Belt unit and image forming apparatus

Abstract

To suppress the development of a bent shape in the endless means compared to when the endless means's position is fixed when rotation stops. [Solution] A belt unit (F) comprising: a support means (4) that supports the endless means (1) in a bent position at the end of the support means (4) along the rotation direction of the endless means (1); an opposing means (Fp) that faces the support means (4) with the endless means (1) in between; a posture changing means (6) that changes the posture of the bent portion of the endless means (1); and a control means (C) that controls the posture changing means (6) to change the posture of the endless means (1) to a posture in which the bending of the bent portion of the endless means (1) is reduced when the rotation of the endless means (1) is completed.

Description

Technical Field

[0001] The present invention relates to a belt unit and an image forming apparatus.

Background Art

[0002] Regarding a fixing device that heats and fixes an unfixed image on the surface of a medium in an image forming apparatus, the techniques described in the following Patent Documents 1 and 2 are known. Japanese Unexamined Patent Application Publication No. 2011-81079 as Patent Document 1 describes a fixing device in which a heating belt (140) and a pressure belt (120) are arranged to face each other. In Patent Document 1, during the fixing operation, the heating belt (140) and the pressure belt (120) are in pressure contact. After the image formation is completed, the pressure belt (120) rotates 10° around the downstream end and shifts to a standby state in which it is separated from the heating belt (140). In the standby state, the heating and rotation of the heating belt (140) continue. When one minute has elapsed from the standby state, it returns to the 3° position and shifts to a sleep state. In the sleep state, the heating and rotation of the heating belt (140) are stopped. When a new image formation is started from the sleep state, it returns to the 0.8° position and performs a preparation operation for heating and rotation of the heating belt (140).

[0003] Japanese Unexamined Patent Application Publication No. 2020-71350 as Patent Document 2 describes a fixing device in which a belt (310) is supported by a heating roller (340), a pad (320), and a steering roller (350). In Patent Document 2, after the belt (310) stops in a state where the temperature is equal to or higher than the glass transition temperature and then stops for a predetermined time in a state where the temperature is lower than the glass transition temperature, the belt (310) is rotated while being heated. By doing so, the unevenness of the surface release layer generated at a temperature lower than the glass transition temperature is suppressed.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

[0005] The technical problem of this invention is to suppress the formation of a bent shape in the endless means when the rotation stops, compared to when the position of the endless means is fixed. [Means for solving the problem]

[0006] To solve the aforementioned technical problems, the belt unit of the invention described in claim 1 is: A rotating endless means, A support means for supporting the endless means, wherein the support means supports the endless means in a bent position at an end of the support means along the rotational direction of the endless means, An opposing means is positioned opposite the support means with the endless means in between, and contacts the endless means with a predetermined contact pressure, A posture changing means for changing the posture of the bent portion of the endless means, When the rotation of the endless means is completed, a control means controls the posture changing means to change the posture of the endless means to a posture in which the bending of the bent portion of the endless means is reduced, It is characterized by having the following features.

[0007] The invention described in claim 2 is the belt unit described in claim 1, At the downstream end of the support means in the rotational direction of the endless means, the support means supports the endless means in a posture in which the endless means is bent more than at the upstream end of the support means. It is characterized by having the following features.

[0008] The invention described in claim 3 is the belt unit described in claim 2, The posture changing means moves the downstream end of the support means in a direction away from the endless means to change the posture of the bent portion of the endless means. It is characterized by having the following features.

[0009] The invention described in claim 4 is the belt unit described in claim 1, The posture changing means moves the support means in a direction that separates it from the opposing means, thereby changing the posture of the bent portion of the endless means. It is characterized by having the following features.

[0010] The invention described in claim 5 is the belt unit described in claim 4, The posture changing means is capable of moving the support means to a position where it is separated from the endless means. It is characterized by having the following features.

[0011] The invention described in claim 6 is the belt unit described in claim 1, A posture changing means positioned downstream of the bent portion of the endless means, along the rotational direction of the endless means, and which changes the posture of the bent portion of the endless means by contacting the endless means and changing its posture, It is characterized by having the following features.

[0012] The invention described in claim 7 relates to the belt unit described in any one of claims 1 to 6, The fixing device is configured such that, as the medium passes between the endless means and the opposing means, the unfixed image on the surface of the medium is fixed by the heat of the heating means and the contact pressure between the endless means and the opposing means. It is characterized by the following:

[0013] To solve the aforementioned technical problems, the image forming apparatus of the invention described in claim 8 is: Image holding means for holding an image on the surface, A transfer means for transferring the image of the image holding means onto a medium, The belt unit according to claim 7 for fixing the image transferred to the medium, characterized by comprising the following.

