Fixing device and image forming apparatus including removing member that removes object attached to outer peripheral surface using rotational speed difference with respect to fixing member

A fixing device includes a fixing member that has an outer peripheral surface and an inner peripheral surface, is rotatably provided, comes into contact with, of a recording material on which an image is formed, a surface on which the image is formed, and fixes the image to the recording material, a rotating member that is rotatably provided and includes, at an outer peripheral portion, a contact surface coming into contact with the inner peripheral surface of the fixing member, and a removing member that is disposed to be in contact with the outer peripheral surface of the fixing member, is rotatably provided, and removes an attached object attached to the outer peripheral surface using a rotation speed difference with respect to the fixing member.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is based on and claims priority under 35 USC 119 from Japanese Patent Application No. 2022-050387 filed Mar. 25, 2022.

BACKGROUND

(i) Technical Field

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

(ii) Related Art

For example, JP2008-158054A discloses a configuration where major portions of a fixing belt module include a fixing belt, a fixing roller that is rotationally driven while stretching the fixing belt, a stretching roller that stretches the fixing belt from an inside, a stretching roller that stretches the fixing belt from an outside, a posture correction roller that corrects a posture of the fixing belt between the fixing roller and the stretching roller, a peeling pad that is disposed at a position close to the fixing roller, which is a downstream region in a nip portion, the region being a region where the fixing belt module and a pressurizing roller are in pressure-contact with each other, and a stretching roller (idler roller) that stretches the fixing belt on a downstream side of the nip portion, and a cleaning web for cleaning a surface of the stretching roller is included.

SUMMARY

Herein, in a configuration where an attached object on a fixing member is transferred to a removing member by bringing the removing member into contact with an outer peripheral surface of the fixing member, it is difficult to remove the attached object that has entered a concave portion of the fixing member having high surface roughness in the outer peripheral surface with the removing member rotating at the same speed, and a residual attached object may transfer again to the next recording medium.

Aspects of non-limiting embodiments of the present disclosure relate to a fixing device and an image forming apparatus that improve a cleaning property of a removing member compared to a case where a fixing member and a removing member are rotated at the same speed.

According to an aspect of the present disclosure, there is provided a fixing device including a fixing member that has an outer peripheral surface and an inner peripheral surface, is rotatably provided, comes into contact with, of a recording material on which an image is formed, a surface on which the image is formed, and fixes the image to the recording material, a rotating member that is rotatably provided and includes, at an outer peripheral portion, a contact surface coming into contact with the inner peripheral surface of the fixing member, and a removing member that is disposed to be in contact with the outer peripheral surface of the fixing member, is rotatably provided, and removes an attached object attached to the outer peripheral surface using a rotation speed difference with respect to the fixing member.

DETAILED DESCRIPTION

FIG.1is a view showing an image forming apparatus1according to the present exemplary embodiment.

The image forming apparatus1shown inFIG.1is an apparatus forming an image on paper P which is an example of a recording material. The image forming apparatus1is provided with an image forming portion10, a paper transport unit20, and a control unit40.

The image forming portion10is provided with an image forming unit11, an intermediate transfer belt12, a secondary transfer unit13, and a fixer14, which is an example of a fixing device.

In the present exemplary embodiment, four image forming units11Y,11M,11C, and11K corresponding to four colors of toners including yellow (Y), magenta (M), cyan (C), and black (K) respectively are provided as the image forming unit11.

The image forming units11Y,11M,11C, and11K are arranged in a moving direction of the intermediate transfer belt12and form a toner image through an electrophotographic method.

Each of the image forming units11Y,11M,11C, and11K has a photoconductor drum111, a charging unit112, an exposure unit113, a developing unit114, and a primary transfer unit115.

Each of the image forming units11Y,11M,11C, and11K forms a toner image of any color of YMCK and transfers the toner image onto the intermediate transfer belt12. Accordingly, a toner image in which the toner images of respective colors including YMCK overlap each other is formed on the intermediate transfer belt12.

The photoconductor drum111rotates in an arrow A direction at a speed determined in advance. In addition, an electrostatic latent image is formed on a peripheral surface of the photoconductor drum111.

The charging unit112charges the peripheral surface of the photoconductor drum111at a potential determined in advance.

