JP2006337518A - Developing roller - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a developing roller which can be efficiently manufactured regardless of the fact that an alumite area which is alumite-treated and a non-alumite area which is not alumite-treated are surely set and separated. <P>SOLUTION: The developing roller 10 is provided with a roller main body 12 which has a cylindrical outer circumferential surface which is alumite-treated and a left shaft part 14a which is projected outward from one end (the left) of the roller main body 12 in an axial direction and is freely rotatably supported by a conductive bearing 16. In the developing roller 10, a non-alumite area B which is not alumite-treated is set on the outer circumferential surface of the left shaft part 14a and circumferential groove parts 141 and 142 are provided near the boundary between the non-alumite area B of the left shaft part 14a and an adjacent alumite area A. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a developing roller used in an image forming apparatus such as a printer, a copying machine, a facsimile machine using an electrophotographic system, or a multifunction machine having these functions.

  A developing roller used in this type of image forming apparatus is generally supported by a roller body having a cylindrical outer peripheral surface and an outer bearing that protrudes outward in the axial direction from both ends of the roller body. And a toner for developing an electrostatic latent image on an adjacent photosensitive member on the roller body.

  As the material of the developing roller, aluminum may be used for weight reduction. On the other hand, a bias voltage for moving the toner on the roller body to the electrostatic latent image on the photoconductor is usually applied to the developing roller. For this reason, if the electrical insulation of the surface of the roller body is low, this bias voltage may leak to the photoconductor adjacent to the roller body. Therefore, in the developing roller of Patent Document 1, a technique is applied in which the electrical insulation of the roller body surface is enhanced by forming an aluminum oxide film on the surface of the aluminum roller body. Furthermore, according to this developing roller, it was possible to improve the wear resistance and corrosion resistance of the surface by the oxide film of aluminum.

On the other hand, if the shaft portions at both ends of the roller body are also made of aluminum having an oxide film formed on the surface, like the roller body, the wear resistance of the shaft portion, particularly the portion that rotates and slides with the bearing. It was possible to improve.
JP 2004-318092 A

  However, since the bias voltage is normally applied to the shaft portion on one end side of the roller body, an oxide film having high electrical insulation is formed over the entire outer peripheral surface of the shaft portion on the one end side. Can not. Therefore, it is necessary not to form an oxide film on at least a portion to which the bias voltage is applied in the outer peripheral surface of the shaft portion.

  Here, the alumite treatment for forming the aluminum oxide film is generally performed by immersing the object to be treated in an alumite treatment tank filled with an electrolytic solution. Therefore, as described above, in order to provide a region where an oxide film is not formed on a part of the outer peripheral surface of the shaft portion, it is necessary to perform the alumite treatment of the developing roller in a state where the region is masked. Specifically, for example, a cylindrical masking member may be put on a part of the shaft portion, and the developing roller may be immersed in the alumite treatment tank in that state. As the material of the masking member, it is preferable to use a material that does not adversely affect the electrolyte during anodizing and can adhere to the shaft part to some extent. Accordingly, it is considered that the material of the masking member is preferably rubber or resin having a certain degree of elasticity, for example.

  However, if a rubber or resin masking member is repeatedly used in mass production of the developing roller, the adhesion of the masking member is reduced due to the inevitably deteriorated rubber or resin. When the deterioration of the masking member progresses, a gap is generated between the masking member and the shaft portion, and the electrolyte enters the inside of the masking member until the bias voltage application portion, which should not be anodized. Is alumite-treated, and a bias voltage cannot be satisfactorily applied to the portion.

  Of course, if the masking member is replaced with a new one before the deterioration of the masking member has progressed to that extent, the above-mentioned problem does not occur. However, it is usually a standard for determining the degree of deterioration of the masking member. Since there is no such thing, it is difficult to properly determine the replacement time of the masking member. For this reason, after the developing roller is anodized, it is necessary to inspect whether or not the shaft portion is anodized (whether electrical insulation is increased) by a continuity check or the like. This has been a factor that deteriorates the manufacturing efficiency of the developing roller.

