JP2011064948A - Cleaning device and image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a cleaning device that properly removes fine particles adhering to a surface of a secondary transfer member, and includes a cleaning member having a long service life, and to provide an image forming apparatus including the cleaning device. <P>SOLUTION: A foaming roller 141 is arranged on the downstream side of the part where the secondary transfer roller 115 faces an intermediate transfer belt 101 when seen from the rotating direction of the secondary transfer roller 115, and a brush roller 142 is arranged on the further downstream side. The aperture ratio on a cell wall surface of polyurethane foam of a surface layer of the foaming roller 141 is within the range of 5-50%. A bias of polarity opposite to that of regular charged toner is applied to the foaming roller 141 via a recovery roller 143. <P>COPYRIGHT: (C)2011,JPO&amp;INPIT

Description

  The present invention relates to a cleaning device for cleaning a secondary transfer member such as a secondary transfer roller and a secondary transfer belt, and an image forming apparatus including the same. More specifically, the present invention relates to a cleaning device that can contact the surface of a secondary transfer member and suitably collect deposits such as toner and paper dust attached to the surface, and an image forming apparatus including the same. is there.

  The image forming apparatus obtains an image by applying toner to an electrostatic latent image formed on a photoreceptor and developing it, and transferring and fixing the toner image on a recording medium. For color image forming apparatuses, YMCK (yellow, magenta, cyan, black) tandem type in which photoconductor units of each color are arranged, or 4-cycle type in which a single photoconductor unit develops each color four times in total. There are things. Some tandem color image forming apparatuses form a color image using an intermediate transfer member such as an intermediate transfer belt.

  In recent years, adjustment of settings for forming an image in an image forming apparatus has been performed by forming a reference patch on an intermediate transfer member such as an intermediate transfer belt and reading the reference patch. This is to maintain the quality of the color image or to improve the productivity of the color image. In many cases, the adjustment of the setting using the reference patch is actually performed between sheets of paper on which no image is formed on the recording medium.

  Since the image is formed between the sheets as described above, the image of the reference patch formed on the intermediate transfer member may adhere to the surface when passing through the location of the secondary transfer member. If toner adheres to the secondary transfer member, it may cause the backside of the recording medium to become dirty. Further, when the toner adhering to the secondary transfer member is melted to cause filming, the transferability for transferring the toner image on the intermediate transfer member to the recording medium is deteriorated. That is, a desired image cannot be formed on the recording medium.

  In order to solve this problem, there is a case where a cleaning device is provided for removing deposits such as toner from the surface of the secondary transfer member. For example, in Patent Document 1, a cleaning blade is disposed at a position downstream of a portion where the secondary transfer roller and the intermediate transfer belt face each other in the rotational direction of the secondary transfer roller, and a brush roller is disposed further downstream. A cleaning device is disclosed. According to Patent Document 1, the surface of the secondary transfer roller can be suitably cleaned with the downstream brush roller by intentionally passing a predetermined amount of toner through the upstream cleaning blade. (See Table 1 in Patent Document 1).

JP 2005-292416 A

  However, even if a predetermined amount of toner is intentionally slipped through on the upstream side as in the cleaning device described in Patent Document 1, it is not always possible to remove fine particles such as paper dust on the downstream side. Absent. In particular, it is difficult to remove the toner that has entered the minute recesses necessarily present on the surface of the secondary transfer member. Also, if the brush roll is poor in discharging foreign matter, the cleaning performance deteriorates as it continues to be used. Such a problem can occur in a cleaning device using other methods as well.

  The present invention has been made to solve the above-described problems of the prior art. That is, it is an object of the present invention to provide a cleaning device having a long cleaning member life and an image forming apparatus including the cleaning member, which can suitably remove deposits attached to the surface of the secondary transfer member. It is.

  In order to solve this problem, an image forming apparatus according to the present invention includes an image forming unit that forms a toner image, an image carrier that carries a toner image formed by the image forming unit, and an image carrier that is carried on the image carrier. In an image forming apparatus having a transfer member for transferring a toner image to a recording medium and a cleaning member for cleaning the surface of the transfer member by contacting a portion other than the contact portion of the transfer member with the image carrier, as a cleaning member, A first cleaning member on the upstream side and a second cleaning member on the further downstream side in the rotation direction of the transfer member, and the first cleaning member has a cell wall opening ratio of 5 to 5 as a surface layer thereof. The foaming roller uses polyurethane foam within a range of 50%, the second cleaning member is a brush roller, and the transfer member, the first cleaning member, A voltage is applied between the transfer member and the second cleaning member to apply a voltage for pulling the normally charged toner to the first cleaning member. It has an application part. Such an image forming apparatus can suitably remove deposits from the surface of the secondary transfer member. In addition, the durability of the cleaning member is long. This is because the polyurethane foam is less likely to be clogged with deposits.

  In the image forming apparatus described above, the image forming apparatus may be disposed so as to rotate in a state where a part of the surface of the first cleaning member and a part of the surface of the second cleaning member are in contact with each other. This is because the first cleaning member and the second cleaning member come into contact with each other, and the toner remaining on each member can be removed.

