JP2006139075A - Developer carrier, and developing device, process cartridge and image forming apparatus using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a developer carrier which suppresses decrease in image density caused by the shape of a groove portion and which can perform stable image formation from an initial stage of using the developing carrier by determining the shape of the groove portion to be the optimum shape in the developer carrying body where groove working is applied. <P>SOLUTION: The surface of a developing sleeve 43 as a developer carrier has a groove portion 43d having a V-shape cross-sectional profile and extending in the longitudinal direction; and the nearly V-shaped bottom of the groove portion 43d is an arc with a radius of r1 satisfying r1>d1, wherein d1 is the radius of developer particles. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a developer carrier, a developing device, a process cartridge, and an image forming apparatus used in a copying machine, a facsimile machine, a printer, and the like. More specifically, the present invention relates to a latent image formed on an image carrier. The present invention relates to a developer carrying member for developing an image, a developing device, a process cartridge, and an image forming apparatus.

  Conventionally, the surface of a developing sleeve or the like as a developer carrier has been subjected to roughening processing such as sandblasting or groove processing, except in the case of a low speed machine. This is to prevent the image density from decreasing due to the developer slipping and stagnating on the developing sleeve rotating at high speed.

In sandblasting, aluminum, brass, stainless steel, or conductive resin can be used as the developing sleeve material, but aluminum is generally used in consideration of cost and accuracy. When sandblasting an aluminum developing sleeve, for example, abrasive grains are sprayed cold on an aluminum tube extruded in a sleeve shape at a high temperature to create irregularities on the surface. A surface roughness of about Rz 5.0 to 15 [μm] is often used. In the developing sleeve subjected to sandblasting in this way, even when the developing sleeve is rotated at a high speed, the developer is caught by the unevenness and the occurrence of slip can be prevented.
However, the development sleeve subjected to the sandblasting has a problem in durability that the unevenness of the surface is worn over time and the developer conveying ability is lowered. This can be improved by making the developing sleeve material stainless steel or by subjecting the surface to a hardening treatment, but this increases the cost.

In the groove processing, aluminum, brass, stainless steel, or conductive resin can be used as the developing sleeve material. However, in consideration of cost and accuracy, aluminum is generally used as in the case of sandblasting. When groove processing is performed on an aluminum developing sleeve, for example, an aluminum tube extruded into a sleeve shape at a high temperature is pulled out cold, and a groove is formed by a die. The shape of the groove is generally rectangular, V-shaped, U-shaped, or the like. The depth of the groove is generally about 0.2 [mm] from the surface of the developing sleeve, and the number of grooves is generally about 50 for a developing sleeve having an outer diameter of φ25, for example. In the developing sleeve subjected to the groove processing as described above, even when the developing sleeve is rotated at a high speed, the developer is caught in the groove portion and the occurrence of slip can be prevented. In addition, there is an advantage that the developer can be stably transported with less wear even when used for a long period of time as compared with a developing sleeve subjected to sandblasting.
Patent document 1 etc. are proposed for this application as a developer carrier which performed such groove processing.

JP 2001-401155 A

  However, the use of a developer bearing member that has been subjected to groove processing causes a phenomenon in which the image density decreases at an early stage of time. As a result of intensive studies by the present inventors on the decrease in image density, it has been found that the decrease in image density is caused by the shape of the groove.

  The present invention has been made in view of the above problems, and the object of the present invention is to set the groove shape of the developer carrier subjected to the groove processing to an optimum shape, thereby causing the shape of the groove portion. The present invention provides a developer carrier capable of suppressing a decrease in image density and performing stable image formation from the initial stage of using the developer carrier, and a developing device, a process cartridge, and an image forming apparatus having the developer carrier. That is.

In order to achieve the above object, a first aspect of the present invention provides a developer carrying member for carrying a developer on a surface and developing a latent image formed on the image carrying member. The cross-sectional shape extending in the direction has a plurality of grooves having a substantially V shape, the bottom of the groove having a substantially V shape has an arc shape with a radius r1, and the radius of the developer particles is d1. The radius r1 satisfies r1> d1.
According to a second aspect of the present invention, in the developer carrying member of the first aspect, the developer is a two-component developer composed of toner and magnetic particles, and the radius d1 is a radius of the magnetic particles. It is what.
According to a third aspect of the present invention, in the developer carrying member of the first aspect, the developer is a two-component developer composed of toner and magnetic particles, and the radius d1 is the radius of the magnetic particles and the diameter of the toner. It is the size which added.
According to a fourth aspect of the present invention, in the developer carrying member according to the first to third aspects, the radius d1 of the developer particles is a maximum particle radius of the developer. .
According to a fifth aspect of the present invention, there is provided a developer carrier for carrying a developer on a surface and developing a latent image formed on the image carrier, wherein a plurality of grooves extending in the longitudinal direction on the surface of the developer carrier. Wherein a round portion having a radius r2 is provided at the boundary between the surface portion of the developer carrying member and the groove portion, and the radius of the developer particles is d2, r2> d2. It is.
According to a sixth aspect of the present invention, in the developer carrying member according to the fifth aspect, the surface of the developer carrying member is one of the two boundary portions between one of the grooves and the surface portion of the developer carrying member. The rounded portion is provided only at the boundary portion on the upstream side in the moving direction.
The invention according to claim 7 is the developer carrying member according to claim 5 or 6, wherein the developer is a two-component developer comprising toner and magnetic particles, and the radius d2 is a radius of the magnetic particles. It is characterized by.
The invention of claim 8 is a developing device having a developer accommodating portion for accommodating a developer and a developer bearing member for developing a latent image formed on the image bearing member with the developer. The developer carrier according to claim 1, 2, 3, 4, 5, 6 or 7 is used as the carrier.
The invention according to claim 9 is a process in which at least the image carrier and the developing means for developing the latent image on the image carrier are integrally supported and are detachable from the image forming apparatus main body. In the cartridge, the developing device according to claim 8 is used as the developing means.
According to a tenth aspect of the present invention, there is provided a charging means for charging the surface of the image carrier, a latent image forming means for forming an electrostatic latent image on the image carrier, and a developer carried on the surface. And developing means for developing the electrostatic latent image into a toner image by using the developer carrying member, wherein the developer carrying member is defined as claim 1, 2, 3, 4, The developer carrying member described in 5, 6 or 7 is used.

If the shape of the groove portion is V-shaped, the wall surface of the groove portion is slanted, so that the groove gradually becomes deeper from the boundary between the groove portion and the surface portion of the developer carrier to the center portion of the groove portion. When the groove portion is gradually deepened, the magnitude of the developing electric field between the image carrier and the developer carrier gradually changes, and the pitch unevenness on the image is less than that of the rectangular or U-shaped groove portion. Less noticeable. However, when the groove portion is V-shaped and the developer and the inner wall of the groove portion are in contact with each other at two or more points, the developer is easily stabilized in a state where the developer is in contact with the inner wall surface of the groove portion. As a result, the developer stays in the groove portion and becomes clogged in the groove portion. As a result, the developer transportability is lowered, and the image density is lowered.
In the developer carrying member according to the first to fourth aspects, since the cross-sectional shape of the groove is substantially V-shaped, it is possible to make the pitch unevenness on the image less noticeable. Furthermore, when the radius of the developer particles is d1, the substantially V-shaped bottom of the groove has an arcuate shape with a radius r1 that satisfies r1> d1, and therefore the spherical surface of the developer, the inner wall of the groove, Touch at only one point. When the spherical surface of the developer and the inner wall of the groove are in contact with each other at only one point, the developer becomes unstable and easily moves even when the developer is in contact with the inner wall of the groove. . As a result, it is possible to prevent the developer from staying in the groove and to prevent the developer carrying capacity of the developer carrier from being lowered due to the developer being clogged in the groove. Therefore, it is possible to suppress a decrease in image density due to the shape of the groove portion of the developer carrying member being a shape that can contact the spherical surface of the developer at two or more points.

