JP2005266353A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent occurrence of deletion such as image streaming or void by removing an electric discharge generation thing stuck on a surface of an image carrier. <P>SOLUTION: Four image forming units 12 comprise rotary brushes 34 each of which rotates in contact with a surface of a photosensitive body 13. The rotary brush 34 is rotated with a driving force from a rotary brush rotating motor 56, and the photosensitive body 13 is rotated with a driving force from a photosensitive body motor 58. The rotary brush 34 moves closer to and back from the photosensitive body 14 by moving a pedestal 70 through the rotation of the rotary brush rotating motor 54. A control circuit 52 accelerates and rotates rotary brush motors 56C, M, Y rather than a printing time using image units 12C, M, Y not to be printed while printing one image forming unit 12K and rotates photosensitive body motors 58C, M, Y at the same speed as the printing time. Furthermore, the rotary brush rotating motors 54C, M, Y are rotated to move the rotary brushes 34 to the side of the photosensitive body 13. Thus, frictional force of the rotary brushes 34 to the photosensitive body 13 increases and an electric discharge generation thing on the surface of the photosensitive body 13 is scraped off by the rotary brushes 34. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an image forming apparatus including a plurality of image forming units in which a contact charging device, an exposure device, a developing device, a transfer device, and the like are arranged around an image carrier.

  In image forming apparatuses such as copying machines and printers that employ an electrophotographic method, the surface of an image carrier such as a photoconductor is uniformly charged by a contact charging device, and then the image carrier is irradiated with image light. Then, an electrostatic latent image is formed, and the electrostatic latent image is developed by a developing device to form a toner image. The toner image on the image carrier is transferred onto a recording medium by a transfer device.

  Each image forming unit includes a plurality of image forming units each including a contact charging device, an exposure device, a developing device, and a transfer device arranged around a plurality of image carriers. The toner image formed in step 1 is primarily transferred onto the intermediate transfer member and superimposed, and the toner image on the intermediate transfer member is secondarily transferred to a recording medium.

  By the way, in the contact-type charging, there is a problem that a discharge product is generated on the surface of the image carrier, and the discharge product causes a defocus such as image flow or white spot in a high temperature and high humidity environment. The reason for the depression is that the resistance of the surface of the image carrier is reduced by the hydrophilic discharge product in a high temperature and high humidity environment. This depletion causes a full-surface image carrier flow in a severe case, and an image with deteriorated graininess in a slight case. In particular, when AC charging is performed, discharge products are likely to be generated as compared to DC charging, and the occurrence of depletion becomes significant.

  As a countermeasure against depletion, a method is adopted in which a rotating brush is brought into contact with the surface of the image carrier and rotated to scrape discharge products. However, if the rotary brush is pressed strongly against the image carrier to rotate it in order to increase the scraping power of the discharge products, the image carrier is subject to uneven wear, and streak-like image quality defects occur early.

  On the other hand, although it is not assumed to be depletion, in a tandem type image forming apparatus, for example, when it corresponds to an image forming area, it is charged by adding AC to DC, and when it corresponds to a non-image area, AC is applied. There is proposed a method in which the battery is cut and charged only by DC (see, for example, Patent Document 1 and Patent Document 2). This method is intended to improve the life of the image carrier by performing DC charging with less wear of the image carrier outside the image forming area.

In this method, the generation of discharge products can be reduced by performing DC charging. However, since the discharge products generated in the image forming area due to AC charging are not scraped off, depletion still occurs.
JP-A-8-190252 JP-A-8-137204

  The present invention has been made in view of the above-described problems, and by preventing discharge products from being removed without reducing the life of the image carrier, it is possible to prevent the occurrence of depression such as image flow and white spots. An object of the present invention is to provide an image forming apparatus capable of performing the above.

  In order to solve the above problems, the invention described in claim 1 is characterized in that a two-component developer comprising an image carrier on which an electrostatic latent image is formed after charging by a contact charging member, and a toner and a carrier is formed on the surface. A developing roller that rotates while adhering and develops the electrostatic latent image with toner, a transfer member that transfers the developed toner image onto the transfer member, and a rotation that disturbs residual toner on the surface of the image carrier after the transfer. An image forming apparatus having a plurality of image forming units having a fixed brush, wherein the contact member is in contact with the surface of the image carrier, and the frictional force of the contact member is increased to generate a discharge product. During the printing of the frictional force changing means to be removed and at least one image forming unit, the image carrier of another image forming unit that is not printed is rotated, and the frictional force changing means is driven to drive the friction member changing means. Image carrier It is characterized by having a control means for increasing the frictional force against the body.

  Here, the transfer member includes a recording medium such as a sheet in addition to the intermediate transfer member and the intermediate transfer belt onto which the toner image is transferred.

  According to the first aspect of the present invention, during printing of at least one image forming unit, the image carrier of another image forming unit that is not printed is rotated and the frictional force changing means is driven to Increase the frictional force against the image carrier. Thereby, during printing in at least one image forming unit, in another image forming unit that is not printed, the discharge product on the surface of the image carrier is scraped off by the contact member. For this reason, discharge products are efficiently removed without interrupting normal printing. As a result, deterioration of the graininess of the image and the occurrence of depression such as image flow and white spots are prevented, and a high-quality image can be stably obtained. Further, since the contact member is not always pressed against the surface of the image carrier, the life of the image carrier is extended.

  According to a second aspect of the present invention, in the configuration according to the first aspect, the control unit rotates the image carriers of all the image forming units at the start of the operation of the image forming apparatus and changes the frictional force. The means is driven to increase the frictional force of the contact member against the image carrier.

  Here, when the operation of the image forming apparatus starts, it means when the power of the image forming apparatus is turned on, when the image forming apparatus operates, and when the operation starts after the image forming apparatus has been on standby for a long time.

  According to the second aspect of the present invention, at the start of the operation of the image forming apparatus, the image carriers of all the image generation units are rotated using the fact that all the image generation units are not printing, and the friction force The frictional force of the contact member against the image carrier is increased by the changing means. Thereby, discharge products on the surface of the image carrier can be efficiently removed in all image forming units during non-printing without interrupting normal image printing.

