JP2009133996A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To reduce consumption of toner used when images are not formed and to prevent a recording medium from being soiled after the detection of the presence or absence of a cartridge, by preventing toner from moving from a developing sleeve to a photoreceptor drum when the presence or absence of the cartridge is detected. <P>SOLUTION: The image forming apparatus includes a cartridge presence/absence detecting means for detecting the presence or absence of the process cartridge based on the information of an electrostatic capacity detecting means that detects electrostatic capacity between a plurality of electrodes in the process cartridge by applying a development high voltage output. During the detection of the presence or absence of the cartridge, the voltage or frequency of the AC component of the development high voltage output and the voltage of the DC component thereof are changed from a regular image formation period. <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 means for detecting whether or not a process cartridge is mounted using a development high voltage output.

  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 a photoreceptor 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, a charging high-voltage circuit. A charging roller 41, which is a charging means for uniformly placing the charge generated by the circuit 43 on the photosensitive drum 40, and a laser for irradiating the charged photosensitive drum surface with laser light according to image data to form an electrostatic latent image. A developing sleeve 39 that is arranged close to the irradiation device 46 and the photosensitive drum 40 and visualizes the electrostatic latent image on the photosensitive drum with toner, a toner container 38 that holds toner as a developer, and a toner developing sleeve A developing high-voltage circuit 36 is provided as a high-pressure generating means for moving the toner 39 to the photosensitive drum 40. Further, a photosensitive drum 40, a charging roller 41, a developing sleeve 39, a toner container 38, and an antenna electrode 37 are incorporated, and a process cartridge 42 that can be attached to and detached from the image forming apparatus main body 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.

In the image forming apparatus 33 configured as described above, since the process cartridge 42 is detachable, as one of usability improvements, cartridge presence / absence detection for determining whether or not the process cartridge 42 is mounted in the apparatus is performed. Is going. As a result, it is possible to avoid problems that occur when printing is performed without the process cartridge 42 being mounted. For example, it is possible to prevent a jam that causes a paper jam in the apparatus because the paper P cannot be transported because there is no process cartridge 42. Alternatively, even if the paper P can be transported, the process cartridge 42 is not present, so that the printing result is blank, and the paper is not wasted because the printing has to be repeated again. And so on. As a representative method for detecting whether or not the cartridge 42 is mounted, a charging high voltage output is applied to the charging roller 41, current value information flowing through the charging roller 41 is detected at that time, and whether or not the cartridge 42 is mounted based on the information. And the electrostatic capacitance of the toner between the developing sleeve 39 and the antenna electrode arranged in the process cartridge is detected by applying a developing high voltage output, and whether or not the cartridge 42 is mounted is detected based on the information. A method of making a determination is known from Patent Document 1.
Japanese Patent Laid-Open No. 10-258957

  The timing for detecting whether or not the cartridge 42 is mounted is a door-like opening / closing door provided in the process cartridge housing portion when the power of the image forming apparatus main body is turned on or the process cartridge 42 is attached / detached. This is the timing when the cover is closed. That is, it is during the initial adjustment operation of the image forming apparatus 33. Here, a case where the presence / absence detection of the cartridge is performed using the development high-voltage output is considered. As described above, the presence / absence detection of the cartridge is performed at a timing other than the time of image formation. At this time, a developing high voltage output is applied to the developing sleeve 39 as a measurement of the electrostatic capacity in the process cartridge. Therefore, the toner that does not need to move by the development high-voltage output moves from the developing sleeve 39 to the photosensitive drum 40. Therefore, useless toner that is not involved in image formation is consumed every time the presence / absence of the cartridge is detected. In the initial adjustment operation after the presence / absence detection of the cartridge, the photosensitive drum 40 is rotated, so that the toner moved onto the photosensitive drum is carried to the transfer roller. As a result, if there is residual paper in the image forming apparatus and the initial adjustment operation is performed, the residual paper is automatically discharged outside the apparatus during the initial adjustment operation. The paper P is soiled by the toner adhering to the transfer roller.

  The present invention has been made in view of such a situation. When the cartridge presence / absence detection is performed by changing the voltage or frequency of the AC component of the development high-voltage output to a value different from that during normal image formation. The toner does not move from the developing sleeve 39 to the photosensitive drum 40, the amount of toner consumed except for image formation is reduced, and the paper P becomes soiled after the presence / absence of the cartridge is detected. An object of the present invention is to provide an image forming apparatus 33 that can prevent the above.