  In addition, the cleaning device according to the present invention is in contact with a transfer member that transfers a toner image carried on an image carrier to a recording medium and a portion of the transfer member other than a contact portion between the image carrier and the surface of the transfer member. In the cleaning device having the cleaning member for cleaning the first cleaning member, the cleaning member has a first cleaning member on the upstream side and a second cleaning member on the downstream side in the rotation direction of the transfer member. The member is a foaming roller using a polyurethane foam having a cell wall opening ratio of 5 to 50% as a surface layer, the second cleaning member is a brush roller, the transfer member and the first cleaning member Between the transfer member and the first cleaning member, a voltage in the direction of pulling the normally charged toner to the first cleaning member is applied. Between the cleaning member and the voltage direction pulling the normally charged toner to the second cleaning member is applied. Such a cleaning device can suitably remove deposits from the surface of the secondary transfer member. It also has a long durability life. This is because the polyurethane foam is less likely to be clogged with deposits.

  In the cleaning device described above, the cleaning device may be arranged so as to rotate in a state in which a part of the surface of the first cleaning member and a part of the surface of the second cleaning member are in contact with each other. This is because the first cleaning member and the second cleaning member come into contact with each other, and the toner remaining on each member can be removed.

  According to the present invention, there are provided a cleaning device that can suitably remove deposits adhering to the surface of a secondary transfer member and a long cleaning member life and an image forming apparatus including the same.

1 is a schematic configuration diagram for explaining an image forming apparatus of the present invention. FIG. 3 is a schematic configuration diagram for explaining a cleaning device for a secondary transfer roller in the image forming apparatus of the present invention. It is a perspective view for demonstrating the structure of the foaming roller of the cleaning apparatus which concerns on this invention. It is a flowchart for demonstrating the manufacturing process of the polyurethane foam used for the foaming roller of the cleaning apparatus which concerns on this invention. FIG. 2 is a schematic configuration diagram for explaining a cleaning device for a secondary transfer belt in the image forming apparatus of the present invention.

  DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments embodying the present invention will be described below in detail with reference to the accompanying drawings.

1. Image Forming Apparatus The image forming apparatus 100 according to the present embodiment is a so-called tandem type color copier having an intermediate transfer belt 101 as schematically shown in FIG. The intermediate transfer belt 101 is an endless belt member. Both ends of the intermediate transfer belt 101 are supported by rollers 102 and 103 and rotate in the direction of arrow A in the drawing. Along the lower portion of the intermediate transfer belt 101 in the drawing, image forming portions 1Y, 1M, 1C, and 1K for each color of yellow (Y), magenta (M), cyan (C), and black (K) are arranged.

  The image forming units 1Y, 1M, 1C, and 1K for the respective colors have the same configuration. Each has a photoreceptor unit 20, an exposure device 30, and a developing unit 10. The photoreceptor unit 20 has a photoreceptor drum 21 that carries an electrostatic latent image. The exposure device 30 is for drawing an electrostatic latent image on the photosensitive drum 21. The developing unit 10 is for applying toner to the electrostatic latent image on the photosensitive drum 21 for development. Further, a primary transfer roller 111 is disposed at a position facing the photosensitive drum 21 with the intermediate transfer belt 101 interposed therebetween. In FIG. 1, the reference numerals of these devices are shown as representatives by the image forming unit 1Y.

  In FIG. 1, a paper feeder 112 that accommodates the paper P is disposed below. A paper feed roller 113 that feeds the paper P is provided above the paper feed device 112. The sheet P is sent upward from the sheet feeding device 112 along the sheet conveyance path 114. A secondary transfer roller 115 is disposed at a position facing the roller 103 with the sheet conveyance path 114 interposed therebetween. A sensor 150 is disposed at a position downstream of the image forming unit 1 </ b> Y and upstream of the secondary transfer roller 115 in the rotation direction of the intermediate transfer belt 101. The sensor 150 is for detecting the position and density of a reference patch to be described later.

  A cleaning device 140 for cleaning the secondary transfer roller 115 is disposed at a position opposite to the roller 103 of the secondary transfer roller 115. Further, a fixing device 130 is disposed on the downstream side (upper side in the drawing). The fixing device 130 includes a roller pair of a pressure roller 131 and a fixing roller 132.

  A paper discharge roller 116 and a paper discharge tray 117 are arranged further downstream of the sheet conveying path 114 from the fixing device 130. A folding roller 119 and a folding tray 120 are disposed further above the paper discharge roller 116. The folding roller 119 is connected to the paper transport path 118 in addition to the paper transport path 114. The paper transport path 118 is a transport path used when performing duplex printing.

  Next, a basic operation of the image forming apparatus 100 of this embodiment will be briefly described. When the image forming apparatus 100 receives an image formation instruction, the image forming apparatus 100 generates image data of each color from the image signal. The generated image data of each color is sent to the corresponding image forming units 1Y, 1M, 1C, and 1K. The image forming units 1Y, 1M, 1C, and 1K for each color form an electrostatic latent image based on the image data. Further, the formed electrostatic latent image is developed to form a toner image.

  The formed toner images are sequentially transferred to the intermediate transfer belt 101 by the primary transfer roller 111 and superimposed. The toner image superimposed on the intermediate transfer belt 101 is transferred onto the paper P by the secondary transfer roller 115. The sheet P carrying the toner image is further conveyed and reaches the fixing device 130, and is heated and pressurized by the fixing device 130. As a result, the toner image is fixed on the paper P. The paper P on which the toner image is fixed is discharged to a paper discharge tray 117 by a paper discharge roller 116. The above is the basic operation of the image forming apparatus 100.

2. Cleaning Device The cleaning device 140 of this embodiment will be described. The toner used in the image forming apparatus 100 of the present embodiment is negatively charged. Therefore, the negatively charged toner is a regular charged toner.

  FIG. 2 is an enlarged view in which a portion of the cleaning device 140 in FIG. 1 is enlarged. The cleaning device 140 is for removing deposits from the surface of the secondary transfer roller 115. In this case, the adhering material includes an external additive and paper powder in addition to the toner adhering when the reference patch is formed.

