JP2007072329A - Developing device, process cartridge and image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a developing device, process cartridge and image forming apparatus, which are designed such that supplied toner is prevented from directly reaching a developing sleeve in a low charged or uncharged state, deterioration of developer is less even when an image forming process is repeated for a long time or when particular use in which toner consumption is less continues for a long time, and soiling of a base and scattering of toner are prevented for a long time. <P>SOLUTION: The torque T2 of the entire developing unit and the axial torque T1 of a conveying screw in a supply-side stir chamber satisfy the following equations: (1) T1>0.2[kgf cm] and (2) T1/T2>0.25. This makes it possible to provide the developing device and image forming apparatus, in which deterioration of developer is less and soiling of the base and scattering of toner are prevented for a long time. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an image forming apparatus such as a copying machine, a facsimile machine, and a printer, and more particularly to an image forming apparatus using a two-component developer.

In recent years, along with demands for downsizing and personalization of image forming apparatuses using electrophotographic technology such as copiers and printers, downsizing of developing devices has been attempted. Further, in response to such a request, when the toner runs out, the disposable developing device that is replaced with the developing device, or a latent image carrier (on which an electrostatic latent image of the original image is formed) in addition to the developing device. A so-called process cartridge in which a photosensitive member) and a cleaning unit for removing toner remaining on the photosensitive member are integrated is also widely used.

However, such a miniaturized developing device has a small amount of developer containing the toner and the magnetic carrier. In addition, since the space for the developer agitating portion is also inevitably reduced, the time required for the replenished toner to reach the development area is short, and the agitation between the toner and the magnetic carrier becomes insufficient, resulting in a charge amount of the toner. Becomes smaller, and floating toner is likely to be generated. When this floating toner is generated, the background stain of the transfer paper becomes severe, which is not preferable. Such a phenomenon occurs remarkably when the amount of toner replenishment increases, such as when the amount of toner replenishment increases, as in the case of continuously printing a document with a high image area ratio.

In addition, as the machine speed increases, the developer agitating / conveying member rotates at high speed, and the toner is 3 to 12 μm fine particles, so that a part of the replenished toner is scattered without being well agitated with the developer. , Float or move on the developer surface. When such toner is transported to the developing roller and transported to the development area, uncharged, reversely charged, weakly charged, poorly charged toner, non-image area ground contamination, density unevenness, and toner scattering occur.

In order to solve such a problem, as in Patent Document 1, for example, the toner replenished from the toner replenishing portion is prevented from sliding on the surface of the agent and being conveyed to the screw portion on the developing roller side without being charged. It has been proposed to provide an anti-scattering member.
However, these means emphasize the uniform dispersion of the toner among the two conditions that must be satisfied before the toner is transported to the developing unit. In other words, the screw portion is provided with a function to uniformly distribute the replenishment toner to the developer, and the toner charging is covered by the rubbing of the developer in the vicinity of the developer regulating blade as before.
In such a development system, there is a problem in that the toner is subjected to a large load in the developer reservoir on the back side of the developer regulating blade and the developer deteriorates. In addition, deteriorated toner tends to be weakly charged / reversely charged toner, and after a long-term image forming process, there is a problem that the charge amount distribution becomes broad, leading to background stains and toner scattering. If the stress on the back of the regulation blade is reduced, the toner will be insufficiently charged, and on the contrary, there will be a problem that the background dirt and toner scattering increase.

Japanese Patent Application Laid-Open No. 2004-228561 proposes that the charge amount is increased by operating the agent path regulating member in the developing device so as to be close to the developing roller. However, in this configuration, although the rubbing force applied to the agent is increased, the location where the agent is regulated is in the vicinity of the doctor blade. There is also a concern that density unevenness may occur.

Patent Document 3 proposes a configuration in which the agent level in the supply side stirring chamber is changed between upstream and downstream by increasing the number of fins attached to the downstream side of the screw in the supply side stirring chamber from the upstream side.
However, in any of these inventions, it is possible to prevent the topping of the replenished toner, to uniformly disperse the toner, to sufficiently impart the toner, and to weaken the mechanical force applied to the developer as compared with the conventional one, thereby extending the life of the developer. There were points that were insufficient to make it easier.

JP-A-9-106161 JP-A-11-202573 JP 2004-272017 A

Therefore, the present invention has been made in view of the above problems, and the problem is that the replenished toner can be prevented from reaching the developing sleeve directly in a low-charged or uncharged state, and the image forming process can be performed over a long period of time. Provides a developing device and an image forming apparatus that are less likely to cause deterioration of the developer and have no background stain or toner scattering over a long period of time even when the process is repeated or when a special usage state in which toner consumption is low extends over a long period of time It is to be.
The present invention also reduces the burden on the developer as a whole by increasing the charge function of the toner even in the first developer agitation unit to which the toner is replenished, thereby extending the life of the developer. It is.

