JP2012042786A - Belt device, transfer device, and image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a belt device capable of preventing a cleaning member from turning up, by suppressing vibrations of the cleaning member due to the slacking of a belt.SOLUTION: The belt device comprises an endless belt 8 tensioned by a plurality of supporting members 9 and 10 and configured so as to peripherally travel, a cleaning member 25 abutting on an outer peripheral surface of the belt 8 for cleaning, a cleaning opposite member 26 abutting on an inner peripheral surface of the belt 8 at a position opposite to the cleaning member 25, and a pressing member 24 pressing the outer peripheral surface of the belt between the cleaning opposite member 26 and the supporting member 9 arranged on the next upstream side in a belt traveling direction. When the amount of cleaning objects on the belt 8 is equal to or greater than a predetermined threshold value, the pressing amount to the belt 8 of the pressing member 24 is controlled to be larger than a case less than the threshold value.

Description

  The present invention relates to a belt device used in an image forming apparatus, a transfer device using the belt device, and an image forming apparatus.

  2. Description of the Related Art As a transfer body device provided in an image forming apparatus such as a copying machine, a printer, a facsimile machine, or a complex machine of these, one provided with a transfer belt composed of an endless belt is known. As shown in FIG. 12, in general, the transfer belt 100 is stretched by a plurality of rollers 200 and 300, and at least one of the rollers 200 and 300 rotates as a drive roller so that the transfer belt 100 runs around. It has become. As shown in FIG. 12, the transfer apparatus often uses a configuration in which a cleaning blade 400 formed of an elastic body such as urethane rubber is brought into contact with the transfer belt 100 at a position facing the cleaning facing member 500. It has been. In this case, when the transfer belt 100 travels in the direction of the arrow in the figure, the cleaning blade 400 removes toner and foreign matters remaining on the transfer belt 100.

  In the transfer device configured as described above, in order to improve the cleaning performance of the cleaning blade, the contact pressure of the cleaning blade to the transfer belt is increased, or the cleaning blade is placed in a direction perpendicular to the transfer belt to perform cleaning. There is a known method for preventing the cleaning blade such as toner from slipping through by increasing the vibration generated in the blade.

  However, when the contact pressure of the cleaning blade with respect to the transfer belt is increased, the resistance of the cleaning blade against the movement of the transfer belt in the traveling direction increases. Therefore, the transfer belt is positioned upstream of the cleaning blade in the belt traveling direction. As a result, the slackness becomes large, and as a result, the behavior of the contact portion of the cleaning blade becomes unstable, and the cleaning blade may be bent. In addition, when the cleaning blade stands vertically with respect to the transfer belt and the vibration generated in the cleaning blade is increased, the resistance to movement of the transfer belt in the running direction during cleaning increases. Becomes larger, and the cleaning blade is bent. In particular, when a spherical toner having a small particle size that is difficult to clean is used, it is necessary to increase the linear pressure of the cleaning blade.

In order to deal with such a problem, for example, Patent Document 1 (Japanese Patent Laid-Open No. 2009-134236) proposes that the edge shape of the tip of the cleaning blade is formed at an obtuse angle so that the cleaning blade is difficult to bend. Yes.
Patent Document 2 (Japanese Patent Laid-Open No. 2000-231314) proposes that the cleaning blade is configured to come in contact with and separate from the surface of the transfer belt to suppress the cleaning blade from curling.
In addition, the transfer device described in Patent Document 3 (Japanese Patent Application Laid-Open No. 2004-35200) includes a cleaning facing member (tension roller) and a roller (two rollers disposed upstream of the belt running direction). A pressing member (outer roller) that presses the outer peripheral surface of the transfer belt is provided between the second transfer roller and the next transfer roller. Here, the pressing member is not provided for the purpose of preventing the cleaning blade from curling, but the transfer belt is pressed by the pressing member to suppress loosening of the transfer belt. Therefore, as a result, it is considered that the behavior of the cleaning member is stabilized and the dripping is suppressed.

  By the way, when the residual toner on the transfer belt is repeatedly removed by the cleaning blade, silica as a toner additive adheres to the tip of the cleaning blade to form a sharp lump called a constituent blade edge. Since this component cutting edge plays a role of scraping off residual toner on the intermediate transfer belt, the cleaning performance is improved by forming the component cutting edge. Therefore, it is preferable to maintain the formed component cutting edge so as to remain at the tip of the cleaning blade.

  However, as described in Patent Document 2, when the cleaning blade is configured so as to be able to contact and separate, there is a problem in that the cleaning performance is deteriorated because the constituent blade edge collapses due to the contact and separation operation of the cleaning blade. Further, the contact / separation operation of the cleaning blade in this case is to prevent the curl when the toner on the transfer belt is small, and is insufficient as a measure for preventing the curl when the toner is large.

  In the configuration described in Patent Document 3, since the transfer belt is always greatly pushed by the pressing member, if the transfer belt is left without running for a long time, the pressing is performed. There is a possibility that the transfer belt may be curled at the portion pressed by the member. In this way, when the transfer belt is curled, there is a problem that an image cannot be transferred satisfactorily at a portion with the curled wrinkle or cleaning cannot be performed satisfactorily, so that good image formation cannot be performed.

  Further, as described in Patent Document 1, when the edge shape of the tip of the cleaning blade is formed at an obtuse angle, there is a problem that productivity and processing accuracy are lowered.

  Therefore, in view of such circumstances, the present invention provides a belt device, a transfer device, and an image forming apparatus that can prevent the cleaning member from curling by suppressing the vibration of the cleaning member due to the slack of the belt. To do.