  Here, the reference patch is a reference image formed as an image for testing separately from the image formed on the paper P. The sensor 150 detects the density and position of the reference patch image formed on the intermediate transfer belt or the like. These detected values are fed back to various settings for image formation and used to maintain image quality.

  As shown in FIG. 2, the cleaning device 140 includes a foaming roller 141, a brush roller 142, a collection roller 143, a scraper 144, a housing 145, and a conveying screw 146.

  The foam roller 141 is a cleaning roller for removing toner, external additives, and paper powder from the surface of the secondary transfer roller 115. The brush roller 142 is also a cleaning roller for removing toner, external additives, and paper dust from the surface of the secondary transfer roller 115. Therefore, the foaming roller 141 and the brush roller 142 are in contact with the secondary transfer roller 115. The foaming roller 141 is arranged at a position downstream of the facing portion between the intermediate transfer belt 101 and the secondary transfer roller 115 when viewed in the rotational direction of the secondary transfer roller 115. The brush roller 142 is disposed at a position downstream of the foaming roller 141.

  The intermediate transfer belt 101 rotates in the direction of arrow B in FIG. This is the same direction as the arrow A in FIG. The secondary transfer roller 115 rotates in the forward direction (arrow C in FIG. 2) with respect to the rotation direction of the intermediate transfer belt 101 (arrow B in FIG. 2). The foaming roller 141 rotates counterclockwise (arrow D in FIG. 2) with respect to the rotation direction of the secondary transfer roller 115 (arrow C in FIG. 2). This is because the foaming roller 141 is rubbed against the secondary transfer belt 115 to suitably collect dirt such as toner on the secondary transfer belt 115. The brush roller 142 also rotates counterclockwise (arrow E in FIG. 2) with respect to the rotation direction of the secondary transfer roller (arrow C in FIG. 2).

  The collection roller 143 is a roller for collecting toner from the foaming roller 141 and the brush roller 142. Therefore, the collection roller 143 is disposed so as to contact the foaming roller 141 and the brush roller 142. The material of the collection roller 143 is a metal such as iron, aluminum, or stainless steel. Further, plating or the like may be applied to improve the smoothness and durability of the surface of the collection roller.

  As shown in FIG. 2, the collection roller 143 rotates in the forward direction, that is, in the direction of the arrow E with respect to the rotation direction of the foaming roller 141. Therefore, the collection roller 143 rotates in the forward direction with respect to the rotation direction of the brush roller 142. However, the collection roller 143 may rotate around the counter with respect to the rotation direction of the foam roller 141 and the brush roller 142, respectively. This is because the adhering matter adhering to the foaming roller 141 and the brush roller 142 can be recovered by electrostatic force.

  The scraper 144 is a member for scraping off toner and the like from the collection roller 143. The housing 145 is a member that covers the foaming roller 141, the brush roller 142, the recovery roller 143, the scraper 144, and the conveying screw 145. This is to prevent foreign matter removed from the secondary transfer roller 115 and collected from scattering inside the image forming apparatus 100 outside the housing. The transport screw 146 is for transporting foreign matter in the housing 145.

  As illustrated in FIG. 2, the image forming apparatus 100 includes a voltage application unit 151 and a voltage application unit 152. The voltage application unit 151 is for applying a voltage between the secondary transfer roller 115 and the roller 103. The voltage applied here is a voltage in a direction in which the toner image formed on the intermediate transfer belt 101 is pulled to the paper P. Therefore, this voltage is applied when the toner image is transferred to the paper P. In addition, the voltage can be applied between the papers. By applying this voltage, the toner image on the intermediate transfer belt 101 is transferred to the paper P passing through the paper transport path 114 at the location of the secondary transfer roller 115.

  The voltage application unit 152 is for applying a voltage between the collection roller 143 and the secondary transfer roller 115. The voltage application unit 152 applies a potential to the collection roller 143, thereby applying a potential to the foaming roller 141 and the brush roller 142 that are in contact with the collection roller 143. The voltage applied here is a voltage in a direction in which the normally charged toner adhering to the secondary transfer roller 115 is pulled to the foaming roller 141 at a location where the secondary transfer roller 115 and the foaming roller 141 face each other. . In addition, a voltage in a direction for pulling the normally charged toner adhering to the secondary transfer roller 115 to the brush roller 142 is applied to a portion where the secondary transfer roller 115 and the brush roller 142 face each other. . Therefore, the toner adhering to the secondary transfer roller 115 is easily removed by the foaming roller 141 or the brush roller 142. This voltage is applied until the secondary transfer roller 115 rotates at least once after the location where the reference patch is formed on the intermediate transfer belt 101 passes the location facing the secondary transfer roller 115. . Further, the voltage may be applied during a period other than the above.

  In FIG. 2, the voltage application units 151 and 152 are depicted as separate bodies, but these may be integrated. In addition, the image forming apparatus 100 includes another voltage application unit that applies a voltage between the photosensitive drum 21 and the primary transfer roller 111. And it is good also as having the integrated voltage application part which unified these functions and integrated instead of said voltage application part.

  The structure of the foam roller 141 will be described. As shown in FIG. 3, the foaming roller 141 includes a cored bar 141a and an elastic layer 141b covering the cored bar 141a. The cored bar 141a shown in FIG. 3 is solid, but may be hollow. The material of the core bar 141a is a metal such as aluminum. The material of the elastic layer 141b is polyurethane foam.

