JP5929582B2 - Image forming apparatus - Google Patents

Description

  The present invention relates to an image forming apparatus.

  2. Description of the Related Art Conventionally, some electrophotographic image forming apparatuses are provided with a lubricant application device that forms a lubricant layer by applying a lubricant to an image carrier (hereinafter referred to as a photosensitive drum). By providing the lubricant application device, it is possible to reduce the friction coefficient of the photosensitive drum, and to extend the life of the cleaning drum that contacts the surface of the photosensitive drum and the photosensitive drum to remove foreign matters. Further, the toner image formed on the surface of the photosensitive drum is easily separated by the lubricant, and the transfer performance (transfer rate) can be improved.

  However, in the case where image formation is not performed for a long time (for example, overnight), the lubricant layer remains on the photosensitive drum while adsorbing discharge products (for example, ozone, NOx, etc.). It sticks to. Therefore, the discharge product cannot be easily removed by the cleaning blade during the next image formation. As described above, when image formation is performed in a state where the discharge product is attached to the photosensitive drum, there is a problem that the electrostatic latent image is disturbed and the image is blurred (hereinafter referred to as image blur).

  In order to solve this problem, a technique has been proposed in which the amount of lubricant adsorbing discharge products is reduced by intermittently applying a lubricant to the photosensitive drum (see, for example, Patent Document 1). ).

JP 2011-59546 A

  However, in the technique described in Patent Document 1, since a new lubricant is still applied on the lubricant that has adsorbed the discharge product, the discharge product cannot be sufficiently removed, and the image still remains. There was a problem that blur may occur.

  An object of the present invention is to provide an image forming apparatus capable of preventing the occurrence of image blur.

An image forming apparatus according to the present invention includes:
A rotatable image carrier;
A lubricant application section for applying a lubricant to the surface of the image carrier;
An exposure unit that exposes the image carrier;
A developing unit for developing the image carrier exposed by the exposing unit with toner;
A cleaning unit for cleaning the surface of the image carrier;
A magnetic brush forming portion for forming a magnetic brush for rubbing the surface of the image carrier;
Equipped with a,
It said magnetic brush forming unit, when the image forming processing by the image forming apparatus is not performed for a predetermined time or more, you form the magnetic brush.

  According to the present invention, it is possible to provide an image forming apparatus capable of preventing the occurrence of image blur.

3 is a control block diagram of the image forming apparatus in the present embodiment. FIG. FIG. 2 is a diagram illustrating a configuration of an image forming unit in the present embodiment. 4 is a flowchart illustrating an operation example of the image forming apparatus in the present embodiment. It is a figure which shows the relationship between the average coverage of an image, and the linear velocity ratio of the sleeve with respect to a photoreceptor drum.

Hereinafter, the present embodiment will be described in detail with reference to the drawings.
[Configuration of Image Forming Apparatus 100]
An image forming apparatus 100 shown in FIG. 1 forms an image on a recording sheet by an electrophotographic process. The image forming apparatus 100 includes a control unit 101, a document reading unit 110, an operation display unit 120, an image processing unit 130, an image forming unit 140, a conveyance unit 150, a fixing unit 160, a temperature / humidity sensor 180, and a torque detection unit 190. Yes. The magnetic brush forming unit 145 included in the image forming unit 140 will be described later.

  The control unit 101 includes a CPU (Central Processing Unit) 102, a ROM (Read Only Memory) 103, a RAM (Random Access Memory) 104, a timing unit 105, and the like. The CPU 102 reads a program corresponding to the processing content from the ROM 103 and develops it in the RAM 104, and centrally controls the operation of each block of the image forming apparatus 100 in cooperation with the developed program. At this time, various data stored in the storage unit 172 are referred to. The storage unit 172 includes, for example, a nonvolatile semiconductor memory (so-called flash memory) or a hard disk drive. The time measuring unit 105 measures a time during which the image forming process is not performed in the image forming apparatus 100 (hereinafter referred to as “leaving time”).

  The control unit 101 transmits and receives various data to and from an external device (for example, a personal computer) connected to a communication network such as a LAN (Local Area Network) or a WAN (Wide Area Network) via the communication unit 171. I do. For example, the control unit 101 receives image data transmitted from an external device, and forms an image on a recording sheet based on the image data (input image data). The communication unit 171 includes a communication control card such as a LAN card, for example.

  The original reading unit 110 optically scans the original conveyed on the contact glass, forms an image of reflected light from the original on a light receiving surface of a CCD (Charge Coupled Device) sensor, and reads the original. The document is conveyed onto the contact glass by an automatic document feeder (ADF). However, the document may be manually placed on the contact glass.

  The operation display unit 120 has a touch panel screen. Input operations for various instructions and settings performed by the user can be performed via a touch panel screen. The user can set, for example, the type of recording paper (paper type) and basis weight as image forming conditions via the operation display unit 120. The image forming conditions set on the operation display unit 120 are recorded in the storage unit 172 as image forming condition information.

