JP6217910B2 - Image forming apparatus - Google Patents

Description

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

  Conventionally, an image forming apparatus that forms a toner image and a cleaner that cleans transfer residual toner are known.

  For example, in Patent Document 1, when the amount of transfer residual toner on the image carrier is large, a part of the transfer residual toner is removed by a cleaning brush, and when the amount of transfer residual toner on the image carrier is small. A cleaning device is disclosed in which toner accumulated on a cleaning brush adheres to the surface of an image carrier.

JP 2003-233282 A

  An object of the present invention is to stabilize the cleaning power.

An image forming apparatus according to claim 1 is provided.
An image carrier that holds a toner image on the surface of which a toner image is formed;
An image forming machine for forming a toner image on the surface of the image carrier;
A transfer device for transferring a toner image from the surface of the image carrier onto a transfer target;
A cleaning device for removing the toner remaining on the surface of the image carrier after the transfer of the toner image by the transfer device and cleaning the surface of the image carrier;
The cleaner is
A removing member that removes the toner from the surface by rubbing against the surface of the image carrier;
A storage tank for storing the toner removed by the removal member;
A charging material disposed in the storage tank and having a charging polarity opposite to that of the toner is held on the surface, the toner is adsorbed by frictional charging between the charging material and the toner, and the adsorbed toner is held in the image. A supply member for supplying to the surface of the body;
With
The image forming machine accommodates the toner inside and forms a toner image on the surface of the image carrier with the toner.
A density detector for detecting the toner density in the image forming machine;
The supply member supplies more toner as the toner density detected by the density detector is lower.

According to engagement Ru images forming apparatus to claim 1, the cleaning power as compared with the case not having the present structure is stabilized.

1 is a schematic configuration diagram of a printer corresponding to a first embodiment of an image forming apparatus. FIG. 3 is a side view conceptually showing the structure of a cleaner provided in each image forming unit. 3 is a top view conceptually showing the structure of a cleaner provided in each image forming unit. FIG. It is the conceptual block diagram which showed notionally the structure of the cleaner in 2nd Embodiment. 3 is a graph showing a relationship between a toner particle size and blade wear amount.

  Specific embodiments of the cleaner and the image forming apparatus of the present invention will be described below with reference to the drawings.

  FIG. 1 is a schematic configuration diagram of a printer corresponding to the first embodiment of the image forming apparatus.

  A printer 1 shown in FIG. 1 is a so-called tandem color printer, and includes an image forming process unit 10 that forms an image corresponding to image data of each color, a control unit 30 that controls the operation of the entire printer 1, and, for example, An image processing unit 35 that is connected to an external device such as a personal computer (PC) 3 or an image reading device 4 and performs image processing on image data received from these devices, and a main power source 36 that supplies power to each unit. I have.

  The image forming process unit 10 includes four image forming units 11Y, 11M, 11C, and 11K (hereinafter collectively referred to simply as “image forming units 11”) arranged in parallel at regular intervals. It has been. Each image forming unit 11 includes a photosensitive drum 12 on which an electrostatic latent image or a toner image is formed, a charger 13 for charging the surface of the photosensitive drum 12, and the surface of the photosensitive drum 12 as image data. An LED print head (LPH) 14 that performs exposure on the basis, a developing device 15 that develops an electrostatic latent image formed on the photosensitive drum 12, and a cleaner 16 that cleans the surface of the photosensitive drum 12 after transfer. Yes.

  The photosensitive drum 12 corresponds to an example of an image holding member according to the present invention, and the combination of the charger 13, the LPH 14, and the developing unit 15 corresponds to an example of an image forming machine according to the present invention.

  Each image forming unit 11 has the same configuration except for the toner stored in the developing device 15. Each image forming unit 11 forms yellow (Y), magenta (M), cyan (C), and black (K) toner images.

  Further, the image forming process unit 10 performs intermediate transfer on the intermediate transfer belt 20 onto which the color toner images formed on the photosensitive drums 12 of the image forming units 11 are transferred, and the color toner images on the image forming units 11. A primary transfer roll 21 that is sequentially transferred to the belt 20, a secondary transfer roll 22 that collectively transfers the superimposed toner image transferred onto the intermediate transfer belt 20 onto a sheet as a recording material, and an image that is secondarily transferred onto the sheet. And a fixing device 45 for fixing the toner image.