  The polyurethane foam used for the elastic layer 141b can also suitably remove the toner that has entered the surface of the intermediate transfer belt 101 up to the minute recesses that are necessarily present. This is because, as will be described later, physical properties such as the opening ratio of the cell wall surface in the polyurethane foam are suitable for collecting toner and the like.

Further, the polyurethane foam of the elastic layer 141b has conductivity. The volume resistivity is preferably in the range of 10 ² to 10 ⁸ Ωcm.

The brush roller 142 of this embodiment is a known brush roller. As shown in FIG. 2, the brush roller 142 is formed by forming a brush layer 142b on the outer periphery of the cored bar 142a. As a material for the brush of the brush layer 142b, synthetic fibers such as nylon, polyester, acrylic, and rayon can be used. The thickness of the fiber is about 0.1 to 1 tex (1 tex is a thickness of 1 g per 1,000 m). The flocking density is about 7,000-47,000 / cm ² . The electrical resistivity of the raw yarn of the brush layer 142b is preferably in the range of 10 ⁵ to 10 ¹³ Ωcm. This is because an electric field is formed between the secondary transfer roller 115 and the secondary transfer roller 115. This conductivity is imparted by adding carbon black or various ionic conductive agents.

3. Polyurethane Foam Physical properties of the polyurethane foam according to the present invention will be described. First, how the physical properties of polyurethane foam affect the cleaning properties when used as a cleaning member will be described.

  Examples of the physical properties of the polyurethane foam include the number of cells, cell diameter, cell wall opening ratio, hardness, density, and the like. The number of cells is the number of cells that the line segment crosses when a line segment of unit length is drawn on the cut surface of the polyurethane foam. The cell diameter is the diameter of the cell formed inside the polyurethane foam. The opening ratio of the cell wall surface is the ratio (S1 × 100 / S) of the area S1 of the opening to the area S of the entire cell wall surface (paragraph [0035] of Japanese Patent Laid-Open No. 2009-175700 and FIG. 3). reference). These shall be expressed as average values.

  First, a case where a single-foam polyurethane foam that is not connected to each other and exists in a single state will be described. When polyurethane foam having a small cell diameter and a large number of cells is used for the foaming roller, the number of times the surface of the foaming roller comes into contact with the toner or external additive of the secondary transfer roller is larger than that of the other. Therefore, in the past, it was considered that if a cell having a small cell diameter and a large number of cells was used, the foaming roller had excellent performance for removing toner and external additives from the transfer member, that is, cleanability.

  However, toner and external additives may clog the polyurethane foam cells of the foam roller. And if it continues using it without replacing | exchanging the foaming roller in such a state, a clogging location will increase with progress of use time. Therefore, the cleaning performance decreases as the number of clogged portions increases. In other words, the cleaning performance, which was good at the beginning of use, decreases with the passage of use time. Moreover, the amount of toner etc. which can be contained in the cell is not sufficient in the single-foam polyurethane foam. Therefore, it is not suitable when a large amount of toner must be collected at once.

  However, in order to avoid clogging, when polyurethane foam having a large cell diameter is used for the foaming roller, the surface of the foaming roller, that is, the number of times the polyurethane foam contacts the surface of the secondary transfer roller is small. End up.

  Then, the case where the open cell type polyurethane foam which exists in the state to which cells connected is used is demonstrated. When open-cell polyurethane foam is used as the material for the elastic layer of the foam roller, it is difficult for toner and external additives to adhere to the inside of the cell. However, a foaming roller using a continuous foam polyurethane foam is not effective in collecting toner and external additives. This is because the opening ratio of the cell wall surface is too large and there are too few resin portions in contact with the secondary transfer roller. In other words, the area that does not come into contact with the resin portion on the surface of the secondary transfer roller is large. Furthermore, if the continuous foamed polyurethane foam is continuously used for the cleaning member, the toner gradually enters the foamed layer, and the flexibility of the foam decreases. As a result, the adhesion with the secondary transfer roller is also reduced. That is, the cleaning property is deteriorated.

Therefore, the polyurethane foam used for the cleaning member is
1) The cell diameter should be large enough to prevent clogging, and the number of contacts should not be reduced.
2) Improve the collection efficiency of deposits by setting the cell opening ratio to an appropriate value.
It is desirable to satisfy these two points.

  The polyurethane foam used for the cleaning member according to the present invention satisfies the above two points.

  Here, the polyurethane foam used for the foaming roller 141 of this form is demonstrated. The polyurethane foam of this embodiment has an intermediate property between a single foam polyurethane foam and a continuous foam polyurethane foam. That is, the polyurethane foam of the present embodiment has lower hardness and lower density than the single foam polyurethane foam. On the other hand, the polyurethane foam of this embodiment has higher hardness and higher density than the open cell polyurethane foam.

  The polyurethane foam of this embodiment has the following properties. That is, the number of cells is 30 to 60 / 25.4 mm (1 inch), the cell wall opening ratio is in the range of 5 to 50%, the cell diameter is in the range of 150 to 500 μm, and the hardness Is in the range of 10 to 50 N / m. Hardness is the repulsive force per unit length in the indentation axis direction. For example, as described later, it can be obtained by pressing a 50 mm aluminum disk to 30% of the elastic body thickness and measuring the repulsive force.

  For comparison, physical properties of a known single-foam polyurethane foam are exemplified. The number of cells is about 100 / 25.4 mm, the aperture ratio of the cell wall surface is about 1%, the cell diameter is about 80 μm, and the hardness is about 85 N / m. Moreover, the physical property of a well-known open cell type polyurethane foam is illustrated. The number of cells is about 25 / 25.4 mm, the cell wall opening ratio is about 60%, the cell diameter is about 700 μm, and the hardness is about 8 N / m.

