Image forming device

Abstract

To reduce an occurrence of an image defect caused by a paper dust removal roller.SOLUTION: A paper dust collection unit 16 includes a paper dust removal roller 17 that can be charged and hold a charge, a sponge 53 that charges the paper dust removal roller 17, and an opposing roller 18 that forms a pressure nip portion while facing the paper dust removal roller 17 and conveys a recording material P. A printer 100 collects paper dust D on the recording material P by electrostatically adsorbing it to the paper dust removal roller 17 in the pressure nip portion, and includes an air blower fan 58 that blows air from the outside to the inside of the image forming device printer 100, the paper dust removal roller 17 has a cavity inside, the air blower fan 58 is arranged at one end of the cavity in a direction perpendicular to a conveying direction, and the paper dust removal roller 17 is cooled by air flowing inside the cavity from one end to the other end.SELECTED DRAWING: Figure 5

Description

[Technical field]

[0001] The present invention relates to an image forming apparatus, such as a laser beam printer, a copying machine, or a facsimile machine, that uses an electrophotographic system. [Background technology]

[0002] Conventionally, in an image forming apparatus using an electrophotographic method, a toner image is formed on an image carrier such as a photosensitive drum by an appropriate image forming process. This toner image is transferred to a recording material by a transfer means, and is fixed on the recording material by a fixing device having a heating means as a fixing means, and then output from the main body of the image forming apparatus as an image formed product. Such an image forming apparatus generally has a double-sided printing mechanism that can form an image on the back side of the recording material by inverting the recording material in the apparatus after forming an image on the front side of the recording material.

[0003] PPC (Plain Paper Copier) paper is used as a recording material for an image forming apparatus using an electrophotographic method. PPC paper usually contains powder called paper dust. In order to ensure good image formation, an image forming apparatus equipped with a paper dust collection unit for capturing paper dust on the recording material is known. For example, Patent Document 1 discloses a configuration in which a paper dust removal roller having approximately the same width as the recording material is provided as a paper dust collection unit upstream of the recording material reaching the photosensitive drum. The paper dust removal roller is rubbed with a charging member such as a sponge to be frictionally charged, thereby electrostatically adsorbing the paper dust on the recording material. Furthermore, a configuration is disclosed in which the paper dust removal roller also functions as a registration roller that adjusts the timing of feeding the recording material. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2010-23987 A Summary of the Invention [Problem to be solved by the invention]

[0005] In recent years, image forming apparatuses are required to be highly productive. As the speed increases due to high productivity, the number of sheets passing through the paper dust removing roller per unit time increases. In such a situation, when the recording material is continuously printed on both sides, the frequency with which the recording material heated and warmed by the fixing unit passes through the paper dust removing roller again per unit time increases. Therefore, the amount of heat transferred from the recording material also increases, and the temperature rise of the paper dust removing roller is likely to become noticeable. When the temperature of the paper dust removing roller increases, the recording material may enter the transfer section at a high temperature without being absorbed by the paper dust removing roller. In this case, the developing section in contact with the photosensitive drum and the toner stored therein may be thermally affected and deteriorated. As a result, there is a problem that development failure occurs and the density of the image part decreases. In addition, another problem with increasing the speed is that the frequency with which the recording material passes through the paper dust removing roller increases, and a large amount of moisture contained in the recording material may adhere to the paper dust removing roller. As a result, there is a problem that the charging performance of the paper dust removing roller decreases and the paper dust collecting performance decreases.

[0006] The present invention has been made under these circumstances, and has an object to reduce the occurrence of image defects caused by the paper dust removing roller. [Means for solving the problem]

[0007] In order to solve the above-mentioned problems, the present invention has the following configuration.

[0008] (1) An image forming apparatus comprising: an image forming unit which forms an image on a recording material; and a paper dust collection unit provided upstream of the image forming unit in a transport direction of the recording material, the paper dust collection unit having a paper dust removal roller which can be charged and hold an electric charge, a charging member which charges the paper dust removal roller, and an opposing member which forms a nip portion opposite the paper dust removal roller and transports the recording material, the image forming apparatus collecting paper dust on the recording material at the nip portion by electrostatically attracting it to the paper dust removal roller, the image forming apparatus further comprising: a blowing means which blows air from the outside to the inside of the image forming apparatus, the paper dust removal roller having a cavity therein, the blowing means being disposed at one end of the cavity in a direction perpendicular to the transport direction, the paper dust removal roller being cooled by air flowing inside the cavity from the one end to the other end.

