JP2006259299A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent the occurrence of defective fixing even when starting print in a pressure release state, in a fixing device wherein a heat means and a pressure means capable of being press-fitted and being released from press-fitting are provided with a belt configuration or an external heat means. <P>SOLUTION: The heating means and the pressure means have driving means and driving sources, respectively so that the heating means and the pressure means can be driven, respectively even when released from press-fitting. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an image forming apparatus such as a copying machine, a printer, a facsimile, and the like. The present invention relates to a forming apparatus.

  In an electrophotographic image forming apparatus, a toner image is formed on an image forming body (photoreceptor) by charging, image exposure, and developing means, and the formed toner image is transferred onto a transfer material (recording paper) by a transferring means. The transfer material holding the toner image is pressed and passed between a heating unit and a pressurizing unit that form a nip portion, and is fixed by heating and pressurizing.

  Since the toner image is fixed to the transfer material within the nip time that passes through the nip portion, a color image forming apparatus in which an overlapping toner layer is formed, or a high-speed machine in which the transfer material moves at high speed, It is necessary to increase the width, and a fixing belt or a pressing roller having an elastic layer that is deformed by pressing is used.

  In the case of using a fixing belt, the fixing belt is stretched between a supporting heating roller and a supporting pressure roller. In an elastic heating roller provided with an elastic layer, an external heating roller is provided around the rotating elastic roller. This is done by abutting.

  Since the fixing belt is heated at the contact point with the supporting heating roller, the fixing belt is kept rotating to be in a uniform heating state over the entire circumference. Even in the case of the elastic heating roller, since it is heated from the point of contact with the external heating roller, the elastic heating roller is kept in a uniform heating state over the entire circumference of the elastic heating roller by maintaining its rotation.

Patent Document 1 describes a fixing device in which a nip portion is formed between a heating belt on a heating side and a hard receiving roller, and the receiving roller side is driven. Although this fixing device is configured to be able to release the pressure bonding, the heating belt on the heating side cannot be driven at the time of releasing the pressure bonding, so the fixing belt cannot be maintained at a uniform temperature over the entire circumference. There is a problem that a fixing failure occurs at the start of printing, or the printing is not immediately started.
JP 2001-159856 A

  According to the present invention, when the heating unit and the pressurizing unit that enable the pressure bonding and the pressure cancellation are used for the fixing device having the belt configuration or the external heating unit, the fixing failure occurs even when printing is started from the pressure cancellation state. An object of the present invention is to provide an image forming apparatus that can immediately start printing.

In order to solve the above problems and achieve the object, the present invention is configured as follows.
(Claim 1)
The toner image formed on the image forming body by the image forming means is transferred directly or via an intermediate transfer body onto the transfer material, and the toner image on the transfer material is heated and pressed by the heating means and the pressurizing means in a pressure-bonded state. In an image forming apparatus that performs fixing by applying pressure,
The heating unit and the pressurizing unit are a fixing device having either a belt configuration or an external heating unit, and the heating unit and the pressurizing unit can be bonded and released, and the heating unit and the pressurizing unit The image forming apparatus according to claim 1, wherein the pressurizing unit includes a driving unit, and each of the pressing units can be driven even when the pressure bonding is released.
(Claim 2)
The image forming apparatus according to claim 1, wherein the heating unit and the driving unit of the pressurizing unit have independent driving sources.
(Claim 3)
The image forming apparatus according to claim 1, wherein the heating unit and the driving unit of the pressurizing unit have the same driving source, and one driving unit has a one-way clutch.

  According to the first aspect of the present invention, both the heating means side and the pressurizing means side can be driven even in the standby state when the pressure is released. In the released state, the surface temperature of the belt peripheral surface or roller peripheral surface can be kept uniform, and good fixing can be performed from the start of printing. In addition, it is possible to immediately make a print ready state when printing is started.

  According to the second aspect of the present invention, the heating means and the pressure means can be driven independently, respectively, and it becomes easy to achieve the target set temperature, and better fixability is obtained. Will be.

