JP2008287000A - Heating device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electrophotographic device capable of performing gloss control, which can obtain a high-gloss print without gloss unevenness and both high-gloss and low-gloss prints. <P>SOLUTION: In a heating device for fixing toner to a material to be conveyed carrying a toner image, a conveying unit comprising a film member, at least two support members supporting the film member, and a pressure member coming into contact with one of the support members across the film member is provided on the downstream portion in the conveying direction of the material to be conveyed. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an image heating apparatus mounted on an electrophotographic copying machine or printer.

  In recent years, image forming apparatuses such as electrophotographic apparatuses have been increased in speed, function, and color, and various types of printers have been put on the market.

  From the standpoint of speeding up the printer, research and development of an inline system that forms images by arranging multiple electrophotographic units that form different color images in series and driving them simultaneously is progressing. Since it is possible to form color images at high speed, it has a wide range of possibilities for business use.

  In color printing, the glossiness of printing (hereinafter referred to as gloss) has a large relationship with the print quality, and it is generally possible to achieve high-quality and vivid colors by realizing high gloss. In particular, high gloss prints are desired for prints intended for photographic image quality.

  The gloss is an index that represents the amount of light reflected from the toner image on the print surface of the print, and in particular, there is a high correlation between the amount of regular reflection from the paper and the glossiness that humans feel. Therefore, the smoother the microscopic shape of the toner surface, the higher the gloss can be obtained.

  On the other hand, low gloss prints are desirable for business documents because the glare of the toner image causes text blur and the document becomes difficult to read.

  As described above, it is required for a single color printer to realize both of two types of glosses of low gloss (business document) and high gloss (photo image quality) in accordance with the usage.

  As a method for smoothing the toner surface after fixing, a method of optimizing the pressure of the fixing device, the fixing temperature, the fixing speed and the toner characteristics is effective.

  When a high temperature is applied to the toner slowly by applying a temperature, the toner can be melted and pressed to obtain high smoothness, and as a result, high gloss can be obtained.

  As another approach, the gloss is also affected by the temperature at which the sheet is separated from the fixing device after the toner is sufficiently melted by applying temperature and pressure. When the paper is separated from the fixing roller in a state where the toner is excessively melted or softened, the cohesive force of the toner decreases, so that the toner layer cries and separates between the paper and the fixing roller. Gross is reduced by roughening the surface layer. On the other hand, pressure was applied after the toner melted in the fixing nip, and the toner was held for a certain time with a smooth surface maintained. When the toner was cooled and solidified, the toner cohesion was maintained. It can be separated as it is. As a result, the toner surface on the paper can be separated while maintaining smoothness, so that a high gloss print can be obtained. Hereinafter, such a separation method is referred to as cooling separation.

  However, slow fixing is an element contrary to high speed printing and high energy saving energy for a high fixing temperature. On the other hand, a fixing device that can apply a high pressure represented by a heat roller fixing device is Generally, there is a tendency to increase the size, and it is common to impair the on-demand property of the fixing device by increasing the heat capacity.

In order to achieve high gloss without impairing the on-demand property of the fixing device, a certain degree of high gloss due to cooling separation can be expected in a technique such as a belt fixing device based on on-demand fixing. In addition, as an advanced form of this technology, the gloss control that provides both low and high gloss by moving up and down the roller on one side of the belt as in Japanese Patent Laid-Open No. 4-338992 can be obtained with a single electrophotographic device. There is something aimed.
Japanese Patent Laid-Open No. 4-338992

  However, there are the following problems.

  When the belt material is only a film as in Japanese Patent Laid-Open No. 4-338992, the belt is less likely to follow the eyes of the paper because of its low elasticity, and the toner is not separated between the surface layer and the back of the paper. Since the melting method is not uniform (the inner part is harder to melt), gloss unevenness occurs. On the other hand, if a rubber layer is provided on the film belt as a countermeasure, the gloss unevenness is improved, but the toner on the paper is difficult to cool because the heat capacity is increased by the rubber, and the toner cohesive force cannot be maintained by cooling and solidification. The surface is not smooth and high gloss cannot be obtained. On the other hand, when a metal belt is used to improve the thermal response, the heat of the heater of the fixing unit is conducted to the entire belt because of high thermal conductivity, and cooling separation cannot be realized.

  As described above, gloss control that can achieve both low-gloss and high-gloss prints in a conventional compact, energy-saving, on-demand fixing device that achieves both high-gloss prints and uniform high-gloss prints. It was difficult to realize.

  The present invention has been made in view of the above-mentioned problems, and is a gloss-controllable heating capable of achieving both a print without gloss unevenness and a uniform high-gloss print and obtaining both low-gloss and high-gloss prints. The purpose is to provide a device.

