JP5026097B2 - Image forming apparatus - Google Patents

Description

  The present invention relates to an image forming apparatus, and more particularly to an image forming apparatus that performs development using a liquid developer.

  An electrophotographic image forming apparatus that performs development using a liquid developer includes a photosensitive drum on which an electrostatic latent image is formed, and a developing roller for supplying the liquid developer to the photosensitive drum. . In this image forming apparatus, the liquid developer is supplied in a stable amount to the photosensitive drum, so that the image quality is kept constant.

  As a conventional image forming apparatus of this type, there is known an apparatus that detects the liquid level of a liquid developer by a liquid level detection sensor in order to maintain an appropriate amount of liquid developer in the developing device (for example, Patent Document 1). The liquid level detection sensor includes a float switch, and detects the liquid amount according to the width of the vertical movement of the float. However, such a float switch cannot be detected with high sensitivity for a liquid developer having a high viscosity or a small specific gravity.

  On the other hand, as a technique for stably supplying the liquid developer to the photosensitive drum without using such a liquid level detection sensor, a photosensitive drum and a developing roller are provided from a developer tank in which the liquid developer is stored. It is known that a developer is supplied during this period, and excess developer that has passed between the photosensitive drum and the developing roller is collected in a developer tank and reused (see, for example, Patent Document 2). ). However, in this technique, it is not desirable to return the developer that has passed between the photosensitive drum and the developing roller to the developer tank because the developer concentration has changed.

On the other hand, a technique for supplying a developer to a developer roller by an anilox roller is known (see, for example, Patent Document 3). In this technique, the liquid developer is temporarily supplied from the developer tank to another storage unit, and the anilox roller is disposed in a state where a part of the developer is immersed in the developer stored in the storage unit. A uniform thin layer is formed on the roller. However, in this technique, since the anilox roller is always immersed in the liquid developer, the developer is excessively attached, and the attached developer may be excessively supplied to the downstream development roller.
JP 2001-92258 A JP 200412710 A JP 59-126570 A

  An object of the present invention is to suppress an excessive supply of a developer to a developing roller in an image forming apparatus that performs development using a liquid developer, and to prevent image quality unevenness from occurring.

  According to a first aspect of the present invention, an image forming apparatus includes an image carrier, a developing roller, a developer storage unit, a developer transport unit, and a developer suction unit. The developing roller is disposed to face the image carrier. The developer storage unit stores a liquid developer. The developer conveying means has a pumping roller disposed in contact with the liquid developer stored in the developer storage section and extending in parallel with the axial direction of the developing roller, and develops the liquid developer pumped up by the pumping roller. Supply to roller. The developer suction means has two suction ports arranged in the vicinity of both end portions in the axial direction of the pumping roller, and can suck the liquid developer.

  In this apparatus, the liquid developer stored in the developer storage section is pumped up by the pump-up roller, and is supplied to the downstream developing roller and further to the downstream image carrier. The drawing-up roller is arranged in a state where it is immersed in the liquid developer, and the developer adheres to both ends of the roller so that it is easy to deposit. When the developer adheres like this, the developer is excessively supplied to the downstream developing roller, which may cause unevenness in image quality.

  However, in the image forming apparatus according to the first aspect, the suction ports of the developer suction means are arranged in the vicinity of both ends of the scooping roller, so that the developer adhering to both ends of the scooping roller can be sucked. And oversupply to the downstream roller is suppressed.

  According to a second aspect of the present invention, in the apparatus of the first aspect, the suction port is disposed above the reference liquid level of the developer storage section.

  By arranging such a suction port, even when the liquid level of the liquid developer is below the reference liquid level, it is possible to suck and remove the developer excessively attached to both ends of the pumping roller, When the level of the liquid developer exceeds the reference level, the developer that has excessively adhered to both ends of the pumping roller is removed by suction, and the developer that exceeds the reference level is suctioned and removed. be able to.

