JP2007065580A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming apparatus equipped with a cleaning function of exhibiting excellent performance for a long period of time. <P>SOLUTION: A CPU 150 decides whether a toner image before transfer is present on a photoreceptor surface 10b at the point of interruption of image forming operation from the detection result of a paper sheet passage detection sensor 170 detecting passage of a recording paper sheet P right before a transfer position P4, and when the toner image before transfer is present on the photoreceptor surface 10b, a brush bias voltage having the same polarity as the charging polarity of toner particles in a developing unit 40 is applied to a cleaning brush 71 to stop untransferred toner particles from being attracted to the cleaning brush 71. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an image forming apparatus using an electrophotographic system such as a copying machine, a facsimile machine, and a printer.

  Conventionally, in the electrophotographic method, the surface of the image carrier that moves along a predetermined circulation path is charged at a predetermined charging position, and the charged image carrier surface is irradiated with exposure light at an exposure position downstream of the charging position. To form an electrostatic latent image on the surface of the image carrier, and supply toner particles charged to a predetermined polarity to the electrostatic latent image at a development position downstream of the exposure position, thereby developing the electrostatic latent image and toner. An image is formed, and the toner image is transferred to a predetermined transfer surface (recording paper or intermediate transfer body) at a transfer position downstream of the development position and finally fixed on the recording paper. An image is formed.

  Here, residual toner particles remaining at the time of transfer exist on the surface of the image carrier after the transfer of the toner image, and it is necessary to remove the residual toner particles prior to the formation of the next toner image. Become.

  Various cleaning methods for removing residual toner particles have been proposed. The following method using a conductive brush is widely known as an effective method. The cleaning method using a conductive brush pays attention to the fact that the toner particles used for developing the electrostatic latent image are in a charged state. In this method, residual toner particles are adsorbed and removed by a conductive brush by rubbing the surface of the image carrier with a brush.

  By the way, in such a cleaning method using a conductive brush, it is known that the following problems occur when a large amount of residual toner particles accumulate on the conductive brush. That is, when the amount of accumulated residual toner particles increases, the electrical resistance of the conductive brush increases, and the charged voltage of the conductive brush abnormally increases. Then, the accumulated residual toner particles receive charge injection from the conductive brush and are charged to the same polarity as the conductive brush, and return to the surface of the image carrier.

Therefore, in the cleaning method using a conductive brush, in order to suppress the accumulation of residual toner particles on the conductive brush, some kind of removal mechanism for removing the residual toner particles adsorbed on the conductive brush is provided. There are many. In addition, the electrical resistance of the conductive brush is monitored in order to suppress an abnormal rise in the charged voltage in the conductive brush and prevent charge injection from the conductive brush to the residual toner particles, A technique for controlling the voltage of a conductive brush has also been proposed (see, for example, Patent Document 1).
JP-A-4-174488

  Here, in an electrophotographic image forming apparatus as described above, in many cases, an image forming operation is interrupted when an error such as a paper jam of a recording sheet occurs. When the error is resolved after the interruption, the image forming operation is resumed. At this time, it is sufficiently conceivable that the image forming operation is interrupted while the toner image before transfer is present on the surface of the image carrier. In such a case, the image forming operation is resumed with a large amount of untransferred toner particles remaining on the surface of the image carrier, and the large amount of untransferred toner particles adheres to the conductive brush, The amount of toner particles deposited on the conductive brush increases rapidly. Such an abnormal increase in the amount of deposition increases the possibility that the above-described problems occur in the conductive brush, and as a result, shortens the life of the cleaning function of the conductive brush.

  In view of the above circumstances, an object of the present invention is to provide an image forming apparatus having a cleaning function capable of exhibiting good performance over a long period of time.

The image forming apparatus of the present invention that achieves the above object charges the surface of the image carrier that moves along a predetermined circulation path at a predetermined charging position on the circulation path, and after charging at an exposure position downstream of the charging position. By exposing the surface of the image bearing member to exposure light, an electrostatic latent image is formed on the surface of the image bearing member, and the electrostatic latent image is charged with a predetermined polarity at the developing position downstream of the exposure position. The electrostatic latent image is developed to obtain a toner image, and the toner image is transferred to a predetermined transfer surface at a transfer position downstream of the development position and finally fixed on a recording medium. In an image forming apparatus for forming an image composed of a fixed toner image on the recording medium,
A conductive brush that rubs the surface of the image carrier, and the conductive brush is charged to a polarity opposite to the predetermined polarity, so that the transfer target is at a cleaning position downstream of the transfer position; A cleaning unit that removes residual toner particles remaining on the surface of the image carrier after the toner image has been transferred to the surface by adsorbing the toner particles to the conductive brush;
An interruption unit for interrupting an image forming operation in the image forming apparatus in response to a predetermined interruption instruction;
In response to a predetermined resumption instruction, the image forming operation is resumed, and when the pre-transfer toner image is present on the surface of the image carrier, the image forming operation is interrupted. Prior to resuming, the conductive brush is charged to the same polarity as the predetermined polarity with respect to the cleaning unit, and the portion of the image carrier surface where the toner image before transfer is formed is the circulation path. And a resuming unit for resuming the image forming operation after waiting to pass through the developing position along the line.