The features of the present invention, which is a means for solving the above problems, are listed below.
In the present invention, the developer accommodating portion on the side where the toner is replenished is defined as a replenishing side agitating chamber, and the developer accommodating portion on the side facing the developer carrying member is defined as a developing side agitating chamber.
In the present invention, the torque T2 of the entire developing unit and the shaft torque T1 of the conveying screw in the replenishing side stirring chamber are
(1) T1> 0.2 [kgf · cm]
(2) T1 / T2> 0.25
It is characterized by satisfying this relationship. This has the following two effects.

When the torque T1 of the supply side stirring chamber is larger than 0.2 [kgf · cm], the agent stays in the supply side stirring chamber, and the developer is in a compacted state. In such a state, the rubbing force of the developer is increased, and the dispersion of the replenishing toner is promoted, and at the same time, the charging of the toner is promoted. Therefore, when the replenished toner is transported to the developing side stirring chamber and used for development, the toner is sufficiently charged, and good image formation without toner scattering and background contamination is performed.

Further, when the developing device having such a configuration is used, since the toner charging function is provided in the replenishing side stirring chamber, charging is not performed by intensive rubbing with a doctor blade as in a conventional developing device. Get better. Accordingly, the mechanical force in the vicinity of the doctor blade can be designed to be weak, the torque of the entire developing unit can be reduced, and the ratio T1 / T2 that is the ratio of the torque T2 of the entire unit and the torque T1 of the replenishment side stirring chamber can be set. By setting the value larger than 0.25, the life of the developer can be extended by reducing the stress of the entire unit.
Note that T1 / T2 <0.25 indicates a state in which the torque of the entire unit is increased, and the stress applied to the agent becomes excessive and causes deterioration of the toner, which is not appropriate.

In the present invention, since the unit torque T2 does not vary so much depending on the environment and the toner density, it is a method of detecting only the torque T1 and controlling the opening area of the shutter. It is possible to provide. Note that the change of the unit torque T2 during actual operation is extremely small and can be ignored. In the present invention, the unit torque value measured in advance in the initial state can be used as T2.

In the present invention, the developer path regulating means for controlling the axial torque of the conveying screw in the replenishing side agitating chamber is transferred to the developer agitating chamber from the downstream side in the developer conveying direction of the replenishing side agitating chamber. By providing the time until the replenished toner is supplied to the doctor developing sleeve, the toner can be charged and image formation without toner scattering and background contamination can be performed.

Furthermore, in the present invention, a plate-like member protruding downward from the ceiling of the stirring chamber or protruding upward from the bottom to the ceiling is provided as a shutter member of the transfer portion at the transfer portion of the supply side stirring chamber and the developing side stirring chamber. By controlling the depth of penetration of the plate-like member, the developer path is regulated so as to satisfy the relational expressions (1) and (2). As a result, the replenishment toner can be prevented from reaching the developing side stirring chamber with insufficient charging, image defects such as background contamination and toner scattering can be prevented, and the life of the developer can be extended.

In the present invention, the shutter member is a plate member that can slide the opening laterally at the transfer portion between the replenishment side stirring chamber and the development side stirring chamber, and the shutter member moves left and right by a drive control means (not shown). Thus, the developer path is regulated so as to satisfy the relational expressions of the above formulas (1) and (2). As a result, the replenishment toner can be prevented from reaching the developing side stirring chamber with insufficient charging, image defects such as background contamination and toner scattering can be prevented, and the life of the developer can be extended. Note that the lateral slide method contributes to space saving of the developing device because the shutter does not protrude outward from the developing device even when the opening is open.

Further, according to the present invention, a plurality of plate members installed in parallel are provided as a shutter member in the transfer portion of the replenishment side stirring chamber and the development side stirring chamber, and the individual plate-like members rotate in conjunction with each other to change the angle. Thus, the developer path is regulated so as to satisfy the relational expressions of the above formulas (1) and (2). As a result, the replenishment toner can be prevented from reaching the developing side stirring chamber with insufficient charging, image defects such as background contamination and toner scattering can be prevented, and the life of the developer can be extended.
In this method, a small plate shutter is driven to rotate inside the developing device to change the area of the opening. Therefore, the size of the developing device does not change regardless of whether the opening is open or closed. Can also contribute to

The present invention has a partition plate having a plurality of holes in the transfer portion between the replenishment side stirring chamber and the development side stirring chamber as a shutter member, and has a plate shape with another hole overlapped in parallel with the partition plate The member slides so as to close the hole of the partition plate, thereby regulating the developer path so as to satisfy the relational expressions (1) and (2) (see FIG. 12). As a result, the replenishment toner can be prevented from reaching the developing side stirring chamber with insufficient charging, image defects such as background contamination and toner scattering can be prevented, and the life of the developer can be extended.

Further, according to the present invention, a plurality of plate members installed in parallel are provided as a shutter member at the transfer portion between the replenishing side stirring chamber and the developing side stirring chamber, and the individual plate-like members automatically rotate in conjunction with each other. By changing the angle, the developer path is regulated so as to satisfy the relational expressions (1) and (2). Part of the plate-like member is connected to the ceiling of the stirring chamber by a coil spring. When the pressure of the agent in the supply side stirring chamber is small, the shutter closes and the pressure increases. When the pressure is high, the shutter opens and the pressure is increased. Acts in the direction of relaxation.
Therefore, according to the present invention, since a torque detection unit, a shutter opening area control unit, and a shutter driving unit are unnecessary, a desired developing device can be provided at low cost.

