JP2008102446A - Method for manufacturing developing roller, developing roller, developing device and image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for manufacturing a developing roller capable of stably and uniformly applying carried toner to a photoreceptor by restraining variance in the depth of a recessed part between a seam part and parts other than the seam part, the very reliable developing roller manufactured by such a manufacturing method, a developing device equipped with the developing roller and restraining developing irregularity and printing irregularity associated with the developing irregularity, and an image forming apparatus. <P>SOLUTION: The method for manufacturing the developing roller 510 includes: a first stage for obtaining a metallic tube having a seam part by butting the ends of a metallic plate at each other and molding the metallic plate in a tubular state and then welding the ends thereof; a second stage for mitigating a hardness difference between the seam part and the parts other than the seam part of the metallic tube by performing heat treatment to the metallic tube; a third stage for obtaining a cylindrical main body 300 by forming a groove on the outer peripheral surface of the metallic tube to which the heat treatment has been performed by using a rolling method; and a fourth stage for inserting a reduced diameter part 310 in both ends of the hollow part of the main body 300. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a developing roller manufacturing method, 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 (magnet roll for an electronic copying machine) having a surface treatment such as blasting or machining on the outer peripheral surface is known as one that carries a powdery material such as toner (for example, a patent) Reference 1).
Here, the conventional developing roller is manufactured using a metal tube. In general, the metal tube is formed by forming a metal plate into a tubular shape and performing seam welding between adjacent ends of the metal plate (seam tube). And the developing roller is obtained by forming the recessed part of a predetermined shape in the outer peripheral surface (outer peripheral part) of this seam pipe | tube using a rolling method.

By the way, in the rolling method, the concave portion is formed by pressing a die having a convex portion of a predetermined shape against the outer peripheral surface of the seam tube and causing it to bite. During such rolling, the amount of biting of the die that bites into the seam pipe changes depending on the hardness of the outer periphery of the seam pipe. For example, there is a difference in hardness between the seam portion of the tubular body and other portions. For this reason, in the outer peripheral part of the developing roller, the depth of the concave part varies between the seam part and other parts.
When variations occur in the depth of the recesses in this way, it is impossible to stably and uniformly apply the carried toner to the photosensitive member in the developing roller. In the printer, problems such as uneven development and accompanying print unevenness occur.

JP 55-26526 A

  An object of the present invention is to easily develop a developing roller capable of stably and evenly imparting a carried toner to a photosensitive member by suppressing variations in the depth of a concave portion between a seam portion and other portions. A developing roller manufacturing method that can be manufactured in a highly reliable manner, a highly reliable developing roller manufactured by such a manufacturing method, and a developing device and an image forming apparatus that include such a developing roller and that can suppress uneven development and accompanying printing unevenness. It is to provide.

The above object is achieved by the present invention described below.
The developing roller manufacturing method of the present invention is a manufacturing method of a developing roller having a concave portion for holding toner on the outer periphery,
Relaxing the difference in hardness between the seam portion of the tubular body and the other portion by applying heat treatment to at least the portion including the seam portion of the metal tubular body having a seam portion;
A step of forming the concave portion on an outer peripheral portion of the tubular body subjected to the heat treatment by a rolling method.
As a result, the variation in the depth of the concave portion is suppressed between the seam portion and the other portions, thereby easily producing a developing roller capable of stably and uniformly applying the carried toner to the photoreceptor. be able to.

In the developing roller manufacturing method of the present invention, it is preferable that the temperature of the heat treatment satisfies a relationship of A to A + 100, where A [° C.] is a recrystallization temperature of a metal constituting the tubular body.
Thereby, it is possible to reliably suppress or prevent wasteful energy consumption due to excessive heat treatment while applying sufficient thermal energy to the tubular body to change the crystal structure.

In the developing roller manufacturing method of the present invention, the heat treatment time is preferably 10 to 120 minutes.
Thereby, sufficient relaxation of the hardness difference in the outer peripheral part of the tubular body can be achieved.
In the developing roller manufacturing method of the present invention, it is preferable that the heated tube is naturally cooled in the heat treatment.
Thereby, it is possible to prevent the heated tubular body from being rapidly cooled, and to suppress generation of new stress accompanying cooling. There is also an advantage that cooling can be performed at a low cost.

In the developing roller manufacturing method of the present invention, the heat treatment is preferably performed a plurality of times.
Thereby, the difference in hardness can be more reliably relieved between the seam portion of the tubular body and other portions.
In the developing roller manufacturing method of the present invention, the plurality of heat treatments include a first heat treatment and a second heat treatment performed at a lower temperature than the first heat treatment after the first heat treatment. Is preferred.
Thereby, the difference in hardness can be more reliably relieved between the seam portion of the tubular body and other portions.

In the developing roller manufacturing method of the present invention, the temperature of the first heat treatment is equal to or higher than the recrystallization temperature of the metal constituting the tube, and the temperature of the second heat treatment is the metal. The temperature is preferably lower than the recrystallization temperature.
Thereby, while the hardness difference between the said seam part of the said tubular body and other site | parts is relieve | moderated reliably, the ductility of the said tubular body can be improved more.

In the developing roller manufacturing method of the present invention, it is preferable that the difference in hardness between the seam portion of the tubular body and the other portion after the heat treatment step is 20 or less in terms of Vickers hardness Hv.
Thereby, it is possible to reliably obtain a developing roller in which the depth of the concave portion is uniform throughout. That is, such a tubular body is particularly useful in manufacturing a highly reliable developing roller.

In the developing roller manufacturing method of the present invention, the recess is a plurality of grooves provided on the outer periphery of the tubular body,
The pitch of each groove in the circumferential direction of the tubular body is preferably smaller than the width of the seam portion.
The present invention can be applied particularly suitably when manufacturing a developing roller having such a large number of grooves.