  The image processing unit 130 includes a circuit that performs analog-digital (A / D) conversion processing and a circuit that performs digital image processing. The image processing unit 130 generates digital image data by A / D conversion processing from the analog image signal acquired by the CCD sensor of the document reading unit 110 and outputs the digital image data to the image forming unit 140.

  The image forming unit 140 emits laser light based on the digital image data generated by the image processing unit 130, and irradiates the photoconductive drum 200 (see FIG. 2) with the emitted laser light. An electrostatic latent image is formed on 200 (exposure process).

  The image forming unit 140 is configured to execute a charging process performed before the exposure process, a development process performed after the exposure process, a transfer process after the development process, and a cleaning process after the transfer process in addition to the exposure process described above. It has.

  In the charging process, the image forming unit 140 uniformly charges the surface of the photosensitive drum 200 by corona discharge from the charging unit 240. In the development process, the image forming unit 140 forms a toner image on the photosensitive drum 200 by attaching toner contained in the developer in the developing unit 280 to the electrostatic latent image on the photosensitive drum 200.

  In the transfer process, the image forming unit 140 primarily transfers the toner image on the photosensitive drum 200 to the intermediate transfer belt. Further, the image forming unit 140 secondarily transfers the toner image on the intermediate transfer belt onto the recording paper conveyed by the conveyance unit 150. In the cleaning process, the image forming unit 140 removes the toner remaining on the photosensitive drum 200 after the transfer process.

  The fixing unit 160 includes a heating roller, a fixing roller, a fixing belt, and a pressure roller. The heating roller and the fixing roller are arranged apart from each other by a predetermined distance. A fixing belt is stretched between the heating roller and the fixing roller. The pressure roller is disposed in a state of being in pressure contact with the fixing belt in a region where the fixing belt and the fixing roller are in contact with each other. A fixing nip portion is formed at a portion where the fixing belt and the pressure roller are in contact with each other.

  The fixing unit 160 fixes the toner image on the recording sheet by applying heat and pressure to the toner image on the recording sheet introduced into the fixing nip (heating fixing) (fixing step). As a result, a fixed toner image is formed on the recording paper. The recording paper heated and fixed by the fixing unit 160 is discharged to the outside of the image forming apparatus 100.

  The temperature / humidity sensor 180 detects the temperature and relative humidity around the image forming apparatus 100 and outputs the detected temperature and relative humidity to the control unit 101.

  The torque detector 190 detects a drive current value that controls a drive motor that drives the photosensitive drum 200. The torque detector 190 calculates the rotational torque of the photosensitive drum 200 according to the detected drive current value, and outputs the rotational torque to the controller 101.

  The torque detector 190 is not limited to a configuration that calculates based on the drive current value of the drive motor that drives the photosensitive drum 200. For example, a configuration in which the rotational torque of the photosensitive drum 200 is detected using a mechanical reaction force using a strain gauge or the like may be used.

[Configuration of Image Forming Unit 140]
Next, the main configuration of the image forming unit 140 will be described with reference to FIG. It should be noted that the components that transfer the toner image transferred to the intermediate transfer belt onto the recording paper at the secondary transfer portion are not shown.

  The photosensitive drum 200 functions as an image carrier and is rotated in the direction of arrow a by a drive motor (not shown). The photosensitive drum 200 has a drum shape with an outer diameter of 80 [mm], and the surface is constituted by a photosensitive layer with a film thickness of 25 to 32 [μm]. The photoreceptor layer includes an organic semiconductor layer in which a phthalocyanine pigment is dispersed in polycarbonate and a charge transport layer. The linear velocity of the photosensitive drum 200 is 400 [mm / s]. Around the photosensitive drum 200, a lubricant application unit 220, a charging unit 240, an exposure unit 260, a magnetic brush forming unit 145, and a developing unit 280 are arranged along the rotation direction of the photosensitive drum 200.

  The lubricant application unit 220 includes a lubricant application brush 222, a lubricant 224, a pressing spring 226, a main blade 228 that functions as a cleaning unit, a toner recovery screw 230, a leveling blade 232, and a housing 234.

  The lubricant application brush 222 is, for example, a metal shaft having an outer diameter of 14 [mm], a base fabric having a thickness of 0.5 [mm], and a bundle of polyester fibers in a loop shape having a height of 2.5 [mm]. It is constructed by winding a woven and planted hair. The lubricant application brush 222 is fixedly positioned so that the lubricant application brush 222 bites into the photosensitive drum 200 by about 1.0 [mm]. The lubricant application brush 222 rotates at, for example, 280 [mm / s] in the same direction (counter direction) as the rotation direction of the photosensitive drum 200. That is, when the linear velocity of the lubricant application brush 222 is S1 and the linear velocity of the photosensitive drum 200 is S2, the linear velocity ratio (S1 / S2) is 0.7. The lubricant application brush 222 is rotationally driven by a control signal from the control unit 101.