  In the printer 1, the image forming process unit 10 performs an image forming operation based on various control signals supplied from the control unit 30. That is, image data input from the PC 3 or the image reading device 4 is subjected to image processing by the image processing unit 35 under the control of the control unit 30 and is supplied to each image forming unit 11 via an interface (not shown). The For example, in the black (K) image forming unit 11K, the photosensitive drum 12 is charged to a predetermined potential by the charger 13 while being rotated in the direction of arrow A, and transmitted from the image processing unit 35. Exposure is performed by the LPH 14 that emits light based on data representing a black component image in the image data. As a result, an electrostatic latent image related to a black (K) color image is formed on the photosensitive drum 12. The electrostatic latent image formed on the photosensitive drum 12 is developed by the developing device 15, and a black (K) toner image is formed on the photosensitive drum 12. Similarly, yellow (Y), magenta (M), and cyan (C) toner images are formed in the image forming units 11Y, 11M, and 11C of other colors, respectively.

  Here, the development by the developing device 15 will be further described. The developing device 15 contains a two-component developer in which toner of a color corresponding to each of the image forming units 11Y, 11M, 11C, and 11K and a magnetic carrier are mixed. When the toner and the magnetic carrier are mixed, they are charged with opposite polarities by mutual friction. When developing by the developing unit 15, a potential difference called a developing bias is applied between the developing unit 15 and the photosensitive drum 12, and only the charged toner in the developer is transferred from the developing unit 15 to the electrostatic latent image by the developing bias. Move on and stick. As a result, the electrostatic latent image is developed and a toner image is formed.

  The respective color toner images formed by the respective image forming units 11 are sequentially electrostatically attracted by the primary transfer roll 21 onto the intermediate transfer belt 20 moving in the direction of arrow B to form a composite toner image in which the respective color toners are superimposed. Is done. Residual toner remaining on the photosensitive drum 12 even after transfer by the primary transfer roll 21 is removed from the photosensitive drum 12 by the cleaner 16 of each image forming unit 11.

  The primary transfer roll 21 corresponds to an example of a transfer device according to the present invention, and the intermediate transfer belt 20 corresponds to an example of a transfer target according to the present invention. Moreover, the cleaner 16 is corresponded to 1st Embodiment of the cleaning device of this invention.

  The synthetic toner image on the intermediate transfer belt 20 is conveyed to a region (secondary transfer portion T) where the secondary transfer roll 22 is disposed as the intermediate transfer belt 20 moves. Further, the sheet is supplied from the sheet holding unit 40 to the secondary transfer unit T in accordance with the conveyance timing of the synthetic toner image by the intermediate transfer belt 20. The composite toner image is collectively electrostatically transferred onto the conveyed paper by the transfer electric field formed by the secondary transfer roll 22 in the secondary transfer portion T.

  Thereafter, the sheet on which the synthetic toner image has been electrostatically transferred is peeled off from the intermediate transfer belt 20 and conveyed to the fixing device 45. The synthesized toner image on the paper conveyed to the fixing device 45 is fixed on the paper by the fixing device 45 by a fixing process using heat and pressure. Then, the sheet on which the fixed image is formed is conveyed to the paper discharge stacking unit 41 provided in the discharge unit of the printer 1.

  On the other hand, toner (transfer residual toner) adhering to the intermediate transfer belt 20 after the secondary transfer is removed from the surface of the intermediate transfer belt 20 by the belt cleaner 25 after the completion of the secondary transfer to prepare for the next image forming cycle. In this way, image formation by the printer 1 is repeatedly executed for the number of printed sheets.

  Here, the cleaner 16 provided in each image forming unit 11 will be further described.

  2 and 3 are conceptual configuration diagrams conceptually showing the structure of the cleaner provided in each image forming unit. FIG. 2 shows a side view (that is, a view seen from the front side of FIG. 1). FIG. 3 shows a top view (that is, a view seen from above in FIG. 1).

