JP5605074B2 - Image forming apparatus - Google Patents

Description

  BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrophotographic image forming apparatus such as a copying machine, a facsimile machine, or a laser beam printer, and in particular, develops an electrostatic latent image formed on an image carrier with a developing device using a two-component developer. The present invention relates to an image forming apparatus that is visualized.

  In an electrophotographic image forming apparatus applied to a copying machine, a facsimile machine, a laser beam printer, etc., after charging a photosensitive member as an image carrier, electrostatic discharge is performed by exposing a document image or writing light according to an image signal. A latent image is formed, and the electrostatic latent image formed on the photoreceptor is developed and visualized by a developing device using a two-component developer, and then the visible image (toner image) on the photoreceptor is transferred. Then, the image is transferred to a transfer material such as transfer paper and fixed by a fixing device to obtain an image.

  A two-component developer (hereinafter referred to as a developer) constitutes a developer by frictionally charging a toner and a carrier, but in general, the charge amount varies depending on environmental conditions, standing time, and the like. That is, even when the same initial agent is used, the developer charge amount changes depending on the installation environment, use environment, etc., and when developing in the state of being changed, the image density increases and becomes excessive, and vice versa. Such a change in density, and in some cases, abnormal images such as background stains, missing images, and carrier adhesion may occur.

  To solve such a problem, a technique is known in which the developer in the developing device is adjusted to an appropriate level by stirring the developer by driving the developing device for a predetermined time. For example, in Patent Document 1, in order to prevent a phenomenon in which a developer in a developing device stays for a long time when image formation with a low image density is continuously performed and the adsorptivity to an image is deteriorated to cause image deterioration. An image forming apparatus in which development is forcibly performed is disclosed. Further, Patent Document 2 discloses an image forming apparatus that forms an image pattern for toner consumption after supplying a developer and forcibly consumes the toner to prevent abnormal images such as scumming or toner scattering generated in the image. Has been.

  Here, the change in the charge amount of the developer is usually mostly in the direction of decreasing due to environmental changes or prolonged standing. Although the developer having a reduced charge amount may be restored to the original proper state by stirring of the developing device, there is a problem that toner scattering occurs during the stirring operation. Further, there is a problem that the developer is deteriorated by stirring for a long time to change the toner surface property and the state of the additive adhered to the toner surface.

  In addition, a technique for adjusting the developer in the developing device to an appropriate level by estimating and detecting the developing characteristics and performing toner consumption and replenishment together with driving of the developing device is known. For example, Patent Document 3 discloses an image forming apparatus that prevents background contamination by detecting in advance conditions under which background contamination is likely to occur and lowering the toner concentration. Patent Document 4 discloses an image forming apparatus that detects a state quantity related to development characteristics and performs stirring of the developer, toner supply, and toner consumption of the development apparatus to achieve desired development characteristics.

  Here, the toner consumption operation as described above (execution of toner consumption) estimates and detects the state of the developer at a certain point in time, calculates the toner consumption to be consumed based on the result, and develops the toner. The image is formed on the photosensitive member by forming an arbitrary photosensitive member potential, developing potential, and latent image potential (toner consumption pattern) so that the amount becomes the consumed amount, and this is collected by a cleaning device. Is done.

  In such a toner consumption operation, unlike a normal image forming operation, a much larger amount of toner is collected than the residual toner collected by the cleaning device after the toner image is transferred to the transfer unit. Become.

  Here, when the amount of toner consumption increases, there arises a problem that the collection capacity of the cleaning device is exceeded. That is, the toner cannot be discharged from the cleaning device to the outside, and the cleaning device fills up with toner, causing leakage of collected toner (waste toner) from the cleaning device and lowering of the cleaning function.

  Also, in order to improve the cleaning performance of the spherical toner that has been adopted in response to the recent increase in image quality, a lubricant application mechanism for applying a lubricant on the photosensitive member is provided in the cleaning device and the rotation direction of the photosensitive member of the cleaning device. However, there is a problem in that the toner filling in the cleaning device also enters the lubricant application mechanism and lowers the lubricant application efficiency. A decrease in the lubricant application function can cause a decrease in cleaning ability, that is, poor cleaning.

  The technique described in Patent Document 1 discloses that the amount of input to the cleaning blade is regulated. However, there is no disclosure about the conveyance of waste toner after cleaning with the blade, and the above problem is not disclosed. It cannot be solved. Patent Document 1 discloses that the operation time of the waste toner discharging unit is made almost twice as long as the time during which the toner is consumed with respect to the capacity of the cleaning unit being exceeded. Since this occurs when toner is input to the cleaning unit in the toner consumption operation, the above-described problem cannot be solved by a configuration in which the discharge operation is performed after the input is completed.

