JP2017076066A - Image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image forming apparatus that comprises a photoreceptor including a lubricant surface layer and a charging member rotated following the photoreceptor, and can suppress the charging member from being rubbed by the photoreceptor at the start of use of a new process cartridge.SOLUTION: There is provided an image forming apparatus comprising a process cartridge B including a rotatable photoreceptor 1 that includes a lubricant surface layer, and a cleaning blade 16 that is arranged in contact with the photoreceptor 1 to scrape off a developer from a surface of the photoreceptor 1, and removably attached to an image forming apparatus body, the image forming apparatus including: a charging member 2 that is arranged in contact with the photoreceptor 1, rotated following the rotation of the photoreceptor 1, and performs charging processing on the surface of the photoreceptor 1 with a charging part; developing means 10 that supplies a developer to the photoreceptor 1; new product detection means that detects if the process cartridge B is a new product; and control means that, when the process cartridge B is detected to be a new product by the new product detection means, performs control of starting drive of the photoreceptor 1 while a voltage less than a discharge start voltage is applied to the charging member 2.SELECTED DRAWING: Figure 1

Description

  The present invention relates to an image forming apparatus from which a process cartridge can be removed.

  Here, the process cartridge is a cartridge in which the photosensitive member and the process means acting on the photosensitive member are integrally formed, and is detachably mounted on the main body of the electrophotographic image forming apparatus. Is. For example, a photosensitive member and at least one of a developing unit, a charging unit, and a cleaning unit as process units are integrally formed into a cartridge. An electrophotographic image forming apparatus forms an image on a recording material (recording medium) using an electrophotographic image forming system. Examples of the image forming apparatus include a copying machine, a printer (such as an LED printer and a laser beam printer), a facsimile machine, and a word processor. The apparatus main body of the image forming apparatus is a part other than the process cartridge of the image forming apparatus.

  Conventionally, in an image forming apparatus using an electrophotographic image forming process, a process cartridge system is often employed. In this apparatus, a photosensitive member (electrophotographic photosensitive member) and process means acting on the photosensitive member are integrally formed into a cartridge that can be attached to and detached from the main body of the image forming apparatus. As the photosensitive member, a rotatable drum type photosensitive drum is widely used. According to this process cartridge system, the maintenance of the apparatus can be performed by the user himself / herself without depending on the service person, so that the operability can be remarkably improved. Therefore, this process cartridge system is widely used in electrophotographic image forming apparatuses.

  By the way, as a cleaning means for removing toner remaining on the surface of the photosensitive drum, a blade cleaning method is often used. A cleaning blade having elasticity is used as a cleaning member, and this is arranged in a counter direction with respect to the rotation direction of the photosensitive drum, and is brought into contact with the photosensitive drum in a predetermined area to form a nip portion. This is a method of wiping off. According to the blade cleaning method, high cleaning performance can be obtained. However, if the frictional resistance between the cleaning blade and the surface of the photosensitive drum is high, the cleaning blade may be deformed, causing problems such as blade squeaking, turning over, and blade breakage (such as chipping).

  For this problem, by applying a particulate lubricant in advance to the area of the cleaning blade that contacts the surface of the photosensitive drum, problems such as the blade squeal when starting to use a new process cartridge are eliminated. There is a way to suppress it. Also, when starting to use a new process cartridge, by supplying the developer adhered to the photosensitive drum by applying a predetermined charging bias and developing bias to the contact portion between the cleaning blade and the photosensitive drum, There is a method for suppressing the problems such as the blade squeal.

  On the other hand, as described in Patent Document 1, it has been proposed to use a surface layer that improves the lubricity of the surface of the photosensitive drum. This suppresses the occurrence of problems such as blade squealing by imparting high lubricity to the surface of the photosensitive drum. According to this method, it is not necessary to previously apply a fine particle lubricant to a region of the cleaning blade that contacts the surface of the photosensitive drum. However, the surface layer (lubricating layer) having lubricity of the photosensitive drum is scraped off by discharge when a charging bias is applied to the charging member in order to charge the surface of the photosensitive drum. Therefore, in Patent Document 1, when the use of a new process cartridge is started, the developer is supplied to the surface of the photosensitive drum only by the developing bias, and the developer is supplied to the contact portion between the cleaning blade and the photosensitive drum. And stay. As a result, before the developer reaches the contact portion between the cleaning blade and the photosensitive drum, it is suppressed that the lubricating layer of the photosensitive drum is scraped by the application of the charging bias, thereby causing problems such as blade squealing. .

JP 2010-038953 A

  However, it has been found that the following problems may occur in a configuration having a charging member such as a charging roller that contacts the photosensitive drum and rotates following the rotation of the photosensitive drum.

  That is, since the lubricating layer of the photosensitive drum has a low frictional resistance, the charging roller does not rotate following the photosensitive drum, and the charging roller and the photosensitive drum slip, and the charging roller is rubbed against the photosensitive drum. is there. When the charging roller is rubbed against the photosensitive drum in this way, unevenness in electrical resistance may occur due to adhesion of components of the memory or the lubricating layer due to rubbing in a part of the circumferential direction of the charging roller. Due to the influence of this uneven electrical resistance, uneven image density due to uneven discharge between the charging roller and the photosensitive drum may occur during image formation.

  Here, when the use of a new process cartridge is started, the lubricant layer is scraped by supplying a charging bias to the charging roller after supplying the developer to the contact portion between the cleaning blade and the photosensitive drum. The coefficient of friction of the photosensitive drum increases. As a result, the charging roller rotates following the photosensitive drum during image formation. However, as described above, when the use of a new process cartridge is started, the lubricant layer of the photosensitive drum is scraped before the developer reaches the contact portion between the cleaning blade and the photosensitive drum. Then, problems such as the above-mentioned blade squeal may occur. Therefore, when starting to use a new process cartridge, it is impossible to apply a charging bias higher than the discharge start voltage from the beginning.

  Accordingly, an object of the present invention is to provide a structure in which a photosensitive member having a surface layer of a lubricant and a charging member that is driven and rotated, and the charging member rubs against the photosensitive member when starting to use a new process cartridge. It is an object of the present invention to provide an image forming apparatus that can suppress the occurrence of the image.