Advantages of the Invention

[0014] According to the inventions described in claims 1 and 8, it is possible to suppress the formation of a bend in the endless means compared to the case where the posture of the endless means is fixed when the rotation stops. According to the invention described in claim 2, it is possible to suppress the formation of a bend at the end of the support means on the downstream side in the rotation direction of the endless means. According to the invention described in claim 3, it is possible to suppress the formation of a bend by moving the downstream end in a direction away from the endless means.

[0015] According to the invention described in claim 4, it is possible to suppress the formation of a bend by moving the support means in a direction away from the opposing means. According to the invention described in claim 5, it is possible to improve the effect of suppressing the formation of a bend compared to the case where the support means is not separated from the endless means. According to the invention described in claim 6, it is possible to suppress the formation of a bend by changing the posture by contacting the endless means on the downstream side of the bent portion. According to the invention described in claim 7, it is possible to suppress the occurrence of a fixing defect due to the formation of a bend in the endless means compared to the case where the bending of the bent portion is not reduced by the posture changing means.

Brief Description of the Drawings

[0016] [Figure 1] FIG. 1 is an overall explanatory view of an image forming apparatus according to Embodiment 1 of the present invention. [Figure 2] FIG. 2 is an enlarged view of a fixing device according to Embodiment 1. FIG. 2A is an explanatory view of a state where the support means has moved to the first position, and FIG. 2B is an explanatory view of a state where the support means has moved to the second position. [Figure 3]Figure 3 is an enlarged view of the fixing device of Example 2, corresponding to Figure 2 of Example 1. Figure 3A is an explanatory diagram showing the state in which the support means has moved to the first position, and Figure 3B is an explanatory diagram showing the state in which the support means has moved to the second position. [Figure 4] Figure 4 is an enlarged view of the fixing device of Example 3, corresponding to Figure 2 of Example 1. Figure 4A is an explanatory diagram showing the state in which the attitude changing means has moved to the first position, and Figure 4B is an explanatory diagram showing the state in which the attitude changing means has moved to the second position. [Modes for carrying out the invention]

[0017] Next, with reference to the drawings, examples of embodiments of the present invention will be described, but the present invention is not limited to the following embodiments. For the sake of easier understanding of the following explanation, 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-to-down direction is the Z-axis direction. The directions or sides indicated by the arrows X, -X, Y, -Y, Z, and -Z are defined as front, rear, right, left, up, down, or front side, rear side, right side, left side, up side, and down side, respectively. Furthermore, in the diagram, a circle with a "·" inside represents an arrow pointing from the back to the front of the paper, and a circle with an "×" inside represents an arrow pointing from the front to the back of the paper. In the following explanation using diagrams, diagrams of components other than those necessary for the explanation have been omitted as appropriate for ease of understanding. [Examples]

[0018] Figure 1 is an overall explanatory diagram of the image forming apparatus of Embodiment 1 of the present invention. In Figure 1, a copier U, as an example of an image forming apparatus, includes a user interface UI as an example of an operating unit, a scanner U1 as an example of an image reading device, a paper feeder U2, a printer U3 as an example of an image recording means, and a paper ejection unit U4.

[0019] The user interface UI includes, as an example of an input unit, a power button, a copy start key, a copy count setting key, a numeric keypad, and a display unit. The scanner device U1 reads a document (not shown), converts it into image information, and inputs it into the printer unit U3. The paper feeder U2 has multiple paper feed trays TR1, TR2, TR3, and TR4, which are examples of paper feed sections. Recording paper S, which is an example of a medium, is contained in each of the paper feed trays TR1 to TR4. A paper feed path SH1, which is an example of a medium transport path, extends from each of the paper feed trays TR1 to TR4 toward the printer section U3.

[0020] In Figure 1, the printer unit U3 includes a control unit C as an example of a control means, and a power supply circuit E that supplies power to each component of the printer unit U3. The control unit C receives image information of the original document scanned by the scanner device U1 and image information transmitted from a personal computer, which is an example of an information transmission device (not shown) connected to the copier U. The control unit C processes the received image information into printing information for Y: yellow, M: magenta, C: cyan, and K: black, and outputs it to a laser drive circuit D, which is an example of a drive circuit for a latent image writing device. The laser drive circuit D outputs the laser drive signal input from the control unit C to exposure devices ROSy, ROSm, ROSc, and ROSk, which are examples of latent image forming means for each color, at a predetermined time.