In the developing roller manufacturing method of the present invention, it is preferable that W / P is 10 or more when the pitch of each groove is P [mm] and the width of the seam portion is W [mm].
As described above, when manufacturing a developing roller in which a large number of the grooves are formed in the seam portion, the effect of the present invention is more remarkably exhibited.
In the developing roller manufacturing method of the present invention, it is preferable that the metal constituting the tubular body is carbon steel.
Since carbon steel is a steel material whose crystal structure can be changed relatively easily when heated, it is easy to adjust the stress in the crystal and is suitable as a metal constituting the tube. is there.
In the developing roller manufacturing method of the present invention, the carbon content in the carbon steel is preferably 0.3% by mass or less.
A metal composed of carbon steel having such a carbon content is excellent in spreadability. In addition, such a metal can easily control properties such as spreadability and hardness by heat treatment.

The developing roller of the present invention is manufactured by the developing roller manufacturing method of the present invention.
Thereby, a highly reliable developing roller can be obtained.
The developing device of the present invention includes the developing roller of the present invention.
Thereby, a developing device capable of suppressing development unevenness is obtained.
The image forming apparatus of the present invention includes the developing device of the present invention.
Thereby, an image forming apparatus capable of suppressing printing unevenness is obtained.

Preferred embodiments of a developing roller manufacturing method, a developing roller, a developing device, and an image forming apparatus according to the present invention will be described below with reference to the accompanying drawings.
FIG. 1 is a schematic cross-sectional view showing a schematic configuration of the image forming apparatus of the present invention, and FIG. 2 is a schematic cross-sectional view showing a schematic configuration of the developing device of the present invention. In the following description, the upper side in FIGS. 1 and 2 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 will be described in detail with reference to FIGS.
3 is a plan view showing a schematic configuration of the developing roller included in the developing device shown in FIG. 2, FIG. 4 is an enlarged plan view of a groove formed in the developing roller shown in FIG. 3, and FIG. It is AA sectional view.

As shown in FIG. 3, the developing roller 510 is provided with a cylindrical main body 300 and two reduced-diameter portions 310, 310 that are provided so as to protrude from both ends of the main body 300 and are reduced in diameter from the outer diameter of the main body 300. And have. Among these, each of the reduced diameter portions 310 and 310 is inserted into both ends of the hollow portion of the main body 300 so as to be along the rotation axis (center axis) O of the main body 300.
The main body 300 of the developing roller 510 is composed mainly of a metal material such as aluminum, stainless steel, or steel. 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.

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 FIGS. 3 and 4, a groove 2 into which toner T particles enter is formed in the outer peripheral portion 301 of the main body 300 in the outer peripheral portion 301 of the developing roller 510.

The groove 2 may have any shape in a plane and a cross section, but in the present embodiment, as an example, the groove 2 includes a plurality of first grooves 21 as shown in FIGS. A case will be described in which each of the first grooves 21 includes a plurality of second grooves 22 that are orthogonal (intersect).
The plurality of first grooves 21 are parallel to each other, and are formed in directions that are inclined with respect to the circumferential direction of the outer peripheral portion 301.
The plurality of second grooves 22 are also parallel to each other and formed in a direction inclined with respect to the circumferential direction of the outer peripheral portion 301, similarly to the plurality of first grooves 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. The particles include particles T1 having a relatively large diameter (for example, 5 to 10 μm) and particles T2 having a diameter smaller than that of the particle T1 (for example, 1 to 5 μm). As described above, the shape of the groove 2 is closely related to the toner T in which the diameter of each particle varies.

In addition, since the shape of the 1st groove | channel 21 and the 2nd groove | channel 22 is substantially the same, below, the 1st groove | channel 21 is demonstrated typically.
The first groove 21 is a groove opened on the outer peripheral surface 301 a of the developing roller 510. The first groove 21 has a U-shaped cross section and has a pair of side surfaces 211 and a bottom surface 212. 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.
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 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 bottom surface 212 is formed substantially parallel to the outer peripheral surface 301a.
The distance between the bottom surface 212 and the outer peripheral surface 301a, that is, the depth D1 of the _first groove 21 is not particularly limited, but is, for example, ½ times the average diameter (average particle diameter) of the toner T particles, The average diameter (average particle diameter) of the toner T particles is preferably not more than twice. The specific numerical range is, for example, preferably 1 to 10 μm, and more preferably 1 to 7 μm.

When the depth D ₁ is within this range, the developing roller 510 can carry a large number of particles T2 (toner T) of uniform and optimum amount, thus, the side surface 211 and bottom surface 212 with an electric field application state The particles T2 that are in contact with and rubbed can be charged. In addition, these charged particles T2 can be reliably applied to the photoconductor 20, so that a uniform latent image without unevenness in density can be obtained. Further, the toner T layer can be formed in one or two layers.
In contrast, when the depth D ₁ is less than the lower limit, the amount of toner T which carries decreases, it is possible that to obtain a clear latent image becomes difficult.

When the depth D ₁ exceeds the upper limit, the first groove 21, it is the toner T is excessively contained, If granted it to the photoconductor 20, a possibility that uneven density occurs in the latent image There is.
The depth of the first groove 21 _{D 1} and the depth _{D 1} of the second groove 22, the depth _{D 1} of the (first depth _D 1 of the groove 21) = (second groove 22 ) made to the relationship may be satisfied, it may also be satisfied (depth D ₁ of the first groove _21)> (the depth D ₁ of the second groove ₂₂₎ the relationship, (the 1 of the depth _D 1 of the groove 21) <(may not satisfy the depth _{D 1)} the relationship of the second groove 22.

Both side surfaces 211 are formed to be inclined symmetrically with respect to the bottom surface 212 in FIG.
Further, these side surfaces 211 are inclined so that the groove width gradually increases in the direction away from the rotation axis O of the developing roller 510. As a result, the charged T2 easily escapes from the first groove 21 toward the photoconductor 20, so that the particles T2 can be reliably applied to the photoconductor 20.

