JP2005078013A - Development device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To always feed fresh developer to a photoreceptor drum by improving the replacement of developer in the vicinity of the magnetic poles of a stir member. <P>SOLUTION: The development device has in a development housing 60: a development roller 40; a screw feeder 30 which distributes toner over the entire length of the development roller 40 in the lengthwise direction; a toner receiving mixer 80 which rotates toner while stirring toner between the screw feeder 30 and the development roller 40, smoothly supplies the toner to the peripheral face of the development roller 40 by magnetic force induction, whereas the mixer 80 scrapes residual toner on the periphery of the development roller 40 with the repulsion of the magnetic force. The toner receiving mixer 80 includes: a cross-shaped support 81, which is turnable around an axis parallel to the development roller 40; a plurality of square barlike magnets 84 fixed to the leading ends of the support projections 83 of the cross-shaped support 81 at regular intervals in a circumferential direction so that the magnetic poles face outside; and tubes 85 which cover the barlike magnets 84 in close contact with them. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a developing device suitable for application to image forming apparatuses such as copying machines, facsimile machines, and various printers.

  A developing device is applied to an image forming apparatus such as a copying machine, a facsimile machine, or various printers. This developing device supplies a developer (mixed toner and magnetic carrier) to the circumferential surface of a photosensitive drum rotating about an axis, and the photosensitive member is supplied with the developer. The electrostatic latent image based on the optically read original image formed in advance on the peripheral surface of the drum becomes a so-called toner image. By transferring the toner image onto the paper, the same image as the original image is formed on the paper.

  Such a developing device includes a double mixer having an inner cylinder and an outer cylinder that are concentric with each other and rotated in opposite directions around an axis, a developing roller disposed opposite to the double mixer, the developing roller, A stirrer that stirs the developer and is interposed between the double mixer is formed by being housed in the housing. The developer supplied into the housing circulates in the longitudinal direction inside and outside the outer cylinder by the rotation of the inner cylinder and the outer cylinder of the double mixer in the opposite directions, thereby removing the developer. In the housing, it is uniformly distributed in the longitudinal direction of the developing roller.

  The developer uniformly dispersed over the entire length in the longitudinal direction of the developing roller in the housing is further stirred by a stirring member rotating around the axis outside the double mixer, and then stirred. The toner is supplied to the peripheral surface of the developing roller disposed opposite to the member. Part of the developer supplied to the peripheral surface of the developing roller is used for forming a toner image on the peripheral surface of the photosensitive drum, and the remaining part remains on the peripheral surface of the developing roller, but returns to the housing. Then, the toner is once peeled off from the peripheral surface of the developing roller by contact with another developer, mixed with the other through a double mixer, and then supplied again to the same peripheral surface. In such a developing device, one in which a so-called magnetic brush system, such as that described in Patent Document 1, in which a cylindrical magnet member is mounted in a developing roller without rotating is known. .

  In the developing device employing this magnetic brush system, the same magnetic pole (for example, N pole) is formed at a predetermined distance in the circumferential direction on the peripheral surface of the magnet member and a desired portion in the housing. On the other hand, the other magnetic pole (for example, S pole) is formed on the circumferential surface of the stirring member at a predetermined pitch in the circumferential direction. Accordingly, the magnetic lines of force are bridged between the peripheral surface of the developing roller and the portion facing the peripheral surface of the photosensitive drum (that is, the N pole portion) and the S pole portion of the stirring member. The developer having the above is attracted by the magnetic lines of force to form a rice-brush shape to form a so-called magnetic brush, and the developer is smoothly supplied to the peripheral surface of the developing roller by the formation of the magnetic brush.

On the other hand, a part of the developer once supplied to the peripheral surface of the developing roller is supplied to the peripheral surface of the photosensitive drum and used for the transfer process, but the remaining developer is accompanied by the rotation of the developing roller. Is returned to the housing. The returned developer on the peripheral surface of the developing roller reaches the position where the same pole (N pole) of the magnet member is disposed. At this time, the peripheral surface of the developing roller is generated by the repulsive force of the magnetic force of the same pole. Therefore, the developer remaining on the peripheral surface of the developing roller is not brought into the developing area again. As a result, the delivery of the developer between the agitating member and the developing roller is performed satisfactorily.
JP 2002-911168 A

  However, since the magnetic pole (S pole) formed on the peripheral surface of the stirring member is in a state where the background is embedded in the developer in the housing, the developer attached to the surface of the magnetic pole It is in a state of being magnetized directly to the surface and is difficult to peel off. Therefore, it is difficult for the developer existing in the vicinity of the magnetic pole of the stirring member to be sufficiently replaced with a new one, which is inconvenient in always supplying fresh developer to the photosensitive drum via the developing roller. There was a problem that occurred.