  Japanese Patent Application Laid-Open No. 2005-228561 discloses means for reducing the load on the cleaning blade by intermittently forming a plurality of toner consumption image patterns. Concerning transport of the collected toner after cleaning with the cleaning blade. Is not disclosed at all. Also, Patent Document 3 and Patent Document 4 do not disclose the problem of cleaning when the toner consumption is performed.

  SUMMARY OF THE INVENTION An object of the present invention is to provide an image forming apparatus capable of improving the toner discharge / conveying capability of a cleaning device during toner consumption and preventing cleaning failure and cleaning toner clogging.

In order to achieve such an object, an image forming apparatus according to claim 1 includes an image carrier, a charging device for uniformly charging the image carrier, and an electrostatic image on the uniformly charged image carrier. An exposure device that forms a latent image, a developing device that develops the electrostatic latent image formed on the image carrier with a two-component developer containing toner and a carrier, and a toner image on the image carrier as a transfer member In an image forming apparatus having a transfer device for transferring, and a cleaning device for removing a toner image remaining on the image carrier after transfer from the image carrier, and transporting and discharging the toner image to a predetermined container, the developer state of the developing device is changed. An image quality adjusting unit that estimates or detects, forms a predetermined toner amount on the image carrier based on the information, performs toner consumption, and stabilizes the charge amount of the developer. The linear velocity of the image carrier is Vp, and the cleaning If the linear velocity of the rotating member to the discharge conveying the toner in the apparatus was Vc, by lowering the linear velocity Vp of the normal image forming time than the image bearing member, a Vc / Vp when the toner consumption running, normal work It is larger than Vc / Vp at the time of image.

Further, an invention according to claim 2, in the image forming apparatus according to claim 1, further comprising a temperature and humidity detecting means for detecting the temperature and / or humidity conditions, the image quality adjusting means, temperature and humidity detecting means those depending on the temperature conditions and / or humidity conditions to increase the Vc / Vp by the Turkey lowering the linear velocity Vp of the image carrier than when image formation of normal during running of toner consumption detected by is there.

  According to the present invention, it is possible to improve the toner discharging / conveying capability of the cleaning device during execution of toner consumption, and to prevent defective cleaning and clogging of cleaning toner.

1 is a cross-sectional view illustrating a configuration of an image forming apparatus according to the present invention. 2 is a cross-sectional view illustrating a configuration of an image forming unit of the image forming apparatus. FIG. It is a graph which shows an example of the detection result of the pattern part and white part electric potential part by an optical sensor. It is a flowchart which shows an example of the image quality adjustment process which an image quality adjustment means performs. It is a flowchart which shows the other example of the image quality adjustment process which an image quality adjustment means performs. It is a flowchart which shows the other example of the image quality adjustment process which an image quality adjustment means performs.

  Hereinafter, a configuration according to the present invention will be described in detail based on the embodiment shown in FIGS. An image forming apparatus (200) according to the present invention includes an image carrier (photosensitive member 205), a charging device (202) for uniformly charging the image carrier, and a uniformly charged image carrier. An exposure device (201) for forming an electrostatic latent image, a developing device (203) for developing the latent image formed on the image carrier with a two-component developer containing toner and carrier, and an image carrier A transfer device (primary transfer device 204) for transferring the toner image to the transfer member, a cleaning device (206) for removing the toner image remaining on the image carrier after the transfer from the image carrier, and conveying and discharging the toner image to a predetermined container; In the image forming apparatus, the developer state of the developer of the developing device is estimated or detected, and a predetermined amount of toner is formed on the image carrier as needed based on the information, and the toner consumption is executed, thereby developing the developer. Image quality that stabilizes the amount of charge And the image quality adjusting means has a linear velocity of the image carrier Vp and a linear velocity of the rotating member (cleaning screw 209) for discharging and conveying the toner in the cleaning device is Vc. Vc / Vp is set larger than Vc / Vp during normal image formation.

(Configuration of image forming apparatus)
FIG. 1 shows the configuration of an image forming apparatus which is an embodiment of the image forming apparatus according to the present invention. The color copying machine 200 has an image forming unit 200A located at the center of the apparatus main body, a paper feeding unit 200B located below the image forming unit 200A, and an image reading unit (not shown) located above the image forming unit 200A. doing.

  The image forming unit 200A is provided with a transfer belt 210 having a transfer surface extending in the horizontal direction, and a configuration for forming an image of a color complementary to the color separation color on the upper surface of the transfer belt 210. Is provided. That is, the photoconductors 205Y, 205M, 205C, and 205K as image carriers that can carry images of toners of complementary colors (yellow (Y), magenta (M), cyan (C), and black (Bk)). Are juxtaposed along the transfer surface of the transfer belt 210.

