JP4978619B2 - Cleaning device and image forming apparatus - Google Patents

Description

  The present invention relates to a cleaning device for cleaning an image bearing member such as a photosensitive member or an intermediate transfer member in an image forming apparatus such as an electrophotographic copying machine, a facsimile, or a laser printer that forms a monochrome image or a color image. And an image forming apparatus provided with the cleaning device.

  Since there are objects to be cleaned such as residual toner, toner external additives, recording medium powder, and recording medium filler on the surface of the image carrier such as a photoreceptor or an intermediate transfer body, the image forming apparatus has such a target. A cleaning device is provided for cleaning and removing the cleaning object.

  There are various types of image forming apparatuses having such a cleaning device. For example, in Patent Document 1, a back surface member disposed on the back surface side of the belt, a first surface member disposed near the belt on the front surface side of the belt and disposed opposite to the back surface member, An image forming apparatus including a second surface member disposed in proximity to the first surface member on the surface side of the belt is disclosed. Moreover, what the surface was formed with the foam material as a 1st surface member is disclosed. Furthermore, it is disclosed that the surface of the second surface member is made of metal, and the first surface member and the second surface member are rotated in the same direction at their contact portions. In such an image forming apparatus, the belt is satisfactorily cleaned by changing the magnitude of the voltage between the back member and the first front member within a predetermined range.

However, once the surface of the first surface member formed of the foam material is captured in the foam cell, the first surface member cannot be sufficiently discharged even if the voltage is controlled. For example, the residual toner trapped in the cell is charged when the bias is applied many times at the contact portion (collection portion) with the image carrier in the foaming roller or the contact portion (discharge portion) with the collection roller. This is because the amount shows a value in the vicinity of zero, and discharge with a bias becomes practically difficult. As a result, when printing was continued for a long period of time, the objects to be cleaned accumulated in the foam cells of the first surface member, the cleaning performance deteriorated, and finally the objects to be cleaned on the belt could not be collected. When the cleaning performance deteriorates, the toner on the image carrier cannot be collected, and noise is generated on the image. When observing the foam cells of the first surface member having deteriorated cleaning performance, it was found that the object to be cleaned, particularly the residual toner, was unevenly distributed in the cells constituting the foam.
JP 2007-41348 A

  The present invention improves a discharge performance of an object to be cleaned such as residual toner captured by a foaming roller, and maintains a good cleaning performance for an image carrier over a long period of time, and an image forming apparatus including the cleaning device The purpose is to provide.

The present invention
A foaming roller rotatably disposed in contact with the surface of the image carrier; and in contact with the surface of the foaming roller, disposed in the contact portion so as to be rotatable in the same direction as the rotation direction of the foaming roller. Has a collection roller,
The present invention relates to a cleaning device that changes a rotational speed ratio θ of a collection roller to a foaming roller in a range that exceeds 1, and an image forming apparatus that includes the cleaning device.

  According to the cleaning device of the present invention, since the discharge performance of the cleaning object captured by the foaming roller is improved, accumulation of the cleaning object in the foaming roller can be suppressed. As a result, good cleaning performance for the image carrier can be maintained over a long period of time. Further, damage such as wear of the image carrier, the foaming roller, and the collecting roller can be suppressed.

  The cleaning apparatus according to the present invention includes a residual toner, a toner external additive, a recording medium powder (paper powder), and a recording medium that are present on the surface of an image carrier that carries a toner image such as an intermediate transfer member and a photosensitive member. It is for cleaning objects to be cleaned such as fillers and carriers (when the developer is a two-component system). Hereinafter, the cleaning apparatus will be described in detail with reference to FIG. 1 showing an image forming apparatus provided with both an intermediate transfer member cleaning device and a photosensitive member cleaning device. There is no limitation, and it is sufficient that at least one of the intermediate transfer member cleaning device and the photosensitive member cleaning device is provided.

(Cleaning device for intermediate transfer member)
FIG. 1 shows a schematic configuration of an embodiment of an image forming apparatus according to the present invention, and FIG. 2 shows an enlarged configuration diagram of the vicinity of an intermediate transfer member cleaning device 50 in the image forming apparatus of FIG.

  The cleaning device 50 is provided from the secondary transfer member 6 to the primary transfer member 2 of the most upstream image forming portion (Y in this example) in the surface movement direction of the intermediate transfer belt 4. In FIGS. 1 and 2, the cleaning device 50 is provided for the intermediate transfer belt portion positioned on the roller 32 around which the intermediate transfer belt 4 is wound. The intermediate transfer belt may be provided.

  The cleaning device 50 includes a foaming roller 51 disposed so as to be rotatable while being in contact with the surface of the intermediate transfer belt 4, and a collection roller 52 disposed so as to be able to be rotated while being in contact with the surface of the foaming roller 51. It is. The cleaning device 50 further includes a blade 53 that is fixedly placed in contact with the surface of the collection roller 52, a conveying screw 54 that carries out the object to be cleaned scraped off by the blade 53, and an object to be cleaned by the blade 53. A seal member (not shown) may be included to prevent the object to be crushed that has swollen in the form of dust during scraping from reattaching to the intermediate transfer belt 4. These components included in the cleaning device 50 are provided in the case 55 in a state of being incorporated in the case 55. However, a part of the foam roller 51 may be exposed from the case and in contact with the belt 4. The rotating members such as the foaming roller 51 and the collecting roller 52 in the cleaning device 50 are independently driven to rotate together with an instruction from a control unit Cont (not shown).

