JP4742245B2 - Developing device and image forming apparatus - Google Patents

Description

  The present invention relates to a developing device used in an image forming apparatus such as a copying machine, a printer, and a fax machine using an electrophotographic system. In particular, the present invention relates to a developing device capable of color image formation and an image forming apparatus including a plurality of developing devices.

The unidirectional circulation system has an advantage in terms of developer life compared to the conventional biaxial system. While the developer makes a round of the developing device, the biaxial system may pass through the developer restricting section (doctor) many times, whereas the unidirectional circulation system may pass more than once. Because there is no. Therefore, the shape of the probability distribution that the developer passes through the doctor is expected to be broad in the biaxial method and sharp in the unidirectional circulation. Since the stress applied to the developer when passing through the doctor is quite large, the correlation between the number of passes and the deterioration of the developer is high. Accordingly, the broader the biaxial system having a distributed shape, the more deteriorated developer is, and the life is shortened. FIG. 16 shows the results obtained by actual calculation for the number of times of passage through the doctor near the life. Here, assuming that the number of times of passage of the doctor, for example, N 'times is set as the life of the developer, it can be seen that there are many developers that reach the life earlier in the biaxial distribution. Therefore, using the one-way circulation method is effective for the developer life.

In addition, by adopting a one-way circulation system, all the developer with reduced toner density after development is collected in the collection unit and not immediately used for development, so a stable image density can be obtained. It became. However, since the carrier of the developer deteriorates with time, the ability to impart charge to the toner decreases, and a normal developing function cannot be obtained. For this reason, there has been a problem of causing fluctuations in image density.
Therefore, there is a developer exchange system as a system for obtaining image density stability in the long term. It is a system to replace the developer while keeping the amount of developer in the developing device constant by discharging the developer in the developing device to the outside while replenishing unused developer in the developing device. The life of the developer can be extended by refreshing the developer.

Patent Documents 1 to 4 are disclosed as conventional developing devices having a vertically arranged triaxial screw configuration. Patent Document 1 discloses a developer circulation area adjacent to a development roll accommodating portion that accommodates a development roll, in which a two-component developer is circulated while being circulated, and a developer that discharges the developer in the developer circulation area. A developer container having a discharge port, a two-component developer adhering to the rotating surface is conveyed to the development area and developed, and the two-component developer in the developer circulation area is circulated while being agitated and conveyed. In addition, the two-component developer is supplied to the developing roll accommodating portion, and a circumferential or outward radial force acting on the developer by rotation of the stirring and conveying member in a region facing the developer discharge port is generated. A developing device (FIG. 17) is disclosed that includes an agitating and conveying member configured to be smaller than other regions.

In Patent Document 2, a developer is carried above a first developer carrier and conveyed to the second developing unit of the image carrier, and can be rotated in the same direction as the first developer carrier. The second developing carrier is provided, the developer is transferred from the first developing carrier to the second developing carrier, and the developing container supplies the developer to the first developing carrier. A stirring chamber that is disposed above the developing chamber, collects the developer that has passed through the first developing portion and the second developing portion from the second developing carrier, and removes the developer between the developing chamber and the stirring chamber. A developing means having a circulating means for circulating is disclosed.

Patent Document 3 discloses a structure in which a developer supply unit and a developer recovery unit are separated, and the recovered developer is circulated and conveyed to the developer supply unit via a toner replenishment unit, and a stirring screw is provided. A developing device (FIG. 18) and an image forming apparatus having a structure in which two stirring paths are long and are provided are disclosed. Thus, the carrier and toner are replenished independently to achieve a longer life of the developer.

Further, Patent Document 4 includes an upper space in which a developer composed of toner and a carrier is replenished, and a lower space into which the developer in the upper space is guided, and development is performed between the upper space and the lower space. While the developer is circulated, the developer in the upper space is supplied to the photosensitive drum by the developing roller, and a developer discharge port is provided at a position above the developer circulation path on the back surface of the lower space (FIG. 19). Is disclosed.

The patent document aims at extending the life of the developer by gradually replacing the developer and maintaining the stability of the image density for a long period of time.
However, in the above-described conventional example, in the developer circulation path, it is necessary to lift the developer in the collection / stirring unit located in the lower part of the developing unit to the supply unit located in the upper part of the developing unit. The lifting mechanism is a system in which the developer is retained downstream from the stirring unit and overflowed from the upper opening, and the developer is excessively stressed in the retaining portion. For this reason, the developer progresses more rapidly, and as a result, the charge imparting ability of the carrier is lowered, so that normal toner charging cannot be obtained, so that a stable development function is not performed, and image density fluctuations occur. Therefore, even if the developer is exchanged with this configuration, there is a problem that the desired developer life cannot be extended and long-term image density stability cannot be obtained.

JP 2000-112238 A Japanese Patent Laid-Open No. 2003-323043 Japanese Patent Laid-Open No. 2004-077587 Japanese Patent Laid-Open No. 2005-017497

  SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and its object is to provide a developing device and an image forming apparatus that can extend the life of the developer and obtain a stable image density over a long period of time. is there.

The features of the present invention, which is a means for solving the above problems, are listed below.
The developing device of the present invention stirs and conveys the developer along the axial direction of the developer carrying member carrying and carrying the developer composed of toner and carrier, and also carries the developer carrying A supply conveyance path having a supply screw for supplying the developer to the body, and collecting the developer after completion of development from the developer carrier, and conveying the collected developer in parallel and in the same direction as the supply screw A recovery conveyance path having a recovery screw, an excess developer that has not been supplied from the supply conveyance path to the developer carrier, and a recovery developer from the recovery conveyance path; An agitating and conveying screw that agitates and conveys the developer in the reverse direction; and a stirring and conveying path that circulates and supplies the developer that has agitated the excess developer and the recovered developer to the supply and conveying path; Said A developer regulating member that regulates the height of the developer layer supplied to the developer carrying member from the feed conveyance path, and the rotation direction of the developer carrying member is immediately after passing the developer regulating member the developer is a direction to move upward, the supply conveyance path, wherein which recovery path you and the stirring conveyance path is substantially horizontally arranged, passing through the center of the developer carrier of the developing device section When virtually divided by a vertical line, the axial center position of the supply screw is arranged in a region different from the region where the photoconductor exists, and the developer delivery in each of the supply screw, the recovery screw, and the stirring screw fins attached to the side, and the recovery screw, Tonariai this recovery screw, and installed partition plate between the screw positioned on the side closer to the developer regulating member In this partition plate, a portion located above a straight line connecting the top of the recovery screw and the top of the screw adjacent to the recovery screw is adjacent to the collection screw and close to the developer regulating member. An inclined passage extending from the developer carrier to the recovery conveyance path is formed by the folded partition plate on the screw side located on the side and with an inclination to the vicinity of the developer carrier. without disposing the transfer member to tilt oblique passage, the inside of the developer carrying member has a plurality of magnets are fixed, the same poles of the magnet across the inlet side of the inclined passage is disposed It is characterized by.

The developing device of the present invention further includes an angle formed by a horizontal line passing through the center of the developer carrying member in a cross section of the developing device and a line connecting the center of the developer carrying member and the shaft center of the supply screw as θ. In this case, θ is in the range of 30 ° ≦ θ ≦ 75 °.
The developing device of the present invention is further characterized in that each transport path is arranged in the order of the supply transport path, the stirring transport path, and the recovery transport path from the vicinity of the developer regulating member. .
In the developing device of the present invention, the delivery unit from the recovery conveyance path to the agitation conveyance path and the delivery unit from the supply conveyance path to the agitation conveyance path are further arranged at positions that do not face each other. And
The developing device of the present invention is further characterized in that each transport path is arranged in the order of the supply transport path, the recovery transport path, and the stirring transport path from the vicinity of the developer regulating member. .

The developing device of the present invention is further characterized in that a toner replenishment position is installed in the collection transport path.
The developing device of the present invention further includes a developer supplying means for supplying a developer containing at least an unused carrier into the developing device, and a developer discharging means for discharging the used developer out of the developing device. It is characterized by having.
The developing device of the present invention is further characterized in that the amount of replacement of the developer at one time by the developer supplying means and the developer discharging means is a part of the total amount of the developer in the developing device. To do.
The developing device of the present invention is further characterized in that the developer supplying means supplies the carrier and toner to the developing device by independent supply operations (amount and timing).
The developing device of the present invention is further characterized in that the developer discharging means is installed in the collection transport path.