  The invention according to claim 1 is an endless belt stretched by a plurality of support members and configured to be able to run around, a cleaning member that contacts and cleans the outer peripheral surface of the belt, and a position facing the cleaning member And pressing the outer peripheral surface of the belt between the cleaning opposing member that contacts the inner peripheral surface of the belt, and the cleaning opposing member and the support member disposed on the upstream side in the belt running direction. In the belt device including the pressing member, when the amount of the cleaning object on the belt is equal to or larger than a predetermined threshold, the pressing amount of the pressing member to the belt is smaller than when the amount is less than the threshold. It is controlled so as to increase.

  When the amount of the object to be cleaned on the belt is equal to or greater than a predetermined threshold, by increasing the pressing amount of the pressing member, it is possible to suppress belt slack due to an increase in the load of the cleaning member during cleaning. Thereby, the vibration of the cleaning member can be reduced and the behavior can be stabilized, so that the cleaning member can be prevented from curling. On the other hand, when the amount of the cleaning object on the belt is less than the threshold value, by not increasing the pressing amount of the pressing member, it is possible to reduce the load on the belt and suppress the curl from being attached to the belt. .

  According to a second aspect of the present invention, in the belt device according to the first aspect, the timing at which the pressing amount of the pressing member against the belt is maximized is the timing at which the load on the cleaning member is maximized during cleaning. It is controlled to be later.

  If the amount of pressing is maximized before the load on the cleaning member is maximized, the vibration of the belt increases and the cleaning member may be swollen. Therefore, as described above, by controlling the timing at which the pressing amount becomes maximum after the timing at which the load on the cleaning member becomes maximum, it is possible to more effectively prevent the cleaning member from curling. become able to.

According to a third aspect of the present invention, in the belt device according to the second aspect, a predetermined threshold value for the amount of the object to be cleaned on the belt is set to 2 [g / mm ² ].

By setting 2 [g / m ² ], which is a boundary of whether or not the cleaning member is swollen, as a threshold value, even when there are many cleaning objects on the belt, the cleaning member can be prevented from being swollen more reliably. Will be able to.

  According to a fourth aspect of the present invention, in the belt device according to any one of the first to third aspects, a pressing amount increase value per unit time of the pressing member to the belt is 1 [mm / s] or more. It is set to become.

  By setting the pressing amount increase value per unit time to be 1 [mm / s] or more, the slack of the belt can be surely suppressed, and the cleaning member can be prevented from curling.

  The invention according to claim 5 is the belt device according to any one of claims 1 to 4, wherein the pressing force of the pressing member to the belt is set to 10 [N / m] or less. .

  By setting the pressing force of the pressing member to the belt to 10 [N / m] or less, an increase in the adhesion force of the object to be cleaned to the belt can be prevented and good cleaning properties can be obtained.

  According to a sixth aspect of the present invention, in the belt device according to any one of the first to fifth aspects, the pressing member is formed of an eccentric rotating body that changes an amount of pressing against the belt by rotating eccentrically. The eccentric rotator is brought into contact with the belt and is driven to rotate following the belt that is driven to travel, and is engaged with an engaging portion provided in the eccentric rotator to rotate the eccentric rotator. A regulating member for regulating and a regulating member driving means for driving the regulating member so as to be disengageable with respect to the eccentric rotating body are provided.

  By configuring the pressing member with an eccentric rotating body that rotates following the belt, a dedicated drive source for rotating the pressing member becomes unnecessary, so that the configuration can be simplified and the cost can be reduced.

  According to a seventh aspect of the present invention, there is provided a belt device according to the sixth aspect, wherein the eccentric rotator is low on a contact surface where the eccentric rotator contacts the belt in a state where the rotation of the eccentric rotator is restricted by the restriction member. A friction protective sheet is provided.

  In a configuration in which the protective sheet is not provided, when the belt is driven while the rotation of the eccentric rotator is restricted, the belt comes into sliding contact with the contact portion with the eccentric rotator. As a result, if the contact surface of the eccentric rotator is worn over time, the eccentric rotator and the belt may not be in contact with each other, and the eccentric rotator may not be able to rotate following the belt. Therefore, as described above, a low-friction protective sheet is disposed on the contact surface of the eccentric rotator to prevent the eccentric rotator from being worn, and the contact between the eccentric rotator and the belt can be maintained over a long period of time. Can be secured.

  The invention according to claim 8 is the belt device according to claim 7, wherein the distance between the end of the protective sheet on the upstream side in the belt traveling direction and the belt is set to 3 [mm] or more.

  By setting the distance between the end of the protective sheet upstream in the belt running direction and the belt to 3 [mm] or more, the distance between the protective sheet and the eccentric rotor from the upstream end of the protective sheet in the belt running direction is set. It is possible to prevent the adhering material on the belt from invading and prevent the protective sheet from being peeled off by the invading material.

  According to a ninth aspect of the present invention, in the belt device according to the sixth aspect of the invention, the contact surface with which the eccentric rotator contacts the belt in a state where the rotation of the eccentric rotator is restricted by the restricting member is reduced. A friction member is used.

  Also in this case, similarly to the seventh aspect, it is possible to prevent the eccentric rotator from being worn and to ensure the contact between the eccentric rotator and the belt over a long period of time. Further, in this case, there is no problem that the deposit on the belt enters between the protective sheet and the eccentric rotating body.

  A tenth aspect of the invention is the belt device according to any one of the sixth to ninth aspects, wherein the eccentric rotating body is formed of an elastic body.

  The eccentric rotating body obtains motive power from the belt and increases its pressing amount while being driven to rotate. At this time, the eccentric rotating body may be rotated while being vibrated by receiving a reaction force from the belt. If the eccentric rotator slips on the belt due to this vibration, a desired pressing amount cannot be obtained, the belt may be loosened, and the cleaning member may be bent. Therefore, as described above, by configuring the eccentric rotator with an elastic body, vibration of the eccentric rotator due to the reaction force can be reduced, and the followability of the eccentric rotator to the belt is improved. A pressing amount can be obtained, and the cleaning member can be more reliably prevented from curling.

