Fixing device and image formation device

Abstract

To provide a fixing device using a cylinder of a fluororesin having a fold as a surface layer which suppresses deterioration of image quality caused by the fold, compared with a prior art not corresponding to a deteriorated fold after operation of an image formation device.SOLUTION: A fixing device (F) includes: fixing means (Fh, Fp) which pressurizes and fixes an image of a surface of a medium (S) while heating, and has a base layer (2) and a surface layer (3) in which a cylinder having a fold (3a) is coated with the base layer (2) and a coefficient of thermal expansion is different from that of the base layer (2); and control means (C) which controls the fixing means (Fh, Fp), and executes a fold elimination operation of stretching the fold (3a) before start of the fixation operation, in a case in which a condition to deteriorate the predetermined fold (3a) is satisfied, when the fixing operation is started.SELECTED DRAWING: Figure 3

Description

[Technical field]

[0001] The present invention relates to a fixing device and an image forming apparatus having the fixing device. [Background technology]

[0002] 2. Description of the Related Art With regard to a fixing device that fixes an image in an image recording device, the technology described in Patent Document 1 below is conventionally known.

[0003] Patent Document 1 describes a configuration in which a fixing member or a pressure member is covered with a fluororesin tube. The fluororesin tube in Patent Document 1 has unevenness at the folds formed during the manufacturing process, and the unevenness at the folds is smoothed by a smoothing process. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2001-109295 A ("0023" to "0035", FIG. 3) Summary of the Invention [Problem to be solved by the invention]

[0005] The present invention has a technical objective of suppressing deterioration in image quality caused by creases in a fixing device that uses a creased fluororesin tube as a surface layer, compared to conventional technology that does not deal with creases that deteriorate after the image forming device is operated. [Means for solving the problem]

[0006] In order to solve the above technical problem, the fixing device of the invention described in claim 1 comprises: A fixing means for fixing an image on a surface of a medium by applying heat and pressure to the image, the fixing means having a base layer and a surface layer formed by covering a folded tube with the base layer and having a thermal expansion coefficient different from that of the base layer; a control means for controlling the fixing means, the control means executing a crease removing operation to straighten the crease before the start of the fixing operation when a predetermined condition for worsening the crease is satisfied when the fixing operation is started; The present invention is characterized by comprising:

[0007] The invention described in claim 2 is the fixing device described in claim 1, the fixing means including a heating means which is heated by a heat source and rotates, and a pressure means which is disposed opposite to the heating means and has the base layer and the surface layer; The present invention is characterized by comprising:

[0008] The invention described in claim 3 is the fixing device described in claim 2, A core material, the base layer being provided on the outer periphery of the core material and being made of an elastic body, and the surface layer being made of the fold-shaped fluororesin tube, The present invention is characterized by comprising:

[0009] The invention described in claim 4 is the fixing device described in claim 1, the control means determining that the condition for the crease to worsen is satisfied when the operating time of the previous fixing operation reaches a predetermined first threshold value and the elapsed time since the end of the previous fixing operation is within a predetermined range; The present invention is characterized by comprising:

[0010] The invention described in claim 5 is the fixing device described in claim 1, the control means for determining that a condition for worsening the crease is satisfied when the temperature of the fixing means is within a predetermined range; The present invention is characterized by comprising:

[0011] The invention as set forth in claim 6 is the fixing device as set forth in claim 1, the crease eliminating operation of heating the fixing means to a predetermined temperature; The present invention is characterized by comprising:

[0012] The invention described in claim 7 is the fixing device described in claim 1, the crease removal operation being performed in a state in which a load applied to the crease is reduced compared to that during the fixing operation; The present invention is characterized by comprising:

[0013] The invention described in claim 8 is the fixing device described in claim 7, the crease removal operation, by reducing the pressure applied to the fixing means compared to that during the fixing operation, so that the load applied to the crease is reduced; The present invention is characterized by comprising:

[0014] The invention as set forth in claim 9 is the fixing device as set forth in claim 7, the crease eliminating operation in which the load applied to the crease is reduced by rotating the fixing means at a speed slower than that during the fixing operation; The present invention is characterized by comprising:

[0015] In order to solve the above technical problem, the image forming apparatus according to the invention described in claim 10 comprises: An image holding means; a transfer means for transferring the image held on the image holding means to a medium; A fixing device according to any one of claims 1 to 9, which fixes an image transferred onto a medium; The present invention is characterized by comprising: Effect of the Invention

[0016] According to the invention described in claims 1 and 10, in a fixing device that uses a folded fluororesin tube as a surface layer, it is possible to suppress deterioration in image quality caused by folds, compared to conventional technologies that do not deal with folds that deteriorate after the image forming device is operated. According to the invention as set forth in claim 2, it is possible to suppress deterioration in image quality caused by creases in the pressing means. According to the invention as set forth in claim 3, it is possible to suppress deterioration in image quality caused by creases in the surface layer of the fluororesin. According to the invention described in claim 4, when the elapsed time is in a state where the crease worsens after the operation time reaches the first threshold and the fixing unit is sufficiently heated, the crease removal operation can be performed. Therefore, it is possible to suppress unnecessary crease removal operations.