[0009] (2) An image forming apparatus comprising: an image forming unit which forms an image on a recording material; and a paper dust collection unit provided upstream of the image forming unit in the transport direction of the recording material, the paper dust collection unit having a paper dust removal roller which can be charged and hold an electric charge; a charging member which charges the paper dust removal roller; and an opposing member which forms a nip portion opposite the paper dust removal roller and transports the recording material, the image forming apparatus collecting paper dust on the recording material at the nip portion by electrostatically adsorbing it to the paper dust removal roller, the image forming apparatus further comprising: a blowing means which blows air from the outside to the inside of the image forming apparatus; and a duct which guides the air blown by the blowing means to the surface of the paper dust removal roller. Effect of the Invention

[0010] According to the present invention, it is possible to reduce the occurrence of image defects caused by the paper dust removing roller. [Brief description of the drawings]

[0011] [Figure 1] Schematic cross-sectional view of an image forming apparatus according to first and second embodiments [Diagram 2] Cross-sectional view of the paper dust collection unit of the first embodiment [Diagram 3] Schematic diagram of the screw in Examples 1 and 2 [Figure 4] Schematic diagram of the paper dust recovery unit in the conveying direction in the first and second embodiments. [Diagram 5] FIG. 1 shows the position of the blower fan and the airflow in the first embodiment. [Figure 6] Cross-sectional view of the paper dust collection unit of the second embodiment [Figure 7] FIG. 2 shows the roller duct of the second embodiment. [Figure 8] FIG. 13 is a diagram showing the airflow of a blower fan according to a second embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS EXAMPLES

[0012] Hereinafter, the embodiments of the present invention will be described with reference to the drawings. Note that the following embodiments do not limit the invention according to the claims, and all combinations of features described in the embodiments are not necessarily essential to the solution of the invention.

[0013] <Image forming device> An outline of the overall configuration of an image forming apparatus according to the first embodiment will be described. Fig. 1 shows an example of an image forming apparatus according to the present invention. The image forming apparatus shown in Fig. 1 is an electrophotographic full-color four-color laser printer, and Fig. 1 is a cross-sectional schematic diagram showing the outline of the image forming apparatus. The image forming apparatus according to the present invention may be an electrophotographic laser printer, an electrophotographic copier, a facsimile, or an electrostatic recording printer, a copier, a facsimile, or the like.

[0014] A laser printer 100 (hereinafter referred to as the printer 100) as an image forming apparatus shown in FIG. 1 includes four process cartridges 5Y, 5M, 5C, and 5K in order from the right side along the conveying direction R of the recording material P. The four process cartridges 5Y, 5M, 5C, and 5K as image forming units have the same structure, but are different in that they form images using toners (developers) of different colors, that is, yellow (Y), magenta (M), cyan (C), and black (K). In addition, the reference characters YMCK will be omitted hereinafter except when a specific cartridge is described. Each process cartridge 5 includes a photosensitive drum 1 as a photosensitive body, a charging roller 2, a developing roller 3, and a toner container 4. An exposure device 6 arranged above the process cartridge 5 exposes the photosensitive drum 1 based on an image signal corresponding to each image data of yellow, magenta, cyan, and black.

[0015] During the rotation process, the photosensitive drum 1 is uniformly charged to a predetermined polarity and a predetermined potential by the charging roller 2. After that, the photosensitive drum 1 is exposed by the exposure device 6 to form electrostatic latent images corresponding to the first to fourth color component images (yellow, magenta, cyan, and black color component images) of the target color image. The charging roller 2 rotates in accordance with the rotation of the photosensitive drum 1. In the developing section, the electrostatic latent image formed on the photosensitive drum 1 is developed into a toner image by attaching toner in a toner container 4 via the developing rollers 3 of the first to fourth cartridges Y, M, C, and K. The toner in each developing section is a negatively charged non-magnetic one-component toner, and the electrostatic latent image is developed by a non-magnetic one-component contact development method. A voltage is applied to the developing roller 3 by a power source (not shown), thereby performing development.

[0016] The transfer device 7 has a conveyor belt 8 that moves (rotates) in a circular motion so as to face and contact the photosensitive drum 1. In the first embodiment, the conveyor belt 8 is made of polyimide. The conveyor belt 8 is stretched over two rollers 9 and 10. The conveyor belt 8 rotates with a recording material P placed on its outer circumferential surface.

[0017] Four transfer rollers 11 are disposed inside the conveyor belt 8 at positions corresponding to the photosensitive drums 1. These transfer rollers 11 are in contact with the rear side of the conveyor belt 8, and sandwich the conveyor belt 8 between the photosensitive drums 1 and the transfer rollers 11. As a result, a transfer portion (transfer nip portion) is formed between the photosensitive drums 1 and the conveyor belt 8. In the first embodiment, a transfer voltage of positive polarity is applied to the transfer rollers 11 by a transfer voltage application power source (not shown), and as a result, each color toner image of negative polarity on the photosensitive drum 1 is transferred sequentially onto the recording material P at the transfer portion.