  An eleventh aspect of the invention is the belt device according to any one of the first to tenth aspects, wherein the belt on the upstream side in the belt traveling direction at the tip surface of the cleaning member and the contact point between the cleaning member and the belt. The cleaning angle formed with the tangent is set to be 70 [°] or less.

  By setting the cleaning angle to be 70 [°] or less, it becomes possible to perform good cleaning with a low linear pressure.

  A twelfth aspect of the present invention is a transfer device including the belt device according to any one of the first to eleventh aspects.

  Since the transfer device includes the belt device according to any one of claims 1 to 11, the above-described effect by these belt devices can be obtained.

  A thirteenth aspect of the invention is an image forming apparatus including the transfer device according to the twelfth aspect.

  Since the image forming apparatus includes the transfer device according to the twelfth aspect, the above effect of the belt device included in the transfer device can be obtained.

  According to the present invention, when the amount of the cleaning object on the belt is equal to or greater than a predetermined threshold, the slack of the belt during cleaning can be suppressed by increasing the pressing amount of the pressing member. Thereby, the vibration of the cleaning member can be reduced and the behavior can be stabilized, so that it is possible to prevent the cleaning member from curling.

  Further, when the amount of the cleaning object on the belt is less than the predetermined threshold value, the pressing amount of the pressing member is not increased, so that the belt can be prevented from being curled. Further, in the configuration of the present invention, the cleaning member does not have to be brought into contact with or separated from the belt, so that there is no possibility of the constituent blade edges being collapsed due to the contact and separation operation of the cleaning member. For this reason, it is easy to maintain the component cutting edge, and the cleaning property can be improved. Furthermore, since the present invention does not require the edge shape of the tip of the cleaning member to be obtuse, it is possible to prevent productivity and processing accuracy from being lowered.

1 is a schematic configuration diagram of an image forming apparatus according to an embodiment of the present invention. FIG. 2 is a schematic diagram illustrating an overall configuration of a transfer device mounted on the image forming apparatus. FIG. 3 is an enlarged view of FIG. 2. 6 is a graph showing a relationship between a residual toner amount on an intermediate transfer belt and a load generated on a cleaning blade during cleaning. (A) is a time change of the swing angle of the regulating member, (b) is a change of the pressing amount with respect to the rotation angle of the pressing member, and (c) is a diagram showing a time change of the load generated in the cleaning blade. FIG. 4 is a diagram illustrating a relationship between a pressing force of a pressing member to an intermediate transfer belt and an adhesion force of toner to the intermediate transfer belt. It is a figure which shows the structure of other embodiment of this invention. It is a figure which shows the state in which the structure blade edge | tip was formed in the front-end | tip of the cleaning blade. It is a figure which shows the state which the said structure cutting edge collapsed. It is a figure for demonstrating the arrangement | positioning position of a cleaning blade. It is a graph which shows the relationship between the cleaning angle of a cleaning blade, and the load increase amount per unit time which arises in a cleaning blade during cleaning. It is a schematic block diagram of the conventional transfer apparatus.

  Hereinafter, the present invention will be described with reference to the accompanying drawings. In the drawings for explaining the present invention, components such as members and components having the same function or shape are denoted by the same reference numerals as much as possible, and once described, the description will be given. Omitted.

  FIG. 1 is a schematic configuration diagram of a color image forming apparatus according to the present invention. The image forming apparatus shown in FIG. 1 includes four process units 1Y, 1C, 1M, and 1Bk configured to be detachable from the image forming apparatus main body 60. The process units 1Y, 1C, 1M, and 1Bk have the same configuration except that they contain toners of different colors of yellow, cyan, magenta, and black corresponding to the color separation components of the color image.

  Specifically, each of the process units 1Y, 1C, 1M, and 1Bk includes a photosensitive drum 2 as an image carrier, a charging device that includes a charging roller 3 that charges the surface of the photosensitive drum 2, and a photosensitive member. The image forming apparatus includes a developing device 4 that supplies toner (developer) to the surface of the drum 2 and a cleaning device that includes a photoconductor cleaning blade 5 for cleaning the surface of the photoconductor drum 2.

  In FIG. 1, an exposure device 6 as an exposure means for exposing the surface of the photosensitive drum 2 is disposed above each process unit 1Y, 1C, 1M, 1Bk. A transfer device 7 is disposed below each process unit 1Y, 1C, 1M, 1Bk. The transfer device 7 has an intermediate transfer belt 8 constituted by an endless belt as a transfer body. The intermediate transfer belt 8 is stretched around a driving roller 9 and a driven roller 10 as support members, and is configured to be able to run around (rotate) in the direction of the arrow in the figure.

  Four primary transfer rollers 11 as primary transfer means are disposed at positions facing the four photosensitive drums 2. Each primary transfer roller 11 presses the inner peripheral surface of the intermediate transfer belt 8 at each position, and a primary transfer nip is formed at a location where the pressed portion of the intermediate transfer belt 8 and each photosensitive drum 2 come into contact with each other. Has been. A secondary transfer roller 12 as a secondary transfer unit is disposed at a position facing the drive roller 9. The secondary transfer roller 12 presses the outer peripheral surface of the intermediate transfer belt 8, and a secondary transfer nip is formed at a location where the secondary transfer roller 12 and the intermediate transfer belt 8 are in contact with each other.

  A belt cleaning device 13 for cleaning the surface of the intermediate transfer belt 8 is disposed on the outer peripheral surface on the right end side of the intermediate transfer belt 8 in the drawing. A waste toner transfer hose (not shown) extending from the belt cleaning device 13 is connected to an entrance of a waste toner container 14 disposed below the transfer device 7.

  At the bottom of the image forming apparatus main body, a paper feed tray 15 that stores recording paper P as a recording medium, a paper feed roller 16 that carries the recording paper P out of the paper feed tray 15, and the like are provided. On the other hand, a pair of paper discharge rollers 17 for discharging recording paper to the outside and a paper discharge tray 18 for stocking the discharged recording medium are disposed on the upper portion of the image forming apparatus main body.