  According to a third aspect of the present invention, in the configuration according to the first or second aspect, the abutting member is a rotating brush, and the frictional force changing means has a rotating shaft of the rotating brush on the image carrier side. It is characterized by being a brush moving means for moving to.

  According to the third aspect of the present invention, the rotating shaft of the rotary brush is moved toward the image carrier by the brush moving means, and the frictional force of the rotary brush against the image carrier is increased. As a result, the discharge product on the surface of the image carrier is scraped off by the rotary brush, thereby preventing the occurrence of depression.

  According to a fourth aspect of the present invention, in the configuration according to the first to third aspects, the contact member is a rotating brush, and the frictional force changing means is a relative movement of the rotating brush with respect to the image carrier. It is characterized by a brush rotating means for increasing the speed.

  According to the fourth aspect of the present invention, the frictional force of the rotary brush with respect to the image carrier is increased by increasing the relative moving speed of the rotary brush with respect to the image carrier with the brush rotating means. As a result, the discharge product on the surface of the image carrier is scraped off by the rotary brush, thereby preventing the occurrence of depression.

  According to a fifth aspect of the present invention, in the configuration according to the first or second aspect, the contact member is a two-component developer carried on a developing roller, and the frictional force changing means is the two-component developer. It is a developer pressing force increasing means for increasing the pressing force of the developer against the image carrier.

  According to the fifth aspect of the present invention, by increasing the pressing force of the two-component developer carried on the developing roller against the image carrier by the developer pushing force increasing means, the friction of the two-component developer against the image carrier is increased. Increase power. As a result, the discharge product on the surface of the image carrier is scraped off by the carrier of the two-component developer carried on the developing roller, thereby preventing the occurrence of depression.

  According to a sixth aspect of the present invention, in the configuration according to the first, second, or fifth aspect, the contact member is a two-component developer carried on a developing roller, and the frictional force changing means is The developing roller rotating means increases the relative movement speed of the developing roller with respect to the image carrier.

  According to the sixth aspect of the present invention, the frictional force of the two-component developer carried on the developing roller to the image carrier is increased by increasing the relative moving speed of the developing roller relative to the image carrier by the developing roller rotating means. increase. As a result, the discharge product on the surface of the image carrier is scraped off by the carrier of the two-component developer carried on the developing roller, thereby preventing the occurrence of depression.

  According to a seventh aspect of the present invention, in the configuration according to the first or second aspect, the contact member is a transfer member, and the frictional force changing means is a belt-shaped transfer that contacts the image carrier. It is a transfer member moving means for pressing the body to the image carrier side.

  According to the seventh aspect of the present invention, the transfer member is moved by the transfer member moving means and the belt-like transfer member is pressed toward the image carrier, thereby increasing the frictional force of the belt-like transfer member against the image carrier. Let As a result, the discharge product on the surface of the image carrier is scraped off by the belt-shaped transfer member, thereby preventing the occurrence of depression.

  According to an eighth aspect of the present invention, in the configuration according to the first or second aspect, the abutting member is a discharge product removing member, and the frictional force changing means is configured to replace the discharge product removing member with the image. It is a removing member moving means for contacting the carrier.

  According to the eighth aspect of the present invention, the discharge product removing member is brought into contact with the image carrier by the removing member moving means, and the frictional force against the image carrier is increased. As a result, the discharge product on the surface of the image carrier is scraped off by the discharge product removing member, thereby preventing the occurrence of depression.

  According to a ninth aspect of the present invention, in the configuration of the eighth aspect, the discharge product removing member is a pad, a fixed brush, or a blade that contacts the image carrier to remove the discharge product. It is a feature.

  According to the ninth aspect of the present invention, the discharge product on the surface of the image carrier is efficiently scraped by bringing the pad, the fixed brush, or the blade into contact with the image carrier. For this reason, the occurrence of depression is prevented. Further, since the pad, the fixed brush or the blade is not always in contact with the image carrier, it is possible to prevent the life of the image carrier from decreasing.

  According to a tenth aspect of the present invention, in the configuration according to the first or second aspect, the control means rotates the image carrier at an increased or decreased speed.

  According to the tenth aspect of the present invention, it is possible to increase the frictional force of the contact member against the image carrier by increasing or decreasing the speed of the image carrier. For this reason, the discharge product on the surface of the image carrier is scraped off by the contact member, thereby preventing the occurrence of depression.

  According to an eleventh aspect of the present invention, in the configuration according to the first to tenth aspects, when the frictional force changing means increases the frictional force against the image carrier and removes the discharge product, the contact is made. It is characterized in that the current applied to the charging member is reduced.

  According to the eleventh aspect of the present invention, it is possible to reduce the occurrence of discharge products on the surface of the image carrier by reducing the current applied to the contact charging member. For this reason, when the frictional force changing means increases the frictional force of the abutting member against the image carrier, no new discharge product is generated, so that the discharge product on the surface of the image carrier can be more reliably removed. Thereby, the occurrence of depression can be further prevented.

  Since the image forming apparatus according to the present invention is configured as described above, it is possible to prevent deterioration of image graininess due to adhesion of discharge products, and occurrence of depression such as image flow and white spots. A high-quality image can be obtained stably. Further, it is possible to prevent the life of the image carrier from being reduced.

  Hereinafter, a first embodiment of an image forming apparatus according to the present invention will be described with reference to the drawings.

  First, the overall configuration and outline of the image forming apparatus will be described first, and then the main part of the present invention will be described.

  As shown in FIG. 1, a color laser printer (hereinafter referred to as a printer) 10 as an image forming apparatus includes four image forming units 12C, 12M, 12Y, on which toner images of cyan, magenta, yellow, and black are formed. This is a so-called tandem type full-color laser printer in which 12K is arranged in parallel facing the intermediate transfer belt 14 and the toner images of four colors are superimposed while the intermediate transfer belt 14 makes one round.