In addition, this automatic shutter control prevents the replenished toner from reaching the developing side stirring chamber with insufficient charging, prevents image defects such as background stains and toner scattering, and extends the life of the developer. Can be achieved.

In the present invention, since at least a part of the ceiling of the replenishing side stirring chamber has a circular shape along the outer diameter of the screw, there is no immovable layer where the driving force due to the rotation of the screw is not transmitted, and good developer dispersion / The conveyance capability can be secured.

As described above, by promoting the dispersion and charging of the replenishment toner in the replenishment side stirring chamber, it is not necessary to apply a strong load to the developer in order to charge the toner in the vicinity of the doctor blade as in the prior art. Then, an excessive load on the developer can be reduced, and deterioration of the developer can be suppressed. Therefore, according to the present invention, not only initial background contamination and toner scattering but also good image formation without background contamination and toner scattering over a long period of time can be achieved.

According to the present invention, it is possible to prevent the replenished toner from directly reaching the developing sleeve in a low or uncharged state by the means for solving the above problem, and when the image forming process is repeated over a long period of time, Even when a special usage state with low consumption extends over a long period of time, it is possible to provide a developing device, a process cartridge, and an image forming apparatus with little developer deterioration and no long-term background contamination and toner scattering.

  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.

FIG. 1 is an internal configuration diagram of a color image forming apparatus to which a developing device according to an embodiment of the present invention is applied, and more specifically, a tandem indirect transfer type electrophotographic copying apparatus. FIG. 2 is a diagram showing the developing device in the present embodiment. FIG. 3 is an internal configuration diagram in the developer container in the present embodiment. FIG. 4 is a diagram showing a developing device in the present embodiment. FIG. 5 is a diagram showing the opening of the transfer section in the present embodiment. FIG. 6 is a view showing a shutter member capable of controlling the cross-sectional area of the transfer portion between the replenishing side stirring chamber and the developing side stirring chamber in the present embodiment. FIG. 7 is a diagram showing the shutter member protruding toward the ceiling from the bottom surface of the transfer portion of the replenishment side stirring chamber and the development side stirring chamber in the present embodiment. FIG. 8 is a diagram showing a shutter member that can slide in the lateral direction between the supply side stirring chamber and the developing side stirring chamber in the present embodiment. FIG. 9 is a diagram showing a plurality of shutter members such as blinds installed in parallel provided in the transfer section of the replenishing side stirring chamber and the developing side stirring chamber in the present embodiment. FIG. 10 is a diagram illustrating the influence on the developer charge amount distribution depending on the presence or absence of the developer path regulating means. FIG. 11 is a diagram showing the screw used in the present embodiment. FIG. 12 is a diagram showing a shutter member of a type that closes a slidable round hole in the present embodiment. FIG. 13 is a diagram showing a shutter member that is automatically controlled by the spring pressure in the present embodiment.

In FIG. 1, reference numeral 100 is a copying apparatus main body, 200 is a paper feed table on which the copying apparatus main body 100 is placed, 300 is a scanner (reading optical system) mounted on the copying apparatus main body 100, and 400 is an automatic document feeder that is further mounted thereon. (ADF). An endless belt-like intermediate transfer member 10 extending in the lateral direction is provided at the center position of the copying apparatus main body 100. In the illustrated example, the intermediate transfer member is wound around three support rollers 14, 15, and 16 so that it can be rotated and conveyed clockwise in the figure. In this illustrated example, an intermediate transfer body cleaning device 17 that removes residual toner remaining on the intermediate transfer body 10 after image transfer is provided to the left of the second support roller 15 among the three support rollers.

Further, among the three support rollers, the intermediate transfer member 10 stretched between the first support roller 14 and the second support roller 15 has black, yellow, magenta, and cyan along the transport direction. The tandem image forming unit 20 is configured by arranging the four image forming units 18 side by side. An exposure device 21 is further provided immediately above the tandem image forming unit 20 as shown in FIG.

On the other hand, a secondary transfer device 22 is provided on the opposite side of the intermediate transfer body 10 from the tandem image forming unit 20. In the illustrated example, the secondary transfer device 22 is configured by spanning a secondary transfer belt 24, which is an endless belt, between two rollers 23, and is pressed against the third support roller 16 via the intermediate transfer body 10. The image on the intermediate transfer body 10 is transferred to a sheet.

A fixing device 25 for fixing the transfer image on the sheet is provided beside the secondary transfer device 22. The fixing device 25 is configured by pressing a pressure roller 27 against a fixing belt 26 that is an endless belt. The secondary transfer device 22 described above also has a sheet transport function for transporting the image-transferred sheet to the fixing device 25. In the illustrated example, a sheet reversing device 28 for reversing the sheet so as to record images on both sides of the sheet is provided below the secondary transfer device 22 and the fixing device 25 in parallel with the tandem image forming unit 20 described above. Is provided.