  In order to achieve the above object, an image forming apparatus according to claim 1, an image carrier, a charging unit 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 unit that forms an electrostatic latent image by performing exposure, and a developing unit that performs development processing for visualizing the electrostatic latent image on the surface of the image carrier as a toner image with toner. A process cartridge including the image carrier, the charging unit, and the developing unit, which is detachably attachable to the main body of the image forming apparatus. The process cartridge includes a plurality of electrodes. On the other hand, developing high voltage output means for generating and applying a high voltage in which an alternating current component and a direct current component are superimposed from a single transformer, and applying the developing high voltage output between a plurality of electrodes in the process cartridge. In the image forming apparatus comprising: a capacitance detecting means for detecting; and a cartridge presence / absence detecting means for detecting whether or not the process cartridge is mounted based on information of the capacitance detecting means, the developing high-voltage output means includes the cartridge In the presence / absence detection, the voltage of the AC component of the development high voltage output is changed from the time of normal image formation.

  According to the present invention, in an image forming apparatus that detects whether or not a process cartridge is mounted using a development high-voltage output, the AC component voltage and frequency of the development high-voltage output when performing cartridge presence / absence detection when performing normal image formation. Control is performed so as to change the value.

  By performing such control, wasteful toner consumption can be reduced by detecting the presence or absence of a cartridge after a recovery process when a jam occurs in the image forming apparatus or after the power of the apparatus main body is turned on, or automatic paper discharge can be performed after detecting the presence or absence of a cartridge. It is possible to prevent the paper from being soiled when it is performed.

(Example 1)
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. 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. Reference numeral 37 denotes an antenna electrode, which is connected to a capacitance detection circuit 35 that detects capacitance. 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. Here, the development high-voltage output has a characteristic that an AC component and a DC component are generated by a single transformer 1.

  The controller (CPU) 32 detects the presence or absence of a cartridge when the main body is turned on or when the cartridge door of the process cartridge storage unit is closed. At that time, the CPU drives DevACPWM 48, DevACCLK 49 and DevDCPWM 50 in order to output a developing high voltage for cartridge detection.

  FIG. 1 shows a flowchart of development high voltage output control, cartridge presence / absence detection control, and initial adjustment operation after the apparatus main body is turned on or after the cartridge door is opened and closed. FIG. 2 shows a timing chart at that time.

  First, in order to output the AC component of the development high-voltage output, a clock signal of 2500 Hz is input to DevACCLK 49 that determines the AC frequency (S1). Next, a 20 kHz PWM signal is input to DevACPWM 48 that determines the AC voltage (S2). The ON duty “Dcd” of DevACPWM 48 at this time is set to be sufficiently larger than the ON duty “Dp” during normal image formation. Here, when the ON duty “Dcd” of DevACPWM 48 is increased, the voltage of the AC component of the development high-voltage output is decreased. Therefore, by making the ON duty “Dcd” sufficiently larger than that during normal image formation, it is possible to suppress the movement of toner to the photosensitive drum 40 when the development high-voltage output is applied to the development sleeve 39. Next, in order to output a DC component, a PWM signal having an ON duty “Ddev” at 20 kHz is input to DevDCPWM 50 that determines the DC voltage (S3).

  Subsequently, the capacitance of the process cartridge 42 is measured (S4). The electrostatic capacity is measured between the developing sleeve 39 and the antenna electrode in the process cartridge. The electrostatic capacity is determined from the relationship between the voltage and frequency of the AC component of the developing high-voltage output applied to the developing sleeve 39 and the current flowing at that time. Measurement is performed by converting the capacitance to current and detecting the current value. When the process cartridge 42 is mounted in the image forming apparatus, a current value corresponding to the amount of toner in the cartridge is measured, and when the process cartridge 42 is not mounted, no current is measured. The current value measured at this time is temporarily stored in the CPU 32.

  After the measurement, in order to cut off the development high-voltage output, a “High” signal is output to DevDCPWM 50 to drop the DC component voltage (S5). Next, a “High” signal is output to DevACPWM 48 to drop the AC component voltage (S6). Finally, a “Low” signal is input to DevACCLK 49 to turn off the clock input, and the development high-voltage output is stopped (S7).

