JP2015079030A - Developing unit and image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent clogging of powder supplied to a developing unit.SOLUTION: A developing unit includes a storage tank that stores a developer including a powder to be attached to and develop a latent image and has the powder supplied onto the developer through a supply port, a stirring and conveying member that is arranged inside the storage tank and receives a driving power to be driven to stir the developer inside the storage tank and convey the developer inside the storage tank, and a rotating member that is arranged at a position where the powder supplied from the supply port passes and is driven to rotate independent of the stirring and conveying member.

Description

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

  Conventionally, a developing device for developing a latent image with powder toner and an image forming apparatus including such a developing device are known.

  For example, Patent Document 1 discloses a powder conveying apparatus including a powder breaking member that breaks powder adhering to a powder inlet in order to reliably prevent clogging of the powder path in the powder conveying path. ing. This powder breaking member has a free end portion whose contact position with the free end contact portion moves along the axial direction of the rotating shaft as the powder conveying rotating member rotates.

JP 2006-171105 A

  An object of the present invention is to prevent clogging of a powder charged into a developing device.

The developing device according to claim 1 is:
A developer containing powder to be developed by being attached to the latent image, and a storage tank in which the powder is put on the developer from a supply port;
An agitation transport member that is deployed in the storage tank and that is driven by driving force to stir the developer in the storage tank and transport the developer in the storage tank;
A rotating member that is deployed at a location where the powder charged from the supply port passes, and is driven to rotate independently of the stirring and conveying member;
It is provided with.

The developing device according to claim 2 is:
When the rotation member is controlled to rotate according to the image density of at least one of the latent image and the developed image obtained by developing the latent image, and the image density is relatively low or low. It is characterized by rotating more.

The developing device according to claim 3 is:
The rotation of the rotating member is controlled according to the environmental temperature of the developing device, and the rotating member rotates more when the temperature is relatively high and when the temperature is relatively low.

The developing device according to claim 4 is:
The rotation of the rotating member is controlled according to the environmental humidity of the developing device, and the rotating member rotates more when the humidity is relatively high and when the humidity is relatively low.

The developing device according to claim 5 is:
The rotating member is controlled to rotate according to the concentration of the powder in the developing unit, and the rotating member rotates more when the concentration is relatively low and when the concentration is relatively low. To do.

The developing device according to claim 6 is:
The powder has a volume average particle diameter of 4.5 μm or less.

An image forming apparatus according to claim 7 is provided.
An image carrier that forms an image on the surface and holds the image;
A latent image forming device for forming a latent image on the surface of the image carrier;
A developing unit that develops the powder by attaching the powder to the latent image on the image carrier,
The developer is
A developer containing the powder, and a storage tank in which the powder is charged onto the developer from a supply port;
An agitation transport member that is deployed in the storage tank and that is driven by driving force to stir the developer in the storage tank and transport the developer in the storage tank;
A rotating member that is deployed at a location where the powder charged from the supply port passes, and is driven to rotate independently of the stirring and conveying member;
It is characterized by having.

An image forming apparatus according to an eighth aspect is the image forming apparatus according to the seventh aspect,
An image density detector for detecting the density of an image formed on the image carrier;
A rotation control unit that controls the rotation of the rotating member according to the image density detected by the image density detector, and rotates the rotation member more when the image density is relatively low and low.
It is provided with.

An image forming apparatus according to a ninth aspect is the image forming apparatus according to the seventh or eighth aspect,
A temperature detector for detecting the temperature in the image forming apparatus;
A rotation control unit that controls the rotation of the rotating member according to the temperature detected by the temperature detector, and rotates the rotation member more when the temperature is relatively high and low.
It is provided with.

An image forming apparatus according to a tenth aspect is the image forming apparatus according to any one of the seventh to ninth aspects,
A humidity detector for detecting humidity in the image forming apparatus;
A rotation control unit that controls the rotation of the rotating member according to the humidity detected by the humidity detector, and rotates the rotation member more when the humidity is relatively high and low.
It is provided with.

An image forming apparatus according to an eleventh aspect is the image forming apparatus according to any one of the seventh to tenth aspects,
A concentration detector for detecting the concentration of the powder in the developing unit;
A rotation control unit that controls the rotation of the rotating member according to the concentration detected by the concentration detector, and rotates the rotation member more when the concentration is relatively low and when the concentration is relatively low.
It is provided with.