When making a copy using the color electrophotographic apparatus in FIG. 1, a document is set on the document table 30 of the automatic document feeder 400. Alternatively, the automatic document feeder 400 is opened, a document is set on the contact glass 32 of the scanner 300, and the automatic document feeder 400 is closed and pressed by it. When a start switch (not shown) is pressed, when a document is set on the automatic document feeder 400, the document is transported and moved onto the contact glass 32, and then the document is set on the other contact glass 32. Immediately, the scanner 300 is driven, and the first traveling body 33 and the second traveling body 34 travel. Then, the first traveling body 33 emits light from the light source and further reflects the reflected light from the document surface toward the second traveling body 34, and is reflected by the mirror of the second traveling body 34 and passes through the imaging lens 35. The document is placed in the reading sensor 36 and the original content is read.

When a start switch (not shown) is pressed, one of the support rollers 14, 15 and 16 is rotationally driven by a drive motor (not shown), and the other two support rollers are driven to rotate, so that the intermediate transfer body 10 is moved. Rotate and convey. At the same time, the individual image forming means 18 rotates the photoconductors 40 to form black, yellow, magenta, and cyan monochrome images on the photoconductors 40, respectively. Then, along with the conveyance of the intermediate transfer member 10, the single color images are sequentially transferred to form a composite color image on the intermediate transfer member 10.

On the other hand, when a start switch (not shown) is pressed, one of the paper feed rollers 42 of the paper feed table 200 is selectively rotated, and the sheet is fed out from one of the paper feed cassettes 44 provided in multiple stages in the paper bank 43, thereby separating rollers 45. Are separated one by one into the paper feed path 46, conveyed by the conveyance roller 47, guided to the paper feed path 48 in the copying machine main body 100, and abutted against the registration roller 49 and stopped. Then, the registration roller 49 is rotated in synchronization with the composite color image on the intermediate transfer member 10, the sheet is fed between the intermediate transfer member 10 and the secondary transfer device 22, and transferred by the secondary transfer device 22. A color image is recorded on the sheet. The image-transferred sheet is conveyed by the secondary transfer device 22 and sent to the fixing device 25. The fixing device 25 applies heat and pressure to fix the transferred image. Are discharged and stacked on the discharge tray 57. Alternatively, it is switched by the switching claw 55 and put into the sheet reversing device 28, where it is reversed and guided again to the transfer position, and an image is recorded also on the back surface, and then discharged onto the discharge tray 57 by the discharge roller 56.

On the other hand, the intermediate transfer body 10 after the image transfer is removed by the intermediate transfer body cleaning device 17 to remove residual toner remaining on the intermediate transfer body 10 after the image transfer, so that the tandem image forming unit 20 can prepare for another image formation.

In the tandem image forming unit 20 described above, each image forming unit 18 includes a charging device, a developing device, a primary transfer device, a photoconductor cleaning device, a static elimination device, and the like around the drum-shaped photoconductor 40. ing. FIG. 2 is a diagram illustrating the developing device 61. The developing device 61 includes, in a developer container 65, a toner replenishing side agitating screw 66, a developer carrying side agitating screw 67, and a developing sleeve (developing roller) 68 as developer agitating / conveying means.

A replenishing port (not shown) is provided on the outer wall of the container of the first developer agitating chamber 86 to supply toner from a toner replenishing device (not shown) (hereinafter, the first developer agitating chamber is referred to as a replenishing side agitating chamber). The agitation screw 66 on the toner replenishment side agitates and conveys the toner replenished from the toner replenishing device and the developer (two-component developer having magnetic particles and toner) in the developer container 65. The stirring screw 67 in the second developer stirring chamber 87 (developer carrier side) stirs and conveys the developer in the developer container 65 (hereinafter, the second developer stirring chamber is referred to as the development side stirring chamber). And). Further, as shown in FIG. 3, the replenishment side stirring chamber and the development side stirring chamber are partitioned by a partition plate 80, and there are openings for delivering the developer at both ends.

Example 1
In this example, an experiment was performed under the condition of a toner concentration of 7 wt% using a carrier having a volume average particle diameter of 35 μm and a toner having a particle diameter of 6 μm. As shown in FIG. 4, in a developing device including a replenishment-side stirring chamber, a development-side stirring chamber, a developer regulating member, and a developing roller, the shaft torque of the transport screw in the replenishment-side stirring chamber and the torque of the entire unit are as follows: And measured.

First, using an experimental device for measuring torque, KYOWA's small torque converter TP-2KCE was connected in series between the end of the screw shaft of the replenishing side stirring chamber and the shaft of the drive motor, and dynamic strain was measured. The output was read by the device DPM-711B.

First, the shaft torque was measured when the motor was rotated at a predetermined rotational speed without putting the developer in the developing unit, and then the shaft torque was measured with 400 g of the developer. The difference was used as the axial torque T1 of the conveying screw in the replenishment side stirring chamber. At this time, the conveying screw and the developing sleeve in the developing side agitating chamber are linked via a gear by another driving motor, and are rotated at a predetermined rotational speed. Therefore, in this measurement, it was possible to measure the axial torque of the conveying screw only on the supply side.

