JP2017026805A - Image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image forming apparatus that is capable of easily performing operation confirmation so as to determine whether a position of a shuter is correctly detected by a shutter sensor.SOLUTION: When a position (opened position) detected by a shutter sensor and a position (closed position) at the last time of shutter rotation do match each other, a shutter checking operation is executed (S3). Control is executed to close a shutter, and whether a position of the shutter has changed from the opened position to the closed position is checked on the basis of the obtained detection result of the shutter. When the position of the shutter has changed to the closed position, control is executed to open the shutter, and whether the position of the shutter has changed from the closed position to the opened position is checked on the basis of the obtained detection result of the shutter. When the detection result of the shutter sensor shows a change of open position→closed position→opened position, it is determined that the detection by the shutter sensor is correct (YES in S4). On the other hand, when the detection result of the shutter sensor shows no change, it is determined that the detection by the shutter sensor is not correct (NO in S4).SELECTED DRAWING: Figure 6

Description

  The present invention relates to an image forming apparatus that forms a toner image on a recording material using an electrophotographic system or the like.

  In an image forming apparatus using an electrophotographic system, a corona charger is used as a charging unit that uniformly charges a photosensitive drum to a predetermined polarity and potential. The corona charger is disposed in contact with the photosensitive drum in a non-contact manner, and charges the surface of the photosensitive drum with charged particles (corona ions) generated by corona discharge. The corona charger has a grid electrode in which a wire grid in which a plurality of wires are stretched, a mesh-like etching grid in which a large number of holes are formed by an etching process, and the like are provided in the opening of the housing. Scorotron is known.

  When corona discharge is performed, a discharge product is generated. The discharge product may pass through the grid electrode and adhere to the photosensitive drum. When the discharge product adhering to the photosensitive drum absorbs moisture in a high humidity environment, it causes image defects such as “image flow” during image formation. In view of this, an apparatus has been proposed in which the grid electrode is covered with a sheet-like shutter and the shutter is appropriately opened and closed to prevent the discharge product from adhering to the photosensitive drum (Patent Document 1). However, if the shutter is closed at the time of image formation, the photosensitive drum is not sufficiently charged, and as a result, another cause of image defects such as carrier adhesion at the developing unit and toner adhesion to the white background portion, etc. Can occur. In order to prevent this, conventionally, for example, a photo interrupt type optical sensor is used to directly detect the position of the shutter to check the open / close state of the shutter.

JP 2013-242553 A

  As described above, the shutter must be in the open position (open position) during image formation. However, a position detection sensor such as the above-described optical sensor may not be able to correctly detect the position of the shutter due to failure or erroneous detection. Therefore, a configuration that can detect the position of the shutter with a simple configuration is desired.

  The present invention has been made in view of the above problems, and is an image forming apparatus in which it is possible to easily check whether the position of the shutter covering the opening of the corona charger is correctly detected by the sensor. For the purpose of provision.

  An image forming apparatus according to the present invention includes a photoconductor, a housing having an opening facing the photoconductor, a corona charger having a discharge electrode disposed in the housing, and the opening can be opened and closed. And a driving means capable of moving the shutter to an open position where the opening is opened and a closed position where the opening is shielded, and the shutter is at least one of an open position and a closed position. Detection means capable of detecting this, and control means for controlling the drive means, the control means, either the open position or the closed position when the shutter was moved last time, When the position detected by the detection means is different, the drive means is controlled to move the shutter to the other position different from one of the closed position and the open position detected by the detection means, System Wherein executing the confirmation mode for notifying an error when the other position is not detected by the detection means, it is characterized after.

  According to the present invention, it is possible to easily check the operation of the detecting means for detecting the position of the shutter that can open and close the opening of the corona charger. As a result, the photosensitive member is not charged while the shutter is in the closed position, which can make it difficult to cause image defects.

1 is a schematic diagram illustrating a configuration of an image forming apparatus according to an embodiment. Schematic which shows an image formation part. It is the schematic which shows a corona charger, (a) is a side view, (b) is a top view, (c) is sectional drawing. FIG. 3 is a control block diagram of a charging control system. The flowchart which shows a shutter closing control process. The flowchart which shows a sensor confirmation control process.

  An embodiment of the present invention will be described with reference to FIGS. First, the image forming apparatus will be described with reference to FIGS.

<Image forming apparatus>
An image forming apparatus 100 shown in FIG. 1 is a tandem intermediate transfer type full-color printer in which yellow, magenta, cyan, and black image forming portions PY, PM, PC, and PK are arranged along an intermediate transfer belt 8. In the image forming unit PY, a yellow toner image is formed on the photosensitive drum 1Y and is primarily transferred to the intermediate transfer belt 8. In the image forming unit PM, a magenta toner image is formed on the photosensitive drum 1M, and is primarily transferred onto the yellow toner image on the intermediate transfer belt 8. In the image forming units PC and PK, a cyan toner image and a black toner image are formed on the photosensitive drums 1C and 1K, respectively, and are sequentially transferred onto the intermediate transfer belt 8 in a primary transfer. The four-color toner images primarily transferred to the intermediate transfer belt 8 are transported to the secondary transfer portion T2 and transferred to the recording material P (sheet, sheet such as OHP sheet) at once.

<Image forming unit>
The image forming units PY, PM, PC, and PK are configured in substantially the same manner except that the color of toner used in the developing devices 4Y, 4M, 4C, and 4K is different from yellow, magenta, cyan, and black. Therefore, in the following, the yellow image forming unit PY will be described as a representative, and the other image forming units PM, PC, and PK will be described by replacing Y at the end of the reference code with M, C, and K. Shall.