A color image forming apparatus according to the present invention includes a plurality of image carriers on which electrostatic latent images are formed and a plurality of developing devices according to any one of claims 1 to 10, and a color image is recorded on a recording material. it shall be the said to be formed.

In the color image forming apparatus of the present invention, the first toner image transferred to the first surface (front surface) of the paper further includes a first image forming unit group having at least a developing device and a photoreceptor for each color, and the first image forming unit group. The second toner image formed by the first image station including the first toner image carrying belt on which the first toner image formed by the image forming unit group is transferred and carried, and transferred to the second side (back side) of the sheet. A second image forming unit group having at least a developing device and a photoconductor for each color, and a second toner image carrying belt on which a second toner image formed by the second image forming unit group is transferred and carried. And a first-pass double-side transfer system in which a first toner image and a second toner image are simultaneously or sequentially transferred onto a sheet before fixing.

According to the present invention, it has become possible to provide a developing device and an image forming apparatus capable of extending the life of a developer and obtaining a stable image density over a long period of time by means for solving the above problems.

The best mode for carrying out the present invention will be described below with reference to the drawings. Note that it is easy for a person skilled in the art to make other embodiments by changing or correcting the present invention within the scope of the claims, and these changes and modifications are included in the scope of the claims. The following description is an example of the best mode of the present invention, and does not limit the scope of the claims.

According to the present invention, the rotation direction of the developing sleeve is a direction in which the developer immediately after passing through the developer regulating member moves so as to be lifted upward. Compared to the case, the position where the developer is supplied to the developing sleeve is closer to the developing sleeve in front of the developer regulating member, so that stable supply can be performed. Furthermore, when the area is divided by a vertical line passing through the center of the developing roller, the supply screw is positioned on the opposite side of the photosensitive member, so that the developer and the developing roller in the supply unit can be brought close to each other, thereby enabling more stable development. The agent can be pumped up. Thereby, the image density and the image quality can be stabilized.
Further, since there is a difference in height between the developing sleeve and the collecting screw in the collection, the developer can be completely separated using gravity without using another peeling member. Therefore, it is possible to maintain a good balance between supply and recovery functions. Furthermore, since each screw is arranged substantially in parallel, it is not necessary to lift the developer upward as in the transfer part from stirring to supply in the conventional example (FIG. 21), and the stress on the developer is greatly reduced. it can. Therefore, a stable image density can be obtained over a long period of time.

In the present invention, when θ shown in FIG. 1 is in the range of 30 ° ≦ θ ≦ 75 °, the supply function for supplying the developer to the developer carrier in the supply unit, and the developer carrier in the recovery unit The recovery function of recovering the developer after development can be made compatible with a good balance. If θ is smaller than 30 °, it is difficult to collect only the gravity in the collecting function, and a collecting member such as a peeling roller is separately required, resulting in an increase in cost. On the other hand, if θ is greater than 75 °, it becomes difficult to supply the agent stably in the supply function, and the margin is particularly reduced in increasing the speed.
In the present invention, since the supply unit and the recovery unit are arranged apart from each other, there is no possibility that the developer after development enters the supply unit. Moreover, since the agent delivery between the screws may be a simple configuration from the paddle to the screw portion, the agent conveyance efficiency is increased.
Furthermore, the backflow of the agent in the delivery portion can be prevented, and the agent delivery between the screws can be performed more efficiently.

In the present invention, the angle of the inclined plate, which is a guide plate when collecting the developer after development from the developer carrying member, can be increased in a direction closer to the vertical, so that the agent easily falls and the recovery function is highly stable. Become. Even when the diameter of the sleeve is small, the functions of recovery and supply can be balanced. Further, the developing device can be downsized.
Furthermore, the replenishment toner is easily dispersed efficiently in the developer by replenishing the toner with the toner concentration lowered in the collection portion. Further, since the replenished toner can take a long distance to reach the developer carrying member, it can be sufficiently dispersed.

The present invention supplies unused carrier into the developing device and discharges the used developer, so that the developer in the developing device is replaced, and the life of the developer is greatly extended. Is possible.
In addition, the developer characteristics can be kept stable by gradually changing the developer instead of changing it all at once. And a stable image density can be obtained.
Furthermore, regardless of the toner supply operation, it is possible to replenish the carrier and replace the developer according to the deterioration state of the carrier. Accordingly, it is possible to prevent the toner charging ability from being lowered due to carrier deterioration, and to suppress fluctuations in image density.
Furthermore, since the developer increases in the recovery conveyance path as it goes downstream, it is easy to recover the deteriorated developer, and it is easy to recover the overflowed agent by providing a discharge port on the downstream side. Further, even if the developer amount is once reduced, the influence on the entire agent circulation is small.

By using the developing device of the present invention, it is possible to always obtain a stable toner adhesion amount over a long period of time, so that it is possible to obtain a high-quality color image with high image density stability and excellent color reproducibility and color balance. It is possible to provide a possible image forming apparatus.
Further, by using the developing device of the present invention in an image forming apparatus having a one-pass double-side configuration, it is possible to obtain a color image excellent in density stability for a long period of time with extremely high productivity. As a result, there is no difference in image quality between the front and back sides, and a color double-sided image with always stable image quality can be obtained.

In the present invention, by using a carrier having a small particle diameter, the development capability can be improved by densifying the magnetic brush, and therefore the amount of developer (pumping amount) necessary for development can be reduced. Thereby, the screw rotation speed in the recovery unit can be reduced, which contributes to stress reduction due to the circulation of the agent. In addition, since the amount of developer passing through the developer restricting member that is stressed is reduced, it contributes to a longer life. Furthermore, since the capacity of the carrier is reduced, the size of the device such as the carrier storage unit can be reduced.
Furthermore, since the magnetic brush in the development area becomes denser, high image quality and stable image quality are achieved.
If the average particle size of the carrier is larger than 60 μm, the amount of developer overflowing in the developer circulation portion increases, and stable developer circulation cannot be performed. Furthermore, since the magnetic brush becomes rough, satisfactory image quality cannot be obtained. On the other hand, if it is smaller than 20 μm, the carrier adheres to the photoreceptor or the carrier is likely to be scattered from the developing device.
In the present invention, by using a toner having a small particle size and a sharp particle size distribution, the gap between the toner particles is reduced, so that the necessary amount of toner can be reduced without impairing the color reproducibility. Therefore, density fluctuation in development can be reduced. Further, the stable reproducibility of a minute dot image is improved, and a stable high image quality can be obtained for a long time. When the average particle diameter (D4) is less than 3 μm, problems such as a decrease in transfer efficiency and a decrease in blade cleaning properties are likely to occur. When the average particle diameter (D4) exceeds 8 μm, the fluidity of the developer is deteriorated, and it is difficult to suppress scattering of characters and lines, and it is difficult to stably maintain image quality for a long time.
Further, since the toner has a nearly spherical shape, the fluidity of the developer is improved, so that stress in the agent circulation is reduced, and the agent circulation and development can be performed stably for a long time.
Furthermore, since the external additive is hardly buried in the toner and the change in the fluidity and charging characteristics of the developer is small with time, it is possible to perform stable agent circulation and development over the long term.

A detailed description of the developing device 401 of the present invention will be given below with reference to FIGS. FIG. 1 is a view showing a developing device of the present invention. FIG. 2 is a diagram showing a main part of the present invention. The developing device includes a developing roller 402 including a cylindrical sleeve that is rotatable in the direction of an arrow and includes a magnet (to be described later) that is fixed to the inside of the photoconductor 101 that is an image carrier, and a developing roller. A supply screw 408 and a supply conveyance path 409 for supplying and conveying the developer to 402; a developer layer regulating member 403 for regulating the layer thickness of the developer held on the surface of the developing roller 402 by the magnetic force of the internal magnet; The collection screw 404 and the collection conveyance path 405 for collecting and conveying the developer, and the developer that has not been supplied to the developing roller and the replenished toner and developer in the collected developer and the supply and conveyance unit are agitated and conveyed. A conveying screw 406 and a stirring conveying path 407, a developer supplying unit, a developer discharging unit, and the like are included. The developer thinned by the developer layer regulating member 403 is conveyed to a developing area which is a gap between the photosensitive member 101 and the developing roller 402, and the toner in the developing area is transferred to the electrostatic latent image portion on the photosensitive member. Development is performed by electrostatically adhering to the surface. In addition, fins, which are flat plates parallel to the axial direction, are provided in the downstream portion of each screw, and have a function of delivering the developer to another conveyance path as will be described later.