[0018] A feeding and conveying device 12 is disposed at the bottom of the printer 100. The feeding and conveying device 12 has a paper feed roller 14 that feeds the recording material P from a paper feed cassette 13 that stores the recording material P, and a pair of conveying rollers 15 that convey the fed recording material P. A paper dust collection unit 16 serving as a paper dust collection section is disposed downstream of the pair of conveying rollers 15 in the conveying direction. The paper dust collection unit 16 is provided upstream of the process cartridge 5 in the conveying direction R of the recording material P.

[0019] The paper dust collection unit 16 includes a paper dust removal roller 17 and an opposing roller 18. The paper dust removal roller 17 has a function of conveying the recording material P, and also has a function of a registration roller (registration function) that adjusts the timing of feeding the recording material P. The opposing roller 18 functions as an opposing member that faces the paper dust removal roller 17 and forms a pressure nip portion (nip portion). The paper dust removal roller 17 is also a part of the paper dust collection unit 16 that removes paper dust from the recording material P. The paper dust removal roller 17 is a roller that can be charged and hold a charge. The paper dust collection unit 16 also has a sponge 53 as a charging member that charges the paper dust removal roller 17 (charging member). The paper dust collection unit 16 collects paper dust from the recording material P by electrostatically adsorbing it to the paper dust removal roller 17 in the pressure nip portion. The paper dust collection unit 16 will be described in detail later.

[0020] During image formation, the recording materials P in the paper feed cassette 13 are separated and fed one by one, and are stopped once by their leading ends hitting the pair of paper dust removal roller 17 and opposing roller 18, forming a loop. Thereafter, the recording materials P are supplied to the conveyor belt 8 by the pair of paper dust removal roller 17 and opposing roller 18, which also function as registration rollers, in synchronization with the rotation of the conveyor belt 8 and the image writing position on the photosensitive drum 1.

[0021] The recording material P supplied to the conveyor belt 8 has each color toner image transferred thereon as it passes through the process cartridges 5Y, 5M, 5C, and 5K. The recording material P that has passed through the process cartridge 5K located at the most downstream position in the conveying direction is separated from the conveyor belt 8. A fixing unit 19 is disposed on the most downstream side of the conveyor belt 8.

[0022] The fixing device 19 fixes the multi-color toner images transferred onto the recording material P, and has a rotating fixing roller (heating roller) 20 and a pressure roller 21 that is pressed against the fixing roller 20 to apply heat and pressure to the recording material P. That is, the recording material P onto which the toner images of the respective colors on the photosensitive drum 1 have been transferred so as to be superimposed one on top of the other is heated and pressurized while being sandwiched and conveyed by the fixing roller 20 and the pressure roller 21 as it passes through the fixing device 19, so that the multi-color toner images are fixed onto the surface.

[0023] When it is specified that an image is formed on only one side of the recording material P, the recording material P on which the toner image is fixed after passing through the fixing unit 19 passes through the conveying roller pair 22, is conveyed to the discharging / reversing roller pair 23, and is discharged and stacked on the discharging tray 24 with the image formed side facing down. When it is specified that an image is also formed on the back side of the recording material P, the conveying direction of the recording material P is reversed by the discharging / reversing roller pair 23, and the recording material P is guided to a double-sided conveying path 25. The recording material P is conveyed again to the conveying roller pair 15 by the double-sided conveying roller pairs 26, 27, and 28. After the conveying roller pair 15, the same process as when an image is formed on the front side of the recording material P is performed, and the recording material P is discharged outside the printer 100 after passing through the fixing unit 19.

[0024] <Explanation of the paper dust collection unit> The configuration of the paper powder collection unit 16 will be described. Fig. 2 is a cross-sectional view of the paper powder collection unit 16. In the first embodiment, the paper powder removal roller 17 has a cavity Sp therein. The details will be described below.

[0025] The paper dust removing roller 17 has a surface layer 52 and a metal roller 51 that is disposed inside the surface layer 52 and forms a cavity Sp. The metal roller 51 has a three-arrow pipe shape, and it is possible to send air into the cavity Sp from a pipe opening at the end of the metal roller 51 in the direction of the rotation axis by a blower fan 58 (see FIG. 5) described later. The surface layer 52 is a tube made of fluororesin that is easily charged, and covers the metal roller 51.

