JP2007093872A - Development device and image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a development device capable of reducing the leakage of a development toner from a peripheral surface end of a development roller and an image forming apparatus having the development device. <P>SOLUTION: The development device 214 supplies the development toner DT to an electrostatic latent image formed on the surface of a photoreceptor drum 211. The development device 214 has a development container 221 which houses the development toner DT, a developing roller 224 which is rotatably supported in the development container 221 and is rotated to supply the development toner DT housed in the development container 221 to the photoreceptor drum 211, a sealing member 225 which is disposed in the development container 221 and seals the peripheral surface end in the longitudinal direction of the developing roller 224 by coming into contact with the peripheral end in the longitudinal direction of the developing roller 224, and a toner 226 for sealing which is applied on the surface of the sealing member 225 on the side in contact with the developing roller 224 and is higher in the glass transition temperature than the development toner DT. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an image forming apparatus such as an electrophotographic printer or a copying machine, and more particularly to a developing device that supplies developing toner to the surface of a photosensitive drum.

  As a conventional developing device, a developing container for containing developing toner, a developing roller rotatably supported by the developing container, and a peripheral surface in the longitudinal direction of the developing roller in contact with an end portion in the longitudinal direction of the developing roller Some have a sealing member that seals the end. A Teflon felt in which a felt is impregnated with Teflon is used for a portion of the seal member that contacts the developing roller (see, for example, Patent Document 1).

JP 2000-206787 A (paragraph number 0040, FIG. 3)

  However, in the conventional developing device, when the developing roller is rotated, the developing toner in the developing container enters between the developing roller and the seal member, and the entered developing toner is between the developing roller and the seal member. There is a case in which a glass transition occurs due to heat generated by rubbing, and the developed toner that has undergone the glass transition solidifies after the development roller stops and becomes a large lump. This large lump of solidified toner creates a gap between the developing roller and the seal member, causing a problem of increasing leakage of the developing toner in the developing device from the end of the developing roller.

  Accordingly, the present invention has been made to solve the above-described problems of the prior art, and an object of the present invention is to provide a developing device capable of reducing leakage of developing toner from the peripheral end portion of the developing roller, and the development thereof. An image forming apparatus having the apparatus is provided.

  The developing device of the present invention is a developing device for supplying developing toner to an electrostatic latent image formed on the surface of an image bearing member, and is rotatably supported by the developing container containing the developing toner and the developing container. A developing roller for supplying the developing toner contained in the developing container to the image carrier by rotating; and a developing roller provided in the developing container, in contact with a circumferential surface end portion of the developing roller in the longitudinal direction. A seal member that seals a peripheral end portion in the longitudinal direction of the developing roller; and a sealing toner that is applied to a surface of the seal member that contacts the developing roller and has a glass transition temperature higher than that of the developing toner. Is.

  The image forming apparatus of the present invention includes an image carrier on which an electrostatic latent image is formed, a developing device that supplies developing toner to the surface of the image carrier, and a developed toner image formed on the surface of the image carrier. And a fixing device for fixing the developed toner image transferred to the recording medium, and the developing device is rotatable to the developing container and a developing container for containing the developing toner. And a developing roller for supplying the developing toner contained in the developing container to the image carrier by rotating, and a developer roller provided in the developing container and in contact with a peripheral end portion in the longitudinal direction of the developing roller And a seal member that seals the end of the circumferential surface of the developing roller in the longitudinal direction, and a sealing toner that is applied to the surface of the seal member that contacts the developing roller and has a glass transition temperature higher than that of the developing toner. And it has a.

  In the present invention, a sealing toner having a glass transition temperature higher than that of the developing toner is previously applied to the sealing member, and the gap between the sealing member and the developing roller is reduced by the applied sealing toner. Further, it is possible to reduce the amount of the developing toner that enters the gap between the seal member and the developing roller from the inside of the developing container. Further, since the glass transition temperature of the sealing toner applied to the seal member is higher than the glass transition temperature of the development toner accommodated in the developing container, the sealing toner is sealed by the frictional heat between the seal member and the developing roller. The toner between the member and the developing roller undergoes a glass transition, and the resulting solidification of the toner is unlikely to occur. Therefore, according to the present invention, leakage of the developing toner in the developing device from the end portion of the developing roller can be reduced.

<< First Embodiment >>
FIG. 1 is a cross-sectional view schematically showing a configuration of an image forming apparatus to which the developing device according to the first embodiment of the present invention is applied.

