JP2007047640A - Developing device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a developing device (102) which achieves stable conveyance of developer (4) and eliminates print defects such as image density irregularities when pole-on bristle cutting development in which a regulating member (3) for the developer (4) is arranged so as to face magnetic poles is used in a fountain type developing device, and even when the pole-on bristle cutting development is used in a full color printer in which a high developer conveying property is required and a printer having a high printing speed. <P>SOLUTION: In the developing device, the pole-on bristle cutting development is configured so that the regulating member (3) faces the magnets of a pair of adjacent developing rolls (1 and 2), the contact surface (X1) of the regulating member (3) with the developer (4) is placed to be inclined toward the side of an image carrier (101) at an angle of 5 to 20 degrees with respect to a vertical direction, and the surface roughness Rmax of the contact surface (X1) is 20μm or less or the static friction coefficient of the contact surface (X1) is 0.2 or less. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a developing device such as an electrophotographic printer or a copying machine provided with a plurality of developing rolls for supplying and conveying a developer to an image carrier.

  In an image recording apparatus such as an electrophotographic printer or copying machine, an image visualization agent called toner is supplied from a developing device to an electrostatic latent image formed on an image carrier called a photoconductor that rotates in one direction. Then, the electrostatic latent image is visualized and a toner image is printed on the recording paper.

  As a developing device applied to the electrophotographic system, a developing device using a two-component developer composed of toner and a magnetic powder called a carrier is widely used, and the two-component developer is stirred in the developer container. By doing so, the toner in the developer and the carrier are rubbed with each other, and each is used by being charged to a predetermined amount.

  The developer charged to a predetermined charge amount is guided from the developer accommodating portion to a developing sleeve comprising a developing sleeve and a plurality of magnetic poles fixed inside the developing sleeve. The developer supplied to the surface of the developing roll is held in a magnetic brush state, conveyed by the rotation of the developing roll, and passed through a regulating member called a doctor blade disposed in the vicinity of the outer periphery of the developing roll, and then the image. It is transported to a development area which is a portion facing the carrier.

  Various configurations have been proposed for the developing device using such a two-component developer. However, particularly in a high-speed process at a process speed of 300 mm / s or more, the developing capability of the electrostatic latent image is insufficient. As a method for increasing the developing ability, a hybrid developing device is used.

  The hybrid developing device has a configuration in which a plurality of developing rolls having different rotation directions are provided to face an image carrier. In the following description, for the sake of convenience, the expressions “forward rotating developing roll” and “reverse rotating developing roll” will be used in describing the hybrid developing device. Here, the “forward rotation developing roll” means a developing roll that rotates counterclockwise when the image carrier rotates clockwise. That is, when viewed in the development area, the forward development roll has the same moving direction. On the other hand, the “reverse rotation developing roll” means a developing roll that rotates in the same clockwise direction when the image carrier rotates in the clockwise direction. That is, when viewed in the development area, the reverse rotation developing roll has the opposite movement direction.

  In a configuration in which a forward rotation developing roll and a reverse rotation developing roll are combined, a reverse rotation developing roll is installed on the upstream side in the rotation direction of the image carrier, and a forward rotation developing roll is installed adjacent to the downstream side, and the reverse rotation is performed. A developing device having a configuration in which a double-blade regulating member is disposed between the developing roll and the forward rotating developing roll is particularly called a fountain type developing device. As described above, this fountain-type developing device has a high developing ability, is less likely to cause image trailing edge chipping, chipping chipping, and the like caused by the rotation direction of the developing roll, and the regulating member has a double-edged blade. Since one is sufficient, there is an advantage that the developing device can be made compact.

  In particular, in the case of a high-speed color printing device, a tandem printing method having a plurality of printing systems is often used, and further, the developing device needs to be made compact, so the fountain type developing device is used, The developing roll is often arranged in the vertical direction.

