JP4706497B2 - Image forming apparatus - Google Patents

Description

  The present invention relates to an electrophotographic image forming apparatus such as a copying machine or a printer. More specifically, at least one structure (a temperature sensor, a separation claw, or the like) is in contact with the developing device having a function of forming a predetermined toner pattern during non-image formation and the surface of the rotating member that forms the nip portion. The present invention relates to an image forming apparatus including a fixing device.

  In the electrophotographic image forming apparatus, when the toner supplied into the developing device is not used for a while or when the toner consumption is lower than usual, the processing is performed to discard the deteriorated toner remaining in the developing device. Is done. Specifically, the deteriorated toner in the developing device is discarded by forming a predetermined toner pattern during the non-printing operation. The deteriorated toner is scraped and collected by a cleaning device attached on the transfer belt. In addition, in an electrophotographic image forming apparatus, various toner patterns are formed during a non-printing operation in order to stabilize the image.

Patent Document 1 discloses an image forming apparatus that suppresses paper dust generated when a paper feed roller conveys recording paper from adhering to a density sensor facing a photoconductor. In this image forming apparatus, the paper feed roller and the density sensor are arranged so that the area occupied by the paper feed roller and the area occupied by the density sensor do not overlap in the axial direction of the photosensitive member.
JP 2001-249484 A

  However, the conventional image forming apparatus described above has the following problems. That is, with the recent reduction in toner particle size, some toner may slip through the cleaning device. The toner that has passed through remains on the transfer belt as it is, or adheres to the secondary transfer roller that is in pressure contact with the transfer belt. Thereafter, the toner adhering to the secondary transfer roller is transferred to the back surface of the recording medium during the printing operation.

  Further, the toner transferred to the recording medium adheres to a rotating member such as a roller that forms a nip portion in the fixing device when the recording medium passes through the fixing device. Therefore, it adheres to a structure that is in contact with the rotating member, such as a thermistor that is in contact with the rotating member to detect the surface temperature of the rotating member, or a separation claw that is in contact with the rotating member to separate the paper from the rotating member. Then, the structure floats from the contact surface with the rotating member. Therefore, the temperature adjustment function and paper separation function of the rotating member are lowered.

  In the image forming apparatus disclosed in Patent Document 1, the arrangement of the paper feed roller and the density sensor is devised to suppress a decrease in the sensor function of the density sensor. However, the above problem cannot be solved only by changing the arrangement of the density sensor and the separation claw.

  The present invention has been made to solve the problems of the conventional image forming apparatus described above. That is, an object of the present invention is to provide an image forming apparatus that suppresses deterioration of characteristics of a structure in contact with a rotating member in a fixing device.

  In order to solve this problem, an image forming apparatus includes a toner image carrier, a developing device that contains toner and forms a toner pattern on the toner image carrier, and fixes an image on the recording medium to the recording medium. A developing device that forms a predetermined toner pattern during a non-printing operation. The fixing device includes a rotating member that forms a nip portion by pressure contact, and a surface of the rotating member. The developing device is characterized in that a toner pattern is formed in a region outside the range of the structure when the toner is conveyed to the fixing device.

  The image forming apparatus of the present invention forms a predetermined toner pattern during the non-printing operation by the developing device. Examples of the toner pattern include a toner discard pattern for discarding deteriorated toner accumulated in the developing device and a resist pattern for image stabilization. Since this toner pattern is performed during the non-printing operation, it is collected by the cleaning device. However, a small amount of toner that is not collected by the cleaning device remains and is carried to the fixing device via the transfer member or the recording medium.

  Therefore, in the image forming apparatus of the present invention, a toner pattern is formed in a region outside the range of the structure even if the toner is carried to the fixing device. That is, the toner pattern is arranged so that the position where the structure is arranged and the position where the toner pattern is formed do not overlap with each other in the direction perpendicular to the moving direction of the toner (the width direction of the transfer member or the rotating member). Form. With such a toner pattern, even if the toner is carried to the fixing device, the toner is different from the structure in which the position of the rotating member in the width direction is in contact with the rotating member. Therefore, toner does not adhere to the structure. As a result, the amount of toner adhering to the structure is extremely reduced. Therefore, the floating of the structure from the rotating member can be avoided, and the characteristic deterioration of the structure is suppressed.

