JP6332227B2 - Image forming apparatus - Google Patents

Description

  The present invention relates to an image forming apparatus including a charging member that charges a photoreceptor.

  Conventionally, in an image forming apparatus such as a laser printer or a digital multi-function peripheral, the surface of a photoconductive photoconductor is uniformly charged by a charging member, and exposed by an exposure device to form an electrostatic latent image. The electrostatic latent image is developed into a toner image by a developing device. Next, the toner image is transferred onto the surface of the printed material such as paper by the transfer unit, and then fixed on the surface of the printed material by the fixing unit, thereby completing a series of image forming steps. Further, the photoconductor after transfer of the toner image is prepared for the next image formation by removing the toner remaining on the surface thereof by a cleaning unit, and further using a static elimination lamp to remove the static electricity as necessary.

  Some photoreceptors have various structures made of various materials having photoconductivity, and in particular, amorphous silicon photoreceptors have high strength and excellent durability and practical sensitivity. In recent years, it has attracted particular attention. However, the amorphous silicon photoconductor has a problem that it tends to cause an image flow.

  That is, when a charging member that charges the photosensitive member is energized and discharged, the components in the air are decomposed by ozone generated at that time, and ion products such as NOx and SOx are generated. At the same time, the surface of the amorphous silicon photoreceptor is oxidized to form an oxide film that easily adsorbs ion products and water molecules. The ion product generated by the discharge is adsorbed on the oxide film. As a result, the ion product is water-soluble and easily absorbs moisture in the air, and the oxide film itself easily adsorbs water. Resistance is significantly reduced. Also, the paper dust generated from the paper to be printed and adhering to the surface of the photoreceptor is water-absorbing and easily adsorbs water, which causes a reduction in the surface resistance of the photoreceptor. For this reason, a lateral flow (leakage) of the potential occurs at the edge portion of the electrostatic latent image formed on the surface of the photoreceptor, and as a result, an image flow occurs in the formed image.

  Therefore, in order to prevent the occurrence of image flow, the surface of the amorphous silicon photoreceptor is periodically refreshed (polished) to remove the adsorbed ion products, moisture, paper dust, etc. together with the oxide film on the surface. Has been proposed (Patent Document 1). In such an image forming apparatus, in order to clean the photosensitive member, a polishing member (polishing roller) is provided as a member separate from or separate from a member (cleaning blade) that removes toner. Then, for example, at any time such as when the operation of the image forming apparatus is started or when the operation is finished, the abrasive or waste toner added with the abrasive is present in the contact portion between the polishing member and the photoconductor, The surface of the photoconductor is refreshed by rotating the photoconductor for a predetermined time while the polishing member is in contact with the surface of the photoconductor.

  In recent years, instead of the corotron or scorotron charging member, a charging member (charging roller or the like) that charges the photosensitive member with a contact arrangement or a proximity arrangement that generates less ozone is used. Some of these charging members apply an oscillating voltage in which a DC voltage and an AC voltage are superimposed to charge the photosensitive member. However, the charging member is related to environmental changes such as temperature and humidity, and secular changes of the photosensitive member and the charging member. However, what can set the appropriate peak-to-peak voltage value (Vpp) of the AC voltage with high accuracy has been proposed (Patent Documents 2 and 3).

JP-A-11-003014 JP 2007-199094 A JP 2012-047879 A

  The surface condition of the photoconductor, that is, the thickness of the oxide film formed on the surface of the photoconductor, the amount of ion products and paper powder adsorbed on the surface, the degree of moisture absorption, etc. In particular, it varies greatly depending on the humidity and the material of the paper used. For this reason, in the image forming apparatus as described above, in order to prevent the image flow from occurring under any use environment, the polishing time or the like is refreshed so that the surface of the photoconductor is excessively polished. It is necessary to set the conditions. In this case, for example, the polishing amount is set on the basis of an environment where a high humidity state continues in summer, rainy weather, etc. and the degree of moisture absorption is extremely high, and the polishing time is set long. However, the image forming apparatus is often used in a normal state where the degree of moisture absorption is not so high. In such a normal state, the photoconductor is scraped excessively, and the life of the photoconductor is shortened more than necessary. There is a fear. Moreover, power consumption will increase uselessly by setting polishing time long.

