JP2018036616A - Fixation device nd image formation device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To bring a polishing roller into uniform pressure contact with a fixation member of a polishing object, and shorten a polishing time with a contact area sufficiently secured.SOLUTION: In a fixation device 25 comprising: a fixation belt 26 rotating with the belt hung to a plurality of supporting members; a pressuring member 27 that forms a fixation nip part between the fixation belt 26 and the pressuring member; a polishing roller 51 that is provided separably and contactably relative to the fixation belt 26, and slides a surface of the fixation belt 26 in a pressed contact state with the fixation belt 26; and a polishing auxiliary member 52 that is composed of at least one supporting member of the plurality of supporting members, and opposes the polishing roller 51 via the fixation belt 26, in a state where the polishing roller 51 is brought into pressure contact with the fixation belt 26, the polishing roller 51 is configured to oppose the polishing auxiliary member 52 via the fixation belt 26 to form a polishing nip part between the fixation belt 26 and the polishing roller, and in the fixation belt 26, a rotation trajectory is changed along at least a partial circumferential face of the polishing roller 51.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a fixing device and an image forming apparatus.

  A so-called electrophotographic fixing device that can fix a toner image transferred to a recording medium such as paper by heat and pressure and transport the recording medium is widely used. In an electrophotographic image forming apparatus, images of different sizes are often printed even by the same user, and various sizes and thicknesses of paper are used depending on applications.

  On the other hand, when a large amount of paper is printed after a relatively large amount of paper having a relatively small size is printed, a glossy streak is placed at a position corresponding to the paper edge portion of the small size paper in the large size image. May occur. This is because the sheet edge portion causes streak-like scratches on the surface of the fixing member of the fixing device when a small-size width sheet is printed. Since the streak-like scratches are caused by burrs at the cut end of the sheet, the streaky scratches become more prominent as the sheets are stacked.

  To solve such problems, an image forming apparatus provided with a polishing roller that repairs streaks on the surface of the fixing member and suppresses image defects such as gloss streaks (hereinafter also referred to as “recovering surface properties”) is proposed. (For example, refer to Patent Document 1).

  In Patent Document 1, as a device configuration that can reduce the total load of the polishing roller while exhibiting sufficient abrasiveness that can eliminate gloss streaks, a fixing roller and a heating roller that are wound around a fixing belt are disclosed. It is disclosed that an opposing roller is disposed between the two, thereby setting the contact pressure at the center portion in the width direction of the sheet passing area of the polishing roller, which is a rubbing member, to be weaker than the end portion. Thus, it is described that the total load of the polishing roller can be reduced, the driving torque can be reduced, and sufficient polishing can be performed in a required polishing region without increasing the size of the driving motor.

  On the other hand, as a polishing means for recovering the surface property of the fixing member, there is one that prevents deposits such as paper dust that has fallen off from the recording medium (for example, see Patent Document 2). In Patent Document 2, it is disclosed that a polishing roller is detachably installed with respect to a fixing roller (heating roller), and that the polishing roller rotates independently or dependently on rotation of the fixing roller.

  Since the printing operation cannot be performed during the polishing operation by the polishing roller, it is required to shorten the polishing operation time. The polishing roller can be rubbed against the surface of the fixing member by rotating in accordance with the fixing member to be polished. For example, the polishing roller can be driven and rotated independently at different speeds to fix in a shorter time. It becomes possible to recover the surface property of the member.

  However, when the polishing roller is driven and rotated independently at different speeds, the total load of the polishing roller is large and the driving torque is large. For example, in a mode in which a gear provided at one end of the polishing roller is driven and rotated while uniformly pressing and contacting a fixing member to be polished by springs provided at both end shafts of the polishing roller, when the driving torque increases, the gear is increased. A reaction force of the driving torque is generated on the side, and it becomes difficult to make the polishing roller come into pressure contact with the fixing member uniformly. That is, since the pressure on one side is insufficient, so-called one-side contact state, the polishing performance is lowered and the polishing time is required longer.

  Also, if the contact area between the polishing roller and the fixing member to be polished is small, the area to be polished is also small. Therefore, regardless of the driving method of the polishing roller, satisfactory surface property recovery can be achieved if the polishing operation time is short. The effect may not be obtained.

  SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a fixing device capable of bringing a polishing roller into uniform pressure contact with a fixing member to be polished and ensuring a sufficient contact area and shortening a polishing time.

  In order to achieve the above object, a fixing device according to the present invention includes a fixing belt that is stretched around a plurality of support members and rotates, a pressure member that forms a fixing nip portion between the fixing belt, A polishing roller that is detachably attached to the fixing belt and rubs the surface of the fixing belt in pressure contact with the fixing belt; and at least one support member of the plurality of support members. In a fixing device comprising a roller and a polishing auxiliary member facing through the fixing belt, the polishing roller is in contact with the polishing auxiliary member through the fixing belt when the polishing roller is in pressure contact with the fixing belt. Oppositely, a polishing nip is formed between the fixing belt and the fixing belt, and the rotation locus of the fixing belt changes along the circumferential shape of at least a part of the polishing roller. A fixing device characterized in that it is.

  According to the present invention, the polishing roller can be uniformly brought into pressure contact with the fixing member to be polished, and a sufficient contact area can be secured to shorten the polishing time.

1 is a schematic configuration diagram showing an embodiment of an image forming apparatus according to the present invention. In the fixing device according to the first embodiment, it is an explanatory diagram showing a state in which the polishing roller is separated. In the fixing device according to the first embodiment, it is an explanatory diagram showing a state in which a polishing roller is in contact. FIG. 10 is an explanatory diagram illustrating a state in which a polishing roller is separated in a fixing device according to a conventional embodiment. FIG. 10 is an explanatory diagram illustrating a state in which a polishing roller is in contact with a fixing device according to a conventional embodiment. In the fixing device according to the second embodiment, it is an explanatory diagram showing a state in which the polishing roller is separated. FIG. 10 is an explanatory diagram illustrating a state in which a polishing roller is in contact with a fixing device according to a second embodiment. FIG. 10 is an explanatory diagram illustrating a state in which a polishing roller is separated in a fixing device according to a conventional embodiment. FIG. 10 is an explanatory diagram illustrating a state in which a polishing roller is in contact with a fixing device according to a conventional embodiment. FIG. 10 is an explanatory diagram illustrating a state where a polishing roller is separated in a fixing device according to a third embodiment. FIG. 10 is an explanatory diagram illustrating a state in which a polishing roller is in contact with a fixing device according to a third embodiment. In the fixing device according to the fourth embodiment, it is an explanatory diagram showing a state in which the polishing roller is separated. FIG. 10 is an explanatory diagram illustrating a state in which a polishing roller is in contact with a fixing device according to a fourth embodiment. FIG. 10 is an explanatory diagram illustrating a state where a polishing roller is separated in a fixing device according to a fifth embodiment. FIG. 10 is an explanatory diagram illustrating a state in which a polishing roller is in contact with a fixing device according to a fifth embodiment. It is explanatory drawing which shows the fixing device which concerns on 6th Embodiment. It is sectional drawing (A) and a partial enlarged view (B) of a grinding | polishing roller.