4). Method for Producing Polyurethane Foam A method for producing the polyurethane foam of this embodiment will be described with reference to the flowchart shown in FIG. The method for producing a polyurethane foam of this embodiment is obtained by partially incorporating a method for producing a continuous foam polyurethane foam into a conventional method for producing a single foam polyurethane foam.

  First, raw materials used for manufacturing polyurethane foam will be described. The polyurethane foam of this embodiment is produced using polyol, isocyanate, organic hydrochloric acid catalyst, amine catalyst, foam stabilizer, and water as raw materials.

  Polyols and isocyanates are the main raw materials. These reactions form urethane bonds. Resinification will proceed by a resinification reaction such as urethane bonding. The organic hydrochloric acid catalyst is mainly a catalyst for promoting these resinification reactions. These raw materials are mainly used for producing the resin part of polyurethane foam.

  Water is a foaming raw material that reacts directly with isocyanate to generate carbon dioxide gas. The amine-based catalyst is a catalyst mainly for promoting the generation of carbon dioxide gas. The foam stabilizer is a surfactant for assisting the generated carbon dioxide gas to form bubbles. These raw materials are mainly used to form foam by generating bubbles in the polyurethane foam.

  As the polyol used here, for example, polyether polyol, polyester polyol, polycarbonate polyol and the like can be used. Moreover, well-known polyols, such as a polydiene type polyol, can also be used individually or in combination of 2 or more types. The polyol used here has a molecular weight in the range of 1000 to 6000, and is preferably a polyether polyol or polyester polyol having 2 to 5 functional groups.

  Further, as the isocyanate, for example, a known aromatic system such as toluene diphenyl diisocyanate (TDI), TDI prepolymer, methylene diphenyl diisocyanate (MDI), crude MDI, polymeric MDI, uretdione-modified MDI, or carbodiimide-modified MDI, aliphatic or Various polyisocyanates such as alicyclic compounds can also be used.

  Examples of amine catalysts include N, N, N ′, N ″, N ″ -pentamethyldiethylenetriamine, bis (dimethylaminoethyl) ether, N, N-dimethylaminoethoxyethoxyethanol, N, N— Known substances such as dimethylaminoethoxyethanol, special tertiary amine mixture, N, N, N ′, N′-tetramethylhexanediamine, N, N, N ′, N′-tetramethylpropanediamine and the like can be used. . It is better that the contribution to the foaming reaction is greater than the contribution to the resinification reaction.

  Examples of organic hydrochloric acid catalysts include organic hydrochloric acids such as 1,8-diazabicyclo (5,4,0) undecene-7 (DBU) and 1,5-diazabicyclo (4,3,0) nonene-5 (DBN). Or an organic metal catalyst in which these organic hydrochloric acid and metal are combined can be used. The organic hydrochloric acid catalyst used here is preferably a catalyst that does not hinder the foaming reaction mainly played by the amine catalyst and is a delayed catalyst. This is to prevent the resinification from proceeding before the foaming reaction sufficiently occurs.

  As shown in FIG. 4, the polyurethane foam production method of this embodiment is a method of producing a polyurethane foam by sequentially performing a raw material adjustment step S1, a mixing step S2, a chemical foaming step S3, and a heating step S4.

  When the raw material adjustment step S1, the mixing step S2, and the heating step S4 are sequentially performed in the polyurethane foam production method of this embodiment, this is equivalent to a mechanical floss method that is a conventional method for producing a single-foam polyurethane foam. That is, the chemical foaming method does not perform the chemical foaming step S3. Details of the mechanical floss method are described in, for example, Japanese Patent Publication No. 53-8735.

S1: Raw Material Adjustment Step First, the raw material adjustment step S1 will be described. In the raw material adjustment step S1, a predetermined amount of water is mixed in advance with the polyol before mixing the raw materials. Also, other materials such as isocyanate are prepared in a predetermined amount to be blended with the polyol. In addition, it is preferable that an isocyanate index exists in the range of 90-110. The mixing ratio of other various raw materials will be described in detail later in the examples.

S2: Mixing step The mixing step S2 is a step of mixing raw materials. That is, a polyol mixed with water, an isocyanate, a catalyst, and a foam stabilizer are mixed. This causes a chemical reaction following this mixing. That is the chemical foaming step S3 described below. Therefore, the mixing step S2 is actually a step that cannot be separated from the chemical foaming step S3. However, here, in order to distinguish between foaming by the conventional mechanical floss method and foaming by the chemical foaming method, it is described as being a separate and separate process. Moreover, bubbles are also mixed inside the mixture by stirring the mixture of raw materials with a mixer.

S3: Chemical Foaming Process The chemical foaming process S3 is a process in which a chemical reaction occurs between the mixed raw materials. In the chemical foaming step S3, a urethane bond or an allophanate bond is generated by the reaction between the polyol and the isocyanate. By these resinification reactions, the mixture of raw materials is resinized. On the other hand, isocyanate also reacts with water. Carbon dioxide is generated by the reaction of isocyanate and water. This carbon dioxide grows with the bubbles mixed by stirring in the mixer as nuclei.

  That is, it grows as a resin and foams inside the resin. For this purpose, an amine catalyst that mainly promotes foaming and an organic hydrochloric acid catalyst that mainly promotes resinification are used in combination. In the chemical foaming step S3, the mixture expands due to foaming.