  Examples of the structure in contact with the rotating member of the fixing device include a sensor (such as a thermistor) for detecting the surface temperature of the rotating member and a separation claw for separating the recording medium from the rotating member. The structure is not limited to these, and any structure that is in the image area and in contact with the surface of the rotating member is applicable. For example, a roller or a belt can be used as the rotating member of the fixing device.

  According to the present invention, it is possible to reduce the amount of toner adhering to a structure in contact with the rotating member of the fixing device. Therefore, an image forming apparatus that suppresses the deterioration of the characteristics of the structure in contact with the rotating member in the fixing device is realized.

  DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of an electrophotographic image forming apparatus according to the present invention will be described below with reference to the drawings. In this embodiment, the present invention is applied to a tandem type color printer.

  The image forming apparatus 100 according to the present embodiment is an electrophotographic tandem color printer. As shown in FIG. 1, the image forming apparatus 100 has yellow (Y), magenta (M), cyan (C), and black (K) colors. Corresponding cartridges 18y, 18m, 18c, 18k, intermediate transfer belt 2, primary transfer rollers 1y, 1m, 1c, 1k corresponding to each color, cleaning blade 8, image stabilization sensor 19, and various devices are provided. And a control unit 20 for controlling. Each cartridge forms a toner image corresponding to each color and transfers the toner image onto the intermediate transfer belt 2. The intermediate transfer belt 2 carries a toner image formed by each cartridge.

  The cartridge 18k has a photosensitive drum 3 that is a toner image carrier, and a roller charging type charging device 5 that uniformly charges the surface of the photosensitive drum 3 around the photosensitive drum 3, and a photosensitive member. An exposure unit 6 that forms an electrostatic latent image on the surface of the drum 3; a developing device 4 that converts the electrostatic latent image on the photosensitive drum 3 into a visible image (toner image); A cleaning device 7 to be removed from the photosensitive drum 3 is disposed along the rotation direction of the photosensitive drum 3. The other cartridges have the same configuration.

  Each cartridge is mounted with a non-volatile memory medium, and the memory medium and the CPU of the image forming apparatus 100 main body are connected by serial communication in a state of being attached to the image forming apparatus 100 main body. If communication between the CPU of the image forming apparatus 100 main body and the memory medium in the cartridge is established, it is determined that the cartridge is mounted at the mounting position of the cartridge. In other words, if communication between the CPU of the main body of the image forming apparatus 100 and the memory medium of the cartridge is not established, it is determined that the cartridge is not attached. In addition, data for identifying a color is stored in the memory medium of each cartridge, and it is possible to determine for each mounting position what color toner is stored.

  Further, the image forming apparatus 100 temporarily stops the paper storage unit 9 that stores paper as a recording medium, the paper supply roller 10 that supplies the paper, and the paper that has been supplied, and sets the conveyance timing to the transfer position. A timing roller 11 for adjusting, a paper passing sensor 12 for detecting paper passing, a secondary transfer roller 13 for transferring the toner image on the intermediate transfer belt 2 to the paper, and fixing the toner image transferred to the paper. The image forming apparatus includes a fixing device 14, a paper discharge roller 15 that discharges a sheet to the outside of the device, and double-sided path conveyance rollers 16 and 17 that form a double-sided conveyance path.

  The fixing device 14 includes a heating roller 14a having a halogen heater 23 and a pressure roller 14b that presses the heating roller 14a to form a nip. Further, as shown in FIG. 2, a thermistor 21 for detecting the surface temperature of the heating roller 14a and a separation claw 22 for separating the paper from the heating roller 14a are disposed in contact with the heating roller 14a. In the fixing device 14, the surface temperature of the heating roller 14a is raised by turning on the halogen heater 23, and the surfaces of both rollers are warmed by rotating the heating roller 14a and the pressure roller 14b. Then, the sheet on which the toner image is transferred is passed between the sufficiently heated rollers, so that the toner is melted and fixed on the sheet. In the case of printing a color image, the surface temperature of the heating roller 14a is set to the color image fixing temperature, and in the case of printing a monochrome image formed only with K color toner having a low melting temperature, the heating roller 14a is used. Is controlled to the monochrome image fixing temperature.

  Next, an image forming operation by the image forming apparatus 100 will be briefly described with reference to the flowchart of FIG. First, the control unit 20 determines whether or not a print request has been made, that is, whether or not a print start signal or image data has been received (S1). When a print request is received (S1: YES), each cartridge starts print processing (S2). If no print request has been received (S1: NO), the process waits until a print request is received.