Further, when the boundary between the surface of the developer carrying member and the groove portion (hereinafter referred to as the groove edge portion) is square, the corner of the groove edge portion is changed from the developer at the initial stage of use of the developer carrying member. As a result of this rubbing, the developer carrying ability continues to decline from the beginning of use of the developer carrying member, and the image density continues to decline accordingly. Then, when the groove edge portion was rounded having a radius substantially the same as the radius of the developer particles, the decrease in the developer conveying ability stopped and the image density was stabilized. When image formation is performed to some extent, the image density becomes stable. However, since the developer carrying ability is different from that immediately after the start of use, it is necessary to adjust the density according to the carrying ability after wear.
In the developer carrying member according to any one of claims 5 to 7, when the radius of the developer particle is d2, r2> d2 is set at a groove edge portion which is a boundary between the surface portion of the developer carrying member and the groove portion. A rounded portion with a radius r2 is provided to fill. By preliminarily rounding the groove edge portion that has been worn from the beginning of use, it is possible to prevent the developer carrying member from deteriorating in the developer carrying capacity due to a change in the shape of the groove edge portion. . Therefore, it is possible to suppress a decrease in image density due to the shape of the groove portion of the developer carrying member being a shape in which the groove edge portion is worn by rubbing with the developer. Then, by setting the image forming conditions so that a desired image density can be obtained with a rounded shape at the groove edge portion, a stable image density can be obtained from the initial stage of using the developer carrier. it can.
In the developing device according to the eighth aspect, by having the developer carrying member according to any one of claims 1 to 7 as the developer carrying member, a decrease in image density due to the shape of the groove portion of the developer carrying member is suppressed. be able to.
The process cartridge according to claim 9 has the developer carrier according to any one of claims 1 to 7 as the developer carrier, thereby suppressing a decrease in image density due to the shape of the groove of the developer carrier. be able to.
In the image forming apparatus according to the tenth aspect, by having the developer carrying member according to any one of claims 1 to 7 as the developer carrying member, a decrease in image density due to the shape of the groove portion of the developer carrying member is suppressed. can do.

  According to the first to tenth aspects of the present invention, it is possible to suppress a decrease in image density due to the shape of the groove of the developer carrying member, so that stable image formation is performed from the initial stage of using the developer carrying member. There is an excellent effect of being able to.

[Embodiment 1]
A first embodiment in which the present invention is applied to a printer 100 that is an image forming apparatus will be described below. FIG. 1 is a schematic configuration diagram of a main part of a printer 100 according to the first embodiment.
Around the photosensitive drum 1 serving as a latent image carrier, a charging device 2 that charges the surface of the photosensitive drum 1 with a charging roller or the like, and a latent image is formed on the uniformly charged surface of the photosensitive drum 1 with a laser beam or the like. An exposure apparatus 3 to be formed is disposed. Further, a developing device 4 is provided on the photosensitive drum 1 to form a toner image by attaching charged toner to the latent image. Further, a transfer device 5 that transfers the toner image formed on the photosensitive drum 1 to the recording paper 6 by a transfer belt, a transfer roller, a charger, or the like, and a cleaning device 7 that removes the toner remaining on the photosensitive drum 1 after the transfer. Is arranged. Further, a static elimination device having a static elimination lamp 8 which is a static elimination means for removing the residual potential on the photosensitive drum 1 is sequentially arranged.

In the printer 100, the photosensitive drum 1 whose surface is uniformly charged by the charging roller of the charging device 2 forms an electrostatic latent image by the exposure device 3 and forms a toner image by the developing device 4. As a developing condition, the photosensitive drum 1 charged to −700 V is exposed and the image portion is attenuated to −150 V. Development is performed by applying a developing bias of −550 V to the electrostatic latent image.
Then, the toner image on the surface of the photosensitive drum 1 is transferred from the surface of the photosensitive drum 1 to the recording paper 6 conveyed from a paper supply tray (not shown) by the transfer device 5. Thereafter, the toner image on the recording paper is fixed on the recording paper by a fixing device (not shown). On the other hand, the toner remaining on the photosensitive drum 1 without being transferred is collected by the cleaning device 7. The photosensitive drum 1 from which the residual toner has been removed is initialized by the charge eliminating lamp 8 and used for the next image forming process.

  In the printer 100, process control is performed in order to suppress image quality fluctuations due to environmental fluctuations and temporal fluctuations. Specifically, first, the developing ability in the developing device 4 is detected. For example, an image of a certain toner pattern is formed on the photosensitive drum 1 under a condition where the developing bias voltage is constant, the image density is detected by the optical sensor 9, and the developing ability is grasped from the density change. Then, the image quality can be kept constant by changing the target value of the toner density so that the developing ability becomes a predetermined target developing ability. For example, when the image density of the toner pattern detected by the optical sensor 9 is lower than the target development density, the CPU 10 controls the motor drive circuit 12 so as to increase the toner density. On the other hand, when the image density of the toner pattern detected by the optical sensor 9 is lower than the target development density, the CPU 10 controls the motor drive circuit 12 so as to lower the toner density. Here, the toner density is detected by a toner density sensor 48 (see FIG. 2). Note that the image density of the toner pattern formed on the photosensitive drum 1 may vary somewhat due to the influence of the uneven image density period caused by the developing sleeve 43.

  Next, the configuration of the developing device 4 will be described with reference to FIG. The developing device 4 includes a developing container 4A and a toner supply unit 4B. Among them, a developing roller 41 having a developing sleeve 43 as a developer carrying member is disposed in the developing container 4A so as to be close to the photosensitive drum 1 as a latent image carrying member. Region D is formed.

  The developing roller 41 is provided with a developing sleeve 43 formed of a nonmagnetic material such as aluminum, brass, stainless steel, or conductive resin in a cylindrical shape. The developing sleeve 43 is rotated in the direction of the arrow, that is, counterclockwise by a rotation driving mechanism (not shown). In the developing sleeve 43, a magnet roller body 44 that forms a magnetic field is provided in a fixed state so as to cause the developer to stand on the surface of the developing sleeve 43. At this time, the carrier constituting the developer is spiked in the form of a chain on the developing sleeve 43 so as to follow the lines of magnetic force emitted from the magnet roller body 44. The charged toner is attached to the carrier spiked in a chain shape to form a magnetic brush. The formed magnetic brush is transferred in the same direction as the developing sleeve 43, that is, in the counterclockwise direction as the developing sleeve 43 rotates. A doctor blade 45 that regulates the height of the spikes of the developer chain, that is, the amount of the developer, is installed in the upstream portion of the development region D in the developer transport direction, that is, in the counterclockwise direction.

  Further, a stirring roller 46 and a paddle wheel 47 are provided in the rear region of the developing roller 41 so that the developer is pumped up by the paddle wheel 47 after being stirred and mixed by the stirring roller 46. A developer case 51 as a developer storage member is disposed on the lower side so as to enclose the developing roller 41, the paddle wheel 47, and the stirring roller 46.

  For example, when the toner concentration sensor 48 detects that the concentration of the toner supplied to the photosensitive drum 1 has decreased, the toner replenishing unit 4B feeds the toner T toward the stirring roller 46 by the rotation of the toner replenishing roller 4B1. It has become. In the vicinity of the doctor blade 45 described above, a separator 49 is disposed in which one end in the extending direction is positioned in the vicinity of the doctor blade 45 and the other end in the extending direction is positioned on the stirring roller 46. A rotatable conveying screw 50 is disposed at the other end of the separator 49 in the extending direction.

  In the developing container 4 </ b> A, the developer is pumped up by the rotation of the paddle wheel 47, released toward the developing roller 41, and carried on the surface of the developing roller 41 by the magnetic force of the magnet roller body 44. The developer carried on the developing roller 41 moves on the surface along with the rotation of the developing sleeve 43, the layer thickness is regulated by the doctor blade 45, and the developing roller 41 and the photosensitive drum 1 face each other. It passes through the developing area D to be processed. Thereafter, it passes through the gap with the developer case 51, falls to the bottom of the developer case 51 at a position where the magnetic force of the magnet roller body 44 does not act, and is again stirred by the paddle wheel 47. The excess developer scraped off by the doctor blade 45 is sequentially conveyed to the back side of the printer 100 by a plurality of inclined fins 49 a arranged on the separator 49. A developer guide path is disposed at the innermost end of the separator 49 and is guided toward the conveying screw 50 located at the other end in the extension direction. Contrary to the above, the conveying screw 50 conveys the ink to the front side of the printer 100 and falls through a slit (not shown) facing the stirring roller 46 disposed at the frontmost end. By this developer transport before and after the developer, stirring is performed so that the toner density is uniform in the front-rear direction of the printer 100, and at the same time, the developer level can be kept constant by setting the transport amounts of the front and rear developers equally. It is.

Next, the developing sleeve 43 will be described.
FIG. 3 is an enlarged view of a partial cross section of the developing sleeve 43 as seen from the axial direction. On the surface of the developing sleeve 43, a plurality of grooves 43d extending in the longitudinal direction are formed at equal intervals. In general, as the groove 43d is deeper, the developer conveyance performance is improved, but pitch unevenness of about 1 [mm] period as shown in FIG. 4 is likely to occur. On the other hand, as the groove 43d is shallower, pitch unevenness is less likely to occur, but the developer conveying performance is degraded. In particular, in recent years, the image reproducibility has been improved due to the progress of image forming technology for small-diameter toner and carrier and the image forming technology for proximity development. In view of this, in the developing sleeve 43, the depth of the groove 43d is set to be shallower than that of the conventional one so as to achieve both the developer transport performance and the prevention of pitch unevenness. Specifically, the groove depth of the developing sleeve 43 is set in the range of 0.05 to 0.15 [mm].