[0021] Below each exposure unit ROSy~ROSk, the image holding units Uy, Um, Uc, and Uk are positioned as Y, M, C, and K. In Figure 1, the black image-holding unit Uk (K) includes a photoreceptor drum Pk as an example of an image-holding means, a charging corotron CCk as an example of a charging means, and a photoreceptor cleaner CLk as an example of a cleaning means for the image-holding means. The image-holding units Uy, Um, and Uc (Y, M, C) also include photoreceptor drums Py, Pm, and Pc, charging corotrons CCy, CCm, and CCc, and photoreceptor cleaners CLy, CLm, and CLc. In Example 1, the K-colored photoreceptor drum Pk, which is frequently used and experiences significant surface wear, is configured with a larger diameter compared to the other colored photoreceptor drums Py, Pm, and Pc, enabling high-speed rotation and extending its lifespan.

[0022] The photoreceptor drums Py to Pk are uniformly charged by the charging corotron CCy to CCk, and then electrostatic latent images are formed on the surface of the photoreceptor drums Py to Pk by the laser beams Ly, Lm, Lc, and Lk, which are examples of latent image writing light output from the exposure device ROSy to ROSk. The electrostatic latent images on the surface of the photoreceptor drums Py to Pk are then developed into toner images of the respective colors Y: yellow, M: magenta, C: cyan, and K: black by the developing device Gy, Gm, Gc, and Gk, which are examples of developing means.

[0023] The toner images on the surface of the photoreceptor drums Py~Pk are sequentially transferred in the primary transfer region Q3 by primary transfer rolls T1y, T1m, T1c, T1k, which are an example of primary transfer means, onto an intermediate transfer belt B, which is an example of an intermediate transfer means and an example of an image holding means, thereby forming a multicolor image, or so-called color image, on the intermediate transfer belt B. The color image formed on the intermediate transfer belt B is then transported to the secondary transfer region Q4. In the case of black image data only, only the black photoreceptor drum Pk and developer Gk are used, and only a black toner image is formed. After the primary transfer, any residual toner remaining on the surface of the photoconductor drums Py to Pk is cleaned by the photoconductor cleaners CLy to CLk. The aforementioned image-holding units Uy to Uk and developing devices Gy to Gk constitute a toner image-forming member, which is an example of an image-forming means.

[0024] A toner dispenser U3a, as an example of a supply mechanism, is located at the top of the printer unit U3. Toner cartridges Ky, Km, Kc, and Kk, as an example of a developer storage mechanism, are detachably mounted on the toner dispenser U3a. When toner is consumed in the developer units Gy to Gk during image formation, toner is supplied from each toner cartridge Ky to Kk to each developer unit Gy to Gk.

[0025] The intermediate transfer belt B, positioned below the photoreceptor drums Py~Pk, is stretched by an intermediate drive roll Rd as an example of a driving means for the intermediate transfer means, an intermediate tension roll Rt as an example of a tensioning means for applying tension to the intermediate transfer belt B, an intermediate steering roll Rw as an example of a first deviation correction means for correcting deviation and meandering of the intermediate transfer belt B, a plurality of intermediate idler rolls Rf as an example of a driven means, and a backup roll T2a as an example of a counter means for the secondary transfer region. The intermediate transfer belt B is supported so as to be rotatable in the direction of arrow Ya by the drive of the intermediate drive roll Rd. The belt module BM, as an example of an intermediate transfer device, is composed of the aforementioned intermediate drive roll Rd, intermediate tension roll Rt, intermediate steering roll Rw, intermediate idler roll Rf, backup roll T2a, primary transfer rolls T1y~T1k, intermediate transfer belt B, etc. In Example 1, the belt module BM is composed of a unit that can be attached to and replaced with the printer unit U3.

[0026] Below the backup roll T2a, a secondary transfer unit Ut is positioned as an example of a transfer transport means. The secondary transfer unit Ut has a secondary transfer roll T2b as an example of a transfer member. The secondary transfer roll T2b is positioned opposite the backup roll T2a. The region where the secondary transfer roll T2b faces the intermediate transfer belt B constitutes a secondary transfer region Q4. In addition, a contact roll T2c, as an example of a contact means for voltage application, is in contact with the backup roll T2a. A secondary transfer voltage with the same polarity as the charging polarity of the toner is applied to the contact roll T2c at a preset time from a power supply circuit E controlled by the control unit C. The aforementioned rolls T2a to T2c constitute a secondary transfer unit T2, which is an example of a secondary transfer means. Furthermore, the intermediate transfer belt B, primary transfer rolls T1y to T1k, secondary transfer unit T2, etc. constitute a transfer apparatus B+T1+T2, which is an example of a transfer means.