The exposure unit113irradiates the charged peripheral surface of the photoconductor drum111with light and forms an electrostatic latent image on the peripheral surface of the photoconductor drum111.

The developing unit114forms a toner image by attaching a toner to the electrostatic latent image formed on the peripheral surface of the photoconductor drum111.

The primary transfer unit115transfers the toner image formed on the peripheral surface of the photoconductor drum111onto the intermediate transfer belt12.

A voltage having a polarity opposite to a charging polarity of a toner is applied to the primary transfer unit115. Accordingly, the toner image formed on the peripheral surface of the photoconductor drum111is sequentially electrostatically sucked onto the intermediate transfer belt12, and one overlapping color toner image is formed on the intermediate transfer belt12.

The intermediate transfer belt12is supported by a plurality of roller-shaped members. The intermediate transfer belt12is formed in an endless shape and circulates and moves in an arrow B direction. In addition, the intermediate transfer belt12includes an outer peripheral surface12aand an inner peripheral surface12b.

The intermediate transfer belt12is used in transporting a toner image. In the present exemplary embodiment, a toner image is formed on the outer peripheral surface12aof the intermediate transfer belt12, and the toner image is transported to the secondary transfer unit13with the movement of the intermediate transfer belt12.

In the present exemplary embodiment, a drive roller121that is driven by a motor (not shown) and drives the intermediate transfer belt12is provided as the roller-shaped member disposed inside the intermediate transfer belt12. In addition, an idle roller123and a backup roller132that support the intermediate transfer belt12are provided as the roller-shaped members.

The roller-shaped members are rotatably provided and are pressed against the inner peripheral surface12bof the intermediate transfer belt12.

The paper transport unit20is provided with a paper accommodating unit21that accommodates a plurality of sheets of paper P in a stacked state and a pickup roller22that takes out and transports the paper P accommodated in the paper accommodating unit21.

In addition, the paper transport unit20is provided with a transport roller23that transports the paper P taken out by the pickup roller22along a paper transport path30and a paper guiding portion24that guides the paper P transported by the transport roller23to the secondary transfer unit13.

Further, the paper transport unit20is provided with a transport belt25that transports the paper P after secondary transfer to the fixer14and a paper guiding portion26that guides the paper P after fixing to a discharge portion27.

The secondary transfer unit13is provided with a secondary transfer roller134that is disposed to be in contact with the outer peripheral surface12aof the intermediate transfer belt12and the backup roller132that is disposed on an inner peripheral surface12bside of the intermediate transfer belt12and forms an electrode facing the secondary transfer roller134.

In addition, in the present exemplary embodiment, a power supplying roller133made of a metal, which applies a secondary transfer bias to the backup roller132, is provided.

The secondary transfer unit13configured in this manner transfers a toner image transported to the secondary transfer unit13by the intermediate transfer belt12onto the transported paper P.

The fixer14is disposed on a downstream side of the secondary transfer unit13in a transport direction of the paper P. The fixer14is provided with a fixing belt module50that has a heating source and a pressurizing roller61provided to face the fixing belt module50.

In a case where the paper P which has passed through the secondary transfer unit13is transported between the fixing belt module50and the pressurizing roller61, an unfixed toner image on the paper P is melted and then fixed onto the paper P. Accordingly, an image consisting of the toner image is formed on the paper P.

Herein, in a general fixing step, a roller is brought into contact with an outer surface of a fixing belt, an attached object on the fixing belt is transferred to the roller, and the attached object attached to the roller is removed by a cleaning web.

However, the fixing belt and the roller respectively have surface roughness, and it is difficult to secure a cleaning property without a toner or wax attached portion attached to the bottom having surface roughness coming into contact with the roller.

Thus, in the present exemplary embodiment, it is possible to secure a cleaning property with respect to a toner or wax attached object attached to the bottom of the fixing belt51having roughness, focusing on a rotation speed difference between a circulating and moving fixing belt51(seeFIG.2) to be described later and an upstream cleaning roller71(seeFIG.2) for removing an attached object remaining on an outer peripheral surface51aof the fixing belt51through rotation, which is to be described later.

Hereinafter, various exemplary embodiments of the fixer14will be described.

FIG.2is a view for describing a configuration of the fixer14according to a first exemplary embodiment.

