JP2015232612A - Belt device, belt fixing device, and image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a belt meandering regulation part over wider areas on both right and left side edge parts of a belt to more effectively suppress meandering of the belt.SOLUTION: A belt 65 is disposed rotatably between a fixing pad 63 that is a first support member and a heating roller 62 that is a second support member. The belt 65 is driven to rotate by a driving roller arranged opposite to the fixing pad 63. The heating roller 62 is supported by a pair of end support plates 621 on both ends, and the end support plates 621 have meandering regulation surfaces 6213 formed thereon that contact both edges in the width direction of the belt.

Description

The present invention relates to a belt device that rotationally drives a belt with a driving roller, a belt fixing device, and an image forming apparatus.

In recent years, a belt fixing method has been adopted as a fixing device used in an electrophotographic image forming apparatus such as a copying machine or a printer (see, for example, Japanese Patent Application Laid-Open No. 2004-286923). In this belt fixing method, a fixing belt is stretched between a fixing roller or a fixing pad and a heating roller, and the fixing roller and the pressure roller are pressed against each other via the fixing belt.

One end of the rotating shaft of the pressure roller is connected to a motor via a reduction gear, and a rotational driving force is applied from the pressure roller to the fixing belt via the fixing nip. In this belt fixing method, there is a problem that meandering of the fixing belt in the width direction is likely to occur due to an inclination of the pressing force in the axial direction of the pressure roller in the fixing nip (fixing load deviation). When this meandering occurs, there is a disadvantage that the edge of the fixing belt is damaged due to wear, resulting in a short life of the fixing belt. Therefore, various meandering regulation techniques have been developed.

In the fixing device of Patent Document 1 (Japanese Patent Application Laid-Open No. 2004-286923), belt meandering restricting protrusions for restricting meandering of the belt are formed at both ends of the fixing pad. However, even if the meandering of the fixing belt is regulated on the fixing pad side, if there is no belt regulation on the opposite heating roller side, the fixing belt is displaced in the width direction on the heating roller side, and meandering is likely to occur. .

The present invention has been made in view of the above problems, and an object of the present invention is to more effectively suppress belt meandering by providing a belt meandering restricting portion over a wider region of the left and right side edges of the belt. And

In order to solve the above problems, a belt device according to the present invention sandwiches a belt rotatably supported by a plurality of support members having a first support member and a second support member as at least two support members. A belt device provided opposite to the first support member and to which a rotational driving force is transmitted, and a pair of end support members that support both ends of the second support member, The belt device is characterized in that a meandering restricting portion for restricting meandering of the belt is formed in contact with both side edges in the width direction of the belt.

  According to the present invention, it is possible to enhance the meandering regulation action of the belt by the meandering restricting part on the side opposite to the driving side of the belt against which the driving roller hits.

1 is a schematic side view of an image forming apparatus according to an embodiment of the present invention. 1 is a schematic side view of a fixing device according to an embodiment of the present invention. 1 is an exploded perspective view of an end portion of a fixing device according to a first embodiment of the present invention. 1 is a schematic cross-sectional view of a fixing device according to a first embodiment of the present invention. It is a schematic sectional view of a conventional fixing device. It is a perspective view of the edge part support plate of the fixing device which concerns on 2nd Embodiment of this invention. It is a schematic sectional drawing of the fixing device which concerns on 2nd Embodiment of this invention. It is sectional drawing of the end plate of the fixing device which concerns on 2nd Embodiment of this invention. FIG. 6 is a partial enlarged cross-sectional view of an end plate of a fixing device according to a second embodiment of the present invention. It is a perspective view of the edge part support plate of the fixing device which concerns on 3rd Embodiment of this invention. It is a schematic sectional drawing of the fixing device which concerns on 3rd Embodiment of this invention.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a schematic configuration diagram illustrating a configuration example of an image forming apparatus according to an embodiment of the present invention. In this embodiment, the case where the image forming apparatus is a printer will be described. However, the present invention can be applied to other image forming apparatuses such as a copying machine, a facsimile machine, and a multifunction machine other than the printer.