The internal magnet in the developing roller 402 will be described with reference to FIG. Five magnets P1 to P5 are fixed inside the developing roller 402, and have a magnetic flux density distribution in the normal direction as shown by a dotted line in FIG. Here, the polarity and peak magnetic force of each magnetic pole are shown as follows: P1 (S pole, 100 mT), P2 (N pole, 90 mT), P3 (S pole, 50 mT), P4 (S pole, 70 mT), P5 (N pole, 80 mT). Further, the normal magnetic force is 5 mT or less between P3 and P4. P1 is a developing pole for forming a magnetic brush in the developing region, P2 and P3 are magnetic poles for transporting the developer after development, and P4 is for pumping and supplying the developer in the supply unit to the developing roller 402. P5 represents a magnetic pole for conveying the developer while thinning the developer on the developer regulating plate. In particular, since P3 and P4 have the same polarity and are repulsive magnetic poles, the developer on the developing roller is separated from the developing roller at this portion, falls on the inclined conveyance plate , and falls to the collection conveyance path 405 by gravity.

Each conveyance path is arranged almost horizontally in the order of the supply conveyance path 409, the stirring conveyance path 407, and the collection conveyance path 405 from the vicinity of the developer layer regulating member 403 below the developing roller 402. The supply conveyance path 409 is the same conveyance direction. The flow of the developer in the developing device will be described with reference to FIG. As shown in FIG. 4, each conveyance path includes a delivery section 420 from the collection conveyance path 405 to the agitation conveyance path 407, a delivery section 421 from the agitation conveyance path 407 to the supply conveyance path 409, and a supply conveyance path 409 to the agitation conveyance path 407. The delivery unit 422 is connected to each other. The dotted line represents the developer entering and exiting the developing roller 402, the white arrow represents the developer circulating in the developing device, and the size of the arrow represents the amount of developer. A fin as shown in FIG. 4 is attached to the transfer portion of each connecting portion, and a force is applied to the developer in a direction perpendicular to the conveyance axis, and the developer is transferred to the next conveyance path in the direction of the arrow in FIG. Can be passed to. Developer after development flows into the collection conveyance path 405 from the developing roller 402, and the collection developer is conveyed while increasing the developer amount as it goes downstream, and flows into the agitation conveyance path 407 through the fins 410.
On the other hand, in the supply conveyance path 409, the developer is conveyed while reducing the developer amount while supplying a constant amount of developer to the developing roller 402. The surplus agent flows into the agitating and conveying path 407 through the fins 412. In the agitating and conveying path 407, the surplus agent, the collected developer and a replenished developer described later are merged, and a certain amount of developer is conveyed. The developer is circulated into the supply conveyance path 409. In the region where the developing roller 402 is located (image forming region), the supply conveyance path 409 and the agitation conveyance path 407 are partition plates 414, and the agitation conveyance path 407 and the collection conveyance path 405 are partition plates 413. Therefore, the inflow of the developer in the image forming area is prevented.
On the other hand, as shown in FIG. 2, the delivery part 420 from the collection conveyance path 405 to the stirring conveyance path 407 and the delivery part 422 from the supply conveyance path 409 to the stirring conveyance path 407 are installed at positions that do not face each other, so The developer is prevented from flowing back at the facing portions.

The conditions of the members used in this example are: the developing sleeve outer diameter is φ25 [mm], the sleeve linear velocity is 500 [mm / s], the screws have a common shape, the outer diameter is φ18 [mm], the shaft The diameter is φ8 [mm], the lead interval is 25 [mm], two strips, and the rotation speed is 500 [rpm]. However, it is not limited to this value.

Replenishment that compensates for the amount of toner consumed by the control unit from the output signal from a toner density sensor (not shown) provided in the lower casing below the stirring and conveying screw 406 and the pixel count value of the output image in the exposure control unit. The toner amount is calculated, and the toner is supplied from the toner supply port 450 of FIG. The position of the toner replenishing port 450 is provided in the upper part of the collection conveyance unit. As a result, the developer having a lowered toner concentration and the replenishment toner are mixed and stirred, so that the replenishment toner is more efficiently dispersed in the developer. Further, since the stirring distance until reaching the developing sleeve becomes long, the replenishment toner is uniformly dispersed in the developer, and the developing sleeve can always supply a developer having a uniform toner concentration. The toner replenishing port 450 may be installed in the paddle part at the end of the collecting and conveying part.

The developer supply means will be described with reference to FIGS.
The developer supply means includes a toner supply means 430 including a toner storage container 432 in which unused toner 431 is stored and a toner supply means 435A, and a carrier in which unused carrier 437 is stored. It comprises carrier supply means 436 provided with a storage container 438 and carrier supply means 435B, and a developer supply transport path 433. The toner storage container 432 and the carrier storage container 438 are joined in the middle of the developer supply transport path 433, transported as a developer, and connected to the toner supply port 450 of the developing device 401. The carrier supply amount is controlled by carrier supply means 435B, and the toner supply amount is controlled by toner supply means 435A.

As the developer supply means 435, for example, a uniaxial eccentric screw pump (common name: Mono pump) as shown in FIG. 5 can be used. As shown in FIG. 5, the MONO pump has a screw-shaped roller 435G eccentric using a rigid member such as a metal or a resin, a stator 435H having a two-screw inner shape with a rubber material, and both of these. It consists of a holder 435C containing a member, and one end of a developer supply / conveyance path 433, which is a tube, is attached to the developer container. When the roller 429A is rotated by the drive motor 435D, a suction pressure is generated in the pump, and the suction in the tube 433 is reduced. The developer in the storage container is transferred by the suction force, and the developing device is supplied from the supply port 435F. It becomes possible to supply in. Further, the replenishment amount of the developer can be set finely by controlling the rotation operation (time) to the roller 435G by the replenishment clutch 435E connected to the drive motor 435D.
According to this method, there are few restrictions on the installation location of the toner cartridge, which is advantageous for space allocation in the image forming apparatus. Further, since the toner can be replenished in a timely manner, it is not necessary to provide a large toner storage space in the developing device, and the developing device can be downsized.

The carrier replenishing means 435B includes an opening / closing mechanism. For example, a hole is attached to the rotating body, and the shutter is opened and closed by the rotation of the rotating body, and the carrier replenishment amount is controlled by the number of rotations. .
As another form of the developer supply means, a system may be used in which a carrier is supplied together with toner replenishment in a state where a predetermined amount of unused carrier is mixed in the toner container 432 in advance. In this case, the developer is replenished by a toner replenishment operation. In the case of this method, advantages such as space saving and simple control due to the fact that only one storage container is required.

Next, developer replenishment control will be described. FIG. 6 shows a configuration diagram for controlling toner and carrier replenishment. Control units for controlling toner and carrier replenishment are respectively connected to a toner density sensor provided in the developing device for each color, a timer for measuring the driving time of the developing device, a toner replenishing unit, and a carrier replenishing unit.
In the control unit, the developer in the developing device is obtained from information on the consumed toner amount, such as the change in the toner concentration of the developer in the developing device detected by the toner concentration sensor and the area ratio of the output image detected by the pixel counting unit. The amount of toner to be replenished is calculated so that becomes a predetermined target toner concentration, and the operation amount of the motor of the toner replenishing means is determined. For example, in the embodiment shown in FIG. 5, the operation amount of the motor can be made variable by controlling the operation time of the supply clutch. On the other hand, the carrier replenishment amount is determined by detecting the accumulated time that the developer circulates in the developing device from the number of prints, the driving time of the developing device, etc., and judging the degree of carrier deterioration, and the carrier replenishing amount is calculated accordingly. Thus, the operation amount of the carrier replenishing means (for example, motor driving time, shutter opening / closing time, etc.) is determined.

FIG. 7 is a flowchart showing the above. First, it is determined whether or not the integrated value of the driving time of the developing device measured by the timer has reached a set value. When the set value is reached, the carrier replenishment amount is calculated, and the operation amount of the carrier replenishing means is set. Next, the toner concentration of the developer in the developing device is monitored by a toner concentration sensor, and when the toner concentration falls below a predetermined value, a toner replenishing amount is calculated so that the toner concentration becomes a predetermined value, and a toner replenishing unit corresponding to the calculated amount. Is set. Each supply means is driven by the set operation amount of the supply means, and a predetermined amount of carrier and toner are supplied into the developing device.

