JP2007147916A - Developing device and image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To achieve a developing device constituted to stably yield an excellent image over a long term by restraining the deterioration of developer regardless of a service condition, and also prevent toner scattering. <P>SOLUTION: The developing device 2 using two-component developer comprising a toner and a carrier is provided with: a developer carrier 11; developer conveying members 9 and 10 conveying a developer in the device to the developer carrier; a layer thickness regulating member 14 regulating the layer thickness of the developer on the developer carrier; a developer stirring member 21 provided on a developer conveying path between the developer conveying members and the layer thickness regulating member; and a control means for controlling the start of actuation of the developer stirring member 21 in accordance with image area, whereby stress applied to the developer is varied (adjusted). Therefore, the deterioration of the developer occurring when the service condition (image area rate) differs, the deterioration of image quality caused thereby and the toner scattering or the like are prevented without downtime. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an electrophotographic image forming apparatus applied to a copying machine, a printer, a plotter, a facsimile machine, a printing machine, or a composite machine thereof, and more particularly to an image using a two-component developer composed of a toner and a carrier. The present invention relates to a developing device that visualizes an electrostatic latent image formed on a carrier as a toner image, and an image forming apparatus using the developing device.

  2. Description of the Related Art A developing device used in an image forming apparatus such as a copying machine or a printer using an electrophotographic system often uses a two-component developer composed of a toner and a carrier. In an image forming apparatus using a two-component developer, only toner is consumed when a toner image is formed. Therefore, in order to continue to form a good image, it is necessary to replenish new toner as much as the consumed toner, and always keep the toner concentration of the developer contained in the developing device at an appropriate level. The developer is conveyed to a developing roller as a developer carrying member while being agitated and mixed with the replenished toner by a conveying mixing member such as a screw, and is held by the doctor blade as a layer thickness regulating member while being held on the developing roller. After the layer thickness is regulated, it is conveyed to the development area. The toner is brought into contact with and rubbed with the carrier by friction mixing by stirring and mixing until the development area is conveyed and the layer thickness is regulated, and a predetermined charge amount is ensured, so that the image carrier ( For example, movement (development) to the photosensitive member is possible.

  The developer is stressed by the agitation, transport and layer thickness regulation, but if this stress is continued after long-term use, the charging ability and fluidity of the developer will change, and the image quality will deteriorate or become unstable. . In particular, there are many cases where different deterioration mechanisms occur depending on the use conditions, particularly the toner consumption rate (image area rate).

  When the image area ratio is large, that is, when the toner balance speed is high, a large amount of toner additive (silica, titanium oxide, etc.) adheres to the carrier, thereby lowering the charging ability of the carrier. Then, the newly replenished toner is not sufficiently charged, and as a result, the average charge amount of the toner is lowered, resulting in image quality fluctuation and deterioration. In addition, the amount of weakly charged or reversely charged toner increases, which easily detach from the carrier, and causes toner to flow out of the developing device from a slight opening around the developing sleeve, which is the so-called toner scattering. Cheap. When such toner scattering occurs, the inside of the image forming apparatus is contaminated with toner, and if the degree is poor, the scattered toner may adhere to the photosensitive member and stain the image. In addition, a toner having a low charge amount also causes a problem of background stains adhering to the background portion (white portion) of an image. In addition, if the replenishment toner is not sufficiently mixed and stirred with the developer and is developed in the form of agglomerates, the toner image has a defect. Further, these cause abnormal images, toner scattering, and background stains.

  On the other hand, when the image area ratio is small, that is, when the toner balance speed is low, a lot of stress is applied to the same toner, and the toner additive is buried. Since the additive is used to adjust the charge amount and the fluidity, the charge amount fluctuates and the fluidity deteriorates when the additive is buried. The variation in the charge amount causes the image quality variation as described above, and the deterioration of the fluidity causes the image quality to deteriorate due to the decrease in the transfer rate from the photoconductor to the transfer body (recording paper, intermediate transfer belt, etc.). Furthermore, since the toner in which the additive is buried increases the adhesion with the carrier and is difficult to separate, the newly replenished toner is less likely to come into contact with the carrier surface and is not sufficiently charged. Cause abnormal image problems. In addition, the carrier coat layer is scraped off due to stress on the carrier. This is because when the image area is large, the amount of toner additive attached to the carrier is large as described above, which prevents the carrier coat layer from being scraped. However, when the image area is small, the toner additive Since the amount of adhesion to the carrier is small, the coating layer of the carrier is scraped off. When the coat layer of the carrier is scraped off, the resistance of the carrier decreases, and the carrier easily adheres to the photoconductor in the developing electric field, causing a problem that the carrier adheres to the image and becomes an abnormal image.