  The printer 10 includes a paper feed tray 16 at the bottom. A paper feed roller 18 is in contact with the leading end of the paper P set in the paper feed tray 16 in the transport direction, and the paper P is fed one sheet at a time by the paper feed roller 18 and a paper handling means (not shown). Paper is fed from the tray 16 to the downstream side in the transport direction. Two sets of transport rollers 20 are arranged on the downstream side in the transport direction of the paper feed roller 18, and the paper P is transported to the upper transfer unit 22 by the transport force from the transport rollers 20.

  The transfer unit 22 is provided with a belt conveyance roller 24A around which the intermediate transfer belt 14 is wound, and a transfer roller 26 pressed against the belt conveyance roller 24A. The intermediate transfer belt 14 is sandwiched between the nip portion between the belt conveying roller 24A and the transfer roller 26, and the toner image is transferred from the intermediate transfer belt 14 when the sheet P passes through the nip portion.

  A fixing unit 28 is disposed above the transfer unit 22 and downstream in the transport direction. The fixing unit 28 is provided with a heat roller 28A that becomes high temperature and a backup roller 28B that is pressed against the heat roller 28A, and the sheet P passes through the nip portion between the heat roller 28A and the backup roller 28B. At this time, the toner is melted and solidified to be fixed on the paper P. Then, the paper P is discharged by a paper discharge roller 29 disposed on the downstream side in the transport direction of the fixing unit 28.

  Here, the printing unit 30 in which the four image forming units 12C, 12M, 12Y, and 12K superimpose the toner images on the intermediate transfer belt 14 will be described. In addition, when distinguishing each color of cyan, magenta, yellow, and black, explanation is made by adding C, M, Y, and K after the code. C, M, Y, and K are omitted.

  As shown in FIG. 2, the intermediate transfer belt 14 includes the above-described belt conveyance roller 24A, a belt conveyance roller 24B disposed below the belt conveyance roller 24A, and an obliquely upper side of the belt conveyance roller 24B and in the sheet conveyance path. It is wound around a belt conveying roller 24C disposed on the opposite side.

  Four image forming units 12C, 12M, 12Y, and 12K are arranged in parallel at a position facing the diagonally downward surface between the belt conveyance roller 24B and the belt conveyance roller 24C of the intermediate transfer belt 14. Yes. Each image forming unit 12 is provided with photoreceptors 13C, M, Y, and K on which toner images are formed. The photoreceptors 13C, M, Y, and K are in contact with the intermediate transfer belt 14, and the transfer roller 32 is pressed against the photoreceptors 13C, M, Y, and K via the intermediate transfer belt 14. The surface of the intermediate transfer belt 14 facing the photoconductors 13C, M, Y, and K is a transfer surface 14A on which a toner image is transferred from the photoconductors 13C, M, Y, and K.

  As shown in FIG. 3, the intermediate transfer belt 14, the rotating brush 34, the charging roller 36, and the developing roller 38 are in contact with the photosensitive surface 13 </ b> A of the photosensitive member 13 in order from the upstream side in the rotation direction. Between the charging roller 36 and the developing roller 38, an LED array head 40 that performs line exposure of the photosensitive surface 13A is disposed.

  The rotating brush 34 rotates in the direction opposite to the rotating direction of the photoconductor 13. That is, the rotating brush 34 rotates in the same direction as the photoconductor 13 at the nip portion with the photoconductor 13.

  As shown in FIG. 7, the developing roller 38 includes a magnet roller 45 inside the rotating sleeve 44, and the rotating sleeve 44 rotates in the reverse direction with respect to the photosensitive member 13 at the nip portion with the photosensitive member 13. doing. On the surface of the developing roller 38, the magnetic carrier C is adsorbed in a spike shape by the magnetic force of the magnet roller 45, and the toner T adheres to the magnetic carrier C to form a two-component developer magnetic brush. The adhesion amount of the magnetic brush carried on the developing roller 38 is regulated by a trimmer 39 provided in the developing device 41 (see FIG. 3), and the magnetic brush is conveyed to a developing area in contact with the photoreceptor 13. In the developing area, the toner T attached to the magnetic carrier C is transferred to the electrostatic latent image formed on the photosensitive surface 13A. The two-component developer carried on the developing roller 38 rotates in the reverse direction at the nip portion with the photosensitive member 13, thereby improving the residual toner recoverability due to the scraping action of the magnetic carrier C.

  On the other hand, in the discharge product removal mode described later, as shown in FIG. 3, the control circuit 52 rotates the rotating brush moving motor 54 to move the rotating shaft 34A of the rotating brush 34 to the photosensitive member 13 side. Will be described in detail later.

  Hereinafter, a flow until the toner image is transferred to the intermediate transfer belt 14 will be described.

  When the photosensitive member 13 rotates counterclockwise in FIG. 5A, first, the photosensitive surface 13A is uniformly charged to a predetermined polarity potential by the charging roller 36 to which a voltage obtained by adding AC to DC is applied. When the photosensitive member 13 further rotates, the charged surface of the photosensitive surface 13A is exposed by the LED array head 40, and the potential of the exposed portion of the charged surface is lowered to form an electrostatic latent image. Thereafter, the electrostatic latent image is developed by electrically attaching the developing toner T1 charged to the same polarity as the charged polarity of the photosensitive member 13 to the potential lowering portion of the charging surface by the developing roller 38. When the photosensitive member 13 further rotates, the toner is electrically attracted to the transfer roller 32 to which a transfer voltage having a polarity opposite to that of the toner is applied. As a result, the toner image on the photoreceptor 13 is transferred to the intermediate transfer belt 14.

  When the toner image is transferred from the photoconductor 13 to the intermediate transfer belt 14, untransferred toner T <b> 2 that remains on the photoconductor 13 without being transferred to the intermediate transfer belt 14 is generated. Further, retransfer toner (hereinafter referred to as retra toner) T3 is generated in which the toner transferred on the upstream side to the intermediate transfer belt 14 is offset to the downstream photoconductor 13.