  As shown in FIGS. 1 and 2, the image forming portion PY surrounds a photosensitive drum 1Y as a photosensitive member, and corona charger 2Y, exposure device 3Y, developing device 4Y, primary transfer roller 5Y, and drum cleaning device 6Y. Is arranged. The photosensitive drum 1Y is a cylindrical photosensitive member having a photosensitive layer formed on the outer peripheral surface of a conductive substrate, and is provided to be rotatable in the direction of arrow R1 in the figure. The photosensitive drum 1Y is formed to have an axial length of 360 mm and an outer diameter of 84 mm, for example, and is rotationally driven by a driving device (not shown) at a peripheral speed of, for example, 400 mm / sec.

  In the photosensitive drum 1Y, a charge generation layer, a charge transport layer, and a surface protection layer made of an organic material are laminated on a metal substrate such as an aluminum cylinder as a conductive substrate. As the charge generation layer, for example, a resin in which a diazo pigment is dispersed and mixed in a resin is used. As the charge transport layer, for example, a polycarbonate resin in which hydrazone is dispersed and mixed is used. As the charge injection layer, for example, a material in which fine particles of tin dioxide (SnO 2) are dispersed and mixed in an insulating binder resin based on an acrylic resin is used.

  The corona charger 2Y irradiates charged particles accompanying corona discharge to charge the photosensitive drum 1Y to a uniform negative polarity dark portion potential. The details of the corona charger 2Y will be described later (see FIGS. 3A to 3C). The exposure device 3Y generates laser light, which is obtained by turning on and off the scanning line image data obtained by developing the separation color image of each color, from a laser light emitting element, and scans this with a rotating mirror to charge the photosensitive drum 1Y. Write an electrostatic latent image.

  The developing device 4Y supplies the negatively charged toner to the photosensitive drum 1Y to develop the electrostatic latent image into a toner image. The developing device 4Y rotates the developing sleeve, which is disposed facing the surface of the photosensitive drum 1Y with a slight gap, in the counter direction of the photosensitive drum 1Y. The developing device 4Y charges the two-component developer including the toner and the carrier, carries the two-component developer on the developing sleeve, and conveys the two-component developer to a portion facing the photosensitive drum 1Y. By applying an oscillating voltage in which an AC voltage is superimposed on a DC voltage to the developing sleeve, the negatively charged toner is transferred to the exposed portion of the photosensitive drum 1Y having a relatively positive polarity, and an electrostatic latent image is formed. Reversal developed.

  The primary transfer roller 5Y is disposed to face the photosensitive drum 1Y with the intermediate transfer belt 8 interposed therebetween, and presses the intermediate transfer belt 8 to form a primary transfer portion T1 between the photosensitive drum 1Y and the intermediate transfer belt 8. By applying a positive primary transfer bias to the primary transfer roller 5Y, a negatively charged toner image on the photosensitive drum 1Y is transferred to the intermediate transfer belt 8. The drum cleaning device 6Y collects primary transfer residual toner, paper dust, and the like remaining on the photosensitive drum 1Y after primary transfer.

<Intermediate transfer belt>
The intermediate transfer belt 8 is an intermediate transfer member that can rotate in contact with the photosensitive drum 1Y. As shown in FIG. 1, the intermediate transfer belt 8 is supported around a tension roller 41, a secondary transfer inner roller 42 and a driving roller 43, and is driven by the driving roller 43 to rotate in the direction of arrow R2. The tension roller 41 stretches the intermediate transfer belt 8 with a constant tension.

  The intermediate transfer belt 8 is an endless belt in which a resin layer, an elastic layer, and a surface layer are laminated in order from a cored bar side on a cored bar as a base. For example, a resin material such as polyimide or polycarbonate is used for the resin layer, and the thickness is 70 to 100 μm. The elastic layer is made of an elastic material such as urethane rubber or chloroprene rubber, and has a thickness of 200 to 250 μm. The surface layer is required to have a small toner adhesion in order to facilitate the transfer of toner from the intermediate transfer belt 8 to the recording material P at the secondary transfer portion T2. Therefore, for the surface layer, for example, one kind of resin materials such as polyurethane, polyester, and epoxy resin, or two or more kinds of elastic materials such as elastic material rubber, elastomer, and butyl rubber are used. In order to reduce the surface energy and improve the lubricity, one or more kinds of powders and particles such as fluororesin, or powders and particles having different particle sizes are dispersed in the surface layer. . The surface layer is formed to have a thickness of 5 to 10 μm. The intermediate transfer belt 8 has a volume resistivity adjusted to, for example, 1E + 8 to 1E + 14 Ω · cm.

  The secondary transfer portion T2 is a toner image transfer nip portion to the recording material P formed by pressing the secondary transfer outer roller 10 against the intermediate transfer belt 8 stretched around the secondary transfer inner roller 42. In the secondary transfer portion T2, a secondary transfer bias is applied to the secondary transfer outer roller 10, whereby the toner image is secondarily transferred from the intermediate transfer belt 8 to the recording material P. The toner remaining on the intermediate transfer belt 8 after the secondary transfer (secondary transfer residual toner) is removed from the intermediate transfer belt 8 by the belt cleaning device 9.

  The recording material P on which the four-color toner images are secondarily transferred by the secondary transfer portion T2 is conveyed to the fixing device 50. The fixing device 50 heats and pressurizes the recording material P while conveying it, and fixes the toner image on the recording material P. The recording material P on which the toner image is fixed by the fixing device 50 is discharged out of the machine body.

