JP2017078838A - Developing device and image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a developing device that can suppress melting of developer on a peripheral surface of a developing roller, and an image forming apparatus.SOLUTION: An image forming apparatus comprises: a housing 51; a developing roller 54; a regulating member that regulates a thickness of developer held on a peripheral surface 54C of the developing roller 54; support parts 56 that are provided at positions closer to upstream sides in a rotation direction of the developing roller 54 than the regulation member so as to face an edge part 54D in the peripheral surface 54C and have arc surfaces formed along the peripheral surface 54C; contact members 57 that are provided among the arc surfaces and the peripheral surface 54C and brought into with the peripheral surface 54C; elastic members 58 that are supported by the support parts 56 and press the contact members 57 toward the peripheral surface 54C; and projection parts 59 that are provided closer to a center part side in an axial direction of a rotation shaft 54A of the developing roller 54 than the contact members 57 along the peripheral surface 54C and project from the support parts 56 toward the peripheral surface 54C.SELECTED DRAWING: Figure 3

Description

  The present invention relates to an electrophotographic image forming apparatus and a developing device mounted on the image forming apparatus.

  An image forming apparatus such as a printer capable of forming an image by an electrophotographic system includes a developing device that develops an electrostatic latent image formed on an image carrier such as a photosensitive drum. For example, the developing device includes a housing that stores the developer, a developing roller that holds the developer stored in the housing on a peripheral surface, and a regulation that regulates the thickness of the developer held by the developing roller. Member.

  Here, an image forming apparatus capable of regulating a movement of the developer on the peripheral surface in the rotation axis direction of the developing roller by providing a contact member in contact with the peripheral surface of the developing roller at an edge of the developing roller. It is known (see Patent Document 1). In this image forming apparatus, the contact member is pressed toward the peripheral surface by the elastic member supported by the housing and comes into contact with the peripheral surface.

JP 2009-3385 A

  By the way, when the developer having a low melting point is used in the image forming apparatus described above, the developer present in the vicinity of the contact position between the contact member and the peripheral surface is in contact with the contact member and the peripheral surface. May be melted by the frictional heat generated. When the developer melts, the developer is combined with the surrounding developer into a lump, and the lump is sandwiched between the regulating member and the circumferential surface, and the thickness of the developer on the circumferential surface by the regulating member is reduced. Regulation is hampered.

  An object of the present invention is to provide a developing device and an image forming apparatus capable of suppressing melting of the developer on the peripheral surface of the developing roller.

  A developing device according to one aspect of the present invention includes a housing, a developing roller, a regulating member, a support portion, a contact member, an elastic member, and a protruding portion. The housing contains a developer. The developing roller is rotatably provided in the housing and holds the developer accommodated in the housing on a peripheral surface. The regulating member is provided with a gap with respect to the peripheral surface of the developing roller, and regulates the thickness of the developer held on the developing roller. The support portion is provided at a position upstream of the regulating member in the rotation direction of the developing roller so as to face an edge portion of the peripheral surface, and has an arc surface formed along the peripheral surface. The contact member is provided between the circular arc surface and the peripheral surface and contacts the peripheral surface. The elastic member is supported by the support portion and presses the contact member toward the peripheral surface. The protruding portion is provided along the peripheral surface on the center side in the rotation axis direction of the developing roller from the contact member, and protrudes from the support portion toward the peripheral surface.

  An image forming apparatus according to another aspect of the present invention includes a developing device and an image forming unit. The developing device includes a housing, a developing roller, a regulating member, a support portion, a contact member, an elastic member, and a protruding portion. The housing contains a developer. The developing roller is rotatably provided in the housing and holds the developer accommodated in the housing on a peripheral surface. The regulating member is provided with a gap with respect to the peripheral surface of the developing roller, and regulates the thickness of the developer held on the developing roller. The support portion is provided at a position upstream of the regulating member in the rotation direction of the developing roller so as to face an edge portion of the peripheral surface, and has an arc surface formed along the peripheral surface. The contact member is provided between the circular arc surface and the peripheral surface and contacts the peripheral surface. The elastic member is supported by the support portion and presses the contact member toward the peripheral surface. The protruding portion is provided along the peripheral surface on the center side in the rotation axis direction of the developing roller from the contact member, and protrudes from the support portion toward the peripheral surface. On the other hand, the image forming unit can form an image based on image data.

