JP2011197145A - Image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image forming apparatus which can restrain electric charges from being discharged to an image formation area of an image carrier from a developing roller, and can restrain image failure resulting from discharge of electric charges from the developing roller to the image carrier.SOLUTION: The image forming apparatus includes a developing sleeve 17A including: a core 171 made of aluminum or aluminum alloy, and an anodized aluminum layer 173 with a film thickness of 10 to 25 μm, which is disposed via an active layer 172 so as to cover part of the core 171. The developing sleeve 17A includes: a first portion 174 which is disposed oppositely to the image formation area 201 of the image carrier 2 in the center of the developing sleeve 17A in the direction of a second rotary shaft J2, and on the surface of which the anodized aluminum layer 173 is arranged; and a second portion 175 which is disposed oppositely to the image non-formation area 202 of the image carrier 2 in the end of the developing sleeve 17A in the direction of the second rotary shaft J2, and on the surface of which the aluminum or aluminum alloy is exposed, and whose surface roughness is greater than the first portion 174.

Description

  The present invention relates to an image forming apparatus including a developing device.

  2. Description of the Related Art Conventionally, as a developing device provided in an image forming apparatus, a developing roller that forms a toner layer (developer layer) with toner (developer) is provided, and a photosensitive drum (image bearing member) is formed by a toner layer formed on the surface of the developing roller. There is known a developing device for developing an electrostatic latent image formed on the surface of the body.

The developing device generally includes a magnet roller having one or a plurality of magnetic poles, and a developing sleeve disposed outside the magnet roller.
As a developing sleeve in a developing roller, a developing sleeve having a core made of aluminum or aluminum alloy whose surface has been roughened and an alumite layer formed so as to cover the surface of aluminum or aluminum alloy is known. (For example, refer to Patent Document 1).

  The developing sleeve in the developing roller described in Patent Document 1 can stably hold the toner on the surface of the developing sleeve by performing a roughening process on the surface of the core made of aluminum or an aluminum alloy. Therefore, a stable toner layer can be formed on the surface of the developing sleeve. Thereby, the toner of the toner layer formed on the developing sleeve can be stably supplied to the photosensitive drum.

  Further, the developing sleeve in the developing roller described in Patent Document 1 can improve the strength of the surface by providing an alumite layer so as to cover the surface of the core made of aluminum or aluminum alloy. Therefore, the surface of the developing sleeve is reduced from being scraped by toner, abrasive, or the like. Therefore, for example, a stable toner layer can be formed on the surface of the developing sleeve even when an image is formed on several hundred thousand sheets or more (transfer material).

Japanese Unexamined Patent Publication No. 1-145674

However, in the developing sleeve in the developing roller described in Patent Document 1, when an alumite layer is provided on the surface of the developing sleeve, electric charges are likely to accumulate on the surface of the developing sleeve due to the insulating property of the surface. In particular, in a low-temperature and low-humidity environment, charges due to static electricity tend to accumulate on the surface of the developing sleeve. For this reason, when the developing device is operated in a low-temperature and low-humidity environment, charges accumulated on the surface of the developing sleeve are easily discharged from the surface of the developing sleeve to the photosensitive drum. As a result, when electric charges are discharged to the image forming area where the electrostatic latent image is formed on the photosensitive drum, leak marks are formed in the image forming area or the toner layer is disturbed. was there. As a result, image defects may occur.
Therefore, it has been desired to suppress the discharge of charges from the developing roller (developing sleeve) to the image forming area in the photosensitive drum.

  The present invention can suppress image discharge caused by charge discharge from the developing roller to the image carrier by suppressing charge discharge from the developing roller to the image forming area on the image carrier. An object is to provide an apparatus.

  The present invention is an image carrier that is formed to be rotatable about a first rotation axis and has an image forming area in which an electrostatic latent image can be formed, and a non-image forming area in which the electrostatic latent image is not formed, A magnet unit having one or a plurality of magnetic poles and a magnet unit disposed opposite to the image carrier so as to be rotatable about a second rotation axis parallel to the first rotation axis outside the magnet unit. A developing sleeve that forms a developer layer on the surface thereof, and has a core made of aluminum or an aluminum alloy, and a thickness of 10 to 25 μm disposed through the active layer so as to cover a part of the core And a developing roller having an alumite layer, and the developing sleeve is disposed on the surface of the developing sleeve at the center side in the second rotation axis direction so as to face the image forming region, and on the surface. A A first portion in which the mate layer is disposed, and an end portion of the developing sleeve in the second rotational axis direction, facing the non-image forming region, and aluminum or an aluminum alloy is exposed on the surface; The present invention relates to an image forming apparatus having a second part whose surface roughness is rougher than the first part.

  The surface roughness of the second part is preferably 10 to 30 μm in ten-point average roughness (Rz).

  The first part and the second part are continuously arranged, and the first part has an outer edge of the first part in the same direction as the outer edge of the image forming region in the first rotation axis direction. Alternatively, it is preferable that the outer edge of the first portion is disposed so as to be positioned closer to the end of the developing sleeve than the outer edge of the image forming area.

  Further, the surface roughness of the second part preferably has a ten-point average roughness (Rz) that increases toward the end of the developing sleeve in the second rotation axis direction.

  Further, it is preferable that the image forming area of the image carrier and the first portion of the developing sleeve are in a non-contact state.

  The developer is preferably a magnetic one-component developer.

  According to the present invention, by suppressing the discharge of charges from the developing roller to the image forming area of the image carrier, it is possible to suppress image defects caused by the discharge of charges from the developer roller to the image carrier. An image forming apparatus can be provided.

It is a front view for demonstrating arrangement | positioning of each component in the printer 1 of 1st Embodiment of this invention. FIG. 2 is a cross-sectional view illustrating an overall configuration of a developing device 16 in the printer 1. 4 is a plan view for explaining the positional relationship between the developing roller 17 and the photosensitive drum 2. FIG. FIG. 4 is a cross-sectional view of the developing roller 17 shown in FIG. FIG. 4 is a cross-sectional view of the developing roller 17 shown in FIG. FIG. 4 is a cross-sectional view illustrating a state of a surface subjected to a roughening process in the developing roller 17. FIG. 4 is a diagram illustrating a state in which charges accumulated on the surface of the developing roller 17 are discharged. It is sectional drawing which shows the state of the surface by which the roughening process of the developing roller 17 in 2nd Embodiment of this invention was carried out.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
With reference to FIG. 1, the overall structure of a printer 1 as an image forming apparatus in the first embodiment of the present invention will be described. FIG. 1 is a front view for explaining the arrangement of components in the printer 1 according to the first embodiment of the present invention.