In order to reduce the developer charge, it has been proposed and used to improve the mixing and stirring performance by providing a large number of stirring blades on the conveying and mixing member in the developing device. In some cases, the deterioration of the developer with time is promoted, and conversely, the life of the developer is reduced.
Therefore, in Patent Document 1 (Japanese Patent Laid-Open No. 5-19621), a stirring auxiliary member that is inclined in the direction of accelerating the flow of the developer is provided on a screw having a helical structure, thereby improving the stirring and mixing performance of the developer and the replenishment toner. There has been proposed a method for improving and reducing the stress applied to the developer. However, the addition of the auxiliary member itself increases the stress of the developer, and if the auxiliary member is attached at an angle to reduce this stress, the mixing agitation performance decreases. appear.

In Patent Document 2 (Japanese Patent Laid-Open No. 2003-57950), the image density is stabilized by preventing the local fluctuation of the toner density at the time of toner replenishment by making the rotation speed of the stirring screw variable according to the image ratio. However, there is little effect in preventing the deterioration of the developer, and no mention is made of the deterioration.
In Patent Document 3 (Japanese Patent Laid-Open No. 2002-258554), the detection result of the reflected light amount of the reference pattern created on the image carrier is used for toner density control, but the calculation result of the usage status information of the image forming apparatus is used. Accordingly, the toner density control is corrected according to the deterioration of the developer by switching the setting value of the development potential at the time of developing the reference pattern. This is the image density caused by the decrease in the toner density due to the deterioration of the developer. It only prevents the decrease, and has no effect of suppressing the developer deterioration itself.

  In Patent Document 4 (Japanese Patent No. 3458888), a toner replenishing stirring mode for increasing the charge amount of toner, which is performed when the image area is large, and a non-image area on the photoreceptor, which is performed when the image area is small, are attached. All the modes to remove the overcharged toner are provided outside of the development process. However, if the chargeability of the carrier is severely reduced even after the toner replenishment stirring mode, the charge amount of the toner is desired. It is not up to the value of. Also, in the toner removal mode, toner that can be sufficiently used is discarded together (rather, normal toner is discharged preferentially), which is wasteful, reducing toner yield, increasing running cost, and increasing waste toner. Causes an increase in the space inside the machine and an increase in maintenance frequency such as replacement of waste toner bottles. Furthermore, since any mode is provided outside of the development process, the waiting time increases and the production efficiency decreases.

Japanese Patent Laid-Open No. 5-19621 JP 2003-57950 A JP 2002-258554 A Japanese Patent No. 3458881

  The present invention has been made in view of the above-mentioned problems of the prior art, and suppresses the deterioration of the developer by preventing the charging ability of the carrier and the resistance from being lowered regardless of the use conditions, and preventing the toner additive from being buried, It is an object (object) to provide a developing device having a configuration capable of stably obtaining a good image for a long period of time and preventing toner scattering, and an image forming apparatus using the developing device. To do.

In order to solve the above problems, the present invention employs the following technical means.
According to a first aspect of the present invention, in a developing device using a two-component developer composed of toner and carrier, a developer carrying member, and a developer carrying member for carrying the developer in the device to the developer carrying member. A layer thickness regulating member that regulates the layer thickness of the developer on the developer carrier, and a developer agitating member provided on a developer conveyance path between the developer conveyance member and the layer thickness regulating member, And a control means for controlling the start of operation of the developer agitating member according to the image area (claim 1).
According to a second means of the present invention, in the developing device of the first means, the control means controls the rotational speed of the developer stirring member.
Further, according to a third means of the present invention, in the developing device of the first or second means, the control means controls the rotation direction of the developer stirring member.