  The restricting member is installed for the purpose of cutting off the magnetic brush of the developer held on the surface of the developing roll and maintaining the developer conveyed to the developing region in an appropriate amount. The developer regulated to a predetermined amount by the regulating member is conveyed by the rotation of the developing roll and is carried to a position (developing area) facing the image carrier, and the developer on the developing roll is transferred to the image carrier in the developing area. The electrostatic latent image is developed while in contact with. At this time, a bias voltage for introducing and supplying only the toner to the image forming portion of the non-image portion and the image forming portion constituting the electrostatic latent image of the image bearing member is applied to the developing roll. A toner image is formed on the image forming unit.

  Conventionally, the regulating member in the fountain type developing device is generally set at a position between the magnetic poles of the developing roll. The reason for this is to improve the developer transportability on the developing roll. Further, it is considered that stress on the developer can be reduced by cutting the head at a position where the magnetic force is small.

  Since the magnetic brush formed on the developing roll is formed along the magnetic field lines, the magnetic pole facing portion is in a sparse state standing up in the normal direction of the developing roll. On the other hand, when the brush of the magnetic brush is cut between the magnetic poles, the gap between the magnetic poles is in a dense state lying along the outer peripheral surface of the developing roll. The fluctuation in the gap between the developing roll and the developing roll has a great influence on the transport development amount, and high accuracy is required for the adjustment accuracy of the doctor gap.

  In intercropping development, where the magnetic brush is trimmed between the magnetic poles, the line connecting the central axes of the two developing rolls and the side surface of the regulating member are installed substantially parallel to reduce the stress on the developer. Has been proposed (for example, Patent Document 1).

  On the other hand, when the regulating member is arranged so as to face the magnetic pole, the magnetic brush is trimmed in a sparse state standing in the normal direction of the developing roll, so even if the doctor gap is set relatively wide, There is a feature that the transport development amount can be reduced. A method has been proposed in which the influence of the gap adjustment error on the developer conveyance amount can be reduced by setting the doctor gap wide, and the thin layer uniform development can be realized more stably (see, for example, Patent Documents 2 and 3). .

  In recent years, with the need for higher image quality and colorization, thin layer uniform development that facilitates obtaining higher-definition images is desired, and reduction and uniformization of the developer transport restriction amount are required. To achieve this, the doctor gap was narrowed and the precision increased. Hereinafter, a developing method in which the regulating member is disposed so as to face the magnetic pole is referred to as the best spike cutting development.

  It is disclosed that the surface roughness Rz of the developing sleeve of the two-component developing device is set to 5 to 20 μm in order to suppress a decrease in the developer pumping amount and to transport a stable amount of developer to the developing region. (For example, see Patent Document 4).

JP 2000-227709 A

JP-A-53-77530

JP-A-63-24268

JP 2003-228240 A

  However, since the above-mentioned top cutting development regulates the developer conveyance amount in a sparse state standing in the normal direction of the developing roll, it is difficult to ensure the uniformity of the standing developer, and the magnetic pole distribution of the regulating member The device has been made to make it wider.

  Furthermore, in a high-speed printing process (for example, a process speed of 300 mm / s or more), high-speed conveyance of the developer is required, but in the superb spike development, the magnetic force lines at the regulating member portion are in the normal direction of the developing roll, Compared to the inter-magnetic pole cutting, the developer conveying ability in the developing roll rotation direction is reduced. In particular, in a fountain type developing device arranged in a vertical direction, the developer is transported so as to rise from a forward rotating developing roll installed below to a reverse rotating developing roll installed above, so that the higher Transportability is required.

  In the case of adopting the best panicle development in the fountain type developing device in which the developing roll is arranged in the vertical direction, the supply of the developer to the counter-rotating developing roll installed above becomes unstable due to insufficient transport force. In addition, image quality deterioration such as uneven printing density has been caused.

  Further, when a developer having low fluidity is used, there is a problem that the developer is easily clogged at the doctor gap portion.