[0026] Paper dust removing roller 17 rotates in the direction of arrow A, and opposing roller 18 rotates in the direction of arrow B, so that the opposing surfaces rotate in the same direction to transport recording material P. Sponge 53, which is a charging member, uses urethane foam resin that easily charges surface layer 52 of paper dust removing roller 17. Sponge 53 is in contact with paper dust removing roller 17, and paper dust removing roller 17 is frictionally charged as paper dust removing roller 17 rotates. When recording material P is sandwiched between paper dust removing roller 17 and opposing roller 18 and transported, paper dust D adhering to recording material P is electrostatically attracted and adheres to paper dust removing roller 17, which is frictionally charged.

[0027] Support member 54 supports sponge 53 and is biased by spring 55 toward paper-powder removing roller 17, so that sponge 53 is pressed against surface layer 52 of paper-powder removing roller 17 to scrape off paper dust D adhering to the surface. The scraped off paper dust D is accumulated in the space around screw 57 inside cover 56.

[0028] FIG. 3 is a schematic diagram of the screw 57. The screw 57 has a long, thin cylindrical shaft 57a on which a spiral rib 57b is formed. The rib 57b is formed so that the spiral direction is reversed with respect to the center of the screw 57 in the longitudinal direction. When the screw 57 rotates, the paper dust D scraped off by the sponge 53 is transported toward both ends in the width direction of the recording material P. The screw 57 rotates in the direction of arrow C shown in FIG. 2. Here, the width direction is a direction perpendicular to the transport direction R of the recording material P. The paper dust D transported to both ends of the screw 57 is collected in paper dust collection boxes (not shown) arranged at both ends of the screw 57. The cover 56 covers the paper dust removing roller 17 and the screw 57, thereby playing a role in preventing the paper dust D from scattering.

[0029] 4 is a schematic diagram of the paper dust collection unit 16 in the longitudinal direction (the width direction described above). The width Lr of the paper dust removal roller 17 is wider than the width Lp of the recording material P so that the paper dust D can be removed from the entire surface of the recording material P (Lr>Lp). The sponge 53 is provided across the entire width of the paper dust removal roller 17 so that the entire area of ​​the paper dust removal roller 17 is frictionally charged. The width Ls of the screw 57 is longer in the width direction of the recording material P than the width Lr of the paper dust removal roller 17 (Ls>Lp). As described above, the paper dust D transported to both ends in the width direction by the screw 57 is stored in paper dust collection boxes (not shown) at both ends of the screw 57.

[0030] <Air duct of blower fan> The cooling of the paper dust removing roller 17, which is a feature of the first embodiment, will now be described. Fig. 5(a) is a side view of the printer 100. The blower fan 58 is a blower means for cooling the paper dust removing roller 17 by generating air by rotating, and supplies air from the outside to the inside of the printer 100. The blower fan 58 is disposed on the side of the printer 100 body.

[0031] FIG. 5(b) is a schematic diagram showing the airflow of the blower fan 58. The blower fan 58 and the duct 59 are disposed at one end 17a of the cavity Sp in a direction perpendicular to the conveying direction R. The duct 59 guides the air sent by the blower fan 58 to the cavity Sp. As a result, the air from the blower fan 58 flows inside the cavity Sp from one end 17a to the other end 17b. The duct 59 guides the air sent by the blower fan 58 to the paper dust removing roller 17. More specifically, the duct 59 is disposed to collect the air generated by the blower fan 58 and guide it into the cavity Sp of the paper dust removing roller 17. The arrows shown in FIG. 5(b) indicate the flow of the air generated by the blower fan 58. Note that M is a position where the speed of the air is measured (hereinafter, referred to as the wind speed measuring position M), which will be described later.

[0032] The air guided into the cavity Sp of the paper-powder removing roller 17 blows directly onto the metal roller 51, which has high thermal conductivity, making it possible to efficiently air-cool the paper-powder removing roller 17. The cooled paper-powder removing roller 17 can remove heat from the recording material P that passes through the paper-powder removing roller 17, making it possible to suppress a rise in temperature of the photosensitive drum 1, which comes into contact with the recording material P immediately after the recording material P is removed, and the developing unit around the photosensitive drum 1. Also, deterioration of the toner stored in the developing unit can be suppressed.

[0033] <Explanation of verification study> The verification results of Example 1 will be described. The occurrence of defects caused by the temperature rise of the paper dust removing roller 17 was compared depending on whether or not the blower fan 58 was used. The verification was carried out in an environment of a temperature of 23° C. and a humidity of 60%. Table 1 shows the results of the test for the recording material P (Xerox Vitality 75 g / m 2 The figures show the results of verifying the temperature and image density of the surface layer 52 of the paper dust removing roller 17 and the surface of the developing roller 3 when 1000 sheets were transported (passed) in continuous double-sided printing using a paper size paper (letter size paper). The temperature of the surface layer 52 of the paper dust removing roller 17 and the surface temperature of the developing roller 3 were measured with a thermocouple. The image density was measured by outputting a solid black image and using a spectrodensitometer X-RITE504 (manufactured by X-RITE).