  In the present invention, the collection roller 52 is disposed so as to be rotatable in the same direction as the rotation direction of the foaming roller 51 at the contact portion with the foaming roller 51, and the rotation speed ratio θ of the collection roller 52 to the foaming roller 51 is in a range over 1. Change with. That is, the speed difference between the foaming roller and the collection roller is changed within a predetermined range. As a result, the degree of collapse of the foam cell in the foam roller changes, and the foam cell deforms over time, so that the discharge of the object to be cleaned captured in the cell to the outside of the cell is promoted. Therefore, accumulation of the cleaning object in the foaming roller 51 is suppressed, and as a result, good cleaning performance for the intermediate transfer belt 4 can be maintained over a long period of time. Even if the rotational speed ratio θ is changed within a range that does not exceed 1, the cleaning target such as the residual toner trapped by the foaming roller is not sufficiently discharged, so that good cleaning performance cannot be maintained for a long time.

The rotational speed ratio θ of the collection roller 52 with respect to the foaming roller 51 is preferably changed in a range of at least 0.95 to 1.05 from the viewpoint of promoting discharge of the cleaning object in the cell. Range speed ratio theta changes, for example, a lower limit theta _L is 0.60 to 0.95, the upper limit theta _H is preferably in the range is from 1.05 to 1.40. From the viewpoint of preventing the change in the rotational speed ratio θ from affecting the moving speed of the intermediate transfer belt, the range in which the rotational speed ratio θ changes is the lower limit value θ _L of 0.78 to 0.95. Thus, the upper limit value θ _H is preferably in the range of 1.05 to 1.22. When the moving speed of the intermediate transfer belt is affected by the change in the rotation speed ratio θ, the resist property is deteriorated, for example, the line width is increased or decreased.

  The rotational speed of the foaming roller and the rotational speed of the collection roller are obtained from the product of the rotational radius of each roller and the angular speed of the shaft. Specifically, the rotation radius of each roller is not the actual radius of the roller, but the radius when the roller roller and the collection roller are brought into contact with each other and become smaller by the amount of bite. For example, when the recovery roller is sufficiently harder than the foam roller, the recovery roller has a real radius as the rotation radius, and the rotation radius of the foam roller is a value obtained by subtracting the amount of biting from the actual radius. The angular velocity of the shaft in each roller can be calculated after obtaining the rotational speed with a tachometer or the like.

The rotation speed of the foam roller 51 is usually preferably 300 to 500 mm / sec.
The rotation speed of the collection roller 52 is usually preferably 220 to 650 mm / second.

  The rotational speed ratio θ of the collection roller 52 with respect to the foaming roller 51 can be controlled by adjusting the rotational speed of at least one of the foaming roller or the collection roller. From the viewpoint of preventing the influence on the moving speed of the intermediate transfer belt, it is preferable to control by adjusting the rotating speed of the collecting roller 52 while keeping the rotating speed of the foaming roller 51 constant.

  As long as the change in the rotation speed ratio θ is performed within the above range, it may be performed regularly or irregularly, particularly arbitrarily, but from the viewpoint of ease of rotation ratio control, It is preferable to carry out regularly, especially periodically. Hereinafter, the case where the rotation speed ratio θ is periodically changed will be described in detail.

When the rotational speed ratio θ is periodically changed, it is preferable that the rotational speed ratio θ has a waveform of a temporal change. Specifically, for example, the rotation speed ratio θ may be continuously changed so as to show a waveform as shown in FIGS. 3A and 3B, or as shown in FIGS. 4A, 4B, and 4C. You may change in steps so that a waveform may be shown as a whole. In FIG. 3A, the change of θ starts from θ = maximum rotation speed ratio θ _H , and in FIG. 3B, the change of θ starts from θ = 1, but is not limited thereto, and in each graph, for example, θ = 1 may be started from, theta = minimum rotational speed ratio may be begun from theta _L, or θ = θ _H, may be started from 1 and theta ratio other than _L. Change in theta in Figure 4A begins theta = maximum rotational speed ratio theta _H, change in theta in Figure 4B begins at theta = minimum speed ratio theta _L, the change in theta in Figure 4C θ = θ _H, 1 and Although starting from the ratio of non-theta _L, but are not limited to, in each graph, for example, it may be started from θ = 1, θ = may be started from the minimum rotational speed ratio theta _L, Alternatively, it may start from a ratio other than θ = θ _H , 1 and θ _L.

  The rotational speed ratio θ may be changed during image formation, or may be changed at times other than image formation (non-image formation). From the viewpoint of preventing image defects caused by the influence on the moving speed of the intermediate transfer belt, it is preferable to change the rotation speed ratio θ during non-image formation. Changing the rotation speed ratio θ during image formation means changing the rotation speed ratio θ while printing, for example, regardless of image formation or non-image formation. The rotation speed ratio θ is changed during non-image formation, for example, from the end of a predetermined number of prints to the start of the next print (generally referred to as a sheet interval), or from the end of printing to the stop of the device drive. In the meantime, the rotation speed ratio θ is changed.

  When the rotational speed ratio θ is changed continuously or stepwise during non-image formation, the rotational speed ratio θ may be changed in one cycle or more, usually 2 to 5 cycles. One cycle in such a case should just be 1 second or more, and is 1.5 to 5 seconds normally. FIG. 5 shows an example of a graph showing a change with time of the rotational speed ratio θ when the rotational speed ratio θ is continuously changed from the end of printing to the stop of driving of the apparatus. FIG. 6 shows an example of a graph showing a change with time of the rotational speed ratio θ when the rotational speed ratio θ is changed stepwise from the end of printing to the stop of driving of the apparatus.

