JP5030262B2 - Developing device and image recording apparatus using the same - Google Patents

Description

  The present invention relates to an image recording apparatus such as an electrophotographic printer or copying machine, and more particularly to a developing apparatus for a high-speed image recording apparatus using a magnetic developer.

  In an image recording apparatus such as an electrophotographic printer or a copying machine, an electrostatic latent image formed by performing exposure according to image information after charging an image carrier called a photoconductor to a predetermined potential is transferred from a developing device to toner. The image is visualized by supplying an image visualization agent called, and printing is performed by transferring and fixing the visible image on a recording medium.

  As a developing device applied to the electrophotographic system, a developing device using a two-component developer in which toner and magnetic powder called a carrier for charging and transporting the toner are mixed at a predetermined mixing ratio is known. ing.

  In the developing device, the two-component developer is stirred by the stirring mechanism, and the toner in the developer and the carrier are rubbed to charge the toner to a predetermined amount and to attach the toner to the carrier, and to make a plurality of magnets. Is adsorbed by a developing roller having a sleeve roller rotatably disposed on the outer periphery thereof. The carrier having the toner adhered to the surface is attracted to the developing roller by magnetic force and is held and conveyed by the rotation of the sleeve roller, and passes through a gap formed by the developing roller and a conveyance amount regulating member called a doctor blade. The carry amount is regulated to a predetermined amount.

  The developer regulated to a predetermined amount by the doctor blade is conveyed to a position facing the photoconductor by the rotation of the sleeve roller and comes into contact with the photoconductor.

  At this time, a bias voltage (hereinafter referred to as “development bias”) is applied to the developing roller, and the charged toner is transferred to the image portion by the electric field formed by the interaction with the electrostatic latent image on the photoreceptor. Adsorption and development are performed.

  In particular, in an image recording apparatus with a high printing speed, it is difficult to obtain a sufficient print quality with a developing device having a single developing roller, and thus a plurality of developing rollers are often used.

  As a developing device using a plurality of developing rollers, a system having a pair of developing rollers rotating in opposite directions is known.

  In Japanese Examined Patent Publication No. 62-45552, the amount of developer conveyed to the lower developing roller is adjusted by a paddle roller and the like, and the developer is conveyed by the magnetic force of the lower developing roller. A system is disclosed in which developer is distributed to both rollers by a deflecting plate provided on the body side, and the distributed developer is conveyed by each developing roller by magnetic force.

  In Japanese Patent Laid-Open No. 3-31876, a developer is attracted to and conveyed by a magnetic force to the lower roller, and has a wide gap that functions only when the conveyance amount is abnormally large, such as at the start of driving, before the minimum gap between both rollers. A system is disclosed in which a doctor blade is provided and developer distribution between both rollers is performed by magnetic force.

  In Japanese Patent Publication No. 54-10869, a two-component developer is adsorbed by a magnetic force to a developing roller disposed below, and a developer whose conveyance amount is adjusted to a specified amount by a doctor blade is placed between both developing rollers. A part of the developer conveyed by the lower developing roller is distributed to the upper roller by the deflection plate provided in the space after passing through the minimum gap, and the distributed developer is developed by the magnetic force for each development. A method of conveying with a roller is disclosed.

  In Japanese Patent No. 3221195, a two-component developer is adsorbed by a magnetic force to a developing roller disposed below, and is conveyed to both rollers by one doctor blade provided before passing through the minimum gap between both rollers. A system is disclosed in which the developer amount is adjusted and the distributed developer is conveyed by each developing roller by magnetic force.

  As described above, a system having a pair of developing rollers rotating in the opposite direction and performing development with the developer passed between both rollers is called a center feed system, and a developing roller rotating in the same direction is combined. It is known as a system that has higher development performance than the system and can perform high-quality printing at high speed.

  However, in the center feed method, the developer passes through a gap in which both rollers are arranged close to each other. Therefore, if the developer transport amount fluctuates, the developer is clogged and the rotation of the developing roller becomes poor. Problems such as reduced lifespan are likely to occur.

  In particular, in a system that does not have means for regulating the amount of developer immediately before the developer enters the gap between both rollers, such as Japanese Patent Publication No. 62-45552 and Japanese Patent Publication No. 54-10869, the developing machine When a larger amount of developer is transported at the start of driving, etc., a large amount of developer enters the gap and the developer is clogged, or the transport amount transported to the developing unit varies and the image quality varies. , Trouble is likely to occur.