Next, in order to measure the torque of the entire unit, the screw on the supply side stirring chamber, the screw on the developing side stirring chamber, and the developing sleeve are connected with a gear, and the development is performed with one drive motor equipped with a torque converter. The entire apparatus is driven. In this state, the torque when driven without the developer was measured in advance, and then the torque when 400 g of developer was added was measured. The difference between the two was used as the torque T2 of the entire unit.

In this embodiment, the opening of the transfer section has a width of 32 mm × height of 26 mm, and a partition plate for the replenishing side stirring chamber and the developing side stirring chamber is extended to the ceiling as shown in FIG. In the form, a plate-like part was attached and the opening area was controlled.
As shown in Table 1, the shaft torque T1 of the conveying screw in the replenishing side stirring chamber is 0.3 [kgf · cm], and the torque T2 of the entire unit is 0.95 [kgf · cm]. there were. Therefore, T1 / T2 = 0.32. (Condition 1)

<Table 1: Conditions and torque of each part>

At this time, the behavior of the developer at a position before the delivery unit (a place where the developer is in a compacted state) will be described. If the opening area of the delivery section is reduced, the amount of developer that can pass through the delivery section is reduced. Therefore, the developer is introduced into the supply side stirring chamber from about 1/2 to 1/3 of the downstream side of the supply side stirring chamber. It comes into contact with the ceiling lid. That is, the 360 ° agent is clogged around the screw.

At this time, there are two concerns. One is a concern that if the replenished toner enters the compaction area without being completely dispersed, the developer is packed and transported as it is without being dispersed, and the other is that the screw rotates. However, there is a concern that a part of the developer (particularly the corner of the stirring chamber where the screw blades do not sweep) may form a non-moving layer and the agent may not circulate. When the machine is moved without leaving the machine for a long period of time and the machine is moved, the developer that has become a non-moving layer due to a decrease in the volume of the developer may cause unevenness of the developer. Cause unevenness.

Since the developer does not pass visible light, the internal flow state cannot be observed with visible light. Therefore, it was decided to check the internal flow state using the X-ray visualization technique of FN200413529. The observation apparatus used is an X-ray transmission image observation apparatus H3150 manufactured by Toshiba IT Control. Further, as a tracer for grasping the behavior of the developer, 50 μm tungsten particles substantially equal to the carrier particle size were used. Since tungsten has a higher absorptance than the carrier (iron oxide) in the developer, when observed with transmitted X-rays, only that portion is observed to be blacker than the surroundings. Further, since the tracer particles are sufficiently small, it is considered that the behavior of the developer is the same as that of the surrounding developer powder. Therefore, the developer behavior can be visualized by observing the flow state of tungsten. In FN200413529, it is shown that when powder is conveyed by screw, even if there is a difference of 20 times or more in density between the tracer particles and the powder particles, the behavior is almost the same.

A small amount of tracer was replenished with a spatula taking care not to disturb the flow of the field at the place where the developer behavior was observed. The developer stirring chamber was gently covered and installed in the apparatus, and the developer behavior when the screw was rotated was visualized by X-ray.
As a result, the tracer that has entered the consolidation area is dispersed in the same manner as the non-consolidation area (agent level is slightly above the screw shaft) from the toner replenishment position of the replenishment side stirring chamber to the vicinity of the center of the replenishment side stirring chamber. It was confirmed that the non-moving layer was not generated in the screw examined here. Therefore, the two concerns have been resolved.

As shown in FIG. 11, the screw used in this example is a helical screw having a pitch of 25 mm, an outer diameter of 20 mm, and an axial diameter of 8 mm, and is provided with a single plate-like member connected to the outer periphery of the screw blade in the longitudinal direction. Is.

On the other hand, when the opening area is further reduced and the axial torque of the screw in the replenishing side stirring chamber is set to 0.35 [kgf · cm], the screw rotates at the corner portion surrounded by the ceiling and the side wall of the stirring chamber. However, a stationary layer in which the developer did not move at all was formed. If the screw shape is changed and a screw whose outer diameter of the screw blade is thinner than the other part at the end downstream of the screw in the supply side stirring chamber is used, the ceiling lid and the supply side stirring In the corner region formed by the outer side wall of the chamber, there is a slight immovable layer, which is not suitable for the combination with the condition of actively using the consolidation region as in the present invention. Therefore, by using a circular member along the shape of the screw, the ceiling shape of the second half of the replenishment-side stirring chamber where the developer becomes compacted eliminates the immobile layer, and the developer in the stirring chamber is transported and stirred well. It became possible.

Next, a method for examining the charge rising property of the toner under the conditions of this embodiment will be described. 1 g of replenishing toner is replenished to the most upstream part (point A in FIG. 3) of the replenishing side stirring chamber. The screw is rotated at a predetermined speed, and the charge amount distribution of the developer immediately after the transfer portion is measured when the peak of the replenished toner is transferred to the developing side stirring chamber. The result is shown in FIG. In this graph, in order to show only the effect of the developer path regulating means, a simple stirring device (replenishment side stirring chamber, development side stirring chamber, screw, partition plate, It is a result measured by only the developer path regulating means). The amount of the developer at this time was usually 250 g by subtracting the amount attached around the developing sleeve.