  The cleaner 16 includes a cleaning blade 161 that is in contact with the surface of the photosensitive drum 12, a storage chamber 162 that stores toner removed from the photosensitive drum 12, and the toner stored in the storage chamber to the outside of the cleaner 16. An unloading auger 163 for unloading and a supply roll 164 for supplying a part of the toner in the storage chamber to the surface of the photosensitive drum 12 are provided.

  The cleaning blade 161 corresponds to an example of a removal member according to the present invention, the storage chamber 162 corresponds to an example of a storage tank according to the present invention, and the supply roll 164 corresponds to an example of a supply member according to the present invention.

  The cleaning blade 161 is formed by attaching a rubber plate-like member 161 b to a metal plate 161 a and extends in the vertical direction of FIG. 3 along the surface of the photosensitive drum 12. As the photosensitive drum 12 rotates, the rubber plate-like member 161b rubs the surface of the photosensitive drum 12, so that residual toner, external additives, paper dust, and the like are scraped off from the surface of the photosensitive drum 12, and the storage chamber. It falls into 162.

  The storage chamber 162 also has a shape extending in the vertical direction in FIG. 3 along the surface of the photosensitive drum 12, and although not shown, one end is connected to a collection box for collecting toner and the like. .

  The carry-out auger 163 has a structure in which a spiral blade 163b is attached around a rotation shaft 163a extending in the vertical direction in FIG. 3 along the surface of the photosensitive drum, and is driven from a drive source (not shown). The rotating shaft 163a is rotationally driven by the force, so that the toner in the storage chamber 162 is carried out to the collection box.

  The supply roll 164 includes a magnet roll 164a and a sleeve 164b, and the sleeve 164b rotates around the magnet roll 164a by a driving force from a driving source (not shown). The sleeve 164 b is made of a nonmagnetic metal, and a potential difference is applied to the photosensitive drum 12 by the power source 37. Further, the magnetic carrier described above is held on the surface of the supply roll 164 (that is, the surface of the sleeve 164b) by the magnetic field generated by the magnet roll 164a. The magnetic carrier held on the surface of the supply roll 164 corresponds to an example of the charging material referred to in the present invention, and causes friction with the toner in the storage chamber 162 as the sleeve 164b rotates. Due to this friction, the toner in the storage chamber 162 is charged and part of the toner is adsorbed on the surface of the supply roll 164. The supply member referred to in the present invention may have a coating layer made of the same material as the magnetic carrier on the surface, but if it is a type that holds the magnetic carrier as in this embodiment, Charging efficiency is high because the toner sufficiently rubs.

  The toner adsorbed on the surface of the supply roll 164 by charging due to friction moves to a region facing the surface of the photosensitive drum 12 as the sleeve 164b rotates, and the photosensitive drum 12 is subjected to a potential difference applied by the power source 37. Migrate and adhere to the surface. Since the potential difference is used for toner transfer, the toner on the supply roll 164 is electrically separated from the magnetic carrier and smoothly transferred onto the photosensitive drum 12.

  The toner adhering to the surface of the photosensitive drum 12 reaches the cleaning blade 161 again as the photosensitive drum 12 rotates. The cleaning blade 161 is capable of scraping off residual toner and the like when a certain amount of toner and external additives accumulate between the tip of the rubber plate-like member 161b and the surface of the photosensitive drum 12 to form a so-called toner dam. It is stable and has a strong scraping power. The toner supplied to the surface of the photosensitive drum 12 by the supply roll 164 prevents the toner dam from being exhausted, and helps maintain the cleaning ability of the cleaner 16. In particular, a toner that is sufficiently charged by friction with a magnetic carrier is a toner in which an external additive is held on the toner surface, and such an external additive is supplied to the surface of the photosensitive drum 12 together with the toner. As a result, a sufficient amount of the external additive in the toner dam is maintained, and a high cleaning ability is exhibited.

  That is, the cleaner 16 having the supply roll 164 as shown in FIG. 2 has a high cleaning capability and is stable as compared with a cleaner not having the supply roll 164.

  Here, the conditions under which toner dams are easily depleted are examined.

