JP2009133997A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To keep the density of a print image constant without being affected by toner electric charges that rise accompanying the operating time of a process cartridge and to prevent an external additive mixed with toner from sticking to a photoreceptor drum and soiling a charging roller. <P>SOLUTION: The image forming apparatus includes: a development high voltage output means by which a high voltage in which an AC component and DC component overlaps is generated and applied to a developing means; a storage means for storing information about the cumulative operating time of the process cartridge. Based on the information on the cumulative operating time of the process cartridge, the voltage of the AC component of the development high voltage output, the ON duty of a frequency, and the voltage of the DC component are changed. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an image forming apparatus using an electrophotographic process such as a copying machine or a printer, and more particularly to a method for controlling a development high-voltage output according to the usage time of a process cartridge.

  FIG. 4 schematically shows an example of a conventional image forming apparatus. In the figure, an image forming apparatus 33 includes a photosensitive drum 40 that is an image carrier for realizing an electrophotographic process, a charging high-voltage circuit 43 that is a high-voltage generating unit that generates charges for charging the surface of the photosensitive drum, An electrostatic latent image is formed by irradiating the charged roller 41, which is a charging means for uniformly placing the charge generated by the high-voltage circuit 43 on the photosensitive drum 40, and the surface (charged surface) of the charged photosensitive drum according to image data. A laser irradiation device 46 that is an electrostatic latent image forming means for forming; a developing sleeve 39 that is disposed in the vicinity of the photosensitive drum 40 and performs a developing process for visualizing the electrostatic latent image on the photosensitive drum with toner; and a developer. A toner container 38 for holding toner and a developing high-voltage circuit 36 which is a high-pressure generating means for moving the toner from the developing sleeve 39 to the photosensitive drum 40 are provided. To have. In addition, a photosensitive drum 40, a charging roller 41, a developing sleeve 39, and a toner container 38 are incorporated, and a process cartridge 42 that is detachable from the main body of the image forming apparatus is provided. In the image forming apparatus 33 configured as described above, an electrostatic latent image is formed on the photosensitive drum uniformly charged via the charging roller 41 by the charging high voltage output by the laser light emitted from the laser irradiation device 46. The electrostatic latent image on the photosensitive drum is developed by a development high-voltage output applied to the developing sleeve 39 to become a toner image. Thereafter, the toner image on the photosensitive drum is transferred to a recording medium (paper) P by the transfer device 44. Finally, the sheet P onto which the toner image has been transferred is conveyed to a fixing unit 45 including a heating / pressurizing unit, where the toner image is fixed on the sheet and discharged outside the image forming apparatus 33.

  Here, attention is paid to the electric charge of the toner filled in the process cartridge. As shown in FIG. 7, this toner charge is known to increase in the negative direction with the operation time of the process cartridge. Accordingly, when the image forming apparatus 33 continues the printing operation without adjusting the settings of the AC component and the DC component voltage of the development high voltage output, the development high voltage output is applied during the development process as shown in FIG. In addition, the amount of toner that moves from the developing sleeve 39 to the photosensitive drum 40 increases as the toner charge increases. Therefore, as a result, the density of the printed image becomes higher as printing continues. Such a change in density of the printed image with time is not preferable in terms of image quality. Therefore, in order to prevent such a phenomenon, a method of changing the voltage value of the DC component of the development high voltage output according to the operation time of the process cartridge 42 is known in the conventional example. This is because the density of the printed image is determined by the difference Vcnt between the surface potential VL of the electrostatic latent image portion on the photosensitive drum and the surface potential DevVdc of the developing sleeve 39 in addition to the magnitude of the toner charge. Specifically, the smaller the potential difference Vcnt between the photosensitive drum 40 and the developing sleeve 39, the lighter the density, and the larger, the darker the density. Therefore, as shown in FIG. 9, the surface potential of the electrostatic latent image portion on the photosensitive drum and the surface of the developing sleeve 39 are increased by increasing the voltage of the DC component of the development high voltage output in accordance with the operation time of the process cartridge 42. The difference from the potential is reduced. For this reason, the density increase of the printed image that becomes dark due to the toner charge increase is canceled out. As a result, the density of the printed image can be kept constant regardless of the operation time of the process cartridge 42.

