JP2007148053A - Developing device, process cartridge and image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a developing device, a process cartridge and an image forming apparatus with little developer deterioration and with no soiling of background/toner scattering, even when an image forming process is repeated over long periods of time, or even when a special state with less consumption of toner is continued over long periods of time, by preventing the replenished toner from directly reaching a developing sleeve in a low charged uncharged state. <P>SOLUTION: The developing device 61, the process cartridge and the image forming apparatus 100 are characterized in that a section, in which the cross-sectional shape of a replenishment-side agitating chamber 86 is a circular shape, going along an outer periphery of a screw is downstream of a developer transporting direction, and in addition, the developer is brought into contact at 360° with the wall surface of the replenishment-side agitating chamber 86 only within that section. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

The present invention relates to a developing device of an image forming apparatus such as a copying machine, a facsimile machine, and a printer. In particular, the present invention relates to a developing device of an image forming apparatus using a two-component developer.
The present invention also relates to a process cartridge having a developing device and an image forming apparatus.

In recent years, along with demands for downsizing and personalization of image forming apparatuses using electrophotographic technology such as copying machines 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 agitation unit 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 a 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 development roller and transported to the development area, uncharged, reversely charged, and weakly charged poorly charged toner causes non-image area background contamination, density unevenness, and toner scattering.

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 is disclosed 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, the deteriorated toner tends to be weakly charged / reversely charged toner, and after a long-time image forming process, the charge amount distribution is broadened, leading to background contamination and toner scattering. If the stress on the back of the developer regulating blade is easily reduced, the toner will be insufficiently charged, and on the contrary, there is a risk that background stains and toner scattering will increase.

Patent Document 2 discloses 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, since the place where the agent is regulated is in the vicinity of the doctor blade, the developer regulating means is used if the toner is not completely dispersed until the position is conveyed. However, there is a concern that density unevenness may occur.

Further, Patent Document 3 discloses a configuration in which the agent level of 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 of the supply side stirring chamber from the upstream side. .
However, in any of these inventions, it is possible to prevent the upper toner from slipping, to uniformly disperse the toner, to sufficiently charge the toner, and to weaken the mechanical force applied to the developer as compared with the conventional technique. There was an insufficient point to extend the life.

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. When the process is repeated, or when a special usage state in which toner consumption is low extends over a long period of time, a developing device, a process cartridge, and an image forming apparatus with little developer deterioration and no background contamination and toner scattering are provided. Is to provide.

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 referred to as a replenishing side stirring chamber, and the developer accommodating portion on the side facing the developer carrying member is referred to as a developing side stirring chamber. .
The present invention consumes the two-component developer composed of toner and carrier by agitating means for agitating and dispersing the two-component developer with two rotatable screws disposed in the developer container and transporting them to a predetermined position. In the developing device having a toner replenishing port for replenishing toner, the developing device has a section in which the cross-sectional shape of the replenishing side stirring chamber is circular along the outer periphery of the screw, and is downstream of the developer conveying direction, and In the developing device, the developer is in contact with the wall surface of the replenishing-side stirring chamber 360 ° only within the section.
According to the present invention, on the downstream side in the developer conveyance direction of the replenishment-side stirring chamber, there is a section in which the cross-sectional shape of the stirring chamber is a circular shape (the cross-sectional shapes of sections C and D in FIG. 1) along the outer periphery of the screw. In the section, a portion where the developer is in contact with the wall surface of the replenishing side stirring chamber is provided at 360 °, and an area where the developer is in contact at 360 ° is not formed outside the section. As a result, it is possible to provide a portion where the developer is consolidated only in a part of the sections C and D. In sections C and D, the ceiling is shaped along the outer diameter of the screw, so there is no immobile layer where the driving force of the screw is not transmitted even if the developer is in a compacted state, and good developer dispersion and transport capability. Can be secured.
In the compacted area, the rubbing force of the developer is increased, and the dispersion of the replenished toner is promoted and 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, it is not necessary to charge by intensive rubbing with a doctor blade as in the conventional developing device. . Therefore, the mechanical force in the vicinity of the doctor blade can be designed to be weak, and the life of the developer can be extended by reducing the stress of the entire unit.