  The present invention has been made to solve the above-described problems, and is premised on a developing device employing a magnetic brush system, which makes it difficult for the developer to adhere to the magnetic poles of the stirring member, and for stirring. It is an object of the present invention to provide an improved developing device that can always feed fresh developer to a photosensitive drum by improving developer replacement performance in the vicinity of a magnetic pole of a member.

  According to the first aspect of the present invention, there is provided a developing roller having a predetermined length opposed to the photosensitive drum, and development distributed to the developing roller side while stirring the developer over the entire length in the length direction of the developing roller. The developer agitating means and the developer delivery means, which is disposed between the developer agitating means and the developing roller, and smoothly supplies the developer to the peripheral surface of the developing roller by induction by a magnetic force accompanying rotation, are provided in the housing. The developer delivery means includes a rotating body having a plurality of arms rotatable around an axis parallel to the developing roller, and each of the magnetic poles facing outward. A plurality of magnets fixed to the tip of the arm and a sheet body made of a non-magnetic material that covers each magnet in a close contact state are provided.

  The invention according to claim 2 is characterized in that, in the invention according to claim 1, the sheet body covers the rotating body with a tube made of a synthetic resin material having heat shrinkability. .

  According to the first aspect of the present invention, since the magnet fixed to the arm tip of the rotating body of the developer delivery means is covered in close contact with the sheet body made of a non-magnetic material, the developer in the housing is There is no direct contact with the magnet, and the performance of peeling off the developer from the magnet is improved as compared with the case of conventional direct contact. Therefore, in the conventional developing device, there is a disadvantage that the developer gathers near the magnet in the housing to form a lump, which makes it difficult to replace the developer near the magnet. Therefore, the developer lump is not occasionally peeled off from the magnet and supplied to the developing roller, and the photosensitive drum is always supplied with fresh photosensitive agent. This contributes to uniform image quality of the transferred image.

  According to the invention of claim 2, a tube having an inner diameter dimension slightly larger than the outer diameter dimension of the rotating body is adopted as the tube, and hot air is blown onto the tube in a state where the tube is covered with the rotating body, or the tube is rotated. By applying a heat treatment such as loading the whole into the heating path, the tube is thermally contracted to adhere to the outer peripheral surface of the rotating body.

  As described above, by adopting a heat-shrinkable synthetic resin material as the material of the tube, it is possible to improve the workability of the mounting work on the rotating body and to obtain a reliable mounting performance that is difficult to come off.

  In addition, since the plurality of magnets attached to the peripheral surface of the rotating body are protected in a pressed state toward the axial direction by the tube, it is possible to reliably prevent the occurrence of problems such as the magnets falling off the rotating body. The

  In addition, since a plurality of magnets are covered with a tube, even if a recess is formed between adjacent magnets, the recess is closed by the tube. Inconvenience that the developer fits into the recess and accumulates is avoided, and smooth movement of the developer on the peripheral surface of the developer delivery means is ensured.

  FIG. 1 is a perspective view showing an embodiment of a copying machine to which a developing device according to the present invention is applied. As shown in this figure, a copying machine (image forming apparatus) 10 is formed by attaching a lid 12 to an upper surface opening of a box-shaped device body 11 and reads a document image on the lid 12 portion. For this purpose, a feeding structure for feeding a document is provided, and various devices for image formation are built in the device main body 11.

  That is, in the apparatus main body 11, an optical system 16 (not shown) that reads a document image of a sheet fed by a sheet feeding structure, and development that transfers the document image read by the optical system 16 to a predetermined sheet as a toner image. A developing unit 17 including devices such as the apparatus 20 and the photosensitive drum 171, a fixing unit 18 including a fixing roller 181 that performs fixing processing on a sheet on which a toner image has been transferred by the developing unit 17, and a transfer sheet A sheet feeding unit 19 (not shown) including a plurality of sheet feeding cassettes 191 and the like for stacking and storing is housed.

  The sheet fed from the sheet feeding unit 19 is sent to the developing unit 17 through a predetermined conveyance path, where a developer (a two-component system that is a mixture of toner and magnetic carrier) from the developing device 20 is sent. The toner image on the circumferential surface of the photosensitive drum 171 (this toner image was once formed on the circumferential surface of the photosensitive drum 171 based on the image data read by the optical system). After the toner image is transferred to the electrostatic latent image, the fixing unit 18 performs heat fixing processing by the fixing roller 181. Paper is discharged toward the paper discharge unit 190 provided.

