JP2008020862A - Developing roller, developing device, and image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a developing roller which carries an optimum amount of toner and prevents an electrostatic charge defect. <P>SOLUTION: In the developing roller, a plurality of first grooves formed at approximately equal intervals in a direction oblique to a circumferential direction and a plurality of second grooves formed in parallel to each other and at approximately equal intervals in a direction oblique to the circumferential direction, and intersecting with each first groove, are formed. Cross sections of the first grooves and the second grooves are formed in U shapes respectively and projecting parts whose top surfaces surrounded by the first grooves and the second grooves are approximately planes. When the width of the first first grooves is defined as A1, the width of the second grooves as B1, the length of the top surfaces parallel to the second grooves of the projecting parts as C1, and the length of the top surfaces parallel to the first grooves of the projecting parts as C2, relationships of A1>C1 and B1>C2 are satisfied and when the maximum depth of the first grooves is defined as D1, and the maximum depth of the second grooves as D2, D1 and D2 are 0.5 to 2 times the average grain size of the toner particles, respectively. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a developing roller, a developing device, and an image forming apparatus.

An image forming apparatus such as a copy or printer that employs an electrophotographic system is made of toner on a recording medium such as paper through a series of image forming processes such as a charging process, an exposure process, a developing process, a transfer process, and a fixing process. Form an image.
In the development process, for example, a charged toner is applied from the developing roller to the latent image in a state where the developing roller that carries the toner is brought into contact with the photosensitive member that carries the electrostatic latent image, and the latent image is converted into the toner image. Visualize as.

2. Description of the Related Art Conventionally, a developing roller (coating rod) as described in Patent Document 1 is known as one that applies (applies) a powdery material such as toner.
As shown in FIG. 8A, the conventional coating rod 100 has a substantially cylindrical shape. A plurality of first grooves 101 parallel to each other and a plurality of second grooves 102 parallel to each other provided so as to intersect with these first grooves 101 are provided on the outer periphery of the coating rod 100. Are formed, and a large number of lattice-shaped convex portions 103 partitioned by a first groove 101 adjacent to each other and a second groove 102 adjacent to each other are formed (FIG. 8B and FIG. c)). And the cross-sectional shape of a groove | channel (the 1st groove | channel 101 and the 2nd groove | channel 102) has made V shape, and the depth is equal in each part of a groove | channel (refer FIG.8 (c)).
However, in the developing roller having such a configuration, when the toner is held, the amount of the toner to be held is too large, and charging failure, toner leakage from the cartridge, and unevenness in density occur in the image.

JP 2002-301411 A

  An object of the present invention is to provide a developing roller that carries an optimal amount of toner and prevents charging failure, a developing device including the developing roller, and an image forming apparatus including the developing roller.

Such an object is achieved by the present invention described below.
The developing roller of the present invention is a developing roller for holding toner on the outer periphery,
A plurality of first grooves that are parallel to each other and formed at substantially equal intervals in a direction inclined with respect to the circumferential direction of the outer peripheral portion of the developing roller, and parallel to each other and the circumference of the outer peripheral portion of the developing roller A plurality of second grooves that are formed at substantially equal intervals in a direction inclined with respect to the direction and intersect with the first grooves,
Each of the first groove and the second groove has a U-shaped cross section,
A convex portion having a substantially flat top surface is provided in a region surrounded by the first groove and the second groove,
The width of the first groove is A ₁ , the width of the second groove is B ₁ , and the length of the top surface in the direction parallel to the second groove passes through the center of the top surface of the convex portion. C ₁ , when the length of the top surface in the direction parallel to the first groove passing through the center of the top surface of the convex portion is C ₂ , A ₁ > C ₁ and B ₁ > C ₂ Satisfy the relationship
When the maximum depth of the first groove is D ₁ and the maximum depth of the second groove is D ₂ , D ₁ and D ₂ are 0.5 to 2 of the average particle diameter of the toner particles, respectively. It is characterized by being double.

  Accordingly, since the first groove and the second groove are provided, an optimal amount of toner can be conveyed. Therefore, toner leakage from the cartridge can be prevented. At this time, since the grooves are U-shaped and the width and depth of the grooves satisfy a predetermined relationship, the toner can roll smoothly and the toner contacts the outer peripheral surface of the developing roller. Therefore, it can be charged uniformly. Therefore, it is possible to suppress fogging and print a high-quality image.

In the developing roller of the present invention, the A ₁ and B ₁ are preferably 1.2 to 9 times the average value of the C ₁ and C ₂ , respectively.
As a result, an appropriate amount of toner can be conveyed, and the chargeability of the toner can be improved.
In the developing roller of the present invention, it is preferable that A ₁ and B ₁ are 50 to 90% of a separation distance between the adjacent convex portions.
As a result, the toner is reliably accommodated in the groove, and an appropriate amount of toner can be conveyed.

In the developing roller of the present invention, it is preferable that the curvature radius of the bottom surface of the first groove and the second groove is 0.6 to 10 times the average particle diameter of the toner particles.
As a result, the toner smoothly rolls at the bottom of the groove without the toner being stacked, so that the chargeability of the toner can be improved.
In the developing roller of the present invention, it is preferable that the distance between the adjacent convex portions is 50 to 100 μm.
Thereby, an appropriate amount of convex portions can be set on the outer peripheral surface of the developing roller. Therefore, the toner can be improved in chargeability by rolling the toner from the groove to the convex portion and from the convex portion to the groove.

In the developing roller of the present invention, the area ratio occupied by the first groove and the second groove on the outer peripheral surface of the developing roller is preferably 40 to 90% of the area of the outer peripheral surface.
Thereby, an appropriate amount of convex portions can be set on the outer peripheral surface of the developing roller. Therefore, the toner can be improved in chargeability by rolling the toner from the groove to the convex portion and from the convex portion to the groove.
In the developing roller of the present invention, it is preferable that at least an outer peripheral portion of the developing roller is made of a metal material.
Thereby, for example, when the groove is formed in the outer peripheral portion of the developing roller by rolling (transfer method), the groove can be easily and reliably formed.