  The printing process of S2 is performed by the following procedure, for example. First, the photosensitive drum 3 is rotationally driven in the direction of the arrow in FIG. Then, it is uniformly charged by the charging member at a position facing the charging device 5. Next, it is exposed with a laser beam from the exposure unit 6, and an electrostatic latent image based on the image data is formed on the surface.

  When the electrostatic latent image reaches the position of the developing device 4, the charged toner moves due to the electric field formed between the developing bias voltage applied to the developing roller and the electrostatic latent image on the photosensitive drum 3. The electrostatic latent image is developed with toner. Thereafter, the toner image on the photosensitive drum 3 is transferred onto the intermediate transfer belt 2 by the primary transfer roller corresponding to each color. The transfer residual toner that is not transferred onto the intermediate transfer belt 2 but remains on the photosensitive drum 3 is scraped off and collected by the cleaning device 7. Each color cartridge operates in the same manner, and four color toner images are superimposed on the intermediate transfer belt 2. Thereby, one color image is formed.

  On the other hand, the paper is conveyed from the paper storage unit 9 by the paper feed roller 10. The transported paper is transported to the secondary transfer position after the transport timing is adjusted by the timing roller 11. Then, the toner image on the intermediate transfer belt 2 is transferred to the sheet by the secondary transfer roller 13. Further, the sheet holding the toner image is further conveyed, and heat and pressure are applied by the fixing device 14 to fix the toner image on the sheet. The transfer residual toner that is not transferred onto the sheet and remains on the intermediate transfer belt 2 is scraped off and collected by the cleaning blade 8. Thereby, the image formation for one sheet is completed.

  After the printing process, post-processing such as post-processing for stabilizing the image, post-processing for discarding the deteriorated toner, and stop processing for the driving unit are performed (S3). After post-processing, the process returns to S1 and waits for the next print request.

  Subsequently, as an example of the post-processing, a process for discarding deteriorated toner in the developing device 4 will be described with reference to the flowchart of FIG. Note that the deteriorated toner discarding process described below is performed individually for each cartridge.

  First, it is determined whether or not the toner consumption rate exceeds a specified value (S31). If the toner consumption rate satisfies the specified value (S31: NO), the process is terminated without discarding the deteriorated toner. On the other hand, if the toner consumption rate does not satisfy the specified value (S31: YES), the deteriorated toner in the developing device 4 is discarded (S32).

Here, the “toner consumption rate” is a toner consumption amount with respect to the cumulative driving time of each developing device 4, and specifically satisfies the following expression (1).
Toner consumption rate = toner consumption (g) / integrated driving time (s) (1)
The integrated driving time and the toner consumption amount of the developing device are updated by the driving of each developing device 4 and the toner consumption, and are stored in the memory medium of each cartridge. Note that the integrated drive time and toner consumption of the developing device may be stored in a memory medium mounted on the image forming apparatus 100 main body.

  In the disposal process of the deteriorated toner, a stripe-shaped toner pattern as shown in FIG. 5 is formed on the photosensitive drum 3 and transferred onto the intermediate transfer belt 2. Specifically, in this process, when the deteriorated toner is conveyed to the fixing device 14, the toner pattern is formed so as to be outside the range where the thermistor 21 and the separation claw 22 are installed. That is, in the direction perpendicular to the moving direction of the toner (the width direction of the intermediate transfer belt 2 and the axial direction of the photosensitive drum 3), the position on the heating roller 14 such as the thermistor 21 and the separation claw 22 is arranged. The toner pattern is formed so as not to overlap the position where the toner pattern is formed. Most of the deteriorated toner transferred onto the intermediate transfer belt 2 is scraped off by the cleaning blade 8.

  On the other hand, the toner that has passed through the cleaning blade 8 is conveyed to the fixing device 14 via the secondary transfer roller 13 and the paper, and adheres to the heating roller 14a. At this time, the deteriorated toner is transferred in advance to the outside of the range where the thermistor 21 and the separation claw 22 are installed. Exists. Therefore, it does not adhere to the thermistor 21 and the separation claw 22, and those structures do not float from the heating roller 14a. Therefore, the deterioration of the roller temperature adjustment function and the sheet separation function is suppressed.