  According to the developing device according to claim 1 and the image forming apparatus according to claim 7, clogging of the powder charged into the developing device can be prevented.

  According to the developing device according to claim 2 and the image forming apparatus according to claim 8, the certainty of preventing clogging of the powder is high as compared with the case where this configuration is not provided.

  According to the developing device according to the third aspect and the image forming apparatus according to the ninth aspect, the certainty of preventing the clogging of the powder is high as compared with the case where this configuration is not provided.

  According to the developing device according to the fourth aspect and the image forming apparatus according to the tenth aspect, the certainty of preventing clogging of the powder is high as compared with the case where this configuration is not provided.

  According to the developing device according to the fifth aspect and the image forming apparatus according to the eleventh aspect, the certainty of preventing clogging of the powder is higher than in the case where the present configuration is not provided.

  According to the developing device of the sixth aspect, prevention of clogging of the powder is more effective than when the volume average particle diameter is larger than 4.5 μm.

1 is an overall configuration diagram of an image forming apparatus according to an embodiment of the present invention. FIG. 2 is a perspective view showing the inside of the developing device schematically shown in FIG. 1 from above. It is the perspective view which showed the inside of the developing device from the side. FIG. 6 is a diagram illustrating a measurement result of an angle of repose [degree] with respect to a volume average particle diameter [μm] of toner.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  FIG. 1 is an overall configuration diagram of an image forming apparatus 100 according to an embodiment of the present invention.

  An image forming apparatus 100 shown in FIG. 1 is a monochrome printer. The image forming apparatus 100 includes a cylindrical photosensitive member 21 that rotates in the direction of arrow A. Around the photosensitive member 21, a charger 22, an exposure unit 23, a developing unit 24, and a transfer unit 25 are provided. And a cleaner 26 are provided. The photoreceptor 21 corresponds to an example of an image holding member according to the present invention.

  The charger 22 charges the surface of the photoconductor 21 to a predetermined potential. The exposure device 23 irradiates the surface of the photoconductor 21 with exposure light modulated based on an image signal, and forms an electrostatic latent image having a charged potential distribution on the surface of the photoconductor 21. A combination of the charger 22 and the exposure device 23 corresponds to an example of a latent image forming device according to the present invention.

  The developer 24 contains a developer containing toner and a carrier. The developer 24 develops the electrostatic latent image on the photoconductor 21 with the toner in the developer, and the toner on the surface of the photoconductor. Form an image. This developing device corresponds to an embodiment of the developing device of the present invention.

  The transfer unit 25 transfers the toner image on the photoreceptor 21 onto the conveyed paper.

  The image forming device 100 is provided with a paper tray 60 that accommodates paper in a stacked state, and one of the papers stacked on the top of the paper in the paper tray 60 is picked up. It is taken out by the roller 40. The taken paper is transported by the transport roller 41, and when the leading edge of the paper reaches the standby roller 42, the paper transport is temporarily stopped, and the paper is in a standby state in that state. The paper in the standby state is sent out from the standby roller with the timing adjusted so that the toner image on the photoconductor 21 reaches the position of the transfer device 25 when the toner image on the photoconductor 21 reaches the transfer device 25. The image is transferred onto the sheet by the action of the transfer unit 25. A fixing device 50 is provided further downstream of the paper transport path. The fixing device 50 is a device that heats and presses the toner image on the conveyed paper and fixes the toner image on the paper. A sheet on which an image composed of a fixed toner image is formed through the fixing device 50 is sent out onto the sheet discharge tray 70 by the sheet discharge roller 43. In FIG. 1, a paper path 44 from the paper tray 60 to the paper discharge tray 70 is indicated by dotted arrows.

  Further, residual toner remaining on the photoconductor 21 after the transfer of the toner image is removed from the photoconductor 21 by the cleaner 26.

  Here, the developing device 24 is provided with two transport members 242 and 243 extending in parallel with each other in a direction perpendicular to the paper surface of FIG. These two conveying members 242 and 243 are members that rotate and agitate while circulating and moving the developer in the case 244.