The developing device of the present invention includes the developing roller of the present invention.
Thereby, a highly reliable developing device can be obtained.
The image forming apparatus of the present invention includes the developing device of the present invention.
Thereby, a highly reliable image forming apparatus can be obtained.

DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, preferred embodiments of a developing roller, a developing device, and an image forming apparatus according to the invention will be described with reference to the accompanying drawings.
<First Embodiment>
FIG. 1 is a schematic cross-sectional view showing a schematic configuration of an image forming apparatus (first embodiment) of the present invention, and FIG. 2 is a schematic cross-sectional view showing a schematic configuration of a developing device (first embodiment) of the present invention. It is. In the following description, the upper side in the figure is referred to as “upper” and the lower side is referred to as “lower”.

(Image forming device)
First, a laser beam printer (hereinafter simply referred to as “printer”) 10 as an example of an image forming apparatus will be described with reference to FIG.
As shown in FIG. 1, the printer 10 has a photoreceptor 20 that carries a latent image and rotates in the direction of the arrow in the figure, and along the rotation direction (clockwise), a charging unit 30, an exposure unit 40, and a development unit. 50, a primary transfer unit 60, an intermediate transfer body 70, and a cleaning unit 75 are arranged in this order. In addition, the printer 10 has a paper feed tray 92 that feeds a recording medium P1 such as paper at the lower part of FIG. 1, and the secondary from the paper feeding tray 92 toward the downstream in the transport direction of the recording medium P1. A transfer unit 80 and a fixing unit 90 are sequentially arranged.

The photoreceptor 20 has a cylindrical conductive substrate and a photosensitive layer formed on the outer peripheral surface thereof, and is rotatable around the axis in the arrow direction (clockwise direction) in FIG. The charging unit 30 is a device for uniformly charging the surface of the photoreceptor 20 by corona charging or the like.
The exposure unit 40 receives image information from a host computer such as a personal computer (not shown), and irradiates the uniformly charged photoconductor 20 with a laser beam in a desired pattern in accordance with the image information. This is an apparatus for carrying (forming) an electrostatic latent image (electrostatic latent image) on the outer peripheral surface.

  The developing unit 50 has four developing devices, a black developing device 51, a magenta developing device 52, a cyan developing device 53, and a yellow developing device 54, and selects these developing devices corresponding to the latent image on the photoconductor 20. In particular, the latent image is visualized as a toner image on the photoconductor 20. The black developing device 51 uses black (K) toner, the magenta developing device 52 uses magenta (M) toner, the cyan developing device 53 uses cyan (C) toner, and the yellow developing device 54 uses yellow (Y) toner. .

  The developing unit 50 in the present embodiment is rotatable so that the above-described four developing devices 51, 52, 53, and 54 can be selectively opposed to the photoreceptor 20 (in a predetermined order). . Specifically, in the developing unit 50, four developing devices 51, 52, 53, and 54 are respectively held by four holding portions 55a, 55b, 55c, and 55d of a holding body that can rotate around a shaft 50a. The rotation of the holder causes the developing devices 51, 52, 53, and 54 to selectively face the photoconductor 20 while maintaining their relative positional relationship. The detailed configuration of each developing device will be described later.

The primary transfer unit 60 is a device for transferring the toner image formed on the photoconductor 20 to the intermediate transfer body 70.
The intermediate transfer member 70 is composed of an endless belt, and is driven to rotate (circulate) in the direction of the arrow shown in FIG. On the intermediate transfer member 70, a toner image of at least one of black, magenta, cyan, and yellow is carried. For example, when a full-color image is formed, four color toner images of black, magenta, cyan, and yellow are sequentially formed. The toner images are transferred to form a full-color toner image.

The secondary transfer unit 80 is a device for transferring a single color or full color toner image formed on the intermediate transfer body 70 to a recording medium P1 such as paper, film, or cloth.
The fixing unit 90 is an apparatus for fixing the toner image as a permanent image by fusing the toner image on the recording medium P1 by heating and pressurizing the recording medium P1 that has received the transfer of the toner image.
The cleaning unit 75 has a rubber cleaning blade 76 that contacts the surface of the photoconductor 20 between the primary transfer unit 60 and the charging unit 30, and a toner image is transferred onto the intermediate transfer body 70 by the primary transfer unit 60. Then, the toner remaining on the photoreceptor 20 is scraped off and removed by the cleaning blade 76.

Next, the operation of the printer 10 configured as described above will be described.
First, in response to a command from a host computer (not shown), a developing roller 510 (see FIGS. 2 and 3) described later provided corresponding to the developing devices 51, 52, 53, and 54 of the photosensitive member 20 and the developing unit 50, Then, the intermediate transfer member 70 starts to rotate. The photoreceptor 20 is sequentially charged by the charging unit 30 by rotating.

The charged region on the photoconductor 20 reaches an exposure position facing the exposure unit 40 as the photoconductor 20 rotates, and the exposure unit 40 causes the latent image corresponding to the image information of the first color, for example, yellow Y. Is formed in the region.
The latent image formed on the photoconductor 20 reaches the developing position as the photoconductor 20 rotates, and is developed with yellow toner by the yellow developing device 54. As a result, a yellow toner image is formed on the photoreceptor 20. At this time, in the developing unit 50, the yellow developing device 54 faces the photoconductor 20 at the developing position (see FIG. 1).

  The yellow toner image formed on the photoconductor 20 reaches the primary transfer position as the photoconductor 20 rotates, and is transferred to the intermediate transfer body 70 by the primary transfer unit 60. Specifically, since the primary transfer unit 60 is applied with a primary transfer voltage (primary transfer bias) having a polarity opposite to the charging polarity of the toner, the primary transfer unit 60 is formed on the photoconductor 20 by the temporary transfer voltage. The yellow toner image is attracted to the intermediate transfer member 70. During this time, the secondary transfer unit 80 is separated from the intermediate transfer member 70.