  Each of the photoconductors 205Y, 205M, 205C, and 205K is configured by a drum that can rotate in the same direction (counterclockwise direction), and around the exposure device 201 that performs image forming processing in the rotation process, and charging Devices 202Y, 202M, 202C and 202K, developing devices 203Y, 203M, 203C and 203K, primary transfer devices 204Y, 204M, 204C and 204K and cleaning devices 206Y, 206M, 206C and 206K are arranged. Each developing device 203Y, 203M, 203C, 203K contains a respective color toner.

  Hereinafter, the charging devices 202Y, 202M, 202C, and 202K, the developing devices 203Y, 203M, 203C, and 203K, the photoconductors 205Y, 205M, 205C, and 205K, and the cleaning devices 206Y, 206M, 206C, and 206K are respectively connected to the image forming units 100Y and 100Y. Called 100M, 100C, 100K. FIG. 2 is a schematic configuration diagram of an image forming unit 100Y for one color (here, yellow) of the image forming apparatus. Since the configuration of each image forming unit is the same, the image forming unit 100Y is taken as an example in the following description.

  The transfer belt 210 is configured to be able to move in the same direction at a position facing the photoconductors 205Y, 205M, 205C, and 205K by being wound around a driving roller and a driven roller. Further, a transfer roller 212 is provided at a position facing the driven roller 211 that is one of the driven rollers. Further, the conveyance path of the sheet P from the transfer roller 212 to the fixing device 100 is a horizontal path.

  The sheet feeding unit 200B separates the sheet P in the sheet feeding tray 214 one by one from the top in order from the top to the position of the transfer roller 212. It has a transport mechanism for transporting.

  In forming an image in the image forming apparatus 200, the surface of the photoconductor 205Y is uniformly charged by the charging device 202Y, and an electrostatic latent image is formed on the photoconductor 205Y based on image information from the image reading unit.

  The electrostatic latent image is visualized as a toner image by a developing device 203Y containing yellow toner, and the toner image is primarily transferred onto the transfer belt 210 by a primary transfer device 204Y to which a predetermined bias is applied. Is done. The other photoconductors 205M, 205C, and 205K also form similar images only with different toner colors, and the toner images of the respective colors are sequentially transferred onto the transfer belt 210 by the electrostatic force and superimposed.

  Next, the toner image T primarily transferred from the photoconductors 205Y, 205M, 205C, and 205K onto the transfer belt 210 is transferred to the sheet P conveyed by the driven roller 211 and the transfer roller 212. The sheet P to which the toner image T has been transferred is further conveyed to the fixing device 213 and is fixed at the fixing nip portion. Further, the sheet P discharged from the fixing nip N is sent out to the stacker 215 along the discharge path.

[Cleaning device]
The cleaning device 206Y includes a static eliminating device 207Y, a cleaning blade (hereinafter also referred to as a blade) 208Y, and a cleaning screw (hereinafter also referred to as a waste toner conveying screw) 209Y.

  The photoconductor 205Y of the image forming unit 100Y after transfer to the transfer belt 210 is discharged from the surface potential by the discharging device 207Y, the residual toner is removed by the cleaning blade 208Y, and a waste toner tank (outside the cleaning device) is removed by the cleaning screw 209Y. It is conveyed and discharged to (not shown). In addition, a series of image forming operations in which the photoreceptor 205Y after cleaning is charged again by the charging device 202Y is repeated.

  More specifically, the cleaning blade 208Y is held and fixed to the blade holder, and a predetermined pressure is applied in a counter direction opposite to the rotation direction of the photoconductor 205Y, and the edge thereof is pressed against the photoconductor 205Y. Further, the residual toner remaining without being transferred from the surface of the photoreceptor is given energy so that charging is uniformly canceled by the charge removal device 207Y. Further, the residual toner is scraped off by the blade 208Y in a state where the adhesive force is weakened by the previous charge removal and disturbance.

  The contact form of the blade 208Y to the photosensitive member 205Y is a counter system, and the cleaning blade 208Y is made of polyurethane blade rubber and is bonded to a blade holder of a galvanized steel plate with a hot melt adhesive. The waste toner scraped off by the blade 208Y is discharged from the cleaning device 206Y by a cleaning screw 209Y installed on the bottom surface of the cleaning device 206Y. In addition, waste toner discharged from each of the cleaning devices 206Y, 206M, 206C, and 206K is transported together in one waste toner transport path and transported to a waste toner tank.

  The cleaning device is configured such that “toner discharge conveyance capability> toner input amount”. Here, the “toner input amount” means the amount of residual toner that is normally input to the cleaning unit and the time when recovery occurs when printing stops due to abnormal operation of the device (for example, jammed transfer paper). The amount of toner to be input is used (untransferred toner remaining between the development position and the transfer position on the photoreceptor). Therefore, a larger amount of input such as during toner consumption operation results in a state of “toner discharging / conveying capacity <toner input amount”, which causes problems such as waste toner overflow / dropping, scattering, and poor cleaning.

