JP2010164621A - Developing device, process cartridge and image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a developing device that prevents flocculation by providing an agitating member at the downstream of screws, thereby relaxing powder pressure (toner pressure), and to provide a process cartridge including the developing device, and an image forming apparatus with the process cartridge mounted thereon. <P>SOLUTION: The developing device having the conveying screws 55Ya, 55Yb for conveying powder stored in a developing housing 76Y, from upstream to downstream along an axial direction includes the agitating member 85 near the bearing side internal wall of the developing housing 76Y downstream of the conveying screws 55Ya and 55Yb. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a developing device used in an image forming apparatus such as a copying machine, a printer, and a facsimile, a process cartridge including the developing device, and an image forming apparatus equipped with the process cartridge.

Conventionally, as shown in Patent Documents 1 and 2, a two-component developing device composed of a magnetic carrier and toner has a toner conveying screw for stirring and conveying the replenished toner and the carrier, The toner conveying screw generally has a spiral shape for conveying in one direction (see, for example, Patent Documents 1 and 2).
Such a developing device has two screws, a screw in the developing roller chamber and a screw in the stirring chamber (mixed with toner), and replenishes toner from the upstream of the stirring chamber according to toner consumption. The carrier and toner are mixed in the stirring chamber, and the mixed carrier and toner are conveyed downstream of the stirring chamber along the spiral shape of the screw.
Patent Document 1 has a screw shape having a small-diameter ejection hole, and Patent Document 2 has a reverse conveying portion in which the inclination of the screw is reversed, or a toner hopper is formed with an inclined surface to circulate the toner. A technique for delivering the developer in between is disclosed.

However, a driving mechanism for rotating a screw, a developing roller, and the like is provided on the outer wall of the developing housing, and heat is generated due to the influence of the pressure angle of the gear meshing and the friction of the sliding portion such as the bearing.
Further, the toner is conveyed downstream by a spiral shape and is sent from the developing chamber to the stirring chamber or from the stirring chamber to the developing chamber by a rib or the like in the direction perpendicular to the axis. There is also a thing that stays due to a change in flow, so that there is a pressure in the most downstream direction.
When the temperature due to driving or the like exceeds the softening point of the toner and a powder pressure is applied, the toner aggregates on the downstream side of the screw or the wall surface of the housing (melt fixation). These agglomerated toners are hardened when the rotation of the drive is stopped, chipped by re-driving, and there is a problem that when the toner rolls around the developing roller portion, the toner does not uniformly get on the developing roller.
In recent years, it is common to place the main body of the image forming apparatus in a standby state in order to save energy, but it is also required to increase the return time from the standby state. Returning from the standby state takes the longest time to return the temperature of the mechanism that fixes the transferred toner to the paper with heat and pressure to a predetermined value.
For this reason, there are many devices that use a low-melting toner and lower the fixing temperature. However, when a low-melting toner is used, there is a problem that melting and fixing easily occur in the developing device.
Accordingly, in view of the above-described circumstances, an object of the present invention is to provide a developing device that provides a stirring member downstream of the screw to relieve powder pressure (toner pressure) and prevent aggregation, a process cartridge including the developing device, and An object of the present invention is to provide an image forming apparatus equipped with this process cartridge.

In order to solve the above problems, the invention according to claim 1 is a developing device having a conveying screw for conveying powder accommodated in the developing housing along the axial direction, and the conveying direction of the conveying screw. The developing device is provided with a stirring member in the vicinity of the inner wall surface on the bearing side of the downstream developing housing.
According to a second aspect of the present invention, there is provided the developing device according to the first aspect, wherein a stirring member at a downstream portion in the transport direction of the transport screw is provided integrally with the transport screw.
According to a third aspect of the present invention, the developing device according to the first or second aspect is characterized in that the stirring member is provided downstream in the transport direction of the transport screw on the side close to a high heat source such as a drive mechanism.
According to a fourth aspect of the invention, there is provided the developing device according to any one of the first to third aspects, wherein a developer having an average circularity of 0.95 or more is used.
In the invention according to claim 5, the volume average particle diameter is 3 to 8 μm, and the ratio (Dv / Dn) of the volume average particle diameter (Dv) to the number average particle diameter (Dn) is 1.00 to 1. 5. A developing device according to claim 1, wherein a developer in the range of .40 is used.
According to a sixth aspect of the present invention, there is provided a process cartridge including at least the developing device according to any one of the first to fourth aspects and an image carrier.
According to a seventh aspect of the present invention, there is provided an image forming apparatus for developing and visualizing an electrostatic latent image formed on an image carrier with toner from a developing device, wherein the developing device and the image carrier are provided. An image forming apparatus comprising the process cartridge according to claim 6 as a process cartridge including the image forming apparatus.