[0027] A paper transport path SH2 is located below the belt module BM. The recording paper S fed from the paper feed path SH1 of the paper feed device U2 is transported to the paper transport path SH2 by a transport roll Ra, which is an example of a transport means. The recording paper S in the paper transport path SH2 is fed out by a register roll Rr, which is an example of a delivery means, in accordance with the timing when the toner image is transported to the secondary transfer area Q4, and is guided by paper guides SG1 and SG2, which are examples of media guiding means, and transported to the secondary transfer area Q4. The toner image on the intermediate transfer belt B is transferred to the recording paper S by the secondary transfer unit T2 as it passes through the secondary transfer region Q4. In the case of a color image, the toner image that was primary transferred onto the surface of the intermediate transfer belt B is transferred to the recording paper S all at once. After secondary transfer, the intermediate transfer belt B is cleaned using a belt cleaner CLB, which is an example of a cleaning means for the intermediate transfer means.

[0028] The recording paper S on which the toner image has been secondarily transferred is sent to a media transport belt BH, which is an example of a transport means. The media transport belt BH transports the recording paper S to a fixing device F, which is an example of a belt unit and an example of a fixing means. The fixing device F has a heating unit Fh, which is an example of a heating means, and a pressure roll Fp, which is an example of a pressure means. A fixing region Q5 is formed by the region where the heating unit Fh and the pressure roll Fp face each other and are in contact. The toner image on the recording paper S is heated and fixed by the fuser unit F as it passes through the fuser area Q5. The recording paper S, with the toner image fixed by the fuser unit F, is discharged into the discharge tray TRh, which is an example of a discharge unit. The paper transport path SH is composed of the aforementioned symbols SH1, SH2, etc. Furthermore, the paper transport device SU is composed of the aforementioned symbols SH, Ra, Rr, SG1, SG2, BH, etc.

[0029] (Explanation of the fixing device) Figure 2 is an enlarged view of the fixing device of Example 1, where Figure 2A is an explanatory diagram showing the state in which the support means has moved to the first position, and Figure 2B is an explanatory diagram showing the state in which the support means has moved to the second position. In Figure 1, the heating unit Fh of the fixing device F of Embodiment 1 has a fixing belt 1 as an example of an endless means. The fixing belt 1 is stretched by a heating roll 2 as an example of a rotating means, a steering roll 3 as an example of a bias correction means, and a heating pad 4 as an example of a support means. The fixing belt 1 can be made of any conventionally known material, but the base material is preferably made of a highly rigid polyimide-based material. Furthermore, the surface layer of the fixing belt 1 is preferably made of a material such as a fluororesin that has high release properties for molten toner, paper dust, etc.

[0030] The heating roll 2 in Example 1 has a heater 2a built inside as an example of a heating means. The heating roll 2, heated by the heater 2a, heats the fixing belt 1 that it contacts. The steering roll 3 corrects any meandering or misalignment of the anchor belt 1.

[0031] The heating pad 4 is positioned opposite the pressure roll Fp, which is an example of an opposing means. The fixing region Q5 is formed in the area between the fixing belt 1, which is supported by the heating pad 4, and the pressure roll Fp. Therefore, the unfixed image on the recording paper S passing through the fixing region Q5 is heated and pressurized and fixed to the recording paper S.

[0032] In Example 1, unlike the heating roll 2 and steering roll 3, the heating pad 4 is positioned in a non-rotating state relative to the fixing belt 1. Furthermore, the heating pad 4 of Example 1 has different shapes at its downstream end 4a and upstream end 4b in the rotational direction of the fixing belt 1. The upstream end 4b has a smaller angle with respect to the paper transport direction than the downstream end 4a, in order to guide the recording paper S into the fixing area Q5. The downstream end 4a has a larger angle with respect to the paper transport direction, in order to improve the release between the recording paper S that has passed through the fixing area Q5 and the fixing belt 1. Therefore, the fixing belt 1 is supported in a bent position at the downstream end 4a. In other words, the radius of curvature of the fixing belt 1 at the downstream end 4a is smaller than the radius of curvature of the upstream end 4b. That is, the R is smaller at the downstream end 4a and larger at the upstream end 4b. Therefore, the posture of the fixing belt 1 changes at a sharp angle at the downstream end 4a.

[0033] The heating pad 4 in Example 1 is rotatably supported around a rotation axis 6a that extends along the width direction of the fixing belt 1. The heating pad 4 rotates in conjunction with the rotation of a posture motor 6, which is an example of a posture changing means. The heating pad 4 in Example 1 is movable between a fixing position, which is an example of a first position shown in Figure 2A, and a reduced bending position, which is an example of a second position shown in Figure 2B. In the fixing position shown in Figure 2A, the heating pad 4 brings the fixing belt 1 into contact with the pressure roll Fp at a predetermined contact pressure. In the reduced bending position shown in Figure 2B, the heating pad 4 rotates in a direction in which the downstream end 4a moves away from the fixing belt 1. Therefore, in the reduced bending position, the bending of the bent portion of the fixing belt 1 (the portion corresponding to the downstream end 4a) is reduced compared to the fixing position.