Here, the specific conditions of the apparatus are as follows.
The mechanical conditions are as follows.
Photosensitive drum 1 linear speed 360 mm / sec (can be set from 100 to 500 mm / sec)
Gap between developing sleeve 43 and photosensitive drum 1 0.3 to 0.6 [mm]
Gap between developing sleeve 43 and doctor blade 45 0.3 to 0.6 [mm]
Development sleeve 43 outer diameter φ25 [mm] (can be set from φ16 to φ40)
Ratio of the developing sleeve 43 to the photosensitive member linear velocity 2 (can be set from 1.5 to 3)
Number of groove portions 43d of developing sleeve 43 100 Resistance value of developing sleeve 43 100Ω or less Strength of magnetic force of magnet roller body 44 60 to 140 mT
The developer conditions are as follows.
Carrier (magnetite, iron or ferrite) 30-80 [μm]
Toner Magnetic amount 15-50wt%
Silica amount 0.1-1.0wt%
Volume average particle diameter 5 to 9.5 [μm]
Toner coverage on carrier 50-120%
Toner charge amount (Q / M) 15-50 μc / g

  FIG. 5 is a graph showing experimental results of pitch unevenness and developer conveyance performance with respect to the depth of the groove 43d. As can be seen from FIG. 5, when the groove depth is deeper than 0.15 [mm], the developer conveying performance is improved, but pitch unevenness occurs. The following can be considered as a cause of the occurrence of this pitch unevenness. When the depth of the groove 43d of the developing sleeve 43 is deeper than 0.15 [mm], the photosensitive drum 1 and the groove 43d of the developing sleeve 43 face each other in the developing region D between the photosensitive drum 1 and the developing roller 41. In this case, the developing electric field between the photosensitive drum 1 and the groove 43d becomes weak. As a result, it is considered that the developing ability is lowered, and the developing density is reduced on the photosensitive drum 1 in the portion facing the groove 43d. On the other hand, if the groove depth is shallower than 0.05 [mm], pitch unevenness does not occur, but the developer conveying performance is deteriorated. As a cause of the deterioration in the developer conveying performance, if the depth of the groove 43d of the developing sleeve 43 is shallower than 0.05 [mm], the developer slips on the developing sleeve 43 or the developer by the groove 43d. This is thought to be because the transport amount decreases. Therefore, in the developing sleeve 43 of the printer 100, the depth of the groove 43d is set within a range of 0.05 [mm] or more and 0.15 [mm] or less, which is set shallower than the conventional configuration, thereby preventing pitch unevenness and developer. Achieving compatibility with transport performance.

  Further, for example, the depth of the groove as the recess is deeper than the unevenness formed on the surface of the developing sleeve by sandblasting. Therefore, the grooves are less likely to be worn compared to the unevenness formed by sandblasting, and the developer transportability can be maintained over time and a stable image density can be maintained. Further, even when used at a high speed, the developer conveying performance can be maintained. Furthermore, since the image density of the toner pattern formed on the photosensitive drum 1 during process control is stabilized, more appropriate process control can be performed.

As described above, by setting the depth of the groove 43d of the developing sleeve 43 within the range of 0.05 [mm] or more and 0.15 [mm] or less, both prevention of pitch unevenness and developer conveyance performance are achieved. I was able to.
However, when image formation was performed using the above-described developing sleeve 43, as shown in FIG. 6, image density cycle unevenness having a relatively long cycle of 30 to 50 [mm] occurred on the recording paper 6. . Here, since the developing sleeve 43 has an outer diameter of φ25 [mm], the outer peripheral length is 78.5 [mm]. Since the linear velocity ratio with respect to the photosensitive drum 1 is 2, about 39 [mm] corresponds to one rotation of the developing sleeve 43 on the image. Therefore, the period of the image density unevenness generated on the recording paper 6 substantially corresponds to the period of one rotation of the developing sleeve 43. Since such image density periodic unevenness often occurs due to the eccentricity of the developing sleeve, the eccentricity amount of the developing sleeve 43 was measured, but the eccentricity amount of the developing sleeve 43 was not so large as to cause the image density periodic unevenness.

Therefore, the present inventor measured the depth of the plurality of grooves 43d formed in the developing sleeve 43 with a laser measuring instrument, and as shown in the graph of FIG. It was seen. As a result, it was found that the amount of pumping is small and the image density is low at the shallow groove portion 43d, and the image density is high and the pumping amount is large at the deep groove. FIG. 8 is a side view schematically showing the variation in the depth of the groove 43d. The following is considered as a cause of variation in the depth of the groove 43d formed in the developing sleeve 43. The groove portion 43d of the developing sleeve is processed with a die. However, when forming a shallow groove portion as compared with the conventional case as in this embodiment, if the processing is performed with the same processing accuracy as that of the conventional deep groove portion, the groove portion 43d This is thought to be due to the relatively large variation in depth.
Here, the variation [%] in the groove depth of the groove 43d can be expressed by the following equation (1).
(Equation 1)
Variation = ± {(maximum groove depth-minimum groove depth) / 2} / average groove depth

  From the graph of FIG. 7, the maximum groove depth was 0.15 [mm], the minimum groove depth was 0.05 [mm], and the average groove depth was 0.1 [mm]. When these numerical values are substituted into Formula 1, calculation is as follows: variation = ± {(0.15-0.05) / 2} /0.1=±50 [%]. When the variation is ± 50 [%], image density cycle unevenness as shown in FIG. 6 occurs.

  Therefore, the present inventor manufactured three developing sleeves having a variation in the depth of the groove 43d of ± 20%, ± 30%, and ± 40%, formed an image under the same conditions, and performed an image density cycle. An unevenness evaluation experiment was conducted. As a result, with the developing sleeve 43 having a variation in the depth of the groove 43d of ± 20%, the developer pumping amount was stabilized, and a good image with no noticeable image density cycle unevenness was obtained. Further, in the developing sleeve 43 in which the variation in the depth of the groove 43d is ± 30%, the variation in the pumping amount of the developer is suppressed, and the unevenness in the image density period is inconspicuous and acceptable. On the other hand, in the developing sleeve 43 having a variation in the depth of the groove 43d of ± 40%, the amount of developer pumped up varies, and the image density period unevenness was conspicuous. Accordingly, it has been found that the variation in the depth of the groove 43d is preferably ± 30% or less, and more preferably ± 20% or less.

  Further, as the shape of the groove 43d formed in the developing sleeve 43, a V-shape as shown in FIG. 9 is effective in preventing pitch unevenness. As shown in the graph of the experimental results in FIG. 10, when the shape of the groove 43 d is V-shaped, the pitch unevenness is not conspicuous compared to the rectangular shape or the U-shape. The reason can be considered as follows. In a square or U-shaped groove, the groove edge portion 43e, which is the boundary between the surface of the developing sleeve 43 and the groove portion 43d, has a step, so that the groove suddenly becomes deeper. However, the V-shaped groove portion 43d has a groove wall surface. Is inclined, the groove gradually becomes deeper from the groove edge 43e to the bottom of the groove. Therefore, it is considered that when the groove portion 43d of the developing sleeve 43 is opposed to the photosensitive drum 1 in the developing region D, the magnitude of the developing electric field changes gradually, and the difference in developing density becomes inconspicuous.

Further, the V-shaped opening angle of the groove 43d is in the range of 60 ° or more and 120 ° or less, which is effective for the developer conveyance performance and the prevention of pitch unevenness. As shown in the graph of the experimental result in FIG. 11, when the V-shaped opening angle is smaller than 60 °, the developer conveying performance is deteriorated. This is presumably because if the V-shaped opening angle is smaller than 60 °, the developer slips on the developing sleeve 43 or the amount of developer transported by the groove 43d decreases. On the other hand, when the V-shaped opening angle is larger than 120 °, pitch unevenness starts to be noticeable. The reason for this is considered as follows. In the developing area D, when the photosensitive drum 1 and the groove 43d of the developing sleeve 43 are opposed to each other, the developing electric field between the photosensitive drum 1 and the groove 43d is weakened and the developing ability is lowered. At this time, if the opening angle of the V-shape is larger than 120 °, the width of the groove 43d is widened, so that the portion where the development density is thinned is widened and the pitch unevenness is likely to be noticeable.
Therefore, in the developing sleeve 43, the shape of the groove 43d is V-shaped, and the opening angle thereof is in the range of 60 ° or more and 120 ° or less so as to achieve both the developer transport performance and the prevention of pitch unevenness. Yes.