<Two-component developer>
In the developing device 4Y, a two-component developer including a negatively charged toner and a positively charged carrier is used as a developer. The toner is a binder resin such as a styrene resin or a polyester resin, a colorant such as carbon black, a dye, or a pigment, and further colored resin particles containing other additives as necessary, and a colloidal silica fine powder. And externally added colored particles. The toner has a volume average particle size of preferably 4 to 10 μm because if the particle size is too small, it will be difficult to rub against the carrier and it will be difficult to control the charge amount. As the carrier, for example, metal such as surface-oxidized or unoxidized iron, nickel, cobalt, manganese, chromium, rare earth, alloys thereof, or oxide ferrite can be preferably used. The method for producing these magnetic particles is not particularly limited. The volume average particle diameter of the carrier is 20 to 60 μm, preferably 30 to 50 μm.

<Drum cleaning device>
As described above, the image forming apparatus 100 includes the drum cleaning device 6Y to remove the toner (primary transfer residual toner) that passes through the primary transfer portion T1 and remains on the photosensitive drum 1Y. As shown in FIG. 2, the drum cleaning device 6Y is provided downstream of the primary transfer portion T1 in the rotation direction of the photosensitive drum 1Y. The drum cleaning device 6 </ b> Y includes a fur brush 60 and a cleaning blade 61 in the housing 20. Fur brush 60 on the outer peripheral surface of for example, a conductive metallic rotating shaft having a diameter of 12 mm (core metal), fiber thickness 6 denier synthetic fibers such as acrylic fibers are flocked at a rate of flocking density of 50,000 / inch ² Is formed. The cleaning blade 61 is formed in a plate shape having an axial length of 340 mm, which is slightly shorter than the photosensitive drum 1Y, using an elastic member such as urethane rubber.

  The fur brush 60 is provided on the upstream side in the rotation direction of the photosensitive drum 1Y (in the direction of arrow R1 in the drawing) so as to rub the surface of the photosensitive drum 1Y. The fur brush 60 is rotated at a peripheral speed of, for example, 110% of the rotational speed of the photosensitive drum 1Y. The cleaning blade 61 is provided downstream of the fur brush 60 in the rotational direction of the photosensitive drum 1Y so as to contact the surface of the photosensitive drum 1Y with a predetermined contact pressure. The transfer residual toner remaining on the surface of the photosensitive drum 1Y is disturbed by the fur brush 60, so that the adhesive force with the photosensitive drum 1Y is weakened. Thereafter, the transfer residual toner is removed from the surface of the photosensitive drum 1 </ b> Y by the cleaning blade 61.

<Corona charger>
The image forming apparatus 100 includes a corona charger 2Y for uniformly charging the surface of the photosensitive drum 1Y. The corona charger 2Y is disposed opposite to the photosensitive drum 1Y along the rotation axis direction (longitudinal direction) of the photosensitive drum 1Y, and charges the surface of the photosensitive drum 1Y by electric discharge. The corona charger 2Y will be described with reference to FIGS. 3 (a) to 3 (c).

  The corona charger 2Y is disposed in an opening housing 90 having a discharge wire 30 as a discharge electrode and a pair of shield plates (shield electrodes) 32 provided so as to sandwich the wire, and an opening in the housing 90. Grid electrode 31 formed. That is, the corona charger 2Y shown in this embodiment is a scorotron type charger.

  The shield plate 32 is formed using stainless steel (SUS), and is arranged so as to face each other at an interval of, for example, 34 mm in the short side direction of the housing 90 (the width direction intersecting the rotation axis direction of the photosensitive drum 1Y). Yes. The distance between the pair of shield plates 32 is substantially equal to the width direction length of the opening of the housing 90.

  The discharge wire 30 is stretched in the longitudinal direction inside the shield plate 32 in the housing. For the discharge wire 30, for example, stainless steel, nickel, molybdenum, tungsten, or the like is used. The discharge wire 30 is preferably formed to have a diameter of 40 μm to 100 μm in order to prevent breakage and disconnection that are likely to occur during voltage application and maintenance, and to obtain stable corona discharge. In this embodiment, tungsten, which is very stable among metals, is used, and the discharge wire 30 having a diameter of 60 μm is formed. The discharge wire 30 is arranged with an interval of, for example, 8 mm from the grid electrode 31, and a high voltage is applied to the discharge wire 30 from a high voltage power source (not shown) so that a current of, for example, −1200 μA flows.

  The grid electrode 31 is disposed between the discharge wire 30 and the photosensitive drum 1Y, and controls the amount of current flowing toward the photosensitive drum 1Y when a charging bias is applied. In the present embodiment, as the grid electrode 31, a mesh (mesh) -shaped etching grid having a large number of through holes formed by etching a thin metal flat plate (thin plate) is used. The grid electrode 31 is made of austenitic stainless steel (SUS304) as a base material, and is formed in a plate shape having a thickness of 100 μm and a width of 28 mm, for example. The grid electrode 31 is provided in the opening of the housing 90 and is close to the outer peripheral surface of the photosensitive drum 1Y. The grid electrode 31 is disposed so that the closest part to the photosensitive drum 1Y is, for example, about 1.3 mm. A high voltage of −900 V to −300 V is applied to the grid electrode 31 from a high voltage power supply (not shown). The voltage applied to the grid electrode 31 is adjusted in voltage according to the charging potential of the photosensitive drum 1Y. In addition, as a base material of the grid electrode 31, you may use another austenitic stainless steel, a martensitic stainless steel, or a ferritic stainless steel.