  In Japanese Patent Laid-Open No. 3-31876, a doctor blade for restricting excess developer is provided on the lower developing roller, but this cannot be dealt with when the developer wraps around from the upper roller.

  On the other hand, as disclosed in Japanese Patent No. 3221195, there is a method in which a doctor blade is provided immediately before the developer enters the gap between both rollers, and the amount of developer conveyed to each developing roller is adjusted to an appropriate amount. Even if there is a change in the amount of developer to be conveyed, the conveyance amount of both rollers can be regulated to be constant by the doctor blade, so that problems are unlikely to occur. Further, since the excess developer that does not pass through the doctor blade is not pushed into a narrow area, it is an excellent system that places little load on the developer.

Japanese Patent Publication No.54-10869 Japanese Examined Patent Publication No. 62-45552 JP-A-3-31876 Japanese Patent No. 3221195

  Even with the above-mentioned center feed method, where the transport amount of both rollers is regulated before the minimum gap between both rollers, the transport amount with a doctor blade is increased when the rotation speed of the developing roller is increased in order to use at a very high printing speed. The developer is partly separated from the developing roller by the centrifugal force and collides with the photosensitive member almost vertically while being transported to the developing region where it is attracted to both rollers by magnetic force and is contacted with the photosensitive member. It becomes like this.

  FIG. 1 shows a schematic configuration of a center feed type developing device in which three developing rolls 1, 2, and 3 are installed to face a photoreceptor 101.

  Among the three developing rolls, the developing roll 1 is 1.1 times to 2.0 times the peripheral speed of the photosensitive member 101 with respect to the rotation direction of the photosensitive member 101 indicated by an arrow A in FIG. The developing rolls 2 and 3 rotate in the same direction at a peripheral speed, and the developing rollers 2 and 3 rotate in the reverse direction at a peripheral speed 1.1 to 2.0 times the peripheral speed of the photoreceptor 101 with respect to the rotational direction of the photoreceptor 101. Rotate to.

  A doctor blade 5 is disposed between the developing roll 1 and the developing roll 2, and the doctor blade 5 regulates the transport amount of the developer on the developing roll 1 and the developing roll 2 at both ends of one blade. It has a configuration (hereinafter referred to as a double-edged doctor).

  The developing rollers 1, 2 and 3 are each provided with a magnet fixed inside, and provided with a rotatable sleeve on the outer periphery.

  The developer 10 conveyed to the vicinity of the developing roller 3 is attracted to the sleeve surface of the developing roller 3 by the magnetic force of the magnet, and is conveyed to the magnetic pole of the developing roller 2 as the sleeve rotates, It is conveyed to the magnetic pole at a position facing the doctor blade 5 by rotation.

  Here, the developer 10 is regulated to a predetermined amount at the regulation position of the doctor blade 5 and then guided to the developing unit.

  At this time, the excess developer due to the passage amount regulation by the doctor blade 5 is transported in the direction of the developing roller 1 with the rotation of the sleeve, and a predetermined amount like the developing roller 2 at the regulation position of the doctor blade 5. After that, the toner is guided to the developing portion of the developing roll 1.

  In the developing sections of the developing rolls 1 and 2, the developer spikes, the developing roll 1 is in the direction opposite to the moving direction of the photoreceptor surface, and the developing roll 2 is in the same direction as the moving direction of the photoreceptor surface. The developer 10 moves and rubs the surface of the photoreceptor. Thereafter, the developer 10 is transferred to the developing roller 3, and after developing by rubbing the surface of the photoreceptor, the developer 10 is separated from the developing roller and is stirred in the axial direction by the cross mixer 7 and flows in the vicinity of the conveying member 6.

  FIG. 6 is a view showing the vicinity of the developing rollers 1 and 2 and the doctor blade 5 that rotate reversely to each other in the developing device.

  The developer 10 on the rollers 1 and 2 whose transport amount is regulated by the doctor blade 5 is transported in the direction of the photosensitive member by the rotation of the sleeve and the magnetic force generated by the magnetic poles arranged on the downstream side. Therefore, the heads of the magnetic poles are conveyed while exhibiting a behavior in which the heads extend in the direction of the magnetic poles.

  At this time, if the rotation speed of the developing roller is increased in order to perform high-speed printing, the centrifugal force acting on the developer increases and scatters away from the sleeve.