  According to the present invention, the stirring member is provided downstream of the screw, and the pressure is relieved by stirring the powder pushed into the downstream wall surface by the screw. As a result, the occurrence of aggregation in the developing device can be prevented, and the toner can be prevented from adhering unevenly on the developing roller, which is caused by sandwiching the aggregate.

1 is a schematic diagram illustrating a configuration of an electrophotographic printer. FIG. FIG. 3 is a schematic diagram illustrating a process cartridge for generating a Y toner image. FIG. 2 is a perspective view illustrating a configuration of a developing device according to the present invention. FIG. 4 is a schematic diagram illustrating a toner flow in the developing device of FIG. 3. It is a schematic perspective view which shows the stirring chamber screw pivotally supported by the bearing with a non-return valve. It is a perspective view which shows a bearing with a non-return valve. It is a schematic perspective view which shows the longitudinal direction end of a developing device. It is a schematic perspective view which shows the longitudinal direction other end of a developing device. It is the schematic which shows 1st Embodiment of the stirring member by this invention provided in the downstream of the stirring chamber screw. It is the schematic which shows 1st Embodiment of 1st Embodiment of the stirring member of FIG. It is the schematic which shows 2nd Embodiment of the stirring member by this invention provided in the downstream of the stirring chamber screw. It is a schematic external view showing a process cartridge.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. As an example of an embodiment of an image forming apparatus to which the present invention is applied, an electrophotographic printer (hereinafter simply referred to as a printer) will be described. The image forming unit will be described as a process cartridge.
FIG. 1 is a schematic diagram showing the configuration of an electrophotographic printer. FIG. 2 is a schematic view showing a process cartridge for generating a Y toner image. First, the basic configuration of the printer will be described.
1 and 2, the printer 100 includes four process cartridges 6Y, 6M, 6C, for generating toner images of yellow, magenta, cyan, and black (hereinafter referred to as Y, M, C, and K). It has 6K. These use Y, M, C, and K toners of different colors as the image forming material, but the other configurations are the same and are replaced when the lifetime is reached.

First, a process cartridge 6Y for generating a Y toner image will be described as an example.
As shown in FIG. 2, the process cartridge 6Y includes a drum-shaped photoreceptor 1Y, a photoreceptor cleaning device 2Y, a charge eliminating device (not shown), a charging device 4Y, a developing device 5Y, and the like. The process cartridge 6Y can be attached to and detached from the main body of the printer 100 so that consumable parts can be replaced at a time.
The charging device 4Y uniformly charges the surface of the photoreceptor 1Y that is rotated clockwise in the drawing by a driving unit (not shown). The uniformly charged surface of the photoreceptor 1 </ b> Y is exposed and scanned by the laser beam L to carry an electrostatic latent image for Y. The Y electrostatic latent image is developed into a Y toner image by the developing device 5Y using Y toner.
This Y toner image is intermediately transferred onto the intermediate transfer belt 8. The drum cleaning device 2Y removes the toner remaining on the surface of the photoreceptor 1Y after the intermediate transfer process. Further, the static eliminator neutralizes residual charges on the photoreceptor 1Y after cleaning. By this charge removal, the surface of the photoreceptor 1Y is initialized and prepared for the next image formation.
In the other process cartridges 6M, 6C, and 6K, M, C, and K toner images are similarly formed on the photoreceptors 1M, 1C, and 1K, and are intermediately transferred onto the intermediate transfer belt 8.