[Development equipment]
Each developing device 203Y includes a developing roller 216Y, a first conveying screw (developing stirring and conveying screw) 217Y, and a second conveying screw (developing stirring and conveying screw) 218Y.

  Specifically, the developing roller 216Y facing the photoconductor 205Y, the first conveying screw 217Y facing the developing roller 216Y, the second conveying screw 218Y facing the first conveying screw 217Y via the partition member 219Y, and the developing roller 216Y. The doctor blade 220Y is opposed to

  The developing device 203Y contains a two-component developer composed of a carrier and toner. The developer in the developing device 203Y circulates in the developing device while being agitated and mixed with the toner supplied from the developer supply device 221Y through the supply port by the rotation of the two conveying screws 217Y and 218Y. The toner that has been frictionally charged and adhered to the carrier is carried on the developing roller 216Y together with the carrier, and after the developer amount is regulated and adjusted to an appropriate amount at the position of the doctor blade 220Y, the developing at the position facing the photosensitive drum 215Y. Conveyed to the area. In the development area, the toner in the developer adheres to the electrostatic latent image formed on the surface of the photosensitive drum.

  More specifically, the toner moves to the electrostatic latent image by an electric field formed by a potential difference (referred to as developing potential) between the electrostatic latent image potential formed by laser exposure irradiation and the developing bias potential applied to the developing roller 216Y. The toner becomes a visible image.

  Further, the developer in the developer supply device 221Y is appropriately supplied from the developer supply device 221Y to the development device 203Y as the toner in the development device 203Y is consumed (change in toner density).

  The toner consumption in the developing device 203Y is directly detected by a magnetic permeability sensor 222Y (not shown) as a toner concentration detecting unit installed in the developing device 203Y, and the toner concentration detecting unit facing the photosensitive drum 205Y. Is indirectly detected by a reflection type photosensor (hereinafter referred to as an optical sensor) 223Y. More specifically, when the toner concentration of the developer contained in the developing device (the ratio of the toner in the developer) is detected by the toner concentration detecting means, the toner concentration falls within a predetermined range based on the detection result. In this way, the conveying screws 217Y and 218Y as toner supply means are operated for a predetermined time to supply toner into the developing device 203Y.

[toner]
Next, the toner will be described. In the present embodiment, the volume average particle diameter of the toner is preferably 3 to 8 μm in order to reproduce minute dots of 600 dpi (dot per inch) or more. The ratio (Dv / Dn) of the volume average particle diameter (Dv) to the number average particle diameter (Dn) is preferably in the range of 1.00 to 1.40. (Dv / Dn) is closer to 1.00, indicating that the particle size distribution is sharper. The particle size distribution of the toner particles can be measured using a measuring device (Coulter counter method) of Coulter Counter TA-II or Coulter Multisizer II (manufactured by Coulter Inc.). Using toner with such a small particle size and a narrow particle size distribution makes the toner charge amount distribution uniform and provides a high-quality image with little background fogging. Can be high.

  In recent years, among the fixing methods of the fixing device 213, the hot-pressure fixing method by heating and pressing is the most common. The toner used in this hot-pressure fixing method is required to have low-temperature fixing properties and high fixing strength in order to promote low energy design in consideration of ecology. For this reason, means for incorporating a fixing aid such as a low melting point wax into the toner is widely used. However, the more the low melting point wax is contained by this means and the lower the melting point, the lower the heat resistance and pressure storage stability of the toner, causing blocking due to agglomeration between the toner particles, and affecting the mechanical function and image quality. . In addition, for the purpose of improving the image quality, it is also a disadvantageous condition for toner aggregation that the toner has a small particle size and a circular shape. In order to prevent toner particles from blocking such a storage problem, it is known that inorganic fine particles such as hydrophobic silica and titanium oxide are adhered to the surface of the toner particles in order to improve fluidity. However, hydrophobic silica has a problem that an increase in toner addition affects charging characteristics, and an increase in addition of titanium oxide has a problem of causing soiling. It is necessary to consider the reduction in hazards to toner.

[Image quality adjustment means]
As described above, the developing device 203Y opposes the optical sensor 223Y as density detecting means for detecting the amount of toner developed on the photoconductor 205Y to the photoconductor 205Y on the downstream side of the developing region in the rotation direction of the photoconductor 205Y. The toner adhesion state on the photoconductor 205Y is detected. This detection signal is transmitted to the control unit of the image forming apparatus, and based on the detection signal, an image forming bias condition such as a toner replenishment condition, a charging potential, a developing bias potential, and a latent image potential (adjusted by the exposure amount) is set. Control.