  At this time, when only the toner in the developer is scattered, a so-called toner cloud is generated in a space sandwiched between both rollers, which may cause adhesion (fogging) to the background, which is a problem in image quality. Become. On the other hand, the toner cloud in this gap also has the effect of increasing the development performance. Therefore, if the toner cloud is blocked from being generated or reaching the photoreceptor, the development performance will be impaired. . When the rotation speed of the developing roller increases, not only the toner but also the carrier is scattered.

  Since the carrier is attracted to the sleeve by the magnetic force, the carrier is scattered when the centrifugal force exceeds the magnetic force. As described above, since the carrier rises at the magnetic pole position, the centrifugal force becomes larger at the tip of the ear, and the magnetic force becomes smaller, so that the carrier is easily scattered.

  In the case of the system in which the developer for the two developing rollers is carried by the lower developing roller and the developer is distributed after passing through the closest part of the roller, the amount of the developer conveyed before the distribution increases, Although it is easy to cause a problem that it is scattered and cannot be transported well, scattering is less likely to occur in the method of transporting the closest part after regulating the transport amount of both rollers in front of the closest part as shown in this figure.

  However, as a result of the examination, even in the above-described method, when the peripheral speed of the developing roller exceeds 1200 mm / s, even after the conveyance amount is properly adjusted, the conveyance magnetic pole (S1 pole in the figure) It was found that carrier scattering began to occur.

  As shown in FIG. 6B, the scattered carrier collides with the photosensitive member almost perpendicularly at the gap between the two rollers due to the structure of the center feed development.

  For this reason, as shown in FIG. 7, the moving direction of the collided developer after the collision becomes indefinite, and the amount of developer conveyed to the developing sections of both rollers fluctuates.

  Further, when the developer collides with the photosensitive member in this way, a large amount of toner is separated from the carrier by a strong impact, the carrier adheres to the photosensitive member by a large counter charge, and the developing unit is moved by the rotation of the photosensitive member. It has been found that even if it passes, it is not collected by the developing roller, and image quality defects increase, or fog increases rapidly due to a large amount of toner cloud at the time of collision.

  It is an object of the present invention to obtain high print density even at a very high printing speed in which the developing roller is rotated at a speed exceeding 1200 mm / s, and to achieve high-quality printing without uneven print density and carrier skipping over a long period of time. It is an object of the present invention to provide a center feed developing device and an image recording apparatus using the same, which can maintain and do not cause problems such as carrier adhesion.

An object of the present invention has at least two developing rollers having a pivotally arranged sleeve roller magnet outer periphery, the development of two-component developer on the developing roller into contact with the electrostatic image bearing member And at least one pair of the developing rollers is disposed adjacent to a developing roller that rotates in the opposite direction and the same direction as the moving direction of the electrostatic image carrier, and the pair of rotating rollers that rotate in the opposite direction. A developing roller that performs development first on the electrostatic image carrier among the rollers conveys developer in contact with the electrostatic image carrier in a direction opposite to the moving direction of the electrostatic image carrier, In a developing device that has a conveyance amount regulating member adjacent to each developing roller that rotates in the opposite direction and regulates the amount of developer conveyed to each roller before the developer passes through the closest part of both rollers, static from the closest part of both roller A position close to the image carrier, the flying direction of the carrier scattered from the developing roller, the entry angle to the electrostatic image bearing member, deflection means for deflecting to be shallower than perpendicular to the electrostatic image holding member surface This can be achieved by providing

  According to the present invention, there is no occurrence of problems such as fluctuations in transport amount and carrier adhesion, and high-density development using a powder cloud can be realized with a very fast printing degree, and high-quality printing can be maintained over a long period of time. It is possible to provide a center feed developing device that can perform the above and an image recording device using the same.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is an enlarged schematic view of a part of a developing device according to an embodiment of the present invention.

  This embodiment relates to a developing device 104 in which three developing rolls 1, 2, and 3 are installed to face the photoreceptor 101.

  Among the three developing rolls 1 to 3, the developing roll 1 is 1.1 to 2 times the peripheral speed of the photoconductor 101 in the same direction as the rotation direction of the photoconductor 101 indicated by an arrow A in FIG. The developing rolls 2 and 3 rotate at a peripheral speed 1.1 to 2.0 times the peripheral speed of the photoconductor 101 in the direction opposite to the rotation direction of the photoconductor 101. .

  In the present embodiment, a developing device having three developing rolls will be described. For example, two developing rollers 1 and 2 or a plurality of developing rollers 1 upstream of the developing roller 1 in the rotation direction of the photoconductor 101 are used. It is also possible to have a configuration having a plurality of developing rolls or a configuration having a plurality of developing rolls downstream of the developing roll 3 in the rotation direction of the photoconductor 101.