As shown inFIG.2, the fixer14according to the first exemplary embodiment includes the fixing belt module50described above that includes the fixing belt51, which is an example of a fixing member, and the pressurizing roller61described above that is in contact with an outer surface of the fixing belt51.

The fixing belt module50includes the fixing belt51described above that circulates and moves in an arrow C direction and a first tension roller52that stretches the fixing belt51from an inside of the fixing belt51. In addition, the fixing belt module50includes a second tension roller55that is an example of a rotating member stretching the fixing belt51from the inside on an upstream side of the first tension roller52in the arrow C direction. Further, the fixing belt module50includes a pressing portion53that is positioned on the downstream side of the first tension roller52in the arrow C direction and has a pad portion53afor forming a nip portion N by pressing the fixing belt51against the pressurizing roller61.

The nip portion N is formed in the fixer14as a part of an outer peripheral surface61aof the pressurizing roller61is pressed against the outer peripheral surface51aof the fixing belt51, which is in contact with the pressing portion53, from the opposite side to the pressing portion53. The nip portion N where the outer peripheral surface61aof the pressurizing roller61and the fixing belt51are in contact with each other is a passing portion through which the paper P on which a toner image is formed passes while being pressurized and heated.

The paper P entering the nip portion N has a toner image forming surface on which a toner image is formed, and the paper P enters the nip portion N in a state where the toner image forming surface faces upward in the present exemplary embodiment. Accordingly, a toner image forming surface side of the paper P comes into contact with the fixing belt51in the present exemplary embodiment.

In addition, in the present exemplary embodiment, the pressurizing roller61is rotationally driven by a motor81, and the fixing belt51circulates and moves, following the pressurizing roller61. That is, the fixing belt51receives a drive force from the rotating pressurizing roller61and circulates and moves (circulation movement) in the arrow C direction. The motor81is driven and controlled by the control unit40.

The first tension roller52and the second tension roller55are rotatably supported and support the fixing belt51such that the fixing belt can be circulated and moved as the fixing belt51is wound at positions separated from each other. The pressing portion53is disposed at a position facing the pressurizing roller61with the fixing belt51nipped therebetween and presses the fixing belt51against the pressurizing roller61without rotating. The pressurizing roller61includes a layer that can elastically deform to an outer peripheral surface side, and the pressurizing roller61is in a shape recessed at the nip portion N as the pressing portion53is in contact therewith via the fixing belt51. In the present exemplary embodiment, the paper P is nipped from both sides by the pressurizing roller61and the pressing portion53, and a pressure is applied to the paper P.

Inside the first tension roller52, a heater52ais provided. In addition, a heater55ais provided inside the second tension roller55. The heaters52aand55aare configured by, for example, halogen heaters. The first tension roller52is heated by the heat of the heater52a, and the second tension roller55is heated by the heat of the heater55a. Then, the fixing belt51is heated by the heat from the first tension roller52and the second tension roller55.

In the example shown inFIG.2, the fixing belt51is wound in a section of approximately a quarter of the circumference of an outer peripheral surface of the first tension roller52, and the fixing belt51is wound in a section of approximately a half or more of the circumference of an outer peripheral surface55b, which is an example of an outer peripheral portion of the second tension roller55. Accordingly, the amount of heat of the heaters52aand55ais applied to the fixing belt51.

The fixing belt module50includes a liquid applying device54that applies an oil to an inner surface of the fixing belt51between the first tension roller52and the second tension roller55. The liquid applying device54includes an oil impregnating member541that is in contact with the inner surface of the fixing belt51, a casing542that holds the oil impregnating member, and a support member543that supports a part including a tip of the oil impregnating member from an opposite side to the fixing belt51.

The oil impregnating member541is formed by a non-woven fabric formed of heat-resistant fibers being soaked with an oil. For example, polytetrafluoroethylene (PTFE) is used for the heat-resistant fibers. As the oil is applied to an inner peripheral surface51bof the fixing belt51by the oil impregnating member541, the coefficient of friction between the pressing portion53and the fixing belt51decreases, and the wear of the fixing belt51is suppressed.

The fixing belt module50includes the upstream cleaning roller71, which is an example of a removing member, as a configuration for cleaning the outer peripheral surface51aof the fixing belt51.