As shown in FIG. 1, a printer 1 as an image forming apparatus includes an apparatus main body M and an image forming unit GK that forms a predetermined toner image on a sheet T as a sheet-like transfer material based on predetermined image information. And a paper supply / discharge unit KH that supplies the paper T to the image forming unit GK and discharges the paper T on which the toner image is formed.
The outer shape of the apparatus main body M is configured by a case body BD as a casing.

  As shown in FIG. 1, the image forming unit GK includes a photosensitive drum 2 as an image carrier (photosensitive member), a charging unit 10, a laser scanner unit 4 as an exposure unit, a developing device 16, and a toner cartridge. 5, a toner supply unit 6, a drum cleaning unit 11, a static eliminator 12, a transfer roller 8, and a fixing unit 9.

  As shown in FIG. 1, the paper feed / discharge unit KH includes a paper feed cassette 52, a manual paper feed unit 64, a transport path L for paper T, a registration roller pair 80, and a paper discharge unit 50.

Hereinafter, each configuration of the image forming unit GK and the paper supply / discharge unit KH will be described in detail.
First, the image forming unit GK will be described.
In the image forming unit GK, in order from the upstream side to the downstream side along the surface of the photosensitive drum 2, charging by the charging unit 10, exposure by the laser scanner unit 4, development by the developing device 16, transfer by the transfer roller 8. Then, static elimination by the static eliminator 12 and cleaning by the drum cleaning unit 11 are performed.

  The photosensitive drum 2 is made of a cylindrical member and functions as a photosensitive member or an image carrier. The photosensitive drum 2 is disposed so as to be rotatable in the direction of an arrow about an axis extending in a direction orthogonal to the conveyance direction of the paper T in the conveyance path L. An electrostatic latent image can be formed on the surface of the photosensitive drum 2.

  The charging unit 10 is disposed to face the surface of the photosensitive drum 2. The charging unit 10 uniformly charges the surface of the photosensitive drum 2 to be negative (minus polarity) or positive (plus polarity).

  The laser scanner unit 4 functions as an exposure unit, and is disposed away from the surface of the photosensitive drum 2. The laser scanner unit 4 includes a laser light source (not shown), a polygon mirror, a polygon mirror driving motor, and the like.

  The laser scanner unit 4 scans and exposes the surface of the photosensitive drum 2 based on image information input from an external device such as a PC (personal computer). By scanning exposure with the laser scanner unit 4, the charge on the exposed portion of the surface of the photosensitive drum 2 is removed. As a result, an electrostatic latent image is formed on the surface of the photosensitive drum 2.

The developing device 16 is provided corresponding to the photosensitive drum 2 and is disposed to face the surface of the photosensitive drum 2. The developing device 16 attaches a single color (usually black) toner to the electrostatic latent image formed on the photoconductive drum 2 to form a single color toner image on the surface of the photoconductive drum 2. The developing device 16 includes a developing roller 17 disposed opposite to the surface of the photosensitive drum 2, stirring rollers 18 and 19 for stirring the toner, and the like.
Details of the developing device 16 will be described later.

  The toner cartridge 5 is provided corresponding to the developing device 16 and stores toner supplied to the developing device 16.

  The toner supply unit 6 is provided corresponding to the toner cartridge 5 and the developing device 16 and supplies the toner contained in the toner cartridge 5 to the developing device 16. The toner supply unit 6 and the developing device 16 are connected by a toner supply path (not shown).

  The transfer roller 8 transfers the toner image developed on the surface of the photosensitive drum 2 to the paper T. A transfer bias for transferring the toner image formed on the photosensitive drum 2 to the paper T is applied to the transfer roller 8 by a transfer bias applying unit (not shown). The transfer roller 8 is configured to be rotatable while being in contact with the photosensitive drum 2.

  A sheet T conveyed through the conveyance path L is sandwiched between the photosensitive drum 2 and the transfer roller 8. The sandwiched paper T is pressed against the surface of the photosensitive drum 2. A transfer nip N is formed between the photosensitive drum 2 and the transfer roller 8. In the transfer nip N, the toner image developed on the photosensitive drum 2 is transferred onto the paper T.

  The static eliminator 12 is disposed to face the surface of the photosensitive drum 2. The static eliminator 12 irradiates the surface of the photosensitive drum 2 with light, thereby neutralizing the surface of the photosensitive drum 2 after the transfer is performed (removing the electric charge).

  The drum cleaning unit 11 is disposed to face the surface of the photosensitive drum 2. The drum cleaning unit 11 removes toner and deposits remaining on the surface of the photosensitive drum 2, and transports the removed toner and the like to a predetermined recovery mechanism (not shown) for recovery.

  The fixing unit 9 melts and presses the toner constituting the toner image transferred to the paper T and fixes the toner on the paper T. The fixing unit 9 includes a heating rotator 9a heated by a heater and a pressure rotator 9b pressed against the heating rotator 9a. The heating rotator 9a and the pressure rotator 9b sandwich and pressurize the paper T on which the toner image has been transferred, and convey the paper T. By transporting the paper T while being sandwiched between the heating rotator 9a and the pressure rotator 9b, the toner transferred onto the paper T is melted and pressurized, and is fixed to the paper T.

Next, the paper supply / discharge unit KH will be described.
As shown in FIG. 1, in the lower part of the apparatus main body M, a single paper feed cassette 52 that stores paper T is disposed. The paper feed cassette 52 is configured to be drawable in the horizontal direction from the right side (the right side in FIG. 1) of the apparatus main body M. In the paper feed cassette 52, a placement plate 60 on which the paper T is placed is disposed. In the paper feed cassette 52, the paper T is stored in a state of being stacked on the placement plate 60. The paper T placed on the placement plate 60 is sent out to the transport path L by the cassette paper feed unit 51 arranged at the paper feed side end of the paper feed cassette 52 (the right end in FIG. 1). The cassette paper feed unit 51 includes a forward feed roller 61 for taking out the paper T on the placement plate 60 and a paper feed roller pair 63 for feeding the paper T one by one to the transport path L. Is provided.

