JP2010230931A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming apparatus capable of suppressing the occurrence of so-called, "ghost upon continuous printing" when continuously forming images from the initial stage of starting the operation of a latent image carrier. <P>SOLUTION: The image forming apparatus includes: the latent image carrier which is rotationally driven so that an electrostatic latent image may be formed on the surface thereof in accordance with image information; a developing means for developing the electrostatic latent image formed on the surface of the latent image carrier with toner; a cleaning means for cleaning the surface of the latent image carrier; a lubricant supply means for supplying lubricant to the surface of the latent image carrier while varying the supply amount; a determination means for determining whether the latent image carrier is in an initial supply mode in which the latent image carrier satisfies a predetermined condition after starting the operation or in a normal supply mode other than the initial supply mode; and a supply amount varying means for varying the supply amount of the lubricant by the lubricant supply means based on the determination result obtained by the determination means. <P>COPYRIGHT: (C)2011,JPO&amp;INPIT

Description

  The present invention relates to an image forming apparatus.

  Conventionally, in the above image forming apparatus, when the image forming process is repeated, the history of the image formed on the latent image carrier is changed into an image formed on the latent image carrier after that due to various factors. It is known that it will affect and cause various image quality degradations.

  Therefore, as a technique for preventing the image quality deterioration caused by repeatedly performing the above-described image forming process, for example, JP-A-08-220936, JP-A-2005-099649, JP-A-2008-122870, and JP-A-2008. No. 139804 has already been proposed.

  The electrophotographic recording apparatus according to Japanese Patent Application Laid-Open No. 08-220936 is moved in one direction, and a toner image is formed along with the movement in the one direction, and the photosensitive member is in pressure contact with the photosensitive member. A transfer roller for transferring the toner image onto the recording paper passing through the pressure contact portion, and a tip portion of the transfer roller that is inclined in the counter direction with respect to the moving direction of the photoconductor, and the photoconductor after the transfer by the transfer roller is completed. In an electrophotographic recording apparatus provided with a cleaning blade for removing toner remaining on the surface, the toner is applied to the transfer roller before the start of use of the apparatus, and after the start of use of the apparatus, the transfer roller is exposed to light when the photoreceptor is moved for the first time. It is configured to include a lubricant that is transferred to the body.

Further, an image forming apparatus according to the above Japanese Patent Application Laid-Open No. 2005-099649 includes an image carrier,
Charging means for charging the surface of the image carrier;
Developing means for supplying toner to the surface of the image carrier;
Lubricant supply means for performing a lubricant supply operation for supplying a lubricant to the surface of the image carrier through a supply member facing the image carrier;
Supply control means for causing the lubricant supply means to execute a lubricant supply operation at a predetermined timing other than the image forming operation.

  Further, the image forming apparatus according to the above-mentioned Japanese Patent Application Laid-Open No. 2008-122870 has an image carrier, and the image carrier before use is one to which a lubricant is applied.

  In addition, the image forming apparatus according to Japanese Patent Application Laid-Open No. 2008-139804 forms an image carrier, a charging unit for uniformly charging the image carrier, and a latent image on the surface of the charged image carrier. A latent image forming means; a developing means for developing a latent image formed on the surface of the image carrier with a developer containing toner to which at least a lubricant is externally added to form a toner image; and the image carrier. The image carrier surface before use in an image forming apparatus comprising: a transfer unit that transfers a toner image formed on the surface of the image carrier to a transfer member; and a cleaning unit that removes residual toner on the surface of the image carrier after transfer. In this configuration, a lubricant is applied in advance.

Japanese Patent Laid-Open No. 08-220936 JP 2005-099649 A JP 2008-122870 A JP 2008-139804 A

  By the way, the problem to be solved by the present invention is an image forming apparatus capable of suppressing the occurrence of so-called “continuous print ghost” during the continuous image formation from the beginning of the use of the latent image carrier. Is to provide.

That is, the invention described in claim 1 is a latent image carrier in which an electrostatic latent image corresponding to image information is formed on the surface by being rotationally driven,
Developing means for developing the electrostatic latent image formed on the surface of the latent image carrier with toner;
Cleaning means for cleaning the surface of the latent image carrier;
Lubricant supply means for supplying a lubricant with a variable supply amount to the surface of the latent image carrier;
Discriminating means for discriminating whether an initial supply mode that satisfies a predetermined condition after the latent image carrier starts use or a normal supply mode other than the initial supply mode;
An image forming apparatus comprising: a supply amount changing unit that changes a supply amount of lubricant by the lubricant supply unit based on a determination result of the determination unit.