  According to the third aspect of the present invention, the cost can be reduced by driving both the heating means and the pressurizing means with one drive source. In addition, since a one-way clutch is used, at the time of crimping, one of the peripheral speeds is driven to the higher speed, and torque increase and speed fluctuation can be suppressed.

  (1) An embodiment of the present invention will be described. The description in this column does not limit the technical scope of the claims or the meaning of terms. In addition, the following assertive description in the embodiment of the present invention shows the best mode, and does not limit the meaning or technical scope of the terms of the present invention.

  An image forming apparatus equipped with a belt fixing device according to the present invention will be described below with reference to FIG.

  In FIG. 1, the image forming apparatus GS includes an image forming apparatus main body GH and an image reading apparatus YS.

  The image forming apparatus main body GH is called a tandem type color image forming apparatus, and includes a plurality of sets of image forming units 10Y, 10M, 10C, and 10K, a belt-like intermediate transfer member 6, a sheet feeding and conveying unit, and a fixing unit to be described later. Device 17.

  An image reading device YS including an automatic document feeder 201 and a document image scanning exposure device 202 is installed on the upper part of the image forming apparatus main body GH. The document d placed on the document table of the automatic document feeder 201 is transported by a transport unit, and an image on one or both sides of the document is scanned and exposed by the optical system of the document image scanning exposure device 202, and the line image sensor CCD is scanned. Is read. At this time, the document D conveyed from the document table is subjected to glossiness level detection sensor PKa used as a gloss level selection unit to determine the glossiness of the document image, monochrome and color of the document image, and double-sided image discrimination. Done.

  The analog signal photoelectrically converted by the line image sensor CCD is subjected to analog processing, A / D conversion, shading correction, image compression processing, etc. in the image processing unit, and once stored in the memory, the image writing unit (exposure means) ) Send signals to 3Y, 3M, 3C, 3K.

  The image forming unit 10Y that forms a yellow (Y) image includes a charging unit 2Y, an exposure unit 3Y, a developing device 4Y, and a cleaning unit 8Y disposed around a photosensitive drum 1Y as an image carrier. The image forming unit 10M that forms a magenta (M) color image includes a photosensitive drum 1M as an image carrier, a charging unit 2M, an exposure unit 3M, a developing device 4M, and a cleaning unit 8M. The image forming unit 10C that forms a cyan (C) image includes a photosensitive drum 1C as an image carrier, a charging unit 2C, an exposure unit 3C, a developing device 4C, and a cleaning unit 8C. The image forming unit 10K that forms a black (K) image includes a photosensitive drum 1K as an image carrier, a charging unit 2K, an exposure unit 3K, a developing device 4K, and a cleaning unit 8K. The charging unit 2Y and the exposure unit 3Y, the charging unit 2M and the exposure unit 3M, the charging unit 2C and the exposure unit 3C, and the charging unit 2K and the exposure unit 3K constitute a latent image forming unit.

  4Y, 4M, 4C, and 4K are developing devices that include a two-component developer composed of a toner having a small particle diameter and a carrier of yellow (Y), magenta (M), cyan (C), and black (K). .

  The intermediate transfer body 6 is wound around a plurality of rollers and is rotatably supported.

  Each color image formed by the image forming units 10Y, 10M, 10C, and 10K is sequentially transferred (primary transfer) by the transfer means 7Y, 7M, 7C, and 7K onto the rotating intermediate transfer body 6 and synthesized. A color image is formed. The recording paper P as a transfer material accommodated in the paper feed cassette 20 is fed by the paper feed means 21 and is conveyed to the transfer means 7A via the paper feed rollers 22A, 22B, 22C, the registration rollers 23, etc. A color image is transferred onto the recording paper P (secondary transfer). The recording paper P onto which the color image has been transferred is sandwiched by a pressure nip portion N (see FIG. 2; not shown in FIG. 1) formed in the fixing device 9, and heat and pressure are applied. As a result, the color toner image (or toner image) on the recording paper P is fixed and fixed on the recording paper P, and is sandwiched between the discharge rollers 24 on the discharge path side and placed on the discharge tray 25 outside the apparatus. Is done.