According to a fourth means of the present invention, in a developing device using a two-component developer comprising a toner and a carrier, a developer carrier, a magnetic field generator provided in the developer carrier, and the magnetic field generator Magnetic field control means for changing the magnetic field and control means for controlling the operation of the magnetic field control means in accordance with the image area are provided (claim 4).
According to a fifth means of the present invention, in the developing device of the fourth means, the magnetic field control means is a control means for controlling an electromagnet and a current value flowing through the electromagnet, and the current value according to an image area. Is controlled (claim 5).
Further, a sixth means of the present invention is the developing device of the fourth or fifth means, wherein the magnetic field generating means is a plurality of electromagnets provided (claim 6).
Furthermore, a seventh means of the present invention is characterized in that, in the developing device of the sixth means, the control means changes the number of operation of the electromagnet according to the image area.

According to an eighth aspect of the present invention, there is provided a developing device using a two-component developer comprising a toner and a carrier, a developer carrying member, and a developer carrying member for carrying the developer in the device to the developer carrying member. , A layer thickness regulating member for regulating the layer thickness of the developer on the developer carrying member, and a developer flow path width provided on the developer carrying path between the developer carrying member and the layer thickness regulating member Control means and control means for controlling the operation of the developer flow path width control means in accordance with the image area are provided (claim 8).
According to a ninth means of the present invention, in the developing device of the eighth means, the developer flow path width controlling means has a central axis and an arcuate outer diameter eccentric from the central axis, and the control The means controls the rotation angle of the developer flow path width control means in accordance with the image area.

  The tenth means of the present invention comprises an image carrier, means for forming an electrostatic latent image on the image carrier, and developing the electrostatic latent image on the image carrier with a developer to make a visible image. In the image forming apparatus provided with the developing means, the developing means of any one of the first to ninth means is used as the developing means.

According to the present invention, by adopting the configuration of any one of the first to ninth means, it is possible to vary the stress applied to the developer, and the development when the use conditions (image area ratio) are different. It is possible to realize a developing device that can prevent agent deterioration, resulting image quality deterioration, toner scattering, and the like without downtime, and an image forming apparatus using the developing device.
Further, in the developing device and the image forming apparatus of the present invention, the toner additive when the image area is large adheres to the carrier, the charging ability of the carrier is lowered, the toner is scattered, the contamination in the image forming apparatus, the image Problems such as stains on the upper surface can be prevented.

Furthermore, in the developing device and the image forming apparatus of the present invention, it is possible to prevent abnormal images such as burying of the toner additive when the image area ratio is small, resulting in a decrease in transfer rate, toner scattering, and carrier adhesion.
Further, in the developing device and the image forming apparatus of the present invention, it can be expected that the maintenance frequency is reduced by extending the life of the developer, the production efficiency is improved by reducing the downtime, the running cost is reduced, and the waste developer is reduced.

Hereinafter, the configuration, operation, and effects of the present invention will be described in detail with reference to the drawings.
First, FIG. 6 is a schematic configuration diagram showing a basic configuration example of a developing device according to the present invention. This developing device 2 is used in a copying machine, a printer, a plotter, a facsimile, a printing machine, or a complex machine thereof. Used in electrophotographic image forming apparatuses to be applied. FIG. 7 is a diagram showing an example of an image forming apparatus according to the present invention, and only a configuration example of an image forming unit (printer unit) is shown. When the image forming apparatus 100 is a copying machine, a facsimile, or the like, a document reading device (scanner) that reads a document image is added to the upper part of the main body.

  6 and 7, reference numeral 1 denotes a drum-shaped photoconductor as an image carrier, which is statically applied to the surface of the photoconductor 1 by charging by the charging device 3 and optical writing according to image information by the optical writing device 4. An electrostatic latent image is formed. The developing device 2 is a developing device using a two-component developer composed of a toner and a carrier. The developer is carried and conveyed by a developing roller 11 which is a developer carrying member, and an electrostatic latent image formed on the photoconductor 1 is formed. The toner is developed with toner to form a visible image. In addition to the charging device 3 and the optical writing device 4, the image forming apparatus 100 includes a transfer device 5 that transfers the toner image on the photoreceptor 1 to a transfer material P such as recording paper, and a cleaning that cleans the surface of the photoreceptor after transfer. An apparatus 6; a charge eliminating device 7 that removes residual charge on the surface of the photosensitive member; a fixing device 29 that fixes an image after transfer onto a transfer material P such as recording paper; and a paper discharge roller that discharges the transfer material P after fixing. 30 and a discharge tray 31 on which the discharged transfer material P is stocked. Further, in this image forming apparatus 100, the multi-stage sheet feeding cassettes 23-1 and 23-2 containing the transfer material P such as recording paper and the sheet feeding cassettes 23-1 and 23-2 are transferred one by one. A transfer material P selectively fed from one of a paper feed roller 24 and a separation roller pair 25 for feeding the material P and one of multi-stage paper feed cassettes 23-1 and 23-2 is conveyed. Conveying rollers 26 and 27, and a registration roller 28 that sends the transfer material P to a transfer portion between the photosensitive member 1 and the transfer device 5 in synchronization with image formation are provided.

