JP2008292890A - Developing device, process cartridge and image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a developing device using a premix developing method preventing image irregularities even when the device is not used for a long time, and to provide a process cartridge and an image forming apparatus. <P>SOLUTION: The developing device 13 is equipped with: a feeding means 28, 29, 80, 81 to newly feed a carrier C into the developing device 13; a discharge means 13d to discharge part of a developer G housed in the developing device 13; and a detection means 85 to detect the suspension time of the developing device 13. According to a detection result by the detection means 85, the feeding means 28, 29, 80, 81 newly feeds the carrier C into the developing device 13 before a developing step is started. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an image forming apparatus using an electrophotographic system such as a copying machine, a printer, a facsimile machine, or a multi-function machine thereof, and a developing device and a process cartridge installed therein. The present invention relates to a premix developing type developing device, a process cartridge, and an image forming apparatus that appropriately supply a carrier and a developer.

  Conventionally, in an image forming apparatus such as a copying machine or a printer, a new carrier is appropriately replenished to a developing device containing a two-component developer composed of toner and carrier (including the case where an additive is added). There is a known technique (referred to as a premix development method) (see, for example, Patent Document 1).

  In a developing device using a two-component developer, toner is appropriately replenished into the developing device from a toner replenishing port provided in a part of the developing device according to toner consumption in the developing device. The replenished toner is agitated and mixed together with the developer in the developing device by a conveying member (agitating member) such as a conveying screw. Part of the stirred and mixed developer is supplied to a developing roller (developer carrier). After the developer carried on the developing roller is regulated to an appropriate amount by the doctor blade, the toner in the two-component developer adheres to the latent image on the photosensitive drum at a position facing the photosensitive drum.

  As described above, since the carrier in the two-component developer accommodated in the developing device in the normal developing process remains in the developing device without being consumed, the carrier deteriorates with time. Specifically, the carrier is agitated and mixed for a long time in the developing device, so that the coating layer of the carrier is worn or peeled off and the charging ability of the carrier is reduced, or the toner on the surface of the carrier. The “spent phenomenon” in which the chargeability of the carrier decreases due to adhesion of components and additives occurs.

The premix development method is for preventing the deterioration of the image quality of the output image due to the deterioration of the carrier over time. That is, a new carrier (or a new two-component developer) is appropriately supplied into the developing device, and a part of the two-component developer accommodated in the developing device is appropriately discharged to the outside of the developing device. The number of deteriorated carriers in the apparatus is reduced to maintain the amount of carriers accommodated in the developing apparatus and the charging ability.
An image forming apparatus using such a premix developing system has an image quality of an output image over time as compared to a developing apparatus or an apparatus that needs to replace the carrier with a new one every time the carrier deteriorates over time. Will be stabilized.

  Patent Document 1 and the like disclose a developing device using a premix developing method, which uses an overflow method as means for discharging developer from the developing device to the outside. Specifically, a developing device is provided with a discharge port (hole), and when the developer surface transported to that position exceeds a predetermined height, the developer (development that has become excessive due to the replenishment of the carrier) Is discharged from the outlet to the outside.

  On the other hand, in Patent Document 2 and the like, there is a premix developing type developing device using an overflow method as a developer discharging means, and the height of the developer discharging port can be varied. A technique for adjusting the height of the discharge port according to the detection value of the environmental sensor during operation is disclosed. In this technology, during operation of the device, the volume of developer in the device fluctuates with changes in the amount of moisture in the atmosphere, the drive torque of the device fluctuates, and the quality of the output image becomes poor due to poor toner agitation. The purpose is to suppress a problem that decreases.

  Further, Patent Document 3 discloses a developing device that uses a two-component developer (a developing device that does not use a premix developing system), and is warmed up according to the time the device is left and the humidity fluctuation. A technique for correcting the rotation time is disclosed. The purpose of this technology is to suppress a problem that an abnormal image is generated due to a change in the charge amount of toner in a developer contained in the apparatus when the apparatus is left for a long time and the humidity fluctuation is large. It is a thing.

JP 2001-183893 A Japanese Patent Laid-Open No. 2003-15418 Japanese Patent Laid-Open No. 11-212343

In the premix developing type developing apparatus described in Patent Document 1 and the like described above, when the apparatus is left for a long time (the time during which the operation is stopped), the height of the developer surface contained in the apparatus is increased. There was a phenomenon that decreased. Specifically, the toner in the developer tends to make the developer bulky, but since the toner sinks so as to fill the gap by standing, the developer contained in the apparatus is static. When the state lasted for a long time, the overall bulk was reduced.
In particular, when the apparatus is operated in a low-humidity environment before being left standing, the charge amount of the developer is increased and the toner concentration (the ratio of toner in the developer) is controlled to be higher. As a result, the bulk of the developer increases and a large amount of developer is discharged to the outside from the discharge port. For this reason, the phenomenon that the bulk of the developer contained in the apparatus is lowered after being left for a long time has become prominent.

When the developing process is performed in such a state that the volume of the developer is reduced in this way, unevenness occurs in the amount of developer (pumping amount) supplied to the developing roller by the conveying member, and image unevenness is generated on the output image. It has occurred. Specifically, image unevenness corresponding to the screw pitch of the conveying member (this is referred to as “screw pitch unevenness”) has occurred on the output image. Referring to FIG. 7, this “screw pitch unevenness M” is particularly prominent on the recording medium P at the end on the downstream side in the transport direction where the supply of the developer amount tends to be insufficient.
Such a phenomenon is peculiar to the premix development system. That is, before the device is left (during operation), the developer exceeding the appropriate amount in that state is discharged from the discharge port, and the device is operated in a state where the bulk of the developer is reduced by leaving it for a long time. However, the bulk of the developer is difficult to return.

  Further, as a result of repeated research by the inventors of the present application, it has been experimentally confirmed that the above-described phenomenon becomes particularly remarkable when the environmental fluctuation before and after being left is large. Specifically, it has been found that when the humidity around the apparatus is greatly reduced during standing, the bulk of the developer contained in the apparatus is greatly reduced.

On the other hand, the technique disclosed in Patent Document 2 described above is for solving a problem associated with an environmental change that occurs during operation of the apparatus, and does not solve the problem associated with leaving the apparatus for a long time.
In addition, the technique described in Patent Document 3 described above corrects the stirring time of the developer at the time of warming up according to the standing time of the apparatus and the humidity fluctuation, and has a problem peculiar to the above-described premix developing system. It does not solve.

  The present invention has been made to solve the above-described problems. A premix developing type developing device and process that does not cause image unevenness on an output image even when the apparatus is left for a long time. An object of the present invention is to provide a cartridge and an image forming apparatus.

  A developing device according to a first aspect of the present invention is a developing device for storing a developer having a carrier and a toner and performing a developing process for developing a latent image formed on an image carrier. Supply means for supplying a new carrier into the apparatus, discharge means for discharging a part of the developer contained in the apparatus to the outside, detection means for detecting the time during which the operation of the apparatus is stopped, The supply means supplies a new carrier into the apparatus before the development process is started according to the detection result of the detection means.