  A doctor blade 5 is disposed between the developing roll 1 and the developing roll 2, and the doctor blade 5 is configured to regulate the amount of developer transported by the developing rolls 1 and 2 at both ends of one blade (hereinafter referred to as a double-edged doctor). It is called.)

  In this embodiment, a carrier having an average particle diameter of 65 μm or less and a saturation magnetization of 45 emu / g or more can be used. The toner 11 is mixed in a weight ratio of 3 to 10% of the total weight of the developer. Since the developer 10 consumes only the toner 11 in the developer 10 by the printing operation of the recording device, the weight ratio of the toner in the developer in the developing device 104 decreases. For this reason, in the developing device 104 of this embodiment shown in FIG. 1, the mixing and stirring member 7 such as a cross mixer that mixes and stirs the toner 11 supplied from the toner supply device 105 into the developing device 104 with the developer 10, A conveying member 6 such as a magnet roller for conveying the developer to the developing roller, and a developer guide plate 8 are installed.

  The toner 11 in the developer 10 is agitated and conveyed by the conveying members 7 and 8, and thus rubs against the carrier 12 and the like in the developer 10 and is charged to a predetermined value between −10 and −40 μc / g. The developer 4 adjusted to a predetermined toner weight ratio and a predetermined charge amount in this way is guided to the vicinity of the developing roll 3.

  The developing rollers 1 to 3 are provided with magnets fixed inside and provided with rotatable sleeves on the outer periphery. The magnetic pole at the position facing the photoconductor 101 has a saturation magnetic flux density of 0.11 T on the sleeve surface, and the other poles have a magnetic force of about 0.04 to 0.06 T. The developer 10 conveyed to the vicinity of the developing roll 3 is attracted to the sleeve surface of the developing roller 3 by the magnetic force of the magnet, and is conveyed to the magnetic pole at a position facing the doctor blade 5 by the rotation of the sleeve.

  Here, the developer 10 is regulated to a predetermined amount that occupies a volume ratio of 20 to 40% with respect to the volume of the developing portion in the developing portion in contact with the photosensitive member 101 of the developing roll 2 at the restricting position of the doctor blade 5. Then, it is guided to the developing unit.

  The surplus developer due to the passage amount regulation by the doctor blade 5 is conveyed in the direction of the developing roller 1 as the sleeve rotates, and is regulated to a predetermined amount at the regulation position of the doctor blade 5 in the same manner as the developing roller 2. Then, it is guided to the developing section of the developing roll 1.

  In the developing part of the developing rolls 1 and 2, the developer 10 rises by the magnetic pole, and the developing roll 1 develops in the direction opposite to the moving direction of the photoreceptor surface, and the developing roll 2 develops in the same direction as the moving direction of the photoreceptor surface. The agent 10 moves and rubs the surface of the light body. Thereafter, the developer 10 is transferred to the developing roller 3, developed by sliding on the surface of the photosensitive member, and then separated from the developing roller 3 and stirred in the axial direction by the cross mixer 7 and flows in the vicinity of the conveying member 6. Go.

  A developing bias voltage is applied to the developing rolls 1 to 3, and in this embodiment, a voltage of −400 V is applied to the developing rollers 1 to 3.

  The doctor blade 5 is provided with a scattering carrier deflection member on the side close to the photosensitive member 101, and FIG. 2 shows the doctor blade having the scattering carrier deflection member. In this embodiment, an inclined portion (scattering carrier deflection portion) having an angle α with respect to the center line of the doctor blade 5 is provided on the side of the doctor blade 5 that is close to the photosensitive member 101.

  When the peripheral speed of the developing roller is 1200 mm / s or more, if this deflection member is not provided, the carrier scattered at the magnetic pole S1 portion collides with the surface of the photosensitive member almost perpendicularly while receiving inertial force and magnetic force. By providing this deflecting member, the scattered carrier first collides with the inclined portion of the deflecting member at a shallow angle to change the traveling direction, and collides with the photoconductor at an angle θ.

  The angle α of the deflecting member is set to an appropriate angle depending on the installation position of the deflecting unit, etc., but the angle θ is smaller and the impact angle becomes shallower than the carrier colliding angle to the photoconductor when the deflecting plate is not provided. Set to an angle.

  Further, the deflecting unit is not brought into contact with the developer that is transported between the magnetic poles without scattering on the sleeve roller, and does not function as a transport amount regulating unit.