  A surface layer is formed on the surface of the grid electrode 31 to prevent corrosion. As a surface layer, a surface layer of tetrahedral amorphous carbon (hereinafter abbreviated as ta-C), which is a material that is chemically inert to discharge products generated by corona discharge, is formed. Yes. The ta-C used for the surface layer in the present embodiment is generally a type of DLC (Diamond Like Carbon). The structure of DLC is an amorphous structure in which diamond bonds (sp3 bonds) and graphite bonds (sp2 bonds) containing some hydrogen are mixed. Therefore, if a surface layer of ta-C is formed on the surface of the grid electrode 31, it can be hardly affected by discharge products even in a high-temperature and high-humidity environment, and oxidation or electrolytic corrosion due to moisture absorption of the substrate can be prevented. Therefore, stable charging without uneven charging can be maintained over a long period of time.

  The corona charger 2Y further includes a cleaning pad 16 for cleaning the discharge wire 30 and a cleaning brush 14 for cleaning the grid electrode 31. The cleaning pad 16 and the cleaning brush 14 are held by a brush holder 71. The brush holder 71 is attached to a drive screw 72 that rotates by receiving the drive of the charger motor M. The cleaning pad 16 and the cleaning brush 14 move in the longitudinal direction together with the shutter 40 described later as the drive screw 72 rotates. The cleaning pad 16 is formed by using, for example, a sponge, and cleans by inserting the discharge wire 30 from both sides.

  As the cleaning brush 14, an acrylic brush that has been flame-treated and woven into a base fabric was used. The cleaning brush 14 contacts the grid electrode 31 and cleans the grid electrode 31. The cleaning brush 14 stands by at a standby position where it does not come into contact with the grid electrode 31 during non-cleaning. The cleaning brush 14 can be moved from the standby position to a position where it can come into contact with the grid electrode 31 according to the rotation of the drive screw 72 to clean the grid electrode 31. The cleaning brush 14 cleans the grid electrode 31 with the brush holder 71 while maintaining a predetermined amount of penetration with respect to the grid electrode 31. That is, the brush holder 71 holds the cleaning brush 14 and also serves as a guide member that defines the amount of the cleaning brush 14 that enters the grid electrode 31. The brush holder 71 is formed using ABS resin, polycarbonate resin, or the like.

  The image forming apparatus 100 includes a pair of guide rails 15 as guide members extending in the longitudinal direction (the rotation axis direction of the photosensitive drum 1Y), and the corona charger 2Y described above is supported by the guide rails 15 on both side surfaces of the housing 90. In this way, it is detachably attached to the apparatus main body 110. The guide rail 15 is attached to the corona charger 2Y in the apparatus main body facing the photosensitive drum 1Y so that the corona charger 2Y does not come into contact with the photosensitive drum 1Y when the corona charger 2Y is attached to or detached from the apparatus main body 110. It functions as a guide to guide the position.

  Further, the corona charger 2Y can blow air into the inside by a fan (not shown) provided outside, and a path (air flow) through which air flows according to the blown air is formed inside the corona charger 2Y. Yes. As shown in FIG. 3C, air is blown from above the corona charger 2Y (see arrow A1 in the figure), passes through the grid electrode 31 on the downstream side in the rotation direction of the photosensitive drum 1Y, and escapes outside. (See arrow A2 in the figure). In order to make it easier for air to escape from the downstream side in the rotational direction of the photosensitive drum 1Y, the length (height) of the pair of shield plates 32 and the guide rail 15 in the direction intersecting the longitudinal direction is upstream in the rotational direction of the photosensitive drum 1Y. It is formed to be shorter on the downstream side.

  That is, the pair of shield plates 32 includes a first shield plate 32a and a second shield plate 32b that are spaced from each other in the rotation direction R1 of the photosensitive drum 1Y and extend in the longitudinal direction of the photosensitive drum 1Y. In the present embodiment, the first shield plate 32a is disposed on the downstream side in the rotational direction of the photosensitive drum 1Y, and the second shield plate 32b is disposed on the upstream side in the rotational direction of the photosensitive drum 1Y. The gap between the second shield plate 32b and the photosensitive drum 1Y is narrower than that of the first shield plate 32a. By doing so, air can easily escape from the downstream side in the rotation direction of the photosensitive drum 1Y.

  The pair of guide rails 15 also function as an air flow guide that regulates the direction of air flow so that the air blown by the fan does not spread outside the corona charger 2Y. Therefore, the gap between the guide rail 15b upstream of the photosensitive drum 1Y in the rotation direction of the photosensitive drum 1Y and the photosensitive rail 1Y of the pair of guide rails 15 is made narrower than the gap between the guide rail 15a downstream in the rotation direction of the photosensitive drum 1Y. Is preferred.

<Charger shutter>
In the corona charger 2Y, a shutter 40 capable of opening and closing an opening of the housing 90 is disposed between the grid electrode 31 and the photosensitive drum 1Y. The shutter 40 is formed into a thin sheet having a thickness of about 100 μm using, for example, a nonwoven fabric containing rayon fibers. Of course, the present invention is not limited to this, and the shutter 40 may be formed using knitted nylon fibers or a film of urethane, polyester, or the like as long as it can be formed into a thin sheet.

  The shutter 40 is provided so as to be movable in the longitudinal direction between the grid electrode 31 and the photosensitive drum 1 </ b> Y, and can open and close the opening of the housing 90. One end of the shutter 40 in the longitudinal direction is connected to the brush holder 71, and the drive screw 72 rotates to move in the longitudinal direction in synchronization with the cleaning brush 14. The other end in the longitudinal direction of the corona charger 2Y is held by a take-up roller 11 as a take-up means, and the take-up roller 11 can take up the shutter 40 in a roll shape and store it. That is, when the brush holder 71 receives the rotational drive from the drive screw 72 and moves to the left (closed direction) in FIG. 3A, the shutter 40 is pulled out from the take-up roller 11. On the other hand, when the brush holder 71 moves to the right side (opening direction) in FIG. 3A, the shutter 40 is wound around the winding roller 11 and stored. When the shutter 40 is in a position (open position) where all the shutters 40 are taken up by the take-up roller 11, the opening of the housing 90 is open. On the other hand, when all the shutters 40 are at the position (closed position) pulled out from the take-up roller 11, the opening of the housing 90 is shielded. As described above, the shutter 40 moves to one end side (left side of FIG. 3A) of the photosensitive drum 1Y to shield the opening of the housing 90, and the other end side (FIG. 3A). ) To the right side) to open the opening of the housing 90.

