JP2007127906A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a developer carrier having twill line-like grooves for a developing device capable of suppressing occurrence of pitch-like vertical black streaks. <P>SOLUTION: In the developer carrier for a developing device having twill line-like grooves formed in such a way that a plurality of grooves extending in a direction inclined at a sharp angle to a rotation thrust direction intersect with a plurality of grooves extending in a direction inclined at a sharp angle to a direction opposite to the thrust direction, the distance between groove intersection points of the twill line-like grooves in the thrust direction is in the range of 1.3-4.8 mm. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a developing sleeve used for making a latent image formed on a photosensitive member a visible image by attaching a toner to an image forming apparatus such as a copying machine, a printer, and a facsimile, a developing device including the developing sleeve, and a developing device. The present invention relates to a process cartridge including the apparatus and an image forming apparatus.

  Recent copying machines and printers have very high demands for high image quality and high reliability. The development device plays a very important role in terms of high image quality, and the following are examples. 1. 1. dot reproducibility; 2. Amount of toner adhering to the photoreceptor without unevenness in the page; Reduce developer stress over time. In order to achieve such problems, conventionally, a developing sleeve having surface irregularities formed by sandblasting and a developing sleeve having a plurality of V-grooves extending parallel to the rotation axis of the developing roller are generally used. It was. Developer sleeves with irregularities using sandblasting have a problem in that the developer conveying ability decreases if the irregularity amount is small, and if the irregularity amount is increased to increase the developer conveying ability, the developing sleeve is deformed during processing. there were. In addition, the developing sleeve provided with the V-groove has a problem that a large stress is applied to the developer because each portion of each developer conveying groove parallel to the developer regulating member passes over the regulating member at the same moment. It was. In addition, there is a problem that unevenness in the pumping amount of the sleeve circumferential pitch occurs due to the groove deviation at the time of processing. The developing sleeves described in Patent Documents 1 to 4 may solve such conventional technical problems. These developing sleeves are developing sleeves in which iris-like grooves are formed.

JP 2003-316146 A JP 2003-208021 A JP 2000-242073 A Japanese Unexamined Patent Publication No. 07-13410

However, even when a developing sleeve having an iris-shaped groove is used, depending on the specific conditions of the iris-shaped groove, the developing sleeve is perpendicular to the thrust direction at a predetermined pitch in the thrust direction (longitudinal direction). It has been found that an abnormal image (hereinafter referred to as a pitch-like vertical black streak) appears in which a portion having a high development density extending in the direction of occurrence occurs and looks like a vertical black streak.
The present invention has been made in view of the above problems, and the object of the present invention is to provide a developer carrying member capable of suppressing the occurrence of the pitch-like vertical black stripes, a developing device provided with the developer carrying member, and the developing device. A process cartridge and an image forming apparatus.

In order to achieve the above object, the invention of claim 1 includes a plurality of grooves extending in a direction inclined at an acute angle with respect to the rotational thrust direction, and a plurality of grooves extending in a direction inclined at an acute angle opposite to the thrust direction. In the developer carrier having an iris-shaped groove formed so as to intersect with the groove, the distance between the groove intersections in the thrust direction of the iris-shaped groove is within the range of 1.3 mm or more and 4.8 mm or less. It is characterized by being.
According to a second aspect of the present invention, in the developing device, the developer carrying member according to the first aspect, a developer container containing a two-component developer composed of toner particles and magnetic particles, and a container 2 accommodated in the developer container. Developer transport means for transporting the component developer while stirring and developer control means for controlling the amount of the developer on the developer carrier to a constant amount are provided.
According to a third aspect of the present invention, in the process cartridge which is detachable from the main body of the image forming apparatus, the developing device of the second aspect and at least one means selected from a photosensitive member, a charging means and a cleaning means are integrally supported. To do.
According to a fourth aspect of the present invention, in the image forming apparatus, the process cartridge according to the third aspect is provided.
The invention of claim 5 is a color image forming apparatus comprising a plurality of process cartridges of claim 3.
According to a sixth aspect of the present invention, in the image forming apparatus according to the fourth or fifth aspect, the toner used in the developing unit has a volume average particle diameter of 3 to 8 μm, a volume average particle diameter (Dv) and a number average particle diameter. The ratio (Dv / Dn) to the diameter (Dn) is in the range of 1.00 to 1.40.
According to a seventh aspect of the present invention, in the image forming apparatus according to the fourth or fifth aspect, the toner used in the developing unit has a shape factor SF-1 in the range of 100 to 180, and the shape factor SF-2. Is in the range of 100-180.