Further, according to experiments, it has been found that a spatial frequency of 1.5 [cycle / mm] or more by the groove 43d of the developing sleeve 43 is effective in preventing pitch unevenness. In this case, the pitch on the image transferred from the photosensitive drum 1 to the recording paper 6 corresponds to 0.66 [mm] or less. In general, it is said that the naked eye has the strongest sensitivity at a pitch of about 1 [mm], and pitch irregularities with higher spatial frequencies are less noticeable. FIG. 12 is a graph showing experimental results of the relationship between spatial frequency and pitch unevenness.
Here, the image on the photoconductive drum 1 is transferred onto the recording paper in a substantially intact form. Therefore, the spatial frequency f is the number of passages of the groove of the developing sleeve per 1 mm in the surface movement direction of the surface of the photosensitive drum, and can be calculated by the following formula 2.
(Equation 2)
f = Linear speed ratio of developing sleeve to photoreceptor × number of grooves / (developing sleeve outer diameter × π)

  In the developing sleeve 43 of the printer 100, the spatial frequency is set to 1.5 [cycle / mm] or more to prevent pitch unevenness. More specifically, the developing sleeve diameter of the developing sleeve 43 is set to φ25 [mm], the developing sleeve to photosensitive member linear velocity ratio is doubled, and the number of grooves is set to 100. By substituting these numerical values into Equation 2 and calculating the spatial frequency, f = 2.5 [cycle / mm] is obtained, and the occurrence of pitch unevenness is effectively suppressed.

  In general, when an image is formed using a toner having a volume average particle size of 8.5 [μm] or less, the reproducibility of the image is remarkably improved as shown in the graph of FIG. It becomes easy to stand out. In the printer 100, by using the developing sleeve 43, even when a toner having a volume average particle diameter of 8.5 [μm] or less is used, a high-quality image with good reproducibility is formed while preventing pitch unevenness. be able to. If the volume average particle diameter is smaller than 4 [μm], the cleaning performance of the toner remaining on the photosensitive drum 1 is deteriorated. Therefore, the volume average particle diameter of the toner is desirably 4 [μm] or more.

Further, the developer used in the printer 100 uses magnetic particles (hereinafter referred to as a carrier), which are constituent components, having a particle size of 60 [μm] or less. A carrier having a particle size of about 70 [μm] is generally used for a conventional two-component developer. In the present embodiment, a carrier having a particle size of 60 [μm] or less is used. Therefore, it is effective for improving the image quality. In a halftone dot image in the brightness 70 to 90 region, when the particle size of the carrier is 60 [μm] or more, even if the particle size is about 0.3, if the particle size is lowered to about 40 [μm], the granularity However, the dot reproducibility is improved even when the value is about 0.1 and 3 times.
FIG. 14 is a graph comparing the graininess of images formed by changing the carrier particle size into three types of 40 [μm], 60 [μm], and 80 [μm]. This graininess is shown by ranks from 0 to 5, and the higher the rank, the better the dot reproducibility on the image, and the lower the rank, the worse the dot reproducibility. From this figure, a (particle size 80 [μm]) is rank 2, b (particle size 60 [μm]) is rank 3, c (particle size 40 [μm]) is rank 4, and the smaller the particle size, the more dots It can be seen that the reproducibility is good.
For this reason, the use of a carrier having a particle size of 60 [μm] or less is effective for improving the image quality.

  The process cartridge integrated with the developing device 4 and the photosensitive drum 1 may be configured to be detachable from the printer 100 main body. By allowing the photosensitive drum 1 and the developing device 4 to be integrated into the printer 100 as a process cartridge, the positions of the photosensitive drum 1 and the developing sleeve 43 are determined within the process cartridge. Therefore, a minute gap can be easily formed between the photosensitive drum 1 and the developing sleeve 43. Further, if the developing device 4 is replaced at the same time as the photosensitive drum 1, it is not necessary to adjust the gap every time the developing device 4 is mounted, so that the user can easily replace it. The process cartridge in which the photosensitive drum 1 and the developing device 4 are integrated has been described. However, the present invention is not limited to this, and the photosensitive member cleaning device 7, the charging device 2, and the like can also be integrated into a process cartridge.

The printer 100 has a plurality of grooves 43d extending in the longitudinal direction on the surface of a developing sleeve 43 as a developer carrying member that carries a developer on the surface and develops a latent image formed on the image carrier. The variation in the depth of the groove 43d is ± 30% or less. Therefore, it is possible to form a good image in which unevenness in the image density period is not noticeable using this developing sleeve.
In the developing sleeve 43, the depth of the groove 43d is 0.05 [mm] or more and 0.15 [mm] or less from the surface of the developing sleeve 43. Therefore, both the prevention of pitch unevenness and the developer conveyance performance can be achieved. As described with reference to FIG. 5, according to an experiment, when the depth of the groove 43d of the developing sleeve 43 as a developer carrying member is deeper than 0.15 [mm], the developer conveying performance is improved, but the pitch unevenness is increased. Will occur. The following can be considered as a cause of the occurrence of this pitch unevenness. If the depth of the groove 43d is deeper than 0.15 [mm], when the photosensitive drum 1 and the groove 43d of the developing sleeve 43 face each other in the developing area with the photosensitive drum 1, the photosensitive drum 1 and The developing electric field between the grooves 43d is weakened. As a result, it is considered that the developing ability is lowered, and the developing density is reduced on the photosensitive drum 1 in the portion facing the groove 43d. On the other hand, when the depth of the groove 43d of the developing sleeve 43 is shallower than 0.05 [mm], pitch unevenness does not occur, but the developer conveying performance is deteriorated. As a cause of the deterioration of the developer conveying performance, if the depth of the groove 43d is shallower than 0.05 [mm], the developer slips on the surface of the developing sleeve 43 or the developer is conveyed by the groove 43d. This is thought to be due to a decrease in the amount.
Further, in the developing sleeve 43 as the developer carrying member, the groove 43d has a V-shaped cross-sectional shape, so that the pitch non-uniformity can be more effectively prevented compared to the rectangular or U-shaped cross-sectional shape of the groove. . This is because in the case of a square or U-shaped groove, there is a step at the groove edge, so the groove suddenly becomes deeper, but since the V-shaped groove is slanted on the inner wall surface, the groove gradually increases from the edge to the bottom. Become deeper. Therefore, it is considered that when the groove of the developing sleeve is opposed to the photosensitive drum in the developing region, the magnitude of the developing electric field changes gently, and the difference in developing density becomes inconspicuous.
Further, in the developing device 4 having a developing sleeve 43 as a developer carrying member for carrying a developer on the surface and developing a latent image formed on the image carrier, a plurality of members extending in the longitudinal direction on the surface of the developing sleeve 43 are provided. The groove portion 43d has a depth variation of ± 30% or less. Therefore, it is possible to form a good image with less noticeable image density cycle unevenness using the developing device 4 including the developing sleeve 43.
Further, in the developing device 4, the depth of 43d in the groove is 0.05 [mm] or more and 0.15 [mm] or less from the surface of the developing sleeve 43 as the developer carrying member. Therefore, as described above, it is possible to achieve both the prevention of pitch unevenness and the developer conveyance performance.
In the developing device 4, a toner having a volume average particle size of 8.5 [μm] or less is used. Thereby, it is possible to form a high-quality image with good reproducibility while preventing pitch unevenness. In general, when an image is formed using a toner having a volume average particle size of 8.5 [μm] or less, the reproducibility of the image is remarkably improved, so that the pitch unevenness becomes conspicuous. However, the use of the developing sleeve 43 can prevent pitch unevenness.
In the developing device 4, the developer is a two-component developer composed of a toner and a carrier, and the volume average particle diameter of the carrier is 60 [μm] or less. As described above with reference to FIG. 14, according to the experiment, the dot reproducibility on the image is improved, so that a better image can be formed as compared with the case of using a larger particle size. It was.
Further, a charging device 2 as a charging unit for charging the surface of the photosensitive drum 1 as an image carrier, and an exposure device as a latent image forming unit for forming an electrostatic latent image on the photosensitive drum 1. 3 and a printer 100 which is an image forming apparatus having a developing device 4 as a developing unit for developing an electrostatic latent image into a toner image, the developer is carried on the surface and formed on the photosensitive drum 1. The developing device 4 is configured by using the developing sleeve 43 as a developer carrying member for developing the latent image, and the developing sleeve 43 has a plurality of grooves extending in the longitudinal direction on the surface, and the depth of the plurality of grooves is The variation is ± 30% or less. Therefore, it is possible to form a good image in which unevenness in the image density is not noticeable using the developing sleeve 43.
Further, in the printer 100 as the image forming apparatus, the depth of the groove 43d is 0.05 [mm] or more and 0.15 [mm] or less from the surface of the developing sleeve 43 as the developer carrier. Therefore, as described above, it is possible to achieve both the prevention of pitch unevenness and the developer conveyance performance.
In the printer 100 as the image forming apparatus, the spatial frequency by the groove 43d of the developing sleeve 43 as the developer carrying member is 1.5 [cycle / mm] or more. Therefore, pitch unevenness can be made inconspicuous. In general, it is said that the naked eye has the strongest sensitivity at a pitch of about 1 [mm]. As described above with reference to FIG. 12, it has been found through experiments that the spatial frequency by the groove 43d of the developing sleeve 43 is 1.5 [cycle / mm] or more effective in preventing pitch unevenness. In this case, the pitch unevenness pitch on the image transferred from the photosensitive drum 1 to the recording paper corresponds to 0.66 [mm] or less. Here, the image on the photoconductive drum 1 is transferred onto the recording paper in a substantially intact form. Therefore, the spatial frequency is the number of times that the groove 43d of the developing sleeve 43 passes per 1 [mm] in the surface movement direction of the surface of the photosensitive drum 1.
In the printer 100 as the image forming apparatus, a toner having a volume average particle size of 8.5 [μm] or less is used as a developer. Therefore, as described above, it is possible to form a high-quality image with good reproducibility while preventing pitch unevenness.
In the printer 100 as the image forming apparatus, the developer is a two-component developer including a toner and a carrier, and the volume average particle diameter of the carrier is 60 [μm] or less. Therefore, since the dot reproducibility on the image is improved, a better image can be formed as compared with the case where a larger particle size is used.