  Thus, the physical properties of the polyurethane foam that is finally produced by the mixing ratio of water that reacts with isocyanate to generate carbon dioxide, an amine catalyst that promotes foaming, and an organic hydrochloric acid catalyst that promotes resinization Will be determined. These blending ratios will be described in detail in Examples described later.

S4: Heating Step The heating step S4 is a step of heating the mixture of raw materials expanded by foaming. Since the mixed material has thermosetting properties, the mixed material is cured as a resin by the heating step S4. Thereby, a polyurethane foam is manufactured.

  Thereafter, the polyurethane foam is subjected to external processing such as drilling and is used as an elastic layer of the cleaning roller. Thus, a cleaning roller using polyurethane foam is manufactured.

5. Modified Example In the cleaning device 140 of the present embodiment, as shown in FIG. 2, the foaming roller 141 and the brush roller 142 are arranged so as not to contact each other. However, you may arrange | position so that the foaming roller 141 and the brush roller 142 may mutually contact. As a result, the foaming roller 141 and the brush roller 142 can clean each other. That is, the foaming roller 141 removes the foreign matter that is sandwiched between the brushes of the brush roller 142, and the brush roller 142 scrapes off the toner adhering to the surface of the foaming roller 141.

  The cleaning device 140 according to the present embodiment is not limited to the image forming apparatus using the secondary transfer roller 115 shown in FIG. For example, in the image forming apparatus using the secondary transfer belt 215 as shown in FIG. 5, the secondary transfer belt 115 can be suitably cleaned. This is because the adhering matter such as toner can be removed from the surface.

6). Summary As described above in detail, the cleaning device according to the present embodiment is a cleaning member disposed on the upstream side of the secondary transfer member in the range of 5 to 50% in terms of the opening ratio of the cell wall surface. A cleaning roller having a polyurethane foam layer was used. For this reason, the cleaning device of the present embodiment can suitably remove deposits from the surface of the secondary transfer member. Also, this polyurethane foam layer is not easily clogged. As a result, a transfer member capable of maintaining transferability for a long period of time and an image forming apparatus using the same are realized.

  Note that this embodiment is merely an example, and does not limit the present invention. Therefore, the present invention can naturally be improved and modified in various ways without departing from the gist thereof. For example, it is not limited to the secondary transfer member. The present invention can also be applied to an image carrier such as a photoreceptor or an intermediate transfer member. The image forming apparatus is not limited to a color copier. That is, it is not limited to color. Moreover, it is not restricted to a copier. The present invention can be applied to a printer, a FAX, and other apparatuses that form images.

  Further, the present invention can also be applied to an image forming apparatus that uses a positively charged toner as a normally charged toner. In this case, the cleaning roller may be charged with a polarity opposite to that shown in the present embodiment. Further, the fixing roller 132 may be a driven roller.

1. Content of Evaluation In this experiment, durability tests for cleaning performance were performed using various cleaning devices. The degree of contamination of the secondary transfer roller and secondary transfer belt after printing 100,000 sheets of an image having a B / W ratio of 5% and the degree of filming were observed. Here, the B / W ratio refers to the ratio of the area of the image (black; image portion) to the paper surface (White; image portion + non-image portion).

2. Evaluation machine As an evaluation machine, a modified version of Bizhub (registered trademark) C450 (manufactured by Konica Minolta) was used. The modified contents are that the secondary transfer roller can be replaced so that various secondary transfer rollers or secondary transfer belts can be attached, and a cleaning device is added to the secondary transfer roller or secondary transfer belt. This means that a bias can be applied to the collecting roller.

2-1. Foaming roller The foaming roller used in the cleaning device of the present embodiment is composed of a cored bar and an elastic layer covering the periphery thereof. The outer diameter of the foam roller is 18.5 mm. The outer diameter of the cored bar is 8.0 mm. The elastic layer is made of the polyurethane foam according to the present invention.

The raw material used for manufacturing the polyurethane foam will be described. In this experiment, polyurethane foam was produced from the following raw materials.
Polyol: Polyether polyol (trade name Actol ED-37B (number average molecular weight 3000); manufactured by Mitsui Takeda Chemical)
Isocyanate: Methylenediphenyl diisocyanate (MDI)
(Product name Millionate MTL-S; made by Nippon Polyurethane)
Amine-based catalyst (Brand name Kao Raiser No.23NP; manufactured by Kao)
Organic hydrochloric acid catalyst (trade name EP73660A; manufactured by PANTECHNOLOGY)
Foam stabilizer: linear dimethylpolysiloxane (trade name Niaxsilicone L5614; manufactured by GE Silicones)
Water: ion exchange water, distilled water, tap water, etc.

The definition and measurement method of the physical properties of the polyurethane foam in this example are as follows. The average cell diameter was determined by measuring 100 cut surfaces of the polyurethane foam with a scanning electron microscope (SEM). The cell wall aperture ratio is expressed by the following equation.
Cell wall opening ratio = (opening area S1) / (total area S) × 100
Opening area S1: Area of the opening on the cell wall
Total area S: The open area ratio of the cell wall surface of the cell area was determined by observing the cut surface of the polyurethane foam with a scanning electron microscope (SEM).

Table 1 shows the blending ratio of the raw materials for the polyurethane foam used in this experiment and the physical properties of the polyurethane foam produced from the raw materials. In addition, carbon black was blended so that the volume resistivity of all samples was 1.0 × 10 ⁵ Ωcm.