  According to the image forming apparatus of the present invention, when the image forming operation is interrupted in a state where the toner image before transfer is present on the surface of the image carrier, the conductive material is conducted prior to resuming the image forming operation. The characteristic brush is charged to the same polarity as the predetermined polarity. As a result, a large amount of untransferred toner particles remaining on the surface of the image carrier upon interruption is repelled by the conductive brush, so that a large amount of untransferred toner particles adhere to the conductive brush when the image forming operation is resumed. Is blocked. Accordingly, abnormal accumulation of toner particles on the conductive brush is suppressed, so that the cleaning unit can exhibit good performance over a long period of time. Further, untransferred toner particles are toner particles in a normal state before foreign matters such as paper dust accompanying transfer are mixed, unlike residual toner particles after transfer. According to the image forming apparatus of the present invention, after waiting for a portion of the surface of the image carrier on which the toner image before transfer has been formed to pass through the development position along the circulation path, the image formation is performed. Since the operation is resumed, normal untransferred toner particles return to the toner particle supply source at this development position. Thereby, such untransferred toner particles can be reused.

  Here, in the image forming apparatus of the present invention, “when the resuming unit interrupts the image forming operation when the toner image is not present on the transfer surface, prior to resuming the image forming operation. In addition, the conductive brush is charged to the same polarity as the predetermined polarity with respect to the cleaning unit, and the portion of the image carrier surface where the toner image before transfer is formed is along the circulation path. The form of “waiting to pass through the development position and then restarting the image forming operation” is a preferable form.

  According to this preferred embodiment of the image forming apparatus, since the resuming operation as described above is performed in a state where no foreign matter generated during transfer such as paper dust adheres to the surface of the image carrier, the development position Thus, very clean toner particles are returned to the toner particle supplier, and the toner particles can be reused in a more preferable state.

  Further, the image forming apparatus of the present invention may be in a form that “the toner particles are toner particles having a volume average particle diameter D50 of 7 μm or less”.

  The volume average particle diameter D50 referred to here is a particle diameter at which accumulation is 50% when a cumulative distribution is drawn from the small diameter side with respect to the particle size range (channel) divided based on the particle size distribution. It is. An image with good image quality can be obtained by using the toner particles having a small particle diameter as described above. On the other hand, the toner particles having such a small particle diameter are easily attached to the conductive brush, and are described above. Such deterioration of the cleaning performance is likely to occur. According to the above configuration, the toner particles having such a small particle diameter can be effectively used while suppressing a decrease in the cleaning performance of the cleaning unit.

  As described above, according to the present invention, it is possible to provide an image forming apparatus having a cleaning function capable of exhibiting good performance over a long period of time.

  Embodiments of the present invention will be described below with reference to the drawings.

  FIG. 1 is a diagram showing a schematic configuration of an image forming apparatus according to an embodiment of the present invention.

  An image forming apparatus 1 shown in FIG. 1 includes a drum-shaped photoconductor 10 that rotates clockwise around a grounded rotary shaft 10a. Around the photoconductor 10, a charger 20 for the photoconductor, An exposure device 30, a developing device 40, a transfer charger 50, a pre-cleaning charger 61, a pre-cleaning static eliminator 62, a cleaning device 70, and a pre-image forming static eliminator 80 are arranged. The image forming apparatus 1 is also provided with a CPU 150, a fixing device 90, a paper jam sensor 160, and a paper passage detection sensor 170.

  A photoreceptor 10 shown in FIG. 1 is obtained by laminating a photosensitive layer including an undercoat layer, a charge generation layer, and a charge transport layer on a conductive support on a cylinder. As the photoconductor 10 rotates in the clockwise direction indicated by the arrow A around the rotation shaft 10a, the photoconductor surface 10b moves along a circulation path around the rotation shaft 10a. This photoreceptor 10 corresponds to an example of an image carrier according to the present invention.

  The photoreceptor charger 20 is a non-contact charging type corotron charger. A negative charging bias voltage is supplied to the photosensitive member charger 20 from a high voltage power source 21 for charging the photosensitive member, and the negative charging bias voltage causes the photosensitive member surface 10b to be negative at a predetermined charging position P1. It is charged with nature.

  The exposure device 30 irradiates the photoconductor surface 10b with laser light modulated based on image information. The negatively charged photoreceptor surface 10b is exposed to the laser beam from the exposure device 30 at the exposure position P2 downstream of the charging position P1 in the circulation path, and the shape of the image represented by the image information. As a result, the potential of the photoreceptor surface 10b is lowered. As a result, an electrostatic latent image that electrostatically represents the image is formed.