  The lubricant 224 is formed by solidifying zinc stearate (ZnSt) having a pencil hardness of F to HB. The lubricant 224 is formed in the depth direction in the drawing in the same length as the axial direction length of the photosensitive drum 200, and the pressure load 1.8 to 3.1 [N] in the direction of the lubricant application brush 222 by the pressing spring 226. ] Is pressed. A lower right end portion of the pressing spring 226 in the drawing is fixed to the housing 234. A plurality of pressing springs 226 are arranged in a balanced manner in the axial direction of the lubricant application brush 222.

  The lubricant application brush 222 scrapes off the lubricant 224 with the bristle portion of the rotating lubricant application brush 222 and applies the fine powder of the lubricant 224 thus scraped off to the surface of the photosensitive drum 200.

  The leveling blade 232 is made of urethane rubber, and is provided on the downstream side of the lubricant application brush 222 with respect to the rotation direction of the photosensitive drum 200. The leveling blade 232 makes the distribution of the lubricant 224 applied to the surface of the photosensitive drum 200 by the lubricant application brush 222 uniform.

  The main blade 228 is made of urethane rubber, and is provided on the upstream side of the lubricant application brush 222 with respect to the rotation direction of the photosensitive drum 200. The main blade 228 functions as a cleaning unit, slidably contacts the surface of the photosensitive drum 200, and scrapes off toner remaining on the surface of the photosensitive drum 200 after the primary transfer. The toner scraped off by the main blade 228 is discharged to the outside by the toner recovery screw 230. The main blade 228 has a free length of 9 [mm], a contact pressure with respect to the photosensitive drum 200 of 20 [N], and a contact angle with respect to the photosensitive drum 200 of 15 [°].

  The charging unit 240 applies a charge to the photosensitive drum 200 and uniformly charges the surface of the photosensitive drum 200. The exposure unit 260 performs an exposure operation on the surface of the photosensitive drum 200 based on image data read from the document, and forms an electrostatic latent image on the photosensitive drum 200.

  The developing unit 280 forms a toner image on the surface of the photosensitive drum 200 by attaching toner to the electrostatic latent image formed on the photosensitive drum 200. The developing unit 280 employs a trickle system that replenishes new carriers while gradually discarding carriers whose charging performance has deteriorated. The developing unit 280 includes a developing roller 282, a stirring roller 284, and a transport roller 286.

  The stirring roller 284 and the conveyance roller 286 are helical screw members. The stirring roller 284 is housed in the first developer supply chamber 288. The transport roller 286 is accommodated in the second developer supply chamber 290. The stirring roller 284 and the transport roller 286 transport the developer to the developing roller 282 while stirring the developer.

  The developing roller 282 includes a rotatable developing sleeve 282A and a developing magnet roll 282B disposed inside the developing sleeve 282A. The developing roller 282 is disposed in the vicinity of the photosensitive drum 200 and conveys the developer to the developing region 292 in the vicinity of the photosensitive drum 200. The developing sleeve 282A rotates counterclockwise in the drawing. In the developing magnet roll 282B, a plurality of magnetic poles (regulating pole, developing pole, peeling pole, etc.) that generate a magnetic field are arranged. Due to the magnetic field generated by the magnetic pole, the developer is carried on the outer peripheral surface of the developing sleeve 282A, and the developing sleeve 282A rotates counterclockwise in the drawing and is conveyed to the developing region 292. A regulating blade 294 that regulates the thickness of the developer layer is disposed in the vicinity of the developing sleeve 282A.

  A part of the developing roller 282, the stirring roller 284, the conveying roller 286, and the regulating blade 294 are accommodated in the developing casing 296. The developing casing 296 forms a first developer supply chamber 288 and a second developer supply chamber 290. The first developer supply chamber 288 and the second developer supply chamber 290 are partitioned by a partition wall portion 298.

  Toner is supplied from the toner supply unit 300 to the first developer supply chamber 288. The toner replenishing unit 300 stores a developer in which toner and a carrier are mixed in advance, and supplies toner to the first developer supply chamber 288 and at the same time, supplies a new carrier little by little. The agitating roller 284 rotates to mix and agitate the toner supplied to the first developer supply chamber 288 and the carrier and frictionally charge the toner. The stirring roller 284 conveys the frictionally charged developer to the second developer supply chamber 290. The transport roller 286 rotates to transport the developer transported from the stirring roller 284 to the developing roller 282.

  A discharge portion 291 extending to the magnetic brush forming portion 145 is provided on the bottom surface portion of the second developer supply chamber 290. The discharge unit 291 discharges a part of the developer present in the second developer supply chamber 290 to the magnetic brush forming unit 145. When the trickle rate (the ratio of carriers in the developer (toner and carrier)) is 5 to 10 [%], the amount of developer discharged by the discharge unit 291 is when a document with a coverage of 5 [%] is continuously printed. , 0.05 to 0.10 [g] per minute.