  The lid 12 is provided with a paper feeding unit 13 for feeding paper (original) on one side, and is directed from the paper feeding unit 13 to the other side of the lid 12. A feed tray 14 that protrudes obliquely upward and a discharge tray 15 that is formed over substantially the entire surface of the lid 12 at a position below the feed tray 14 are provided. A pair of paper width setting members 141 in the width direction are provided at the base end portion (left side in FIG. 1) of the feeding tray 14, and between the pair of paper width setting members 141 according to the size of the paper to be read. By adjusting the inner dimension, the sheet is positioned in the width direction on the feeding tray 14.

  FIG. 2 is a perspective view showing one embodiment of the developing device 20 according to the present invention, and FIG. 3 is a partially cutaway skeleton perspective view for explaining the drive structure. 4 is a side view as seen from line A in FIG. 2, and FIG. 5 is a side view as seen from line B in FIG. 6 is a cross-sectional view taken along line CC in FIG. 2 and 3, the XX direction is referred to as the width direction, in particular, the −X direction is referred to as the left side, and the + X direction is referred to as the right side. The Y-Y direction is referred to as the front-rear direction, and in particular, the -Y direction is referred to as the front, and the + Y direction is referred to as the rear.

  As shown in these drawings, the developing device 20 sensitizes a screw feeder (developer stirring means) 30 that circulates and moves toner in the device, and toner that is uniformly distributed in the width direction by driving the screw feeder 30. A developing roller 40 supplied toward the body drum 171 (FIG. 1), a toner delivery mixer (developer delivery means) 80 interposed between the developing roller 40 and the screw feeder 30, and the screw feeder 30. The gear mechanism 50 that transmits the driving force of the driving motor 91 to the developing roller 40 and the toner delivery mixer 80 via the electromagnetic clutch 90 is formed by being mounted on a predetermined developing housing 60.

  The developing housing 60 includes a pair of side plates 61 (a right side plate 611 and a left side plate 612) in the width direction, a bottom plate 62 installed between lower edges of the pair of side plates 611 and 612, and a rear side of the bottom plate 62. And a rearward extending portion 63 formed in the formed portion. As shown in FIGS. 4 and 5, the side plate 61 is formed in a rectangular shape that is inclined upward (upwardly left in FIG. 4 and upwardly right in FIG. 5), whereby the bottom plate 62 is also inclined upward. . A toner storage space 64 for storing toner is formed between the forwardly rising bottom plate 62, the pair of left and right side plates 611 and 612, and the front wall of the rearward extending portion 63.

  A toner supply groove 631 toward the toner storage space 64 is recessed at a substantially central position in the width direction of the rearward extending portion 63, and toner from a toner hopper (not shown) passes through the toner supply groove 631 and is stored in the toner. It is introduced into the space 64.

  The screw feeder 30 includes an inner screw feeder 31 and an outer screw feeder 32 that is concentrically fitted to the inner screw feeder 31. The inner screw feeder 31 includes a feeder shaft 311 penetrating through a pair of side plates 611 and 612 so as to be rotatable around an axis, and a spiral fin 312 formed in a spirally wound state around the feeder shaft 311. I have.

  In the present embodiment, the spiral fin 312 is formed in a left-handed manner around the feeder shaft 311 (a winding method in which the spiral fin 312 advances downward from the top toward the left as viewed from the end surface of the feeder shaft 311). Yes. Therefore, in FIG. 3, when the feeder shaft 311 is rotated counterclockwise around the axis, the toner in contact with the surface of the inner screw feeder 31 is moved toward the right.

  On the other hand, the outer screw feeder 32 includes a cylindrical feeder cylinder 321 and a spiral strip 322 spirally wound around the outer peripheral surface of the feeder cylinder 321. In the present embodiment, the spiral strip 322 is also formed in a left-handed manner like the spiral fin 312. Therefore, in FIG. 3, when the outer screw feeder 32 is rotated clockwise around the feeder shaft 311, the toner in contact with the surface of the outer screw feeder 32 moves toward the left.

  A predetermined number of ribs 323 provided between adjacent spiral strips 322 are provided on the outer peripheral surface of the feeder cylinder 321, and the presence of the ribs 323 improves the toner stirring effect.

  As shown in FIG. 3, a toner distribution window 33 is opened at each end and substantially central portion of the feeder cylinder 321, and the toner passes through the toner distribution window 33 and the inside and outside of the feeder cylinder 321. It has come to circulate.