  The present invention has been made in view of the circumstances as described above, and efficiently manufactures an anodized region to which an anodized treatment is applied and a non-anodized region to which an anodized product is not applied while being reliably set. It is an object of the present invention to provide a developing roller that can be used.

  In order to solve the above problems, the present invention provides a roller body having a cylindrical outer peripheral surface to be anodized and a roller body that protrudes axially outward from one end of the roller body and is rotatably supported by a conductive bearing. A non-alumite region that is not anodized on the outer peripheral surface of the shaft portion, and the non-alumite region of the shaft portion has a boundary with an adjacent anodized region. It is characterized in that at least one circumferential groove is provided in the vicinity of the portion.

  According to this developing roller, a non-alumite region that is not anodized is set on the outer peripheral surface of the shaft portion that protrudes axially outward from one end of the roller body and is rotatably supported by the conductive bearing. In the anodized region, at least one circumferential groove is provided in the vicinity of the boundary with the adjacent anodized region, so that the non-anodized region of the shaft portion is masked during anodizing processing. When using a masking member having an inner peripheral surface that can be in close contact with the outer peripheral surface, even if this masking member is somewhat degraded by repeated use in the mass production process of the developing roller, it is ensured that the anodized region and the non-anodized region Can be set separately. That is, when the developing roller is immersed in the alumite treatment tank filled with the electrolytic solution, if the adhesion of the masking member is reduced due to deterioration, the electrolytic solution enters the non-anodized region of the shaft portion of the masking member. However, if a groove is provided in the vicinity of the boundary portion of the non-alumite region as described above, the electrolytic solution is further stored in the non-alumite region by accumulating the invading electrolytic solution in the groove portion. Intrusion can be prevented, and as a result, a portion of the non-alumite region excluding the region where the groove is formed can be surely not subjected to the alumite treatment. If a bias voltage is applied to the portion via a conductive bearing, the bias voltage can be reliably applied to a portion having good conductivity because an oxide film is not formed. it can.

  However, if the same masking member is used in the subsequent development of the developing roller after the state in which the electrolytic solution is accumulated in the groove, the deterioration of the masking member further proceeds and the amount of intrusion of the electrolyte increases. However, the groove cannot absorb the electrolyte. Therefore, it is preferable to replace the masking member with a new one when the groove is anodized. In other words, according to the developing roller of the present invention, it is possible to accurately determine the replacement time of the masking member due to the presence of the groove. That is, the masking member replacement time can be determined such that the masking member is continuously used while the groove portion is not anodized and the masking member is replaced when the groove portion is anodized. Moreover, even when the groove portion is anodized, the portion of the non-alumite region other than the region where the groove portion is formed is not yet anodized, so that the developing roller at this time can also be used as a non-defective product. In this way, the criteria for determining the replacement timing of the masking member are clear, and good products can be reliably manufactured for the period up to that point, so unlike the conventional developing roller, there is no need to perform a continuity check. The production efficiency of the developing roller can be increased.

  In this configuration, it is preferable that the number of the groove portions provided in the non-alumite region is more than one in that the replacement period of the masking member can be increased. That is, if a plurality of groove portions are provided, the groove portions are sequentially anodized toward the one farthest from the groove portion closest to the boundary portion of the non-alumite region, so the groove portion furthest from the boundary portion is anodized. The masking member can continue to be used until it is done. However, even if the number of the groove portions is excessively increased, the time required for the groove processing is increased and the manufacturing efficiency is deteriorated. Therefore, considering both of these points, it is preferable that the number of the groove portions be two.

  Here, the operation of placing the masking member on the shaft during anodizing is performed by inserting the shaft into the masking member from the tip side. For this reason, it is preferable to form chamfers at the corners at the tip of the shaft and at least the corners on the roller body side among the corners of the groove. If it does in this way, the operation | work which covers a masking member on a shaft part can be performed smoothly.

  Further, the shaft portion is constituted by a stepped member having a small diameter portion formed on the tip end side thereof and a large diameter portion formed on the roller main body side, and the outer peripheral surface of the small diameter portion includes the A non-alumite region may be set. In this way, since the step portion between the large diameter portion and the small diameter portion corresponds to the boundary portion of the non-alumite region, the operator who performs the anodizing process can easily determine the region to be covered with the masking member. Can do. In addition, since the operator can position the masking member by bringing the masking member into contact with the large diameter portion, the masking operation can be easily performed.