In FIG. 1, the exposure device 7 is disposed below the process cartridges 6Y, 6M, 6C, and 6K. The exposure device 7 serving as a latent image forming unit irradiates the respective photosensitive members in the process cartridges 6Y, 6M, 6C, and 6K with a laser beam L emitted based on the image information to perform exposure.
By this exposure, electrostatic latent images for Y, M, C, and K are formed on the photoreceptors 1Y, 1M, 1C, and 1K. The exposure device 7 irradiates the photoconductor with a laser beam (L) emitted from a light source through a plurality of optical lenses and mirrors while scanning with a polygon mirror rotated by a motor.
In the drawing, below the exposure device 7, a sheet feeding means having a transfer sheet storage cassette 26, a sheet feeding roller 27 incorporated therein, a registration roller pair 28, and the like are disposed.
The transfer paper storage cassette 26 stores a plurality of transfer papers P, which are recording media, and a paper feed roller 27 is in contact with the uppermost transfer paper P.
When the paper feeding roller 27 is rotated counterclockwise in the drawing by a driving means (not shown), the uppermost transfer paper P is fed toward the rollers of the registration roller pair 28. The registration roller pair 28 rotationally drives both rollers to sandwich the transfer paper P, but temporarily stops rotating immediately after the sandwiching. Then, the transfer paper P is sent out toward a later-described secondary transfer nip at an appropriate timing.

In the sheet feeding unit having such a configuration, a conveying unit is configured by a combination of the sheet feeding roller 27 and the registration roller pair 28 which is a timing roller pair. This conveying means conveys the transfer paper P from a transfer paper storage cassette 26 which is a storage means of the transfer paper P to a secondary transfer nip described later.
Above the process cartridges 6Y, 6M, 6C, and 6K in the figure, an intermediate transfer unit 15 that moves the intermediate transfer belt 8 that is an intermediate transfer member endlessly while stretching is disposed. In addition to the intermediate transfer belt 8, the intermediate transfer unit 15 includes four primary transfer bias rollers 9Y, 9M, 9C, and 9K, a cleaning device 10, and the like.
A secondary transfer backup roller 12, a cleaning backup roller 13, a tension roller 14 and the like are also provided. The intermediate transfer belt 8 is endlessly moved in the counterclockwise direction in the figure by the rotational drive of at least one of the rollers while being stretched around these three rollers.

The primary transfer bias rollers 9Y, 9M, 9C, and 9K sandwich the intermediate transfer belt 8 that is moved endlessly in this manner from the photoreceptors 1Y, 1M, 1C, and 1K to form primary transfer nips, respectively. Yes.
These primary transfer bias rollers 9Y, 9M, 9C, and 9K are of a system that applies a transfer bias having a polarity opposite to that of toner (for example, plus) to the back surface (loop inner peripheral surface) of the intermediate transfer belt 8. All the rollers except the primary transfer bias rollers 9Y, 9M, 9C, and 9K are electrically grounded.
The intermediate transfer belt 8 passes through the primary transfer nips for Y, M, C, and K sequentially along with the endless movement thereof, and the Y, M, and Y on the photoreceptors 1Y, 1M, 1C, and 1K are sequentially transferred. The C and K toner images are superimposed and primarily transferred. As a result, a four-color superimposed toner image (hereinafter referred to as a four-color toner image) is formed on the intermediate transfer belt 8.
The secondary transfer backup roller 12 described above forms a secondary transfer nip with the intermediate transfer belt 8 sandwiched between the secondary transfer backup roller 19 and the secondary transfer roller 19. The four-color toner image formed on the intermediate transfer belt 8 is transferred to the transfer paper P at the secondary transfer nip.

Untransferred toner that has not been transferred onto the transfer paper P adheres to the intermediate transfer belt 8 after passing through the secondary transfer nip. This is cleaned by the cleaning device 10.
In the secondary transfer nip, the transfer paper P is sandwiched between the intermediate transfer belt 8 whose surface moves in the forward direction and the secondary transfer roller 19 and conveyed in the opposite direction to the registration roller pair 28 side. The On the transfer paper P sent out from the secondary transfer nip, the four-color toner image transferred to the surface is fixed by heat and pressure when passing between the rollers of the fixing device 20.
Thereafter, the transfer paper P is discharged out of the printer through the rollers of the paper discharge roller pair 29. A stack unit 30 is formed on the upper surface of the printer main body, and the transfer sheets P discharged to the outside by the discharge roller pair 29 are sequentially stacked on the stack unit 30. A bottle storage container 31 is provided below the stack portion 30 and stores toner bottles 32Y, 32M, 32C, and 32K of the respective colors.