  According to a second aspect of the present invention, there is provided the developing device according to the first aspect of the invention, wherein the supplying means performs the developing step when the leaving time detected by the detecting means exceeds a predetermined value. Before starting, a new carrier is supplied into the apparatus.

Further, a developing device according to a third aspect of the present invention is the invention according to the first or second aspect, further comprising a second detecting means for detecting an environmental change around the device,
The supply means supplies a new carrier into the apparatus before the development process is started according to the detection result of the second detection means.

  According to a fourth aspect of the present invention, in the developing device according to the third aspect, the second detection means is a humidity sensor that detects a humidity fluctuation around the apparatus, and the supply means When the humidity fluctuation detected by the humidity sensor exceeds a predetermined value, a new carrier is supplied into the apparatus before the development process is started.

  According to a fifth aspect of the present invention, there is provided a developing device according to any one of the first to fourth aspects, wherein the developer carrying member faces the image carrier and carries a developer. A first conveying member facing the developer carrying member and supplying the developer to the developer carrying member while conveying the developer in the longitudinal direction; and below the first conveying member and the developer carrying member A second conveying member arranged in a position facing the body and conveying the developer detached from the developer carrying member in the longitudinal direction; and the developer conveyed by the second conveying member in the first conveying direction. A third conveying member that conveys the developer that has reached the downstream side of the conveying path by the first conveying member to the upstream side of the conveying path by the first conveying member, while conveying the developer upstream of the conveying path by the member It is provided.

  The developing device according to a sixth aspect of the present invention is the developing device according to any one of the first to fifth aspects, wherein the discharge means has a predetermined height of the developer surface conveyed to that position. In this case, a discharge port is provided for discharging the developer to the outside.

  According to a seventh aspect of the present invention, there is provided the developing device according to any one of the first to sixth aspects, wherein the toner has a volume average particle size in the range of 3 to 8 μm. It is formed.

  The developing device according to an eighth aspect of the present invention is the developing device according to any one of the first to seventh aspects, wherein the toner has an average circularity within a range of 0.93 to 1.00. It is formed as follows.

  A developing device according to a ninth aspect of the invention is the developing device according to any one of the first to eighth aspects, wherein the toner is added with hydrophobic silica.

  The developing device according to the invention of claim 10 is the developing apparatus according to claim 9, wherein the hydrophobic silica is formed so as to contain a material having a primary particle size of less than 20 nm. .

  Further, in the developing device according to an eleventh aspect of the present invention, in the invention according to the ninth or tenth aspect, the mass ratio of the hydrophobic silica to the toner is 0.3 to 5.0 mass%. It is formed as follows.

  A developing device according to a twelfth aspect of the present invention is the developing device according to any one of the first to eleventh aspects, wherein the supply means newly supplies toner together with the carrier into the apparatus. is there.

  A process cartridge according to a thirteenth aspect of the present invention is a process cartridge that is detachably installed on the main body of the image forming apparatus, and is according to any one of the first to twelfth aspects. The developing device and the image carrier are integrated.

  An image forming apparatus according to a fourteenth aspect of the present invention includes the developing device according to any one of the first to twelfth aspects and the image carrier.

  In the present application, the “process cartridge” refers to a charging unit that charges the image carrier, a developing unit (developing device) that develops a latent image formed on the image carrier, and a cleaning on the image carrier. At least one of the cleaning units and the image carrier are defined as a unit that is integrated and detachably installed on the image forming apparatus main body.

  According to the present invention, since the carrier is newly supplied into the apparatus before the development process is started according to the time during which the operation of the apparatus is stopped, the output is performed even if the apparatus is left for a long time. It is possible to provide a premix developing type developing device, a process cartridge, and an image forming apparatus in which image unevenness does not occur on an image.

Embodiment.
Hereinafter, the best mode for carrying out the present invention will be described in detail with reference to the drawings. In addition, in each figure, the same code | symbol is attached | subjected to the part which is the same or it corresponds, The duplication description is simplified or abbreviate | omitted suitably.

First, the configuration and operation of the entire image forming apparatus will be described with reference to FIG.
In FIG. 1, reference numeral 1 denotes an apparatus main body of a tandem color copier as an image forming apparatus, 2 a writing unit that emits laser light based on input image information, and 3 an original conveying unit that conveys an original D to an original reading unit 4. 4 is a document reading unit that reads image information of the document D, 7 is a paper feeding unit that accommodates a recording medium P such as transfer paper, 9 is a registration roller that adjusts the conveyance timing of the recording medium P, and 11Y, 11M, and 11C. , 11BK are photosensitive drums on which toner images of respective colors (yellow, magenta, cyan, and black) are formed, 12 is a charging unit that charges the photosensitive drums 11Y, 11M, 11C, and 11BK, and 13 is each photosensitive drum. A developing device for developing electrostatic latent images formed on 11Y, 11M, 11C, and 11BK, and a toner image formed on each of the photosensitive drums 11Y, 11M, 11C, and 11BK Transfer bias roller for transferring superimposed on the recording medium P (1 transfer bias roller), 15 denotes the photosensitive drums 11Y, 11M, 11C, cleaning unit for collecting the untransferred toner on 11BK, a.

Reference numeral 16 denotes an intermediate transfer belt cleaning unit that cleans the intermediate transfer belt 17, 17 an intermediate transfer belt on which toner images of a plurality of colors are transferred and superimposed, and 18 a color toner image on the intermediate transfer belt 17 on the recording medium P. A secondary transfer bias roller 20 for transferring the toner image onto the recording medium P indicates a fixing device for fixing an unfixed image on the recording medium P.
Although not shown in the drawing, a carrier (magnetic carrier) and toner (toner particles) of each color (yellow, cyan, magenta, black) are developed above the photosensitive drums 11Y, 11C, 11M, and 11BK. Each color agent cartridge is installed as a supply means for supplying to 13.

Hereinafter, an operation during normal color image formation in the image forming apparatus will be described. Note that FIG. 2 can also be referred to for the image forming process performed on the photosensitive drums 11Y, 11M, 11C, and 11BK.
First, the document D is transported from the document table in the direction of the arrow in the drawing by the transport rollers of the document transport unit 3 and placed on the contact glass 5 of the document reading unit 4. Then, the document reading unit 4 optically reads the image information of the document D placed on the contact glass 5.

  Specifically, the document reading unit 4 scans the image of the document D on the contact glass 5 while irradiating light emitted from an illumination lamp. Then, the light reflected by the document D is imaged on the color sensor via the mirror group and the lens. The color image information of the document D is read for each RGB (red, green, blue) color separation light by the color sensor, and then converted into an electrical image signal. Further, color conversion processing, color correction processing, spatial frequency correction processing, and the like are performed by the image processing unit based on the RGB color separation image signals to obtain yellow, magenta, cyan, and black color image information.

  Then, the image information of each color of yellow, magenta, cyan, and black is transmitted to the writing unit 2. The writing unit 2 emits laser light L (see FIG. 2) based on the image information of each color toward the corresponding photosensitive drums 11Y, 11M, 11C, and 11BK.