  The image forming apparatus according to claim 3, in the apparatus according to claim 1, wherein the developer conveying means is two discs arranged with a predetermined gap in the axial direction from both axial ends of the drawing roller. It further has a shaped member. The suction port is disposed between the pumping roller and the disk-shaped member in the axial direction.

  In this device, the developer adhering to both ends of the pumping roller tends to accumulate in the gap between the pumping roller and the disk-like member. The developer adhering to both ends of the roller can be sucked efficiently.

  According to a fourth aspect of the present invention, in the image forming apparatus according to any one of the first to third aspects, the image forming apparatus further includes a developer supply unit that supplies the liquid developer to the developer storage section.

  In this apparatus, when the liquid developer is supplied to the developer reservoir by the developer supply means, the liquid level of the developer may rise and overflow. However, when the liquid level in the developer reservoir reaches the height at which the suction port is disposed, the developer is sucked by the developer suction means, so that the amount of the developer can be kept below a certain level.

  According to the present invention, since the suction ports of the developer suction means are arranged in the vicinity of both ends of the pumping roller, the developer attached to both ends of the pumping roller can be sucked, and the downstream side can be sucked. Oversupply to the roller is suppressed.

  Hereinafter, an embodiment of an image processing apparatus of the present invention will be described based on the drawings.

  In the following embodiments, a printer will be described as an example of the image processing apparatus of the present invention, but the present invention is not limited to this. That is, the image processing apparatus of the present invention only needs to include an image forming unit, and may be a so-called multi-function peripheral (MFP) having a function as a copying machine or a facsimile machine or only a copying function. Specific configurations of these members described below, other members, and the like can be appropriately changed.

<Schematic configuration of image forming apparatus>
A schematic configuration of the wet image forming apparatus X1 according to the present embodiment will be described with reference to FIG. FIG. 1 is a vertical cross-sectional view showing a main configuration of an image forming apparatus according to an embodiment of the present invention.

  The image forming apparatus X1 includes a tandem image forming unit A1 that forms a toner image based on image data, a paper storage unit 2 that stores paper, and a secondary that transfers the toner image formed by the image forming unit A1 to the paper. A transfer unit 3, a fixing unit 4 that fixes the transferred toner image on the paper, a paper discharge device 5 that discharges the fixed paper, and a paper discharge tray 7 that receives the discharged paper are provided. The image forming apparatus X1 further includes a paper transport unit 6 that transports paper from the paper storage unit 2 to the paper discharge device 5.

  The image forming unit A1 includes an intermediate transfer belt B1, an intermediate transfer belt cleaning unit B2, and image forming units FY corresponding to yellow (Y), magenta (M), cyan (C), and black (Bk), respectively. , FM, FC, and FB.

  The intermediate transfer belt B1 is an endless or loop-like belt member having conductivity, and is circulated and driven clockwise in FIG. Hereinafter, the surface facing outward in the circulation drive may be referred to as a front surface, and the other surface may be referred to as a back surface.

  The image forming units FY, FM, FC, and FB are disposed downstream of the cleaning unit B2 of the intermediate transfer belt B1 and upstream of the secondary transfer unit 3 in the moving direction of the intermediate transfer belt B1 along the intermediate transfer belt B1. , Arranged in this order. Note that the order of arrangement of the image forming units FY, FM, FC, and FB is not limited to this, but this arrangement is preferable in consideration of the influence of the color mixture on the completed image.

<Image forming unit>
The image forming units FY, FM, FC, and FB have substantially the same configuration. As an example, FIG. 2 shows a cross-sectional view illustrating a schematic configuration of the image forming unit FY.

  The image forming unit FY includes a photosensitive drum (image carrier) 10, a charger 11, an LED exposure device 12, a developing device HY for yellow, a primary transfer roller 20, a cleaning blade 31a for the photosensitive drum 11, a static elimination device 13, A carrier removal roller 30 is provided.

  The other image forming units FM, FC, and FB include developing devices HM, HC, and HB corresponding to the respective colors. Further, among the image forming units, the image forming unit FB located on the most downstream side in the moving direction of the intermediate transfer belt B1 is not provided with the carrier removing roller 30 because the image forming unit is not located downstream thereof. Other configurations are the same.