  The above object is achieved by the image forming apparatus according to the present invention. In summary, the present invention is a process cartridge comprising: a rotatable photosensitive member provided with a surface layer of a lubricant; and a cleaning blade disposed in contact with the photosensitive member and scraping off the developer from the surface of the photosensitive member. The image forming apparatus is removable from the main body of the image forming apparatus, is disposed in contact with the photoconductor, is rotated following the rotation of the photoconductor, and the surface of the photoconductor is rotated by a charging unit. A charging member that performs charging processing; and a developing unit that supplies developer to the photoconductor downstream of the charging unit and upstream of a contact portion between the cleaning blade and the photoconductor in the rotation direction of the photoconductor And a new article detecting means for detecting whether or not the process cartridge is new, and when the new cartridge detecting means detects that the process cartridge is new, it is released to the charging member. Control means for voltage below the starting voltage while applying a performs control to start driving of the photosensitive member, an image forming apparatus characterized by having a.

  According to the present invention, the charging member is rubbed against the photosensitive member when the use of a new process cartridge is started in the configuration including the photosensitive member having the surface layer of the lubricant and the driven rotating charging member. This can be suppressed.

1 is a schematic sectional view of an image forming apparatus. It is a schematic sectional drawing of a process cartridge. It is a partial expanded sectional view of a cleaning unit. It is a schematic diagram which shows the layer structure of a photosensitive drum. FIG. 2 is a block diagram illustrating a schematic control mode of a main part of the image forming apparatus. 6 is a schematic diagram illustrating an operation sequence of the image forming apparatus. FIG. It is a graph for demonstrating a discharge start voltage. It is a flowchart figure of initial stage rotation operation | movement. FIG. 6 is a timing chart of an initial rotation operation in a new process cartridge.

  The image forming apparatus according to the present invention will be described below in more detail with reference to the drawings.

[Example 1]
1. FIG. 1 is a schematic cross-sectional view of an electrophotographic image forming apparatus 100 according to an embodiment of the present invention. A process cartridge (hereinafter, referred to as an image forming apparatus main body A) is shown in FIG. (It is also simply referred to as “cartridge”.) B is shown in a mounted state.

  A photosensitive drum 1, which is a rotatable drum type photosensitive member (electrophotographic photosensitive member), has a predetermined peripheral speed (process speed) in the direction of arrow R1 in the figure by a driving motor (main motor) M (FIG. 5) as a driving source. ). The surface (outer peripheral surface) of the rotating photosensitive drum 1 has a predetermined polarity (negative polarity in this embodiment) by a charging roller 2 which is a rotatable roller-type charging member (charging rotating body) as a charging unit. Is substantially uniformly charged. The charging roller 2 is disposed in contact with the surface of the photosensitive drum 1 and rotates following the rotation of the photosensitive drum 1. At the time of image formation, a DC voltage of −1100 V is applied to the charging roller 2 as a charging bias (charging voltage) by a charging power supply (high voltage power supply circuit) E1 (FIG. 5) as a charging bias applying means. As a result, the surface of the photosensitive drum 1 is charged substantially uniformly at −500V. The surface of the charged photosensitive drum 1 is scanned and exposed by a laser beam L output according to image information by an exposure device (laser scanner) 3 serving as an exposure unit (image writing unit). Thereby, an electrostatic latent image (electrostatic image) corresponding to the image information is formed on the surface of the photosensitive drum 1.

  The electrostatic latent image formed on the photosensitive drum 1 is supplied with toner T as a developer by a developing unit (developing device) 4 and developed (visualized) as a toner image. In the developing unit 4, the toner T in the toner chamber 5 is agitated and conveyed by the rotation of the first conveyance member 6 and the second conveyance member 7, and is sent out to the toner supply chamber 8. In the toner supply chamber 8, a developing roller 10 that is a roller-type developer carrier as a developing unit is disposed. The developing roller 10 includes a magnet roller (fixed magnet) 9. The toner T in the toner supply chamber 8 is carried on the surface of the developing roller 10 by the magnetic force of the magnet roller 9. The toner T carried on the developing roller 10 is regulated in layer thickness on the peripheral surface of the developing roller 10 while being frictionally charged by a developing blade 11 as a developer regulating member. The toner T on the developing roller 10 is conveyed toward the portion facing the photosensitive drum 1 by the rotation of the developing roller 10. Further, at the time of image formation, a developing bias (developing voltage) is applied to the developing roller 10 by a developing power supply (high voltage power supply circuit) E2 (FIG. 5) as a developing bias applying means. In this embodiment, an oscillating voltage in which a DC voltage of −400 V and a frequency of 3000 Hz and an AC voltage of 1.8 kV at peak-peak is superimposed is applied as the developing bias. Thereby, due to the potential difference between the photosensitive drum 1 and the developing roller 10, the toner T on the developing roller 10 is transferred onto the photosensitive drum 1 in accordance with the electrostatic latent image. In this embodiment, the same polarity as the charging polarity of the photosensitive drum 1 (negative polarity in this embodiment) is applied to the exposed portion on the photosensitive drum 1 where the absolute value of the potential has been lowered by being exposed after being uniformly charged. ) Is attached to the charged toner T (reverse development). In the rotation direction of the photosensitive drum 1, a position where the toner T is supplied by the developing roller 10 (a portion where the photosensitive drum 1 and the developing roller 10 face each other) is a developing portion (developing position) b.

  Along with the output timing of the laser beam L, a recording material (recording medium, sheet material) P such as a recording paper or an OHP sheet is sent out from the sheet tray 12. The recording material P is conveyed to a transfer portion (transfer nip portion) N formed by contacting the photosensitive drum 1 and a transfer roller 13 which is a roller-type transfer member as a transfer unit. In the transfer portion N, the toner image on the photosensitive drum 1 is sequentially transferred onto the recording material P that is nipped between the photosensitive drum 1 and the transfer roller 13 and conveyed. At this time, the transfer roller 13 is supplied with a transfer power supply (high-voltage power supply circuit) E3 (FIG. 5) as a transfer bias applying means, and has a polarity opposite to the charge polarity (normal charge polarity) of the toner T during development (this embodiment). In the example, a transfer bias (transfer voltage) which is a DC voltage of positive polarity is applied. The recording material P to which the toner image has been transferred is separated from the photosensitive drum 1 and conveyed to a fixing device 14 as a fixing unit. The recording material P is pressurized and heated when passing through the fixing device 14, and a toner image fixing process is performed. The recording material P that has undergone the toner image fixing process is discharged to a discharge tray 15.