The same processing as described above is repeatedly executed for the second color, the third color, and the fourth color, so that the toner images of the respective colors corresponding to the respective image signals are transferred onto the intermediate transfer body 70 in an overlapping manner. The As a result, a full-color toner image is formed on the intermediate transfer member 70.
On the other hand, the recording medium P 1 is conveyed from the paper feed tray 92 to the secondary transfer unit 80 by the paper feed roller 94 and the registration roller 96.

  The full-color toner image formed on the intermediate transfer member 70 reaches the secondary transfer position where the secondary transfer unit 80 is disposed as the intermediate transfer member 70 rotates, and is transferred to the recording medium P1 by the secondary transfer unit 80. Is done. Specifically, since the secondary transfer unit 80 is pressed against the intermediate transfer body 70 and a secondary transfer voltage (secondary transfer bias) is applied, the secondary transfer voltage is applied onto the intermediate transfer body 70 by the secondary transfer voltage. The formed full-color toner image is attracted and transferred to the recording medium P1 interposed between the intermediate transfer body 70 and the secondary transfer unit 80.

The full-color toner image transferred to the recording medium P1 is heated and pressed by the fixing unit 90 and fused onto the recording medium P1, thereby obtaining a fixed toner image.
On the other hand, after the primary transfer position has passed, the photoreceptor 20 is prepared for charging to form the next latent image by scraping off the toner adhering to the surface thereof by the cleaning blade 76 of the cleaning unit 75. The toner scraped off is collected by a residual toner collecting unit (not shown) in the cleaning unit 75.

(Developer)
Next, the developing devices 51, 52, 53, and 54 of the developing unit 50 will be described in detail. Since these devices have almost the same configuration, the yellow developing device 54 will be described as a representative based on FIG. To do.
A yellow developing device 54 shown in FIG. 2 includes a housing 540 that accommodates toner T, which is yellow toner, a developing roller 510 that is a toner carrier, a toner supply roller 550 that supplies toner T to the developing roller 510, and a developing roller. And a regulating blade 560 for regulating the layer thickness of the toner T carried on 510.

  The housing 540 stores the toner T in a storage portion 530 formed as an internal space thereof. In the housing 540, the toner supply roller 550 and the developing roller 510 are supported so as to be able to press and rotate with each other at an opening formed in the lower portion of the housing portion 530 and in the vicinity thereof. A regulating blade 560 is attached to the housing 540 and is in pressure contact with the developing roller 510. Further, a seal member 520 for preventing leakage of toner from between the housing 540 and the developing roller 510 in the opening is attached to the housing 540.

The developing roller 510 holds (carryes) the toner T on the outer peripheral portion, and applies the held toner T to the photoconductor 20, that is, conveys the held toner T to a developing position facing the photoconductor 20. To do. Further, the developing roller 510 is a cylindrical object that can rotate around an axis, and in this embodiment, rotates in a direction opposite to the rotation direction of the photoconductor 20.
In this embodiment, the developing roller 510 and the photoconductor 20 face each other in a non-contact state with a minute gap during development by the yellow developing device 54. Then, by applying an alternating electric field between the developing roller 510 and the photosensitive member 20 (hereinafter, this state is referred to as “electric field applying state”), the toner T is caused to fly from the developing roller 510 to the photosensitive member 20, The latent image on the photoconductor 20 is developed.

  The toner supply roller 550 supplies the toner T stored in the storage unit 530 to the developing roller 510. The toner supply roller 550 is made of polyurethane foam or the like and is pressed against the developing roller 510 in an elastically deformed state. In the present embodiment, the toner supply roller 550 rotates in a direction opposite to the rotation direction of the developing roller 510. The toner supply roller 550 not only has a function of supplying the toner T stored in the storage unit 530 to the developing roller 510, but also peels off the toner T remaining on the developing roller 510 after the development from the developing roller 510. It also has a function.

The regulating blade 560 regulates the layer thickness of the toner T carried on the developing roller 510, and applies a charge to the toner T carried on the developing roller 510 by frictional charging at the time of regulation. This regulating blade 560 also functions as a seal member on the upstream side of the developing position in the rotation direction of the developing roller 510. The regulating blade 560 includes a rubber portion 560a as a contact member that is contacted along the axial direction of the developing roller 510, and a rubber support portion 560b as a support member that supports the rubber portion 560a. . The rubber part 560a is made of silicon rubber, urethane rubber or the like as a main material, and the rubber support part 560b also has a function of urging the rubber part 560a toward the developing roller 510. A sheet-like thin plate having elasticity) is used. One end of the rubber support portion 560 b is fixed to the blade support metal plate 562. The blade support metal plate 562 is attached to the housing 540, and the seal member 520 is also attached to the housing 540. Further, with the developing roller 510 attached, the rubber portion 560a is pressed against the developing roller 510 by the elastic force due to the bending of the rubber support portion 560b.
In the present embodiment, a blade back member 570 is provided on the side opposite to the developing roller 510 side of the regulating blade 560 to prevent the toner T from entering between the rubber support portion 560b and the housing 540. The rubber portion 560a is pressed against the developing roller 510, and the rubber portion 560a is pressed against the developing roller 510.

In this embodiment, the free end portion of the regulating blade 560, that is, the end portion opposite to the side supported by the blade support metal plate 562, is not contacted with the developing roller 510 at the end edge. It is in contact with the developing roller 510 at a slightly separated site. The regulating blade 560 is disposed so that the tip thereof faces the upstream side in the rotation direction of the developing roller 510, and is in a so-called counter contact.
The configuration, operation, and effects of the developing devices 51, 52, and 53 of the developing unit 50 are the same as those of the developing device 54.