  Thereafter, it is determined whether or not the process cart lodge 42 is mounted (S8). Whether the process cartridge 42 is attached or not is determined by determining whether or not the current value of the measurement result obtained by converting the electrostatic capacity performed in S4 stored in the CPU into a current value exceeds a predetermined value. If so, it is determined that there is a cartridge, and an initial adjustment operation is started (S9). When the time necessary for the initial adjustment operation has elapsed, the control is terminated.

  On the other hand, if the predetermined current value is not exceeded, it is determined that there is no cartridge, the fact that there is no cartridge is notified to the outside (S10), and the control is terminated.

  As described above, in this embodiment, when the presence / absence of the cartridge is detected, the voltage of the AC component of the development high-voltage output is set to a value sufficiently smaller than that during normal image formation, whereby the toner from the developing sleeve 39 to the photosensitive drum 40 is detected. The movement can be suppressed. Therefore, the life of the process cartridge 42 can be extended by suppressing wasteful toner consumption. Further, it is possible to prevent the paper P from being smeared when the residual paper in the apparatus is automatically discharged during the initial adjustment operation.

(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 detects the presence or absence of a cartridge when the main body is turned on or when the cartridge door of the process cartridge storage unit is closed. At that time, the CPU drives DevACPWM 48, DevACCLK 49 and DevDCPWM 50 in order to output a developing high voltage for cartridge detection.

  FIG. 5 shows a flowchart of development high voltage output control, cartridge presence / absence detection control, and initial adjustment operation after the apparatus main body is turned on or after the cartridge door is opened and closed. FIG. 6 shows a timing chart at that time.

  First, in order to output an AC component of the development high-voltage output, a clock signal of “Fcd” Hz is input to DevACCLK 49 that determines the AC frequency (S11). The frequency “Fcd” of DevACCLK 49 at that time is set to be sufficiently higher than 2500 Hz during normal image formation. Here, when the frequency “Fcd” of DevACCLK 49 is increased, the time required for the toner to move from the developing sleeve to the photosensitive drum is shortened. Therefore, the clock frequency “Fcd” is sufficiently higher than 2500 Hz at the time of normal image formation. It is possible to suppress the movement of the toner to the photosensitive drum when the development high voltage output is applied to the sleeve. Next, a PWM signal having an ON duty “Dp” at 20 kHz is input to DevACPWM 48 that determines the AC voltage (S12). In order to output a DC component, a PWM signal having an ON duty “Ddev” at 20 kHz is input to DevDCPWM 50 that determines the DC voltage (S13).

  Subsequently, the capacitance of the process cartridge 42 is measured (S14). The electrostatic capacity is measured between the developing sleeve 39 and the antenna electrode in the process cartridge. The electrostatic capacity is determined from the relationship between the voltage and frequency of the AC component of the developing high-voltage output applied to the developing sleeve 39 and the current flowing at that time. Measurement is performed by converting the capacitance to current and detecting the current value. When the process cartridge 42 is mounted in the image forming apparatus, a current value corresponding to the amount of toner in the cartridge is measured, and when the process cartridge 42 is not mounted, no current is measured. The current value measured at this time is temporarily stored in the CPU 32.

  After the measurement, in order to cut off the development high-voltage output, a “High” signal is output to DevDCPWM 50 to drop the DC component voltage (S15). Next, a “High” signal is output to DevACPWM 48 to drop the AC component voltage (S16). Finally, a “Low” signal is input to DevACCLK 49 to turn off the clock input, and the development high-voltage output is stopped (S17).

  Thereafter, it is determined whether or not the process cart lodge is mounted (S18). Whether or not the process cartridge 42 is attached is determined by determining whether or not the current value of the measurement result obtained by converting the electrostatic capacity in S14 stored in the CPU into a current value exceeds a predetermined value. If so, it is determined that there is a cartridge, and the initial adjustment operation is started (S19). When the time necessary for the initial adjustment operation has elapsed, the control is terminated.

  On the other hand, if the predetermined current value is not exceeded, it is determined that there is no cartridge, the fact that there is no cartridge is notified to the outside (S20), and the control is terminated.

  As described above, in this embodiment, when the presence / absence of the cartridge is detected, the frequency of the AC component of the development high-voltage output is set to a value sufficiently higher than that during normal image formation, so that the toner from the developing sleeve 39 to the photosensitive drum 40 can be obtained. The movement can be suppressed. Therefore, the life of the process cartridge 42 can be extended by suppressing wasteful toner consumption. Further, it is possible to prevent the paper P from being smeared when the residual paper in the apparatus is automatically discharged during the initial adjustment operation.