  On the other hand, the residual toner on the photosensitive drum 1 after the transfer process is scraped off from the photosensitive drum 1 by a cleaning blade 16 which is a cleaning member having elasticity as a cleaning unit. Thereafter, the photosensitive drum 1 is used again for the above-described image forming process. The toner removed from the photosensitive drum 1 is stored in the waste toner chamber 19 by a screw 17 as a conveying member.

  In this embodiment, the charging roller 2, the developing roller 10, the transfer roller 13, and the cleaning blade 16 are process means that act on the photosensitive drum 1.

2. Cartridge Next, the cartridge B will be further described. FIG. 2 is a schematic cross-sectional view of the cartridge B. The cartridge B has a cleaning unit 18 and a developing unit 4.

  The developing unit 4 includes a developing frame 26 that forms the toner chamber 5 and the toner supply chamber 8, a developing blade 11, a developing roller 10, a first conveying member 6, and a second conveying member 7. The developing roller 10, the first conveying member 6, and the second conveying member 7 are rotatably provided on the developing frame 26, and are driven via gears from a driving motor M (FIG. 5) provided on the apparatus main body A. Is transmitted and driven to rotate. Further, the developing roller 10 is held with a predetermined gap between the developing roller 10 and the photosensitive drum 1 by a gap holding member (not shown) attached to both ends in the rotation axis direction.

  On the other hand, the cleaning unit 18 includes a cleaning frame 25 that forms a waste toner chamber 19, a photosensitive drum 1, a charging roller 2, a cleaning blade 16, a screw 17, and a drum abutting sheet 20. The photosensitive drum 1 and the screw 17 are rotatably provided on the cleaning frame 25, and are driven to rotate by being transmitted via a gear from a drive motor M (FIG. 5) provided on the apparatus main body A. The support structure of the charging roller 2 and the cleaning blade 16 will be described later. The charging roller 2, the cleaning blade 16, and the drum contact sheet 20 are arranged in contact with the surface of the photosensitive drum 1. In this embodiment, the contact positions with respect to these photosensitive drums 1 are as follows. The charging roller 2 is in contact with the uppermost end in the gravity direction of the photosensitive drum 1 at the 90 ° position on the downstream side in the rotational direction of the photosensitive drum 1 and the cleaning blade 16 is at the 10 ° position, and the upstream side is at the 10 ° position. The drum contact sheet 20 is in contact.

  The cleaning blade 16 includes a rubber blade 16a that is a blade-like (plate-like) elastic member formed of rubber as an elastic material, and a support member 16b that supports the rubber blade 16a. The support member 16b is attached to the cleaning frame 25. The cleaning blade 16 is disposed in contact with the photosensitive drum 1 in a counter direction with respect to the rotation direction of the photosensitive drum 1. That is, the rubber blade 16 a is in contact with the photosensitive drum 1 such that the tip end portion (free end portion) faces the upstream side in the rotation direction of the photosensitive drum 1. In this embodiment, the angle formed between the tangent line of the photosensitive drum 1 and the rubber blade 16b at the contact position between the cleaning blade 16 and the photosensitive drum 1 is 21 °. Further, the rubber blade 16a is pressed and arranged so as to enter the surface of the photosensitive drum 1 with a width of 1.0 mm (circumferential direction of the photosensitive drum 1). In the rotation direction of the photosensitive drum 1, a contact portion (cleaning nip portion) between the cleaning blade 16 and the photosensitive drum 1 is a cleaning portion (cleaning position) c.

  In the present embodiment, no coating or the like is performed on the region of the cleaning blade 16 that contacts the surface of the photosensitive drum 1 to reduce the frictional resistance. That is, in the cartridge B in the new state, particles (particulate lubricant) that provide a lubricating action between the cleaning blade 16 and the photosensitive drum 1 are not applied to the region of the cleaning blade 16 that contacts the photosensitive drum 1. .

  Here, with respect to the cartridge B, the new state or the new state means an unused state until the cartridge B is shipped from the factory and mounted on the apparatus main body A and starts to be used for image formation.

  The charging roller 2 includes a conductive substrate (core metal) 2a and a conductive resin layer (conductive elastic layer) 2b as a surface layer. The conductive resin layer 2b has a single layer structure in which conductive fine particles and bowl-shaped resin particles are dispersed in a binder. As the binder, a known rubber such as natural rubber, a vulcanized product thereof, or a synthetic rubber can be used. As the conductive fine particles, metal oxide, metal fine particles, carbon black and the like can be used. In this example, the conductive resin layer has a surface property of 20 μm in terms of 10-point average surface roughness (Rzjis) and a rubber hardness of 80 ° in terms of an MD-1 hardness meter.

  FIG. 3 is a schematic sectional view showing the periphery of the photosensitive drum 1 in the cleaning unit 18 in more detail. The charging roller 2 is rotatably supported by charging roller bearings 23 at both ends in the longitudinal direction of the cleaning unit 18 (substantially parallel to the rotational axis direction of the photosensitive drum 1). The charging roller bearing 23 is attached to the cleaning frame 23 so as to be slidable. A pressure spring 24 as an urging unit is provided between the charging roller bearing 23 and the cleaning frame 25. As a result, the charging roller 2 is biased (pressed) toward the photosensitive drum 1 via the charging roller bearing 23. In the present embodiment, the pressure spring 24 presses the charging roller 2 with a force of 400 gf at each of both ends in the rotation axis direction of the charging roller 2. The charging roller 2 is usually driven to rotate as the photosensitive drum 1 rotates.

  In the contact charging method using the charging roller 2, the charging roller 2 is brought into pressure contact with the photosensitive drum 1 and a voltage is applied to the charging roller 2, whereby a minute gap between the charging roller 2 and the photosensitive drum 1. The photosensitive drum 1 is charged by the discharge at. A position where the charging process is performed by the charging roller 2 (opposed portion between the photosensitive drum 1 and the charging roller 2) in the rotation direction of the photosensitive drum 1 is a charging portion (charging position) a. In this embodiment, a DC charging method is employed in which charging is performed by applying a DC voltage (DC voltage) obtained by adding the required surface potential Vd of the photosensitive drum 1 to the discharge start voltage Vth.