  Here, during the machine aging operation immediately after the start of the image forming apparatus, the developer is in a non-uniform state of toner density and chargeability. Therefore, the developer is agitated by the rotation of the development agitating and conveying screws 217Y and 218Y. Is started.

  Using the charging device 202Y and the exposure device 201Y, a solid pattern as a potential portion to which toner having sufficient detection sensitivity adheres and a white portion potential without an image are formed in parallel with driving the developer stirring unit. Then, after the image is developed on the photosensitive member 205Y, the toner adhesion amounts of the pattern portion and the white potential portion are detected and measured by the reflected light read by the optical sensor 223Y.

Based on the detection value of the solid pattern of the optical sensor 223Y at this time, the toner adhesion amount of the solid portion having the desired maximum image density on the transfer paper is set to a predetermined amount (for example, 0.005 mg / mm ² on the photosensitive member). As described above, the image forming bias conditions and the like are controlled as described above to maintain a desired image density.

  Further, the degree of contamination of the background portion is detected from the detection value of the white portion potential portion by the optical sensor 223Y, and the charging abnormality of the developer in the developing device 203Y is detected. If the background stain exceeds a predetermined threshold, it is determined that the apparatus and image quality are abnormal, and the developer is stirred or consumed to adjust the charge state to an appropriate charged state, thereby eliminating the background stain. ing.

  Further, the solid pattern and the white portion potential portion are alternately formed and read by the optical sensor 223Y. When the charge amount of the developer in the developing device 203Y is non-uniform, the adhesion amount state also varies, so whether the developing device is stirred until a plurality of detection values are read and the values fall within a predetermined range. Alternatively, the state of the developer is measured by using a value obtained by using an average value of detection values at a predetermined time.

FIG. 3A is a graph showing an example of the detection result of the pattern portion and the white portion potential portion by the optical sensor 223Y. The horizontal axis indicates the stirring time (operation time (sec)), and the vertical axis indicates the detection value of the optical sensor. (Drum adhesion amount (mg / cm ² )). FIG. 3B shows an enlarged view of a dotted line portion in FIG.

  As shown in FIG. 3, when the charge amount of the developer is reduced as a whole, the solid pattern adhesion amount at a predetermined development potential is larger than the target value (the development ability is higher than the desired control value). At the same time, when the toner adhesion amount at the white potential portion exceeds a desired value, it is presumed that internal contamination due to toner scattering occurs as described above, and it can be presumed that the background portion of the image becomes dirty.

  Therefore, the image quality adjusting means (configured as a part of the control unit) of the image forming apparatus performs a “toner consumption operation” that forms a predetermined amount of toner image and lowers the toner density of the developer in the developing device. Is. In other words, the toner consumption operation is an operation at the time of toner consumption for removing the neglected toner when the initial agent is charged. Further, after the toner consumption operation, the image quality adjusting unit detects the toner adhesion state of the solid pattern and the white portion potential portion again, and repeatedly executes the toner consumption operation until the white portion potential portion is free from contamination, and thereafter, the solid portion consumption operation is repeated. The development potential is adjusted so that the pattern has a predetermined density.

  In this embodiment, in order to detect the toner density on the measurement potential portion, the optical sensor 223Y directly detects the toner concentration on the photoreceptor 205Y. Instead, the measurement potential portion is detected. The upper toner may be transferred to the conveying belt 210 of the primary transfer device 204Y, and then the upper surface of the transfer belt 210 may be detected and controlled by the optical sensor 223Y. In any of the detection methods on the photosensitive member and on the transfer belt, the detection value of each sensor may be set to an optical sensor output level according to the relationship between the background and the image density on the transfer paper.

[Control example of image quality adjustment means (1)]
The “toner discharging / conveying capability” in the cleaning device 206Y is determined by the linear velocity Vc of the cleaning screw 209Y, and the “toner input amount” is determined by the photosensitive member linear velocity Vp. Therefore, the image quality adjusting means, during the toner consumption operation, in order to satisfy the condition of “toner discharge conveyance capability> toner input amount” as described above, the linear speed of the cleaning screw 209Y (hereinafter, screw linear speed) Vc ( The ratio (hereinafter referred to as Vc / Vp linear velocity ratio) between the toner discharge / conveying capacity) and the photosensitive member linear velocity Vp (= input amount) is made higher than usual. Thereby, the waste toner conveyance capability in the cleaning device can be improved.

As means for increasing the Vc / Vp linear velocity ratio,
(A): Increase screw linear velocity Vc (than normal time) (B): Decrease photoreceptor linear velocity Vp (than normal time). In this control example, an example will be described in which the Vc / Vp linear velocity ratio is increased by performing (A).