  The transfer residual toner T2 and the retraction toner T3 are removed from the photoreceptor 13 as follows. As shown in FIG. 5B, a voltage (for example, −500 V) having a polarity opposite to the polarity (for example, +) of the retractor toner T3 is applied to the rotating brush 34 to electrically adsorb the retractor toner T3 to the rotating brush 34. Further, the transfer residual toner T <b> 2 passes through the charging area by the charging roller 36 and the exposure area by the LED array head 40 while being attached to the photoreceptor 13. That is, charging and exposure are performed while the transfer residual toner T2 remains attached to the photosensitive member 13.

  As shown in FIG. 6A, the transfer residual toner T2 attached to the non-exposed non-image portion (for example, −500V) is electrically collected by the developing roller 38 to which a voltage of −400V is applied, for example. Then, it is detached from the developing roller 38 by the repulsive magnetic pole of the magnet roller 45 in the developing device 41 and scraped off to the toner containing portion 49. At the same time, the developing roller 38 moves the developing toner T1 to the potential lowering portion of the photosensitive surface 13A. Thus, a toner image can be formed while removing the transfer residual toner T2 from the photosensitive member 13.

  The re-toner T3 temporarily held on the rotating brush 34 is removed in the cleaning mode or at the job end. As shown in FIG. 6B, first, the polarity of the applied voltage of the rotating brush 34 is reversed from minus (−) to plus (+), and the retraction toner T3 charged to + from the rotating brush 34 to the photosensitive member 13 is loaded. Release. Then, by turning off the minus (−) voltage applied to the developing roller 38, the retraction toner T3 is allowed to pass through the portion facing the developing roller 38. Then, the voltage polarity of the transfer roller 32 is reversed from plus (+) to minus (−) and transferred to the intermediate transfer belt 14. Thereafter, the re-toner T3 is collected by the cleaner 42 (see FIG. 2) on the intermediate transfer belt 14.

  5 and 6 schematically show the developing toner T1, the transfer residual toner T2, and the retractor toner T3 for easy understanding of the flow of the toner image.

In such a printer 10, when the photosensitive surface 13A of the photosensitive member 13 is contact-charged by the charging roller 36, discharge products such as O ₃ and NO _X are generated. If this discharge product is left attached to the photosensitive member 13, a degeneration such as image flow or white spot occurs. Therefore, in the present invention, the following discharge product removal mechanism 50 is provided.

  As shown in FIG. 2, the printer 10 includes four rotating brush moving motors 54C, M, Y, K, four rotating brush rotating motors 56C, M, Y, K, and four photosensitive member motors 58C. , M, Y and K are provided with a control circuit 52 comprising a CPU for controlling the rotation.

  The rotating brush rotation motors 56C, M, Y, and K are stepping motors that can finely adjust the rotation speed. The image forming units 12C, M are driven by the driving force from the rotating brush rotation motors 56C, M, Y, and K. , Y, K rotary brushes 34 rotate. Similarly, the photoconductor motors 58C, M, Y, and K are stepping motors capable of finely adjusting the rotation speed, and the photoconductors 13C, M, Y, and K are driven by the driving force from the photoconductor motors 58C, M, Y, and K. K rotates. The rotational speeds of the rotary brush rotating motors 56C, M, Y, K and the photoreceptor motors 58C, M, Y, K are controlled by the control circuit 52.

  During printing of one image forming unit 12 (for example, 12K), the control circuit 52 uses another image forming unit 12 (for example, 12C, M, Y) that does not print, and a photoreceptor motor 58 (for example, 58C, M, Y). ) Is rotated at the same speed as during printing, and the rotating brush rotating motor 56 (for example, 56C, M, Y) is rotated at a speed higher than that during printing. As a result, the other image forming unit 12 that does not print is in the discharge product removal mode, the relative movement speed of the rotary brush 34 with respect to the photoconductor 13 increases, and the frictional force of the rotary brush 34 on the photoconductor 13 increases. In the present embodiment, the rotation speed of the rotary brush 34 is set to 200 mm / sec during printing, but in the discharge product removal mode, the rotation speed is increased twice as much as the printing speed. The rotational speed of the photosensitive member 13 is set to 100 mm / sec during printing and in the discharge product removal mode.

  As shown in FIG. 4, the rotating shaft 34A of the rotating brush 34 is supported by bearings 60 at both ends, and a gear 68 is provided on the rotating shaft 34A. The gear 68 meshes with a gear 66 provided coaxially with the rotary brush rotating motor 56. As a result, the driving force of the rotating brush rotating motor 56 is transmitted to the rotating brush 34 via the gear 66 and the gear 68, and the rotating brush 34 rotates.

  The bearing 60 is fixedly supported on a base 70, and the base 70 is movable along a rail 72 provided on a frame (not shown) of the printer 10. A rack and pinion 64 is formed in the width direction of the base 70 (direction perpendicular to the axis of the photosensitive member 13). A gear 62 provided coaxially with the rotary brush moving motor 54 meshes with the rack and pinion 64.

  During the printing of one image forming unit 12 (for example, 12K), another image forming unit 12 (for example, 12C, M, Y) that is not printed is in the discharge product removal mode, and the control circuit 52 has a rotating brush moving motor 54 ( For example, 54C, M, Y) are rotated. As a result, the gear 62 rotates in the arrow direction, and the rack and pinion 64 meshes with the gear 62, whereby the base 70 moves in the arrow direction. Due to the movement of the base 70, the rotation shaft 34 </ b> A of the rotary brush 34 approaches the photoconductor 13 and the frictional force of the rotary brush 34 against the photoconductor 13 increases.

  On the other hand, during printing, the rotating brush moving motor 54 is rotated in the reverse direction and the gear 62 is rotated in the reverse direction, thereby moving the base 70 in the direction opposite to the arrow. As a result, the rotating shaft 34A of the rotating brush 34 is retracted from the photoreceptor 13, and the frictional force of the rotating brush 34 on the photoreceptor 13 is reduced. In this embodiment, the rotating brush 34 is φ10 mm, the brush is made of nylon, and the amount of biting of the rotating brush 34 with respect to the photosensitive member 13 is 0.3 mm at the time of printing and 0.5 mm in the discharge product removal mode. ing.