  FIG. 4 is a schematic cross-sectional view showing the layer structure of the photosensitive drum 1 (the charging roller 2 is also shown). The photosensitive drum 1 has a conductive support 30. The conductive support 30 is electrically grounded (connected to ground). A charge generation layer 31 is formed on the conductive support 30. Further, on the charge generation layer 31, a charge transport layer 32 having lubricity constituting the surface layer (outermost layer) of the photosensitive drum 1 is formed. Thus, the photosensitive drum 1 in this embodiment has a lubricating layer formed on the outermost surface. Since the lubricating layer is formed on the outermost surface of the photosensitive drum 1, the toner T is not supplied to the contact portion between the cleaning blade 16 and the photosensitive drum 1. It is possible to reduce the friction coefficient. Thereby, generation | occurrence | production of problems, such as the above-mentioned blade noise, can be suppressed.

  The surface layer 32 can be formed by applying and drying a paint in which a charge transport material, a binder resin, and a slipping material (lubricant) are dissolved in a solvent. As the binder resin, for example, polyester resin, polyacryl resin, polyvinyl carbazole resin, phenoxy resin, polycarbonate resin, polystyrene resin, polyvinyl acetate resin, polysulfone resin, and the like are used. In addition, polyarylate resin, vinylidene chloride / acrylonitrile copolymer resin, polyvinyl benzal resin, and the like are used. In addition, a comb polymer can be used as the slipping material, and commercially available products include US270, US380, US450 (trade name, manufactured by Toagosei Co., Ltd.). In this example, US270 was used.

3. Control Mode FIG. 5 is a block diagram showing a schematic control mode of the main part of the image forming apparatus 100 of the present embodiment. The operation of each unit of the image forming apparatus 100 is controlled by a control unit (control circuit) 50 as a control unit provided in the apparatus main body A. The control unit 50 includes an arithmetic control unit, a storage unit (ROM, RAM), and the like, and comprehensively controls the operation of each unit of the image forming apparatus 100 according to programs and data stored in the storage unit. For example, the control unit 50 is connected to the drive motor M, the charging power source E1, the exposure device 3, the developing power source E2, the transfer power source E3, and the like. Further, an external host device such as a personal computer is connected to the control unit 50 so as to be communicable. The control unit 50 causes an image forming operation to be executed in accordance with image information input from an external host device.

  In the present embodiment, the cartridge B includes a memory 27 as a storage unit that stores various information related to the cartridge B, and a cartridge-side transmission unit 28 for controlling reading and writing of information with respect to the memory 27. The memory 27 and the cartridge side transmission unit 28 are integrated on the substrate and attached to the cartridge B. The apparatus main body A is provided with a main body side transmission unit 29 that controls reading and writing of information with respect to the memory 27 via the cartridge side transmission unit 28. In a state where the cartridge B is mounted on the apparatus main body A, the controller 50 can read / write information from / to the memory 27 via the cartridge side transmission unit 28 and the main body side transmission unit 29. In the present embodiment, the communication between the cartridge side transmission unit 28 and the main body side transmission unit 29 is performed in a non-contact manner by electromagnetic waves, but these may be capable of communicating by contacting via a contact point. In this embodiment, the memory 27 stores at least information (use history information) regarding whether or not the cartridge B is new. Based on this information, the control unit 50 can determine whether or not the cartridge B attached to the apparatus main body A is new. As described above, in this embodiment, the memory 27, the cartridge side transmission unit 28, the main body side transmission unit 29, and the like constitute a new article detection unit that detects whether or not the cartridge B is new. In addition, the memory 27 may store various information such as a characteristic value of the cartridge B and a parameter value for changing the process condition.

  The cartridge B is mounted on the apparatus main body A by opening and closing an opening / closing door (not shown) provided on the apparatus main body A and inserting / removing the cartridge B with respect to the guide means and positioning means provided on the apparatus main body A. And can be removed. When the cartridge B is mounted on the apparatus main body A and the opening / closing door of the apparatus main body A is closed, the cartridge B is mechanically and electrically coupled to the apparatus main body A side, and an image forming operation is possible. The apparatus main body A is provided with a power switch (not shown) and a door switch (not shown) for detecting the open / closed state of the open / close door. When the power switch is turned from OFF to ON while the door switch is ON (the open / close door is closed), or when the door switch is turned from OFF to ON while the power switch is ON, the image forming apparatus 100 is turned on. Is in the state of being put in.

  The cartridge B is replaced with a new one when, for example, the remaining amount detecting means (not shown) detects that the amount of the toner T in the toner chamber 5 has fallen below a predetermined value. As the remaining amount detection means, any known means such as a capacitance detection type or an optical detection type can be used. When the remaining amount detecting means detects that the amount of toner T has fallen below a predetermined value, the control unit 50 displays the operation unit 60 provided in the apparatus main body A or the display means (display or the like) of the external host device. Then, information prompting replacement of the cartridge B is displayed.

4). Operation Sequence FIG. 6 is a schematic diagram illustrating an operation sequence of the image forming apparatus 100.

  (1) Initial rotation operation (initial operation, pre-multi-rotation process): The initial rotation operation is an operation during a start operation period (start operation period, warming period) when the image forming apparatus 100 is started. In the initial rotation operation, when the image forming apparatus 100 is turned on, the drive motor M is activated to start the rotational driving of the photosensitive drum 1, and the fixing device 14 is raised to a predetermined temperature. A process device preparation operation is performed. In this embodiment, a developer application (toner purge) sequence, which will be described later, is executed during the initial initial rotation operation of a new cartridge B.

  (2) Print preparation rotation operation (pre-rotation process): The print preparation rotation operation is performed after an image formation start instruction (print signal) is input to the image forming apparatus 100 until a print process described later is actually started. This is a preparatory operation for the period. When a print signal is input to the image forming apparatus 100 during the initial rotation operation, the print preparation rotation operation is executed following the initial rotation operation. When the print signal is not input during the initial rotation operation, the drive motor M is temporarily stopped after the initial rotation operation is finished, the rotation of the photosensitive drum 1 is stopped, and the image forming apparatus 100 receives the print signal. Until it is kept in the standby (standby) state. When a print signal is input, a print preparation rotation operation is executed.