  In the present invention, a plurality of developing rolls for supplying and transporting a developer to an image carrier that is rotatably supported are disposed in a vertical direction, and at least one pair of the developing rolls is a rotation of the image carrier. A reverse rotation developing roll that rotates in a direction opposite to the direction of rotation, and a forward rotation developing roll that rotates in the same direction as the rotation direction of the image carrier, and is developed at a position facing the magnets of the reverse rotation developing roll and the forward rotation developing roll. In a developing device including a regulating member that regulates the transport amount of the agent, an angle of contact between the regulating member and the developer that contacts the developer is 5 ° to 20 ° with respect to a vertical direction toward the image carrier. It is characterized by being inclined.

  The contact surface has a surface roughness Rmax of 20 μm or less.

  Further, the static friction coefficient of the contact surface is 0.2 or less.

  According to the present invention, in the developing device in which the forward rotation developing roll and the reverse rotation developing roll are arranged in the vertical direction and the restriction member is disposed to face the magnetic poles of the forward rotation developing roll and the reverse rotation developing roll, the restriction By installing the member at an angle of 5 ° to 20 ° and inclining toward the image bearing body, the regulated amount of developer at the doctor gap is stabilized, and developer transportability can be stably maintained. Therefore, even in a full-color printing apparatus that requires a high printing density or a printing apparatus that has a high printing speed, it is possible to prevent printing defects such as image density unevenness due to variations in the developer conveyance amount in the doctor gap portion.

In the present invention, for the purpose of ensuring the developer transport performance in the superb panicle development in which the developer transport performance is lowered, the side surface of the regulating member is set at an appropriate angle with respect to the vertical direction regardless of the position of the developing roll ( It is characterized in that it is inclined toward the image carrier at a large angle. The following examples illustrate embodiments of the present invention.
[Example 1]
One embodiment of the present invention will be described with reference to FIGS. FIG. 1 is a schematic view of a fountain-type developing device 102 that uses super-high-cut development that is a form of an embodiment of the present invention, and FIG. 2 is a view of a regulating member portion of the fountain-type developing device used in Embodiment 1. It is an enlarged view.

  In the present embodiment shown in FIG. 2, the reverse rotation developing roll 1 and the forward rotation developing roll 2 face the photoconductor 101 as an image carrier, and both developing rolls (1 and 2) overlap in the vertical direction. This relates to the developing device 102 installed as described above.

  The reverse rotation developing roll 1 rotates in the direction indicated by the arrow E and the forward rotation developing roll 2 rotates in the direction indicated by the arrow F with respect to the rotation of the photosensitive member 101 indicated by the arrow A in the drawing.

  In this embodiment, the drum-shaped photoconductor 101 is used as the image carrier. However, for example, a configuration like a photoconductor belt that circulates on a specific track may be used.

  In the developing device 102, a doctor blade 3 as a regulating member is disposed between the reverse rotation developing roll 1 and the forward rotation developing roll 2.

  The developer 4 as an image visualization agent is composed of a positively charged magnetic carrier and a negatively chargeable nonmagnetic toner 5 called a powder that forms a visible image on the photoconductor 101 and has a total weight. The toner 5 is mixed in a weight ratio of 2 to 10%. Since only the toner 5 of the developer 4 is consumed by a printing operation (not shown), the toner weight ratio of the developer 4 in the developing device 102 is reduced. For this reason, in the developing device 102 of this embodiment, mixing stirring members 7 and 8 for mixing and stirring the toner 5 supplied from the toner storage and supply device 9 into the developing device 102 and the developer 4 are installed. The mixing and agitating members 7 and 8 are in the form of spiral screws, and the developer 4 is agitated and mixed by rotating in the direction of arrow C or D in the figure. In addition, the toner 5 is frictionally charged with the carrier in the developer 4 by being conveyed and stirred by the mixing and stirring members 7 and 8, and is charged to a predetermined value. In this embodiment, the charge amount of the toner 5 is −10 μC / g to −30 μC / g.