Next, the developer discharging means 440 will be described with reference to FIGS.
The developer discharge means 440 includes a discharge agent storage container 442 for storing a used developer 441 and a discharge agent transport path 443 for transporting the developer discharged from the developing device. On the other hand, the developing device has a discharge opening 451 in the side surface on the downstream side of the recovery conveyance path 405 where the recovery screw 404 is provided, and the overflowed developer is recovered in the discharge agent storage container 442 through the discharge agent conveyance path 443. The The discharge agent conveyance path 443 may be a hollow tube having a spiral screw member therein and conveyed to the container 442, or the agent may be dropped only by gravity and stored in the container 442. Further, the discharge opening 451 of the developing device may be on the side surface of the collecting portion of the developing device, or may be provided with a shutter that can be opened and closed at the bottom. Further, it is desirable that the developer exchange amount is substantially equal between supply and discharge. In the overflow method, a constant developer amount can be automatically set in the developing device, and in the case of a lower opening / closing shutter, the opening / closing time may be controlled in accordance with the supply amount. With the developer supply means and developer discharge means having the above-described configuration, unused developer is charged and deteriorated developer is recovered, and a part of the developer in the developing device is gradually replaced. ing.

Another embodiment of the developing device will be described with reference to FIGS. FIG. 8 is a view showing a developing device of the present invention. FIG. 9 is a diagram showing a main part of the present invention. The basic components are the same as in FIG. The difference from FIG. 1 is that each conveyance path below the developing roller is arranged substantially horizontally in the order of the supply conveyance path 409, the collection conveyance path 405, and the stirring conveyance path 407 from the vicinity of the developer regulating member. The fins are provided at both ends of the recovery screw 404. The flow of the developer in the developing device will be described with reference to FIG. As shown in FIG. 10, each conveyance path includes a delivery unit 423 from the collection conveyance path 405 to the agitation conveyance path 407, a delivery unit 424 from the agitation conveyance path 407 to the supply conveyance path 409, and a supply conveyance path 409 to the collection conveyance path 405. In the delivery part 425, each is connected. The dotted line represents the developer entering and exiting the developing roller 402, the white arrow represents the developer circulating in the developing device, and the size of the arrow represents the amount of developer. Fins as shown in FIG. 9 are attached to the delivery portions of the respective connecting portions, and a force is applied to the developer in the direction perpendicular to the transport axis, so that the developer is moved to the next transport path in the direction of the arrow in FIG. Can be passed to. Developer after development flows into the collection conveyance path 405 from the developing roller 402, and the collection developer is conveyed while increasing the developer amount as it goes downstream, and flows into the agitation conveyance path 407 through the fins 410.
On the other hand, in the supply conveyance path 409, the developer is conveyed while reducing the developer amount while supplying a constant amount of developer to the developing roller 402. The surplus agent flows into the fin 410 on the collection conveyance path 405 by the fin 412 and is mixed with the above-described collection agent. In the agitation transport path 407, the surplus agent, the recovered developer, and a replenished developer described later merge to transport a certain amount of developer and flow into the supply transport path 409 through the fins 411 and fins 415. It is a drug circulation.
In the area where the developing roller is present (image forming area), the supply conveyance path 409 and the agitation conveyance path 407 are separated by a partition plate 414, and the agitation conveyance path 407 and the collection conveyance path 405 are separated by a partition plate 413, respectively. Thus, the inflow of the developer in the image forming area is prevented. The developer supply means and the developer discharge means are the same as in FIG.

Hereinafter, an embodiment according to the present invention will be described first in detail, and the operation will be described in detail later with reference to the drawings.
FIG. 11 is a schematic central sectional view showing the internal configuration of the image forming apparatus to which the present invention is applied. In the image forming apparatus main body 100 shown in FIG. 11, the first image carrier unit 20 including the first image carrier belt 21 that moves endlessly in the direction of the arrow with the recording material conveyance path 40 as a boundary, A second image carrier unit 30 having a second image carrier belt 31 that moves endlessly in the direction of the arrow is disposed at the bottom. Four first image forming units 80Y, 80C, 80M, and 80K are provided on the lower tension surface of the first image carrier belt 21, and four second image forming units 80Y, 80C, 80M, and 80K are provided on the lower tension surface of the second image carrier belt 31. Image forming units 81Y, 81C, 81M, and 81K are provided. Y, C, M, and K along the numbers of the first and second image forming units correspond to the colors of the toner to be handled. Y is yellow, C is cyan, M is magenta, and K is black. Means. Y, C, M, and K are also used in the same meaning with respect to the photoreceptor 1 provided in the first and second image forming units and rotating together with the first image carrying belt 21 and the second image carrying belt 31. . The photoreceptors 1Y to 1K are arranged at the same interval, and at least at the time of image formation, are in contact with a part of the stretched portion between the image bearing belts 21 and 31, respectively.

FIG. 12 is a diagram showing an internal configuration of an image forming apparatus to which the present invention is applied. In FIG. 12, during operation of the image forming apparatus 100, charging means is provided around a cylindrical photosensitive member 1 rotatably supported so as to rotate in the direction of an arrow by a driving source (not shown) according to an electrophotographic process. Image forming members such as the scorotron charger 2, the exposure device 3, the developing device 4, the transfer device 5, the cleaning device 6, and the photostatic device Q are disposed. Although not shown, a potential sensor, an image sensor, or the like may be arranged.
The photoreceptor 1 is obtained by forming an organic photosensitive layer (OPC), which is a photoconductive substance, on an aluminum cylinder surface having a diameter of about 30 to 120 mm, for example. A photoconductor on which an amorphous silicon (a-Si) layer is formed can also be used. A belt-like photoreceptor can also be employed. The cleaning device 6 includes a cleaning brush, a cleaning blade, and a recovery member, and removes and recovers foreign matters such as toner remaining on the surface of the photoreceptor.
The exposure device 3 scans the light corresponding to the image data for each color on the surface of each photoreceptor 1 that has been uniformly charged by the charging means, and forms an electrostatic latent image. The exposure apparatus 3 in the illustrated example is an exposure apparatus that includes an LED (light emitting diode) array and an imaging element as light emitting elements, but uses a laser light source, a polygon mirror, etc., and beam light modulated according to image data to be formed. It is also possible to adopt a laser scanning type exposure apparatus.
In addition to the charger 2, a type that makes contact with the surface of the photoreceptor 1, such as a charging roller, can be used as the charging means.
The development in this embodiment is a development system that employs a two-component developer comprising a toner and a carrier. The electrostatic latent image for each color formed on the surface of each photoconductor 1 by the exposure device 3 with respect to the negatively charged photoconductor 1 is a toner of a predetermined color having the same polarity (negative polarity) as the charged polarity of the photoconductor. Developed to become a visible image. So-called reversal development is performed. The detailed description of the configuration of the developing device is as described above.

In FIG. 11, a first image carrying belt 21 as an image carrier that is supported by a plurality of rollers 22, 23, 24, 25, 26, 27, etc. and runs in the direction of the arrow is a first image forming unit 80Y to 80Y. It is provided above the photoconductors 1Y, 1C, 1M, and 1K at 80K. The image bearing belt 21 is endless, and is stretched and arranged so that a part of each photoconductor after the developing process comes into contact. Further, a primary transfer roller 22 is provided on the inner peripheral portion of the first image carrying belt 21 so as to face each of the photoreceptors 1Y, 1C, 1M, and 1K.
A cleaning device 20 </ b> A is provided on the outer periphery of the first image carrying belt 21 at a position facing the roller 23. The cleaning device 20 </ b> A wipes off unnecessary toner remaining on the surface of the image bearing belt 21 and foreign matters such as paper dust.
The members related to the image carrier belt 21 are integrally configured as the first image carrier unit 20 and can be attached to and detached from the image forming apparatus 100.
A second image carrier belt 31 as an image carrier that is supported by a plurality of rollers 32, 33, 34, 35, 36, 37, etc. and runs in the direction of the arrow is a photoconductor in the second image forming units 81Y to 81K. Provided in contact with 1Y, 1C, 1M, and 1K. The image carrying belt 31 is endless and is stretched and arranged so that a part of each photoconductor after the developing process comes into contact. A primary transfer roller 32 is provided on the inner peripheral portion of the image carrying belt 31 so as to face the photoreceptors 1Y, 1C, 1M, and 1K.