  (3) Printing process (image forming process, image forming process): The printing process is a period during which toner image formation and toner image transfer are actually performed. When the predetermined print preparation rotation operation is completed, the toner image is formed on the rotating photosensitive drum 1, the toner image is transferred to the recording material P, and the toner image is fixed on the recording material P. Is output. In the case of continuous printing (continuous printing), the above printing process is repeated for a predetermined set number of prints n (3 in the illustrated example).

  (4) Inter-sheet process: In the inter-sheet process, in continuous printing, after the trailing end of one recording material P passes through the transfer portion N, the leading end of the next recording material P reaches the transfer portion N. In this period, there is no recording material P in the transfer portion N.

  (5) Post-rotation operation: In the post-rotation operation, after the printing process of the last recording material P is completed, the drive motor M is continuously driven for a while and the photosensitive drum 1 is continuously rotated. This is a period during which post-operations (organization operation, preparation operation) are executed.

  (6) Standby (standby): When a predetermined post-rotation operation is completed, the drive motor M is stopped and the rotation of the photosensitive drum 1 is stopped, and the image forming apparatus 100 inputs the next print signal to the image forming apparatus 100. It is kept in the standby state until it is done. In the case of printing only one sheet, after the end of the printing, the image forming apparatus 100 enters a standby state through a post-rotation operation. When a print signal is input to the image forming apparatus 100 in the standby state, the image forming apparatus 100 starts a print preparation rotating operation.

  Here, the time of the printing process of (3) is the time of image formation, the time of the initial rotation operation of (1), the time of printing preparation rotation operation of (2), the time of paper interval of (4), (5) The post-rotation operation is during non-image formation.

5. Charging Roller Slip The charging roller 2 normally rotates following the rotation of the photosensitive drum 1. However, as described above, when driving of the photosensitive drum 1 is started in the initial initial rotation operation of the new cartridge B, the charging roller 2 and the photosensitive drum are not driven and rotated by the photosensitive drum 1. 1 may slip.

  Whether the charging roller 2 rotates following the photosensitive drum 1 depends on the frictional force F1 between the photosensitive drum 1 and the charging roller 2, and between the charging roller bearing 23 and the core metal 2a of the charging roller 2. It is determined in relation to the frictional force F2. The friction force is determined by the product of the friction coefficient and the normal force. Regarding the frictional force F1 between the photosensitive drum 1 and the charging roller 2, the friction coefficient μ1 is determined by the surface state of the photosensitive drum 1 and the charging roller 2. The vertical drag N1 is determined by the sum of the pressing force of the pressure spring 24 and the vector gravity in the direction perpendicular to the tangent of the photosensitive drum 1 at the contact portion between the photosensitive drum 1 and the charging roller 2. Is done. On the other hand, the friction coefficient μ2 of the frictional force F2 between the metal core 2a and the charging roller bearing 23 is determined by the surface state of the metal core 2a and the charging roller bearing 23. The vertical drag N2 is determined by the force with which the single charging roller bearing 23 presses the cored bar 2a, the pressure of the pressing spring, and the weight (gravity) of the charging roller 2.

  As will be described later, due to the influence of the charging bias applied to the charging roller 2, the coefficient of friction between the photosensitive drum 1 and the charging roller 2 increases after the initial rotation operation than before the initial rotation operation. Therefore, during normal image formation after the initial rotation operation, F1 (= μ1 × N1)> F2 (= μ2 × N2), and the charging roller 2 rotates following the photosensitive drum 1. However, before the initial rotation operation, μ1 is lower than that after the initial rotation operation, and thus F1 <F2.

  Therefore, in this embodiment, when the control unit 50 determines that the cartridge B is new, the control unit 50 performs the initial rotation operation with the rotation drive of the photosensitive drum 1 as follows. That is, a voltage lower than the discharge start voltage is applied to the charging roller 2 during a period from when it is new to when a voltage higher than the discharge start voltage is applied to the charge roller 2. Thus, when driving of the photosensitive drum 1 is started in the initial initial rotation operation of the new cartridge B, the electrostatic attractive force between the photosensitive drum 1 and the charging roller 2 is increased, and the charging roller 2 is exposed to light. The drum 1 is driven to rotate.

  In the present embodiment, in the initial initial rotation operation of the new cartridge B, the voltage less than the discharge start voltage is −300 V from about 100 to 200 ms before the drive start timing of the photosensitive drum 1 to about 100 to 200 ms. A voltage is applied to the charging roller 2. By applying a voltage lower than the discharge start voltage to the charging roller 2, a potential difference is generated between the electrically conductive support 30 of the photosensitive drum 1 that is electrically grounded and the charging roller 2, and is proportional to the applied voltage. The electrostatic attraction force N3 is generated. Therefore, by applying a voltage lower than the discharge start voltage to the charging roller 2, F1 = μ1 × (N1 + N3), and the frictional force between the charging roller 2 and the photosensitive drum 1 can be increased. The electrostatic attraction force N3 is the applied voltage, the total thickness of the charge transport layer 32 and the charge generation layer 31 of the photosensitive drum 1, the diameter of the charging roller 2 and the photosensitive drum 1, and the charging roller 2 and the photosensitive drum 1. , And the volume resistivity of the charging roller 2. Accordingly, a voltage lower than an appropriate discharge start voltage sufficient to suppress the slip between the charging roller 2 and the photosensitive drum 1 can be determined in advance according to the configuration of the image forming apparatus 100.

  Here, the discharge start voltage (discharge threshold) is a voltage value at which discharge starts when the absolute value of the voltage applied to the charging roller 2 is gradually increased. The discharge start voltage is obtained as follows. FIG. 7 schematically shows measurement results of current when the DC voltage applied to the charging roller 2 is changed. The horizontal axis represents voltage (V) (negative polarity in this example. The absolute value increases as it goes to the right), and the vertical axis represents current (μA). As shown in FIG. 7, the relationship between the voltage and the current increases substantially linearly until the absolute value of the voltage exceeds a predetermined value. However, the current increases rapidly from around the predetermined value. This is because discharge started between the charging roller 2 and the photosensitive drum 1, and the current flowing between them suddenly increased. The voltage value in the vicinity where this current changes rapidly can be obtained as the discharge start voltage (for example, the voltage corresponding to the intersection of the approximate straight line for the voltage below the discharge start voltage and the approximate straight line for the voltage above the discharge start voltage. can do.). In this embodiment, the discharge start voltage is about -600V.