The printer 100 has a plurality of grooves 43d extending in the longitudinal direction on the surface of a developing sleeve 43 as a developer carrying member for carrying a developer on the surface and developing a latent image formed on the image carrier. The variation in the depth of the groove 43d is ± 30% or less. Therefore, it is possible to form a good image in which unevenness in the image density period is not noticeable using this developing sleeve.
In the developing sleeve 43, the depth of the groove 43d is 0.05 [mm] or more and 0.15 [mm] or less from the surface of the developing sleeve 43. Therefore, both the prevention of pitch unevenness and the developer conveyance performance can be achieved. As described with reference to FIG. 5, according to an experiment, when the depth of the groove 43d of the developing sleeve 43 as a developer carrying member is deeper than 0.15 [mm], the developer conveying performance is improved, but the pitch unevenness is increased. Will occur. The following can be considered as a cause of the occurrence of this pitch unevenness. If the depth of the groove 43d is deeper than 0.15 [mm], when the photosensitive drum 1 and the groove 43d of the developing sleeve 43 face each other in the developing area with the photosensitive drum 1, the photosensitive drum 1 and The developing electric field between the grooves 43d is weakened. As a result, it is considered that the developing ability is lowered, and the developing density is reduced on the photosensitive drum 1 in the portion facing the groove 43d. On the other hand, when the depth of the groove 43d of the developing sleeve 43 is shallower than 0.05 [mm], pitch unevenness does not occur, but the developer conveying performance is deteriorated. As a cause of the deterioration of the developer conveying performance, if the depth of the groove 43d is shallower than 0.05 [mm], the developer slips on the surface of the developing sleeve 43 or the developer is conveyed by the groove 43d. This is thought to be due to a decrease in the amount.
Further, in the developing sleeve 43 as the developer carrying member, the cross-sectional shape of the groove 43d is substantially V-shaped, so that the cross-sectional shape of the groove can prevent pitch unevenness more effectively than the rectangular shape or the U-shape. it can. This is because in a rectangular or U-shaped groove, there is a step at the groove edge, so the groove suddenly becomes deeper. However, a substantially V-shaped groove has a slanted inner wall surface, so the groove extends from the edge to the bottom. Gradually deepens. Therefore, it is considered that when the groove of the developing sleeve is opposed to the photosensitive drum in the developing region, the magnitude of the developing electric field changes gently, and the difference in developing density becomes inconspicuous.
Further, in the developing device 4 having a developing sleeve 43 as a developer carrying member for carrying a developer on the surface and developing a latent image formed on the photosensitive drum 1 as an image carrier, The surface has a plurality of grooves 43d extending in the longitudinal direction, and the variation in the depth of the grooves 43d is ± 30% or less. Therefore, it is possible to form a good image with less noticeable image density cycle unevenness using the developing device 4 including the developing sleeve 43.
Further, in the developing device 4, the depth of the groove 43d is 0.05 [mm] or more and 0.15 [mm] or less from the surface of the developing sleeve 43 as the developer carrier. Therefore, as described above, it is possible to achieve both the prevention of pitch unevenness and the developer conveyance performance.
Further, in the developing device 4, a toner having a volume average particle size of 8.5 [μm] or less is used as a developer. Thereby, it is possible to form a high-quality image with good reproducibility while preventing pitch unevenness. In general, when an image is formed using a toner having a volume average particle size of 8.5 [μm] or less, the reproducibility of the image is remarkably improved, so that the pitch unevenness becomes conspicuous. However, the use of the developing sleeve 43 can prevent pitch unevenness.
In the developing device 4, the developer is a two-component developer composed of a toner and a carrier, and the volume average particle diameter of the carrier is 60 [μm] or less. As described above with reference to FIG. 14, according to the experiment, the dot reproducibility on the image is improved, so that a better image can be formed as compared with the case of using a larger particle size. It was.

  As described with reference to FIG. 10, by making the shape of the groove 43 d V-shaped, it is possible to reduce pitch unevenness as compared with a square or U-shaped shape. However, when image formation was performed using the developing sleeve 43, which is a developer carrying member having a plurality of V-shaped groove portions 43d, the image density decreased over time. The inventors of the present invention have observed the groove 43d of the developing sleeve 43 after performing the image forming operation with a microscope, and have confirmed that the developer particles are sandwiched between the wedge-shaped tips of the V-shaped bottom. It has been found that the developer particles are sandwiched between the wedge-shaped bottom portions of the V-shaped groove 43d, whereby the developer transportability is lowered, and the image density is lowered with time.

[Comparative Example 1]
Hereinafter, as Comparative Example 1, a conventional configuration in which the shape of the groove portion 43d of the developing sleeve is V-shaped will be described.
FIG. 15 is an enlarged explanatory view of the groove portion of Comparative Example 1 in which the shape of the groove portion 43d of the developing sleeve 43 is a simple V-shape. As shown in FIG. 15, in the V-shaped groove 43d, the developer particles 40 come into contact with the two groove side surfaces 43s at the wedge-shaped bottom, and are easily stabilized in a sandwiched state. The developer particles 40 that are stable while being sandwiched between the wedge-shaped bottom portions stay in the grooves 43d, leading to a decrease in developer transportability. If the groove 43d has a V-shape, it is advantageous for suppressing the occurrence of pitch unevenness, but the bottom part is wedge-shaped, so that the developer particles are likely to be caught and cause a decrease in image density over time. It was. Note that the developer used in Embodiment 1 is a two-component developer composed of toner and carrier, and both the toner and the carrier may be sandwiched between the wedge-shaped bottom portions of the groove 43d. A carrier made of a hard material is more likely to get caught in a soft groove made of aluminum or the like, and the influence on the decrease in the fluidity of the developer is greater when the carrier is caught.

[Comparative Example 2]
Next, as the shape of the groove 43d for preventing the developer particles 40 from being clogged in the V-shaped groove 43d, the shape of the groove 43d is substantially V-shaped, and the bottom thereof is not wedge-shaped but the particle diameter of the developer. A comparative example 2 that adopts a planar shape having a large width will be described. FIG. 16 shows that when the particle diameter of the developer particles is d0, the width W is
d0 <W
It is a groove part expansion explanatory drawing explaining the shape of the groove part 43d of the comparative example 2 which provided the plane bottom part 43b which satisfy | fills. Note that developer particles 40 in the figure are carrier particles of a two-component developer. As shown in FIG. 16, since the width W of the flat bottom portion 43b is larger than the particle size d0 of the developer particles 40, the developer particles 40 are in contact with only one of the two groove side surfaces 43s. It is not sandwiched between the two groove side surfaces 43s. Thus, since the developer particles 40 are not sandwiched between the two groove side surfaces 43s at the wedge-shaped bottom of the groove 43d, the occurrence of developer clogging can be suppressed as compared with the comparative example 1 shown in FIG.