On the other hand, the four photosensitive drums 11Y, 11M, 11C, and 11BK are rotated clockwise in FIG. First, the surfaces of the photoconductor drums 11Y, 11M, 11C, and 11BK are uniformly charged at a portion facing the charging unit 12 (this is a charging process). Thus, a charged potential is formed on the photosensitive drums 11Y, 11M, 11C, and 11BK. Thereafter, the charged surfaces of the photosensitive drums 11Y, 11M, 11C, and 11BK reach the irradiation positions of the respective laser beams.
In the writing unit 2, laser light corresponding to the image signal is emitted from the four light sources corresponding to each color. Each laser beam passes through a separate optical path for each of the yellow, magenta, cyan, and black color components (this is an exposure process).

  Laser light corresponding to the yellow component is irradiated on the surface of the first photosensitive drum 11Y from the left side of the drawing. At this time, the yellow component laser light is scanned in the rotation axis direction (main scanning direction) of the photosensitive drum 11Y by a polygon mirror that rotates at high speed. Thus, an electrostatic latent image corresponding to the yellow component is formed on the photosensitive drum 11Y charged by the charging unit 12.

  Similarly, the laser beam corresponding to the magenta component is irradiated onto the surface of the second photosensitive drum 11M from the left side of the paper, and an electrostatic latent image corresponding to the magenta component is formed. The cyan component laser light is applied to the surface of the third photosensitive drum 11C from the left side of the paper, and an electrostatic latent image of the cyan component is formed. The black component laser beam is applied to the surface of the fourth photosensitive drum 11BK from the left side of the paper, and an electrostatic latent image of the black component is formed.

Thereafter, the surfaces of the photoconductive drums 11Y, 11M, 11C, and 11BK on which the electrostatic latent images of the respective colors are formed reach positions facing the developing device 13, respectively. Then, the respective color toners are supplied from the developing devices 13 onto the photosensitive drums 11Y, 11M, 11C, and 11BK, and the latent images on the photosensitive drums 11Y, 11M, 11C, and 11BK are developed (development process). .)
Thereafter, the surfaces of the photoconductive drums 11Y, 11M, 11C, and 11BK after the development process reach the facing portions of the intermediate transfer belt 17, respectively. Here, a transfer bias roller 14 is installed at each facing portion so as to contact the inner peripheral surface of the intermediate transfer belt 17. Then, the toner images of the respective colors formed on the photosensitive drums 11Y, 11M, 11C, and 11BK are sequentially superimposed and transferred onto the intermediate transfer belt 17 at the position of the transfer bias roller 14 (in the primary transfer process). is there.).

Then, the surfaces of the photosensitive drums 11Y, 11M, 11C, and 11BK after the transfer process reach positions facing the cleaning unit 15, respectively. Then, the untransferred toner remaining on the photosensitive drums 11Y, 11M, 11C, and 11BK is collected by the cleaning unit 15 (this is a cleaning process).
Thereafter, the surfaces of the photoconductive drums 11Y, 11M, 11C, and 11BK pass through a neutralization unit (not shown), and a series of image forming processes on the photoconductive drums 11Y, 11M, 11C, and 11BK is completed.

On the other hand, the intermediate transfer belt 17 on which the toners of the respective colors on the photosensitive drums 11Y, 11M, 11C, and 11BK are transferred (carrying) are run in the clockwise direction in the drawing and are connected to the secondary transfer bias roller 18. Reach the opposite position. Then, a color toner image carried on the intermediate transfer belt 17 is transferred onto the recording medium P at a position facing the secondary transfer bias roller 18 (secondary transfer step).
Thereafter, the surface of the intermediate transfer belt 17 reaches the position of the intermediate transfer belt cleaning unit 16. Then, the untransferred toner adhered on the intermediate transfer belt 17 is collected by the intermediate transfer belt cleaning unit 16, and a series of transfer processes in the intermediate transfer belt 17 is completed.

Here, the recording medium P transported between the intermediate transfer belt 17 and the secondary transfer bias roller 18 (secondary transfer nip) is transported from the paper supply unit 7 via the registration roller 9 and the like. It is a thing.
Specifically, the recording medium P fed by the paper feeding roller 8 from the paper feeding unit 7 that stores the recording medium P is guided to the registration roller 9 after passing through the conveyance guide. The recording medium P that has reached the registration roller 9 is conveyed toward the secondary transfer nip at the same timing.

Then, the recording medium P on which the full-color image is transferred is guided to the fixing device 20 by the transport belt. In the fixing device 20, the color image (toner) is fixed on the recording medium P at the nip between the fixing belt and the pressure roller.
Then, the recording medium P after the fixing step is discharged as an output image outside the apparatus main body 1 by a paper discharge roller, and a series of image forming processes is completed.

Next, the image forming unit in the image forming apparatus will be described in detail with reference to FIGS.
FIG. 2 is a configuration diagram illustrating the image forming unit and the agent cartridge 28. FIG. 3A is a schematic cross-sectional view of the upper portion of the developing device 13 (the position of the first conveying screw 13b1) in the longitudinal direction, and FIG. 3B is the lower portion of the developing device 13 (the second conveying screw). It is the position of the screw 13b2 and the 3rd conveyance screw 13b3.) It is the schematic sectional drawing which looked at the longitudinal direction. FIG. 4 is a cross-sectional view showing an end portion of the developing device 13 (the position of the third relay portion 13h).
Since each image forming unit has almost the same structure and each agent cartridge has almost the same structure, the image forming unit and the agent cartridge in FIGS. 2 to 4 are indicated by alphabets (Y, C, M, BK) is shown in the figure.

As shown in FIG. 2, the image forming unit includes a photosensitive drum 11 as an image carrier, a charging unit 12, a developing device 13 (developing unit), a cleaning unit 15, and the like.
The photosensitive drum 11 as an image carrier is a negatively charged organic photosensitive member, and is rotated counterclockwise by a rotation driving mechanism (not shown).

The charging unit 12 is a charging roller having elasticity in which a medium-resistance foamed urethane layer in which a urethane resin, carbon black as conductive particles, a sulfurizing agent, a foaming agent, and the like are formed in a roller shape is formed on a core metal. The material of the middle resistance layer of the charging unit 12 is urethane, ethylene-propylene-diene polyethylene (EPDM), butadiene acrylonitrile rubber (NBR), silicone rubber, isoprene rubber, etc. It is also possible to use a rubber material in which a conductive material such as the above is dispersed or a foamed material of these materials.
The cleaning unit 15 is provided with a cleaning brush (or a cleaning blade) that is in sliding contact with the photosensitive drum 11, and mechanically removes and collects untransferred toner on the photosensitive drum 11.

  The developing device 13 is arranged so that a developing roller 13a as a developer carrying member is close to the photosensitive drum 11, and a developing region where the photosensitive drum 11 and the magnetic brush are in contact with each other is formed. Is done. A developer G (two-component developer) composed of toner T and carrier C is accommodated in the developing device 13. The developing device 13 develops the electrostatic latent image formed on the photosensitive drum 11 (forms a toner image). The configuration and operation of the developing device 13 will be described in detail later.