  The photosensitive drum 10 is a substantially cylindrical member that is arranged to be rotatable about a rotation axis that is perpendicular to the moving direction of the intermediate transfer belt B1 and parallel to the surface direction of the intermediate transfer belt B1, and is opposite to that in FIG. It can rotate clockwise. The photosensitive drum 10 can carry a toner image including toner charged on its surface (in this embodiment, charged positively).

  The cleaning blade 32 a, the charge eliminating device 13, the charger 11, the exposure device 12, and the yellow developing device HY have the photosensitive drum 10 and the primary transfer roller 20 around the photosensitive drum 10 along the rotation direction described above. They are arranged in this order as seen from the primary transfer position in contact.

  The charger 11 can uniformly charge the surface of the photosensitive drum 10.

  The LED exposure device 12 has an LED light source, and irradiates the charged surface of the photosensitive drum 10 with light corresponding to the image information in accordance with the image information from the external device described above, and electrostatically irradiates the surface of the photosensitive drum 10. A latent image can be formed.

  The yellow developing device HY holds a liquid developer containing yellow toner and a liquid carrier (hereinafter simply referred to as a developer) so as to face the electrostatic latent image, thereby electrostatically Toner can be applied to the latent image and the electrostatic latent image can be developed as a toner image. This toner image is primarily transferred by the primary transfer roller 20 to the intermediate transfer belt B1. Details of the primary transfer roller 20 will be described later.

  The cleaning blade 31 a is a blade-like member disposed so as to be in contact with the photosensitive drum 10. The cleaning blade 31a removes the developer remaining on the surface of the photosensitive drum 10 after the primary transfer.

  The neutralization device 13 includes a light source. After the developer is removed by the cleaning blade 31a, the surface of the photosensitive drum 10 is neutralized by light from the light source to prepare for the next image formation.

  The primary transfer roller 20 is disposed in contact with the back surface of the intermediate transfer belt B1. The primary transfer roller 20 is applied with a voltage having a polarity (minus in this embodiment) opposite to the charging polarity of the toner in the toner image from a power source (not shown). Since the intermediate transfer belt B1 has conductivity, the applied voltage attracts toner to the surface side of the intermediate transfer belt B1 and its periphery.

  During primary transfer, a small amount of carrier may be transferred from the photosensitive drum 10 to the intermediate transfer belt B1 together with the toner. This carrier transfer may interfere with primary transfer in the downstream image forming unit and cause image defects such as image blurring and blurring. Providing the carrier removal roller 30 can prevent such an image defect.

  In the present embodiment, the carrier removal roller 30 is incorporated in the cleaning unit 31 together with the above-described cleaning blade 31a. The cleaning unit 31 is provided in the image forming unit FY. In addition to the cleaning blade 31a and the carrier removing roller 30, the cleaning unit 31 is in contact with the surface of the carrier removing roller 30 to remove the carrier liquid attached to the surface of the carrier removing roller 30. The carrier removal blade 31b, the carrier removed from the carrier removal roller 30, and the developer (including toner and carrier) removed from the surface of the photosensitive drum 10 by the cleaning blade 31a are conveyed to the outside of the cleaning unit 31. The transport member 31c is provided. The image forming unit FY may further include a separation unit that separates the carrier and the toner in order to reuse the carrier and the toner conveyed by the conveyance member 31c.

  The image forming unit FY further includes a developer tank 51, a supply device (developer supply means) 52, and a suction device (developer suction means) 53, as shown in FIGS. In FIG. 3, for convenience of explanation, the developing container 40 (described later) and its periphery are shown in plan view, and the developer tank 51 and its periphery are shown in side view. FIG. 4 is a view taken along the line IV-IV in FIG. 3 to 5, arrows indicate directions in which the developer is sucked and discharged from the tubes 52b and 53b (described later).