Compared with the result of FIG. 10A in which the developer path regulating means is not used, the rising of the charge is clearly promoted, and the amount of uncharged toner is very small. In an actual developing device, rubbing by a doctor blade is also applied, so that this charging rise is sufficient.

Next, this condition was carried out in an actual developing unit, and a printing test was conducted. As a result, even under strict toner replenishment conditions (when developing solid images), the replenished toner is sufficiently dispersed and charged before reaching the development-side stirring chamber, and good image formation with no background contamination or toner scattering is achieved. Was done.

(Comparative Example 1)
Furthermore, the experiment was performed under conditions 2 to 4 in Table 1. Under condition 2, since the shaft torque T1 of the replenishing side agitating screw is small and the unit torque T2 is also small, the charging start-up of the replenishing toner is insufficient, and toner scattering and background contamination occur in a low temperature and low humidity environment.

(Comparative Example 2)
Condition 3 is a condition in which both the unit torque and the shaft torque T1 of the replenishing agitating screw are large. In the initial state, the toner is sufficiently charged and good image formation is performed. As a result of the deterioration, an image with noticeable roughness was output, and there were also problems of toner scattering and background contamination.

(Comparative Example 3)
Condition 4 is a condition in which the unit torque T2 is large but the supply side torque T1 is small. As the developer deteriorates with time, problems such as image quality deterioration, toner scattering, and background contamination occur over time.

(Example 2)
In this embodiment, as a developer path regulating member, a shutter member capable of controlling the cross-sectional area of the transfer portion between the supply side stirring chamber and the development side stirring chamber is used as shown in FIGS. 6 (a) and 6 (b). The shutter member is a plate-like member inserted downward from the ceiling of the transfer portion of the supply side stirring chamber and the development side stirring chamber, and the shutter member is driven up and down by a drive control means (not shown), thereby supplying the supply side stirring chamber. The opening area of the shutter is changed so that the shaft torque T1 and the unit torque T2 of the conveying screw satisfy the relational expressions (1) and (2), and a rubbing force can be appropriately applied to the developer. It has a configuration.

The reason why the axial torque of the screw in the replenishing side stirring chamber fluctuates in the developing unit is dominated by the change in the volume of the developer, and the reason why the volume fluctuates is as follows. First, there is a change in charge amount due to a change in temperature and humidity environment. For example, in a high-temperature and high-humidity environment, since the charge amount is low, the carrier is densely packed and the bulk is reduced. Therefore, even if it is the opening area of the same delivery part, the area | region of a compaction part decreases and axial torque becomes small. As a result, the rubbing force at the compacted portion is weakened, so that the charging effect cannot be obtained unless the opening area is further reduced.

Second, there is a toner density fluctuation. For example, when the toner concentration is lowered, the carrier is densely packed and the bulk is reduced. Therefore, even if it is the opening area of the same delivery part, the area | region of a compaction part decreases and axial torque becomes small. As a result, the rubbing force at the compacted portion is weakened, so that the charging effect cannot be obtained unless the opening area is further reduced.

For this reason, in an actual image forming apparatus, the torque T1 varies depending on image forming conditions. On the other hand, since the unit torque T2 does not change as much as T1, the torque T2 measured at the time of design is stored in advance as an invariable value without incorporating the measuring device for the torque T2 in the image forming apparatus, and replenishment. It can be set as the machine structure which measures only the axial torque T1 of the conveyance screw of a side stirring chamber. Since only one torque measurement is required, the machine configuration is simplified and the cost can be reduced.

Under the condition that the shaft torque of the conveying screw in the replenishing side stirring chamber is smaller than 0.2 [kgf · cm], the charge rising when the toner is replenished is insufficient. On the other hand, there is a problem that even if the shutter is closed too much, mechanical stress is applied to the developer and the deterioration of the developer is accelerated.

When the shutter moves in the closing direction, the developer stays in the upstream portion in the transport direction with respect to the shutter, and the rubbing force of the developer increases. As a result, the rising of charging is promoted simultaneously with the promotion of the dispersion of the replenishing toner. After the charge has risen sufficiently, or when the image forming process continues with little image area ratio and almost no toner replenishment, it is not necessary to raise the charge amount any further. It is more preferable to drive so that the area is widened so that unnecessary stress is not applied to the developer.

As described above, under the torque condition shown in the present invention, there is no problem that the stress is too strong to accelerate the deterioration of the developer, and the developer in the developing side stirring chamber is insufficient, resulting in poor pumping. And good image formation was possible.

(Example 3)
In this embodiment, the same developing unit as that of Embodiment 2 is used except for the transfer section, and the shutter member is formed from the bottom surface of the transfer section of the supply side stirring chamber and the development side stirring chamber as shown in FIGS. 7 (a) and 7 (b). It is a plate-shaped member protruding toward the ceiling direction, and the shutter member is configured to change the opening area by moving up and down by a drive control means (not shown). With the configuration of this example, it was possible to perform good image formation without toner scattering and background stains.