  Therefore, the scattered carrier collides with the photosensitive member at a shallow angle and in the vicinity of the developing unit after a small amount of toner cloud is generated by the collision at the deflecting unit as compared with the case of colliding with the photosensitive member almost perpendicularly. As a result, when the toner collides with the photosensitive member with a strong force, the toner peels off and a large counter charge is generated, so that a strong electrostatic adhesion force does not work, and the adhered carrier can be easily collected by the developing unit.

  Further, the toner cloud can be appropriately generated in an area close to the developing portion, and the developing performance can be improved without increasing the fog.

  FIG. 3 shows a deflecting member used in another embodiment of the present invention. FIGS. 7A and 7B show an example in which a scattering carrier deflecting member 20 is provided independently of the doctor blade 5, and FIG. 10C shows a scattering carrier deflecting member 20 which is a member different from the doctor blade 5, as shown in FIG. An example fixed to 5 is shown. Each scattering carrier deflecting member 20 includes a deflecting portion that is widened toward the photosensitive member 101 at an angle α with respect to the center line of the doctor blade 5. The scattering carrier deflecting member 20 is made of a nonmagnetic or magnetic material, and preferably made of aluminum, a metal such as SUS304 or SUS303, or a polymer material such as polypropylene or polyamide.

  FIG. 4 is a schematic configuration diagram showing an embodiment of an image recording apparatus using the developing device of the present invention. After the photoreceptor 101 is charged by the charger 102, image information is written by laser exposure by the exposure device 103 to form an electrostatic latent image. After the electrostatic latent image is developed by the developing device 104, the image is transferred to the paper 200 by the transfer device 107, and the image is fixed on the paper 200 by the fixing device 108. The toner remaining on the photosensitive member 101 is cleaned by a cleaner 106.

  By using the developing device of the present invention, the peripheral speed of the developing roller can be used at 1200 mm / s or more, and even when recording is performed at a recording speed of 1500 mm / s or more, the print density is high, carrier adhesion, etc. High-quality printing can be performed over a long period of time without any problems.

  In addition to image recording apparatuses such as electrophotographic printers and copiers using a magnetic developer, the present invention can also be applied to apparatuses that magnetically convey magnetic powder.

1 is a schematic configuration diagram of a developing device according to an embodiment of the present invention. It is the figure which expanded a part of the developing device. It is the figure which showed the scattering carrier deflection | deviation member concerning other embodiment of this invention. 1 is a schematic configuration diagram of an image recording apparatus using a developing device according to an embodiment of the present invention. It is a schematic block diagram of the conventional developing device. It is a figure for demonstrating scattering of a carrier. A diagram explaining the flying state of a flying carrier

Explanation of symbols

1, 2: 3, developing roller, 5: doctor blade, 10: developer, 11: toner, 6: conveying member, 7: mixing and stirring member, 105: toner storage and supply device, 101: photoconductor, 104: developing device

Claims (4)

The developing roller has at least two developing rollers including a sleeve roller rotatably disposed on the outer periphery of the magnet, and the two-component developer on the developing roller is brought into contact with the electrostatic image carrier to perform development. At least a pair of the rollers is arranged adjacent to a developing roller that rotates in the opposite direction and the same direction as the moving direction of the electrostatic image carrier, and the electrostatic image of the pair of rollers rotating in the opposite direction. A developing roller that performs development on the carrier first conveys the developer in contact with the electrostatic image carrier in a direction opposite to the moving direction of the electrostatic image carrier, and the pair of rollers rotate in opposite directions. In a developing device that has a conveyance amount regulating member adjacent to the developing roller and regulates the amount of developer conveyed to each roller before the developer passes through the closest part of both rollers,
The closer to the electrostatic image bearing member from the closest portions of the rollers, the flight direction of the carrier scattered from the developing roller, the entry angle to the electrostatic image bearing member, perpendicular to the electrostatic image holding member surface developing apparatus is characterized in that a deflection means for deflecting to be shallower than.   2. The developing device according to claim 1, wherein the deflecting unit is configured to be integrated with a conveyance amount regulating member. The deflecting means is independent of the transport amount regulating member, and the deflecting means for deflecting the entrance angle to the electrostatic image carrier to be shallow is a constant angle with respect to the center line of the transport amount regulating member. 3. The developing device according to claim 1, wherein the developing device is arranged so as to form the following.   An image recording apparatus using the developing device according to any one of claims 1 to 3.

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