[0034] In Example 1, at the bending reduction position, the downstream end 4a does not completely separate from the anchoring belt 1. Therefore, at the bending reduction position, the contact pressure between the downstream end 4a and the anchoring belt 1 is lower than at the anchoring position. In the configuration where the downstream end 4a does not completely separate from the anchoring belt 1, the overall posture of the anchoring belt 1 changes less with respect to the posture at the anchoring position. Therefore, problems such as the anchoring belt 1 falling off the heating pad 4 due to unforeseen circumstances such as external vibrations are more easily suppressed. Furthermore, the configuration is not limited to the configuration in which the downstream end 4a is not completely separated from the anchoring belt 1. For example, it is possible to configure the configuration so that the downstream end 4a is completely separated from the anchoring belt 1 at the bending reduction position. When the downstream end 4a is completely separated from the anchoring belt 1, the bending reduction effect is higher compared to when it is not completely separated.

[0035] (Description of the control unit in Example 1) In Figure 2, the control unit (controller) C of the copier U has an input / output interface (I / O) for inputting and outputting signals to and from the outside. The control unit C also has a ROM (read-only memory) where programs and information for necessary processing are stored. Furthermore, the control unit C has a RAM (random-access memory) for temporarily storing necessary data. Finally, the control unit C has a CPU (central processing unit) that performs processing according to the programs stored in the ROM, etc. Therefore, the control unit C in Embodiment 1 is composed of a small information processing device, a so-called microcomputer. Thus, the control unit C can realize various functions by executing programs stored in the ROM, etc. In Embodiment 1, the control unit C receives a signal from the signal output element and outputs a signal to the controlled element to control it.

[0036] (Functions of Control Unit C) The control unit C of Example 1 has the following functional means (functional module, program module). The fixing control means C1 includes a fixing temperature control means C11, a rotation control means C12, and a posture control means C13. The fixing control means C1 controls the operation and stopping of the fixing device F. The fixing temperature control means C11 controls the on / off state of the heater 2a to maintain the temperature of the fixing belt 1 at a predetermined fixing temperature. When a job, which is an image forming operation, starts, the fixing temperature control means C11 starts controlling the heater 2a to reach the fixing temperature. When the job ends, the fixing temperature control means C11 turns off the heater 2a.

[0037] The rotation control means C12 controls the rotation of the pressure roll Fp. Therefore, the rotation of the driven fixing belt 1 is indirectly controlled in conjunction with the control of the rotation of the pressure roll Fp. In Embodiment 1, the rotation control means C12 drives the pressure roll Fp when the job starts and stops it when the job ends. The attitude control means C13 controls the attitude motor 6 to move the heating pad 4 between the fixed position and the bending reduction position. When the job starts, the attitude control means C13 moves the heating pad 4 to the fixed position. When the job ends and the rotation of the fixing belt 1 stops, the attitude control means C13 moves the heating pad 4 to the bending reduction position.

[0038] In Example 1, the timing of the heating pad 4's movement was illustrated to coincide with the start and end of the job, but the invention is not limited to this. For example, it is possible to move the heating pad 4 with a margin of error from the start or end of the job. It is also possible to keep the heating pad 4 in the fixed position for a certain period of time after the job is completed, in a so-called standby state. After a certain period of time has elapsed, it is possible to move the heating pad 4 to the reduced bending position when transitioning to a so-called sleep state. The rotation of the fixing belt 1 may be based on the posture supported by the heating pad 4. Therefore, if the fixing belt 1 is rotated while the heating pad 4 is in the reduced bending position, the rotation of the fixing belt 1 may become unstable. For this reason, it is preferable to move the heating pad 4 between the time the fixing belt 1 stops and the time before it starts rotating. Therefore, it is possible to move the heating pad 4 at the same time as the fixing belt 1 stops, or to move the heating pad 4 after a certain period of time has elapsed since it stopped.

[0039] (Effect of Example 1) In the fixing apparatus F of Embodiment 1, which has the above configuration, when the image forming operation (job) is started, the fixing belt 1 is heated, and the developer on the surface of the recording paper S passing through the fixing area Q5 is heated, melted, and fixed. When the job starts, the heating pad 4 moves to the fixing position. As a result, the contact pressure, which is one of the fixing conditions for the fixing area Q5, is maintained at a predetermined contact pressure. Also, when the heating pad 4 is in the fixing position, the fixing belt 1 smoothly guides the recording paper S to the fixing area Q5 at the part corresponding to the upstream end 4b of the heating pad 4. Furthermore, the fixing belt 1 facilitates the release of the recording paper S at the part corresponding to the downstream end 4a of the heating pad 4. In other words, the recording paper S is prevented from sticking to the fixing belt 1 after fixing.