  Next, the operation of the printer 10 provided with the discharge product removal mechanism 50 will be described.

  Among the plurality of image forming units 12C, M, Y, and K, for example, when performing black and white printing by the image forming unit 12K, the other image forming units 12C, M, and Y that are not printed are in the discharge product removal mode. In the discharge product removal mode, the control circuit 52 rotates the rotating brush rotating motors 56C, M, and Y to rotate and rotate the rotating brushes 34 of the image forming units 12C, M, and Y faster than during printing. At the same time, the photoreceptor motors 58C, M, and Y are rotated, and the photoreceptors 13C, M, and Y are rotated at the same speed as during printing. Further, the control circuit 52 rotates the rotary brush moving motors 54C, M, Y to move the rotary brushes 34 of the image forming units 12C, M, Y to the photosensitive member 13 side. As a result, the frictional force of the rotating brush 34 against the photoconductors 13C, M, and Y increases, and the discharge products attached to the surfaces of the photoconductors 13C, M, and Y are scraped off by the rotating brush 34.

  Further, when the operation of the printer 10 is started (when the printer is in operation or when the operation after standby is started), the discharge product removal mode is set in all of the image forming units 12C, M, Y, and K. The rotating brush 34 is moved to the photoconductors 13C, M, Y, K side by the same operation as described above. As a result, the frictional force of the rotating brush with respect to the photoreceptors 13C, M, Y, and K increases, and the discharge products attached to the surfaces of the photoreceptors 13C, M, Y, and K are scraped off by the rotating brush 34.

  In the discharge product removal mode, the voltage applied by the charging roller 36 is controlled to be small. Thereby, generation | occurrence | production of the discharge product by the charging roller 36 can be suppressed, and the removal effect of a discharge product can be improved.

  In such a printer 10, it is possible to suppress deterioration of image graininess and the occurrence of depression such as image flow and white spots, and it is possible to stably obtain high-quality images even under high temperature and high humidity. During printing, discharge products are removed by other non-printing image forming units 12, and discharge is generated by all image forming units 12C, M, Y, and K when the printer 10 starts operating (not printing). Since the object is removed, high productivity can be realized without interrupting normal printing. Further, since the frictional force of the rotating brush 34 is increased only in the discharge product removal mode, it is possible to prevent the life of the photoreceptor 13 from being reduced.

  In the first embodiment, the rotation speed of the rotary brush 34 is increased in the discharge product removal mode and the rotary brush 34 is moved to the photosensitive member 13 side. However, only one of them may be performed. Good. By either one of the operations, the frictional force of the rotating brush 34 against the photosensitive member 13 can be increased.

  In the first embodiment, in the discharge product removal mode, the rotation speed of the rotary brush 34 is increased as compared with the time of printing. However, the rotary brush rotation motor 56 is rotated in the reverse direction to print the rotation direction of the rotary brush 34. The direction may be opposite to the time. Thereby, the frictional force of the rotating brush 34 against the photosensitive member 13 can be increased.

  In the first embodiment, the photosensitive member 13 is rotated at the same speed as that in printing in the discharge product removal mode. However, the photosensitive member motor 58 is controlled to increase or decrease the speed of the photosensitive member 13. May be set. By increasing or decreasing the speed of the photosensitive member 13, the relative movement speed of the rotating brush 34 with respect to the photosensitive member 13 can be increased, and the discharge product on the surface of the photosensitive member 13 can be removed by the rotating brush 34.

  Next, a printer according to a second embodiment of the invention will be described with reference to the drawings.

  In addition, the same code | symbol is attached | subjected to the member same as 1st Embodiment, and the overlapping description is abbreviate | omitted.

  As shown in FIG. 8, the discharge product removal mechanism 80 of this printer includes four developing device moving solenoids 84C, M, Y, K and four developing roller rotating motors 86C, M, Y, K. A control circuit 82 for controlling the rotation of the four photoconductor motors 58C, M, Y, and K is provided.

  The developing roller rotating motors 86C, M, Y, and K are stepping motors that can finely adjust the rotation speed, and each image forming unit 12C, M is driven by the driving force from the developing roller rotating motors 86C, M, Y, and K. , Y and K developing rollers 38 rotate.

  During the printing of one image forming unit 12 (for example, 12K), the control circuit 82 uses another image forming unit 12 (for example, 12C, M, Y) that does not print, and the photoreceptor motor 58 (for example, 58C, M, Y). ) Is rotated at the same speed as during printing, and the developing roller rotating motor 86 (for example, 86C, M, Y) is rotated at a speed higher than that during printing. As a result, another image forming unit 12 that does not print is in the discharge product removal mode, and the relative movement speed of the developing roller 38 relative to the photoreceptor 13 increases. Then, the frictional force of the two-component developer (magnetic brush, see FIG. 7) carried on the developing roller 38 against the photosensitive member 13 increases. In the present embodiment, the rotation speed of the developing roller 38 is set to 100 mm / sec during printing, but in the discharge product removal mode, the rotation speed is increased twice as much as the printing speed. The rotational speed of the photosensitive member 13 is set to 100 mm / sec during printing and in the discharge product removal mode.

  A trimmer 92 is attached to the support 90 at a position opposed to the longitudinal direction of the developing roller 38, and the two-component developer carried on the developing roller 38 is regulated by the trimmer 92, and a portion facing the photoconductor 13. To be transported.

  As shown in FIG. 9, on the rear side of the developing device 41, developing device moving solenoids 84C, M, Y, K including a movable portion 88 are arranged. Protrusions 94 are provided on both sides of the developing device 41. Guide holes 98 are formed in the frames 96 on both sides of the printer 10, and the protrusions 94 can move along the guide holes 98. By energizing the developing device moving solenoids 84C, M, Y, and K based on a signal from the control circuit 82, the movable portion 88 expands and contracts, and the developing device 41 (developing roller 38) approaches or retracts from the photosensitive member 13. It is like that.