  When an image with a low image density continues as an image formation target image, the residual toner on the photosensitive drum 12 decreases, but the rotation of the photosensitive drum 12 continues for the number of images formed regardless of the image density. . As a result, the residual toner and external additives accumulated in the toner dam gradually decrease and may eventually be exhausted.

  Further, when the density of the toner stored in the developing device 15 shown in FIG. 1 is low, the toner adhering to the background portion of the image is reduced and the residual toner is also reduced. Also in this case, there is a possibility that residual toner and external additives accumulated in the toner dam gradually decrease and eventually become exhausted.

  As described above, when a low density image is formed or when the toner density in the developing device 15 is low, the toner dam is easily depleted. Therefore, in this embodiment, the image processing unit 35 shown in FIG. The image density of the component is calculated and notified to the control unit 30. Such calculation of the image density corresponds to indirectly detecting the image density of the toner image actually formed on the photosensitive drum 12. Further, a density sensor (not shown) is provided in the developing device 15 shown in FIG. 1, and the toner density in the developing device 15 detected by this density sensor is also notified to the control unit 30. The image processing unit 35 corresponds to an example of an image density detector according to the present invention, and the developing device 15 provided with the density sensor corresponds to an example of a density detector according to the present invention. Or you may think that the control part 30 is an example which served as the image density detector and density detector said to this invention.

  The control unit 30 rotates the supply roll 164 of FIGS. 2 and 3 more frequently for each color as the image density is lower, and for each color, the lower the toner density in the developing device 15 is, the supply roll 164 of FIGS. Rotate frequently. When the toner dam is easily depleted by such control of the control unit 30, the amount of toner supplied to the photosensitive drum 12 by the supply roll 164 is increased, so that the toner dam is not depleted and the cleaner 16 is cleaned. Power is maintained.

  This is the end of the description of the first embodiment of the cleaning device and the image forming apparatus of the present invention. Next, the second embodiment will be described.

  Since this second embodiment is the same as the first embodiment except that the cleaner has a different structure, the following description will focus on the cleaner and will not be repeated.

  FIG. 4 is a conceptual configuration diagram conceptually showing the structure of the cleaner in the second embodiment.

  As in the first embodiment, the cleaner 200 according to the second embodiment includes a cleaning blade 161 in contact with the surface of the photosensitive drum 12. Unlike the first embodiment, the cleaner 200 of the second embodiment is provided with two-stage storage chambers 162_1 and 162_2, and residual toner and the like accumulate in a predetermined level in the upper storage chamber 162_1. Further residual toner or the like overflows from the upper storage chamber 162_1 to the lower storage chamber 162_2. The lower storage chamber 162_2 is provided with a discharge auger 163 similar to that of the first embodiment, and the toner accumulated in the lower storage chamber 162_2 is transferred out of the cleaner 200 by the discharge auger 163. .

  The cleaner 200 of the second embodiment is provided with a supply roll 164 similar to that of the first embodiment, and a part of the toner collected in the upper storage chamber 162_1 is supplied to the surface of the photosensitive drum 12. In the second embodiment, since a constant amount of residual toner or the like is always stored in the upper storage chamber 162_1, the amount of toner and external additives supplied to the surface of the photosensitive drum 12 by the supply roll 164 is the first level. More stable than the form.

  Finally, the toner particle size for which the toner supply to the surface of the photosensitive drum 12 is effective will be examined.

  FIG. 5 is a graph showing the relationship between the toner particle size and the blade wear amount.

  The horizontal axis in FIG. 5 represents the toner particle size as a volume average particle size, and the vertical axis represents the blade wear amount. The graph of FIG. 5 represents the result when the image forming is repeated until the supply roll is removed from the cleaner of the first embodiment and the total number of rotations of the photosensitive body reaches 5200 rotations.

It is known that the blade wear amount has a strong correlation with the cleaning ability of the toner dam and the cleaner. When the blade wear amount is high, the toner dam is reduced and the cleaning ability of the cleaner is lowered. The region 300 where the blade wear amount has reached 15 μm ² or more is a red zone, and the cleaning power of the cleaner is insufficient, and apparent image quality deterioration appears in the formed image.