  On the right side (right side in FIG. 1) of the apparatus main body M, a manual paper feed unit 64 is provided. The manual paper feed unit 64 is provided mainly for supplying the apparatus main body M with a paper T of a size and type different from the paper T set in the paper feed cassette 52. The manual paper feed unit 64 includes a manual feed tray 65 that forms a part of the front surface of the apparatus main body M in the closed state, and a paper feed roller 66. The lower end of the manual feed tray 65 is attached to the vicinity of the paper feed roller 66 so as to be rotatable (openable and closable). The paper T is placed on the open manual feed tray 65. The paper feed roller 66 feeds the paper T placed on the open manual feed tray 65 to the manual feed path La.

  A paper discharge unit 50 is provided on the upper side of the apparatus main body M. The paper discharge unit 50 discharges the paper T to the outside of the apparatus main body M by the third roller pair 53. Details of the paper discharge unit 50 will be described later.

  The conveyance path L for conveying the paper T is a first conveyance path L1 from the cassette paper feeding unit 51 to the transfer nip N, a second conveyance path L2 from the transfer nip N to the fixing unit 9, and a discharge from the fixing unit 9. A third conveyance path L3 to the section 50, a manual conveyance path La that joins the paper supplied from the manual sheet feeding unit 64 to the first conveyance path L1, and a third conveyance path L3 from the downstream side to the upstream side. And a return transport path Lb that reverses the front and back and returns the sheet to the first transport path L1.

Moreover, the 1st junction part P1 and the 2nd junction part P2 are provided in the middle of the 1st conveyance path L1. A first branch portion Q1 is provided in the middle of the third transport path L3.
The first joining part P1 is a joining part where the manual feed path La joins the first transport path L1. The second junction P2 is a junction where the return conveyance path Lb merges with the first conveyance path L1.
The first branch portion Q1 is a branch portion where the return transport path Lb branches from the third transport path L3, and includes a first roller pair 54a and a second roller pair 54b. One roller of the first roller pair 54a and one roller of the second roller pair 54b are combined.

  A sensor (not shown) for detecting the paper T and a skew of the paper T (oblique feeding) are in the middle of the first conveyance path L1 (specifically, between the second joining portion P2 and the transfer roller 8). ) A registration roller pair 80 is arranged for matching the timing of correction and toner image formation in the image forming unit GK. The sensor is disposed immediately before the registration roller pair 80 in the transport direction of the paper T (upstream in the transport direction). The registration roller pair 80 conveys the paper T by performing the above-described correction and timing adjustment based on detection signal information from the sensor.

The return conveyance path Lb is a conveyance path that is provided so that the opposite surface (unprinted surface) to the surface that has already been printed faces the photosensitive drum 2 when performing duplex printing on the paper T.
According to the return conveyance path Lb, the sheet T conveyed from the first branching section Q1 to the paper discharge section 50 side by the first roller pair 54a is reversed and returned to the first conveyance path L1 by the second roller pair 54b. , And can be conveyed to the upstream side of the registration roller pair 80 disposed on the upstream side of the transfer roller 8. A predetermined toner image is transferred onto the unprinted surface at the transfer nip N on the paper T that is reversed upside down by the return conveyance path Lb.

  A paper discharge unit 50 is formed at the end of the third transport path L3. The paper discharge unit 50 is disposed on the upper side of the apparatus main body M. The paper discharge unit 50 opens toward the right side of the apparatus main body M (the right side in FIG. 1, the manual paper feed unit 64 side). The paper discharge unit 50 discharges the paper T conveyed on the third conveyance path L3 to the outside of the apparatus main body M by the third roller pair 53.

On the opening side of the paper discharge unit 50, a paper discharge stacking unit M1 is formed. The paper discharge stacking unit M1 is formed on the upper surface (outer surface) of the apparatus main body M. The paper discharge stacking unit M1 is a part formed by the upper surface of the apparatus main body M being depressed downward. The bottom surface of the paper discharge stacking unit M1 constitutes a part of the top surface of the apparatus main body M. In the paper discharge stacking unit M1, sheets T formed with a predetermined toner image and discharged from the paper discharge unit 50 are stacked and stacked.
A paper detection sensor is disposed at a predetermined position on each conveyance path.

Hereinafter, a configuration related to the developing device 16 that is a characteristic part of the printer 1 of the first embodiment will be described with reference to the drawings.
FIG. 2 is a cross-sectional view showing the overall configuration of the developing device 16 in the printer 1. FIG. 3 is a plan view for explaining the positional relationship between the developing roller 17 and the photosensitive drum 2. 4A is a cross-sectional view of the developing roller 17 shown in FIG. 4B is a cross-sectional view of the developing roller 17 shown in FIG. FIG. 5 is a cross-sectional view showing the state of the surface of the developing roller 17 that has been subjected to the roughening treatment.

First, the photosensitive drum 2 will be described.
As shown in FIGS. 2 and 3, the photosensitive drum 2 is rotatable in the direction of arrow R about the first rotation axis J1. The photosensitive drum 2 is formed to extend in a direction along the first rotation axis J1.

  The photosensitive drum 2 has an image forming area 201 capable of forming an electrostatic latent image on the surface at the center in the direction of the first rotation axis J1. In addition, the photosensitive drum 2 has a non-image forming area 202 where an electrostatic latent image is not formed on the surface at both ends in the direction of the first rotation axis J1.

Next, the developing device 16 will be described.
As shown in FIG. 2, the developing device 16 includes a storage chamber 20, a first stirring roller 18, a second stirring roller 19, a developing roller 17, and a regulation blade 21. The first stirring roller 18, the second stirring roller 19, the developing roller 17, and the regulation blade 21 are disposed inside the storage chamber 20.

  A developer is stored in the storage chamber 20. The developer is a magnetic one-component developer made of magnetic toner having magnetism. An opening 23 is formed in a portion of the storage chamber 20 that faces the photosensitive drum 2. The toner as the developer stored in the storage chamber 20 is supplied from the developing roller 17 to the photosensitive drum 2 through the opening 23. The developing device 16 develops the electrostatic latent image formed on the surface of the photosensitive drum 2.

The storage chamber 20 has a space of a predetermined shape for storing each member therein. The storage chamber 20 includes a stirring chamber 25 that stores and stirs toner.
The stirring chamber 25 is partitioned by a partition plate 24 into two chambers, a first stirring chamber 25A on the right side in FIG. 1 and a second stirring chamber 25B on the left side in FIG. The 1st stirring roller 18 and the 2nd stirring roller 19 are arrange | positioned in the storage chamber 20 across the partition plate 24 in parallel in the horizontal direction. The first stirring roller 18 is disposed in the first stirring chamber 25A. A second stirring roller 19 is disposed in the second stirring chamber 25B.