  Further, a conveyance path R for guiding the recording paper from the lower paper feed tray 15 to the upper paper discharge tray 18 is formed in the image forming apparatus main body. In the conveyance path R, a pair of registration rollers 19 are disposed on the way from the paper feed roller 16 to the secondary transfer roller 12. In addition, a fixing device 20 for fixing an image on the recording paper is provided on the way from the secondary transfer roller 12 to the paper discharge roller 17. The fixing device 20 includes a fixing roller 21 as a fixing member that is heated by a heating source, a pressure roller 22 as a pressure member that pressurizes the fixing roller 21, and the like. A fixing nip is formed at a location where the fixing roller 21 and the pressure roller 22 are in pressure contact with each other.

The basic operation of the image forming apparatus will be described below with reference to FIG.
When the image forming operation is started, the photosensitive drums 2 of the process units 1Y, 1C, 1M, and 1Bk are rotationally driven clockwise by a driving device (not shown), and the surface of each photosensitive drum 2 is charged with the charging roller 3. Are uniformly charged to a predetermined polarity. The surface of each charged photoconductive drum 2 is irradiated with laser light from the exposure device 6 to form an electrostatic latent image on the surface of each photoconductive drum 2. At this time, the image information to be exposed to each photosensitive drum 2 is single-color image information obtained by separating a desired full-color image into color information of yellow, cyan, magenta, and black. Thus, the electrostatic latent image is visualized as a toner image (developer image) by supplying toner to the electrostatic latent image formed on the photosensitive drum 2 by each developing device 4. .

  By driving the drive roller 9 counterclockwise in the figure, the intermediate transfer belt 8 is driven to travel in the direction indicated by the arrow in the figure. Further, a constant voltage or a constant current controlled voltage having a polarity opposite to the toner charging polarity is applied to each primary transfer roller 11. Thereby, a transfer electric field is formed at the primary transfer nip between each primary transfer roller 11 and each photosensitive drum 2. Then, the toner images of the respective colors formed on the photosensitive drums 2 of the process units 1Y, 1C, 1M, and 1Bk are sequentially superimposed and transferred onto the intermediate transfer belt 8 by the transfer electric field formed in the primary transfer nip. Is done. Thus, the intermediate transfer belt 8 carries a full-color toner image on its surface.

  Residual toner adhering to the surface of each photosensitive drum 2 after the toner image is transferred is removed by the photosensitive member cleaning blade 5, and then the surface is subjected to a static eliminating action by a static eliminator (not shown). The potential is initialized to prepare for the next image formation.

  Further, in the lower part of the image forming apparatus, the recording paper P stored in the paper feed tray 15 is sent out to the transport path R by the paper feed roller 16 being driven to rotate. The recording paper P sent to the transport path R is timed by the registration roller 19 and sent to the secondary transfer nip between the secondary transfer roller 12 and the driving roller 9 facing it. At this time, a transfer voltage having a polarity opposite to the toner charging polarity of the toner image on the intermediate transfer belt 8 is applied to the secondary transfer roller 12, thereby forming a transfer electric field in the secondary transfer nip. Then, the toner images on the intermediate transfer belt 8 are collectively transferred onto the recording paper P by the transfer electric field formed in the secondary transfer nip. The recording paper P to which the toner image has been transferred is conveyed to the fixing unit 20, and the recording paper P is heated and pressed by the fixing roller 21 and the pressure roller 22 to fix the toner image. Then, the recording paper P on which the toner image is fixed is discharged to a paper discharge tray 18 by a discharge roller 17. Further, the toner remaining on the intermediate transfer belt 8 after the transfer is removed by the belt cleaning device 13, and the removed toner is conveyed to the waste toner container 14 and collected.

  The above description is an image forming operation when a full-color image is formed on a recording sheet. A single-color image can be formed using any one of the four process units 1Y, 1C, 1M, and 1Bk. Two or three process units may be used to form a two or three color image.

Next, the configuration of the transfer device 7 will be described in detail with reference to FIGS.
FIG. 2 is a schematic view showing the overall configuration of the transfer device 7, and FIG. 3 is an enlarged view of FIG.
As shown in FIG. 2, the transfer device 7 includes an intermediate transfer belt other than the intermediate transfer belt 8, the four primary transfer rollers 11, and the belt cleaning device 13 that are stretched around the driving roller 9 and the driven roller 10. 8 includes a toner amount detection sensor 23 that detects the amount of toner on the surface 8 and a pressing member 24 that presses the surface of the intermediate transfer belt 8.

  The belt cleaning device 13 includes a belt cleaning blade 25 (hereinafter simply referred to as “cleaning blade”) as a cleaning member that contacts and cleans the outer peripheral surface of the intermediate transfer belt 8, and the intermediate transfer belt at a position facing the cleaning blade 25. 8 includes a cleaning counter roller 26 as a cleaning counter member that abuts against the inner peripheral surface 8. The drive roller 9 rotates counterclockwise in the figure, and the intermediate transfer belt 8 travels in the direction of arrow Y in the figure, so that the cleaning blade 25 removes cleaning objects such as toner and foreign matters remaining on the intermediate transfer belt 8. It is supposed to be removed.

  As shown in FIG. 3, the pressing member 24 is composed of an eccentric rotating body that rotates eccentrically around a shaft 28 held by a bearing 27. The pressing member 24 is in contact with the outer peripheral surface of the intermediate transfer belt 8, and when the intermediate transfer belt 8 travels in the direction of the arrow Y in the figure, the pressing member 24 has a frictional resistance with the intermediate transfer belt 8 that is driven to travel. Thus, it is driven to rotate in the direction of arrow X in the figure.