A cleaning device 30 </ b> A is provided on the outer periphery of the second image carrying belt 31 at a position facing the roller 33. The cleaning device 30 </ b> A wipes away unnecessary toner remaining on the surface of the image bearing belt 31 and foreign matters such as paper dust.
The members related to the image carrier belt 31 are integrally configured as the second image carrier unit 30 and can be attached to and detached from the image forming apparatus 100.
Further, a first secondary transfer roller 41 is provided in the vicinity of the support roller 24 on the outer periphery of the first image carrying belt 21. The first image carrying belt 21 is carried by applying a bias to the first secondary transfer roller 41 while passing a recording medium (hereinafter referred to as paper P) between the first image carrying belt 21 and the secondary transfer roller 41. The toner image is transferred onto the paper P.
A transfer charger 42 as a second secondary transfer unit is provided on the outer periphery of the second image bearing belt 31 and in the vicinity of the support roller 35. The transfer charger 42 is a known type, and a thin wire of tungsten or gold is used as a discharge electrode, held by a casing, and a transfer current is applied to the discharge electrode from a power source (not shown). By applying a transfer current while passing the paper P between the image carrying belt 31 and the transfer charger 42, an image formed by the toner carried by the second image carrying belt 31 is transferred onto the paper P. The polarity of the transfer current applied to the transfer roller 41 and the transfer charger 42 is a positive polarity opposite to the polarity of the toner.

On the right side of the image forming apparatus 100, a paper feeding device 43 that accommodates paper is provided, and only one sheet is reliably sent to the recording material conveyance path 40 by a plurality of conveyance roller pairs.
A recording for transporting the sheet that has passed through the second transfer station on the extension of the recording medium conveyance path 40 to the fixing nip in the fixing device 60 provided downstream in the conveyance direction of the recording medium while maintaining a flat state. Body transport means 50 is provided. The recording medium transport means 50 has a roller for supporting the conveying belt 51 that moves endlessly in the direction of the arrow. On the outside of the conveying belt 51, the recording medium is opposed to the roller 55 and facing the cleaning device 50A and the roller 56. An electrostatic charger / separator charger 58 is provided so as to oppose the adsorption charger 57 for adsorbing P and the roller 54.
The conveyance belt 51 that moves together with the recording medium P in contact with the unfixed toner image is negatively charged by the suction charger 57 with the same polarity as the polarity of the toner. As the conveyance belt 51, a metal belt, a polyimide belt, a polyamide belt, or the like can be employed. The surface is provided with releasability from the toner and has a chargeable resistance value. The traveling speed of the belt 51 is matched with the traveling speed of the recording medium in the fixing device.

A fixing device 60 having a heating unit is provided on the downstream side of the recording material transport unit 50 in the paper transport direction. A type having a heater inside the roller, a belt fixing device that runs a heated belt, a fixing device that employs induction heating as a heating method, and the like can be employed. In order to make the color and glossiness of the images on both sides of the paper the same, the material, hardness, surface properties, etc. of the fixing roller and fixing belt are made equal. Further, the fixing condition is controlled by a full-color and monochrome image, or single-sided or double-sided, or is controlled by a control unit (not shown) so as to obtain an optimal fixing condition according to the type of paper. A cooling roller pair 70 having a cooling function is provided in the conveyance path after fixing in order to cool the sheet after fixing and stabilize the unstable toner state at an early stage. A heat pipe structure roller having a heat radiating portion can be employed. The cooled sheet is discharged and stacked by a discharge roller pair 71 on a discharge stack unit 75 provided on the left side of the image forming apparatus 100. The discharge stacking unit employs a mechanism in which a receiving member moves up and down according to a stack level by an elevator mechanism (not shown) so that a large amount of sheets can be stacked.
It is also possible to pass the paper through the paper discharge stack unit 75 and transport the paper toward another post-processing apparatus. Another post-processing apparatus is an apparatus for bookbinding such as punching, cutting, folding, and binding.

Each color cartridge 86Y, 86C, 86M, 86K storing unused toner and a cartridge 87 storing unused carrier are detachably stored in the storage space 85. A developer conveying means (not shown) supplies the developer to each developing device as necessary. In the configuration of this embodiment, the cartridge is common to the image forming units 80 and 81 arranged above and below, but they can be separated. The black toner cartridge 86K that is highly consumed can have a particularly large capacity. This storage space 85 is on the back side when viewed from the operation direction on the upper surface of the image forming apparatus, and a plane portion is secured on the front side of the upper surface of the image forming apparatus, so that it can be used as a work table.

An operation during single-sided recording in which a full-color image is formed on one side of the paper P in the above configuration will be described.
There are basically two types of single-sided recording methods that can be selected. One of the two types is a method of directly transferring an image carried on the first image carrying belt 21 to one side of the paper, and the other method is an image carried on the second image carrying belt 31. Is directly transferred onto one side of the paper. In the present embodiment, because of the configuration of the image forming apparatus 100, when an image carried on the first image carrying belt 21 is directly transferred to one side of the paper, the image is placed on the upper surface of the paper and the second image carrying belt. When the image carried on 31 is directly transferred to one side of the paper, the image is formed on the lower surface of the paper. In the case where the data to be recorded is a plurality of pages, it is convenient to control the image forming order so that the pages are aligned on the paper discharge stack unit 75.

An explanation will be given of a method in which an image is carried on the first image carrying belt 21 and then transferred to a sheet so that the pages are arranged in order from the image data of the last page.
When the image forming apparatus 100 is operated, the photoreceptors 1Y, 1C, 1M, and 1K in the first image carrying belt 21 and the first image forming units 80Y to 80K rotate. At the same time, the second image carrier belt 31 rotates. However, the photoreceptors 1Y, 1C, 1M, and 1K in the second image forming units 81Y to 81K are separated from the second image carrier belt 31 and are not rotated. Is done. First, image formation by the image forming unit 80Y is started. By the operation of an exposure device comprising an LED (light emitting diode) array and an imaging element, light corresponding to image data for yellow emitted from the LED is irradiated onto the surface of the photoreceptor 1Y uniformly charged by the charging device. An electrostatic latent image is formed.
The electrostatic latent image is developed with yellow toner by the developing roller, becomes a visible image, and electrostatically 1 on the first image carrying belt 21 that moves in synchronization with the photoreceptor 1Y by the transfer action of the primary transfer roller 22. Next transferred. Such latent image formation, development, and primary transfer operations are sequentially performed in the same manner on the photosensitive members 1C, 1M, and 1K.
As a result, yellow, cyan, magenta, and black toner images are carried on the first image carrying belt 21 as sequentially overlapping full-color toner images, and are moved in the direction of the arrow together with the first image carrying belt 21. .

At the same time, the paper P used for recording is fed out from a paper feed tray or a paper cassette in the paper feed device 43 by one of the paper feed / separation means for supplying the paper P, and a recording material transport path by a transport roller pair 44 40. Before the leading edge of the paper is picked up by the registration roller pair 45, the jogger operates to push both sides of the paper from both sides with respect to the paper conveyance direction, and the paper is aligned in the horizontal direction. . The registration roller pair 45 is stationary, and the leading edge of the sheet is stationary while entering the nip of the registration roller pair 45, but the timing is set so that the position with the image on the first image carrier belt 21 is normal. Then, the registration roller pair 45 is rotated to convey the sheet to the transfer area.
The full-color toner image on the first image carrying belt 21 is transferred to the upper surface of the paper P conveyed in synchronization with the first image carrying belt 21 by receiving a transfer action by the secondary transfer roller 41. The bias applied to the secondary transfer roller 41 has a positive polarity opposite to the toner charging polarity.
Thereafter, the surface of the first image carrying belt 21 is cleaned by the belt cleaning device 20A. Further, foreign matters such as toner remaining on the surfaces of the photoreceptors 1Y, 1C, 1M, and 1K in the first image forming units 80Y to 80K that have finished the primary transfer are removed by the cleaning brush 6a and the cleaning blade 6b of the cleaning device 6, respectively. It is removed from the surface of the photoreceptor. The surface of each photoconductor is neutralized by a residual potential by the static eliminator Q to prepare for the next image formation / transfer process. The removed foreign matter such as toner is sent to the collection unit 88 by the collection unit 6c.
The sensor detects whether the surface potential of the photosensitive member surface after exposure and the density of the toner adhering to the photosensitive member surface after the development process are appropriate, and appropriately sets and controls image forming conditions. Therefore, information is output to a control means (not shown).