Here, the developing device 13 in the present embodiment is of a premix developing system, and a new carrier C (developer G) is appropriately supplied from the agent cartridge 28 into the developing device 13 and deteriorated. The developer G thus discharged is discharged toward the agent storage container 70 installed outside the developing device 13.
Referring to FIG. 2, the agent cartridge 28 accommodates developer G (toner T and carrier C) to be supplied into the developing device 13 therein. The agent cartridge 28 functions as a toner cartridge that supplies new toner T to the developing device 13, and also functions as a supply unit that supplies new carrier C to the developing device 13. Specifically, based on information of toner density (which is a ratio of toner in the developer G) detected by a magnetic sensor (not shown) installed in the developing device 13, the shutter driving unit 81 The shutter mechanism 80 is opened and closed, and the developer G is appropriately supplied from the agent cartridge 28 as supply means into the developing device 13. Here, in the present embodiment, the mixing ratio (toner concentration) of the toner T with respect to the carrier C in the developer G of the agent cartridge 28 is set to be relatively high.
The supply of the developer G is not limited to the toner density information, but is performed based on the image density information detected from the reflectance of the toner image formed on the photosensitive belt or the intermediate transfer belt. Also good. Further, the implementation of the supply of the developer G may be determined by combining these different pieces of information.

  The supply pipe 29 as a supply means is for reliably guiding the developer G (toner T and carrier C) supplied from the agent cartridge 28 into the developing device 13. That is, the developer G discharged from the agent cartridge 28 is supplied into the developing device 13 from the supply port 13 e via the supply pipe 29.

Hereinafter, the developing device 13 in the image forming apparatus will be described in detail.
2 to 4, the developing device 13 includes a developing roller 13 a as a developer carrier, transport screws 13 b 1 to 13 b 3 (auger screws) as a transport member, a doctor blade 13 c, and the like.
The developing roller 13a is configured such that a sleeve formed of a non-magnetic material such as aluminum, brass, stainless steel, conductive resin or the like in a cylindrical shape is rotated clockwise by a rotation driving mechanism (not shown). Referring to FIG. 3, a magnet 13 a 1 that forms a magnetic field is fixed in the sleeve 13 a 2 of the developing roller 13 a so as to cause the developer G to rise on the peripheral surface of the sleeve. The carrier C in the developer G rises in a chain shape on the sleeve 13a2 so as to follow the normal line of magnetic force emitted from the magnet 13a1. The charged toner T is attached to the carrier C that is spiked in a chain shape to form a magnetic brush. The magnetic brush is transferred in the same direction (clockwise) as the sleeve 13a2 by the rotation of the sleeve 13a2.

Referring to FIG. 2, the doctor blade 13c is installed on the upstream side of the developing area, and regulates the developer G on the developing roller 13a to an appropriate amount.
The three conveying screws 13b1 to 13b3 stir and mix the developer G accommodated in the developing device 13 while circulating in the longitudinal direction (the direction perpendicular to the paper surface of FIG. 2).
The first conveying screw 13b1 as the first conveying member is disposed at a position facing the developing roller 13a, and conveys the developer G in the horizontal direction (the rightward direction indicated by the dashed arrow in FIG. 3A). At the same time, the developer G is supplied onto the developing roller 13a (in the direction of the white arrow in FIG. 3A).

  The second conveyance screw 13b2 as the second conveyance member is disposed below the first conveyance screw 13b1 and at a position facing the developing roller 13a. Then, the developer G separated from the developing roller 13a (the developer G forcibly separated from the developing roller 13a by the agent separation pole after the developing process, and separated in the direction of the white arrow in FIG. 3B). Is transported in the horizontal direction (the transport in the right direction indicated by the broken line arrow in FIG. 3B).

The 3rd conveyance screw 13b3 as a 3rd conveyance member is a position adjacent to the 2nd conveyance screw 13b2, and is arrange | positioned diagonally below the 1st conveyance member 13b1. The third transport screw 13b3 transports the developer G transported by the second transport screw 13b2 to the upstream side of the transport path by the first transport member 13b1, and from the downstream side of the transport path by the first transport screw 13b1. The developer G circulated through the first relay portion 13f is transported to the upstream side of the transport path by the first transport member 13b1 (the transport in the left direction indicated by the broken-line arrow in FIG. 3B).
The three conveying screws 13b1 to 13b3 are arranged so that the rotation shaft is substantially horizontal, like the developing roller 13a and the photosensitive drum 11.

In addition, the conveyance path by the 1st conveyance screw 13b1, the conveyance path by the 2nd conveyance screw 13b2, and the conveyance path by the 3rd conveyance screw 13b3 are isolated by the wall part.
With reference to FIG. 3 (B), the downstream side of the conveyance path by the second conveyance screw 13b2 and the upstream side of the conveyance path by the third conveyance screw 13b3 communicate with each other via the second relay portion 13g. Also, referring to FIGS. 3A and 3B, the downstream side of the conveyance path by the first conveyance screw 13b1 and the upstream side of the conveyance path by the third conveyance screw 13b3 are the first relay portion 13f. It communicates through. Further, referring to FIGS. 3A, 3B, and 4, the downstream side of the transport path by the third transport screw 13b3 and the upstream side of the transport path by the first transport screw 13b1 are the third. It communicates via the relay part 13h. Referring to FIG. 4, the developer G staying and rising in the vicinity of the third relay portion 13 h in the transport route by the third transport screw 13 b 3 is transported by the first transport screw 13 b 1 via the third relay portion 13 h. It is conveyed (supplied) to the upstream side.

With such a configuration, a circulation path for circulating the developer G in the longitudinal direction in the developing device 13 is formed by the three transport screws 13b1 to 13b3. That is, when the developing device 13 is operated, the developer G accommodated in the device flows in the direction of the broken line arrow in FIG. In this way, the developer G supply path to the developing roller 13a (the transport path by the first transport screw 13a1) and the developer G recovery path to be separated from the developing roller 13a (by the second transport screw 13a2). , The density deviation of the toner image formed on the photosensitive drum 11 can be reduced.
Although illustration is omitted, a magnetic sensor for detecting the toner concentration of the developer circulating in the apparatus is installed in the conveyance path by the third conveyance screw 13b3. Then, based on the toner density information detected by the magnetic sensor, a developer G having a predetermined toner density is supplied from the agent cartridge 28 serving as a supply unit into the developing device 13 through the supply port 13e.

Here, with reference to FIG. 2 and FIG. 3, a part of the developer G accommodated in the developing device 13 is discharged to the outside (agent storage container 70) in the transport path by the first transport screw 13 b 1. A discharge port 13d as discharge means is provided. Specifically, the discharge port 13d is a developer agent that is supplied to the developing device 13 by the supply means 28, 29, 80, 81, and the developer amount in the device is increased and conveyed to that position. When the surface (upper surface) exceeds a predetermined height, the excess developer G is discharged toward the agent storage container 70. That is, the excess developer G exceeds the lower portion of the discharge port 13d, is discharged from the discharge port 13d, and falls by its own weight toward the agent storage container 70 via the discharge path. As described above, the carrier deteriorated by being contaminated with the base resin or the external additive of the toner T is automatically discharged to the outside of the developing device, so that deterioration of the image quality can be suppressed over time.
In the present embodiment, the replenishment port 13e and the discharge port 13d are disposed in the transport path by the first transport screw 13a1, but the positions of the replenishment port 13e and the discharge port 13d are not limited to this.