  An image forming apparatus illustrated in FIG. 1 includes a transport unit 101 that transports a recording sheet 1 as a recording medium, and black (K), yellow (Y), magenta (M), and cyan (C) arranged to face the transport unit 101. C) image forming units 201 to 204, and transfer rollers 301 to 304 that transfer the developed toner image formed on the photosensitive drum 211 by the image forming units 201 to 204 onto the recording paper 1 conveyed by the conveying unit 101. A fixing device 401 that fixes the developed toner image transferred onto the recording paper 1 onto the recording paper 1.

  The transport unit 101 includes a transport belt 102 and drive rollers 103 and 104 that support the transport belt 102 and advance the transport belt 102 in the D1 direction. One or both of the driving rollers 103 and 104 are rotated by receiving a driving force from a driving motor (not shown) to advance the conveying belt 102 in the D1 direction. Further, the transport unit 101 includes a cleaning unit 110 that removes unnecessary toner attached to the surface of the transport belt 102. The cleaning unit 110 includes a cleaning blade 111 that contacts the surface of the transport roller 102 and a waste toner box 112 that stores unnecessary toner 113 scraped off by the cleaning blade 111.

  Each of the image forming units 201 to 204 includes a photosensitive drum 211 as an image carrier on which an electrostatic latent image is formed, a charger 212 that uniformly charges the surface of the photosensitive drum 211, and a uniformly charged photosensitive drum. An exposure device 213 that forms an electrostatic latent image by performing exposure according to image information on the surface of 211, a developing device 214 that supplies developing toner to the surface of the photosensitive drum 211 on which the electrostatic latent image is formed, and a photosensitive And a cleaning device 215 for removing toner remaining on the photosensitive drum 211 after transfer of the toner image formed on the drum 211. The exposure device 213 is a device that irradiates light based on input image information, and includes an exposure light source using an LED array or a semiconductor laser. Although not shown in FIG. 1, the image forming units 201 to 204 include a driving device for the photosensitive drum 211 and a supply unit for the recording paper 1.

  Each developing device 214 of the image forming units 201 to 204 contains black (K), yellow (Y), magenta (M), and cyan (C) developing toners DT.

  The fixing device 401 has a pair of fixing rollers 402 and 403. The fixing rollers 402 and 403 are heated by a heater provided in the fixing roller by passing the recording paper 1 on which the developing toner image is transferred between the fixing rollers 402 and 403, and simultaneously pressurizing the developing toner image. Fix on the recording paper 1.

  Although FIG. 1 shows an example in which the image forming units 201 to 204 are arranged in a tandem manner and a direct printing method in which images are sequentially transferred onto the recording paper 1 is employed, the developing device of the present invention can be applied. The image forming apparatus is not limited to the configuration shown in FIG. The developing device of the present invention can also be applied to an image forming apparatus of a type in which the conveyance belt 102 is an intermediate transfer belt and an image once formed on the intermediate transfer belt is transferred to a recording sheet. The developing device of the present invention can also be applied to a single color image forming apparatus, a color image forming apparatus using three or less colors or five or more colors of toner. Further, the developing device of the present invention can be applied to an MFP (multifunction printer), a facsimile machine, a copying machine, and the like in addition to a printer.

  FIG. 2 is a side view schematically showing the configuration of the developing device 214 of FIG. 1, and FIG. 3 is an enlarged view of a main part of the developing device 214. FIG. 4 is a perspective view schematically showing a state in which the developing roller 224 is removed from the developing device 214.

  As shown in FIGS. 2 to 4, the developing device 214 contains the developing toner DT and has an opening 222 (shown in FIG. 4) for supplying the containing developing toner DT to the photosensitive drum 211. A developing container (developer cartridge) 221 and a bearing 223 of the developing container 221 are rotatably supported. The developing toner DT accommodated in the developing container 221 is opened by being opposed to the photosensitive drum 211 and rotated. And a developing roller 224 that supplies the photosensitive drum 211 through 222. The developing toner DT is prepared by adding an external additive such as a colorant, a charge control agent, a release agent, and hydrophobic silica to a polyester resin having a glass transition temperature Tg (DT) of about 40 ° C., for example. 8 μm.