According to the present invention, in the developing device described above, in the developing device, the developer is placed on the wall surface of the replenishing side stirring chamber in a section where the cross-sectional shape of the replenishing side stirring chamber is circular along the outer periphery of the screw. The portion in contact with 360 ° is a continuous section including the downstream end portion of the replenishing side stirring chamber, and the section length is 10 to 40% of the total length of the developer carrying portion of the developer carrying member. There is a developing device. Note that the portion carrying the developer of the developer carrying member is a portion excluding the shaft.
In the present invention, the length of the section where the developer contacts the 360 ° wall surface in the supply side stirring chamber is defined. As shown in FIG. 2, the total length of the replenishment side stirring chamber is L (assuming that the length of the developing sleeve and the length of the replenishment side stirring chamber are substantially the same), and the section C and the section D (delivery part) are summed up. If the section length is d, the length of the section where the developer is in a compacted state and in contact with the surrounding wall surface at 360 ° is x,
0.1L <x <0.4L (1)
It can be expressed.
If the compacted area where the developer is in contact with the 360 ° wall surface is too larger than 40% of the total length L of the stirring chamber, the area with a low agent level suitable for replenishing toner replenishment will be 60% or less. Dispersibility will deteriorate. On the other hand, if it is 10% or less, sufficient rubbing cannot be obtained, and the toner is carried to the development area without sufficiently rising the charge.
Therefore, by making it within the scope of the present invention, it is possible to achieve both high-level dispersion of replenishment toner and charging.

According to the present invention, in the developing device described above, in the developing device, a circular section in which the cross-sectional shape of the replenishing side stirring chamber is along the outer periphery of the screw includes the downstream end portion of the replenishing side stirring chamber. The developing device is characterized in that the section length is longer than the section length in which the developer is in contact with the wall surface of the replenishing side stirring chamber at 360 °.
In the present invention, the length of the section in which the cross-sectional shape of the replenishment side stirring chamber is a circular shape along the screw shape is defined. When the present invention is expressed by a mathematical formula,
x <d (2)
It can be expressed.
A section in which the cross-sectional shape of the replenishment-side stirring chamber is circular (cross-sectional shape of section C in FIG. 1) along the outer periphery of the screw is a continuous section including the downstream end of the replenishment-side stirring chamber, and the section length is It is longer than the length of the section where the developer is in contact with the wall surface of the stirring chamber at 360 °, and is 40% or less of the total length of the portion carrying the developer (portion excluding the shaft). As a result, since the area where the developer is in a compacted state is a 360 ° circular wall surface, the developer is smoothly conveyed without generating a non-moving layer. In addition, the developer and the wall surface, the developer and the screw member, and the developer are sufficiently rubbed with each other, and the charging of the toner is promoted. Therefore, charging can be performed before the replenished toner is supplied to the developing sleeve, and an image can be formed without toner scattering and background contamination.

According to the present invention, in the developing device described above, the developing device has an opening area through which the developer is transferred from the replenishing side agitating chamber to the developing side agitating chamber, from the developing side agitating chamber to the replenishing side agitating chamber. The developing device is characterized in that it is less than 30% of the area of the opening through which the developer is delivered.
In the present invention, the opening area where the developer is transferred from the replenishing side stirring chamber to the developing side stirring chamber is less than 30% of the area of the opening where the developer is transferred from the developing side stirring chamber to the replenishing side stirring chamber. As a result, it becomes difficult to transfer to the developing side stirring chamber. At this time, a compacted state is easily created in the downstream portion of the replenishment side stirring chamber. Therefore, the developer and the wall surface, the developer and the screw member, and the developer are sufficiently rubbed with each other, and the charging of the toner is promoted. Therefore, charging can be performed before the replenished toner is supplied to the developing sleeve, and an image can be formed without toner scattering and background contamination.

