JP4532942B2 - Developing device and image forming apparatus having the same - Google Patents

Description

  The present invention relates to a developing device used in an image forming apparatus such as a printer, a copying machine, a facsimile machine, and a printing apparatus, and an image forming apparatus including the developing device.

  Patent Documents 1 to 5 describe the following contents as developing devices corresponding to speeding up of image forming apparatuses such as printers, copying machines, facsimile machines, and printing machines.

  Japanese Patent Application Laid-Open No. 2004-228561 describes a technique that uses a plurality of developing sleeves (developer carriers) using a two-component magnetic brush.

  Japanese Patent Application Laid-Open No. H10-228561 describes a technique in which the distance from the photosensitive member is made closer to the developing sleeve on the downstream side so that the toner supply amount from the developing sleeve is made uniform.

  Japanese Patent Application Laid-Open No. H10-228561 describes the downsizing of a developing device having a plurality of developing sleeves.

  Patent Documents 4 and 5 describe the magnetic force of a plurality of developing sleeves using a two-component developer.

JP-A-3-204084 JP-A-2-188778 Japanese Patent Publication No. 3-5579 Japanese Patent Laid-Open No. 9-80919 Japanese Patent No. 3017514

  However, the developing devices described in Patent Documents 1 to 5 have the following problems (1) to (3).

  (1) Development in which a plurality of developing sleeves are arranged close to each other in a developing method using a magnetic one-component developer, and the upstream developing sleeve also serves as a developer (toner) layer thickness regulating member of the downstream developing sleeve In the apparatus, although it is space-saving and small, unlike conventional two-component development using a carrier, it is difficult to uniformly coat the developer.

  In particular, replenishment system development devices that replenish the developer as needed instead of the cartridge system and development devices that use multiple development sleeves are suitable for high-speed machines, but when higher speeds are required There were problems with durability and stability.

  (2) In a high-speed machine, toner deterioration is likely to occur due to temperature rise and mechanical share associated with high-speed rotation of a developing sleeve that is in durability, and as a result, density reduction and image quality deterioration in durability are caused.

  (3) Recently, environmental measures have been demanded, and it has become necessary to reduce toner consumption in order to reduce waste.

  Accordingly, the present invention is a developing device that performs development using a magnetic one-component developer, in which a plurality of developer carriers are arranged close to each other, and an upstream developer carrier is a downstream developer carrier. In the developing device that also serves as a developer layer thickness regulating member of the body, a developing device capable of realizing a uniform and stable coating of the developer on the upstream developer carrying member, maintaining a high image quality and a stable density, and An object of the present invention is to provide an image forming apparatus provided with this.

  Another object of the present invention is to reduce the consumption of developer in such a developing device and image forming apparatus.

  Furthermore, another object of the present invention is to provide a high-speed machine suitable for distributed small print-on-demand by making the developing apparatus and image forming apparatus space-saving and compact.

The present invention (the invention according to claim 1) is arranged so as to rotate in the same direction in the proximity of each other on the upstream side and the downstream side along the moving direction of the surface of the image carrier. An upstream developer carrier for developing an electrostatic latent image on a surface with a one-component developer and a downstream developer carrier, wherein the upstream developer carrier is the downstream developer carrier In the developing device that also serves as a developer layer thickness regulating member of
A first magnetic member disposed inside the upstream developer carrier;
A second magnetic member disposed inside the developer carrier on the downstream side,
The first magnetic member has a magnetic pole facing the developer carrier on the downstream side,
The second magnetic member includes a magnetic pole A that faces the image carrier, a magnetic pole B that faces the upstream developer carrier, and the rotation direction of the downstream developer carrier. Magnetic poles C and D having the same polarity disposed on the downstream side of the magnetic pole A and on the upstream side of the magnetic pole B and constituting repulsive poles,
The downstream side is continuously arranged so as to include a position where the magnetic force in the normal direction is maximum at a position facing the magnetic pole C and a position where the magnetic force in the normal direction is maximum at a position facing the magnetic pole D. developer carrying member facing the distance between the downstream side of the developer carrying member surface has a wall provided so as to be 0.5 to 3 mm,
It is characterized by that.

  According to the present invention, the developer can be uniformly and stably coated on the upstream developer carrying member, and the toner consumption can be suppressed while maintaining a high image quality and a stable concentration.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In addition, what attached | subjected the same code | symbol in each drawing has the same structure or effect | action, The duplication description about these was abbreviate | omitted suitably.

<Embodiment 1>
[Image forming apparatus]
FIG. 1 schematically shows a schematic configuration of a digital copying machine as an example of an image forming apparatus to which the present invention can be applied.

  The copying machine (hereinafter referred to as “image forming apparatus”) shown in FIG. 1 is supported by an image forming apparatus main body (not shown) so as to be rotatable in the direction of arrow R1 (hereinafter referred to as “image bearing member”). 1). Around the photosensitive drum 1, a primary charger 2 as a charging unit that uniformly charges the surface of the photosensitive drum 1 in almost the order along the rotation direction, and the charged surface of the photosensitive drum 1 is electrostatically exposed by exposure. An exposure device 3 as an exposure means for forming a latent image, a development device 4 as a development means for developing an electrostatic latent image as a toner image, a post charger 5 for charging the surface of the photosensitive drum 1 after development, and a photosensitive A transfer charger 6 as a transfer means for transferring the toner image on the drum 1 onto the recording material P, a separation charger 7 as a separation means for separating the recording material P after the toner image transfer from the photosensitive drum surface, and toner As a fixing means for fixing the toner image on the recording material P after being transferred by a cleaning device 8 as a cleaning means for cleaning the surface of the photosensitive drum 1 after image transfer and a feeding and conveying means (not shown). Fixing device When, are disposed. The developing device 4 described above is provided with a hopper 10 for supplying toner. Further, the developing device 4 includes two developing sleeves as developer (toner) carriers, that is, an upstream developing sleeve 11 and a downstream developing sleeve 12 along the rotation direction of the photosensitive drum 1 (the direction of the arrow R1). And have. In the following description, “upstream developing sleeve 11” is referred to as “first developing sleeve 11” and “downstream developing sleeve 12” is referred to as “second developing sleeve 12” as appropriate.

  In the image forming apparatus having the above-described configuration, a highly durable amorphous silicon (a-Si) photoreceptor having a diameter of 108 mm is used as the photosensitive drum 1. Amorphous silicon (a-Si) photoreceptors have positive charging characteristics. The photosensitive drum 1 is driven to rotate at a process speed (circumferential speed) of 470 mm / sec in the direction of arrow R1 by a driving means (not shown). As the recording material P, sheet-like paper (plain paper, coated paper, envelope, etc.) and a transparent film can be used. In the case where the A4-sized recording material P is passed vertically (attitude where the short side of the recording material P is directed in the transport direction), the throughput is approximately 90 sheets / min.