Although angle (theta) ₁ which both the side surfaces 211 make is not specifically limited, For example, it is preferable that it is 60-150 degrees, and it is more preferable that it is 60-90 degrees.
If the angle θ ₁ is less than the lower limit value, the number of irregularities in the circumferential direction of the developing roller increases, so that there are too many opportunities for contact between the toner and the irregularities at the time of rotation, and the toner charge amount becomes too high, causing the toner to fly. Therefore, it may be difficult to apply a sufficient amount of the particles T2 to the photoconductor 20.
If the angle theta ₁ is greater than the upper limit, the number of the developing roller circumferential direction of the unevenness is reduced, less chance of contact toner and irregularities during rotation, the toner because they are not sufficiently charged, causing the toner fogging The amount of wasted toner can be increased.

Now, as shown in FIG. 4, each first groove 21 is formed with a plurality of enlarged portions 23 formed by enlarging the width and depth of a part of the first groove 21.
As shown in FIG. 5, each enlarged portion 23 is formed so that toner particles (particles T <b> 1 and T <b> 2), particularly the particles T <b> 1 can surely enter into the internal space. In other words, each enlarged portion 23 has a U-shaped cross section and has a pair of side surfaces 231 and a bottom surface 232.

The bottom surface 232 is formed substantially parallel to the outer peripheral surface 301a.
The distance between the bottom surface 232 and the outer peripheral surface 301a, i.e., the depth D ₂ of the enlarged portion 23 is not particularly limited, the average diameter of the particles of the toner T (average particle diameter) 1/2 or more, the toner T particles The average diameter (average particle diameter) is preferably 2 times or less. The specific numerical range is, for example, preferably 1 to 10 μm, and more preferably 1 to 7 μm.

When the depth D ₂ is within this range, it is possible that the developing roller 510 carries the toner T of uniform and optimum amount, thus rubbed in contact with the side surface 231 and bottom surface 232 with an electric field application state The particles T1 and T2 (toner T) can be charged. In addition, the charged particles T1 and T2 can be reliably applied to the photoconductor 20, so that a uniform latent image without unevenness in density can be obtained. Further, the toner T layer can be formed in one or two layers.

In contrast, when the depth D ₂ is less than the lower limit, the amount of toner T which carries decreases, it is possible that to obtain a clear latent image becomes difficult.
Further, when the depth D ₂ exceeds the upper limit, the expansion unit 23 becomes the toner T is excessively contained, If granted it to the photoconductor 20, a possibility that uneven density occurs in the latent image There is.

Both side surfaces 231 are formed so as to be inclined symmetrically with respect to the bottom surface 232 in FIG.
Further, these side surfaces 231 are inclined so that the groove width gradually increases in a direction away from the rotation axis O of the developing roller 510. As a result, the charged particles T1 and T2 easily escape from the enlarged portion 23 toward the photoconductor 20, so that the particles T1 and T2 can be reliably applied to the photoconductor 20.

Although angle (theta) ₂ which both side surfaces 231 make is not specifically limited, For example, it is preferable that it is 60-150 degrees, and it is more preferable that it is 60-90 degrees.
When the angle θ ₂ is a value within the above range, for example, the toner T positioned on the outer peripheral surface 301 a can easily enter the enlarged portion 23.
When the angle θ ₂ is less than the lower limit value, each side surface 231 becomes steep, and the charged particles T1 and T2 may not easily come off from the enlarged portion 23. Further, the angle theta ₂ is less than the lower limit, the area of each side 231 is reduced, the total contact area between the particles T1 and T2 becomes smaller. For this reason, it is difficult to charge a large number of particles T1 and T2, and it may be difficult to apply a sufficient amount of particles T1 and T2 to the photoconductor 20.
If the angle theta ₂ exceeds the upper limit, there is a possibility that increased the amount of the toner wasted.

As shown in FIG. 4, each side surface 231 of the enlarged portion 23 is curved so as to swell in the width direction of the enlarged portion 23. Thereby, since the area becomes larger than the case where each side surface 231 is planar, the total contact area with the particles T1 and T2 is increased. For this reason, a large number of particles T1 and T2 can be charged. Therefore, a necessary and sufficient amount of particles T1 and T2 can be applied to the photoconductor 20.
Each enlarged portion 23 configured as described above contains particles T1 and contains particles T2 so as to fill a space excluding the particles T1 (see FIG. 5).

  As shown in FIG. 4, the plurality of enlarged portions 23 are intermittently arranged along the longitudinal direction of each first groove 21. That is, the plurality of enlarged portions 23 are uniformly distributed along the circumferential direction of the outer peripheral surface 301a of the developing roller 510 and / or the longitudinal direction of the roller. As a result, similarly to the enlarged portion 23, the particles T1 are also uniformly distributed, so that the developing roller 510 can carry a more uniform and optimum amount of toner T. Further, by applying such a toner T to the photoconductor 20, a more uniform latent image without uneven density can be obtained.

The enlarged portion 23 is a portion where each first groove 21 and each second groove 22 do not intersect, that is, two intersections where each first groove 21 and each second groove 22 intersect. One is provided between the portions 24.
Further, as described above, each enlarged portion 23 is provided in a portion between the two intersecting portions 24 of the first groove 21 (hereinafter, this portion is referred to as “unit groove 213”). The unit grooves 213 provided with the enlarged portions 23 and the unit grooves 213 provided with no enlarged portions 23 are alternately arranged.

  By arranging the enlarged portions 23 in this way, the particles T1 located in the first groove 21 roll toward the enlarged portion 23 as the developing roller 510 rotates, and the enlarged portions 23 is trapped. As a result, the particles T1 are stored in the enlarged portion 23, and are prevented from detaching from the enlarged portion 23 (groove 2), so that the amount of wasted toner T can be reduced.