2-2. Brush roller Two types of brush roller F and brush roller G were used as the brush roller in the cleaning device of this example. They are as follows.
Brush roller F
Core: 11mm
Outer diameter: 18.5mm
Conductive nylon fiber Fiber density (37,200 / cm ² )
Brush roller G
Core: 11mm
Outer diameter: 18.5mm
Conductive polyester fiber Fiber density (21,700 / cm ² )

2-3. Other conditions Negatively charged cyan toner was used as the toner. The average particle size is 6.5 μm. Conductive polyimide was used as a raw material for the intermediate transfer belt. The rotational speed of the intermediate transfer belt was set to 250 mm / s. As a power source for applying a bias to the collection roller, a constant current power source of plus 40 μA was used. If the current value to be set is small, the toner cannot be collected sufficiently. On the other hand, if the current value to be set is large, the toner once collected is reversely charged. As a result, a force pulled from the cleaning member to the secondary transfer member is received, and it adheres again to the secondary transfer member. Therefore, suitable cleaning cannot be performed. In this experiment, a constant current power supply was used, but a constant voltage power supply may be used.

  Further, gradation 255/255 is set as the maximum value of the image density setting. The primary transfer current was set to +30 μA, and the secondary transfer current was set to −40 μA.

  A cleaning member disposed on the upstream side of the rotation as viewed from the secondary transfer belt is referred to as a first cleaning member. The cleaning member disposed on the downstream side of the rotation is referred to as a second cleaning member. In Table 2, the first cleaning member is referred to as “first cleaning”, and the second cleaning member is referred to as “second cleaning”.

  As shown in Table 2, the amounts of the first cleaning member and the second cleaning member that bite into the secondary transfer member were both 1.3 mm. The first cleaning member and the second cleaning member are rotated around the counter with respect to the rotation direction of the secondary transfer member. The rotational speeds of the first cleaning member and the second cleaning member were both 250 mm / s. That is, it is the same as the rotation speed of the intermediate transfer belt.

  As shown in Table 2, the amount of the first cleaning member and the second cleaning member biting into the collection roller was also 1.3 m. The first cleaning member and the second cleaning member are rotated in the forward direction with respect to the rotation direction of the collection roller.

3. Experimental Results A specific evaluation method in this experiment will be described. In this experiment, a belt-like pattern having a width of 1 cm and a length of 20 cm was used as a reference patch. Then, the reference patches were formed at the back, center, and front positions in the width direction of the intermediate transfer belt. The portion of the intermediate transfer belt on which the reference patch was formed was passed through the portion of the secondary transfer member without passing the paper. The evaluator was forcibly stopped when a part of the secondary transfer roller or the secondary transfer belt in contact with the reference patch passed the cleaning member. Then, the toner adhering to the surface of the secondary transfer roller or the secondary transfer belt that passed through the cleaning member was collected. In other words, the part of the secondary transfer roller or the secondary transfer belt where the toner of the reference patch seems to have adhered was examined after the surface was wiped off by the cleaning member.

  The cleaning property was evaluated as follows. The toner on the secondary transfer roller or the secondary transfer belt was collected with a booker tape, and then affixed to the same mount. The color difference was measured with a spectrocolorimeter CM-512m3 (manufactured by Konica Minolta Sensing). There are a total of nine locations where toner is collected. That is, the toner is collected from three locations of the three reference patches at the back, center, and front in the width direction of the intermediate transfer belt. In FIG. 2, the location where these toners are collected is selected from an area downstream of the brush roller 142 and upstream of the location where the secondary transfer roller 115 faces the roller 103. Then, the case where the color difference ΔE ≦ 0.7 or less at all nine locations was determined as “◯”. If ΔE> 0.7 even at one location, “×” was assigned.

  The experimental results of this experiment are shown in Table 3. In Table 3, “100K” means that the cleaning performance and filming were evaluated after printing out 100,000 sheets. Filming here means that the toner adhering to the surface of the secondary transfer member melts and covers part or all of the surface of the secondary transfer member. When filming occurs, the secondary transfer member cannot perform suitable transfer.

  Filming was evaluated as follows. The surface of the secondary transfer roller or the secondary transfer belt after the above test for evaluating the cleaning property was observed. Here, the evaluation was made based on two points: 1) presence or absence of adhered matter such as toner, and 2) color difference. “○” was given when there was no adhered toner or the like visually and the color difference ΔE ≦ 5 between the start and end of the test in the cleaning property evaluation. “X” is given when there is an adhering substance such as toner or when the color difference ΔE> 5 between the start and end of the test in the evaluation of the cleaning property. The spectral colorimeter CM-512m3 was also used when measuring this color difference.

3-1) Example 1
In Example 1, the foam roller B shown in Table 1 was used as the first cleaning member, and the brush roller F was used as the second cleaning member. In Example 1, the cleaning performance of the secondary transfer roller and the secondary transfer belt was good. In addition, filming does not occur.

3-2) Example 2
In Example 2, the foam roller C shown in Table 1 was used as the first cleaning member, and the brush roller F was used as the second cleaning member. In Example 2, the cleaning performance of the secondary transfer roller and the secondary transfer belt was good. In addition, filming does not occur.

3-3) Example 3
In Example 3, the foam roller D shown in Table 1 was used as the first cleaning member, and the brush roller F was used as the second cleaning member. In Example 3, the cleaning performance of the secondary transfer roller and the secondary transfer belt was good. In addition, filming does not occur.

3-4) Example 4
In Example 4, the foam roller B shown in Table 1 was used as the first cleaning member, and the brush roller G was used as the second cleaning member. In Example 4, the cleaning performance of the secondary transfer roller and the secondary transfer belt was good. In addition, filming does not occur.