  As described above, according to the present invention, it is possible to provide a developing roller that can be efficiently manufactured while reliably setting and separating an anodized region to be anodized and a non-anodized region to which no anodized is applied. can do.

  A preferred embodiment of the present invention will be described with reference to the drawings.

  1 and 2 are diagrams illustrating a developing roller according to an embodiment of the present invention, FIG. 3 is a diagram illustrating an example of a developing device in which the developing roller is preferably used, and FIG. 4 is an image in which the developing device is mounted. It is a figure which shows an example of a formation apparatus.

  First, the overall configuration of the image forming apparatus will be described with reference to FIG. As shown in this figure, the image forming apparatus 70 is a quadruple tandem type full-color image forming apparatus, and includes four image forming units 22 provided for each color of black, yellow, magenta, and cyan, and this image forming apparatus. A sheet is conveyed downstream (to the left in FIG. 4) by a transfer belt 62 disposed below the unit 22 and rotating counterclockwise, and a toner image formed on the image forming unit 22 in the process is conveyed. A paper transport unit 60 for transferring the paper, a paper feed unit 64 for feeding paper selectively picked up from a plurality of paper feed cassettes 66 between the paper transport unit 60 and the image forming unit 22, and the paper A fixing unit 6 that is disposed on the downstream side (left side in FIG. 4) of the transport unit 60 and performs a fixing process by heating the sheet on which the toner image is transferred. Bets is configured by being furnished to a body 72 of substantially box shape.

  Each of the image forming units 22 includes four toner containers (toner cartridges) 21 corresponding to the respective colors of black, yellow, magenta, and cyan, a developing device 20 disposed below the toner containers 21, and the developing unit. And a photosensitive drum 50 facing the apparatus 20.

  Each of the photosensitive drums 50 is configured to rotate in the clockwise direction in FIG. 4, and a charging device 52 and an exposure device 54 are provided above the photosensitive drum 50, respectively. The photosensitive drum 50 is uniformly charged on the outer peripheral surface by the charging device 52, and the exposure device based on the image data input from the document image reading device (not shown) on the outer peripheral surface after charging. By being irradiated with light from LED 54 (for example, LED light or semiconductor laser), an electrostatic latent image is formed on the outer peripheral surface thereof. By supplying toner from the developing device 20 to the electrostatic latent image, a toner image is formed on the outer peripheral surface of the photosensitive drum 50.

  Next, the developing device 20 will be described with reference to FIG.

  FIG. 3A is a diagram schematically showing a cross-sectional structure of the developing device 20, and FIG. 3B is a perspective view showing the overall configuration of the developing device 20 with the upper lid removed. The developing device 20 shown in this figure is preferably used when a two-component developer composed of a magnetic carrier and a non-magnetic toner is used. The developing device 20 includes an internal carrier and the toner container 21 (FIG. 4). The toner supplied from the toner is agitated to charge the toner, and the charged toner is caused to fly to the electrostatic latent image on the photosensitive drum 50 via a predetermined path, thereby forming a toner image. This is a non-contact developing type developing device.

  The developing device 20 includes a stirring mixer 32 and a paddle mixer 34 that charge the toner by mixing and stirring the toner supplied from the toner container 21 (FIG. 4) with the carrier, and holding the carrier on the outer peripheral surface and magnetically. A magnetic roller 30 that forms a brush, and a developing roller 10 that forms a thin toner layer on the outer peripheral surface upon receiving toner from the magnetic brush on the magnetic roller 30 are arranged in a predetermined positional relationship inside the case 35. It is configured by being installed.

  The case 35 includes a case main body 36 that houses the developing roller 10 and the like, and a lid 37 that covers the upper portion of the case main body 36. In the vicinity of the magnetic roller 30 inside the case body 36, a regulating blade 38 for controlling the thickness of the magnetic brush is provided. Further, the lid 37 is provided with a toner supply hole 37a for receiving toner from the toner container 21 (FIG. 4) located at the upper part thereof.