[0017] According to the invention as set forth in claim 5, when the temperature of the fixing unit is within a predetermined range, the crease removal operation can be executed, thereby making it possible to prevent unnecessary crease removal operations. According to the invention as set forth in claim 6, the fixing means can be heated to thermally expand the base layer and the surface layer, thereby smoothing out the folds. According to the seventh aspect of the invention, the life of the fixing device can be extended, compared to a case in which the load on the fold is not reduced. According to the invention as set forth in claim 8, the pressure applied to the fixing means can be reduced, thereby reducing the load on the fold. According to the invention as set forth in claim 9, the rotation speed of the fixing means can be slowed down, thereby reducing the load on the fold. [Brief description of the drawings]

[0018] [Figure 1] FIG. 1 is an overall explanatory diagram of an image forming apparatus according to a first embodiment. [Diagram 2] FIG. 2 is a diagram illustrating a main part of the image recording unit of the first embodiment. [Diagram 3] FIG. 3 is a cross-sectional view of the fixing unit of the fixing device according to the first embodiment. [Figure 4] FIG. 4 is a functional block diagram of the control unit according to the first embodiment. [Diagram 5] FIG. 5 is a flowchart of a control process of the fixing device according to the first embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0019] Next, examples of the present invention will be described with reference to the drawings. However, the present invention is not limited to the following examples. In order to make the following explanation easier to understand, in the drawings, the front-to-back direction is the X-axis direction, the left-to-right direction is the Y-axis direction, and the up-down direction is the Z-axis direction, and the directions or sides indicated by arrows X, -X, Y, -Y, Z, and -Z are respectively the front, rear, right, left, upper, and lower, or the front side, rear side, right side, left side, upper side, and lower side. In addition, in the figures, a "·" inside a "○" means an arrow going from the back to the front of the page, and an "×" inside a "○" means an arrow going from the front to the back of the page. In the following description using the drawings, illustrations of components other than those necessary for the description are omitted as appropriate to facilitate understanding. EXAMPLES

[0020] FIG. 1 is an overall explanatory diagram of an image forming apparatus according to a first embodiment. 1, a copier U as an example of an image forming apparatus according to the first embodiment of the present invention has a printer U1 as an example of an image recording means and an example of an image recording device. A scanner U2 as an example of a reading means and an example of an image reading device is supported above the printer U1. An auto feeder U3 as an example of a document conveying device is supported above the scanner U2.

[0021] An original tray TG1, which is an example of a medium storage means, is disposed above the auto feeder U3. A plurality of originals Gi to be copied can be stacked and stored in the original tray TG1. Below the original tray TG1, an original discharge tray, which is an example of an original discharge section, is disposed. Between the document tray TG1 and the document discharge tray TG2, document transport rollers U3b are disposed along the document transport path U3a.

[0022] A platen glass PG, which is an example of a transparent document table, is disposed on the upper surface of the scanner unit U2. In the scanner unit U2 of the first embodiment, a reading unit U2a, which is an example of a reading unit, is disposed below the platen glass PG. The reading unit U2a of the first embodiment is supported along the lower surface of the platen glass PG so as to be movable in the left-right direction, which is an example of a sub-scanning direction. The reading unit U2a is electrically connected to the image processing unit GS.

[0023] FIG. 2 is a diagram illustrating a main part of the image recording unit of the first embodiment. The image processing unit GS is electrically connected to a writing circuit DL of the printer unit U1. The writing circuit DL is electrically connected to exposure devices LHy, LHm, LHc, and LHk, which are an example of a latent image forming means. The exposure devices LHy to LHk of the first embodiment are configured, for example, with an LED head in which a plurality of LEDs are arranged in the main scanning direction. The exposure devices LHy to LHk are configured to be able to output writing light corresponding to each of the colors Y, M, C, and K in response to a signal input from a writing circuit DL. The write circuit DL and the power supply circuit E have their write timing and power supply timing controlled in response to control signals from a control unit C, which is an example of a control means. In Fig. 1, photoconductors PRy, PRm, PRc, and PRk as an example of an image holding means are disposed above the exposure devices LHy to LHk. In Fig. 1 and Fig. 2, writing areas Q1y, Q1m, Q1c, and Q1k are formed by areas on the photoconductors PRy to PRk where the writing light is irradiated.

[0024] Charging rollers CRy, CRm, CRc, and CRk as an example of a charging means are disposed upstream of the writing areas Q1y to Q1k in the rotation direction of each of the photoconductors PRy to PRk. The charging rollers CRy to CRk in the first embodiment are supported in contact with the photoconductors PRy to PRk so as to be rotatable by the photoconductors PRy to PRk. Developing devices Gy, Gm, Gc, and Gk, which are an example of developing means, are disposed downstream of the writing areas Q1y-Q1k in the rotation direction of the photoconductors PRy-PRk. The developing areas Q2y, Q2m, Q2c, and Q2k are formed by the areas where the photoconductors PRy-PRk and the developing devices Gy-Gk face each other.

[0025] Primary transfer rollers T1y, T1m, T1c, and T1k, which are an example of a primary transfer means, are disposed downstream of the developing devices Gy-Gk in the rotation direction of the photoconductors PRy-PRk. Primary transfer areas Q3y, Q3m, Q3c, and Q3k are formed by areas where the photoconductors PRy-PRk and the primary transfer rollers T1y-T1k face each other. Photoconductor cleaners CLy, CLm, CLc, and CLk, which are an example of a cleaning means, are disposed downstream of the primary transfer rollers T1y to T1k with respect to the rotation direction of the photoconductors PRy to PRk. Dischargers Jy, Jm, Jc, and Jk, which are an example of a discharge means and an example of a discharge device, are disposed downstream of the photoconductor cleaners CLy-CLk with respect to the rotation direction of the photoconductors PRy-PRk.

[0026] The Y-color photoconductor PRy, charging roller CRy, exposure device LHy, developing device Gy, primary transfer roller T1y, photoconductor cleaner CLy, and static eliminator Jy constitute a Y-color image forming unit Uy as an example of a Y-color visible image forming means in Example 1 for forming a Y-color toner image. Similarly, the photoconductors PRm, PRc, and PRk, charging rollers CRm, CRc, and CRk, exposure devices LHm, LHc, and LHk, developing devices Gm, Gc, and Gk, primary transfer rollers T1m, T1c, and T1k, photoconductor cleaners CLm, CLc, and CLk, and static eliminators Jm, Jc, and Jk form a Y-color toner image. The image forming units Um, Uc, and Uk for the M, C, and K colors are configured as above.