Example 4
In this embodiment, the same developing unit as that of Embodiment 2 is used except for the transfer section, and the shutter member moves in the horizontal direction between the supply side stirring chamber and the transfer section of the development side stirring chamber as shown in FIGS. 8 (a) and 8 (b). The shutter member is configured to change the opening area by moving the shutter member left and right by a drive control means (not shown). With the configuration of this example, it was possible to perform good image formation without toner scattering and background stains.

(Example 5)
In this embodiment, the same developing device as that of the second embodiment is used except for the transfer section, and the shutter member is provided in the transfer section between the supply side stirring chamber and the development side stirring chamber as shown in FIGS. 9 (a) and 9 (b). In addition, it is composed of a plurality of plate members such as blinds installed in parallel, and the opening cross-sectional area is changed by changing the angle in the same direction in conjunction with the individual shutter members by a drive control means (not shown). At this time, a plate-like member having a sufficiently small width is used so as not to interfere with the screw blades even when the plate-like member of each shutter is horizontal. In this example, a member having a width of 4 mm was used. With the configuration of this example, it was possible to perform good image formation without toner scattering and background stains.

(Example 6)
In this embodiment, the same developing unit as that of Embodiment 2 is used except for the transfer section, and another shutter sheet is overlapped with the transfer section having a hole as shown in FIGS. 12 (a) and 12 (b). A plate-like member having a hole is slidably disposed, and the slidable plate-like member slides to close the hole as shown in FIG. 12B to change the area of the opening. It was. In this embodiment, a shutter having eight φ5 holes was used. The shape and number of the holes are not limited to the conditions of this embodiment, but may be rectangular or other shapes, and the sliding direction may be the vertical direction instead of the horizontal direction. With the configuration of this example, it was possible to perform good image formation without toner scattering and background stains.

(Example 7)
In this embodiment, the same developing device as that in Embodiment 2 is used except for the transfer section, and the shutter member is similar to the shutter of the type used in Embodiment 5 as shown in FIGS. 13 (a) and 13 (b). The rotation axis of the plate-like member is not at the center of the plate-like member but at either end, and when the developer is pushed out from the supply side stirring chamber, the inclination of the plate-like member is changed in the horizontal direction. It is inclined in the direction of increasing the opening area. Further, these plate-like members are connected to each other and rotate in conjunction with each other. A coil spring is connected to the top plate-like member, and in a state where there is no developer pressure, the shutter is pulled upward by the elastic force of the spring, and the shutter is closed. Yes. When the developer is in the developer unit, when the developer conveyed by the screw in the replenishing side stirring chamber reaches the most downstream side of the replenishing side stirring chamber, the pressure pushing the wall surface increases, and the shutter of the transfer unit Is opened, and the developer flows into the developing side stirring chamber.

Since the opening and closing of the shutter is automatically controlled according to the compaction state of the developer, if a unit is made by selecting a spring that is driven with an appropriate screw torque T1 at the time of design, the torque detector and the shutter can be installed. It is possible to omit a control unit, an actuator, and the like for driving, and it is possible to create a developing unit at low cost.
At this time, the maximum rotation angle of the plate-like member is set so as not to interfere with the screw blades of the developing side stirring chamber, and a stopper is provided so as not to tilt further. With the configuration of this example, it was possible to perform good image formation without toner scattering and background stains.

FIG. 1 is an internal configuration diagram of a color image forming apparatus to which the developing device according to the present embodiment is applied. FIG. 2 is a diagram showing a developing device in the present embodiment. FIG. 3 is an internal configuration diagram in the developer container in the present embodiment. FIG. 4 is a diagram showing a developing device in the present embodiment. FIG. 5 is a diagram showing the opening of the transfer section in the present embodiment. FIG. 6 is a view showing a shutter member capable of controlling the cross-sectional area of the transfer portion between the replenishing side stirring chamber and the developing side stirring chamber in the present embodiment. FIG. 7 is a diagram showing the shutter member protruding toward the ceiling from the bottom surface of the transfer portion of the replenishment side stirring chamber and the development side stirring chamber in the present embodiment. FIG. 8 is a diagram showing a shutter member that can slide in the lateral direction between the supply side stirring chamber and the developing side stirring chamber in the present embodiment. FIG. 9 is a diagram showing a plurality of shutter members such as blinds installed in parallel provided in the transfer section of the replenishing side stirring chamber and the developing side stirring chamber in the present embodiment. FIG. 10 is a diagram illustrating the influence on the developer charge amount distribution depending on the presence or absence of the developer path regulating means. FIG. 11 is a diagram showing the screw used in the present embodiment. FIG. 12 is a diagram showing a shutter member of a type that closes a slidable round hole in the present embodiment. FIG. 13 is a diagram showing a shutter member that is automatically controlled by the spring pressure in the present embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Intermediate transfer body 14 Support roller 15 Support roller 16 Support roller 17 Intermediate transfer body cleaning device 18 Image forming means 20 Tandem image forming unit 21 Exposure device 22 Secondary transfer device 23 Roller 24 Secondary transfer belt 25 Fixing device 26 Fixing belt 27 Pressure roller 28 Sheet reversing device 30 Document table 32 Contact glass 33 First traveling body 34 Second traveling body 35 Imaging lens 36 Reading sensor 40 Image carrier (photosensitive body)
42 paper feed roller 43 paper bank 44 paper feed cassette 45 separation roller 46 paper feed path 47 transport roller 48 paper feed path 49 registration roller 55 switching claw 56 discharge roller 57 paper discharge tray 65 developer container 66 toner supply side stirring screw 67 development Agent carrying member side agitating screw 68 Developer sleeve 75 Toner density sensor 77 Doctor blade 78 Developer path regulating member 80 Partition plate 86 Supply side agitating chamber 87 Developing side agitating chamber 100 Copying device main body 200 Paper feeding table 300 on which the copying device main body 100 is placed Scanner (reading optical system) mounted on the copying machine main body 100
400 Automatic Document Feeder (ADF)