As a technique for controlling the voltage applied to the developer carrying member in order to suppress the density change, Patent Document 1 is known.
JP 2000-250294 A

  The toner filled in the process cartridge described above usually has a certain degree of viscosity. Therefore, the toner sticks to each other due to stirring in the process cartridge, and deviation occurs when trying to put the toner uniformly on the developing sleeve, resulting in uneven density in the printed image. It can be considered. In addition, when the toner is moved from the developing sleeve 39 to the photosensitive drum 40 in the developing process, it is difficult to move because the toners stick to each other, and the developing process is normal, such as difficult to move due to the viscosity of the toner itself. Therefore, it is conceivable that the quality of the printed image is deteriorated. Therefore, a countermeasure is taken to lower the viscosity of the toner and increase the fluidity by mixing an additive having high fluidity called an external additive with the toner. As a result, the toner can be uniformly placed on the developing sleeve. Further, since the toners are separated from each other without sticking, a normal development process can be performed, and a desired amount of toner can be moved to a desired location on the photosensitive drum. Therefore, the quality of the printed image can be maintained. However, the external additive normally remains on the developing sleeve even after the toner has moved to the photosensitive drum 40. However, if the development high-voltage output exceeds a certain value (external additive movement start voltage), the external additive is also photosensitive. Begin moving to drum 40. Therefore, as shown in FIG. 10, control is performed to increase the DC component voltage of the development high-voltage output in accordance with the operation time of the process cartridge 42. As a result, when the upper limit voltage of the AC component begins to exceed the external additive movement start voltage, the external additive originally remaining on the developing sleeve 39 starts to move to the photosensitive drum 40. As a result, the external additive that has moved onto the photosensitive drum adheres to the charging roller 41 installed adjacent to the photosensitive drum 40. If the external additive adheres to the charging roller 41 and a large amount of the external additive adheres, the charging process is affected and the quality of the printed image is degraded.

  The present invention has been made in view of such a situation, and the AC component voltage, frequency duty, and DC component voltage of the development high-voltage output are changed in accordance with the operation time of the process cartridge 42. . Accordingly, an object of the present invention is to provide an image forming apparatus 33 that can keep the density of a printed image constant without being affected by the toner charge that rises with the operation time of the process cartridge 42. It is another object of the present invention to provide an image forming apparatus 33 that can prevent the charging roller 41 from becoming dirty due to the external additive mixed with the toner adhering to the photosensitive drum 40.

  In order to achieve the above object, the present invention comprises exposing an image carrier, a charging means for charging the surface of the image carrier, and a charged surface of the surface of the image carrier according to image data. An electrostatic latent image forming means for forming an electrostatic latent image with a developing means for developing the electrostatic latent image on the surface of the image carrier as a toner image with toner, A process cartridge including an image bearing member, the charging unit, and the developing unit is detachable from the main body of the image forming apparatus, a storage unit that stores an accumulated operation time of the process cartridge, an alternating current component and a direct current with respect to the developing unit A development high voltage output means for generating and applying a high voltage with superimposed components from a single transformer, and a development high voltage setting changing means for changing each setting of the AC component and the DC component of the development high voltage output. In the image forming apparatus performing the developing process, the development high voltage setting changing unit changes each setting of the AC component and the DC component of the development high voltage output based on the information in the storage unit, and the development high voltage output unit A development high voltage output based on setting information of the development high voltage setting changing means is applied to the development means.

  According to the present invention, in the image forming apparatus using toner in which the toner charge increases with the operation time of the process cartridge 42, the voltage and frequency duty of the AC component of the development high-voltage output according to the operation time of the process cartridge 42. And control is performed to change the voltage of the DC component.

  By performing such control, it is possible to keep the density of the print image that changes with the operation time of the process cartridge 42 without changing. Further, it is possible to prevent the charging roller 39 from being contaminated by the external additive mixed with the toner.

(Example 1)
FIG. 4 is a diagram showing an example of the electrophotographic process of the image forming apparatus according to the embodiment of the present invention, and the configuration thereof is the same as the conventional example. Reference numeral 40 denotes a photosensitive drum, and a charging roller 41, a developing sleeve 39, and a transfer roller 44 are disposed adjacent to each other. The photosensitive drum 40 is grounded, and the charging roller 41, the developing sleeve 39, and the transfer roller 44 are connected to a high voltage power source for applying respective biases. A cartridge motor 35 drives the process cartridge, and drives the photosensitive drum 40, the charging roller 41, the developing sleeve 39, and the like. Reference numeral 37 denotes a non-volatile memory that stores process cartridge information. P is a printing sheet as a recording medium.