  Hereinafter, a fixing device and an image forming apparatus according to the present invention will be described with reference to the drawings. The present invention is not limited to the embodiments described below, and other embodiments, additions, modifications, deletions, and the like can be changed within a range that can be conceived by those skilled in the art, and any aspect is possible. As long as the functions and effects of the present invention are exhibited, the scope of the present invention is included.

[Image forming apparatus]
FIG. 1 is a schematic configuration diagram showing an example of an image forming apparatus to which the present invention is applied. In the figure, reference numeral 100 denotes a tandem intermediate transfer type image forming apparatus main body as an image forming apparatus, and 200 denotes a paper feed table on which the image forming apparatus main body 100 is placed.

  Further, a tandem type intermediate transfer type image forming unit (hereinafter referred to as a tandem type image forming unit) in which a plurality of image forming units 18 (18Y, 18M, 18C, 18K) are arranged in parallel inside the image forming apparatus main body 100. ) 20 is provided. The subscripts Y, M, C, and K attached to the above symbols indicate yellow, cyan, magenta, and black colors, respectively.

  The image forming apparatus main body 100 is provided with an endless belt-like intermediate transfer member (hereinafter referred to as an intermediate transfer belt) 10 in the vicinity of the center of the sheet passing area. The intermediate transfer belt 10 is wound around a plurality of rollers (intermediate transfer belt drive roller 14, intermediate transfer belt support rollers 15a and 15b, secondary transfer counter roller 16a, etc.) and can be rotated and conveyed clockwise in the drawing.

  In the illustrated form, an intermediate transfer belt cleaning device 17 is provided on the left side of the secondary transfer counter roller 16a. The cleaning device 17 removes residual toner remaining on the intermediate transfer belt 10 after image transfer.

  On the intermediate transfer belt 10 stretched between the intermediate transfer belt driving roller 14 and the intermediate transfer belt support rollers 15a and 15b, yellow (Y), cyan (C), magenta (M), The tandem type image forming unit 20 is configured by arranging four black (K) image forming units 18 (18Y, 18M, 18C, 18K) side by side. Each image forming unit 18 of the tandem type image forming unit 20 has a photosensitive drum 40 (40Y, 40M, 40C, 40K) as an image carrier that carries toner images of yellow, cyan, magenta, and black. doing.

  On the tandem type image forming unit 20, two exposure devices 21 are provided as shown in FIG. Each exposure device 21 corresponds to two image forming means (18Y and 18M, 18C and 18K). For example, it is composed of two light source devices (semiconductor laser, semiconductor laser array, or multi-beam light source) and a coupling optical system, a common optical deflector (polygon mirror, etc.), two scanning imaging optical systems, etc. This is an optical scanning exposure apparatus. As a result, each photosensitive drum 40 is exposed according to image information of each color of yellow, cyan, magenta, and black to form an electrostatic latent image.

  Further, around the photosensitive drum 40 of each image forming unit 18, a developing device for developing the electrostatic latent image formed by the charging device and the exposure device with toner of each color, and a cleaning device for the photosensitive member are provided. The charging device uniformly charges each photosensitive drum 40 prior to exposure. The photoconductor cleaning device removes transfer residual toner on each photoconductor drum 40.

  Further, primary transfer rollers 62 (62Y, 62M, 62C, 62K) as constituent elements of the primary transfer means are provided at the primary transfer positions where the toner images are transferred from the respective photosensitive drums 40 to the intermediate transfer belt 10. The primary transfer rollers 6 (6Y, 6M, 6C, 6K) are provided so as to face the respective photosensitive drums 40 with the intermediate transfer belt 10 interposed therebetween.

  The intermediate transfer belt drive roller 14 is a drive roller that rotationally drives the intermediate transfer belt 10, and is connected to a motor via a drive transmission mechanism (gear, pulley, belt, etc.). When a black single color image is formed on the intermediate transfer belt 10, the intermediate transfer belt support rollers 15 a and 15 b other than the intermediate transfer belt driving roller 14 are moved by the moving mechanism. Thus, the yellow, cyan, and magenta photosensitive drums 40Y, 40M, and 40C can be separated from the intermediate transfer belt 10.

  A secondary transfer device 22 is provided on the opposite side of the intermediate transfer belt 10 from the tandem image forming unit 20. In the illustrated example, the secondary transfer device 22 presses the secondary transfer roller 16b against the secondary transfer counter roller 16a and applies a transfer electric field to thereby transfer an image on the intermediate transfer belt 10 as a transfer medium, That is, the image is transferred onto the sheet-like transfer paper S.

  Next to the secondary transfer device 22, a fixing device 25 of the present invention for fixing the transfer image on the transfer paper S is provided. A specific aspect of the fixing device of the present invention will be described later. The fixing device 25 is configured by pressing a pressure roller 27 against a fixing belt 26 that is an endless belt. The fixing belt 26 is wound around a support roller including a fixing roller 29 and a heating roller 30, and at least one of the rollers. The (heating roller 30) is provided with heating means (a heater, a lamp, an electromagnetic induction heating device, or the like).

  The transfer sheet S on which the image is transferred by the secondary transfer device 22 is transported to the fixing device 25 by the transport belt 24 supported by the two transport belt support rollers 23a and 23b. Of course, the conveyance belt 24 may be a fixed guide member, a conveyance roller, a conveyance roller, or the like.