By forming the groove 2 having the above-described configuration, the developing roller 510 can carry a more uniform and optimum amount of toner T. Further, by applying such toner T to the photoconductor 20, it is possible to prevent occurrence of uneven density in the visualized latent image on the photoconductor 20.
Note that the number of enlarged portions 23 formed between the two intersecting portions 24 where each first groove 21 and each second groove 22 intersect is not limited to one, and may be two or more, for example. Good.
The angles θ ₁ and θ ₂ may satisfy the relationship θ ₁ = θ ₂ , may satisfy the relationship θ ₁ > θ ₂ , or may satisfy the relationship θ ₁ <θ _2. You may be satisfied.
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 1.01 to 5, in the range of 1.01 to 1.5 More preferred.

  Further, in the outer peripheral surface 301a of the developing roller 510 shown in FIG. 3, the area ratio of the portion occupied by the groove 2 (hereinafter, the portion where the groove 2 is formed is referred to as “groove forming portion 320”) is the area of the outer peripheral surface 301a. It is preferably 40 to 90%, more preferably 60 to 80%. 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 carried. Further, by applying such a toner T to the photoconductor 20, a more uniform latent image without uneven density can be obtained.

The conditions for forming the enlarged portion such as the arrangement of the enlarged portions 23, the spacing between the enlarged portions 23, and the ratio of the area occupied by the enlarged portion 23 to the first groove 21 and / or the second groove 22 are the particles T1 and T2. Depending on the diameter, it can be set appropriately.
For example, the number of enlarged portions formed per rotation of the developing roller 510 is preferably 100 or more, and more preferably 150 to 300.
Each enlarged portion 23 is not limited to being formed in each first groove 21, and enlarged portions 23 may be formed in each first groove 21 and each second groove 22.
Further, the plurality of second grooves 22 are not limited to being formed so as to be orthogonal to the plurality of first grooves 21, but may be formed so as to intersect with an acute angle or an obtuse angle.

Next, a method for manufacturing such a developing roller 510 (a developing roller manufacturing method of the present invention) will be described.
FIG. 6 and FIG. 7 are schematic diagrams for explaining the method for producing the developing roller of the present invention.
In the manufacturing method of the developing roller 510 shown in FIG. 3, the metal plates are bent and the ends are butted together to form a tubular shape, and then the edges of the butted metal plates are welded to each other to form a metal tube (metal tube). ), A second step of heat-treating the metal tube, a groove (concave portion) is formed in the outer peripheral surface (outer peripheral portion) of the heat-treated metal tube, and the cylindrical main body 300 is formed. A third step of obtaining, and a fourth step of inserting reduced-diameter portions 310 serving as rotation axes at both ends of the hollow portion of the main body 300, respectively. Hereinafter, each process will be described sequentially.

[1] First, a metal plate 511 as shown in FIG. 6A is prepared, the metal plate 511 is curved as shown in FIG. 6B, and the end portions 512 and 512 are brought into contact with each other to form a tubular shape. To form.
The forming method is not particularly limited, but a method of continuously forming a metal plate into a tubular shape (roll forming) with a forming roll, a method of forming a metal plate into a spiral shape (spiral forming), and a metal plate having a U-shape. Various molding methods such as a method of performing press molding (UO press molding) into an O-shape after press molding are included. Note that FIG. 6B illustrates the case of roll forming.

Moreover, as a material which comprises the metal plate 511, various metal materials like aluminum, stainless steel, steel, etc. are mentioned as mentioned above.
Among such metal materials, steel materials such as alloy steels such as carbon steel and chromium steel, special steels, high tensile steels, and corrosion resistant steels such as stainless steels are particularly preferable, and carbon steel is more preferable. Carbon steel is a steel material whose crystal structure can be changed relatively easily when heated. For this reason, it is easy to adjust the stress in the crystal and is suitable as a material constituting the metal plate 511.

The carbon content in the carbon steel is preferably 0.3% by mass or less, more preferably about 0.01 to 0.3% by mass, and 0.05 to 0.2% by mass. More preferably, it is about. Carbon steel having such a carbon content is also called “low carbon steel”, and is particularly excellent in ductility. For this reason, the metal plate comprised with low carbon steel is excellent in ductility, and can be shape | molded with high dimensional accuracy. Further, it is a material whose properties such as spreadability and hardness can be controlled particularly easily by heat treatment described later.
As the low-carbon steel, for example, a low-carbon steel material used for a carbon steel pipe for mechanical structure defined in JIS G 3445 is particularly suitable.

Subsequently, as shown in FIG. 6C, the end portions 512 and 512 that are brought into contact with each other in the tubular shape of the metal plate 511 are welded (seam welding) (first step).
This welding method is not particularly limited, and methods such as high-frequency welding and resistance heating welding can be used.
Next, if necessary, burrs at the welded portion of the metal plate 511 are removed to obtain a circular metal tube 513.

As shown in FIG. 6D, the metal pipe 513 formed in this way has a seam welded portion (seam portion 513b) along the longitudinal direction of the outer peripheral portion (the axial direction of the metal tube 513). It will be formed.
Note that the metal tube 513 manufactured by the method as described above is inexpensive and has high dimensional accuracy.

[2] Next, heat treatment is performed on the obtained metal tube 513 (see FIG. 6D).
When heat treatment is performed on the metal tube 513, the crystal structure in the metal tube 513 changes. Specifically, the hardness of the entire metal tube 513 is made uniform by making the crystal grain size uniform. Thereby, the difference in hardness is reduced between the seam portion 513b of the metal tube 513 and the other portion 513c (second step).
Here, conventionally, when there is a difference in hardness between the seam portion 513b and the other portion 513c, when forming a groove on the outer peripheral surface of the metal tube 513 in the third step described later, There were the following problems.