  According to the first to seventh aspects of the invention, there is an effect that generation of pitch-like vertical black stripes can be suppressed.

  Hereinafter, an example of an image forming apparatus according to an embodiment of the present invention will be described. FIG. 1 is a schematic configuration diagram of the image forming portion. This image forming apparatus is a so-called tandem type color copier and is of a type provided with an intermediate transfer belt 5. A plurality of photoconductors 1 a to 1 d are arranged so as to face the extended portion of the intermediate transfer belt 5. Writing is performed by the writing unit 3 at the writing positions 3a to d on the photoconductors 1a to d uniformly charged by the charging rollers 2a to d which are charging units, and a latent image is optically formed. The latent image is developed by the developing means 4a to 4d to form a visible image made of toner. The toner images formed on the photoreceptors 1a to 1d are sequentially transferred onto the intermediate transfer belt 5 by the intermediate transfer belt transfer units 12a to 12d. The toner image on the intermediate transfer belt 5 is transferred onto the transfer paper by the paper transfer belt 7 serving as a paper transfer means onto the transfer paper conveyed through the resist roller pair 6. The toner image transferred onto the transfer paper is conveyed to the fixing means 8 by the paper transfer belt 7 and fixed on the transfer paper by heat. The transfer on which the toner image is fixed is discharged upward to a paper discharge tray (not shown). Untransferred toner that has not been transferred to the intermediate transfer belt 5 on the photoreceptors 1a to 1d is scraped off from the photoreceptor by the photoreceptor cleaning blades 9a to 9d. The remaining charge on the photoreceptor is neutralized by a neutralizing unit (not shown) to prepare for the next image forming operation. The untransferred toner scraped off by the photoconductor cleaning blades 9a to 9d is accommodated in the waste toner container 15 through the collected toner conveyance paths 14a to 14d. Further, the untransferred toner on the intermediate transfer belt and the pattern image for process control are scraped off from the intermediate transfer belt 5 by the intermediate transfer cleaning blade 13, and are also stored in the waste toner storage container 15 through the recovered toner transport path 14e. The

  New toner is supplied to the developing devices 4a to 4d. The new toner filled in the toner bottle is supplied to the toner hoppers 11a to 11d on the rear side of the machine body by the toner supply devices 10a to 10d. When the toner concentration detection means (reference numeral 21 in FIG. 2) in the developing device determines that the toner concentration in the developing device is low, the toner replenishing screw (not shown) in the toner hopper is rotated to supply an appropriate amount of toner. The toner is supplied from the toner hopper to the developing device. The toner remaining amount in the toner bottle is detected using a toner presence / absence sensor (not shown) in the toner hopper. Specifically, when this sensor detects the absence of toner, the toner supply devices 10a to 10d are requested to supply toner. If the presence of toner is not detected even if requested for a predetermined time, it is determined that there is no toner.