  When the rotational speed ratio θ is changed continuously or stepwise at the time of image formation, the rotational speed ratio θ may be changed in one cycle or more, usually 1 to 3 cycles. When the rotational speed ratio θ is continuously changed during image formation, one cycle may be 1 second or longer, but the intermediate transfer is performed by setting it to 2 seconds or longer, particularly 4 seconds or longer, more preferably 6 to 10 seconds. The influence on the moving speed of the belt can be prevented.

When the rotational speed ratio θ is changed stepwise during image formation, one cycle can be expressed by, for example, the number of printed sheets or the number of printing operations. FIG. 7 shows an example of a graph showing a change with time of the rotational speed ratio θ when the rotational speed ratio θ is changed stepwise while printing. Specifically, for example, θ can be changed for every 1000 printed sheets. In FIG. 7, when θ is changed stepwise for every 1000 printed sheets, in detail, θ = 1 when the number of accumulated printed sheets is 1 to 1000, and θ = θ _H when printing 1001 to 2000 sheets, 2001. 3000 sheets during printing θ = 1,3001~4000 sheets during printing can be stepwise changed in one cycle 4000 of θ = θ _L. If the interval for keeping θ constant is too long, for example, if the number of printed sheets or the number of printing operations for keeping θ constant is too large, the number of objects to be cleaned accumulated in the cell increases. Therefore, the interval should be short. For example, θ can be changed for each sheet (one operation) or during printing of one sheet. The number of printed sheets that keeps θ constant may be, for example, 1 to 10,000. For example, the number of printing operations for keeping θ constant can be 1 to 100 times. When the rotational speed ratio θ is changed stepwise during image formation, from the viewpoint of preventing the influence on the moving speed of the intermediate transfer belt, the rotational speed ratio θ is 5 or more, particularly 7 as shown in FIG. 4C. It is preferable to change in 10 steps. For example, in FIG. 4C, the rotation speed ratio θ changes in nine stages. As the number of stages is increased, the amount of change in the rotation ratio at each stage decreases, so the influence on the rotation speed of the foaming roller is reduced, and consequently the influence on the moving speed of the intermediate transfer belt is reduced.

  The foaming roller 51 is formed by forming a layer 512 made of a foam on the surface of a cored bar 511 serving as a shaft. The foaming roller 51 is rotatably arranged while continuously contacting the surface of the intermediate transfer belt 4 in the axial direction, and the object to be cleaned on the surface of the intermediate transfer belt 4 is captured and collected in its own foam layer by the rotation.

  The metal core 511 is made of a conductive metal, and may be, for example, a bar or pipe made of aluminum, iron, stainless steel, or the like.

The foam material that forms the foam layer 512 is not particularly limited, and for example, a foamed urethane resin, silicone resin, or rubber material can be used. The foam layer 512 is usually conductive. The conductive foam layer can be produced by foaming a foam material made by adding a conductive material. As the conductive material, for example, known carbon black, metal fine particles, and an ionic conductive material can be used. The resistance value of the foam layer is preferably about 1 × 10 ³ Ω to 1 × 10 ⁹ Ω.

The resistance of the foam layer is determined by R (resistance value) = V / (from the voltage V when a current of 50 μA is passed between the core metal of the foam roller and a metal roller having a diameter of 18 mm in contact with the foam layer. 50 × 10 ⁻⁶ ) (Ω). The biting setting of the foam layer is 1.0 mm.

  The foam layer 512 has an average cell diameter of 200 μm to 1000 μm, particularly preferably 250 to 500 μm, and a thickness of 3 to 10 mm, particularly 4 to 7 mm, from the viewpoint of recoverability of the object to be cleaned.

  The average cell diameter of the foam layer was measured by observing the cut surface of the foam with a scanning electron microscope (SEM). 100 cells were randomly selected from the captured image, and the average of the cell diameters was calculated.

  Although the rotation direction of the foaming roller 51 is not particularly limited, it is preferable that the moving direction of the intermediate transfer belt is opposite to the moving direction of the intermediate transfer belt from the viewpoint of recoverability of the object to be cleaned.

  The speed ratio of the foaming roller 51 to the intermediate transfer belt 4 is preferably 0.5 to 2 from the viewpoint of improving the recoverability of the foaming roller and preventing the deterioration of the intermediate transfer belt. The speed ratio can be calculated by dividing the rotational speed (mm / second) of the foaming roller 51 by the moving speed (mm / second) of the intermediate transfer belt.

  The amount of biting of the foaming roller 51 into the intermediate transfer belt is preferably 0.5 to 2 mm from the viewpoints of recoverability of the object to be cleaned, rotational torque, breakage and wear of the intermediate transfer belt.

  The collection roller 52 is made of a metal roller such as aluminum, stainless steel, or iron, or a metal roller formed with a conductive resin layer, and the object to be cleaned captured and collected by the foam roller 51 is stored in the collection roller 52. Further capture and collection on the surface. The metal roller may be plated for the purpose of preventing corrosion such as surface smoothness and rust. The conductive resin layer is a non-foamed layer in which a conductive material is dispersed in the resin. The resin material is not particularly limited, but a material excellent in wear resistance is preferable. Examples of such a preferable resin material include polyamide-based resin, polyethylene, and polypropylene. The conductive material can be exemplified by the same material as the conductive material contained in the foam layer.

  The collection roller 52 is disposed so as to be rotatable in the same direction as the rotation direction of the foaming roller 51 at the contact portion with the surface of the foaming roller 51. When the collection roller rotates in the direction opposite to the rotation direction of the foaming roller at the contact portion with the foaming roller, the recoverability of the object to be cleaned decreases.