  Thus, the pressing amount of the pressing member 24 against the intermediate transfer belt 8 changes as the pressing member 24 is driven to rotate (following rotation). That is, when the pressing member 24 is in the state indicated by the solid line in the figure, the amount of pressing to the intermediate transfer belt 8 is small or 0 (the state where the pressing member 24 is simply in contact without being pressed). When the pressing member 24 rotates and enters the state indicated by the two-dot chain line in the figure, the amount of pressing to the intermediate transfer belt 8 increases. Here, the “pressing amount” refers to the moving distance D of the belt surface of the intermediate transfer belt 8 in the direction in which the pressing force of the pressing member 24 acts.

  Further, the rotation of the pressing member 24 in the arrow X direction is regulated by the regulating member 29. Specifically, a protrusion-like engagement portion 30 is provided on the side surface of the pressing member 24, and the engagement portion 30 is engaged with the distal end portion of the restricting member 29 formed in an L shape to The rotation of the contact member 24 is restricted. The restricting member 29 is attached so as to be swingable in the Z direction in the figure around a support shaft 31 provided at the base end thereof, and the restricting member 29 is swung by a restricting member driving means (not shown). Thus, the restricting member 29 can be engaged with and disengaged from the engaging portion 30.

  Whether to increase the pressing amount of the pressing member 24 is determined by a control unit (not shown) provided in the image forming apparatus. Specifically, when the control unit determines that the amount of residual toner on the intermediate transfer belt 8 is equal to or greater than a predetermined threshold, the pressing member 24 is changed from the state indicated by the solid line in FIG. 3 to the state indicated by the two-dot chain line. Rotate to increase the pressing amount. In the present embodiment, the threshold value of the residual toner amount that is a determination criterion when increasing the pressing amount is determined as follows.

FIG. 4 is a graph showing the relationship between the residual toner amount on the intermediate transfer belt and the load generated on the cleaning blade during cleaning when the pressing amount by the pressing member 24 is not increased.
In the figure, the horizontal axis represents the residual toner amount [g / m ² ] on the intermediate transfer belt, and the vertical axis represents the load [N] generated on the cleaning blade. Here, an angle θ (hereinafter referred to as “below”) formed by the front end surface 25a of the cleaning blade 25 shown in FIG. 3 and the belt tangent upstream of the belt traveling direction at the contact point between the cleaning blade 25 and the intermediate transfer belt 8. Cleaning angle ”) is set to 65 [°].

As shown in FIG. 4, the load on the cleaning blade increases as the residual toner amount on the belt increases. However, when the residual toner amount reaches a certain value, the load on the cleaning blade does not increase even if the residual toner amount increases. It becomes constant. This is because when the residual toner amount exceeds a certain value, the residual toner does not adhere directly to the intermediate transfer belt but overlaps the toner on the intermediate transfer belt. That is, the amount of toner directly adhering to the intermediate transfer belt increases until the residual toner amount increases to a certain value, and accordingly, the load when scraping the residual toner from the intermediate transfer belt by the cleaning blade increases. However, if the amount of residual toner that directly adheres to the intermediate transfer belt is saturated, the residual toner overlaps with the toner on the intermediate transfer belt, so the load generated on the cleaning blade is a load that only scrapes the toner on the bottom layer. Stays and no longer rises. In the example shown in FIG. 4, the cleaning blade load reaches a constant value when the residual toner amount reaches 4 [g / m ² ].

In FIG. 4, the region above the alternate long and short dash line A is a region where the cleaning blade may be bent due to an increased load on the cleaning blade. Specifically, when the residual toner amount is 2 [g / m ² ] or more, the cleaning blade may be bent. In the present embodiment, 2 [g / m ² ], which is a boundary for the presence or absence of the occurrence of wobbling, is set as a threshold value as a determination criterion for increasing the pressing amount.

Hereinafter, the pressing operation of the pressing member 24 against the intermediate transfer belt 8 will be described with reference to FIG.
5A is a time change of the swing angle of the regulating member, FIG. 5B is a change of the pressing amount with respect to the rotation angle of the pressing member, and FIG. 5C is a time change of the load generated in the cleaning blade. .
First, in FIG. 5A, the residual toner amount on the intermediate transfer belt 8 is detected by a detection unit (not shown) at the timing T0. If the control unit determines from the detection result that the residual toner on the intermediate transfer belt 8 is 2 [g / m ² ] or more as the threshold value, the regulating member 29 shown in FIG. The engagement between the restricting member 29 and the engaging portion 30 is released. More specifically, the swinging of the regulating member 29 is started at the timing T1 in FIG. 5A where the swinging angle of the regulating member 29 is 0 [°], and the swinging angle is set to 20 [°]. At the timing T2 that is reached, the engagement between the restricting member 29 and the engaging portion 30 of the pressing member 24 is released. Thereafter, the regulating member 29 oscillates until the oscillating angle reaches 30 [°], and then oscillates downward, and returns to the original position (oscillating angle 0 [°]) at the timing of T3.

  As shown in FIG. 5 (b), the pressing member 24 starts rotating as the intermediate transfer belt 8 travels by releasing the restriction at the timing T2, and the pressing member 24 becomes intermediate as the rotation angle increases. The amount of pressing on the transfer belt 8 increases. The pressing amount becomes maximum at the timing when the rotation angle is 210 [°], and then the pressing amount decreases. When the pressing member 24 rotates 360 [°] and returns to the original position, the restricting member 29 returning to the original position at the timing T3 and the engaging portion 30 of the pressing member 24 are engaged. , Rotation is restricted.