  According to a second aspect of the present invention, the latent image carrier is integrally formed as an image forming unit together with members disposed around the latent image carrier, and the image formation The unit is configured to be detachable from the main body of the image forming apparatus, and the determination unit detects a replacement of the image forming unit and satisfies a predetermined condition after the latent image carrier starts use. The image forming apparatus according to claim 1, wherein it is determined whether or not an initial supply mode is set.

  Further, in the invention described in claim 3, the lubricant supply means supplies the lubricant supplied to the surface of the latent image carrier by changing a bias voltage applied to the lubricant supply means. The image forming apparatus according to claim 1, wherein the image forming apparatus is configured to be variable.

  According to a fourth aspect of the present invention, the determination means detects whether or not the initial supply mode is detected by detecting the cumulative number of rotations of the latent image carrier after detecting the replacement of the image forming unit. 4. The image forming apparatus according to claim 1, wherein the image forming apparatus discriminates the image forming apparatus.

  Further, in the invention described in claim 5, the supply amount changing means changes the supply amount of the lubricant during non-image formation when it is determined that the determination means has shifted from the initial supply mode to the normal supply mode. The image forming apparatus according to claim 1, wherein the image forming apparatus is an image forming apparatus.

  The invention described in claim 6 further comprises image density changing means for changing the image density when the supply amount changing means changes the supply amount of the lubricant. 6. The image forming apparatus according to any one of items 1 to 5.

  Furthermore, the invention described in claim 7 includes an environment detection unit that detects an environmental condition in which the image forming apparatus is installed, and the determination unit is predetermined after the latent image carrier starts to be used. 7. The apparatus according to claim 1, wherein the initial supply mode is determined when a predetermined condition is satisfied and a detection result of the environment detection unit satisfies a predetermined condition. The image forming apparatus according to any one of the above.

  In the invention described in claim 8, the lubricant supply means is configured to supply a lubricant to the surface of the latent image carrier by being driven to rotate, and the supply amount changing means includes: 8. The image forming apparatus according to claim 1, wherein the supply amount of the lubricant is changed by changing a rotation speed of the lubricant supply unit.

  According to the first aspect of the present invention, compared to the case where the present configuration is not provided, the image quality referred to as so-called “continuous print ghost” is formed at the time of continuous image formation from the beginning of using the latent image carrier. It is possible to suppress the occurrence of the decrease.

  According to the second aspect of the present invention, the replacement of the latent image carrier can be easily detected as compared with the case where the present configuration is not provided.

  According to the invention described in claim 3, the supply amount of the lubricant can be changed.

  According to the fourth aspect of the present invention, it is possible to easily determine whether or not it is the initial supply mode.

  According to the fifth aspect of the present invention, it is possible to avoid the change in the supply amount of the lubricant from appearing on the image.

  According to the sixth aspect of the present invention, it is possible to avoid fluctuations in the image density.

  According to the seventh aspect of the present invention, the consumption of the lubricant can be saved as compared with the case where the present configuration is not provided.

  According to the eighth aspect of the present invention, the supply amount can be changed without depending on the type of the lubricant.

FIG. 1 is a schematic configuration diagram showing a tandem type full-color printer as an image forming apparatus according to Embodiment 1 of the present invention. FIG. 2 is a block diagram showing an image forming unit of a tandem type full color printer as an image forming apparatus according to Embodiment 1 of the present invention. FIG. 3 is a block diagram of the control circuit in the present invention. FIG. 4 is a graph showing the Zn coverage on the surface of the photoreceptor when AC is applied. FIG. 5 is a graph showing the change in Zn coverage when the photoreceptor is rotated by applying AC. FIG. 6 is an explanatory diagram showing the mechanism of occurrence of continuous print ghosts. FIG. 7 is an explanatory diagram showing an image in which a continuous print ghost has occurred. FIG. 8 is a flowchart showing the operation. FIG. 9 is a chart showing Vh of the photosensitive member when Vpp is changed at the time of transition from the initial mode to the normal coating mode. FIG. 10 is a graph showing the effect of continuous print ghosting by Vpp and the effect on blade noise.

  Embodiments of the present invention will be described below with reference to the drawings.

Embodiment 1
FIG. 2 is a schematic configuration diagram showing a tandem type digital color printer as an image forming apparatus according to Embodiment 1 of the present invention. The tandem type digital color printer includes an image reading device, and functions as a full-color copying machine or a facsimile. Of course, the image forming apparatus may not include an image reading apparatus and may form an image based on image data output from a personal computer (not shown).