  The blade 53 is a member that scrapes off an object to be cleaned on the collection roller 52, and an elastic member is used in contact with the surface of the collection roller 52. As the constituent material of the blade 53, for example, metals such as stainless steel, iron and copper, rubbers such as natural rubber and synthetic rubber, and various thermoplastic resins such as vinyl chloride resin, polyethylene, polypropylene, polystyrene and ABS resin can be used.

  The blade 53 is fixed and installed at a contact portion with the collection roller 52 so as to oppose the rotation direction of the collection roller.

The intermediate transfer belt 4 is not particularly limited, and may be made of, for example, a resin such as Teflon (registered trademark), polyester, polyvinylidene fluoride, triacetate, polycarbonate, polyimide, polyphenylene sulfide, and the like. Preferably, the above-described conductive material is dispersed to impart conductivity. The intermediate transfer belt 4 may be provided with a coat layer on the surface of the belt for the purpose of improving toner transfer properties and preventing the belt surface from being worn or scratched, or from foreign matter. As a constituent material of the coat layer, for example, rubber, elastomer, resin, or the like can be used. In the coat layer, a conductive material may be dispersed in order to impart conductivity. The intermediate transfer belt 4 does not have to have a belt shape, and may have a drum shape, for example.
The surface resistance value of the intermediate transfer belt 4 is preferably about 10 ⁶ to 10 ¹² Ω / cm.

  The surface resistance value of the intermediate transfer belt 4 can be measured based on JIS K6991 using, for example, a high-reester IP manufactured by Mitsubishi Oil Chemical Co., Ltd.

  In the cleaning device 50, the foam roller, the recovery roller, and the intermediate transfer belt can be independently rotated by a driving device. In each drive device, the rotation speed or the movement speed can be controlled by the control device.

  The rotation speed of the collection roller 52 can be controlled by means shown in FIG. 8 or FIG. 9, for example.

  In FIG. 8, a signal for controlling the number of rotations of the motor is sent to a motor as a drive unit of the collection roller 52, and as a result, the rotation speed of the collection roller is controlled. There is a method of changing the frequency and voltage in controlling the rotation speed of the motor, and either method may be used.

  In FIG. 9, the rotational speed of the collection roller 52 can be controlled by installing a rotation speed variable device between the motor as the drive device and the collection roller. Examples of the rotation speed variable device include gears and pulleys. A signal for controlling the rotational speed of the motor is sent to such a rotational speed variable device.

  In the cleaning device 50, the object to be cleaned on the surface of the intermediate transfer belt 4 is collected by the foaming roller 51 and further collected by the collecting roller 52. Next, the object to be cleaned on the collection roller 52 is scraped off by the blade 53 and is carried out by a conveying screw 54 to a container or the like (not shown).

In the cleaning device 50, it is preferable to form a cleaning electric field for collecting the object to be cleaned on the intermediate transfer belt 4 from the viewpoint of further improving the cleaning performance. The cleaning electric field is formed by the power source PW1. The power source PW1 is connected (grounded) to the core of the collecting roller 52 and the belt winding roller 32 is connected to the ground via the switch SW1.
When the cleaning electric field is formed, a voltage having a polarity opposite to the normal charging polarity of the toner on the belt 4 [for example, positive (+)] is applied to the foaming roller 51 via the recovery roller 52, and intermediate transfer is performed from the foaming roller 51. A current flows through the belt 4 to the belt winding roller 32.
The electric field formed by the power source PW1 may be either a constant voltage or a constant current, and may be set to, for example, several kV or less for a constant voltage, or to 100 μA or less for a constant current, for example.

(Photoconductor cleaning device)
FIG. 11 is an enlarged configuration diagram in the vicinity of the photoconductor cleaning device 60 in the image forming apparatus of FIG.

  The cleaning device 60 is provided between the primary transfer member 2 and the charging device 12 in the surface movement direction of the photoconductor 11.

  The cleaning device 60 is arranged in the same direction as the rotation direction of the foaming roller 51 at the contact portion while being in contact with the surface of the foaming roller 51 while being in contact with the surface of the photoconductor 11. It has the collection | recovery roller 52 arrange | positioned rotatably. The cleaning device 60 further includes a blade 53 that is fixedly placed in contact with the surface of the collection roller 52, a conveying screw 54 that carries out the cleaning object scraped off by the blade 53, and an object to be cleaned by the blade 53. A seal member (not shown) may be included to prevent the object to be crushed that has swollen in the form of dust during scraping from reattaching to the photoreceptor 11. These components included in the cleaning device 60 are provided in the case 55 in a state of being incorporated in the case 55. However, a part of the foaming roller 51 may be exposed from the case and in contact with the photoreceptor 11. Rotating members such as the foaming roller 51 and the collection roller 52 in the cleaning device 60 are rotationally driven together with an instruction from a control unit Cont (not shown).

  In the cleaning device 60, the object to be cleaned is the photosensitive member 11, and therefore the dimensions of the foaming roller 51, the recovery roller 52, the blade 53, the conveying screw 54, and the case 55 constituting the device 60 are different. Since it is the same as that of the cleaning device 50 except that the shape of 55 is different, the description thereof will be omitted below unless otherwise specified.

In FIG. 11, members denoted by the same reference numerals as those in FIG. 2 are the same as the members denoted by the corresponding numerals in FIG. 2.
The description of the cleaning device 60 and its constituent members can be applied by replacing the intermediate transfer belt 4 with the photoconductor 11 and the above description of the cleaning device 50 and its constituent members.