[0027] A belt module BM, which is an example of an intermediate transfer device, is disposed above the photoconductors PRy to PRk. The belt module BM is an example of an image holding means, and has an intermediate transfer belt B, which is an example of an intermediate transfer means. The intermediate transfer belt B is made of an endless belt-like member. The intermediate transfer belt B in the first embodiment is rotatably supported by a tension roller Rt as an example of a tensioning means, a walking roller Rw as an example of a deviation correcting means, an idler roller Rf as an example of a driven means, a backup roller T2a as an example of an opposing means in the secondary transfer region, primary transfer rollers T1y to T1k, and a drive roller Rd as an example of a drive member. In the first embodiment, when the drive force is transmitted to the drive roller Rd, the intermediate transfer belt B rotates.

[0028] A secondary transfer roller T2b as an example of a secondary transfer means is disposed at a position facing the backup roller T2a across the intermediate transfer belt B. The backup roller T2a and the secondary transfer roller T2b constitute a secondary transfer unit T2 of the first embodiment as an example of a transfer device. A secondary transfer area Q4 is constituted by an area where the secondary transfer roller T2b and the intermediate transfer belt B contact each other. A belt cleaner CLb is disposed downstream of the secondary transfer area Q4 in the rotation direction of the intermediate transfer belt B, as an example of a cleaning device for the intermediate transfer body. The primary transfer rollers T1y-T1k, the intermediate transfer belt B, the secondary transfer unit T2, etc., constitute a transfer device T1+T2+B of the first embodiment as an example of a transfer means. The image forming units Uy-Uk and the transfer device T1+T2+B constitute an image recording unit Uy-Uk+T1+T2+B of the first embodiment.

[0029] In Fig. 1, four pairs of left and right guide rails GR as an example of a guide means are provided below the imaging units Uy to Uk. Each guide rail GR supports paper feed trays TR1, TR2, TR3, and TR4 as an example of a medium storage means so that they can be moved in and out in the front-rear direction. Recording paper S as an example of a medium is stored in the paper feed trays TR1 to TR4. A pickup roller Rp, which is an example of a take-out means, is disposed above and to the left of the paper feed trays TR1 to TR4. A separation roller Rs, which is an example of a separation means, is disposed downstream of the pickup roller Rp in the transport direction of the recording paper S. A paper feed path SH1, which is an example of a medium transport path, is formed downstream of the separation roller Rs in the transport direction of the recording paper S, extending upward. A plurality of transport rollers Ra, which are an example of a transport means, are disposed on the paper feed path SH1.

[0030] A manual feed tray TR0, which is an example of a medium storage means, is disposed in the lower left portion of the copier U. A pickup roller Rp0 is disposed in the upper right portion of the manual feed tray TR0, and a manual feed path SH0 extends from the manual feed tray TR0. The manual feed path SH0 merges with the feed path SH1. In the sheet feed path SH1, a registration roller Rr as an example of a conveyance timing adjustment unit is disposed upstream of the secondary transfer area Q4. A conveyance path SH2 extends from the registration roller Rr toward the secondary transfer area Q4.

[0031] A fixing device F is disposed downstream of the secondary transfer area Q4 in the conveying direction of the recording paper S. The fixing device F has a heating roller Fh as an example of a fixing means for heating, and a pressure roller Fp as an example of a fixing means for pressurizing. A fixing area Q5 is formed by a contact area between the heating roller Fh and the pressure roller Fp. A lower paper discharge tray TRh, which is an example of a medium discharge section, is formed on the upper surface of the printer unit U1. In the first embodiment, a finisher U4, which is an example of a post-processing device, is installed on the lower paper discharge tray TRh. Above the fixing device F, a paper discharge path, which is an example of a transport path, is installed. The path SH3 extends toward the lower discharge tray TRh. Discharge rollers Rh, which are an example of a medium transport means, are disposed at the downstream end of the discharge path SH3.

[0032] An upper discharge tray TRh2 as an example of a medium discharge section is disposed above the lower discharge tray TRh. An upper conveying path SH4 is formed above the fixing device F, branching off from the discharge path SH3 and extending toward the upper discharge tray TRh2. A reversible roller Rb, which is an example of a medium transport means, is disposed on the upper transport path SH4. A reversible path SH6, which is an example of a medium transport path, branches off to the lower left from the upper transport path SH4 above the branching position of the paper discharge path SH3 and the upper transport path SH4.

[0033] A gate GT1, which is an example of a switching means, is disposed across a branching portion between the discharge path SH3 and the upper transport path SH4 and a branching portion between the upper transport path SH4 and the reverse path SH6. The gate GT1 guides the recording paper S from the fixing device F toward the lower discharge tray TRh, and is supported switchably between a first guide position (second position) where the recording paper S is guided from the upper transport path SH4 to the reverse path SH6, and a second guide position (first position) where the recording paper S from the fixing device F is guided to the upper transport path SH4. A plurality of transport rollers Ra, which are an example of a medium transport means, are disposed on the reversing path SH6. The downstream end of the reversing path SH6 joins the paper feed path SH1 on the upstream side of the registration rollers Rr.

[0034] (Explanation of Image Forming Operation) In the copying machine U of the first embodiment having the above configuration, when an operator places an original Gi on the platen glass PG by hand to perform copying, the reading unit U2a moves from the initial position in the left-right direction, and the original Gi on the platen glass PG is exposed to light and scanned. When the automatic feeder U3 is used to automatically transport the original Gi to perform copying, the multiple originals Gi accommodated in the original tray TG1 are transported sequentially to the original reading position on the platen glass PG, pass through it, and are discharged to the original discharge tray TG2. Each original Gi that passes sequentially through the reading position on the platen glass PG is exposed to light and scanned by the reading unit U2a. The reflected light from the original Gi is received by the reading unit U2a. The reading unit U2a converts the received reflected light from the original Gi into an electrical signal. When double-sided reading of the original Gi is performed, the original Gi is also read by the reading sensor.

[0035] The image processing unit GS receives the electrical signals output from the reading unit U2a. The image processing unit GS converts the electrical signals of the R, G, and B color image read by the reading unit U2a into image information of yellow (Y), magenta (M), cyan (C), and black (K) for forming a latent image. The image processing unit GS outputs the converted image information to the writing circuit DL of the printer unit U1. Note that when the image is a single-color image, that is, a monochrome image, the image processing unit GS outputs image information of only black (K) to the writing circuit DL. The writing circuit DL outputs a control signal corresponding to the input image information to the exposure devices LHy to LHk. The exposure devices LHy to LHk output writing light corresponding to the control signal.