  FIG. 2 is an enlarged view of an image forming unit for one photoconductor. Since all the photoconductors have the same configuration, the suffixes a to d are omitted in FIG. In this image forming apparatus, a photosensitive cartridge 1, a developing unit 4, a charging roller 2 as a charging unit, and a cleaning blade 9 as a cleaning unit are integrated into a process cartridge. The process cartridge can be attached to and detached from the apparatus main body. The developing device 4 includes a developing roller 16 that supplies toner to the photoreceptor. The developing roller 16 also has a developing doctor 17 as a regulating member that regulates the amount of developer on the developing roller 16 to a certain fixed amount upstream of the developing region where the developing roller 16 faces the photoreceptor 1. A two-component developer in which toner particles and magnetic particles (carriers) are mixed is stored in a developing tank portion in the developing device, and the developer is transported by two transports of a first transport screw 18 and a second transport screw 19. It is designed to be circulated with a screw. A toner concentration sensor 21 is disposed below the second conveying screw 19, and the toner concentration in the developing tank is measured at any time and controlled so as to be within an appropriate value. The toner from the toner replenishing unit is temporarily stored in a sub hopper unit (not shown), and when the toner concentration value in the developing tank is detected to be low by the toner concentration sensor, the toner is supplied for the time converted by a predetermined conversion formula. The supply screw 22 is rotated to supply an appropriate amount of toner to the developing toner supply port 23. An inlet seal 20 for preventing toner scattering from the developing nip portion is disposed on the right side of the developing doctor 17 in the drawing.

  FIG. 3 is a perspective view of the entire developing device 4. The upper case 28 of the developing device 4 has a preset space 28 'in which a developer is placed when the unit is shipped. This is because the developer is put into this part during transportation as a unit and sealed with a removable seal member, and this seal is pulled when it arrives, so that it can be used. Mechanism. FIG. 4 is a perspective view of the developing device with the upper case 28 (see FIG. 3) removed. The developing roller 16, the first conveying screw 18, and the second conveying screw 19 are visible, and the developer is circulated between the first developer reservoir and the second developer reservoir by these conveying screws.

  FIG. 5 is an exploded perspective view of a part of the developing device. The developing roller 16 includes a magnet portion 25 fixed inside and a developing sleeve portion 26 that is built in the magnet portion 25 and is rotatable to convey the developer. The internal fixed magnet portion 25 exists slightly outside the image forming area, and has a magnet length positional relationship in consideration of transfer paper transfer variation. The outer developing sleeve 26 is usually made of an aluminum material, and is provided with an iris-like groove to facilitate transport of the developer. This iris-shaped groove will be described in detail later. The developing doctor 17 is composed of two parts, a developing doctor base 17 'made of a nonmagnetic member and a developing doctor auxiliary 24 made of a magnetic member. By fixing the developing doctor base 17 ′ to the developing casing 27, the developing doctor base 17 ′ is opposed to the developing roller 16 with a predetermined gap. The developing doctor base 17 ′ has a role of regulating the amount of developer on the developing roller to a certain fixed amount, and receives the developer pressure at the doctor when regulating the developer. Generally, a certain degree of thickness (about 1.5 to 2 mm) and straightness of about 0.05 mm at the tip are required. The developing doctor auxiliary 24 has a role of supplementing the charging of the toner conveyed to the developing area, and is usually constituted by a sheet metal (about 0.2 mm) that is considerably thinner than the developing doctor base. The positional relationship between the two parts needs to be maintained with high accuracy in order to make the toner charging property uniform in the longitudinal direction, so that the distance from the developing roller is made constant by integration by spot welding or caulking. I have to. In the illustrated example, the developing doctor is below the center of the developing roller. A first conveying screw 18 and a second conveying screw 19 are incorporated into the developing casing 27 via bearings (not shown). On the inner side of the front and rear side plates of the developing casing 27, a magnetic plate 28 is attached to suppress the developer scattering from the end of the developing roller.

Next, a toner suitably used in the above image forming apparatus will be described.
In order to reproduce minute dots of 600 dpi or more, the toner preferably has a volume average particle diameter of 3 to 8 μm. The ratio (Dv / Dn) of the volume average particle diameter (Dv) to the number average particle diameter (Dn) is preferably in the range of 1.00 to 1.40. The closer (Dv / Dn) 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.