  The developing device 40 carries a developer containing body 41 containing a developer containing toner particles and a fine particle external additive exhibiting a polishing effect, and the negatively charged toner particles in the developer containing body 41. And a developing roll 42 that rotates in a state of facing the photoreceptor surface 10b. Here, in this embodiment, the volume average particle diameter D50 of the toner particles accommodated in the developer accommodating body 41 is 7 μm or less. The volume average particle diameter D50 referred to here is a particle diameter at which accumulation is 50% when a cumulative distribution is drawn from the small diameter side with respect to the particle size range (channel) divided based on the particle size distribution. It is. The toner particles positively charged in the developer container 41 are negatively charged at the development position P3 on the downstream side of the exposure position P2 between the development roll 42 and the photoconductor 10 and close to each other. Shifts to the photoreceptor surface 10b due to the potential difference. At this time, the toner particles adhere to the portion of the electrostatic latent image having a low potential, avoiding the negatively charged portion of the photoreceptor surface 10b. Thereby, the electrostatic latent image is developed with the toner particles.

  In FIG. 1, the recording paper P is conveyed in the direction indicated by the arrow B. The conveyed recording paper P is sent to a transfer position P4 between the photoreceptor 10 and a transfer charger 50 which is a non-contact charging type corotron charger. The transfer charger 50 is supplied with a transfer bias voltage having a polarity opposite to the charging polarity of the toner particles in the developing device 40 from the high voltage power supply 51 for transfer charging, that is, a positive polarity transfer bias voltage. The toner image formed on the body surface 10b is transferred from the photoreceptor surface 10b to the recording paper P at the transfer position P4. In the image forming apparatus 1 of the present embodiment, the surface of the recording paper P corresponds to a predetermined transfer surface according to the present invention.

  In the present embodiment, a transfer system using the transfer charger 50 is employed. However, the image forming apparatus of the present invention is not limited to an image forming apparatus employing such a transfer system. For example, an image forming apparatus that employs a transfer method using a transfer roll supplied with a bias voltage having a polarity opposite to the charging polarity of the toner particles may be used.

  Further, in the image forming apparatus 1 shown in FIG. 1, a fixing device 90 is disposed downstream of the transfer position P4 in the paper transport direction. The fixing device 90 includes a fixing roll 91 having a heating mechanism and a pressure roll 92 provided so as to face the fixing roll 91. The recording paper P that has passed the transfer position P4 is conveyed between the fixing roll 91 and the pressure roll 92 that face each other. The toner particles constituting the toner image on the recording paper P are melted by the heating mechanism of the fixing roll 91 and are fixed on the recording paper P by receiving pressure from the pressure roll 92, so that an image composed of the fixing toner image is formed.

  On the other hand, on the surface 10b of the photoconductor 10 that has passed through the transfer region, residual toner particles that could not be transferred to the recording paper P at the transfer position P4 and the polishing effect attached to the residual toner particles. The external additive particles exhibiting the above remain. At the time of transfer, paper dust from the recording paper P also adheres to the photoreceptor surface 10b.

  The cleaning device 70 shown in FIG. 1 is a device for removing these residues, and is downstream of the circulation path from the transfer position P4 and in the direction of rotation of the photoconductor than the photoconductor charger 20. The upstream side cleaning position P7 is disposed so as to remove the residue, and corresponds to an example of the cleaning unit according to the present invention. Further, a pre-cleaning charger 61 and a pre-cleaning static eliminator 62 are provided in front of the cleaning device 70. Since there are residual toner particles having both polarities on the surface 10b of the photosensitive member 10 that has passed the transfer position P4, the residual toner particles having both polarities have the same negative polarity as the charging polarity of the toner particles in the developing device 40. The pre-cleaning charger 61 supplied with the bias voltage of the pre-charging from the pre-charging high-voltage power supply 63 makes the polarity of the residual toner particles negative at the pre-charging position P5 on the downstream side of the transfer position P4. By 62, the residual potential level on the photoreceptor surface 10b is lowered at the neutralization position P6 on the downstream side of the precharge position P5 so that the residual toner particles are easily removed by the cleaning device 70.

  A cleaning device 70 shown in FIG. 1 includes a cleaning brush 71, a recovery roll 72, and a scraper member 73.

  The cleaning brush 71 has conductive bristles 712 extending radially from a central axis 711 extending in parallel with the rotation axis 10a of the photoreceptor 10, and corresponds to an example of the conductive brush referred to in the present invention. The cleaning brush 71 rotates around the central axis 711 with the tips of the hairs 712 biting into the peripheral surfaces of both the photoconductor 10 and the collection roll 72.

  Here, in this embodiment, as a detailed configuration of the cleaning brush 71, the amount of biting of the cleaning brush 71 into the photoreceptor surface 10b, the material of the hair 712 of the cleaning brush 71, a method of imparting conductivity to the hair 712, The electrical resistance of the bristles 712, the thickness of the bristles 712, and the density of the bristles 712 are not particularly limited, and only some preferred examples will be introduced.