Such an upstream cleaning roller71is a cleaning member for cleaning the outer peripheral surface51aof the fixing belt51, and more specifically, removes an attached object attached to the outer peripheral surface51aof the fixing belt51, which has passed through the nip portion N.

The upstream cleaning roller71is provided at a position where the fixing belt51is nipped between the second tension roller55and the upstream cleaning roller, which is an upstream position of the second tension roller55. In other words, the upstream cleaning roller71is disposed such that a portion of the fixing belt51, which is separated from the second tension roller55at an entrance portion of the second tension roller55, is pressed against the second tension roller55.

A surface of the upstream cleaning roller71according to the first exemplary embodiment is formed of a non-woven fabric, a felt material, or a porous member. In addition, the upstream cleaning roller71according to the first exemplary embodiment is a driven roller that rotates by being in contact with the circulating and moving fixing belt51.

To describe further, as shown inFIG.2, the fixing belt51which has passed through the nip portion N is deformed in a so-called S-shape by being nipped between the upstream cleaning roller71and the second tension roller55. That is, the fixing belt51deforms in a shape in which an inner peripheral surface side convex portion51cthat is an example of a second portion, which is a convex portion on an inner peripheral surface51bside of the fixing belt51along the upstream cleaning roller71, and an outer peripheral surface side convex portion51dthat is an example of a first portion, which is a convex portion on an outer peripheral surface51aside of the fixing belt51along the second tension roller55, are continuous.

The inner peripheral surface side convex portion51cdeforms due to pressing by the upstream cleaning roller71at the entrance portion with respect to the second tension roller55of the fixing belt51.

Such a deformation in an S-shape forms a trajectory of the fixing belt51due to the pressing the upstream cleaning roller71at the entrance portion with respect to the second tension roller55of the fixing belt51.

Herein, a strain in a case where the fixing belt51comes into contact with the second tension roller55and the upstream cleaning roller71, which are adjacent to each other, to form an S-shape (hereinafter, referred to as S-shape contact) and a strain in a case where the fixing belt51is not in contact with the upstream cleaning roller71while being in contact with the only second tension roller55(hereinafter, referred to as simple contact) are compared to each other.

FIG.3is a graph showing strains in a circumferential direction in the simple contact and the S-shape contact. The vertical axis shows the strain (%) of the fixing belt51, and the horizontal axis shows a position (mm) in the arrow C direction. InFIG.3, the simple contact is shown by a solid line, and the S-shape contact is shown by a broken line. In addition, herein, the arrow C direction is shown inFIG.2. The strain shows extension (contraction) as a percentage.

As shown inFIG.3, the simple contact shown by the solid line is a case where the fixing belt51is wound around the second tension roller55(seeFIG.2), but the upstream cleaning roller71is not included. The case of the simple contact is a graph that is symmetrical with respect to position 0 mm, and there is no difference in strain between a case where a distance is from position 0 mm to the left (upstream side) and a case where a distance is from position 0 mm to the right (downstream side).

To describe further, the strain of the fixing belt51is high at the entrance portion of the second tension roller55(seeFIG.2). In the S-shape contact shown by the broken line, an S-shaped trajectory is formed by disposing the upstream cleaning roller71at such an entrance portion.

That is, in the S-shape contact shown by the broken line, the upstream cleaning roller71is disposed on the upstream side (seeFIG.2). According to the graph, it can be read that the fixing belt51contracts on the left from position 0 mm and extends on the right from position 0 mm since the sign of the strain is negative on the left from position 0 mm, and the sign of the strain is positive on the right from position 0 mm.

On the left from position 0 mm, the fixing belt51contracts by the action of the upstream cleaning roller71. On the right from position 0 mm where the action of the upstream cleaning roller71is not received, the strain is positive and becomes similar to the case of the simple contact (solid line).

To describe further, at the entrance of the second tension roller55(seeFIG.2) at a position on the left from position 0 mm, there is a portion where the negative value of the strain increases, and after then, the negative value of the strain decreases and becomes a positive value. Because of such strain fluctuations of the fixing belt51, a rotation speed difference between the fixing belt51and the upstream cleaning roller71occurs.

FIG.4is a view for describing relative movement between the upstream cleaning roller71, which is an example of the removing member, and the fixing belt51, which is an example of the fixing member.