  In a third step to be described later, grooves are formed on the outer peripheral surface of the metal tube 513 by a rolling method. In the rolling method, the groove is formed by pressing a die having a convex portion of a predetermined shape against the outer peripheral surface of the metal tube 513 and causing it to bite. During such rolling, the amount of dies that bite into the outer peripheral surface of the metal tube 513 varies depending on the hardness of the outer peripheral surface of the metal tube 513. Accordingly, the seam portion 513b of the metal tube 513 and the other portion 513c have different amounts of biting into the dies, and the depths of the formed grooves are different. For this reason, the depth of the formed groove varies on the outer peripheral surface of the main body 300 of the developing roller 510 finally obtained.

In order to deal with such a problem, in the present invention, the difference in hardness is reduced between the seam portion 513b of the metal tube 513 and the other portion 513c by performing heat treatment on the metal tube 513. Thereby, in the 3rd process mentioned later, the depth of the groove formed between seam part 513b and other parts 513c can be made uniform.
In addition, since the overall ductility of the metal tube 513 is improved (hardness is reduced), dies are likely to bite into the outer peripheral surface of the metal tube 513 when grooves are formed in the outer peripheral surface of the metal tube 513. For this reason, it is possible to efficiently form a groove with high dimensional accuracy in a short time.

Further, with the heat treatment, there is an advantage that the crystal grain size and carbide distribution in the metal tube 513 are made uniform, and the stress (residual stress) remaining in the metal tube 513 is reduced.
Here, this residual stress is the stress accumulated in the metal tube in the process of manufacturing the metal tube (the first step in the present embodiment).
In a metal tube including residual stress, the residual stress of the metal tube is released or the residual stress is increased when a groove is formed on the outer peripheral surface of the metal tube as in a third step described later. In the conventional developing roller manufacturing method, when the residual stress is released, or when the residual stress increases and the allowable range of stress that the metal tube can withstand is exceeded, the metal tube is deformed.

In the present invention, such residual stress is reduced, so that deformation of the metal tube 513 in the third step to be described later can be reliably prevented.
Here, such heat treatment may be performed at least once, but is preferably performed a plurality of times. In this way, by performing the heat treatment a plurality of times, the difference in hardness can be more reliably reduced between the seam portion 513b of the metal tube 513 and the other portion 513c.

  The number of heat treatments is not particularly limited, but in this embodiment, the heat treatment is performed twice: a first heat treatment (first heat treatment) and a second heat treatment (second heat treatment) performed at a lower temperature than the first. The heat treatment is performed separately. By performing such heat treatment at two different temperatures, the difference in hardness between the seam portion 513b and the other portion 513c can be more reliably reduced.

  The temperature of the first heat treatment preferably satisfies the relationship of A to A + 100 when the recrystallization temperature of the metal material constituting the metal tube 513 is A [° C.], and the relationship of A + 30 to A + 50. It is more preferable to satisfy. By applying heat treatment to the metal tube 513 in the above temperature range, it is possible to reliably suppress or prevent wasteful energy consumption due to excessive heat treatment while imparting sufficient heat energy to the metal tube 513 to change the crystal structure. Can do.

  Further, the time of the first heat treatment is slightly different depending on the temperature of the first heat treatment, but is preferably about 10 to 120 minutes, more preferably about 30 to 90 minutes. By setting the time of the first heat treatment within the above range, the hardness difference on the outer peripheral surface 513a of the metal tube 513 can be sufficiently relaxed. In addition, although the time of 1st heat processing may exceed the said upper limit, it cannot be anticipated that relaxation of a hardness difference will advance any more.

Note that examples of the atmosphere in performing the first heat treatment include an inert gas atmosphere such as nitrogen and argon, a reducing gas atmosphere such as hydrogen and carbon monoxide, and a reduced pressure atmosphere.
In the first heat treatment, when the heated metal tube 513 is cooled, any method of natural cooling or forced cooling may be used, but natural cooling is preferable. Thereby, it is possible to prevent the heated metal tube 513 from being rapidly cooled, and to suppress generation of new stress accompanying cooling. Furthermore, there is an advantage that cooling can be performed at low cost.

  Next, if necessary, after the first heat treatment, the metal tube 513 may be subjected to various processes such as cold drawing and cold rolling. By performing such various processes after the first heat treatment, it is possible to prevent the residual stress in the metal tube 513 from being released or increased by the various processes. For this reason, high processing quality is ensured in various processing. The shape of the metal tube 513 can be changed to a desired shape by various processes.

Next, a second heat treatment is performed after the first heat treatment.
The temperature of the second heat treatment is preferably lower than the temperature of the first heat treatment. In particular, when the temperature of the first heat treatment is equal to or higher than the recrystallization temperature A [° C.], the recrystallization is performed. It is more preferable that the temperature is lower than the crystallization temperature A [° C.]. If the temperature of the first heat treatment and the temperature of the second heat treatment are set as described above, the difference in hardness between the seam portion 513b of the metal tube 513 and the other portion 513c is set in the first heat treatment. Make sure to ease. In the second heat treatment, the uniformization of the crystal grain size in the metal tube 513 is further promoted. Thereby, the residual stress of the metal tube 513 can be further reduced, and the spreadability of the metal tube 513 can be further enhanced. That is, the hardness difference between the seam portion 513b of the metal tube 513 and the other portion 513c can be reliably reduced, and the spreadability of the metal tube 513 can be further improved.

  The time for the second heat treatment varies slightly depending on the temperature of the second heat treatment, but is preferably about 10 to 120 minutes, more preferably about 30 to 90 minutes. By setting the time of the second heat treatment within the above range, the crystal grain size in the metal tube 513 can be sufficiently uniformed in the second heat treatment. Thereby, the spreadability of the metal tube 513 can be sufficiently enhanced. The time for the second heat treatment may exceed the upper limit value, but it cannot be expected to make the crystal grain size more uniform.

Note that examples of the atmosphere in performing the second heat treatment include an inert gas atmosphere such as nitrogen and argon, a reducing gas atmosphere such as hydrogen and carbon monoxide, and a reduced pressure atmosphere.
Also in the second heat treatment, when the heated metal tube 513 is cooled, either natural cooling or forced cooling may be used, but natural cooling is preferable. Thereby, since the whole heated metal tube 513 can be cooled uniformly, the uniformization of the crystal grain size is further promoted. In addition, since the cooling rate is relatively slow, crystal growth is promoted. As a result, the spreadability of the metal tube 513 can be further enhanced.