  In the casing 12 constituting the developing device 2, there are provided a developing roller 11 and conveying screws 9 and 10 having spiral fins as developer conveying members for conveying the developer in the device to the developing roller 11. The conveying screws 9 and 10 rotate in the directions of arrows B and C in FIG. 6, respectively, and a developer containing a mixture of toner and carrier is contained in these portions. On the right side of the partition plate 13 in the figure, the developer is transported forward from the back side in the figure by the transport screws 9 and 10, and on the left side of the partition plate 13, the developer is transported from the near side to the back side. A portion without a central partition plate 13 is provided on the back side and the near side, and the developer is mixed and stirred while being circulated by the conveying screws 9 and 10.

  The developing roller 11 includes a developing sleeve 16 in which a nonmagnetic material is formed in a cylindrical shape, and a magnet roller 17 in which a plurality of magnetic poles are magnetized, and the magnet roller 17 is disposed inside the developing sleeve 16. The developer mixed and stirred while being circulated by the conveying screws 9 and 10 is magnetically attracted by the magnetic force of the magnet 17 in the developing roller 11, and the developing sleeve 16 rotates in the direction of arrow A as the developing sleeve 16 rotates. It is carried and conveyed by unevenness (not shown) provided on the surface. The developer carried and conveyed by the developing sleeve 16 is uniformly regulated by a doctor blade 14 which is a layer thickness regulating member, and then conveyed to a developing region facing the photoreceptor 1 to be static on the photoreceptor 1. The electrostatic latent image is developed with toner in the developer.

Here, only the toner adheres to the electrostatic latent image on the photosensitive member 1, and the toner that has not been developed and the carrier that has transported the toner are again agitated and conveyed in the developing device as the developing sleeve 16 rotates. It is carried to the department and released.
Further, in order to keep the amount of toner in the developer circulating in the developing device constant, the amount of toner used for development is replenished by the toner replenishing device (toner cartridge 18 and toner transport pump 19).

  Reference numeral 8 in the drawing denotes a toner concentration sensor, which is a sensor that detects the toner concentration in the developer by measuring the magnetic permeability of the developer inside the developing device 11. A control unit (not shown) of the image forming apparatus detects the toner density based on the fluctuation of the detection output of the toner density sensor 8 and maintains a constant toner density in the developer inside the developing device 11. The toner is replenished by the toner replenishing device. However, since the magnetic permeability of the two-component developer fluctuates due to changes in the environment, changes in the bulk density of the developer, and the like, the output target value of the toner concentration sensor 8 is corrected as appropriate. Specifically, a control unit (not shown) of the image forming apparatus converts the image density of a reference toner image formed on the photoreceptor 1 into an optical device composed of a light source (such as a light emitting diode) and a light receiving element (such as a photodiode). Measurement is performed using the image density sensor 15 of the equation, and the output target value of the toner density sensor 8 is corrected according to the output result of the image density sensor 15.

  The toner developed on the photoconductor 1 is selectively fed and conveyed from one of the multistage paper feed cassettes 23-1 and 23-2 and is transferred between the photoconductor 1 and the transfer device 5 by the registration roller 28. The unfixed toner image on the transfer material P after the transfer is transferred onto the upper surface of the transfer material P sent to the transfer portion of the toner, and is fixed by the heating roller 29a and the pressure roller 29b of the fixing device 29. The fixed transfer material P is stocked on a paper discharge tray 31 by a paper discharge roller 30. Further, the residual toner on the surface of the photoconductor after the image transfer is removed by the cleaning device 6, and the residual charge on the surface of the photoconductor is removed by the static eliminator 7.