  According to the present invention, it is possible to suppress melting of the developer on the peripheral surface of the developing roller.

FIG. 1 is a diagram illustrating a configuration of an image forming apparatus according to an embodiment of the present invention. FIG. 2 is a diagram showing the configuration of the developing device of the image forming apparatus according to the embodiment of the present invention. FIG. 3 is a view showing a configuration around the edge of the developing roller of the image forming apparatus according to the embodiment of the present invention. FIG. 4 is a view showing a configuration around the edge of the developing roller of the image forming apparatus according to the embodiment of the present invention. FIG. 5 is a diagram illustrating an example of the configuration of the contact member, the elastic member, and the protruding portion of the image forming apparatus according to the embodiment of the present invention. FIG. 6 is a diagram illustrating another example of the configuration of the contact member, the elastic member, and the protruding portion of the image forming apparatus according to the embodiment of the present invention. FIG. 7 is a diagram illustrating another example of the configuration of the contact member, the elastic member, and the protruding portion of the image forming apparatus according to the embodiment of the present invention.

  Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. The following embodiment is an example embodying the present invention, and does not limit the technical scope of the present invention.

[Schematic Configuration of Image Forming Apparatus 10]
First, a schematic configuration of an image forming apparatus 10 according to an embodiment of the present disclosure will be described with reference to FIG. Here, FIG. 1 is a schematic cross-sectional view showing the configuration of the image forming apparatus 10.

  The image forming apparatus 10 is a multifunction machine having a plurality of functions such as a facsimile function and a copy function, as well as a scan function for reading image data from a document and a print function for forming an image based on the image data. The present invention is applicable to image forming apparatuses such as printers, facsimile machines, and copiers.

  As shown in FIG. 1, the image forming apparatus 10 includes an ADF (automatic document feeder) 1, an image reading unit 2, an image forming unit 3, and a paper feeding unit 4.

  The ADF 1 includes a document setting unit, a plurality of conveyance rollers, a document pressing unit, and a paper discharge unit. In the ADF 1, the document P set on the document setting unit is conveyed by the plurality of conveyance rollers to the paper discharge unit via the image reading position by the image reading unit 2.

  The image reading unit 2 includes a document table, a light source, a plurality of mirrors, an optical lens, and a CCD. The image reading unit 2 reads image data from the document P placed on the document table or the document P conveyed by the ADF 1. Specifically, in the image reading unit 2, image data of the document P is input by inputting light reflected on the document P from the light source to the CCD via the plurality of mirrors and the optical lens. Is read.

  The image forming unit 3 can form an image by electrophotography based on the image data read by the image reading unit 2. The image forming unit 3 can also form an image based on image data input from an information processing apparatus such as an external personal computer. As shown in FIG. 1, the image forming unit 3 includes a photosensitive drum 31, a charging device 32, an optical scanning device (LSU) 33, a developing device 5, a developer supply unit 34, a transfer roller 35, a cleaning device 36, and a fixing roller. 37, a pressure roller 38, and a paper discharge tray 39.

  The paper feeding unit 4 feeds the sheet S on which an image is formed in the image forming unit 3. As shown in FIG. 1, the paper feed unit 4 includes a paper feed cassette 41 that stores sheets S. In the paper feeding unit 4, the sheets S stored in the paper feeding cassette 41 are taken out one by one and fed to an image forming position by the image forming unit 3.

  In the image forming unit 3, an image is formed on the sheet S supplied from the paper feeding unit 4 according to the following procedure, and the sheet S after the image formation is discharged to the paper discharge tray 39. The sheet S is a sheet material such as paper, coated paper, postcard, envelope, and OHP sheet.

  First, the surface of the photosensitive drum 31 is uniformly charged to a predetermined potential by the charging device 32. Next, the light scanning device 33 irradiates the surface of the photosensitive drum 31 with light based on the image data. Thereby, an electrostatic latent image corresponding to the image data is formed on the surface of the photosensitive drum 31. The electrostatic latent image on the photosensitive drum 31 is developed (visualized) as a toner image by the developing device 5. The developing device 5 is replenished with a developer from a developer replenishing unit 34 that can be attached to and detached from the image forming unit 3.