  In the present invention, a film member, at least two support members 1 and 2 that support the film member, and one of the support members sandwiching the film member are disposed downstream of the normal fixing device in the sheet conveyance direction. A film unit having a conveyance unit comprising a pressing member in contact with the surface on which a toner image is carried on a nip portion formed by contact between one of the supporting members and the pressing member; And the film member and the surface on which the toner image of the paper is carried are kept in close contact with each other, and while being cooled to the separation point between the film member and the paper, The film and paper are separated.

  According to the present invention, it is possible to obtain a high gloss print by cooling and separating the fixing function and the gloss up function into two units, thereby making it possible to achieve both gloss unevenness and high gloss.

  Further, in the present invention, by retracting one of the support members in the direction of peeling from the paper, it can be separated without cooling, and a low gloss print can be obtained.

  Furthermore, further gloss-up is possible by providing a heating member in the transport unit.

  In the present invention, the user can freely select high-gloss and low-gloss printing according to the print mode, so that it is possible to perform gloss control that can realize both high-gloss and low-gloss in one printer.

  As described above, according to the present invention, a conveyance unit having a conveyance unit or a heating mechanism is provided on the downstream side in the sheet moving direction with respect to the fixing device, and the belt member is brought into contact with the sheet to perform cooling separation. Gloss and gloss-free prints can be obtained, and further, gloss control can be realized that can realize low-gloss prints without gloss unevenness by peeling the belt member from the paper immediately after passing through the nip.

<Example 1>
FIG. 3 is a schematic sectional view of a color image forming apparatus (laser printer or copying machine) using an electrophotographic process. Four independent color stations each having YMCK photosensitive drum, developing device, and cleaning device are arranged in a vertical line, and a sheet adsorbed on the electrostatic transfer belt is transferred to these to transfer a full color image. It is the structure to obtain.

  Reference numerals 11 to 14 denote rotating drum type electrophotographic photosensitive members (hereinafter referred to as photosensitive drums) that are repeatedly used as an image carrier, and are rotationally driven at a predetermined peripheral speed (process speed) in the counterclockwise direction indicated by an arrow. The

  The photosensitive drum is a negatively charged OPC photosensitive member having a diameter of 30 mm, and the process speed of the image forming apparatus of this embodiment is 94 mm / sec.

  The photosensitive drum is uniformly charged to a predetermined polarity / potential by the primary charging rollers 21 to 24 during the rotation process, and then constituted by image exposure means 31 to 34 (laser diodes, polygon scanners, lens groups, etc.). The electrostatic latent image corresponding to each color component image (for example, yellow, magenta, cyan, black component image) of the target color image is formed.

  The charging device is a DC contact charging method in which a roller having an actual resistance of 1e6Ω to which a DC voltage of −1.2 kV is applied is driven and brought into contact with the photosensitive drum at a total pressure of 9.8 N, and the surface of the photosensitive drum is −600 V. Is charged. The image exposure means used in this embodiment is a polygon scanner using a laser diode, and forms an electrostatic latent image by forming an image of a laser beam modulated by an image signal on a photosensitive drum.

  Laser exposure is written in the main scanning direction (perpendicular to the paper travel) from the position signal in the polygon scanner called BD for each scanning line, and the sub-scanning direction (paper travel direction) is a switch in the paper transport path. Each color station can always perform exposure at the same position on the paper by performing a predetermined time delay from the TOP signal starting from.

  Next, the electrostatic latent image is developed by the developing unit of each station. Each of the developing devices 41 to 44 (yellow, magenta, cyan, black) is rotated in the direction of the arrow in the drawing by a rotation driving device (not shown) so that each developing device faces the photosensitive drum in the developing process. It is arranged.

  The Y, M, C, and BK toners are so-called non-mag toners that do not contain a magnetic material, and are developed by a non-contact one-component jumping development system.

  The developing devices 41 to 44 coat toner with a developing blade in which a thin metal plate is coated with nylon on a developing sleeve made of aluminum having a diameter of 16 mm facing the photosensitive member with a distance of 250 μm. A rectangular wave having a frequency of 1 kHz and a peak-to-peak voltage of 1600 V is applied to a developing sleeve that is driven to rotate at a constant speed, and development is performed by flying toner between the photosensitive member and the developing sleeve.

  The toner is a spherical toner having a two-layer structure manufactured by a polymerization method, and a resin binder layer called a shell surrounds a central wax.

  The transfer belt 8 is rotationally driven at the same peripheral speed as the photosensitive drum in the direction of the arrow.