  The magnetic brush MB (that is, the developer layer) is formed on the outer peripheral surface of the developing sleeve 282A by the magnetic field generated by the developing magnet roll 282B. The developing sleeve 282A rotates counterclockwise in the drawing, and conveys the developer to the developing region 292 closest to the photosensitive drum 200 while carrying the developer on the outer peripheral surface of the developing sleeve 282A by a magnetic field. In the middle, the regulating blade 294 regulates the thickness of the developer layer, so that a certain amount of developer is conveyed to the developing area 292.

  In the development region 292, the developer layer contacts the surface of the photosensitive drum 200. In the developing region 292, the toner electrostatically moves from the developing sleeve 282A to an electrostatic latent image formed on the surface of the photosensitive drum 200. In this way, the developing unit 280 visualizes the electrostatic latent image on the photosensitive drum 200 with the toner.

  The magnetic brush forming unit 145 forms a magnetic brush MB for scraping off the lubricant 224 applied to the surface of the photosensitive drum 200. The magnetic brush MB is formed into a brush shape by forming spikes of developer particles by magnetism. The magnetic brush forming unit 145 is disposed on the upstream side of the developing unit 280 and on the downstream side of the exposure unit 260 in the rotation direction of the photosensitive drum 200. The magnetic brush forming unit 145 includes a magnetic brush forming roller 310 and a transport roller 320.

  The conveyance roller 320 is a helical screw member. The transport roller 320 is housed in the developer supply chamber 322. The developer supply chamber 322 communicates with the discharge unit 291 of the developing unit 280. The developer supply chamber 322 is initially filled with a carrier. As the developer is discharged from the discharge unit 291 of the developing unit 280, the carrier in the developer supply chamber 322 is replaced.

  The transport roller 320 transports the developer discharged from the discharge unit 291 to the magnetic brush forming roller 310. The magnetic brush forming unit 145 is not provided with a stirring roller. This is because the developer discharged from the discharge unit 291 is not used for image formation, and toner is not supplied to the developer supply chamber 322.

  A discharge unit (not shown) is provided on the bottom surface of the developer supply chamber 322. When the magnetic brush forming unit 145 forms the magnetic brush MB, the discharging unit discharges a part of the toner present in the developer supply chamber 322 to the outside. The amount of toner discharged by the discharge unit is 0.05 to 0.10 [g] per minute. By this discharge, the toner density of the magnetic brush MB is lowered to a predetermined density or less.

  The magnetic brush forming roller 310 has an outer diameter of 12 [mm] and a surface roughness Rz of 10 [μm]. A rotatable sleeve 310A and a magnet roll 310B disposed inside the sleeve 310A are provided. The magnetic brush forming roller 310 is disposed in the vicinity of the photosensitive drum 200 and conveys the developer to the magnetic brush forming region 350 in the vicinity of the photosensitive drum 200. The sleeve 310 </ b> A rotates at 400 to 800 [mm / s] in the same direction (counter direction) as the rotation direction of the photosensitive drum 200 in accordance with a control signal from the control unit 101. That is, when the linear velocity of the sleeve 310A is S1, and the linear velocity of the photosensitive drum 200 is S2, the linear velocity ratio (S1 / S2) is 1.0 to 2.0.

In the magnet roll 310B, a plurality of magnetic poles (regulating pole, developing pole, peeling pole, etc.) that generate a magnetic field are arranged. By the magnetic field generated by the magnetic pole, the developer is carried on the outer peripheral surface of the sleeve 310A, and the sleeve 310A rotates counterclockwise in the drawing, and is conveyed to the magnetic brush forming region 350. The developer conveyance amount is, for example, 160 to 350 [g / m ² ]. A predetermined gap (for example, 0.25 to 0.35 [mm]) is formed between the magnetic brush forming region 350 and the photosensitive drum 200. A magnetic plate 330 that restricts the thickness of the developer layer is disposed in the vicinity of the sleeve 310A. The plate thickness of the magnetic plate 330 is 2.0 [mm]. A part of the magnetic brush forming roller 310, the transport roller 320, and the magnetic plate 330 are housed in the casing 340.

[Specific Configuration of Magnetic Brush Forming Roller 310]
Next, a specific configuration of the magnetic brush forming roller 310 will be described. As shown in FIG. 2, seven magnetic poles N1, N2, N3, N4, S1, S2, and S3 are arranged on the magnet roll 310B of the magnetic brush forming roller 310.

  The magnetic pole N3 is composed of N poles, and pumps (adsorbs) the developer conveyed by the conveying roller 320 onto the sleeve 310A. As for the seven magnetic poles, if the N pole and the S pole are alternately arranged, the pumping magnetic pole may be the S pole. Further, the number of magnetic poles arranged in the magnet roll 310B may be five, for example.