  The developing roll 241 has a role of rotating in the direction of arrow B and transporting the developer in the case 244 to a region facing the photoconductor 21. The electrostatic latent image on the photoconductor 21 is developed with toner in the developer conveyed by the developing roll 241. Therefore, when this development is repeated, the toner in the developer in the case 244 becomes insufficient. For this reason, the image forming apparatus 100 includes a detachable toner cartridge 30 that contains toner. The toner contained in the toner cartridge 30 is supplied to the developing device 24 via the toner supply path 30a as the toner in the developing device 24 decreases. Here, the toner supply path 30 a includes a first supply path 31 that conveys the toner supplied from the toner cartridge 30, and the toner conveyed through the first supply path 31 in the case 244 of the developing device 24. And a second supply path 32 to be dropped. In the first supply path 31, a conveying member 33 is provided that extends and rotates in the direction in which the first supply path 31 extends to convey toner. As the conveying member 33 rotates by the number of rotations corresponding to the decrease in the toner in the developing device 24, the toner is replenished to the developing device 24 by the amount of toner in the developing device 24 decreased. The second supply path 32 is not provided with a conveying member, and the second supply path 32 is supplied to the developing device 24 from the toner receiving port 247 formed on the upper surface of the case 244 due to the natural fall of the toner. It has a structure.

  Further, the toner remaining on the photosensitive member 21 is accommodated in the case 261 in the cleaner 26. The toner in the case 261 is transported to the corner in that direction by a transport member 262 provided in the case 261 and extending in a direction perpendicular to the paper surface of FIG. 28.

  FIG. 2 is a perspective view showing the inside of the developing device 24 schematically shown in FIG. 1 as viewed from above.

  As described with reference to FIG. 1, the developing device 24 includes two conveying members 242 and 243 that extend in parallel to each other and a developing roll 241 that rotates in the direction of arrow B shown in FIG. 1.

  In the case 244, a partition wall 245 is provided between the two transport members 242 and 243, and the case 244 is partitioned into two rooms 242a and 243a. However, openings 246a and 246b are formed at both ends in the longitudinal direction of the partition wall 245, respectively.

  The two conveying members 242 and 243 are both round rod-shaped rotary shafts 242b and 243b and spirals provided around the rotary shaft while drawing a spiral in the extending direction of the rotary shafts 242b and 243b. And blades 242c and 243c. These transport members 242 and 243 rotate so that the first transport member 243 transports the toner in the case 244 in the arrow X direction, and the second transport member 242 transports the toner in the arrow Y direction. . A toner receiving port 247 that receives toner supplied from the toner cartridge 30 through the supply path 31 is provided on the upper surface portion of the case 244 corresponding to the end of the second conveying member 242 (see FIG. 1). New toner supplied from the toner receiving port 247 is sent to the first transport member 243 by the rotation of the second transport member 242.

  The new toner sent to the first conveying member 243 is conveyed in the direction of the arrow X in the room 243a in which the first conveying member 243 is disposed, and the developer in the chamber 243a is agitated in the middle of the conveyance. Mixed. The developer in which the new toner is agitated and mixed passes through the opening 246b and moves to the room 242a in which the second conveying member 242 is disposed. This time, the inside of the room 242a is moved in the direction of arrow Y by the conveying member 242. It is conveyed and moves to the room 243a through the other opening 246a.

  The developer in the developing unit 24 is circulated and moved as described above, and new toner is stirred and mixed together.

  The developing roll 241 receives the developer from the room 242a in which the second conveying member 242 is disposed, and carries the developer to the area facing the photoconductor 21 shown in FIG. The developer is returned to the case 244 again. The developer having the increased carrier ratio is conveyed and stirred as described above, mixed with new toner, and circulated as a developer having the original ratio of toner and carrier.

  The case 244 of the developing device 24 corresponds to an example of a storage tank according to the present invention, the toner receiving port 247 corresponds to an example of a supply port according to the present invention, and each of the two transport members 242 and 243 corresponds to the present invention. It corresponds to an example of the stirring and conveying member.

  FIG. 3 is a perspective view showing the inside of the developing device 24 as viewed from the side.

  FIG. 3 shows a state when the end portions of the conveying members 242 and 243 near the toner receiving port 247 of FIG. 2 are viewed from the lower side of FIG.

  As described above, new toner falls from the toner receiving port 247 above the end of the second conveying member 242. The new toner that falls is sent out toward the first conveying member 243 by the second conveying member 242 that rotates in the direction of arrow D.

  When the toner feeding from the rotating second conveying member 242 to the first conveying member 243 is repeated, a toner wall may be formed between the two conveying members 242 and 243. .