  When the shutter 40 is moved from the open position to the closed position, the opening of the housing 90 is shielded, so that discharge products such as NOx generated by the discharge of the corona charger 2Y are generated on the photosensitive drum 1Y. It can prevent adhesion. By the way, the gap between the grid electrode 31 and the photosensitive drum 1Y is only about 1.3 mm, and when the shutter 40 having a thickness of 100 μm is moved by the slight gap, the shutter 40 moves while contacting the grid electrode 31 or the photosensitive drum 1Y. Can do. However, it is preferable that the shutter 40 is brought into contact with the shield plate 32, the guide rail 15 and the like because discharge products are less likely to leak from the corona charger 2Y, and the amount of discharge products adhering to the photosensitive drum 1Y can be reduced. . Therefore, the shutter 40 is formed so that the length in the width direction (short direction) is longer than the interval between the pair of shield plates 32. In the present embodiment, for example, the length of the shutter 40 in the width direction is 40 mm, and the shutter 40 is formed wider than the interval 34 mm between the pair of shield plates 32. Thereby, the guide rail 15 outside the pair of shield plates 32 can be covered with the shutter 40.

  In order to detect whether the shutter 40 is in the open position or the closed position, a shutter sensor 506 is provided as a detection unit. Only one shutter sensor 506 is disposed above the shaft on the side of the take-up roller 11 of the drive screw 72, and the position of the shutter 40 is detected. Specifically, the shutter 40 is taken up by the take-up roller 11 (open position). Whether it is unwound (closed position) can be detected. In the present embodiment, the shutter sensor 506 can output a predetermined signal only when the shutter 40 is in the closed position. In the present embodiment, the control unit 200 described later determines that the shutter 40 is in the closed position when a predetermined signal is output from the shutter sensor 506, and the predetermined signal is not output from the shutter sensor 506. In this case, it is determined that the shutter 40 is in the open position.

  As such a shutter sensor 506, for example, there is a photo interrupt type optical sensor in which a light emitting unit 506a that emits light and a light receiving unit 506b that receives light emitted from the light emitting unit 506a are arranged to face each other. In the case of the photo-interrupt optical sensor, the shielding member 81 is provided on the brush holder 71, that is, the front end side in the closing direction of the shutter 40, and the shielding member 81 is movable together with the shutter 40. When the shutter 40 is wound around the winding roller 11, the shielding member 81 enters between the light emitting unit 506a and the light receiving unit 506b, and the shutter sensor 506 is shielded. When the shielding member 81 is in the shielding position where the shutter sensor 506 is shielded, a predetermined signal (here, a signal corresponding to the amount of light) is not output from the shutter sensor 506, and the shutter 40 is determined to be in the open position. On the other hand, when the shutter 40 is pulled out from the take-up roller 11, the shielding member 81 does not enter between the light emitting unit 506a and the light receiving unit 506b, and the shutter sensor 506 is not shielded. When the shielding member 81 is in the non-shielding position where the shutter sensor 506 is not shielded, a predetermined signal is output from the shutter sensor 506, and the shutter 40 is determined to be in the closed position.

  In the shutter sensor 506 of the present embodiment, it may be determined that the shutter 40 is in the closed position even if the shielding member 81 does not shield the shutter sensor 506. That is, when toner adheres to the light emitting unit 506a and the light receiving unit 506b of the shutter sensor 506, it is erroneously detected that the actual shutter 40 is in the open position although it is in the closed position. Alternatively, even when the shutter sensor 506 is out of order and no light is emitted from the light emitting unit 506a, it is erroneously detected that the shutter 40 is in the open position even though the actual shutter 40 is in the closed position.

<Control unit>
The image forming apparatus 100 includes a control unit 200 as shown in FIG. The control unit 200 will be described with reference to FIGS. FIG. 4 is a control block diagram of the charging control system. The control unit 200 is connected to various devices such as a photosensitive drum 1Y, an exposure device 3Y, a developing device 4Y, a primary transfer roller 5Y, a fixing device 50, a motor for driving them, and a power source other than those illustrated. However, since it is not the gist of the present invention, illustration and description are omitted.

  The control unit 200 as a control unit is, for example, a CPU that performs various controls such as an image forming operation. As shown in FIG. 4, a memory 501 is connected to the control unit 200. A memory 501 serving as a storage unit is a ROM, a RAM, a hard disk, or the like, and stores various programs and data for controlling the image forming apparatus 100. In addition, the memory 501 can temporarily store calculation processing results and the like accompanying execution of various programs. For example, the number of cleanings of the discharge wire 30 and the grid electrode 31 associated with each predetermined temperature and humidity, a threshold such as a predetermined specified time (for example, 2 hours) and a specified number of sheets (for example, 3000), or charging described later Device shutter flag (shutter drive information) and the like are stored.

  The operation unit 507 is connected to the control unit 200 via an interface (not shown), and is an operation panel, an external terminal, or the like that accepts an instruction to execute various programs such as an image forming job and various data inputs by a user. The control unit 200 executes various controls such as an image forming job (image forming program) stored in the memory 501 based on the image data or the like input from the operation unit 507. The control unit 200 controls the image forming apparatus 100 to perform image formation by executing an image forming job (program).