  The toner cartridge 18 constituting the toner replenishing device stores toner, and the toner transport pump 19 operates only when a toner replenishment signal is input by the toner density sensor 8 to generate suction pressure in the replenishment path 19a. Then, the toner in the toner cartridge 18 is replenished onto the developer in the casing 12 (on the conveying screw 9).

  The above is an example of the basic configuration of the developing device according to the present invention and an example of the configuration and operation of the image forming apparatus. In the present invention, the developing device having the above-described configuration is improved and the use conditions are improved. Regardless of the charging ability of the carrier and the reduction of resistance, the prevention of the embedment of the toner additive, etc., to suppress the deterioration of the developer, so that a good image can be obtained stably over a long period of time, The toner scattering can be prevented. Hereinafter, specific examples of the developing device according to the present invention will be described.

[Example 1]
FIG. 1 is a schematic configuration diagram of a developing device showing an embodiment of the present invention, and components having the same reference numerals as those in FIG. 6 are the same components. The illustration of the toner supply device (toner cartridge 18 and toner transport pump 19) is omitted.

  In the developing device 2 shown in FIG. 1, in addition to the configuration of FIG. 6, a developer stirring member 21 provided on the developer transport path between the transport screw 10 and the doctor blade 14, and a developer corresponding to the image area Control means for controlling the start of operation of the stirring member 21 is provided. That is, in this embodiment, as a means for applying a stress to the developer, a stirring blade 21 that is a developer stirring member is newly provided in the developer conveyance region, and the operation of the stirring blade 21 is started by the control means according to the image area. Control is performed by a control unit (not shown) of an image forming apparatus.

  For example, when the image area of the document (or the image area of the image data input from the outside) exceeds a predetermined value, the stirring blade 21 is controlled by a control unit (not shown) of the image forming apparatus. , And the stress applied to the developer passing through this vicinity is increased. The stirring blade 21 is formed of a flat plate as shown in FIG. 4, and a relatively large stress is applied to the developer by rotation, so that the additive adhering to the carrier when the image area is large is scraped off. It is possible to prevent a decrease in charging ability of the carrier. The amount of stress applied to the developer is varied (adjusted) by setting the size and the rotational speed of the stirring blade 21 so that the additive adhering to the carrier can be removed. Conversely, by rotating the stirring blade 21 in the direction opposite to the rotation direction E, the amount of stress can be changed in two stages. In this case, the amount of stress applied is reduced. Further, if the control unit (not shown) of the image forming apparatus uses a variable speed motor as a driving means (not shown) so that the rotation speed of the stirring blade 21 can be controlled, the stirring speed is increased according to the image area. By increasing the amount of stress, an optimal amount of stress can be applied to any image area. Note that the relationship between the rotational speed and the image area is set as appropriate in view of the state of the additive adhering to the carrier.

[Example 2]
FIG. 2 is a schematic configuration diagram of a developing device showing another embodiment of the present invention, and components having the same reference numerals as those in FIG. 6 are the same components. The illustration of the toner supply device (toner cartridge 18 and toner transport pump 19) is omitted.

  In addition to the configuration shown in FIG. 6, the developing device 2 shown in FIG. 2 includes a magnetic field generating means 20a provided in the developing roller 11, a magnetic field control means for changing the magnetic field of the magnetic field generating means 20a, and the image area. Control means for controlling the operation of the magnetic field control means. Here, as a magnetic field generating means, an electromagnet 20a is additionally provided to the magnet roller 17, and a current is supplied to the electromagnet 20a by a driving power source (not shown) as a magnetic field control means, whereby a magnetic flux in the vicinity thereof is provided. The density is increasing. For example, when the image area of the document (or the image area of the image data input from the outside) is large, the magnetic flux density is increased by the electromagnet 20a to increase the stress applied to the developer passing therethrough. As a result, when the image area is large, the additive adhering to the carrier can be peeled off, and the charging ability of the carrier can be prevented from being lowered.