The paper P onto which the toner image that has been superposed and carried on the image carrying belt 21 is transferred is transferred toward the fixing device 60 by the carrying belt 51 of the carrying device 50. The surface of the conveyance belt 51 is charged in advance by a sheet adsorption charger 57 so that the sheet P can be reliably transferred together with the conveyance belt 51. The neutralization / separation charger 58 operates so that the paper P is separated from the transport belt 51 and is reliably sent to the fixing device 60.
The toners of the respective colors superimposed on the paper P are subjected to the fixing action by the heat of the fixing device 60, and are melted and mixed to completely form a color image. Since toner is contained only on one side (upper surface) of the paper, less heat energy is required for fixing compared to double-sided recording with toner on both sides. A control means (not shown) optimally controls the power used by the fixing device according to the image. Until the fixed toner is completely fixed on the paper, it is rubbed by a guide member or the like on the conveyance path, and an image is lost or distorted. In order to prevent this problem, the cooling roller pair 70, which is a cooling means, operates to cool the toner and the paper. Thereafter, the paper is discharged by the paper discharge roller 71 onto the paper discharge stack 75 with the image surface facing upward. In the paper discharge stack section 75, the image forming order is programmed so that the recorded matter of the young pages is stacked so as to be sequentially stacked on top, so the page order is aligned. Since the paper discharge stack unit 75 is lowered as the number of discharged paper sheets increases, the paper sheets can be stacked in an orderly and reliable manner, and the page order is not disturbed. Instead of directly stacking the recorded paper on the paper discharge stack section 75, a punching process can be performed, or the paper can be conveyed to a post-processing device such as a sorter, a collator, a binding device, or a folding device.
In another method for forming an image on one side of the paper P, image formation is not performed in the first image forming units 80Y to 80K, and image formation is performed in order from image data of young pages for page alignment. However, it is basically the same as the one-side recording process described above.

Next, the operation during double-sided recording in which images are formed on both sides of the paper P will be described. When a start signal is input to the image forming apparatus, the first image carrying belt 21 displays an image for each color sequentially formed by the first image forming units 80Y, 80C, 80M, and 80K described in the single-sided recording operation. The image for each color sequentially formed by the second image forming units 81Y, 81C, 81M, 81K is applied to the second image carrier belt 31 substantially in parallel with the step of carrying out the primary transfer sequentially and carrying it as the first image. A step of sequentially performing primary transfer and carrying as a second image is performed. With the configuration shown in FIG. 11, in order for the first image and the second image to coincide with each other at the leading edge in the sheet conveyance direction, the formation of the second image is delayed from the start of the formation of the first image. Is started. Further, since the sheet is stopped and retransmitted by the registration roller pair 45, the sheet is fed in consideration of the time and aligned by the jogger. The registration roller pair 45 transports the sheet to a first transfer station constituted by a transfer roller 41 as a first secondary transfer unit and a first image carrying belt 21 at a timing. A positive polarity transfer current is applied to the transfer roller 41, and the image is transferred from the first image carrying belt to one side (upper surface in the drawing) of the paper P.
Thus, the sheet P having an image on one side is continuously sent to the second transfer station having the transfer charger 42 as the second secondary transfer means by the transfer action of the transfer roller 46. Then, by applying a positive transfer current to the charger, the full-color second image previously carried on the second image carrying belt 31 is transferred onto the lower surface of the paper P at a time.

The paper P on which the full color toner images are transferred on both sides in this way is transported to the fixing device 60 by the transport belt 51. The surface of the transport belt 51 is charged with the same negative polarity as the polarity of the toner by the suction charger. The unfixed toner on the lower surface of the paper is prevented from transferring to the belt. An alternating current is applied to the charge removal / separation charger 58, and the sheet is separated from the belt 51 and transferred to the fixing device 60. The toner images on both sides of the sheet are melted and mixed in response to a fixing process by heat of the fixing device 60. The sheet subsequently passes through the cooling roller pair and is discharged onto the discharge stack unit 75 by the discharge roller 71.
When double-sided recording is performed on a plurality of pages of paper, the image formation order is controlled so that the image of a young page becomes the bottom surface and is stacked on the paper discharge stack unit 75. The order of the pages is 1 page in order from the top, 2 pages on the back, 3 pages on the second sheet, and 4 pages on the back. Such control of image forming sequence and control such as increasing the power input to the fixing device compared to the one-side recording are executed by a control means (not shown).
As for the single-sided recording and the double-sided recording operation, an example in which full-color recording is executed has been described, but monochrome recording using only black toner is also possible.

Next, another embodiment is shown in FIG. FIG. 13 is a diagram illustrating an internal configuration of a tandem type image forming apparatus. This is a tandem configuration, which is a color system that forms an image on only one side at a time with respect to FIG. A schematic configuration is shown below.
The color image forming apparatus of FIG. 13 has a configuration in which process cartridges for respective colors are arranged in series. As shown in FIG. 12, the process cartridge for each color includes a charging device 2, an exposure device 3, a developing device 4, a cleaning device 6 and the like centering on the photosensitive member 1. In addition, an intermediate transfer device 5 is arranged for the photosensitive member of each process cartridge, and in addition, a paper transport unit 48, a paper transfer device 49, a fixing device 60 and the like are provided. In the present invention, a plurality of components such as the photosensitive member 1, the charging device 2, the developing device 4, and the cleaning device 6 described above are integrally coupled as a process cartridge, and this process is performed. The cartridge is configured to be detachable from a main body of an image forming apparatus such as a copying machine or a printer.
These image forming operations are merely the absence of image formation on the back surface (second surface) in FIG. 11 described above.

Next, the characteristics of the developer used in the present invention will be described.
The carrier preferably has a volume average particle size of 20 to 60 μm. By using a carrier having a small particle diameter having an average particle diameter of 60 μm or less, the amount of pumping can be reduced without reducing the developing ability, and the amount of developer circulating in the developing device can be reduced. In particular, since the amount of developer passing through the stress-regulating developer regulating member is reduced, it contributes to a longer life. In addition, since the capacity of the carrier is reduced, it is possible to reduce the size of the device such as the carrier storage unit. Furthermore, since the magnetic brush in the development area becomes denser, high image quality and stable image quality are achieved. If the average particle size of the carrier is larger than 60 μm, overflow tends to occur in the developer circulation portion, and stable agent circulation cannot be performed. On the other hand, if it is smaller than 20 μm, the carrier adheres to the photoreceptor or the carrier is likely to be scattered from the developing device.
The average particle size of the carrier can be measured using a SRA type of a Microtrac particle size analyzer (Nikkiso Co., Ltd.) with a range setting of 0.7 [μm] or more and 125 [μm] or less.

Next, toner characteristics will be described. Regarding the particle size, the volume average particle size of the toner is preferably 3 to 8 μm. By using a toner having a small particle size and a sharp particle size distribution, the gap between the toner particles is reduced, so that the necessary amount of toner can be reduced without impairing the color reproducibility. Therefore, density fluctuation in development can be reduced. Further, the stable reproducibility of a minute dot image of 600 dpi or more is improved, and a stable high image quality can be obtained for a long time. On the other hand, when the volume average particle diameter (D4) is less than 3 μm, phenomena such as a decrease in transfer efficiency and a decrease in blade cleaning properties tend to occur. When the volume average particle diameter (D4) exceeds 8 μm, the pile height of the image becomes large and it is difficult to suppress scattering of characters and lines. At the same time, the ratio (D4 / D1) of the weight average particle diameter (D4) to the number average particle diameter (D1) is preferably in the range of 1.00 to 1.30. The closer (D4 / D1) is to 1.00, the sharper the particle size distribution. With such a toner having a small particle size and a narrow particle size distribution, the toner charge amount distribution is uniform, a high-quality image with little background fogging can be obtained, and the electrostatic transfer method has a high transfer rate. can do.