[0034] [Table 1] As a comparative example, double-sided continuous printing was performed without rotating the blower fan 58. When the first sheet was printed on both sides, the temperature of the outer layer 52 of the paper dust removing roller 17 and the surface temperature of the developing roller 3 were both 23°C in both Example 1 and the comparative example. In addition, when the first sheet was printed on both sides, the image density was 1.4.

[0035] In contrast, as the time of double-sided continuous printing, in other words the number of sheets, increases, when recording material P heated and fixed by fixing unit 19 passes paper-powder removing roller 17, the heat of recording material P is transferred to paper-powder removing roller 17, causing the temperature of paper-powder removing roller 17 to rise. In addition, the surface temperature of developing roller 3 also increases.

[0036] In the comparative example, the temperature of the paper dust removing roller 17 was 45°C when 1000 sheets were printed on both sides. In addition, since the recording material P passed over the photosensitive drum 1 without being cooled, the temperature of the photosensitive drum 1 also rose, and the temperature of the photosensitive drum 1 was also transferred to the developing roller 3, so that the temperature of the developing roller 3 also rose to 45°C. When the temperature of the developing roller 3 rose, the toner in the toner container 4 was thermally affected and deteriorated, causing a problem of reduced density in the image area. While the image density of the first sheet was 1.4, the image density of the 1000th sheet when printed on both sides fell to 1.1.

[0037] On the other hand, in Example 1, double-sided continuous printing was performed while rotating the blower fan 58 to cool the paper dust removing roller 17. The temperature of the paper dust removing roller 17 after double-sided printing of 1000 sheets was 32°C. Since the temperature rise of the paper dust removing roller 17 could be suppressed, the recording material P could be cooled when passing through the paper dust removing roller 17, and the temperature of the developing roller 3 after double-sided printing of 1000 sheets was 35°C. As a result, the toner was not thermally affected, and the image density after double-sided printing of the 1000th sheet was 1.4, and no problem of density reduction occurred.

[0038] In Example 1, the wind speed when the blower fan 58 was rotated was 0.1 m / s. This wind speed was measured in the space between the duct 59 and the paper dust removing roller 17 by placing an anemometer at the wind speed measurement position M shown in Fig. 5(b) to measure the wind guided into the cavity Sp of the paper dust removing roller 17. The anemometer used was a multi-point Anemomaster PRO MODEL1590 (manufactured by Nippon Kanomax Co., Ltd.).

[0039] As described above, according to the first embodiment, it is possible to provide an image forming apparatus capable of preventing the temperature rise of the paper dust removing roller 17. Note that the first embodiment has been described using a color image forming apparatus of a conveyor belt type in which a toner image is transferred to the recording material P while conveying the recording material P using the conveyor belt 8, but the present invention is not limited to this configuration. For example, it may be a color image forming apparatus of an intermediate transfer type in which a toner image is transferred to an intermediate transfer belt, and then the toner is transferred from the intermediate transfer belt to the recording material P at once. Furthermore, the present invention may be applied to a monochrome image forming apparatus that does not have a conveyor belt 8.

[0040] As described above, according to the first embodiment, it is possible to reduce the occurrence of image defects caused by the paper dust removing roller. EXAMPLES

[0041] <Explanation of the paper dust collection unit> The basic configuration and operation of the image forming apparatus of the second embodiment are the same as those of the printer 100 of the first embodiment. Therefore, in the image forming apparatus of the second embodiment, elements having the same or corresponding functions or configurations as those of the printer 100 of the first embodiment are denoted by the same reference numerals as those of the first embodiment, and detailed explanations are omitted. The second embodiment aims to provide a printer 100 capable of maintaining the charging performance of the paper dust removing roller 17 even in a high humidity environment.

[0042] FIG. 6 is a cross-sectional view of the paper dust collection unit 70 in the second embodiment. The roller duct 71 is provided downstream of the pressurized nip portion in the conveying direction R and upstream of the position where the paper dust removal roller 17 and the sponge 53 contact each other in the rotation direction of the paper dust removal roller 17. The wind generated by the blower fan 58 is guided to the surface layer 52 of the paper dust removal roller 17 through the roller duct 71. In the second embodiment, the position where the wind is blown onto the paper dust removal roller 17 is between the downstream of the nip portion between the paper dust removal roller 17 and the opposing roller 18 in the conveying direction R and the upstream side of the sponge 53 in the conveying direction. By removing moisture from the paper dust removal roller 17 at this position, adhesion of moisture to the sponge 53 is suppressed, and the deterioration of the charging performance of the sponge 53, which is a charging member, is prevented. The position where the wind is blown onto the paper dust removal roller 17 is not limited to the position in the second embodiment as long as it can prevent the deterioration of the charging performance of the sponge 53, which is a charging member.