  Further, a disk wall 34 (the right disk wall 341 and the left disk wall 342) having the same diameter as that of the feeder cylinder 321 is fixed to each end portion of the feeder cylinder 321 so as to close the end surface opening. Each of the disk walls 341 and 342 is formed with a center hole 343 through which the feeder shaft 311 is inserted so as to be rotatable around the axis thereof, so that the inner and outer screw feeders 31 and 32 can be connected to the axis of the feeder shaft 311. They can rotate relative to each other. In particular, the left disc wall 342 is provided with a sleeve 35 concentrically projecting outward at the center position, and an outer feeder gear 73 described later is concentrically and integrally fixed to the sleeve 35. .

  In the screw feeder 30 configured as described above, the feeder shaft 311 passes through the pair of side plates 611 and 612 and protrudes to the outside, and thereby the shaft center between the pair of side plates 611 and 612 in the toner storage space 64. It is in a state of being erected around and rotatable.

  The feeder shaft 311 is connected to the drive shaft of the drive motor 91 via the electromagnetic clutch 90 at the end of the right disk wall 341 passing through the center hole 343, and the drive rotation of the drive motor 91 is performed via the electromagnetic clutch 90. Then, it is transmitted to the feeder shaft 311.

  The electromagnetic clutch 90 transmits the rotation of the drive shaft of the drive motor 91 to the feeder shaft 311, while it is necessary only for the first drive gear 51 to be described later that is concentrically fitted to the feeder shaft 311. It is comprised so that rotation of a drive shaft may not be transmitted.

  The developing roller 40 includes a roller shaft 41, a developing roller main body 42 fitted in a sliding contact with the roller shaft 41, and a cylindrical magnet interposed between the developing roller main body 42 and the roller shaft 41. It consists of a member 43. The roller shaft 41 is attached to the pair of side plates 611 and 612 in a non-rotating state, and the magnet member 43 is externally fitted to the roller shaft 41 in a non-rotating state. An annular gap for mounting the magnet member 43 is formed between the developing roller main body 42 and the roller shaft 41.

  In order to secure the annular gap, discs 411 are fixed to the left and right ends of the developing roller main body 42, respectively. At the center position of these discs 411, through holes are formed to allow the roller shaft 41 to pass through in a sliding contact state. By inserting the roller shaft 41 into these through holes, the roller body 42 is rotated around the roller shaft 41. It can be rotated. Further, a sleeve with a roller shaft 41 penetrating therethrough is integrally provided between the right circular plate 411 and a roller gear 56 to be described later, and the rotation of the roller gear 56 is a roller through the sleeve and the circular plate 411. It is transmitted to the main body 42.

  The magnet member 43 is externally fitted to the roller shaft 41 in a non-rotating state, and the outer diameter dimension is set slightly smaller than the inner diameter dimension of the developing roller body 42, whereby the roller shaft 41 and the developing roller body 42 are Can be fitted into the annular gap formed between the two. The magnet member 43 has a length slightly shorter than the inner dimension between the pair of disks 411. A predetermined magnetic pole is formed on the outer peripheral surface of the magnet member 43 as shown in FIG.

  The developing roller 40 is set at an installation position so that the peripheral surface of the developing roller main body 42 protrudes slightly outward from the front edge of the bottom plate 62 of the developing housing 60, and thereby the peripheral surface of the developing roller main body 42. The surface faces the peripheral surface of the photosensitive drum 171 with a slight gap. Therefore, the toner carried on the peripheral surface of the developing roller main body 42 is delivered to the peripheral surface of the photosensitive drum 171 in a state along the electrostatic latent image by the rotation of the developing roller main body 42.

  The toner delivery mixer 80 is interposed between the screw feeder 30 and the developing roller 40 in the toner storage space 64 of the developing housing 60, and is rotated concentrically with a third driven gear shaft 551, which will be described later. The toner is transferred to the developing roller 40.

  FIG. 7 is a perspective view showing an embodiment of the toner delivery mixer 80, and FIG. 8 is a partially enlarged perspective view thereof. As shown in these drawings, the toner delivery mixer 80 includes a pair of cross-shaped support bodies (rotating bodies) 81 in the longitudinal direction, and four pieces that are laid between the pair of cross-shaped support bodies 81 at an equal pitch in the circumferential direction. , And a synthetic resin tube 85 that is externally fitted to the four square-shaped magnets 84.