(Development roller)
Next, the developing roller 510 of the present invention will be described in detail with reference to FIGS.
3 is a plan view showing a schematic configuration of the developing roller, FIG. 4 is an enlarged plan view of a groove formed in the developing roller shown in FIG. 3, and FIG. 5 is a sectional view taken along line AA in FIG. 6 is a perspective view of FIG.
As shown in FIG. 3, the developing roller 510 protrudes from both ends of the main body 300 along the columnar main body 300 and the rotation axis (center axis) O of the main body 300, and is reduced in diameter from the outer diameter of the main body 300. And a reduced diameter portion 310. The main body 300 of the developing roller 510 is mainly composed of a metal material such as aluminum, stainless steel, or iron. Thereby, when the groove | channel 2 mentioned later is formed in the outer peripheral part 301 of the main body 300 (developing roller 510), for example by rolling (transfer method), the said groove | channel 2 can be formed easily and reliably. Further, the toner T can be efficiently charged by conveying the toner T on the outer peripheral portion 301 of the main body 300.
The outer peripheral surface 301a (outer peripheral portion 301) of the main body 300 may be subjected to nickel plating, chrome plating, or the like as necessary.
The diameter of the main body 300 is not particularly limited, but is preferably 10 to 30 mm, for example, and more preferably 15 to 20 mm.

As shown in FIG. 3, a groove 2 into which toner T particles enter is formed in the outer peripheral portion 301 of the developing roller 510. The groove 2 includes a plurality of first grooves 21 and a plurality of second grooves 22 intersecting with the first grooves 21.
As shown in FIG. 4, the plurality of first grooves 21 are parallel to each other and are formed at substantially equal intervals in a direction inclined with respect to the circumferential direction of the outer peripheral portion 301.
Further, as shown in FIG. 4, the plurality of second grooves 22 are also parallel to each other like the plurality of first grooves 21, and are each substantially in a direction inclined with respect to the circumferential direction of the outer peripheral portion 301. It is formed at equal intervals. In this embodiment, as shown in FIGS. 4 and 6, the second groove 22 is orthogonal to the first groove 21.

As shown in FIG. 5, the toner T particles supplied from the toner supply roller 550 enter the first grooves 21 and the second grooves 22, respectively. Then, the toner T rolls in each of the first groove 21 and the second groove 22 so that the toner T comes into contact with the developing roller 510 and is rubbed. As a result, the toner is uniformly charged.
In addition, since each shape of the 1st groove | channel 21 and the 2nd groove | channel 22 is substantially the same, the 1st groove | channel 21 is demonstrated typically below.

As described above, the first grooves 21 are parallel to each other, and are formed at substantially equal intervals in a direction inclined with respect to the circumferential direction of the outer peripheral portion 301. Thereby, the toner T is accommodated in the first groove 21, and an appropriate amount of toner T can be conveyed.
Here, the maximum width A1 of the _first groove 21 is preferably 50 to 90%, more preferably 60 to 80% of the separation distance between the adjacent convex portions.

  By setting the width of the first groove 21 in such a range, the ratio of the first groove 21 to the outer peripheral surface 301a increases, and the toner T is sufficiently accommodated in the first groove 21. A sufficient amount of toner T can be conveyed. Further, the convex portion 3 having an appropriate size is formed, and the contact surface between the toner T particles and the outer peripheral surface 301a of the developing roller 510 is increased. Therefore, the toner T is well charged by rolling on the outer peripheral surface 301a. As a result, high-quality printing with little fogging is possible.

If the maximum width A1 of the _first groove 21 is smaller than the lower limit value, the toner T is difficult to be accommodated in the first groove 21 and cannot be conveyed sufficiently. Further, the toner T accumulates in the first groove 21 and the charging becomes non-uniform.
On the other hand, if the maximum width A1 of the _first groove 21 is larger than the upper limit value, a large amount of toner T is accommodated in the first groove 21 and causes toner T leakage. In addition, the contact surface with the outer peripheral surface 301a becomes smaller than in the above preferable range, and the chargeability is lowered.

The maximum depth D ₁ of the first groove 21 is preferably 0.5 times or more and 2 times or less, more preferably 1 time or more and 1.5 times or less the average diameter (average particle diameter) of the toner T particles. . Within this range, the toner T can be accommodated in the first groove 21 without the toner T being stacked. Therefore, the toner T can be appropriately charged by contact with the outer peripheral surface 301a, and high-quality printing with less fogging is possible.

If the maximum depth D1 of the _first groove 21 is smaller than the lower limit value of the average diameter (average particle diameter) of the toner T particles, the depth of the first groove 21 becomes shallow. There is a possibility that the transport amount decreases. Further, since the rate at which the toner T comes into contact with the outer peripheral surface 301a is also reduced, there is a possibility that the charging property is lowered.
On the other hand, if the maximum depth D1 of the _first groove 21 is larger than the upper limit value of the average diameter (average particle diameter) of the toner T particles, the toner T is difficult to roll in the first groove 21. Become. Therefore, the transportability of the toner T is lowered and the charging property is also deteriorated.

Here, the specific range of the average particle size of the toner T is preferably, for example, 1 to 10 μm, and more preferably 1 to 7 μm. When the toner T having such an average particle size is used, the toner T is not stacked and stored in the first groove 21, and smoothly rolls on the outer peripheral surface 301a. Uniformly charged.
If the average particle size of the toner T is smaller than the lower limit value, the toner T is stacked and accommodated in the first groove 21, and the toner T is non-uniformly charged.
On the other hand, if the average particle size of the toner T is larger than the upper limit value, the toner T does not appropriately roll on the outer peripheral surface 301a, and the chargeability may deteriorate.