[0043] <Roller duct> FIG. 7(a) is a cross-sectional view of the roller duct 71 in the short direction. The roller duct 71 is provided with a cavity 72 through which the wind generated by the blower fan 58 passes. FIG. 7(b) is a longitudinal view of the roller duct 71 and a diagram showing the relationship with the width Lp of the recording material P. The roller duct 71 has a plurality of holes H so that the wind passing through the roller duct 71 can hit the surface of the paper dust removing roller 17 in the longitudinal direction. In the second embodiment, the area Lh where the holes H of the roller duct 71 are opened is wider than the width Lp of the recording material P (Lh>Lp) so that the wind can hit the area where the recording material P and the paper dust removing roller 17 contact each other. Note that the area Lh where the holes H of the roller duct 71 are opened may have a width that can remove moisture from the paper dust removing roller 17, and the area Lh where the holes H of the roller duct 71 are opened is not limited to a width relationship.

[0044] <Air duct of blower fan> 8 is a schematic diagram showing an airflow of the blower fan 58 in the second embodiment. In the second embodiment, the paper powder collection unit 70 has a roller duct 71 as a duct that blows the air introduced by the inlet duct 73 against the surface of the paper powder removing roller 17. The blower fan 58 and the inlet duct 73 are disposed at one end 71a of the roller duct 71 in a direction perpendicular to the conveying direction R. The roller duct 71 has an area Lh in which a plurality of holes H are provided. As a result, the air from the blower fan 58 blows against the surface of the paper powder removing roller 17 through the plurality of holes H while flowing inside the roller duct 71 from one end 71a to the other end 71b.

[0045] The blower fan 58 is a blowing means that generates air by rotating to remove moisture adhering to the surface layer 52 of the paper dust removing roller 17. The blower fan 58 is disposed on the side of the printer 100 body, similar to the first embodiment. Note that N is a position where the wind speed is measured (hereinafter, referred to as wind speed measurement position N), which will be described later.

[0046] The inlet duct 73 guides the air blown by the blower fan 58 to the paper dust removing roller 17. More specifically, the inlet duct 73 is disposed to guide the air generated by the blower fan 58 to the surface layer 52 of the paper dust removing roller 17. The arrows in the drawing indicate the airflow in which the air generated by the blower fan 58 is guided by the inlet duct 73 to the roller duct 71, and the air blows out from multiple holes H of the roller duct 71 to hit the surface of the surface layer 52 of the paper dust removing roller 17.

[0047] By blowing air onto surface layer 52 of paper-powder removing roller 17, it is possible to remove moisture adhering to surface layer 52 of paper-powder removing roller 17. Therefore, even if recording material P that has absorbed moisture in a high humidity environment passes through paper-powder removing roller 17 and moisture adheres to surface layer 52 of paper-powder removing roller 17, the moisture can be efficiently removed by air blown by blower fan 58. As a result, it is possible to prevent a decrease in the charging performance of sponge 53, which is a charging member, and to exhibit stable paper-powder collection performance.

[0048] <Explanation of verification study> The verification results of Example 2 will be described. The occurrence of a defect phenomenon caused by an increase in the amount of moisture contained in the recording material P adhering to the paper dust removing roller 17 was compared with and without the blower fan 58. Recording material P (Vitality 75 g / m manufactured by XEROX) left in a high humidity environment of 30° C. and 80% was 2 The moisture content of the recording material P was 9%. The moisture content was measured using a moisture meter MOISTEREX MX8000 (manufactured by INFRARED ENGINEERING).

[0049] To compare the charging performance of the paper-powder removing roller 17, the surface potential of the paper-powder removing roller 17 was measured. The surface potential was measured using a high-speed surface potential meter Model 370 (manufactured by TREK Corporation). The larger the absolute value of the surface potential, the easier it is to electrostatically adsorb paper dust D, and therefore the better the paper-powder collection performance. Table 2 shows the results of verifying the surface potential of the paper-powder removing roller 17 and the charging failure, which is a defect, when 1,000 sheets were passed through in continuous single-sided printing.

[0050] [Table 2] For the first sheet, in both Example 2 and the comparative example, the surface potential of the paper dust removing roller 17 was −3000 V, and no image defects due to charging defects occurred ("not occurred").