  The surface of the photosensitive drum 40 is uniformly negatively charged by a bias applied to the charging roller 41. The surface of the photosensitive drum is exposed in accordance with image data by laser light emitted from the laser scanner 46, and an electrostatic latent image is formed by removing the charge from the exposed portion. The electrostatic latent image on the surface of the photosensitive drum is developed by toner that moves to the exposed portion on the photosensitive drum 40 by a bias applied to the developing sleeve 39, and becomes a visible image as a toner image. The toner image on the surface of the photosensitive drum is transferred to the paper P by a plus bias applied to the transfer roller 44. The paper P on which the toner image has been transferred is conveyed to the fixing device 45, and after being subjected to fixing processing by heat and pressure, it is discharged out of the image forming apparatus 33 as a final print image.

  FIG. 3 shows the configuration of the development high-voltage output circuit at this time. The development high-voltage output is a bias 47 in which an alternating current component and a direct current component are superimposed, and the voltage and frequency of the alternating current component and the voltage of the direct current component can be varied. The signal that varies the voltage of the AC component is DevACPWM 48 that is a PWM signal, and the signal that varies the frequency of the AC component is DevACCLK49 that is a clock signal. A signal that varies the voltage of the DC component is DevDCPWM50, which is a PWM signal.

  The controller (CPU) 32 sets each setting value of the development high voltage output at the start of printing based on information read from the storage means 37. The control signals DevACPWM 48, DevACCLK 49, and DevDCPWM 50 are driven at the set values to output a desired development high voltage value. At this time, the information stored in the storage unit 37 is information on the cumulative number of printed sheets.

  FIG. 1 is a flowchart showing a development high voltage output control of the main body of the image forming apparatus and an operation time determination method of the process cartridge.

  When printing by the image forming apparatus 33 is started, the CPU 32 first reads the cumulative number of prints performed by the process cartridge 42 stored in the storage unit 37 (S1). Here, the control is performed by regarding the cumulative number of printed sheets as the cumulative operation time of the process cartridge 42. Next, according to the read accumulated print number information, the set values of the control signals DevACPWM48, DevACCLK49, and DevDCPWM50 for developing high-voltage output are determined and set (S2). At this time, the DevDCPWM 50 that determines the DC voltage value of the development high voltage output is set so that the ON duty of the signal is gradually increased in order to control the voltage value to increase with the cumulative operation time. On the other hand, DevACCLK49, which determines the clock frequency of the AC component of the development high-voltage output, is set to gradually increase the ON duty of the signal in order to control to increase the clock ON duty with the cumulative operation time. I do. Further, DevACPWM 48 that determines the voltage of the AC component is set so as to gradually increase the ON duty of the signal in order to control the voltage value to decrease with the cumulative operation time. Then, the development high voltage output is applied with the value set in S2 (S3). As described above, the control for changing the development high-voltage output with the operation time of the process cartridge 42 is performed. As a result, the phenomenon in which the density of the printed image increases due to the toner charge increasing with the operation time of the process cartridge 42 can be dealt with by increasing the voltage of the DC component of the development high-voltage output. I can do it. As the actual movement, as described above, the density of the printed image is determined by the potential difference Vcnt between the surface potential VL of the electrostatic latent image portion on the photosensitive drum and the surface potential DevVdc of the developing sleeve 39. Change the component voltage to be higher. By doing so, the potential difference Vcnt is reduced and the print image density is shifted in the direction of lightening, thereby canceling the phenomenon that the density of the print image is increased due to an increase in toner charge. Further, there is a phenomenon in which the external additive moves from the developing sleeve 39 to the photosensitive drum 40 as the development that occurs when the voltage of the DC component of the development high voltage output is increased. The external additive normally stays on the developing sleeve 39 and acts to increase the fluidity of the toner. However, when the development high-voltage output reaches the external additive movement start voltage, the movement of the external additive to the photosensitive drum 40 starts. As a result, the external additive adheres to the charging roller 41 and the charging roller becomes dirty. As countermeasures against this phenomenon, as shown in FIG. 2, it is possible to respond by increasing the ON duty of the frequency of the alternating current component of the development high voltage output and decreasing the voltage of the alternating current component. The actual movement is to first increase the NO duty of the frequency so that the AC component voltage does not reach the external additive movement start voltage when the DC component voltage of the development high voltage output is increased. The upper limit is lowered. In addition, since the image defect called fog occurs due to the relationship between the lower limit value of the AC component voltage of the developing high voltage output and the DC voltage of the charging high voltage output, the lower limit of the DC voltage of the charging high voltage output and the AC component voltage of the developing high voltage output. The relationship with the value needs to be constant. Therefore, the relationship between the DC voltage of the charging high voltage output and the lower limit value of the AC component voltage of the developing high voltage output is kept constant by lowering the voltage of the AC component of the developing high voltage output.