  The magnetic pole S2 is an S pole, and is provided next to the downstream side of the magnetic pole N3 in the rotation direction of the sleeve 310A. The developer pumped up on the surface of the sleeve 310A by the lines of magnetic force formed by the magnetic pole S2 is conveyed downstream in the rotation direction of the sleeve 310A. The developer on the surface of the conveyed sleeve 310 </ b> A is made to have a constant layer thickness (for example, 0.28 to 0.38 [mm]) by the magnetic plate 330.

  The magnetic pole N2 is an N pole, and is provided adjacent to the downstream side of the magnetic pole S2 in the rotation direction of the sleeve 310A. Due to the lines of magnetic force formed by the magnetic pole N2, the developer having a constant layer thickness formed on the sleeve 310A by the magnetic pole S2 and the magnetic plate 330 is conveyed from the magnetic pole N2 to the magnetic pole S1 in the downstream direction of the rotation of the sleeve 310A. The

  The magnetic pole S1 is an S pole, and is provided next to the downstream side of the magnetic pole N2 in the rotation direction of the sleeve 310A. The developer formed on the sleeve 310A is conveyed downstream from the magnetic pole S1 in the rotation direction of the sleeve 310A by the magnetic field lines formed in the magnetic pole S1.

  The magnetic pole N <b> 1 is an N pole, and is disposed to face the photosensitive drum 200. The magnetic pole N1 functions as a main magnetic pole that scrapes off the lubricant 224 applied to the surface of the photosensitive drum 200. The developer conveyed from the magnetic pole S1 rubs the photosensitive drum 200 with the magnetic brush MB formed by the magnetic field lines of the magnetic pole N1. A region where the photosensitive drum 200 and the sleeve 310 </ b> A are opposed to each other where the magnetic brush MB is formed is a magnetic brush forming region 350.

  The magnetic pole S3 is an S pole, and is provided next to the downstream side of the magnetic pole N1 in the rotation direction of the sleeve 310A. The developer conveyed from the position of the magnetic pole N1 by the magnetic lines formed by the magnetic pole S3 is held by the sleeve 310A and conveyed downstream in the rotation direction of the sleeve 310A.

  The magnetic pole N4 is an N pole, and is provided next to the downstream side of the magnetic pole S3 in the rotation direction of the sleeve 310A. The polarity of the magnetic pole N4 is the same as the polarity of the magnetic pole N3 (in this embodiment, N pole), and no magnetic pole is provided in the region between the magnetic pole N4 and the magnetic pole N3 in the sleeve 310A. A repulsive magnetic field is formed between the magnetic pole N4 and the magnetic pole N3. Therefore, the developer held by the magnetic pole N4 comes off from the sleeve 310A. The developer removed from the sleeve 310 </ b> A falls and is collected in the developer supply chamber 322.

[Operation of Image Forming Apparatus 100]
Next, the operation of the image forming apparatus 100 will be described with reference to the flowchart of FIG. The processes in steps S100 to S220 are executed each time a predetermined time (for example, 10 minutes) elapses while the image forming apparatus 100 is activated. Here, the rotation of the lubricant application brush 222 is stopped, and the leveling blade 232 is in a separated state with respect to the photosensitive drum 200. The main blade 228 is in contact with the photosensitive drum 200.

  First, the control unit 101 determines whether or not the relative humidity detected by the temperature / humidity sensor 180 is 50 [%] or more (step S100). As a result of this determination, when the relative humidity is not 50% or more (step S100, NO), the image forming apparatus 100 ends the processing in FIG.

  On the other hand, when the relative humidity is 50 [%] or more (step S100, YES), the control unit 101 determines whether or not the standing time measured by the time measuring unit 105 is 30 [min] or more (step). S120). If the result of this determination is that the neglected time is not 30 [minutes] or more (step S120, NO), the image forming apparatus 100 ends the processing in FIG.

  On the other hand, when the leaving time is 30 [minutes] or longer (step S120, YES), the control unit 101 starts to rotate the photosensitive drum 200 and the sleeve 310A constituting the magnetic brush forming roller 310 (step S140). ). The controller 101 controls the linear velocity ratio (S1 / S2) to be 2.0 when the linear velocity of the sleeve 310A is S1 and the linear velocity of the photosensitive drum 200 is S2. By performing the process of step S140, the scraping operation of the lubricant 224 by the magnetic brush MB is started.

  Next, the torque detection unit 190 calculates the rotational torque of the photosensitive drum 200 and outputs the rotational torque to the control unit 101 (step S160). Next, the controller 101 determines whether or not the rotational torque calculated by the torque detector 190 is 0.9 [N · m] or more (step S180). As a result of this determination, when the rotational torque is not 0.9 [N · m] or more (step S180, NO), the controller 101 sufficiently scrapes the lubricant 224 on the surface of the photosensitive drum 200 by the magnetic brush MB. Judge that it is not. The process transitions to step S160.