  The photosensitive drum 1 is uniformly charged to, for example, +450 V by the primary charger 2, and then subjected to image exposure at 600 dpi by the exposure device 3. The exposure apparatus 3 oscillates a laser beam modulated based on an image signal using, for example, a semiconductor laser as a light source. The oscillated laser light is polarized by a polygon mirror (not shown) that rotates at a constant rotation speed by a motor, passes through an imaging lens (not shown), is reflected by a folding mirror (not shown), and then is photosensitive. The drum 1 is raster scanned. The surface of the photosensitive drum 1 is subjected to this scanning (exposure) to remove the charge at the exposed portion and attenuated to, for example, +100 V, thereby forming an electrostatic latent image. The wavelength of the laser light is 680 nm.

  The electrostatic latent image thus formed on the photosensitive drum 1 is developed with a toner attached by the developing device 4 and developed as a toner image.

  Subsequently, the post charger 5 charges the toner image by flowing a differential current +100 μA (AC + DC), and weakens the attractive force between the photosensitive drum 1 and the toner image so that transfer and separation can be easily performed.

  The toner image on the photosensitive drum 1 is transferred by the transfer charger 6 to the recording material P that has been conveyed in the direction of arrow K by a feeding and conveying device (not shown). The recording material P after the toner image is transferred is separated from the surface of the photosensitive drum 1 by the separation charger 7.

  The photosensitive drum 1 from which the recording material P has been separated is not transferred to the recording material P, but the toner remaining on the surface (transfer residual toner) is removed by the cleaning device 8 and used for the next image formation.

  On the other hand, the recording material P separated from the photosensitive drum 1 is conveyed to the fixing device 9 where it is heated and pressurized to fix the toner image on the surface. Thereby, the image formation on one recording material P is completed.

  An outline of the developing device 4 used in the image forming apparatus described above, that is, the developing device 4 to which the present invention can be applied will be described.

The developing device 4 uses a plurality (two) of developing sleeves 11 and 12 to enable image formation at high speed. In the present embodiment, as the developing method of the developing device 4, black (which is a highly durable developing method that has a simple configuration and does not require maintenance of the developing sleeves 11 and 12 up to 2000k sheets (2,000,000 sheets) that has a lifetime. Development using a black magnetic one-component developer. The toner is a positive toner (positively charged toner) and has a weight average particle diameter of 8.0 μm. The resin is made of styrene acrylic resin and contains 90 parts by weight of a magnetic material. Moreover, 0.8% (weight%) SiO ₂ is coated as an external additive. In this embodiment, reversal development using a plurality of developing sleeves 11 and 12 is performed. When the toner near the stirring member 13a out of the stirring members 13a, 13b, and 13c in FIG. 2 runs out of toner, the controller 15 causes the controller 15 to send a new toner (new toner) of the hopper 10 according to a signal from the piezoelectric element 14. Toner) A signal for rotating the magnet roller 16 disposed at the bottom of the storage chamber 10 a is output, and the toner is supplied from the hopper 10 into the developing container 18 by the rotation of the magnet roller 16. Reference numeral 17 in the figure denotes a screw that conveys the toner in the new toner storage chamber 10 a along the longitudinal direction of the magnet roller 16. Reference numeral 19 denotes a magnetic blade as a developer (toner) layer thickness regulating member.

As the developing device 4, jumping development is performed by a magnetic one-component developing method. As described above, the developing device 4 has two developing sleeves, that is, a first developing sleeve 11 and a second developing sleeve 12 as a developer carrier. As shown in FIG. 3, the first developing sleeve 11 and the second developing sleeve 12 are arranged substantially vertically and rotate in the same direction, that is, in the directions of the arrows R11 and R12 , respectively.

  As shown in FIG. 4, the toner flow of the two-component development having a carrier receives the developer from the first developing sleeve 11 to the second developing sleeve 12 in the vicinity of the two developing sleeves 11 and 12. I am trying to pass it. That is, the developer is conveyed on the circumference of the developing sleeve facing the photosensitive drum 1. This is because in the two-component development, the toner is mainly charged by the carrier, so that the developing sleeves 11 and 12 need only be able to transport the developer.

  However, when the magnetic one-component toner whose developing sleeve contributes to charging is mainly used, it is necessary to sufficiently charge the toner by forming a stable thin layer coat on the developing sleeve. The flow of the developer is as shown in FIG. 5, which is clearly different from the case of the two-component developer of FIG.

  Therefore, this embodiment proposes a new technique for the problem of uniform and stable coating and charging in addition to toner conveyance.

  A plurality of developing sleeves using a one-component developer and rotating in the same direction are arranged close to each other, and the upstream (first) developing sleeve along the rotating direction of the photosensitive drum is the downstream (second). In the developing device that also serves as the toner layer thickness regulating member of the developing sleeve), the toner amount and the toner density near the area Z in FIG. 6 are the toner amount and the charge amount of the toner coat layer on the second developing sleeve 12. Especially sensitive to.

  In the case of a two-component developer, for example, in the magnetic pole pattern as described in JP-A-6-317987 and JP-A-8-101585, the state varies depending on the durability or when the power is turned on in the morning. It fluctuated even in a low and high humidity environment, resulting in poor coating. In a high-speed machine, the developing sleeve rotates at a high speed, so that the toner receives a mechanical share (shearing force) at the toner layer thickness regulating portion (toner coat regulating portion). As the durability progresses, the temperature in the vicinity of the developing device also rises, and in an extreme case, a toner lump is formed and hardened in the area Z as shown in FIG. 6, and the developing sleeve may lock and not rotate. This is solved by adopting the configuration of the present embodiment.

  In this embodiment, as shown in FIG. 7, a fixed magnet (first magnetic member) 21 disposed in the first developing sleeve 11 includes a magnetic pole a facing the photosensitive drum 1 and a first magnetic member a. 2 and a magnetic pole b facing the developing sleeve 12. On the other hand, the fixed magnet (second magnetic member) 22 disposed inside the second developing sleeve 12 has at least a magnetic pole A facing the photosensitive drum 1 and a magnetic pole B facing the first developing sleeve 11. And magnetic poles C and D (magnetic pole pairs) of the same polarity that are disposed downstream of the magnetic pole A and upstream of the magnetic pole B along the direction of the arrow R12 and constitute repulsive poles.

As described above, one of the features of the present embodiment is that the magnetic poles C and D that are repulsive poles are provided, and that the maximum position of the normal magnetic force of both the magnetic poles C and D is all covered with a wall (in other words, The second developing sleeve continuously includes a position where the magnetic force in the normal direction is maximum at the position facing the magnetic pole C and a position where the magnetic force in the normal direction is maximum at the position facing the magnetic pole D. 12) . This will be described in detail later.

  Another feature of the present invention is that the strength of the most downstream magnetic pole D among the magnetic poles C and D of the second developing sleeve 12 is 60 mT (millitesla) or more.

  This makes it possible to stabilize the toner coat on the developing sleeve and to reduce toner deterioration even at high speed rotation of the developing sleeve.

  This point will be described.