In FIG. 1, the image forming apparatus according to the present embodiment is an example of a tandem type electrophotographic color image forming apparatus that forms an image in accordance with a general electrophotographic image forming process. The image forming apparatus includes a writing device 1 as an optical writing unit (exposure unit), a process cartridge 2 as an image forming unit in which toners of four different colors (black, cyan, magenta, and yellow) are sealed. It has. As the toner, for example, a toner containing oil-containing silica as an external additive can be used.

The image forming apparatus further includes a primary transfer device 3 as a primary transfer unit, a paper feeding device 4 as a recording medium supply unit, a secondary transfer device 5 as a secondary transfer unit, a fixing device 6 as a fixing unit, and a recording medium. A paper discharge roller 7 is provided as a discharge means.

The fixing device 6 can be detachably or non-detachable from a printer as an image forming apparatus. Maintenance can be improved by making the fixing device 6 detachable. Further, by making the fixing device 6 unremovable, cost reduction and compactness can be achieved.

The primary transfer device 3 superimposes the toner image formed by the process cartridge 2 on an intermediate transfer belt as an intermediate transfer member. The secondary transfer device 5 transfers the toner image on the intermediate transfer belt transferred by the primary transfer device 3 onto a sheet as a recording medium, and the sheet feeding device 4 stacks the sheets and uses the secondary transfer device 5. Supply paper to the transfer position.

The fixing device 6 fixes the toner image on the paper, and the paper discharge roller 7 discharges the paper after the toner image is fixed. The primary transfer device 3, the paper feeding device 4, the secondary transfer device 5, and the fixing device 6 are each configured as a unit that can be attached to and detached from the apparatus main body. For this reason, these apparatuses are also called a primary transfer unit, a paper feed unit, a secondary transfer unit, and a fixing unit.

FIG. 2 is a cross-sectional view showing a schematic configuration of a main part of the fixing device 6 according to the embodiment of the present invention. The fixing device 6 is hung between a fixing pad 63 as a first support member, a heating roller 62 as a second support member, a fixing stay 64 that supports the fixing pad 63, and the heating roller 62 and the fixing pad 63. A fixed fixing belt 65 and a pressure roller 66 as a driving roller are provided. The fixing stay 64 holds the fixing pad 63 so as to be movable forward and backward along the direction facing the pressure roller 66, and has a predetermined rigidity to prevent deformation due to pressure.

The heating roller 62 includes a heater 61 as a heating unit that generates heat for heating a fixing nip formed between the pressure roller 66 and the fixing belt 65. Then, the recording medium carrying the unfixed image is passed through the fixing nip so that the image is fixed on the recording medium. In the present embodiment, the base layer of the fixing belt 65 is made of PI (polyimide).

The pressure roller 66 is transmitted with a rotational driving force to one end in the axial direction, and is in pressure contact with the fixing pad 63 with the fixing belt 65 interposed therebetween. The fixing belt 65 includes the heating roller 62 and the fixing pad 63, and is rotatably supported by the fixing pad 63 and the heating roller 62 so as to form a fixing nip through which the sheet passes between the fixing roller 65 and the pressure roller 66. Yes.

In the fixing device 6 shown in FIG. 2, when the pressure roller 66 is rotationally driven in the direction of arrow A, the fixing belt 65 is driven to rotate in the direction of arrow B while sliding on the fixing pad 63. Note that a sheet component having a low friction coefficient may be attached to the fixing pad 63 in order to improve the slidability of the fixing belt 65.

(First embodiment)
FIG. 3A is a diagram illustrating a configuration of an end support plate 621 as an end support member that supports both ends of the heating roller 62 and the fixing stay 64 of the fixing device 6. The end support plate 621 is formed in a rectangular plate shape with a resin having slidability and heat resistance.

In the present embodiment, the material of the end support plate 621 is PTFE (polytetrafluoroethylene), which is less aggressive to the fixing belt 65. In addition to this, the material of the end support plate 621 may be a liquid crystal polymer, PPS (polyphenylene sulfide), PAI (polyamideimide), or the like, which is a resin having heat resistance and excellent slidability. The material of the end support plate 621 may be a heat resistant fluororesin. Thereby, both heat resistance and slidability can be achieved, and the life of the fixing belt 65 can be extended.

The end support plate 621 has a circular hole 6211 and a rectangular hole 6212 side by side. The circular hole 6211 is a shaft hole 6211 that rotatably supports the end of the heating roller 62. The rectangular hole 6212 is a stay support hole 6212 that supports the end portion of the fixing stay 64.