  Subsequently, the toner image formed on the photosensitive drum 31 is transferred onto the sheet S by the transfer roller 35. Thereafter, the toner image transferred to the sheet S is heated and fixed by the fixing roller 37 when the sheet S passes between the fixing roller 37 and the pressure roller 38. The toner remaining on the surface of the photosensitive drum 31 is removed by the cleaning device 36.

[Configuration of Developing Device 5]
Next, the developing device 5 will be described in detail with reference to FIGS. Here, FIG. 2 is a schematic cross-sectional view showing the configuration of the developing device 5. 3 is a cross-sectional view taken along the line III-III in FIG. 4 is a schematic cross-sectional view showing a configuration common to each of the edge portions 54D (see FIG. 3) of the developing roller 54. FIG. 5 is a schematic diagram showing the configuration of the contact member 57, the elastic member 58, and the protruding portion 59 before being attached to the support portion 56. In FIG. 3, the description of the second conveying screw 53 is omitted. Further, in FIG. 4, description of a part of the configuration of the second conveying screw 53 and the housing 51 is omitted. 3 and 4, for convenience of explanation, the housing 51, the developing roller 54, the regulating member 55, the contact member 57, the elastic member 58, and the protruding portion 59 are not hatched.

  The developing device 5 develops the electrostatic latent image on the photosensitive drum 31 using toner contained in the developer. For example, the developer is a one-component developer whose main component is magnetic toner. The developer may be a one-component developer mainly composed of nonmagnetic toner.

  As shown in FIGS. 2 to 4, the developing device 5 includes a housing 51, a first conveying screw 52, a second conveying screw 53, a developing roller 54, a regulating member 55, a support portion 56, a contact member 57, an elastic member 58, And a protrusion 59.

  The housing 51 houses the constituent members of the developing device 5 and the developer. The housing 51 is elongate along the left-right direction of the image forming apparatus 10 (the depth direction in FIG. 2). As shown in FIG. 2, the inside of the housing 51 is divided into a first transport path 51B and a second transport path 51C by a partition wall 51A. The partition wall 51 </ b> A is provided in a long shape along the longitudinal direction of the housing 51. At both ends of the partition wall 51A in the longitudinal direction, a communication path (not shown) that connects the first transport path 51B and the second transport path 51C is provided.

  As shown in FIG. 2, an opening 51 </ b> D is provided on the upper surface of the housing 51 in the first conveyance path 51 </ b> B. The developer replenishing section 34 is connected to the opening 51D. The developer supplied from the developer supply unit 34 is accommodated in the first transport path 51B via the opening 51D. An opening 51E is provided at the rear end of the image forming apparatus 10 in the second conveyance path 51C of the housing 51. In the image forming apparatus 10, the developing device 5 is disposed at a position where the opening 51 </ b> E faces the photosensitive drum 31.

  The first conveying screw 52 is rotatably provided in the first conveying path 51 </ b> B of the housing 51. As shown in FIG. 2, the 1st conveyance screw 52 has the spiral blade 52B around the rotating shaft 52A. A driving force is supplied to the first conveying screw 52 from a driving source (not shown) such as a motor. As a result, the first transport screw 52 is rotated in the rotational direction 52C, and the developer contained in the first transport path 51B is transported along the axial direction of the rotary shaft 52A while being stirred by the spiral blade 52B. . The developer is triboelectrically charged by stirring with the spiral blade 52B.

  The developer conveyed by the first conveying screw 52 is accommodated in the second conveying path 51C via the communication path.

  The second conveying screw 53 is rotatably provided in the second conveying path 51 </ b> C of the housing 51. As shown in FIG. 2, the second conveying screw 53 has a spiral blade 53B around the rotation shaft 53A. Similarly to the first conveying screw 52, the second conveying screw 53 is supplied with a driving force from a driving source (not shown). As a result, the second transport screw 53 is rotated in the rotational direction 53C, and the developer contained in the second transport path 51C is transported along the axial direction of the rotational shaft 53A while being stirred by the spiral blade 53B. . The developer is triboelectrically charged by stirring with the spiral blade 53B.

  A part of the developer conveyed by the second conveying screw 53 is supplied to the developing roller 54. Further, the remaining part of the developer conveyed by the second conveying screw 53 is accommodated in the first conveying path 51B via the communication path. That is, the developer accommodated in the housing 51 is in a circulation conveyance path formed by the first conveyance screw 52 and the second conveyance screw 53 by the first conveyance path 51B, the second conveyance path 51C, and the communication path. It is conveyed by circulating.