  FIG. 8 (a) shows a halftone image of the conventional developing device in a high humidity and during durability. The arrow K direction is the conveyance direction of the recording material P. When the toner coat is defective, the image becomes uneven in this way. The white background is uneven. The evaluation criteria for fogging will be described later. As shown in FIG. 6, after the toner is left in a poor fluidity state, the toner is solidified and conveyed by the magnetic pole N2 of the second developing sleeve 12, and a part thereof is the first developing sleeve 11. However, the region Z starts to be clogged after a certain degree. When the toner is clogged, an abrupt pressure is applied to the toner itself, so that a so-called blocking phenomenon occurs, and the toner passes between the developing sleeves 11 and 12 as a solid state, not as a powder. The toner on the top is not uniform, resulting in a non-uniform and uneven coat. This is the cause of the unevenness in FIG. In an extreme case, a phenomenon that the developing sleeve stops rotating due to its resistance, so-called blocking, occurs.

  This is because when the magnetic one-component toner is used, the developer flow is different from the two-component as described above, and the toner layer thickness regulation method needs to be a thin layer coat to sufficiently charge the toner. This is a problem that arises.

  On the other hand, as shown in FIG. 3, repulsive poles (repulsive magnetic poles) N2 and N3 are provided on the portion of the second developing sleeve 12 not facing the surface of the photosensitive drum 1, and these magnetic poles are provided in the developing container 18. A wall 20 was provided so as to cover N2 and N3. Note that the magnetic poles N2 and N3 in FIG. 3 correspond to the magnetic poles C and D in FIG. 7, respectively. Also, the magnetic poles N1 and S1 in FIG. 3 correspond to the magnetic poles A and B in FIG. 7, respectively. FIG. 8B shows a halftone image with a durability of 100k (100,000) according to the configuration shown in FIG. In this way, an image having no unevenness in durability was obtained, and this did not change even after the toner was left in a poor fluidity state.

  Further, as shown in FIG. 9, the image density is 1.3 in the present embodiment, while the density is 1.1 in the normal temperature environment in the conventional 100k continuous copy as shown in FIG. This has the effect of reducing the compression of the developer in the region Z in FIG. 6 by forming a repulsion pole, reducing the mechanical share in the toner layer thickness regulating portion, and repelling these. By covering the poles with the wall 20, the magnetic poles N2 and N3 for taking the clogged toner into the second developing sleeve 12 are covered with the wall 20, so that no new toner is supplied onto the second developing sleeve 12. Further, this is due to the effect of preventing excessive toner pressure on the area Z. In the present embodiment, the first developing sleeve 11 has four magnetic poles. For example, a magnetic pole N3 that is a repulsive pole with respect to the magnetic pole N2 may be provided between the magnetic pole N2 and the magnetic pole S2. .

  FIG. 10 shows a comparison of the coatability with the conventional example.

  Conventionally, coating failure, charging failure, and toner deterioration occur, resulting in uneven images and image density reduction. Moreover, it fluctuated also in low humidity environment and high humidity environment. On the other hand, in the present embodiment, there is no blocking (in a high temperature and high humidity environment), no image unevenness (charging failure, toner coat unevenness), the density can be stabilized, and development that does not cause problems in the entire environment and durability. The system was achieved. This durability means that there is no problem both at the time of image formation in the morning and after the durability.

[Wall and magnetic force]
Next, the relationship between the wall 20 (see FIG. 3) provided in the developing container 18 and the magnetic force will be described in detail. First, the effect of the wall 20 will be considered in the case where the wall 20 is not a repulsive pole as shown in FIG. FIG. 12 shows a case where the magnetic force of the magnetic pole D (here, the magnetic pole N2) is changed without providing the wall 20. FIG. This is a result of the relationship between the magnetic pole strength, the toner transportability and the blocking property.

  From the figure, when the magnetic force is simply decreased (80 mT → 20 mT), the toner conveying force decreases. On the other hand, although toner blocking is improved when the magnetic force is lowered, the magnetic force is about 20 to 30 mT, which indicates that the toner conveying force is insufficient and there is no design range that satisfies both.

  Therefore, it can be seen from this that it is meaningful to provide the wall 20, and not merely providing the wall 20 to lower the magnetic force of the intake portion.

  Moreover, when the relationship between the maximum magnetic force position and the wall 20 was examined, it was found that the effect was exhibited from the point where the position of the maximum normal direction magnetic force was covered with the wall 20.

[Repulsive effect]
Next, the effect of the repulsion pole will be described with reference to FIG. Conventionally, the toner on the second developing sleeve 12 passes through the developing portion and then moves again to the region Z in FIG. 6. In the multiple developing sleeve system, the first developing sleeve 11 causes the toner on the photosensitive drum 1. Since the toner image formed in this step is further developed by the second developing sleeve 12, the final image density is determined by the downstream developing unit. That is, when the toner on the second developing sleeve 12 deteriorates, the density becomes low as a result. For this reason, when the first developing sleeve 11 is used as the toner layer thickness regulating member of the second developing sleeve 12 as in the configuration of the present embodiment, the region on the first developing sleeve 11 in the region Z is used. Since the toner moves in the opposite direction to the second developing sleeve 12, the toner is particularly susceptible to mechanical share. Therefore, when the developing sleeves 11 and 12 rotate at a high speed, the toner is significantly deteriorated and the density becomes low.

  In the present embodiment, in order to prevent this, the take-in pole is a repulsive pole. By using repulsive poles, about 60% of the toner on the developing sleeve 12 is naturally peeled off from the developing sleeve 12 between the repelling poles. The peeled toner crosses the wall 20 with rotation. In this way, it is possible to reduce the amount of toner that has conventionally been carried around on the developing sleeve 12 even after the end of development. Since there is no accompanying rotation, toner compression in the region Z can be reduced. As a result, as described above, it was possible to maintain the density at the endurance of 100k sheets from the conventional 1.1 at 1.3.

[Wall distance, toner transportability, blocking property]
Next, FIG. 13 shows the results of the relationship between the distance between the wall 20 (the distance between the wall 20 and the developing sleeve 12; the same applies hereinafter) and the toner transportability and blocking property. From the figure, it can be seen that the distance of the wall 20 is preferably 0.5 to 3.0 mm.

[Magnetic force of the most downstream magnetic pole when a wall is provided]
Next, regarding the magnetic force of the most downstream magnetic pole when the wall 20 is provided, 60 to 100 mT is preferable as shown in FIG. In this case, the distance of the wall 20 is 2 mm, but this tendency is the same even when the distance is 1 mm. In addition, about 100 mT or more, it was difficult to produce a magnetic force and could not be examined.

  As described above, the second developing sleeve 12 is provided with a repulsive pole, and the highest magnetic force portion of the repelling pole is covered with the wall 20 to stabilize the coating property, charging property, and image density of the second developing sleeve 12. I was able to. The distance of the wall 20 is preferably 1 to 5 mm, and the magnetic force of the most downstream magnetic pole (take-in pole) of the same polarity magnetic pole pair is preferably 60 to 100 mT from the viewpoint of toner transportability.