[0036] When image formation starts, each of the photoconductors PRy-PRk is rotated. A charging voltage is applied to the charging rollers CRy-CRk from a power supply circuit E. Thus, the surfaces of the photoconductors PRy-PRk are charged by the charging rollers CRy-CRk. An electrostatic latent image is formed on the surface of the charged photoconductors PRy-PRk by the exposure devices LHy-LHk in the writing areas Q1y-Q1k. The electrostatic latent images on the photoconductors PRy-PRk are developed into toner images, which are an example of visible images, by the developing devices Gy-Gk in the developing areas Q2y-Q2k.

[0037] The developed toner images are transported to primary transfer areas Q3y-Q3k that come into contact with intermediate transfer belt B, which is an example of an intermediate transfer body. In primary transfer areas Q3y-Q3k, a primary transfer voltage having a polarity opposite to the charge polarity of the toner is applied from a power supply circuit E to primary transfer rollers T1y-T1k. Therefore, the toner images on the photoconductors PRy-PRk are transferred to intermediate transfer belt B by primary transfer rollers T1y-T1k. In the case of a multi-color toner image, the toner image on the downstream side is transferred and superimposed on the toner image transferred to intermediate transfer belt B in the upstream primary transfer area. After the primary transfer, residues and deposits on the photoconductors PRy-PRk are cleaned by the photoconductor cleaners CLy-CLk. The surfaces of the photoconductors PRy-PRk after cleaning are neutralized by the static eliminators Jy-Jk. The surfaces of the photoconductors PRy-PRk after static elimination are recharged by the charging rollers CRy-CRk. The single-color or multi-color toner images transferred onto the intermediate transfer belt B by the primary transfer rollers T1y to T1k in the primary transfer areas Q3y to Q3k are transported to the secondary transfer area Q4.

[0038] The recording paper S on which an image is recorded is picked up by the pickup roller Rp of the paper feed tray TR1 to TR4 being used. If multiple sheets of recording paper S are picked up by the pickup roller Rp and stacked, they are separated one by one by the separation roller Rs. The recording paper S separated by the separation roller Rs is transported along the paper feed path SH1 by the transport roller Ra. The recording paper S transported along the paper feed path SH1 is sent to the registration roller Rr. The recording paper S loaded on the manual feed tray TR0 is also sent to the paper feed path SH1 by the pickup roller Rp0 via the manual feed path SH0 by the manual feed path SH0. The registration roller Rr transports the recording paper S to the secondary transfer area Q4 in time with the toner image formed on the intermediate transfer belt B being transported to the secondary transfer area Q4. A secondary transfer voltage of a polarity opposite to the charge polarity of the toner is applied to the secondary transfer roller T2b by the power supply circuit E. Therefore, the toner image on the intermediate transfer belt B is transferred from the intermediate transfer belt B to the recording paper S.

[0039] After the secondary transfer, the intermediate transfer belt B has any adhering matter or the like on its surface cleaned by a belt cleaner CLb. The recording paper S onto which the toner image has been secondarily transferred is heated and fixed when passing through a fixing area Q5. If post-processing is performed on the recording paper S with the image fixed thereon, the recording paper S is transported to a finisher U4, which is an example of a post-processing device installed in the lower paper output tray TRh. If post-processing is not performed on the recording paper S, the recording paper S is transported to the upper paper output tray TRh2. When the recording paper S is transported to the lower paper output tray TRh, the gate GT1 moves to the first guide position. Therefore, the recording paper S sent out from the fixing device F is transported along the paper output path SH3. The recording paper S transported along the paper output path SH3 is transported by the paper output rollers Rh toward the finisher U4 and the lower paper output tray TRh. The finisher U4 performs a binding process, which is an example of post-processing, on the recording paper S, and then discharges the recording paper S onto a lower paper discharge tray TRh.

[0040] When the recording paper S is discharged onto the upper discharge tray TRh2, the gate GT1 moves to the second guiding position, and the recording paper S is discharged onto the upper discharge tray TRh2. When the recording paper S is printed on both sides, the gate GT1 moves to the second guide position. Then, when the trailing edge of the recording paper S passes through the gate GT1, the gate GT1 moves to the first guide position and the reversing roller Rb rotates in the reverse direction. Therefore, the recording paper S is guided by the gate GT1 and sent to the reversing path SH6. The recording paper S conveyed through the reversing path SH6 is sent to the registration roller Rr in an inverted state.

[0041] (Description of Fixing Device) FIG. 3 is a cross-sectional view of the fixing unit of the fixing device according to the first embodiment. In FIG. 3, the heating roller Fh, which is an example of the fixing means and an example of the heating means of the first embodiment, and the pressure roller Fp, which is an example of the fixing means and an example of the pressure means of the first embodiment, each have a core 1, which is an example of a shaft portion and an example of a core material. An elastic layer 2, which is an example of a base layer, is formed on the outer periphery of the core 1. A release layer 3, which is an example of a surface layer, is laminated on the outer surface of the elastic layer 2. The release layer 3 of the first embodiment is made of a fluororesin, for example. The release layer 3 is preferably made of a fluororesin that has good releasability for toner and recording paper S, but is not limited thereto, and any material can be used. The release layer 3 in Example 1 can be produced by integral molding on the surface of the elastic layer 2, or the release layer 3 can be laminated on the outer surface of the elastic layer 2 by penetrating the elastic layer 2 into the inside of a fluororesin tube.

[0042] As described in Patent Document 1, folds may be formed in the fluororesin tube during the manufacturing process, and the folds 3a may remain even after the tube is laminated to the elastic layer 2. As described in Patent Document 1, it is also possible to perform a process to smooth out the folds 3a. In the first embodiment, the heating roller Fh and the pressure roller Fp are both configured in the same manner, but the present invention is not limited to this. Either one of them may be configured to use a fixing belt.