  A first flow port (not shown) connecting the first stirring chamber 25A and the second stirring chamber 25B to both ends of the first stirring roller 18 and the second stirring roller 19 in the rotation axis direction with respect to the partition plate 24. ) And a second distribution port (not shown).

  A developer supply opening 29 for supplying toner to the storage chamber 20 is formed at a predetermined position above the first stirring chamber 25A. The toner is supplied from the toner cartridge 5 to the storage chamber 20 through the toner supply unit 6 and the developer supply opening 29.

  The first stirring roller 18 is disposed in the first stirring chamber 25A. The first stirring roller 18 rotates in the direction of arrow A. The first agitation roller 18 agitates the toner supplied from the developer supply opening 29 to the first agitation chamber 25A, and conveys the toner from the first agitation chamber 25A to the second agitation chamber 25B via the first flow port. .

  The second stirring roller 19 is disposed in the second stirring chamber 25B. The second stirring roller 19 rotates in the arrow B direction. The second agitation roller 19 agitates and conveys the toner conveyed to the second agitation chamber 25B, and supplies a part of the conveyed toner to the developing roller 17 described later. The second stirring roller 19 conveys toner from the second stirring chamber 25B to the first stirring chamber 25A through the second flow port.

  As shown in FIG. 3, the developing roller 17 is formed to extend in a direction along a second rotation axis J2 parallel to the first rotation axis J1. The developing roller 17 is formed so that the length in the direction along the second rotation axis J2 is shorter than the length in the direction along the first rotation axis J1 of the photosensitive drum 2.

  As shown in FIG. 2, the developing roller 17 is disposed between the second stirring roller 19 and the photosensitive drum 2. The developing roller 17 is disposed to face the photosensitive drum 2 in a non-contact state. For example, the distance between the surface of the developing roller 17 and the surface of the photosensitive drum 2 is set in the range of 0.27 mm to 0.33 mm.

The developing roller 17 includes a magnet roller 17B as a magnet portion and a developing sleeve 17A disposed outside the magnet roller 17B.
The magnet roller 17B is formed in a cylindrical shape with one or more magnetic poles embedded therein. The magnet roller 17B is fixed to a predetermined position inside the developing sleeve 17A without rotating.

  The developing sleeve 17A is formed in a cylindrical shape. The developing sleeve 17A is disposed to be rotatable on the outer periphery of the magnet roller 17B. The developing sleeve 17A is configured to be rotatable in the direction of arrow C about the second rotation axis J2. The developing sleeve 17A is rotationally driven by a developing roller driving unit (not shown). The rotation directions of the developing sleeve 17A and the second stirring roller 19 are the same in the portions where the second stirring roller 19 and the developing sleeve 17A face each other.

  As shown in FIGS. 3 to 4B, the developing sleeve 17A includes a cylindrical core 171 made of aluminum or an aluminum alloy, and an alumite layer 173 disposed so as to cover the surface of the core 171 with the active layer 172 interposed therebetween. Have

  As shown in FIG. 5, the surface of the core 171 is roughened. By roughening the surface of the core 171, the toner is easily held on the developing sleeve 17 </ b> A, and the amount of toner transported to the photosensitive drum 2 is ensured.

The surface of the core 171 is roughened in an uneven shape over the entire region in the direction along the second rotation axis J2. For example, by performing a blasting process using a sphere such as glass beads, irregularities having a wavy cross section are formed on the surface of the core 171. The roughness of the unevenness formed on the surface of the core 171 defines the surface roughness as the surface roughness of the developing sleeve 17A.
The surface roughness of the developing sleeve 17A will be described later.

The alumite layer 173 is formed so as to cover the surface of the core 171 after the surface of the core 171 is roughened.
The alumite layer 173 is formed by anodizing the surface of the core 171 made of aluminum or an aluminum alloy. When the surface of the core 171 made of aluminum or an aluminum alloy is anodized, an oxide film is formed on the surface of the core 171 made of aluminum or an aluminum alloy. This oxide film is an alumite layer 173.

  When an oxide film is formed on the surface of the core 171 made of aluminum or an aluminum alloy by anodization, an active layer (barrier layer) 172 is formed between the aluminum or aluminum alloy and the alumite layer. The active layer 172 has a thickness of several tens of nm.

  The alumite layer 173 is formed to protect the irregularities formed on the surface of the core 171. Therefore, an alumite layer 173 having a relatively high hardness is formed on the surface of the core 171. By providing the alumite layer 173 on the surface of the developing sleeve 17A, the unevenness formed on the developing sleeve 17A is reduced from being scraped by toner, an abrasive, or the like.

  The thickness of the alumite layer 173 is set in the range of 10 to 25 μm. The reason for setting the film thickness of the alumite layer 173 to 10 to 25 μm is that when the film thickness is less than 10 μm, for example, when an image is formed on tens of thousands of sheets or more, alumite is used with a toner or an abrasive. This is because, since the layer 173 is cut, sufficient durability for protecting the unevenness formed on the core 171 cannot be obtained. Further, when the film thickness exceeds 25 μm, the charge accumulated on the surface of the developing sleeve 17A is difficult to be discharged.

As shown in FIGS. 3 to 5, the developing sleeve 17 </ b> A has a first portion 174 on the surface of which the alumite layer 173 is disposed, and a second portion 175 from which the core 171 made of aluminum or aluminum alloy is exposed. .
The first portion 174 is formed on the surface of the developing sleeve 17A on the center side in the direction along the second rotation axis J2 so as to face the image forming area 201. The second portion 175 is disposed continuously with the first portion 174 and is formed on the surface of both end portions of the developing sleeve 17A in the direction along the second rotation axis J2.

  As shown in FIG. 3, the first part 174 is located in the same direction as the outer edge of the image forming area 201 in the direction of the first rotation axis J1, or the outer edge of the first part is the image forming area 201. It is arranged so as to be located closer to the end portion side of the developing sleeve 17A than the outer edge. The first portion 174 is disposed in a non-contact state with respect to the image forming area 201 of the photosensitive drum 2.

The second portion 175 is disposed opposite to the non-image forming region 202 on the end side of the first portion 174 in the direction along the second rotation axis J2. That is, the second portion 175 is disposed so as not to overlap the image forming area 201 of the photosensitive drum 2 when viewed from a direction orthogonal to the direction along the first rotation axis J1 and the second rotation axis J2.
In other words, the second portion 175 is disposed closer to the end of the developing sleeve 17A in the direction of the second rotation axis J2 than the first portion 174, and faces the non-image forming area 202 away from the image forming area 201. Arranged.