  When such a toner wall grows greatly, the toner that has fallen and sent out from the toner receiving port 247 is blocked by the toner wall and does not reach the first transport member 243, and the second transport member 242. It is considered that toner accumulates in the vicinity of the end of the toner and causes toner clogging. In particular, in the field of image forming apparatuses in recent years, the diameter of toner has been reduced in order to improve the resolution of the image. However, in such a small diameter toner, the friction between toner particles per unit volume is large, so that the fluidity of the toner is low. It is low and the above-mentioned toner wall is easily formed.

  In view of this, the developing device 24 of the present embodiment has a rotating blade 248 disposed in the case 244, and the rotating blade 248 is disposed at a location through which the toner charged from the toner receiving port 247 passes. When the rotary blade 248 is driven by a motor 80 outside the developing unit 24, the above-described toner wall is surely broken even if it is made, and toner clogging is prevented. The rotating blade 248 corresponds to an example of the rotating member referred to in the present invention, and a member having a rod-like protrusion may be adopted as the rotating member in addition to the blade-shaped member.

  Since the rotation of the rotary blade 248 is considered to wind up toner in the developing device 24, the rotary blade 248 is preferably rotated only when necessary. Therefore, in the present embodiment, a rotation control unit 81 that controls the rotation of the rotary blade 248 by controlling the motor 80 is provided, and the rotation control unit 81 includes the rotation control unit 81 in the image forming apparatus 100 shown in FIG. An environment sensor 82 that detects temperature and humidity, an image density calculation unit 83 that calculates an image density based on an image signal given to the exposure device 23 shown in FIG. 1, and a developer contained in a case 244 of the developing device 24 A density sensor 249 for detecting the toner density inside is connected. Then, a temperature and humidity detection signal is sent from the environmental sensor 82 to the rotation control unit 81, a calculated value of the image density is sent from the image density calculation unit 83 to the rotation control unit 81, and the rotation sensor 81 is sent from the density sensor 249. A toner density detection signal is sent. Based on the temperature and humidity detection signals sent from the environment sensor 82, the rotation control unit 81 drives the motor 80 more frequently in a high temperature environment exceeding a predetermined temperature than in a low temperature environment below that temperature. Then, the rotary blade 248 is rotated. Further, the rotation control unit 81 is based on the calculated value of the image density sent from the image density calculation unit 83, and when the density is lower than the predetermined image density, the rotation control unit 81 is higher than when the density exceeds the image density. The motor 80 is frequently driven to rotate the rotary blade 248. Further, based on the toner density detection signal sent from the density sensor 249, the rotation control unit 81 is more frequent when the density is lower than a predetermined toner density than when the density is higher than the toner density. The motor 80 is driven to rotate the rotary blade 248. By controlling the rotation like this, the rotating blades 248 rotate more under the above-described conditions where the toner wall is likely to be generated, and the toner clogging is efficiently prevented.

  The rotation control unit 81 corresponds to an example of the rotation control unit according to the present invention, the environment sensor 82 corresponds to an example of both the temperature detector and the humidity detector according to the present invention, and the image density calculation unit 83 The density sensor 249 corresponds to an example of the density detector according to the present invention, and the density sensor 249 corresponds to an example of the density detector according to the present invention.

  Here, the toner particle size that is effective in preventing toner clogging will be examined.

  Assuming that a toner is dropped on a flat plate to form a mountain, and defining the angle of inclination θ [degree] as an angle of repose, in general, in a toner having high fluidity, the angle of repose θ is small and the fluidity is reduced. With a low toner, the angle of repose θ increases. Therefore, the degree of fluidity in toners having various volume average particle diameters [μm] can be examined by measuring the angle of repose for toners having various volume average particle diameters [μm].

  FIG. 4 is a graph showing the measurement result of the angle of repose [degree] with respect to the volume average particle diameter [μm] of the toner. Differences in symbols for the same volume average particle diameter represent different types of toner with the same volume average particle diameter.

  As can be seen from FIG. 4, the smaller the volume average particle diameter, the larger the angle of repose. In particular, when the volume average particle size is smaller than about 4.5 μm, the angle of repose exceeds 60 degrees and suddenly increases. From this result, when a toner having a small volume average particle diameter of 4.5 μm or less is used, the fluidity of the toner is considerably lowered as compared with the case where a toner having a larger volume average particle diameter is used. I understand. That is, it can be said that prevention of toner clogging is particularly effective when a toner having a volume average particle diameter of 4.5 μm or less is used. From the viewpoint of toner manufacturability, the volume average particle size is preferably 2.0 μm or more.