Next, if necessary, after the second heat treatment, the metal tube 513 may be subjected to various processes such as cold drawing and cold rolling. By performing such various types of processing after the second heat treatment, the processing can be performed in a state in which the ductility of the metal tube 513 is increased, so that workability in various types of processing can be improved. And by various processes, while changing the shape of the metal pipe 513 to a desired shape, the dimensional accuracy can be improved.
As described above, a metal tube 513 having a target shape is obtained.

  In addition, the metal pipe 513 has a Vickers hardness HV of preferably 20 or less, more preferably 10 or less, after the end of this step, between the seam portion 513b and the other portion 513c. . By producing the developing roller 510 using such a metal tube 513 having a small hardness difference, it is possible to reliably obtain a developing roller having a uniform groove depth throughout. That is, such a metal tube 513 is particularly useful in manufacturing the developing roller 510 with high reliability.

[3] Next, a groove is formed in the outer peripheral surface 513a of the metal tube 513 subjected to the heat treatment according to [2] (third step).
A rolling method can be used as a method of forming the groove.
In the rolling method, the convex portion corresponding to the shape of the groove to be formed on the outer peripheral surface 513a of the metal tube 513 is pressed against the outer peripheral surface 513a of the metal tube 513 with a die provided on the outer peripheral surface. This is a processing method for forming a groove.
In rolling, first, the metal tube 513 subjected to the heat treatment in [2] is brought into contact with the outer peripheral surface of a cylindrical die 514 as shown in FIG.

In FIG. 7, two dies 514 and 514 are arranged so that their axes are parallel to each other. The separation distance between the dies 514 and 514, that is, the distance between the dies 514 and 514, is determined from the outer diameter in consideration of the outer diameter of the metal tube 513 and the depth of the groove formed on the outer peripheral surface. Make it slightly smaller.
The number of dice 514 may be one or three.

Next, the dies 514 and 514 are rotated in the same direction with the axis of each cylinder as the rotation axis.
Next, the metal tube 513 is inserted into the gap between the rotating dies 514 and 514. Thereby, the outer peripheral surface of each die 514, 514 is pressed against the outer peripheral surface 513a of the metal tube 513, respectively. At this time, the convex portion 514a provided on the outer peripheral surface of each die 514, 514 bites into the outer peripheral surface 513a of the metal tube 513, whereby the groove 2 shown in FIG. 7 is formed. In this state, the metal tube 513 rolls along the outer peripheral surface of each of the dies 514 and 514, so that the groove 2 is formed on the entire outer peripheral surface 513a.
Thus, the cylindrical main body 300 is obtained.

  In the developing roller 510 shown in FIG. 7, a plurality of grooves are formed along the outer peripheral surface 513a. The pitch of each groove is preferably smaller than the width of the seam portion 513b. If the pitch of each groove is smaller than the width of the seam portion 513b, a large number of grooves cross the seam portion 513b. When such a large number of grooves are formed on a conventional developing roller, there are inevitably many areas where the depth of the groove formed in the seam portion is different from the depth of the groove formed in a portion other than the seam portion. Become.

On the other hand, according to the present invention, even when a large number of grooves are formed on the outer peripheral surface 513a of the metal tube 513, the depth of the formed grooves can be uniform throughout. Therefore, when the developing roller 510 having a large number of grooves is manufactured, the developing roller manufacturing method of the present invention can be particularly suitably applied.
Further, when the pitch of each groove is P [mm] and the width of the seam portion 513b is W [mm], W / P is preferably 10 or more, and more preferably 20 or more. Thus, when manufacturing the developing roller 510 in which a large number of grooves are formed with respect to the width of the seam portion 513b, the effect of the developing roller manufacturing method of the present invention is more remarkably exhibited.

In the present embodiment, the heat treatment is performed on the entire metal tube 513 to reduce the hardness difference between the seam portion 513b and the other portion 513c. However, the heat treatment is not limited to such a form.
For example, each heat treatment condition such as the temperature, time, atmosphere, cooling rate, and heat treatment portion of the heat treatment may be performed between the seam portion 513b and the other portion 513c regardless of the material of the metal tube 513. It is appropriately set so that the hardness difference is alleviated.

Specifically, the hardness of only the seam portion 513b may be reduced by performing heat treatment only on the seam portion. Thereby, the hardness difference between the seam part 513b and the other site | part 513c is relieve | moderated more reliably.
Alternatively, the entire metal pipe 513 may be heated so that the cooling rate of the seam portion 513b is different from the cooling rate of the other portion 513c.

[4] Next, the reduced diameter portions 310 are inserted into both ends of the hollow portion of the main body 300, respectively. At this time, the respective axis lines of the reduced diameter portions 310 and 310 are set to coincide with the rotation axis of the main body 300. And the main body 300 and each reduced diameter part 310,310 are each fixed. Thereby, the developing roller 510 is obtained.
According to the above method, the developing roller 510 in which the depth of the groove formed on the outer peripheral surface 513a is uniform over the entire outer peripheral surface 513a can be obtained. In the developing device 51 including such a developing roller 510, the amount of toner applied to the photoconductor 20 by the developing roller 510 is uniform over the entire circumference of the developing roller 510. For this reason, the occurrence of uneven development in the developing device 51 can be reliably prevented. Further, in the printer 10 including such a developing device 51, it is possible to reliably prevent the occurrence of printing unevenness.

Further, since the residual stress of the metal tube 513 can be reduced, it is possible to reliably prevent the metal tube 513 from being deformed (warped) when forming the groove. As a result, in the developing device 51, the separation distance between the developing roller 510 and the regulating blade 560 can be maintained constant even while the developing roller 510 is rotating. As a result, the occurrence of uneven development in the developing device 51, and hence the occurrence of uneven printing in the printer 10, can be more reliably prevented.
Further, since it is not necessary to correct the deformation of the metal tube 513, the manufacturing cost of the developing device 51 and the printer 10 can be reduced.