However, even with the developing sleeve 43 having the groove portion 43d having the shape of the comparative example 2 described with reference to FIG. 16, the developer clogging in the groove portion 43d could not be completely suppressed.
Hereinafter, a mechanism in which the developer particles 40 are clogged in the groove 43d having the shape of Comparative Example 2 will be described.
FIG. 17 is an enlarged explanatory view of a groove portion illustrating a state in which three developer particles 40 are sandwiched between the bottom portions of the groove portions 43d as an example in which the developer particles 40 are clogged in the groove portions 43d having the shape described in the second comparative example. 17A is a top view of the state in which the developer particles 40 are sandwiched as viewed from the opening direction of the groove 43d, and FIG. 17B is a view in which the grooves 43d in which the developer particles 40 are sandwiched are formed in the developing sleeve. It is the side view seen from the rotating shaft direction of 43. The carrier diameter has variations in range, and it is sufficiently assumed that large and small carriers are sandwiched as shown in FIG.

  As shown in FIG. 17A, developer particles A, B, and C are in contact with each other at contact points AB, BC, and AC, respectively. Further, the contact points As, Bs, and Cs are in contact with the two groove side surfaces 43s. As described above, when the three particles are in contact with the groove side surface 43s, pressed against each other, and balanced, the degree of freedom of movement in the parallel direction with respect to the flat bottom portion 43b is reduced. Furthermore, in practice, such a combination of three developer particles is continuously generated in the longitudinal direction of the groove 43d, the particles are pressed against each other, and the degree of freedom of movement of the developer particles in the longitudinal direction of the groove 43d is small. Become.

  Further, as shown in FIG. 17B, the developer particles A, B, and C are in contact with the flat bottom portion 43b at contact points Ab (not shown), Bb, and Cb, respectively. When the developer particles are in contact with the flat bottom portion 43b as described above, there is a degree of freedom in moving the groove 43d in the opening direction (upward in the figure), but there is no degree of freedom in movement in the bottom direction. When the developer particles further enter from the opening direction, the degree of freedom of movement in the direction of the opening is reduced, and the degree of freedom of movement in the direction perpendicular to the flat bottom portion 43b is also reduced. And since it is in the state which is in contact with and supported by the flat bottom part 43b, even if the balance of the force applied from an opening part direction changes, it is hard to move to a perpendicular direction with respect to the flat bottom part 43b.

As described above, even when the flat bottom portion 43b having a width larger than the developer particle diameter is provided, the degree of freedom of movement is reduced both in the horizontal direction and in the vertical direction with respect to the flat bottom portion 43b. May be balanced and stable in the state shown in FIGS. 17A and 17B, and may be in a state where it does not move by being sandwiched by the groove 43d.
Further, when developer particles are clogged in a part of the groove 43d, the developer particles are also easily clogged around the groove 43d, leading to deterioration of developer fluidity over time.

In the groove portion 43d having the shape of Comparative Example 1, since one developer particle can come into contact with the two groove side surfaces 43s, the developer particle may be balanced and stabilized in the groove portion 43d. Developer clogging at 43d occurred.
Further, in the groove portion 43d having the shape of Comparative Example 2, one developer particle can come into contact with the two surfaces of the groove side surface 43s and the flat bottom portion 43b, so that a plurality of developer particles are pressed against each other. The groove 43d may be balanced and stable, and the developer clogged in the groove 43d.

[Example 1]
Next, as a shape of the groove 43d for preventing the developer particles 40 from being clogged in the V-shaped groove 43d, Example 1 in which the shape of the groove 43d is substantially V-shaped and the bottom of the groove 43d is arcuate. explain.
In FIG. 18, when the radius of the developer particle is d1, the radius r1 is
d1 <r1
It is a groove part expansion explanatory drawing explaining the shape of the groove part 43d of Example 1 which provided the circular arc-shaped bottom part 43c which satisfy | fills. Note that the developer particles 40 in the figure are carriers of a two-component developer.
As shown in FIG. 18, since the radius r1 of the arc-shaped bottom 43c is larger than the radius d1 of the developer particle 40, the developer particle 40 is in contact with only one of the two groove side surfaces 43s. Like Example 1, it is not pinched by two groove part side surfaces 43s. Accordingly, since the developer particles 40 are not sandwiched between the two groove side surfaces 43s at the wedge-shaped bottom of the groove 43d, the occurrence of developer clogging can be suppressed as compared with the comparative example 1 shown in FIG.

Next, consideration will be given to the fact that the plurality of developer particles described in Comparative Example 2 are balanced against each other and cause developer clogging.
FIG. 19 is an enlarged explanatory view of a groove portion for explaining a state in which three developer particles are sandwiched in the groove portion 43d of the configuration of Example 1, similarly to the case where the developer clogging occurs in Comparative Example 2. 19A is a top view of the state in which the developer particles are sandwiched as viewed from the direction of the opening of the groove 43d, and FIG. 19B is a view of the grooves 43d in which the developer particles are sandwiched in the developing sleeve 43. It is the side view seen from the rotating shaft direction.
As shown in FIG. 19A, the developer particles A ′, B ′, and C ′ are in contact with each other at the contact points A′B ′, B′C ′, and A′C ′, respectively. Furthermore, the contact points A ′s, B ′s, and C ′s are in contact with the two groove side surfaces 43s. Thus, when the three particles are in contact with the groove side surface 43s, pressed against each other, and balanced, the degree of freedom of movement in the direction parallel to the plane shown in FIG. Get smaller. Furthermore, in practice, such a combination of three developer particles is continuously generated in the longitudinal direction of the groove 43d, the particles are pressed against each other, and the degree of freedom of movement of the developer particles in the longitudinal direction of the groove 43d is small. Become.

On the other hand, as shown in FIG. 19B, unlike Comparative Example 2, the developer particles A ′, B ′ and C ′ are grooves 43d at points other than the contact points A ′s, B ′s and C ′s. There is no contact with the inner wall. Then, in a state where a plurality of developer particles are gathered and pressed and balanced, as shown in FIG. 19B, the developer particles are in a state of floating in the hollow, so the particles are unstable. The freedom of movement is great. That is, even when a plurality of developer particles are sandwiched between the two groove side surfaces 43s and the pressing force between the particles is balanced, it is easy to escape toward the bottom, which is hollow. Under the situation where the developing sleeve 43 rotates, the balance is easily lost even if the developing sleeve 43 is in a balanced state due to vibration during rotation and shocks of starting and stopping.
In this way, by forming the bottom of the substantially V-shaped groove 43d in an arc shape larger than the radius of the developer, even if a plurality of developers are sandwiched between the grooves 43d, the groove is not stabilized as it is. It is possible to more reliably prevent developer clogging at 43d.

In Example 1, the case where the developer particle 40 is the carrier of the two-component developer and the radius d1 is the radius of the carrier was studied. When the two-component developer is used, the actual carrier on the developing sleeve 43 is in a state where the surface thereof is covered with toner particles. When the radii of the toner particles and the carrier particles are compared, the radius of the carrier particles is sufficiently larger. Further, the carrier is made of a material harder than the toner particles, such as magnetite, iron or ferrite.
The toner particles are softer than the carrier particles and easily deform. As for developer clogging when using a two-component developer, carrier particles of high hardness made of magnetite, iron, ferrite, etc. are eroded into the groove portion of the high development sleeve made of aluminum or the like and cannot be removed in most cases. is there. Therefore, the carrier is actually covered with toner. However, as in the first embodiment, only the radius of the carrier is set to the radius d1, and d1 <r1 is satisfied to prevent most of the developer clogging. can do.

  As described above, if the radius r1 of the arc-shaped bottom 43c is larger than the radius of the carrier particles, most of the developer clogging can be prevented. However, the toner particles coated on the carrier particles may adhere firmly to the carrier particles due to spent or the like. In such a case, if the radius r1 of the arc-shaped bottom 43c is larger than the radius of the carrier particles, the developer particles 40 may be clogged in the groove 43d. Therefore, as the radius d1 of the developer particle 40, not only the carrier particle but also the toner particle covering the surface thereof is taken into consideration, and the radius d1 of the developer particle 40 is a size obtained by adding the diameter of the toner particle to the radius of the carrier particle. By doing so, it is possible to more reliably prevent the developer particles 40 from clogging the groove 43d.