A concave groove 6214 and a concave groove 6215 are formed at both upper and lower edges of the end support plate 621. These concave grooves 6214 and 6215 are for attaching the end support plate 621 to the plate-like frame 67 of the fixing device 6 shown in FIG. 5A. That is, the concave grooves 6214 and 6215 of the end support plate 621 can be engaged with the upper and lower edges of the lateral cutout 671 formed in the plate frame 67 from the horizontal direction.

The end support plates 621 having the same shape are arranged in parallel with each other in a pair of left and right. Accordingly, the shaft hole 6211 and the stay support hole 6212 can be arranged symmetrically, and the heating roller 62 and the fixing pad 63 can be accurately paralleled. By accurately paralleling the heating roller 62 and the fixing pad 63, the lateral deviation of the belt tension that causes the meandering is prevented, and the life of the belt can be extended due to the difficult meandering property of the fixing belt 65.

The stay support hole 6212 can also apply a predetermined tension to the fixing belt 65 by supporting the fixing stay 64 so as to be slidable in the left-right direction in FIG. 3A. In this case, the lateral width of the stay support hole 6212 is formed to be slightly wider than the fixing stay 64, and biasing means such as a spring for biasing the fixing stay 64 in the right direction in FIG.

Further, as will be described later with reference to FIGS. 4A and 4B, it is also possible to apply belt tension by pressing the intermediate portion of the fixing belt 65. In that case, the stay support hole 6212 is set to have substantially the same size as the end of the fixing stay 64, and the fixing stay 64 is fixed to the end support plate 621. By doing so, the positions of the fixing stay 64 or the fixing pad 63 with respect to the end support plate 621 are uniquely determined.

The opposing surfaces of the pair of end support plates 621 facing each other are planar meandering restricting surfaces 6213 as meandering restricting portions. The meandering restricting surface 6213 is formed on the entire surface of one end of the end support plate 621 so that the entire circumferential direction of the left and right side edges of the fixing belt 65 can contact the meandering restricting surface 6213.

In this embodiment, since the meandering restriction surface 6213 is formed on the end support plate 621 that is a support member for the heating roller 62 and the fixing stay 64, the size and cost of the fixing device 6 can be reduced. The meandering restriction surface 6213 is not necessarily formed on the entire surface of one side of the end support plate 621. In the prior art, meandering is restricted at both ends of the fixing pad 63 as in Patent Document 1 (Japanese Patent Application Laid-Open No. 2004-286923), so that at least a necessary region such as around the shaft hole 6211 on the side opposite to the fixing pad 63 is provided. You may form only. As a result, friction between the meandering restriction surface 6213 and the fixing belt 65 can be reduced.

In this embodiment, as shown in FIG. 3B, the end support plates 621 are positioned on the sides of the entire circumference of both ends of the fixing belt 65, so that the entire circumference of both ends of the fixing belt 65 is formed in the width direction by the end support plates 621. Regulated by That is, when the fixing belt 65 meanders in the direction of arrow C in FIG. 3A, the entire periphery of one end of the fixing belt 65 abuts on the meandering restricting surface 6213 of the end support plate 621 and is restricted in position.

On the other hand, as a comparative example, for example, as shown in FIG. 3C, compared to the meandering restricting protrusion 6219 of Japanese Patent Laid-Open No. 2004-286923 described above, a relatively short length L is provided at both ends of the fixing pad 63 in FIG. Only the meandering restricting protrusion 6219 can be formed. For this reason, compared with the embodiment of the present invention of FIG. 3B, the length ratio of the meandering restricting portion is conventionally only about 15% of the embodiment of the present application. Therefore, the meandering restricting surface 6212 as the meandering restricting portion of the embodiment of the present invention shown in FIG.

In order to verify the meandering regulation action, durability evaluation by actual printing was carried out using this embodiment and a conventional fixing device. As a result of repeatedly printing 3 pages on one side of A4 plain paper, the conventional technique caused 200K sheets to be damaged by belt meandering. However, in the fixing device 6 according to the embodiment of the present invention, no belt damage occurred even at 240K sheets. From this, it was confirmed that the meandering restricting portion of the embodiment of the present invention is remarkably superior in the meandering restricting action as compared with the conventional case.