  Next, it is determined whether the disposal of the deteriorated toner in the developing device 14 has been completed (S33). If the disposal of the deteriorated toner is not completed (S33: NO), the same toner pattern formation is repeated. When the disposal of the deteriorated toner is finished (S33: YES), this process is finished.

  The toner pattern is not limited to this embodiment. For example, when the separation claw 22 is not in contact with the heating roller 14a, a toner pattern outside the range of the thermistor 21 is formed as shown in FIG. That is, the toner pattern is determined by the arrangement of the structures in contact with the rollers in the fixing device 14.

  Further, the formation of the toner pattern during the non-printing operation is not limited to the disposal process of the deteriorated toner. For example, a resist pattern formed by image stabilization processing is applicable. Even in this case, the resist pattern is formed at a position outside the range of the thermistor 21 and the separation claw 22.

  As described in detail above, the image forming apparatus 100 of the present embodiment forms a predetermined toner pattern during the non-printing operation in the developing device 4. The toner pattern is formed in a region outside the range of the structure when the toner is conveyed to the fixing device 14. That is, the toner pattern is formed so that the region where the structure is arranged and the region where the toner pattern is formed do not overlap in the region perpendicular to the toner moving direction. With such a toner pattern, even if the toner is carried to the fixing device 14, the carried toner does not adhere to these structures. As a result, the amount of toner adhering to the structure is extremely reduced. Therefore, the floating of the structure from the roller can be avoided, and the characteristic deterioration of the structure is suppressed. Therefore, an image forming apparatus that suppresses the deterioration of characteristics of the structure in contact with the roller in the fixing device is realized.

  Note that this embodiment is merely an example, and does not limit the present invention. Therefore, the present invention can naturally be improved and modified in various ways without departing from the gist thereof. For example, in the embodiment, the present invention is applied to a printer, but the present invention is not limited to this. In other words, a copying machine, a scanner, a FAX, a word processor, or the like can be applied as long as it has a function of discarding deteriorated toner. Moreover, it is not limited to color but may be dedicated to monochrome images. Further, a tandem method or a four-cycle method may be used.

  Further, although a roller-shaped photosensitive drum is used as the image carrier, a belt-shaped photosensitive belt may be used. In addition to the roller charging method, the charging device may use a corona discharge charging charger, blade, brush, or the like. The exposure apparatus may be a laser or LED. The primary transfer device may use a transfer charger in addition to the transfer roller. In addition to the cleaning blade, the cleaning device may be a cleaning brush, a cleaning roller, or a combination thereof. In addition to the roller, the fixing device may use a belt.

1 is a diagram illustrating a schematic configuration of a color printer according to an embodiment. It is a figure which shows arrangement | positioning of the structure around a heating roller. 6 is a flowchart illustrating print execution processing of the image forming apparatus. 7 is a flowchart illustrating a process for discarding deteriorated toner in the developing device. FIG. 6 is a diagram illustrating an example of a toner pattern formed in a process for discarding deteriorated toner. FIG. 10 is a diagram illustrating an application example of a toner pattern formed by a disposal process of deteriorated toner.

Explanation of symbols

2 Intermediate transfer belt 3 Photosensitive drum (toner image carrier)
4 Developing device 8 Cleaning blade 14 Fixing device 14a Heating roller (roller member)
14b Pressure roller (roller member)
18k cartridge 20 control unit 21 thermistor (structure)
22 Separation nail (structure)
100 Image forming apparatus

Claims (4)

A toner image carrier, a developing device that contains toner and forms a toner pattern on the toner image carrier, and a fixing device that fixes an image on the recording medium to the recording medium. In an image forming apparatus that forms a predetermined toner pattern during a printing operation,
The fixing device includes:
A rotating member that forms a nip portion by pressure welding;
A structure in contact with the surface of the rotating member;
The developing device is
An image forming apparatus, wherein a toner pattern is formed in a region outside a range of the structure when toner is conveyed to the fixing device. The image forming apparatus according to claim 1,
The image forming apparatus according to claim 1, wherein the structure is a sensor used for detecting a surface temperature of the rotating member. The image forming apparatus according to claim 1,
The image forming apparatus according to claim 1, wherein the structure is a separation claw for separating a recording medium from the rotating member. The image forming apparatus according to any one of claims 1 to 3,
The image forming apparatus, wherein the developing device forms a toner pattern when the deteriorated toner is discarded.

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