  The developing roller 54 is rotatably provided in the housing 51. As shown in FIG. 2, the developing roller 54 is provided opposite to the second conveying screw 53 at a position on the rear side of the image forming apparatus 10 with respect to the second conveying screw 53 in the second conveying path 51 </ b> C. Part of the peripheral surface 54C of the developing roller 54 is exposed to the outside of the housing 51 from the opening 51E. A part of the peripheral surface 54 </ b> C exposed to the outside of the housing 51 faces the photosensitive drum 31. The developing roller 54 holds the developer contained in the housing 51 on the peripheral surface 54C.

  As shown in FIG. 2, the developing roller 54 includes a developing sleeve 541 and a magnet 542. The developing sleeve 541 has a cylindrical shape and is rotatably provided in the housing 51. For example, the developing sleeve 541 is made of a nonmagnetic material such as aluminum. For example, the peripheral surface 54C of the developing sleeve 541 is subjected to a roughening process to adjust the developer holding amount and the friction amount except for the edge portion 54D (see FIG. 3).

  The magnet 542 is fixedly provided inside the developing sleeve 541. The magnet 542 has a plurality of magnetic poles. For example, the magnet 542 includes a regulation pole that generates a peak magnetic force at a position facing the regulation member 55, and a development pole that generates a peak magnetic force at a position facing the photosensitive drum 31.

  In the developing roller 54, the magnetic developer is attracted to the peripheral surface 54 </ b> C by the magnetic pole of the magnet 542. On the other hand, the developer is frictionally charged by agitation by the first conveying screw 52 and the second conveying screw 53, and adheres to the peripheral surface 54C by electrostatic force. Therefore, a part of the developer conveyed by the second conveying screw 53 adheres to the peripheral surface 54C at the supply position P1 (see FIG. 2) where the second conveying screw 53 and the developing roller 54 face each other. Accordingly, the developer is held on the peripheral surface 54C.

  A driving force is supplied to the developing roller 54 from the driving source (not shown). As a result, the developing roller 54 is rotated in the rotation direction 54B, and the developer held on the peripheral surface 54C is conveyed from the supply position P1 to the developing position P2 (see FIG. 2) facing the photosensitive drum 31. . When a one-component developer made of non-magnetic toner that does not have magnetism is used instead of the magnetic toner, it is not necessary to provide a magnetic pole in the developing sleeve 541.

  The regulating member 55 is provided with a gap with respect to the peripheral surface 54 </ b> C of the developing roller 54. As shown in FIG. 2, the regulating member 55 is provided at a position downstream of the supply position P1 in the rotational direction 54B and upstream of the development position P2 in the rotational direction 54B. The restricting member 55 is provided in a long shape along the longitudinal direction of the housing 51. As shown in FIG. 4, the end of the regulating member 55 in the longitudinal direction is supported by the support portion 56. For example, the restricting member 55 has a blade shape and is made of a metal having magnetism. The layer thickness of the developer held on the peripheral surface 54 </ b> C of the developing roller 54 is regulated by the regulating member 55. As a result, a thin layer of the developer having a uniform thickness is formed on the peripheral surface 54 </ b> C of the developing roller 54. The gap between the regulating member 55 and the peripheral surface 54C of the developing roller 54 may be arbitrarily set according to the layer thickness of the developer formed by the regulating member 55.

  As shown in FIGS. 3 and 4, the support portion 56 is provided at a position upstream of the regulating member 55 in the rotation direction 54 </ b> B of the developing roller 54 and facing the edge portion 54 </ b> D on the peripheral surface 54 </ b> C. As shown in FIG. 4, the support part 56 has the circular arc surface 561 formed in strip | belt shape along 54 C of surrounding surfaces. The circular arc surface 561 is formed so as to cover a lower region and a front region of the peripheral surface 54 </ b> C of the developing roller 54. For example, the support part 56 is formed integrally with the housing 51. Note that the support portion 56 may be provided only on one edge portion 54D of the developing roller 54. Further, the support portion 56 is not limited to be formed integrally with the housing 51, and may be a member different from the housing 51.