  The cruciform support 81 includes a connecting cylinder 82 concentrically connected to a third driven gear shaft 551 described later, and one side portion of the connecting cylinder 82 (the pair of cruciform supports 81 facing each other). 4 support projecting pieces (arms) 83 projecting outward in the radial direction at equal pitches in the circumferential direction. A key projecting piece 821 is provided on the inner peripheral surface of the connecting cylinder 82 so as to protrude toward the cylinder center, and the connecting cylinder 82 is fitted on the third driven gear shaft 551 (FIG. 3). When the key protrusion 821 is fitted into a key groove (not shown) of the third driven gear shaft 551, the cross-shaped support body 81 is connected to the third driven gear shaft 551 so as to be integrally rotatable about the axis. ing.

  The support protrusion 83 has a mounting recess 831 formed by being recessed from the radial end surface of the connecting cylinder 82 toward the center, and the end of the square-shaped magnet 84 is formed in the mounting recess 831. Can be installed by fitting. In this embodiment, the square-shaped magnet 84 is attached to the support protrusion 83 so that the outer surface side in the radial direction becomes the south pole.

  Therefore, since the magnetic field lines are bridged between the square-shaped magnet 84 and the peripheral surface of the magnet member 43 in which the N pole faces the toner delivery mixer 80 in the toner accommodating space 64, the magnetic force derived from the screw feeder 30 is obtained. The toner containing the material is attracted by the magnetic field lines and is effectively delivered from the toner delivery mixer 80 toward the developing roller 40.

  The tube 85 is formed of a heat-shrinkable synthetic resin. As such a synthetic resin, those made of polyolefin terephthalate are suitable, but in this embodiment, polyethylene terephthalate is adopted. The tube 85 is dimensioned so that the inner diameter can be loosely fitted to the four square-shaped magnets 84 supported by the cross-shaped support body 81. Therefore, four tubes 85 are mounted in a state where the four square-shaped magnets 84 are mounted on the mounting recesses 831 of the corresponding support protrusions 83 via a predetermined adhesive and are laid between the pair of cross-shaped supports 81. Since the tube 85 is heat-shrinked and the diameter is reduced by heat-fitting the tube 85 by, for example, loosely fitting it to the square-shaped magnet 84 and then blowing hot air or loading it into a heating furnace, the four square members are contracted. The magnet 84 is surely fixed to the cross-shaped support 81.

  In the present embodiment, the tube 85 is dimensioned to have a thickness within the range of 0.04 mm to 0.9 mm in a state in which the tube 85 is externally fitted to the square-shaped magnet 84. Such a range is set when the tube 85 is tightly fitted to the four square-shaped magnets 84 and the thickness thereof is less than 0.04 mm, and the toner is repeatedly thinned due to being too thin. This is because there is an inconvenience that breakage is likely to occur due to the contact, and conversely, if it exceeds 0.9 mm, the magnetic force is difficult to act on the toner because it is too thick.

  As shown in FIG. 6, the toner delivery mixer 80 configured as described above is interposed between the screw feeder 30 and the developing roller 40 in the toner accommodating space 64 of the developing housing 60 and around the connecting cylinder 82. By rotating (rotating counterclockwise in FIG. 6), the toner sent from the screw feeder 30 is smoothly transferred to the developing roller 40.

  In this embodiment, as shown in FIG. 6, the square-shaped magnet 84 is fixed to the end surface of the cross-shaped support 81 so that the south pole is on the outer surface side. When rotating in the clockwise direction, the toner positioned between the screw feeder 30 and the toner delivery mixer 80 is similarly magnetically bridged between the N pole on the peripheral surface of the roller body 42 rotating in the counterclockwise direction. Thus, the toner is uniformly and smoothly fed toward the upper surface of the roller main body 42 and supplied to the peripheral surface of the photosensitive drum 171 from the upper side.

  The residual toner remaining on the peripheral surface of the roller main body 42 is attracted and peeled off by the square-shaped magnet 84 of the toner delivery mixer 80 rotating in the counterclockwise direction at the lower portion of the roller main body 42. Since the toner is removed from the peripheral surface of the roller 42, it is possible to reliably prevent the occurrence of inconvenience that the residual toner remaining on the peripheral surface of the roller body 42 faces the peripheral surface of the photosensitive drum 171.

  The gear mechanism 50 includes a first drive gear 51 that is concentrically fitted to the feeder shaft 311 in contact with the left end surface of the electromagnetic clutch 90, and a feeder shaft 311 that is slightly to the left of the first drive gear 51. And a second drive gear 52 that is concentrically fitted and fixed.