As described above, the developing roller manufacturing method, the developing roller, the developing device, and the image forming apparatus of the present invention have been described based on the preferred embodiments, but the present invention is not limited thereto.
For example, in the above embodiment, when the developing roller is manufactured, the heat treatment is performed twice, but may be performed three times or more.
Moreover, the manufacturing method of the developing roller of this invention can also add arbitrary processes as needed.

Moreover, what was prepared beforehand (for example, commercially available metal tube etc.) can be used for a metal tube, In this case, the said 1st process can be abbreviate | omitted.
Further, the shape of the groove formed on the outer peripheral surface of the developing roller is not particularly limited, and may be any shape. Regardless of the shape of the groove formed on the outer peripheral surface of the developing roller, the operation and effect of the developing roller manufacturing method of the present invention as described above are exhibited.

Next, specific examples of the present invention will be described.
1. Production of printer (image forming apparatus) (Example 1)
<1> First, a steel plate (metal plate) made of carbon steel used for the carbon steel pipe STKM11A for machine structure was prepared. Then, this steel plate was formed into a tubular shape by roll forming. The recrystallization temperature of STKM11A is 880 ° C.
Next, the end portions of the steel plates formed into a tubular shape were seam welded by high-frequency welding. Then, the burr | flash of the welding part was removed. Thereby, a steel pipe (metal pipe) having a seam portion having a width of 5 mm was obtained.

<2> Next, the obtained steel pipe was put into a heat treatment furnace and subjected to heat treatment under the following conditions.
<Heat treatment conditions (first time)>
・ Temperature: 930 ℃
-Time: 60 minutes-Atmosphere: N ₂ gas atmosphere-Cooling method: Natural cooling <3> Next, the steel pipe subjected to heat treatment was subjected to cold drawing. Thereby, the outer diameter and inner diameter of the steel pipe were adjusted.

<4> Next, the processed steel pipe was placed in a heat treatment furnace and subjected to heat treatment under the following conditions.
<Heat treatment conditions (second time)>
・ Temperature: 600 ℃
-Time: 60 minutes-Atmosphere: N ₂ gas atmosphere-Cooling method: natural cooling <5> Next, the steel pipe subjected to heat treatment was subjected to cold drawing. Thereby, the outer diameter and inner diameter of the steel pipe were adjusted.

<6> Next, the groove | channel (recessed part) shown in FIG. 4 was formed in the outer peripheral surface of the steel pipe which adjusted the outer diameter and the internal diameter by the rolling method. In addition, main conditions, such as a dimension and an angle of each part of the formed groove | channel, are as follows.
<Conditions for each part of the groove>
・ D ₁ : 3 μm
・ D ₂ : 4 μm
・ Θ ₁ : 60 °
・ Θ ₂ : 90 °
-Groove area ratio: 70%
・ Pitch of each groove in the circumferential direction: 0.08 mm
Thereby, a developing roller was obtained.
<7> Next, the developing device shown in FIG. 2 incorporating this developing roller was obtained.
<8> Next, the printer shown in FIG. 1 incorporating this developing device was obtained.

(Example 2)
A developing roller was produced in the same manner as in Example 1 except that the temperature of the first heat treatment of the developing roller was changed to 900 ° C., and a developing device and a printer incorporating this developing roller were produced.
(Example 3)
A developing roller was manufactured in the same manner as in Example 1 except that the temperature of the first heat treatment of the developing roller was changed to 850 ° C., and a developing device and a printer incorporating the developing roller were manufactured.

Example 4
A developing roller was manufactured in the same manner as in Example 1 except that the temperature of the first heat treatment of the developing roller was changed to 600 ° C., and a developing device and a printer incorporating the developing roller were manufactured.
(Example 5)
A developing roller was produced in the same manner as in Example 1 except that the steps <4> to <5> were omitted, and a developing device and a printer incorporating the developing roller were produced.
(Comparative example)
The developing roller was produced in the same manner as in Example 1 except that the steps <2> to <5> were omitted and the cold drawing was performed after the step <1>. Development devices and printers incorporating the

2. Evaluation 2.1 Evaluation of hardness of steel pipe Five steel pipes used for manufacturing the developing roller in each example and comparative example were prepared, and the Vickers hardness HV of each part of the outer peripheral surface of each steel pipe was determined according to JIS Z. It was measured by the method specified in 2244. And the difference of the hardness of a seam part and the hardness of parts other than a seam part was computed, and it evaluated according to the following references | standards.
◎: Hardness difference is less than HV10 ○: Hardness difference is HV10 or more and less than 30 △: Hardness difference is HV30 or more and less than 50 ×: Hardness difference is HV50 or more

2.2 Evaluation of Groove Depth of Developing Roller Prepare five developing rollers obtained in each of the examples and comparative examples, and in each developing roller, the depth of the groove formed in each part of the outer peripheral surface is set. It was measured. And the depth of the groove | channel formed in the seam part was compared with the depth of the groove | channel formed in parts other than a seam part, and the difference was computed. In addition, the compared groove | channel was a groove | channel formed so that the depth might be the same by the seam part and other site | parts, The difference of the depth of these grooves was evaluated in accordance with the following references | standards.
A: The difference in groove depth is less than 20% of the groove depth. O: The difference in groove depth is not less than 20% and less than 40% of the groove depth. The difference is 40% or more and less than 60% of the groove depth. X: The difference of the groove depth is 60% or more of the groove depth.