  In FIG. 2, reference numeral 1 denotes a main body of a tandem type digital color printer. The digital color printer main body 1 reads an image of an original 2 on the upper side of one side (left side in the illustrated example). A device 3 is provided. Further, inside the color printer main body 1, image data output from the image reading device 3, a personal computer (not shown) or the like, or image data sent via a telephone line or a LAN is previously stored. An image processing device 4 that performs predetermined image processing is disposed, and an image based on image data that has been subjected to predetermined image processing by the image processing device 4 is provided inside the digital color printer main body 1. Is output.

  The image reading device 3 opens and closes the platen cover 6 to place the document 2 on the platen glass 7 and illuminates the document 2 placed on the platen glass 7 with the light source 8. The reflected light image is scanned and exposed on an image reading element 13 made of a CCD or the like through a reduction scanning optical system made up of a full rate mirror 9, half rate mirrors 10, 11 and an imaging lens 12, and this image reading element 13 is configured to read the image of the document 2 at a predetermined dot density.

  The image of the document 2 read by the image reading device 3 is, for example, the image processing device 4 as document reflectance data of three colors of red (R), green (G), and blue (B) (for example, 8 bits each). In this image processing apparatus 4, shading correction, position shift correction, lightness / color space conversion, gamma correction, frame deletion, color / moving editing, etc. are predetermined for the reflectance data of the document 2. Image processing is performed.

  The image data that has been subjected to the predetermined image processing by the image processing device 4 as described above is similarly processed by the image processing device 4 in yellow (Y), magenta (M), cyan (C), and black (K). After being converted into image data of four colors, image forming units 14Y, 14M, 14C, and 14K for image forming units 14Y, 14M, 14C, and 14K for yellow (Y), magenta (M), cyan (C), and black (K) are provided. The image exposure apparatuses 15Y, 15M, 15C, and 15K perform image exposure with the laser beam LB in accordance with the corresponding color image data.

  Incidentally, inside the tandem type digital color printer main body 1, as described above, four image forming units 14Y, 14M of yellow (Y), magenta (M), cyan (C), and black (K) are provided. 14C and 14K are arranged in parallel at a certain interval in the horizontal direction.

  As shown in FIG. 2, these four image forming units 14Y, 14M, 14C, and 14K are configured in the same manner except for the color of the image to be formed, and are roughly classified in advance along the direction of arrow A. A photosensitive drum 16 as an image carrier that is rotationally driven at a speed, a scorotron 17 for primary charging that uniformly charges the surface of the photosensitive drum 16, and a surface of the photosensitive drum 16 corresponding to each color. An image exposure device 15 as image writing means for performing image exposure based on image data to form an electrostatic latent image, and a developing device 18 for developing the electrostatic latent image formed on the photosensitive drum 16 with toner. And a cleaning device 19 that removes toner and the like remaining on the surface of the photosensitive drum 16, a cleaning corotron 20, and a static elimination lamp 48. .

  The digital color printer according to this embodiment is a highly productive machine with a large number of recording media capable of forming an image per unit time. The surface of the photosensitive drum 16 has a hardness. Those having a long life by being covered with a high overcoat layer are used, and the rotational speed (peripheral speed) of the photosensitive drum 16 is set to about 440 mm / sec, for example.

  As shown in FIG. 2, the image exposure device 15 modulates the semiconductor laser LD in accordance with the corresponding color image data output from the image processing device 4, and converts the laser beam LB from the semiconductor laser LD into image data. In response, it emits. The laser beam LB emitted from the semiconductor laser LD is irradiated onto the surface of the rotary polygon mirror 23 via the mirrors 21, 22 and the like, and after being deflected and scanned by the rotary polygon mirror 23, an f-θ lens (not shown) Scanning exposure is performed on the photosensitive drum 16 through the reflection mirrors 22, 24, 25, and the like along the rotation axis direction (main scanning direction).

  As shown in FIG. 2, the image processing device 4 exposes the image forming units 14Y, 14M, 14C, and 14K for the respective colors of yellow (Y), magenta (M), cyan (C), and black (K). Corresponding color image data is sequentially output to the devices 15Y, 15M, 15C, and 15K, and laser light LB emitted according to the image data from these image exposure devices 15Y, 15M, 15C, and 15K corresponds. The surfaces of the photosensitive drums 16Y, 16M, 16C, and 16K are scanned and exposed to form electrostatic latent images. The electrostatic latent images formed on the surfaces of the photosensitive drums 16Y, 16M, 16C, and 16K are respectively yellow (Y), magenta (M), and cyan (C) by the developing devices 18Y, 18M, 18C, and 18K. , And developed as a toner image of each color of black (K).