  The image forming job is a series of operations from the start of image formation to the completion of the image forming operation based on a print signal for forming an image on a recording material. In other words, after the preliminary operation (so-called pre-rotation operation) necessary for image formation is started, the preliminary operation (so-called post-rotation) necessary for ending the image formation is completed through the image formation process. It is a series of operations up to. Specifically, it refers to the period from pre-rotation (preparation operation before image formation) after receiving a print signal (input of an image formation job) to post-rotation (operation after image formation). , Including paper space.

  The control unit 200 is also connected to an environmental sensor 502, a counter 503, a fan 504, a high voltage power source 505, a corona charger 2Y, and a shutter sensor 506 (charger shutter sensor) via an interface (not shown). The environment sensor 502 detects the environment (specifically, the temperature and humidity of the outside air) where the apparatus is placed. The counter 503 counts the number of recording materials P on which image formation has been performed, the number of times the shutter 40 has been opened and closed, the time elapsed since the end of the image forming job, the time elapsed since the shutter 40 was closed, and the like. The fan 504 generates air to be blown into the corona charger 2Y in order to form an air flow inside the corona charger 2Y as described above. The high voltage power source 505 applies a voltage to the discharge wire 30 and the grid electrode 31. The control unit 200 acquires the detection result (detection signal) from the environmental sensor 502 and the count value (the number of sheets, the number of times, the time, etc.) from the counter 503, and appropriately controls the fan 504 and the high-voltage power supply 505. To do.

  When an image is formed on a large number of recording materials P, dirt may adhere to the discharge wires 30 and the grid electrodes 31 and an image defect may occur. Control for cleaning the grid electrode 31 is performed. In this case, the control unit 200 cleans the discharge wire 30 and the grid electrode 31 when the number of image-formed recording materials P counted by the counter 503 exceeds a specified number (threshold value) stored in the memory 501. Control. At this time, the control unit 200 can operate the cleaning brush 14 and the cleaning pad 16 (wire cleaning pad) via the driving screw 72 as described above by controlling the charger motor M as the driving means.

  Further, the control unit 200 can operate the shutter 40 (charger shutter) via the drive screw 72 as described above by controlling the charger motor M as the driving means. The control unit 200 can determine whether the shutter 40 is in the open position or the closed position based on the signal acquired from the shutter sensor 506.

  By the way, in the present embodiment, after the execution of the image forming job, the control unit 200 controls to close the shutter 40 when the elapsed time from the end of the image forming job has passed a predetermined time (for example, 2 hours), and enters the sleep mode. A shutter closing control process executed after the image forming job is completed by the control unit 200 will be described with reference to FIG.

  As shown in FIG. 5, after the end of the image forming job, the control unit 200 has passed the predetermined time (specified time) stored in the memory 501 after the end of the image forming job counted by the counter 503. It is determined whether or not (S51). When it is determined that a predetermined time has elapsed since the end of the image forming job (YES in S51), the control unit 200 performs control to close the shutter 40 that has been maintained at the open position during the execution of the image forming job (S52). Then, the control unit 200 determines whether or not the detection result of the shutter sensor 506 is the open position (S53). When it is determined that the detection result of the shutter sensor 506 is not the open position (NO in S53), the control unit 200 stores the charger shutter flag “closed position (1)” in the memory 501 (S54) and enters the sleep mode. (S55). In this case, the shutter sensor 506 can correctly detect the position of the shutter 40. For this reason, the present process is terminated without notifying the operation unit 507 or the like of an error indicating that the shutter sensor 506 has erroneously detected.

  On the other hand, when it is determined that the detection result of the shutter sensor 506 is the open position (YES in S53), the control unit 200 determines that the shutter sensor 506 is not operating normally. In that case, the control unit 200 notifies the operation unit 507 or the like of an error indicating that the shutter sensor 506 has erroneously detected (S56). In this case, the control unit 200 does not enter the sleep mode.

  At the time of image formation, the control unit 200 uses the shutter sensor 506 to check the position of the shutter 40 and then performs a charging process on the photosensitive drum 1Y. However, as described above, the shutter sensor 506 may erroneously detect the position of the shutter 40 due to adhesion of scattered toner or the like. In the first place, if the shutter sensor 506 is out of order, the correct position of the shutter 40 cannot be detected. In the present embodiment, only one shutter sensor 506 is provided from the viewpoint of installation space and cost. For this reason, if the single shutter sensor 506 cannot correctly detect the position of the shutter 40, the charging process may be performed even though the shutter 40 is closed, and the carrier adhering to cause image defects may occur. And toner adhesion may occur.

<Confirmation mode>
In this embodiment, the shutter sensor 506 can check whether the position of the shutter 40 can be correctly detected before the charging process to the photosensitive drum 1Y is performed by the corona charger 2Y. This is realized by the control unit 200 executing sensor confirmation control (confirmation mode). Hereinafter, the sensor confirmation control will be described with reference to FIG. FIG. 6 is a flowchart showing the sensor confirmation control process. The sensor confirmation control process is started by the control unit 200 at a predetermined timing such as when an image forming job is started or when the apparatus main body is turned on and when the sleep mode is released.