  Increasing the screw linear speed Vc may cause the cleaning device to vibrate due to the high-speed rotation of the screw, thereby causing image distortion and lowering the durability. In order to prevent this vibration and a decrease in durability, it is necessary to increase the rigidity of the screw. For this purpose, however, there are restrictions on the device design such as an increase in the cost of device parts and an increase in the size of the parts (devices). However, in the present embodiment, the screw linear velocity is set to a predetermined value during normal printing and the screw linear velocity is increased only during the toner consumption operation, so the above-described vibration and durability problems do not occur.

  An example of the image quality adjustment process executed by the image quality adjusting means described above is shown in the flowchart of FIG. When the apparatus is turned on (S101), the elapsed time from the previous power-off is determined (S102). If the predetermined time or more has elapsed (S102: Yes), the image quality adjustment process is started (S103). First, optical sensor calibration is executed (S104), gradation pattern creation / detection is executed, development γ is calculated, and image formation potential is set (S105). Next, white portion creation / detection is executed (S106), and toner consumption / agent stirring necessity determination is performed (S107).

  In the toner consumption / agent stirring necessity determination (S107), one of “end”, “toner consumption execution”, and “developer stirring execution” is determined (see FIG. 3). In the case of “end”, the image quality adjustment process ends (S115).

  On the other hand, in the case of “execution of toner consumption”, the screw linear velocity Vc is increased (S108), and the toner consumption operation is executed (S109). In addition, the photosensitive member linear velocity Vp may be lowered. Thereafter, the changed linear velocity is restored (S110). Further, it is determined whether the toner consumption operation has been executed a predetermined number of times (S111). If the toner consumption operation has been executed a predetermined number of times (S111: Yes), a message such as “Developer replacement request” is displayed on the display unit of the image forming apparatus. In step S114, after prompting for replacement of the developer, the image quality adjustment processing ends (S115). If it has not been executed a predetermined number of times (S111: No), the process returns to S104.

  On the other hand, in the case of “developer agitation”, the developer agitation is executed (S112), it is determined whether the toner consumption operation is executed a predetermined number of times (S113), and when the predetermined number of times is executed (S113: Yes). Then, the image quality adjustment process ends (S115). If it has not been executed a predetermined number of times (S113: No), the process returns to S104.

[Control example of image quality adjustment means (2)]
Here, when the cleaning screw 209Y is rotated at a high speed, the action of ejecting the waste toner to the outside of the spiral diameter of the screw increases, and when the force is applied for a long time, the waste toner is aggregated between the periphery of the screw and the casing of the conveyance path. This causes toner to bridge around the screw (toner bridge, waste toner bridge).

  In particular, it is known that when the surface property is changed by receiving a hazard with a cleaning blade, a brush, or the like, or when paper dust or a cleaning aid is included, the waste toner is more likely to aggregate and form a bridge. In recent years, high-precision reproducibility of images has been demanded, so that the toner has a smaller particle size. However, this also causes a decrease in toner fluidity and facilitates bridging.

  In other words, the screw rotation conditions are normally designed so that the spiral surface of the screw is correctly conveyed along the screw axis in the conveyance / discharge direction, but increasing the rotation of the conveyance screw is necessary to increase the discharge efficiency. There is a possibility that a waste toner partial bridge is caused around the toner, and toner leakage is poor, and toner leakage from the cleaning unit, poor cleaning, and waste toner clogging are likely to occur.

  Therefore, it is more preferable that the image quality adjusting means lowers the photosensitive member linear velocity Vp in (B) as means for increasing the Vc / Vp linear velocity ratio. In this way, it is possible to improve the toner discharge / conveyance capability of the cleaning device when the toner is consumed without generating a toner bridge.

  An example of the image quality adjustment process executed by the image quality adjustment means described above is shown in the flowchart of FIG. Although a description of the same process as in FIG. 4 is omitted, a process of lowering the photosensitive member linear velocity Vp is performed in S208, and a process of returning the photosensitive member linear velocity Vp to the original is performed in S210.

[Control example of image quality adjustment means (3)]
Further, the ease of aggregation of waste toner greatly depends on the temperature and humidity environment, and the toner bridge is likely to occur in a high temperature and high humidity environment. In recent years, toners used in the hot-pressure fixing system have been required to have low-temperature fixability for the purpose of reducing energy. For this reason, a fixing aid such as a low melting point wax is widely contained in the toner.

  However, if a low-melting-point wax is contained in a large amount, the storage stability of the toner is lowered, the toner particles are blocked, and the image quality is lowered. Depending on the installation environment and operating conditions of the image forming apparatus, there is a risk that waste toner bridge is likely to occur due to high temperature and high humidity conditions.