  Further, the developing device 214 is provided in the developing container 221 and contacts the circumferential surface end portion of the developing roller 224 in the longitudinal direction (D2 direction in FIG. 4) to seal the circumferential surface end portion of the developing roller 224 in the longitudinal direction. It has a seal member 225 for preventing leakage of development toner, and a seal toner 226 that is applied to the surface of the seal member 225 that contacts the development roller 224 and has a glass transition temperature higher than that of the development toner DT. The seal member 225 includes, for example, a sponge material 225a and a felt material 225b provided outside the sponge material 225a (that is, on the developing roller side). The sponge material 225 a functions as an elastic body that presses the felt material 225 b against the developing roller 224. The sealing toner 226 is applied to the surface of the felt material 225b, for example, by brushing at the manufacturing stage. The applied sealing toner 226 is held on the surface of the felt material 225b and the inside of the felt material (that is, the gap between the fibers constituting the felt material).

  The sealing toner 226 has a glass transition temperature Tg (226) of about 110 ° C., for example, by changing the molecular weight of the polyester resin of the developing toner DT. In addition, as the sealing toner 226, the same colorant as that of the developing toner DT and an average particle diameter of 8 μm composed of the same charge control agent, releasing agent and external additive as in the developing toner DT can be used. . As the developing toner DT and the sealing toner 226, toner manufactured by a pulverization method may be used, or polymerized toner manufactured by a polymerization method may be used. Further, the average particle diameters of the developing toner DT and the sealing toner 226 are not limited to 8 μm, and may be other values.

  Further, the developing device 214 includes a developing toner DT supply roller 227 inside the developing container 221 and a layer forming blade 228 for regulating the thickness of the toner layer formed on the surface of the developing roller 224.

  FIG. 5 is a diagram showing the relationship between time and the surface temperature of the seal member 225 during the continuous printing operation. As shown in FIG. 5, the temperature of the felt material 225b of the seal member 225 in the developing device 214 reaches about 50 ° C. in about one hour from the start of the continuous printing operation.

  Therefore, in the conventional developing device, during continuous printing, the temperature of the contact portion increases due to the friction between the developing roller 224 and the felt material 225b of the sealing member 225, and enters between the sealing member 225 and the developing roller 224. The development toner (for example, glass transition temperature Tg (DT) is about 40 ° C.) undergoes glass transition, and then solidifies (for example, after the printing operation is stopped) to solidify and adhere to the seal member 225 as a large lump. Had occurred. The large lump of toner fixed on the seal member 225 creates a gap between the developing roller 224 and the seal member 225, reducing the sealing effect of the seal member 225, and developing toner DT in the developing container 221 is developed. Leakage from the end of the roller 224 may occur. Further, the leaked developing toner DT may adhere to the recording paper 1 and deteriorate the quality of the printed image.

  On the other hand, in the developing device 214 of the first embodiment, since the sealing toner 226 having a glass transition temperature higher than that of the developing toner DT is applied in advance to the surface of the felt material 225b of the sealing member 225, it is applied. The sealing toner 226 reduces the gap between the felt material 225b of the sealing member 225 and the developing roller 224 and the gap between the fibers constituting the felt material 225b. Therefore, it is possible to reduce the amount of the developing toner DT that enters the gap between the seal member 225 and the developing roller 224 and the gap between the fibers constituting the felt material 225b from the inside of the developing container 221.

  In the developing device 214 of the first embodiment, the glass transition temperature Tg (226) of the sealing toner 226 applied to the felt material of the sealing member 225 is equal to that of the developing toner DT contained in the developing container 221. Since it is higher than the glass transition temperature Tg (DT) (more strictly speaking, higher than the maximum temperature of the seal member 225 reached during continuous printing), the heat of rubbing between the seal member 225 and the developing roller 224 causes The toner between the seal member 225 and the developing roller 224 undergoes glass transition, and the resulting solidification of the toner is unlikely to occur.

  For the reason described above, in the developing device 214 of the first embodiment, leakage of the developing toner DT in the developing container 221 from the end of the developing roller can be reduced.

  In the above description, the glass transition temperature Tg (226) of the sealing toner 226 is about 110 ° C., but the glass transition temperature Tg (226) of the sealing toner 226 is the seal during continuous printing. Any material can be used as long as it is higher than about 50 ° C., which is the maximum temperature of the member 225 (preferably 60 ° C. or higher, which is about 10 ° C. higher).

<< Second Embodiment >>
The developing device according to the second embodiment of the present invention uses a seal toner 226 having an average particle size smaller than the average particle size of the developing toner DT accommodated in the developing container 214. This is different from the developing device of the first embodiment. Therefore, in the second embodiment, reference is also made to FIGS.