  On the other hand, when the rotational torque is 0.9 [N · m] or more (step S180, YES), the control unit 101 determines that the lubricant 224 on the surface of the photosensitive drum 200 is sufficiently scraped off by the magnetic brush MB. Then, the rotational speed of the sleeve 310A is changed (step S200). Specifically, the control unit 101 slows the rotational speed of the sleeve 310A so that the linear speed ratio (S1 / S2) when the linear speed of the sleeve 310A is S1 and the linear speed of the photosensitive drum 200 is S2. Control to be 1.0.

  Next, the control unit 101 determines whether one minute has elapsed after changing the rotation speed of the sleeve 310A (step S220). As a result of this determination, if one minute has not elapsed (step S220, NO), the process transitions to step S220.

  On the other hand, when one minute has passed (step S220, YES), the control unit 101 ends the rotational driving of the photosensitive drum 200 and the sleeve 310A (step S240). When the process of step S240 is completed, the image forming apparatus 100 ends the process in FIG. In one minute after changing the rotational speed of the sleeve 310 </ b> A, the discharge product adhering to the surface of the photosensitive drum 200 is scraped by the main blade 228.

  In the flowchart of FIG. 3, the relative humidity detected by the temperature / humidity sensor 180 is used to determine whether to form the magnetic brush MB. However, the temperature and relative humidity detected by the temperature / humidity sensor 180 are used. It is also possible to use absolute humidity calculated according to the above.

[Effects of the present embodiment]
As described above in detail, in the present embodiment, the rotatable photosensitive drum 200, the exposure unit 260 that exposes the photosensitive drum 200, and the photosensitive drum 200 that is exposed by the exposure unit 260 are developed with toner. The developing unit 280 includes a main blade 228 that cleans the surface of the photosensitive drum 200, and a magnetic brush forming unit 145 that forms a magnetic brush MB that rubs the surface of the photosensitive drum 200.

  According to the present embodiment configured as described above, first, the lubricant 224 fixed on the surface of the photosensitive drum 200 is scraped off by the magnetic brush MB having a strong scraping force, and then the photosensitive drum 200. The discharge product adhering to the surface is scraped off by the main blade 228. Therefore, it is possible to prevent the electrostatic latent image from being disturbed and causing image blurring by performing the image forming process with the discharge product attached to the photosensitive drum 200. Furthermore, since the state where the amount of the lubricant 224 on the surface of the photosensitive drum 200 does not exceed the predetermined amount by the scraping operation of the magnetic brush MB, the lubricant 224 exceeding the predetermined amount is developed. It is possible to prevent the toner charge amount of the developer from being lowered by entering the portion 280. Therefore, it is possible to prevent the toner from adhering to the photosensitive drum 200 and image defects such as white spots from occurring.

  In the present embodiment, the magnetic brush forming unit 145 is disposed on the upstream side of the developing unit 280 and on the downstream side of the exposure unit 260 in the rotation direction of the photosensitive drum 200. With this configuration, when an image forming process is performed in the image forming unit 140, the toner contained in the developer for forming the magnetic brush MB is attached to the electrostatic latent image on the photosensitive drum 200, whereby the photosensitive member A toner image can be formed on the drum 200. That is, the developer used in the magnetic brush forming unit 145 can be effectively used for purposes other than magnetic brush formation. Therefore, the amount of toner used for toner image formation in the developing unit 280 can be reduced.

  In the present embodiment, the magnetic brush forming unit 145 forms the magnetic brush MB by using the developer discharged from the developing unit 280. With this configuration, the developer to be discarded in the developing unit 280 can be effectively used in the magnetic brush forming unit 145.

  In the present embodiment, the magnetic brush forming unit 145 discharges toner contained in the developer before forming the magnetic brush MB, thereby setting the toner concentration of the magnetic brush MB to a predetermined concentration (for example, toner concentration 3). 0.0 [%]) or less. Therefore, the rigidity of the magnetic brush MB formed by the magnetic brush forming unit 145, that is, the degree of connection between carriers constituting the magnetic brush MB is increased. Therefore, when the magnetic brush MB rubs the surface of the photoconductive drum 200, the carriers are not easily separated, and the surface of the photoconductive drum 200 can be rubbed by strong stress. As described above, the lubricant 224 fixed on the surface of the photosensitive drum 200 can be more reliably scraped off.