  The magnetic roller 30 has a magnetic body therein, and when supplied with the developer (toner and carrier) mixed and stirred by the stirring mixer 32 and the paddle mixer 34, the magnetic roller 30 generates magnetic force based on the internal magnetic body. A carrier is attracted to the outer peripheral surface to form a magnetic brush, and toner is caused to accompany the magnetic brush. The magnetic brush is formed with a certain thickness by cutting the head with the regulating blade 38. The magnetic roller 30 is applied with a DC bias Vd2 from a DC power supply 44.

  On the other hand, a DC bias Vd1 from a DC power source 42 is applied to the developing roller 10. Due to the potential difference | Vd2−Vd1 | (hereinafter referred to as potential difference Δ) between the DC bias Vd1 and the DC bias Vd2 applied to the magnetic roller 30, the toner attached to the magnetic brush on the magnetic roller 30 is applied to the developing roller 10. As a result, a thin toner layer is formed on the outer peripheral surface of the developing roller 10. The thickness of the toner thin layer varies depending on the resistance of the developer and the rotational speed difference between the developing roller 10 and the magnetic roller 30 but can also be controlled by the potential difference Δ. When the potential difference Δ is increased, the toner thin layer becomes thicker, and when the potential difference Δ is decreased, the toner layer becomes thinner. The range of this potential difference Δ is generally about 100 to 250 v.

  The developing roller 10 selectively applies toner from the toner thin layer formed on the outer peripheral surface to the electrostatic latent image formed on the opposing photosensitive drum 50 (potential is lower than the surroundings). The toner image is formed on the photosensitive drum 50 by flying the toner. At this time, in order to weaken the degree of toner adsorption to the developing roller 10 and smooth the flight of the toner (in order to improve developability), an AC bias Va from an AC power supply 40 is applied to the developing roller 10. Applied in a superimposed manner to Vd1. The application of the AC bias Va is performed immediately before development in order to prevent scattering of toner. Here, the function of the developing roller 10 has been mainly described, but the specific form thereof will be described in detail later in the text.

  The undeveloped toner that is not used for development and remains on the developing roller 10 may cause fogging if left as it is. Therefore, the potential difference Δ is periodically changed, whereby the undeveloped toner is collected by the magnetic brush on the magnetic roller 30. In this way, it is possible to easily collect the development residual toner and suppress the occurrence of fogging and form a clear image without providing a special device such as a peeling blade.

  Here, the gap between the developing roller 10 and the photosensitive drum 50 is determined by a gap roller 17 attached to both ends of the developing roller 10, and the gap value is more preferably about 150 to 400 μm. Is set to about 200 to 300 μm. When the gap value is smaller than 150 μm, it causes fogging and easily causes leakage of the voltage applied to the developing roller 10 to the photosensitive drum 50. On the other hand, when the width is larger than 400 μm, it becomes difficult to cause the toner to fly to the photosensitive drum 50 and a sufficient image density cannot be obtained. It also becomes a factor that causes selective development.

  On the other hand, the gap value between the magnetic roller 30 and the developing roller 10 is preferably set to about 0.3 to 1.5 mm.

  A specific form of the developing roller 10 used in the developing device 20 as described above, that is, an embodiment of the developing roller 10 according to the present invention will be described with reference to FIG.

  FIG. 1A is a perspective view showing the entire configuration of the developing roller 10, and FIGS. 1B to 1D are enlarged views of one end side thereof. As shown in the figure, the developing roller 10 includes a roller main body 12 having a cylindrical outer peripheral surface, and a shaft portion 14 provided so as to protrude outward in the axial direction from both ends of the roller main body 12. .

  The roller body 12 is constituted by a so-called three-headed tube made of an aluminum alloy. Specifically, the outer tube 12a and a shaft 12c arranged in parallel with the outer tube 12a are connected by three ribs 12b.