  The developer tank 51 is a container for storing a liquid developer composed of yellow toner particles and a liquid carrier. Further, a toner concentration sensor (not shown) is disposed in the developer tank 51 to detect the toner concentration of the developer in the developer tank 51. When it is detected that the toner concentration is lower than a predetermined value, toner (a developer having a toner concentration higher than the predetermined value) is supplied from a toner cartridge (not shown) to the developer tank 51, and the toner concentration is higher than the predetermined value. The carrier liquid is supplied to the developer tank 51 from a carrier liquid cartridge (not shown).

  The supply device 52 is a device for supplying the developer in the developer tank 51 to the developing container 40. The supply device 52 includes a supply tube 52b, a supply nozzle 52a attached to an end of the supply tube 52b on the downstream side in the supply direction, and a pump 52c provided in the middle of the supply tube 52b. The supply tube 52 b has an upstream end disposed at a predetermined height from the bottom surface of the developer tank 51. The supply nozzle 52a is arranged to supply the developer from above in the vicinity of the central portion in the axial direction of the pumping roller 40c described later. A known pump is used as the pump 52c.

  The suction device 53 is a device for returning excess developer in the developer container 40 to the developer tank 51. The suction device 53 includes two suction tubes 53b, suction nozzles 53a attached to the upstream ends of the suction tubes 53b in the suction direction, and pumps 53c respectively provided in the middle of the suction tubes 53b. Have. The downstream end of each suction tube 53b is disposed at a higher height in the developer tank 51 than the upstream end of the supply tube 52b. Further, the tip of each suction nozzle 53a is located at a predetermined height from the bottom surface of the developing container 40, here, just above the reference liquid level S of the developer in the developing container 40, and slightly from the rotation shaft 40j of the pumping roller 40c. It is an upper part and is arranged in a gap between both ends of the pumping roller 40c and a pulley (disk-shaped member) 54 described later. By disposing the tip of the suction nozzle 53a in this way, even when the developer liquid level is below the reference liquid level S, the developer excessively adhered to both ends of the pumping roller 40c at the tip of the suction nozzle 53a. When the liquid level of the developer exceeds the reference liquid level S, the developer excessively adhering to both ends of the pumping roller 40c is removed by suction, and the reference liquid level S is removed. The excess developer can be removed by suction. In the case where the pulley 54 is not provided, the liquid level of the developer adhering to both ends of the pumping roller 40c is gently inclined, so that it does not reach the tip position of the suction nozzle 53a sufficiently and does not reach the tip of the developer and the suction nozzle 53a. There may be some space. If so, air is also sucked in by the suction nozzle 53a, and suction removal may be insufficient. By providing the pulley 54, the developer rises through a narrow gap between the end of the pumping roller 40c and the pulley 54. Therefore, the liquid level of the developer becomes almost horizontal, and the tip of the suction nozzle 53a becomes the developer. Since it is completely immersed, the developer excessively attached to both ends of the pumping roller 40c can be sufficiently removed by suction.

  A known pump is used for each pump 53 c, and here, the suction capability of the suction device 53 exceeds the supply capability of the supply device 52. Specifically, each pump 53c operates during the developing operation and during the operation in which the developer is supplied from the developer tank 51, and at least operates when the pump 52c of the supply device 52 is operating. It has become. The suction device 53 may be configured such that each pump 53c stops operating when it is detected by the sensor that detects passage of the developer provided in the middle of the tube 53b that the developer does not pass. .

<Developing device>
Next, the configuration of the developing device HY will be described. The configurations of the developing devices HY, HM, HC, and HB are the same.

  The developing device HY includes a developing container (developer reservoir) 40, a developing roller 40a, a supply roller 40b, a pumping roller 40c, a pulley 54, stirring spirals 40d and 40e, a developing cleaning blade 40f, and a supply roller doctor blade 40g. The supply roller 40b, the scooping roller 40c, and the pulley 54 constitute the developer conveying means of the present invention.