  Each color of yellow (Y), magenta (M), cyan (C), and black (K) sequentially formed on the photosensitive drums 16Y, 16M, 16C, and 16K of the image forming units 14Y, 14M, 14C, and 14K. As shown in FIG. 2, the toner image is transferred onto the intermediate transfer belt 26 as an endless belt-like intermediate transfer member disposed below each of the image forming units 14Y, 14M, 14C, and 14K at the primary transfer position N1. Multiple transfer is performed by the primary transfer rolls 27Y, 27M, 27C, and 27K. The intermediate transfer belt 26 is wound around the drive roll 28, the tension applying roll 29, the meandering control roll 30, the driven roll 31, the back support roll 32, and the driven roll 33 with a constant tension. It is circulated and driven at a predetermined moving speed along the direction of arrow B by a drive roll 28 that is rotationally driven by a dedicated drive motor with excellent constant speed (not shown). As the intermediate transfer belt 26, for example, a belt formed of a flexible synthetic resin film such as polyimide or polyamideimide having flexibility is used.

  The yellow (Y), magenta (M), cyan (C), and black (K) toner images transferred onto the intermediate transfer belt 26 in a multiple manner are transferred to the back support roll 32 and the secondary transfer means. By a transfer bias applied between the secondary transfer roll 34 and the secondary transfer position N2, the toner image corresponding to the color of the image to be transferred is transferred onto the recording paper 35 as a recording medium by the electrostatic force at the secondary transfer position N2. The recorded recording paper 35 is transported to the fixing device 38 by two transport belts 36 and 37. The recording paper 35 onto which the toner images of the respective colors have been transferred undergoes a fixing process with heat and pressure by a fixing device 38 and is discharged onto a discharge tray 39 provided outside the printer main body 1.

  As shown in FIG. 2, the recording paper 35 is of a desired size and material from a paper feed tray 40 disposed at the bottom of the printer main body 1, and includes a paper feed roll 41 and a pair of paper separation rolls (not shown). Are fed one by one by one and are temporarily transported to a registration roll 46 through a paper transport path 45 in which a plurality of transport rolls 42, 43, 44 are arranged. The recording paper 35 supplied from the paper feed tray 40 is sent to the secondary transfer position N2 of the intermediate transfer belt 26 by a registration roll 46 that is rotationally driven at a predetermined timing. Although only one sheet feeding tray 40 is illustrated, a plurality of sheet feeding trays having recording papers 35 having different sizes or the same size may be provided. A large number of recording sheets 35 can be fed.

  The photosensitive drums 16Y, 16M, 16C, and 16K are charged with residual toner by the pre-cleaning corotron 20 after the toner image transfer process is completed, and are also remained by the cleaning devices 19Y, 19M, 19C, and 19K. The toner and the like are removed, and the residual charge is removed by the charge removal lamp 48 to prepare for the next image forming process. Further, residual toner, paper dust, and the like are removed from the intermediate transfer belt 26 by a belt cleaner 47 disposed so as to face the driven roll 33.

  FIG. 1 is a block diagram showing an image forming unit of a digital color printer configured as described above.

  As shown in FIG. 1, the image forming unit for each color of yellow (Y), magenta (M), cyan (C), and black (K) of this digital color printer has a photosensitive drum 16 and the photosensitive drum 16. The charging device 17 and the developing device 18, the pre-cleaning corotron 20, the cleaning device 19, the static elimination lamp 48, and the like disposed around are integrally united to form the image forming units 14Y, 14M, 14C, and 14K. These image forming units 14Y, 14M, 14C, and 14K are configured to be detachable from the digital color printer main body 1 individually. The image forming units 14Y, 14M, 14C, and 14K are integrated with the image forming units 14Y, 14M, 14C, and 14K including the photosensitive drum 16 when the photosensitive drum 16 reaches the end of its life. It can be easily exchanged by attaching to and detaching from the color printer main body 1. The image forming units 14Y, 14M, 14C, and 14K are attached with a crumb 49 as a storage means for determining whether the image forming unit is new or used. 49, when the image forming unit 14 is mounted on the digital color printer main body 1, reads and writes information stored in the crumb 49 by wired or wireless communication with the digital color printer main body 1 side via a socket or the like. It is possible.

  As shown in FIG. 1, the cleaning device 19 of the image forming unit 14 includes a cleaning blade 50 that contacts the surface of the photosensitive drum 16 and a lubricant supply unit that applies a lubricant to the surface of the photosensitive drum 16. The application brush 51, the lubricant 52 made of a rod-like solid such as zinc stearate (ZnSt) that contacts the surface of the application brush 51, and the unnecessary lubricant 52 that contacts the surface of the application brush 51 are scraped off. As a result, the flicker bar 53 for adjusting the supply amount of the lubricant 52 to the surface of the photosensitive drum 16 and the toner removed by the cleaning blade 50 are rotationally driven at a predetermined timing to be discharged to the outside. And a discharge auger 54.