  The shaft portion 14 is a member that is integrally extended from the shaft 12c of the roller body 12 toward the outer side in the axial direction. The left shaft portion 14a protrudes in the left direction in the drawing and the right portion protrudes in the right direction in the drawing. It is comprised from the axial part 14b. The left shaft portion 14a and the right shaft portion 14b are rotatably supported by external bearings and gap rollers 17 (FIG. 3), respectively.

  A bias voltage is applied to the left shaft portion 14a by the AC / DC power supplies 40 and 42 (FIG. 3) via a bearing. For this reason, the bearing which supports the left-shaft part 14a is comprised by the electroconductive bearing 16 shown to Fig.1 (a) (b). The conductive bearing 16 has an outer peripheral surface (not rotated) that is in contact with a bias voltage contact (not shown) fixed to the outside. The voltage supplied from the contact is supplied to the conductive bearing 16. This is a mechanism for transmission to the left shaft portion 14a that rotates and slides with the inner peripheral surface of 16. Further, as shown in FIG. 1C, the left shaft portion 14a is a stepped member having a small-diameter portion 114a on the distal end side and a large-diameter portion 214a on the roller body 12 side, and the conductive bearing 16 Is configured to support the small diameter portion 114a.

  Then, the outer peripheral surface of the roller body 12 and the outer peripheral surface of the right shaft portion 14b are entirely anodized so that aluminum having high electrical insulation and excellent wear resistance can be obtained. An oxide film is formed. For this reason, in the roller main body 12, the applied bias voltage is prevented from leaking to the photosensitive drum 50 (FIG. 3), and in one right shaft portion 14b, a bearing or gap roller 17 (FIG. 3). The generation of wear due to rotational sliding is reduced. Furthermore, the alumite treatment is also applied to the outer peripheral surface of the large diameter portion 214a in the left shaft portion 14a. Thus, the alumite treatment is applied to the outer peripheral surface of the large-diameter portion 214a among the outer peripheral surface of the roller body 12, the outer peripheral surface of the right shaft portion 14b, and the left shaft portion 14a. That is, the outer peripheral surface of these members is an anodized region A (FIG. 1 (c)) that has been subjected to anodizing.

  On the other hand, the outer peripheral surface of the small diameter portion 114a of the left shaft portion 14a is not subjected to an alumite treatment. That is, the outer peripheral surface of the small diameter portion 114a is a non-anodized region B that is not subjected to an alumite treatment. Further, circumferential grooves 141 and 142 are provided at the end of the small diameter portion 114a on the roller body 12 side (at the end of the non-anodized region B on the anodized region A side).

  The non-alumite region B is further divided into a groove portion forming region B1 where the groove portions 141 and 142 are formed, and a main region B2 which is located on the tip side of the small diameter portion 114a and occupies most of the non-alumite region B. It is done. Of these, the groove forming region B1 is not basically anodized, but may be anodized depending on the state of masking when the developing roller 10 is anodized (details will be described later). On the other hand, this region B2 is surely not subjected to the alumite treatment (this will also be described in detail later). A portion of the left shaft portion 14a that is supported by the conductive bearing 16 and to which a bias voltage is applied via the conductive bearing 16 is set to be included in the main region B2. That is, the application of the bias voltage is surely performed in a part of the main region B2 where the oxide film is not formed and the conductivity is good. Thereby, it is possible to reliably prevent the occurrence of an abnormal image due to poor conduction. On the other hand, the gap roller 17 supports the large-diameter portion 214a in which an oxide film is formed on the outer peripheral surface by anodizing. Thereby, the occurrence of wear due to rotational sliding with the gap roller 17 is reduced.

  Further, a chamfer 15 is formed at the corner of the tip of the left shaft portion 14a. Furthermore, chamfers 141a · b and 142a · b are formed at the left and right corners of the grooves 141 and 142, respectively.

  Next, a method for manufacturing the developing roller 10 having the above configuration will be described with reference to FIGS.

  The developing roller 10 is manufactured by first forming an aluminum alloy three-ply tube by extrusion or drawing of an aluminum alloy, and further cutting it to form the roller body 12 and the left and right shafts as described above. It shape | molds in the shape which has the parts 14a and 14b. At this time, the grooves 141 and 142 are also formed at the same time.