As shown inFIG.4, there is an attached object D on the outer peripheral surface51aof the fixing belt51. Such an attached object D is removed by the upstream cleaning roller71having a speed different from the speed of the fixing belt51. That is, the upstream cleaning roller71removes the attached object D attached to the outer peripheral surface51aof the fixing belt51using the rotation speed difference with respect to the fixing belt51.

As described above, the surface of the upstream cleaning roller71is formed of a non-woven fabric or a felt material. For this reason, a toner or wax in a liquid state, which is the attached object D, can be removed by the upstream cleaning roller71, and the generation of an offset image, which is generated as the attached object D is again transferred to the paper P transported next, is suppressed.

FIG.5is a graph showing a wax amount of the fixing belt51before and after cleaning by the upstream cleaning roller71in the simple contact and the S-shape contact. The vertical axis represents a wax area proportion (%), and the horizontal axis represents each of the simple contact and the S-shape contact separately before (before the roller) and after (after the roller) the upstream cleaning roller71.

As is clear from the graph shown inFIG.5, in a case of the simple contact, the wax area proportion is 15.6% before the roller and is 12.9% after the roller, which means cleaned by the upstream cleaning roller71. On the other hand, in a case of the S-shape contact, the wax area proportion is 15.9% before the roller and greatly decreases to 8.1% after the roller, which means cleaned by the upstream cleaning roller71.

As described above, a cleaning property is improved in the case of the S-shape contact, compared to the case of the simple contact. The wax area proportion herein is a wax amount attached to the outer peripheral surface51aof the fixing belt51per unit area, which is shown in an area proportion. In addition, the fact that the simple contact before cleaning is 15.6% and the S-shape contact before cleaning is 15.9%, which are values not identical to each other, is attributable to a measurement error.

FIG.6is a view for describing a configuration of the fixer14according to a second exemplary embodiment. Since the second exemplary embodiment has a portion common to the configuration of the first exemplary embodiment described above, the same reference sign will be used for the common portion, and description thereof will be omitted in some cases.

In the second exemplary embodiment shown inFIG.6, a cleaning mechanism72is included as a configuration for cleaning the outer peripheral surface51aof the fixing belt51, in addition to including the upstream cleaning roller71.

The cleaning mechanism72includes a holding portion722that holds and sends out an unused cleaning web721in a wound form and a supply portion723around which the cleaning web721is wound and that supplies the cleaning web721from the holding portion722to an outer peripheral surface of the upstream cleaning roller71. In addition, the cleaning mechanism72includes a pressing member724that presses the cleaning web721against a surface of the upstream cleaning roller71.

The upstream cleaning roller71according to the second exemplary embodiment is a metal roller, and an attached object on the upstream cleaning roller71which is removed from the fixing belt51is removed from the upstream cleaning roller71by the cleaning web721. The cleaning web721cleans the upstream cleaning roller71which is a metal roller.

In addition, the upstream cleaning roller71according to the second exemplary embodiment is a driven roller as in the first exemplary embodiment.

FIG.7is a view for describing a configuration of the fixer14according to a third exemplary embodiment. Since the third exemplary embodiment has a portion common to the configuration of the second exemplary embodiment described above, the same reference sign will be used for the common portion, and description thereof will be omitted in some cases.

In the third exemplary embodiment shown inFIG.7, a downstream cleaning roller73which is an example of another removing member is included at an exit portion with respect to the second tension roller55of the fixing belt51as a configuration for cleaning the outer peripheral surface51aof the fixing belt51, in addition to including the upstream cleaning roller71and the cleaning mechanism72which are examples of the removing member.

The downstream cleaning roller73is disposed at a downstream position of the second tension roller55and removes an attached object which has not been able to be removed by the upstream cleaning roller71.

To describe further, the downstream cleaning roller73is disposed such that a portion of the fixing belt51, which is separated from the second tension roller55at the exit portion of the second tension roller55, is pressed against the second tension roller55. With such disposition, the S-shape contact at the entrance portion of the second tension roller55, which is described for the upstream cleaning roller71, is formed also at the exit portion of the second tension roller55by the downstream cleaning roller73. Accordingly, the cleaning property of the downstream cleaning roller73improves.