According to the present invention, in the developing device described above, the screw shape of the replenishing-side stirring chamber is such that the conveying force in the longitudinal direction is large in the upstream, and the circumferential stirring is relatively performed in the downstream. The developing device is characterized in that the force increases.
According to the present invention, in the developing device described above, the developing device is provided with a plate-like member in which the screw shape of the replenishment-side stirring chamber is connected to the outermost periphery of the screw in the longitudinal direction at the downstream portion in the developer transport direction. A developing device.
According to the present invention, in the developing device described above, the developing device is characterized in that the screw shape of the replenishing side stirring chamber is longer in the upstream in the developer transport direction than in the downstream.
FIG. 3 is a view showing a plate-like member connected to the outermost periphery of the screw in the longitudinal direction. In the present invention, the screw shape of the replenishment side stirring chamber is such that the conveying force in the longitudinal direction is large in the upstream and the stirring force in the circumferential direction (shearing force in the vertical direction) is increased toward the downstream. As a result, the developer level of the developer is lowered in the upstream, the agent level is increased in the downstream, and in some sections, an area that contacts the ceiling of the wall surface, that is, 360 ° around is created.
In such an agent level state, there are three effects. The first effect is that the low agent level in the vicinity of the toner supply port means that the supplied toner is likely to be caught in the developer that moves as the screw rotates, and the supplied toner is immediately dispersed with the carrier. . Conversely, when toner is replenished to a position where the agent level is high, a so-called upslip phenomenon occurs in which the replenished toner is conveyed while being layered on the surface of the original developer. Since the toner that has slipped does not have an opportunity to come into contact with the carrier, it is not charged and causes toner scattering.
The second effect is that the agent level increases in the middle of the stirring chamber. Even if the upslip of the replenishment toner cannot be eliminated 100% on the upstream side, the replenishment toner blocks at the position where the agent level is high. This is to prevent the undispersed toner from being transported as it is downstream.
The third effect is that the agent level on the downstream side is high, and the developer is in a compacted state, so that the developer and the wall surface, the developer and the screw member, and the developer are sufficiently rubbed with each other, and toner charging is promoted. That is. Therefore, charging can be performed before the replenished toner is supplied to the developing sleeve, and an image can be formed without toner scattering and background contamination.

The present invention is a process cartridge characterized in that the developing device described above is integrated with at least one of the latent image carrier, the charging device, and the latent image carrier cleaning device. is there.

The present invention is an image forming apparatus including the developing device described above.
The present invention is an image forming apparatus including the process cartridge described above.

According to the present invention, the charge function of the toner is shared even in the replenishing side agitation chamber where the toner is replenished, thereby reducing the burden on the developer as a whole of the developing device and extending the life of the developer.

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, It has become possible to provide a developing device, a process cartridge, and an image forming apparatus that cause little developer deterioration even when a special usage state with low consumption extends over a long period of time, and that does not cause 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. 4 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. Specifically, this is a tandem indirect transfer type electrophotographic copying apparatus. In the figure, reference numeral 100 denotes an image forming apparatus main body, 200 denotes a paper feed table on which the image forming apparatus main body 100 is placed, 300 denotes a scanner (reading optical system) attached to the image forming apparatus main body 100, and 400 denotes an automatic document conveyance attached thereon. Device (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 as to be able to rotate and convey clockwise in the drawing. 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 this color image forming apparatus, the 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, and the separation roller 45. Are separated one by one into the paper feed path 46, transported by the transport roller 47, guided to the paper feed path 48 in the image forming apparatus 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 the 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 60, a developing device 61, a primary transfer device 62, a photoconductor cleaning device 63, and a charge removal device 64 around the drum-shaped photoconductor 40. Etc. FIG. 5 is a diagram illustrating the developing device. As shown in FIG. 5, the developing device 61 includes a toner supply side stirring screw 66 as a developer stirring / conveying means, a developer carrying member stirring screw 67, and a developer carrying member (developing roller) 68 in a developer container 65. Is provided. A supply port (not shown) is provided on the outer wall of the container of the first developer stirring chamber 86, and toner is supplied from a toner supply device (not shown) (hereinafter, the first developer stirring chamber is referred to as a supply side stirring chamber). Call it.) The agitation screw 66 on the toner replenishing side agitates and conveys the toner replenished from the toner replenishing device and the developer in the developer container 65 (two-component developer having magnetic particles and toner). 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). Call it.)