As described above, when the image density is low, the residual toner is decreased and the toner dam is easily depleted. When the volume average particle diameter of the toner is 6.0 μm or more, the blade wear amount is 15 μm ² when the image density is low. Reach up close. The relationship between the toner particle size and blade wear when the image density is the central density is shown by a graph curve 310. When the volume average particle size of the toner is 4.0 μm, the central image density is Since the blade wear amount reaches the red zone 300, it is desirable to supply toner as in the above-described embodiments. Looking at this graph curve 310, the blade wear amount at the central image density is about 6.0 μm and the low image density when the volume average particle size of the toner reaches 4.5 μm or less. It can be seen that the amount of blade wear exceeds. That is, when the volume average particle diameter of the toner is 4.5 μm or less, it can be said that the toner supply as in the above-described embodiments is effective. Further, the lower limit of the volume average particle diameter of the toner is desirably 2.0 μm or more from the viewpoint of manufacturing.

  This is the end of the description of each embodiment.

  In the above description, an example in which the magnetic carrier is held on the surface as the supply member according to the present invention is shown. However, the supply member according to the present invention has a coat layer of the same material as the magnetic carrier on the surface. You may have.

  In the above description, an example in which the toner is transferred onto the photosensitive drum by the potential difference applied from the power source is shown as the supply member in the present invention. However, the supply member in the present invention is a physical means. The toner may be transferred onto the photosensitive drum.

  In the above description, an example in which the image density is indirectly detected based on image data is shown as the image density detector according to the present invention. However, the image density detector according to the present invention is an optical sensor or the like. Alternatively, the image density of the toner image may be directly detected.

  In the above description, as an embodiment of the image forming apparatus, a so-called tandem type color machine including a plurality of image carriers is illustrated, but the image forming apparatus of the present invention has a plurality of colors on one image carrier. It may be a so-called rotary color machine that forms a toner image, or a monochrome-only machine.

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

  In the above description, an indirect transfer type image forming apparatus using an intermediate transfer belt is shown as an example of the image forming apparatus. However, in the image forming apparatus of the present invention, a toner image is directly transferred from an image forming unit to a sheet. The direct transfer type image forming apparatus may be used.

  In the above description, an electrophotographic apparatus is shown as an example of the image forming apparatus according to the present invention. However, the image forming apparatus according to the present invention separately supplies individual toner particles to an image carrier using an electrode array. It is also possible to use an electrode array type device that causes the flight.

  In the above description, a contact-type charging roll is shown as an example of the transfer device according to the present invention. However, the transfer device according to the present invention is a non-contact type such as a scorotron or a corotron. Also good.

DESCRIPTION OF SYMBOLS 1 ... Printer, 10 ... Image formation process part, 12 ... Photosensitive drum,
13 ... Charger, 14 ... LED print head (LPH), 15 ... Developer,
30 …… Control unit 36 …… Power supply 16,200 …… Cleaner 161… Cleaning blade,
162, 162_1, 162_2 ... storage chamber, 163 ... unloading auger,
164 …… Supply roll, 164a …… Magnet roll, 164b …… Sleeve

Claims (1)

An image carrier that holds a toner image on the surface of which a toner image is formed;
An image forming machine for forming a toner image on the surface of the image carrier;
A transfer device for transferring a toner image from the surface of the image carrier onto a transfer target;
A cleaning device for removing the toner remaining on the surface of the image carrier after the transfer of the toner image by the transfer device and cleaning the surface of the image carrier;
The cleaner is
A removal member for removing the toner from the surface by rubbing in contact with the surface of the image carrier;
A storage tank for storing the toner removed by the removal member;
A charging material disposed in the storage tank and having a charging polarity opposite to that of the toner is held on the surface, the toner is adsorbed by frictional charging between the charging material and the toner, and the adsorbed toner is held in the image. A supply member for supplying to the surface of the body;
With
The image forming machine accommodates the toner inside and forms a toner image on the surface of the image holding body with the toner.
A density detector for detecting the toner density in the image forming machine;
The image forming apparatus, wherein the supply member supplies more toner as the toner density detected by the density detector is lower.

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