  Next, the developing roller 10 formed in this manner is subjected to an alumite treatment, but before that, the small diameter portion 114a (non-anodized region B) of the left shaft portion 14a is covered with the masking member 18 shown in FIG. . The masking member 18 is a cylindrical member having an inner diameter that can be inserted into the small-diameter portion 114a, and has a bottom portion 18a at one end thereof. The masking member 18 is made of urethane rubber having elasticity, and is covered in a state of being in close contact with the small diameter portion 114a to some extent. The operation of covering the masking member 18 on the small diameter portion 114a is performed by pushing the masking member 18 until the end edge portion 18b of the masking member 18 contacts the large diameter portion 214a. That is, since the operator can position the masking member 18 by bringing the masking member 18 into contact with the large diameter portion 214a, it is easy to perform the operation. Furthermore, the chamfer 15 at the tip corner of the small diameter portion 114a and the chamfers 141b and 142b on the roller body 12 side of the corners of the grooves 141 and 142 are formed, so that the masking member 18 is pushed in. It can be carried out smoothly without being disturbed by the corners.

  Then, the developing roller 10 is alumite-treated by immersing the developing roller 10 in the alumite treatment tank filled with the electrolytic solution with the masking member 18 covered with the small diameter portion 114a of the left shaft portion 14a. . Then, the alumite region A which is an unmasked portion of the outer peripheral surface of the developing roller 10, that is, the outer peripheral surface of the roller body 12, the outer peripheral surface of the right shaft portion 14b, and the large diameter portion 214a of the left shaft portion 14a. Alumite treatment is applied to the outer peripheral surface of the. (In this embodiment, since the electrolytic solution also enters the space formed between the outer tube 12a and the shaft 12c of the roller main body 12, the inner peripheral surface of the outer tube 12a and the surface of the rib 12b are associated with this. On the other hand, the outer peripheral surface of the shaft 12c is also anodized.) On the other hand, the non-anodized region B, that is, the outer peripheral surface of the small-diameter portion 114a of the left shaft portion 14a is basically covered with the masking member 18. Since it does not come into contact with the electrolytic solution, the outer peripheral surface (non-alumite region B) of the small diameter portion 114a is not subjected to an alumite treatment.

  Here, when the developing roller 10 is mass-produced, when the masking member 18 is repeatedly used, the degree of adhesion between the masking member 18 and the small-diameter portion 114a may decrease due to deterioration of the rubber constituting the masking member 18. is there. Thus, when the adhesion degree of the masking member 18 decreases, the electrolyte enters from a slight gap between the end edge portion 18b of the masking member 18 and the small diameter portion 114a, and the non-alumite region B is erroneously anodized. There is a risk. However, according to the developing roller 10 of the present embodiment, the groove portions 141 and 142 are provided at the end portion (groove portion forming region B1) of the small diameter portion 114a on the roller body 12 side. Since the electrolyte solution that has entered into the groove first accumulates in the groove 142 on the roller body 12 side, the electrolyte solution does not further enter the distal end side (the main region B2 side) of the small diameter portion 114a. However, when a large amount of electrolyte enters, the groove 142 is filled with the electrolyte, and the electrolyte that overflows further attempts to enter the tip side of the small-diameter portion 114a. Since the other groove portion 141 provided on the side prevents the intrusion, the intrusion of the electrolyte solution to the region B2 is more reliably prevented.

  As described above, when the cylindrical masking member 18 is placed on the small diameter portion 114a (non-alumite region B) of the left shaft portion 14a and the developing roller 10 is immersed in the alumite treatment tank in this state, the grooves 141, 142 are obtained. As a result, the anodizing process of the developing roller 10 can be performed while reliably preventing the main area B2 corresponding to most of the non-alumite area B from being anodized. The developing roller 10 is completed through the above steps.