  Table 1 shows the density unevenness of the halftone image after the initial rotation operation when the voltage applied to the charging roller 2 is changed when driving of the photosensitive drum 1 is started in the initial initial rotation operation of the new cartridge B. The result of examining the level of is shown. ○ represents that no density unevenness occurred on the halftone image, and x represents that density unevenness occurred. It should be noted that the magnitude of the bias (strong or weak) here refers to the case where the absolute values are compared.

  When the voltage of the charging roller 2 is not applied (0 V), the charging roller 2 and the photosensitive drum 1 slip, and the horizontal belt-like shape along the rotational axis direction of the photosensitive drum 1 is formed on the halftone image at the pitch of the charging roller 2. Image density unevenness occurred. Slip is less likely to occur than when no voltage is applied, but the same was true for -100V and -150V.

  There are mainly the following two causes for the occurrence of the horizontal band-shaped image density unevenness on the halftone image due to the slip between the charging roller 2 and the photosensitive drum 1. The first cause is as follows. When the charging roller 2 is rubbed against the photosensitive drum 1 without being rotated by being driven by the photosensitive drum 1, electric charge remains in the high resistance region on the surface of the charging roller 2 (memory by rubbing). As a result, the electric potential on the surface of the charging roller 2 changes, leading to uneven discharge between the charging roller 2 and the photosensitive drum 1. When this discharge unevenness occurs, unevenness occurs in the surface potential on the photosensitive drum 1 after the charging process, and horizontal stripes of 2 pitches of the charging roller due to the uneven surface potential occur on the halftone image. The second cause is as follows. When the charging roller 2 is rubbed against the photosensitive drum 1, a part of the lubricating layer of the photosensitive drum 1 adheres to the charging roller 2 and the surface resistance of the charging roller 2 changes. As a result, uneven resistance occurs in the circumferential direction of the charging roller 2, leading to uneven discharge between the charging roller 2 and the photosensitive drum 1. When this discharge unevenness occurs, a horizontal band-like streak occurs on the halftone image as described above.

  On the other hand, when a voltage of −200 V or more (but less than the discharge start voltage) is applied, slip between the charging roller 2 and the photosensitive drum 1 is sufficiently suppressed, and image density unevenness due to this slip does not occur. .

  Thus, when driving of the photosensitive drum 1 is started in the initial initial rotation operation of a new cartridge B, a voltage lower than the discharge start voltage is applied to the charging roller 2. As a result, the vertical drag between the charging roller 2 and the photosensitive drum 1 can be increased, and image defects due to the slip between the charging roller 2 and the photosensitive drum 1 can be suppressed.

  Note that the voltage required to sufficiently suppress the slipping of the charging roller 2 may vary depending on the environment (atmosphere temperature or humidity). For example, in a relatively low temperature (or low humidity) environment, the electrical resistance of the charging roller 2 is high, and thus a voltage having a larger absolute value is required than in a relatively high temperature (or high humidity) environment. There is. Therefore, the control unit 50 applies the charging roller 2 to the charging roller 2 based on the relationship between the environment obtained in advance and the necessary voltage value based on the detection result of the environment detection unit (temperature / humidity sensor or the like) provided in the image forming apparatus 100. The applied voltage can be variably controlled. The environment detection means may detect at least one of temperature and humidity inside or outside the apparatus main body A. That is, the control unit 50 changes the voltage less than the discharge start voltage applied to the charging roller 2 when starting the driving of the photosensitive drum 1 in the initial initial rotation operation of the new cartridge B based on the ambient temperature or humidity. can do.

6). Flow of Initial Rotation Operation FIG. 8 is a flowchart showing the procedure of the initial rotation operation in the present embodiment. FIG. 9 is a timing chart showing the operation state of each part of the initial rotation operation when it is determined that the cartridge B is new according to the procedure of FIG.

  S1: When the power of the image forming apparatus 100 is turned on (when the door switch is turned on, the power switch is turned from OFF to ON, or when the power switch is turned on, the door switch is turned from OFF to ON) Start rotating motion.

  S2: The controller 50 determines whether or not the cartridge B is attached to the apparatus main body A based on the presence or absence of communication with the memory 27 of the cartridge B. In this embodiment, the determination is made based on the presence / absence of communication with the memory 27, but the present invention is not limited to this. For example, the cartridge B is mounted on the mounting body A based on detection results of a remaining amount detection unit that detects the remaining amount of toner T, a current detection unit that detects a current when a voltage is applied to the transfer roller 13, and the like. It is also possible to detect whether or not It suffices if the controller 50 can determine whether or not the cartridge B is mounted on the apparatus main body A.

  S3: The control unit 50 determines whether or not the cartridge B is new based on the data read from the memory 27 of the cartridge B. Specifically, the control unit 50 determines that the cartridge B is not new if the use history of the cartridge B is recorded in the memory 27, and determines that the cartridge B is new if the use history is not recorded. can do. In this embodiment, the determination is made using the memory 27, but the present invention is not limited to this. For example, it is possible to detect whether or not the cartridge B is new by detecting the opening / closing (ON / OFF) of an electric circuit such as a fuse provided in the cartridge B. It is only necessary that the control unit 50 can determine whether or not the cartridge B is new.

  S4: When the controller 50 determines that the cartridge B is new, it starts to apply a voltage of −300 V, which is a voltage lower than the discharge start voltage, from the charging power source E1 to the charging roller 2.

  S5: The control unit 50 turns on the drive motor M 100 ms after starting the application of the voltage to the charging roller 2 in S4, and starts the rotation of the photosensitive drum 1 and the developing roller 10. In this embodiment, the peripheral speed (surface moving speed) of the photosensitive drum 1 is 100 mm / s. In this embodiment, the drive motor M is started 100 ms after the application of the voltage to the charging roller 2 is started in S4. However, the present invention is not limited to this. For example, when the photosensitive drum 1 actually starts to rotate slightly behind the start of the drive motor M due to the influence of gear play or the like, almost simultaneously with the start of the voltage application to the charging roller 2 or the application The drive motor M may be activated slightly earlier than that. If the rotation of the photosensitive drum 1 starts almost simultaneously with the application of voltage to the charging roller 2 or after the voltage is applied, the charging roller 2 is exposed to light almost simultaneously with the start of rotation of the photosensitive drum 1. There is no problem because it rotates following the drum 1. Here, the charging roller 2 is driven and rotated by the photosensitive drum 1 substantially simultaneously with the start of the rotation of the photosensitive drum 1 as well as when the charging roller 2 is rubbed against the photosensitive drum 1 at the same time. This includes the case in which the above-described problem does not occur.