Next, the configuration of the developing device 5Y in the process cartridge 6Y will be described mainly with reference to FIG. The developing device 5Y has a magnetic field generating means inside, a developing roller 51Y as a developer carrying member for carrying and transporting a two-component developer containing magnetic particles and toner on the surface, and the developing roller 51Y carried on the developing roller 51Y. And a doctor blade 52Y as a developer regulating member that regulates the layer thickness of the developer conveyed.
Here, a place where the developing roller 51Y is accommodated is a developing roller chamber 53Y which is a first chamber. Further, a place for storing the developer is a second agitation chamber 54Y, which is a toner conveying screw (conveying body) 55Y (first conveying screw 55Ya, first conveying screw) for agitating and conveying toner. 2 conveying screw 55Yb), a toner replenishing port 58Y for taking the toner into the stirring chamber 54Y, a partition wall 59Y between the developing roller chamber 53Y and the stirring chamber 54Y, and a communication port between the developing roller chamber 53Y and the stirring chamber 54Y ( 3).

Above the toner supply port 58Y, a shutter 71Y for closing the toner supply port 58Y and a toner supply port case 72Y provided to hold the shutter 71Y and cover the toner supply port 58Y are provided.
Reference numeral 56Y denotes a density detection sensor for detecting the toner density of the developer. When the density detection sensor 56Y detects that the toner density is insufficient in the stirring chamber 54Y, it is driven by a replenishment signal from the control unit 57Y. The toner is replenished when the motor 41Y rotates and the toner bottle 32Y (FIG. 1) rotates.
Further, the entire developing device 5Y is formed by a first member 75Y (upper case) including the inner wall of the developing roller chamber 53Y forming a developing housing and a second member 76Y (lower case) including the inner wall of the stirring chamber 54Y. ing.

FIG. 3 is a perspective view showing the structure of the developing device according to the present invention. FIG. 4 is a schematic view showing the flow of toner in the developing device of FIG. The schematic diagram showing the process cartridge for generating the Y toner image shown in FIG. 2 is a view seen from the right side of FIG. 3 in correspondence with FIG.
In FIG. 3, the upper case 75Y of FIG. 2, the toner supply port 58Y, the shutter 71Y for closing the toner supply port 58Y, the toner supply port case 72Y provided so as to cover the toner supply port 58Y, and the like are omitted.
The two-component developing device 5Y made of a carrier and toner, which are magnetic materials, has a toner conveying screw for agitating and conveying the replenished toner and the carrier, and this toner conveying screw is for conveying in one direction. It has a spiral shaped part.
3 and 4, in this embodiment, the first transport screw 55Ya that is the toner transport screw of the developing roller chamber 53Y that is the first chamber and the toner transport screw of the stirring chamber 54Y that is the second chamber. A second transport screw 55Yb. The toner is replenished from the toner replenishing port 58Y upstream of the stirring chamber 54Y according to the consumption of the toner.
The replenished toner is mixed with the carrier in the agitating chamber 54Y, and conveyed to the downstream of the agitating chamber 54Y along the helical portion 55Yb1 of the second conveying screw 55Yb. The arrows in FIG. 4 indicate the toner conveyance direction.
In particular, as shown in FIG. 4 in which the developing roller 51Y is omitted, the partition wall 59Y between the developing roller chamber 53Y and the stirring chamber 54Y does not extend to a position crossing both ends of the developing housing, and both ends of the partition wall 59Y. And portions where the partition walls between the two ends of the developing housing are missing are provided as communication ports A and B between the developing roller chamber 53Y and the stirring chamber 54Y, respectively.