(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 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 detects the presence or absence of a cartridge when the main body is turned on or when the cartridge door of the process cartridge storage unit is closed. At that time, the CPU drives DevACPWM 48, DevACCLK 49 and DevDCPWM 50 in order to output a developing high voltage for cartridge detection.

  FIG. 7 shows a flowchart of development high voltage output control, cartridge presence / absence detection control, and initial adjustment operation after the apparatus main body is turned on or after the cartridge door is opened and closed. FIG. 8 shows a timing chart at that time.

  First, in order to output an AC component of the development high-voltage output, a clock signal of “Fcd” Hz is input to DevACCLK 49 that determines the AC frequency (S21). The frequency “Fcd” of DevACCLK 49 at this time is set to be sufficiently higher than 2500 Hz at the time of normal image formation. Here, when the frequency “Fcd” of DevACCLK 49 is increased, the time for the toner to move from the developing sleeve to the photosensitive drum is shortened. Therefore, by making the clock frequency “Fcd” sufficiently higher than 2500 Hz during normal image formation, it is possible to suppress the movement of toner to the photosensitive drum when the development high-voltage output is applied to the development sleeve. Next, a 20 kHz PWM signal is input to DevACPWM 48 that determines the AC voltage (S22). The ON duty “Dcd” of DevACPWM 48 at this time is set to be sufficiently larger than the ON duty “Dp” during normal image formation. Here, by increasing the ON duty “Dcd” of DevACPWM 48, the voltage of the AC component of the development high-voltage output decreases. Therefore, by making the ON duty “Dcd” sufficiently larger than that during normal image formation, it is possible to further suppress the movement of the toner to the photosensitive drum 40 when the developing high-voltage output is applied to the developing sleeve 39. In order to output a direct current component, a PWM signal having an ON duty “Ddev” at 20 kHz is input to DevDCPWM 50 that determines the direct current voltage (S23).

  Subsequently, the capacitance of the process cartridge 42 is measured (S24). The electrostatic capacity is measured between the developing sleeve 39 and the antenna electrode in the process cartridge. The electrostatic capacity is determined from the relationship between the voltage and frequency of the AC component of the developing high-voltage output applied to the developing sleeve 39 and the current flowing at that time. Measurement is performed by converting the capacitance into current and detecting the current value. When the process cartridge 42 is mounted in the image forming apparatus, a current value corresponding to the amount of toner in the cartridge is measured, and when the process cartridge 42 is not mounted, no current is measured. The current value measured at this time is temporarily stored in the CPU 32.

  After the measurement, in order to cut off the development high-voltage output, a “High” signal is output to DevDCPWM 50 to drop the DC component voltage (S25). Next, a “High” signal is output to DevACPWM 48 to drop the AC component voltage (S26). Finally, a “Low” signal is input to DevACCLK 49 to turn off the clock input, and the development high-voltage output is stopped (S27).

  Thereafter, it is determined whether or not the process cart lodge 42 is mounted (S28). Whether or not the process cartridge 42 is attached is determined by determining whether or not the current value of the measurement result obtained by converting the electrostatic capacity in S24 stored in the CPU into a current value exceeds a predetermined value. If so, it is determined that there is a cartridge, and an initial adjustment operation is started (S29). When the time necessary for the initial adjustment operation has elapsed, the control is terminated.

  On the other hand, if the predetermined current value is not exceeded, it is determined that there is no cartridge, the fact that there is no cartridge is notified to the outside (S30), and the control is terminated.

  As described above, in this embodiment, when detecting the presence or absence of a cartridge, the frequency of the AC component of the development high-voltage output is set to a value sufficiently higher than that during normal image formation, and the voltage of the AC component is sufficiently higher than that during normal image formation. A small value is set. Thereby, the movement of the toner from the developing sleeve 39 to the photosensitive drum 40 can be sufficiently suppressed, and the life of the process cartridge 42 can be extended by suppressing wasteful toner consumption. Further, it is possible to prevent the paper P from being smeared when the residual paper in the apparatus is automatically discharged during the initial adjustment operation.

Example 4
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 detects the presence or absence of a cartridge when the main body is turned on or when the cartridge door of the process cartridge storage unit is closed. At that time, the CPU drives DevACPWM 48, DevACCLK 49 and DevDCPWM 50 in order to output a developing high voltage for cartridge detection.