The amount of biting of the cleaning brush 71 into the photoreceptor surface 10b is desirably in the range of 0.1 mm to 2.5 mm, preferably in the range of 0.2 mm to 2.0 mm, and more preferably 0. Within the range of 5 mm to 1.5 mm. Examples of the material of the hair 712 of the cleaning brush 71 include resin fibers such as nylon (registered trademark), acrylic, polyolefin, and polyester. In addition, regarding the method of imparting conductivity to the hair 712 of the cleaning brush 71, the resin fiber is mixed with a conductive powder or an ionic conductive material to impart conductivity, or inside or on the surface of the resin fiber. Although the method of providing electroconductivity by forming a conductive layer is mentioned, Preferably it is the method of mix | blending the material which provides electroconductivity uniformly in a resin fiber. Further, the electric resistance of the hair 712 of the cleaning brush 71 is desirably in the range of 10 ² Ω to 10 ¹⁵ Ω, and more preferably in the range of 10 ⁴ Ω to 10 ¹³ Ω. The thickness of the hair 712 of the cleaning brush 71 is desirably 30 denier (about 66 μm) or less, preferably 20 (about 54 μm) or less, more preferably 0.2 denier (about 5.4 μm). -10 denier (about 38 μm). The density of the hair 712 of the cleaning brush 71 is desirably 20,000 or more per 1 inch ² (about 6.45 cm ² ), preferably 30,000 or more per 1 inch ² (about 6.45 cm ² ). More preferably, the number is 60,000 or more per inch ² (about 6.45 cm ² ). Specific conductive resin fibers employed as the hair 712 of the cleaning brush 71 include Beltron (registered trademark: manufactured by Kanebo), SA-7 (registered trademark: manufactured by Toray), UU nylon (registered trademark: Unitika). Manufactured) and the like.

  When collecting the residual toner particles, such a cleaning brush 71 attracts the residual toner particles remaining on the photoreceptor surface 10b, so that the positive polarity brush bias voltage having a polarity opposite to the charged polarity of the residual toner particles is obtained. Is supplied from the first brush power source 74, and residual toner particles are attracted to the hair 712 of the cleaning brush 71 by the action of the brush bias voltage and scraped off by the hair 712. That is, the cleaning brush 71 removes residual toner particles remaining on the photoreceptor surface 10b that has passed through the transfer region of the photoreceptor from the photoreceptor surface 10b. Further, the external additive particles, paper powder, etc., which are separated from the toner particles and remain on the photoreceptor surface 10b, are also removed from the photoreceptor surface 10b by the cleaning brush 71. The cleaning brush 71 is less deteriorated with time in cleaning performance, and is more advantageous than a plate-shaped cleaning blade, particularly in a high-speed machine. Further, since the cleaning brush 71 shown in FIG. 1 is a cleaning method that actively uses an electric field, it is superior to cleaning of spherical toner particles, which is difficult with a cleaning blade that mechanically scrapes without using an electrical action. There is sex. Residual toner particles and external additive particles (hereinafter collectively referred to as residual components) transferred to the hair 712 of the cleaning brush 71 are held on the hair 712 by the action of the brush bias voltage.

  The collection roll 72 that collects the residual component held by the bristles 712 also rotates about a central axis 721 that extends parallel to the rotation axis 10 a of the photoreceptor 10, and the brush applied to the cleaning brush 71. A recovery roll bias voltage having a positive polarity higher than the bias voltage is supplied from the power supply 75 for the recovery roll, and the residual component held by the bristles 712 of the cleaning brush 71 by this recovery roll bias voltage is greater than the holding power of the bristles 712. Pull strongly to collect.

  Here, in this embodiment, the material of the collection roll 72 is not particularly limited, and only some preferred examples will be introduced. First, properties related to elasticity, properties related to wear, properties related to hardness, and properties related to electrical resistance required for the material of the collection roll 72 will be described.

First, as for the properties related to elasticity, the collection roll 72 is required to have a rigidity that does not cause bending, and specifically, the bending elastic modulus according to JIS-K7171: 94 is 700 Kpa or more. preferable. As for the properties related to wear, the collection roll 72 is constantly in contact with the cleaning brush 71 and a scraper member 73 described later, and therefore, it is required to be resistant to wear. Specifically, the wear amount in JIS-K6902: 98 is required. Is preferably 20 mg or less. In addition, as for the properties relating to hardness, it is required that molding with high dimensional accuracy is possible at the time of manufacturing the collecting roll 72, and it is required to be strong against scraping at the time of use. Rockwell hardness (M scale) in JIS-K7202: 95 Is preferably 100 or more. As for the properties relating to the electric resistance, it is required that the residual component transferred to the hair 712 in the cleaning brush 71 can be adsorbed satisfactorily, and the specific resistance value is in the range of 1 × 10 ⁵ Ω to 1 × 10 ¹⁰ Ω. It is desirable to be within the range, and preferably within the range of 1 × 10 ⁶ Ω to 1 × 10 ⁸ Ω. Next, a preferable example of the material of the collection roll 72 that satisfies these properties will be described.