The depth of the first groove 21 D ₁ and the depth D ₂ of the second groove 22, as long as it satisfies the relationship between the average particle diameter of the toner particles, (the depth of the first groove 21 D ₁ ) = (depth D ₂ of second groove 22) may be satisfied, or (depth D ₁ of first groove 21)> (depth D of second groove 22). may also be satisfied ₁₎ the relationship may be satisfied (depth D ₁ of the first groove ₂₁₎ <(depth D ₁₎ the relationship of the second groove 22. In the present embodiment, the relationship D ₁ = D ₂ is satisfied. As a result, the outer peripheral surface 301a of the developing roller 510 has a smooth shape without a step, so that the toner T can smoothly roll on the outer peripheral surface 301a.
The ratio _D 2 / _{D 1} between the depth _{D 1} and the depth _{D 2} is not particularly limited, for example, is preferably from 0.5 to 2, and even 0.8 to 1.5 More preferred. As a result, the outer peripheral surface 301a of the developing roller 510 has a smooth shape without a step, so that the toner T can smoothly roll on the outer peripheral surface 301a.

As shown in FIG. 5, the first groove 21 has a U-shaped cross section, and has a side surface 211 and a bottom surface 212. Thereby, the toner T can roll smoothly. Then, when the toner T comes into contact with the outer peripheral surface 301a of the developing roller 510, the toner T is uniformly charged.
Moreover, as shown in FIG. 5, the U-shape of the first groove 21 is formed symmetrically. As a result, the toner T particles are smoothly accommodated and separated from the first groove 21, and the toner T can be smoothly conveyed. Therefore, the toner T can be uniformly charged when the toner T contacts the outer peripheral surface 301a.

At this time, the radius of curvature of the bottom surface 212 of the first groove 21 is preferably larger than half of the average particle diameter of the toner T particles, and preferably 0.6 to 10 times. More specifically, the radius of curvature of the bottom surface 212 of the first groove 21 is preferably larger than 0.5 μm, and preferably 0.6 to 50 μm.
As a result, the toner T particles have a groove shape that is easy to roll in the first groove 21, and the toner T particles are favorably charged when the toner T and the outer peripheral surface 301 a come into contact with each other.
If the radius of curvature of the bottom surface 212 of the first groove 21 is smaller than the lower limit value, the toner T is stacked and accommodated in the first groove 21 and the toner T is non-uniformly charged.
On the other hand, if the radius of curvature of the bottom surface 212 of the first groove 21 is larger than the upper limit value, the toner T does not roll smoothly in the first groove 21 and the chargeability of the toner T is deteriorated.

The intervals between the first grooves 21 are formed at substantially equal intervals. Specifically, it is preferably in the range of length of C ₁ to be described later. Within this range, the first grooves 21 are formed at an appropriate interval with respect to the outer peripheral surface 301a, and an appropriate amount of toner T can be conveyed. Further, the toner T is uniformly charged by the contact with the outer peripheral surface 301a. Therefore, high-quality printing with less fogging is possible.
The second groove 22 is the same as that of the first groove 21 with respect to the size and shape of each part. The operation and effect are also the same.

The convex portion 3 is formed in a region surrounded by each of the first groove 21 and the second groove 22 that is generated when the first groove 21 and the second groove 22 intersect. By forming the convex portion in such a region, for example, the toner T located in the first groove 21 rolls toward the convex portion 3 as the developing roller 510 rotates, It is accommodated in the second groove 22. As a result, the toner T comes into much contact with the outer peripheral surface 301a of the developing roller 510, and the toner T is uniformly charged. Further, since the toner T is collected in the groove 2, an appropriate amount of toner T can be conveyed.
As for the convex part 3, the top surface 31 is formed in a substantially plane, and the convex part 3 has comprised the truncated cone shape as a whole. By making the top surface 31 flat, the surface is hardly worn by friction with the toner T and the regulating blade, and the performance of the developing roller 510 is maintained for a long time. Further, since the toner T rolls on the top surface 31, the charging property of the toner T can be improved.

In the present embodiment, as shown in FIGS. 4, 5, and 6, the top surface 31 is formed in a substantially square shape. Thereby, since the top surface 31 is obtained simply by making the first groove 21 and the second groove 22 orthogonal to each other, the convex portion 3 in which the top surface 31 is a substantially square can be easily obtained.
Since the convex portion 3 is formed on the outer peripheral surface 301 a of the developing roller 510, the top surface 31 is curved to approximately the same radius of curvature as the outer diameter of the developing roller 510. This degree of curvature is included in the “substantially plane”.

The size of the top surface 31 of the convex portion 3 is determined by the distance between the first grooves 21 and the second grooves 22. Specifically, when the length of the top surface 31 around the streets of the second groove 22 parallel to the direction of the top surface 31 of the convex portion 3 and a C _1, preferably C ₁ is 10~50μm 10 to 30 μm is more preferable.
Further, when the length of the top surface 31 around the streets of the first groove 21 parallel to the direction of the top surface 31 of the convex portion 3 and _{C 2,} preferably _{C 2} is 10 to 50 [mu] m,. 10 to More preferably, it is 30 μm.

By setting each of C ₁ and C ₂ within the above ranges, the top surface 31 has an appropriate size, and the toner T can be efficiently charged by rolling the toner T on the top surface 31.
If each of C ₁ and C ₂ is smaller than the lower limit value, the convex portion is likely to be worn by friction with the regulating blade and the toner after a long period of use, and the toner conveyance amount and the charge amount cannot be maintained. .
On the other hand, if each of C ₁ and C ₂ is larger than the upper limit value, the ratio of the groove 2 to the outer peripheral surface 301a becomes small, and thus toner T leakage occurs. Further, since the surface where the toner T and the outer peripheral surface 301a come into contact is smaller than the above preferable range, the charging property of the toner T is deteriorated.
The height of the convex portion 3 is the same as the depth D ₂ of the first depth D ₁ of the groove 21 and the second groove 22.