Note that this embodiment differs from the second embodiment described below in that there is no contact member for applying tension on the inner surface or the outer surface of the fixing belt 65 between the heating roller 62 and the fixing pad 63. No friction is applied and the belt life can be increased.

(Second Embodiment)
FIG. 4A shows an appearance of the end support plate 621 according to the second embodiment. The end support plate 621 of the second embodiment is different from the first embodiment described above in that a tension adjusting unit 6216 that applies tension to the fixing belt 65 is provided. Others are the same as in the first embodiment. The tension adjusting unit 6216 is one of a plurality of support members that support the fixing belt 65 together with the heating roller 62 and the fixing pad 63.

As shown in FIGS. 4A to 4C, the tension adjusting unit 6216 is formed to be continuous with the lower part of the inner surface of the stay support hole 6212 of the end support plate 621. That is, the tension adjusting unit 6216 protrudes from the meandering restriction surface 6213 of the end support plate 621 by a predetermined length in the horizontal direction so as to be continuous with the lower edge of the inner surface of the stay support hole 6212.

FIG. 4C is a view of a longitudinal section passing through the tension adjusting unit 6216 as viewed from the direction of arrow D in FIG. 4B. The upper surface of the tension adjustment unit 6216 is formed in a cylindrical shape so as to ensure strength and reduce wall thickness. In addition, the lower surface of the tension adjusting unit 6216 is configured by a first guide portion 6216a having a partial conical shape on the distal end side and a second guide portion 6216b having a partial cylindrical shape on the proximal end side.

As shown in FIG. 4C, the inclination of the first guide portion 6216a is preferably 5 to 30 degrees when the angle at which the straight line extending in the lowest generatrix crosses the horizontal line is θ. θ = 20 degrees.

When the angle θ is less than 5 degrees, the amount of movement in the meandering direction necessary for applying a predetermined magnitude of tension increases, and as a result, the action of the tension adjusting unit 6216 is hardly obtained. Further, when the angle θ exceeds 30 degrees, a slight fluctuation in the meandering direction causes a large tension fluctuation, so that the fixing belt 65 is easily damaged. If θ is in the range of 5 to 30 degrees, both can be avoided.

By providing the inclination angle θ in this manner, the belt tension increases as the fixing belt 65 meanders and approaches the meandering restricting surface 6213, and if not meandering, the belt tension is reduced to reduce the friction on the inner surface of the belt. Can be reduced. Thereby, the life of the fixing belt 65 can be extended.

It is desirable that the tip of the tension adjusting unit 6216 be disposed outside the both ends of the maximum width of the paper that contacts the fixing belt 65. As a result, the tension of the fixing belt 65 is uniform in the portion in contact with the sheet in the width direction, and the conveyance stability of the sheet is enhanced. Note that if the leading end of the tension adjusting unit 6216 is brought into contact with the inner side of the maximum width of the sheet, the surface of the fixing surface of the fixing belt 65 may be disturbed, which may cause image defects.

In a normal state in which the fixing belt 65 does not meander, as shown by a solid line in FIG. 4D, both end edges of the inner peripheral surface of the fixing belt 65 are guided by being in contact with the second guide portion 6216b. As a result, an outward (downward) force is applied from the tension adjusting unit 6216 to both ends of the inner peripheral surface of the fixing belt 65, so that the necessary tension is evenly applied to the fixing belt 65.

By applying tension in this way, it is possible to suppress the occurrence of buckling that the belt edge is bent inward when the belt is regulated by the meandering regulation surface 6213 of the end support plate 621, and the belt life is further prolonged. be able to.

In the embodiment of FIGS. 4A to 4D, the tension adjusting unit 6216 is disposed inside the fixing belt 65, but the tension adjusting unit 6216 may be disposed outside the fixing belt 65. In this case, a predetermined belt tension is applied to one end edge of the outer peripheral surface of the fixing belt 65 by applying a pressing force upward from below in FIG. 4D.

However, when the tension adjusting unit 6216 is disposed outside the fixing belt 65, the tension adjusting unit 6216 is in contact with the toner fixing surface of the fixing belt 65. Therefore, as described above, care is taken so that the tip of the tension adjusting unit 6216 does not enter the inside of the maximum width of the sheet.

