JP2018040885A - Image forming apparatus, control program, and control method - Google Patents

Abstract

CONSTITUTION: An image forming apparatus (10) comprises a pre-transfer charger 100, and the pre-transfer charger provides a toner carried on an outer peripheral surface of an intermediate transfer belt 54 with electrical charge having the same polarity as the charging polarity of the toner before secondary transfer during printing. When the temperature inside the image forming apparatus is changed from a temperature lower than a first predetermined value to a temperature higher than the value, or when the humidity inside the image forming apparatus is changed from a humidity lower than a second predetermined value to a humidity higher than the value, the image forming apparatus causes a current to flow during printing, the current having a current value with an absolute value larger than that of the current value of a current caused to flow in a discharge electrode (104) of a transfer charger. A large repulsive force thus acts on a toner attached to the discharge electrode, and the toner is removed.EFFECT: A discharge electrode can be cleaned without separately providing a cleaning device.SELECTED DRAWING: Figure 2

Description

  The present invention relates to an image forming apparatus, a control program, and a control method, and more particularly to, for example, an image forming apparatus, a control program, and a control method for uniformly charging a toner image before transfer onto a recording sheet.

  An example of background art is disclosed in Patent Document 1. The image forming apparatus disclosed in Patent Document 1 includes a temperature sensor, a humidity sensor, a cleaning device, and a control unit, and the temperature sensor and the humidity sensor detect the temperature and humidity inside the image forming apparatus every predetermined time. . The controller causes the cleaning device to clean the discharge electrode of the main charger when there is a sudden change in the detected temperature and humidity.

Japanese Patent No. 2014-235331

  However, in the technique of Patent Document 1, since a cleaning device including a cleaning roller for cleaning the discharge electrode is provided, there is a problem that the structure of the device becomes complicated and the device becomes large. In addition, when the cleaning roller is damaged due to repeated use of the cleaning roller, it may be considered that the charged portion such as the discharge electrode cannot be sufficiently cleaned.

  Therefore, a main object of the present invention is to provide a novel image forming apparatus, control program, and control method.

  Another object of the present invention is to provide an image forming apparatus, a control program, and a control method capable of sufficiently cleaning a charging unit without separately providing a cleaning device.

  A first invention is an image forming apparatus that charges a toner image before the toner image is printed on a recording sheet, and includes a first current control unit and a second current control unit. The first current control unit causes a current of a first predetermined value to flow through the charging unit when charging the toner image during printing. The second current control means flows a current of a second predetermined value having a larger absolute value than the first predetermined value to the charging unit at a predetermined timing other than when printing is performed. Therefore, a large repulsive force acts on the toner adhering to the charging portion, and the adhering toner is removed from the charging portion.

  According to the first invention, the charging unit can be sufficiently cleaned without providing a separate cleaning device.

  The second invention is dependent on the first invention, and the predetermined timing is when the temperature inside the image forming apparatus becomes equal to or higher than the first predetermined value and when the humidity inside the image forming apparatus is equal to or higher than the second predetermined value. Including at least one of When the temperature inside the image forming apparatus is lower than the first predetermined value, the toner charge amount on the intermediate transfer belt is large. In this case, if the pre-transfer charging is performed, the toner is hardly separated from the intermediate transfer belt. Become. Further, when the humidity is lower than the second predetermined value, it is difficult for the discharge to occur, and thus the toner on the intermediate transfer belt 54 may not be sufficiently charged. For this reason, when the temperature is lower than the first predetermined value or / and when the humidity is lower than the second predetermined value, the pre-transfer charging is not performed. When the image forming apparatus is used for a long period of time without performing pre-transfer charging, or when a large number of sheets are printed in such a state, scattered toner adheres to the charging portion. Therefore, the toner adhering to the charging unit is removed by supplying the second predetermined value of current at the predetermined timing as described above.

  According to the second invention, the charger can be cleaned at an appropriate timing.

  The third invention is dependent on the first invention, and the predetermined timing is when the power of the image forming apparatus is turned on.

  According to the third invention, the charger can be cleaned regardless of changes in temperature and humidity.

  A fourth invention is dependent on any one of the first to third inventions, and the second current control means gradually increases the current value of the current flowing through the charging unit to a second predetermined value.

  According to the fourth aspect, since the current value is gradually increased to the second predetermined value, it is possible to prevent the current flowing through the charging unit from leaking.

  The fifth invention is dependent on the fourth invention, and the second current control means changes the current value of the current flowing through the charging unit so as to increase stepwise or linearly, and at the initial stage, printing is executed. Sometimes it is smaller than the current value of the current flowing through the charging unit, and at the later stage, it is larger than the current value of the current flowing through the charging unit during printing.

  In the fifth invention, as in the fourth invention, it is possible to prevent the current flowing through the charging portion from leaking.

  A sixth invention is dependent on any one of the first to fourth inventions, and the second current control means changes the polarity of the current when a current of a second predetermined value is passed through the charging unit.

  According to the sixth aspect of the invention, since the polarity of the current is changed, it is possible to clean even a part of the toner charged to the reverse polarity.

  A seventh invention is dependent on any one of the first to sixth inventions, and further includes a plate member and a voltage control means. The plate member is a conductive plate member (metal plate) surrounding the charging unit. The voltage control means applies, to the case, a voltage having a polarity opposite to that of the current flowing through the charging unit when the second current control unit causes the second predetermined current to flow through the charging unit. Therefore, a force that draws the toner adhering to the charging portion toward the case works.

  According to the seventh aspect, the charging portion can be effectively cleaned.

  An eighth invention is according to any one of the first to seventh inventions, wherein the charging unit includes a wire stretched around the axis in the housing so as to be rotatable around the axis, and the wire rotates. A member is further provided.

  According to the eighth aspect, since the wire is rotated, the toner attached to the charging unit can be dropped. Therefore, the charger can be cleaned more effectively.

  A ninth aspect of the invention is a control program for an image forming apparatus that charges a toner image before the toner image is printed on a recording paper. When the toner image is charged during printing, the charging unit A first current control step for controlling the power supply control unit to flow a current of the first predetermined value, and a second predetermined value having an absolute value larger than the first predetermined value in the charging unit at a predetermined timing other than during printing. It is a control program which performs the 2nd electric current control step which controls a power supply control part so that current of this may flow.