  At the time of double-sided image formation, a color image (color toner image) is formed on one side (front surface), and the recording paper P discharged from the fixing device 9 is branched from the sheet discharge path by the branching unit 26 and is fed respectively. Through the lower circulating paper path 27A constituting the conveying means, the front and back are reversed by the reverse conveying path 27B which is a refeeding mechanism (ADU mechanism), and passes through the refeeding conveying section 27C to be fed by the feed roller. Merge at 22D. The recording paper P that has been reversely conveyed (circulated and reversed) is conveyed again to the secondary transfer roller 7A via the timing roller 23, and a color image (color toner image) is formed on the other side (back surface) of the recording paper P. Batch transfer. The recording paper P to which the color image has been transferred is fixed by the fixing device 9 and is sandwiched between the paper discharge rollers 24 on the paper discharge path side and placed on a paper discharge tray 25 outside the apparatus.

  On the other hand, after the color image is transferred to the recording paper P by the transfer means 7A, the residual toner is removed by the cleaning means 8A from the intermediate transfer body 6 from which the recording paper P is separated by curvature.

  (2) A belt fixing device used in the image forming apparatus of the present invention will be described below with reference to FIG.

  The fixing device 9 includes a fixing belt 91 in which a metal substrate or a heat-resistant resin substrate and silicon rubber are molded into a belt shape, and supports and conveys the fixing belt 91 with the transfer material and the fixing belt 91 sandwiched therebetween. It comprises a roller 92, an external pressure roller 93 opposed thereto, and a support heating roller 94 incorporating a heater 94a that supports and conveys the fixing belt 91. Further, in order to maintain the surface temperature of the external pressure roller 93 at a temperature suitable for fixing, an external heating roller 95 that contacts the outer periphery of the external pressure roller 93 may be provided. In the belt fixing device 9 configured as described above, the pressure nip portion N is formed by the support pressure roller 92 and the external pressure roller 93.

  The supporting pressure roller 92 includes a rotating shaft 921 using a cylindrical metal pipe or a metal shaft having a thickness of 2 to 5 mm, and an outer surface of the rotating shaft 921 fixed with an elastic layer 922 of 10 mm thick Si sponge. A soft roller having a diameter of 45 mm. The hardness of the soft roller having the Si sponge elastic layer 922 fixed to the rotating shaft 921 according to the Asker C display is Asker C30 ° in this embodiment. The Asker C display conforms to JIS K7312 and JIS 6050, and is a display used for measuring the hardness of soft rubber or sponge.

  The external pressure roller 93 has a rotating shaft 931 using a cylindrical metal pipe having a thickness of 2 to 5 mm, and a 3 mm thick Si rubber elastic layer 932 fixed to the outer peripheral surface of the rotating shaft 931, and further to the outside. And a soft roller having an outer diameter of 50 mm covered with a PFA (perfluoroalkoxy) tube 933 as a release layer. In this embodiment, the hardness of the soft roller having the Si rubber elastic layer 932 fixed to the rotating shaft 931 is 65 ° in Asker C.

  The elastic layer 922 of the support pressure roller 92 uses a softer material than the elastic layer 932 of the external pressure roller 93, and the elastic layer is thicker. 92 is mainly deformed to maintain the pressure contact state. In the embodiment, a nip portion of 16 mm is formed by applying a load of 900 N.

  The fixing belt 91 wound around the supporting pressure roller 92 is an endless belt having a diameter of 80 mm having a 200 μm Si rubber layer and a 30 μm PFA (perfluoroalkoxy) tube layer outside a 70 μm thick polyimide substrate. The fixing belt 91 is heat-transferred and heated through a heating roller by a heater 94a built in a support heating roller 94 that is also wound around.

  The support heating roller 94 is a roller having an outer diameter of 50 mm in which a fluororesin layer is provided on the outer periphery of an aluminum core having a thickness of 2 mm, and a fixing belt is provided at the end of the roller so that the fixing belt extends in the axial direction. The position is regulated so as not to slip.