Here, in this embodiment, as the toner T used in the developing process, a small particle diameter toner formed so that the volume average particle diameter is in the range of 3 to 8 μm is used. This increases the resolution of the output image and achieves high image quality.
Further, as the toner T, a substantially spherical toner formed so that the average circularity is in the range of 0.93 to 1.00 is used. As a result, transferability is enhanced and high image quality is achieved.
Further, the toner T has a hydrophobic silica formed so as to contain a toner having a primary particle size of less than 20 nm in a mass ratio (a mass ratio of the hydrophobic silica to the toner) of 0.3 to 5. It is added as an external additive so that it may become 0.0 mass%. Thereby, the fluidity of the toner can be ensured even when a small particle size toner is used.

Here, the volume average particle diameter of the toner described above can be measured using a measuring apparatus for the particle size distribution of toner particles by a Coulter counter method. Examples of these measuring devices include “Coulter Counter TA-II” and “Coulter Multisizer II” (both manufactured by Coulter). The measurement method is described below.
First, 0.1 to 5 ml of a surfactant (preferably alkylbenzene sulfonate) is added as a dispersant to 100 to 150 ml of an aqueous electrolytic solution. Here, the electrolytic solution is a solution prepared by preparing a 1% NaCl aqueous solution using primary sodium chloride. For example, ISOTON-II (manufactured by Coulter) can be used. Here, 2 to 20 mg of a measurement sample is further added. The electrolytic solution in which the sample is suspended is subjected to a dispersion treatment with an ultrasonic disperser for about 1 to 3 minutes, and the volume and number of toner particles or toner are measured with the above-described measuring apparatus using an aperture of 100 μm. The volume distribution and the number distribution are calculated. From the obtained distribution, the volume average particle diameter (D4) and the number average particle diameter (D1) of the toner can be obtained.
As channels, 2.00 to less than 2.52 μm; 2.52 to less than 3.17 μm; 3.17 to less than 4.00 μm; 4.00 to less than 5.04 μm; 5.04 to less than 6.35 μm; 6 Less than 35 to 8.00 μm; less than 8.00 to less than 10.08 μm; less than 10.08 to less than 12.70 μm; less than 12.70 to less than 16.00 μm; less than 16.00 to less than 20.20 μm; Uses 13 channels of less than 40 μm; 25.40 to less than 32.00 μm; 32.00 to less than 40.30 μm, and targets particles having a particle size of 2.00 μm to less than 40.30 μm.

The circularity of the toner described above is a value obtained from the following equation. This circularity is an index of the degree of unevenness of the toner particles, and indicates 1.00 when the toner is a perfect sphere, and the circularity becomes smaller as the surface shape becomes more complicated.
Circularity a = L ₀ / L
In the above equation, L ₀ represents the circumference of a circle having the same projected area as the particle image, and L represents the circumference of the projected image of the particle.
The circularity can be measured using a “flow type particle image analyzer FPIA-1000” (manufactured by Toa Medical Electronics Co., Ltd.).
As a specific measuring method, 0.1 to 0.5 ml of a surfactant, preferably alkylbenzene sulfonate, is added as a dispersant to 100 to 150 ml of water from which impure solids have been previously removed, and further measurement is performed. Add about 0.1-0.5g of sample. The suspension in which the sample is dispersed is subjected to dispersion treatment with an ultrasonic disperser for about 1 to 3 minutes, and the shape of the toner is measured with the above-mentioned apparatus with the dispersion concentration being 3000 to 10000 / μl.

Hereinafter, characteristic control performed in the developing device 13 will be described in detail.
With reference to FIG. 2, in the present embodiment, a timer 85 is provided as a detection unit that detects a time during which the operation of the developing device 13 is stopped (a leaving time). Then, according to the detection result of the timer 85 (detection means), the supply means 28, 29, 80, 81 supplies a new carrier C (developer G) into the developing device 13 before the development process is started. is doing. Specifically, when the standing time detected by the timer 85 exceeds a predetermined value (8 hours in the present embodiment), the agent is warmed up before the development process is restarted. Developer G is supplied from the cartridge 28 toward the developing device 13.
As a result, in the premix developing type developing device 13, the developing process is performed even when the device is left for a long time and the height (bulk) of the developer G contained in the device decreases. In some cases, the developer G is replenished in the apparatus to return to a normal volume, and therefore, "screw pitch unevenness" (the screw rotation pitch of the first conveying screw 23b1 is reduced) due to the poor supply of the developer to the developing roller 13a. The corresponding image unevenness (see FIG. 7) can be prevented from occurring on the image of the recording medium P.

Further, in the present embodiment, a humidity sensor 86 is installed as a second detection unit that detects environmental changes around the developing device 13. Then, according to the detection result of the humidity sensor 86 (second detection means), a new carrier C (developer G) is supplied into the developing device 13 by the supply means 28, 29, 80, 81 before the development process is started. ). Specifically, when the humidity fluctuation detected by the humidity sensor 86 exceeds a predetermined value (in this embodiment, 20% is set), at the warm-up before the development process is restarted, The developer G is supplied from the agent cartridge 28 toward the developing device 13.
As a result, in the premix developing type developing device 13, the height (bulk) of the developer G contained in the device is further reduced due to a significant decrease in the humidity around the device during standing. However, when the developing process is performed, the developer G is replenished into the apparatus and the normal volume is restored, so that “screw pitch unevenness” due to a poor supply of the developer to the developing roller 13a occurs on the recording medium P. It is possible to suppress problems that occur on the image.

  In particular, the developing device 13 according to the present embodiment has a developer G supply path to the developing roller 13a (a transport path by the first transport screw 13a1) and a developer G recovery path (from the developing roller 13a). Is separated from the second conveyance screw 13a2), the agent balance in the conveyance path is likely to be non-uniform, and screw pitch unevenness is likely to appear when the volume of the agent is reduced. Therefore, the effect of supplying the developer G into the developing device 13 before the start of the developing process is increased according to the standing time and environmental fluctuation.

  Further, in the present embodiment, since the toner having a small particle diameter is used, the volume of the developer is likely to increase during operation of the apparatus, and the void in the developer becomes small while the apparatus is left and the development is performed. The bulk of the agent tends to decrease. In addition, since the toner having a small particle size has a relatively large surface area, the charge amount tends to be high, and the toner concentration of the developer in the developing device is controlled to be high. For this reason, the bulk fluctuation of the developer is likely to increase before and after being left (at the time of operation). Further, in the present embodiment, since the substantially spherical toner is used, the developer is likely to be finely packed, and the bulk after being left is greatly reduced. Therefore, the effect of supplying the developer G into the developing device 13 before starting the developing process is increased according to the standing time.

  Further, in the present embodiment, hydrophobic silica having a small particle diameter, which has a high effect of improving toner fluidity, is used as an external additive for the toner. Such hydrophobic silica having a small particle size has a large specific surface area and a high hygroscopic property, so that the change in the charge amount of the toner due to the environment becomes large. Therefore, the effect of supplying the developer G into the developing device 13 before the start of the developing process is increased according to environmental fluctuations.