  A tenth aspect of the invention is a control method of an image forming apparatus that charges a toner image before the toner image is printed on a recording paper, and (a) when the toner image is charged during printing, A step of controlling the power supply controller so that a current of a first predetermined value flows through the charging unit; and (b) a second value having an absolute value larger than the first predetermined value at the charging unit at a predetermined timing other than during printing. It is a control method including the step of controlling the power supply control unit so as to pass a current of a predetermined value.

  In the ninth and tenth inventions, similarly to the first invention, the charging unit can be sufficiently cleaned without providing a separate cleaning device.

  According to the present invention, it is possible to sufficiently clean the charging portion without separately providing a cleaning device.

  The above object, other objects, features and advantages of the present invention will become more apparent from the following detailed description of embodiments with reference to the drawings.

FIG. 1 is a schematic sectional view showing the internal structure of the image forming apparatus according to the first embodiment of the present invention. FIG. 2 is an illustrative view schematically showing a configuration of an image forming unit provided in the image forming apparatus of FIG. FIG. 3 is a perspective view of the external configuration of the pre-transfer charger shown in FIGS. 1 and 2 as viewed obliquely from above. FIG. 4 is a top view of a part of the pre-transfer charger shown in FIG. 3 as viewed from above. FIG. 5 is a cross-sectional view showing a schematic configuration of a part of the pre-transfer charger shown in FIGS. 3 and 4. FIG. 6 is a block diagram showing an example of the electrical configuration of the image forming apparatus of FIG. FIG. 7A is a graph showing the time change of the current flowing through the discharge electrode when printing is performed, and FIG. 7B is a graph showing the time change of the current flowing through the discharge electrode when cleaning is executed. FIG. 8 is an illustrative view showing one example of a memory map of the RAM shown in FIG. FIG. 9 is a flowchart showing an example of the cleaning control process of the CPU shown in FIG. FIG. 10 is a schematic cross-sectional view and an illustrative view showing an electrical configuration of a discharge electrode and a shield of the pre-transfer charger according to the second embodiment. FIG. 11A is an illustrative view of the discharge electrode of the pre-transfer charger of the third embodiment as viewed from above, and FIG. 11B is a cross-sectional view taken along the line XIB-XIB in FIG.

[First embodiment]
Referring to FIG. 1, an image forming apparatus 10 according to an embodiment of the present invention is a multifunction peripheral (MFP) having a copying function, a printer function, a scanner function, a facsimile function, and the like, and a color printing mode. Alternatively, it operates in a monochrome printing mode to form a multicolor or single color image on a sheet (recording medium). As will be described in detail later, the image forming apparatus 10 includes an intermediate transfer type image forming unit 30, and includes an intermediate transfer belt (primary transfer belt) 54 and the like that are stretched around a plurality of rollers 56 and 58. The toner image formed on the photosensitive drum 36 is transferred to a sheet.

  First, the basic configuration of the image forming apparatus 10 will be schematically described. As shown in FIGS. 1 and 2, the image forming apparatus 10 includes an apparatus main body 12 including an image forming unit 30 and the like, and an image reading apparatus 14 disposed above the apparatus main body 12.

  The image reading device 14 includes a document placing table 16 formed of a transparent material. A document pressing cover 18 is attached above the document placing table 16 through a hinge or the like so as to be freely opened and closed. The document pressing cover 18 is provided with an ADF (automatic document feeder) 24 that automatically feeds documents placed on the document placing tray 20 one by one to the image reading position 22. An operation unit 28 (see FIG. 6) that accepts an input operation by the user is provided on the front side of the document table 16. The operation unit 28 includes a touch panel, operation buttons, and a main switch for turning on / off the apparatus power of the image forming apparatus 10.

  Further, the image reading device 14 is provided with an image reading unit 26 including a light source, a plurality of mirrors, an imaging lens, a line sensor, and the like. The image reading unit 26 exposes the document surface with a light source, and guides the reflected light reflected from the document surface to the imaging lens by a plurality of mirrors. Then, the reflected light is imaged on the light receiving element of the line sensor by the imaging lens. The line sensor detects the luminance and chromaticity of the reflected light imaged on the light receiving element, and generates image data based on the image on the document surface. As the line sensor, a CCD (Charge Coupled Device), a CIS (Contact Image Sensor), or the like may be used.

  The apparatus main body 12 is provided with a control unit including the CPU 200 and memories (204, 206, 208) and the like (see FIG. 6), the image forming unit 30, and the like. The control unit transmits a control signal to each part of the image forming apparatus 10 according to an input operation to the operation unit 28 by the user, and causes the image forming apparatus 10 to execute various operations.

  The image forming unit 30 includes an exposure unit 32, a developing unit 34, a photosensitive drum 36, a cleaner unit 38, a charger 40, an intermediate transfer belt unit 42, a secondary transfer roller 44, a fixing unit 46, a pre-transfer charger 100, and the like. In addition, an image is formed on a sheet conveyed from the sheet feeding tray 48 or the manual sheet feeding tray 50, and the image-formed sheet is discharged to a sheet discharge tray 52. As image data for forming an image on a sheet, image data read by the image reading unit 26, image data transmitted from an external computer, or the like is used.

  Here, the image data handled in the image forming apparatus 10 corresponds to four color images of black (BK), magenta (M), cyan (C), and yellow (Y). For this reason, each of the developing device 34, the photosensitive drum 36, the cleaner unit 38, and the charging device 40 is provided so as to form four types of latent images corresponding to the respective colors, thereby providing four image stations. Composed. The four image stations are arranged in a line along the traveling direction (circumferential movement direction) of the surface of the intermediate transfer belt 54, and are located close to the secondary transfer roller 44 from the downstream side in the traveling direction of the intermediate transfer belt 54. From the side, they are arranged in the order of black, magenta, cyan and yellow. However, the arrangement order of the colors can be changed as appropriate.

  Note that the subscripts BK, M, C, and Y given to the reference numerals are for indicating elements provided for any color, and the subscripts BK, M, C, and Y are respectively , Black, magenta, cyan and yellow. For example, reference numeral 36BK in FIG. 2 indicates that the photosensitive drum is for black (for BK). Further, in the description of each part, when it is not particularly necessary to distinguish which color is used, the subscripts BK, M, C, and Y are omitted, and the description will be made comprehensively.