  (3) In the fixing device 9 according to the present embodiment, it is possible to press and release the pressure between the heating unit and the pressure unit. In this example, the external pressure roller 93 is moved to move the fixing belt 91. Thus, a contact and separation operation is performed with respect to the support pressure roller 92 in a pressure-bonded state.

  The heating means and the pressurizing means each have a gear connected to and driven by the heating means or the pressurizing means as the driving means, and each has a motor as an independent driving source or the same driving source. Therefore, it is connected to the drive means, and can be driven regardless of the contact between the heating means and the pressurizing means.

  3 and 4 show an example in which two motors M1 and M2 are provided as drive sources, and FIG. 3 shows a state in which the heating means and the pressure means are pressure-bonded to form a nip portion N. FIG. 4 shows a separated state.

  A gear G10 is coaxially attached as a driving means to the supporting pressure roller 92 on the heating means side, and the gear G10 is in mesh with the gear G11. A motor M1, which is a drive source, is provided directly on the shaft core G11a of the gear G11 or via a gear, and the support pressure roller 92 is rotated by the rotation of the motor M1.

  A gear G20 is coaxially attached as a driving means to the external pressure roller 93 which is a pressure means, and the gear G20 is in mesh with the gear G21. A motor M2 which is a drive source is provided directly on the shaft core G21a of the gear G21 or further via a gear, and the external pressure roller 93 is rotated independently of the contact and separation by the rotation of the motor M2. ing.

  The pressure-bonding and pressure-release of the external pressure roller 93 with respect to the support pressure roller 92 via the fixing belt 91 are performed by a mechanism described below.

  The shafts 93a on both sides of the external pressure roller 93 are supported by a support lever 96 that can swing around the shaft core G21a of the gear G21, and the tension spring 97 acts on the support lever 96 in the pressure-bonding direction. is doing. Reference numeral 98 denotes a switching cam. When the cam position of the switching cam 98 is controlled, the external pressure roller 93 is pressed or separated. At this time, the gear G21 and the gear G20 are in meshing relationship regardless of the posture, the driving rotation by the motor M2 is transmitted, and the positional relationship between the external heating roller 95 and the external pressure roller 93 is maintained. The contact state where heat transfer is performed is maintained.

  Further, since the nip pressure when the external pressure roller 93 is pressed is determined by the tension of the tension spring 97, the tension of the tension spring 97 is adjusted in advance.

  5 and 6 show an example in which the same motor M0 is provided as a drive source, and FIG. 5 shows a state in which the heating means and the pressure means are pressure-bonded to form a nip portion N. 6 shows a separated state. Members having the same functions as those already described with reference to FIGS. 3 and 4 are denoted by the same reference numerals and description thereof is omitted.

  In the present embodiment, the gear G10 attached to the support pressure roller 92 and the gear G20 attached to the external pressure roller 93 are connected via a gear G11 and a gear G21. A motor M0 is provided directly or via a gear on the shaft core G11a of the gear G11, and the support pressure roller 92 and the external pressure roller 93 rotate simultaneously with the rotation of the motor M0.

  However, the peripheral speed of the supporting pressure roller 92 rotating at the same time and the peripheral speed of the external pressure roller 93 are slower, in this embodiment, between the roller shaft of the supporting pressure roller 92 and the gear G10. The one-way clutch 99 is provided, and at the time of press-fitting rotation, the support pressure roller 92 is driven and rotated by the external pressure roller 93 having a high peripheral speed to suppress an increase in torque and speed fluctuation.

  Other configurations are the same as those described with reference to FIGS.

  (4) In FIG. 2, the temperature sensor S1 is at a position facing the support heating roller 94 with a slight gap across the fixing belt 91, and the temperature sensor S2 is at a position facing the external pressure roller 93 with a slight gap. A temperature sensor S3 is provided at a position facing the external heating roller 95 with a slight gap. The temperature sensor S3 is a sensor provided mainly for the purpose of monitoring an excessive temperature rise of the external heating roller 95. The fixing operation is performed based on the temperature detected by the temperature sensors S1 and S2, and the fixing is performed. Is performed under a fixing temperature condition in which the temperature detected by the temperature sensor S1 is T1 and the temperature detected by the temperature sensor S2 is T2.