  During printing of one image forming unit 12 (for example, 12K), another image forming unit 12 (for example, 12C, M, Y) that is not printed is in a discharge product removal mode, and the developing device moves based on a signal from the control circuit 52 The power solenoid 84 (eg, 84C, M, Y) is energized. As a result, the movable portion 88 extends and the developing device 41 approaches the photoconductor 13. Due to the movement of the developing device 41, the rotation shaft 38A of the developing roller 38 moves to the photosensitive member 13 side, and the frictional force of the two-component developer carried on the developing roller 38 to the photosensitive member 13 increases. In the present embodiment, the developing roller 38 has a diameter of 18 mm, and the gap between the developing roller 38 and the photosensitive member 13 is 0.5 mm during printing and 0.35 mm in the discharge product removal mode.

  Next, the operation of the printer provided with the discharge product removal mechanism 80 will be described.

  Among the plurality of image forming units 12C, M, Y, and K, for example, when performing black and white printing by the image forming unit 12K, the other image forming units 12C, M, and Y that are not printed are in the discharge product removal mode. In the discharge product removal mode, the control circuit 82 accelerates and rotates the developing roller rotating motors 86C, M, and Y, and rotates the developing rollers 38 of the image forming units 12C, M, and Y faster than during printing. At the same time, the photoreceptor motors 58C, M, and Y are rotated, and the photoreceptors 13C, M, and Y are rotated at the same speed as during printing. Further, the control circuit 82 energizes the developing device moving solenoids 84C, M, Y to move the developing device 41 of the image forming units 12C, M, Y to the photosensitive member 13 side. As a result, the frictional force of the two-component developer carried on the developing roller 38 against the photoreceptors 13C, M, and Y increases, and the discharge product adhering to the surfaces of the photoreceptors 13C, M, and Y is the two-component developer. It is scraped off.

  Further, at the start of the operation of the printer 10, all the image forming units 12C, M, Y, K are in the discharge product removal mode, and the developing device 41 is moved to the photoreceptors 13C, M, Y, K side by the same operation as described above. Move. As a result, the frictional force of the two-component developer carried on the developing roller 38 against the photoreceptors 13C, M, Y, and K increases, and two discharge products adhered to the surfaces of the photoreceptors 13C, M, Y, and K are generated. Scraped with a component developer.

  In such a printer, it is possible to suppress the deterioration of the graininess of the image and the occurrence of a depression such as image flow or white spot, and it is possible to stably obtain a high-quality image even under high temperature and high humidity. In addition, during printing, the discharge products are removed by the other non-printing image forming units 12, and the discharge products are discharged by all the image forming units 12 </ b> C, M, Y, and K at the start of printer operation (non-printing). Therefore, high productivity can be realized without interrupting normal printing. Further, since the frictional force of the two-component developer carried on the developing roller 38 is increased only in the discharge product removal mode, it is possible to prevent the life of the photoreceptor 13 from being reduced.

  In the second embodiment, the rotation speed of the developing roller 38 is increased in the discharge product removal mode and the developing roller 38 is moved to the photosensitive member 13 side. However, only one of them may be performed. Good. By either one of the operations, the frictional force of the two-component developer carried on the developing roller 38 against the photosensitive member 13 can be increased.

  In the second embodiment, the photosensitive member 13 is rotated at the same speed as during printing in the discharge product removal mode. However, the photosensitive member 13 is set to increase in speed by controlling the photosensitive member motor 58. May be. By accelerating the photosensitive member 13, the relative moving speed of the two-component developer carried on the developing roller 38 with respect to the photosensitive member 13 can be increased, and the discharge products on the surface of the photosensitive member 13 can be removed.

  In the second embodiment, the developing roller 38 is set to rotate in the opposite direction at the portion facing the photoconductor 13, but the developing roller 38 rotates in the same direction at the portion facing the photoconductor 13. It can also be applied to printers. In this case, the friction force of the two-component developer against the photosensitive member 13 can be increased by rotating the developing roller 38 in the reverse direction in the discharge product removal mode.

  Further, in place of the configuration in which the developing roller 38 is moved to the photosensitive member 13 side, as shown in FIG. 10, a discharge product removing mechanism 100 that increases the weight of the two-component developer carried on the developing roller 38 is provided. Also good.

In this discharge product removing mechanism 100, a trimmer 106 is provided in the housing 110 of the developing device 41 in the vicinity of the developing roller 38, and can be brought into and out of contact with the developing roller 38 by guide means (not shown). Yes. The trimmer 106 extends to the outside of the housing 110 on the back side in the longitudinal direction, and a rack and pinion 107 is formed on the side of the trimmer 106. The rack and pinion 107 meshes with a gear 108 that is rotatably attached to the housing 110. The control circuit 102 rotates the gear 108 by rotating the developer adjusting motors 104C, M, Y, and K. The trimmer 106 moves in the vertical direction (the arrow direction in FIG. 10) by the rotation of the gear 108. As a result, the trimmer 106 can be retracted from the developing roller 38 and the layer thickness of the two-component developer can be increased. At the time of printing, the gears 108 are rotated in reverse by rotating the developer adjusting motors 104C, M, Y, and K in reverse. Thereby, the trimmer 106 approaches the developing roller 38, and the layer thickness of the two-component developer can be reduced. In the present embodiment, the weight of the two-component developer is set to 300 g / m ² during printing, and the weight of the two-component developer is set to 450 g / m ² in the discharge product removal mode.

  In such a discharge product removing mechanism 100, the trimmer 106 is moved backward from the developing roller 38 in the discharge product removing mode, and the weight of the two-component developer carried on the developing roller 38 is increased, so that the two-component developer is removed. The frictional force with respect to the photoreceptor 13 can be increased. Thereby, the discharge product on the surface of the photoreceptor 13 can be scraped off with the two-component developer.

  Next, a printer according to a third embodiment of the invention will be described with reference to the drawings.

  In addition, the same code | symbol is attached | subjected to the member same as 1st Embodiment, and the overlapping description is abbreviate | omitted.

  As shown in FIG. 11, the discharge product removal mechanism 120 of this printer controls the rotation of the four transfer roller moving solenoids 124C, M, Y, K and the photoreceptor motors 58C, M, Y, K. A control circuit 122 is provided.