  Next, the surface roughness of the developing sleeve 17A will be described. In the present embodiment, the surface roughness of the developing sleeve 17A is defined by the first part 174 and the second part 175. The surface roughness of the developing sleeve 17A is the surface roughness after the anodized layer 173 is formed on the core 171 on which the irregularities are formed in the first portion 174, and the surface roughness of the core 171 in the second portion 175. It is surface roughness in the state where the formed unevenness | corrugation was exposed. The surface roughness of the first portion 174 is defined in a state in which the anodized layer 173 is formed on the core 171 on which the unevenness is formed. However, even when the anodized layer 173 is not formed, the anodized layer 173 Since it is formed along the unevenness of the core 171, it is substantially the same.

  As shown in FIG. 5, the unevenness formed on the surface of the first portion 174 is such that the interval between the protrusions is the interval p1, and the difference in the thickness direction between the bottom of the recess and the top of the protrusion (depth of the unevenness). Is formed to be d1. The depth of the unevenness on the surface of the alumite layer 173 and the depth of the unevenness on the surface of the core 171 are substantially the same.

  The unevenness formed on the surface of the second portion 175 is formed such that the interval between the protrusions is the interval p2, and the difference in thickness direction between the recesses and the protrusions (the depth of the unevenness) is d2. . That is, the unevenness depth d2 formed on the surface 175A of the second portion 175 is larger than the unevenness depth d1 formed on the surface 174A of the first portion 174. The surface roughness of the developing sleeve 17A increases as the depth of the unevenness increases.

  Thus, the surface roughness of the surface 175A of the second part 175 is formed to be rougher than the surface roughness of the surface 174A of the first part 174. Specifically, the surface roughness of the first portion 174 is set to 7.5 μm, for example, in terms of ten-point average roughness (Rz). Further, the surface roughness of the second portion 175 is set in a range of 10 to 30 μm, for example, in ten-point average roughness (Rz).

The ten-point average roughness (Rz) is an average line of a portion obtained by extracting a reference length from an extraction curve (a curve connecting a bottom point and a vertex of a wavy uneven portion continuous in the second rotation axis J2 direction). Average absolute value of elevation (yp) from the highest peak to the fifth peak when measured in the direction of vertical magnification and average absolute value of elevation (yv) from the lowest peak to the fifth peak The value obtained from the sum of the values. A known measuring device (for example, SURFCOM 1500DX manufactured by Tokyo Seimitsu Co., Ltd.) is used to measure the ten-point average roughness (Rz).
The ten-point average roughness (Rz) can be obtained by the following equation (1).

  A toner layer is formed on the developing sleeve 17A by holding (attaching) toner on the outer peripheral surface (surface) by the magnetic force of the magnet roller 17B. A predetermined voltage is applied to the developing sleeve 17A by a voltage applying unit (not shown).

  As shown in FIG. 2, the developing roller 17 is disposed so that a part of the developing roller 17 faces the photosensitive drum 2 through the opening 23. The toner constituting the toner layer formed on the developing roller 17 is moved to the photosensitive drum 2 through the opening 23 due to a voltage difference between the voltage of the developing roller 17 and the photosensitive drum 2. Thereby, the developing roller 17 develops the electrostatic latent image formed on the photosensitive drum 2.

  As shown in FIG. 2, the restriction blade 21 is a member that extends in the first rotation axis J1 direction and the second rotation axis J2 direction. The regulating blade 21 is disposed with its tip close to the outer peripheral surface of the developing sleeve 17 </ b> A of the developing roller 17. The regulating blade 21 is disposed upstream of the photosensitive drum 2 with respect to the rotation direction C of the developing roller 17. The regulating blade 21 is disposed so as to be in a positional relationship substantially perpendicular to the outer peripheral surface of the developing roller 17.

  The regulating blade 21 regulates the thickness of the toner layer formed on the developing roller 17. That is, the regulating blade 21 regulates the amount of toner formed on the surface of the developing roller 17, thereby forming a thin toner layer having a constant thickness of about several tens of μm on the surface of the developing roller 17. The regulating blade 21 charges the toner in the toner layer when regulating the thickness of the toner layer formed on the developing roller.

Next, the operation of the developing device 16 will be described with reference to FIGS.
FIG. 6 is a diagram for explaining how electric charges accumulated on the surface of the developing roller 17 are discharged.
First, as shown in FIG. 2, the toner supplied from the developer supply opening 29 is supplied to the first stirring chamber 25A. The toner supplied to the first stirring chamber 25 </ b> A is conveyed while being stirred by the rotation of the first stirring roller 18. The toner conveyed by the first agitation roller 18 is conveyed from the first agitation chamber 25A to the second agitation chamber 25B via a first circulation port (not shown).

  The toner supplied to the second stirring chamber 25 </ b> B is conveyed while being stirred by the rotation of the second stirring roller 19. A part of the toner conveyed to the second stirring roller 19 is supplied to the surface of the developing sleeve 17 </ b> A in the developing roller 17. Thus, the toner is formed on the outer surface (surface) of the developing sleeve 17A by the magnetic force of the magnet roller 17B to form a toner layer.

  Next, as shown in FIG. 2, the toner layer formed on the surface of the developing roller 17 is conveyed to a position facing the regulating blade 21 by the rotation of the developing roller 17. The toner layer conveyed by the rotation of the developing roller 17 passes through a position close to the regulating blade 21. Before the toner layer formed on the surface of the developing roller 17 is moved to a position facing the photosensitive drum 2 (upstream in the rotational direction C of the developing roller 17 with respect to the photosensitive drum 2), the regulating blade 21 Therefore, the layer thickness is regulated. Specifically, the toner on the developing roller 17 is regulated by the regulation blade 21 and formed into a thin layer of toner having a constant thickness of about several tens of μm. Further, the toner in the toner layer on the developing roller 17 is charged by the regulating blade 21.

Next, the toner layer whose layer thickness is regulated by the regulating blade 21 is conveyed to a position facing the photosensitive drum 2 by the rotation of the developing roller 17.
On the other hand, the surface of the photosensitive drum 2 is uniformly charged negative (minus polarity) or positive (plus polarity) by the charging unit 10. Then, the scanning exposure of the laser scanner unit 4 removes the charges on the exposed portion of the surface of the photosensitive drum 2. Thereby, an electrostatic latent image is formed on the surface of the photosensitive drum 2.