  As for the convex part 3, it is preferable that the separation distance d with the adjacent convex part 3 is 50-100 micrometers, and it is more preferable that it is 60-90 micrometers. Within this range, an appropriate number of convex portions 3 are present on the outer peripheral surface 301a of the developing roller 510, and an appropriate amount of toner T can be conveyed. Further, the toner T efficiently rolls from the first groove 21 and / or the second groove 22 to the convex portion 3, so that the outer peripheral surface 301a of the developing roller 510 and the toner T efficiently come into contact with each other. The chargeability of T becomes good. Further, the toner T remaining on the developing roller 510 after development is peeled off from the developing roller 510, and the reset property is excellent. In addition, the function (charging and conveying performance) as a developing roller is good, and at the same time, the balance with durability for maintaining the performance is excellent.

If the distance d between adjacent convex portions 3 is smaller than the lower limit value, the charging performance is improved. However, when the conditions such as the groove width (A ₁ , B ₁ ) are satisfied, the area of the convex portion 3 is small. Therefore, it is worn by friction and the initial performance as the developing roller 510 cannot be maintained.
On the other hand, if the distance d between the adjacent convex portions 3 is larger than the upper limit value, the maximum width A1 of the _first groove 21 is increased, which may cause toner T leakage. Further, since the surface where the toner T and the outer peripheral surface 301a come into contact is smaller than the above preferable range, the charging property of the toner T is deteriorated.

4 and 6, in the present invention, the maximum width of the first groove 21 is A ₁ , the width of the second groove 22 is B ₁ , and the center of the top surface 31 of the convex portion 3. The length of the top surface 31 in the direction parallel to the second groove 22 through C _{1 is} the length of the top surface 31 in the direction parallel to the first groove 21 through the center of the top surface 31 of the convex portion 3. When C ₂ is satisfied, the condition is that A ₁ > C ₁ and B ₁ > C ₂ are satisfied.
Thereby, a sufficient amount of toner T can be conveyed. Further, the ratio of contact between the toners T is reduced, and the ratio of contact between the toner T and the outer peripheral surface 301a is increased, so that the chargeability of the toner T is improved. Therefore, it is possible to perform high-quality printing without unevenness while suppressing fogging.

If the relationship between A ₁ and C ₁ and B ₁ and C ₂ does not satisfy the above relationship, a sufficient amount of toner T cannot be conveyed. Further, the toner T is stacked and accommodated in the first groove 21 or the second groove 22, so that the toner T is non-uniformly charged.
Specifically, the maximum width _{B 1} of the maximum width _{A 1} and the second groove 22 of the first groove 21, it is 1.2 to 9 times the average value of _{C 1} and _{C 2} respectively preferably 2 to 6 times more preferable.
As a result, a sufficient amount of toner T can be transported, and the ratio of contact between the toners T decreases, so that the chargeability of the toner T is improved. Therefore, it is possible to perform high-quality printing without unevenness while suppressing fogging.

Each of the maximum width B ₁ of the maximum width A ₁ and the second groove 22 of the first groove 21 is smaller than the lower limit value of the average value of C ₁ and C _2, transport a sufficient amount of toner T Can not do it. Further, the toner T is stacked and accommodated in the first groove 21 and the second groove 22, so that the toner T is non-uniformly charged.
On the other hand, each of the maximum width B ₁ of the maximum width A ₁ and the second groove 22 of the first groove 21 is greater than the upper limit value of the average value of the C ₁ and C _2, the first groove 21 and A large amount of toner T is accommodated in the second groove 22, which may cause toner T leakage. Further, since the surface where the toner T and the outer peripheral surface 301a come into contact is smaller than the above preferable range, the charging property of the toner T is deteriorated.

The maximum width _{B 1} of the maximum width _{A 1} and the second groove 22 of the first groove 21 is preferably 2.5 to 20 times the average particle diameter of each toner T particles, 3-10 times It is more preferable that
Thereby, the toner T is reliably accommodated in the first groove 21, and an appropriate amount can be conveyed. Further, the contact surface between the toner T particles and the outer peripheral surface 301a of the developing roller 510 becomes large, and the toner T is charged well.

Is smaller than the lower limit of the average particle diameter of the maximum width B ₁ is each toner T particles of maximum width A ₁ and the second groove 22 of the first groove 21, the toner T is first groove 21 and a second Therefore, the toner T may not be accommodated in the width of the groove 22, and the chargeability of the toner T is deteriorated. Further, a sufficient amount of toner T cannot be conveyed.
On the other hand, is larger than the upper limit of the average particle diameter of the maximum width B ₁ is each toner T particles of maximum width A ₁ and the second groove 22 of the first groove 21, the toner T is first groove 21 and A large amount is accommodated in the width of the second groove 22, which may cause toner T leakage. Further, since the surface where the toner T and the outer peripheral surface 301a come into contact is smaller than the above preferable range, the charging property of the toner T is deteriorated.

  Further, the area ratio occupied by the first groove 21 on the outer peripheral surface 301a of the developing roller 510 (hereinafter, the portion where the groove 2 is formed is referred to as “groove forming portion 320”) is 40 to 40 of the area of the outer peripheral surface 301a. 90% is preferable, and 60 to 80% is more preferable. When the area ratio of the groove forming portion 320 is a value within the above range, a more uniform and optimum amount of toner T can be conveyed. Further, since the ratio of contact between the developing roller 510 and the toner T is increased, the charging property of the toner T is improved. Accordingly, it is possible to print with high image quality with less fog and without unevenness.

If the area ratio of the groove forming portion 320 is smaller than the lower limit value of the area of the outer peripheral surface 301a, the surface where the toner T comes into contact with the outer peripheral surface 301a becomes small, and the charging property of the toner T is deteriorated. Further, since the ratio of the groove 2 to the outer peripheral surface 301a is small, a sufficient amount of toner T cannot be conveyed.
On the other hand, if the area ratio of the groove forming portion 320 is larger than the upper limit value of the area of the outer peripheral surface 301a, the ratio of rolling from the first groove 21 to the convex portion 3 decreases, and the charging property of the toner T is poor. Become. Further, since the surface where the toner T and the outer peripheral surface 301a come into contact is smaller than the above preferable range, the charging property of the toner T is deteriorated.