[0043] (Description of the control unit of the first embodiment) FIG. 4 is a functional block diagram of the control unit according to the first embodiment. In FIG. 4, the control unit (controller) C, which is an example of a control means of the copier U, has an input / output interface I / O for inputting and outputting signals from and to the outside. The control unit C also has a ROM (read-only memory) in which programs and information for performing necessary processing are stored. The control unit C also has a RAM (random access memory) for temporarily storing necessary data. The control unit C also has a CPU (central processing unit) for performing processing according to the programs stored in the ROM or the like. Therefore, the control unit C in the first embodiment is composed of a small information processing device, a so-called microcomputer. Therefore, the control unit C can realize various functions by executing programs stored in the ROM or the like. The control unit C in the first embodiment receives a signal from the signal output element and outputs a signal to the controlled element to control it.

[0044] (Description of signal output elements) To the control unit C, signals are input from a user interface UI and signal output elements such as sensors (not shown). The user interface UI inputs the contents input by a user or an operator to the control unit C. In the first embodiment, for example, when a copy start command is input as an example of a print command through the user interface UI, a control signal is input to the control unit C.

[0045] (Description of controlled element) The control unit C outputs signals to a power supply circuit E, a fixing control circuit D1, and other controlled elements (not shown). The power supply circuit E controls the power supply and the like for the charging bias of the charging rollers CRy to CRk, the developing bias of the developing devices Gy to Gk, the primary transfer bias of the primary transfer rollers T1y to T1k, the secondary transfer bias of the secondary transfer roller T2b, and the like. The fixing control circuit D1 controls the supply of power to the heater F1, which is an example of a heat source and an example of a heat generating means. The fixing control circuit D1 also controls the drive of the fixing motor M1, which is an example of a fixing drive means, to control the rotation of the pressure roller Fp. Note that the fixing control circuit D1 is not limited to a configuration that drives the pressure roller Fp, and may also be configured to drive the heating roller Fh, or may be configured to drive both the heating roller Fh and the pressure roller Fp.

[0046] (Function of control unit C) The control unit C of the first embodiment has the following functional means (functional modules, program modules) C1 to C7. The job control means C1 controls jobs, which are image forming operations. When a copy start command is input or when print data is input from an external information processing device or the like, that is, when an instruction to start a job is given, the job control means C1 controls the power supply circuit E and a motor (not shown) to execute the job. The printing time measurement unit C2 measures a printing time t1 as an example of an operation time. The printing time measurement unit C2 of the first embodiment starts measuring the printing time t1 when a job is started, and ends measuring the printing time t1 when the job is finished.

[0047] The fixing device control means C3 has a fixing temperature control means C3a and a fixing pressure control means C3b, and controls the fixing device F via a fixing control circuit D1. The fixing temperature control means C3a controls the fixing temperature of the fixing area Q5 by controlling the operation / stop of the heater F1 via the fixing control circuit D1. During a job, the fixing temperature control means C3a controls the heater F1 so that the fixing temperature is within a predetermined fixing temperature range. The fixing pressure control means C3b controls the fixing pressure, which is the contact pressure between the heating roller Fh and the pressure roller Fp. The fixing pressure control means C3b controls the fixing device F during a job so that the fixing pressure is a predetermined value.

[0048] A standby mode control means C4, which is an example of a standby operation control means, controls the operation of the copier U in the standby mode. In the first embodiment, after a job is completed, the copier U transitions to the standby mode, which is an example of a standby operation, and waits until an instruction to start the next job is given. In the standby mode of the first embodiment, the heater F1 of the fixing device F is turned off. Also, in the standby mode, the pressure in the fixing area Q5 is controlled to a standby pressure that is lower than the fixing pressure during a job. A standby time measurement means C5 as an example of a standby time control means measures a standby time t2, which is the duration of the standby mode. The standby time measurement means C5 of the first embodiment starts measuring the standby time t2 when the standby mode starts, and ends measuring the standby time t2 when the standby mode ends.

[0049] The storage means C6 for the fold worsening condition stores a fold worsening condition that is a condition for worsening the fold 3a. The storage means C6 for the fold worsening condition in the first embodiment includes a storage means C6a for continuous printing time as an example of a storage means for a first threshold, a storage means C6b for a lower limit elapsed time as an example of a storage means for a second threshold, and a storage means C6c for an upper limit elapsed time as an example of a storage means for a third threshold. The continuous printing time storage unit C6a stores a continuous printing time ta as an example of the first threshold value. In the first embodiment, the continuous printing time ta is determined in advance, and as an example, ta=30 minutes is set. The continuous printing time ta is not limited to the exemplified value, and can be set based on a printing time t1 that has been confirmed through experiments or the like to deteriorate the fold 3a.

[0050] The elapsed lower limit time storage means C6b stores the elapsed lower limit time tb1 as an example of the second threshold. In the first embodiment, the elapsed lower limit time tb1 is preset, and as an example, tb1=30 minutes is set. The elapsed lower limit time tb1 is not limited to the exemplified value, and can be set based on a standby time t2 that is confirmed by an experiment or the like to start to deteriorate the crease 3a. The elapsed upper limit time storage means C6c stores the elapsed upper limit time tb2 as an example of the third threshold. In the first embodiment, the elapsed upper limit time tb2 is preset, and as an example, tb2=5 hours is set. The elapsed upper limit time tb2 is not limited to the exemplified value, and can be set based on a standby time t2 that has been confirmed by an experiment or the like to eliminate the crease 3a.

[0051] The crease removal mode control means C7, which is an example of a control means for the crease removal operation, controls the execution of the crease removal mode, which is an operation for removing the crease 3a. The crease removal mode control means C7 of the first embodiment includes an execution determination means C7a, a removal temperature control means C7b, a removal pressure control means C7c, an idle rotation control means C7d, an idle rotation time measurement means C7e, and a removal mode end determination means C7f.