  The contact member 57 is provided between the circular arc surface 561 and the peripheral surface 54C of the developing roller 54, and contacts the peripheral surface 54C. Specifically, as shown in FIGS. 3 and 4, the contact member 57 is provided in a strip shape along the arc surface 561, and the downstream end in the rotation direction 54 </ b> B is in the rotation direction 54 </ b> B of the restriction member 55. It is in contact with the upstream side. The contact member 57 is a part of a region facing the circular arc surface 561 on the peripheral surface 54C of the developing roller 54, and is in contact with a region where the rough surface treatment is not performed. For example, the contact member 57 is a non-woven fabric formed of fluorine fibers. The contact member 57 is not limited to a non-woven fabric, and other members having a small coefficient of friction with the peripheral surface 54C may be used.

  The elastic member 58 is supported by the support portion 56 and presses the contact member 57 toward the peripheral surface 54 </ b> C of the developing roller 54. Specifically, as shown in FIG. 4, the contact member 57 is provided in a strip shape along the arc surface 561 similarly to the contact member 57, and the first end 58 </ b> A on the downstream side in the rotational direction 54 </ b> B is a regulating member. 55 is in contact with the upstream side surface in the rotational direction 54B. The elastic member 58 supports the surface of the contact member 57 opposite to the contact surface with the peripheral surface 54C. For example, the elastic member 58 is made of microcell urethane foam. The elastic member 58 is not limited to the microcell urethane foam, and may be any member that can be elastically deformed.

  A predetermined separation distance is provided between the arc surface 561 and the peripheral surface 54 </ b> C of the developing roller 54. Specifically, the separation distance is set to a distance shorter than the total value of the thickness of the contact member 57 and the thickness of the elastic member 58 in the direction perpendicular to the circumferential surface 54C. Therefore, the elastic member 58 is elastically deformed between the arc surface 561 and the peripheral surface 54C of the developing roller 54. As a result, the contact member 57 is pressed toward the peripheral surface 54C of the developing roller 54 by the elastic member 58, and the contact member 57 comes into close contact with the peripheral surface 54C. Accordingly, movement of the developer in the axial direction of the rotation shaft 54A (see FIG. 3) of the developing roller 54 is restricted, and the developer is prevented from leaking from the developing roller 54 beyond the edge portion 54D.

  Here, when a non-woven fabric is used for the contact member 57, the contact surface with the peripheral surface 54C of the contact member 57 is different from the case where other members are used due to the characteristics of the non-woven fabric having a large number of gaps on the surface. It is possible to reduce the contact area. Thereby, generation | occurrence | production of the frictional heat by contact with the contact member 57 and 54 C of surrounding surfaces is suppressed. The developer that has entered the gaps of the nonwoven fabric is melted by frictional heat. As a result, the gap is filled with the developer, and the degree of adhesion between the contact member 57 and the peripheral surface 54C is increased.

  By the way, in the image forming apparatus 10, the elastic member 58 is deformed by a force along the rotation direction 54 </ b> B received from the developing roller 54 via the contact member 57. As a result, the first end 58A (see FIG. 4) on the downstream side in the rotation direction 54B of the developing roller 54 of the elastic member 58 is pressed against the upstream side surface in the rotation direction 54B of the regulating member 55, and the density increases. To do. Therefore, the pressing force against the contact member 57 by the elastic member 58 is increased downstream in the rotation direction 54B, and the frictional force between the contact member 57 and the peripheral surface 54C is increased. In this case, the developer existing in the vicinity of the contact position P3 (see FIG. 3) between the contact member 57 and the peripheral surface 54C may be melted by frictional heat generated by the contact between the contact member 57 and the peripheral surface 54C. is there. When the developer melts, the developer is combined with the surrounding developer to form a lump, and the lump is sandwiched between the regulating member 55 and the circumferential surface 54C, and the thickness of the developer on the circumferential surface 54C by the regulating member 55 is reduced. Regulation is hampered. In this case, problems such as a local decrease in the density of the image formed by the image forming apparatus 10 occur. On the other hand, in the image forming apparatus 10 according to the embodiment of the present invention, it is possible to suppress melting of the developer on the peripheral surface 54C of the developing roller 54 as described below.