[0040] When a job is completed and the fixing belt 1 stops rotating, the heating pad 4 moves to the reduced-bend position. When the heating pad 4 moves to the reduced-bend position, the force on the fixing belt 1 from the downstream end 4a of the heating pad 4 is released and reduced. Therefore, the bending of the fixing belt 1 at the portion corresponding to the downstream end 4a of the heating pad 4 is eased. The heating pad 4 is then held in the reduced-bend position, and the reduced bending of the fixing belt 1 is maintained until the next job starts. In the technology described in Patent Document 1, the contact pressure between the heating belt and the pressure belt is reduced, but the position of the belt itself does not change, and there is a risk that it may develop a kink while the rotation is stopped. When the belt develops a kink, the bent portion is stretched as it passes the position of the heating roll 2 and the fixing area Q5, and is subjected to physical load. Therefore, the force in contact with the heating roll 2 and the pressure roll Fp becomes locally stronger, which may cause fixing failure or damage such as abrasions. In addition, repeated deformation and stretching can lead to wear over time such as fatigue and deterioration, which shortens the product life. In the technology described in Patent Document 2, belt deformation is mitigated, but the fixing device operates periodically even when no image formation is taking place. Therefore, the technology described in Patent Document 2 has the problem of incurring electricity costs and causing wear and tear on parts due to operation. In addition, if the fixing device operates when the user is not forming an image, it will make noise, which may cause the user to mistakenly think that there is a malfunction.

[0041] In contrast to these, in the fixing device F of Example 1, the heating pad 4 simply moves to the bending reduction position when the job is completed. Therefore, compared to the case where the fixing belt 1's position is fixed when the rotation of the fixing belt 1 stops, the formation of a bending habit in the fixing belt 1 is suppressed. Furthermore, as in Patent Document 2, the fixing device F does not operate periodically; the heating pad 4 is simply held in the bending reduction position and returns to the fixing position for the next job. Therefore, issues such as increased costs, wear and tear on parts, and operating noise can be resolved. [Examples]

[0042] Figure 3 is an enlarged view of the fixing device of Example 2, corresponding to Figure 2 of Example 1. Figure 3A is an explanatory diagram showing the state in which the support means has moved to the first position, and Figure 3B is an explanatory diagram showing the state in which the support means has moved to the second position. Next, we will describe Embodiment 2 of the present invention. Components similar to those in Embodiment 1 will be denoted by the same reference numerals, and detailed descriptions will be omitted.

[0043] In Figure 3, unlike the heating pad 4 of Example 1, the heating pad 4' of Example 2 is supported so that its entirety can move toward or toward the center of the pressure roll Fp. The heating pad 4' moves toward or toward the pressure roll Fp as the eccentric cam 11, which is an example of a posture changing means, rotates. The heating pad 4' of Example 2 is movable between a fixed position, which is an example of a first position shown in Figure 3A, and a reduced bending position, which is an example of a second position shown in Figure 3B. In the fixed position shown in Figure 3A, the heating pad 4' brings the fixing belt 1 into contact with the pressure roll Fp at a predetermined contact pressure. In the reduced bending position shown in Figure 3B, the heating pad 4' moves to a position further away from the center of the pressure roll Fp than in the fixed position.

[0044] In Example 2, the timing of the movement of the heating pad 4' between the fixed position and the bending reduction position is set in the same way as in Example 1. In Example 2, the attitude control means C13 controls the movement of the heating pad 4' by controlling the rotation of the eccentric cam 11. Furthermore, in Example 2, at the bending reduction position, the heating pad 4' is completely separated from the fixing belt 1. However, the embodiment is not limited to complete separation. For example, at the bending reduction position, the heating pad 4' is not completely separated from the fixing belt 1, and the contact pressure between the heating pad 4' and the fixing belt 1 is lower than at the fixing position.

[0045] (Effect of Example 2) In the fixing device F of Embodiment 2, which has the above configuration, the heating pad 4' moves to a bending reduction position after the rotation of the fixing belt 1 stops. Therefore, in the fixing device F of Embodiment 2, as in Embodiment 1, the formation of a bend in the fixing belt 1 is suppressed. [Examples]

[0046] Figure 4 is an enlarged view of the fixing device of Example 3, corresponding to Figure 2 of Example 1. Figure 4A is an explanatory diagram showing the state in which the attitude changing means has moved to the first position, and Figure 4B is an explanatory diagram showing the state in which the attitude changing means has moved to the second position. Next, we will describe Embodiment 3 of the present invention. Components similar to those in Embodiment 1 will be denoted by the same reference numerals, and detailed descriptions will be omitted.