  The application brush 51 is rotationally driven at a predetermined speed along the direction of arrow C as shown in FIG. The application brush 51 is formed in a cylindrical shape by flocking conductive fibers 56 at a predetermined density on the outer peripheral surface of a metal core member 55, for example. For example, Vpp 1.5 kV and frequency 780 Hz are applied as the first alternating voltage, and Vpp 1.0 kV and frequency 780 Hz are applied in a switchable manner as the second alternating voltage. Note that the DC voltage Vdc is not applied to the cored bar member 55 (Vdc = 0V).

  By the way, in this embodiment, a lubricant supply means for supplying a lubricant with a variable supply amount to the surface of the latent image carrier, and a predetermined condition after the latent image carrier starts to be used. Discriminating means for discriminating between an initial supply mode and a normal supply mode other than the initial supply mode, and a supply amount changing means for changing the amount of lubricant supplied by the lubricant supply member based on the determination result of the discriminating means. It is comprised so that it may be provided.

  FIG. 3 is a block diagram showing a control circuit of the digital color printer.

  In FIG. 3, reference numeral 100 denotes a CPU as a control means that also has a function as a discrimination means, and this CPU 100 is an environment for detecting at least one environmental condition of temperature and humidity where the digital color printer is installed. Signals from the sensor 101 and a crumb detection unit 102 that detects information stored in a crumb 49 provided in the image forming unit 14 are input.

  In addition, the CPU 100 rotates the photosensitive drum 14 of each image forming unit 14, and the photosensitive member motor 103 separately provided for the photosensitive drum 14 and the coating member 51 that rotationally drives the coating brush 51. Control signals are output to the motors 104, respectively. Further, the photosensitive drum 16 is provided with a rotational speed counter 105 that cumulatively counts the rotational speed, and the count value from the rotational speed counter 105 is input to the CPU 100.

  Further, the CPU 100 outputs a signal for changing the supply amount of the lubricant by changing the AC bias application voltage to the coating member AC bias application power source 106 as supply amount changing means. This application member AC bias application power source 106 is, for example, an AC bias applied to the cored bar member 55 of the application brush 51, Vpp 1.5 kV as the first AC voltage, frequency 780 Hz, and Vpp 1.0 kV as the second AC voltage. The frequency is switched to 780 Hz and applied.

  Further, a process control signal is output from the CPU 100 to the process control unit 107 of the printer, and the process control unit 107 executes process control such as an image density control operation.

  In this embodiment, as shown in FIG. 1, the image forming unit 14 including the photosensitive drum 16 is configured to be detachable from the printer main body 1, and a crumb 49 provided in the image forming unit 14 is provided. Depending on the information, the initial state in which the digital color printer is used for the first time after being installed in the user's office or the like, or the initial state of each image forming unit that starts using one of the image forming units 14 replaced with a new image forming unit 14 The CPU 100 determines whether the initial supply mode is in the state or the normal supply mode other than the initial supply mode.

  Here, the initial supply mode is determined as the initial supply mode when a predetermined condition is satisfied after the use of the image forming unit 14 is started as well as immediately after the use of the image forming unit 14 is started. Is done. As the predetermined condition, for example, the cumulative rotation number counted by the rotation number counter 105 of the photosensitive drum 16 of the image forming unit 14 after the use of the image forming unit 14 is started is a predetermined value. Or a case where an image is formed on a predetermined number of recording sheets by the image forming unit 14 after the use of the image forming unit 14 is started.

  The CPU 100 is configured to change the amount of lubricant supplied to the surface of the photosensitive drum 16 of the image forming unit 14 depending on whether or not the initial supply mode is set. As a means for the CPU 100 to change the supply amount of the lubricant, an AC bias voltage applied to the application brush 51 of the cleaning device 19 is applied to the first AC of Vpp 1.5 kV and frequency 780 Hz by the application member AC bias application power source 106. The voltage is switched to the second AC voltage of Vpp 1.0 kV and frequency 780 Hz.

  When the AC bias voltage applied to the application brush 51 of the cleaning device 19 is changed, the amount of lubricant supplied to the surface of the photosensitive drum 16 changes as shown in FIG. Here, the supply amount of zinc stearate as the lubricant is measured by, for example, the coverage of zinc stearate that covers the surface of the photosensitive drum 16.

  In the above configuration, in the digital color printer according to the present embodiment, the image formed before the start of the use of the latent image carrier from the beginning when the image is continuously formed as a ghost as follows. It is possible to suppress the occurrence of a so-called “continuous print ghost” image quality degradation that appears.