  The transfer roller moving solenoids 124C, M, Y, and K move the transfer roller 32 close to and behind the photosensitive member 13 by the same mechanism as in FIG.

  During printing of one image forming unit 12 (for example, 12K), another image forming unit 12 (for example, 12C, M, Y) that is not printed is in a discharge product removal mode, and the transfer roller moves based on a signal from the control circuit 52 The solenoid 124 (for example, 124C, M, Y) is energized. As a result, the transfer roller 32 moves to the photoconductor 13 side, and the frictional force of the intermediate transfer belt 14 against the photoconductor 13 increases. In the present embodiment, the nip pressure of the transfer roller 32 with respect to the photosensitive member 13 is set to double that in printing in the discharge product removal mode.

  Next, the operation of the printer provided with the discharge product removal mechanism 120 will be described.

  Among the plurality of image forming units 12C, M, Y, and K, for example, when performing black and white printing by the image forming unit 12K, the other image forming units 12C, M, and Y that are not printed are in the discharge product removal mode. In the discharge product removal mode, the control circuit 122 rotates the photoconductor motors 58C, M, and Y and simultaneously energizes the transfer roller moving solenoids 124C, M, and Y to transfer the transfer rollers of the image forming units 12C, M, and Y. 32 is moved to the photosensitive member 13 side. As a result, the frictional force of the intermediate transfer belt 14 against the photoreceptors 13C, M, and Y increases, and the discharge product adhering to the surfaces of the photoreceptors 13C, M, and Y is scraped off by the intermediate transfer belt 14.

  When the operation of the printer 10 is started, the discharge product removal mode is set in all the image forming units 12C, M, Y, and K, and the transfer roller 32 is moved to the photoconductors 13C, M, Y, and K sides. As a result, the frictional force of the intermediate transfer belt 14 against the photoconductors 13C, M, Y, and K increases, and the discharge products adhering to the surfaces of the photoconductors 13C, M, Y, and K are scraped off by the intermediate transfer belt 14. .

  In such a printer, it is possible to suppress the deterioration of the graininess of the image and the occurrence of a depression such as image flow or white spot, and it is possible to stably obtain a high-quality image even under high temperature and high humidity. In addition, during printing, the discharge products are removed by the other non-printing image forming units 12, and the discharge products are discharged by all the image forming units 12 </ b> C, M, Y, and K at the start of printer operation (non-printing). Therefore, high productivity can be realized without interrupting normal printing. Further, since the transfer roller 32 is moved only in the discharge product removal mode and the frictional force of the intermediate transfer belt 14 is increased, it is possible to prevent the life of the photoreceptor 13 from being shortened.

  Next, a printer according to a fourth embodiment of the invention will be described with reference to the drawings.

  In addition, the same code | symbol is attached | subjected to the member same as 1st Embodiment, and the overlapping description is abbreviate | omitted.

  As shown in FIG. 12, the discharge product removal mechanism 140 of this printer is provided with a discharge product removal device 146 on the upstream side in the rotation direction from the rotating brushes 34 of the photoconductors 13C, M, Y, and K. .

  Further, four removal member motors 144C, M, Y, and K and a control circuit 142 that controls the rotation of the four photosensitive member motors 58C, M, Y, and K are provided.

  As shown in FIG. 13, the discharge product removing device 146 is provided with a pad 150 made of foaming synthetic resin in a housing 148. The pad 150 is fixed to a support body 152 that is movably supported in the housing 148. The support body 152 extends to the back side in the longitudinal direction of the housing 148, and a rack and pinion 153 is provided in the width direction of the support body 152 (a direction orthogonal to the longitudinal direction). The rack and pinion 153 meshes with a gear 154 that is rotatably attached to the housing 148. The gear 154 is connected to each removal member motor 144C, M, Y, K.

  During printing, the pad 150 is retracted from the photoreceptor 13. In the discharge product removal mode, the control circuit 142 rotates the removal member motors 144C, M, Y, and K, and rotates the gear 154 with the driving force. The rack and pinion 153 meshes with the gear 154 and the support 152 moves toward the photoconductor 13, whereby the pad 150 is pressed against the photoconductor 13.

  On the other hand, at the time of printing, the removal circuit motors 144C, M, Y, and K are reversely rotated by the control circuit 142, whereby the gear 154 is reversely rotated. As a result, the support 152 moves in the reverse direction, and the pad 150 is retracted from the photoreceptor 13.

  Next, the operation of the printer provided with the discharge product removal mechanism 140 will be described.

  Among the plurality of image forming units 12C, M, Y, and K, for example, when performing black and white printing by the image forming unit 12K, the other image forming units 12C, M, and Y that are not printed are in the discharge product removal mode. In the discharge product removal mode, the control circuit 142 rotates the photoconductor motors 58C, M, and Y, and simultaneously rotates the removal member motors 144C, M, and Y. As shown in FIG. 14, the gear 154 is rotated by the rotation of the removal member motors 144 </ b> C, M, and Y, and the pad 150 is pressed against the photoconductor 13. A frictional force is applied to the photoreceptors 13C, M, and Y by the pad 150, and discharge products attached to the surfaces of the photoreceptors 13C, M, and Y are scraped off by the pad 150.

  At the start of the operation of the printer 10, all image forming units 12C, M, Y, and K are in a discharge product removal mode, and the pad 150 is pressed by the photosensitive members 13C, M, Y, and K, thereby The discharge products adhering to the surfaces of 13C, M, Y, and K are scraped off by the pad 150.

  In such a printer, it is possible to suppress the deterioration of the graininess of the image and the occurrence of a depression such as image flow or white spot, and it is possible to stably obtain a high-quality image even under high temperature and high humidity. In addition, during printing, the discharge products are removed by the other non-printing image forming units 12, and the discharge products are discharged by all the image forming units 12 </ b> C, M, Y, and K at the start of printer operation (non-printing). Therefore, high productivity can be realized without interrupting normal printing. Further, since the pad 150 is pressed against the photoconductor 13 only in the discharge product removal mode, it is possible to prevent the life of the photoconductor 13 from being reduced.