As described above, since the developing roller of the present invention has the first groove 21 and the second groove 22 that intersect each other, the toner T can be accommodated and conveyed. At this time, since D ₁ and D ₂ are 1/2 to 2 times the average particle diameter of the toner T, the toner T rolls without being stacked in the groove 2. Further, since the cross-sectional shape is a symmetrical U-shape, the toner T rolls smoothly and the toner T is detached from the groove 2. The detached toner T rolls on the substantially flat top surface 31 of the convex portion 3 and is accommodated in the groove 2 again. Further, since the width of the first groove 21 and the width of the second groove 22 satisfy the predetermined relationship, the contact surface with the outer peripheral surface a of the toner T becomes large, and the toner T is made uniform and satisfactory. Can be charged. Therefore, it is possible to print a high-quality image with little fog and without unevenness.
In FIGS. 5 and 6, the first groove 21 and the second groove 22 have substantially the same U-shape, but may have different U-shapes. For example, the first groove 21 has a semicircular shape, but the second groove 22 may have a semielliptical shape. Moreover, the U-shape of a part of the first groove 21 or the second groove 22 may be different from the U-shape of other parts.

<Second Embodiment>
FIG. 7 is an enlarged plan view of the groove 2 formed in the developing roller 510.
Hereinafter, the second embodiment of the developing roller 510 of the present invention will be described with reference to this drawing. However, the difference from the above-described embodiment will be mainly described, and description of similar matters will be omitted.
This embodiment is different from the first embodiment in the shape of the convex portion 3 and the angle at which the first groove 21 and the second groove 22 intersect.

  As shown in FIG. 7, the top surface 31 of the convex portion 3 has a rhombus substantially planar shape. That is, the plurality of first grooves 21 and the plurality of second grooves 22 intersect without being orthogonal to each other. At this time, the angle θ at which the first groove 21 and the second groove 22 cross each other is preferably 20 to 135 °, and more preferably 45 to 90 °. By setting the angle at which the first groove 21 and the second groove 22 intersect to such an angle, a diamond-shaped top surface 31 is obtained, and the moving distance of the toner around the unit lattice increases. Then, the toner T does not catch on the convex portion 3 and rolls more smoothly than in the case of the first embodiment (in the case of being orthogonal). For this reason, the toner T comes into contact with the outer peripheral surface 301a of the developing roller 510 more efficiently, so that the charging property of the toner T becomes better. Accordingly, it is possible to realize high-quality printing with less fog and no unevenness.

As described above, the developing roller, the developing device, and the image forming apparatus of the present invention have been described with respect to the illustrated embodiment. However, the present invention is not limited to this, and each part constituting the developing roller, the developing device, and the image forming apparatus. Can be replaced with any structure capable of performing the same function. Moreover, arbitrary components may be added.
In addition, the developing roller, the developing device, and the image forming apparatus of the present invention may be a combination of any two or more configurations (features) of the above embodiments.
EXAMPLES Hereinafter, although this invention is demonstrated based on an Example, this invention is not limited to this.

1. Production of developing device (Example 1)
[1.1] Manufacture of developing roller The outer peripheral surface of the developing roller made of STKM11A was rolled into a predetermined shape, and then NiP plating was applied to the surface. Thus, a developing roller having a first groove having a depth of 7 μm and a second groove having a depth of 7 μm was manufactured.
Table 1 shows the maximum width (A ₁ , B ₁ ) of each groove, the size of the top surface of the convex portion (C ₁ , C ₂ ), the radius of curvature, the convex portion separation distance (d), and the like.
[1.2] Manufacture of developing device A developing device having the structure shown in FIG. 2 incorporating the developing roller was manufactured.
[1.3] Manufacture of image forming apparatus An image forming apparatus having the structure shown in FIG.

(Example 2) to (Example 19)
In Example 1, an image forming apparatus was manufactured in the same manner as in Example 1 except that the conditions such as the maximum width of the groove of the developing roller and the size of the convex portion were changed as shown in Table 1.
(Comparative Example 1) to (Comparative Example 6)
In Example 1, an image forming apparatus was manufactured in the same manner as in Example 1 except that the conditions such as the maximum width of the groove of the developing roller and the size of the convex portion were changed as shown in Table 1.

2. Evaluation With respect to each developing roller obtained as described above, charging characteristics and toner leakage were evaluated by the following methods. The toner used was a polyester resin composition having an average particle diameter of 5 μm.
[2.1] Charging characteristics In the image forming apparatuses obtained in Examples 1 to 19 and Comparative Examples 1 to 6, the image forming apparatus was stopped during printing, and the cartridge was removed. Then, the charge amount distribution was measured using a powder dust charge amount distribution measuring device (E-spart analyzer, manufactured by Hosokawa Micron Corporation). From the result, the charge amount was determined.
Regarding the charge amount, the initial charge amount and the charge amount after printing 30000 sheets were obtained. And it evaluated in accordance with the following four steps of criteria.
A: The amount of change from the initial charge amount (absolute value) is 3 μC / g or more.
A: The amount of change (absolute value) from the initial charge amount is 1 μC / g or more and less than 3 μC / g.
Δ: The amount of change (absolute value) from the initial charge amount is 0.5 μC / g or more and less than 1 μC / g.
X: The amount of change from the initial charge amount (absolute value) is less than 0.5 μC / g.

[2.2] Toner Leakage In the image forming apparatuses obtained in Examples 1 to 19 and Comparative Examples 1 to 6, first, toner leakage was confirmed at the initial stage of use and evaluated according to the following four criteria. Next, the image forming apparatus was stopped during printing, and the cartridge was removed (after printing 30000 sheets). At that time, the presence or absence of toner leakage from the cartridge was visually confirmed and evaluated according to the following four criteria.
A: No toner leakage was observed.
○: Slight toner leakage was observed.
Δ: Toner leakage was observed.
X: Remarkable toner leakage was observed.
These results are summarized in Table 1. In Table 1, A in the conditions of A ₁ > C ₁ and B ₁ > C ₂ means that the condition is satisfied, and x indicates that the condition is not satisfied.