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. Next, a method for examining the charge rising property of the toner will be described. FIG. 6 is a diagram showing the replenishment side stirring chamber and the development side stirring chamber. In order to evaluate the dispersion and charging start-up performance in the replenishment side stirring chamber 86, a simple stirring device in which the developing roller and the doctor blade were removed from the above developing device was used. The specified amount of developer in this developing device is 400 g, but 150 g held magnetically around the developing sleeve is subtracted, 250 g is put into the stirring device, and 1 g of toner is added to the toner supply port (point A in FIG. 6). ). Further, the screw rotation speed of the replenishment side agitating chamber 86 is appropriately changed so that the flow rate to the developing side agitating chamber 87 becomes a predetermined amount, so that the peak of the replenishing toner is transferred to the developing side agitating chamber 87. The charge amount distribution of the developer immediately after the transfer unit 78 was measured using an E-spart analyzer manufactured by Hosokawa Micron. At the time when the replenishment toner flows to the developing side stirring chamber 87, the peak of the replenishing toner is detected using a toner concentration sensor 75-b (see FIG. 6) provided on the bottom surface on the upstream side of the developing side stirring chamber 87. Measured by.

From the obtained charge amount distribution, the number frequency of the toner on the positive side from −0.1 [fC / μm] was evaluated as a WST rate (Wron Sign Toner) (in this embodiment, negatively charged toner was used). .
In an actual developing device, the amount replenished at one time is 0.2 g / s or less, and the replenishment amount 1 g in this experiment is an extreme condition for evaluating the charging performance of the stirring unit. It is noted. Furthermore, in an actual developing device, rubbing is also applied in the vicinity of the doctor blade before the developer is carried to the developing region, so that it is not necessary to completely raise the toner charge in the replenishment side stirring chamber 86. As a result of intensive studies by the present inventors, if the WST rate is 15% or less in this evaluation, the replenishment amount after solid image formation in a printing test using a developing device equipped with a developing roller and a doctor blade However, it has been found that good image formation without toner scattering and background smearing can be performed. Therefore, whether or not the condition is acceptable was determined using this index.

The developing device (stirring device) used in the experiment will be described in more detail.
FIG. 1 is a longitudinal sectional view of a partition plate 80 that separates the replenishment side stirring chamber 86 and the development side stirring chamber 87. At both ends of the partition plate, a developer delivery part 78 from the supply side stirring chamber 86 to the development side stirring chamber 87 and a delivery part 79 from the development side stirring chamber 87 to the supply side stirring chamber 86 are provided. In this embodiment, the transfer opening area from the developing side stirring chamber 87 to the replenishing side stirring chamber 86 is 800 mm ² , and the opening area from the replenishing side stirring chamber 86 to the developing side stirring chamber 87 is 180 mm ² .
The shape of the opening 78 from the replenishment side stirring chamber 86 to the development side stirring chamber 87 is not limited to a rectangle, and a plurality of circles or polygons arranged in a mesh shape may be used. The opening position does not need to be at the lower part of the partition plate 80 as shown in FIG. 1, and it is sufficient if the opening is at a height where the developer exists. Further, a variable shutter having a mechanism capable of controlling the opening area may be used.
The screw of the replenishing side agitating chamber 86 has a total length L of 320 mm, and has a helical screw blade with a pitch of 25 mm as shown in FIG.

Next, the wall surface of the supply side stirring chamber 86 will be described in detail. A cross-sectional view of the stirring chamber in each of the sections A to D is shown on the lower side of FIG. In the section A, an opening 79 is provided for the developer to return from the development side stirring chamber 86 to the replenishment side stirring chamber 87. In the middle of the section B, there is a toner supply port, and toner is supplied from the outside. Therefore, in the section B, it is an important function to uniformly distribute the supplied toner in the developer. Next, section C is a feature of the present invention, and the ceiling portion of the replenishment side stirring chamber 86 is circular so as to follow the outer peripheral surface of the screw. In the last section D, the wall surface of the supply side stirring chamber 86 is the same as that of the section C, but an opening 78 for delivering the developer to the developing side stirring chamber 87 is provided. The area of the opening 78 is smaller than that of the opening 79 from the developing side stirring chamber 87 to the replenishing side stirring chamber 86.
In the present embodiment, the gap between the screw blade and the wall surface of the replenishing side stirring chamber 86 in the sections C and D was 1 mm. Further, as shown in Condition 1 of Table 1, the opening area was 180 mm ^2, and the total length of sections C and D was 0.4 L.