  As described above, in a toner having a low margin for heat-resistant storage stability, the margin for aggregation at a high temperature is low. It is well known that any toner has a low margin for aggregation when it absorbs moisture. For this reason, there is disclosed a technique for avoiding toner aggregation by restricting the installation environment of the apparatus to be used or providing a mechanism for lowering the temperature and humidity in the apparatus. In the environment of high temperature and high humidity. It is preferable to prepare in advance a means for avoiding aggregation in the case of becoming.

  Therefore, the image forming apparatus further includes a temperature / humidity detection sensor (temperature / humidity detection means) for detecting the temperature condition and the humidity condition, and the image quality adjustment means is configured to perform (A) according to the temperature / humidity condition at the time of toner consumption execution. It is preferable to increase Vc / Vp by increasing the screw linear velocity Vc or decreasing the photosensitive member linear velocity (B). That is, even in a highly durable toner or low hazard image forming apparatus that has sufficient margin for aggregation between toners in a cleaning device except in a high temperature or high humidity environment, the internal environment when the toner is consumed is higher than a predetermined temperature or humidity. In the case where it is determined as described above, the photosensitive member linear velocity is lowered when the toner is consumed, and the linear velocity ratio with the cleaning screw linear velocity is changed.

  An example of the image quality adjustment process executed by the image quality adjustment means described above is shown in the flowchart of FIG. Although the description of the same processing as in FIG. 4 is omitted, in S308-1 to S308-3, the detection result (that is, temperature condition and humidity condition) of the temperature / humidity detection means is determined (S308-1), and the high temperature or In the case of high humidity conditions (S308-1: Yes), the photosensitive member linear velocity of (B) is decreased (S308-2), otherwise (S308-1: No), screw linear velocity Vc of (A). (S308-3) increases the Vc / Vp linear velocity ratio.

  As described above, by selectively executing the methods (A) and (B) based on the environmental conditions, it is possible to avoid the toner bridge and perform the toner consuming operation in the shortest possible time.

  The above-described embodiment is a preferred embodiment of the present invention, but is not limited thereto, and various modifications can be made without departing from the gist of the present invention.

<Example 1>
In the toner consumption operation described above, the total amount of the developer in the developing device is 400 g, and the target toner concentration is normally controlled with 7 wt% as one target value. However, the toner concentration is controlled in the range of 4 to 8 wt% based on the environment and the developer charge amount variation with time. In order to avoid the toner concentration being excessively lowered by the toner consumption operation, the toner consumption operation in which the toner concentration is reduced by about 0.5 wt% estimated from the total amount of developer is set as one set, and the consumption operation → the optical sensor The cycle of detection of soiling due to → consumption judgment (consumption end or consumption operation execution) was turned.

The linear speed conditions during normal printing are as follows.
・ Photoconductor linear velocity = 350 mm / sec
-Image interval (transfer paper transfer interval) margin = 40 mm, A4 horizontal (210 mm) feed, 84 cpm output performance-Developing roller linear velocity = 560 mm / sec
・ Rotation speed of cleaning screw = 60 rpm (however, screw outer diameter = 10 mm, outer diameter linear velocity = 10 mm / sec)
When printing on thick paper and OHP paper, the speed condition is set to half speed.
・ Photoconductor linear velocity = 175 mm / sec
・ Developing roller linear velocity = 280 mm / sec
・ Cleaning screw rotation speed = 30 rpm (however, screw outer diameter = 10 mm, outer diameter linear velocity = 5 mm / sec)

On the other hand, the toner consumption mode aims at reducing the toner concentration in 400 g of developer by about 0.5 wt% in one consumption operation, and the development potential (photosensitive material adhesion amount = 0.005 mg / mm ² ). (Development bias potential-latent image potential)
・ Photoconductor linear velocity = 350 mm / sec
・ Developing roller linear velocity = 560 mm / sec
・ Rotation speed of cleaning screw = 90 rpm (however, screw outer diameter = 10 mm, outer diameter linear velocity = 15 mm / sec)
Under the above conditions, 6 pages of solid images corresponding to A4 landscape paper were formed (image spacing margin was 40 mm).

  Further, the transfer bias to the intermediate transfer belt is set to zero, and the image is sent to the cleaning device. After the creation of 6 pages, the amount of adhesion between the background portion and the solid portion was again detected by the optical sensor as described above, and it was determined again whether or not the toner consumption should be re-executed from the background state.

Here, when the photosensitive member linear velocity = Vp and the cleaning screw linear velocity = Vc, Vc / Vp = 15/350 when toner is consumed, whereas Vc / Vp = 10/350 during normal printing. In this way, by increasing the rotational speed of the cleaning screw and increasing the screw: photoreceptor linear velocity ratio (Vc / Vp), more toner is input to the cleaning unit during normal printing. Even if it was input, it could be discharged without accumulation. Note that the photoreceptor adhesion amount = 0.005 mg / mm ² is the adhesion amount that gives the maximum image density on the transfer paper, and may be adjusted by the image quality adjusting means according to the toner density and charge amount state of the developer at that time. .