  The photosensitive drum 36 is an image carrier in which a photosensitive layer is formed on the surface of a cylindrical substrate having conductivity. The charger 40 is a corona discharge type charger, and charges the surface of the photosensitive drum 36 to a predetermined potential (for example, −600 V) by performing corona discharge from a sawtooth discharge electrode. However, as the charger 40, other chargers such as a brush-type charger, a roller-type charger, and an ion generator can be used. Further, the exposure unit 32 is configured as a laser scanning unit (LSU) including a laser emitting portion and a reflection mirror, and exposes the surface of the charged photosensitive drum 36 so that an electrostatic latent image corresponding to image data is obtained. An image is formed on the surface of the photosensitive drum 36. The developing device 34 visualizes the electrostatic latent image formed on the surface of the photosensitive drum 36 with four color toners. The cleaner unit 38 removes toner remaining on the surface of the photosensitive drum 36 after development and image transfer, and conveys the toner to a waste toner box (not shown).

  The intermediate transfer belt unit 42 includes an intermediate transfer belt 54, a drive roller 56, a driven roller 58, four intermediate transfer rollers 60, and the like, and is disposed above the photosensitive drum 36.

  The intermediate transfer belt 54 is a flexible endless belt, and is composed of polyimide (PI), polyamide (PA), polyvinylidene fluoride (PVDF), or the like, which is appropriately mixed with a conductive material such as carbon black. It is formed of resin or rubber. The intermediate transfer belt 54 is stretched by a plurality of rollers such as a driving roller 56 and a driven roller 58, and is provided so that an outer peripheral surface thereof is in contact with each photosensitive drum 36. As the drive roller 56 is driven to rotate, it moves around in a predetermined direction (counterclockwise in FIGS. 1 and 2).

  The intermediate transfer roller (primary transfer roller) 60 is a roller-like member in which an elastic layer is laminated on the outer peripheral surface of the core metal. The core metal of the intermediate transfer roller 60 is formed of a metal such as stainless steel or aluminum, and the elastic layer is made of ethylene-propylene rubber (EPDM), foamed EPDM, foamed urethane, or the like appropriately mixed with a conductive material such as carbon black. Formed by rubber. However, as the intermediate transfer roller 60, a metal roller that does not have an elastic layer on the outer peripheral surface can be used from the viewpoint of cost reduction and downsizing of the apparatus.

  The intermediate transfer roller 60 is provided at a position facing each of the photosensitive drums 36 with the intermediate transfer belt 54 interposed therebetween, and is brought into pressure contact with the inner peripheral surface of the intermediate transfer belt 54 to rotate as the intermediate transfer belt 54 rotates. To do. Here, the position at which the intermediate transfer roller 60 is pressed against the intermediate transfer belt 54 (transfer current supply position) is more intermediate than the position at which the intermediate transfer belt 54 and the photosensitive drum 36 are in contact (primary transfer position). Preferably, the position is slightly shifted to the downstream side in the traveling direction (circumferential movement direction), that is, the position in the vicinity of the photosensitive drum 36. Specifically, the distance in the traveling direction of the intermediate transfer belt 54 between the transfer current supply position and the primary transfer position is preferably set to 2 to 5 mm. This is because when the distance between the transfer current supply position and the primary transfer position is increased, an image defect due to the contact trace is likely to occur when the intermediate transfer belt 54 has a contact trace. Because. By setting the transfer current supply position and the primary transfer position as the vicinity positions, the occurrence of image defects due to contact marks is suppressed.

  However, the distance in the running direction of the intermediate transfer belt 54 between the transfer current supply position and the primary transfer position can be changed as appropriate. For example, the distance between the transfer current supply position and the primary transfer position is 0 mm. (That is, the line connecting the rotation axis of the photosensitive drum 36 and the rotation axis of the intermediate transfer roller 60 and the line extending in the running direction of the intermediate transfer belt 54 are orthogonal to each other). You may arrange | position with the drum 36 facing. Further, the intermediate transfer roller 60 and the photosensitive drum 36 may be arranged to face each other so that the distance between the transfer current supply position and the primary transfer position exceeds 5 mm.

  Further, a high voltage power supply circuit 214 a (see FIG. 6) included in the power supply control unit 214 is connected to each of the intermediate transfer rollers 60. Under the instruction of the CPU 200, the high voltage power supply circuit 214a is charged with the polarity of the toner constituting the toner image formed on the surface of the photosensitive drum 36 during image formation (printing) (in the first embodiment, minus). ) Is applied to the intermediate transfer roller 60 with a reverse polarity (primary transfer voltage). As a result, a current corresponding to the voltage applied from the high voltage power supply circuit 214a flows through the intermediate transfer roller 60 (primary transfer current is supplied).

  In the first embodiment, a constant current controlled voltage is applied to the intermediate transfer roller 60. That is, the voltages applied to the intermediate transfer rollers 60BK, M, C, and Y from the high-voltage power supply circuit 214a are substantially constant at the target current values of the currents flowing through the intermediate transfer rollers 60BK, M, C, and Y, respectively. In other words, each detected current value detected by a transfer current detecting unit (not shown) is changed so that each target current value matches.

  When the primary transfer current is supplied to the intermediate transfer roller 60, the primary transfer current passes through the transfer current supply position and flows to the intermediate transfer belt 54. At the primary transfer position, the photosensitive drum 36 and the intermediate transfer belt 54 meet. A transfer electric field is formed between them. The toner image formed on the photosensitive drum 36 is transferred (primary transfer) to the outer peripheral surface of the intermediate transfer belt 54 by the action of the transfer electric field formed at the primary transfer position.

  For example, when forming a color image, each color toner image formed on each photosensitive drum 36 is sequentially transferred onto the intermediate transfer belt 54 and a multicolor toner image is formed on the intermediate transfer belt 54. Is done. On the other hand, when forming a monochrome image, an electrostatic latent image and a toner image are formed only on the black photosensitive drum 36BK, and only the black toner image is transferred to the outer peripheral surface of the intermediate transfer belt 54. .

  The pre-transfer charger 100 is provided so as to be parallel to the outer peripheral surface of the intermediate transfer belt 54 and extend in a direction perpendicular to the traveling direction of the intermediate transfer belt 54. Further, the pre-transfer charger 100 is disposed in the vicinity of the driving roller 56 on the downstream side in the traveling direction of the intermediate transfer belt 54 with respect to the photosensitive drum 36BK (image station) for BK. Further, the opposing roller 150 is a position facing the pre-transfer charger 100 and is provided with the intermediate transfer belt 54 interposed therebetween.