  S6: The controller 50 turns off the application of voltage to the charging roller 2 200 ms after the drive of the photosensitive drum 1 is started in S6. Thus, the state where a voltage lower than the predetermined discharge start voltage is applied to the charging roller 2 is maintained for a predetermined time (300 ms in this embodiment). Here, in a state in which the charging roller 2 is rotated following the photosensitive drum 1, the friction coefficient between the charging roller bearing 23 and the cored bar 2a is lower than that at rest. Therefore, even if the voltage applied to the charging roller 2 is turned off and the vertical effect between the charging roller 2 and the photosensitive drum 1 is reduced, the charging roller 2 and the photosensitive drum 1 do not slip.

  S7: The controller 50 starts the application of a −300 V developing bias from the developing power source E2 to the developing roller 10 substantially simultaneously with the voltage applied to the charging roller 2 being turned off in S6. Up to now, since no discharge has occurred between the charging roller 2 and the photosensitive drum 1, the surface potential of the photosensitive drum 1 remains substantially 0V. On the other hand, since the developing bias is −300 V, the toner T on the developing sleeve 10 charged to the negative polarity is transferred onto the photosensitive drum 1 having a relatively high potential on the positive polarity side. In this embodiment, the application of the development bias is started almost simultaneously with the application of the voltage less than the start of discharge to the charging roller 2 being turned off, but the timing of starting the application of the development bias is the start of the discharge. It may be before or after the voltage less than OFF is turned off.

  S8: The control unit 50 starts applying a charging bias of −1100 V, which is a voltage equal to or higher than the discharge starting voltage, from the charging power source E1 to the charging roller 400 ms after starting the application of the developing bias in S7. The surface potential of the photosensitive drum 1 after applying the charging bias is −500V. When this charged region of the photosensitive drum 1 reaches the developing portion b, the potential of the developing roller 10 to which a developing bias of −300 V is applied becomes relatively higher on the positive side, so that the toner T The transfer onto the photosensitive drum 1 is completed.

  Here, in this embodiment, the toner T is transferred from the developing roller 10 to the photosensitive drum 1 from when the developing bias is turned on until the charged region of the photosensitive drum 1 reaches the developing portion b. Therefore, the toner T adheres to an area of about 64 mm in the rotation direction of the photosensitive drum 1 represented by 400 ms × 100 mm / s + the distance from the charging unit a to the developing unit b (the circumferential direction of the photosensitive drum 1). The toner T adhering to the photosensitive drum 1 has a width over substantially the entire area of the developing sleeve 10 where the toner T is carried in the rotation axis direction. That is, a belt-like toner image is formed on the photosensitive drum 1. A part of the toner T transferred onto the photosensitive drum 1 is conveyed to the contact portion between the cleaning blade 16 and the photosensitive drum 1, and the friction coefficient between the cleaning blade 16 and the photosensitive drum 1 can be lowered. Further, by applying a charging bias higher than the discharge start voltage to the charging roller 2, at least a part of the lubricating layer of the photosensitive drum 1 is scraped off. As a result, the friction coefficient between the photosensitive drum 1 and the charging roller 2 increases. Therefore, after that, even when a voltage (less than the discharge start voltage or more than the discharge start voltage) is not applied to the charging roller 2, the occurrence of slip between the charging roller 2 and the photosensitive drum 1 when the photosensitive drum 1 is driven is suppressed. The The developing bias ON time and the developing bias value are not limited to the values in this embodiment, but are changed according to the desired amount of toner supplied to the contact portion between the cleaning blade 16 and the photosensitive drum 1. can do. Further, in this embodiment, the photosensitive drum 1 that has passed through the charging portion a when the voltage lower than the discharge start voltage is applied to the charging roller 2 and when the application of the voltage to the charging roller 2 is stopped, respectively. Although the toner T is attached to the region, it may be attached to only one of them.

  Here, in order to suppress the transfer of the toner T adhering to the photosensitive drum 1 to the transfer roller 13, at least when the toner T passes through the transfer portion N, a voltage having the same polarity as the toner T is applied to the transfer roller 13. Can be applied. Alternatively, at least when the toner T passes through a position corresponding to the transfer portion N, the transfer roller 13 and the photosensitive drum 1 may be separated from each other.

  S9: The controller 50 turns off the developing bias and the charging bias 2s after starting the application of the charging bias to the charging roller 2 in S8.

  S10: The controller 50 turns off the drive motor M and stops the photosensitive drum 1 and the developing roller 10.

  S11: When the control unit 50 determines that the cartridge B is not attached to the apparatus main body A, the control unit 50 displays a warning that the cartridge B is not attached, an operation unit 60 provided in the apparatus main body A or an external host. It is performed in the display means (display etc.) of the device.