  In the developing device 214 of the second embodiment, for example, when the developing toner DT having an average particle diameter of 8 μm is used, a developer having an average particle diameter of, for example, 4 μm is used as the sealing toner 226 by classification. . The sealing toner 226 includes the same colorant, charge control agent, release agent, and external additive as those of the developing toner DT.

  In the developing device 214 of the second embodiment, since the sealing toner 226 having a glass transition temperature higher than that of the developing toner DT is previously applied to the surface of the felt material 225b of the sealing member 225, the applied sealing toner The gap between the felt material 225b of the seal member 225 and the developing roller 224 and the gap between the fibers constituting the felt material 225b are reduced by 226. Further, as the toner for sealing 226, the average particle diameter of which is smaller than the average particle diameter of the developing toner DT is used. Therefore, the toner for sealing 226 is composed of the felt material 225b of the sealing member 225 and the developing roller 224. A very narrow gap between them and a very narrow gap between fibers constituting the felt material 225b are held and held. Therefore, in the developing device of the second embodiment, the developing toner DT in the developing container 221 is a gap between the felt material 225b of the seal member 225 and the developing roller 224, and the fibers constituting the felt material 225b. The structure is more difficult to enter due to the gap.

  For this reason, in the developing device 214 of the second embodiment, the leakage of the developing toner DT in the developing container 221 from the end of the developing roller can be further reduced.

  In the above description, the average particle size of the sealing toner 226 is 4 μm. However, the average particle size of the toner required for sealing may be other values as long as it is smaller than the average particle size of the developing toner. .

  In the second embodiment, points other than those described above are the same as in the case of the first embodiment.

<< Third Embodiment >>
The developing device 214 according to the third embodiment of the present invention is different from the first embodiment in that the color of the sealing toner 226 is the same as the color of the developing toner DT in each of the image forming units 201 to 204. Different from the developing device 214. Further, in the developing device 214 of the third embodiment, in each of the image forming units 201 to 204, the glass transition temperature Tg (226) of the sealing toner 226 is changed to the glass transition temperature of the developing toner DT in the developing container 221 (for example, , 50 ° C.) and lower than the heating temperature (for example, 100 ° C.) in the fixing device 401, for example, 60 ° C. is different from the developing device of the first embodiment. Therefore, in the third embodiment, reference is also made to FIGS.

  In the developing device 214 of the third embodiment, for example, in the developing device of the image forming unit 201 in which the color of the developing toner is black (K), the sealing toner colored black is used, and the color of the developing toner is yellow. In the developing device of the image forming unit 202 that is (Y), a yellow-colored sealing toner is used, and in the developing device of the image forming unit 203 in which the color of the developing toner is magenta (M), magenta is colored. In the developing device of the image forming unit 204 that uses a sealing toner and the color of the developing toner is cyan (C), the sealing toner colored cyan is used.

  The sealing toner 226 is applied to the sealing member 225, is held in the gap between the felt members 225b of the sealing member 225, and is not firmly held. Accordingly, some of the sealing toner 226 applied to the sealing member 225 moves away from the sealing member 225 into the developing container 221.

  According to the developing device 214 of the third embodiment, since the pigment (colorant) having the same color as the developing toner DT is used for the sealing toner 226, a part of the sealing toner 226 is being printed. Even when the toner is transferred into the developing container 221, moved to the surface of the photosensitive drum 211 by the developing roller 224, and transferred to the recording paper 1, the toners of different colors are not mixed in the developing toner DT, and the recording is performed. The color of the image formed on the paper 1 is not adversely affected.

  Further, according to the developing device of the third embodiment, the glass transition temperature Tg (226) of the sealing toner 226 is lower than the heating temperature (for example, 100 ° C.) by the heater (not shown) of the fixing device 401. Since the temperature is set, similarly to the developing toner DT transferred to the recording paper 1, the sealing toner 226 transferred to the recording paper 1 is also fixed to the recording paper 1, so that the image quality is not deteriorated. Note that the glass transition temperature of the sealing toner 226 in the third embodiment is not limited to 60 ° C., and is about 10 ° C. higher than the maximum temperature reached by the sealing member 225 rubbed against the developing roller 224 by continuous printing. Any other temperature may be used as long as it is in the range of not less than the temperature and not more than about 10 ° C. lower than the heating temperature given by the fixing device 401.