  As shown in FIG. 6, the control unit 200 determines whether or not the charger shutter flag stored in the memory 501 is “closed position (1)” (S <b> 1). The charger shutter flag indicates whether or not the control for closing the shutter 40 has been performed after the end of the previous image forming job. If the charger shutter flag is in the “closed position (1)”, the shutter 40 is closed. Consider it in position. On the other hand, if the charger shutter flag is in the “open position (0)”, the control unit 200 considers the shutter 40 to be in the open position. Here, the shutter 40 is considered to be in the closed position or the open position because the shutter 40 may be manually opened and closed for maintenance or the like after the previous image forming job. In that case, the actual position of the shutter 40 may be different from the shutter position indicated by the charger shutter flag.

  When the charging shutter flag is “open position (0)” (NO in S1), the control unit 200 determines whether or not the detection result of the shutter sensor 506 is the open position (S11). When it is determined that the detection result of the shutter sensor 506 is the open position (YES in S11), that is, when the detection result (open position) of the shutter sensor 506 matches the charging shutter flag (open position), the control unit 200 This process ends. In this case, the shutter 40 is in the open position, and the shutter sensor 506 detects that the shutter 40 is in the open position. For this reason, the present process is terminated without notifying the operation unit 507 or the like of an error indicating that the shutter sensor 506 has erroneously detected.

  On the other hand, if it is determined that the detection result of the shutter sensor 506 is the closed position (NO in S11), that is, if the detection result of the shutter sensor 506 (closed position) and the charging shutter flag (open position) do not match, the control unit 200 performs control to open the shutter 40 (S12). That is, the position (open position) when the shutter 40 was moved last time is different from the position (closed position) detected by the shutter sensor 506. Therefore, the control unit 200 moves the shutter 40 to the open position that is the other (opposite) position different from the position (closed position) detected by the shutter sensor 506.

  After controlling to open the shutter 40 (S12), the control unit 200 determines whether or not the detection result of the shutter sensor 506 has changed from the “closed position” to the “open position” (S13). When the detection result of the shutter sensor 506 is changed from the “closed position” to the “open position” (YES in S13), the control unit 200 determines that the shutter sensor 506 is operating normally, and sets the charging shutter flag. "Open position (0)" is recorded (S14), and this process is terminated. That is, the control unit 200 performs control to move the shutter 40 to the open position, and if the detection result of the shutter sensor 506 indicates the open position, the shutter sensor 506 can detect that the position of the shutter 40 has been correctly detected. Start operation.

  On the other hand, when the detection result of the shutter sensor 506 remains “closed position” (NO in S13), the control unit 200 determines that the shutter sensor 506 is not operating normally. In that case, the control unit 200 notifies the operation unit 507 or the like of an error indicating that the shutter sensor 506 has erroneously detected (S15), and ends this process. That is, even if the control unit 200 performs control to move the shutter 40 to the open position, if the detection result of the shutter sensor 506 remains in the closed position, the shutter sensor 506 can correctly detect the position of the shutter 40. Suppose not. In this case, the control unit 200 notifies an error without starting the image forming operation.

  When the charging shutter flag is “closed position (1)” in the process of S1 described above (YES in S1), the control unit 200 determines whether the detection result of the shutter sensor 506 is the open position (S2). . When it is determined that the detection result of the shutter sensor 506 is the closed position (NO in S2), that is, when the detection result (closed position) of the shutter sensor 506 matches the charging shutter flag (closed position), the control unit 200 Control to open the shutter 40 is performed (S12). In this case, it is necessary to move the shutter 40 to the open position for image formation. Therefore, when the control for moving the shutter 40 from the closed position to the open position is performed, the shutter sensor 506 is made to detect the position, thereby confirming whether the shutter sensor 506 has correctly detected the position of the shutter 40. For this purpose, the processes of S12 to S15 described above are executed. Since the processing of S12 to S15 has already been described, the description thereof is omitted here.

  When it is determined in the process of S2 that the detection result of the shutter sensor 506 is the open position (YES in S2), that is, the detection result of the shutter sensor 506 (open position) and the charged shutter flag (closed position) do not match. The control unit 200 performs a shutter check operation (S3). That is, the position (closed position) when the shutter 40 was moved last time and the position (open position) detected by the shutter sensor 506 are different. In this case, the control unit 200 considers that the shutter sensor 506 has not correctly detected the position of the shutter 40 due to erroneous detection or the like. Therefore, the control unit 200 moves the shutter 40 to the closed position opposite to the position (open position) detected by the shutter sensor 506. Here, the reason why the shutter sensor 506 is erroneously detected is that the shutter 40 may have been artificially moved from the position (closed position) when it was previously moved to the open position for maintenance or the like. Because there is. If the shutter 40 is artificially moved to the open position, the shutter sensor 506 correctly detects that the shutter 40 is in the open position. On the other hand, the shutter sensor 506 may only be detected as being in the open position due to toner adhesion or the like. Therefore, a shutter check operation is performed to confirm whether the shutter sensor 506 is erroneously detected by actually moving the shutter 40 and causing the shutter sensor 506 to detect the position at that time.

  The control unit 200 performs a shutter check operation (S3), and confirms whether the shutter sensor 506 is normally detecting (S4). In the shutter check operation, first, since the detection result of the shutter sensor 506 is the open position, the control unit 200 performs control to close the shutter 40. Then, the control unit 200 confirms whether the position of the shutter 40 has changed from the open position to the closed position based on the detection result of the shutter sensor 506 obtained with the control for closing the shutter 40. Next, when the position of the shutter 40 has changed to the closed position, the control unit 200 performs control to open the shutter 40. Then, the control unit 200 confirms whether the position of the shutter 40 has changed from the closed position to the open position based on the detection result of the shutter sensor 506 obtained with the control for opening the shutter 40.