  As the photoreceptor 11, any conventionally known inorganic or organic photoreceptor can be used.

(Image forming device)
FIG. 1 shows a schematic configuration of an embodiment of an image forming apparatus according to the present invention. The image forming apparatus 100 in FIG. 1 is an electrophotographic image forming apparatus, which is a tandem type full color image forming apparatus, but is not limited thereto, and is, for example, a so-called cycle type full color image forming apparatus. It may be a monochromatic image forming apparatus.

  The image forming apparatus 100 includes an intermediate transfer member 4 that is wound around rollers 31, 32, and 33 and is driven to rotate counterclockwise in the figure (arrow direction in the figure). Here, the intermediate transfer body 4 is the endless belt-type intermediate transfer belt 4, but may be a drum-type intermediate transfer drum.

  A cleaning device 50 that cleans an object to be cleaned such as residual toner on the intermediate transfer belt 4 faces the roller 32. The intermediate transfer member cleaning device 50 is as described above. The secondary transfer member 6 faces the roller 31. The secondary transfer member 6 is here a secondary transfer roller 6 in the form of a roller. A fixing device 7 is installed above the secondary transfer roller 6.

  Between the rollers 32 and 31, the yellow image forming unit Y, the magenta image forming unit M, the cyan image forming unit C, and the black image forming unit K are arranged in this order along the intermediate transfer belt 4 from the rollers 32 to 31. Is arranged in. Each image forming unit includes a drum-type photoconductor 11 as an electrostatic latent image carrier, and a charging device 12, an image exposure device 13, a developing device 14, a primary transfer member 2, and a photosensitive member are provided around the photoconductor. Cleaning devices 60 for removing objects to be cleaned such as residual toner on the body are arranged in this order. The photoconductor cleaning device 60 is as described above. Here, the primary transfer member 2 is a primary transfer roller 2 in the form of a roller, and is disposed to face the photoreceptor 1 with the intermediate transfer belt 4 in between.

  The developing device 14 in each image forming unit employs a negatively chargeable toner, and reversely develops the electrostatic latent image formed on the photoconductor 11. The toner is not limited to those having negative chargeability, and may have positive chargeability. The development method is not limited to the reversal development method, and may be a regular development method. The photosensitive member 11, the charging device 12, the image exposure device 13, the developing device 14, and the cleaning device 60 in each image forming unit are attached and held in one case 1, and the photosensitive member 11 is attached to the transfer belt 4 from the case 1. Facing it, it is in contact with the belt 4.

  Below the four image forming portions Y, M, C, and K, a supply cassette 8 for a recording medium (recording paper S in this example) is provided, and the recording paper S accommodated therein is fed to the paper feed roller 81. Are pulled out and supplied one by one.

  A predetermined high voltage for charging the photoconductor is applied to the charging device 12 of each image forming unit from a power supply (not shown) at a predetermined timing under the instruction of a control unit Cont (not shown). A predetermined developing bias from a developing bias power supply (not shown) is applied to the developing roller 141 of the developing device 14 of each image forming unit at a predetermined timing under the instruction of the control unit Cont.

A primary transfer voltage is applied to the primary transfer roller 2 from an unillustrated primary transfer power source for the image forming unit, and the toner image on the photosensitive drum 11 is intermediately transferred to the primary transfer roller 2 under the instruction of the control unit Cont It is applied at the timing of primary transfer to the belt 4.
A secondary transfer voltage is applied to the secondary transfer roller 6 at the timing of secondary transfer of the toner image on the intermediate transfer belt 4 from the power supply (not shown) to the recording paper S under the instruction of the control unit Cont. The

  In each image forming unit, the photosensitive member 11, the primary transfer roller 2, the rotating member such as the developing roller 141 in the developing device 14, the operation of the image exposure device 13, and the secondary transfer roller 6 and the intermediate transfer belt 4 are wound. Among the applied rollers, the operation of the driving roller 31, the fixing device 7, the paper feeding roller 81, the cleaning devices 50, 60, and the like are also operated at a predetermined timing under the instruction of the control unit Cont.

According to the image forming apparatus 100, image formation is performed as follows.
First, an image is formed in at least one of the image forming portions Y, M, C, and K according to an image to be finally formed. Taking a case where a full color image is formed using all of the image forming portions Y, M, C and K as an example, first, a yellow toner image is formed in the yellow image forming portion Y, and this is formed on the intermediate transfer belt 4 as a primary. Transcribed. That is, in the yellow image forming portion Y, the photoconductor 11 is rotated in the clockwise direction in the drawing, and the surface of the photoconductor 11 is uniformly charged to a predetermined potential by the charging device 12, and the image exposure device 13 is placed in the charged area. Then, image exposure for yellow image is performed, and an electrostatic latent image for yellow is formed on the photoreceptor 11. The electrostatic latent image is developed by a developing roller 141 to which a developing bias of a developing device 14 having yellow toner is applied to become a visible yellow toner image, and the toner image is subjected to primary transfer to which a primary transfer voltage is applied. The image is transferred onto the intermediate transfer belt 4 by the roller 2. Similarly, a magenta toner image is formed in the magenta image forming unit M and transferred to the intermediate transfer belt 4, and a cyan toner image is formed and transferred to the intermediate transfer belt 4 in the cyan image forming unit C. A black toner image is formed at K and transferred to the intermediate transfer belt 4. Yellow, magenta, cyan, and black toner images are formed at the timing when these toner images are transferred onto the intermediate transfer belt 4 in an overlapping manner. Thus, the multiple toner image formed on the intermediate transfer belt 4 moves toward the secondary transfer roller 6 by the rotation of the intermediate transfer belt 4.