  In the third embodiment, points other than those described above are the same as those in the first or second embodiment.

<< Fourth Embodiment >>
The developing device according to the fourth embodiment of the present invention is that, in each of the image forming units 201 to 204, the charging property of the sealing toner 226 is lower than the charging property of the developing toner DT. This is different from the developing device of the embodiment. Therefore, in the fourth embodiment, reference is also made to FIGS.

  In the developing device 214 of the fourth embodiment, for example, a developer not added with an external additive such as hydrophobic silica is used as the sealing toner 226, and the charge amount is 30 μC / mg for the development toner DT. A sealing toner 226 having a low charge amount of 5 μC / mg can be used. As the sealing toner 226, for example, a resin having a glass transition temperature higher than that of the developing toner DT by adjusting the molecular weight of the polyester resin is used, and the same colorant, charge control agent, and release agent as the developing toner 70 are used. What was comprised by can be used.

  According to the developing device 214 of the fourth embodiment, since the toner having a lower charging property than the developing toner DT is used as the sealing toner 226, a part of the sealing toner 226 is mixed in the developing container 221. Even if it exists, the electrostatic attraction force acting on the mixed toner 226 can be reduced. Therefore, the sealing toner 226 is hardly attracted to the developing roller 224, and the amount of the sealing toner 226 carried to the photosensitive drum 211 by the developing roller 224 can be reduced. For this reason, the adverse effect of the sealing toner 226 on the image quality of the recording paper 1 can be reduced.

  In the fourth embodiment, points other than those described above are the same as those in the first, second, or third embodiment.

1 is a cross-sectional view schematically showing a configuration of an image forming apparatus to which a developing device according to first to fourth embodiments of the present invention can be applied. It is a side view which shows roughly the structure of the developing device which concerns on 1st thru | or 4th embodiment. It is a principal part enlarged view of the developing device which concerns on 1st thru | or 4th embodiment. It is a perspective view which shows roughly the state which removed the developing roller from the developing device which concerns on 1st thru | or 4th embodiment. It is a figure which shows the relationship between time and the surface temperature of a sealing member in continuous printing operation | movement.

Explanation of symbols

1 Recording paper (recording medium)
DESCRIPTION OF SYMBOLS 101 Conveying part 102 Conveying belt 103,104 Driving roller 110 Cleaning part 111 Blade 112 Waste toner container 113 Toner 201-204 Image forming part 211 Photosensitive drum (image carrier)
212 Charging Device 213 Exposure Device 214 Developing Device 215 Cleaning Unit 221 Developer Container (Developer Cartridge)
222 Opening part 223 Bearing part 224 Developing roller (developer carrier)
225 Seal member 225a Sponge material 225b Felt material 226 Seal toner 227 Supply roller 228 Layer forming blade 301-304 Transfer roller 401 Fixing device 402, 403 Fixing roller

Claims (7)

A developing device for supplying developing toner to an electrostatic latent image formed on the surface of an image carrier,
A developer container containing developer toner;
A developing roller that is rotatably supported by the developing container and supplies the developing toner contained in the developing container to the image carrier by rotating;
A seal member that is provided in the developing container and seals a peripheral end portion in the longitudinal direction of the developing roller in contact with a peripheral end portion in the longitudinal direction of the developing roller;
A developing device, comprising: a sealing toner which is applied to a surface of the sealing member that contacts the developing roller and has a glass transition temperature higher than that of the developing toner. A portion of the seal member that contacts the developing roller is made of a felt material,
The developing device according to claim 1, wherein the sealing toner is held on a surface and inside of the felt material.   The developing device according to claim 1, wherein an average particle diameter of the sealing toner is smaller than an average particle diameter of the developing toner.   4. The developing device according to claim 1, wherein the color of the sealing toner is the same as the color of the developing toner.   5. The developing device according to claim 1, wherein a glass transition temperature of the sealing toner is lower than a heating temperature given by a fixing device when the developing toner is fixed on a recording medium.   6. The developing device according to claim 1, wherein the charging property of the sealing toner is lower than the charging property of the developing toner. An image carrier on which an electrostatic latent image is formed;
A developing device for supplying developing toner to the surface of the image carrier;
A transfer device for transferring the developed toner image formed on the surface of the image carrier to a recording medium;
A fixing device for fixing the developed toner image transferred to the recording medium,
The image forming apparatus, wherein the developing device is the developing device according to claim 1.

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