  In the illustrated embodiment, a sheet reversing device 28 is provided below the secondary transfer device 22 and the fixing device 25. The sheet reversing device 28 reverses and conveys the transfer sheet S so as to record images on both sides of the transfer sheet S in parallel with the tandem image forming unit 20 described above.

[Fixing device]
The fixing device 25 includes a fixing belt 26 that rotates while being stretched around a plurality of support members, a pressure member (pressure roller) 27 that forms a fixing nip portion between the fixing belt 26, and a fixing belt 26. The polishing roller 51 is provided so as to be separable from the fixing belt 26 and rubs against the surface of the fixing belt 26 while being in pressure contact with the fixing belt 26, and at least one of the plurality of supporting members. In a fixing device provided with a polishing auxiliary member (polishing auxiliary roller) 54 opposed via the belt 26, when the polishing roller 51 is in pressure contact with the fixing belt 26, the polishing roller 51 supports the polishing via the fixing belt 26. A polishing nip is formed between the fixing belt 26 and the member 54, and the fixing belt 26 rotates along the circumferential shape of at least a part of the polishing roller 51. The trajectory is changed.

The plurality of support members that stretch the fixing belt 26 include a fixing roller 29 that forms a fixing nip portion between the fixing belt 26 and the pressure member 27, and a heating roller 30 that heats the fixing belt 26. It is.
The polishing auxiliary member 54 may be the fixing roller 29, and may be a support member provided separately from the fixing roller 29 and the heating roller 30.

The polishing roller 51 has an angle θ formed by a straight line connecting the center of the polishing roller 51 and the center of the auxiliary polishing member 54 and a straight line passing through the center of the polishing roller 51 and perpendicular to the surface of the fixing belt 26. Also called “wrapping angle”.
The magnitude of the winding angle θ is preferably 10 ° or more, and more preferably 20 ° or more.

  It is preferable that the surface layer of at least one of the polishing roller 51 and the polishing auxiliary member 54 is made of an elastic body.

Even if the polishing roller 51 is brought into contact with the fixing belt 26 by moving the polishing roller 51 toward the polishing auxiliary member 54, the polishing roller 51 is moved toward the polishing roller 51. It may be.
Further, as a configuration in which the polishing roller 51 is detachable, the user can install it during the polishing operation and remove it except during the polishing operation.

The polishing auxiliary member 54 may always be in contact with the inner peripheral surface side of the fixing belt 26.
Further, the polishing auxiliary member 54 can stretch the fixing belt 26 and urge the tension (having a function as a tension roller).
The polishing auxiliary member 54 is not limited to the form of a rotating body (roller), and may be a pad-like form. Although it is possible to ensure a wide polishing nip width by adopting a pad shape, the inner peripheral surface of the fixing belt 26 that contacts and the polishing auxiliary member 54 itself are easily worn compared to the form of the rotating body. May be.

  Hereinafter, specific examples will be described with reference to the drawings.

<First Embodiment>
A first embodiment will be described with reference to FIGS. In the fixing device 25 of this embodiment, a fixing belt 26 is wound around a fixing roller 29 and a heating roller 30, and the heating roller 30 is provided with a heater as a heating unit 31. The fixing roller 29 is rotatably supported by the fixing device frame, and the heating roller 30 is rotatably supported while being pulled by a spring in the direction 32 in the drawing, and the fixing belt 26 is stretched.

  The pressure roller 27 presses the fixing roller 29 via the fixing belt 26. The fixing roller 29 is rotationally driven by a driving unit to rotate the fixing belt 26. It is also possible to rotate the fixing belt 26 by rotating the pressure roller 27 instead of the fixing roller 29.

  The surface layer of the fixing roller 29 is made of an elastic material, and the surface layer is deformed when pressed by the polishing roller 51, so that the nip width of the pressing portion is obtained. The nip width obtained in this embodiment is, for example, 2.4 mm.

  The polishing unit 50 includes a polishing roller 51, a holder 52 that holds the polishing roller, and a spring 53 that pressurizes the polishing roller toward the fixing belt. The polishing unit 50 is brought into and out of contact with the fixing belt 26 by the contact and separation means. The contacting / separating means is not particularly limited, and known means can be employed. Further, the polishing roller 51 may be driven to rotate by a driving unit.

  In the present embodiment, the diameter of the fixing roller 29, the heating roller 30, and the pressure roller 27 is, for example, 50 mm, and the diameter of the polishing roller 51 is, for example, 25 mm.

  FIG. 2 shows a state in which the polishing roller 51 is separated from the fixing belt 26, and FIG. 3 shows a state in which the polishing roller 51 is in contact with the fixing belt 26. In this embodiment, the polishing roller 51 abuts on a portion where the fixing belt 26 starts to separate from the fixing roller 29 (near the end of the abutting region), and is applied to the fixing roller side via the fixing belt 26 by a spring 53. Pressed.

  As shown in FIG. 3, the polishing roller 51 is abutted and pressed to form a polishing nip portion, and the fixing belt 26 is wound around a part of the peripheral surface of the polishing roller 51 to rotate the fixing belt 26. The trajectory is changed. Further, the area around the fixing roller 29 of the fixing belt 26 also increases.

  Since the fixing belt 26 bites into the portion where the polishing roller 51 comes into contact, for example, about 3 mm, the position of the heating roller 30 is displaced in the direction opposite to the direction indicated by 32 in FIG. . However, the amount of change is small and does not cause a problem.

  An angle formed by a straight line L1 connecting the center of the polishing roller 51 and the center of the fixing roller 29 as a polishing auxiliary member and a straight line L2 passing through the center of the polishing roller 51 and perpendicular to the surface of the fixing belt 26 ( When the winding angle is θ, the fixing belt 26 is wound around the polishing roller 51 within the range of θ. In the example shown in FIG. 3, the winding angle θ is 25 °.

  The polishing roller 51 is arranged such that the winding angle θ at the position in contact with the fixing belt 26 is larger than the winding angle θ at a position away from the fixing belt 26. The direction in which the polishing roller 51 presses the fixing belt 26 (the pressing direction of the spring 53) is preferably within the range of the winding angle θ. In the example shown in FIG. 3, the pressing direction of the spring 53 is a direction of a straight line L <b> 2 that passes through the center of the polishing roller 51 and is perpendicular to the surface of the fixing belt 26.