In order to confirm whether it is advantageous to arrange the tension adjusting unit 6216 inside or outside the fixing belt 65, the tension adjusting unit 6216 is arranged inside and outside the fixing belt 65, and the other configurations are the same except for the above. Durability evaluation was performed with the apparatus.

As a result, in the fixing device having the tension adjusting unit 6216 arranged outside, a side effect in which an abnormal image is generated due to a change in the surface state of the fixing belt 65 was recognized. In the fixing device having the tension adjusting unit 6216 arranged on the inner side, no side effects were particularly observed. For this reason, it is desirable that the tension adjusting unit 6216 is in contact with one end edge of the inner peripheral surface of the fixing belt 65 as an inner arrangement of the fixing belt 65.

(Third embodiment)
Next, a third embodiment is shown in FIGS. 5A and 5B. The third embodiment is different from the first embodiment in that there is a U-shaped spring portion 6217. A shaft hole 6211 is connected to the end support plate 621 through the spring portion 6217.

The spring portion 6217 rises vertically upward from the end of the concave groove 6214, forms an inverted U-shaped folded portion, and then folds in parallel vertically downward. The shaft hole 6211 is integrally connected to the lower end on the folded side. The shaft hole 6211 can be elastically swung in the direction of arrow E by a spring portion 6217. Therefore, the distance between the shaft hole 6211 and the stay support hole 6212 is variable by the tension acting on the fixing belt 65.

As described above, the end support plate 621 has the horizontal concave grooves 6214 and 6215 formed at the upper and lower end edges. The horizontal grooves 6214 and 6215 can be fitted to both upper and lower edges of a lateral cutout 671 formed in the plate frame 67 of the fixing device 6. By engaging the end support plate 621 with the notch 671 of the plate-like frame 67 by the horizontal concave grooves 6214 and 6215, the swinging direction (arrow E direction) of the shaft hole 6211 is determined.

FIG. 5B shows a cross-sectional view of the third embodiment. The end support plate 621 is formed so that the interval between the shaft hole 6211 and the stay support hole 6212 is larger than the interval after assembly in a state before being attached to the plate frame 67.

Thus, in a state where the fixing belt 65 is stretched between the heating roller 62 and the fixing pad 63, the fixing belt 65 can be urged in the direction of arrow F to apply a predetermined tension. In this embodiment, since the frictional parts on the inner surface of the fixing belt 65 are reduced as compared with the case where the tension adjusting unit 6216 of the second embodiment is provided, there is an effect that the fixing belt 65 has a longer life. In addition, it is possible to realize a fixing device with a small number of parts, a simple structure and a compact structure at a low cost.

As a modification of the third embodiment, the end support plates 621 provided at both ends of the heating roller 62 can be the same component on the left and right. By doing so, it is possible to eliminate the positional deviation and the left-right deviation of the tension due to the component tolerance, and it is possible to make the fixing belt 65 difficult to meander, and it is possible to extend its life.

Although the embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments, and it goes without saying that various modifications can be made within the scope of the technical idea described in the claims. For example, in each of the above-described embodiments, the example in which the heater 61 as the heating unit is provided in the heating roller 62 has been described. However, instead of or in addition to the heater 61 in the heating roller 62, the pressure roller 66 and the fixing stay 64 have a heater. May be provided. Other heating means may be used as long as it generates heat for heating the fixing nip.

In each of the above embodiments, the example in which the supporting member facing the pressure roller (driving roller) is the fixing pad has been described. However, the present invention may be applied to a modified embodiment in which the fixing roller is replaced with the fixing pad. Applicable.

Further, the tension adjusting unit 6216 is fixedly disposed on the end support plate 621, and is attached to the end support plate 621 or the plate-like stay 67 as a tension adjustment roller, and the inner surface or outer periphery of the fixing belt 65 with the tension adjustment roller. It is good also as a structure which presses a surface.

In each of the above embodiments, the fixing device 6 using the fixing belt 65 has been described. However, the present invention is not limited to this, and the present invention can be applied to general belt devices in which a belt is rotatably supported by a plurality of support members. .