By reducing the area of the opening 78 from the supply side stirring chamber 86 to the development side stirring chamber 87, the developer is consolidated in the downstream portion of the supply side stirring chamber 86. At this time, if the shape of the wall surface is such that the upper half of the screw is open as in the section B, even if the screw rotates, the force in the conveying direction is applied to the developer at the corner portion at the top of the supply side stirring chamber 86. Will not pass through and will form a non-moving layer.
On the other hand, in the present invention, the region where the developer is brought into a compacted state is always a region of a circular wall surface. Therefore, even if the developer is brought into a compacted state, the developer is not generated without generating a stationary layer. Is smoothly transported.

In the configuration of this embodiment, of the total section length d of sections C and D is 128 mm (= 0.4 L), the section length in which the developer is in contact with the ceiling is 110 mm from the most downstream side of the supply side stirring chamber 86. (= 0.33L). The axial torque of the supply side stirring screw was measured and found to be 0.35 [kgf · cm].
When charging start-up evaluation of the replenishing toner was performed under these conditions, a sufficient level of both toner dispersion and charge start-up could be secured. When an image is output using a developing device equipped with a developing roller under these conditions and the amount of developer is 400 g, the replenished toner reaches the developing-side stirring chamber 87 even under conditions where toner replenishment is severe (during solid image development). In the meantime, the image was sufficiently dispersed and charged, and good image formation without background stains and toner scattering could be performed.

On the other hand, the same evaluation was performed under conditions 2 to 7 in Table 1 as a comparative example.
Under condition 2, when the opening area of the transfer portion 78 from the supply side stirring chamber 86 to the development side stirring chamber 87 is set to 800 mm ² , the developer does not become compact, and the developer is 360 on the wall surface of the supply side stirring chamber 86. ° Could not make contact section. The WST rate after toner replenishment was as poor as 30%, and toner scattering occurred.

Under condition 3, when the opening area is narrowed to 140 mm ² , the compacted area where the developer contacts the wall surface of the replenishing side stirring chamber 86 at 360 ° becomes as long as 192 mm (= 0.6 L), and the toner is replenished. Soon after it was fully dispersed, it entered the consolidation area. At this time, the toner is transported to the development area without the toner density being made uniform. Therefore, when the image is actually output by the developing device provided with the developing roller under these conditions, density unevenness appears.

In condition 4, the section length d for making the wall surface of the replenishing side stirring chamber 86 circular is as long as 0.8L. As shown in FIG. 8, the developer level in the section B immediately after replenishment includes a portion 96 where the developer 90 protrudes from the screw projection surface at the left and right ends of the replenishment side stirring chamber 86. Since the developer in the end portion is not easily applied with a force in the transport direction even if the screw 95 rotates, a transport speed difference occurs between the developer in the screw projection surface and the developer at the end portion. When the toner is replenished, this speed difference promotes dispersion of the toner in the longitudinal direction. On the other hand, since all the developer is present in the screw projection surface on the wall surfaces in the sections C and D, a speed difference in the transport direction is unlikely to occur. Therefore, as in Condition 4, if the section length d for making the wall surface of the replenishing side stirring chamber 86 circular is too long, 0.8 L, the dispersion of the replenishing toner is slightly insufficient.

Condition 5 is that the area of the compacted state becomes as long as 0.6 L by reducing the opening area to 140 mm ² , but the condition of the circular wall surface section is only 0.3 L. In this case, the developer contacts the wall surface of the section B with the 360 ° wall surface, but the developer stays in the corner portion of the replenishment side stirring chamber 86 where the force of the screw does not reach and a non-moving layer is formed. End up.