The developer is not limited to the two-component developer as in Example 1, and can be applied even when a one-component developer is used. When the one-component developer is used, the radius d1 of the developer particle 40 is the radius of the toner particle.
In addition, the developer particle 40 is a carrier particle only, a carrier particle is covered with a toner particle, or a toner particle using a one-component developer. There are variations. Therefore, the radius r1 of the arc-shaped bottom 43c is preferably larger than the maximum radius d1 of the developer particles 40. Since the radius r1 of the arc-shaped bottom portion 43c is larger than the average value of the radii d1 of the developer particles 40, most of the developer particles 40 can be prevented from clogging in the groove portions 43d.
However, when the variation of the radius of the developer particles is large, even when the radius r1 of the arcuate bottom 43c is larger than the average value of the radii d1 of the developer particles 40, the developer particle whose radius is considerably larger than the average value. 40 may be included. If developer particles 40 having a radius d1 larger than the radius r1 of the arcuate bottom 43c are present, the developer particles 40 may be sandwiched in contact with both of the two groove side surfaces 43s of the groove 43d, and the developer may be clogged. Therefore, the radius r1 of the arc-shaped bottom 43c is larger than the maximum radius d1 of the developer particles 40 in the developer, so that the developer particles 40 can be more reliably prevented from clogging the groove 43d.

The carrier particles are substantially spherical, and the toner particles are often polymerized toner having a high sphericity in order to improve the image quality, and the shape thereof is substantially spherical. If the shape of the developer particles 40 is spherical, the radius r1 of the arc-shaped bottom 43c is made larger than the radius d1, thereby preventing the developer particles 40 from being clogged in the groove 43d.
Next, a description will be given of the case of using a non-spherical developer such as pulverized toner, in which the developer particles have irregularities on the surface and the outer diameter varies depending on the position to be measured. In the case where the developer particles are not spherical, a spherical shape having the longest outer diameter as a diameter, that is, a circumscribed sphere of developer particles, is considered in consideration of the convex portions on the uneven surface. The radius of the circumscribed sphere of developer particles that are not spherical is d1, and the radius r1 of the arc-shaped bottom 43c of the groove 43d satisfies r1> d1, thereby preventing the developer particles that are not spherical from clogging the groove 43d. be able to.

As described above, according to the first embodiment, the surface of the developing sleeve 43 as the developer carrying member has the groove portion 43d having a substantially V-shaped cross section extending in the longitudinal direction. When the cross-sectional shape of the groove 43d is substantially V-shaped, pitch unevenness on the image can be made inconspicuous. Further, the substantially V-shaped bottom of the groove 43d has an arcuate shape with a radius r1, and when the radius of the developer particle 40 is d1, the radius r1 of the arc-shaped bottom satisfies r1> d1. That is, the bottom of the substantially V-shaped groove 43 d has an arc shape having a radius larger than the radius of the developer particle 40. This is a groove 43d having such a shape that the inner wall of the groove 43d and the spherical surface of the developer particle 40 are in contact with each other only at one point. Since the spherical surface of the developer particle 40 contacts only at one point, even if the developer particle 40 is in contact with the groove side surface 43s or the arcuate bottom 43c which is the inner wall surface of the groove 43d, the developer particle 40 becomes unstable and moves. It becomes easy to do. As a result, the developer particles 40 are prevented from staying in the groove portions 43d, and the developer conveying ability of the developing sleeve 43, which is a developer carrier, is reduced due to the developer particles 40 being clogged in the groove portions 43d. Can be prevented. Therefore, it is possible to suppress a decrease in image density due to the shape of the groove 43d of the developing sleeve 43 being a shape that can contact the spherical surface of the developer at two or more points.
Further, a two-component developer composed of toner and carrier is used as the developer, and the radius d1 of the developer particle 40 is the radius of the carrier particle. Since the carrier particles have a sufficiently large radius and sufficiently high hardness compared to the toner particles, most of the developer clogging can be prevented by preventing the carrier particles from clogging the groove 43d.
Further, the radius d1 of the developer particle 40 may be a size obtained by adding the diameter of the toner particle to the radius of the carrier particle. The carrier particles actually carried by the developing sleeve are coated with toner particles on the surface thereof. If the toner particles are continuously used, the toner particles coated on the carrier particles may adhere firmly to the carrier particles due to spent or the like. Even in such a case, it is assumed that the radius d1 of the developer particle 40 is obtained by adding the diameter of the toner particle to the radius of the carrier particle, and the radius r1 of the arc-shaped bottom portion satisfies d1 <r1, so that the developer clogging occurs. Occurrence can be prevented more reliably.
Further, it is preferable that the size of d1 that satisfies r1> d1 is the size of the radius of the largest developer particle 40 among the developer particles 40 included in the developer. When the radius of the arc-shaped bottom portion 43c is larger than the largest radius among the developer particles 40, the groove 43d can be more reliably prevented from being clogged with the developer particles 40.
Further, the printer 100 having the developing sleeve 43 as the developer carrying member provided with the groove portion 43d whose lower portion is the arcuate bottom portion 43c suppresses a decrease in image density due to the shape of the groove portion of the developer carrying member. be able to.
Since a decrease in image density can be prevented, stable image formation can be performed from the initial stage in which the developing sleeve 43 is used.

[Embodiment 2]
Next, a description will be given of another cause that causes a decrease in developer conveyance capability and a decrease in image density when the diameter of the conventional developer carrier is present, and Embodiment 2 that solves this.
Other than the shape of the groove 43d of the developing sleeve 43 is the same as that of the first embodiment, and a description thereof will be omitted.

When a conventional developer carrier is used, a phenomenon occurs in which the image density decreases from the initial stage when the developer is used. Hereinafter, the cause of the decrease in image density that occurs from the initial stage of use will be examined.
FIG. 20 shows changes in the number of sheets to be passed and the image density ID when an image is formed by using a developer carrier having a plurality of grooves proposed in Japanese Patent Laid-Open No. 15-255692 as a conventional developer carrier. It is a graph which shows. As can be seen from FIG. 20, when the conventional developer carrier is used, the image density starts to decrease from the initial stage when it is used, and after 1000 sheets of A4 paper is passed, the image density is the initial stage when it is used. Stable at a lower concentration than the step. Further, the density at which the image density is stable is lower than the target density indicated by the broken line in the figure. FIG. 21 shows changes in the amount of developer (hereinafter referred to as “pumping amount”) on the developer carrying member at this time. Since the graph of FIG. 21 has the same shape as the graph of FIG. 20, it can be seen that the decrease in the image density is caused by the decrease in the pumping amount.

  When the groove portion on the developer carrying member at this time was observed with a microscope, the progress of wear was observed at the groove edge portion which is the boundary between the surface of the developer carrying member and the groove portion. FIG. 22 is an enlarged explanatory view of the groove for explaining the progress of the wear. 22A shows the state of the groove 43d at the initial stage of use, FIG. 22B shows the state of the groove 43d after passing 5000 sheets of A4 paper, and FIG. 22C shows 10000 sheets of A4 paper. It is a groove part expansion explanatory drawing explaining the state of the groove part 43d after paper passing. As shown in FIG. 22A, the groove edge portion 43e, which is the boundary between the groove portion side surface 43s of the groove portion 43d and the developing sleeve surface 43f at the initial stage of use, has a square shape. When 5000 sheets of A4 paper were passed, it was confirmed that the groove edge portion 43e, which was square at the beginning of use, had a rounded shape as shown in FIG. 22 (b). Furthermore, when 10,000 sheets of A4 paper are passed, the rounded radius of the groove edge portion 43e is R, as shown in FIG. It was. Further, even when A4 sheets were further passed through and 10,000 sheets or more were passed, the radius of the roundness of the groove edge portion 43e remained R and remained unchanged.

  Next, in order to examine the relationship between the radius of the developer particles and the radius R of the rounded edge after wear of the groove edge portion 43e, an image is formed when several sheets of developer are used to form 10,000 or more sheets. The radius R was measured. In addition, as a kind of the developer, not only those having different particle diameters but also those using a one-component developer and those using a two-component developer were examined. Table 1 shows the toner radius and carrier radius of the verified developer.

  Next, the relationship between the radius of the developer and the size of the radius R is shown in FIG. In FIG. 23, the radius of the developer is the radius of the toner if it is a one-component developer, and the radius of a carrier that is a magnetic particle if it is a two-component developer. From Table 1 and FIG. 23, it can be seen that the radius of the developer and the radius R of the rounded groove edge portion 43e are substantially equal.