As is clear from Table 1, all of the developing rollers of the present invention were excellent in charging characteristics and toner leakage.
Particularly in Examples 1 to 5, since the maximum depth of the first groove and the second groove is in the range of 0.5 to 2 times the average particle diameter of the toner, the charging characteristics and the toner leakage are particularly excellent. It was.
In Examples 9 to 13, since the curvature radii of the bottom surfaces of the first groove and the second groove are in the range of 0.6 to 10 times the average particle diameter of the toner, charging characteristics and toner leakage are improved. Especially excellent.
In Examples 15 to 17, since the distance between adjacent convex portions was 50 to 100 μm, the charging characteristics and toner leakage were particularly excellent.
In Examples 6 to 8, 14, 18, and 19, the relationship of A ₁ > C ₁ and B ₁ > C ₂ is satisfied, and the maximum depth of the first groove and the second groove is the average particle diameter of the toner. Therefore, although the toner leakage was slightly recognized, the charging characteristics were excellent.

On the other hand, since the toner of the comparative example does not satisfy the predetermined condition of the present invention, both the charging characteristics and the toner leakage are inferior to those of the examples.
In particular, Comparative Examples 1 and 2 were inferior in charging characteristics because the maximum depth of the first groove and the second groove was outside the range of 0.5 to 2 times the average particle diameter of the toner.
In Comparative Examples 3 to 6, since the relationship of A ₁ > C ₁ and B ₁ > C ₂ was not satisfied, both charging characteristics and toner leakage were inferior.

1 is a schematic cross-sectional view showing a schematic configuration of an image forming apparatus of the present invention. 1 is a schematic cross-sectional view showing a schematic configuration of a developing device of the present invention. It is a top view which shows schematic structure of the developing roller of this invention. FIG. 4 is an enlarged plan view of a groove formed in the developing roller shown in FIG. 3. It is the sectional view on the AA line in FIG. FIG. 4 is an enlarged perspective view of a groove formed in the developing roller shown in FIG. 3. It is an enlarged plan view of a groove formed in the developing roller of the present invention. It is a figure which shows schematic structure of the conventional coating rod, (a) is a top view, (b) is an enlarged view which shows arrangement | positioning of the groove | channel formed in the outer peripheral part of the coating rod, (c) These are sectional drawings which show the shape of the groove | channel formed in the outer peripheral part.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 10 …… Printer 2 …… Groove 21 …… First groove 211 …… Side surface 212 …… Bottom surface 22 …… Second groove 20 …… Photoreceptor 3 …… Convex part 31 …… Top surface 30 …… Charging unit 300 …… Main body 301 …… Outer peripheral portion 301a …… Outer peripheral surface 310 …… Reduced diameter portion 320 …… Groove forming portion 40 …… Exposure unit 50 …… Developing unit 50a …… Shaft 51 …… Black developing device 52 …… Magenta Developing device 53... Cyan developing device 54... Yellow developing device 55 a to 55 d .. Holding unit 510... Developing roller 520... Seal member 530. Blade 560a …… Rubber part 560b …… Rubber support part 562 …… Blade support sheet metal 570 …… Blade back member 60 …… Primary roll Unit 70 ... Intermediate transfer member 75 ... Cleaning unit 76 ... Cleaning blade 80 ... Secondary transfer unit 90 ... Fixing unit 92 ... Paper feed tray 94 ... Paper feed roller 96 ... Registration roller 100 ... Coating Rod 101 ... First groove 102 ... Second groove 103 ... Convex part P1 ... Recording medium T ... Toner O ... Rotation axis (central axis)

Claims (9)

A developing roller for holding toner on the outer periphery,
A plurality of first grooves that are parallel to each other and formed at substantially equal intervals in a direction inclined with respect to the circumferential direction of the outer peripheral portion of the developing roller, and parallel to each other and the circumference of the outer peripheral portion of the developing roller A plurality of second grooves that are formed at substantially equal intervals in a direction inclined with respect to the direction and intersect with the first grooves,
Each of the first groove and the second groove has a U-shaped cross section,
A convex portion having a substantially flat top surface is provided in a region surrounded by the first groove and the second groove,
The width of the first groove is A ₁ , the width of the second groove is B ₁ , and the length of the top surface in the direction parallel to the second groove passes through the center of the top surface of the convex portion. C ₁ , when the length of the top surface in the direction parallel to the first groove passing through the center of the top surface of the convex portion is C ₂ , A ₁ > C ₁ and B ₁ > C ₂ Satisfy the relationship
When the maximum depth of the first groove is D ₁ and the maximum depth of the second groove is D ₂ , D ₁ and D ₂ are 0.5 to 2 of the average particle diameter of the toner particles, respectively. A developing roller characterized by being doubled. The developing roller according to claim 1, wherein the A ₁ and B ₁ are 1.2 to 9 times the average value of the C ₁ and C ₂ , respectively. The developing roller according to claim _1, wherein A ₁ and B ₁ are 50 to 90% of a separation distance between the adjacent convex portions.   4. The developing roller according to claim 1, wherein the first groove and the second groove have a radius of curvature of a bottom surface of 0.6 to 10 times an average particle diameter of the toner particles. 5.   The developing roller according to claim 1, wherein a distance between adjacent convex portions is 50 to 100 μm.   The developing roller according to claim 1, wherein an area ratio occupied by the first groove and the second groove on the outer peripheral surface of the developing roller is 40 to 90% of an area of the outer peripheral surface. .   The developing roller according to claim 1, wherein at least an outer peripheral portion of the developing roller is made of a metal material.   A developing device comprising the developing roller according to claim 1.   An image forming apparatus comprising the developing device according to claim 8.

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