  In view of the above circumstances, the present invention has an object to prevent the occurrence of image flow by accurately refreshing the surface of the photoconductor without shortening the life of the photoconductor or wasting power consumption. And

  The image forming apparatus of the present invention generates an image carrier that carries a toner image, a charging member that charges the image carrier, and an oscillating voltage in which a DC voltage and an AC voltage are superimposed, and applies the vibration voltage to the charging member. A high voltage generator, a voltage controller for controlling a peak-to-peak voltage value of the AC voltage, a current detector for detecting a direct current value between the charging member and the image carrier, and a surface of the image carrier. A cleaning unit for cleaning, and a cleaning control unit for controlling execution of the cleaning unit, wherein the voltage control unit controls the high-voltage generation unit so as to boost the peak-to-peak voltage value. To calculate an assumed characteristic curve on a two-dimensional coordinate representing the relationship between the peak-to-peak voltage value and the DC current value when the DC current value is detected, and the cleaning control unit 2 appears in the assumed characteristic curve. And sets long the smaller the voltage difference between the inflection point execution time of the cleaning unit of.

  By adopting such a configuration, the cleaning control unit sets the execution time of the cleaning unit longer as the voltage difference between the two inflection points appearing in the assumed characteristic curve is smaller, thereby reducing the surface resistance of the image carrier. When it decreases, the cleaning unit can be executed with a relatively long execution time to refresh the image carrier to avoid a decrease in surface resistance. As a result, the image carrier can appropriately maintain the electrostatic latent image on the surface, and can prevent the lateral flow of the potential at the edge portion of the electrostatic latent image and the image flow of the formed image. it can. The cleaning control unit sets the execution time of the cleaning unit to be relatively short when the voltage difference between the two inflection points appearing in the assumed characteristic curve is relatively large, so that the surface resistance of the image carrier is normal. In this case, the execution time of the cleaning unit can be shortened. As a result, the cleaning unit does not waste the image carrier excessively, the life of the image carrier is not shortened more than necessary, and the power consumption required for execution of the cleaning unit can be suppressed. In this way, by measuring the direct current value of the charging member whose characteristics change depending on the environmental conditions, it is possible to accurately grasp the environment in the vicinity of the surface of the image carrier and the charging member and perform appropriate refresh (polishing) control. Can do.

  The cleaning unit may include a rubbing polishing member that refreshes the surface of the image carrier.

  By adopting such a configuration, the cleaning control unit realizes the control of the execution time for refreshing the surface of the image carrier by a simple method of controlling the time for driving and controlling the rubbing polishing member such as the polishing roller. can do.

  The cleaning control unit may not execute the cleaning unit when the two inflection points do not exist in the assumed characteristic curve.

  By adopting such a configuration, when the surface resistance of the image carrier is normal, the cleaning unit is not executed, so that the cleaning unit avoids shaving the image carrier and the life of the image carrier is shortened. In addition, the power consumption required for execution of the cleaning unit can be further suppressed.

  When the two inflection points exist in the assumed characteristic curve, the cleaning control unit may continue the execution of the cleaning unit until the inflection point in the assumed characteristic curve becomes one.

  By adopting such a configuration, the cleaning control unit can properly refresh the image carrier by executing the cleaning unit until the surface resistance of the image carrier becomes normal.

  The image forming apparatus described above further includes a storage unit that stores a peak-to-peak voltage value table including a plurality of peak-to-peak voltage values corresponding to various combinations of temperature and humidity in the apparatus body, and the voltage control unit includes: Based on the temperature and humidity in the apparatus main body, the peak-to-peak voltage value is read from the peak-to-peak voltage value table stored in the storage unit.

  By adopting such a configuration, the voltage control unit can appropriately control the high voltage generation unit and calculate an appropriate assumed characteristic curve according to the environment of the image forming apparatus (apparatus body). Become.

  According to the present invention, it is possible to accurately refresh the surface of the photoconductor to prevent the occurrence of image flow without shortening the life of the photoconductor or wasting power consumption.

1 is a schematic diagram illustrating an outline of a configuration of a printer according to an embodiment of the present invention. 1 is a block diagram illustrating a configuration of a printer according to an embodiment of the present invention. It is a graph which shows the relationship between the peak-to-peak voltage value of a charging member and a direct current value with an assumed characteristic curve. It is a graph which shows the relationship between the peak-to-peak voltage value of a charging member and a direct current value with an assumed characteristic curve.