  As described above, the developer 4 containing the toner 5 charged to a predetermined charge amount further rotates the conveying member 6 in the direction of the arrow B, so that the upper side of the conveying member 6 is changed from right to left (mixed) in the drawing. It is conveyed from the stirring member 7 side to the forward rotation developing roll 2 side) and guided to the vicinity of the forward rotation developing roll 2. At this time, as shown in FIG. 2, the reverse rotation developing roll 1 and the forward rotation developing roll 2 are fixedly installed with magnets 20 and 21 magnetized with N and S poles alternately. Rotating sleeves 22 and 23 are provided on the outer peripheral portions of the roll 1 and the forward rotation developing roll 2. For this reason, the developer 4 in the vicinity of the forward rotation developing roll 2 is conveyed to the doctor blade 3 by the magnetic force of the magnet 21 as the sleeve 23 rotates.

  Thereafter, the developer 4 is diverted at the tip of the doctor blade 3, and a part thereof is conveyed to the forward rotation developing roll 2, and the other is conveyed to the reverse rotation developing roll 1 adjacent to the upper side. It passes through the doctor gap G1 formed by the doctor blade 3 or the doctor gap G2 formed by the forward rotation developing roll 2 and the doctor blade 3. At this time, the developer 4 is given by the passage amount restriction in the doctor blade 3. The amount is regulated and guided to the developing section of each developing roll (1 or 2). Further, the doctor blade 3 is made of a non-magnetic material (SUS material) having a blade shape at both ends.

  The developer 4 guided to the developing unit rubs the surface of the photoconductor 101 and forms a toner image corresponding to the electrostatic latent image formed on the surface of the photoconductor 101 by a charging and exposure process (not shown). In the developing unit, the photosensitive member 101 and the counter-rotating developing roller 1 are opposed to each other with a developing gap G3, and the photosensitive member 101 and the forward rotating developing roller 2 are opposed to each other with a developing gap G4.

  Thereafter, the visible toner image on the photosensitive member 101 is printed on a sheet by a transfer process (not shown) and then fixed on the sheet by a fixing process (not shown).

  In the series of printing operations as described above, in order for the developing device 102 to obtain a predetermined developing performance, the flow of the developer 4 to the reverse rotating developing roll 1 and the forward rotating developing roll 2 in the doctor blade 3 and the doctor gap ( It is important that the passage amount regulation in the G1 or G2) portion is performed stably, and this method will be further described with reference to FIG.

  In the present invention, the doctor blade 3 faces the magnetic pole N2 (peak magnetic force: about 0.045T) of the reverse rotation developing roll 1 and also faces the magnetic pole N3 (peak magnetic force: about 0.045T) of the forward rotation developing roll 2. In addition, the developer 4 of the doctor blade 3 is diverted and the angle θ1 of the scooping angle of the contact surface X1 to be conveyed is set to 5 °. Here, the angle θ1 of the scooping angle is an angle that the surface of the doctor blade 3 in contact with the developer 4 makes a perpendicular line, and has an inclination on the photosensitive member 101 side.

  Further, the surface of the contact surface X1 has a mirror finish, and the surface roughness Rmax is 5 μm as measured by a stylus type surface roughness meter (manufactured by Mitutoyo Corp., Surf Test SV-624). It was. The static friction coefficient was 0.2. The static friction coefficient was measured with a tilt type static friction coefficient measuring machine manufactured by Trinity Lab.

  As described above, the developer regulating position by the doctor blade 3 is set at the magnetic pole position of the reverse rotation developing roll 1 and the forward rotation developing roll 2, and the developing device 102 in which the polarities of the opposing magnetic poles are the same polarity is used as the high speed printing apparatus ( The result of examining the development characteristics by carrying out a continuous printing experiment with a printing pattern of high printing density mounted on a process speed of 500 mm / sec is described below.

  Each setting condition at the time of the printing experiment is as follows.