  The transfer belt is a 100 μm thick PVDF single-layer resin belt with resistance adjusted to 1e11 Ωcm, and is configured to regulate the meandering and deviation of the belt by ribs bonded to both sides of the back surface.

  As the transfer member, epichlorohydrin rubber transfer rollers 51 to 54 capable of applying a high voltage adjusted to a volume resistivity of 1e7 Ωcm are used, and are in contact with the OPC nip portion from the back of the transfer belt.

  The sheet fed from the sheet cassette contacts the transfer belt through the transfer inlet guide after passing through the registration roller.

  In this embodiment, the printer is arranged vertically so that the desired purpose can be achieved by opening and closing only the front door for minimizing the ground contact area and for cartridge replacement and jam processing. The main body is divided between the two.

  From the above configuration, since the paper is conveyed upward against gravity, it is necessary that the paper and the transfer belt are sufficiently adsorbed.

  A suction roller 7 to which a bias is applied is provided in the vicinity of the contact point between the paper and the transfer belt, and a suction conveyance force is generated by applying a voltage of +1 KV and applying a charge to the paper during image formation.

  The suction roller 7 is a solid rubber roller having a diameter of 12 mm in which carbon black is dispersed for resistance adjustment in EPDM rubber, and is configured to be able to apply a high-pressure bias for suction to the core metal. The resistance value of the suction roller is adjusted to 1e6Ω when a metal foil having a width of 1 cm is wound around the outer periphery of the roller and a voltage of 500 V is applied between the core and the metal core.

  Paper that is fed from a paper feed cassette (not shown), passes through a transfer inlet guide and a suction roller, and obtains a suction force with the transfer belt enters the first color transfer station. In the transfer unit, the toner image from the first color photosensitive drum is transferred by a transfer blade provided on the back surface of the transfer belt. The bias applied to the transfer roller is calculated from the impedance of the transfer belt and paper calculated from the current flowing through the suction roller while the paper is being passed. In single-sided printing in a normal environment, a DC bias of about +1.5 kV is high for each station. Applied from the power supply.

  Thereafter, each time passing through each color station, a different color toner image is transferred from the photosensitive drum to form a full color image.

  After the transfer of all colors is completed, the paper separated by the curvature from the rear end of the transfer belt is fixed by the fixing device 9 and discharged to the outside of the apparatus via the transport unit to obtain a final print.

  In this example, an on-demand fixing device using an induction overheating method as shown in FIG. 1A was used. A heat generating sleeve 91 with a diameter of 34 mm in which a 50 μm thick silicone rubber and a 50 μm thick PFA tube as a release layer are laminated on a 50 μm thick nickel electroformed sleeve and an induction coil 92 and a magnetic path forming layer. For this purpose, the plastic core holder 95 including the ferrite core 93 is held from the inner surface, and the sliding plate 96 is pressurized by the pressure stay 94. The fixing device is configured to press and press with a pressure roller 97 having a diameter of 30 mm as a pressure member of the paper.

  At the time of fixing, a high-frequency current is passed through the coil 92, and thereby nickel is heated by an eddy current induced in the nickel layer of the sleeve 91. The temperature control is performed by controlling the amount of high-frequency current flowing through the coil in accordance with the temperature detected by a thermistor (not shown) that is in contact with the inner surface of the sleeve, and is not fixed to the fixing nip N constituted by the fixing sleeve and the pressure roller. Thermal pressure fixing is performed by passing paper p containing toner t.

  The fixing device is driven by driving and rotating the pressure metal core 98, and the sleeve is frictionally driven by the pressure roller surface.

  A transport unit capable of obtaining a print with a high gloss value in this embodiment will be described. A conveyance unit as shown in FIG. 1B is provided in the downstream portion of the fixing device. Reference numeral 108 denotes a film member, which is an endless belt type heat resistant film (hereinafter abbreviated as a belt). This belt is wound between two members, a driving roller 104 and a tension roller 106, and is driven to rotate without wrinkles at a predetermined process speed in the direction of the arrow by driving and tensioning by the rollers 104 and 106. Reference numeral 105 denotes a pressure contact roller that is brought into pressure contact with the drive roller 104 with the belt 108 interposed therebetween, and is driven to rotate in the direction indicated by the arrow by driving the drive roller 104. A pressure nip portion between the driving roller 104 and the pressure roller 105 sandwiching the belt 108 is a nip N ′.

  As an example, the belt 108 has a release layer in which a conductive material is added to a fluororesin such as PTFE or PAF on at least the image contact surface side of a heat resistant film such as polyimide, polyetherimide, PES, or PFA having a thickness of 20 μm. 10 μm coated. The belt generally has a total thickness of 100 μm, more preferably less than 40 μm.