  The drive motor 91 has a drive shaft concentrically and integrally connected to the feeder shaft 311 and is rotated only in the counterclockwise direction (indicated by an arrow) in FIG. The feeder shaft 311 is rotated by the drive motor 91 regardless of whether the electromagnetic clutch 90 is on or off, while the first drive gear 51 is driven by the drive motor 91 in a state where the electromagnetic clutch 90 is off. Is not transmitted.

  The gear mechanism 50 includes a developing roller side gear group that transmits the driving force of the driving motor 91 to the developing roller 40 via the electromagnetic clutch 90 and the first driving gear 51, and the driving force of the driving motor 91 is transmitted to the electromagnetic clutch 90. A feeder-side gear group that transmits directly to the feeder shaft 311 without being interposed and also transmits to the outer screw feeder 32 via the second drive gear 52 integral with the feeder shaft 311 is provided.

  The developing roller side gear group includes a first driven gear 53 that meshes with the first drive gear 51 and a second driven gear that is concentrically fixed to the first driven gear 53 via the first driven gear shaft 531. A gear 54, a third driven gear 55 that meshes with the second driven gear 54 and is supported by the right side plate 611 and is rotatably supported around the third driven gear shaft 551, and the third driven gear 55 A fourth driven gear 552 that meshes with the roller gear 56 that meshes with the fourth driven gear 552 and rotates around the roller shaft 41 in a sliding state.

  Therefore, when the drive shaft of the drive motor 91 rotates in the counterclockwise direction when viewed from the drive motor 91 side in FIG. 3, this rotation is caused by the first drive gear 51, the first driven gear 53, the second driven gear 54, This is transmitted to the roller gear 56 via the third driven gear 55 and the fourth driven gear 552, whereby the developing roller main body 42 integral with the roller gear 56 slides and rotates counterclockwise around the roller shaft 41.

  The feeder-side gear group meshes with the second drive gear 52, and rotates around a shaft 571 supported by the right side plate 611, and the feeder shaft that meshes with the fifth driven gear 57. A sixth driven gear 58 concentrically fixed to 311, a seventh driven gear 59 meshing with the sixth driven gear 58, and a right end portion of the connecting cylinder 82 of the toner delivery mixer 80 are connected to be rotatable together. The scraping member right gear 86, the scraping member left gear 87 connected to the left end portion so as to be integrally rotatable, the eighth driven gear 71 meshing with the scraping member left gear 87, and the first A ninth driven gear 72 that meshes with the eight driven gear 71 and a sleeve 35 that meshes with the ninth driven gear 72 and that projects concentrically from the left disk wall 342 of the outer screw feeder 32; It has fitted been an outer feeder gear 73.

  According to the gear mechanism 50, by driving the drive motor 91 with the electromagnetic clutch 90 turned on, both the first drive gear 51 and the second drive gear 52 are counteracted as shown by arrows in FIG. Rotate clockwise. With respect to the developing roller side gear group, the rotation of the first drive gear 51 is transmitted to the roller gear 56 via the first driven gear 53, the second driven gear 54, the third driven gear 55, and the fourth driven gear 552. As a result, the roller body 42 rotates counterclockwise as indicated by an arrow in FIG.

  On the other hand, in the feeder side gear group, the rotation of the second drive gear 52 is transmitted to the scraping member right gear 86 via the fifth driven gear 57, the sixth driven gear 58, and the seventh driven gear 59. As a result, the toner delivery mixer 80 rotates counterclockwise as indicated by an arrow in FIG.

  Then, the counterclockwise rotation of the toner delivery mixer 80 is caused through the scraping member left gear 87, the eighth driven gear 71, the ninth driven gear 72, the outer feeder gear 73, the sleeve 35, and the left disk wall 342. This is transmitted to the outer screw feeder 32, whereby the outer screw feeder 32 rotates in the clockwise direction. On the other hand, since the drive of the drive motor 91 is directly transmitted to the feeder shaft 311 without a gear, the inner screw feeder 31 rotates counterclockwise.

  Therefore, the screw feeder 30 rotates the inner screw feeder 31 and the outer screw feeder 32 in opposite directions by the drive of the drive motor 91 regardless of whether the electromagnetic clutch 90 is on or off. The toner delivery mixer 80 also rotates regardless of whether the electromagnetic clutch 90 is on or off, whereas the roller body 42 rotates only when the electromagnetic clutch 90 is on and does not rotate when the electromagnetic clutch 90 is off.

  Then, the toner accommodated in the toner accommodating space 64 passes through the toner distribution window 33 provided in the feeder cylinder 321 due to the rotation of the inner and outer screw feeders 31 and 32 in the opposite directions, and the feeder cylinder 321. The toner is circulated between the inside and the outside of the feeder cylinder 321, whereby the toner distribution in the longitudinal direction on the peripheral surface of the developing roller main body 42 is uniformly maintained.