<Setting conditions>
Photoconductor 101: OPC drum (outer diameter: φ100 mm), peripheral speed 500 mm / sec
・ Developing sleeves 22 and 23: outer diameter φ40 mm, peripheral speed 600 mm / sec
・ Doctor gap G1: 0.6mm
・ Doctor gap G2: 0.6mm
・ Development gap G3: 0.5 mm
・ Development gap G4: 0.5 mm
・ Vease angle angle θ1: 5 °
Developer 4: Carrier average particle diameter: 60 μm,
Toner average particle size: 7 μm
Toner mixing ratio: 2.5 wt% (black toner)
-Printing pattern: 1 inch square solid patch (printing density: 100%)
50% halftone (print density: 50%)
FIG. 3 shows the image density measurement results for solid printing (printing density 100%) and 50% halftone printing when 3000 pages of continuous printing experiments were performed under the above printing conditions. The image density is an average O.D. D. 1.2 (density variation is ± 0.1 or less), 50% halftone image with an average O.D. D. Was as good as 0.8 (concentration fluctuation was ± 0.08 or less). In addition, there was no clogging at the doctor gaps G1 and G2 of the developer 4 even in continuous printing of 3000 pages. Furthermore, the doctor blade 3 can be installed easily and accurately, and the supply of the developer 4 to the doctor gaps G1 and G2 can be made smooth.
[Example 2]
The doctor blade 3 is installed so as to face the magnetic pole N2 (peak magnetic force: about 0.045T) of the reverse rotation developing roll 1 and also to face the magnetic pole N3 (peak magnetic force: about 0.045T) of the forward rotation developing roll 2. In addition, the angle θ1 of the creeping angle of the contact surface X1 was set to 20 °.

  The surface of the contact surface X1 has a mirror finish, and the surface roughness Rmax is 20 μm. The coefficient of static friction was 0.2.

A developing device in which the developer regulating position by the doctor blade 3 as described above is installed at the magnetic pole position of the reverse rotation developing roll 1 and the forward rotation developing roll 2 and the opposite magnetic pole polarities are the same as in the first embodiment is the same. FIG. 4 shows the measurement results of the image density of solid printing (printing density 100%) and 50% halftone printing when mounted on a high-speed printing apparatus and subjected to continuous printing experiments under the same printing conditions. The image density is an average O.D. D. Is 1.2 (the variation in density is ± 0.08 or less), and a 50% halftone image has an average O.D. D. Was 0.8 (concentration fluctuation was ± 0.06 or less), and a better result was obtained. Further, it was confirmed that the developer was transported stably without any clogging of the developer 4 even in continuous printing of 3000 pages.
[Example 3]
The doctor blade 3 is installed so as to face the magnetic pole N2 (peak magnetic force: about 400 gauss) of the reverse rotation developing roll 1 and also to face the magnetic pole S1 (peak magnetic force: about 400 gauss) of the forward rotation developing roll 2, In addition, the angle θ1 of the narrow angle of the contact surface X1 was set to 10 °.

  The surface of the contact surface X1 has a mirror finish, and the surface roughness Rmax is 10 μm. The coefficient of static friction was about 0.2.

  This developing apparatus is mounted on the same high-speed printing apparatus as in Example 1, and the image density measurement results of solid printing (printing density 100%) and 50% halftone printing when a continuous printing experiment is performed under the same printing conditions. Is shown in FIG. The image density is an average O.D. D. Is 1.2 (the density variation is ± 0.09 or less), and the average O.D. D. Was 0.8 (concentration fluctuation was ± 0.07 or less), and good results were obtained. Further, it was confirmed that the developer was transported stably without any clogging of the developer 4 even in continuous printing of 3000 pages.

  By setting the angle θ1 of the scooping angle to 5 ° to 20 ° as described above, even when adopting the top panning development in which the transportability is difficult to obtain in the fountain type developing device in which the developing roll is installed in the vertical direction, The transfer of the developer 4 from the forward rotation developing roll 2 to the upper reverse rotation developing roll 1 is facilitated, and the transport amount of the developer 4 in the doctor gap G1 or G2 portion is stabilized, resulting in image density unevenness and the like. The occurrence of poor image quality can be prevented.