  The pressure roller 105 is a roller having a rubber elastic layer having good releasability, such as silicon rubber, and is in pressure contact with the driving roller 104 with the belt 108 sandwiched at a total pressure of 4-7N. In this example, a core metal having an outer diameter of 10 mm was wound with a silicon rubber having a thickness of 5 mm, and a PFA tube having a thickness of 30 μm was provided as the outermost layer.

  The sheet p that has passed through the fixing nip N of the upstream fixing device is sandwiched by the nip N ′ between the driving roller 104 and the pressure roller 105 disposed opposite thereto via the belt 108. At this time, since the toner on the paper p is just after passing through the fixing device, it is not completely hardened and is in close contact with the belt 108 at the nip N ′. Thereafter, the belt member 108 and the surface on which the toner image t on the paper p is held are in close contact with each other, and are conveyed to the tension roller 106 by driving the driving roller 104. In this process, the sheet is conveyed while being sufficiently cooled by heat radiation through the belt member, and then separated through the tension roller 106. In this cooling process, the toner surface becomes smoother than after passing through the fixing nip N, and a print with a high gloss value can be obtained. As described above, the cooling unit is realized by the conveyance unit provided downstream of the fixing device, and printing with a high gloss value is possible.

  Next, a method for obtaining a low gloss print will be specifically described. In order to obtain a low-gloss print, the tension roller 106 is lifted up to the position Y, and the belt member 108 is peeled from the paper p immediately after passing through the nip N ′. As a result, since the paper p carrying the toner image t is separated immediately after passing through the nip N ′, it is not cooled and separated, and a low-gloss print in which the toner surface is not so smooth is obtained.

As described above, in this embodiment, after the paper passes through the nip N ′, it is possible to obtain both high and low gloss prints by bringing the belt member into contact with or peeling from the paper, and the gloss control is possible. A simple fixing device is realized.
An example of printing in the high / low gloss mode in the above-described electrophotographic apparatus will be shown below. The host computer is configured so that gloss can be selected on the menu of the printer driver. When the user selects the high gloss mode, the printer places the tension roller 106 at the position X, and the belt member contacts the paper. As a result, a high gloss print as shown in Table 1 is obtained by cooling separation.

  The gloss evaluation was performed using a gloss meter PG-3D manufactured by Nippon Denshoku Co., Ltd., at an input / output angle of 75 ° with respect to the vertical direction of the paper surface.

  Table 1 shows the results for a process speed of 94 mm / s and a fixing temperature of 180 ° C, but the gross value is about 15 for a conventional induction heating type on-demand fixing unit without a transport unit (part A in Fig. 1). On the other hand, the gloss value in the high gloss mode in this embodiment is about 60, which is a very high gloss value.

  When the user selects the low gloss mode, the tension roller 106 is lifted to the position Y, and the belt member 108 is peeled from the paper p after passing through the nip N ′. As a result, as shown in Table 1, in the low gloss mode of this embodiment, a print with a gloss value as low as about 15 similar to that of the conventional fixing device can be obtained.

  As described above, in the present embodiment, a high gloss mode is selected for a print that requires a high gloss, and a low gloss mode is selected for a print that requires a low gloss to meet the user's request. Gross control is possible.

  In this embodiment, the fixing function is provided by the fixing unit alone, and the gloss-up function is provided by the transport unit. For this reason, high-gloss printing without gloss unevenness is realized by function separation. Further, since the toner t is once fixed on the paper p by the fixing device, gloss unevenness can be prevented as shown in Table 1 without providing a thick rubber member layer on the belt 108 in the transport unit.

  As described above, in this embodiment, a conveyance unit is provided on the downstream side of the fixing device in the sheet conveyance direction, and the belt member after passing through the nip is brought into contact with or separated from the paper, thereby preventing high gloss / low gloss without uneven gloss. It is possible to perform gloss control to obtain both prints.

  Further, the present invention is not limited to the configuration of the fixing device and the conveyance unit of the present embodiment.

<Example 2>
The present embodiment is characterized in that a higher gloss than in the first embodiment can be achieved by providing a heating function to the drive roller in the transport unit of the first embodiment.

  Specific examples are shown below. The electrophotographic apparatus used in this embodiment is the same as that used in the first embodiment except for the fixing apparatus, and the fixing apparatus is basically the same as FIG. 1 as shown in FIG. 1 differs from FIG. 1 only in that a halogen heater is incorporated in the cored bar 109 of the roller 104. The method for obtaining high gloss is described below.