  First, an overall configuration of an electrophotographic printer 1 (image forming apparatus) according to an embodiment of the present invention will be described with reference to FIG.

  The printer 1 includes a box-shaped printer main body 2 (apparatus main body). A paper feed cassette 3 that stores paper S (recording medium) is stored in the lower portion of the printer main body 2. A paper discharge tray 4 is provided. An upper cover 5 is attached to the upper surface of the printer main body 2 so as to be openable and closable on the side of the paper discharge tray 4, and a toner container 6 is stored below the upper cover 5.

  An exposure unit 7 composed of a laser scanning unit (LSU) is disposed below the discharge tray 4 above the printer body 2, and an image forming unit 8 is provided below the exposure unit 7. The image forming unit 8 is rotatably provided with a photosensitive drum 10 (image carrier) that is an image carrier. Around the photosensitive drum 10, a charging roller 11 (charging member), a developing device 12, and the like. The transfer roller 13 and the cleaning unit 14 are arranged along the rotation direction of the photosensitive drum 10 (see the arrow X in FIG. 1).

  The photosensitive drum 10 is formed, for example, by depositing an amorphous silicon layer as a positively chargeable photoconductor on the surface of an aluminum cylinder, and has a diameter of about 30 mm. The photosensitive drum 10 is configured to be driven to rotate at a constant speed around a support shaft by a drum driving unit 42 (see FIG. 2).

  As shown in FIG. 2, the charging roller 11 is configured by covering a cored bar 23 with a conductive layer 24 made of a material such as chlorohydrin rubber having conductivity and elasticity. The charging roller 11 is rotatably provided while the surface of the conductive layer 24 is in contact with the surface of the photosensitive drum 10. The charging roller 11 is connected to the high voltage generator 25 and is configured to be charged when an oscillating voltage is applied from the high voltage generator 25.

  The high voltage generator 25 includes an AC power source 26 that outputs an AC voltage, a DC power source 27 that outputs a DC voltage, and a DC current value Idc (hereinafter referred to as a DC current value) generated between the photosensitive drum 10 and the charging roller 11. Current detection unit 28 for detecting (referred to as Idc). The high voltage generator 25 generates an oscillating voltage by superimposing the AC voltage from the AC power source 26 and the DC voltage from the DC power source 27, and applies it to the charging roller 11. AC power supply 26 outputs an AC voltage having a peak-to-peak voltage value Vpp controlled by voltage control unit 43 described below, and DC power supply 27 outputs a constant DC voltage.

  The cleaning unit 14 includes a box-shaped casing 30, a cleaning blade 31, and a polishing roller 32. The housing 30 has an opening 33 at one end, and the opening 33 is arranged with the surface facing the surface of the photosensitive drum 10. The cleaning blade 31 is attached to the edge of the opening 33 of the housing 30 on the downstream side in the rotation direction X of the photosensitive drum 10, and is arranged so that one end abuts the surface of the photosensitive drum 10. The polishing roller 32 is a rubbing polishing member that refreshes the surface of the photosensitive drum 10, and is provided to be rotatable inside the housing 30 upstream of the cleaning blade 31 in the rotation direction X of the photosensitive drum 10. The surface of the polishing roller 32 is disposed so as to contact the surface of the photosensitive drum 10 through the opening 33.

  A conveyance path 15 for the paper S is provided inside the printer body 2. A paper feed unit 16 is provided at the upstream end of the conveyance path 15, and a transfer unit 17 configured by the photosensitive drum 10 and the transfer roller 13 is provided at a middle portion of the conveyance path 15. Is provided with a fixing unit 18, and a paper discharge unit 20 is provided at the downstream end of the conveyance path 15. A reverse path 21 for double-sided printing is formed below the transport path 15.

  Next, an image forming operation of the printer 1 having such a configuration will be described.

  When the printer 1 is turned on, various parameters are initialized, and initial settings such as temperature setting of the fixing unit 18 are executed. Then, when image data is input from a computer or the like connected to the printer 1 and an instruction to start printing is given, an image forming operation is executed as follows.