  The fixing belt 26 and the polishing roller 51 are in contact with each other when the nip width is 2.4 mm, and the angle (winding angle) θ between the straight line L1 and the straight line L2 is 25 °, and the polishing is performed by rubbing at a predetermined peripheral speed difference. Perform the action. In the present embodiment, the linear velocity of the polishing roller 51 is rubbed at a linear velocity three times faster in the forward direction than the linear velocity of the surface of the fixing belt 26. The linear speed of the polishing roller 51 is not limited to this.

<Conventional example 1>
An example of a conventional embodiment will be described with reference to FIGS. The polishing roller 51 is in contact with a portion where the fixing belt 26 is in contact with (wound around) the fixing roller 29 and is pressed toward the fixing roller 29 via the fixing belt 26 by a spring 53. Therefore, as shown in FIG. 5, even if the polishing roller 51 contacts and presses against the fixing belt, the fixing belt 26 does not wind around the polishing roller 51.

  On the other hand, in the above-described first embodiment of the present invention, the fixing belt 26 is wound around the polishing roller 51 in the range of the angle (winding angle) θ formed by the straight line L1 and the straight line L2, and the polishing roller 51 is wound. A sufficient contact area between the fixing belt 51 and the fixing belt 26 can be secured, and the polishing operation time required for recovering the surface property can be shortened. Specifically, the polishing operation time in the embodiment shown in FIG. 3 is shortened by 20% compared to the polishing operation time in the conventional example shown in FIG.

<Second Embodiment>
A second embodiment will be described with reference to FIGS. In the fixing device 25 of this embodiment, a fixing belt 26 is wound around a fixing roller 29 and a heating roller 30, and the heating roller 30 is provided with a heater as a heating unit 31. The fixing roller 29 is rotatably supported by the fixing device frame, and the heating roller 30 is rotatably supported while being pulled by a spring in the direction 32 in the drawing, and the fixing belt 26 is stretched. In the present embodiment, a polishing auxiliary member (polishing auxiliary roller) 54 is provided inside the fixing belt 26. The auxiliary polishing roller 54 is rotatably supported while being separated from the fixing belt 26. In the example shown in FIG. 6, the separation distance is 1 mm.

  The pressure roller 27 presses the fixing roller 29 via the fixing belt 26. The fixing roller 29 is rotationally driven by a driving unit to rotate the fixing belt 26. It is also possible to rotate the fixing belt 26 by rotating the pressure roller 27 instead of the fixing roller 29.

  The surface layer of the auxiliary polishing roller 54 is made of an elastic material, and the surface layer is deformed when pressed by the polishing roller 51 to obtain the nip width of the contact portion. The nip width obtained in this embodiment was 2.0 mm. The auxiliary polishing roller 54 does not rotate in the separated state shown in FIG.

  The polishing unit 50 includes a polishing roller 51, a holder 52 that holds the polishing roller, and a spring 53 that pressurizes the polishing roller toward the fixing belt. The polishing unit 50 is brought into and out of contact with the fixing belt 26 by the contact and separation means. The contacting / separating means is not particularly limited, and known means can be employed. Further, the polishing roller 51 may be driven to rotate by a driving unit.

  In this embodiment, the fixing roller 29, the heating roller 30, and the pressure roller 27 have a diameter of 50 mm, and the polishing roller 51 and the polishing auxiliary roller 54 have a diameter of 25 mm.

  FIG. 6 shows a state where the polishing roller 51 is separated from the fixing belt 26, and FIG. 7 shows a state where the polishing roller 51 is in contact with the fixing belt 26. In the present embodiment, the polishing roller 51 is fixed to the fixing belt at a position where the polishing auxiliary roller 54 is shifted to the left or right with respect to the portion closest to the fixing belt 26 (the position shifted to the left side in FIG. 7). 26 is pressed against the polishing auxiliary roller side by a spring 53.

  The polishing auxiliary roller 54 comes into contact with the fixing belt 26 and rotates in the driven state in the state shown in FIG. As shown in FIG. 7, the polishing roller 51 abuts and is pressed to form a polishing nip portion, and the fixing belt 26 is wound around a part of the peripheral surface of the polishing roller 51 to rotate the fixing belt 26. The trajectory is changed. Similarly, a region where the fixing belt 26 is wound around the auxiliary polishing roller 54 also occurs.

  Since the fixing belt 26 is bitten by about 3 mm at the portion where the polishing roller 51 abuts, the position of the heating roller 30 is displaced in the direction opposite to the direction indicated by 32 (the direction in which tension is applied). However, the amount of change is small and does not cause a problem.

  An angle (winding angle) formed by a straight line L3 connecting the center of the polishing roller 51 and the center of the auxiliary polishing roller 54 and a straight line L2 passing through the center of the polishing roller 51 and perpendicular to the surface of the fixing belt 26 is formed. When θ is set, the fixing belt 26 is wound around the polishing roller 51 within a range of θ. In the example shown in FIG. 7, the winding angle θ is 29 °.

  The polishing roller 51 is arranged such that the winding angle θ at the position in contact with the fixing belt 26 is larger than the winding angle θ at a position away from the fixing belt 26. The direction in which the polishing roller 51 presses the fixing belt 26 (the pressing direction of the spring 53) is preferably within the range of the winding angle θ. In the example shown in FIG. 7, the pressing direction of the spring 53 is a direction of a straight line L <b> 3 passing through the center of the polishing roller 51 and perpendicular to the surface of the fixing belt 26.

  The fixing belt 26 and the polishing roller 51 are in contact with each other when the nip width is 2.0 mm, the angle (winding angle) θ between the straight line L2 and the straight line L3 is 29 °, and the polishing is performed by rubbing at a predetermined peripheral speed difference. Perform the action. In the present embodiment, the linear velocity of the polishing roller 51 is rubbed at a linear velocity three times faster in the forward direction than the linear velocity of the surface of the fixing belt 26. The linear speed of the polishing roller 51 is not limited to this. With such a configuration, a sufficient contact area between the polishing roller 51 and the fixing belt 26 can be secured, and the polishing operation time required for recovering the surface property can be shortened.

  In the example shown in FIGS. 6 and 7, the polishing roller 51 and the fixing belt are brought into contact with and separated from each other when the polishing unit 50 moves. However, the polishing unit 50 is fixed and the polishing auxiliary roller 54 is moved to perform polishing. The roller 51 and the fixing belt may be in contact with each other. The polishing auxiliary roller 54 may be a fixed member that slides on the fixing belt 26 without being driven to rotate.