The toner shape factor SF-1 is preferably in the range of 100 to 180, and the shape factor SF-2 is preferably in the range of 100 to 180. FIG. 6 is a diagram schematically illustrating the shape of the toner in order to explain the shape factor SF-1, and FIG. 7 is a diagram illustrating the shape factor SF-2. The shape factor SF-1 indicates the ratio of the roundness of the toner shape and is represented by the following formula (1). This is a value obtained by dividing the square of the maximum length MXLNG of the shape formed by projecting the toner on a two-dimensional plane by the figure area AREA and multiplying by 100π / 4.
SF-1 = {(MXLNG) ² / AREA} × (100π / 4) (1)
When the value of SF-1 is 100, the shape of the toner becomes a true sphere, and becomes larger as the value of SF-1 increases. The shape factor SF-2 indicates the ratio of the unevenness of the toner shape, and is represented by the following formula (2). A value obtained by dividing the square of the perimeter PERI of the figure formed by projecting the toner on the two-dimensional plane by the figure area AREA and multiplying by 100π / 4.
SF-2 = {(PERI) ² / AREA} × (100π / 4) Expression (2)
When the value of SF-2 is 100, there is no unevenness on the toner surface, and as the value of SF-2 increases, the unevenness of the toner surface becomes more prominent. Specifically, the shape factor is measured by taking a photograph of the toner with a scanning electron microscope (S-800: manufactured by Hitachi, Ltd.), introducing it into an image analyzer (LUSEX 3: manufactured by Nireco) and analyzing it. Calculated. When the shape of the toner is close to a spherical shape, the contact state between the toner and the toner or the toner and the photoconductor becomes a point contact, so that the adsorbing force between the toners becomes weak and the fluidity increases, and the toner and the photoconductor The attraction force becomes weaker and the transfer rate becomes higher. If either of the shape factors SF-1 and SF-2 exceeds 180, the transfer rate is lowered, which is not preferable.

  The iris groove of the developing roller 16 of the present invention will be described. FIG. 8 is a perspective view of the developing roller 16, and FIG. 9 is an explanatory view showing the developing roller surface in a developed shape. An iris-like groove is formed on the surface of the developing roller (the surface of the developing sleeve) of the present invention. The iris-shaped groove is formed by intersecting a plurality of grooves formed at an acute angle with respect to the developing roller rotation axis direction (thrust direction) and a plurality of grooves formed at an acute angle on the opposite side to the thrust direction. It is what is done. The acute angle in the former plurality of grooves and the acute angle in the latter plurality of grooves are not necessarily the same. According to such an iris groove-shaped sleeve, when the developer passes through the developing doctor 17 that regulates the developer amount to a certain amount, the conveying groove is not inclined and stressed, so that the developer life is shortened. In addition, since the agent conveying groove is slanted, the impact when passing through the doctor can be mitigated and the shock jitter can be improved.

FIG. 10 is an enlarged view of the iris groove of FIG. 9, and the symbol m in FIG. 10 indicates the distance between the intersections of the iris grooves in the thrust direction. The developing sleeve according to this embodiment is characterized in that the distance m between the intersections is in the range of 1.3 mm or more and 4.8 mm or less. The lower limit is set to 1.3 mm for the following reason. That is, in recent years, the gap between the developing roller and the photosensitive member 1 is generally set to 1 mm or less in order to improve image quality. In this way, as the development gap is set narrower, the developer holding amount (conveyance amount) per unit area on the surface of the developing roller can be reduced. For example, 40 mg / cm ² . The narrower the setting of the distance between the intersections m, the more the number of grooves and the larger the developer holding amount. However, as described above, in order to secure the developer holding amount according to the recent development gap, A number corresponding to 1.3 mm is sufficient. Even if the distance m between the intersections is made narrower and the number is increased, there are problems that it takes a long time for the grooving process, or stress is applied to the developing sleeve during the process and distortion occurs. Therefore, the lower limit was set to 1.3 mm. The upper limit is set to 4.8 mm for the following reason. When the distance m between the intersections exceeds 4.8 mm, a vertical black streak image is generated. Since the amount of the agent transported in the groove is larger than that in the surface portion that is not the groove, the developer is accumulated in the groove portion. In the case of the iris groove, since the grooves intersect, there is a difference in the pumping amount between the groove intersection portion and the other groove portions, and there are more intersection points. As a result, a development density difference occurs between the intersection of the grooves and the other portion. FIG. 11 is an explanatory diagram schematically showing this state. In order to actually become prominent in an image, it does not become prominent unless the interval between dark portions becomes wide. In other words, it is inconspicuous. As a result of the evaluation, if the thickness exceeds 4.8 mm, vertical black streaks appear and become apparent. Therefore, the upper limit was set to 4.8 mm.