[0047] In Figure 4, in the fixing device F of Example 3, a posture-changing roll 21, as an example of a posture-changing means, is positioned between the heating pad 4'' and the heating roll 2. Unlike Example 1, the heating pad 4'' does not move in Example 3. The posture-changing roll 21 is positioned inside the fixing belt 1. The posture-changing roll 21 is supported so as to be movable in the direction of contact with and away from the inner surface of the fixing belt 1. The posture-changing roll 21 moves in the direction of contact with and away from the fixing belt 1 as the eccentric cam 22, which is an example of an actuation means, rotates. In Embodiment 3, the posture-changing roll 21 is movable between a fixing position, which is an example of a first position shown in Figure 4A, and a bending reduction position, which is an example of a second position shown in Figure 4B. In the fixing position shown in Figure 4A, the posture-changing roll 21 moves away from the inner surface of the fixing belt 1. In the bending reduction position shown in Figure 4B, the posture-changing roll 21 pushes the inner surface of the fixing belt 1 outward. Therefore, the posture of the fixing belt 1 changes to a posture in which the bending is reduced at the bending portion corresponding to the downstream end 4a of the heating pad 4.

[0048] In Example 3, the posture-changing roll 21 is completely separated from the fixing belt 1 at the fixing position. However, the system is not limited to complete separation. For example, at the fixing position, the posture-changing roll 21 is not completely separated from the fixing belt 1, and the contact pressure between the posture-changing roll 21 and the fixing belt 1 is lower than at the bending reduction position. In Embodiment 3, the attitude control means C13 controls the rotation of the eccentric cam 22 to control the movement of the attitude changing roll 21.

[0049] (Effect of Example 3) In the fixing device F of Embodiment 3, which has the above configuration, the attitude changing roll 21 moves to the bending reduction position after the rotation of the fixing belt 1 stops. Therefore, in the fixing device F of Embodiment 3, as in Embodiment 1, the formation of a bent shape in the fixing belt 1 is suppressed.

[0050] (Example of change) Although embodiments of the present invention have been described in detail above, the present invention is not limited to the embodiments described above, and various modifications can be made within the scope of the gist of the present invention as described in the claims. Examples of modifications to the present invention (H01) to (H07) are shown below. (H01) In the above embodiment, a copier U was given as an example of an image forming apparatus, but the apparatus is not limited to this, and can also be configured with, for example, a fax machine, a printer, or a multifunction device. (H02) In the above embodiment, a configuration in which four colors of developer are used as the image forming apparatus was illustrated, but the invention is not limited to this, and can also be applied to, for example, a single-color image forming apparatus or a multi-color image forming apparatus with three or fewer colors or five or more colors.

[0051] (H03) In the above embodiment, the shape of the downstream end 4a and the upstream end 4b of the heating pads 4, 4', 4'' are not limited to the shapes exemplified in the embodiment. The downstream end 4a can also be the same shape as the upstream end 4b. Conversely, the upstream end 4b can also be the same shape as the downstream end 4a. In this case, the heating pads 4, 4' are moved so that the portion where bending to be reduced occurs moves away from the fixing belt 1, thereby reducing bending. (H04) In the above embodiment, the heater 2a, which is the heating means, is shown to be built into the heating roll 2 as an example, but the embodiment is not limited to this. It is also possible to build it into the heating pads 4, 4', 4''.

[0052] (H05) In the above embodiment, the fixing device F was exemplified as the belt unit, but it is not limited to this. For example, it can be applied to any belt unit having a belt, such as an intermediate transfer belt, a photoreceptor belt, a transfer transport belt, or a secondary transfer belt, where abrasion is a problem. (H06) In the above embodiment, a configuration in which the pressure roll Fp is driven and the fixing belt 1 is driven to rotate was illustrated, but the invention is not limited thereto. It is also applicable to a configuration in which the fixing belt 1 is driven and the pressure roll Fp is driven to rotate. Furthermore, it is also applicable when the pressure roll Fp is a pressure belt configuration. (H07) In the above embodiment, it is also possible to add the posture changing roll 21 of Embodiment 3 to Embodiments 1 and 2.