  First, as a material satisfying the properties of elasticity, wear, and hardness related to the recovery roll 72, the recovery roll has good dimensional accuracy because it is hard to shrink after molding because the curing (crosslinking) proceeds by heating at the time of molding. A thermosetting resin from which 72 is obtained is preferred. Examples of such thermosetting resins include phenolic resin, urea resin, melamine resin, unsaturated polyester, epoxy resin, polyimide resin, etc. Among them, phenolic resin has good dimensional accuracy and smooth surface. It is particularly preferable because an excellent molded product can be obtained at low cost. Furthermore, the following organic fillers and inorganic fillers may be mentioned as those to be blended in the thermosetting resin as described above in order to satisfy the properties relating to the electrical resistance. As the organic filler, first, carbon black, carbon powder, graphite, magnetic powder, metal oxides such as zinc oxide, tin oxide and titanium oxide, metal sulfides such as copper sulfide and zinc sulfide, so-called strontium, barium and rare earth Examples thereof include hard ferrite, magnetite, copper, zinc, ferrite such as nickel and manganese, and those obtained by subjecting the surface of the above substances to a conductive treatment as necessary. Furthermore, as organic fillers, oxides, hydroxides, carbonates, metals containing different metal elements such as copper, iron, manganese, nickel, zinc, cobalt, barium, aluminum, tin, lithium, magnesium, silicon, phosphorus, etc. Examples include so-called composite metal oxides, which are solid solutions of metal oxides obtained by firing a compound or the like at a high temperature. Examples of the inorganic filler include metal powders such as tin, iron, and aluminum, metal fibers, and glass fibers. In order to satisfy the above-described properties relating to electrical resistance, any one of these organic fillers and inorganic fillers may be used alone, or a plurality of types may be mixed and used.

  The scraper member 73 is a thin metal plate that plays a role of scraping off the residual components recovered by the recovery roll 72 from the recovery roll 72. In the present embodiment, the detailed configuration of the scraper member 73 is not particularly limited with respect to the material and thickness of the scraper member 73, and only some preferred examples will be introduced. The material of the scraper member 73 is preferably stainless steel or phosphor bronze from the viewpoint of durability and cost, and the thickness is desirably 0.02 mm to 2 mm, preferably 0.05 mm to 1 mm. .

  In such a cleaning device 70, a second brush power source 76 that outputs a negative polarity brush bias voltage having a polarity opposite to the positive polarity brush bias voltage to the cleaning brush 71, and a brush bias to the cleaning brush 71 are provided. A power supply switching unit 77 that switches the power supply for supplying voltage from the first brush power supply 74 to the second brush power supply 76 in accordance with an instruction from the CPU 150 is provided. Details of operations of the CPU 150, the second brush power source 76, and the power source switching unit 77 will be described later.

  Since unevenness of the potential still remains on the photoreceptor surface 10b that has passed through the cleaning device 70 described above, the unevenness of the potential is made uniform by the pre-image forming static eliminator 80 in preparation for the next image formation. It is arranged.

  Further, the image forming apparatus 1 according to the present embodiment includes a paper jam sensor 160 and a paper passage detection sensor 170. The paper jam sensor 160 detects a paper jam of the recording paper P in the image forming apparatus 1 and sends the detection result to the CPU 150. The CPU 150 plays a role of interrupting the image forming operation in the image forming apparatus 1 in accordance with the detection result of the paper jam sensor 160, and corresponds to an example of the interrupting unit referred to in the present invention. The detection result of the paper jam sensor 160 corresponds to an example of an interruption instruction according to the present invention.

  When the paper jam is cleared by the user's manual operation or the like after the interruption, the paper jam sensor 160 enters an undetected state. Then, in response to the fact that the paper jam sensor 160 has not been detected after the interruption, the CPU 150 instructs each component in the image forming apparatus 1 to redo the image forming operation from the formation of the electrostatic latent image. With the function of the CPU 150, in the image forming apparatus 1 of this embodiment, the image forming operation is automatically restarted when the paper jam is resolved. Here, the CPU 150 corresponds to an example of a resuming unit according to the present invention. In addition, the fact that the paper jam sensor 160 is not detected after the interruption corresponds to an example of a restart instruction according to the present invention.