[0052] The execution determination means C7a determines whether or not to execute the crease removal mode. The execution determination means C7a of the first embodiment determines that the crease removal mode is executed if the crease worsening condition is satisfied when the fixing operation is started. That is, when an instruction to start a job is given, the crease removal mode is executed if the crease worsening condition is satisfied. In the first embodiment, it is determined that the crease worsening condition is satisfied when the printing time t1 reaches the continuous printing time ta, the standby time t2 reaches the elapsed lower limit time tb1, and the standby time t2 does not reach the elapsed upper limit time tb2. That is, it is determined that the crease worsening condition is satisfied when the printing time t1, which is the operating time in the previous fixing operation, reaches the predetermined continuous printing time ta, and the standby time t2, which is the elapsed time since the previous fixing operation was completed, is within a predetermined range (the elapsed lower limit time tb1 to the elapsed upper limit time tb2).

[0053] In the first embodiment, the printing time t1 and the standby time t2, which are parameters related to the temperature of the elastic layer 2 and the release layer 3 of the heating roller Fh, are used to determine whether or not to perform the crease removal mode, but the present invention is not limited to this. For example, the temperature of the heating roller Fh can be measured by a temperature sensor or the like, and the crease removal mode can be performed when the temperature of the heating roller Fh is within a predetermined temperature range. In addition, other parameters linked to the temperature of the heating roller Fh, such as the heater power supply time, power consumption, and the cumulative number of rotations of the motor, can also be used.

[0054] The resolution temperature control means C7b controls the fixing temperature when the crease resolution mode is executed. In the first embodiment, when the crease resolution mode is started, the heater F1 is controlled via the fixing control circuit D1 so that the resolution temperature becomes the fixing temperature when the job is executed. The resolution temperature is not limited to the same temperature as the fixing temperature, and can be higher or lower than the fixing temperature depending on the heat resistance temperature of each member and the target time until the crease is resolved. The higher the resolution temperature, the easier it is to eliminate the crease, so a high resolution temperature is preferable.

[0055] The release pressure control means C7c controls the fixing temperature when the crease removal mode is executed. In the first embodiment, when the crease removal mode is started, the fixing device F is controlled via the fixing control circuit D1 so that the release pressure is lower than the fixing pressure when the job is executed. In the first embodiment, the release pressure is set to the same pressure as the pressure in the standby mode, but is not limited to this, and it is also possible to increase or decrease the pressure, or to set the fixing pressure to zero, that is, to separate the heating roller Fh and the pressure roller Fp. Note that the lower the fixing pressure, the less the load and stress on the crease 3a, so a lower pressure is preferable. However, when the heating roller Fh and the pressure roller Fp are separated, the heating roller Fh cannot be rotated in the configuration in which the pressure roller Fp is driven and the heating roller Fh is driven by the pressure roller Fp as in the first embodiment. Therefore, when separating them, it is preferable to have a configuration in which both the heating roller Fh and the pressure roller Fp are driven.

[0056] The idling control means C7d controls the rotation of the heating roller Fh and the pressure roller Fp when the crease removal mode is executed. In the first embodiment, when the crease removal mode is started, the heating roller Fh and the pressure roller Fp are rotated via the fixing control circuit D1. That is, the heating roller Fh and the pressure roller Fp are rotated without performing the fixing operation of the developer, that is, they are rotated idly. The idling rotation is preferable because it suppresses the temperature unevenness of the heating roller Fh compared to the case where the idling rotation is not executed. In the crease removal mode of the first embodiment, the heating roller Fh and the like are rotated at a lower speed than the rotation speed during job execution. In the first embodiment, the rotation speed is set to a speed lower than that during the job, but this is not limited to this, and it is also possible to set it to a higher or lower speed. Note that a lower rotation speed is preferable because it reduces the load and stress on the crease 3a.

[0057] The idling time measurement means C7e measures an idling time t3 as an example of an execution time of the crease elimination mode. The idling time measurement means C7e of the first embodiment starts measurement when the idling control means C7d starts idling, and ends measurement when the idling ends. The crease removal mode end determination means C7f determines whether the crease removal mode is to be ended. The crease removal mode end determination means C7f of the first embodiment determines that the crease removal mode is to be ended when the idling time t3 reaches a predetermined removal end time tc. The removal end time tc can be set to tc=1 minute, for example. The removal end time tc is not limited to the exemplified time, and can be changed arbitrarily according to the design, specifications, and the like. The removal end time tc is not limited to a fixed value. For example, the removal end time tc can be set to a variable value such as shortening the removal end time tc as the standby time t2 is shorter, or shortening the removal end time tc as the removal temperature at the start of the crease removal mode is higher.

[0058] (Flowchart explanation) FIG. 5 is a flowchart of a control process of the fixing device according to the first embodiment. Next, a control flow chart of the copying machine U of the first embodiment, that is, a flow chart, will be described. Processing necessary for explaining the invention will be described in detail, and other processing will be omitted. The process shown in FIG. 5 is executed in parallel with other processes in the copier U. The process of FIG. 5 is started when the copier U is powered on, that is, when the power is turned on.

[0059] 5, it is determined whether or not a job start instruction has been issued. If yes (Y), proceed to ST2. If no (N), repeat ST1. In ST2, it is determined whether the printing time t1 is longer than the continuous printing time ta. If the answer is yes (Y), proceed to ST3. If the answer is no (N), proceed to ST10. In ST3, it is determined whether the standby time t2 is greater than the lower limit elapsed time tb1. If the answer is yes (Y), the process proceeds to ST4. If the answer is no (N), the process proceeds to ST10. In ST4, it is determined whether the standby time t2 is smaller than the upper limit elapsed time tb2. If the answer is yes (Y), the process proceeds to ST5. If the answer is no (N), the process proceeds to ST10.

[0060] In ST5, the crease removal mode is started, the heater F1 is controlled, and the fixing temperature is increased to the removal temperature, and then the process proceeds to ST6. In ST6, the fixing device F is controlled to set the fixing pressure to the release pressure, and the process then proceeds to ST7. In ST7, the following processes (1) and (2) are executed, and then the process proceeds to ST8. (1) Start idling. (2) Measurement of the idling time t3 is started. In ST8, it is determined whether the idling time t3 is equal to or longer than the end time tc of the cancellation. If the answer is yes (Y), the process proceeds to ST9. If the answer is no (N), the process repeats ST8. In ST9, the crease removal mode is ended, i.e., the control of the idling rotation, temperature, and pressure is ended, and the process proceeds to ST10.