  On the other hand, the recording paper S is pulled out from the recording paper supply cassette 8 by the paper supply roller 81, and then, by the timing roller pair 91 and 92, the intermediate transfer belt 4 and the secondary transfer are synchronized with the multiple toner images on the belt 4. The multiple toner images are secondarily transferred onto the recording paper S by the secondary transfer roller 6 supplied between the rollers 6 and applied with a secondary transfer voltage. Thereafter, the recording paper S is passed through the fixing device 7 where the multiple toner images are fixed on the recording paper S under heat and pressure, and a predetermined color image is formed on the recording paper S. Thereafter, the recording paper S is discharged onto the paper discharge tray T by the paper discharge roller pair R.

  After the primary transfer in each image forming unit, an object to be cleaned such as a primary transfer residual toner remaining on the photoreceptor 11 is cleaned and collected by the cleaning device 60. Further, after the secondary transfer, the cleaning object 50 such as secondary transfer residual toner remaining on the intermediate transfer belt 4 is cleaned and collected by the cleaning device 50. Most of the toner remaining on or adhering to the photoconductor 11 after the primary transfer is the primary transfer residual toner, but what remains or adheres to the belt 4 after the secondary transfer. In addition to the secondary transfer residual toner, there are paper dust derived from the recording paper S, filler for the recording paper (such as talc), and the like. If the developing device 14 employs a two-component developer in the image forming unit, the carrier contained in the two-component developer may adhere.

<Experimental Example 1; Pseudo Experiment>
(Foaming roller for intermediate transfer belt)
The foaming roller had a foam layer formed around the cored bar. The foam was urethane foam having an average cell diameter of about 500 μm and a resistance value of 9 × 10 ⁸ Ω. The outer diameter of the foam roller was 15 mm, the core metal diameter was 7 mm, and the thickness of the foam layer was 4 mm. The amount of biting of the foam roller with respect to the intermediate transfer belt was 1.0 mm.

(Recovery roller for intermediate transfer belt)
The collection roller was an iron roller with a nickel plating on the surface. The surface roughness Rz was 1.6 μm or less, and the core metal diameter was φ12 mm. The amount of biting of the foam roller with respect to the collection roller was 1.3 mm.

(Blade for intermediate transfer belt)
The blade in contact with the collecting roller was applied with a thin plate (thickness 80 μm) of SUS304 so that the tip contacted.

(toner)
As the toner, a negatively chargeable toner (polymerized toner, styrene acrylic resin, particle size 7.2 μm) was used.
(Intermediate transfer belt)
A belt made of conductive polyimide resin (surface resistance 5 × 10 ¹¹ Ω) was used for the intermediate transfer belt.

(Evaluation A)
The above-described foaming roller, recovery roller and blade for the intermediate transfer member were mounted on Bizhub C450 (manufactured by Konica Minolta) as shown in FIG. Unless otherwise stated, the standard conditions for the above copiers were adopted.
First, pseudo transfer residual toner was formed on the transfer belt, the recovery roller was removed, and the transfer residual toner was recovered by a cleaning device using only the foam roller, and the toner was accumulated in the foam cell. Conditions were set so that the amount of toner to be accumulated was approximately 500 mg.
Next, the collecting roller is brought into contact with the foaming roller in which the toner is accumulated, and the foaming roller and the collecting roller are rotated for 10 seconds under the conditions described in the examples / comparative examples. It was magnified with a microscope, and the remaining state of the toner was observed and evaluated. In discharging, a constant current of 50 μA was set between the collecting roller and the foaming roller. The collection roller side was the + pole and the foaming roller was the-pole (earth).

×: Concentration of residual toner was observed in all cells;
Δ: Dense portions of residual toner were observed in some cells, but there was no practical problem;
○: Concentration of residual toner was not recognized in all cells, and the toner was uniformly present.

Comparative Example 1
The rotation speed of the foaming roller was fixed at 300 mm / s, the rotation speed of the recovery roller was fixed at 200 mm / s, and the rotation was performed for 10 seconds.
Comparative Example 2
The recovery roller was rotated by the same method as in Comparative Example 1 except that the rotation speed of the recovery roller was fixed at 300 mm / s.
Comparative Example 3
The recovery roller was rotated by the same method as in Comparative Example 1 except that the rotation speed of the collection roller was fixed at 400 mm / s.
When the toner in the cell was observed, dense toner spots were observed.
Comparative Example 4
As shown in FIG. 3A, the rotation speed of the collecting roller is rotated in the same manner as in Comparative Example 1 except that θ _H → θ _L → θ _H is continuously changed in a cycle of 5 seconds of 290 → 230 → 290 mm / s. I let you.

Example 1
As shown in FIG. 3A, the rotation speed of the collecting roller is rotated in the same manner as in Comparative Example 1, except that θ _H → θ _L → θ _H is continuously changed in a cycle of 5 seconds of 330 → 270 → 330 mm / s. I let you.

Comparative Example 5
As shown in FIG. 3A, the rotation speed of the collecting roller is rotated in the same manner as in Comparative Example 1, except that θ _H → θ _L → θ _H is continuously changed in a cycle of 370 → 310 → 370 mm / s. I let you.

Example 2
As shown in FIG. 3A, the rotation speed of the collection roller is rotated in the same manner as in Comparative Example 1 except that θ _H → θ _L → θ _H is continuously changed in a cycle of 360 → 240 → 360 mm / s. I let you.
Example 3
As shown in FIG. 3A, the rotation speed of the collecting roller is rotated in the same manner as in Comparative Example 1 except that θ _H → θ _L → θ _H is continuously changed in a cycle of 375 → 225 → 375 mm / s. I let you.