  In the present invention, since the toner delivery mixer 80 is interposed between the screw feeder 30 and the development roller 40 in the toner storage space 64 of the development housing 60, the screw is rotated by the rotation of the toner delivery mixer 80. The toner derived from the feeder 30 is reliably delivered to the developing roller 40.

  As described in detail above, the developing device 20 of the present invention includes a developing roller 40 having a predetermined length disposed opposite to the photosensitive drum 171, and the toner over the entire length in the length direction of the developing roller 40 while rotating. The screw feeder 30 that distributes the toner, and stirring while rotating the toner between the screw feeder 30 and the developing roller 40, and the toner is smoothly supplied to the peripheral surface of the developing roller 40 by the induction of magnetic force, while the magnetic force A toner delivery mixer 80 that peels off the residual toner on the circumferential surface of the developing roller 40 with the repulsive force is provided in the developing housing 60.

  The toner delivery mixer 80 includes a cruciform support 81 that can rotate about an axis parallel to the developing roller 40, and a circumferential surface of the cruciform support 81 at equal intervals in the circumferential direction (supported in the above embodiment). Since the mounting recess 831) of the projecting piece 83 includes a plurality of square-shaped magnets 84 fixed with the magnetic poles facing outward, and the tubes 85 that cover the square-shaped magnets 84 in close contact with each other, The toner does not come into direct contact with the square-shaped magnet 84, and the performance of the toner peeling off from the square-shaped magnet 84 is improved as compared with the conventional direct contact. Therefore, in the conventional developing device, the toner gathers in the vicinity of the square-shaped magnet 84 in the developing housing 60 to form a lump, which makes it difficult for the toner near the square-shaped magnet 84 to be replaced. However, since the conventional inconvenience is improved, the toner lump is not occasionally peeled off from the square-shaped magnet 84 and supplied to the developing roller 40, and the photosensitive drum 171 is always freshly developed. Since the agent is supplied, it is possible to contribute to uniforming the image quality of the transferred image onto the paper.

  Further, since the plurality of square-shaped magnets 84 attached to the peripheral surface of the cross-shaped support 81 are protected in a pressed state toward the axial direction by the tube 85, the square-shaped magnet 84 is protected from the cross-shaped support 81. It is possible to surely prevent the occurrence of problems such as peeling off.

  Further, since the tube 85 is formed of a heat-shrinkable synthetic resin material, the inner diameter of the tube 85 is such that it can be loosely fitted to the four square-shaped magnets 84 attached to the support protrusion 83. A slightly larger one is used, and heat treatment such as blowing hot air on the tube 85 with the tube 85 covered on the four square-shaped magnets 84 or loading the tube 85 together with the square-shaped magnet 84 into the heating path is performed. By applying, the tube 85 can be brought into close contact with the four square-shaped magnets 84 by thermal contraction.

  As described above, by adopting a heat-shrinkable synthetic resin material as the material of the tube 85, the workability of the mounting work on the square-shaped magnet 84 is improved, and the square-shaped magnet 84 is used as the support protrusion 83. It can be fixed securely.

  In addition, since polyethylene terephthalate is used as the synthetic resin material for the tube 85, polyethylene terephthalate is an extremely tough synthetic resin material and has an appropriate heat shrink performance, and constantly rubs against the toner. The inconvenience that the tube 85 in contact is damaged in a short period can be effectively prevented, and the service life of the toner delivery mixer 80 can be lengthened.

  Further, since the tube 85 is set to have a thickness so as to be within a range of 0.04 mm to 0.9 mm in a state in which the thickness dimension is closely fitted to the four square-shaped magnets 84, the tube 85 is It is difficult to be damaged by contact with the overlapping toner, and the toner is effectively transferred from the peripheral surface of the tube 85 to the developer roller 40 by ensuring the effective delivery of the toner to the developing roller 40 by the action of the magnetic force of the square magnet 84 on the developer. The toner release performance can be improved.

  The present invention is not limited to the above embodiment, and includes the following contents.

  (1) In the above embodiment, polyethylene terephthalate is employed as the heat-shrinkable synthetic resin, but the present invention is not limited to the heat-shrinkable synthetic resin being polyethylene terephthalate, Polypropylene terephthalate or the like may be employed, and other than these, urethane-based synthetic resins such as urethane foam may be employed.