  Here, it is fully conceivable that the image forming operation is interrupted due to a paper jam as described above in a state where the toner image before transfer remains on the photoreceptor surface 10b. In such a case, after the paper jam is resolved, the image forming operation is resumed while the toner image before transfer remains on the photoreceptor surface 10b. In order to prevent a large amount of untransferred toner particles from adsorbing to the cleaning brush 711 and causing the performance of the cleaning device 70 to deteriorate when such a situation occurs, in this embodiment, the paper passage detection sensor 170 is Arranged immediately before the transfer position P4, the passage of the recording paper P is monitored by the paper passage detection sensor 170. When the image forming operation is resumed, the following processing using the detection result of the paper passage detection sensor 170 is executed, and the toner particles on the photoreceptor surface 10b are not developed by the cleaning device 70 but by the developing device 40. Collected.

  Hereinafter, the description will be continued by paying attention to the processing when the image forming operation is resumed in the image forming apparatus 1.

  FIG. 2 is a flowchart showing the flow of toner particle recovery processing when the image forming operation interrupted by a paper jam is resumed.

  The collection process shown in this flowchart starts when the paper jam that causes the interruption of the image forming operation is cleared.

  Here, in the image forming apparatus 1 of the present embodiment, when the recording paper jammed in the apparatus is removed by the user, the CPU 150 instructs the resumption of the image forming operation (step S101). In this embodiment, when the restart of the image forming operation is instructed in this step S101, the toner particle collecting process is executed by the processing after step S102 prior to the restart, and then the image forming operation is restarted. The

  In step S102, whether or not passage of the leading edge of the recording paper P has not been detected by the paper passage detection sensor 170 from when an image forming operation is started until it is interrupted, that is, the image forming operation is performed. At the time of interruption, it is determined whether or not the leading edge of the recording paper P was before entering the transfer position P4 (see FIG. 1).

  If it is determined in step S102 that the leading edge of the recording paper P has not entered the transfer position P4 when the image forming operation is interrupted (Yes in step S102), the process proceeds to step S103. In this case, the toner image before transfer remains as it is on the photoreceptor surface 10b. In this case, in step S103, the CPU 150 switches the power source for supplying the brush bias voltage to the cleaning brush 71 from the first brush power source 74 to the second brush power source 76 to the power source switching unit 77. Instruct. By this switching instruction, the charging polarity of the cleaning brush 71 becomes negative with the same polarity as the charging polarity of the toner particles in the developing device 40. In this state, the photoconductor 10 is rotated (step S104). In this case, untransferred toner particles forming the toner image before transfer on the photoreceptor surface 10 b pass through the cleaning device 70 without adhering to the cleaning brush 71 having the same polarity. After the passage, the residual potential level on the photoreceptor surface 10b is lowered by the pre-image forming static eliminator 80, and the photoreceptor surface 10b is again charged to the negative polarity by the photoreceptor charger 20. When the toner reaches the developing device 40, untransferred toner particles are attracted to the developing roll 42 and collected by the developing device 40 in step S <b> 105. The collected untransferred toner is reused.

  On the other hand, if it is determined in the processing of step S102 that the leading edge of the recording paper P is not before entering the transfer position P4 when the image forming operation is interrupted (No determination in step S102), the process proceeds to step S106. In this case, the recording paper P has already entered the transfer area, and the transfer of the toner image to the recording paper P is started, and the image forming operation is interrupted during or after the transfer. In this state, foreign matter accompanying transfer is adhered to the photosensitive member surface 10b, and in this embodiment, even if untransferred toner particles remain on the photosensitive member surface 10b, the reuse is postponed. Therefore, in this case, the instruction to switch the power source for applying the brush bias voltage to the cleaning brush 71 as in step S103 is not executed, and the photosensitive member 10 rotates (step S106). Then, when a residue such as toner particles on the photoreceptor surface 10b reaches the cleaning device 70 that remains positive with the charging polarity of the cleaning brush 71 being opposite to the charging polarity of the toner particles, in step S107, These residues are collected by the cleaning device 70.

  When the toner particles are recovered by the developing device 40 or the cleaning device 70 through the process of step S105 or the process of step S107, the recovery process represented by this flowchart ends. Thereafter, the normal image forming operation is resumed from the formation of the electrostatic latent image.

  As described above, according to the image forming apparatus 1 of the present embodiment, when an image forming operation is interrupted while an untransferred toner image remains on the photoreceptor surface 10b, the image forming operation is performed. Prior to resuming the operation, untransferred toner particles forming the untransferred toner image are collected by the developing device 40 instead of the cleaning device 70. Accordingly, the performance of the cleaning device 70 is prevented from being deteriorated by the large amount of untransferred toner particles, and the untransferred toner particles that can be reused before transfer can be effectively used. .

  In the above description, the CPU 150 that interrupts the image forming operation when a paper jam occurs in the image forming apparatus is illustrated as an example of the interrupting unit in the present invention. However, the present invention is not limited to this, and the interrupting of the present invention is not limited thereto. For example, the unit may interrupt the image forming operation even when an error other than a paper jam occurs, or may interrupt the image forming operation upon receiving an operation such as an emergency stop by the user. There may be.