Example 4
The rotation speed of the foaming roller is fixed to 500 mm / s, and the rotation speed of the recovery roller is continuously changed in a cycle of 5 seconds of θ _H → θ _L → θ _H from 550 → 450 → 550 mm / s as shown in FIG. 3A. It was rotated by the same method as Comparative Example 1 except that it was changed.
Example 5
The rotation speed of the collecting roller is rotated in the same manner as in Example 4 except that θ _H → θ _L → θ _H is continuously changed in a cycle of 5 seconds of 600 → 400 → 600 mm / s as shown in FIG. 3A. I let you.
Example 6
The rotation speed of the collecting roller is rotated in the same manner as in Example 4 except that θ _H → θ _L → θ _H is continuously changed in a cycle of 5 seconds of 650 → 350 → 650 mm / s as shown in FIG. 3A. I let you.

Comparative Example 6
As shown in FIG. 3A, the rotation speed of the collecting roller is rotated in the same manner as in Example 4 except that θ _H → θ _L → θ _H is continuously changed in a cycle of 470 → 370 → 470 mm / s for 5 seconds. I let you.
Comparative Example 7
The rotation speed of the collecting roller is rotated in the same manner as in Example 4 except that θ _H → θ _L → θ _H is continuously changed in a cycle of 5 seconds of 630 → 530 → 630 mm / s as shown in FIG. 3A. I let you.

  From these results, it was found that the toner accumulation amount in the cell of the foaming roller is reduced by changing the rotation speed of the collecting roller over θ = 1.

<Experimental Example 2; Printing Experiment; Cleaning of Intermediate Transfer Belt>
(Evaluation B)
The foaming roller, the recovery roller and the blade for the intermediate transfer belt similar to those in Experimental Example 1 are mounted on Bizhub C450 (manufactured by Konica Minolta) as shown in FIG. 2, and foaming is performed under the predetermined conditions shown in Examples 1 to 6 below. Printing was performed by rotating the roller and the collection roller. Unless otherwise specified, the same conditions as in Experimental Example 1 were adopted. The collection unit was biased so that the collection roller had a positive polarity and the opposite roller had a negative polarity (ground), and a constant current of 50 μA flowed.

Examples 1-6
100 patterns with a BW ratio of 5% were printed continuously. The rotation speed of the collecting roller was changed from the end of printing to the stop of driving of the apparatus. During printing, the collection roller was rotated at a setting of θ = 1, and the rotation speed of the collection roller was changed in 4 seconds from the end of printing to the stop of driving of the apparatus. As the rotation speed of the collection roller, the values of θ _H and θ _L described in each example in Experimental Example 1 are adopted, and θ _H (1 second) → θ = 1 (1 second) → θ as shown in FIG. _L (1 second) → θ = 1 (1 second) was changed stepwise in a 4 second cycle. The inside of the cell of the foaming roller was enlarged with an optical microscope, and the remaining state of the toner was observed and evaluated.

×: Concentration of residual toner was observed in all cells;
Δ: Dense portions of residual toner were observed in some cells, but there was no practical problem;
○: Concentration of residual toner was not recognized in all cells, and the toner was uniformly present.

(Evaluation C)
Unless otherwise specified, evaluation was performed in the same manner as in Evaluation B.

Examples 1-6
The rotation speed of the collecting roller was changed every time 1000 sheets were printed, and 10,000 sheets of a pattern with a BW ratio of 5% were printed. The rotation speed of the collecting roller was changed stepwise while printing. Specifically, as the rotation speed of the collection roller, the values of θ _H and θ _L described in each example in Experimental Example 1 are adopted, and as shown in FIG. When 2000 sheets were printed, θ = θ _H , θ = 1 when 2001-3000 sheets were printed, and θ = θ _L when 3001-4000 sheets were printed, and gradually changed in a 4000 sheet cycle. Note that the speed of the collecting roller was switched after the copying machine was temporarily stopped.

comparing the image of the time when the theta = theta _L of θ = θ _H.
×: Printed line widths or line intervals were clearly different, causing practical problems;
Δ: Printed line width or line spacing was slightly different, but there was no practical problem;
○: There was no difference in the printed line width or line spacing.

(Evaluation D)
100,000 sheets were printed by the same method as in Evaluation C. The filming on the 100,000th intermediate transfer belt was evaluated. Comparative examples were also evaluated. In the comparative examples, the values of θ _H and θ _L described in each comparative example were adopted.
X: Filming was observed over the entire surface of the intermediate transfer belt;
Δ: Filming was observed in part of the intermediate transfer belt, but there was no practical problem;
○: Filming was not observed over the entire surface of the intermediate transfer belt.

<Experimental Example 3; Printing Experiment; Photoconductor Cleaning>
(Foaming roller for photoconductor)
The foaming roller had a foam layer formed around the cored bar. The foam was urethane foam having an average cell diameter of about 500 μm and a resistance value of 9 × 10 ⁸ Ω. The outer diameter of the foam roller was 14 mm, the core metal diameter was 6 mm, and the thickness of the foam layer was 4 mm. The amount of biting of the foam roller with respect to the photosensitive member was 1.0 mm.

(Recovery roller for photoconductor)
The collection roller was an iron roller with a nickel plating on the surface. The surface roughness was Rz = 1.6 μm, and the core metal diameter was φ12 mm. The amount of biting of the foam roller with respect to the collection roller was 1.0 mm.

(Photosensitive blade)
The blade in contact with the collecting roller was applied with an SUS304 80 μm thin plate so that the tip contacted.