  As described above, the image forming apparatus 100 according to the present exemplary embodiment includes the rotatable photoreceptor 1 provided with the surface layer of the lubricant, and the cleaning blade 16 disposed in contact with the photoreceptor and scraping off the developer from the surface of the photoreceptor. Is removable from the apparatus main body A. In addition, the image forming apparatus 100 includes a charging member 2 that is disposed in contact with the photosensitive member 1, rotates following the rotation of the photosensitive member 1, and charges the surface of the photosensitive member 1 with the charging unit a. . Further, the image forming apparatus 100 supplies the developer to the photosensitive member 1 in the rotation direction of the photosensitive member 1 on the downstream side of the charging portion a and on the upstream side of the contact portion c between the cleaning blade 16 and the photosensitive member 1. Developing means 10 is provided. Further, the image forming apparatus 100 includes a new article detecting unit (such as the memory 27) that detects whether the process cartridge B is new. Then, the image forming apparatus 100 performs control to start driving the photosensitive member 1 in a state where a voltage lower than the discharge start voltage is applied to the charging member 2 when the new cartridge detecting unit detects that the process cartridge B is new. It has the control means 50 to perform. Thereby, it is possible to suppress the charging member 2 and the photosensitive member 1 from slipping when the driving of the photosensitive member 1 is started, and to prevent the charging member 2 from being rubbed against the photosensitive member 1. Further, when the driving of the photosensitive member 1 is started, the period for maintaining the lubricating layer of the photosensitive member 1 can be made longer than when a voltage higher than the discharge starting voltage is applied to the charging member 2 from the beginning. In addition, the control unit 50 starts driving the photosensitive member 1 with a voltage less than the discharge start voltage applied to the charging member 2, and then applies a voltage higher than the discharge start voltage to the charging member 2. The developer is attached to the region of the photoreceptor 1 that is not charged by the developing means 10. Then, the control means 50 removes the developer before the region of the photosensitive member 1 that has been in the charging portion a reaches the contact portion c when application of a voltage equal to or higher than the discharge start voltage to the charging member 2 is started. Control is performed so that the region of the photoconductor 1 attached reaches the contact portion c. As a result, the region where the lubricant layer of the photoreceptor 1 is scraped by applying a voltage equal to or higher than the discharge start voltage to the charging member 2 after supplying the developer as the lubricant to the contact portion c is the contact portion. By reaching c, problems such as blade noise can be suppressed. In particular, in this embodiment, the control unit 50 performs control so that application of a voltage lower than the discharge start voltage to the charging member 2 is started before the rotation of the photoreceptor 1 is started. That is, in this embodiment, the slip prevention sequence control between the charging roller 2 and the photosensitive drum 1 is executed at the time of the initial initial rotation operation of the new cartridge B.

  As described above, according to the present embodiment, even before the highly lubricious surface layer of the photosensitive drum 1 is scraped off, the charging roller 2 and the photosensitive drum 1 are prevented from slipping, and the charging roller 2 is rubbed against the photosensitive drum 1. It is possible to suppress the density unevenness of the halftone image resulting from this.

[Others]
As mentioned above, although this invention was demonstrated according to the specific Example, this invention is not limited to the above-mentioned Example.

  Unless otherwise specified, the functions, materials, physical properties, shapes, rotational directions, relative arrangements, and the like of the components described in the above-described embodiments limit the scope of the present invention to them. It is not intended.

  In the above-described embodiment, the DC charging method is adopted, but the AC charging method may be adopted. In the AC charging method, a oscillating voltage obtained by superimposing a DC voltage corresponding to the required surface potential Vd of the photosensitive drum and an AC voltage (AC voltage) having a peak-to-peak voltage Vpp that is at least twice the discharge start voltage Vth. Is applied to the charging roller to perform a charging process. The oscillating voltage may be a superimposed voltage of an AC component (AC component) and a DC component (DC component), and a sine wave, a rectangular wave, a triangular wave, or the like can be appropriately used as the AC component waveform. It may be a rectangular wave voltage formed by periodically turning on and off a DC power supply. In this case, the voltage applied to the charging roller when driving the photosensitive drum in the initial initial rotation operation of a new process cartridge is a vibration voltage in which the DC voltage and the AC voltage are superimposed, even if only the DC voltage is used. May be. However, both the DC voltage and the AC voltage are lower than the discharge start voltage.

  In the above-described embodiments, the photosensitive member is a rotatable drum type photosensitive drum. However, other forms such as a rotatable endless belt may be used. Similarly, in the above-described embodiments, the charging member is a rotatable roller-type charging roller, but other forms such as a rotatable endless belt may be used.

DESCRIPTION OF SYMBOLS 1 Photosensitive drum 2 Charging roller 3 Exposure apparatus 4 Development unit (development apparatus)
DESCRIPTION OF SYMBOLS 10 Developing roller 13 Transfer roller 16 Cleaning blade 18 Cleaning unit (cleaning apparatus)
31 Charge generation layer 32 Charge transport layer (lubricant layer, surface layer)
A Image forming apparatus body (apparatus body)
B Process cartridge (cartridge)
T Toner (Developer)

Claims (8)

A process cartridge including a rotatable photosensitive member having a surface layer of a lubricant and a cleaning blade disposed in contact with the photosensitive member and scraping off the developer from the surface of the photosensitive member is removed from the image forming apparatus main body. A possible image forming apparatus,
A charging member that is disposed in contact with the photoconductor, rotates following the rotation of the photoconductor, and charges the surface of the photoconductor with a charging unit;
Developing means for supplying a developer to the photoconductor downstream of the charging unit and upstream of the contact portion between the cleaning blade and the photoconductor in the rotation direction of the photoconductor;
New article detecting means for detecting whether the process cartridge is new,
Control means for performing control to start driving of the photosensitive member in a state where a voltage lower than a discharge start voltage is applied to the charging member when the process cartridge is detected as new by the new article detection means;
An image forming apparatus comprising:   The control means starts driving the photoconductor with a voltage less than a discharge start voltage applied to the charging member, and then applies a voltage higher than the discharge start voltage to the charging member and charges the charging member with the charging member. The developer is attached to the unexposed area of the photoconductor by the developing means, and the area of the photoconductor in the charging portion when the voltage higher than the discharge start voltage is started to be applied to the charging member. The image forming apparatus according to claim 1, wherein control is performed so that the area of the photoconductor to which the developer is attached reaches the contact portion before reaching the contact portion.   The control means applies a voltage lower than the discharge start voltage to the charging member for a predetermined time, stops applying the voltage to the charging member for a predetermined time, and then exceeds the discharge start voltage to the charging member. The charging is started when the application of voltage is stopped and the application of the voltage to the region of the photosensitive member or the charging member that has passed through the charging unit is stopped when a voltage less than the start of discharge is applied to the charging member. The image forming apparatus according to claim 2, wherein control is performed so that the developer is attached to at least one of the regions of the photoconductor that have passed through the portion.   The image forming apparatus according to claim 2, wherein the control unit controls the developer to be transferred from the developing unit to the photoreceptor by applying a voltage to the developing unit.   5. The image according to claim 1, wherein in the process cartridge in a new state, a particulate lubricant is not applied to a region of the cleaning blade that contacts the photoconductor. 6. Forming equipment.   The image forming apparatus according to claim 1, wherein the process cartridge includes a storage unit that stores information regarding whether or not the process cartridge is new.   The image forming apparatus according to claim 1, wherein the process cartridge includes the developing unit.   The image forming apparatus according to claim 1, wherein the process cartridge includes the charging member.

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