  Specifically, the elastic member 58 has a thickness in the direction perpendicular to the circumferential surface 54C of the first end portion 58A on the downstream side in the rotation direction 54B of the developing roller 54 upstream of the first end portion 58A in the rotation direction 54B. It is formed to be smaller than the thickness of the other part. For example, as shown in FIG. 5, the elastic member 58 has a part on the side of the contact surface 58 </ b> C that contacts the contact member 57 at the first end portion 58 </ b> A. Therefore, in the image forming apparatus 10, the thickness T3 of the first end 58A of the elastic member 58 is equal to the thickness T1 of the upstream second end 58B in the rotation direction 54B of the elastic member 58 and the rotation direction 54B of the elastic member 58. It is smaller than the thickness T2 of the central part. Thereby, it is possible to reduce the frictional force between the contact member 57 and the peripheral surface 54 </ b> C on the downstream side in the rotation direction 54 </ b> B, which increases due to the force received from the developing roller 54. Here, the difference between the thickness at the first end portion 58A and the thickness at the other portion is appropriately set according to the amount of increase in the frictional force at the first end portion 58A due to the force received from the developing roller 54. It may be.

  In the image forming apparatus 10, the elastic member 58 may have the same thickness at the first end portion 58A as the thickness of the other portion upstream of the first end portion 58A in the rotation direction 54B. .

  In the image forming apparatus 10, the elastic member 58 may be formed so that the thickness continuously increases from the first end 58A toward the second end 58B on the upstream side in the rotation direction 54B. . For example, as shown in FIG. 6, the elastic member 58 may be inclined such that the contact surface 58C gradually increases in thickness from the first end 58A toward the second end 58B. Also in this case, it is possible to reduce the frictional force between the contact member 57 and the peripheral surface 54C on the downstream side in the rotation direction 54B, which is increased by the force received from the developing roller 54. In addition, the elastic member 58 may be inclined such that the thickness of the contact surface that contacts the circular arc surface 561 gradually increases from the first end portion 58A toward the second end portion 58B. The elastic member 58 is inclined such that both the contact surface 58C and the contact surface that contacts the arc surface 561 are gradually increased in thickness from the first end portion 58A toward the second end portion 58B. Also good.

  The elastic member 58 may be formed so that the thickness increases stepwise from the first end portion 58A toward the second end portion 58B. For example, as shown in FIG. 7, the elastic member 58 may be formed in a stepped shape so that the contact surface 58C gradually increases in thickness from the first end 58A toward the second end 58B. Good. Also in this case, it is possible to reduce the frictional force between the contact member 57 and the peripheral surface 54C on the downstream side in the rotation direction 54B, which is increased by the force received from the developing roller 54. The elastic member 58 may be formed in a stepped shape so that the contact surface that contacts the circular arc surface 561 gradually increases in thickness from the first end 58A toward the second end 58B. Further, the elastic member 58 is formed in a stepped shape so that both the contact surface 58C and the contact surface in contact with the circular arc surface 561 gradually increase in thickness from the first end portion 58A toward the second end portion 58B. May be.

  Further, instead of adjusting the thickness of the elastic member 58, the separation distance between the arc surface 561 and the peripheral surface 54C of the developing roller 54 may be adjusted. Specifically, the separation distance between the first end portion 561A on the downstream side in the rotation direction 54B of the circular arc surface 561 and the peripheral surface 54C in the rotation direction 54B is upstream of the first end portion 561A in the rotation direction 54B. The circular arc surface 561 may be formed so as to be larger than the separation distance of the other part on the side. Also in this case, it is possible to reduce the frictional force between the contact member 57 and the peripheral surface 54C on the downstream side in the rotation direction 54B, which is increased by the force received from the developing roller 54.

  Further, in the image forming apparatus 10, the arcuate surface 561 may be formed such that the separation distance continuously decreases from the first end 561A toward the second end 561B on the upstream side in the rotation direction 54B. Good. Further, the circular arc surface 561 may be formed so that the separation distance gradually decreases from the first end 561A toward the second end 561B. Also in this case, it is possible to reduce the frictional force between the contact member 57 and the peripheral surface 54C on the downstream side in the rotation direction 54B, which is increased by the force received from the developing roller 54.

  By the way, when the developer having a low melting point is used in the image forming apparatus 10, the developer present in the vicinity of the contact position P <b> 3 (see FIG. 3) between the contact member 57 and the peripheral surface 54 </ b> C is separated from the contact member 57. It may be melted by frictional heat generated by contact with the surface 54C. Therefore, in the image forming apparatus 10, the developing device 5 is provided with a protrusion 59.