  Subsequently, image forming processes such as charging, exposure, development, transfer, and fixing are sequentially performed (S4). Then, it is determined whether or not the printing operation for one sheet is completed (S5), and when the printing for one sheet is completed, the printed sheet counter is counted up (S6). Subsequently, the steps S4, S5, and S6 are continued until there is no image data for printing (S7), and the number counter is incremented every time printing for one sheet is completed during this repetition. When there is no more image data for printing, the value counted by the number counter is added to the accumulated number of prints stored in the storage unit 37, and the sum is added to the storage unit 37 as a new accumulated print number. Update storage is performed (S8).

  Finally, the application of the development high voltage output is stopped (S9), and the image forming apparatus stops the printing operation.

  As described above, in this embodiment, each setting of the development high voltage output is changed with the operation time of the process cartridge 42. Each setting is changed so that the voltage of the DC component is high, the voltage of the AC component is low, and the frequency ON duty of the AC component is increased. The operation time is counted as the cumulative number of printed sheets. Thereby, it is possible to cope with a change in density of the printed image with the cartridge operation time, and it is possible to prevent the charging roller from being soiled by the external additive.

(Example 2)
FIG. 4 is a diagram showing an example of an electrophotographic process of the image forming apparatus according to the embodiment of the present invention. The configuration is the same as in the conventional example, but the development high-pressure control is different from the conventional example. Each component is the same as that described in the first embodiment.

  The photosensitive drum 40 is uniformly charged by a bias applied to the charging roller 41. The surface of the photosensitive drum is exposed with laser light to form an electrostatic latent image. The electrostatic latent image on the surface of the photosensitive drum is developed by a bias applied to the developing sleeve 39 and becomes a visible image as a toner image. The toner image is transferred onto the paper P by a plus bias applied to the transfer roller 44. The paper P is conveyed to the fixing device 45, and after being subjected to fixing processing by heat and pressure, the paper P is discharged out of the image forming apparatus 33.

  The configuration of the development high-voltage output circuit at this time is shown in FIG. Each component is the same as that described in the first embodiment.

  The controller (CPU) 32 sets each setting value of the development high voltage output at the start of printing based on information read from the storage means. Then, DevACPWM 48, DevACCLK 49, and DevDCPWM 50, which are control signals, are driven with the set values to output a desired development high voltage value. At this time, the information stored in the storage means 37 is information on the cumulative cartridge motor operating time of the cartridge motor 35.

  FIG. 5 is a flowchart showing a development high voltage output control of the image forming apparatus main body and a process cartridge operating time determination method.