  In the present invention, the external pressure roller 93 is always kept apart except when the transfer paper holding the toner image passes and is fixed. During the warm-up, the supporting pressure roller 92 and the external pressure roller 93 are heated in a stopped posture until the temperature detected by the temperature sensor S1 reaches T1-ΔT1 and the temperature detected by the temperature sensor S2 reaches T2-ΔT2. When the temperature is reached, the supporting pressure roller 92 and the external pressure roller 93 start rotating under the separated conditions, the temperature detected by the temperature sensor S1 reaches T1, and the temperature detected by the temperature sensor S2 reaches T2. Until the detected temperature reaches T1 and T2, the print OK is displayed.

  Heating without rotating at the initial stage of warming up is effective for energy saving by shortening the time for temperature to rise to a predetermined temperature from the point where heat is dissipated to the surroundings during rotation more than when stationary. can get.

  At the time of standby, while the temperature detected by the temperature sensor S1 is maintained at T1 and the temperature detected by the temperature sensor S2 is maintained at T2, the support pressure roller 92 and the external pressure roller 93 are alternately stopped and rotated for an appropriate time. Operations such as intervals, for example, 30 sec stop and 30 sec rotation are alternately performed.

  By performing such an operation, the ambient temperature of the fixing belt 91 and the external pressure roller 93 is kept uniform regardless of the fixing time, and good fixing is immediately performed.

  When the start button is turned on, the support pressure roller 92 and the external pressure roller 93 are rotated, and the external pressure roller 93 is pressed to form a nip portion N, which continues during the printing operation. In the initial stage of fixing, measures such as temporarily setting the set temperature of the temperature sensors S1 and S2 may be performed.

  According to the present invention, since the external pressure roller 93 is not in a pressure-bonded state except during fixing, it is stopped for a long time and the same portion is in a pressure-bonded state. 91, the phenomenon that the characteristics of the supporting pressure roller 92 and the like are deteriorated or damaged is avoided.

FIG. 3 is a cross-sectional view illustrating a configuration of an image forming apparatus. Sectional drawing which shows the structure of a belt fixing apparatus. Sectional drawing which shows the crimping | compression-bonding state of the belt fixing apparatus which shows a drive system. FIG. 4 is a sectional view showing an open state of the fixing device shown in FIG. 3. Sectional drawing which shows the crimping | compression-bonding state of the belt fixing apparatus which shows another drive system. FIG. 6 is a cross-sectional view illustrating an open state of the fixing device illustrated in FIG. 5.

Explanation of symbols

DESCRIPTION OF SYMBOLS 9 Belt fixing apparatus 91 Fixing belt 92 Support pressure roller 93 External pressure roller 94 Support heating roller 95 External heating roller 96 Support lever 97 Tension spring 98 Switching cam 99 One-way clutch G10, G11, G20, G21 Gear M0, M1, M2 motor

Claims (3)

The toner image formed on the image forming body by the image forming means is transferred directly or via an intermediate transfer body onto the transfer material, and the toner image on the transfer material is heated and pressed by the heating means and the pressurizing means in a pressure-bonded state. In an image forming apparatus that performs fixing by applying pressure,
The heating unit and the pressurizing unit are a fixing device having either a belt configuration or an external heating unit, and the heating unit and the pressurizing unit can be bonded and released, and the heating unit and the pressurizing unit The image forming apparatus according to claim 1, wherein the pressurizing unit includes a driving unit, and each of the pressing units can be driven even when the pressure bonding is released. The image forming apparatus according to claim 1, wherein the heating unit and the driving unit of the pressurizing unit have independent driving sources. The image forming apparatus according to claim 1, wherein the heating unit and the driving unit of the pressurizing unit have the same driving source, and one driving unit has a one-way clutch.

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