  As shown in FIG. 3, the protrusion 59 extends from the support portion 56 to the circumferential surface 54 </ b> C at a position closer to the center in the axial direction of the rotation shaft 54 </ b> A of the developing roller 54 than the contact position P <b> 3 between the contact member 57 and the circumferential surface 54 </ b> C. It protrudes toward the side. Similar to the contact member 57 and the elastic member 58, the protruding portion 59 is provided along the arc surface 561.

  For example, as shown in FIG. 3, the protrusion 59 is formed integrally with the elastic member 58. Further, the protruding portion 59 is formed in a tapered shape toward the protruding tip. Further, the projecting tip of the projecting portion 59 is provided so as to be opposed to a region of the peripheral surface 54 </ b> C that has been subjected to the roughening process with a predetermined distance therebetween. Protrusion 59 is provided at a position closer to the center in the axial direction of rotation shaft 54A of developing roller 54 than contact position P3, so that the approach of developer to contact position P3 is limited. Further, the protrusion 59 suppresses transmission of the frictional heat generated at the contact position P3 to the central portion side in the axial direction of the rotation shaft 54A of the developing roller 54.

  The protruding portion 59 may be formed of a member different from the elastic member 58 and provided on the arc surface 561 of the support portion 56.

  Further, the shape of the protruding portion 59 is not limited to the tapered shape toward the protruding tip, but may be other shapes as long as the approach of the developer to the contact position P3 can be limited. Further, the projecting tip of the projecting portion 59 may be provided in contact with a region of the peripheral surface 54C where the roughening treatment is not performed. The shape of the protruding portion 59 and the distance between the protruding tip of the protruding portion 59 and the peripheral surface 54C are appropriately set according to the amount of the developer that passes through the protruding portion 59 and reaches the contact position P3. It may be.

  As described above, in the image forming apparatus 10, the protruding portion 59 is provided at a position closer to the center in the axial direction of the rotation shaft 54 </ b> A of the developing roller 54 than the contact position P <b> 3. As a result, the approach of the developer to the contact position P3 is restricted, and the transmission of frictional heat generated at the contact position P3 to the central portion side in the direction of the rotation shaft 54A of the developing roller 54 is suppressed. Therefore, melting of the developer on the peripheral surface 54C of the developing roller 54 is suppressed.

1 ADF
2 Image Reading Unit 3 Image Forming Unit 4 Paper Feeding Unit 5 Developing Device 10 Image Forming Device 51 Housing 52 First Conveying Screw 53 Second Conveying Screw 54 Developing Roller 55 Restricting Member 56 Supporting Portion 57 Contact Member 58 Elastic Member 59 Protruding Portion

Claims (7)

A housing for containing the developer;
A developing roller rotatably provided in the housing and holding the developer contained in the housing on a peripheral surface;
A regulating member which is provided with a gap with respect to the peripheral surface of the developing roller and regulates the thickness of the developer held by the developing roller;
A support portion having an arcuate surface formed along the peripheral surface, provided opposite to the edge of the peripheral surface at a position upstream of the regulating member in the rotation direction of the developing roller;
A contact member provided between the arcuate surface and the peripheral surface and in contact with the peripheral surface;
An elastic member supported by the support portion and pressing the contact member toward the peripheral surface;
A projecting portion that is provided along the peripheral surface on the center side in the rotation axis direction of the developing roller from the contact member, and protrudes from the support portion toward the peripheral surface;
A developing device comprising:   The developing device according to claim 1, wherein the protruding portion has a tapered shape toward a protruding tip.   The developing device according to claim 1, wherein the protruding portion is formed by the elastic member.   The developing device according to claim 1, wherein the contact member is a nonwoven fabric. The contact member has an end on the downstream side in the rotation direction that contacts an upstream side surface in the rotation direction of the restriction member,
The thickness of the elastic member in a direction perpendicular to the peripheral surface of the downstream end portion in the rotation direction is smaller than the thickness of the other portion upstream of the end portion in the rotation direction. The developing device according to any one of the above. The contact member has an end on the downstream side in the rotation direction that contacts an upstream side surface in the rotation direction of the restriction member,
The arcuate surface has a separation distance between the end portion on the downstream side in the rotation direction and the peripheral surface that is larger than the separation distance on the other portion on the upstream side with respect to the end portion in the rotation direction. 4. The developing device according to any one of 4 above.   An image forming apparatus comprising the developing device according to claim 1 and comprising an image forming unit capable of forming an image based on image data.

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