JP2007127809A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a developer carrying member that is a developing sleeve having crosshatched grooves to be used for a developing device and that can suppress a decrease in a developer holding amount with time. <P>SOLUTION: The developer carrying member to be used for a developing device has crosshatched grooves in which a plurality of grooves running in a direction inclined at an acute angle with respect to the rotation thrust direction and a plurality of grooves running in a direction inclined at an acute angle in the opposite side with respect to the thrust direction are formed so as to be crossed each other, wherein the groove is shaped to have a falling portion, a bottom portion and a rising portion. <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 copiers and printers have very high demands for high image quality, high reliability, and high stability. In order to satisfy these requirements, the temporal stability and uniformity of the developer amount on the developer carrying member are important points. Conventionally, a developing sleeve in which irregularities are formed on the surface by sandblasting and a developing sleeve in which a plurality of V-grooves extending in parallel with the rotation axis of the developing roller are formed on the surface are generally used. 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, when a developing sleeve having an iris groove is used, depending on the specific conditions of the iris groove, a decrease in developer conveyance amount over time may occur due to a V groove parallel to the rotation axis. It was found that this was remarkable as compared with the formed developing sleeve.
The present invention has been made in view of the above problems, and an object of the present invention is to provide a developer carrier capable of suppressing a decrease in developer conveyance amount over time while having an iris-like groove, and a developer carrier. A developing device, a process cartridge including the developing device, and an image forming apparatus are provided.

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 carrying member having an iris-shaped groove formed so as to intersect with the groove, a groove having a shape having a falling portion, a bottom portion, and a rising portion is formed as the groove. .
According to a second aspect of the present invention, in the developer carrying member of the first aspect, the bottom portion has a width of 30 μm or more.
According to a third aspect of the invention, in the developer carrying member of the first or second aspect, the width of the bottom portion is 800 μm or less.
According to a fourth aspect of the invention, there is provided the developer carrying member according to any one of the first to third aspects, a developing container containing a two-component developer comprising toner particles and magnetic particles, and the developing container accommodated in the developing container. A developing device comprising developer conveying means for conveying a two-component developer while stirring, and developer regulating means for regulating the amount of developer on the developer carrying member to a constant amount.
According to a fifth aspect of the present invention, there is provided a process cartridge which integrally supports the developing device of the fourth aspect and at least one means selected from a photosensitive member, a charging means and a cleaning means, and is detachable from the main body of the image forming apparatus. .
The invention of claim 6 is an image forming apparatus comprising the process cartridge of claim 5.
The invention of claim 7 is a color image forming apparatus comprising a plurality of process cartridges of claim 5.
According to an eighth aspect of the present invention, in the image forming apparatus of the sixth or seventh 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.
The invention according to claim 9 is the image forming apparatus according to claim 6 or 7, wherein 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 ninth aspects of the present invention, it is possible to suppress a decrease in developer transport amount over time.

  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. The developing doctor 17 is composed of two parts: a developing doctor base composed of a non-magnetic member and a developing doctor auxiliary 24 composed of a magnetic member. The development doctor base has a role of regulating the amount of developer on the developing roller to a certain amount, and the developer pressure is received by this doctor when regulating the developer. In general, 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.

  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 region, and is usually formed of 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 integrating them 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.

  A developing roller will be described as the developing carrier of the present invention. FIG. 8 is a perspective view of the developing sleeve 26, and FIG. 9 is an enlarged view of the surface of the developing sleeve 26. 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 such that a plurality of grooves inclined with respect to the developing roller rotation axis direction (thrust direction) and a plurality of grooves inclined opposite to the thrust direction intersect. is there. The angle of inclination in the former plurality of grooves and the angle of inclination 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.

  As shown in FIG. 9, the groove of the developing sleeve of this embodiment has a shape having a falling portion, a bottom portion, and a rising portion. The width a of the bottom is set in the range of 30 μm or more and 800 μm or less. When the width a is less than 30 μm, the decrease in the developer pumping amount with time is the same as when the groove bottom is not provided. That is, the clogging of the developer at the bottom of the groove occurs and the pumping amount is reduced. When the width a exceeds 800 μm, the decrease in developer pumping amount over time can be reduced, but the developer pumping amount by the iris groove becomes too large. As a countermeasure, the doctor gap amount should be narrowed, but the doctor gap needs to be narrowed more than necessary. As a result, foreign matter (toner lump etc.) gets caught in the doctor gap part, and abnormal images such as white streaks are generated. Problem arises.

As described above, according to the image forming apparatus of the present embodiment, it is possible to suppress a decrease in developer transport amount over time.
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 sleeve. The expansion perspective view of the groove | channel on the surface of a developing sleeve.

Explanation of symbols

1 Photoconductor 2 Developing roller

Claims (9)

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 characterized by forming a groove having a falling part, a bottom part, and a rising part as the groove. The developer carrier of claim 1,
A developer carrier, wherein the width of the bottom is 30 μm or more. In the developer carrier of claim 1 or 2,
The developer carrying member according to claim 1, wherein a width of the bottom is 800 μm or less.   A developer carrying member according to any one of claims 1 to 3, a developer container containing a two-component developer composed of toner particles and magnetic particles, and conveying the two-component developer contained in the developer container while stirring. A developing device comprising: a developer transporting unit that controls the amount of the developer on the developer carrying member;   A process cartridge that integrally supports the developing device according to claim 4 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 5.   A color image forming apparatus comprising a plurality of process cartridges according to claim 5. The image forming apparatus according to claim 6 or 7,
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 6 or 7,
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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