1: Writing device 2: Process cartridge 3: Primary transfer device 4: Paper feeding device 5: Secondary transfer device 6: Fixing device 7: Paper discharge roller 61: Heater 62: Heating roller 63: Fixing pad 64: Fixing stay 65 : Fixing belt 66: Pressure roller 67: Plate frame 621: End support plate 671: Notch 6211: Shaft hole (circular hole)
6212: Stay support hole (rectangular hole)
6213: Meandering restriction surface 6214: Concave groove 6215: Concave groove 6216: Tension adjusting part 6216a: First guide part 6216b: Second guide part 6217: Spring part 6219: Protruding part for meandering restriction

JP 2004-286923 A

Claims (16)

A belt rotatably supported by a plurality of support members having a first support member and a second support member, which are at least two support members, and a rotational drive provided to face the first support member across the belt A belt device comprising a driving roller to which force is transmitted,
A belt device characterized in that a pair of end support members that support both ends of the second support member are formed with meandering restricting portions that abut on both side edges in the width direction of the belt and restrict meandering of the belt.   Both ends of the first support member and the second support member are supported by the pair of end support members, and the pair of end support members between the first support member and the second support member are mutually connected. 2. The belt fixing device according to claim 1, wherein the meandering restricting portion is formed in a flat shape on the opposing surface. A biasing means for biasing at least one support member of the first support member or the second support member in a direction away from the other support member is provided, and a predetermined tension is applied to the belt by the biasing means. The belt device according to claim 1 or 2, wherein A tension adjusting portion that abuts against the inner peripheral surface edge or outer peripheral surface edge of the belt is disposed, and as the belt meanders, the tension adjusting portion further increases the inner peripheral surface edge or outer peripheral surface edge of the belt. The belt device according to any one of claims 1 to 3, wherein the tension on the meandering side of the belt is relatively increased by pressing strongly, compared with the tension on the opposite side. The belt device according to claim 4, wherein the tension adjusting unit has an inclined surface inclined with respect to the meandering direction of the belt. 6. The belt device according to claim 5, wherein an angle of the inclined surface is in a range of 5 to 30 degrees. The belt device according to any one of claims 4 to 6, wherein the tension adjusting portion is integrally formed with the end portion supporting member. 8. The belt device according to claim 1, wherein the end support member and the tension adjusting portion are made of heat-resistant fluororesin. The belt device according to claim 7 or 8, wherein the end support member has the same shape on both ends of the second support member. A fixing belt that moves on the surface in a state of being stretched over a plurality of support members having a first support member and a second support member that are at least two support members;
A pressure roller comprising a drive roller provided opposite to a fixing pad supported by a fixing stay serving as the first support member with the fixing belt interposed therebetween, to which a rotational driving force is transmitted;
Heating means for heating at least one of the plurality of support members, the fixing belt or the pressure roller,
In a belt fixing device configured to fix an image on the recording medium by passing a recording medium carrying an unfixed image through a fixing nip formed between the pressure roller and the fixing belt,
A belt fixing device comprising: an end supporting member that supports both ends of the second supporting member; and a meandering restricting portion that abuts on both lateral edges of the fixing belt to restrict meandering of the fixing belt. .   The said 2nd support member is comprised by the rotatable heating roller which has the said heating means in the inside, and the both ends of the said heating roller are rotatably supported by the said edge part support member, Belt fixing device.   Both ends of the pressure roller and the fixing stay are supported by the pair of end support members, and the meandering restricting portion is provided on the mutually opposing surfaces of the pair of end support members between the pressure roller and the fixing stay. The belt fixing device according to claim 10 or 11, wherein the belt fixing device is formed in a planar shape. A tension adjusting portion that contacts an inner peripheral surface edge or an outer peripheral surface edge of the fixing belt positioned outside both ends of the maximum width of the recording medium that contacts the fixing belt is disposed, and the fixing belt meanders. As the tension adjusting section presses the inner peripheral surface edge or outer peripheral surface edge of the fixing belt more strongly, the tension on the meandering side of the fixing belt is relatively increased compared to the tension on the opposite side. The belt fixing device according to claim 10, wherein the belt fixing device is a belt fixing device. 14. An image forming apparatus comprising the belt fixing device according to claim 10 as an optical writing unit, an image forming unit, a transfer unit, a recording medium supply unit, and a fixing unit. The image forming apparatus according to claim 14, wherein the belt fixing device according to claim 10 is provided so as to be removable or not removable. 16. The image forming apparatus according to claim 14, wherein oil-containing silica is contained in an external additive of the toner.

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