[0051] As a comparative example, continuous one-sided printing was performed without rotating the blower fan 58. The surface potential of the paper-powder removing roller 17 was -3000V for the first sheet, while it was -1500V for the 1000th sheet, so that the absolute value decreased. When the recording material P passed through the paper-powder removing roller 17, the amount of moisture contained in the recording material P that adhered to the paper-powder removing roller 17 increased, the charging performance of the paper-powder removing roller 17 decreased, and the paper-powder collecting performance decreased. Since the amount of paper powder that could not be collected by the paper-powder removing roller 17 increased, the amount of paper powder transferred to the photosensitive drum 1 increased, and the paper powder adhered to the charging roller 2, causing an image defect due to poor charging ("occurred").

[0052] On the other hand, in Example 2, continuous single-sided printing was performed while rotating the blower fan 58 to blow air onto the surface layer 52 of the paper-powder removing roller 17. Even if moisture from the left-behind paper adhered to the paper-powder removing roller 17, the moisture could be removed by blowing air onto the surface layer 52 of the paper-powder removing roller 17, and therefore a decrease in the charging performance of the paper-powder removing roller 17 could be suppressed. The surface potential of the paper-powder removing roller 17 after single-sided printing of 1000 sheets was -2500V, and a decrease in the charging performance of the paper-powder removing roller 17 could be suppressed. No charging problems occurred due to paper powder D adhering to the charging roller 2 ("not occurring").

[0053] In Example 2, the wind speed when the blower fan 58 was rotated was 0.05 m / s. This wind speed was measured by placing an anemometer at the wind speed measurement position N shown in Fig. 8, and measuring the wind blowing out of the hole H of the roller duct 71 and hitting the surface of the outer layer 52 of the paper dust removing roller 17. A multi-point Anemometer, Anemomaster PRO MODEL1590 (manufactured by Nippon Kanomax Co., Ltd.), was used as the anemometer.

[0054] As described above, according to the second embodiment, it is possible to provide an image forming apparatus that blows air onto the paper-powder removing roller 17, reduces the amount of moisture adhering to the surface layer 52 of the paper-powder removing roller 17, and exhibits stable paper-powder collecting performance. In the second embodiment, the air generated by the blower fan 58 is guided to the roller duct 71 by the inlet duct 73, and the air blows out from the multiple holes H of the roller duct 71, so that the air hits the surface of the surface layer 52 of the paper-powder removing roller 17. However, the blower is not limited to the blower fan 58. In addition, the configuration is not limited to the roller duct 71, the holes H of the roller duct 71, and the inlet duct 73, and it is sufficient if the amount of moisture adhering to the surface layer 52 of the paper-powder removing roller 17 can be reduced. Furthermore, the air from the blower fan 58 may be configured to be blown into the inside of the paper-powder removing roller 17 while also being blown to the roller duct 71.

[0055] As described above, according to the second embodiment, it is possible to reduce the occurrence of image defects caused by the paper dust removing roller.

[0056] The disclosure of this embodiment includes the following configuration. (Configuration 1) an image forming section for forming an image on a recording material; a paper dust collecting section provided upstream of the image forming section in a conveying direction of the recording material; Equipped with the paper dust collecting unit includes a paper dust removing roller that is electrically charged and can hold an electric charge, a charging member that charges the paper dust removing roller, and an opposing member that forms a nip portion facing the paper dust removing roller and conveys a recording material, and collects paper dust from the recording material at the nip portion by electrostatically attracting it to the paper dust removing roller, in an image forming apparatus, a blower for blowing air from the outside to the inside of the image forming apparatus, The paper dust removing roller has a cavity therein, The air blowing means is disposed at one end of the cavity in a direction perpendicular to the conveying direction, The image forming apparatus according to claim 1, wherein the paper-dust removing roller is cooled by air flowing through the interior of the cavity from the one end to the other end. (Configuration 2) The above-mentioned image forming apparatus, wherein the paper dust removing roller has a surface layer and a metal roller that is covered with the surface layer and forms the cavity. (Configuration 3) an image forming section for forming an image on a recording material; a paper dust collecting section provided upstream of the image forming section in a conveying direction of the recording material; Equipped with the paper dust collecting unit includes a paper dust removing roller that is electrically charged and can hold an electric charge, a charging member that charges the paper dust removing roller, and an opposing member that forms a nip portion facing the paper dust removing roller and conveys a recording material, and collects paper dust from the recording material at the nip portion by electrostatically attracting it to the paper dust removing roller, in an image forming apparatus, a blowing unit for blowing air from the outside to the inside of the image forming apparatus; a duct for guiding the air sent by the air blowing means to the surface of the paper dust removing roller. (Configuration 4) The image forming apparatus described above, wherein the paper powder recovery unit includes the duct. (Configuration 5) The air blowing means is disposed at one end of the duct in a direction perpendicular to the conveying direction, the duct has an area with a plurality of holes; The image forming apparatus as described above, wherein the air flows through the duct from one end to the other end and impinges on the surface of the paper dust removing roller through the plurality of holes. (Configuration 6) The above-mentioned image forming apparatus, characterized in that the duct is provided downstream of the nip portion in the conveying direction and upstream of a position where the paper powder removing roller and the charging member abut in the rotation direction of the paper powder removing roller. (Configuration 7) The image forming apparatus according to any one of the above, wherein the region is longer than the width of the recording material in a width direction perpendicular to the transport direction. (Configuration 8) The image forming apparatus according to any one of the above, wherein the paper dust removing roller is longer than the width of the recording material in a width direction perpendicular to the conveying direction. (Configuration 9) The image forming apparatus according to any one of the above, wherein the paper dust removing roller is longer than the width of the recording material in a width direction perpendicular to the conveying direction. (Configuration 10) The image forming apparatus according to any one of the above, wherein the paper dust collecting section has a registration function for adjusting a timing of feeding the recording material. (Configuration 11) The image forming apparatus according to any one of the above, wherein the paper dust collecting section has a registration function for adjusting a timing of feeding the recording material. [Explanation of symbols]