  Furthermore, if a drive power source (not shown), which is a magnetic field control means, can use a variable current, and this is controlled by a control unit (not shown) of the image forming apparatus, the amount of increase in magnetic flux density can be increased. It can be controlled easily. In other words, the larger the image area, the larger the magnitude of the current flowing through the electromagnet 20a, and the larger the magnetic flux density can be controlled so that more stress is applied. In FIG. 2, the electromagnet 20 a is arranged so as to apply stress to the area of the conveyance part D until the developer pumped from the vicinity of the conveyance screw 10 passes through the doctor blade 14. Stress can also be increased by arranging an electromagnet near 20b or near the pumping portion 20c of the agent near the conveying screw 10. In addition, a power supply that cannot vary the current by arranging a plurality of electromagnets at these positions and controlling the number of operations by controlling the operation (ON / OFF) by a control unit (not shown) of the image forming apparatus. Even if equipped, the amount of stress can be changed stepwise by changing the number of electromagnets operated according to the image area.

[Example 3]
FIG. 3 is a schematic configuration diagram of a developing device showing still another embodiment of the present invention, and components having the same reference numerals as those in FIG. 6 are the same components. The illustration of the toner supply device (toner cartridge 18 and toner transport pump 19) is omitted.

  In the developing device 2 shown in FIG. 3, in addition to the configuration of FIG. 6, the developer flow path width control means 22 provided on the developer transport path between the transport screw 10 and the doctor blade 14, and the image area Control means for controlling the operation of the developer flow path width control means 22. That is, in this embodiment, a half-moon roller 22 as a developer flow path width control means is newly provided as a stress applying means in the developer transport region, and the start of operation of the half-moon roller 22 is controlled according to the image area. It is controlled by a control unit (not shown) of the forming apparatus.

The half-moon roller 22 has a half-moon shaped cross section as shown in the figure, and the stop position in the rotation direction can be controlled by controlling a driving means such as a stepping motor (not shown) by a control unit (not shown). ing.
For example, when the image area of the document (or the image area of the image data input from the outside) is a predetermined value or more, the driving unit such as a stepping motor (not shown) is controlled by the control unit (not shown) of the image forming apparatus. Then, the rotation of the half-moon roller 22 is controlled, and the half-moon roller 22 is rotated, for example, by 180 degrees from the position 22a indicated by the broken line to the position of the solid line in the figure, and the flow path width of the developer passing therethrough is narrowed, The stress applied to the developer passing therethrough can be increased. As a result, as described above, the additive added to the carrier when the image area is large can be scraped off, and a decrease in the charging ability of the carrier can be prevented.

  Further, as shown in FIG. 5, the meniscal roller 22 has a central axis and an arcuate outer diameter that is eccentric from the central axis, that is, the rotation center axis of the semimoon roller 22 is an arc as shown in FIG. The control unit (not shown) of the image forming apparatus controls a driving unit such as a stepping motor (not shown) to control (adjust) the rotation angle of the meniscal roller 22 according to the image area. Thus, the amount of stress applied to the developer can be continuously varied by varying the width of the flow path, that is, by decentering the rotation center axis.

  In the first to third embodiments, the electromagnet (magnetic field generating means), the power source (magnetic field control means), the stirring blade (developer stirring member) 21, the half moon roller (developer flow width control means) 22 and the like are controlled. As a control means for performing the above, a dedicated controller may be provided in the developing device 2. However, the cost can be reduced by performing control by the control unit of the existing image forming apparatus. That is, although not shown, the control unit of the image forming apparatus includes a central processing unit (CPU) composed of a microcomputer, a memory (ROM, RAM) storing a control program and various control information, a clock, a timer, a counter, and various controls. Since it includes an input device for inputting signals from various sensors provided in each part of the circuit and the image forming apparatus, an output device for outputting a control signal to the driving means of each part of the image forming apparatus, the developing device 2 and image forming Along with the control of each part of the apparatus, the electromagnet (magnetic field generating means), the power source (magnetic field control means), the stirring blade (developer stirring member) 21, the half moon roller (developer flow path width control means) 22, etc. are easily controlled. Can be made.

As described above, in the developing device 2 of the present invention, the stress applied to the developer can be varied (adjusted) by employing any one of the configurations of the first to third embodiments. It is possible to prevent developer deterioration, image quality deterioration, toner scattering, and the like due to different area ratios without downtime.
In addition, in the present invention, the toner charging ability when the image area is large adheres to the carrier, the charging ability of the carrier is reduced, toner scattering, contamination in the image forming apparatus, background stains on the image, etc. The problem can be prevented.