  In FIG. 5C, the load generated on the cleaning blade 25 increases at the timing T4. That is, the residual toner on the intermediate transfer belt 8 reaches the position of the cleaning blade 25 at the timing T4, and the residual toner is scraped off by the cleaning blade 25, so that the load on the cleaning blade 25 increases. Thereafter, the load becomes maximum at the timing of T5. The reason why it takes time from the timing T4 to the timing T5 for the load of the cleaning blade 25 to increase is that the cleaning blade 25 is made of an elastic body and has flexibility, so that the cleaning blade 25 begins to receive a load from the toner. This is because it takes a certain amount of time until the force necessary to push back the toner is obtained. From the timing T6 when all the residual toner is scraped off by the cleaning blade 25, the load on the cleaning blade 25 is reduced thereafter.

On the other hand, when it is determined by the control means that the amount of residual toner on the intermediate transfer belt 8 is less than 2 [g / m ² ], the pressing member 24 is not rotated and the pressure on the intermediate transfer belt 8 is not rotated. The residual toner is removed by the cleaning blade 25 while the amount is small or 0 (a state where the pressure is not pressed and is simply in contact).

As described above, in this embodiment, when the residual toner amount is 2 [g / m ² ] or more, which may cause the cleaning blade 25 to be swung, the pressing member 24 is rotated to increase the pressing amount. Therefore, it is possible to suppress the slack of the intermediate transfer belt 8 (slack on the upstream side in the belt running direction from the contact position with the cleaning blade 25) accompanying an increase in the load of the cleaning blade 25 during cleaning. Thereby, since the vibration of the cleaning blade 25 can be reduced and the behavior can be stabilized, the cleaning blade 25 can be prevented from being twisted. In addition, since the pressing amount of the pressing member 24 is controlled only at the timing necessary for cleaning, it is possible to extend the life without applying unnecessary load to the intermediate transfer belt 8. . On the other hand, when the residual toner amount is less than 2 [g / m ² ], the pressing amount of the pressing member 24 is not increased, so the load generated on the intermediate transfer belt 8 is reduced and the intermediate transfer belt 8 is curled. Can be suppressed.

  Further, in the present embodiment, as shown in FIGS. 5B and 5C, the timing at which the pressing amount becomes maximum (the timing at which the rotation angle of the pressing member 24 becomes 210 °) is set to the cleaning blade 25. Control is performed after the timing T5 when the load becomes maximum. This is because if the pressing amount is maximized before the load on the cleaning blade 25 is maximized (while the load is increasing), the vibration of the intermediate transfer belt 8 is increased, and the cleaning blade 25 may be wrinkled. It is. Therefore, by controlling the timing at which the pressing amount becomes maximum after the timing at which the load on the cleaning blade 25 becomes maximum, it is possible to more effectively prevent the cleaning blade 25 from curling.

  Further, in order to more reliably suppress the looseness of the intermediate transfer belt 8, the pressing amount increase value per unit time of the pressing member 24 to the intermediate transfer belt 8 is set to be 1 [mm / s] or more. It is preferable. When the pressing amount increase value per unit time is less than 1 [mm / s], the intermediate transfer belt 8 is slackened, the vibration of the cleaning blade 25 is generated, the behavior becomes unstable, and the wrinkle occurs. This is because there is a fear. In this embodiment, the pressing amount increase value per unit time is set to 1.5 [mm / s]. As a result, the looseness of the intermediate transfer belt 8 can be reliably suppressed, and the cleaning blade 25 can be prevented from wobbling.

  Further, as a method of determining the residual toner amount on the intermediate transfer belt 8, there is a method of predicting the residual toner amount from, for example, print image information in addition to the detection on the intermediate transfer belt 8 by the detecting means. If the amount of residual toner is predicted from the print image information and it is equal to or greater than the threshold value, the amount of pressing by the pressing member 24 can be increased to prevent the cleaning blade 25 from curling as described above.

  Further, when a pattern image is formed on the intermediate transfer belt 8 for image color misregistration correction or toner density adjustment, the pattern image is not transferred to the recording paper, and therefore the toner on the intermediate transfer belt 8 exceeds the threshold value. Also in this case, the cleaning blade 25 can be prevented from curling similarly to the above by increasing the pressing amount by the pressing member 24 at the timing when the toner on the intermediate transfer belt 8 is sent to the cleaning blade 25.

  Also, when the recording paper is jammed and a jam occurs, the toner on the intermediate transfer belt 8 is not transferred to the recording paper, so the toner on the intermediate transfer belt 8 may exceed the threshold value. When a jam is detected, the residual toner amount is predicted from the print image information or the like, and when it is equal to or greater than the threshold value, the pressing amount by the pressing member 24 is increased. Here, the timing at which the pressing force of the pressing member 24 is increased is the timing at which the toner on the intermediate transfer belt 8 is sent to the cleaning blade 25 when the driving of the apparatus is resumed after the jam processing. Thereby, it is possible to prevent the cleaning blade 25 from curling.

  By the way, in this embodiment, the pressing member 24 is rotated while being driven by the intermediate transfer belt 8, and the pressing amount is increased. At this time, the pressing member 24 reacts with the reaction force from the intermediate transfer belt 8. By receiving, there is a case where the driven rotation while vibrating. When the pressing member 24 slips with respect to the intermediate transfer belt 8 due to this vibration, a desired pressing amount cannot be obtained, the intermediate transfer belt 8 may be loosened, and the cleaning blade 25 may be bent. Therefore, in order to reduce the vibration of the pressing member 24 due to such reaction force, the pressing member 24 is made of an elastic material such as ethylene-propylene-diene polyethylene rubber (EPDM), butadiene acrylonitrile rubber (NBR), or urethane rubber. It is desirable to be composed of bodies. In this embodiment, butadiene acrylonitrile rubber (NBR) is applied as the material of the pressing member 24. Thereby, the vibration of the pressing member 24 due to the reaction force can be reduced, and the followability of the pressing member 24 with respect to the intermediate transfer belt 8 is improved, so that a desired pressing amount is obtained and the cleaning blade 25 is swung. Can be more reliably prevented.