  When printing of the image forming apparatus 33 is started, first, the CPU 32 reads the accumulated drive time of the cartridge motor that is responsible for driving the process cartridge 42 stored in the storage unit 37 (S11). Here, the control is performed by regarding the accumulated cartridge motor driving time as the accumulated operation time of the process cartridge 42. Next, according to the read accumulated cartridge motor driving time information, the set values of the control signals DevACPWM48, DevACCLK49, and DevDCPWM50 of the development high voltage output are determined and set (S12). At this time, the DevDCPWM 50 that determines the DC voltage value of the development high-voltage output is set so that the ON duty of the signal is gradually increased in order to control the voltage value to increase with the cumulative operation time. On the other hand, DevACCLK49, which determines the clock frequency of the AC component of the development high-voltage output, is set to gradually increase the ON duty of the signal in order to control to increase the clock ON duty with the cumulative operation time. I do. Further, DevACPWM 48 that determines the voltage of the AC component is set so as to gradually increase the ON duty of the signal in order to control the voltage value to decrease with the cumulative operation time. Then, the development high voltage output is applied with the value set in S2 (S13). As described above, the control for changing the development high-voltage output with the operation time of the process cartridge 42 is performed. As a result, the phenomenon in which the density of the printed image increases due to the toner charge increasing with the operation time of the process cartridge 42 can be dealt with by increasing the voltage of the DC component of the development high-voltage output. I can do it. As the actual movement, as described above, the density of the printed image is determined by the potential difference Vcnt between the surface potential VL of the electrostatic latent image portion on the photosensitive drum and the surface potential DevVdc of the developing sleeve 39. Change the component voltage to be higher. By doing so, the potential difference Vcnt is reduced and the print image density is shifted in the direction of lightening, thereby canceling the phenomenon that the density of the print image is increased due to an increase in toner charge. Further, there is a phenomenon in which the external additive moves from the developing sleeve 39 to the photosensitive drum 40 as the development that occurs when the voltage of the DC component of the development high voltage output is increased. The external additive normally stays on the developing sleeve 39 and acts to increase the fluidity of the toner. However, when the development high-voltage output reaches the external additive movement start voltage, the movement of the external additive to the photosensitive drum 40 starts. As a result, the external additive adheres to the charging roller 41 and the charging roller becomes dirty. As countermeasures against this phenomenon, as shown in FIG. 2, it is possible to respond by increasing the ON duty of the frequency of the alternating current component of the development high voltage output and decreasing the voltage of the alternating current component. The actual movement is to first increase the NO duty of the frequency so that the AC component voltage does not reach the external additive movement start voltage when the DC component voltage of the development high voltage output is increased. The upper limit is lowered. In addition, image defects called fogging occur due to the relationship between the lower limit value of the AC component voltage of the developing high voltage output and the DC voltage of the developing high voltage output, and the lower limit of the DC voltage of the charging high voltage output and the AC component voltage of the developing high voltage output. The relationship with the value needs to be constant. Therefore, the relationship between the DC voltage of the charging high voltage output and the lower limit value of the AC component voltage of the developing high voltage output is kept constant by lowering the voltage of the AC component of the developing high voltage output.

  Next, the driving of the cartridge motor 35 which is a driving means for driving the process cartridge 42 is started (S14). This motor is responsible for all driving of the process cartridge 42, such as rotational driving of the photosensitive drum 40, developing sleeve 39 and charging roller 41, and stirring of the toner in the toner container. Then, measurement of the drive time of the cartridge motor 35 is started in synchronization with the drive of the process cartridge 42 (S15).

  Subsequently, image forming processes such as charging, exposure, development, transfer, and fixing are sequentially performed (S16). Each image forming process is repeated in order until there is no image data for printing (S17), and when there is no image data for printing, the cartridge motor 35 is stopped (S18). At this time, measurement of the drive time of the cartridge motor 35 is stopped in synchronization with the stop of the cartridge motor 35 (S19). Then, the measured drive time of the cartridge motor 35 is added to the accumulated cartridge motor drive time stored in the storage means 37, and the added result is updated and stored in the storage means 37 as a new accumulated print number (S20).

  Finally, the application of the development high voltage output is stopped (S21), and the image forming apparatus 33 stops the printing operation.

  As described above, in this embodiment, each setting of the development high voltage output is changed with the operation time of the process cartridge 42. Each setting is changed so that the voltage of the DC component is high, the voltage of the AC component is low, and the frequency ON duty of the AC component is increased. The operation time is counted as the cumulative drive time of the cartridge motor. Thereby, it is possible to cope with a change in density of the printed image with the cartridge operation time, and it is possible to prevent the charging roller from being soiled by the external additive.

(Example 3)
FIG. 4 is a diagram showing an example of an electrophotographic process of the image forming apparatus according to the embodiment of the present invention. The configuration is the same as that of the conventional example, but the development high pressure control is different from the conventional example. Each component is the same as that described in the first embodiment.

  The photosensitive drum 40 is uniformly charged by a bias applied to the charging roller 41. The surface of the photosensitive drum is exposed with laser light to form an electrostatic latent image. The electrostatic latent image on the surface of the photosensitive drum is developed by a bias applied to the developing sleeve 39 and becomes a visible image as a toner image. The toner image is transferred onto the paper P by a plus bias applied to the transfer roller 44. The paper P is conveyed to the fixing device 45, and after being subjected to fixing processing by heat and pressure, the paper P is discharged out of the image forming apparatus 33.

  The configuration of the development high-voltage output circuit at this time is shown in FIG. Each component is the same as that described in the first embodiment.