  In the digital color printer configured as described above, as shown in FIG. 2, in each of the yellow, magenta, cyan, and black image forming units 14Y, 14M, 14C, and 14K, the photosensitive drums 16Y, 16M, and 16C. A toner image corresponding to the image information is formed on 16K, and the toner images formed on the photosensitive drums 16Y, 16M, 16C, and 16K are primary-transferred onto the intermediate transfer belt 26 in a multiplexed manner, and then recorded. Secondary transfer is performed collectively on the paper 35 to form a full-color or monochrome image.

  At this time, the surfaces of the photosensitive drums 16Y, 16M, 16C, and 16K are charged to a predetermined negative potential by a scorotron 17 as a primary charger as shown in FIG. 18, the image portion is subjected to image exposure to form an electrostatic latent image corresponding to the image information, and the electrostatic latent images formed on the surfaces of the photosensitive drums 16 </ b> Y, 16 </ b> M, 16 </ b> C, and 16 </ b> K are developed by the developing device 18. The toner image is formed by reversal development.

  To the surface of the toner used in the developing device 18, an external additive made of fine particles having a very small particle diameter made of silica, metal oxide particles, or the like is added in order to control charging characteristics, graininess, and the like. . Since this external additive controls the charging characteristics, graininess, etc. of the toner, it basically has the characteristic of being charged negatively with the same polarity as the original charging polarity of the toner.

  By the way, as the photosensitive drum 16, the one whose surface is coated with a hard overcoat layer and has a long life is used. In the initial mode, the photosensitive drum 16 has just started to be used. The surface of the photosensitive drum 16 is not supplied with sufficient lubricant by the application brush 51.

  Therefore, in the developing device 18, when developing the electrostatic latent image formed on the surface of the photosensitive drum 16 by the rising of the developer, a part of the external additive added to the surface of the toner together with the toner. However, it peels off from the toner surface and adheres to the surface of the photosensitive drum 16. As shown in FIG. 1, most of the external additive adhering to the surface of the photosensitive drum 16 passes through the primary transfer position of the intermediate transfer belt 26 as it is to reach the cleaning device 19, and the cleaning device 19 performs cleaning. It is scraped off by the blade 50 and removed.

  However, in the digital color printer, when the photosensitive drum 16 is in the initial mode shortly after use, the lubricant coverage on the surface of the photosensitive drum 16 is low as shown in FIG. In particular, in an environment of low temperature and low humidity, due to the physical properties of the cleaning blade 50 of the cleaning device 19 and the like, the external additive adhering to the surface of the photosensitive drum 16 cannot be reliably removed, and the photosensitive drum 16 The external additive adhering to the surface may pass through the cleaning blade 50 of the cleaning device 19 as it is and remain on the surface of the photosensitive drum 16, and may shift to the next image forming process.

  As described above, when the external additive attached to the surface of the photosensitive drum 16 passes through the cleaning blade 50 of the cleaning device 19 and remains on the surface of the photosensitive drum 16, the process proceeds to the next image forming process. When the image forming process is repeatedly performed such as when a plurality of identical images are printed so that the same area on the surface of the photosensitive drum 16 continuously becomes an image area a plurality of times, the developing device 18 Thus, the development with the developer is repeatedly received, and the external additive attached to the surface of the photosensitive drum 16 together with the toner is gradually accumulated. The external additive gradually accumulated on the surface of the photosensitive drum 16 is not only accumulated at the original developing position, but also the rotational direction of the photosensitive drum 16 from the original developing position by a plurality of image forming steps. It moves gradually to the downstream side along.

Then, as shown in FIG. 6A, the negatively charged external additive 81 that has passed through the cleaning blade 50 of the cleaning device 19 remains on the surface of the photosensitive drum 16 for the next image forming process. In addition, when the surface of the photosensitive drum 16 is charged by the scorotron 17, the surface of the photosensitive drum 16 including the region where the negatively charged external additive 81 is attached is negatively charged. At this time, the scorotron 17 charges the surface of the photosensitive drum 16 so that the surface of the photosensitive drum 16 becomes equal to a predetermined negative polarity potential V _H, and therefore, the negatively charged external additive 81 is charged. As shown in FIG. 6B, the region of the photosensitive drum 16 where the toner adheres is charged such that the potential including the negative charge of the external additive 81 is equal to the predetermined potential V _H. Is done. As a result, in the region of the photosensitive drum 16 to which the negatively charged external additive 81 is adhered, the surface potential excluding the negatively charged external additive 81 has an external potential as shown by a broken line in FIG. The potential is lower than the area of the photosensitive drum 16 where the additive 81 is not attached. In FIG. 6, a small circle 82 with a minus sign drawn therein indicates a negative charge for charging the surface of the photosensitive drum 16 by the scorotron 17.