  The printer 1 operates at a system speed of 408 mm / s, for example. First, after the surface of the photosensitive drum 10 is charged by the charging roller 11, the laser light from the exposure unit 7 (see the two-dot chain line in FIG. 1). ), The photosensitive drum 10 is exposed in accordance with the image data, and an electrostatic latent image is formed on the surface of the photosensitive drum 10. Next, the developing device 12 develops the electrostatic latent image into a toner image with toner (for example, a magnetic one-component developer).

  On the other hand, the paper S taken out from the paper feed cassette 3 by the paper feed unit 16 is conveyed to the transfer unit 17 in synchronization with the image forming operation described above, and the toner image on the photosensitive drum 10 is transferred to the transfer unit 17. Transferred onto the paper S. The sheet S to which the toner image is transferred is conveyed downstream in the conveyance path 15 and enters the fixing unit 18, and the toner image is fixed on the sheet S in the fixing unit 18. The paper S on which the toner image is fixed is discharged from the paper discharge unit 20 to the paper discharge tray 4. The toner remaining on the photosensitive drum 10 is collected by the cleaning unit 14.

  Next, the control system of the printer 1 will be described with reference to FIG.

  The printer 1 is provided with a control unit 40 configured by a CPU or the like, and the control unit 40 is connected to a storage unit 41 including a ROM, a RAM, and the like. The control unit 40 is configured based on a control program and control data stored in the storage unit 41 (charge roller 11, developing device 12, transfer roller 13, cleaning unit 14, paper supply unit 16, fixing unit 18). Etc.).

  For example, the control unit 40 is connected to the drum driving unit 42, the voltage control unit 43, the cleaning control unit 44, the temperature sensor 45, and the humidity sensor 46. The voltage control unit 43 and the cleaning control unit 44 may be configured with a control program stored in the storage unit 41. The temperature sensor 45 detects the temperature in the printer body 2, and the humidity sensor 46 detects the humidity in the printer body 2.

  The storage unit 41 includes a peak-to-peak voltage value table 47 in which a plurality of different peak-to-peak voltage values Vpp are stored in advance as the peak-to-peak voltage values Vpp used for controlling the vibration voltage applied to the charging roller 11. For example, the peak-to-peak voltage value table 47 stores peak-to-peak voltage values Vpp (A), Vpp (B), Vpp (C), Vpp (D), and Vpp (E) as shown in FIG. The peak-to-peak voltage values Vpp (A) and Vpp (B) are set to values assumed to be lower than the voltage value at the inflection point O appearing in the following assumed characteristic curve L (see FIG. 3). The peak-to-peak voltage values Vpp (D) and Vpp (E) are set to values that are assumed to be higher than the voltage value at the inflection point O appearing in the following assumed characteristic curve L (see FIG. 3). Further, the peak-to-peak voltage value table 47 includes a plurality of peak-to-peak voltage values Vpp (A), Vpp (B), Vpp (C), and Vpp (D) corresponding to various combinations of temperature and humidity in the printer main body 2. ), Vpp (E) may be stored.

  The drum driving unit 42 is configured by a drum motor or the like that is controlled by the control unit 40 to rotationally drive the photosensitive drum 10.

  The voltage controller 43 is configured to control the high voltage generator 25 to cause the high voltage generator 25 to apply an oscillating voltage to the charging roller 11. Specifically, voltage control unit 43 controls AC power supply 26 of high voltage generation unit 25 so as to generate an AC voltage having appropriate peak-to-peak voltage value Vpp.

  For example, the appropriate peak-to-peak voltage value Vpp is determined at a timing before the printing operation or the like, and the method for determining the appropriate peak-to-peak voltage value Vpp is as follows. The voltage control unit 43 reads the plurality of peak-to-peak voltage values Vpp from the peak-to-peak voltage value table 47 of the storage unit 31 and sequentially generates a plurality of AC voltages each having a plurality of peak-to-peak voltage values Vpp. The AC power supply 26 of the high voltage generator 25 is controlled while boosting the voltage value Vpp. The voltage control unit 43 preferably uses the peak-to-peak voltage value table 47 based on the combination of the temperature in the printer main body 2 detected by the temperature sensor 45 and the humidity in the printer main body 2 detected by the humidity sensor 46. It is preferable to read a plurality of peak-to-peak voltage values Vpp.