<Conventional example 2>
An example of a conventional embodiment will be described with reference to FIGS.
In the fixing device 25, a fixing belt 26 is wound around a fixing roller 29 and a heating roller 30, and the heating roller 30 is provided with a heater as a heating unit 31. The fixing roller 29 is rotatably supported on the fixing device frame, and the heating roller 30 is rotatably supported while applying tension to the fixing belt 26 in the direction 32 by a spring, and the fixing belt 26 is stretched.

  The pressure roller 27 presses the fixing roller 29 via the fixing belt 26. The fixing roller 29 is rotationally driven by a driving unit to rotate the fixing belt 26. It is also possible to rotate the fixing belt 26 by rotating the pressure roller 27 instead of the fixing roller 29.

On the outer peripheral side of the fixing belt 26, a polishing roller 51 is provided apart from the fixing belt 26. A polishing auxiliary roller 54 is provided on the inner peripheral side of the fixing belt 26. The polishing auxiliary roller 54 is supported by the frame so as to be rotatable to a position slightly away from the fixing belt 26.
As shown in FIG. 8, the straight line formed by the center of the polishing roller 51 and the center of the auxiliary polishing roller 54 and the locus of the fixing belt are substantially perpendicular.

  The polishing roller 51 is brought into contact with the fixing belt 26 at a position where the polishing auxiliary roller 54 is closest to the fixing belt 26, and is pressed toward the polishing auxiliary roller 54 via the fixing belt 26 by the spring 53. In the state shown in FIG. 8, the polishing auxiliary roller 54 is 1 mm away from the fixing belt. For this reason, in the state shown in FIG. 9, the fixing belt 26 is slightly wound around the polishing roller 51, but the fixing belt 26 is not wound around the auxiliary polishing roller 54.

  Specifically, in the state shown in FIG. 9, the angle (winding angle) θ formed by the straight lines L2 and L3 perpendicular to the surface of the fixing belt 26 through the center of the polishing roller 51 is 3 °. The contact width between the polishing roller 51 and the fixing belt 26 obtained by calculation from the value is 0.6 mm. This is included in the nip width of 2.0 mm between the polishing roller 51 and the fixing belt 26 described above, and does not enlarge the wrapping area (contact area).

  In the separated state shown in FIG. 8, by setting the separation distance between the auxiliary polishing roller 54 and the fixing belt 26 to 1 mm or more, the amount of the abrasive roller 51 biting into the fixing belt 26 increases, and the fixing belt wound around the abrasive roller 51. The winding angle θ of the belt 26 can be set to 3 ° or more. In this case, however, the amount of change in the rotation locus of the fixing belt 26 becomes excessive, resulting in trouble in conveyance.

Next, problems associated with the driving of the polishing roller 51 will be described.
Both ends of the polishing roller 51 are supported by a holder 52 via springs 53, and are driven to rotate by a gear provided on a shaft on one end side.
The polishing unit 50 is moved to the auxiliary polishing roller 54 side by means such as a cam, and the polishing roller 51 is pressed against the fixing belt 26 as shown in FIG.

In the state shown in FIG. 9, when a large driving torque is generated on the gear side shaft of the polishing roller 51, the reaction force of the driving torque deteriorates the pressure balance of the springs 53 provided at both ends of the polishing roller 51. 51 becomes unable to make uniform pressure contact with the fixing belt 26 (becomes a one-sided state). In order to polish the insufficiently pressurized side to a predetermined state, a long polishing time is required.
Further, since the angle formed by the straight line formed by the center of the polishing roller 51 and the center of the auxiliary polishing roller 54 and the locus of the fixing belt is substantially a right angle, the fixing belt 26 is hardly wound around the polishing roller 51. Since a sufficient contact area cannot be obtained, a long polishing time is required.

<Third Embodiment>
A third embodiment will be described with reference to FIGS. 10 shows a state in which the polishing roller 51 is separated from the fixing belt 26, and FIG. 11 shows a state in which the polishing roller 51 is in contact with the fixing belt 26.
In the fixing device 25 of this embodiment, a fixing belt 26 is wound around a fixing roller 29 and a heating roller 30, and the heating roller 30 is provided with a heater as a heating unit 31. The fixing roller 29 and the heating roller 30 are rotatably supported by the fixing device frame, and stretch the fixing belt 26.

  In the present embodiment, a first polishing auxiliary roller 54 and a second polishing auxiliary roller 55 as polishing auxiliary members are provided inside the fixing belt 26. Hereinafter, the first polishing auxiliary roller is simply referred to as “polishing auxiliary roller 54”, and the second polishing auxiliary roller is referred to as “tension roller 55”. The auxiliary grinding roller 54 is instructed to rotate together with the fixing roller 29 and the heating roller 30 to the fixing device frame. On the other hand, the tension roller 55 is rotatably supported while applying tension to the outer peripheral side from the inner peripheral side to the fixing belt 26 by a spring, and stretches the fixing belt 26.

  The pressure roller 27 presses the fixing roller 29 via the fixing belt 26. The fixing roller 29 is rotationally driven by a driving unit to rotate the fixing belt 26. It is also possible to rotate the fixing belt 26 by rotating the pressure roller 27 instead of the fixing roller 29.

  The surface layer of the auxiliary polishing roller 54 is made of an elastic material, and the surface layer is deformed when pressed by the polishing roller 51 to obtain the nip width of the contact portion. The nip width obtained in this embodiment was 1.8 mm.

  The polishing unit 50 includes a polishing roller 51, a holder 52 that holds the polishing roller, and a spring 53 that pressurizes the polishing roller toward the fixing belt. The polishing unit 50 is brought into and out of contact with the fixing belt 26 by the contact and separation means. The contacting / separating means is not particularly limited, and known means can be employed. Further, the polishing roller 51 may be driven to rotate by a driving unit.

  In this embodiment, the fixing roller 29, the heating roller 30 and the pressure roller 27 have a diameter of 50 mm, and the polishing roller 51, the polishing auxiliary roller 54 and the tension roller 55 have a diameter of 25 mm.

  In the present embodiment, the polishing roller 51 abuts on the fixing belt 26 between the polishing auxiliary roller 54 and the tension roller 55 and pressurizes the polishing auxiliary member side (the polishing auxiliary roller 54 and the tension roller 55 side) by the spring 53. Is done.