[Magnetic pole arrangement]
Next, the magnetic pole arrangement of the present embodiment will be described.

In the configuration of the developing device 4, first, the polarity at the facing portion M between the first developing sleeve 11 and the second developing sleeve 12 will be described. As shown in FIG. 15, the state of the toner coat of the second developing sleeve 12 was examined by changing the polarity. The magnetic force in the facing part M is 70 mT, and the positions of the magnetic poles are facing each other. The result is shown in FIG. Thus, the toner coat of the second developing sleeve 12 is stabilized by making the magnetic poles of the facing portion M different from each other.

  Unlike the two-component development as described above, the positions of the repulsive poles N2 and N3 in FIG. 3 are studied, and as a result, the magnetic pole N2 and the magnetic pole N3 are connected to the centers of the two developing sleeves 11 and 12, respectively. If the toner is discharged to the photosensitive drum 1 side (outside the developing device 4) from the line H, the toner charging at the second developing sleeve 12 cannot be stabilized. It is preferable to arrange on the side (inside the developing device 4). In the present embodiment, the angle θ in FIG. 3 is 5 °. In addition, although the same examination was performed at an angle θ of 0 to 20 °, these relationships were qualitatively almost the same.

[Developer]
Next, the developing device 4 used in this embodiment will be described in detail.

As described above, a positively chargeable one-component magnetic toner that is easy to handle and does not require maintenance as described above, has high durability, high reliability, and high productivity is used. As shown in FIG. 2, the developing device 4 has two developing sleeves 11 and 12 as developer carriers. They are an upstream (first) developing sleeve 11 and a downstream (second) developing sleeve 12 along the rotation direction of the photosensitive drum 1 (arrow R1 direction).

  As shown in FIG. 17, the first developing sleeve 11 has a core metal 11a and a cylindrical base 11b. The base 11b is obtained by blasting the surface of SUS (stainless steel) 305, which is a nonmagnetic member having a diameter of 20 mm, with FGB # 600, and then coating the surface of the base 11b to provide a coat layer 11c. The same applies to the second developing sleeve 12. That is, as shown in FIG. 17, it has a metal core 12a and a cylindrical base 12b. The base 12b is obtained by blasting the surface of SUS305, which is a nonmagnetic member having a diameter of 20 mm, with FGB # 600, and then coating the surface of the base 12b to provide a coat layer 12c. The surface roughness of the first and second developing sleeves 11 and 12 after blasting was set to Rz 3 μm. Here, a contact-type surface roughness meter (Surfcoder SE-3300, Kosaka Laboratory) was used for the measurement of the surface roughness. The measurement conditions are a cut-off value of 0.8 mm, a measurement length of 2.5 mm, a feed speed of 0.1 mm / sec, and a magnification of 5000 times.

  Inside the first developing sleeve 11, a first fixed magnet 21 as a magnetic member having a four-pole magnetic field pattern as shown in FIGS. 3 and 18 is disposed in a fixed state. As shown in these figures, the magnetic poles N1, S1, N2, and S2 are counterclockwise (counterclockwise) 0 ° in this order with reference to the position directly above the fixed magnet 21 (the 12 o'clock position). , 100 °, 200 °, and 270 °, respectively. The strength of the magnetic poles is 95.0 mT, 100.0 mT, 90.0 mT, and 60.0 mT in this order.

  The first developing sleeve 11 rotates at a peripheral speed of 150% with respect to the photosensitive drum 1. The layer thickness of the toner was regulated by the magnetic blade 19 and S-Bgap (distance between the developing sleeve 11 and the magnetic blade 19) was 250 μm. The distance S-Dgap between the first developing sleeve 11 and the photosensitive drum 1 is 200 μm. The developing sleeve 11 has a DC bias of +300 V, a rectangular wave as shown in FIG. 19, that is, a peak-to-peak voltage Vpp of 1200 V, and a frequency. A rectangular wave of 2.5 kHz was applied as an AC bias. Thereby, magnetic one-component non-contact development is performed. Accordingly, the development contrast is 200 V in the flight direction, and the fog removal contrast is 150 V.

  Inside the second developing sleeve 12, a second fixed magnet 22 as a magnetic member having a five-pole magnetic field pattern as shown in FIGS. 3 and 20 is disposed in a fixed state. As shown in these drawings, the magnetic poles S1, N1, S2, N2, and N3 are counterclockwise (counterclockwise) in this order with respect to the fixed magnet 22 (position at 12 o'clock). It arrange | positions at the position of -5 degrees, 85 degrees, 180 degrees, 220 degrees, and 260 degrees, respectively. The strength of the magnetic poles is 70.0 mT, 100.0 mT, 60.0 mT, 70.0 mT, and 70.0 mT in this order.

  A DC bias of +300 V and a rectangular wave as shown in FIG. 19, that is, a rectangular wave having a peak-to-peak voltage Vpp of 1200 V and a frequency of 2.5 kHz, were applied to the second developing sleeve 12 as an AC bias. These numerical values are the same as those of the first developing sleeve 11 described above, and therefore, the power source for applying the developing bias to the first and second developing sleeves 11 and 12 may be common (one). Therefore, the configuration can be simplified correspondingly, and the number of spacers can be reduced and the cost can be reduced. The developing sleeve 12 rotates with respect to the photosensitive drum 1 at a peripheral speed of 150%. The first developing sleeve 11 controls the thickness of the toner on the second developing sleeve 12. S-Dgap (distance between the first and second developing sleeves 11 and 12) is 250 μm.

  As shown in FIG. 2, the developing device 4 has an opening at a portion of the developing container 18 that faces the photosensitive drum 1, and the first developing sleeve 11 and the second developing sleeve 12 described above are opened in the opening. The above-described magnetic blade 19 is disposed above the developing sleeve 11. Inside the developing container 18, stirring members 13a, 13b, and 13c that stir the toner and convey the toner toward the developing sleeve are disposed.

  The evaluation criteria for fogging and unevenness are as shown below.

Cover
○: Less than 2% ×: 2% or more Coat stability (subjective evaluation)
X: Halftone image (reflection density D: 0.5) has unevenness Uneven density difference of 0.1 or more

  Next, the magnetic seal member will be described. As shown in FIG. 3, the first developing sleeve 11 is a developing sleeve having a fixed magnet 21 made of a four-pole magnetic pole inside, and the second developing sleeve 12 has a five-pole magnetic pole inside. A developing sleeve having a fixed magnet 22 made of Magnetic seal members 23 and 23 having the shapes shown in FIGS. 21 and 22 are provided in the vicinity of both end portions of the first and second developing sleeves 11 and 12 along the outer peripheral surface. The magnetic seal member 23 is a magnetic seal member made of Moldaroy (KN plating, permeability 10-6) mainly made of iron. The gap G between the surfaces of the first and second developing sleeves 11 and 12 and the magnetic seal member 23 was set to 400 μm ± 100 μm at any position in the circumferential direction. The length L1 of the first fixed magnet 21 was 305 mm, and the length L2 of the second fixed magnet 22 was also 305 mm.