[0061] In ST10, the following processes (1) and (2) are executed, and then the process proceeds to ST11. (1) Execute the job. (2) Measurement of printing time t1 begins. In ST11, it is determined whether the job is completed. If the answer is yes (Y), the process proceeds to ST12. If the answer is no (N), the process repeats ST11. In ST12, the following steps (1) to (3) are executed, and then the process returns to ST1. (1) Measurement of printing time t1 is completed. (2) Start standby mode, i.e. reduce fixing pressure and turn off heater F1. (3) Measurement of standby time t2 begins.

[0062] (Function of Example 1) In the copying machine U of the first embodiment having the above configuration, when an instruction to start a job is given, such as input of a copy start key or input of print data from a personal computer, it is determined whether or not to execute the crease removal mode. If the crease worsening condition is met, the crease removal mode is executed. Then, the job starts after the crease removal mode is completed. If the crease worsening condition is not met, the crease removal mode is not executed (if NO (N) in ST2 to ST4) and the job starts.

[0063] In Patent Document 1, in a configuration in which a creased fluororesin tube is used as a surface layer, a smoothing process of the creases is performed before use in an image forming apparatus and before shipping from the factory. Therefore, even if the creases become worse during use in an image forming apparatus, it is not possible to deal with them. Here, in the heating roller Fh and the pressure roller Fp, the elastic layer 2 and the release layer 3 have different thermal expansion coefficients, and the elastic layer 2 generally has a larger thermal expansion coefficient than the release layer 3. Therefore, during a job, the elastic layer 2 is heated to the fixing temperature and thermally expands, and tension acts on the release layer 3 (in other words, the release layer 3 stretches and stretches), making the creases 3a less noticeable. After the job is completed, as the temperature of the heating roller Fh and the like decreases, the elastic layer 2 experiences greater thermal contraction, making the creases 3a more noticeable and deeper. If the next job is started in a state in which the creases 3a are noticeable, the printing of several sheets immediately after the start of the job will be fixed before the release layer 3 is stretched. Therefore, due to the influence of the fold 3a, there is a problem in that horizontal stripes, so-called gloss lines, appear in the image along the fold 3a, resulting in degradation of image quality.

[0064] In contrast, in the first embodiment, when the condition for the crease 3a to deteriorate is satisfied, the crease elimination mode is executed. That is, before the start of the job, the heating roller Fh or the like is heated to thermally expand the elastic layer 2, and the release layer 3 is tensed to make the crease 3a less noticeable. Then, the job is started in a state in which the crease 3a is less noticeable. Therefore, it is possible to suppress the deterioration of image quality caused by the crease, compared to the conventional technology described in Patent Document 1, which cannot deal with the crease that has deteriorated after the operation of the image forming apparatus.

[0065] Incidentally, when the temperature of the heating roller Fh is still high immediately after the end of a job, the thermal shrinkage of the crease 3a is still small and the crease 3a is not noticeable. Therefore, if the next job is started in this state, the crease 3a is unlikely to have any adverse effects. Therefore, if the standby time t2 does not reach the elapsed lower limit time tb1, it is determined that the thermal shrinkage is still small, the crease 3a is not noticeable, and the crease 3a has little adverse effects, and the crease elimination mode is not executed. Therefore, compared to executing the crease elimination mode every time, unnecessary execution of the crease elimination mode is suppressed. Therefore, a decrease in productivity: the number of printed sheets per unit time, is suppressed.

[0066] Furthermore, when sufficient time has passed since the end of the job, the thermal contraction of the release layer 3 catches up with the thermal contraction of the elastic layer 2, and the crease 3a becomes less noticeable as in the initial state. Therefore, when the next job is started in this state, the adverse effects of the crease 3a are less likely to occur. Therefore, when the standby time t2 reaches the upper limit elapsed time tb2, it is determined that sufficient time has passed, the crease 3a is not noticeable, and the adverse effects of the crease 3a are small, and the crease elimination mode is not executed. Therefore, compared to executing the crease elimination mode every time, unnecessary execution of the crease elimination mode is suppressed. Therefore, a decrease in productivity: the number of printed sheets per unit time, is suppressed.

[0067] Furthermore, in the crease removal mode in the first embodiment, the fixing pressure is reduced. Therefore, the load on the crease 3a is reduced compared to when the fixing pressure is high. Therefore, the life of the fixing device F is extended. Similarly, in the crease removal mode in the first embodiment, the rotation speed of the heating roller Fh is slowed. Therefore, the load on the crease 3a is reduced compared to when the rotation speed is high. Therefore, the life of the fixing device F is extended.

[0068] (Example of change) Although the embodiment of the present invention has been described above in detail, the present invention is not limited to the above embodiment, and various modifications can be made within the scope of the gist of the present invention described in the claims. Modifications (H01) to (H02) of the present invention are illustrated below. (H01) In the above embodiment, a copier U is shown as an example of an image forming apparatus, but the present invention is not limited to this and may be configured as, for example, a printer, a FAX, or a multifunction machine having multiple or all of these functions. Also, the present invention is not limited to an electrophotographic image forming apparatus and may be applied to any image forming apparatus such as an inkjet type or a thermal transfer type.

[0069] (H02) In the above embodiment, a configuration in which four color developers are used as the copier U is exemplified, but this is not limited to this and can also be applied to, for example, a monochrome image forming device or a multi-color image forming device having three or less colors or five or more colors.