[0057] 5 Process cartridge 16 Paper dust collection unit 17 Paper dust removal roller 53 Sponge 58 Blower fan

Claims

1. an image forming section for forming an image on a recording material; a paper dust collecting section provided upstream of the image forming section in a conveying direction of the recording material; Equipped with the paper dust collecting unit includes a paper dust removing roller that is electrically charged and can hold an electric charge, a charging member that charges the paper dust removing roller, and an opposing member that forms a nip portion facing the paper dust removing roller and conveys a recording material, and collects paper dust from the recording material at the nip portion by electrostatically attracting it to the paper dust removing roller, in an image forming apparatus, a blower for blowing air from the outside to the inside of the image forming apparatus, The paper dust removing roller has a cavity therein, The air blowing means is disposed at one end of the cavity in a direction perpendicular to the conveying direction, The image forming apparatus according to claim 1, wherein the paper-dust removing roller is cooled by air flowing through the interior of the cavity from the one end to the other end.

2. 2. The image forming apparatus according to claim 1, wherein the paper dust removing roller has a surface layer and a metal roller that is covered with the surface layer and forms the cavity.

3. an image forming section for forming an image on a recording material; a paper dust collecting section provided upstream of the image forming section in a conveying direction of the recording material; Equipped with the paper dust collecting unit includes a paper dust removing roller that is electrically charged and can hold an electric charge, a charging member that charges the paper dust removing roller, and an opposing member that forms a nip portion facing the paper dust removing roller and conveys a recording material, and collects paper dust from the recording material at the nip portion by electrostatically attracting it to the paper dust removing roller, in an image forming apparatus, a blowing unit for blowing air from the outside to the inside of the image forming apparatus; a duct for guiding the air sent by the air blowing means to the surface of the paper dust removing roller.

4. The image forming apparatus according to claim 3 , wherein the paper dust collecting section includes the duct.

5. The air blowing means is disposed at one end of the duct in a direction perpendicular to the conveying direction, the duct has an area with a plurality of holes; 5. The image forming apparatus according to claim 4, wherein the air flows through the duct from the one end to the other end and impinges on the surface of the paper dust removing roller through the plurality of holes.

6. 6. The image forming apparatus according to claim 5, wherein the duct is provided downstream of the nip portion in the transport direction and upstream of a position where the paper dust removing roller and the charging member abut in the rotation direction of the paper dust removing roller.

7. 6. The image forming apparatus according to claim 5, wherein the area is longer than a width of the recording material in a width direction perpendicular to the transport direction.

8. 2. The image forming apparatus according to claim 1, wherein the paper dust removing roller is longer than a width of the recording material in a width direction perpendicular to the conveying direction.

9. 4. The image forming apparatus according to claim 3, wherein the paper dust removing roller is longer than a width of the recording material in a width direction perpendicular to the transport direction.

10. 2. The image forming apparatus according to claim 1, wherein the paper dust collecting section has a registration function for adjusting a timing of feeding the recording material.

11. 4. The image forming apparatus according to claim 3, wherein the paper dust collecting section has a registration function for adjusting a timing of feeding the recording material.

Images