  The developing container 40 stores a developer therein. The stirring spirals 40d and 40e are provided so as to be entirely immersed in the developer in the developing container 40, and stir the developer. The toner particles are uniformly dispersed in the carrier liquid by the rotation of the stirring spirals 40d and 40e.

  The drawing-up roller 40c is arranged so that a part of the drawing-up roller 40c is immersed in the developer in the developing container, and the developer is pumped up by adhering to the surface. In addition, disc-shaped pulleys 54 are arranged on the rotation shaft 40j of the drawing roller 40c with a predetermined gap from both axial ends of the drawing roller 40c. Each gap between the drawing roller 40c and the pulley 54 has an axial length slightly wider than the outer diameter of the suction nozzle 53a.

  A supply roller 40b is disposed so as to be in contact with the drawing roller 40c, and the developer is supplied from the drawing roller 40c. The developer on the surface of the supply roller 40b is downstream of the position where the supply roller 40b is in contact with the pumping roller 40c in the rotation direction and upstream of the supply roller 40b in the position where the later-described development roller 40a and supply roller 40b are in contact. A supply roller doctor blade 40g is provided to regulate the layer thickness. The supply roller doctor blade 40g regulates the developer layer thickness on the surface of the supply roller 40b to be a predetermined amount. A developing roller 40a is disposed so as to be in contact with the supply roller 40b, and a developer is applied to the surface thereof from the supply roller 40b. Since the developer layer thickness of the supply roller 40b is regulated to a predetermined value, the layer thickness of the developer formed on the surface of the developing roller 40a is also kept at the predetermined value. The developing roller 40a is in contact with the photosensitive drum 10, and a toner corresponding to an image instructed to be formed from an external device based on a potential difference between an electrostatic latent image on the surface of the photosensitive drum 10 and a developing bias applied to the developing roller 40a. An image is formed on the surface of the photosensitive drum 10 (development operation).

  The developer on the surface of the developing roller 40a that has completed the developing operation on the photosensitive drum 10 is downstream of the position in contact with the photosensitive drum 10 in the rotation direction of the developing roller 40a, and the developing roller 40a and the supply roller 40b are in contact with each other. The development is removed by the development cleaning blade 40f disposed on the upstream side in the rotation direction of the development roller 40a at the position, flows down along the surface of the development cleaning blade 40f, and is stored in the developer tank 51 through a flow path (not shown). Mixed with the agent.

  Further, a developer liquid level sensor 40i is disposed in the developer container 40, and detects whether or not the developer liquid level in the developer container 40 is a predetermined value. When it is detected that the liquid level of the developer is lower than the predetermined value, the pump 52c of the supply device 52 is operated and the developer in the developer tank 51 is supplied until the liquid level reaches the predetermined value. .

<Operation of Image Forming Apparatus>
Next, an image forming operation of the wet image forming apparatus X1 will be described.

  Upon receiving an image formation instruction from an external device such as a personal computer (PC), the wet image forming apparatus X1 converts the toner images of each color corresponding to the image information received with the creation instruction into image forming units FY, FM, FC, and FB. Use to form. The image formed by each image forming unit is transferred to the intermediate transfer belt B1, and is superimposed on the intermediate transfer belt B1 to form a color toner image.

  In synchronism with the formation of the color toner image, the paper stored in the paper storage unit 2 is taken out from the paper storage unit 2 one by one by a paper feeding device (not shown) and transported on the paper transport unit 6. Then, the sheet is fed to the secondary transfer unit 3 in synchronization with the primary transfer to the intermediate transfer belt B1, and the color toner image on the intermediate transfer belt B1 is secondarily transferred to the sheet by the secondary transfer unit 3. The sheet on which the color toner image has been transferred is further conveyed to the fixing unit 4 where the color toner image is fixed on the sheet by heat and pressure. Further, the paper is discharged by a paper discharge device 5 to a paper discharge tray 7 provided on the outer periphery of the wet image forming apparatus X1. The toner remaining on the intermediate transfer belt B1 after the secondary transfer is removed from the intermediate transfer belt B1 by the cleaning unit B2 of the intermediate transfer belt.