[0070] (Additional Note) (((1))) A fixing means for fixing an image on a surface of a medium by applying heat and pressure to the image, the fixing means having a base layer and a surface layer formed by covering a folded tube with the base layer and having a thermal expansion coefficient different from that of the base layer; a control means for controlling the fixing means, the control means executing a crease removing operation to straighten the crease before the start of the fixing operation when a predetermined condition for worsening the crease is satisfied when the fixing operation is started; A fixing device comprising: (((2))) the fixing means including a heating means which is heated by a heat source and rotates, and a pressure means which is disposed opposite to the heating means and has the base layer and the surface layer; The fixing device according to (((1))) is characterized by comprising: (((3))) A core material, the base layer being provided on the outer periphery of the core material and being made of an elastic body, and the surface layer being made of the fold-shaped fluororesin tube, The fixing device according to (((2))) is characterized by comprising: (((4))) the control means determining that the condition for the crease to worsen is satisfied when the operating time of the previous fixing operation reaches a predetermined first threshold value and the elapsed time since the end of the previous fixing operation is within a predetermined range; The fixing device according to any one of ((1))) to (((3))), comprising: (((5))) the control means for determining that a condition for worsening the crease is satisfied when the temperature of the fixing means is within a predetermined range; The fixing device according to any one of ((1))) to (((3))), comprising: (((6))) the crease eliminating operation of heating the fixing means to a predetermined temperature; The fixing device according to any one of ((1))) to (((5))), comprising: (((7))) the crease removal operation being performed in a state in which a load applied to the crease is reduced compared to that during the fixing operation; The fixing device according to any one of ((1))) to (((6))), comprising: (((8))) the crease removal operation, by reducing the pressure applied to the fixing means compared to that during the fixing operation, so that the load applied to the crease is reduced; The fixing device according to (((7))) is characterized by comprising: (((9))) the crease eliminating operation in which the load applied to the crease is reduced by rotating the fixing means at a speed slower than that during the fixing operation; The fixing device according to (((7))) is characterized by comprising: (((10))) An image holding means; a transfer means for transferring the image held on the image holding means to a medium; A fixing device according to any one of ((1)) to ((9)) for fixing an image transferred to a medium; An image forming apparatus comprising:

[0071] According to the fixing device of (((1))), in a fixing device that uses a folded fluororesin tube as a surface layer, it is possible to suppress deterioration in image quality caused by folds, compared to conventional technology that does not deal with folds that deteriorate after the image forming apparatus is operated. According to the fixing device of (((2))), it is possible to suppress deterioration in image quality caused by creases in the pressure means. According to the fixing device of (((3))), it is possible to suppress deterioration in image quality caused by creases in the surface layer of the fluororesin. According to the fixing device of (((4))), when the operation time reaches the first threshold and the temperature of the fixing unit is sufficiently increased, and the elapsed time is in a state where the crease worsens, the crease removal operation can be performed. Therefore, it is possible to suppress unnecessary crease removal operations. According to the fixing device of (((5))), when the temperature of the fixing means is within a predetermined range, the crease removal operation can be executed, and thus unnecessary crease removal operations can be suppressed. According to the fixing device of (((6))), the fixing means can be heated to thermally expand the base layer and the surface layer, thereby straightening out the folds. According to the fixing device of (((7))), the life of the fixing device can be extended, compared to a case in which the load on the fold is not reduced. According to the fixing device of (((8))), the pressure applied to the fixing means can be reduced, thereby reducing the load on the fold. According to the fixing device of (((9))), the rotation speed of the fixing means can be slowed down, thereby reducing the load on the fold. According to the image forming apparatus of (((10))), in a fixing device that uses a folded fluororesin tube as a surface layer, degradation in image quality caused by folds can be suppressed compared to conventional technology that does not deal with folds that deteriorate after the image forming apparatus is operated. [Explanation of symbols]

[0072] 1...Core material, 2...Base layer, 3...Surface layer, 3a…crease, C…control means; F: Fixing device, F1…heat source, Fh...Heating means, Fh, Fp: fixing means, Fp: Pressurizing means, PRy, PRm, PRc, PRk...image holding means, S...medium, t1: operating time, T1+T2+B: transcription means; t2: Time elapsed since the fixing operation was completed. ta…first threshold, tb1, tb2... are within a predetermined range, U...Image forming device.

Claims

1. A fixing means for fixing an image on a surface of a medium by applying heat and pressure to the image, the fixing means having a base layer and a surface layer formed by covering a folded tube with the base layer and having a thermal expansion coefficient different from that of the base layer; a control means for controlling the fixing means, the control means executing a crease removing operation to straighten the crease before the start of the fixing operation when a predetermined condition for worsening the crease is satisfied when the fixing operation is started; A fixing device comprising:

2. the fixing means including a heating means which is heated by a heat source and rotates, and a pressing means which is disposed opposite to the heating means and has the base layer and the surface layer; The fixing device according to claim 1 , further comprising:

3. A core material, the base layer being provided on the outer periphery of the core material and being made of an elastic body, and the surface layer being made of the fold-shaped fluororesin tube, The fixing device according to claim 2 , further comprising:

4. the control means for determining that a condition for the crease to worsen is satisfied when the operating time of the previous fixing operation reaches a predetermined first threshold value and the elapsed time since the end of the previous fixing operation is within a predetermined range; The fixing device according to claim 1 , further comprising:

5. the control means for determining that a condition for worsening the crease is satisfied when the temperature of the fixing means is within a predetermined range; The fixing device according to claim 1 , further comprising:

6. the crease eliminating operation of heating the fixing means to a predetermined temperature; The fixing device according to claim 1 , further comprising:

7. the crease removal operation being performed in a state in which a load applied to the crease is reduced compared to that during the fixing operation; The fixing device according to claim 1 , further comprising:

8. the crease removal operation, by reducing the pressure applied to the fixing means compared to that during the fixing operation, so that the load applied to the crease is reduced; The fixing device according to claim 7 , further comprising:

9. the crease eliminating operation in which the load applied to the crease is reduced by rotating the fixing means at a speed slower than that during the fixing operation; The fixing device according to claim 7 , further comprising:

10. An image holding means; a transfer means for transferring the image held on the image holding means to a medium; a fixing device according to any one of claims 1 to 9 for fixing an image transferred onto a medium; An image forming apparatus comprising:

Images