  As for the mounting position of the magnetic seal member 23, the positions of the outer end portions 23a and 23a of the magnetic seal members 23 and 23 and the positions of the end portions 21a, 21a, 22a and 22a of the fixed magnets 21 and 22 are determined. Most preferably, they match. This is because when the end portions 21a and 22a of the fixed magnets 21 and 22 protrude outward from the end portion 23a of the magnetic seal member 23, the magnetic force also exists outside the longitudinal direction. This is because the toner is carried outside and causes toner leakage. On the other hand, if the end portions 21a and 22a of the fixed magnets 21 and 22 enter too much inside the end portion 23a of the magnetic seal member 23, the magnetic seal member 23 and the fixed magnets 21 and 22 A magnetic seal that forms a magnetic brush between them to eliminate toner leakage is present on the developing sleeves 21 and 22 even though there is no magnetic force at the outer end of the magnetic seal member 23. In order to form a magnetic brush with a width, the toner on the outside leaks to the end portion, and at the same time, the toner layer thickness increases, and there is a case where the toner drops. Further, since there is a backlash in the longitudinal direction due to the relationship between the developing sleeves 11 and 12 and the fixed magnets 21 and 22, in consideration of this, as shown in FIG. The end 23a of the magnetic seal member 23 is positioned 1 mm inside from the end 21a, 22a.

[Image processing]
In the present embodiment, the image processing is binarized by the dither method. As shown in FIG. 23, an image processing unit (signal processing unit) 31 performs image processing desired by an operator (user) such as resolution conversion on an input image signal. The γ correction unit 32 performs γ correction on the input image signal with reference to an LUT (lookup table) 32a. Then, the binary processing unit 33 generates a drive signal for the laser oscillation unit 34 of the exposure apparatus 3 based on the image signal after γ correction. Based on the drive signal output from the laser oscillation unit 34, image exposure corresponding to the image portion on the surface of the charged photosensitive drum 1 is performed. Reference numeral 35 in the figure denotes an LUT calculation unit. In the present embodiment, the LUT calculation unit 35 makes the LUT 32a in the γ correction unit 32 appropriate for the development contrast in the current operating environment. In the present embodiment, appropriate gradation correction (for example, γ correction) is performed in addition to appropriate development contrast. Then, the LUT 32 a of the γ correction unit 32 is updated in the LUT calculation unit 35 so that the obtained gradation characteristics become an ideal density reproduction curve (TRC).

  In the embodiment described above, the case where the photosensitive drum 1 uses the a-Si photosensitive member having the positive charging characteristic and the reversal development is performed using the positive toner has been described as an example. However, the present invention is not limited thereto. However, the present invention can be similarly applied to the case of performing reversal development using a negatively charged photosensitive drum (for example, an OPC photosensitive member) or negative toner (negatively charged toner). The same effect can be produced.

  In addition, in the above description, since the AC component developing bias is applied, as another effect, the portion developed excessively by the first developing sleeve 11 is returned again into the developing container 18 by the second developing sleeve 12. Toner consumption can be reduced. When the repulsion pole and the wall 20 are provided to reduce the toner deterioration as in the configuration of the present embodiment, the toner chargeability is maintained, which is more advantageous because there is no excess uncharged toner. Actually, the toner consumption was measured with a document having an image ratio of 6%, and it was 50 to 60 mg / sheet in a conventional developing device using a magnetic one-component developer. In this embodiment, 42.5 mg / sheet. As a result, the toner consumption was reduced.

  As described above, according to the present invention, in a small maintenance-free developing device using a magnetic one-component toner, that is, using a magnetic one-component developer, a plurality of developer carriers (developing sleeves 11 and 12). In the developing device (developing device 4) in which the first developer carrying member (developing sleeve 11) also serves as a developer (toner) layer thickness regulating member of the second developer carrying member (developing sleeve 12). In addition, it is possible to provide a developing device that realizes a uniform and stable coating of the developer on the upper flow developer carrying member, and that maintains a high image quality and a stable concentration even in durability and consumes less toner.

  In addition, in a developing device having a plurality of developer carriers, a compact space-saving developing device that can be used in a high-speed machine can be configured. Therefore, an image forming apparatus using this developing device is dispersed. It is possible to provide a high-speed machine suitable for small-sized print on demand.

<Embodiment 2>
In the present embodiment, the toner deterioration in the first developing sleeve is further reduced, and the magnetic pole and wall configuration is optimized. In general, when the developing sleeve is formed of a SUS or Al (aluminum) element tube, it is difficult to control the developer tribo carried on the surface.

  In this embodiment, in view of this, in order to control the toner tribo between the first developing sleeve and the second developing sleeve, an optimum coat prescription is adopted, respectively, and a negatively chargeable magnetic material is used. Component toner was used. Furthermore, the magnetic pole of the fixed magnet in the first developing sleeve has a five-pole configuration in consideration of toner transportability, and a repulsive pole is provided in a portion of the first developing sleeve located in the developing container, A large lump of toner is once separated from the developing sleeve to reduce the toner traveling to the developing sleeve. In the case of the first developing sleeve, since there is no direct supply of the developing sleeve by the stirring member, it is not necessary to provide a wall. The coating is for preventing the sleeve ghost image generated at the sleeve period, which is a problem in JP-A-3-36570, and enhancing the durability of the sleeve surface (it is a film protecting the Al surface).

  The present embodiment can be applied to an image forming apparatus that is substantially the same as the image forming apparatus described in the first embodiment. However, as the photosensitive drum 1, an OPC photosensitive member (organic photosensitive member) having a negative charging characteristic is used instead of the a-Si photosensitive member having a positive charging characteristic. The toner (developer) is a negative toner instead of a positive toner.

In this embodiment, the image forming apparatus is a monochrome digital copying machine, and an OPC photosensitive member having a diameter of 108 mm is used as the photosensitive drum 1. The process speed is 470 mm / sec, and the throughput is 90 sheets / min with an A4 size recording material. The developer is a negative toner having a weight average particle diameter of 7.5 μm, the resin is made of a polyester resin, and 90 parts by weight of a magnetic material is placed therein. Further, 1.0% (weight%) of SiO ₂ is applied as an external additive.

  Next, the formulation of the coating on the surface of the developing sleeve will be described.

  The coating film for the developing sleeve was prepared by mixing a phenol resin, crystalline graphite, and carbon at a certain weight ratio on the surface of the Al sleeve and curing the film at a film thickness of 10 μm in a 150 ° C. environment. The thickness for forming a stable and uniform film is about 20 μm. In this case, the P / B ratio was 1 / 2.5 where B is the weight of the resin and P is the weight of the material other than the resin (crystalline graphite + carbon).

  When the toner coating amount of the second developing sleeve 12 is regulated by the first developing sleeve 11 as in this configuration, the charging characteristics for the negative toner are slightly high. Therefore, a phenol resin having 70 parts by weight of a quaternary ammonium salt was used only for the second developing sleeve 12.