Next, a method for measuring the particle size distribution of toner particles will be described.
Examples of the measuring device for the particle size distribution of toner particles by the Coulter counter method 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 the electrolytic aqueous 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 measurement device is used to measure the volume and number of toner particles or toner using a 100 μm aperture as an aperture. Volume distribution and number distribution are calculated. From the obtained distribution, the weight 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 toner shape factor SF-1 is preferably in the range of 100 to 180, and the shape factor SF-2 is preferably in the range of 100 to 180. 14 and 15 are diagrams schematically showing the shape of the toner in order to explain the shape factor SF-1 and the shape factor SF-2. The shape factor SF-1 indicates the ratio of the roundness of the toner shape and is represented by the following formula (1). This is a value obtained by dividing the square of the maximum length MXLNG of the shape formed by projecting the toner on a two-dimensional plane by the figure area AREA and multiplying by 100π / 4.
SF-1 = {(MXLNG) ² / AREA} × (100π / 4) (1)
When the value of SF-1 is 100, the shape of the toner becomes a true sphere, and becomes larger as the value of SF-1 increases.
The shape factor SF-2 indicates the ratio of the unevenness of the toner shape, and is represented by the following formula (2). A value obtained by dividing the square of the perimeter PERI of the figure formed by projecting the toner onto the two-dimensional plane by the figure area AREA and multiplying by 100 / 4π.
SF-2 = {(PERI) ² / AREA} × (100 / 4π) (2)
When the value of SF-2 is 100, there is no unevenness on the toner surface, and as the value of SF-2 increases, the unevenness of the toner surface becomes more prominent.
Specifically, the shape factor is measured by taking a photograph of the toner with a scanning electron microscope (S-800: manufactured by Hitachi, Ltd.), introducing it into an image analyzer (LUSEX 3: manufactured by Nireco) and analyzing it. Calculated.
When the shape of the toner is close to a sphere, the contact state between the toners becomes a point contact, so that the attractive force between the toners is weakened and the fluidity is increased. Therefore, since the circulatory property of the agent is improved, the stress is reduced, and it becomes possible to perform a stable unidirectional circulation for a long time. In addition, since the contact state between the toner and the photoconductor is a point contact, the attractive force between the toner and the photoconductor is weakened, and the transfer rate is increased, contributing to the improvement in image quality. On the other hand, if any of the shape factors SF-1 and SF-2 exceeds 180, the fluidity is deteriorated and the agent circulation property is poor. Further, the transfer rate is lowered, which is not preferable.

In the toner of the present invention, fine particles (hereinafter, simply referred to as fine particles) having an average primary particle size of 50 to 500 nm and a bulk density of 0.3 mg / cm ³ or more are adhered to the surface of the toner particles. In addition, although silica etc. are often used for a normal fluid improvement agent, for example, the average primary particle diameter of this silica is usually 10 to 30 nm, and the bulk density is 0.1 to 0.2 mg / cm ³ .

In the present invention, since fine particles having appropriate characteristics are present on the surface of the toner, an appropriate gap is formed between the toner particles and the object. Further, the fine particles have a very small contact area with the toner particles, the photoconductor, and the charge imparting member and are evenly contacted with each other, so that the effect of reducing the adhesive force is great and effective in improving the development / transfer efficiency. Moreover, since the fluidity of the developer is increased, it has an effect of reducing stress and contributes to a longer life. Furthermore, since it plays the role of a roller, it is difficult to be buried in toner particles even during cleaning under high stress (high load, high speed, etc.) between the cleaning blade and the photoconductor without wearing or damaging the photoconductor. Or, even if it is buried a little, it can be detached and returned, so that stable characteristics can be obtained over a long period of time. Further, the toner is moderately detached from the surface of the toner and accumulated at the tip of the cleaning blade, and the so-called dam effect has an effect of preventing a phenomenon that the toner passes from the blade. Since these characteristics have an effect of reducing the share received by the toner particles, the filming effect of the toner itself due to the low rheological component contained in the toner is exhibited for high-speed fixing (low energy fixing). In addition, if fine particles having an average primary particle size in the range of 50 to 500 μm are used, the excellent cleaning performance can be fully utilized, and the toner has a very small particle size. There is no reduction. Further, although the details are not clear, even if the surface-treated fine particles are externally added to the toner or the carrier is contaminated, the degree of developer deterioration is small. Accordingly, since the change in toner fluidity and chargeability with time is small, the developer can be circulated stably over a long period of time. Also, the stability of image quality is increased.

The average primary particle size (hereinafter referred to as the average particle size) of the fine particles is 50 to 500 nm, and preferably 100 to 400 nm. If the thickness is less than 50 nm, the fine particles may be buried in the concave and convex portions on the toner surface to lower the role of the rollers. On the other hand, when the particle size is larger than 500 μm, when the fine particles are located between the blade and the surface of the photosensitive member, the order is the same level as the contact area of the toner itself, and the toner particles to be cleaned pass, that is, defective cleaning occurs. It becomes easy.
If the bulk density is less than 0.3 mg / cm ³ , it contributes to improvement of fluidity, but the scattering and adhesion of the toner and fine particles are increased, so that the toner and roller effect and the accumulation in the cleaning section are accumulated. As a result, the so-called dam effect that prevents toner cleaning failure is reduced.

In fine particles of the present invention, as the inorganic _{compound, SiO 2, TiO 2, Al} 2 O 3, MgO, CuO, ZnO, SnO 2, CeO 2, Fe 2 O 3, BaO, CaO, K 2 O, Na 2 O ZrO ₂ , CaO · SiO ₂ , K ₂ O (TiO ₂ ) n, Al ₂ O ₃ · 2SiO ₂ , CaCO ₃ , MgCO ₃ , BaSO ₄ , MgSO ₄ , SrTiO _{3 and the} like, preferably _{, SiO 2, TiO 2, Al} 2 O 3 and the like. In particular, these inorganic compounds may be hydrophobized with various coupling agents, hexamethyldisilazane, dimethyldichlorosilane, octyltrimethoxysilane, and the like.
The organic compound fine particles may be thermoplastic resins or thermosetting resins, such as vinyl resins, polyurethane resins, epoxy resins, polyester resins, polyamide resins, polyimide resins, silicon resins, phenol resins, melamine resins, Examples include urea resins, aniline resins, ionomer resins, and polycarbonate resins. As the resin fine particles, two or more of the above resins may be used in combination. Of these, vinyl resins, polyurethane resins, epoxy resins, polyester resins, and combinations thereof are preferred because an aqueous dispersion of fine spherical resin particles is easily obtained.
Specific examples of vinyl resins include polymers obtained by homopolymerization or copolymerization of vinyl monomers, such as styrene- (meth) acrylic acid ester copolymers, styrene-butadiene copolymers, (meth) acrylic acid. -Acrylic ester copolymer, styrene-acrylonitrile copolymer, styrene-maleic anhydride copolymer, styrene- (meth) acrylic acid copolymer, and the like.

The bulk density of the fine particles was measured by the following method. Using a 100 mL graduated cylinder, fine particles were gradually added to make 100 mL. At that time, no vibration was applied. The bulk density was measured by the difference in weight before and after placing the fine particles of the graduated cylinder.
Bulk density (g / cm ³ ) = Amount of fine particles (g / 100 mL) ÷ 100
The fine particles of the present invention can be externally added and adhered to the toner surface by mechanically mixing and adhering the toner base particles and fine particles using various known mixing devices, or in the liquid phase. There is a method in which the base particles and the fine particles are uniformly dispersed with a surfactant or the like, and are dried after the adhesion treatment.

(Comparative Example 1)
Using the conventional biaxial development system (initial developer 1000 g) shown in FIG. 20 and the image forming apparatus shown in FIG. 11, image formation was performed while changing the developer for independent carrier replenishment. When the durability was evaluated, a decrease in image density was observed after printing about 250,000 sheets.

(Comparative Example 2)
Using the triaxial development system (initial developer 1000 g) of FIG. 21 (see JP-A-11-167260) and the image forming apparatus of FIG. 11, image formation was performed while changing the developer for independent carrier replenishment. When the durability was evaluated, a decrease in image density was observed after printing about 350,000 sheets.

Example 1
In the example of the configuration shown in FIGS. 1 and 11 (initial developer 1000 g), image formation was performed while changing the developer of this example. When the durability was evaluated, a decrease in image density was observed after printing about 500,000 sheets. As compared with Comparative Examples 1 and 2, it was confirmed that the developer life was greatly extended and the image density was stably obtained for a long time.