Claims (14)

Agitating means that agitates and disperses two-component developer consisting of toner and carrier with two rotatable screws disposed in the developer container and conveys it to a predetermined position, and replenishes toner consumed by development In the developing device provided with toner replenishing means, between the torque T2 of the entire developing unit and the shaft torque T1 of the conveying screw in the replenishing side stirring chamber,
(1) T1> 0.2 [kgf · cm]
(2) T1 / T2> 0.25
A developing device characterized by the following relationship: The developing device includes a detection unit that detects the axial torque T1 of the conveying screw in the replenishment-side stirring chamber, and the detected axial torque T1 is
(1) T1> 0.2 [kgf · cm]
(2) T1 / T2> 0.25
2. The developing device according to claim 1, further comprising a control unit configured to control the shaft torque T <b> 1 of the conveying screw of the replenishing side stirring chamber so as to be in the range of 2. The developing device is provided with a detection unit that detects axial torque around the developing side stirring chamber and the sleeve, and the torque T2 of the entire unit and the axial torque T1 detected by the axial torque detection unit are:
(1) T1> 0.2 [kgf · cm]
(2) T1 / T2> 0.25
3. The developing device according to claim 1, further comprising a control unit configured to control the axial torque T <b> 1 of the conveying screw in the replenishing side stirring chamber so as to fall within the range of 3. Means for controlling the axial torque of the conveying screw in the replenishment side agitating chamber is a developer path regulation provided between the central portion of the replenishment side agitating chamber and the connecting portion connecting the replenishing side agitating chamber and the developing side agitating chamber. The developing device according to claim 1, wherein the developing device is a means. 5. The developer path regulating means is configured by a shutter member capable of changing an opening area and shape of a transfer portion between the replenishing side stirring chamber and the developing side stirring chamber. The developing device described in one. The shutter member is a plate-like member inserted downward from the ceiling of the transfer portion of the replenishing side stirring chamber and the development side stirring chamber, and the opening area is changed by moving the plate-like member up and down. The developing device according to claim 1, wherein: The shutter member is a plate-like member protruding toward the ceiling from the bottom surface of the transfer portion of the replenishing side stirring chamber and the developing side stirring chamber, and the opening area is changed by moving the plate-like member up and down. The developing device according to claim 1, wherein the developing device is provided. The shutter member is a plate-like member that can slide in the lateral direction through the opening of the transfer portion between the replenishing side stirring chamber and the developing side stirring chamber, and the opening area is changed by moving the plate-like member left and right. The developing device according to claim 1, wherein the developing device is provided. The shutter member is composed of a plurality of parallel plate-like members provided in a transfer portion between the replenishing side stirring chamber and the developing side stirring chamber, and the plate-like member changes the opening area by changing the angle. The developing device according to claim 1, wherein the developing device is a developing device. The shutter member is provided with a partition plate having a plurality of holes formed in the transfer portion and stacked in parallel with the partition plate, and another plate-shaped member having a hole closes the hole of the partition plate. The developing device according to claim 1, wherein the opening area is changed by sliding movement as described above. The shutter member is composed of at least one or more plate-like members, and the plate-like member has a rotation shaft that is rotatable at an end portion, and the angle of the plate-like member is freely set around the axis. Each plate-like member is connected so that the angle moves in conjunction with each other, and a part of the plate-like member is connected to the ceiling portion of the stirring chamber by a coil spring. 6. The apparatus according to claim 1, wherein the shutter member is rotated by the pressure with which the developer in the replenishing side stirring chamber presses the shutter member, and the opening area is increased. Development device. The shape of the ceiling of the supply side stirring chamber is circular along the outer diameter of the screw at least at a part of the supply side stirring chamber on the downstream side in the developer transport direction. The developing device according to one. 13. A process cartridge comprising the developing device according to claim 1 and at least two or more of a latent image carrier, a charging device, and a latent image carrier cleaning device. 13. An image forming apparatus, wherein an image forming apparatus for recording an image formed by a series of image forming processes on a recording medium comprises one or more developing devices according to claim 1.

Images