  Here, the toner layer formed on the surface of the developing roller 17 is conveyed to a position facing the photosensitive drum 2. A predetermined voltage is applied to the developing sleeve 17A by a voltage applying unit (not shown). As a result, the electrostatic latent image formed on the surface of the photosensitive drum 2 due to the voltage difference between the photosensitive drum 2 and the developing roller 17 at the position where the developing roller 17 and the photosensitive drum 2 face each other is The toner is developed with the toner constituting the toner layer on the developing roller 17.

  Here, as shown in FIGS. 3 to 5, the surface roughness of the first portion 174 in the developing sleeve 17 </ b> A of the developing roller 17 is set to 7.5 μm, for example, in ten-point average roughness (Rz). Yes. Further, an alumite layer 173 is disposed on the surface of the first portion 174 disposed opposite to the image forming area 201 of the photosensitive drum 2 in the surface of the developing sleeve 17A.

  Therefore, the surface 174A of the first portion 174 is suppressed from being scraped by toner, an abrasive, or the like due to the formation of the alumite layer 173. As a result, even when an image is formed on several hundred thousand sheets or more of paper T, the uneven shape formed on the surface of the first portion 174 is easily maintained, so that a toner layer is formed on the surface of the developing sleeve 17A. It is formed stably. As a result, the developing sleeve 17A can stably supply the toner to the photosensitive drum 2. Therefore, it is possible to suppress a decrease in image density of the toner image.

By the way, it is assumed that the developing sleeve 17A is rotated in a low temperature and low humidity environment.
As shown in FIG. 6, when the developing sleeve 17 </ b> A is rotated in a low temperature and low humidity environment, charges due to static electricity are likely to accumulate in the alumite layer 173 that forms the surface of the first portion 174.

  Here, among the surface of the developing sleeve 17A, the surface 175A of the second portion 175 disposed to face the non-image forming area 202 of the photosensitive drum 2 has a core 171 made of aluminum or aluminum alloy exposed, and The surface roughness of the exposed core 171 is set to be rougher than that of the first portion 174. The surface roughness of the second part 175 is set in a range of 10 to 30 μm, for example, in ten-point average roughness (Rz).

  Therefore, as shown in FIG. 6, the electric charge accumulated in the alumite layer 173 that forms the surface of the first part 174 is transmitted through the core 171 made of conductive aluminum or aluminum alloy, and the surface of the second part 175. Are intensively moved to the convex portions of the concaves and convexes formed.

  This is because the charge accumulated on the surface of the developing sleeve 17A is moved to the portion of the developing sleeve 17A that is most likely to be discharged when being discharged to the surface of the photosensitive drum 2 that is disposed to face the developing sleeve 17A. In the present invention, the second portion 175 disposed opposite to the non-image forming area 202 of the photosensitive drum 2 is set as a portion for discharging the charge accumulated on the surface of the developing sleeve 17A. By discharging the charge to the non-image forming area 202 of the photosensitive drum 2, the charge is hardly discharged to the image forming area 201 of the photosensitive drum 2. Thereby, generation | occurrence | production of the image defect can be suppressed.

  Specifically, the second part 175 has a core 171 made of aluminum or an aluminum alloy exposed, and has a surface roughness that is rougher than that of the first part 174 and is 10 to 10 in average roughness (Rz). The range is set to 30 μm. Thereby, the electric charge accumulated on the surface of the developing sleeve 17A is easily discharged to the surface of the photosensitive drum 2 from the convex portion of the surface of the second portion 175 where the conductive portion is exposed. Further, since the core 171 is formed of conductive aluminum or aluminum alloy, the charge accumulated on the surface of the alumite layer 173 of the developing sleeve 17A is moved inside the core 171 and is easily discharged. It is moved toward the convex portion formed on the surface of 175.

Therefore, as shown in FIG. 6, the electric charge accumulated in the alumite layer 173 is discharged from the convex portion of the second portion 175 toward the surface of the photosensitive drum 2.
Accordingly, the electric charge accumulated on the surface of the developing sleeve 17A is discharged from the convex portion of the surface of the second portion 175 of the developing sleeve 17A to the non-image forming area 202 of the photosensitive drum 2. As a result, the electric charge accumulated on the surface of the developing sleeve 17A is suppressed from being discharged to the image forming area 201 of the photosensitive drum 2. As a result, it is possible to suppress the occurrence of image defects due to the formation of leak marks due to the discharge of charges in the image forming area 201 or the disturbance of the toner layer.

Further, the second portion 175 is opposed to a region away from the image forming region 201 in the direction along the first rotation axis J1 in the region of the developing sleeve 17A facing the non-image forming region 202. Be placed. Therefore, the electric charge discharged from the second part 175 to the photosensitive drum 2 is discharged to an area away from the image forming area 201 on the photosensitive drum 2.
As a result, the electric charge accumulated on the surface of the developing sleeve 17A can be safely discharged to an area away from the image forming area 201 on the photosensitive drum 2.

According to the printer 1 of the first embodiment, for example, the following effects are exhibited.
In the printer 1 of the first embodiment, the developing sleeve 17A has a core 171 made of aluminum or an aluminum alloy, and a film thickness of 10 to 25 μm disposed via the active layer 172 so as to cover a part of the core 171. And an alumite layer 173.
Therefore, the hardness of the surface 174A of the first part 174 is increased by forming the alumite layer 173. Thereby, even when an image is formed on several hundred thousand sheets or more of paper T, the toner layer can be stably formed on the surface of the developing sleeve 17A. Then, it is possible to stably supply the toner from the toner layer on the developing sleeve 17A to the photosensitive drum 2. Therefore, it is possible to suppress a decrease in image density of the toner image.

  Further, the developing sleeve 17A is disposed to face the image forming area 201 of the photosensitive drum 2, and the alumite layer 173 is disposed on the surface of the central portion of the developing sleeve 17A in the direction along the second rotation axis J2. Aluminum or an aluminum alloy is exposed on the surface of both end portions in the direction along the second rotation axis J2 of the developing sleeve 17A, which is disposed to face the one portion 174 and the non-image forming region 202 of the photosensitive drum 2. The second portion 175 has a surface roughness that is rougher than that of the first portion 174.