  Further, the voltage controller 43 generates a DC current value Idc generated between the photosensitive drum 10 and the charging roller 11 when generating an AC voltage having each peak-to-peak voltage value Vpp, that is, each peak-to-peak voltage value Vpp. The DC current value Idc corresponding to is acquired from the current detection unit 28. For example, as shown in FIG. 3, the voltage control unit 43 has a plurality of peak-to-peak voltage values Vpp (A), Vpp (B), Vpp (C), and Vpp (D) stored in the peak-to-peak voltage value table 47. , Vpp (E), a plurality of DC current values Idc (A), Idc (B), Idc (C), Idc (D), and Idc (E) are obtained.

  Then, the voltage control unit 43 calculates an assumed characteristic curve L on the two-dimensional coordinates representing the relationship between the plurality of peak-to-peak voltage values Vpp and the corresponding DC current values Idc, and refers to the assumed characteristic curve L. Inflection points O and P appearing on the assumed characteristic curve L are detected. For example, the voltage control unit 43 corresponds to a plurality of peak-to-peak voltage values Vpp (A), Vpp (B), Vpp (C), Vpp (D), and Vpp (E) as shown in FIG. An assumed characteristic curve L representing the relationship between the plurality of DC current values Idc (A), Idc (B), Idc (C), Idc (D), and Idc (E) is calculated.

  Here, the voltage control unit 43 determines the peak-to-peak voltage values Vpp (A) and Vpp (B) that are assumed to be lower than the voltage value at the inflection point O, and the DC current value Idc (A) corresponding thereto. , Idc (B) and the straight line M1 passing through the coordinate A (Vpp (A), Idc (A)) and the coordinate B (Vpp (B), Idc (B)) on the assumed characteristic curve L is calculated. Further, the voltage control unit 43 has coordinates C (Vpp (C), Idc (C) on the assumed characteristic curve L composed of the intermediate peak-to-peak voltage value Vpp (C) and the corresponding DC current value Idc (C). C)), a straight line M2 parallel to the coordinate axis representing the peak-to-peak voltage value Vpp is calculated. And the voltage control part 43 detects the intersection coordinate of the straight line M1 and the straight line M2 as the inflection point O, and uses the peak-to-peak voltage value Vpp corresponding to the inflection point O as the appropriate peak-to-peak voltage value Vpp (O). decide.

  Further, the voltage control unit 43 outputs peak-to-peak voltage values Vpp (D) and Vpp (E) that are assumed to be higher than the voltage value at the inflection point, and DC current values Idc (D) and Idc corresponding thereto. A straight line M3 passing through coordinates D (Vpp (D), Idc (D)) and coordinates E (Vpp (E), Idc (E)) on the assumed characteristic curve L consisting of (E) is calculated. And the voltage control part 43 calculates the voltage value Vpp (P) between peaks corresponding to the inflection point P while detecting the intersection coordinate of the straight line M2 and the straight line M3 as the inflection point P. FIG. In this way, the voltage control unit 43 can detect the two inflection points O and P from the assumed characteristic curve L shown in FIG.

  The cleaning control unit 44 is configured to control the cleaning unit 14 to cause the cleaning unit 14 to perform cleaning of the surface of the charging roller 11 for a predetermined execution time (aging time). The cleaning control unit 44 sets the execution time of the cleaning unit 14 based on the two inflection points O and P detected from the assumed characteristic curve L by the voltage control unit 43. Specifically, the two inflection points are set. The smaller the voltage difference between the points O and P (the difference between the peak-to-peak voltage values Vpp), the longer the execution time of the cleaning unit 14 is set. For example, when the voltage difference between the two inflection points O and P is 200 V or less, the cleaning control unit 44 sets the execution time to 8 minutes, and when the voltage difference is 200 to 500 V, the execution time is set to 5 minutes. If it is set to 500V or more, the execution time is set to 2 minutes.