FIG. 5 is a schematic perspective view showing a stirring chamber screw pivotally supported by a bearing with a check valve. FIG. 6 is a perspective view showing a bearing with a check valve. In FIG. 5, if the forward spiral portion 55Yb1 only feeds the toner downstream, the pressure of the toner conveyed to the bearing downstream of the stirring chamber screw (second conveyance screw) 55Yb is applied, and the toner is discharged from a minute gap in the bearing. It will leak out.
For this reason, a reverse spiral-shaped portion 55Yb2 that is a reverse spiral portion in the reverse direction is provided at the downstream position of the second transport screw 55Yb. Although it is difficult to clearly understand in FIG. 5, the bearing 66 is provided with a check valve 66a as shown in FIG. 6 to prevent the toner from leaking to the outside.
In the case of the embodiment shown in FIG. 3, the second conveying screw 55Yb in the stirring chamber 54Y sends the toner to the high heat source side, and the first conveying screw 55Ya in the developing roller chamber 53Y moves to the opposite side to the drive mechanism 63. And feed the toner. Although pressure is present in both conveyance screw downstream portions, since the temperature is low in a non-driving portion without a high heat source, aggregation is difficult even if the same pressure exists.

FIG. 7 is a schematic perspective view showing one end in the longitudinal direction of the developing device. FIG. 8 is a schematic perspective view showing the other longitudinal end of the developing device. 7 and 8 show the right end and the left end of FIG. 3, respectively. In the present embodiment shown in FIG. 3, the drive train is on both the front side (right side) and the rear side (left side).
The front side (the right side in FIG. 3) shown in FIG. 7 is a drive train for turning only the conveying screw, and the front gear 69 of the developing roller chamber screw and the front gear 71 of the stirring chamber screw are shown in the drawing. Since these conveyance screws 55Ya and 55Yb have a low rotational torque, the temperature does not rise excessively.
On the other hand, the rear (left side in FIG. 3) drive train shown in FIG. 8 is a high heat source side described later. In addition to the developing roller chamber screw post-gear 69a, there is a developing roller gear 80 with a large torque. There is also a drive input gear 81 for inputting drive force. These gears 69a, 80, 81 constituting the drive mechanism 63 of FIG.

Here, the high heat source side means the drive mechanism 63 side that receives a driving force from the image forming apparatus main body. That is, although not shown, the developing roller gear 80 and the developing roller chamber screw post-gear 69a which are the gears of the driving mechanism 63 of the developing device 5Y in which the driving input gear 81 which is a gear extending from a motor provided in the main body is a high heat source. When the gears 80 and 69a are driven, the developing roller 51Y and the conveying screws 55Ya and 55Yb are driven.
Since the developing roller gear 80 of the driving mechanism 63 and the developing roller chamber screw post-gear 69a, which are the sources of the driving force of the developing device 5Y, have a strong meshing force, the frictional heat and the like increase, and a heat source having a higher temperature than the other parts. Become. Therefore, in this specification, the drive mechanism 63 side is the high heat source side.

FIG. 9 is a schematic view showing a first embodiment of a stirring member according to the present invention provided downstream of a stirring chamber screw. FIG. 10 is a schematic diagram showing the first embodiment of the stirring member of FIG. 9 alone. FIG. 11 is a schematic view showing a second embodiment of the stirring member according to the present invention provided downstream of the stirring chamber screw.
9 and 10, a stirring member 85 is disposed in the vicinity of the bearing-side inner wall surface of the developing housing 76Y downstream of the stirring chamber screw (second transport screw) 55Yb. The agitating member 85 includes an inverted U-shaped portion 85a straddling the shaft 55Yb3 of the agitating chamber screw 55Yb and an inverted U-shaped portion having an angle that obstructs the conveying direction of the toner, which is powder, in order to enhance the agitation effect. A plate-like portion 85b extending above 85a and horizontally extending with a stirring bar 85c is provided at the upper end.
By adopting such a shape, the stirring rod 85c performs stirring while diving during development, so that the stirring property is improved.
For example, the plate-like member simply has stirring ability, but in this case, since the developer is stirred while being pressed on the surface, the ability to loosen the developer is higher in the present embodiment.