  FIG. 3 is a perspective view of the external configuration of the pre-transfer charger 100 as viewed obliquely from above. FIG. 4 is a schematic view of a part of the pre-transfer charger 100 as viewed from above. FIG. 5 is a sectional view of a schematic configuration of a part of the pre-transfer charger 100.

  As shown in FIG. 3, the pre-transfer charger 100 includes a housing 102 having a U-shaped cross section and extending in the width direction of the intermediate transfer belt 54 when mounted. Inside the housing 102, a discharge electrode (charging portion) 104 is provided so as to extend in the longitudinal direction. In the first embodiment, as shown in FIG. 4, the discharge electrode 104 is formed of a wire and is stretched inside the housing 102. More specifically, in the discharge electrode 104, conductive round terminals 104a and 104b are fixed to both ends of the wire. One of the round terminals 104a is locked to the housing 102 via a spring 106, and the other round terminal 104a. The terminal 104 b is locked to the hook 108 a of the electrode 108 fixed to the housing 102. The electrode 108 is provided so that the end opposite to the end where the hook 108 a is provided protrudes outside the housing 102. A voltage from the high voltage power supply circuit 214a (see FIG. 6) is applied to the electrode.

  As shown in FIG. 5, shields 110 a and 110 b are provided in the housing 102, and the shields 110 a and 110 b are provided parallel to the discharge electrode 104 and extending in the longitudinal direction of the housing 102. The shields 110a and 110b are L-shaped in cross section and are arranged at a predetermined distance so that the L-shaped horizontal bars face each other, and correspond to L-shaped vertical bars as shown in FIG. A portion is attached along the side perpendicular to the opening of the housing 102. Discharge electrode 104 is disposed between shields 110a and 110b (center). That is, the shields 110 a and 110 b are arranged so as to surround (pinch) the discharge electrode 104. However, the shields 110a and 110b are conductive plate members (metal plates).

  The pre-transfer charger 100 discharges toward the counter roller 150, so that the toner carried on the outer peripheral surface of the intermediate transfer belt 54 has a charge having the same polarity as the charging polarity of the toner (minus in the first embodiment). Is granted. Therefore, the potential of the toner carried on the outer peripheral surface of the intermediate transfer belt 54 is made uniform, and toner scattering is prevented. Therefore, when secondary transfer is executed, transfer defects such as transfer spots are prevented from occurring.

  In the first embodiment, under the instruction of the CPU 200 (see FIG. 6), a voltage is applied to the discharge electrode 104 of the pre-transfer charger 100 from the DC power supply Vd of the high-voltage power supply circuit 214a. A constant current controlled voltage is applied to the discharge electrode 104. For example, during image formation (printing), a current of −200 μA flows, and a voltage for this (for example, −3 kV) is applied from the DC power supply Vd to the discharge electrode 104 via the electrode 108. However, the voltage applied from the DC power supply Vd is such that the current flowing through the discharge electrode 104 is substantially constant at the target current value, that is, the detected current value detected by a discharge (charging) current detector (not shown). And the target current value are changed.

  A secondary transfer roller 44 is disposed in the vicinity of the driving roller 56. A transfer power supply (not shown) is connected to the secondary transfer roller 44, and a voltage (secondary transfer voltage) is applied by the transfer power supply. The intermediate transfer belt is moved while the sheet passes through the transfer nip region between the intermediate transfer belt 54 and the secondary transfer roller 44 by the action of a transfer electric field formed by the secondary transfer roller 44 to which a voltage is applied. The toner image formed on the outer peripheral surface 54 is transferred (secondarily transferred) to the paper.

  The fixing unit 46 includes a heat roller 62 and a pressure roller 64 and is disposed above the secondary transfer roller 44. The heat roller 62 is set to have a predetermined fixing temperature. When the paper passes through the nip area between the heat roller 62 and the pressure roller 64, the toner image transferred to the paper is melted. The toner image is heat-fixed on the sheet by mixing and pressing.

  In the apparatus main body 12, the paper placed on the paper feed tray 48 or the manual paper feed tray 50 is sent to the paper discharge tray 52 via the registration roller 68, the secondary transfer roller 44 and the fixing unit 46. Therefore, a first paper transport path P1 is formed. Further, when performing duplex printing on a sheet, the sheet after the one-side printing is finished and passed through the fixing unit 46 is moved to the first sheet conveyance path P1 upstream of the secondary transfer roller 44 in the sheet conveyance direction. A second paper transport path P2 for returning is formed. In the first paper transport path P1 and the second paper transport path P2, a plurality of transport rollers 66 for transporting paper are appropriately provided.

  When single-sided printing is performed in the apparatus main body 12, the paper placed on the paper feed tray 48 or the manual paper feed tray 50 is guided to the first paper transport path P 1 one by one by the pickup roller 70, and is transported by the transport roller 66. It is conveyed to the registration roller 68. Then, the registration roller 68 conveys the paper to the secondary transfer roller 44 at a timing when the leading edge of the paper and the leading edge of the image information on the intermediate transfer belt 54 are aligned, and the toner image is transferred onto the paper. Thereafter, when the toner passes through the fixing unit 46, the unfixed toner on the paper is melted and fixed by heat, and the paper is discharged onto the paper discharge tray 52 through a conveyance roller (paper discharge roller) 66.

  On the other hand, when performing double-sided printing, when the trailing edge of the paper that has passed through the fixing unit 46 after single-sided printing has reached the paper discharge roller 66 near the paper discharge tray 52, the paper discharge roller 66 is reversed. By rotating, the sheet runs backward and is guided to the second sheet conveyance path P2. The paper guided to the second paper transport path P2 is transported through the second paper transport path P2 by the transport roller 66, and is guided to the first paper transport path P1 on the upstream side of the registration roller 68 in the paper transport direction. At this time, the front and back sides of the paper are reversed, so that the paper passes through the secondary transfer roller 44 and the fixing unit 46, and printing is performed on the back side of the paper.

  FIG. 6 is a block diagram illustrating an example of an electrical configuration of the image forming apparatus 10. The image forming apparatus 10 includes a CPU 200. The CPU 200 is connected to the ROM 204, the RAM 206, the HDD 208, the temperature sensor 210, the humidity sensor 212, and the power supply control unit 214 via the bus 202, and the image reading unit 26, the operation unit 28, and the image forming unit 30 described above. Etc. are connected. Since the operation unit 28, the image reading unit 26, and the image forming unit 30 have been described above, description thereof will be omitted here.