FIG. 6 shows the relationship between the pressing force of the pressing member to the intermediate transfer belt and the adhesion force of the toner to the intermediate transfer belt. In FIG. 6, the horizontal axis represents the pressing force [N / m] of the pressing member, and the vertical axis represents the toner adhesion [g].
When the toner on the intermediate transfer belt passes through the pressing member, the toner is pressed against the intermediate transfer belt by the pressing member. At this time, if the contact area between the toner and the intermediate transfer belt increases due to the crushing or micro deformation of the toner, the adhesion force of the toner to the intermediate transfer belt may increase and the cleaning performance may deteriorate. However, when the pressing force of the pressing member is equal to or less than a certain value, the toner hardness exceeds the pressing force, so the toner adhesion does not increase. In this case, as shown in FIG. 6, if the pressing force of the pressing member is about 15 [N / m] or less, the adhesion force of the toner does not increase. Therefore, in this embodiment, the pressing force of the pressing member to the intermediate transfer belt is set to 10 [N / m]. This prevents an increase in the adhesion force of the toner to the intermediate transfer belt and provides good cleaning properties.

FIG. 7 is a diagram showing the configuration of another embodiment of the present invention.
In the embodiment shown in FIG. 7, a low-friction protective sheet 32 such as PET is disposed on the pressing member 24. Other than that, the configuration is the same as in the above embodiment. The protective sheet 32 is disposed on a contact surface where the pressing member 24 contacts the intermediate transfer belt 8 in a state where the rotation of the pressing member 24 is restricted by the regulating member 29.

  In the configuration in which the protective sheet 32 is not provided (see FIG. 3), when the intermediate transfer belt 8 travels in a state where the rotation of the pressing member 24 is restricted, the intermediate transfer belt 8 and the pressing member 24 Slidably contact at the contact portion. As a result, when the contact surface of the pressing member 24 is worn over time, the pressing member 24 and the intermediate transfer belt 8 do not come into contact with each other, and the pressing member 24 may not be driven to rotate following the intermediate transfer belt 8. . Therefore, as in the present embodiment, the protective sheet 32 is disposed on the contact surface of the pressing member 24 to prevent the pressing member 24 from being worn, and the pressing member 24 and the intermediate transfer belt 8 are contacted with each other. The contact can be secured over a long period of time.

  In FIG. 7, it is preferable to set the distance h between the end 32a of the protective sheet 32 upstream in the belt running direction and the intermediate transfer belt 8 to 3 [mm] or more. By setting in this way, it is possible to prevent toner and the like from entering between the protective sheet 32 and the pressing member 24 from the end 32a upstream of the protective sheet 32 in the belt running direction. It is possible to prevent the protective sheet 32 from being peeled off by toner or the like.

  Further, the pressing member 24 itself, or at least the contact surface when the rotation of the pressing member with the intermediate transfer belt 8 is restricted, may be formed of a low wear member. Also in this case, it is possible to suppress wear of the pressing member 24 and to ensure contact between the pressing member 24 and the intermediate transfer belt 8 over a long period of time. Further, in this case, there is no problem that toner or the like enters between the protective sheet 32 and the pressing member 24.

  In the embodiment shown in FIG. 7, the pressing amount adjusting operation by the pressing member 24 is the same as that described in the above embodiment, and thus the description thereof is omitted.

FIG. 8 is a view showing a state in which the constituent cutting edge C is formed at the tip of the cleaning blade 25.
As shown in FIG. 8, when the residual toner on the intermediate transfer belt 8 is repeatedly removed by the cleaning blade 25, silica as a toner additive adheres to the tip of the cleaning blade 25, and a sharp lump C called a constituent blade edge is formed. Is formed. Since the constituent cutting edge C plays a role of scraping off the residual toner on the intermediate transfer belt 8, the cleaning performance is improved by forming the constituent cutting edge C. Therefore, it is preferable to maintain the formed cutting edge C so as to remain at the tip of the cleaning blade 25 as it is.

However, as shown in FIG. 9, when the intermediate transfer belt 8 is displaced along with the pressing operation of the pressing member, the cleaning angle of the cleaning blade 25 with respect to the intermediate transfer belt 8 changes from θ ₁ to θ _2. The cutting edge collapses.

  Therefore, in this embodiment, as shown in FIG. 10, when the intermediate transfer belt 8 is displaced in accordance with the pressing operation of the pressing member (in a state where the cleaning blade 25 is not in contact with the intermediate transfer belt 8). The cleaning blade 25 is brought into contact with the intermediate transfer belt 8 at a location E where the cleaning facing roller 26 and the intermediate transfer belt 8 are always in contact. Accordingly, even when the intermediate transfer belt 8 is displaced in accordance with the pressing operation of the pressing member, the cleaning angle θ of the cleaning blade 25 with respect to the intermediate transfer belt 8 can be kept constant, so that the constituent blade edges are prevented from collapsing. Thus, good cleaning properties can be maintained.

  As described above, according to the embodiment of the present invention, when the residual toner amount on the intermediate transfer belt is equal to or larger than the predetermined threshold value, the pressing amount of the pressing member is increased to thereby increase the intermediate transfer belt during cleaning. Sag can be suppressed. Thereby, the vibration of the cleaning blade can be reduced and the behavior can be stabilized, so that it is possible to prevent the cleaning blade from curling.

FIG. 11 is a graph showing the relationship between the cleaning angle of the cleaning blade and the amount of load increase per unit time that occurs in the cleaning blade during cleaning when the pressing amount by the pressing member is not increased. In the figure, the horizontal axis represents the cleaning angle [°], and the vertical axis represents the load increase [N / s] per unit time. Here, the relationship between the cleaning angle and the load increase per unit time when the residual toner amount on the intermediate transfer belt reaches 4 [g / m ² ] is shown.