  In accordance with such an image forming operation, each developing device performs the above-described developing operation and appropriately adjusts the liquid level according to the detection result of the developer liquid level sensor 40i. When the suction device 53 is operated along with this liquid level adjustment, the developer accumulated in the gap between the both ends of the pumping roller 40c and the pulley 54 is sucked, so that the developer adheres to both ends of the pumping roller 40c. Can be suppressed. That is, the suction device 53 has both a function of suppressing the rise of the liquid level and a function of sucking the developer attached to both ends of the scooping roller 40c.

  By preventing the developer from adhering to both ends of the pumping roller 40c, the developer is prevented from being excessively supplied to the supply roller 40b and the developing roller 40a on the downstream side, and the developer layer on the surface of the developing roller 40a. The thickness can be kept constant, and the image quality can be kept constant.

In particular, in this image forming apparatus X1, since the pulley is arranged with a predetermined gap from the pumping roller, the developer tends to stay in this gap due to its viscosity, so that the developer can be sucked efficiently. This is particularly effective when the amount of adhesion is large.
<Other embodiments>
(A) In the said embodiment, a pulley is not essential and the aspect of arrangement | positioning of a suction nozzle is not specifically limited to what was mentioned above. For example, the suction nozzle 153a may be arranged in a manner as shown in FIG. In FIG. 6, the developer adhering to both ends of the scooping roller 40j is indicated by a region shown bulging outward from both ends of the roller. An arrow indicates a direction in which the developer is sucked by the suction nozzle.

  (B) The suction port is not limited to an aspect in which the suction port is disposed on the outer side in the axial direction from both ends of the pumping roller, and may be disposed on the outer peripheral side with respect to both ends of the pumping roller. That is, the suction port may be arranged to face the peripheral surfaces of both ends of the pumping roller.

  (C) The developing device may supply the developer directly from the drawing roller to the developing roller, or may be supplied via a plurality of other rollers or a conveying belt.

1 is a longitudinal cross-sectional view illustrating a main configuration of an image forming apparatus in which an embodiment of the present invention is employed. FIG. 3 is a longitudinal sectional view illustrating a main configuration of an image forming unit FY of the image forming apparatus. FIG. 4 is an explanatory diagram for explaining a positional relationship among a developing container, a developer tank, a supply device, and a suction device of the image forming unit. The side view which shows the principal part structure of the said developing container, a drawing-up roller, a supply apparatus, and a suction device. The front view which shows the principal part structure of the said developing container, a disk-shaped member, and a suction device. The front view which shows the principal part structure of the drawing-up roller and suction device of the image forming apparatus by which other embodiment of this invention was employ | adopted.

Explanation of symbols

1 Image forming apparatus 10 Photosensitive drum (image carrier)
40a Developing roller 40 Developer container (developer reservoir)
40c Pumping roller (developer conveying means)
40b Supply roller (developer conveying means)
52 Supply device (developer supply means)
53 Suction device (Developer suction means)
53a Suction nozzle (suction port)
54 Pulley (disc-shaped member)
S reference liquid level

Claims (3)

An image carrier;
A developing roller disposed to face the image carrier;
A developer reservoir for storing a liquid developer;
A pumping roller disposed in contact with the liquid developer stored in the developer storage section and extending in parallel with the axial direction of the developing roller; and the liquid developer pumped up by the pumping roller is transferred to the developing roller A developer conveying means to supply;
A developer suction means having two suction ports arranged in the vicinity of both ends in the axial direction of the pumping roller, and capable of sucking the liquid developer ;
The developer conveying means further includes two disk-like members arranged with a predetermined gap in the axial direction from both axial ends of the scooping roller,
The image forming apparatus , wherein the suction port is disposed between the pumping roller and the disk-shaped member in the axial direction . The suction port is disposed above the reference liquid surface of the developer storage unit, an image forming apparatus according to claim 1. Wherein provided in the developer reservoir further a developer supply means for supplying liquid developer, an image forming apparatus according to claim 1 or 2.

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