  As shown in FIG. 11, the polishing roller 51 abuts and is pressed to form a polishing nip portion, and the fixing belt 26 is wound around a part of the peripheral surface of the polishing roller 51 to rotate the fixing belt 26. The trajectory is changed. Similarly, a region where the fixing belt 26 is wound around the polishing auxiliary roller 54 and the tension roller 55 is also generated.

  Since the fixing belt 26 is bitten by about 5.5 mm at the portion where the polishing roller 51 contacts, the tension roller 55 is displaced. However, the amount of change is small and does not cause a problem.

  An angle (winding angle) θ1 formed by a straight line connecting the center of the polishing roller 51 and the center of the auxiliary polishing roller 54 and a straight line passing through the center of the polishing roller 51 and perpendicular to the surface of the fixing belt 26; An angle (winding angle) formed by a straight line connecting the center of the polishing roller 51 and the center of the tension roller 55 as a polishing auxiliary member and a straight line passing through the center of the polishing roller 51 and perpendicular to the surface of the fixing belt 26. ) Is θ2, the fixing belt 26 is wound around the polishing roller 51 within a winding angle θ3 that is the sum of θ1 and θ2. In the example shown in FIG. 11, the winding angle θ is 80 °.

  The polishing roller 51 is arranged such that the angle θ at the position in contact with the fixing belt 26 is larger than the angle θ of the winding angle at a position away from the fixing belt 26. The direction in which the polishing roller 51 presses the fixing belt 26 (the pressing direction of the spring 53) is preferably within the range of the angle θ.

  The fixing belt 26 and the polishing roller 51 are in contact with each other at a nip width of 1.8 mm and a winding angle indicated by a winding angle θ3 of 80 °, and the polishing operation is performed by rubbing with a predetermined peripheral speed difference. In the present embodiment, the linear velocity of the polishing roller 51 is rubbed at a linear velocity three times faster in the forward direction than the linear velocity of the surface of the fixing belt 26. The linear speed of the polishing roller 51 is not limited to this. With such a configuration, a sufficient contact area between the polishing roller 51 and the fixing belt 26 can be secured, and the polishing operation time required for recovering the surface property can be shortened.

<Fourth Embodiment>
A fourth embodiment will be described with reference to FIGS. FIG. 12 shows a state in which the polishing roller 51 is separated from the fixing belt 26, and FIG. 13 shows a state in which the polishing roller 51 is in contact with the fixing belt 26.
In the fixing device 25 of this embodiment, the fixing belt 26 is wound around a fixing roller 29, a heating roller 30, and a tension roller 55, and the heating roller 30 is provided with a heater as a heating unit 31. The fixing roller 29 and the heating roller 30 are rotatably supported by the fixing device frame. Further, a polishing auxiliary member 54 and a pressurizing unit that pressurizes the polishing auxiliary member 54 toward the polishing roller 51 are further provided. Further, a tension roller 55 is provided. The tension roller 55 is supported by a spring 55a so as to be rotatable while applying tension to the fixing belt 26 from the inner peripheral side to the outer peripheral side, and stretches the fixing belt 26.

  The pressure roller 27 presses the fixing roller 29 via the fixing belt 26. The fixing roller 29 is rotationally driven by a driving unit to rotate the fixing belt 26. It is also possible to rotate the fixing belt 26 by rotating the pressure roller 27 instead of the fixing roller 29.

A polishing auxiliary roller 54 is provided on the inner peripheral side of the fixing belt 26.
Both end portions of the auxiliary polishing roller 54 are slidably supported by the elongated hole portion 59 of the holding member 58 and are urged by springs 57 in the direction of the fixing belt 26. Hereinafter, the polishing auxiliary roller 54, the holding member 58, and the spring 57 are also referred to as “polishing auxiliary roller unit”.
The auxiliary polishing roller unit is supported so as to be slidable in the longitudinal direction thereof, and is slid by a cam 60 provided on the side opposite to the auxiliary polishing roller 54.

A polishing roller 51 is provided on the outer peripheral side of the fixing belt 26. The polishing roller 51 is supported by the frame so as to be rotatable at a position facing the polishing auxiliary roller 54 on the inner peripheral surface side of the fixing belt.
A gear is provided on the shaft on one end side of the polishing roller 51 and is driven to rotate.
Since the polishing roller 51 can support the reaction force generated by the rotation drive with the frame, the polishing roller 51 can rotate stably even if the rotation drive force is large.

The surface layer of the auxiliary polishing roller 54 is made of an elastic material, and the surface layer is deformed when pressed by the polishing roller 51 to obtain the nip width of the contact portion.
The nip width obtained in this embodiment was 1.8 mm.

  In this embodiment, the fixing roller 29, the heating roller 30 and the pressure roller 27 have a diameter of 50 mm, and the polishing roller 51, the polishing auxiliary roller 54 and the tension roller 55 have a diameter of 25 mm.

A state in which the polishing roller 51 is separated from the fixing belt 26 will be described with reference to FIG.
The polishing roller 51 is positioned slightly away from the fixing belt 26.
The polishing auxiliary roller unit is slid by the rotation of the cam 60, and the polishing auxiliary roller 54 is positioned away from the inner peripheral surface of the fixing belt 26. The polishing auxiliary roller 54 is pressed against the end of the long hole portion 59 of the holding member 58 by a spring 57.

A state in which the polishing roller 51 is in contact with the fixing belt 26 will be described with reference to FIG.
The polishing auxiliary roller unit slides as the cam 60 rotates, and the polishing auxiliary roller 54 moves toward the polishing roller 51. During the rotation of the cam 60, the polishing auxiliary roller 54 contacts the fixing belt 26. When the cam 60 further rotates, the polishing auxiliary roller 54 contacts the polishing roller 51 via the fixing belt 26. When the rotation of the cam 60 is completed, the polishing auxiliary roller 54 is separated from the long hole portion 59 of the holding member 58. At this time, the auxiliary polishing roller 54 is pressed against the polishing roller 51 by the spring 57.

As shown in FIG. 13, the polishing roller 51 abuts and is pressed to form a polishing nip portion, and the fixing belt 26 is wound around a part of the peripheral surface of the polishing roller 51 to rotate the fixing belt 26. The trajectory is changed.
Since the present embodiment includes the tension roller 55, an appropriate tension is always applied to the fixing belt 26 even when the rotation locus is changed.

