when the transfer material P is smooth paper. As a result, the unevenness is temporarily reduced by the large pressing force, and the fixing property of the paper having a rough surface is improved without increasing the temperature and pressure of the simultaneous transfer fixing device 9 and without decreasing the productivity. It was possible to improve.

  Although a specific example of the pressurizing mechanism 83 is omitted in the drawing, for example, a pressurizing mechanism using a pressurizing spring, a pressurizing mechanism using fluid pressure, and the like can be appropriately configured. The pressure adjusting mechanism can also be appropriately configured, for example, a rotating cam mechanism or a fluid pressure adjusting motor mechanism.

  FIG. 3 is a control flowchart performed by the control circuit 100 in the third embodiment.

1 is a longitudinal sectional view illustrating a schematic configuration of an image forming apparatus according to an embodiment. Control flowchart Control flowchart

Explanation of symbols

  Y, M, C, K: image forming unit, 1: photoconductor, 2: charging unit, 3: exposure unit, 4: developing unit, 5: primary transfer unit, 6: photoconductor cleaning unit, 7: intermediate transfer belt , 71: driving roller, 72/73: driven roller, 8: heating and pressing means, 81: upper roller, 82: lower roller, 9: transfer simultaneous fixing device, 91: upper heating roller, 92: lower heating roller, 10 : Cooling device, 11: Intermediate transfer belt cleaning means, P: Transfer material, R: Direction of rotation of intermediate transfer belt

Claims (4)

In an image forming apparatus that primarily transfers a toner image formed on an image carrier onto an intermediate transfer belt, and then secondarily transfers the toner image on the intermediate transfer belt to a transfer material by a transfer simultaneous fixing device, and fixes the toner image simultaneously.
An image forming apparatus, wherein a heating and pressurizing unit for heating and pressurizing a transfer material introduced into the simultaneous transfer fixing device is disposed upstream of the simultaneous transfer fixing device.   The image forming apparatus according to claim 1, wherein the intermediate transfer belt is an intermediate transfer belt having an elastic layer.   The image forming apparatus according to claim 1, wherein the heating and pressing unit is a roller pair, and the roller temperature is controlled by the heat capacity of the transfer material.   The image forming apparatus according to claim 1, wherein the heating and pressing unit is a pair of rollers, and the pressure between the rollers is controlled by the surface roughness of the transfer material.

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