  (2) In the above embodiment, a heat-shrinkable synthetic resin is used as the material of the tube 85, but an elastomer such as synthetic rubber or natural rubber may be used instead of the heat-shrinkable synthetic resin. Good. When the elastomer is used as the material of the tube 85, the tube 85 is set to a slightly smaller inner diameter and is covered with the four square-shaped magnets 84 while expanding the diameter. Can be adhered to.

  (3) In the above-described embodiment, four square-shaped magnets 84 are adopted, but the number is not limited to four, and may be three or may be five or more. Good. However, it is necessary to change the number of support protrusions 83 according to the number of the square-shaped magnets 84 employed.

  (4) In the above embodiment, the toner conveying and stirring means is of a double structure in which the outer screw feeder 32 is externally fitted to the inner screw feeder 31. However, in the present invention, the toner conveying means is It is not limited to having a double structure, and the first screw feeder and the second screw feeder may be provided in parallel.

  (5) In the above embodiment, both the spiral fin 312 provided in the inner screw feeder 31 and the spiral strip 322 provided in the outer screw feeder 32 are formed in a left-handed manner. The winding direction may be different (ie, one may be right-handed while the other is left-handed). In this way, even if the rotational directions of the inner screw feeder 31 and the outer screw feeder 32 are the same, the toner conveying direction can be made different between the inner screw feeder 31 and the outer screw feeder 32, and the driving force is transmitted accordingly. The structure can be simplified.

1 is a perspective view showing an embodiment of a copying machine to which a developing device according to the present invention is applied. 1 is a perspective view showing an embodiment of a developing device according to the present invention. It is a skeleton perspective view for explaining a drive structure of a developing device. FIG. 3 is a side view of the developing device shown in FIG. FIG. 3 is a side view of the developing device shown in FIG. FIG. 3 is a cross-sectional view of the developing device shown in FIG. FIG. 6 is a perspective view illustrating an embodiment of a toner delivery mixer. FIG. 5 is a partially enlarged perspective view of a toner delivery mixer.

Explanation of symbols

10 Copying machine (image forming device)
DESCRIPTION OF SYMBOLS 11 Apparatus main body 12 Cover body 13 Paper feed part 14 Feed tray 15 Paper discharge tray 16 Optical system 17 Developing part 171 Photosensitive drum 18 Fixing part 181 Fixing roller 19 Paper feed part 190 Paper discharge part 20 Developing device 30 Screw feeder ( Developer stirring means)
31 Inner screw feeder 311 Feeder shaft 312 Spiral fin 32 Outer screw feeder 321 Feeder cylinder 322 Spiral strip 323 Rib 33 Toner distribution window 34 Disc wall 341 Right disc wall 342 Left disc wall 343 Center hole 35 Sleeve 40 Developing roller 41 Roller shaft 411 Disk 42 Developing roller body 43 Magnet member 50 Gear mechanism 51 First drive gear 52 Second drive gear 53 First driven gear 531 First driven gear shaft 54 Second driven gear 55 Third driven gear 551 Third driven gear shaft 552 Fourth driven gear 56 Roller gear 57 Fifth driven gear 58 Sixth driven gear 59 Seventh driven gear 60 Developing housing 61 Side plate 611 Right side plate 612 Left side plate 62 Bottom plate 63 Rear extension 64 Toner accommodating space 71 Eighth driven gear 72 9 Driven gear 73 Side feeder gear 80 toner receiving mixer (developer transfer means)
81 Cross support (rotating body)
82 Connecting cylinder 821 Key protrusion 83 Support protrusion (arm) 831 Mounting recess 84 Square bar magnet 85 Tube 86 Right gear for scraping member 87 Left gear for scraping member 90 Electromagnetic clutch 91 Drive motor 92 Rotation direction switcher

Claims (2)

A developing roller having a predetermined length opposed to the photosensitive drum, a developer stirring means for distributing the developer to the developing roller side while stirring the developer over the entire length of the developing roller, and the developer In a developing device provided between a stirring means and the developing roller and provided in the housing with a developer delivery means for smoothly supplying the developer to the peripheral surface of the developing roller by induction by a magnetic force accompanying rotation. ,
The developer delivery means includes a rotating body having a plurality of arms that can rotate around an axis parallel to the developing roller, and a plurality of magnetic poles fixed to the tips of the arms with one of the magnetic poles facing outward. A developing device comprising: a magnet; and a sheet body made of a nonmagnetic material that covers each magnet in close contact.   2. The developing device according to claim 1, wherein the sheet body covers the rotating body with a tube made of a synthetic resin material having heat shrinkability.