  The CPU 200 comprehensively controls the operation of each part of the image forming apparatus 10 such as the image reading device 14 and the image forming unit 30. The ROM 204 is used to store a program (Boot program) and data that are executed when the main processing program (operating system) of the image forming apparatus 10 is activated.

  The RAM 206 is used as a work memory or buffer memory for the CPU 200. The HDD 208 is a main storage device of the image forming apparatus 10, and appropriately stores a control program and data for the CPU 200 to control the operation of each part of the image forming apparatus 10. However, another nonvolatile memory such as a flash memory may be provided instead of the HDD 208 or together with the HDD 208.

  The temperature sensor 210 is used to detect the temperature (° C.) inside the image forming apparatus 10. The humidity sensor 212 is used to detect the humidity (%) inside the image forming apparatus 10.

  The power control unit 214 supplies and stops necessary power to each part of the image forming apparatus 10 under the instruction of the CPU 200. However, commercial power is supplied to the power supply control unit 214, and the commercial power is stepped down or boosted and rectified to generate necessary power for each part. The power supply control unit 214 includes a high-voltage power supply circuit 214a for supplying and stopping a high-voltage power supply for charging, transfer, exposure, and development.

  In such an image forming apparatus 10, when an image forming process (printing process) is executed, a voltage is applied from the high voltage power supply circuit 214a to the discharge electrode 104 of the pre-transfer charger 100 as described above.

  However, when the temperature is lower than the first predetermined value, the charge amount of the toner on the intermediate transfer belt 54 is large. In this case, if charging is performed by the pre-transfer charger 100, the toner is transferred from the intermediate transfer belt 54. It becomes difficult to leave. Further, when the humidity is lower than the second predetermined value, it is difficult for the discharge to occur, and thus the toner on the intermediate transfer belt 54 may not be sufficiently charged. Therefore, when the temperature is lower than the first predetermined value or / and when the humidity is lower than the second predetermined value, charging by the pre-transfer charger 100 is not performed.

  The first predetermined value and the second predetermined value are values empirically obtained through experiments or the like, and are stored (set) in the HDD 208 in advance.

  As described above, when the temperature or / and humidity is low and charging is not performed by the pre-transfer charger 100 for a long period of time, or when a large number of sheets are printed in such a state, the discharge electrode (wire) 104 is applied. A large amount of scattered toner adheres. That is, the scattered toner is laminated on the discharge electrode 104.

  If pre-transfer charging is performed by the pre-transfer charger 100 in a state where a large amount of scattered toner is attached to the discharge electrode 104, charge spots are generated on the toner on the intermediate transfer belt 54. As a result, image defects such as white streaks or spots occur in the output image.

  However, the white streak means a white streak line (density is lower than other portions) generated in the output image.

  Therefore, it is necessary to clean the discharge electrode 104 when the temperature changes from a state lower than the first predetermined value to a high state or when the humidity changes from a state lower than the second predetermined value to a high state. is there. However, the temperature may change from a state lower than the first predetermined value to a high state, and the humidity may change from a state lower than the second predetermined value to a high state.

  Therefore, for example, it is conceivable to provide a cleaning device for cleaning the discharge electrode 104 as in the background art, but a space for providing the cleaning device is necessary, and the image forming apparatus 10 becomes large. Further, when the cleaning device is provided, the cost of the image forming apparatus 10 is increased.

  Therefore, in the first embodiment, the discharge electrode 104 is cleaned without providing a separate cleaning device for cleaning the discharge electrode 104.

  Specifically, when the temperature changes from a state lower than the first predetermined value to a state where the temperature is equal to or higher than the first predetermined value, or when the humidity is lower than the second predetermined value, it is higher than the second predetermined value. Cleaning of the discharge electrode 104 is performed at the timing when the state changes. However, when the temperature changes from a state lower than the first predetermined value to a state higher than the first predetermined value, the humidity may change from a state lower than the second predetermined value to a state higher than the second predetermined value. is there. Further, when the printing process is executed at the above timing, the cleaning is executed after the printing process is completed. Further, the cleaning of the discharge electrode 104 may be executed when the power of the image forming apparatus 10 is turned on.

  Further, in the first embodiment, the image forming apparatus 10 (CPU 200) has a timing when the temperature changes to a state lower than the first predetermined value or a timing when the humidity changes to a state lower than the second predetermined value. Then, control is performed so that charging by the pre-transfer charger 100 is not performed. However, when the temperature is lower than the first predetermined value, the humidity may be lower than the second predetermined value.

  FIG. 7A is a graph showing the change over time of the current value flowing through the discharge electrode 104 during printing, and FIG. 7B is a graph showing the change over time of the current value flowing through the discharge electrode 104 during cleaning.

  As described above, since the current flowing through the discharge electrode 104 is controlled at a constant current, as shown in FIG. 7A, a current having a constant current value (−200 μA) flows through the discharge electrode 104 when printing is performed. The voltage applied to the discharge electrode 104 from the DC power supply Vd of the high-voltage power supply circuit 214a is controlled so that such a current flows.

  On the other hand, when cleaning is performed, as shown in FIG. 7B, the discharge electrode 104 is supplied from the DC power supply Vd of the high-voltage power supply circuit 214a so that a current having a larger absolute value (−400 μA) flows than when printing is performed. The voltage applied to is controlled. The polarity of the current flowing through the discharge electrode 104 during cleaning is the same as the charging polarity of the toner, and the current value has a larger absolute value than that during printing. Therefore, a large repulsive force is exerted on the negatively charged toner. Occur. The toner adhering to the discharge electrode 104 is removed (removed) by this repulsive force. Further, when a current having a larger current value than that at the time of printing is passed through the discharge electrode 104, the discharge electrode 104 attached to the housing 102 is vibrated as described above. This vibration also removes the toner attached to the discharge electrode 104.

  However, as shown in FIG. 7B, when cleaning is performed, the voltage applied to the discharge electrode 104 is controlled so that the absolute value of the current value gradually increases. In the first embodiment, the voltage applied to the discharge electrode 104 is controlled so that the current value changes stepwise.