Further, both ends of the stirring bar are provided with a protruding portion that is slightly larger than the stirring rod, and the protruding portion also has a function of improving the stirring ability.
Since the stirrer 85 and the stirrer chamber screw 55Yb are separate parts, there is no need to consider the mold configuration for the stirrer shapes such as the inverted U-shaped portion 85a and the stirrer rod 85c, and a complicated shape that further enhances the stirrer effect it can.
Even if the stirring member 85 is provided in the middle of the stirring chamber screw 55Yb, the provided portion is stirred and the pressure can be reduced. However, since pressure is generated downstream from the provided portion, it is not appropriate, as in the present embodiment. Providing at the most downstream has a high effect of preventing aggregation.
In the present embodiment, it is provided between the one that hits the most downstream of the blade provided in the shaft portion of the stirring chamber screw and the bearing of the shaft portion. That is, immediately upstream of the bearing.
A stirring member 85 is provided downstream of the screws 55Ya and 55Yb, and the pressure is relieved by stirring the powder (toner) pushed into the downstream wall surface by the screws 55Ya and 55Yb. As a result, the occurrence of aggregation in the developing device 5Y can be prevented, and the toner can be prevented from adhering unevenly on the developing roller 51Y, which is caused by sandwiching the aggregate.

As described above, in the present embodiment, the temperature is high and the pressure is present, and in contact with the inner wall surface on the bearing side downstream of the rear (left side) screw (first conveying screw) 55Ya, as shown in FIG. A stirring member 85 is provided. As a result, the powder pressure (toner pressure) can be reduced at locations where the temperature and the powder pressure are high.
In the case of the embodiment of the developing device 5Y shown in FIG. 3, the stirring chamber screw (second transport screw) 55Yb feeds the toner to the high heat source (drive mechanism 63) side, and the first transport screw 55Ya in the developing roller chamber 53Y. Feeds toner to the side opposite to the drive mechanism 63.
Thus, the stirring member 85 is provided downstream of the stirring chamber screw 55Yb, and the pressure is relieved by stirring the powder (toner) pushed into the downstream wall surface by the stirring chamber screw 55Yb. As a result, the aggregation of the powder (toner) in the developing device 5Y can be prevented, and the toner can be prevented from adhering unevenly on the developing roller 51Y, which is caused by the sandwiching of the aggregate.
Although pressure exists in both screw downstream portions, on the side where there is no high heat source, the temperature is low even in the screw downstream portion, so that aggregation is difficult to occur even if the same pressure exists. By providing the stirring member 85 according to the present invention downstream of the screw on the side where the temperature is high and the pressure is present, a great effect can be obtained by preventing toner aggregation.

As shown in FIG. 11, in another embodiment of the present invention, the stirring member 86 is provided integrally with the screws 55Ya and 55Yb. Thereby, it is possible to prevent the powder from agglomerating in the developing device 5Y and to achieve it by an inexpensive method. Further, the stirring member 86 cannot correspond to a complicated shape due to the structure of the mold, but is provided with an angle with respect to the powder conveying direction to enhance the stirring effect.
FIG. 12 is a schematic external view showing a process cartridge. In the embodiment of the present invention, the developing device 5Y is implemented in the form of a process cartridge including at least a photosensitive member (photosensitive drum) 1Y. As a result, agglomeration occurs in the developing device 5Y and the toner rolls around the developing roller 51Y (not shown in FIG. 12), and the toner on the developing roller 51 is not uniform, and the photosensitive member transfers the toner from the developing roller 51. The toner does not become uneven even on 1Y.
In the embodiment of the present invention, the above-described process cartridge 6Y is mounted on the image forming apparatus. As a result, aggregation in the developing device 5Y is suppressed, and the toner flows around the developing roller 51Y, causing non-uniform adhesion of the toner on the developing roller 51Y, and the toner on the photoreceptor 1Y transferring the toner from the developing roller 51Y is uniform. become. Therefore, it is possible to suppress the occurrence of white streak images due to the sandwiching of aggregates.