  The fixing belt 26 has an angle (winding) between a straight line connecting the center of the polishing roller 51 and the center of the auxiliary polishing roller 54 and a straight line passing through the center of the polishing roller 51 and perpendicular to the surface of the fixing belt 26. It is in a state of being wound around the polishing roller 51 within a range of (angle) θ. In the example shown in FIG. 13, the winding angle θ is 19 °.

  The polishing auxiliary roller 54 is pressed by the spring 57 toward the polishing roller 51 via the fixing belt 26, so that the fixing belt 26 and the polishing roller 51 come into contact with each other with a nip width of 1.8 mm and a winding angle of 19 °.

The polishing roller 51 is rotationally driven by a driving means provided at at least one end, and a polishing operation is performed by rubbing with the rotating fixing belt 26 with a predetermined peripheral speed difference.
In this embodiment, the polishing roller 51 is rubbed at a linear speed three times faster in the forward direction than the surface linear speed of the fixing belt 26, but the linear speed of the polishing roller 51 is not limited to this.

  With the above-described configuration, the polishing roller 51 can be brought into uniform pressure contact with the fixing belt 26 and a sufficient contact area between the polishing roller 51 and the fixing belt 26 can be secured. The operation time can be shortened.

<Fifth Embodiment>
A fifth embodiment will be described with reference to FIGS. 14 shows a state in which the polishing roller 51 is separated from the fixing belt 26, and FIG. 15 shows a state in which the polishing roller 51 is in contact with the fixing belt 26.
In the fixing device 25 of this embodiment, the fixing belt 26 is wound around a polishing auxiliary roller 54 having functions as a fixing roller 29, a heating roller 30, and a tension roller. The heating roller 30 is provided with a heater as the heating means 31. The fixing roller 29 and the heating roller 30 are rotatably supported by the fixing device frame. The polishing auxiliary roller 54 is rotatably supported by a spring 57 while applying tension to the outer peripheral side of the fixing belt 26 from the inner peripheral side, and can tension the fixing belt 26 to urge the tension.

  In the fixing device of the present embodiment, the functions of the polishing auxiliary roller 54 and the tension roller 55 that are separately provided in the fourth embodiment are realized by the polishing auxiliary roller 54 alone. As a result, the number of parts is reduced and the circumference of the fixing belt 26 can be shortened, so that the effect of downsizing the fixing device can be expected.

  The pressure roller 27 presses the fixing roller 29 via the fixing belt 26. The fixing roller 29 is rotationally driven by a driving unit to rotate the fixing belt 26. It is also possible to rotate the fixing belt 26 by rotating the pressure roller 27 instead of the fixing roller 29.

Both end portions of the auxiliary polishing roller 54 are slidably supported by the elongated hole portion 59 of the holding member 58 and are urged by springs 57 in the direction of the fixing belt 26. The polishing auxiliary roller unit constituted by these includes a rotation fulcrum 56 in the vicinity of the center in the longitudinal direction, is rotatably supported by the rotation fulcrum 56, and is provided with a cam 60 and a spring 61 provided on the opposite side of the polishing auxiliary roller 54. Is rotated and pressurized.
The polishing auxiliary roller 54 is urged in a direction away from the center of the rotation fulcrum 56 by a spring 57 constituting the unit, and is urged by a spring 61 in the rotation direction about the center of the rotation fulcrum 56. Each biasing direction is substantially orthogonal.

A polishing roller 51 is provided on the outer peripheral side of the fixing belt 26. The polishing roller 51 is rotatably supported by the frame at a position facing the rotation direction of the auxiliary polishing roller 54 on the inner peripheral surface side of the fixing belt 26.
The polishing roller 51 is rotationally driven by a gear provided on one end side shaft.
Since the polishing roller 51 can support the reaction force generated by the rotational drive with the frame, stable rotation can be obtained even if the rotational drive force is large.

  The surface layer of the auxiliary polishing roller 54 is made of an elastic material, and the surface layer is deformed when pressed by the polishing roller 51 to obtain the nip width of the contact portion. The nip width obtained in this embodiment is 1.8 mm.

  In this embodiment, the fixing roller 29, the heating roller 30, and the pressure roller 27 have a diameter of 50 mm, and the polishing roller 51 and the tension roller 55 have a diameter of 25 mm.

  As shown in FIG. 14, in the state where the polishing roller 51 is positioned slightly away from the fixing belt 26, the polishing auxiliary roller unit is moved to the position where the polishing auxiliary roller 54 is rotated in the left direction in the drawing by the cam 60. In addition, a tension is applied to the fixing belt 26 from the inner peripheral side by a spring 57.

  As shown in FIG. 15, in the state where the polishing roller 51 is in contact with the fixing belt 26, the polishing auxiliary roller unit starts rotating the polishing auxiliary roller 54 in the right direction in the drawing by the rotation of the cam 60. During rotation, the cam 60 is separated from the holding member 58, and the polishing auxiliary roller 54 is urged rightward by the spring 61. The auxiliary polishing roller 54 comes into contact with the polishing roller 51 via the fixing belt 26 and is pressed toward the polishing roller 51 by a spring 61. The polishing auxiliary roller 54 urges the fixing belt 26 from the inner peripheral surface by a spring 57.

  Further, as shown in FIG. 15, the polishing roller 51 abuts against the polishing auxiliary roller 54 and is pressed to form a polishing nip portion, and the fixing belt 26 is wound around a part of the peripheral surface of the polishing roller 51. Thus, the rotation locus of the fixing belt 26 is changed.

  The fixing belt 26 has an angle (winding) between a straight line connecting the center of the polishing roller 51 and the center of the auxiliary polishing roller 54 and a straight line passing through the center of the polishing roller 51 and perpendicular to the surface of the fixing belt 26. It is in a state of being wound around the polishing roller 51 within a range of (angle) θ. In the example shown in FIG. 15, the winding angle θ is 30 °.

  The auxiliary polishing roller 54 is pressed by the spring 61 through the fixing belt 26 toward the polishing roller 51, so that the fixing belt 26 and the polishing roller 51 have a nip width of 1.8 mm and a winding angle indicated by a winding angle θ. Contacts at 30 °.