(toner)
As the toner, a negatively chargeable toner (polymerized toner, styrene acrylic resin, particle size 7.2 μm) was used.
(Photoconductor)
As the photoreceptor, an organic photoreceptor provided as standard equipment in a copying machine was used.

(Evaluation D)
The above-described foaming roller, collection roller and blade for the photoreceptor are mounted on Bizhub C450 (manufactured by Konica Minolta) as shown in FIG. Printed by rotating. Unless otherwise specified, the same conditions as in Experimental Example 1 were adopted. A positive bias was applied to the collecting roller so that a constant current of 20 μA would flow between the collecting roller and the photoreceptor. As the bias of the primary transfer portion for transferring the toner from the photoreceptor to the transfer belt, a voltage was applied to the primary transfer roller on the back surface of the transfer belt so that a constant current of 30 μA flows.

Examples 1-6
100 patterns with a BW ratio of 5% were printed continuously. The rotation speed of the collecting roller was changed from the end of printing to the stop of driving of the apparatus. During printing, the collection roller was rotated at a setting of θ = 1, and the rotation speed of the collection roller was changed in 4 seconds from the end of printing to the stop of driving of the apparatus. As the rotation speed of the collection roller, the values of θ _H and θ _L described in each example in Experimental Example 1 are adopted, and θ _H (1 second) → θ = 1 (1 second) → θ as shown in FIG. _L (1 second) → θ = 1 (1 second) was changed stepwise in a 4 second cycle. The inside of the cell of the foaming roller was enlarged with an optical microscope, and the remaining state of the toner was observed and evaluated.

×: Concentration of residual toner was observed in all cells;
Δ: Dense portions of residual toner were observed in some cells, but there was no practical problem;
○: Concentration of residual toner was not recognized in all cells, and the toner was uniformly present.

  The cleaning apparatus of the present invention can effectively clean the surface of an image carrier over a long period of time in an image forming apparatus such as an electrophotographic copying machine, a facsimile machine, or a laser printer that forms a monochrome image or a color image.

1 is a schematic configuration diagram illustrating an example of an image forming apparatus of the present invention. FIG. 2 is an enlarged view of the intermediate transfer belt cleaning device in FIG. 1. It is an example of the graph which shows a time-dependent change of rotational speed ratio (theta) when changing rotational speed ratio (theta) continuously in this invention. It is an example of the graph which shows a time-dependent change of rotational speed ratio (theta) when changing rotational speed ratio (theta) continuously in this invention. It is an example of the graph which shows a time-dependent change of rotational speed ratio (theta) when changing rotational speed ratio (theta) in steps in this invention. It is an example of the graph which shows a time-dependent change of rotational speed ratio (theta) when changing rotational speed ratio (theta) in steps in this invention. It is an example of the graph which shows a time-dependent change of rotational speed ratio (theta) when changing rotational speed ratio (theta) in steps in this invention. In the present invention, it is an example of a graph showing a change over time of the rotational speed ratio θ when the rotational speed ratio θ is continuously changed from the end of printing to the stop of driving of the apparatus. In the present invention, it is an example of a graph showing a change over time of the rotational speed ratio θ when the rotational speed ratio θ is changed stepwise from the end of printing to the stop of driving of the apparatus. In the present invention, it is an example of a graph showing a change with time of the rotational speed ratio θ when the rotational speed ratio θ is changed stepwise while printing. It is a schematic block diagram which shows an example of the means for controlling the rotational speed of a collection | recovery roller in this invention. It is a schematic block diagram which shows an example of the means for controlling the rotational speed of a collection | recovery roller in this invention. FIG. 3 is a schematic configuration diagram for explaining means for forming a cleaning electric field in the intermediate transfer belt cleaning device of the present invention. FIG. 2 is an enlarged view of the photoconductor cleaning device in FIG. 1.

Explanation of symbols

  50: cleaning device for intermediate transfer belt, 51: foaming roller, 52: recovery roller, 53: blade, 54: conveying screw, 55: case, 60: cleaning device for photoconductor.

Claims (10)

A foaming roller rotatably disposed in contact with the surface of the image carrier; and in contact with the surface of the foaming roller, disposed in the contact portion so as to be rotatable in the same direction as the rotation direction of the foaming roller. Has a collection roller,
A cleaning device, wherein a rotation speed ratio θ of a collection roller to a foaming roller is periodically changed in a range exceeding 1.   The cleaning device according to claim 1, wherein the rotation speed ratio θ of the collection roller to the foaming roller is changed in a range of at least 0.95 to 1.05.   The cleaning device according to claim 2, wherein the rotation speed ratio θ of the collection roller to the foaming roller is changed in a range where the lower limit value is 0.60 to 0.95 and the upper limit value is 1.05 to 1.40. .   The cleaning device according to claim 3, wherein the rotation speed ratio θ of the collection roller to the foaming roller is changed in a range where the lower limit value is 0.78 to 0.95 and the upper limit value is 1.05 to 1.22. .   The cleaning device according to claim 1, wherein the rotational speed ratio θ is changed at a time other than during image formation.   The cleaning device according to claim 1, wherein the image carrier is an intermediate transfer member or a photosensitive member. The cleaning apparatus according to claim 1, wherein the rotation speed ratio θ is changed in a stepwise manner. The cleaning apparatus according to claim 7, wherein the rotation speed ratio θ is changed for each sheet. The cleaning device according to claim 1, wherein the rotation speed ratio θ is continuously changed. An image forming apparatus having a cleaning device according to any one of claims 1 to 9.

Images