  The above is the description of the embodiment of the present invention.

  In the above description, a monochrome printer is shown as an example of the image forming apparatus of the present invention. However, the image forming apparatus of the present invention may be a color printer, a facsimile, a copier, or a multifunction machine. It may be.

  In the above description, an exposure system is shown as an example of the latent image forming device according to the present invention. However, the latent image forming device according to the present invention is directly latent on the image carrier by an electrode array or the like. It may form an image.

  In the above description, an image density calculation unit that calculates an image density based on image data is shown as an example of an image density detector according to the present invention. The density of the toner image on the image holding member may be detected by an optical sensor or the like.

DESCRIPTION OF SYMBOLS 100 ... Image forming apparatus, 21 ... Photoconductor, 22 ... Charger, 23 ... Exposure device 24 ... Developer, 241 ... Developing roll, 242, 243 ... Conveying member 244 ... Case, 247 ... ... Toner receiving port 248... Rotating blade 249... Density sensor 80... Motor 81.

Claims (11)

A developer containing powder to be developed by being attached to the latent image, and a storage tank in which the powder is charged onto the developer from a supply port;
An agitation transport member that is disposed in the storage tank and is driven by receiving a driving force to stir the developer in the storage tank and transport the developer in the storage tank;
Rotating member that is deployed at a location where the powder charged from the supply port passes, and is driven to rotate independently of the stirring and conveying member;
A developing device comprising:   When the rotation member is controlled to rotate according to the image density of at least one of the latent image and the developed image obtained by developing the latent image, and the image density is relatively low or low The developing device according to claim 1, wherein the developing device rotates more.   2. The rotating member according to claim 1, wherein rotation of the rotating member is controlled in accordance with an environmental temperature of the developing device, and the rotating member rotates more when the temperature is relatively high and when the temperature is relatively low. Or the developing device of 2.   2. The rotating member according to claim 1, wherein the rotation of the rotating member is controlled according to the environmental humidity of the developing unit, and the rotating member rotates more when the humidity is relatively high and when the humidity is relatively low. 4. The developing device according to any one of items 1 to 3.   The rotation of the rotating member is controlled in accordance with the concentration of the powder in the developing unit, and the rotation of the rotating member is increased when the concentration is relatively low and when the concentration is relatively low. The developing device according to any one of claims 1 to 4.   The developing device according to claim 1, wherein the powder has a volume average particle diameter of 4.5 μm or less. An image carrier that forms an image on the surface and holds the image;
A latent image forming device for forming a latent image on the surface of the image carrier;
A developing unit for developing powder by attaching the powder to the latent image on the image carrier,
The developer is
A developer tank containing the powder, and a storage tank into which the powder is charged onto the developer from a supply port;
An agitation transport member that is disposed in the storage tank and is driven by receiving a driving force to stir the developer in the storage tank and transport the developer in the storage tank;
Rotating member that is deployed at a location where the powder charged from the supply port passes, and is driven to rotate independently of the stirring and conveying member;
An image forming apparatus comprising: An image density detector for detecting the density of an image formed on the image carrier;
A rotation control unit that controls the rotation of the rotating member according to the image density detected by the image density detector, and rotates the rotation member more when the image density is relatively low and when the image density is relatively low;
The image forming apparatus according to claim 7, further comprising: A temperature detector for detecting the temperature in the image forming apparatus;
A rotation control unit that controls the rotation of the rotating member according to the temperature detected by the temperature detector, and rotates the rotation member more when the temperature is relatively high and when the temperature is relatively low;
The image forming apparatus according to claim 7 or 8, further comprising: A humidity detector for detecting humidity in the image forming apparatus;
A rotation control unit that controls the rotation of the rotating member according to the humidity detected by the humidity detector, and rotates the rotation member more when the humidity is relatively high and when the humidity is relatively low,
The image forming apparatus according to claim 7, further comprising: A concentration detector for detecting the concentration of the powder in the developing unit;
A rotation control unit that controls the rotation of the rotating member according to the concentration detected by the concentration detector, and rotates the rotation member more when the concentration is relatively low and when the concentration is relatively low;
The image forming apparatus according to claim 7, further comprising:

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