  Specifically, when cleaning is started, a current having a current value (in this case, −100 μA) whose absolute value is smaller than the current value at the time of printing is discharged in the first 30 seconds (0 to 30 seconds). The voltage applied to the discharge electrode 104 is controlled so as to flow to 104. In the next 30 seconds (30 seconds to 60 seconds), the voltage applied to the discharge electrode 104 is controlled so that a current having the same current value as when printing is performed flows through the discharge electrode 104. Further, in the next (last) 30 seconds (60 seconds to 90 seconds), a current having a current value (in this case, −400 μA) larger than the current value at the time of printing is caused to flow through the discharge electrode 104. In addition, the voltage applied to the discharge electrode 104 is controlled.

  The reason why the absolute value of the current value is gradually increased is to prevent the current flowing through the discharge electrode 104 from leaking.

  In the first embodiment, the current value is changed stepwise (stepwise), but linearly until a current value having a larger absolute value than the current value at the time of printing is reached. The current value may be changed.

  Further, although the current value is changed stepwise every 30 seconds, this is an example and should not be limited. If no leak occurs, the current value may be changed in a time shorter than 30 seconds. Further, the time for changing the current value may not be the same length.

  Furthermore, the time (substantially cleaning time) in which the current having a current value larger than the current value at the time of printing is flowing to the discharge electrode 104 is set to 30 seconds, but this is an example. Should not be limited.

  FIG. 8 is an illustrative view showing one example of a memory map 300 of the RAM 206 shown in FIG. As shown in FIG. 8, the RAM 206 includes a program storage area 302 and a data storage area 304.

  The program storage area 302 stores a control program for cleaning the discharge electrode 104, and the control programs include a power supply control program 302a, a detection program 302b, a pre-transfer exposure control program 302c, a cleaning determination program 302d, and a cleaning execution program 302e. Etc.

  The power control program 302 a is a program for controlling the power control unit 214 to supply and stop power to each circuit (component) constituting the image forming apparatus 10.

  The detection program 302b is a program for detecting outputs from the temperature sensor 210 and the humidity sensor 212. The pre-transfer exposure control program 302c is a program for determining whether to perform pre-transfer exposure based on the outputs of the temperature sensor 210 and the humidity sensor 212, and controlling pre-transfer exposure by the pre-transfer charger 100. .

  The cleaning determination program 302d is a program for determining whether or not the discharge electrode 104 is to be cleaned. The cleaning execution program 302e is a program for executing the cleaning of the discharge electrode 104 when it is determined that the cleaning is performed according to the cleaning determination program 302d.

  Although not shown, the program storage area 302 also stores other programs for executing processing necessary for the operation of the image forming apparatus 10 such as image reading processing and image forming processing.

  The data storage area 304 stores data such as temperature data 304a, humidity data 304c, and threshold data 304e. The data storage area 304 stores a pre-transfer exposure flag 304f and a cleaning flag 304g.

  The current temperature data 304a is an output of the current temperature sensor 210 detected according to the detection program 302b, and is updated each time it is detected. The previous temperature data 304b is an output of the temperature sensor 210 detected last time according to the detection program 302b, and is updated when the current temperature data 304a is updated. That is, when temperature data is detected according to the detection program 302b, the current temperature data 304a stored in the RAM 206 is overwritten on the previous temperature data 304b, and the temperature data detected this time is stored (overwritten) as the current temperature data 304a. The

  The current humidity data 304c is an output of the current humidity sensor 212 detected according to the detection program 302b, and is updated each time it is detected. The previous humidity data 304d is the output of the humidity sensor 212 detected last time according to the detection program 302b, and is updated when the current humidity data 304c is updated. That is, when humidity data is detected according to the detection program 302b, the current humidity data 304c stored in the RAM 206 is overwritten on the previous humidity data 304d, and the humidity data detected this time is stored (overwritten) as the current humidity data 304c. The

  The threshold data 304e is numerical data regarding the first predetermined value and the second predetermined value, and is read from the HDD 208 when the power of the image forming apparatus 10 is turned on. However, when the power supply of the image forming apparatus 10 is turned on, the case where the power saving mode returns to the normal mode (transition) is also included. The same applies hereinafter.

  The pre-transfer exposure flag 304f is a flag for determining whether to perform pre-transfer exposure, and is turned on / off according to the pre-transfer exposure control program 302c. In the first embodiment, the pre-transfer exposure flag 304f is turned on when the pre-transfer exposure is executed, and the pre-transfer exposure flag 304f is turned off when the pre-transfer exposure is not executed.

  The cleaning flag 304g is a flag for determining whether or not the discharge electrode 104 has been cleaned, and is turned on / off according to the cleaning determination program 302d. In the first embodiment, the cleaning flag 304g is turned on when the discharge electrode 104 is cleaned, and the cleaning flag 304g is turned off when the discharge electrode 104 is not cleaned.

  Note that the pre-transfer exposure flag 304f and the cleaning flag 304g are save data, and are stored in the HDD 208 when the power of the image forming apparatus 10 is turned off. However, when the power supply of the image forming apparatus 10 is turned off, the case of shifting from the normal mode to the power saving mode is also included. The same applies hereinafter.

  Although not shown, the data storage area 304 stores other data and flags necessary for the operation of the image forming apparatus 10 and is provided with a timer (counter) necessary for the operation of the image forming apparatus 10. It is done.

  FIG. 9 is a flowchart showing an example of the cleaning control process of the CPU 200 shown in FIG. The CPU 200 starts the cleaning control process when the power of the image forming apparatus 10 is turned on, and ends the cleaning control process when the power of the image forming apparatus 10 is turned off.

  As shown in FIG. 9, when starting the cleaning control process, the CPU 200 sets a threshold and a flag in step S1. Here, the threshold data 304e, the pre-transfer exposure flag 304f, and the cleaning flag 304g are read from the HDD 208 and stored in the RAM 206.

  In the next step S3, it is determined whether or not the cleaning flag 304g is on. If “YES” in the step S3, that is, if the cleaning flag 304g is turned on, it is determined whether or not printing is being performed in a step S5. If “YES” in the step S5, that is, if printing is being executed, the process returns to the step S5.

  On the other hand, if “NO” in the step S5, that is, if printing is not being executed, the discharge electrode 104 is cleaned in a step S7. That is, in step S7, the CPU 200 controls the power supply control unit 214 (high voltage power supply circuit 214a), and as shown in FIG. 7B, the absolute value of the current value increases stepwise as time passes. As described above, a voltage (discharge voltage) having the same polarity as that of the toner is applied to the discharge electrode 104. Then, the toner attached to the discharge electrode 104 is removed. In step S9, the cleaning flag 304g is turned off, and the process returns to step S3.