  FIG. 9 shows a flowchart of development high voltage output control, cartridge presence / absence detection control, and initial adjustment operation after the apparatus main body is turned on or after the cartridge door is opened and closed. FIG. 10 shows a timing chart at that time.

  First, in order to output an AC component of the development high-voltage output, a clock signal “Fcd” is input to DevACCLK 49 that determines the AC frequency (S31). The frequency “Fcd” of DevACCLK 49 at this time is set to be sufficiently higher than 2500 Hz at the time of normal image formation. Here, when the frequency “Fcd” of DevACCLK 49 is increased, the time for the toner to move from the developing sleeve 39 to the photosensitive drum 40 is shortened. Therefore, by making the clock frequency “Fcd” sufficiently higher than 2500 Hz at the time of normal image formation, it is possible to suppress the movement of toner to the photosensitive drum when the development high-voltage output is applied to the development sleeve 39. Next, the PWM signal of ON duty “Dcd” at 20 kHz is input to DevACPWM 48 that determines the AC voltage (S32). The ON duty “Dcd” of DevACPWM 48 at this time is set to be sufficiently larger than the ON duty “Dp” during normal image formation. Here, by increasing the ON duty “Dcd” of DevACPWM 48, the voltage of the AC component of the development high-voltage output decreases. Therefore, by making the ON duty “Dcd” sufficiently larger than that during normal image formation, it is possible to further suppress the movement of the toner to the photosensitive drum 40 when the development high-voltage output is applied to the development sleeve 39. Then, in order to make the development high-voltage output only the AC component and not the DC component, a “High” signal is input to DevDCPWM 50 that determines the DC voltage (S33). Here, by not outputting the DC component of the development high voltage output, the potential difference between the photosensitive drum 40 and the development sleeve is reduced, and the force for moving the toner is reduced. Therefore, by not outputting the DC component of the development high voltage output, it is possible to further suppress the movement of the toner to the photosensitive drum 40 when the development high voltage output is applied to the development sleeve 39.

  Subsequently, the capacitance of the process cartridge 42 is measured (S34). The electrostatic capacity is measured between the developing sleeve 39 and the antenna electrode in the process cartridge. The electrostatic capacity is determined from the relationship between the voltage and frequency of the AC component of the developing high-voltage output applied to the developing sleeve 39 and the current flowing at that time. Measurement is performed by converting the capacitance to current and detecting the current value. When the process cartridge 42 is mounted in the image forming apparatus, a current value corresponding to the amount of toner in the cartridge is measured, and when the process cartridge 42 is not mounted, no current is measured. The current value measured at this time is temporarily stored in the CPU 32.

  After the measurement, DevDCPWM 50 continues to output a “High” signal to drop the DC component voltage in order to cut off the development high voltage output (S35). Next, a “High” signal is output to DevACPWM 48 to drop the AC component voltage (S36). Finally, a “Low” signal is input to DevACCLK 49 to turn off the clock input, and the development high-voltage output is stopped (S37).

  Thereafter, it is determined whether or not the process cart lodge 42 is mounted (S38). Whether or not the process cartridge 42 is attached is determined by determining whether or not the current value of the measurement result obtained by converting the electrostatic capacity in S34 stored in the CPU into a current value exceeds a predetermined value. If so, it is determined that there is a cartridge, and an initial adjustment operation is started (S39). When the time necessary for the initial adjustment operation has elapsed, the control is terminated.

  On the other hand, if the predetermined current value is not exceeded, it is determined that there is no cartridge, the fact that there is no cartridge is notified to the outside (S40), and the control is terminated.

  As described above, in this embodiment, when detecting the presence or absence of a cartridge, the frequency of the AC component of the development high-voltage output is set to a value sufficiently higher than that during normal image formation, and the voltage of the AC component is sufficiently higher than that during normal image formation. Set to a smaller value. In addition, since only the alternating current component is output without outputting the direct current component of the development high voltage output, the movement of the toner from the developing sleeve 39 to the photosensitive drum 40 can be sufficiently suppressed, and wasteful toner consumption is suppressed, thereby reducing the process cartridge 42. Can extend the lifespan. Further, it is possible to prevent the paper P from being smeared when the residual paper in the apparatus is automatically discharged during the initial adjustment operation.