  Further, in the above description, as an example of the cleaning unit according to the present invention, as a power source for applying a brush bias voltage to the cleaning brush 71, a cleaning device provided with two brush power sources 74 and 76 whose output voltage polarities are opposite to each other. Although the apparatus 70 is illustrated, the present invention is not limited to this. The cleaning unit of the present invention may be, for example, one having a brush power source having a function of changing the polarity or voltage level of the output voltage in accordance with an instruction from the CPU. In this case, the power supply for one brush changes the polarity of the output voltage in the direction opposite to that at the time of normal image formation according to an instruction from the CPU, or the voltage of the output voltage according to an instruction from the CPU. The level will be changed to 0V.

In the above description, as an example of the resuming unit according to the present invention, untransferred toner particles are transferred to the developing device 40 only when the toner image is not transferred on the surface of the recording paper P at the time of interruption. However, the present invention is not limited to this. The resuming unit of the present invention, for example, causes the developing device 40 to collect untransferred toner particles even when a toner image is being transferred onto the surface of the recording paper P at the time of interruption. Also good.
(Example)
EXAMPLES Hereinafter, although this invention is demonstrated more concretely based on an Example and a comparative example, this invention is not limited to a following example at all.

[Example 1]
As a testing machine, a color DocuTech60V (registered trademark) manufactured by Fuji Xerox was remodeled like the image forming apparatus shown in FIG. That is, the cleaning device shown in FIG. 1 provided with a cleaning brush, a collection roll, a scraper member, a first brush power supply, a second brush power supply, a collection roll power supply, and a power supply switching unit is used. It was. Details of the cleaning brush, the collection roll, the scraper member, the first brush power supply, the second brush power supply, and the collection roll power supply will be described below. The power supply switching unit will not be described in detail because it does not particularly affect the table results for the embodiment.
(1) Cleaning brush Brush material: Conductive nylon (registered trademark), fiber thickness: 2 denier (about 17 μm), electrical resistance: 1 × 10 ⁸ Ω, hair length: 3.5 mm, fiber density: 120, 000 / inch ² , amount of biting into the photoconductor: about 0.5 mm, rotation speed: 171 mm / s, rotation direction: reverse rotation with respect to the rotation direction of the photoconductor (2) Collection roll Material: Conductive carbon dispersed Phenol resin, electric resistance: 1 × 10 ⁸ Ω, flexural modulus (JIS K7171: 94): 100 MPa, wear amount (JIS K6902: 98): 2 mg, Rockwell hardness (JIS K7202: 95, M scale): 120 Biting amount into the cleaning brush: 1.0 mm, rotation speed: 171 mm / s
(3) Scraper member Material: SUS304, thickness: 80 μm, amount of biting into the collecting roll: 1.3 mm, free length (free length): 8.0 mm
(4) First brush power supply Brush bias voltage: + 260V
(5) Second brush power supply Brush bias voltage: -100V
(6) Power supply for recovery rolls Recovery roll bias voltage: 660V
As described above, in the image forming apparatus shown in detail in (1) to (6), 100,000 images on which three strips having an image density of 5%, 50%, and 100% are drawn, and 10,000 in the middle. After each image forming operation is interrupted and output, the amount of toner remaining on the photoreceptor after passing through the cleaning device, the amount of toner accumulated on the cleaning brush in the cleaning device, and the cleaning performance of the cleaning device Were evaluated visually. Here, the cleaning performance was evaluated by outputting two A3 size solid images with the image forming apparatus after outputting the 100,000 images, and then outputting a 10% halftone image. Evaluation was made by visually confirming the image quality of a 10% halftone image. These evaluation results are shown in Table 1. Table 1 also shows evaluation results for Example 2 and Comparative Example 2 described later.

  The evaluation criteria in Table 1 are as follows.

[Residual toner amount on photoconductor]
○: It can be visually confirmed that no toner particles remain on the surface of the photoreceptor.
X: The presence of toner particles on the surface of the photoreceptor can be visually confirmed.

[Toner amount accumulated on the cleaning brush]
○: The amount of toner particles accumulated on the cleaning brush is large by visual judgment.
X: The amount of toner particles deposited on the cleaning brush is small by visual judgment.

[Cleaning performance]
○: It can be visually confirmed that there is no abnormal color streak in the 10% halftone image.
X: The presence of abnormal color streaks can be visually confirmed in a 10% halftone image.
[Example 2]
The cleaning brush was replaced with one having the same structure as that of Example 1 except that the fiber density was 240,000 fibers / inch ² , the rotation speed of the collection roll was changed to 201 mm / s, and the second brush The same image forming apparatus as in the first embodiment is used except that the brush bias output from the power supply for output is changed to 0V and the recovery roll bias voltage output from the power supply for the recovery roll is changed to + 760V. Tests and evaluations were performed. The results are shown in Table 1.
[Comparative example]
The same image forming apparatus as that in Example 1 was used except that the brush bias voltage output from the second brush power source was changed to +260 V, the same as the brush bias voltage output from the first brush power source. Similar tests and evaluations were performed. The results are shown in Table 1.