  If “NO” in the step S3, that is, if the cleaning flag 304g is turned off, the temperature and the humidity are detected in a step S11. Here, the CPU 200 detects the outputs of the temperature sensor 210 and the humidity sensor 212, and stores (overwrites) the detected temperature data 304a and humidity data 304c in the RAM 206.

  In a succeeding step S13, it is determined whether or not the temperature is lower than the first predetermined value. That is, the CPU 200 determines whether or not the temperature corresponding to the temperature data 304a is less than the first predetermined value included in the threshold data 304e. If “YES” in the step S13, that is, if the temperature is lower than the first predetermined value, the pre-transfer exposure flag 304f is turned off in a step S17. However, if the pre-transfer exposure flag 304f has already been turned off, the process of step S17 is skipped.

  On the other hand, if “NO” in the step S13, that is, if the temperature is equal to or higher than the first predetermined value, it is determined whether or not the humidity is lower than a second predetermined value in a step S15. That is, the CPU 200 determines whether the humidity corresponding to the humidity data 304c is less than the second predetermined value included in the threshold data 304e. If “YES” in the step S15, that is, if the humidity is less than the second predetermined value, the process proceeds to a step S17.

  On the other hand, if “NO” in the step S15, that is, if the humidity is not lower than the second threshold value, it is determined whether or not the temperature has changed from less than the first predetermined value to not less than the first predetermined value in a step S19. Here, CPU 200 determines whether or not the temperature corresponding to previous temperature data 304b is less than a first predetermined value.

  If “YES” in the step S19, that is, if the temperature changes from less than the first predetermined value to the first predetermined value or more, the process proceeds to a step S23. On the other hand, if it is ON in step S19, that is, if the temperature has not changed from the first predetermined value to the first predetermined value or higher, the humidity is changed from the second predetermined value to the second predetermined value or higher in step S21. Determine if it has changed. Here, the CPU 200 determines whether or not the humidity corresponding to the previous humidity data 304d is less than the second predetermined value.

  If “NO” in the step S21, that is, if the humidity has not changed from the second predetermined value to the second predetermined value or more, the process returns to the step S3. On the other hand, if “YES” in the step S21, that is, if the humidity changes from less than the second predetermined value to the second predetermined value or more, the process proceeds to a step S23.

  In step S23, the pre-transfer exposure flag 304f is turned on. In step S25, the cleaning flag 304g is turned on, and the process returns to step S3.

  Although not shown, in the printing process, pre-transfer exposure is executed if the pre-transfer exposure flag 304f is on, but pre-transfer exposure is not executed if the pre-transfer exposure flag 304f is off. .

  According to the first embodiment, since a current having a larger current value than that at the time of printing is supplied to the discharge electrode 104, the toner charged to the same polarity can be removed from the discharge electrode 104 by a large repulsive force. . That is, the discharge electrode 104 can be cleaned without separately providing a cleaning device.

  In the first embodiment, when the power is turned on, the temperature changes from less than the first predetermined value to the first predetermined value or more, or the humidity changes from less than the second predetermined value to the second predetermined value or more. In this case, the discharge electrode 104 is cleaned, but the present invention is not limited to this. For example, the discharge electrode 104 may be cleaned when the temperature changes from less than a first predetermined value to a first predetermined value or more and the humidity changes from less than a second predetermined value to a second predetermined value or more. .

  In the first embodiment, the temperature sensor 210 and the humidity sensor 212 are provided to determine whether to perform pre-transfer exposure and whether to perform cleaning based on both outputs. These sensors may be provided, and these may be determined based on one output.

  Further, in the first embodiment, even when the power of the image forming apparatus 10 is turned on, the cleaning of the discharge electrode 104 is performed if the cleaning flag 304g is turned on. The discharge electrode 104 may be cleaned regardless of whether the cleaning flag 304g is on or off. That is, the discharge electrode 104 can be cleaned regardless of changes in temperature and humidity.

  Furthermore, in this first embodiment, since the toner is negatively charged, a negative current having a larger absolute value than that at the time of printing is caused to flow to the discharge electrode 104 when the discharge electrode 104 is cleaned. However, in the case of the image forming apparatus 10 in which the toner is positively charged, when the discharge electrode 104 is cleaned, a positive current having a larger absolute value than that at the time of printing is supplied to the discharge electrode 104 from the DC power source Vd. This voltage may be applied. That is, the current flowing through the discharge electrode 104 has the same polarity as the charged toner.

In the first embodiment, since the toner is negatively charged, when the discharge electrode 104 is cleaned, a current having the same polarity as that of the toner is supplied to the discharge electrode 104, but the positively charged toner ( Inversely charged toner) may be included. When cleaning such a reversely charged toner, it is necessary to apply a positive current to the discharge electrode 104. Therefore, for example, a negative voltage and a positive voltage may be alternately applied to the discharge electrode 104 during cleaning. In this case, a rectangular wave-shaped DC current in which minus and plus are alternately repeated is supplied to the discharge electrode 104. However, an alternating current may be passed through the discharge electrode 104 by applying an alternating voltage to the discharge electrode 104. Alternatively, instead of repeatedly flowing negative and positive currents alternately through the discharge electrode 104, as shown in the first embodiment, after flowing a negative current, a positive current may be allowed to flow for a certain period of time. Good.
[Second Embodiment]
The image forming apparatus 10 of the second embodiment is the same as the first embodiment except that a voltage having a polarity opposite to that of the charged toner is applied to the shields 110a and 110b when the discharge electrode 104 is cleaned. Therefore, redundant description is omitted.

  FIG. 10 is a cross-sectional view of a schematic configuration of a part of the pre-transfer charger 100 in the second embodiment. As shown in FIG. 10, in the second embodiment, the shields 110a and 110b are connected to the terminal T1 of the switch SW. The terminal T2 of the switch SW is grounded, and the terminal T3 of the switch SW is grounded via the DC power supply Vp. Therefore, by switching the switch SW, the shields 110a and 110b can be grounded or a positive voltage can be applied to the shields 110a and 110b.

  However, the switch SW and the DC power supply Vp are provided in the high voltage power supply circuit 214a.