Hereinafter, specific control performed by the developing device 13 will be described in detail with reference to the flowchart of FIG.
First, it is determined by the timer 85 whether the developing device 13 is left for a predetermined time T1 or more (steps S1 to S2). In the present embodiment, the predetermined time T1 is set to 8 hours.
As a result, if it is determined that the standing time is not equal to or longer than the predetermined time T1, it is assumed that the bulk of the developer is not significantly reduced, and the image forming conditions are adjusted (development bias, charging bias, exposure amount, toner concentration, etc. (Step S10), and warming up is completed (Step S11).

On the other hand, if it is determined in step S2 that the standing time is equal to or longer than the predetermined time T1, it is assumed that the decrease in the volume of the developer is not small, and the humidity fluctuation around the developing device 13 is further predetermined. It is determined whether the value is greater than or equal to value A (step S3). In the present embodiment, the predetermined value A is set to 20%.
As a result, if it is determined that the humidity fluctuation is not equal to or greater than the predetermined value A, it is assumed that the decrease in the volume of the developer is not so great, the image forming conditions are adjusted (step S10), and the warming up is finished. (Step S11).

On the other hand, if it is determined in step S3 that the humidity fluctuation is equal to or greater than the predetermined value A, it is assumed that the bulk of the developer is greatly reduced, and the developing device 13 is first driven idle to remove the developer. Stirring and mixing are performed (step S4). Thereafter, the toner concentration of the developer in the developing device 13 is detected by the magnetic sensor (step S5), and it is determined whether or not the detection result C is equal to or greater than the predetermined value B (step S6). Here, the predetermined value B is set to about 4%.
As a result, when it is determined that the toner density is not equal to or higher than the predetermined value B, the carrier C (developer G) is replenished from the agent cartridge 28 into the developing device 13 (step S12). Repeat the flow. That is, the carrier C (developer G) is supplied from the agent cartridge 28 into the developing device 13 until the toner density reaches a predetermined value B. At this time, the bulk of the developer increases.

On the other hand, if it is determined in step S6 that the toner density is equal to or higher than the predetermined value B, the photosensitive member is used to restore the bulk of the developer while maintaining the toner density C at that time. A belt pattern (scanning direction × sub-scanning direction is a solid image with a maximum developing width × about 3 cm) is created on the drum 11 and the toner is discharged from the developing device 13 (step S7), while the toner density C is in the vicinity. Then, the carrier C (developer G) is replenished from the agent cartridge 28 into the developing device 13 (step S8). Then, it is determined whether or not the total replenishment amount of the carrier has reached a predetermined value D (step S9). As a result, when it is determined that the total replenishment amount of the carrier has not reached the predetermined value D, the flow after Step S7 (toner discharge by band creation and developer replenishment) is repeated. The predetermined value D described above is a value determined in advance based on experiments. The total amount of carrier replenishment in step S9 includes the amount of carrier replenished in step S12 when it is determined in step S6 that the toner density is not equal to or greater than the predetermined value B. As a result, the bulk increases according to the increased amount of carrier while maintaining the toner concentration.
Thereafter, the image forming conditions are adjusted (step S10), and the warming up is finished (step S11).

In the above-described control, the developer G is replenished from the agent cartridge 28 into the developing device 13 when both the condition relating to the standing time and the condition relating to the humidity fluctuation are satisfied. When the conditions are satisfied (especially when the conditions regarding the standing time are satisfied), it is possible to control the developer G to be supplied from the agent cartridge 28 into the developing device 13.
Further, the determination standard based on the toner density detection performed in steps S5 to S6 and the determination standard for toner density adjustment performed when adjusting the image forming conditions in step S10 are not necessarily the same.

Hereinafter, with reference to FIG. 6, an experiment performed for confirming the effect of the present embodiment described above will be described.
FIG. 6 is a table showing experimental results for 12 experiments of Examples 1-6 and Comparative Examples 1-6. In Examples 1 to 6, the above-described control (control to replenish the developer before the start of the developing process) is performed using the image forming apparatus main body in the present embodiment, and in Comparative Examples 1 to 6, the present embodiment is performed. The above-described control was not performed using the image forming apparatus main body in (the conventional control was performed).

Specifically, in Examples 1 to 6 and Comparative Examples 1 to 6, 5000 images with an image area ratio of 5% were printed in an environment of 25 ° C. and 50%. Thereafter, the environment was changed to 10 ° C. and 15% and left for 12 hours. When the apparatus main body 1 was turned on after being left, it was confirmed that the detected leaving time was a predetermined time T1 or more and the detected humidity fluctuation was a predetermined value A or more.
Further, in Examples 1 to 6, after that, the developing device was idle-driven, and it was confirmed by the magnetic sensor that the toner density was higher than the predetermined value B. Therefore, the operation of supplying a developer in an amount capable of maintaining the toner concentration was repeated while creating a belt pattern having a constant area and discharging the toner in the developing device.
And in Examples 1-6 and Comparative Examples 1-6, it was confirmed whether the screw pitch nonuniformity has generate | occur | produced on the output image formed after being left. Furthermore, when the screw pitch unevenness did not occur, the image density, fine line reproducibility, background stain, and transferability of the solid image were also evaluated.

(1) Evaluation of screw pitch unevenness Solid images were formed on three A3 size recording media, respectively, and the presence or absence of screw pitch unevenness was observed. In FIG. 6, “◯” indicates a state where no screw pitch unevenness occurs. “Δ” indicates that the screw pitch unevenness occurs, but there is a portion where there is no screw pitch unevenness from the front end to the rear end of the image, and the portion where the screw pitch unevenness occurs is less than 1 cm in width from the image end portion. “X” indicates a state in which screw pitch unevenness occurs over the entire area. Results other than ○ were at unacceptable levels.

(2) Evaluation of image density A solid image was formed on an A3 size recording medium, and a total of 6 points (4 cm from both ends and 4 cm from the upper end or lower end, 4 points from the upper end or lower end, 10 cm from the center and upper end or lower end) The image density was measured for 2 points). For the measurement, a spectrometer “938 Spectrodensitometer” (manufactured by X-Light) was used. The average value and variation of the six points measured here were calculated, and the following ranking was performed. The variation is obtained by multiplying 100 by the value obtained by dividing the difference between the maximum value and the minimum value by the average value.
As for the average values in FIG. 6, “◯” is 1.4 or more, “Δ” is 1.2 or more and less than 1.4, and “X” is less than 1.2. Regarding the variation, “◯” is less than 10%, “Δ” is 10% or more and less than 20%, and “X” is 20% or more. In all cases, results other than “x” were acceptable levels.

(3) Evaluation of fine line reproducibility A 1-dot grid line image of 600 dots / inch and 150 lines / inch was output in both the main scanning direction and the sub-scanning direction, and line image breakage and blurring were visually evaluated in three stages. In FIG. 6, “◯” is a good level, “Δ” is a normal level, and “X” is a bad level.