Further, in the present embodiment, the control unit 101, when the rotational torque of the photosensitive drum 200 is less than the predetermined value, the rotational speed of the sleeve 310A is much larger than the case where the rotational torque is the predetermined value or more Thus, the sleeve 310A is controlled. With this configuration, when the lubricant 224 on the surface of the photosensitive drum 200 is sufficiently scraped off by the magnetic brush MB and the role of the magnetic brush MB is finished, it is received by rubbing the surface of the photosensitive drum 200 thereafter. The stress of the magnetic brush MB can be reduced. Therefore, it is possible to prevent unnecessary deterioration of the carrier constituting the magnetic brush MB.

  In the present embodiment, the magnetic brush forming unit 145 forms the magnetic brush MB only when the humidity around the image forming apparatus 100 is equal to or higher than a predetermined humidity and the leaving time is equal to or longer than a predetermined time. With this configuration, the magnetic brush MB is formed only when the lubricant 224 in which the discharge product is adsorbed easily adheres to the photosensitive drum 200. Therefore, the magnetic brush MB is unnecessarily formed until the lubricant 224 having adsorbed the discharge product is not necessarily fixed, that is, when the possibility of image blurring is low. Can be prevented. Note that when the humidity around the image forming apparatus 100 is equal to or higher than a predetermined humidity, the surface resistance of the photosensitive drum 200 is lowered and electric discharge is likely to occur, and the amount of discharge products increases, resulting in image blurring. The possibility is high.

[Modification]
In the above embodiment, the example in which the photosensitive drum 200 functions as the image carrier has been described. However, a photosensitive belt provided instead of the photosensitive drum 200 may function as the image carrier.

  In the above-described embodiment, the magnetic brush forming unit 145 has been described with respect to the rotation direction of the photosensitive drum 200 as an example disposed on the upstream side of the developing unit 280 and the downstream side of the exposure unit 260. The present invention is not limited to this. For example, the magnetic brush forming unit 145 may be disposed on the downstream side of the lubricant application unit 220 and on the upstream side of the charging unit 240 in the rotation direction of the photosensitive drum 200. Even in this case, a toner image can be formed on the photosensitive drum 200 by attaching the toner contained in the developer for forming the magnetic brush MB to the electrostatic latent image on the photosensitive drum 200. . Further, the magnetic brush forming unit 145 may be disposed on the downstream side of the developing unit 280 in the rotation direction of the photosensitive drum 200.

  In the above embodiment, the example in which the lubricant application unit 220 applies the lubricant 224 to the surface of the photosensitive drum 200 has been described, but the present invention is not limited to this. For example, the lubricant 224 may be included in an external additive in the toner used for developing the photosensitive drum 200. In this case, the lubricant 224 can be applied to the surface of the photosensitive drum 200 without providing the lubricant application unit 220.

  In the above embodiment, an example in which the magnetic brush MB is formed by using the developer discharged from the developing unit 280 has been described, but the present invention is not limited to this. For example, the magnetic brush MB may be formed by connecting a developer replenishment unit (not shown) to the magnetic brush forming unit 145 and using the developer replenished from the developer replenishment unit. This configuration is effective when the trickle method is not adopted for the developing unit 280 and the magnetic brush forming unit 145 cannot use the developer of the developing unit 280.

In the above embodiment, when the rotational torque of the photosensitive drum 200 is turned on a predetermined value or more, an example has been described to slow the rotational speed of the sleeve 310A, more degradation of the carrier constituting the magnetic brush MB From the viewpoint of prevention, the rotation operation of the sleeve 310A may be stopped.

  In the above embodiment, the example in which the sleeve 310 </ b> A rotates in the same direction (counter direction) as the rotation direction of the photosensitive drum 200 has been described. However, the sleeve 310 </ b> A rotates in the opposite direction (with direction) to the rotation direction of the photosensitive drum 200. It may rotate. However, from the viewpoint of increasing the scraping efficiency of the lubricant 224, the sleeve 310A is preferably rotated in the same direction as the rotation direction of the photosensitive drum 200.

  In the above embodiment, as shown in FIG. 4, when forming the magnetic brush MB, the sleeve 310 </ b> A for the photosensitive drum 200 is formed according to the average coverage of the image formed before the magnetic brush MB is formed. The linear speed ratio may be changed. In the example of FIG. 4, the linear velocity ratio is reduced as the average coverage increases. If an image with high coverage is continuously formed, a large amount of toner adheres to the lubricant application brush 222, and the speed at which the toner adheres to the lubricant application brush 222 becomes larger than the speed at which the toner is scraped off by flicker or the like. . As a result, the amount of lubricant 224 that can be applied by the lubricant application brush 222 is reduced. Therefore, even if the linear velocity ratio of the sleeve 310A to the photosensitive drum 200 is small, that is, the rigidity of the magnetic brush MB is small, the lubricant 224 fixed on the surface of the photosensitive drum 200 is sufficiently scraped off. be able to.