  In the present embodiment, as described above, the printer 1 includes the photosensitive drum 10 (image carrier) that carries the toner image, the charging roller 11 (charging member) that charges the photosensitive drum 10, the DC voltage, and the AC voltage. Between the charging roller 11 and the photosensitive drum 10, a high-voltage generating unit 25 that generates a vibration voltage that is superimposed on the charging roller 11 and applies it to the charging roller 11, a voltage control unit 43 that controls the peak-to-peak voltage value Vpp of the AC voltage, A current detection unit 28 that detects the DC current value Idc, a cleaning unit 14 that cleans the surface of the photosensitive drum 10, and a cleaning control unit 44 that controls the execution of the cleaning unit 14 are provided. The voltage control unit 43 controls the high voltage generation unit 25 so as to boost the peak-to-peak voltage value Vpp, and the peak-to-peak voltage value Vpp and the DC current value Idc when the current detection unit 28 detects the DC current value Idc. Assumed characteristic curve L on the two-dimensional coordinates representing the relationship is calculated. The cleaning control unit 44 sets the execution time of the cleaning unit 14 longer as the voltage difference between the two inflection points O and P appearing in the assumed characteristic curve L is smaller.

  By the way, when ion products, moisture, paper dust, or the like adheres to the surface of the photosensitive drum 10 and the surface resistance of the photosensitive drum 10 decreases, the photosensitive drum 10 generates an electrostatic latent image formed on the surface. Without being held, a potential lateral flow (leakage) occurs at the edge portion of the electrostatic latent image, and as a result, image flow occurs in the formed image. If the surface resistance of the photosensitive drum 10 is normal, the alternating voltage peak-to-peak voltage value Vpp is increased from the low-voltage side to the high-voltage side with respect to the appropriate peak-to-peak voltage value Vpp, and the vibration voltage based on the alternating voltage is charged. When applied to the roller 11, the direct current value Idc detected by the current detector 28 is easily maintained in the vicinity of the appropriate peak-to-peak voltage value Vpp. That is, the voltage difference between the two inflection points O and P appearing in the assumed characteristic curve L shown in FIG. 3 is relatively large. However, when the surface resistance of the photosensitive drum 10 decreases, when the peak-to-peak voltage value Vpp of the AC voltage is increased as described above, the DC current value Idc detected by the current detection unit 28 is the appropriate peak-to-peak voltage value Vpp. It is difficult to maintain in the vicinity. That is, the voltage difference between the two inflection points O and P appearing in the assumed characteristic curve L shown in FIG. 3 is shortened.

  Therefore, in the present embodiment, the cleaning control unit 44 sets the execution time of the cleaning unit 14 to be longer as the voltage difference between the two inflection points O and P appearing in the assumed characteristic curve L is smaller. When the surface resistance decreases, the cleaning unit 14 can be executed in a relatively long execution time to refresh the photosensitive drum 10 to avoid a decrease in surface resistance. As a result, the photosensitive drum 10 can appropriately maintain the electrostatic latent image on the surface, and prevent the lateral flow of the potential at the edge portion of the electrostatic latent image and the image flow of the formed image. Can do.

  The cleaning control unit 44 sets the execution time of the cleaning unit 14 to be relatively short when the voltage difference between the two inflection points O and P appearing in the assumed characteristic curve L is relatively large. If the surface resistance is normal, the execution time of the cleaning unit 14 can be shortened. As a result, the cleaning unit 14 does not waste the photoconductor drum 10 excessively, the life of the photoconductor drum 10 is not shortened more than necessary, and the power consumption required for execution of the cleaning unit 14 can be suppressed.

  In this way, by measuring the DC current value Idc of the charging roller 11 whose characteristics change depending on the environmental conditions, the environment in the vicinity of the surface of the photosensitive drum 10 and the charging roller 11 can be accurately grasped, and appropriate refresh (polishing) can be performed. Control can be performed.

  In the present embodiment, the cleaning unit 14 includes a polishing roller 32 (sliding polishing member) that refreshes the surface of the photosensitive drum 10. As a result, the cleaning control unit 44 can realize the control of the execution time for refreshing the surface of the photosensitive drum 10 by a simple method of controlling the time for driving and controlling the polishing roller 32.

  In another embodiment, the cleaning control unit 44 may perform control so that the cleaning unit 14 is not executed when there are no two inflection points O and P in the assumed characteristic curve L. For example, The execution time of the cleaning unit 14 is set to zero. For example, FIG. 4 shows assumed characteristic curves calculated under various combinations of temperature and humidity in the printer main body 2. As shown in FIG. 4, there are two inflections in the assumed characteristic curve L1 under the environment of temperature 32.5 ° C. and humidity 80% and the assumed characteristic curve L2 under the environment of temperature 28 ° C. and humidity 80%. Points O and P exist. However, there is only one inflection point O in the assumed characteristic curve L3 under the environment of temperature 23 ° C. and humidity 50% and the assumed characteristic curve L4 under the environment of temperature 10 ° C. and humidity 15%. In these cases, the cleaning control unit 44 performs control so that the cleaning unit 14 is not executed.