In condition 6, the screw shape was changed. When a member extending in the longitudinal direction is provided on the outer periphery of the screw, the stirring force in the circumferential direction (longitudinal direction) is increased. However, in the c-type screw in FIG. It has been. Therefore, although it is once in a compacted state, the pressure is released at the most downstream portion of the replenishment side stirring chamber 86, and efficient sliding is not possible. An object of the present invention is to provide a lot of sections with a low agent level in the upstream portion of the replenishment-side stirring chamber 86 to improve toner dispersion, and to efficiently create a compacted portion in the downstream portion to promote the sliding of the developer. Therefore, a configuration in which the compaction part is moved upstream as in Condition 6 and the pressure is relaxed again at the most downstream part as in Condition 6 can be obtained from both the dispersion surface and the toner charge surface. It is not preferable.

Under condition 7, when the opening area of the transfer portion 78 from the supply side stirring chamber 86 to the development side stirring chamber 87 is set to 400 mm ² , the developer does not become compact, and the developer is 360 on the wall surface of the supply side stirring chamber 86. ° Could not make contact section. The WST rate after toner replenishment was as poor as 30%, and toner scattering occurred.

(Example 2)
In Example 2, as shown in the conditions 8 to 12, the area of the transfer opening 78 was 180 mm ² , the section of the circular wall surface was fixed to 0.4 L, and the screw shape of the supply side stirring chamber 86 was changed.
In condition 8, as shown in (a-1) of FIG. 7, out of the total length of 320 mm with the helical screw blades, the upstream side 160 mm was 50 mm pitch, and the downstream part was 25 mm pitch. When this screw is used, the conveyance speed on the upstream side is faster than that on the downstream side, so that the developer is in a compacted state on the downstream side. Accordingly, the sliding of the developer is promoted, the toner is charged, and good image formation without toner scattering can be performed.

In condition 9, as shown in (b-2) of FIG. 7, out of the total length of 320 mm with a helical screw blade having a pitch of 25 mm, the outer peripheral portion of the screw blade in the longitudinal direction 94 by three pitches from the most downstream portion. A screw provided with a connected plate-like member 93 was used. When this screw is used, the advection speed becomes slow at the portion where the plate-like stirring member is attached. Further, since the plate-like member 93 is attached, the stirring force in the circumferential direction (longitudinal direction) is strong, so that the developer can be further compressed to create a strong compacted state. Therefore, the rubbing of the developer is promoted, the toner is charged, and good image formation without toner scattering can be performed.

The condition 10 is the same as the condition 9 except that the stirring member provided in the most downstream portion is set to 5 pitches as shown in (b-3) of FIG. Even under these conditions, a compacted portion is formed, the rubbing of the developer is promoted, the toner is charged, and good image formation without toner scattering can be performed.

In condition 11, as shown in (a-2) of FIG. 7, among the total length of 320 mm with the helical screw blades, the upstream side 160 mm was set to 50 mm pitch, and the downstream portion was set to 25 mm pitch. Of the portions with helical screw blades with a pitch of 25 mm, a screw provided with a plate-like member 93 connected in the longitudinal direction 94 to the outer periphery of the screw blades by 3 pitches from the most downstream portion was used. When this screw is used, since the pitch is large in the upstream, the conveyance speed is faster than that on the downstream side, and the advection speed is further lowered in the portion where the plate-like stirring member is attached. Further, since the plate-like member 93 is attached, the stirring force in the circumferential direction (longitudinal direction) is strong, so that the developer can be further compressed to create a strong compacted state. Therefore, the rubbing of the developer is promoted, the toner is charged, and good image formation without toner scattering can be performed.

Condition 12 is the same as Condition 9 except that the stirring member provided in the most downstream portion is set to 5 pitches as shown in FIG. Even under these conditions, the compacted portion is formed, the sliding of the developer is promoted, the toner is charged, and good image formation without toner scattering can be performed.

As a result of the examination by the inventors, in the state where the agent level shown in the present invention is maintained, there is no problem that the stress is too strong and the deterioration of the developer is accelerated, and the developer in the developing side stirring chamber 87 is insufficient. As a result, good image formation could be performed without causing any pumping failure.