Furthermore, in the developing device and the image forming apparatus of the present invention, it is possible to prevent abnormal images such as burying of the toner additive when the image area ratio is small, resulting in a decrease in transfer rate, toner scattering, and carrier adhesion.
Further, in the developing device and the image forming apparatus of the present invention, it can be expected that the maintenance frequency is reduced by extending the life of the developer, the production efficiency is improved by reducing the downtime, the running cost is reduced, and the waste developer is reduced.

1 is a schematic configuration diagram of a developing device showing an embodiment of the present invention. It is a schematic block diagram of the developing device which shows another Example of this invention. It is a schematic block diagram of the developing device which shows another Example of this invention. It is a perspective view of the stirring blade which shows an example of the developer stirring member used for the developing device of FIG. FIG. 4 is a plan view of a meniscal roller showing an example of a developer flow path width control means used in the developing device of FIG. 3. 1 is a schematic configuration diagram illustrating a basic configuration example of a developing device according to the present invention. 1 is a schematic configuration diagram illustrating an example of an image forming apparatus according to the present invention.

Explanation of symbols

1: Photoconductor (image carrier)
2: Developing device 3: Charging device 4: Optical writing device 5: Transfer device 6: Cleaning device 7: Static eliminating device 8: Toner concentration sensor 9, 10: Conveying screw (developer conveying member)
11: Development roller (developer carrier)
12: Casing 13: Partition plate 14: Doctor blade (layer thickness regulating member)
15: Image density sensor 16: Developing sleeve 17: Magnet roller 18: Toner cartridge 19: Toner transport pump (toner supply device)
20a: Electromagnet (magnetic field generating means)
21: Stirring blade (developer stirring member)
22: Half-moon roller (developer channel width control means)
23-1, 23-2: paper feed cassette 24: paper feed roller 25: separation roller pair 26, 27: transport roller 28: registration roller 29: fixing device 30: paper discharge roller 31: paper discharge tray 100: image forming apparatus P: Transfer material

Claims (10)

In a developing device using a two-component developer composed of a toner and a carrier,
A developer carrier;
A developer conveying member for conveying the developer in the apparatus to the developer carrying member;
A layer thickness regulating member that regulates the layer thickness of the developer on the developer carrier;
A developer stirring member provided on a developer transport path between the developer transport member and the layer thickness regulating member;
Control means for controlling the start of operation of the developer stirring member according to the image area;
And a developing device. The developing device according to claim 1,
The developing device according to claim 1, wherein the control means controls a rotation speed of the developer stirring member. The developing device according to claim 1 or 2,
The developing device according to claim 1, wherein the control means controls a rotation direction of the developer stirring member. In a developing device using a two-component developer composed of a toner and a carrier,
A developer carrier;
Magnetic field generating means provided in the developer carrying body;
Magnetic field control means for changing the magnetic field of the magnetic field generating means;
Control means for controlling the operation of the magnetic field control means according to the image area;
And a developing device. The developing device according to claim 4.
The magnetic field control means is a control means for controlling an electromagnet and a current value flowing through the electromagnet, and controls the current value according to an image area. In the developing device according to claim 4 or 5,
The developing device according to claim 1, wherein the magnetic field generating means is a plurality of electromagnets. The developing device according to claim 6.
The developing device according to claim 1, wherein the control unit changes the number of operating electromagnets according to an image area. In a developing device using a two-component developer composed of a toner and a carrier,
A developer carrier;
A developer conveying member for conveying the developer in the apparatus to the developer carrying member;
A layer thickness regulating member that regulates the layer thickness of the developer on the developer carrier;
Developer flow path width control means provided on a developer transport path between the developer transport member and the layer thickness regulating member;
Control means for controlling the operation of the developer flow path width control means according to the image area;
And a developing device. The developing device according to claim 8.
The developer flow path width control means has a central axis and an arcuate outer diameter that is eccentric from the central axis, and the control means adjusts the rotation angle of the developer flow path width control means according to the image area. A developing device characterized by controlling. Image forming apparatus comprising an image carrier, means for forming an electrostatic latent image on the image carrier, and developing means for developing the electrostatic latent image on the image carrier with a developer to visualize the image In
An image forming apparatus using the developing device according to claim 1 as the developing unit.

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