  Thus, when the surface resistance of the photosensitive drum 10 is normal, the cleaning unit 14 is not executed, so that the cleaning unit 14 avoids scraping the photosensitive drum 10 and extends the life of the photosensitive drum 10 further. At the same time, it is possible to further suppress the power consumption required for the execution of the cleaning unit 14.

  In another embodiment, after the cleaning control unit 44 detects two inflection points O and P from the assumed characteristic curve L, the cleaning control unit 44 determines whether the cleaning unit 14 has one inflection point in the assumed characteristic curve L. You may control to continue execution.

  Thereby, the cleaning control unit 44 can execute the cleaning unit 14 until the surface resistance of the photosensitive drum 10 becomes normal, and can appropriately refresh the photosensitive drum 10.

  According to the above-described embodiment, the printer 1 stores the peak-to-peak voltage value table 47 including a plurality of peak-to-peak voltage values corresponding to various combinations of temperature and humidity in the printer body 2 (apparatus body). The voltage control unit 43 is configured to read the peak-to-peak voltage value from the peak-to-peak voltage value table 47 stored in the storage unit 41 based on the temperature and humidity in the printer main body 2. The Thereby, the voltage control unit 43 can appropriately control the high voltage generation unit 25 according to the environment of the printer 1 (printer body 2) and calculate an appropriate assumed characteristic curve.

  In the present embodiment, the case where the configuration of the present invention is applied to the printer 1 has been described. However, in another different embodiment, the configuration of the present invention is applied to other image forming apparatuses such as a copying machine, a facsimile, and a multifunction peripheral. May be.

1 Printer (image forming device)
8 Image forming unit 10 Photosensitive drum (image carrier)
11 Charging roller (charging member)
DESCRIPTION OF SYMBOLS 14 Cleaning part 25 High voltage generation part 26 AC power supply 27 DC power supply 28 Current detection part 31 Cleaning blade 32 Polishing roller (rubbing polishing member)
DESCRIPTION OF SYMBOLS 40 Control part 41 Memory | storage part 42 Drum drive part 43 Voltage control part 44 Cleaning control part 45 Temperature sensor 46 Humidity sensor 47 Peak-to-peak voltage value table

Claims (5)

An image carrier for carrying a toner image;
A charging member for charging the image carrier;
A high-voltage generator that generates an oscillating voltage in which a DC voltage and an AC voltage are superimposed and applies them to the charging member;
A voltage control unit for controlling a peak-to-peak voltage value of the AC voltage;
A current detector for detecting a direct current value between the charging member and the image carrier;
A cleaning unit for cleaning the surface of the image carrier;
A cleaning control unit that controls execution of the cleaning unit,
The voltage control unit controls the high voltage generation unit so as to boost the peak-to-peak voltage value, and a relationship between the peak-to-peak voltage value and the DC current value when the current detection unit detects a DC current value Calculate the assumed characteristic curve on the two-dimensional coordinates representing
The image forming apparatus, wherein the cleaning control unit sets a longer execution time of the cleaning unit as a voltage difference between two inflection points appearing in the assumed characteristic curve is smaller.   The image forming apparatus according to claim 1, wherein the cleaning unit includes a rubbing polishing member that refreshes a surface of the image carrier.   The image forming apparatus according to claim 1, wherein the cleaning control unit does not execute the cleaning unit when the two inflection points do not exist in the assumed characteristic curve.   When the two inflection points exist in the assumed characteristic curve, the cleaning control unit continues the execution of the cleaning unit until the inflection point in the assumed characteristic curve becomes one. The image forming apparatus according to claim 1. A storage unit storing a peak-to-peak voltage value table composed of a plurality of peak-to-peak voltage values corresponding to various combinations of temperature and humidity in the apparatus body;
The voltage control unit reads the peak-to-peak voltage value from the peak-to-peak voltage value table stored in the storage unit based on the temperature and humidity in the apparatus main body. 5. The image forming apparatus according to any one of 4 above.

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