(4) Evaluation of background stains Using A4 size PPC paper “Type 6200” (manufactured by Ricoh) as a recording medium, a solid white image was output, and the image density was measured at any five points. At the same time, the image density was measured at arbitrary five points on the same type of white paper that did not pass through the image forming apparatus. And the background dirt was evaluated from each average value. Here, when the image density shows a value equivalent to the density of the paper, there is no background stain, and the larger the image density difference, the worse the background stain.
In FIG. 6, “◯” indicates an increase from the blank paper density of less than 0.005, “Δ” indicates an increase from the blank paper density of 0.005 to less than 0.01, and “x” indicates an increase from the blank paper density. Is 0.01 or more. Results other than “x” were acceptable levels.

(5) Evaluation of transferability In the middle of forming an image in which a black solid portion of 1 inch × 1 inch is arranged in 4 columns × 4 rows across the background on the photosensitive drum 11, the image forming apparatus is forcibly In this state, there is a solid portion before transfer on the photosensitive drum and a solid portion after transfer on the intermediate transfer belt. For the solid part before and after the transfer, the transfer rate is calculated by comparing the toner adhesion amount. The toner adhesion amount is a value obtained by transferring (attaching) the solid toner to the tape and subtracting the tape weight before transfer from the tape weight after transfer. The transfer rate is calculated by the following formula.
Transfer rate (%) = 100− [Attached amount of solid part after transfer (mg) / Attached amount of solid part before transfer (mg)] × 100
In FIG. 6, “◯” indicates a transfer rate of 95% or more, “Δ” indicates a transfer rate of 90% or more and less than 95%, and “X” indicates a transfer rate of less than 90%. Results other than “x” were acceptable levels.

Here, in the experiment, five types of toners a to e and two types of developing devices a to b were prepared.
(1) Toner a The materials constituting the toner base are resin: 95 parts of polyester resin, release agent: 5 parts of carnauba wax, charge control agent: 1 part of zirconium salicylate, and colorant: 10 of carbon black. Part. These materials were charged into a Henschel mixer “MF20C / I type” (manufactured by Mitsui Miike Processing Co., Ltd.), sufficiently stirred and mixed, then melt-kneaded with a twin screw extruder (manufactured by Toshiba Machine Co., Ltd.), and cooled. Next, the volume average particle diameter (D4) is 9.0 ± 0.5 μm, and the ratio (D4 / D1) of the volume average particle diameter to the number average particle diameter (D1) is 1.15 to 1.20. Then, pulverization and classification were performed to prepare a toner base. To 100 parts of the toner base, an additive (titanium oxide having a primary particle size of 20 nm: 1.0 part) was added and mixed with a Henschel mixer to obtain toner a. The average circularity of the toner a was 0.91.

(2) Toner b The same toner base material as that of toner a is used, and the toner base is removed in the same manner as toner a except that the volume average particle diameter (D4) is 5.5 ± 0.5 μm. Produced. To 100 parts of the toner base, an additive (titanium oxide having a primary particle diameter of 20 nm: 2.0 parts) was added and mixed with a Henschel mixer to obtain toner b. The average circularity of the toner b was 0.91.

(3) Toner c In a reaction vessel equipped with a cooling tube, a stirrer, and a nitrogen introducing tube, 724 parts of bisphenol A ethylene oxide 2-mole adduct, 276 parts of isophthalic acid and 2 parts of dibutyltin oxide were placed under normal pressure. The mixture was reacted at 230 ° C. for 8 hours, further reacted at a reduced pressure of 10 to 15 mmHg for 5 hours, cooled to 160 ° C., 32 parts of phthalic anhydride was added thereto, and reacted for 2 hours. Subsequently, it cooled to 80 degreeC and reacted with 188 parts of isophorone diisocyanate in ethyl acetate for 2 hours, and the isocyanate containing prepolymer (1) was obtained. Subsequently, 267 parts of prepolymer (1) and 14 parts of isophoronediamine were reacted at 50 ° C. for 2 hours to obtain a urea-modified polyester resin (1) having a mass average molecular weight of 64,000. In the same manner as above, 724 parts of bisphenol A ethylene oxide 2-mole adduct and 276 parts of terephthalic acid were polycondensed at 230 ° C. for 8 hours under normal pressure, and then reacted for 5 hours at a reduced pressure of 10 to 15 mmHg. An unfinished polyester resin (a) was synthesized.
200 parts of urea-modified polyester resin (1) and 800 parts of the above-mentioned unmodified polyester resin (a) are dissolved and mixed in 2000 parts of an ethyl acetate / MEK (1/1) mixed solvent to prepare a toner binder resin (1 ) In ethyl acetate / MEK. Part of the mixture was dried under reduced pressure to isolate the toner binder resin (1). In a beaker, 240 parts of the above-mentioned toner binder resin (1) in ethyl acetate / MEK solution, 20 parts of pentaerythritol tetrabehenate (melting point: 81 ° C., melt viscosity: 25 cps), and 10 parts of carbon black were placed at 60 ° C. The mixture was stirred at 12000 rpm using a TK homomixer, and uniformly dissolved and dispersed.
Next, 706 parts of ion exchange water, 294 parts of hydroxyapatite suspension “Superite 10” (manufactured by Nippon Chemical Industry Co., Ltd.) and 0.2 part of sodium dodecylbenzenesulfonate are uniformly dissolved in a beaker. did. Next, the temperature was raised to 60 ° C., and the above-mentioned toner material solution was added and stirred for 10 minutes while stirring at 12000 rpm with a TK homomixer.
Next, the obtained mixed liquid is transferred to a Kolben equipped with a stir bar and a thermometer, heated to 98 ° C. to partially remove the solvent, returned to room temperature, and then stirred at 12000 rpm using the same homomixer. The toner was deformed from a spherical shape, and the solvent was completely removed. Next, after filtering, washing and drying, air classification was performed to obtain toner base particles. Toner c was produced by mixing 2.0 parts of titanium oxide (primary particle size 20 nm) with 100 parts of the obtained toner base particles using a Henschel mixer. The volume average particle diameter of the toner c was 5.54, Dv / Dn was 1.14, and the average circularity was 0.978.

(4) Toner d / Toner e Toner d and toner e were prepared by obtaining toner base particles by the same method as toner c, and changing only the external additive to the following.
External additive for toner d: 2.0 parts of hydrophobic silica (primary particle size 50 nm) External additive for toner e: 0.7 part of hydrophobic silica (primary particle size 15 nm)
0.7 parts of titanium oxide (primary particle size 15nm)

The developer was prepared by mixing 7% by mass of each toner and 95% by mass of a copper-zinc ferrite carrier having an average particle diameter of 40 μm coated with a silicone resin using a tumbler shaker mixer.
Further, the developer for replenishment was filled in the agent cartridge 28 so that each toner and carrier had a carrier concentration of 10% by mass.

(1) About the developing device a A developing device of a premix developing type and provided with two conveying screws as conveying members (for example, a developing device of Patent Document 3, etc. Is.)
(2) Developing device b A developing device (a developing device in the present embodiment) which is of a premix developing system and has three conveying screws as conveying members.