3-5) Example 5
In Example 5, the foam roller C shown in Table 1 was used as the first cleaning member, and the brush roller G was used as the second cleaning member. In Example 5, the cleaning performance of the secondary transfer roller and the secondary transfer belt was good. In addition, filming does not occur.

3-6) Example 6
In Example 6, the foam roller D shown in Table 1 was used as the first cleaning member, and the brush roller G was used as the second cleaning member. In Example 6, the cleaning performance of the secondary transfer roller and the secondary transfer belt was good. In addition, filming does not occur.

3-7) Comparative Example 1
In Comparative Example 1, the brush roller F was used as the first cleaning member, and the brush roller F was used as the second cleaning member. Comparative Example 1 is different from the cleaning device according to the present invention in that a brush roller is used as the first cleaning member. In Comparative Example 1, there was a problem with the cleaning performance of the secondary transfer roller and the secondary transfer belt. Filming also occurred.

3-8) Comparative Example 2
In Comparative Example 2, the brush roller G was used as the first cleaning member, and the brush roller G was used as the second cleaning member. Comparative Example 2 is different from the cleaning device according to the present invention in that a brush roller is used as the first cleaning member. In Comparative Example 2, there was a problem with the cleaning performance of the secondary transfer roller and the secondary transfer belt. Filming also occurred.

3-9) Comparative Example 3
In Comparative Example 3, the foam roller A was used as the first cleaning member, and the brush roller F was used as the second cleaning member. In Comparative Example 3, the opening ratio of the cell wall surface of the foaming roller A of the first cleaning member is smaller than that of the cleaning device according to the present invention. In Comparative Example 3, there was a problem with the cleaning performance of the secondary transfer roller and the secondary transfer belt. However, filming has not occurred.

3-10) Comparative Example 4
In Comparative Example 4, the foam roller E was used as the first cleaning member, and the brush roller F was used as the second cleaning member. In Comparative Example 4, the opening ratio of the cell wall surface of the foaming roller E of the first cleaning member is larger than that of the cleaning device according to the present invention. In Comparative Example 4, there was a problem with the cleaning performance of the secondary transfer roller and the secondary transfer belt. Further, no filming occurred on the secondary transfer roller, but filming occurred on the secondary transfer belt.

3-11) Comparative Example 5
In Comparative Example 5, the foam roller A was used as the first cleaning member, and the brush roller G was used as the second cleaning member. In Comparative Example 5, the opening ratio of the cell wall surface of the foaming roller A of the first cleaning member is smaller than that of the cleaning device according to the present invention. In Comparative Example 5, there was a problem with the cleaning performance of the secondary transfer roller and the secondary transfer belt. However, filming has not occurred.

3-12) Comparative Example 6
In Comparative Example 6, the foam roller E was used as the first cleaning member, and the brush roller G was used as the second cleaning member. In Comparative Example 6, the opening ratio of the cell wall surface of the foaming roller E of the first cleaning member is larger than that of the cleaning device according to the present invention. In Comparative Example 6, there was a problem with the cleaning performance of the secondary transfer roller and the secondary transfer belt. Filming did not occur on the secondary transfer roller, but filming occurred on the secondary transfer belt.

  As described above in detail, when the aperture ratio of the cell wall surface of the foaming roller is in the range of 5 to 50% in this embodiment, the secondary transfer member is suitably cleaned.

DESCRIPTION OF SYMBOLS 1 ... Image forming part 100 ... Image forming apparatus 115 ... Secondary transfer roller 140 ... Cleaning apparatus 141 ... Foaming roller 142 ... Brush roller 143 ... Collection roller 151, 152 ... Voltage application part 215 ... Secondary transfer belt

Claims (4)

An image forming unit that forms a toner image, an image carrier that carries the toner image formed by the image forming unit, a transfer member that transfers the toner image carried on the image carrier to a recording medium, and the transfer member An image forming apparatus having a cleaning member for cleaning the surface of the transfer member in contact with a portion other than the contact portion with the image carrier in
The cleaning member has a first cleaning member on the upstream side and a second cleaning member on the downstream side in the rotational direction of the transfer member,
The first cleaning member is a foaming roller using a polyurethane foam as a surface layer in a range of 5 to 50% in the opening ratio of the cell wall surface;
The second cleaning member is a brush roller;
A voltage is applied between the transfer member and the first cleaning member in a direction that pulls the normally charged toner to the first cleaning member.
An image forming apparatus comprising: a voltage application unit that applies a voltage in a direction in which the normally charged toner is pulled to the second cleaning member between the transfer member and the second cleaning member. The image forming apparatus according to claim 1,
An image forming apparatus, wherein a part of the surface of the first cleaning member and a part of the surface of the second cleaning member are arranged to rotate in contact with each other. A transfer member that transfers the toner image carried on the image carrier to a recording medium, and a cleaning member that contacts a portion of the transfer member other than the contact portion with the image carrier to clean the surface of the transfer member. Having a cleaning device,
The cleaning member has a first cleaning member on the upstream side and a second cleaning member on the downstream side in the rotational direction of the transfer member,
The first cleaning member is a foaming roller using a polyurethane foam as a surface layer in a range of 5 to 50% in the opening ratio of the cell wall surface;
The second cleaning member is a brush roller;
A voltage is applied between the transfer member and the first cleaning member in a direction to pull the normally charged toner to the first cleaning member.
A cleaning device, wherein a voltage is applied between the transfer member and the second cleaning member in a direction for pulling the normally charged toner to the second cleaning member. The cleaning device according to claim 3,
A cleaning device, wherein the cleaning device is arranged to rotate in a state in which a part of the surface of the first cleaning member and a part of the surface of the second cleaning member are in contact with each other.

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