<Example 2>
Under the same linear velocity conditions as in Example 1, the toner consumption mode aims to reduce the toner concentration in the developer 400 g by about 0.5 wt% by one consumption operation, and the photosensitive member adhesion amount = 0.005 mg / mm ^2. By setting the development potential,
・ Photoconductor linear velocity = 175 mm / sec
・ Developing roller linear velocity = 280 mm / sec (therefore, the ratio of photosensitive member linear velocity: developing roller linear velocity is fixed)
・ Rotation speed of cleaning screw = 60 rpm (however, screw outer diameter = 10 mm, outer diameter linear velocity = 10 mm / sec)
It was.

  Here, if the photosensitive member linear velocity = Vp and the cleaning screw linear velocity = Vc, Vc / Vp = 10/175 when toner is consumed while Vc / Vp = 10/350 during normal printing. As described above, the photosensitive member linear speed is lowered to half the same speed as when printing on thick paper and OHP (by increasing the screw: photosensitive linear speed ratio), so that more toner is input to the cleaning unit during normal printing. Even when the toner is input to the cleaning portion, the toner does not accumulate, and waste toner that has become easy to aggregate due to poor fluidity can be discharged while preventing the toner bridge in the cleaning portion.

<Example 3>
When the in-machine temperature at the time of toner consumption mode is 35 ° C. or higher, or when the mechanical humidity exceeds 80% RH, the development potential is set such that the photoreceptor adhesion amount is 0.005 mg / mm ² .
・ Photoconductor linear velocity = 175 mm / sec
・ Developing roller linear velocity = 280 mm / sec
・ Rotation speed of cleaning screw = 60 rpm (however, screw outer diameter = 10 mm, outer diameter linear velocity = 10 mm / sec)
It was. Further, when the other environmental conditions are not satisfied, the development potential is set such that the adhesion amount of the photoreceptor is 0.005 mg / mm ² .
・ Photoconductor linear velocity = 350 mm / sec
・ Developing roller linear velocity = 560 mm / sec
・ Rotation speed of cleaning screw = 90 rpm (however, screw outer diameter = 10 mm, outer diameter linear velocity = 15 mm / sec)
As a result, toner consumption was performed according to environmental conditions. As a result, it was possible to avoid the toner bridge and perform the toner consuming operation in the shortest possible time.

200 Image forming apparatus 200A Image forming unit 200B Paper feeding unit 201 Exposure devices 202Y, 202C, 202M, 202K Charging devices 203Y, 202C, 202M, 202K Developing devices 204Y, 204M, 204C, 204K Primary transfer devices 205Y, 205C, 205M, 205K photoconductors 206Y, 206M, 206C, 206K cleaning device 207Y neutralization device 208Y cleaning blade 209Y cleaning screw 210 transfer belt 211 driven roller 212 transfer roller 213 fixing device 214 paper feed tray 215 stacker 216Y developing roller 217Y first transport screw 218Y second Conveying screw 219Y Partition member 220Y Doctor blade 221Y Developer supply device 222Y Magnetic permeability sensor 223Y Optical sensor

Japanese Patent No. 3922301 Japanese Patent No. 4070400 JP 2009-186505 A JP 2004-118224 A

Claims (2)

An image carrier;
A charging device for uniformly charging the image carrier;
An exposure apparatus for forming an electrostatic latent image on the uniformly charged image carrier;
A developing device for developing the electrostatic latent image formed on the image carrier with a two-component developer containing toner and carrier;
A transfer device for transferring a toner image on the image carrier to a transfer member;
A cleaning device that removes a toner image remaining on the image carrier after the transfer from the image carrier, and transports and discharges the toner image to a predetermined container;
Image quality adjustment that estimates or detects the developer state of the developing device, forms a predetermined toner amount on the image carrier based on the information, consumes the toner, and stabilizes the charge amount of the developer Having means,
When the linear velocity of the image carrier is Vp and the linear velocity of the rotating member that discharges and conveys the toner in the cleaning device is Vc,
An image forming apparatus characterized in that Vc / Vp at the time of toner consumption is made larger than Vc / Vp at the time of normal image formation by lowering the linear velocity Vp of the image carrier from that at the time of normal image formation. . It further has temperature / humidity detection means for detecting temperature conditions and / or humidity conditions,
The image quality adjustment unit is configured to perform the toner consumption detected by the temperature / humidity detection unit according to the temperature condition and / or the humidity condition at the time of execution .
The image forming apparatus according to claim 1, characterized in that to increase the Vc / Vp by the Turkey lowering the linear velocity Vp of the image bearing member than when the image formation of normal.

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