  In the above-described embodiment, the example in which the magnetic brush MB is formed only when the humidity around the image forming apparatus 100 is equal to or higher than the predetermined humidity and the leaving time is equal to or longer than the predetermined time has been described. It is not limited to this. For example, the magnetic brush MB may be formed when either the condition that the humidity around the image forming apparatus 100 is equal to or higher than a predetermined humidity or the condition that the leaving time is equal to or longer than a predetermined time is satisfied.

[Example]
Finally, the results of experiments performed by the present inventors to confirm the effectiveness of the above embodiment will be described.

[Configuration of Image Forming Apparatus According to Embodiment]
As the experimental image forming apparatus, the image forming apparatus 100 having the configuration shown in FIGS.

[Configuration of Image Forming Apparatus According to Comparative Example]
As an experimental image forming apparatus, a configuration in which the magnetic brush forming unit 145 is not provided in the image forming apparatus 100 having the configuration of FIGS.

[experimental method]
In the experiment, after image formation processing of 5000 sheets is continuously performed, image formation is performed for a long time (for example, overnight) in a high-temperature and high-humidity environment (for example, 30 [° C.], 80 [%]). If not, the state of the toner image on the recording paper on which image formation processing was subsequently performed was visually confirmed.

[Experimental result]
As a result of the confirmation, in the example in which the magnetic brush forming unit 145 is provided, image blurring does not occur and the lubricant 224 enters the developing unit 280 compared to the comparative example in which the magnetic brush forming unit 145 is not provided. There was no occurrence of white spots caused by. Therefore, the effectiveness in the above embodiment could be confirmed.

  In addition, each of the above-described embodiments is merely an example of actualization in carrying out the present invention, and the technical scope of the present invention should not be construed as being limited thereto. That is, the present invention can be implemented in various forms without departing from the gist or the main features thereof.

DESCRIPTION OF SYMBOLS 100 Image forming apparatus 101 Control part 102 CPU
103 ROM
104 RAM
105 Timekeeping Unit 110 Document Reading Unit 120 Operation Display Unit 130 Image Processing Unit 140 Image Forming Unit 145 Magnetic Brush Forming Unit 150 Conveying Unit 160 Fixing Unit 171 Communication Unit 172 Storage Unit 180 Temperature / Humidity Sensor 190 Torque Detection Unit 200 Photosensitive Drum 220 Lubrication Agent application unit 222 Lubricant application brush 224 Lubricant 226 Press spring 228 Main blade 230 Toner recovery screw 232 Leveling blade 234 Housing 240 Charging unit 260 Exposure unit 280 Development unit 282 Development roller 282A Development sleeve 282B Development magnet roll 284 Stirring roller 286 , 320 Conveying roller 288 First developer supply chamber 290 Second developer supply chamber 291 Discharge unit 292 Development region 294 Restriction blade 296 Development casing 298 Partition unit 30 Toner replenishing unit 310 magnetic brush formed roller 310A sleeve 310B magnet roll 322 developer feeding chamber 330 the magnetic plate 340 casing 350 magnetic brush formed area MB magnetic brush

Claims (7)

A rotatable image carrier;
A lubricant application section for applying a lubricant to the surface of the image carrier;
An exposure unit that exposes the image carrier;
A developing unit for developing the image carrier exposed by the exposing unit with toner;
A cleaning unit for cleaning the surface of the image carrier;
A magnetic brush forming portion for forming a magnetic brush for rubbing the surface of the image carrier;
Equipped with a,
Said magnetic brush forming unit, when the image forming processing by the image forming apparatus is not performed for a predetermined time or more, the image forming apparatus that to form the magnetic brush.   The image forming apparatus according to claim 1, wherein the magnetic brush forming unit is disposed upstream of the developing unit and downstream of the exposure unit in the rotation direction of the image carrier.   The image forming apparatus according to claim 1, wherein the magnetic brush forming unit forms the magnetic brush by using a developer discharged from the developing unit.   The image forming apparatus according to claim 1, wherein the lubricant is contained in an external additive in the toner. 5. The image according to claim 3, wherein the magnetic brush forming unit discharges toner contained in the developer before forming the magnetic brush, thereby reducing the toner concentration of the magnetic brush to a predetermined concentration or less. Forming equipment. The magnetic brush forming unit includes a roller having a plurality of magnetic poles fixedly arranged in an inner circumferential direction, and a rotatable sleeve provided on the surface of the roller, and the magnetic brush forming unit is configured to rotate by the magnetic force of the magnetic pole and the rotating operation of the sleeve. Forming the magnetic brush,
Before when the rotational torque of Kizo carrier is less than the predetermined value, the rotational speed of the sleeve is provided with a control unit for the rotating torque for controlling the sleeve on the size Kunar so than is the predetermined value or more the image forming apparatus according to any one of claims 1-4. Said magnetic brush forming unit, when the humidity in the surrounding of the image forming apparatus is not less than the predetermined humidity, the image forming apparatus according to any one of claim 1 to 6 forming the magnetic brush.

Images