It is a figure which shows the image development apparatus of this invention. It is a figure which shows the principal part of this invention. It is the figure shown about the internal magnet in a developing roller. FIG. 5 is a diagram illustrating a flow of a developer in a developing device. It is a figure which shows a uniaxial eccentric screw pump. FIG. 6 is a configuration diagram for controlling toner and carrier replenishment. It is the figure which showed the flowchart. It is a figure which shows the image development apparatus of this invention. It is a figure which shows the principal part of this invention. FIG. 5 is a diagram illustrating a flow of a developer in a developing device. 1 is a schematic central sectional view showing an internal configuration of an image forming apparatus to which the present invention is applied. 1 is a diagram illustrating an internal configuration of an image forming apparatus to which the present invention is applied. 1 is a diagram illustrating an internal configuration of a tandem type image forming apparatus. FIG. FIG. 4 is a diagram schematically illustrating the shape of a toner for explaining a shape factor SF-1. FIG. 6 is a diagram schematically illustrating the shape of a toner for explaining a shape factor SF-2. It is a figure which shows the result actually obtained by calculation in the frequency | count of doctor passage close | similar to a lifetime. It is a figure which shows the conventional developing device. It is a figure which shows the conventional developing device. It is a figure which shows the conventional developing device. It is a figure which shows the conventional biaxial developing system. It is a figure which shows a triaxial developing system.

Explanation of symbols

1 Photoconductor 2 Scorotron charger (charging device)
3 Exposure device 4 Developing device 5 Transfer device 6 Cleaning device 6a Cleaning brush 6b Cleaning blade 6c Recovery means 20 First image carrier unit 20A Cleaning device 21 First image carrier belt 22 Primary transfer roller 23 Roller 24 Roller 25 Roller 26 Roller 27 Roller 30 Second image carrier unit 30A Cleaning device 31 Second image carrier belt 32 Primary transfer roller 33 Roller 34 Roller 35 Roller 36 Roller 37 Roller 40 Recorder conveyance path 41 Secondary transfer roller 42 Transfer charger 43 Paper feed device 44 Conveying roller pair 45 Registration roller pair 46 Transfer roller 48 Paper conveying unit 49 Paper transfer device 50 Recording medium transfer means 50A Cleaning device 51 Conveying belt 54 Roller 55 Roller 56 Roller 57 Adsorption charger 58 Static elimination / separation charger Jer 60 Fixing device 70 Cooling roller pair 71 Paper discharge roller pair 75 Paper discharge stack unit 80Y, 80C, 80M, 80K First image forming unit 81Y, 81C, 81M, 81K Second image forming unit 85 Storage space 86Y, 86C, 86M , 86K Cartridge 87 Cartridge 88 Collection unit 100 Image forming apparatus main body 101 Photoconductor 401 Developing device 402 Developing roller 403 Developer layer regulating member 404 Collection screw 405 Collection conveyance path 406 Agitation conveyance screw 407 Agitation conveyance path 408 Supply screw 409 Supply conveyance path 410 Fin 411 Fin 412 Fin 413 Partition plate 414 Partition plate 415 Fin 420 Delivery unit 421 from the recovery conveyance path to the agitation conveyance path Delivery unit 422 from the agitation conveyance path to the supply conveyance path Delivery from the supply conveyance path to the agitation conveyance path 423 transfer unit from the delivery unit 424 agitation path from the collection conveyance path to the agitation path to the recovery conveyance path from the transfer unit 425 supplying path to the supply conveyance path
429A Roller 430 Toner supply means 431 Unused toner 432 Toner storage container 433 Developer supply transport path 435 Developer supply means 435A Toner supply means 435B Carrier supply means 435C Holder 435D Drive motor 435E Supply clutch 435F Supply port 435G Roller 435H Stator 436 Carrier supply means 437 Unused carrier 438 Carrier storage container 440 Developer discharge means 441 Used developer 442 Discharge agent storage container 443 Discharge agent conveyance path 450 Toner supply port 451 Discharge openings P1, P2, P3, P4, P5 Magnet P Paper Q Light neutralizer

Claims (12)

A developer carrier for carrying and conveying a developer composed of toner and carrier;
Agitating and conveying the developer along the axial direction of the developer carrier, and a supply conveyance path having a supply screw for supplying the developer to the developer carrier,
A collection conveyance path having a collection screw for collecting the developer after completion of development from the developer carrying body and conveying the collected developer in parallel and in the same direction as the supply screw;
An agitation conveying screw that receives supply of excess developer that has not been supplied from the supply conveyance path to the developer carrier and the recovered developer from the recovery conveyance path, and that agitates and conveys in a direction opposite to the supply screw; A stirring conveyance path that circulates and supplies the developer that has stirred the surplus developer and the collected developer to the supply conveyance path,
A developer regulating member that regulates the height of the developer layer supplied to the developer carrying body from the supply conveyance path so as to face the developer carrying body;
Comprising
The rotation direction of the developer carrying member is a direction in which the developer immediately after passing through the developer regulating member moves upward,
The supply conveyance path, the collection conveyance path it and the stirring conveyance path is substantially horizontally disposed,
When virtually divided by a vertical line passing through the center of the developer carrying member of the developing device cross section,
The axial center position of the supply screw is arranged in a region different from the region where the photoconductor exists,
Fins are attached to the developer delivery side in each of the supply screw, the recovery screw and the stirring screw,
A partition plate is installed between the recovery screw and the screw that is adjacent to the recovery screw and located on the side close to the developer regulating member, and the partition plate includes the top of the recovery screw and the recovery screw. The part located above the straight line connecting the apex of the screw adjacent to the screw is adjacent to the collecting screw and located on the side close to the developer regulating member and to the vicinity of the developer carrier. Bend with an inclination,
The bent partition plate forms an inclined passage from the developer carrying member to the recovery conveyance path,
Without disposing the transfer member is in the inclined oblique passage,
A developing device, wherein a plurality of magnets are fixed inside the developer carrying member, and the same polarity of the magnets is disposed across the entrance side of the inclined passage. The developing device according to claim 1,
A horizontal line passing through the center of the developer carrying member in the cross section of the developing device;
When the angle formed by the line connecting the center of the developer carrier and the axis center of the supply screw is θ,
The developing device, wherein θ is in a range of 30 ° ≦ θ ≦ 75 °. The developing device according to claim 1 or 2,
Each conveyance path from the vicinity of the developer regulating member,
The developing device, wherein the supply conveyance path, the agitation conveyance path, and the recovery conveyance path are arranged in this order. The developing device according to claim 3,
The developing device, wherein the delivery unit from the recovery conveyance path to the agitation conveyance path and the delivery unit from the supply conveyance path to the agitation conveyance path are arranged at positions that do not face each other. The developing device according to claim 1 or 2,
Each conveyance path from the vicinity of the developer regulating member,
The developing device, wherein the supply conveyance path, the recovery conveyance path, and the agitation conveyance path are arranged in this order. The developing device according to any one of claims 1 to 5,
A developing device, wherein a toner replenishment position is installed in the collection conveyance path. In the developing device according to any one of claims 1 to 6,
Developer supply means for supplying a developer containing at least an unused carrier into the developing device;
And a developer discharging means for discharging the used developer out of the developing device. The developing device according to any one of claims 1 to 7,
The developing device, wherein the amount of developer exchange performed by the developer supplying means and the developer discharging means at one time is a part of the total amount of developer in the developing device. The developing device according to any one of claims 1 to 8,
The developing device, wherein the developer supplying means supplies the carrier and the toner to the developing device by independent supply operations. The developing device according to any one of claims 1 to 9,
The developing device, wherein the developer discharging means is installed in the collection conveyance path. A color image comprising: an image carrier on which an electrostatic latent image is formed; and a plurality of developing devices according to claim 1, and forming a color image on a recording material. Forming equipment. The color image forming apparatus according to claim 11.
The first toner image transferred to the first surface (front surface) of the paper is
A first image forming unit group having at least a developing device and a photoreceptor for each color;
Formed by a first image station comprising a first toner image carrying belt on which a first toner image formed by the first image forming unit group is transferred and carried;
The second toner image transferred to the second side (back side) of the paper is
A second image forming unit group having at least a developing device and a photoreceptor for each color;
Formed by a second image station comprising a second toner image carrying belt on which a second toner image formed by the second image forming unit group is transferred and carried;
A color image forming apparatus, wherein the first toner image and the second toner image are transferred onto a sheet simultaneously or sequentially before fixing.

Images