  When added, the quaternary ammonium salt compound is uniformly dispersed in the phenolic resin, and is further taken into the structure of the phenolic resin when it is cured by heating to form a film. The resin composition itself changes to a material having negative chargeability. Therefore, if a developer carrier (developing sleeve) having a coating layer formed using such a material is used, the developer can be charged slightly lower.

  Examples of the quaternary ammonium salt compound having the functions described above that are preferably used in the present embodiment include compounds represented by the following general formula.

（式中のＲ１，Ｒ２，Ｒ３，Ｒ４は、それぞれ置換基を有してもよいアルキル基、置換基を有してもよいアリール基、アルアルキル基を表し、Ｒ１〜Ｒ４はそれぞれ同一でもあるいは異なっていてもよい。Ｘ⁻は、酸の陰イオンを表す。）

(In the formula, R1, R2, R3 and R4 each represents an alkyl group which may have a substituent, an aryl group which may have a substituent, and an aralkyl group, and R1 to R4 may be the same or It may be different .X ^- represents an anion of acid).

In the above general formula, X ^- Specific examples of the acid ions, organic sulfate ions, organic sulfonate ions, organic phosphate ions, molybdate ions, tungstate ions, such as heteropoly acid containing molybdenum atoms or tungsten atoms Can be mentioned.

When a coating layer is formed using a resin composition obtained by adding the specific quaternary ammonium salt compound used in this embodiment to a phenol resin as in (1), as described above, the binder resin When the coating layer is formed by heating and curing the phenol resin, the quaternary ammonium salt compound is incorporated into the structure of the phenol resin. For this reason, unlike the case of the particle addition system such as the negative silica particles or the negative Teflon (registered trademark) particles described above, the positive triboelectric chargeability to the positive toner is improved as a whole coating layer, not partially. . Furthermore, unlike the particle-added coating, the processability is not impaired and the strength of the coating layer is not reduced.

  Specific examples of the quaternary ammonium salt compound suitably used in the present embodiment include the following, but of course, the present embodiment is not limited to these. .

  As the phenol resin constituting the binder resin used in the present embodiment, in the production process, when a product produced using a nitrogen-containing compound as a catalyst is used, in particular, a quaternary ammonium salt compound is obtained during heat curing. It was found that it is easy to be taken into the structure of the phenol resin and is preferable for preventing charge-up of the toner.

  Therefore, in the present embodiment, a phenol resin having such an action and manufactured using a nitrogen-containing compound as a catalyst in the manufacturing process is used as one of the materials constituting the coating layer on the developer carrier. If used, it is possible to realize a developing device that prevents the toner from being charged up.

  Examples of the nitrogen-containing compound used as a catalyst in the phenol resin production process that can be suitably used in the present embodiment include, for example, ammonium sulfate, ammonium phosphate, ammonium sulfamate, ammonium carbonate, ammonium acetate, maleic as acidic catalysts. Examples of the basic catalyst include ammonia, dimethylamine, diethylamine, diisopropylamine, diisobutylamine, diamylamine, trimethylamine, triethylamine, tri-n-butylamine, triamylamine, and dimethylbenzyl. Amine, diethylbenzylamine, dimethylaniline, diethylaniline, N, N-di-n-butylaniline, N, N-diamilaniline, N, N-di-t-a Ruaniline, N-methylethanolamine, N-ethylethanolamine, diethanolamine, triethanolamine, dimethylethanolamine, diethylethanolamine, ethyldiethanolamine, n-butyldiethanolamine, di-n-butylethanolamine, triisopropanolamine, ethylenediamine, hexa Amino compounds such as methylenetetramine, pyridine such as pyridine, α-picoline, β-picoline, γ-picoline, 2,4-lutidine, 2,6-lutidine, and derivatives thereof, quinoline compounds, imidazole, 2-methylimidazole, 2 , 4-dimethylimidazole, 2-ethyl-4-methylimidazole, 2-phenylimidazole, 2-phenyl-4-methylimidazole, 2-heptadecylimidazole, etc. Imidazole and nitrogen-containing heterocyclic compounds such derivatives thereof.

  In this Embodiment, in order to adjust the resistance value of a coating layer to said value, it is preferable to contain the electroconductive substance mentioned below in a coating layer. Examples of the conductive material used at this time include metal powders such as aluminum, copper, nickel, and silver, metal oxides such as antimony oxide, indium oxide, and tin oxide, carbon fiber, carbon black, and graphite. Examples include carbon materials. In the present embodiment, among these, carbon black, particularly conductive amorphous carbon, is particularly excellent in electrical conductivity, and is charged into a polymer material to impart electrical conductivity or only to control its addition amount. Therefore, it is preferably used because an arbitrary conductivity can be obtained to some extent.

  The final film formulation is 90 parts by weight of graphite having an average particle size of 7.5 μm, 10 parts by weight of carbon and 70 parts by weight of quaternary ammonium with respect to 250 parts by weight of phenol resin. Incidentally, the ratio of graphite to carbon is preferably at least 3 times that of carbon in order to stabilize the resistance of the entire film. The film is applied to the sleeve by spraying and then dried at 150 degrees for 30 minutes.

  By optimizing this coat, the tribo (charge amount) on the second developing sleeve side is usually large, but in this embodiment, 9 μC / g on the first developing sleeve, the second developing is performed. It was possible to control to a value almost equivalent to 9.2 μC / g on the sleeve. As a result, the development characteristics are stabilized because both development sleeves are optimized against changes in the environment such as high temperature and high humidity and low temperature and humidity.

  A fixed magnet 21 having a five-pole magnetic field pattern as shown in FIGS. 24 and 25 is provided inside the first developing sleeve 11 (the magnetic force is omitted). The first developing sleeve 11 rotates with respect to the photosensitive drum 1 at a peripheral speed of 125%. The layer thickness of the toner is regulated by the magnetic blade 19, and the distance S-Bgap between the first developing sleeve 11 and the magnetic blade 19 is 250 μm. The distance S-Dgap between the first developing sleeve 11 and the photosensitive drum 1 is 250 μm, the first developing sleeve 11 has a DC bias of −550 V, a peak-to-peak voltage Vpp 1500 V, and a frequency 2.7 kHz as shown in FIG. The rectangular wave was applied with an AC bias superimposed. Thereby, magnetic one-component non-contact development is performed. Therefore, the development contrast is 350V in the flight direction, and the fog removal contrast is 150V.

  The second developing sleeve 12 is a non-magnetic member made of aluminum A2017 having a diameter of 20 mm and having a film formed thereon. Inside, a fixed magnet 22 having a five-pole magnetic field pattern shown in FIGS. 24 and 25 is provided. To the second developing sleeve 12, a DC bias of −550 V and a rectangular wave having a peak-to-peak voltage Vpp of 1500 V and a frequency of 2.7 kHz as shown in FIG. Since the power sources of the first and second developing sleeves 11 and 12 can be shared (one), there is an advantage that the cost is reduced and the space for the power source can be reduced. The second developing sleeve 12 rotates at a peripheral speed of 125% with respect to the photosensitive drum 1. The toner layer thickness on the second developing sleeve 12 is regulated by the first developing sleeve 11. The distance between the first developing sleeve 11 and the second developing sleeve 12 was 400 μm.