  In general, the smaller the cleaning angle, the lower the linear pressure, and the lower the linear pressure. However, as shown in FIG. 11, the smaller the cleaning angle, the larger the load increase per unit time. In this case, when the cleaning angle is smaller than 75 [°] and the load increase amount per unit time is 0.5 [N / s] or more (in the region above the one-dot chain line B), the cleaning blade There is a possibility that the intermediate transfer belt is slackened on the upstream side of the contact position and the behavior of the cleaning blade becomes unstable, which causes wrinkles.

  However, as described above, even when the amount of residual toner on the intermediate transfer belt is large, loosening of the intermediate transfer belt can be suppressed by increasing the pressing amount of the pressing member. Even if the cleaning angle is set to be smaller than 75 [°] shown in FIG. In the present embodiment, even when the cleaning angle is set to 65 [°], no wrinkling occurs and good cleaning properties are obtained. By setting the cleaning angle to 70 [°] or less, even when a large amount of toner (circularity is 0.96 to 0.1) and a large amount of toner adheres to the intermediate transfer belt, the linear pressure is low. It becomes possible to clean well.

  Further, according to the embodiment of the present invention, when the amount of residual toner on the intermediate transfer belt is less than the predetermined threshold value, the pressing amount of the pressing member is not increased, so that the intermediate transfer belt is not curled. Can be suppressed. Even when the residual toner amount is equal to or greater than the threshold value, the timing for increasing the pressing amount of the pressing member is only the timing necessary for cleaning, so that no unnecessary load is applied to the intermediate transfer belt. Long life can be achieved.

  Further, in the configuration of the present invention, the cleaning blade does not have to be brought into contact with or separated from the intermediate transfer belt, so that there is no possibility of the component blade edges being collapsed due to the contact and separation operation of the cleaning blade. For this reason, it is easy to maintain the component cutting edge, and the cleaning property can be improved. Furthermore, since the present invention does not require the edge shape of the tip of the cleaning blade to be obtuse, it is possible to prevent productivity and processing accuracy from being lowered.

  Further, as in the above embodiment, the pressing member is formed of an eccentric rotating body that is driven to rotate by the intermediate transfer belt, so that a dedicated drive source for rotating the pressing member becomes unnecessary, and the configuration is simplified. In addition, the cost can be reduced.

  The embodiment of the present invention has been described above, but the present invention is not limited to the above-described embodiment, and it is needless to say that various modifications can be made without departing from the gist of the present invention. In the above-described embodiment, the configuration of the present invention is applied to a transfer apparatus. However, the configuration of the present invention is a photosensitive belt as an electrostatic latent image carrier that carries an electrostatic latent image on the surface, and a surface. The present invention is also applicable to a belt device that drives a conveyance belt that carries and conveys a recording medium. Further, the image forming apparatus according to the present invention is not limited to the color image forming apparatus shown in FIG. 1, and may be a monochrome image forming apparatus, other copying machines, printers, facsimiles, or complex machines thereof.

7 Transfer Device 8 Intermediate Transfer Belt 13 Belt Cleaning Device 24 Pressing Member 25 Cleaning Blade (Cleaning Member)
29 Restriction member 32 Protective sheet D Pressing amount θ Cleaning angle

JP 2009-134236 A JP 2000-231314 A JP 2004-35200 A

Claims (13)

An endless belt stretched by a plurality of support members and configured to be able to run around, a cleaning member that contacts and cleans the outer peripheral surface of the belt, and an inner peripheral surface of the belt at a position facing the cleaning member And a pressing member that presses the outer peripheral surface of the belt between the cleaning counter member and the support member disposed upstream of the cleaning counter member in the belt traveling direction. In the belt device,
When the amount of the object to be cleaned on the belt is equal to or greater than a predetermined threshold value, the pressing amount of the pressing member to the belt is controlled to be larger than when the amount is less than the threshold value. Belt device.   The belt device according to claim 1, wherein the timing at which the pressing amount of the pressing member to the belt is maximized is controlled to be after the timing at which the load on the cleaning member is maximized during cleaning. The belt device according to claim 2, wherein a predetermined threshold value of the amount of cleaning object on the belt is set to 2 [g / mm ² ].   The belt device according to any one of claims 1 to 3, wherein a pressing amount increase value per unit time of the pressing member to the belt is set to be 1 [mm / s] or more.   The belt device according to any one of claims 1 to 4, wherein a pressing force of the pressing member to the belt is set to 10 [N / m] or less. The pressing member is composed of an eccentric rotating body that changes the amount of pressure applied to the belt by rotating eccentrically, and the eccentric rotating body is brought into contact with the belt and driven to rotate following the belt that is driven to travel. To configure
A restricting member that engages with an engaging portion provided on the eccentric rotating body and restricts the rotation of the eccentric rotating body; and a restricting member driving unit that drives the restricting member to be disengageable with respect to the eccentric rotating body. The belt device according to any one of claims 1 to 5, wherein the belt device is provided.   The belt device according to claim 6, wherein a low-friction protective sheet is disposed on a contact surface on which the eccentric rotating body contacts the belt in a state where the rotation of the eccentric rotating body is restricted by the restricting member. .   The belt device according to claim 7, wherein a distance between the end of the protective sheet on the upstream side in the belt traveling direction and the belt is set to 3 [mm] or more.   The belt device according to claim 6, wherein a contact surface on which the eccentric rotator contacts the belt in a state where the rotation of the eccentric rotator is restricted by the restricting member is configured by a low friction member.   The belt device according to any one of claims 6 to 9, wherein the eccentric rotating body is formed of an elastic body.   The cleaning angle formed by the front end surface of the cleaning member and the belt tangent on the upstream side in the belt running direction at the contact point between the cleaning member and the belt is set to be 70 [°] or less. The belt device according to any one of 1 to 10.   A transfer device comprising the belt device according to claim 1.   An image forming apparatus comprising the transfer device according to claim 12.

Images