  In the fourth embodiment, the pad 150 is provided in the discharge product removing device 146, but a blade or a fixed brush may be provided instead. The discharge product on the surface of the photoconductor can be similarly removed by retracting the blade or the fixed brush from the photoconductor 13 at the time of printing and pressing the blade or the fixed brush against the photoconductor 13 in the discharge product removal mode.

  In the fourth embodiment, the photosensitive member 13 is rotated at the same speed as in printing in the discharge product removal mode. However, the photosensitive member 13 is set to increase in speed by controlling the photosensitive member motor 58. May be. By increasing the speed of the photoconductor 13, the frictional force of the pad 150 against the photoconductor 13 can be increased, and the discharge product removal effect is improved.

1 is a schematic configuration diagram illustrating a color laser printer according to a first embodiment of the present invention. It is a block diagram which shows the discharge product removal mechanism provided in the color laser printer which concerns on 1st Embodiment of this invention. It is the elements on larger scale which show the discharge product removal mechanism provided in the color laser printer which concerns on 1st Embodiment of this invention. It is a perspective view which shows the rotating brush moving mechanism of the color laser printer which concerns on 1st Embodiment of this invention. FIG. 5 is a view for explaining a transfer residual toner collection method during printing by the color laser printer according to the first embodiment of the present invention. FIG. 5 is a view for explaining a transfer residual toner collection method during printing by the color laser printer according to the first embodiment of the present invention. It is the figure which showed typically the state of the magnetic brush formed between the developing roller and photoconductor of the color laser printer which concerns on 1st Embodiment of this invention. It is a block diagram which shows the discharge product removal mechanism provided in the color laser printer which concerns on 2nd Embodiment of this invention. It is a perspective view which shows the developing roller moving mechanism provided in the color laser printer which concerns on 2nd Embodiment of this invention. It is the elements on larger scale which show the discharge product removal mechanism provided in the color laser printer which concerns on the modification of 2nd Embodiment of this invention. It is a block diagram which shows the discharge product removal mechanism provided in the color laser printer which concerns on 3rd Embodiment of this invention. It is a block diagram which shows the discharge product removal mechanism provided in the color laser printer which concerns on 4th Embodiment of this invention. It is the elements on larger scale which show the discharge product removal mechanism provided in the color laser printer which concerns on 4th Embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Printer 12 Image forming unit 13 Photoconductor (Image carrier)
14 Intermediate transfer belt 32 Transfer roller 34 Rotating brush 36 Charging roller 38 Developing roller 50 Discharge product removal mechanism 52 Control circuit (control means)
54 Rotating brush moving motor (brush moving means)
56 Rotating brush rotation motor (brush rotating means)
58 photoconductor motor 60 gear (brush moving means)
80 Discharge product removal mechanism 82 Control circuit (control means)
84 Solenoid for moving developing device (developer pressing force increasing means)
86 Developing roller rotating motor (Developing roller rotating means)
100 discharge product removal mechanism 102 control circuit (control means)
104 Developer adjustment motor (developer pressing force increasing means)
106 Trimmer (Developer pressing force increasing means)
120 discharge product removal mechanism 122 control circuit (control means)
124 Transfer roller moving solenoid (transfer member moving means)
140 Discharge Product Removal Mechanism 142 Control Circuit (Control Unit)
144 Removal member motor (removal member moving means)
146 Discharge Product Removal Device 150 Pad (Removal Member)

Claims (11)

An image carrier on which an electrostatic latent image is formed after charging by a contact charging member; and a developing roller for rotating the two-component developer composed of toner and carrier while adhering to the surface to develop the electrostatic latent image with toner. An image forming apparatus having a plurality of image forming units each including a transfer member that transfers a developed toner image onto a transfer member, and a rotating or fixed brush that disturbs residual toner on the surface of the image carrier after transfer. There,
A contact member that contacts the surface of the image carrier;
Friction force changing means for removing discharge products by increasing the friction force of the contact member;
During printing of at least one image forming unit, the image carrier of another image forming unit not to be printed is rotated, and the frictional force changing means is driven to increase the frictional force of the contact member against the image carrier. And an image forming apparatus characterized by comprising:   The control means rotates the image carriers of all the image forming units at the start of the operation of the image forming apparatus and drives the friction force changing means to increase the friction force of the contact member against the image carrier. The image forming apparatus according to claim 1, wherein: The contact member is a rotating brush;
The image forming apparatus according to claim 1, wherein the frictional force changing unit is a brush moving unit that moves a rotation shaft of the rotary brush toward the image carrier. The contact member is a rotating brush;
The image forming apparatus according to claim 1, wherein the frictional force changing unit is a brush rotating unit that increases a relative moving speed of the rotating brush with respect to the image carrier. apparatus. The contact member is a two-component developer carried on a developing roller,
The image forming apparatus according to claim 1, wherein the frictional force changing unit is a developer pressing force increasing unit that increases a pressing force of the two-component developer against the image carrier. The contact member is a two-component developer carried on a developing roller,
The image forming apparatus according to claim 1, wherein the frictional force changing unit is a developing roller rotating unit that increases a relative moving speed of the developing roller with respect to the image carrier. . The contact member is a transfer member;
The image forming apparatus according to claim 1, wherein the frictional force changing unit is a transfer member moving unit that presses a belt-shaped transfer member that contacts the image carrier toward the image carrier. apparatus. The contact member is a discharge product removing member;
The image forming apparatus according to claim 1, wherein the frictional force changing unit is a removing member moving unit that brings a discharge product removing member into contact with the image carrier.   The image forming apparatus according to claim 8, wherein the discharge product removing member is a pad, a fixed brush, or a blade that contacts the image carrier and removes the discharge product.   The image forming apparatus according to claim 1, wherein the control unit rotates the image carrier while increasing or decreasing the speed. When the frictional force changing means increases the frictional force against the image carrier and removes the discharge products,
The image forming apparatus according to claim 1, wherein an applied current to the contact charging member is reduced.

Images