  The sheet p that has passed through the fixing nip N of the upstream fixing device is sandwiched by the nip N ′ between the driving roller 104 and the pressure roller 105 disposed opposite thereto via the belt 108. At that time, the toner t is once melted in the nip N ′ by the driving roller 104 heated by the halogen heater in the core metal 109 and is in close contact with the belt 108. Then, as in the first embodiment, the belt member 108 and the surface on which the toner image t on the paper p is held are in close contact with each other, and are conveyed to the tension roller 106 by driving the driving roller 104. In the conveying process, the sheet is conveyed while being sufficiently cooled by heat radiation through the belt member, and separated after passing through the tension roller 106.

  In this embodiment, since the toner t is melted by the heated driving roller 104 in the nip N ′, the adhesion with the surface of the toner t when contacting the belt 108 is higher than that in the first embodiment. As a result, the smoothness of the surface of the toner t is increased as compared with Example 1, and a gloss value higher than that of Example 1 can be obtained.

  Similarly to the first embodiment, the technique for obtaining a low-gloss print is raised by moving the tension roller 106 in FIG. 2 to the Y position and separating the belt 108 from the paper p immediately after passing through the nip N ′. Although a print is obtained, a higher gloss value than that in the low gloss mode of the first embodiment can be obtained by melting the toner by the driving roller 104 heated in the nip N ′ portion.

  Also in the present embodiment, as in the first embodiment, since the user can select the gloss mode on the printer driver, the user can perform the gloss control.

  The gloss values obtained in this example are shown in Table 2. In the present embodiment, a high gloss mode of about 80 can be obtained and a low gloss mode of about 30 can be obtained in comparison with the conventional induction overheating type fixing unit which is about 15 gloss. it can.

  Further, the present embodiment can also be realized with the configuration as shown in FIG. 4, and the same effect as the effect in FIG. 3 described above can be obtained. In FIG. 4, 112 is a driving roller, 113 is a conveying roller, and 104 'is a heating roller. In the configuration of FIG. 4, the belt 108 is driven by a driving roller 112. After passing through the fixing nip N, the paper p is sandwiched between the driving roller 112 and the transport roller 113 via the belt 108 and transported, and then enters the nip N ′. Thereafter, high gloss and low gloss prints are realized in the same manner as in FIG. .

  As described above, in this embodiment, in addition to the first embodiment, the driving roller can be provided with a heating mechanism, so that a higher gloss value than that in the first embodiment can be realized and the belt is passed after passing through the nip N ′. Provided is an electrophotographic apparatus capable of gloss control which can realize a low gloss value by being separated from a sheet.

  Further, the present invention is not limited to the configuration of the fixing device and the conveyance unit of the present embodiment.

Sectional view of the fixing device of Example 1 Sectional view of the fixing device of Example 2 Cross section of electrophotographic device Sectional drawing of the fixing device of the modification of Example 2

Explanation of symbols

11, 12, 13, 14 Photosensitive drum 21, 22, 23, 24 Charging roller 31, 32, 33, 34 Exposure device 41, 42, 43, 44 Developing device 51, 52, 53, 54 Transfer roller 61, 62, 63 , 64 Photoconductor cleaning device 7 Adsorption roller 8 Transfer belt 9 Fixing device
91 Fusing sleeve
92 induction coil
93 Excitation core
94 Pressurized stay
95 Sleeve guide
96 sliding plate
97 Pressure roller
98 Pressure roller core
99 Pressure backup roller
104 Drive roller
104 'heating roller
105 Pressure roller
106 Tension roller
108 belt
109 Driving roller core
110 Pressure roller cored bar
111 Roller core with built-in halogen heater
112 Drive roller
113 Conveyor roller
114 Drive roller core
115 Conveyor roller core

Claims (3)

  A heating device for fixing toner to a transported material carrying a toner image, a film member, at least two support members for supporting the film member, and a film member at a downstream portion in the transport direction of the transported material A conveyance unit including a pressure member that is in contact with one of the support members with the nipping portion interposed therebetween, and the nip portion formed by the contact between one of the support members and the pressure member; The film member is held so that the surface on which the toner image is carried and the film member are in contact with each other, and the film member and the surface on which the toner image of the conveyed material is carried are kept in close contact with each other. A heating apparatus, wherein the film member and the transported material are separated after being transported while being cooled to a separation point between the film member and the transported material.   In the transport unit, by retracting one of the support members in a direction of peeling from the transported material, the transported material is brought into contact with the pressure member by contacting one of the support members. 2. The heating apparatus according to claim 1, wherein the film member and the material to be transported are separated simultaneously with passing through the formed nip portion.   3. The heating apparatus according to claim 1, wherein one of the support members in the transport unit has a heating mechanism.

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