  For this reason, the charge accumulated on the surface of the developing sleeve 17A is from the uneven convex portions formed on the second portions 175 at both ends in the second rotation axis J2 direction of the developing sleeve 17A to the non-image forming area 202 of the photosensitive drum 2. It is easy to be discharged towards. Accordingly, it is possible to discharge the charge from the second portion 175, particularly in a low temperature and low humidity environment where charge tends to accumulate on the surface of the developing sleeve 17A. As a result, the discharge of electric charges to the image forming area 201 of the photosensitive drum 2 is suppressed. Accordingly, it is possible to suppress the occurrence of image defects or the like due to leak marks formed in the image forming area 201 of the photosensitive drum 2 or the disturbance of the toner layer on the developing sleeve 17A.

In the printer 1 of the first embodiment, the surface roughness of the second portion 175 in the developing sleeve 17A is 10-point average roughness (Rz) of 10 to 30 μm.
Therefore, the charge accumulated on the surface of the developing sleeve 17A is easily moved to the second portion 175 of the developing sleeve 17A, and the second portion 175 is easy to discharge the charge toward the photosensitive drum 2.
Thereby, it is possible to discharge from the second portion 175 toward the photosensitive drum 2. Therefore, in the image forming area 201 of the photosensitive drum 2, it is possible to further suppress the formation of leak marks and the toner layer disturbance.

  In the printer 1 of the first embodiment, the first part 174 and the second part 175 are continuously arranged, and the first part 174 is an outer edge of the first part 174 in the first rotation axis J1 direction. Is located at the same position as the outer edge of the image forming area 201 or the outer edge of the first part is positioned closer to the end of the developing sleeve 17A than the outer edge of the image forming area 201.

  For this reason, the second portion 175 in which the charge accumulated on the surface of the developing sleeve 17A is likely to be discharged is disposed so as to face an area away from the image forming area 201 of the photosensitive drum 2. As a result, the electric charge accumulated on the surface of the developing sleeve 17A is discharged to a safe area away from the image forming area 201 of the photosensitive drum 2. Thereby, in the image forming area 201 of the photosensitive drum 2, it is possible to further suppress the formation of leak marks and the disturbance of the toner layer.

  In the printer 1 of the first embodiment, the image forming area 201 on the photosensitive drum 2 and the first portion 174 on the developing sleeve 17A are not in contact with each other. For this reason, electric charges are likely to fly from the surface of the developing sleeve 17A toward the photosensitive drum 2 and be easily discharged. Even in such a case, due to the above configuration of the present invention, the electric charge is discharged from the second portion 175 to the photosensitive drum 2, so that a leak mark is formed in the image forming area 201 or the toner on the developing sleeve 17 </ b> A. It is possible to suppress the occurrence of image defects and the like due to the occurrence of layer disturbance.

Next, a second embodiment of the present invention will be described. FIG. 7 is a cross-sectional view showing the state of the surface of the developing roller 17 subjected to the roughening process in the printer 1 according to the second embodiment of the present invention.
The second embodiment will be described with a focus on differences from the first embodiment, the same configurations and the same components as those of the first embodiment will be denoted by the same reference numerals, and detailed descriptions thereof will be omitted. . Further, in the second embodiment, the description and drawings (FIGS. 1 to 4B) of the first embodiment are applied to points that are not particularly described and not illustrated.

  As shown in FIG. 7, in the developing sleeve 17A in the printer 1 of the second embodiment, the surface roughness (ten-point average roughness Rz) of the surface 175A of the second portion 175 is the direction along the second rotation axis J2. In FIG. 2, the outer diameter is formed so as to increase toward the end. Specifically, the unevenness formed on the surface 175A of the second portion 175 is the end in the direction along the second rotation axis J2 in which the difference in thickness direction between the concave bottom and the convex top (the depth of the unevenness) is It is formed so as to become deeper sequentially toward the part.

  For example, the depth of the unevenness of the second portion 175 is d3 at the outermost end portion in the second rotation axis J2 direction of the developing sleeve 17A. And the depth of the unevenness of the second part 175 is formed so as to become gradually shallower toward the center part side. The depth of the unevenness of the second part 175 is d2 in the portion adjacent to the first part 174, similarly to the depth of the unevenness of the second part 175 of the first embodiment. Further, the depth of the unevenness of the first part 174 is d1, similarly to the depth of the unevenness of the first part 174 of the first embodiment.

According to the printer 1 of the second embodiment, for example, the following effects are exhibited.
In the printer 1 according to the second embodiment, the surface roughness of the second portion 175 increases in ten-point average roughness (Rz) toward the end side in the second rotation axis J2 direction.
For this reason, the electric charge discharged from the second part 175 is mostly discharged on the end side of the second part 175, and the electric charge discharge decreases as the area of the photosensitive drum 2 facing the image forming area 201 is approached. can do. As a result, the discharge of charges to the image forming area 201 of the photosensitive drum 2 and the non-image forming area 202 close to the image forming area 201 can be reduced, and the charges can be discharged safely. Accordingly, it is possible to further suppress the formation of leak marks and the toner layer disturbance due to the discharge of electric charges.

As mentioned above, although preferred embodiment of this invention was described, this invention can be implemented with a various form, without being limited to embodiment mentioned above.
For example, in the above-described embodiment, the developer is a magnetic one-component developer, but is not limited thereto. For example, the developer may be a magnetic two-component developer composed of toner and carrier.
The type of the image forming apparatus of the present invention is not particularly limited, and may be a copier, a facsimile, or a complex machine of these in addition to a printer.
The sheet-shaped transfer material is not limited to paper, and may be a film sheet, for example.

Hereinafter, the present invention will be described in more detail using Examples and Comparative Examples of the present invention. However, the present invention is not limited to the following examples.
In addition, the surface roughness (Rz) in the following examples and comparative examples was measured using a surface roughness measuring device (SURFCOM 1500DX manufactured by Tokyo Seimitsu Co., Ltd.).
Example 1: Aluminum tube (outer diameter 16 mm, length 240 mm, wall thickness 1 mm) Both end portions (second portion) (each 10 mm) of the surface are left, and Rz = 7.5 μm unevenness in the central portion (first portion) (Blasting conditions; glass beads # 100 1 kg / cm ² 60 seconds).
Next, unevenness of the roller axis direction average Rz = 15 μm (blasting condition; glass beads # 200 2 kg / cm ² 90 seconds) was applied only to both ends (second part) (each 10 mm) of the aluminum tube.
Furthermore, both ends (10 mm each) were masked with acid-resistant tape or the like and anodized (treatment time 50 min). At the same time, an aluminum plate having a thickness of 1 mm (40 mm × 40 mm) was anodized under the same conditions. As a result of analyzing the cross section of the surface portion of the aluminum plate with an energy dispersive X-ray analyzer (EDX) and a scanning electron microscope (SEM), a barrier layer and an alumite layer of about 15 μm were formed on the aluminum surface.