[Example 2]
Next, the shape of the groove 43d that prevents the developer carrying capacity of the developer carrying member from being lowered and the image density from being lowered due to wear of the groove edge 43e will be described. FIG. 24 is an enlarged explanatory view of the groove portion for explaining the shape of the groove portion 43d on the surface of the developing sleeve 43 that is the developer carrying member according to the second embodiment.
In FIG. 24, when the radius of the developer particle is d2, the radius r2 of the roundness of the groove edge portion 43e is
d2 <r1
It is a groove part expansion explanatory drawing explaining the shape of the groove part 43d which satisfy | fills.
Since the roundness of the groove edge portion 43e is a radius r2 larger than the radius d2 of the developer particles, wear does not occur from the initial stage of use and stable developer conveyance is possible. As a result, it is possible to prevent the developer carrying capacity of the developer carrying member from being lowered and the image density from being lowered due to wear of the groove edge portion 43e.
Since the groove edge portion 43e is rounded, the amount of developer that can be carried on the developing sleeve 43 is smaller than that in which the groove edge portion 43e is square. Therefore, by adjusting before shipment so that a desired image density can be obtained in a rounded state, a stable image density can be obtained from the initial stage of use.
In the case of using a developer of two or more components comprising toner and carrier, and further additives, the radius of the largest particle size (usually carrier) is defined as d2.
Further, as described in the prior art, the method of rounding the groove edge portion 43e with the radius r2 is to round the aluminum tube pushed out on the sleeve at a high temperature and form a groove by a die. There is a way. Further, it is possible to form a groove and roundness at the same time as the extrusion.

  As described above, according to the second embodiment, d2 <r2 at the groove edge portion 43e that is the boundary between the developing sleeve surface 43f of the developing sleeve 43 that is the developer carrying member and the groove portion 43d when the radius of the developer particles is d2. And a rounded portion with a radius r2 is provided. In other words, the conventional groove portion 43d is rounded in advance by the amount of wear of the groove edge portion 43e that has occurred since the beginning of use. As a result, it is possible to prevent a decrease in the developer conveying ability of the developing sleeve 43 due to a change in the shape of the groove edge portion 43e, and the shape of the groove portion 43d of the developing sleeve 43 is the same as that of the groove edge portion 43e. It is possible to suppress a decrease in image density due to the shape that is worn by rubbing. Then, by setting an image forming condition suitable for a shape in which the groove edge portion 43e is rounded, stable image formation can be performed from the initial stage of using the developing sleeve 43.

[Modification 1]
As shown in FIG. 22, when the groove edge portion 43e has a square shape, the wear of the groove edge portion 43e on the upstream side in the surface movement direction of the developing sleeve 43 indicated by the arrow α in the drawing is significant for one groove portion 43d. It was. Hereinafter, Modification 1 in which only the groove edge portion 43e on the upstream side in the surface moving direction of the developing sleeve 43 is rounded with the radius r2 will be described. As in Example 3, the radius r2 satisfies d2 <r2 when the radius of the developer particles is d2.
FIG. 25 is an enlarged explanatory view of the groove 43d of the developing sleeve 43 according to the first modification. 24 is different from the third embodiment described with reference to FIG. 24 in that only the groove edge portion 43e on the upstream side in the surface movement direction of the developing sleeve 43 is rounded. This makes it possible to reduce the number of places to be rounded, and to reduce the number of places to be managed with high accuracy compared to the case where both of the two groove edge portions 43e are rounded, making it easy to create. become. And it becomes easy to create, leading to cost reduction.

In the third embodiment and the first modification described above, the configuration in which the groove edge portion 43e of the groove portion 43d having a V-shaped cross section is rounded has been described, but the cross sectional shape of the groove portion is not limited thereto. For example, the present invention may be applied to a groove having a cross-sectional shape shown in FIGS.
Furthermore, it can be applied to the groove edge portion of the groove portion 43d having a substantially V-shaped cross-section and an arc-shaped bottom portion as described in the first embodiment. Therefore, it is possible to prevent a decrease in image density and a decrease in image density due to wear of the groove edge portion, and further stable image formation can be performed.

1 is a schematic configuration diagram of a main part of a printer according to an embodiment. The block diagram of a developing device. The partial cross-section enlarged view which looked at the developing sleeve from the axial direction. Explanatory drawing of the pitch nonuniformity on a recording paper. The graph which shows the experimental result of the pitch nonuniformity with respect to a groove depth, and a developer conveyance performance. FIG. 3 is an explanatory diagram of image density cycle unevenness on recording paper. 6 is a graph showing the relationship between the groove depth of the developing sleeve, the developer pumping amount, and the image density. Explanatory drawing which showed typically the dispersion | variation in the groove depth of a developing sleeve. Explanatory drawing which formed the V-shaped groove | channel in the developing sleeve. The graph which shows the relationship between pitch irregularity, a square groove, a U-shaped groove, and a V-shaped groove. The graph which shows the relationship between the opening angle of a V-shaped groove | channel, pitch nonuniformity, and a developer conveyance performance. The graph which shows the relationship between a spatial frequency and pitch nonuniformity. 6 is a graph showing the relationship between the volume average particle diameter of toner and pitch unevenness. The graph which compared the granularity of the image by the particle size of a magnetic particle. The groove part expansion explanatory drawing which concerns on the comparative example 1. FIG. The groove part expansion explanatory drawing which concerns on the comparative example 2. FIG. (A) of the groove part which concerns on the comparative example 2 is a top view, (b) is a side view. The groove part expansion explanatory drawing which concerns on Example 1. FIG. (A) of the groove part which concerns on Example 1 is a top view, (b) is a side view. The graph which shows the relationship between the sheet passing number in the groove part of the conventional shape, and the change of a density | concentration. The graph which shows the number of paper passing in the groove part of the conventional shape, and the change of the amount of pumping. FIG. 6 is an enlarged explanatory view of a groove portion according to Comparative Example 3, where (a) shows the initial use of the developing sleeve, (b) after 5000 sheets have passed, and (c) after 10,000 sheets have passed. The graph which shows the relationship between the radius of the particle | grains of a developer, and the radius of roundness of the groove | channel edge part which was worn out. The groove part expansion explanatory drawing which concerns on Example 2. FIG. The groove part expansion explanatory drawing which concerns on the modification 1. FIG. The groove part cross-section example which can apply the structure which gives a groove edge part roundness beforehand.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Photosensitive drum 2 Charging apparatus 3 Exposure apparatus 4 Developing apparatus 5 Transfer apparatus 6 Recording paper 7 Cleaning apparatus 8 Static elimination lamp 9 Optical sensor 10 CPU
41 developing roller 43 developing sleeve 43b flat bottom 43c arcuate bottom 43d groove 43e groove edge 43f developing sleeve surface 43s groove side 44 magnet roller body 45 doctor blade

Claims (10)

In the developer carrying member for carrying the developer on the surface and developing the latent image formed on the image carrying member,
A plurality of grooves having a substantially V-shaped cross section extending in the longitudinal direction on the surface of the developer carrying member;
The substantially V-shaped bottom of the groove has an arc shape with a radius r1,
When the radius of the developer particles is d1,
The radius r1 is
A developer carrier characterized by satisfying r1> d1. The developer carrier of claim 1,
The developer is a two-component developer composed of toner and magnetic particles,
The developer carrying member, wherein the radius d1 is a radius of the magnetic particles. The developer carrier of claim 1,
The developer is a two-component developer composed of toner and magnetic particles,
The developer carrying member according to claim 1, wherein the radius d1 is a size obtained by adding the diameter of the toner to the radius of the magnetic particles. The developer carrying member according to any one of claims 1 to 3,
The developer carrier according to claim 1, wherein a radius d1 of the developer particles is a maximum particle radius of the developer. In the developer carrying member for carrying the developer on the surface and developing the latent image formed on the image carrying member,
A plurality of grooves extending in the longitudinal direction on the surface of the developer carrying member;
A rounded portion with a radius r2 is provided at the boundary between the surface portion of the developer carrying member and the groove portion,
When the radius of the developer particles is d2,
A developer carrying member, wherein r2> d2. In the developer carrier of claim 5,
Of the two boundary portions between one of the groove portions and the surface portion of the developer carrying member,
A developer carrier, wherein the rounded portion is provided only at the boundary portion on the upstream side in the surface movement direction of the developer carrier. The developer carrying member according to claim 5 or 6,
The developer is a two-component developer composed of toner and magnetic particles,
The developer carrying member, wherein the radius d2 is a radius of the magnetic particles. A developer accommodating portion for accommodating the developer;
In a developing device having a developer carrier for developing a latent image formed on an image carrier with the developer,
A developing device using the developer carrying member according to claim 1, 2, 3, 4, 5, 6 or 7 as the developer carrying member. At least a process cartridge in which an image carrier and a developing unit for developing a latent image on the image carrier are integrally supported and configured to be detachable from the image forming apparatus main body.
9. A process cartridge using the developing device according to claim 8 as the developing means. Charging means for charging the surface of the image carrier;
Latent image forming means for forming an electrostatic latent image on the image carrier;
In an image forming apparatus having a developing means for developing the electrostatic latent image into a toner image using a developer carrying member carrying a developer on its surface,
An image forming apparatus using the developer carrying member according to claim 1, as the developer carrying member.

Images