2.3 Evaluation of Warpage of Developing Roller Five developing rollers obtained in each of Examples and Comparative Examples were prepared, and the degree of warping (warping amount) of the axis of each developing roller was measured. And the difference of this curvature amount and the grade (warpage amount) of the curvature of the steel pipe in the said process <1> measured beforehand was computed, and it evaluated according to the following references | standards.
A: Increase amount of warpage is less than 5 μm ○: Increase amount of warpage is 5 μm or more and less than 20 μm Δ: Increase amount of warpage is 20 μm or more and less than 50 μm ×: Increase amount of warpage is 50 μm or more Is

2.4 Evaluation of printing unevenness Five printers obtained in each example and comparative example were prepared, and a predetermined pattern was printed on each printer. Then, the printing unevenness of the pattern was evaluated according to the following criteria. The toner used was a polyester resin composition having an average particle diameter of 5 μm.
A: Printing unevenness was not recognized at all. ○: Printing unevenness was slightly recognized. Δ: Printing unevenness was observed. X: Printing unevenness was observed remarkably. The results of the above evaluation are shown in Table 1. In addition, for example, ◯ to ◎ indicate a case where, among five samples (developing roller, steel pipe, printer), a sample with an evaluation of ◯ and a sample with an evaluation of ◎ are mixed. .

As apparent from Table 1, the steel pipe used in each example had a smaller hardness difference between the seam portion and the other parts than the steel pipe used in the comparative example. Moreover, about the depth of the groove | channel formed in the outer peripheral surface of a steel pipe, it was recognized that the variation of the steel pipe used in each Example was smaller than the steel pipe used also in the comparative example. From this, in each Example, the hardness difference between the seam portion of the steel pipe and the other portion was alleviated by heat treatment, and thereby a developing roller having a uniform groove depth formed by rolling was obtained. Inferred.
Furthermore, the developing roller obtained in each example had a smaller amount of increase in warpage before and after the rolling process than the developing roller obtained in the comparative example. In addition, the printers obtained in each example showed less printing unevenness and better printing performance than the printers obtained in the comparative examples.

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 which the developing device shown in FIG. 2 has. 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. It is a schematic diagram for demonstrating the manufacturing method of the developing roller of this invention. It is a schematic diagram for demonstrating the manufacturing method of the developing roller of this invention.

Explanation of symbols

  10 …… Printer 2 …… Groove 21 …… First groove 211 …… Side surface 212 …… Bottom surface 213 …… Unit groove 22 …… Second groove 23 …… Enlarged portion 231 …… Side surface 232 …… Bottom surface 24… ... Intersection 20 ... Photoconductor 30 ... Charging unit 300 ... Body 301 ... Outer peripheral part 301a ... Outer peripheral surface 310 ... Reduced diameter part 320 ... Groove forming part 40 ... Exposure unit 50 ... Developing unit 50a …… Axis 51 …… Black developing device 52 …… Magenta developing device 53 …… Cyan developing device 54 …… Yellow developing device 55a to 55d …… Holding portion 510 …… Developing roller 511 …… Metal plate 512 …… End portion 513 …… Metal pipe 513a …… Outer peripheral surface 513b …… Seam portion 513c …… Part 514 …… Die 514a …… Protrusion 520 …… Seal member 53 …… Housing 540 …… Housing 550 …… Toner supply roller 560 ...... Regulating blade 560 a ...... Rubber 560 b ...... Rubber support 562 …… Blade support sheet metal 570 …… Blade back member 60 …… Primary transfer unit 70 ...... ... Intermediate transfer body 75 ... Cleaning unit 76 ... Cleaning blade 80 ... Secondary transfer unit 90 ... Fixing unit 92 ... Paper feed tray 94 ... Paper feed roller 96 ... Registration roller P1 ... Recording medium T ... Toner T1, T2 ... Particle O ... Rotation axis (center axis)

Claims (15)

A method for producing a developing roller having a recess for holding toner on the outer periphery,
Relaxing the difference in hardness between the seam portion of the tubular body and the other portion by applying heat treatment to at least the portion including the seam portion of the metal tubular body having a seam portion;
And a step of forming the concave portion on the outer peripheral portion of the pipe body subjected to the heat treatment by a rolling method.   2. The developing roller manufacturing method according to claim 1, wherein the temperature of the heat treatment satisfies a relationship of A to A + 100, where A [° C.] is a recrystallization temperature of a metal constituting the tubular body.   The method for manufacturing a developing roller according to claim 2, wherein the heat treatment time is 10 to 120 minutes.   The method for manufacturing a developing roller according to claim 1, wherein in the heat treatment, the heated tube body is naturally cooled.   The method for manufacturing a developing roller according to claim 1, wherein the heat treatment is performed a plurality of times.   The developing roller manufacturing method according to claim 5, wherein the plurality of heat treatments include a first heat treatment and a second heat treatment performed at a lower temperature than the first heat treatment after the first heat treatment. .   The temperature of the first heat treatment is a temperature equal to or higher than the recrystallization temperature of the metal constituting the tubular body, and the temperature of the second heat treatment is a temperature lower than the recrystallization temperature of the metal. The manufacturing method of the developing roller of Claim 6.   8. The developing roller according to claim 1, wherein a hardness difference between the seam portion of the tubular body and the other portion after the heat treatment step is 20 or less in terms of Vickers hardness Hv. 9. Production method. The recess is a plurality of grooves provided on the outer periphery of the tubular body,
The developing roller manufacturing method according to claim 1, wherein a pitch of each groove in a circumferential direction of the tube body is smaller than a width of the seam portion.   The method for manufacturing a developing roller according to claim 9, wherein W / P is 10 or more, where a pitch of each groove is P [mm] and a width of the seam portion is W [mm].   The method for manufacturing a developing roller according to claim 1, wherein the metal constituting the tubular body is carbon steel.   The method for producing a developing roller according to claim 11, wherein a carbon content in the carbon steel is 0.3% by mass or less.   A developing roller manufactured by the method for manufacturing a developing roller according to claim 1.   A developing device comprising the developing roller according to claim 13.   An image forming apparatus comprising the developing device according to claim 14.

Images