  If the angle θ1 of the crawl angle is smaller than 5 °, it is difficult to obtain the effect of improving the transportability of the developer 4 due to the inclination, and if the angle θ1 of the crawl angle is larger than 20 °, an excessive transport amount For this reason, the developer 4 tends to accumulate in the doctor gap G1 portion of the upper reverse rotation developing roll 1, and clogging failure of the doctor gap G1 portion occurs.

  Further, as described above, the surface roughness Rmax of the contact surface X1 is set to 20 μm or less, or the static friction coefficient of the contact surface X1 is set to 0.2 or less, so that the slip of the developer 4 on the surface of the doctor blade 3 is further improved. And stable transportability of the developer 4 can be maintained for a long time. When the surface roughness Rmax is larger than 20 μm or when the static friction coefficient is larger than 0.2, the developer 4 tends to adhere to the surface of the doctor blade 3 due to its surface properties, and the transportability is lowered.

  According to the present invention, in the fountain type developing device using the forward rotation developing roll 1 and the reverse rotation developing roll 2 arranged in the vertical direction, the angle θ1 of the scooping angle of the doctor blade 3 is set to 5 ° to 20 °. As a result, the installed doctor blade 3 faces the magnetic poles of the adjacent developing rolls (forward rotating developing roll 1 and reverse rotating developing roll 2), so that it is difficult to obtain a stable transport of the developer 4. Even in this case, stable developer transportability can be maintained, and the regulated amount of developer in the doctor blade 3 part is also stabilized. Therefore, even in a full-color printing apparatus that requires a high printing density or a printing apparatus that has a high printing speed, printing defects such as uneven image density due to variations in the transport amount of developer 4 in the doctor gaps G1 and G2 can be prevented. .

  Furthermore, the installation conditions of the doctor blade 3 and the surface conditions thereof are particularly effective in an image forming apparatus having a process speed of 300 mm / sec or more that requires high developer transportability.

  In addition, when the doctor blade 3 installed in the fountain-type developing device faces the magnetic poles of the adjacent developing rolls (1 and 2) and the opposing magnetic poles of both developing rolls are set to different polarities, the doctor blade 3 faces the doctor blade 3. The magnetic force is transferred between the magnetic poles of the two developing rolls (forward rotating developing roll 1 and reverse rotating developing roll 2), and a stable magnetic field is distributed in the normal direction of the developing roll in the doctor gaps G1 and G2. As a result, it becomes difficult to maintain the transportability of the developer 4, and the present invention for improving the transportability of the developer becomes more effective.

1 is a schematic configuration diagram of a developing device according to an embodiment of the present invention. FIG. 3 is an enlarged view of the vicinity of a regulating member used in Example 1. 3 is a graph showing an image density measurement result of an image printed by the developing device of Example 1. 6 is a graph showing an image density measurement result of an image printed by the developing device of Example 2. 10 is a graph showing an image density measurement result of an image printed by the developing device of Example 3.

Explanation of symbols

1: Reverse rotation developing roll 2: Forward rotation developing roll 3: Doctor blade 4: Developer 5: Toner 6: Conveying member 7: Mixing stirring member 8: Mixing stirring member 101: Photoconductor 102: Developing device

Claims (3)

  A plurality of developing rolls for supplying and transporting the developer to the image carrier that is rotatably supported are arranged in a vertical direction, and at least one pair of the developing rolls is opposite to the rotation direction of the image carrier. A reverse rotation developing roll that rotates in the same direction and a forward rotation developing roll that rotates in the same direction as the rotation direction of the image carrier, and the amount of developer transported to a position facing the magnet of the reverse rotation developing roll and the forward rotation developing roll In the developing device having a regulating member that regulates the angle, the angle of the contact surface of the regulating member that contacts the developer is inclined toward the image carrier at an angle of 5 ° to 20 ° with respect to the vertical direction. A developing device.   The developing device according to claim 1, wherein a surface roughness Rmax of the contact surface is 20 μm or less. The developing device according to claim 1, wherein a static friction coefficient of the contact surface is 0.2 or less.

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