  In the second embodiment, when the discharge electrode 104 is cleaned, as shown in FIG. 7B, a current having the same polarity as the charged toner is supplied to the discharge electrode 104, and the switch SW is switched to the terminal T3 side. Then, a positive voltage (for example, 500 V) is applied from the DC power supply Vp to the shields 110a and 110b. That is, the shields 110a and 110b are charged with a polarity opposite to that of the toner. Accordingly, a force that attracts the toner attached to the discharge electrode 104 acts on the shields 110a and 110b side. For this reason, the toner adhering to the discharge electrode 104 is more easily removed than in the case shown in the first embodiment.

  On the other hand, when the discharge electrode 104 is not cleaned, the switch SW is switched to the terminal T2 side. Therefore, shields 110a and 110b are grounded.

  According to the second embodiment, since the positive voltage is applied to the shields 110a and 110b when the discharge electrode 104 is cleaned, the toner attached to the discharge electrode 104 is easily removed. That is, cleaning can be performed more effectively.

In the second embodiment, since the toner is negatively charged, a positive voltage is applied to the shields 110a and 110b when the discharge electrode 104 is cleaned. However, in the case of the image forming apparatus 10 in which the toner is positively charged, a negative voltage may be applied to the shields 110a and 110b when the discharge electrode 104 is cleaned. That is, the polarity of the voltage applied to the shields 110a and 110b is opposite to that of the charged toner.
[Third embodiment]
The image forming apparatus 10 of the third embodiment is the same as that of the first embodiment except that the discharge electrode 104 is configured to be rotatable around the axis, and thus a duplicate description is omitted.

  FIG. 11A is an illustrative view showing an example of the discharge electrode 104 of the third embodiment as viewed from above, and FIG. 11B is a cross-sectional view taken along the line XIA-XIA in FIG.

  In the third embodiment, as shown in FIGS. 11A and 11B, one end of the discharge electrode 104 is fixed to a conductive fixing member 1040, and the other end of the discharge electrode 104 is The conductive fixing member 1042 is fixed. The fixing member 1040 is connected (joined) to the round terminal 104 a so as to be rotatable around the axis of the discharge electrode 104. Similarly, the fixing member 1042 is connected (joined) to the round terminal 104 b so as to be rotatable around the axis of the discharge electrode 104.

  Further, a non-conductive disk member 120 a having a diameter extending in a direction perpendicular to the axial direction of the discharge electrode 104 is fixed to the fixing member 1040. Similarly, a non-conductive disk member 120 b having a diameter extending in a direction perpendicular to the axial direction of the discharge electrode 104 is fixed to the fixing member 1042. As shown in FIG. 11B, the diameter of the disk member 120a (120b is the same) is set to a length that does not contact the shields 110a and 110b.

  Therefore, for example, if the pre-transfer charger 100 is periodically removed from the image forming apparatus 10 and the disk members 120a and 120b are rotated (rotated), the toner adhered (laminated) to the discharge electrode 104 is directed downward. Can be dropped. For this reason, it is possible to remove toner that cannot be removed when cleaning is performed.

  According to the third embodiment, since the discharge electrode 104 is rotated around the axis, the toner remaining on the discharge electrode 104 can be removed. Therefore, cleaning can be performed more effectively.

  The modification of the second embodiment can also be provided to the third embodiment.

  In addition, the specific numerical values and the like shown in the above-described embodiments are merely examples and should not be limited, and may be changed as appropriate according to the actual product.

  Furthermore, in the flowchart of the reading process shown in each of the above-described embodiments, the order of steps can be changed when the same result is obtained.

DESCRIPTION OF SYMBOLS 10 ... Image forming apparatus 12 ... Apparatus main body 14 ... Image reading part 30 ... Image forming part 36 ... Photoconductor drum (image carrier)
54 ... Intermediate transfer belt (transfer belt)
60 ... Intermediate transfer roller (transfer roller)
100: Pre-transfer charger 200: CPU
204… ROM
206 ... RAM
208 ... HDD
210 ... Temperature sensor 212 ... Humidity sensor 214 ... Power supply control unit 214a ... High-voltage power supply circuit

Claims (10)

An image forming apparatus that charges a toner image before the toner image is printed on recording paper,
A first current control means for supplying a first predetermined current to the charging unit when the toner image is charged at the time of printing; and the charging unit at a predetermined timing other than at the time of printing. An image forming apparatus comprising: a second current control unit configured to flow a current of a second predetermined value having an absolute value larger than the predetermined value.   The predetermined timing includes at least one of when an internal temperature of the image forming apparatus becomes equal to or higher than a first predetermined value and when an internal humidity of the image forming apparatus becomes equal to or higher than a second predetermined value. Item 2. The image forming apparatus according to Item 1.   The image forming apparatus according to claim 1, wherein the predetermined timing is when a power source of the image forming apparatus is turned on.   4. The image forming apparatus according to claim 1, wherein the second current control unit gradually increases a current value of a current flowing through the charging unit to the second predetermined value. 5.   The second current control unit changes the current value of the current flowing through the charging unit so as to increase stepwise or linearly, and at an initial stage, the current value of the current flowing through the charging unit at the time of printing is determined. 5. The image forming apparatus according to claim 4, wherein, in a later stage, the current value of the current flowing through the charging unit during the printing is larger.   The image forming apparatus according to claim 1, wherein the second current control unit changes a polarity of the current when the second predetermined value of current flows through the charging unit. When a current of the second predetermined value is passed through the charging unit by the conductive plate member surrounding the charging unit and the second current control means, the current has a polarity opposite to that of the current flowing through the charging unit. The image forming apparatus according to claim 1, further comprising a voltage control unit that applies a voltage to the plate member. The charging unit includes a wire stretched in the housing so as to be rotatable around an axis in the housing,
The image forming apparatus according to claim 1, further comprising a rotating member that rotates the wire. A control program for an image forming apparatus that charges a toner image before the toner image is printed on recording paper,
At the time of printing, a first current control step for controlling the power supply control unit to flow a current of a first predetermined value to the charging unit when charging the toner image, and at a predetermined timing other than at the time of printing. A control program for causing the charging unit to execute a second current control step for controlling the power supply control unit so that a current having a second predetermined value larger in absolute value than the first predetermined value flows. A method of controlling an image forming apparatus for charging a toner image before the toner image is printed on a recording paper,
(A) controlling the power supply control unit so that a first predetermined value of current flows through the charging unit when the toner image is charged during printing, and (b) a predetermined value other than during printing. A control method comprising: controlling the power supply control unit so that a current of a second predetermined value having an absolute value larger than the first predetermined value flows through the charging unit at a timing.

Images