Moreover, Examples 1-6 and Comparative Examples 1-6 were performed on the following conditions.
(1) Example 1 and Comparative Example 1
The developing device a and toner a were used.
(2) Example 2 and Comparative Example 2
The developing device b and toner a were used.
(3) Example 3 and Comparative Example 3
The developing device b and toner b were used.
(4) Example 4 and Comparative Example 4
A developing device b and a toner c were used.
(5) Example 5 and Comparative Example 5
A developing device b and a toner d were used.
(6) Example 6, Comparative Example 6
A developing device b and toner e were used.

From the experimental results shown in FIG. 6, no screw pitch unevenness occurred in any of Examples 1 to 6. Further, compared to the first embodiment, the solid image has less density deviation in the second embodiment. Furthermore, compared with Example 2, the image quality generally improved in Examples 3 to 6.
On the other hand, in Comparative Examples 1 to 6 in which the control in the present embodiment is not performed, screw pitch unevenness occurred in all cases, although there was a difference in degree.

  As described above, in the present embodiment, a new developer G (carrier C) is added into the developing device 13 before the development process is started, according to the time during which the operation of the developing device 13 is stopped. Therefore, even if the developing device 13 is left for a long time, the occurrence of image unevenness on the output image can be suppressed.

In the present embodiment, the present invention is applied to the developing device 13 in which three conveying screws 13b1 to 13b3 as conveying members are installed. However, the developing device in which two or four or more conveying screws are installed. The present invention can also be applied to. Even in this case, the same effect as in the present embodiment can be obtained by newly supplying the developer G into the developing device 13 before the development process is started in accordance with the standing time and the environmental change. .
Moreover, in this Embodiment, although the 3rd conveyance screw 13b3 was arrange | positioned horizontally, the 3rd conveyance screw 13b3 can also be arrange | positioned diagonally with respect to a horizontal direction.

  In this embodiment, the developer G (toner T and carrier C) is supplied from the agent cartridge 28 serving as the supply unit toward the developing device 13. However, only the carrier C is supplied from the supply unit toward the developing device 13. It can also be supplied. In that case, a toner cartridge containing only toner is installed separately from the agent cartridge (carrier cartridge), and the toner contained in the toner cartridge is developed based on the detection result of the magnetic sensor installed in the developing device 13. It will be replenished appropriately toward 13. Even in such a case, the same effect as in the present embodiment can be obtained.

  Further, in the present embodiment, the present invention is applied to an image forming apparatus in which the developing device 13 is configured as a unit that is detachably attached to the main body of the image forming apparatus. However, the application of the present invention is not limited to this, and the present invention can naturally be applied to an image forming apparatus in which the image forming unit is a process cartridge.

  Further, in the present embodiment, the developer G is newly supplied into the developing device 13 before the development process is started in accordance with the humidity variation. However, in the developing device 13 due to environmental variation such as temperature variation and atmospheric pressure variation. When the volume of the developer fluctuates, the developer G may be newly supplied into the developing device 13 before the development process is started in accordance with temperature fluctuation, atmospheric pressure fluctuation, or the like.

  It should be noted that the present invention is not limited to the present embodiment, and it is obvious that the present embodiment can be modified as appropriate within the scope of the technical idea of the present invention, other than suggested in the present embodiment. is there. In addition, the number, position, shape, and the like of the constituent members are not limited to the present embodiment, and the number, position, shape, and the like suitable for implementing the present invention can be achieved.

1 is an overall configuration diagram illustrating an image forming apparatus according to an embodiment of the present invention. It is a block diagram which shows an image creation part. (A) The schematic sectional view which looked at the upper part of the developing device in the longitudinal direction, (B) The schematic sectional view which looked at the lower part of the developing device in the longitudinal direction. It is sectional drawing which shows the edge part of a developing device. It is a flowchart which shows the control performed with a developing device. It is a table | surface figure which shows an experimental result. It is the schematic which shows the state which the screw pitch nonuniformity produced on the output image.

Explanation of symbols

1 image forming apparatus body (apparatus body),
11, 11Y, 11C, 11M, 11BK Photosensitive drum (image carrier),
13 Developing device (developing part),
13a Development roller (developer carrier),
13b1 first conveying screw (first conveying member),
13b2 second conveying screw (second conveying member),
13b3 third conveying screw (third conveying member),
13c doctor blade,
13d discharge port (discharge means),
13e Supply port,
13f 1st relay part, 13g 2nd relay part, 13h 3rd relay part,
28 agent cartridge (supply means),
29 supply pipe (supply means), 70 agent storage container,
85 Timer (detection means),
86 Humidity sensor (second detection means),
G developer (two-component developer), T toner, C carrier,
P Recording medium.

Claims (14)

A developing device that stores a developer having a carrier and a toner and performs a developing process for developing a latent image formed on an image carrier,
Supply means for supplying a new carrier into the apparatus;
Discharging means for discharging a part of the developer contained in the apparatus to the outside;
Detection means for detecting the time during which the operation of the apparatus is stopped;
With
The developing device according to claim 1, wherein the supply unit supplies a new carrier into the apparatus before the development process is started in accordance with a detection result of the detection unit.   2. The carrier according to claim 1, wherein when the leaving time detected by the detection unit exceeds a predetermined value, the supply unit newly supplies a carrier into the apparatus before the development process is started. Development device. Comprising a second detection means for detecting environmental changes around the device;
3. The development according to claim 1, wherein the supply unit supplies a new carrier into the apparatus before the development process is started in accordance with a detection result of the second detection unit. apparatus. The second detection means is a humidity sensor for detecting a humidity fluctuation around the apparatus,
4. The supply unit according to claim 3, wherein when the humidity fluctuation detected by the humidity sensor exceeds a predetermined value, a new carrier is supplied into the apparatus before the development process is started. Development device. A developer carrying body facing the image carrying body and carrying a developer;
A first conveying member facing the developer carrying member and supplying the developer to the developer carrying member while conveying the developer in the longitudinal direction;
A second conveying member disposed below the first conveying member and facing the developer carrying member and conveying the developer detached from the developer carrying member in the longitudinal direction;
The developer transported by the second transport member is transported to the upstream side of the transport path by the first transport member, and the developer that has reached the downstream side of the transport path by the first transport member is transferred to the first transport member. A third transport member for transporting upstream of the transport path by
The developing device according to claim 1, further comprising:   The discharge means includes a discharge port for discharging the developer to the outside when the surface of the developer conveyed to the position exceeds a predetermined height. Item 6. The developing device according to Item 5.   The developing device according to claim 1, wherein the toner has a volume average particle diameter of 3 to 8 μm.   The developing device according to claim 1, wherein the toner is formed so that an average circularity is in a range of 0.93 to 1.00.   The developing device according to claim 1, wherein hydrophobic silica is added to the toner.   The developing device according to claim 9, wherein the hydrophobic silica is formed so as to contain a primary particle size of less than 20 nm.   The developing device according to claim 9, wherein the developing device is formed so that a mass ratio of the hydrophobic silica to the toner is 0.3 to 5.0 mass%.   The developing device according to claim 1, wherein the supply unit newly supplies toner together with the carrier into the apparatus. A process cartridge that is detachably installed on the main body of the image forming apparatus,
13. A process cartridge in which the developing device according to claim 1 and the image carrier are integrated.   An image forming apparatus comprising the developing device according to claim 1 and the image carrier.

Images