  As shown in FIG. 20, the first developing sleeve 11 has five poles as shown in FIGS. 24 and 25, and the second developing sleeve 12 has FIGS. 24 and 20 as shown in FIG. 5 poles as shown. The reason for the five poles is as described above.

  Next, the size in the normal direction of the most downstream magnetic pole D of the repelling pole will be described. FIG. 14 shows toner transportability and magnetic pole strength when the distance between the walls 20 is 2.0 mm. Although the wall 20 can be provided to stabilize the toner amount and toner density in the vicinity of the area Z, the toner transportability is reduced by providing the wall 20. Therefore, as shown in the figure, there is an appropriate place where the magnetic pole strength is effective as a developing system. As shown in the figure, 60 mT or more is preferable. In the present embodiment, the tendency is the same when the distance of the wall 20 is changed within a range that is established as a developing system. FIG. 13 shows blocking properties and toner transport properties with respect to the distance between the wall 20 and the second developing sleeve 12. This is because it is difficult to supply toner when the wall 20 is far away, and magnetic toner spikes at the repulsion pole are clogged and blocked when the wall 20 is too close. As shown in the figure, the wall thickness is preferably 0.5 to 3.0 mm. In this embodiment, it is 1.5 mm.

  According to the present embodiment, in addition to the effects of the first embodiment described above, by adopting the optimum coat formulation as described above, the toner of the first developing sleeve 11 and the second developing sleeve 12 can be obtained. The control of tribo could be facilitated. Further, a negatively chargeable magnetic one-component toner is used. Further, the magnetic pole of the fixed magnet 21 in the first developing sleeve 11 is configured to have a five-pole configuration in consideration of toner transportability, and repels a portion of the first developing sleeve 11 located in the developing container 18. The poles N2 and N3 were provided, and a large lump of toner was once separated from the first developing sleeve 11 to reduce the accompanying toner to the first developing sleeve 11.

<Embodiment 3>
FIG. 26 shows a schematic configuration of an image forming apparatus capable of reusing (reusing) toner, to which the present invention can be applied.

  The reuse toner is basically waste toner (transfer residual toner) that is not transferred to the recording material P during transfer but remains on the photosensitive drum 1 and is collected by the cleaning device 8. This reuse toner is deteriorated, and the tribo is extremely small as compared with new toner (new toner). For this reason, the amount of reversal component toner is large, and charging stability and toner coatability are further deteriorated. Since the reuse toner has a high degree of aggregation, the mechanical share of the toner in the toner layer thickness regulating portion of the second developing sleeve (see region Z in FIG. 6) further increases.

  The present embodiment has been implemented in view of these points. The magnetic poles and coat prescriptions of the first and second developing sleeves 11 and 12 are the same as those in the second embodiment.

  As an image forming apparatus according to the present embodiment, a digital copying machine using an OPC photoreceptor as the photosensitive drum 1 will be described as shown in FIG.

  The process speed of the photosensitive drum 1 is 500 mm / sec, and the throughput of the A4 size recording material P is 110 sheets / min. The surface of the photosensitive drum 1 is uniformly charged to −700 V by the primary charger 2. Next, the exposure apparatus 3 performs PWM exposure at 600 dpi using a semiconductor laser having a wavelength of 680 nm. As a result, the charge at the exposed portion is removed, and an electrostatic latent image is formed on the photosensitive drum 1.

  Next, it is reversely developed by the developing device 4 and visualized as a toner image. The developer is a jumping development using a magnetic one-component negative toner. The toner particle size is 8.0 μm. In the conventional two-component developer, the service man must be replaced every 100,000 sheets, and the advantage of reuse cannot be prosperous because it is not maintenance free. On the other hand, a dry magnetic one-component toner having infinite durability and no maintenance is used. The developing bias is applied to both the first and second developing sleeves 11 and 12 by applying a developing bias in which an alternating voltage (frequency 2400 Hz, peak-to-peak voltage 1500 Vpp, Duty 50%) is superimposed on a +200 V DC voltage. For S-Bgap, the first developing sleeve 11 was 250 μm, and for S-Dgap, both the first and second developing sleeves 11 and 12 were 250 μm. Thereafter, a total current of −200 μA is flowed by the post charger 5 to charge the toner image, and then the toner image is transferred by the transfer charger 6 to the recording material P conveyed in the arrow K direction. The recording material P after the toner image is transferred is separated from the surface of the photosensitive drum 1 by the separation charger 7. The separated recording material P is heated and pressurized by the fixing device 9 to fix the toner image on the surface.

  On the other hand, waste toner (transfer residual toner) that is not transferred to the recording material P during transfer but remains on the surface of the photosensitive drum 1 is removed and collected by the cleaning device 8. The waste toner is then returned to the hopper 10 through the transport pipe 36.

  The conveying pipe 36 has a screw-shaped conveying member (not shown) disposed therein, and the conveying member rotates to convey waste toner from the cleaning device 8 to the hopper 10. Yes.

  More specifically, as shown in FIG. 26, the hopper 10 has two toner storage chambers 10a and 10b. One of the toner storage chambers 10a is a storage chamber for storing new toner (new toner), and the other toner storage chamber 10b is waste toner (reused toner) that has been transported through the transport pipe 36 described above. A storage chamber in which toner is stored. The new toner and the reuse toner stored in the respective toner storage chambers 10a and 10b are attracted by magnetic force by the magnet rollers 16a and 16b arranged at the bottom of the hopper, and the developing container 18 is rotated by the rotation of the magnet rollers 16a and 16b. Supplied in. In the present embodiment, a method of mixing new toner and reuse toner in the developing container 18 is adopted, but a space for mixing in the hopper 10 may be provided and mixed. The toner mixed in the developing container 18 is sent again to the developing sleeves 11 and 12 and is used for developing the electrostatic latent image on the photosensitive drum 1.

  The amount of new toner and reuse toner supplied to the developing container 18 is adjusted by controlling the rotation of the magnet rollers 16a and 16b. The magnet roller 16a for supplying the new toner is usually rotated at a constant rotation speed (for example, 2 rotations / minute), and the rotation rate of the magnet roller 16b for supplying the reuse toner is controlled. It is adjusted. Normally, the magnet roller 16b is set to 10/90 (the rotation speed of the magnet roller 16a: the rotation speed of the magnet roller 16b = 9: 1) with respect to the magnet roller 16a. A signal for starting the rotation of the magnet rollers 16a and 16b is generated when a piezo sensor (manufactured by TDK: not shown) in the developing container 18 is not subjected to its own weight and vibrates. Thereby, the rotation of both developing sleeves 11 and 12 is started.