The polishing roller 51 is driven to rotate by a gear provided at an end thereof, and the polishing operation is performed by rubbing with the rotating fixing belt 26 at a predetermined peripheral speed difference.
In the present embodiment, the linear velocity of the polishing roller 51 is rubbed at a linear velocity three times faster in the forward direction than the linear velocity of the surface of the fixing belt 26. The linear speed of the polishing roller 51 is not limited to this.

  With the above-described configuration, the polishing roller 51 can be brought into uniform pressure contact with the fixing belt 26 and a sufficient contact area between the polishing roller 51 and the fixing belt 26 can be secured. The operation time can be shortened.

The following is a specification example of the component parts that can be used in the fixing device according to the embodiment of the present invention described above. 2, 3, 6, 7, and 10 to 15 show the heat fixing device having the heating side biaxial belt configuration. For example, as shown in FIG. 16, the fixing roller Instead of 29, a fixed pressing member 33 that does not rotate may be provided, and the fixing belt 26 may be stretched between the pressing member 33 and the heating roller 30.
The heating means 31 may be a halogen heater or an IH (electromagnetic induction) heating device.

  The fixing belt 26 is an endless belt having a multilayer structure in which an elastic layer such as silicone rubber and a release layer are sequentially laminated on a base layer made of PI (polyimide) resin and having a layer thickness of 90 μm.

  The elastic layer of the fixing belt 26 has a layer thickness of about 200 μm, for example, and can be formed of an elastic material such as silicone rubber, fluorine rubber, and foamable silicone rubber.

  The release layer of the fixing belt 26 has a layer thickness of about 20 μm, for example, and is made of PFA (tetrafluoroethylene bar fluoroalkyl vinyl ether copolymer resin), polyimide, polyetherimide, PES (polyether sulfide), or the like. Can be formed. By providing a release layer on the surface layer of the fixing belt 26, the releasability (peelability) with respect to the toner (toner image) is secured, the paper (recording medium) having the toner image is well fixed, and the paper is fixed. Good separation from the belt 26 becomes possible.

  FIG. 17 shows an example of a cross-sectional shape of the polishing roller 51 which is a rubbing member. The polishing roller 51 is pressed against the fixing belt 26 with a predetermined pressure, and rotates with a linear velocity difference in the forward direction or the reverse direction with respect to the rotation direction of the fixing belt 26.

  The polishing roller 51 includes, for example, a cored bar 51a and an abrasive layer (abrasive layer: a rubbing layer 51b in the illustrated example) in which abrasive grains 51c are dispersed in a binder resin. The surface of the rubbing layer 51b is assumed to have fine irregularities formed by the abrasive grains 51c protruding. As the abrasive grains 51c, it is preferable to use alumina abrasive grains, which are more general abrasive particles, for example, # 1500 white alumina, but the present invention is not limited to this, and various types can be adopted. It is preferable that the abrasive grains of the abrasive grains have the same conditions over the entire area to be rubbed with the rubbing member.

DESCRIPTION OF SYMBOLS 10 Intermediate transfer belt 14 Intermediate transfer belt drive roller 15 Intermediate transfer belt support roller 16a Secondary transfer counter roller 16b Secondary transfer roller 17 Cleaning device 18 Image forming means 20 Tandem type image forming unit 21 Exposure device 22 Secondary transfer device 23 Conveyance Belt support roller 24 Conveyor belt 25 Fixing device 26 Fixing belt 27 Pressure roller 28 Sheet reversing device 29 Fixing roller (abrasive auxiliary member)
30 Heating roller 31 Heating means 40 Photosensitive drum 51 Polishing roller 51a Core metal 51b Rub layer 51c Abrasive grain 52 Holder 53 Spring 54 Polishing auxiliary roller (polishing auxiliary member)
55 Tension roller (Abrasive auxiliary member)
56 rotation fulcrum 57 spring 58 holding member 59 long hole portion 60 cam 61 spring 62 primary transfer roller 100 image forming apparatus main body S transfer sheet

Japanese Patent Laying-Open No. 2015-94921 JP-A-9-230731

Claims (10)

A fixing belt that is stretched around a plurality of support members and rotates;
A pressure member that forms a fixing nip portion with the fixing belt;
A polishing roller that is detachable from the fixing belt and rubs the surface of the fixing belt in pressure contact with the fixing belt;
A fixing device comprising at least one support member among the plurality of support members, and comprising a polishing auxiliary member facing the polishing roller via the fixing belt,
In a state where the polishing roller is in pressure contact with the fixing belt,
The polishing roller is opposed to the polishing auxiliary member via the fixing belt and forms a polishing nip portion with the fixing belt.
The fixing device is characterized in that a rotation locus of the fixing belt is changed along a circumferential shape of at least a part of the polishing roller.   The fixing device according to claim 1, wherein the polishing auxiliary member is a fixing roller that forms the fixing nip portion between the fixing belt and the pressure member.   The polishing auxiliary member is a support member provided separately from a fixing roller that forms the fixing nip portion between the fixing belt and the pressure member, and a heating roller that heats the fixing belt. The fixing device according to claim 1.   The fixing device according to claim 1, further comprising a pressing unit that presses the polishing auxiliary member toward the polishing roller.   The fixing device according to claim 1, wherein the polishing auxiliary member stretches the fixing belt and biases the tension. The angle formed by a straight line connecting the center of the polishing roller and the center of the polishing auxiliary member and a straight line passing through the center of the polishing roller and perpendicular to the surface of the fixing belt is:
The fixing device according to claim 1, wherein an angle at a position where the polishing roller is in contact with the fixing belt is larger than an angle at a position where the polishing roller is separated from the fixing belt. .   The angle between the straight line connecting the center of the polishing roller and the center of the auxiliary polishing member and the straight line passing through the center of the polishing roller and perpendicular to the surface of the fixing belt is determined by the polishing roller. The fixing device according to claim 1, wherein the fixing device is 10 ° or more at a position in contact with the fixing belt.   The fixing device according to claim 1, wherein a surface layer of at least one of the polishing roller and the polishing auxiliary member is made of an elastic body.   The fixing device according to claim 1, further comprising a driving unit that drives the polishing roller, wherein the polishing roller is rotationally driven at a speed different from a rotational speed of the fixing belt.   An image forming apparatus comprising the fixing device according to claim 1.

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