Example 2: The same treatment as in Example 1 was performed except that the treatment time of the anodizing treatment was changed to 30 minutes. As a result of the analysis, the alumite layer was about 10 μm.
Example 3 The same process as in Example 1 was performed, except that the anodizing treatment time was 80 min. As a result of analysis, the alumite layer was about 25 μm.
Example 4: The unevenness of the both ends in the roller axis direction was set to an average Rz = 10 μm on both ends of the aluminum tube under different blasting conditions (glass beads # 100 2 kg 60 seconds). Except this, the same processing as in Example 1 was performed.
Example 5: Both ends of the aluminum tube were subjected to different blasting conditions (glass beads # 300, 4 kg, 120 seconds), and the unevenness at both ends in the roller axis direction was set to an average Rz = 30 μm. Except this, the same processing as in Example 1 was performed.

Comparative Example 1: The same treatment as in Example 1 was performed except that the treatment time for anodizing treatment was set to 20 minutes. As a result of the analysis, the alumite layer was about 8 μm.
Comparative Example 2: The same treatment as in Example 1 was performed except that the treatment time for the anodizing treatment was set to 100 min. As a result of the analysis, the alumite layer was about 30 μm.
Comparative Example 3: The entire surface of the aluminum tube was anodized without masking both ends, and the other treatments were the same as in Example 1.
Comparative Example 4: An aluminum tube was produced in which unevenness was applied to Example 1 without performing anodization treatment (without an alumite layer).
Comparative Example 5: The same process as in Example 1 was performed, except that the blasting conditions at both ends of the aluminum tube were the same as the central part, and the unevenness in the roller axis direction was made equal to the average Rz = 7.5 μm. It was.
Comparative Example 6: The same as in Example 1 except that both the first and second parts of the aluminum tube were made to have an unevenness equal to the average Rz = 10 μm under different blasting conditions (glass beads # 100 2 kg 60 seconds). Processed.
Comparative Example 7: The same treatment as in Example 1 was performed except that the both ends of the aluminum tube were subjected to different blasting conditions (glass beads # 300, 5 kg, 120 seconds) and the irregularities at both ends in the roller axis direction were set to an average Rz = 40 μm. went.

The aluminum pipe (alumite pipe) treated in Example 1 to Comparative Example 7 was mounted on a LS-4020DN remodeling machine manufactured by Kyocera Mita, and the following evaluation was performed.
An initial evaluation under a low-temperature and low-humidity environment and an evaluation after printing 200,000 sheets were performed for those having no problem in the initial evaluation. Evaluation items were image density and image quality.

The image density was evaluated according to the following criteria.
○: Image density (ID) is 1.2 or more ×: Image density (ID) is less than 1.2

The image quality was evaluated according to the following criteria.
○: No abnormal image ×: Leak mark, black spot, layer disturbance occurrence ×: Other image defect occurrence Evaluation results are shown in Table 1 below.

  As shown in Table 1, in the initial evaluation under a low-temperature and low-humidity environment, Comparative Examples 1 to 4 can obtain the same or substantially the same image density as Examples 1 to 5, and there is no abnormality in the image quality. On the other hand, in Comparative Examples 5 to 7, although the same or substantially the same image density as in Examples 1 to 5 was obtained, leak marks and black spots were generated, and deterioration in image quality was confirmed.

  And after printing 200,000 sheets, the electrostatic run (electrostatic provision test) was performed about Comparative Examples 1-4 and Examples 1-5 which had no problem by initial evaluation, and it evaluated similarly to the initial stage. As a result, as shown in Table 1, Comparative Examples 1, 2, and 4 have a large decrease in image density as compared with Examples 1 to 5, and image quality is reduced due to generation of leak marks, layer disturbance, and streak images. Deterioration was confirmed. In Comparative Example 3, the image density was not lowered as compared with Examples 1 to 5, but leak marks and black spots were generated, and deterioration in image quality was confirmed.

  DESCRIPTION OF SYMBOLS 1 ... Printer (image forming apparatus), 2 ... Photosensitive drum (image carrier), 16 ... Developing device, 17 ... Developing roller, 17A ... Developing sleeve, 17B ... Magnet roller (magnet part), J2: Second rotation axis, 171: Core, 172 ... Active layer, 173 ... Anodized layer, 174 ... First part, 174A ... Irregular surface, 175 ... Second part, 175A ... Irregular surface , 201... Image forming area, 202... Non-image forming area, J 1... First rotation axis, J 2.

Claims (6)

An image carrier that is formed to be rotatable about a first rotation axis and that can form an electrostatic latent image, and a non-image forming region in which the electrostatic latent image is not formed;
A magnet unit having one or a plurality of magnetic poles and a magnet unit disposed opposite to the image carrier so as to be rotatable about a second rotation axis parallel to the first rotation axis outside the magnet unit. A developing sleeve that forms a developer layer on the surface thereof, and has a core made of aluminum or an aluminum alloy, and a thickness of 10 to 25 μm disposed through the active layer so as to cover a part of the core A developing sleeve having an alumite layer, and a developing roller,
The developing sleeve is
A first portion that is disposed on the center side in the second rotation axis direction of the developing sleeve so as to face the image forming region, and on which the anodized layer is disposed;
The developing sleeve is disposed on the end side in the second rotation axis direction so as to face the non-image forming region, and aluminum or an aluminum alloy is exposed on the surface, and the surface roughness is rougher than that of the first part. And an image forming apparatus. The image forming apparatus according to claim 1, wherein the second portion has a surface roughness of 10 to 30 μm in ten-point average roughness (Rz). The first part and the second part are arranged continuously,
In the first rotation axis direction, the first part has the outer edge of the first part at the same position as the outer edge of the image forming area, or the outer edge of the first part is more than the outer edge of the image forming area. The image forming apparatus according to claim 2, wherein the image forming apparatus is disposed so as to be positioned on an end portion side of the sleeve. 4. The image forming apparatus according to claim 2, wherein the surface roughness of the second part has a ten-point average roughness (Rz) that increases toward the end of the developing sleeve in the second rotation axis direction. . 5. The image forming apparatus according to claim 1, wherein the image forming area of the image carrier and the first portion of the developing sleeve are in a non-contact state. The image forming apparatus according to claim 1, wherein the developer is a magnetic one-component developer.

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