3 is a flowchart showing control of cartridge presence / absence detection according to the first embodiment of the present invention. The timing chart of the control shown in FIG. The figure which shows an example of the circuit structure which produces | generates the image development high voltage output based on this 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 control of cartridge presence / absence detection according to a second embodiment of the present invention. 6 is a timing chart of the control shown in FIG. 9 is a flowchart showing control of cartridge presence / absence detection according to a third embodiment of the present invention. The timing chart of the control shown in FIG. 10 is a flowchart showing control of cartridge presence / absence detection according to a fourth embodiment of the present invention. 10 is a timing chart of control shown in FIG.

Explanation of symbols

33 Image forming apparatus main body 34 Engine controller 35 Capacitance measuring circuit 36 Development high voltage circuit 37 Antenna electrode 38 Toner container 39 Developing sleeve 40 Photosensitive drum 41 Charging roller 42 Process cartridge 43 High voltage charging circuit 44 Transfer device 45 Fixing device 46 Laser irradiation device P paper

Claims (6)

  An image carrier, a charging unit that charges the surface of the image carrier, and an electrostatic latent image forming unit that forms an electrostatic latent image by exposing the charging surface of the image carrier surface according to image data And a developing means for performing development processing for visualizing the electrostatic latent image on the surface of the image carrier as a toner image with toner, and a process including the image carrier, the charging means, and the developing means The cartridge can be detachably attached to the image forming apparatus main body, the process cartridge has a plurality of electrodes, and a high voltage in which an AC component and a DC component are superimposed on the developing unit is generated from a single transformer. Information on the development high voltage output means to be applied, capacitance detection means for detecting capacitance between a plurality of electrodes in the process cartridge by applying the development high voltage output, and information on the capacitance detection means Accordingly, in the image forming apparatus having the cartridge presence / absence detecting means for detecting whether or not the process cartridge is mounted, the developing high voltage output means changes the voltage of the AC component of the developing high voltage output from the normal image forming time when the cartridge presence or absence is detected. An image forming apparatus.   An image carrier, a charging unit that charges the surface of the image carrier, and an electrostatic latent image forming unit that forms an electrostatic latent image by exposing the charging surface of the image carrier surface according to image data And a developing means for performing development processing for visualizing the electrostatic latent image on the surface of the image carrier as a toner image with toner, and a process including the image carrier, the charging means, and the developing means The cartridge can be detachably attached to the image forming apparatus main body, the process cartridge has a plurality of electrodes, and a high voltage in which an AC component and a DC component are superimposed on the developing unit is generated from a single transformer. Information on the development high voltage output means to be applied, capacitance detection means for detecting capacitance between a plurality of electrodes in the process cartridge by applying the development high voltage output, and information on the capacitance detection means Accordingly, in the image forming apparatus having the cartridge presence / absence detecting means for detecting whether or not the process cartridge is mounted, the developing high voltage output means changes the frequency of the AC component of the developing high voltage output from the normal image forming time when the cartridge presence or absence is detected. An image forming apparatus.   An image carrier, a charging unit that charges the surface of the image carrier, and an electrostatic latent image forming unit that forms an electrostatic latent image by exposing the charging surface of the image carrier surface according to image data And a developing means for performing development processing for visualizing the electrostatic latent image on the surface of the image carrier as a toner image with toner, and a process including the image carrier, the charging means, and the developing means The cartridge can be detachably attached to the image forming apparatus main body, the process cartridge has a plurality of electrodes, and a high voltage in which an AC component and a DC component are superimposed on the developing unit is generated from a single transformer. Information on the development high voltage output means to be applied, capacitance detection means for detecting capacitance between a plurality of electrodes in the process cartridge by applying the development high voltage output, and information on the capacitance detection means Accordingly, in the image forming apparatus having the cartridge presence / absence detecting means for detecting whether or not the process cartridge is mounted, the development high voltage output means detects the presence or absence of the cartridge, and the voltage and frequency of the AC component of the development high voltage output from the normal image formation time. An image forming apparatus characterized by changing both.   2. The development high-voltage output that changes when the presence / absence of a cartridge is detected, wherein the AC component voltage is made sufficiently smaller than that during normal image formation, and the AC component frequency is made sufficiently higher than during normal image formation. 4. The image forming apparatus according to any one of items 1 to 3.   5. The image forming apparatus according to claim 1, wherein at least one of the plurality of electrodes is the developing unit, and at least one of the plurality of electrodes is an antenna electrode.   6. The image forming apparatus according to claim 1, wherein the developing high-voltage output applied when the presence / absence of a cartridge is detected is an output of only an AC component of an AC component and a DC component.

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