When an image was formed with the image forming apparatus shown in FIG. 1 using the next developing roller as the developing roller, a good image without vertical black stripe unevenness could be formed.
The diameter of the developing roller is 18 mm.
40 grooves on one side and 80 grooves on both sides were formed.
The inclination angle of each groove with respect to the thrust direction is 25 degrees and the opening angle is 90 degrees.
The width of the square groove is 240 μm and the depth is 90 μm.
The pumping amount is 48 mg / cm ² (plus or minus 8 mg / cm ² ).
Doctor gap is 0.34mm.
Development gap is 0.3mm (plus or minus 0.05m)

As described above, according to the image forming apparatus of the present embodiment, since the distance between the groove intersections in the thrust direction of the iris-shaped grooves is within the range of 1.3 mm or more and 4.8 mm or less, the generation of pitch-like vertical black stripes is prevented. Can be suppressed.
The toner has a volume average particle diameter of 3 to 8 μm and a ratio (Dv / Dn) of the volume average particle diameter (Dv) to the number average particle diameter (Dn) in the range of 1.00 to 1.40. If one having a particle size distribution is used, a higher quality image can be obtained.
Further, if a toner having a shape factor SF-1 in the range of 100 to 180 and a shape factor SF-2 in the range of 100 to 180 is used, a higher quality image can be obtained.

1 is a schematic configuration diagram of a printer according to an embodiment of the present invention. FIG. 2 is a schematic configuration diagram of a process cartridge constituting a toner image forming unit of the printer. 1 is an overall perspective view of a developing device. The perspective view which shows the internal structure of a developing device. FIG. 3 is an exploded perspective view of a part of the developing device. FIG. 3 is an explanatory diagram schematically showing a toner shape for explaining a shape factor SF-1. FIG. 4 is an explanatory diagram schematically showing a toner shape for explaining a shape factor SF-2. The perspective view of a developing roller. Explanatory drawing which showed the developing roller surface in the developed shape. Explanatory drawing of an iris-shaped groove. Explanatory drawing of a pitch-like vertical black stripe.

Explanation of symbols

1 Photoconductor 2 Developing roller

Claims (7)

Iridescent groove formed so that a plurality of grooves extending in a direction inclined at an acute angle with respect to the rotational thrust direction and a plurality of grooves extending in a direction inclined at an acute angle on the opposite side to the thrust direction intersect. In a developer carrier having
A developer carrier, wherein a distance between groove intersections in the thrust direction of the iris-shaped grooves is in a range of 1.3 mm or more and 4.8 mm or less.   2. A developer carrying member according to claim 1, a developer container containing a two-component developer comprising toner particles and magnetic particles, and a developer carrying means for carrying the two-component developer contained in the developer container while stirring. And a developer regulating means for regulating the amount of the developer on the developer carrying member to a constant amount.   A process cartridge which integrally supports the developing device according to claim 2 and at least one unit selected from a photosensitive member, a charging unit, and a cleaning unit, and is detachable from an image forming apparatus main body.   An image forming apparatus comprising the process cartridge according to claim 3.   A color image forming apparatus comprising a plurality of process cartridges according to claim 3. The image forming apparatus according to claim 4 or 5,
The toner used in the developing unit has a volume average particle diameter of 3 to 8 μm and a ratio (Dv / Dn) of the volume average particle diameter (Dv) to the number average particle diameter (Dn) of 1.00 to 1.40. An image forming apparatus characterized by being in the range. The image forming apparatus according to claim 4 or 5,
The image forming apparatus according to claim 1, wherein the toner used in the developing unit has a shape factor SF-1 in the range of 100 to 180 and a shape factor SF-2 in the range of 100 to 180.

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