  Then, as shown in FIG. 6C, the surface of the photosensitive drum 16 is subjected to image exposure on the image portion to form an electrostatic latent image, but then passes through the developing region of the developing device 18. In this case, when the amount of the negatively charged external additive 81 adhering to the surface of the photosensitive drum 16 reaches a certain amount, the negatively charged external additive 81 is transferred to the development nip as shown in FIG. By being scraped off by the magnetic brush in the region, the potential of the portion is further lowered (negative charge potential is lowered).

  The external additive 81 adhering to the surface of the photosensitive drum 16 passes through the developing nip region of the developing device 18 every time the photosensitive drum 16 makes one rotation, but the amount of the external additive 81 is small. The inside passes through the developing nip region 31 as it is, and when the accumulated amount reaches a certain amount, the negatively charged external additive 81 is scraped off by the magnetic brush in the developing nip region.

  As a result, the surface of the photosensitive drum 16 after passing through the developing device 18 is, as shown in FIG. 6 (e), a portion 83 where the negatively charged external additive 81 is scavenged. A large amount of negative polarity toner 84 is reversal-developed by the amount corresponding to the decrease in potential as compared with the surroundings, and an image continuously formed before that is, for example, as shown in FIG. With respect to a solid image 85 having a predetermined width W along the axial direction and linearly formed along the rotation direction of the photosensitive drum 16, the photosensitive drum 16 of the solid image 85 has a predetermined width W. A so-called “continuous print ghost” occurs in which an image that does not originally exist on the downstream side in the rotation direction appears as a ghost image 86.

  Such a so-called “continuous print ghost” is an initial state immediately after the start of use of the digital color printer, or when the photosensitive drum 16 is in a new initial state after the image forming unit 14 is replaced, and / or a cleaning device. It has been found that the cleaning performance of the 19 cleaning blades 50 is likely to occur in a low-temperature and low-humidity environment where the cleaning performance tends to deteriorate.

  Therefore, in this embodiment, as shown in FIG. 8, when the CPU 100 detects the replacement of the image forming unit 14 (step 101), it is determined whether the environment is a low temperature or low humidity environment based on the signal from the environment sensor 101. Is determined (step 102), and when it is determined that the environment is a low temperature or low humidity environment, the initial application mode is executed (step 103), and after the initial application mode ends (step 104), the process control unit A process control for controlling the image density and the like is performed by 107 (step 105), and a normal operation state is entered (step 106). If it is determined that the environment is not low temperature or low humidity, the process control unit 107 performs process control for controlling the image density and the like in the normal application mode (step 105), and shifts to a normal operation state (step 105). Step 106).

  Here, the low temperature or low humidity environment is, for example, a case where the temperature is 15 ° C. or lower and the relative humidity is 30% RH or lower.

  Note that the process control for changing the image density by the process control unit 107 after performing the initial coating mode is performed when the AC bias voltage applied to the coating brush 51 is switched as shown in FIG. 16 charging potential Vh may fluctuate and there is a possibility that density fluctuation may occur as the AC bias voltage applied to the application brush 51 is switched. Therefore, process control is performed to suppress density fluctuation. is there.

  On the other hand, when the CPU 100 determines that the environment is a low temperature or low humidity environment (step 102), the CPU 100 executes the initial application mode (step 103). In this initial application mode, the CPU 100 switches the AC bias voltage applied to the application brush 51 from the second AC voltage having the normal Vpp of 1.0 kV and the frequency of 780 Hz to the first AC voltage having the frequency of Vpp of 1.5 kV and the frequency of 780 Hz. Thus, the amount of lubricant applied to the surface of the photosensitive drum 16 is increased from about 1.4 (atm%) to about 1.7 (atm%), and the photosensitive drum 16 is set to a predetermined number of times. Only rotationally drive.

  In this way, the external additive remaining on the surface of the photoconductive drum 16 increases the amount of lubricant applied to the surface of the photoconductive drum 16, whereby the cleaning blade 50 and the photoconductive drum 16 of the cleaning device 19 are increased. Since the frictional force with the surface increases, it is effectively removed by the cleaning blade 50, and the occurrence of continuous print ghost is suppressed.

Embodiments The inventors made a prototype of an image forming unit bench model as shown in FIG. 1 and performed continuous printing when the amount of lubricant supplied to the surface of the photosensitive drum 16 by the application brush 51 was changed. We confirmed how the occurrence of ghost changes.

As a cleaning member, an elastic blade made of urethane was used, and a ZnSt rod-like body was used as a lubricant, and only 9 mg / kcyc was supplied. The developing roll of the developing device was driven to rotate with respect to the photosensitive drum 16 at a peripheral speed ratio of 1.65, and the toner amount on the developing roll was set to 350 ± 50 mg / m ² . Further, as the developer, a toner obtained by adding silica powder particles as a charge control agent to the outer surface of the toner was used.