It is a figure which shows sectional drawing of the longitudinal direction of the partition plate which separates the replenishment side stirring chamber and the image development side stirring chamber. It is a figure which shows the full length of the replenishment side stirring chamber, the section length d, and the section length x. It is a figure which shows the plate-shaped member connected to the outermost periphery of the screw in the longitudinal direction. 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. It is a figure which shows a developing device. It is a figure which shows the replenishment side stirring chamber and the image development side stirring chamber. It is a figure which shows a screw shape. It is a figure which shows the developer level of the area B immediately after replenishment.

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 Photosensitive body 42 Paper feeding roller 43 Paper bank 44 Paper feeding cassette 45 Separating roller 46 Paper feeding Path 47 conveying roller 48 sheet feeding path 49 registration roller 55 switching claw 56 discharge roller 57 sheet discharge tray 60 charging device 61 developing device 62 primary transfer device 63 photoconductor cleaning device 64 charge removing device 65 developer container 66 toner supply side stirring screw 67 Developer carrier side stirring disk -Menu 68 developer carrying member (developing roller)
75-b Toner Concentration Sensor 78 Developer transfer section (opening section) from the replenishment side stirring chamber to the development side stirring chamber
79 Transfer section 80 from the development side stirring chamber to the replenishment side stirring chamber 80 Partition plate 86 Supply side stirring chamber 87 Development side stirring chamber 90 Developer 91 Developer transport direction 92 Toner supply port 93 Plate member 94 Longitudinal direction 95 Screw 96 Screw Developer 100 outside projection surface Image forming apparatus main body 200 Paper feed table 300 Scanner (reading optical system)
400 Automatic Document Feeder (ADF)
Point A Toner supply point Point B Delivery section

Claims (10)

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 a developing device having a toner supply port for
In the developing device, a section in which the cross-sectional shape of the replenishing side stirring chamber is a circular shape along the outer periphery of the screw is downstream in the developer transport direction,
In addition, the developing device is characterized in that the developer is in contact with the wall surface of the replenishing side stirring chamber 360 ° only within the section. The developing device according to claim 1,
In the developing device, in a section in which the cross-sectional shape of the replenishing side stirring chamber is a circular shape along the outer periphery of the screw, a portion where the developer is in contact with the wall surface of the replenishing side stirring chamber is 360 °. It is a continuous section including the downstream end of the replenishment side stirring chamber,
The section length is 10 to 40% of the total length of the portion of the developer carrying member carrying the developer. The developing device according to claim 1 or 2,
In the developing device, a section in which the cross-sectional shape of the replenishing side stirring chamber is a circular shape along the outer periphery of the screw is a continuous section including a downstream end portion of the replenishing side stirring chamber.
The developing device is characterized in that the section length is longer than the section length in which the developer is in contact with the wall surface of the replenishing side stirring chamber at 360 °. In the developing device according to any one of claims 1 to 3,
The developing device has an opening area where the developer is transferred from the replenishing side agitating chamber to the developing side agitating chamber, and an opening area where the developer is transferred from the developing side agitating chamber to the replenishing side agitating chamber. A developing device characterized by being less than 30%. The developing device according to any one of claims 1 to 4,
The developing device is characterized in that the screw shape of the replenishing side stirring chamber is such that the upstream conveying force is large in the longitudinal direction and the circumferential stirring force is relatively large toward the downstream. Developing device. The developing device according to claim 5,
The developing device is characterized in that the screw shape of the replenishing-side stirring chamber is provided with a plate-like member connected to the outermost periphery of the screw in the longitudinal direction at the downstream portion in the developer transport direction. The developing device according to claim 5 or 6,
In the developing device, the screw shape of the replenishing side stirring chamber has a screw pitch longer in the upstream in the developer transport direction than in the downstream. A process cartridge includes: a developing device according to any one of claims 1 to 7;
At least one of a latent image carrier, a charging device, and a latent image carrier cleaning device; and
Is a process cartridge that is integrated. An image forming apparatus comprising the developing device according to claim 1. An image forming apparatus comprising the process cartridge according to claim 8.

Images