  In this way, the control unit 200 performs control to move the shutter 40, and if the detection result of the shutter sensor 506 changes from open position → closed position → open position, the control unit 200 indicates that the shutter sensor 506 is normally detecting. Judgment is made (YES in S4). Then, the control unit 200 stores the charger shutter flag in the memory 501 as “open position (0)” (S5). In this case, the control unit 200 starts the image forming operation on the assumption that the shutter sensor 506 has correctly detected the position of the shutter 40.

  Even if the shutter check operation (S3) is performed, if the shutter sensor 506 is erroneously detected, the detection result of the shutter sensor 506 remains unchanged at the open position. That is, if the detection result of the shutter sensor 506 is an open position → open position → open position, the control unit 200 determines that the shutter sensor 506 is not detecting correctly (NO in S4) and notifies an error ( S6) This process is terminated. In this case, the control unit 200 does not start an image forming operation.

  As described above, in the image forming apparatus 100 according to the present embodiment, it is confirmed whether the detection operation of the shutter sensor 506 that detects the position of the shutter 40 provided so that the opening of the corona charger 2Y can be opened and closed is correctly performed. Can be done easily. In addition, when the shutter sensor 506 can correctly detect the position of the shutter 40, the image forming operation can be started continuously with the position of the shutter 40 as the open position. As a result, it is possible to reduce the possibility of carrier adhesion, toner adhesion, and the like due to the charging process being performed with the shutter 40 closed, thereby making it difficult to cause image defects caused by these.

  In the above-described embodiment, a photo interrupt type sensor is used as the shutter sensor 506, but the present invention is not limited to this. For example, a piezoelectric sensor or a contact sensor that outputs a signal when pressed according to the shutter position may be used. Further, the shutter sensor 506 is not limited to the side close to the winding roller 11 but may be provided on the side far from the winding roller 11. Further, not only one shutter sensor 506 but two shutter sensors 506 may be provided on the side closer to the take-up roller 11 and the side farther from the take-up roller 11.

  In the above-described embodiment, the toner images of the respective colors are primarily transferred from the photosensitive drums 1Y to 1K of the respective colors to the intermediate transfer belt 8, and then the composite toner images of the respective colors are collectively transferred to the recording material P. Although the image forming apparatus has been described, the present invention is not limited to this. For example, a direct transfer type image forming apparatus configured to directly transfer the photosensitive drums 1Y to 1K to the recording material P may be used.

DESCRIPTION OF SYMBOLS 1Y-1K ... Photoconductor (photosensitive drum), 2Y-2K ... Corona charger, 30 ... Discharge electrode (discharge wire), 40 ... Shutter, 81 ... Shield member, 90 ... Housing | casing, 110 ... Apparatus main body, 200 ... Control Means (control section), 501... Storage means (memory), 506... Detection means (shutter sensor), 506a... Light emitting section, 506b.

Claims (9)

A photoreceptor,
A corona charger having a housing having an opening facing the photoconductor, and a discharge electrode disposed in the housing;
A shutter capable of opening and closing the opening;
Driving means capable of moving the shutter between an open position where the opening is opened and a closed position where the opening is shielded;
Detecting means capable of detecting that the shutter is in at least one of an open position and a closed position;
Control means for controlling the drive means,
The control means is arranged to open and close the closed position detected by the detection means when the position detected by the detection means is different from either the open position or the closed position when the shutter was moved last time. A confirmation mode in which the driving means is controlled to move the shutter to the other position different from any one of the positions, and an error is notified when the other position is not detected by the detecting means after the control. Run,
An image forming apparatus. The detection means is one piece.
The image forming apparatus according to claim 1. The control unit executes the confirmation mode at the start of an image forming job.
The image forming apparatus according to claim 1. The control means drives the control means to move the shutter to the closed position in the confirmation mode, and moves the shutter to the open position when the closed position is detected as the other position by the detection means. Start the image forming operation after
The image forming apparatus according to claim 3. The control means drives the control means to move the shutter to the open position in the confirmation mode, and starts an image forming operation when the open position is detected as the other position by the detection means.
The image forming apparatus according to claim 3. The control unit controls the driving unit to move the shutter to a closed position when a predetermined time has elapsed since the end of the previous image forming job.
The image forming apparatus according to claim 1, wherein the image forming apparatus is an image forming apparatus. The detection means can output a predetermined signal only when the shutter is in one of an open position and a closed position,
The control means determines that the shutter is in the one position when the predetermined signal is output from the detection means, and the shutter when the predetermined signal is not output from the detection means. Is in the other position,
The image forming apparatus according to claim 1, wherein the image forming apparatus is an image forming apparatus. The detection means includes: a light emitting unit that emits light; a light receiving unit that is disposed opposite to the light emitting unit and that receives light emitted from the light emitting unit; a shielding position that shields the light emitting unit and the light receiving unit; And a shielding member that can move together with the shutter at a non-shielding position that does not shield the light receiving part and the light receiving part.
The image forming apparatus according to claim 7. A photoreceptor,
A corona charger having a housing having an opening facing the photoconductor, and a discharge electrode disposed in the housing;
A shutter capable of opening and closing the opening;
Driving means capable of moving the shutter between an open position where the opening is opened and a closed position where the opening is shielded;
Detecting means capable of detecting that the shutter is in at least one of an open position and a closed position;
Control means for controlling the drive means;
Storage means for storing shutter drive information indicating whether control is performed to move the shutter to an open position or a closed position when the control means controls the drive means;
If the position detected by the detection means at a predetermined timing does not match the shutter drive information stored in the storage means when the control for moving the shutter was performed last time, the detection means When the drive unit is controlled to move the shutter to the other position different from one of the open position and the closed position detected by the step, and the other position is not detected by the detection unit after the control. Run confirmation mode to notify the error,
An image forming apparatus.

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