  Here, the groove forming region B1 may be anodized or not anodized depending on how closely the masking member 18 is in close contact with the small diameter portion 114a. That is, when the deterioration of the masking member 18 has not progressed so much, the masking member 18 adheres to the small-diameter portion 114a with a certain amount of force due to its own elastic force, and the electrolytic solution passes from the end edge portion 18b of the masking member 18 to the groove portion. Since there is no room for entering the formation region B1, the groove formation region B1 is not anodized. On the other hand, when the masking member 18 deteriorates and the degree of adhesion decreases, the electrolyte is allowed to enter the groove forming area B1 to some extent, and therefore the groove forming area B1 is alumite treated over a certain range. Conversely, it is also possible to determine the replacement time of the masking member 18 by utilizing this fact. That is, when the deterioration of the masking member 18 has not progressed so much, both the grooves 141 and 142 are not anodized, or even if anodized, only the groove 142 on the roller body 12 side is anodized. At this point, it is not necessary to replace the masking member 18. When the deterioration of the masking member 18 has progressed considerably, both the grooves 141 and 142 are alumite-treated, and therefore the masking member 18 may be replaced at this point.

  As described above, according to the developing roller 10 of the present embodiment, the outer peripheral surface of the left shaft portion 14a that protrudes outward in the axial direction from one end (left side) of the roller body 12 and is rotatably supported by the conductive bearing 16. In addition, a non-alumite region B that is not anodized is set, and circumferential grooves 141 and 142 are provided in the non-alumite region B of the left shaft portion 14a in the vicinity of the boundary with the adjacent anodized region A. Therefore, even if the masking member 18 used for masking the non-alumite region B of the left shaft portion 14a at the time of anodizing is somewhat deteriorated due to repeated use in the mass production process of the developing roller 10, the anodized region A and the non-alumite region B can be reliably set and separated. That is, when the developing roller 10 is immersed in the alumite treatment tank, if the adhesion of the masking member 18 is reduced due to deterioration, the masking member 18 allows the electrolytic solution to enter the non-alumite region B. However, if the groove portions 141 and 142 are provided at the end portion (groove portion forming region B1) of the small diameter portion 114a on the roller body 12 side as described above, the infiltrated electrolyte solution is accumulated in the groove portions 141 and 142. Therefore, it is possible to prevent the electrolyte from further entering the tip side of the small diameter portion 114a, and as a result, the main region B2 corresponding to the majority of the non-alumite region B is reliably prevented from being anodized. be able to. If a bias voltage is applied to the main region B2, the bias voltage can be reliably applied to a portion having good conductivity because no oxide film is formed.

  In addition, according to the developing roller 10 of the present embodiment, the presence of the grooves 141 and 142 makes it possible to accurately determine the replacement time of the masking member 18. That is, in a state where both the groove portions 141 and 142 are not anodized, or only the groove portion 142 on the roller body 12 side is anodized, the masking member 18 is continuously used, and the groove portion 141 on the tip side of the small diameter portion 114a is anodized. The replacement time of the masking member 18 can be determined such that the masking member 18 is replaced at a later time. Moreover, even when the groove portion 141 is anodized, the main region B2 in the non-anodized region B has not yet been anodized, so that the developing roller 10 at this time can also be used as a non-defective product. In this way, the criteria for determining the replacement timing of the masking member 18 are clear, and since a good product can be manufactured reliably until that time, unlike the conventional developing roller, there is no need to perform a continuity check. As a result, the manufacturing efficiency of the developing roller 10 can be increased.

  Here, the small-diameter portion 114a of the left shaft portion 14a is configured so that a bias voltage is favorably applied because an oxide film is not formed on the outer peripheral surface thereof. Since it is a moving part, it is easy to wear. Therefore, if the amount of wear increases due to long-term use, wear powder generated thereby accumulates in the gap between the small diameter portion 114a and the conductive bearing 16, or between the large diameter portion 214a and the gap roller 17. Or the like, which may cause a torque increase of the rotational driving torque of the developing roller 10 or the like. However, even in such a case, according to the developing roller 10 of the present embodiment, since the groove portions 141 and 142 are provided, the wear powder accumulates in the groove portions 141 and 142, as described above. Problems such as wear powder entering the gap roller 17 can also be eliminated.