  Hereinafter, the evaluation results in the two examples and the comparative example will be described with reference to Table 1.

  In the above comparative example, a brush bias voltage having a polarity opposite to that of the toner particles is always applied to the cleaning brush regardless of the interruption of the image forming operation. As a result, if the image forming operation is interrupted before the toner image is transferred to the recording paper, a large amount of untransferred toner particles remaining on the surface of the photoreceptor are collected by the cleaning device when the image forming operation is resumed. The Rukoto. It can be seen from the evaluation result of the comparative example that the cleaning performance of the cleaning device deteriorates when such a large amount of untransferred toner particles is collected. That is, after outputting the above 100,000 images, the cleaning performance of the cleaning device is reduced, and the toner particles on the surface of the photoreceptor cannot be sufficiently removed. It can be seen from the evaluation results for. In addition, it can be seen from the evaluation result of the amount of toner deposited on the cleaning brush that a large amount of toner particles have accumulated on the cleaning brush after outputting the above 100,000 images. It can be inferred that the cause of the decrease is the toner particles accumulated in a large amount on the cleaning brush due to the repeated collection of a large amount of untransferred toner particles. Further, it can be seen from the evaluation result of the cleaning performance that an image formed by the image forming apparatus in such a state that the cleaning performance is deteriorated causes an abnormal color streak to deteriorate the image quality.

  On the other hand, in the above-described two embodiments, when the image forming operation is resumed after the interruption, if the interruption is before the toner image is transferred to the recording paper, the toner particles are not included in the cleaning brush. A brush bias voltage of the same polarity or 0V is applied. As a result, collection of untransferred toner particles remaining in large quantities on the surface of the photoreceptor by the cleaning device is prevented. The evaluation results in these two examples are the same as the evaluation results for the residual toner amount on the photoconductor after outputting the 100,000 images, and the amount of toner deposited on the cleaning brush at that time. Both the evaluation results on the cleaning performance and the evaluation results on the cleaning performance after outputting the 100,000 images are good. Accordingly, it is understood that the cleaning performance of the cleaning device is maintained in a good state for a long time by preventing the collection of a large amount of untransferred toner particles with the cleaning device as described above.

1 is a diagram illustrating a schematic configuration of an image forming apparatus according to an embodiment of the present invention. 6 is a flowchart illustrating a flow of toner particle recovery processing when an image forming operation interrupted by a paper jam is resumed.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Image forming apparatus 10 Photoconductor 101 Protective layer 110 Surface 20 Photoconductor charging device 21 Photoconductor charging high-voltage power supply 30 Exposure device 40 Developer 41 Developer container 42 Developing roll 50 Transfer charger 51 High-voltage power supply for transfer charging 61 Pre-cleaning charger 62 Pre-cleaning static eliminator 63 Pre-charger power supply 70 Cleaning device 71 Cleaning brush 711 Central shaft 712 Hair 72 Recovery roll 721 Central shaft 73 Scraper member 74 First brush power supply 75 Recovery roll power supply 76 Second Power source for brush 80 Static eliminator before image formation 90 Fixing device 91 Fixing roll 92 Pressure roll 150 CPU
160 Paper jam sensor 170 Paper passage detection sensor

Claims (1)

By charging the surface of the image carrier moving along a predetermined circulation path at a predetermined charging position on the circulation path and irradiating the charged image carrier surface with exposure light at an exposure position downstream of the charging position. An electrostatic latent image is formed on the surface of the image carrier, and the electrostatic latent image is developed by supplying toner particles charged with a predetermined polarity to the electrostatic latent image at a development position downstream of the exposure position. An image composed of a fixed toner image on the recording medium is obtained by transferring the toner image onto a predetermined transfer surface at the transfer position downstream of the developing position and finally fixing the toner image on the recording medium. In an image forming apparatus for forming
A conductive brush for rubbing the surface of the image carrier, and charging the conductive brush to a polarity opposite to the predetermined polarity, so that the transfer target is at a cleaning position downstream of the transfer position; A cleaning unit that removes residual toner particles remaining on the surface of the image carrier after the toner image is transferred to the surface by adsorbing the conductive toner to the conductive brush;
An interruption unit for interrupting an image forming operation in the image forming apparatus in response to a predetermined interruption instruction;
In response to a predetermined restart instruction, the image forming operation is restarted, and the image forming operation is interrupted when the pre-transfer toner image exists on the surface of the image carrier. Prior to resuming, the conductive portion of the cleaning brush is charged to the same polarity as the predetermined polarity, and the portion of the image carrier surface where the toner image before transfer is formed is the circulation path. An image forming apparatus comprising: a resuming unit that waits for the image forming operation to resume after passing through the developing position.

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