  The controller (CPU) 32 sets each setting value of the development high voltage output at the start of printing based on information read from the storage means. The control signals DevACPWM 48, DevACCLK 49, and DevDCPWM 50 are driven at the set values to output a desired development high voltage value. At this time, the information stored in the storage means 37 is information on the number of accumulated image data of the image data.

  FIG. 6 is a flowchart showing a development high-voltage output control of the image forming apparatus main body and a process cartridge operating time determination method.

  When printing of the image forming apparatus 33 is started, the CPU 32 first reads the cumulative number of image data printed by the process cartridge 42 stored in the storage unit 37 (S31). Here, the control is performed by regarding the cumulative number of image data as the cumulative operation time of the process cartridge 42. Next, the set values of the control signals DevACPWM48, DevACCLK49, and DevDCPWM50 for developing high-voltage output are determined and set in accordance with the read cumulative image data number information (S32). At this time, the DevDCPWM 50 that determines the DC voltage value of the development high-voltage output is set so that the ON duty of the signal is gradually increased in order to control the voltage value to increase with the cumulative operation time. On the other hand, DevACCLK49, which determines the clock frequency of the AC component of the development high-voltage output, is set to gradually increase the ON duty of the signal in order to control to increase the clock ON duty with the cumulative operation time. I do. Further, DevACPWM 48 that determines the voltage of the AC component is set so as to gradually increase the ON duty of the signal in order to control the voltage value to decrease with the cumulative operation time. Then, the development high voltage output is applied with the value set in S2 (S33). As described above, the control for changing the development high-voltage output with the operation time of the process cartridge 42 is performed. As a result, the phenomenon in which the density of the printed image increases due to the toner charge increasing with the operation time of the process cartridge 42 can be dealt with by increasing the voltage of the DC component of the development high-voltage output. I can do it. As the actual movement, as described above, the density of the printed image is determined by the potential difference Vcnt between the surface potential VL of the electrostatic latent image portion on the photosensitive drum and the surface potential DevVdc of the developing sleeve 39. Change the component voltage to be higher. By doing so, the potential difference Vcnt is reduced and the print image density is shifted in the direction of lightening, thereby canceling the phenomenon that the density of the print image is increased due to an increase in toner charge. Further, there is a phenomenon in which the external additive moves from the developing sleeve 39 to the photosensitive drum 40 as the development that occurs when the voltage of the DC component of the development high voltage output is increased. The external additive normally stays on the developing sleeve 39 and acts to increase the fluidity of the toner. However, when the development high-voltage output reaches the external additive movement start voltage, the movement of the external additive to the photosensitive drum 40 starts. As a result, the external additive adheres to the charging roller 41 and the charging roller becomes dirty. As countermeasures against this phenomenon, as shown in FIG. 2, it is possible to respond by increasing the ON duty of the frequency of the alternating current component of the development high voltage output and decreasing the voltage of the alternating current component. The actual movement is to first increase the NO duty of the frequency so that the AC component voltage does not reach the external additive movement start voltage when the DC component voltage of the development high voltage output is increased. The upper limit is lowered. In addition, image defects called fogging occur due to the relationship between the lower limit value of the AC component voltage of the developing high voltage output and the DC voltage of the developing high voltage output, and the lower limit of the DC voltage of the charging high voltage output and the AC component voltage of the developing high voltage output. The relationship with the value needs to be constant. Therefore, the relationship between the DC voltage of the charging high voltage output and the lower limit value of the AC component voltage of the developing high voltage output is kept constant by lowering the voltage of the AC component of the developing high voltage output.

  Next, reading of image data that is a basis for image formation is started (S34). Based on this image data, the laser scanner 46 emits a laser to form an electrostatic latent image on the photosensitive drum. Then, the count of the number of image data being read is started (S35).

  Subsequently, image forming processes such as charging, exposure, development, transfer, and fixing are sequentially performed (S36). Each image forming process is repeated in order until there is no image data for printing (S37), and when there is no image data for printing, counting of the number of image data is stopped (S38). Then, the counted number of image data is added to the cumulative number of image data stored in the storage unit 37, and the addition result is updated and stored in the storage unit 37 as a new cumulative number of prints (S39).

  Finally, the application of the development high voltage output is stopped (S40), and the image forming apparatus stops the printing operation.

  As described above, in this embodiment, each setting of the development high voltage output is changed with the operation time of the process cartridge 42. Each setting is changed so that the voltage of the DC component is high, the voltage of the AC component is low, and the frequency ON duty of the AC component is increased. Also, the operation time is counted as the number of accumulated image data. Thereby, it is possible to cope with a change in density of the printed image with the cartridge operation time, and it is possible to prevent the charging roller from being soiled by the external additive.