  In the present embodiment, the left shaft portion 14a is constituted by a stepped member having a small diameter portion 114a and a large diameter portion 214a. However, the step may not be provided unless particularly required. Further, the non-alumite region B is provided in a part (small diameter portion 114a) on the tip side of the left shaft portion 14a. However, the arrangement of the conductive bearing 16 and the gap roller 17 causes the left shaft portion 14a on the roller body 12 side. It may be provided in a part. In this case, since it is necessary to cover the masking member 18 up to the root portion of the left shaft portion 14a, the masking member 18 may be constituted by a cylindrical member that does not have the bottom portion 18a and is open at both ends. Further, in this case, the groove portions 141 and 142 may be provided at both left and right end portions of the non-alumite region B, respectively.

  Further, the number of the groove portions (141, 142) provided in the boundary region B of the left shaft portion 14a is not necessarily two, and may be one. However, it is preferable that the number of the groove portions is more than one from the viewpoint that the replacement cycle of the masking member 18 can be lengthened. On the contrary, the number of the groove portions may be more than two, but it is preferable that the number of groove portions is not excessive from the viewpoint of manufacturing efficiency. In the present embodiment, two grooves are provided in consideration of both of these points.

  Here, a groove similar to the groove (141, 142) may be provided on the inner peripheral surface of the masking member 18. That is, like the masking member 180 shown in FIG. 5, the grooves 181 and 182 may be provided at the end of the inner peripheral surface of the masking member 180. This makes it unnecessary to provide a groove in the left shaft part 14a.

  The masking member 18 is made of urethane rubber. However, the masking member 18 is not limited to this as long as it has a certain degree of elasticity and does not adversely affect the electrolyte during anodizing. For example, other types of rubber Or resin may be used.

  Furthermore, the roller main body 12 is constituted by a three-headed tube formed by connecting the outer tube 12a and the shaft 12c by three ribs 12b. However, the number of the ribs 12b may not be three as long as necessary strength is obtained. In addition, the shaft portion 14 is integrally extended from the roller main body 12 (the shaft 12c thereof), but may be a separate member from the roller main body 12. For example, the roller body 12 is constituted by a thin pipe-shaped member that does not have the shaft 12c or the rib 12b inside, and the shaft portion 14 is a stepped member having a large-diameter portion and a small-diameter portion. The large diameter portion may be press-fitted into the thin pipe-shaped roller body 12.

(A) is a perspective view which shows the whole structure of the developing roller concerning embodiment of this invention, (b)-(d) is an enlarged view of the one end side. (A) is a figure which shows the condition where the masking member was covered on the axial part of the one end side of the said developing roller. (A) is a diagram schematically showing a cross-sectional structure of a developing device in which the developing roller is preferably used, and (b) is a perspective view showing an overall configuration of the developing device with an upper lid removed. . FIG. 2 is a diagram schematically illustrating an entire configuration of an image forming apparatus on which the developing device is mounted. It is sectional drawing which shows the modification of the said masking member.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Developing roller 12 Roller main body 14 (14a, 14b) Shaft part 114a Small diameter part 214a Large diameter part 141,142 Groove part 114a, 141a * b, 142a * b Chamfer 18 Masking member A Anodized area B Non anodized area

Claims (4)

A developing roller having a roller main body having a cylindrical outer peripheral surface to be anodized, and a shaft portion that protrudes axially outward from one end of the roller main body and is rotatably supported by a conductive bearing,
On the outer peripheral surface of the shaft portion, a non-anodized region that is not anodized is set,
The developing roller according to claim 1, wherein at least one circumferential groove is provided in a non-alumite region of the shaft portion in the vicinity of a boundary portion between adjacent anodized regions.   The developing roller according to claim 1, wherein the number of the groove portions is two. The developing roller according to claim 1 or 2,
A developing roller, wherein a chamfer is formed at each of a corner portion at a tip end of the shaft portion and at least a corner portion on the roller body side among corner portions of the groove portion. In the developing roller according to any one of claims 1 to 3,
The shaft portion is a stepped member having a small diameter portion formed on the tip side thereof and a large diameter portion formed on the roller body side,
The developing roller according to claim 1, wherein the non-alumite region is set on an outer peripheral surface of a small-diameter portion.

Images