  According to the present embodiment, in addition to the effects of the first and second embodiments described above, the waste toner (reused toner) is reused so that the waste toner is not discarded and the toner consumption is reduced. be able to.

<Embodiment 4>
In this embodiment, the present invention is applied to a developing device in an image forming apparatus using a network.

  In an image forming apparatus connected to a plurality of computers, since the number of print signals increases, further speeding up of image formation is required. Further, in addition to image formation performed as a normal copy or printer, image formation with a high image ratio that is output by a computer using the Internet increases. In such an image forming apparatus, an image forming apparatus that is maintenance-free at high speed and can further reduce toner consumption is particularly effective.

  A case where 20 computers are actually connected through a network will be described. When the developing device of Embodiment 2 was used, the amount consumed per month could be reduced to three-fourths of the conventional amount.

  Furthermore, for example, when a network connecting convenience stores is constructed, it is necessary to eliminate downtime due to machine maintenance time, so this embodiment uses a magnetic one-component developer because it is maintenance-free. Effective because it is a long-lived system.

1 is a diagram schematically illustrating a schematic configuration of an image forming apparatus including a developing device to which the present invention can be applied. It is a longitudinal cross-sectional view which shows the structure of the image development apparatus with which this invention can be applied. It is a figure explaining the arrangement | positioning of the magnetic pole of the upstream and downstream developer carrier (development sleeve), and the position of a wall. FIG. 6 is a diagram illustrating the flow of toner of a two-component developer having a carrier. It is a figure explaining the flow of the magnetic one component toner. In the developing device in which the upstream developing sleeve also serves as the toner layer regulating member of the downstream developing sleeve, toner is aggregated in the vicinity of a region Z. FIG. It is a figure explaining arrangement | positioning of the magnetic pole of the fixed magnet in this invention. (A) shows a halftone image output by a conventional developing device at high humidity and durability. (B) shows a halftone image output during durability by a developing device to which the present invention is applied. It is a figure compared with the past and this invention about the relation between endurance and concentration. It is a figure compared with the past and this invention about coat nature. It is a figure explaining the influence of a wall in case the downstream development sleeve does not have a repulsion pole. FIG. 6 is a diagram illustrating a relationship between magnetic pole strength, toner transportability, and toner blocking when there is no wall. FIG. 5 is a diagram illustrating a relationship between a distance between a wall and a developing sleeve, toner blocking, and toner transportability when the strength of a magnetic pole D is 60 mT. It is a figure which shows the relationship between magnetic force (strength of a magnetic pole) and toner conveyance property when the distance of a wall is 2 mm. It is a figure explaining the relationship between the polarity in the opposing part of the upstream developing sleeve and the downstream developing sleeve, and a coating property. It is a figure explaining the relationship between the polarity in the opposing part of the upstream developing sleeve and the downstream developing sleeve, and a coating property. It is a perspective view which shows the structure of a developing sleeve. It is a figure explaining the magnetic pole of the fixed magnet inside the developing sleeve on the upstream side, and its magnetic force, angle, and half value width. FIG. 5 is a diagram for explaining AC bias rectangular waves of a developing bias applied to upstream and downstream developing sleeves. It is a figure explaining the magnetic pole of the fixed magnet inside the developing sleeve on the downstream side, and its magnetic force, angle, and half value width. It is a figure explaining the shape and arrangement | positioning position of the magnetic seal member of a developing sleeve. It is a figure explaining the shape and arrangement | positioning position of the magnetic seal member of a developing sleeve. It is a block diagram which shows the flow of an image process. It is a figure explaining arrangement | positioning of a magnetic pole when the magnetic pole of the fixed magnet inside a developing sleeve of an upstream is 5 poles. It is a figure explaining the magnetic pole in case the magnetic pole of the fixed magnet inside an upstream developing sleeve is 5, and its magnetic force, an angle, and a half value width. 1 is a diagram illustrating a schematic configuration of an image forming apparatus capable of reusing toner.

Explanation of symbols

1 Photosensitive drum (image carrier)
2 Primary charger (charging means)
3 Exposure equipment (exposure means)
4 Developing device (Developing means)
6 Transfer charger (transfer means)
7 Separating charger 8 Cleaning device (cleaning means)
11 First developing sleeve (upstream developer carrier)
12 Second developing sleeve (downstream developer carrier)
20 Wall 21 Fixed magnet (first magnetic member)
22 Fixed magnet (second magnetic member)
A, B, C, D
Magnetic pole H Line connecting the center of the first developing sleeve and the center of the second developing sleeve (line connecting the center of the upstream developer carrier and the center of the downstream developer carrier)

Claims (8)

An upstream side and a downstream side along the moving direction of the image carrier surface are arranged so as to rotate in the same direction in close proximity to each other, and the electrostatic latent image on the image carrier surface is In a developing device comprising an upstream developer carrier to be developed and a downstream developer carrier, wherein the upstream developer carrier also serves as a developer layer thickness regulating member of the downstream developer carrier ,
A first magnetic member disposed inside the upstream developer carrier;
A second magnetic member disposed inside the developer carrier on the downstream side,
The first magnetic member has a magnetic pole facing the developer carrier on the downstream side,
The second magnetic member includes a magnetic pole A that faces the image carrier, a magnetic pole B that faces the upstream developer carrier, and the rotation direction of the downstream developer carrier. Magnetic poles C and D having the same polarity disposed on the downstream side of the magnetic pole A and on the upstream side of the magnetic pole B and constituting repulsive poles,
The downstream side is continuously arranged so as to include a position where the magnetic force in the normal direction is maximum at a position facing the magnetic pole C and a position where the magnetic force in the normal direction is maximum at a position facing the magnetic pole D. developer carrying member facing the distance between the downstream side of the developer carrying member surface has a wall provided so as to be 0.5 to 3 mm,
A developing device. The magnetic pole D has a magnetic pole strength of 60 to 100 mT.
The developing device according to claim 1. The magnetic pole B is disposed on the opposite side of the image carrier with respect to a line connecting the center of the upstream developer carrier and the center of the downstream developer carrier.
The developing device according to claim 2. A developing bias having an AC component and a DC component is applied to the upstream developer carrier and the downstream developer carrier.
The developing device according to claim 1, wherein: The upstream developer carrier and the downstream developer carrier are coated with a coating member having crystalline graphite and phenolic resin on the surface,
The developing device according to claim 1, wherein The upstream developer carrier and the downstream developer carrier are covered with metal plating on their surfaces,
An apparatus according to any one of claims 1 to 4, characterized in that. Reusing the developer recovered from the image carrier by a cleaning means;
An apparatus according to any one of claims 1 to 6, characterized in that. A charging unit that charges the surface of the image carrier, an exposure unit that exposes the surface of the image carrier after charging, a developing unit that develops the electrostatic latent image, and a transferred developer image to the member to be transferred An image forming apparatus comprising:
The developing device is the developing device according to any one of claims 1 to 7.
An image forming apparatus.

Images