  Further, in the image forming apparatus having the above-described configuration, the process cartridge may be provided with a nonvolatile storage unit 37 that stores the accumulated operation time of the process cartridge 42. By installing the storage means 37 in the process cartridge 42, it is possible to control the development high voltage output corresponding to the operation time of each process cartridge. Therefore, even when the process cartridge mounted on the image forming apparatus 33 is replaced in the middle, an appropriate development high voltage output can be set according to the state of the process cartridge 42 at that time, and stable image quality can be achieved. An output image can be obtained.

6 is a flowchart showing development high-pressure control according to the first embodiment of the present invention. The figure which shows the control waveform of the development high voltage | pressure output which concerns on this invention. FIG. 3 is a diagram illustrating an example of a circuit configuration that generates a development high-voltage output according to the image forming apparatus of the present invention. 1 is a schematic configuration diagram illustrating an example of a conventional image forming apparatus in which the present invention is embodied. 9 is a flowchart showing development high-pressure control according to a second embodiment of the present invention. 10 is a flowchart showing development high-pressure control according to a third embodiment of the present invention. FIG. 10 is a diagram illustrating a process cartridge operation time transition of toner charge. FIG. 9 is a diagram illustrating a difference in toner movement amount due to a change in toner charge. The figure which shows the control waveform of the conventional image development high voltage | pressure output. The figure which shows the outline of the movement start voltage of an external additive.

Explanation of symbols

34 Engine controller 36 Developing circuit 37 Non-volatile memory 39 Developing sleeve ram 40 Photosensitive drum 41 Charging roller 42 Process cartridge 44 Transfer roller 45 Thermal fixing device

Claims (6)

  Electrostatic latent image formation for forming an electrostatic latent image by exposing an image carrier, charging means for charging the surface of the image carrier, and charging the surface of the image carrier according to image data And a developing means for performing a developing process for visualizing the electrostatic latent image on the surface of the image carrier as a toner image with toner, the image carrier, the charging means, and the developing means. A process cartridge including the image forming apparatus main body is detachable from the image forming apparatus main body, a storage means for storing the accumulated operation time of the process cartridge, and a high voltage in which an AC component and a DC component are superimposed on the developing means are generated from one transformer. An image forming apparatus having a developing high-voltage output means to be applied and a developing high-voltage setting changing means for changing each setting of an AC component and a DC component of the developing high-voltage output and performing a developing process by a one-component developing system The development high voltage setting change means changes the settings of the AC component and the DC component of the development high voltage output based on the information in the storage means, and the development high voltage output means sets the setting information of the development high voltage setting change means. An image forming apparatus characterized by applying a development high voltage output based on the above to a developing means.   Regarding each development high voltage setting that changes with the integrated operation time of the process cartridge, the AC component voltage setting is gradually lowered according to the integrated operation time, and the ON width setting of the AC component frequency is integrated operation. 2. The image forming apparatus according to claim 1, wherein the voltage is gradually increased according to the time, and the voltage setting of the DC component is gradually increased according to the integration operation time.   Regarding the operation time measurement method for measuring the accumulated operation time of a process cartridge, when printing is performed on the process cartridge, the number of sheets on which printing has been performed is cumulatively counted, and the total number of sheets is used as the accumulated operation time of the process cartridge. The image forming apparatus according to claim 1, wherein the image forming apparatus is an image forming apparatus.   Regarding the operation time measurement method for measuring the accumulated operation time of a process cartridge, when printing is performed on the process cartridge, the time during which the driving means for driving the process cartridge is operated is cumulatively measured, and the process cartridge is calculated with the total time. The image forming apparatus according to claim 1, wherein the integrated operation time is set to a predetermined time.   Regarding the operation time measurement method for measuring the accumulated operation time of a process cartridge, when printing is performed on the process cartridge, the number of data constituting the printed image is cumulatively counted, and the accumulated operation of the process cartridge is performed using the total number. 3. The image forming apparatus according to claim 1, wherein time is set.   Regarding the storage means for storing the accumulated operation time of the process cartridge, the storage means is a non-volatile memory that is mounted on the process cartridge and updates the stored information at any time when it is attached to the image forming apparatus. The image forming apparatus according to claim 1.

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