The inner peripheral surface side convex portion51cin the S-shape contact at the exit portion of the second tension roller55is a deformation due to pressing by the downstream cleaning roller73.

In the third exemplary embodiment, the upstream cleaning roller71at the entrance portion is a metal roller as in the case of the second exemplary embodiment, and a surface of the downstream cleaning roller73added to the exit portion is a removing surface formed of a non-woven fabric, a felt material, or a porous member. That is, the upstream cleaning roller71made of a metal generally removes powdered toner, and the non-woven fabric surface having the downstream cleaning roller73removes residual liquid wax. In the third exemplary embodiment, the upstream cleaning roller is useful in a case of color printing in which a large amount of toner is used. In addition, since the exit portion of the fixing belt51with respect to the second tension roller55is higher than the entrance portion, residual wax is efficiently removed.

The upstream cleaning roller71and the downstream cleaning roller73according to the third exemplary embodiment are driven rollers.

FIG.8is a block diagram for describing a fourth exemplary embodiment.FIGS.9A and9Bare block diagrams for describing other exemplary embodiments.FIG.9Ais a block diagram for describing a fifth exemplary embodiment, andFIG.9Bis a block diagram for describing a sixth exemplary embodiment. In the exemplary embodiments, a rotation speed difference between the fixing belt51and the upstream cleaning roller71is realized by a configuration of a drive source or a drive transmission system.

Hereinafter, description will be made.

In the fourth exemplary embodiment shown inFIG.8, the fixing belt module50includes a cleaning roller motor82which is an example of another drive source, in addition to including the motor81described above which is an example of a drive source driving the fixing member. That is, as shown inFIG.8, the fixing belt module50includes two motors including the motor81described above that rotationally drives the pressurizing roller61and the cleaning roller motor82that rotationally drives the upstream cleaning roller71. Such a motor81and such a cleaning roller motor82are driven and controlled by the control unit40.

In the fixing belt module50according to the fourth exemplary embodiment, the control unit40controls the motor81and the cleaning roller motor82such that a rotation speed difference between the fixing belt51and the upstream cleaning roller71occurs.

In the fifth exemplary embodiment shown inFIG.9A, the fixing belt module50includes the motor81described above, a drive force branch portion83where a drive force of the motor81branches, and a decelerating device84that reduces the speed of one drive force branched at the drive force branch portion83.

Then, the drive force of which the speed is reduced by the decelerating device84is transmitted to the upstream cleaning roller71. In addition, the other drive force branched at the drive force branch portion83is transmitted to the fixing belt51via the pressurizing roller61.

In the fixing belt module50according to the fifth exemplary embodiment, the upstream cleaning roller71is driven by the drive force which branches at a transmission system from the motor81described above and of which the speed is reduced, and the pressurizing roller61and the fixing belt51are driven by a drive force of which a speed is not reduced. Accordingly, the rotation speed of the upstream cleaning roller71becomes lower than the rotation speed of the fixing belt51, and a rotation speed difference between both is realized.

As described above, a rotation speed difference between the fixing belt51and the upstream cleaning roller71occurs due to a configuration of transmitting the drive force of one motor81.

In the sixth exemplary embodiment shown inFIG.9B, the motor81, the drive force branch portion83, and the decelerating device84are included as in the case of the fifth exemplary embodiment. On the other hand, the sixth exemplary embodiment is different from the case of the fifth exemplary embodiment in that the pressurizing roller61and the fixing belt51are driven by the drive force of which the speed is reduced, and the upstream cleaning roller71is driven by the drive force of which the speed is not reduced. Accordingly, the rotation speed of the fixing belt51becomes lower than the rotation speed of the upstream cleaning roller71, and a rotation speed difference between both is realized.

As described above, also in the sixth exemplary embodiment, a rotation speed difference between the fixing belt51and the upstream cleaning roller71occurs due to the configuration of transmitting the drive force of one motor81.

The fourth exemplary embodiment, the fifth exemplary embodiment, and the sixth exemplary embodiment described above may be applied to the case of the S-shape contact (seeFIG.2,6, or7) described above and may be applied to a case of the simple contact by disposing the upstream cleaning roller71at a relative position with respect to the second tension roller55such that the S-shape contact is not caused.