Next, powder (toner) as a developer used in the developing device of the present invention will be described. Even if powder (toner) has high average circularity that improves image quality and powder (toner) with a small particle size, the pressure during stirring in the developing device is relieved and aggregation is prevented. It is desirable to be able to
The circularity of the powder (toner) is an index of the degree of unevenness of the toner particles, and indicates 1.00 when the powder is completely spherical, and the circularity becomes smaller as the surface shape becomes more complicated. When the average circularity is in the range of 0.94 to 1.00, the surface of the powder particles is smooth, and the contact area between the powder particles and between the powder particles and the photosensitive member is small, so that the transferability is excellent.
Since the powder particles have no corners, the developer agitation torque in the developing device is small, and the agitation drive is stabilized, so that an abnormal image hardly occurs. Since there are no angular powder particles in the powder that forms the dots, the pressure is evenly applied to the entire powder that forms the dots when it is pressed against the transfer medium during transfer, and the transfer is less likely to occur. .
Since the powder particles are not angular, the polishing power of the powder particles themselves is small, and the surface of the photoreceptor, charging member, etc. is not damaged or worn. However, since there are no corners, it is easy to adhere and easily aggregate when subjected to pressure.

Next, a method for measuring the circularity of the powder will be described. The circularity can be measured using a flow type particle image analyzer FPIA-1000 manufactured by Toa Medical Electronics. As a specific measuring method, 0.1 to 0.5 ml of a surfactant, preferably an alkylbenzene sulfonate, is added as a dispersant to 100 to 150 ml of water from which impure solids have been removed in advance, and a measurement sample is further added. About 0.1 to 0.5 g. The suspension in which the sample is dispersed is subjected to a dispersion process for about 1 to 3 minutes with an ultrasonic disperser. taking measurement.
In order to reproduce minute dots of 600 dpi or more, the powder used in the present invention preferably has a weight average particle diameter of 3 to 8 μm. In this range, since the toner particles have a sufficiently small particle size with respect to the minute latent image dots, the dot reproducibility is excellent.
When the weight average particle diameter (D4) is less than 3 μm, phenomena such as a decrease in transfer efficiency and a decrease in blade cleaning properties tend to occur. When the weight average particle diameter (D4) exceeds 8 μm, it is difficult to suppress scattering of characters and lines.
Moreover, it is preferable that ratio (D4 / D1) of a weight average particle diameter (D4) and a number average particle diameter (D1) exists in the range of 1.00-1.40. The closer (D4 / D1) is to 1.00, the sharper the particle size distribution.
With such a toner having a small particle size and a narrow particle size distribution, the toner charge amount distribution is uniform, a high-quality image with little background fogging can be obtained, and the electrostatic transfer method has a high transfer rate. can do. If the particle size is fine, the image quality is improved, but the space ratio when subjected to pressure is low and the particles are likely to aggregate.

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

  1Y image carrier (photosensitive member, photosensitive drum), 5Y developing device, 6Y process cartridge, 51Y developing roller, 55Ya toner conveying screw (first conveying screw), 55Yb toner conveying screw (second conveying screw), 55Yb3 shaft ( Toner conveying screw 55Yb), 76Y developing housing (lower case), 85 stirring member, 85a reverse U-shaped portion of stirring member, 85b plate-like portion of stirring member, 85c stirring rod of stirring member, 86 stirring member, 100 printer ( Image forming device)

JP 2001-139153 A Japanese Patent Laid-Open No. 08-146765

Claims (7)

  In a developing device having a conveying screw that conveys the powder stored in the developing housing along the axial direction, a stirring member is provided in the vicinity of the inner wall surface on the bearing side of the developing housing downstream in the conveying direction of the conveying screw. A developing device.   The developing device according to claim 1, wherein a stirring member at a downstream portion in the transport direction of the transport screw is provided integrally with the transport screw.   The developing device according to claim 1, wherein the stirring member is provided downstream in the transport direction of a transport screw on a side close to a high heat source including a driving mechanism.   The developing device according to claim 1, wherein a developer having an average circularity of 0.95 or more is used.   Use a developer having a volume average particle size of 3 to 8 μm and a ratio (Dv / Dn) of the volume average particle size (Dv) to the number average particle size (Dn) in the range of 1.00 to 1.40. The developing device according to claim 1, wherein:   A process cartridge comprising at least the developing device according to any one of claims 1 to 4 and an image carrier.   7. An image forming apparatus for developing and visualizing an electrostatic latent image formed on an image carrier with toner from a developing device, wherein the process cartridge includes the developing device and the image carrier. An image forming apparatus comprising a process cartridge.

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