[0053] (Note) (((1))) A rotating endless means, A support means for supporting the endless means, wherein the support means supports the endless means in a bent position at an end of the support means along the rotational direction of the endless means, An opposing means is positioned opposite the support means with the endless means in between, and contacts the endless means with a predetermined contact pressure, A posture changing means for changing the posture of the bent portion of the endless means, When the rotation of the endless means is completed, a control means controls the posture changing means to change the posture of the endless means to a posture in which the bending of the bent portion of the endless means is reduced, A belt unit characterized by having the following features. (((2))) At the downstream end of the support means in the rotational direction of the endless means, the support means supports the endless means in a posture in which the endless means is bent more than at the upstream end of the support means. The belt unit according to (((1))), characterized by comprising the above. (((3))) The posture changing means moves the downstream end of the support means in a direction away from the endless means to change the posture of the bent portion of the endless means. The belt unit according to (((2))) characterized by comprising the above. (((4))) The posture changing means moves the support means in a direction that separates it from the opposing means, thereby changing the posture of the bent portion of the endless means. The belt unit according to (((1))), characterized by comprising the above. (((5))) The posture changing means is capable of moving the support means to a position where it is separated from the endless means. The belt unit according to (((4))) characterized by having the following: (((6))) A posture changing means positioned downstream of the bent portion of the endless means, along the rotational direction of the endless means, and which changes the posture of the bent portion of the endless means by contacting the endless means and changing its posture, A belt unit according to any one of (((1))) to (((5))) characterized by comprising: (((7))) The fixing device is configured such that, as the medium passes between the endless means and the opposing means, the unfixed image on the surface of the medium is fixed by the heat of the heating means and the contact pressure between the endless means and the opposing means. A belt unit according to any one of (((1))) to (((6))) characterized by the above. (((8))) Image holding means for holding an image on the surface, A transfer means for transferring the image of the image holding means onto a medium, A belt unit described in (((7))) for fixing the image transferred to the medium, An image forming apparatus characterized by comprising the following:

[0054] According to the belt unit described in (((1))), it is possible to suppress the formation of a bent shape in the endless means compared to the case where the position of the endless means is fixed when rotation stops. According to the belt unit of (((2))), the formation of a bent shape at the end of the support means downstream in the rotational direction of the endless means is suppressed. According to the belt unit of (((3))), the downstream end is moved in a direction away from the endless means, thereby suppressing the formation of a bent shape. According to the belt unit of (((4))), the support means is moved in a direction that separates it from the opposing means, thereby suppressing the formation of a bent shape. According to the belt unit of (((5))), the effect of suppressing deformation can be improved compared to the case in which the support means is not separated from the endless means. According to the belt unit of (((6))), the endless means contacts the bent portion downstream of the bent portion and changes its posture, thereby suppressing the formation of a permanent bend. According to the belt unit of (((7))), compared to the case where the bending of the bent portion is not reduced by the posture changing means, it is possible to suppress the occurrence of a bent shape in the endless means and the resulting fixing failure. According to the image forming apparatus described in (((8))), it is possible to suppress the formation of a bent shape in the endless means compared to the case where the position of the endless means is fixed when rotation stops. [Explanation of symbols]

[0055] 1...Endless means, 4...support means, 4a...end, 6, 11, 21... means of changing posture, B+T1+T2...Transfer method, C... control means, F... Belt unit, fixing device, Fp... Countermeasure, Py, Pm, Pc, Pk...image holding means, S...media, U...Image forming apparatus.

Claims

1. A rotating endless means, A support means for supporting the endless means, wherein the support means supports the endless means in a bent position at an end of the support means along the rotational direction of the endless means, An opposing means is positioned opposite the support means with the endless means in between, and contacts the endless means with a predetermined contact pressure, A posture changing means for changing the posture of the bent portion of the endless means, When the rotation of the endless means is completed, a control means controls the posture changing means to change the posture of the endless means to a posture in which the bending of the bent portion of the endless means is reduced, A belt unit characterized by having the following features.

2. At the downstream end of the support means in the rotational direction of the endless means, the support means supports the endless means in a posture in which the endless means is bent more than at the upstream end of the support means. The belt unit according to claim 1, characterized by comprising the following:

3. The posture changing means moves the downstream end of the support means in a direction away from the endless means, thereby changing the posture of the bent portion of the endless means. The belt unit according to claim 2, characterized by comprising:

4. The posture changing means moves the support means in a direction that separates it from the opposing means, thereby changing the posture of the bent portion of the endless means. The belt unit according to claim 1, characterized by comprising the following:

5. The posture changing means is capable of moving the support means to a position where it is separated from the endless means. The belt unit according to claim 4, characterized by comprising the above.

6. A posture changing means positioned downstream of the bent portion of the endless means, along the rotational direction of the endless means, and which changes the posture of the bent portion of the endless means by contacting the endless means and changing its posture, The belt unit according to claim 1, characterized by comprising the following:

7. The fixing device is configured such that, as the medium passes between the endless means and the opposing means, the unfixed image on the surface of the medium is fixed by the heat of the heating means and the contact pressure between the endless means and the opposing means. The belt unit according to any one of features 1 to 6.

8. Image holding means for holding an image on the surface, A transfer means for transferring the image of the image holding means onto a medium, A belt unit according to claim 7 for fixing an image transferred to the medium, An image forming apparatus characterized by comprising the following:

Images