Example 1
Initial application mode The clearing of the rotation speed counter 105 that is performed when the image forming unit is replaced is detected, and the temperature and humidity detected by the environment sensor 101 are monitored to determine whether the environment is a predetermined low temperature or low humidity environment. .

  As the coating brush 51, a conductive fiber: a beltron having a thickness of 10 d and 50 kf planted per unit is used, and the photosensitive drum 16 is driven to rotate at a peripheral speed ratio of 0.86. 16 was rotated 180 times to apply the lubricant.

  Further, Vpp 1.5 kV, frequency 780 Hz, and Vdc = 0 V were applied to the application brush 51 as an AC bias voltage.

Normal operation mode After the initial coating mode is completed, an image patch is formed on the surface of the photoconductor drum 16, the density of the image patch is measured, and the surface potential of the photoconductor drum 16 is adjusted so as to obtain a predetermined density. Controlled.

  The applied voltage of the application brush 51 was changed to Vpp 1.0 kV, frequency 780 Hz, and Vdc = 0 V as an AC bias voltage.

  FIG. 10 shows the results of Example 1 above.

As apparent from FIG. 10, in the initial application mode, by applying Vpp 1.5 kV, frequency 780 Hz, and Vdc = 0 V as the AC bias voltage to the application brush 51, the density change ΔL ^* due to the continuous print ghost is targeted. It can be seen that it can be substantially suppressed to 0.5 or less.

Here, the density change ΔL ^* due to the continuous print ghost is, as shown in FIG. 7, the density of the low density band pattern on the downstream side of the central linear solid image 85 and the downstream of the linear solid image 85 in the central area. This is a lightness difference ΔL ^* with the density of the low-density band-shaped pattern in the region other than the downstream of the linear solid image 85 adjacent to the side.

  Note that a lubricant amount detecting means for detecting the amount of lubricant on the surface of the photosensitive drum may be provided, and the amount of lubricant applied may be changed based on the detection result of the lubricant amount detecting means. .

  16: photosensitive drum, 18: developing device, 19: cleaning device, 51: coating brush, 52: lubricant, 100: CPU, 106: AC bias application power source.

Claims (8)

A latent image carrier that is driven to rotate and forms an electrostatic latent image according to image information on the surface;
Developing means for developing the electrostatic latent image formed on the surface of the latent image carrier with toner;
Cleaning means for cleaning the surface of the latent image carrier;
Lubricant supply means for supplying a lubricant with a variable supply amount to the surface of the latent image carrier;
Discriminating means for discriminating whether the latent image carrier is in an initial supply mode that satisfies a predetermined condition after starting use or a normal supply mode other than the initial supply mode;
An image forming apparatus comprising: a supply amount changing unit that changes a supply amount of the lubricant by the lubricant supply unit based on a determination result of the determination unit.   The latent image carrier is integrally formed as an image forming unit together with members disposed around the latent image carrier, and the image forming unit is detachable from the image forming apparatus main body. The discriminating means detects the replacement of the image forming unit and discriminates whether or not the latent image carrier is in an initial supply mode that satisfies a predetermined condition after starting use. The image forming apparatus according to claim 1.   The lubricant supply means is configured to vary the supply amount of lubricant supplied to the surface of the latent image carrier by changing a bias voltage applied to the lubricant supply means. The image forming apparatus according to claim 1.   4. The discriminating unit according to claim 1, wherein the discriminating unit discriminates whether or not the initial supply mode is set by detecting the cumulative number of rotations of the latent image carrier after detecting the replacement of the image forming unit. The image forming apparatus according to any one of the above.   5. The supply amount change unit according to claim 1, wherein the supply amount change unit changes the supply amount of the lubricant during non-image formation when the determination unit determines that the normal supply mode is changed from the initial supply mode. An image forming apparatus according to claim 1.   6. The image forming apparatus according to claim 1, further comprising an image density changing unit that changes an image density when the supply amount changing unit changes a supply amount of the lubricant.   An environmental detection unit that detects an environmental condition in which the image forming apparatus is installed; and the determination unit is a case where a predetermined condition is satisfied after the latent image carrier starts use, and 7. The image forming apparatus according to claim 1, wherein when the detection result of the environment detection unit satisfies a predetermined condition, it is determined that the initial supply mode is set.   The lubricant supply means is configured to supply a lubricant to the surface of the latent image carrier by being rotationally driven, and the supply amount changing means changes a rotation speed of the lubricant supply means. The image forming apparatus according to claim 1, wherein the supply amount of the lubricant is changed according to the method.

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