JP2018163230A - Developing device and image formation apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain an image of higher quality than before.SOLUTION: Developer supply spiral members 10A, 10B are rotated in the same direction while a developer G is supplied from the respective developer supply spiral members 10A, 10B to a developing sleeve 15 making a difference between phases along axes of rotation so that uneven supply states that the developer supply spiral members 10A, 10B have in supplying the developer to the developing sleeve 15 respectively cancel each other. Consequently, the developer G can be carried onto the developing sleeve 15 neither too coarse nor too dense, and an image of high quality can be obtained.SELECTED DRAWING: Figure 7

Description

  The present invention relates to a developing device and an image forming apparatus, and is suitable for application to, for example, a developing device that performs development using a developer and an image forming apparatus including such a developing device.

  2. Description of the Related Art Conventionally, in an image forming apparatus using an electrophotographic system, toner is supplied from a developer carrier provided in a developing device to an image carrier, and an electrostatic latent image formed on the image carrier is developed with toner. It has become common to do. As a developing device used in such an image forming apparatus, a one-component developing type developing device using only toner as a developer and a two-component type developing device using a toner and carrier mixture as a developer are known. ing.

  Among these, in the two-component developing device, a spiral member having a rotation axis parallel to the rotation axis of the developer carrying member is provided in the developer circulation conveyance path, and by rotating this spiral member, The developer is supplied to the developer carrying member while conveying the developer in the direction of the rotation axis of the developer carrying member. Further, the developing device is provided with a developer regulating member at a position upstream from the position facing the image carrier on the developer carrier in the rotation direction so as to leave a certain gap with the surface of the developer carrier. The developer supplied on the developer carrying member is passed through the gap between the developer regulating member and the developer carrying member by further rotation of the developer carrying member. The amount of developer is regulated so that the thickness of the developer is constant (see, for example, Patent Document 1).

JP-A-2006-139024

  However, in the developing device that supplies the developer to the developer carrier while conveying the developer in the direction of the rotation axis of the developer carrier by the spiral member, the spiral member is supplied when the developer is supplied to the developer carrier. There has been a problem that image quality deteriorates due to unevenness.

  The present invention has been made in consideration of the above points, and an object of the present invention is to propose a developing device and an image forming apparatus capable of obtaining a higher-quality image as compared with the conventional art.

  The present invention includes a rotatable developer carrying member for carrying a developer, and a rotatable developer carrying member disposed along a circumferential direction of the developer carrying member. A plurality of developer supply spiral members for supplying the developer to the developer carrier, wherein the plurality of developer supply spiral members are respectively positioned in the rotational axis direction for supplying the developer to the developer carrier. It was made to rotate in the same direction with the phase difference produced.

  As described above, according to the present invention, a plurality of developer supply spiral members are provided, and the plurality of developer supply spiral members rotate in the same direction with a phase difference in the developer supply to the developer carrier. Thus, it is possible to cancel the supply unevenness that occurs when the developer is supplied between the plurality of developer supply spiral members.

  Thus, according to the present invention, it is possible to realize a developing device and an image forming apparatus capable of obtaining a higher quality image as compared with the conventional case.

1 is a diagram illustrating a schematic configuration of a developing device according to an embodiment. 1 is a diagram illustrating a schematic configuration of an image forming apparatus according to an embodiment. 1 is a block diagram illustrating a functional configuration of an image forming apparatus according to an embodiment. It is a figure which shows the structure of the developer conveyance spiral member by embodiment. It is a figure which shows the structure of the developer supply spiral member by embodiment. It is a figure which shows a mode that the developer supply spiral member by embodiment, and a developer conveyance spiral member convey a developer. FIG. 4 is a schematic diagram illustrating a state of a developer carried on a developing sleeve according to an embodiment. FIG. 4 is a diagram illustrating a toner image transferred to a sheet according to an embodiment. It is a figure which shows a mode that the developer supply spiral member of the developing device used as a comparison object, and a developer conveyance spiral member convey a developer. FIG. 6 is a diagram illustrating a toner image developed by a developing device to be compared and transferred to a sheet.

  Hereinafter, modes for carrying out the invention (hereinafter referred to as embodiments) will be described in detail with reference to the drawings.

[1. Configuration of developing device]
First, the configuration of the developing device 1 of the present embodiment will be described with reference to FIG. FIG. 1 is a diagram illustrating a schematic configuration example of the developing device 1. The developing device 1 is a device that forms a toner image using the toner G1, and is mounted, for example, on an image forming device (described later) that forms an image on a recording medium such as paper.

  As illustrated in FIG. 1, the developing device 1 includes a main body 2 and a toner cartridge 3 mounted on the upper portion of the main body 2. The toner cartridge 3 is a container for storing the toner G1, and a toner discharge port 4 is provided in the lower part.

  The main body 2 includes a first portion 2A and a second portion 2B, and the toner cartridge 3 is mounted on the first portion 2A. The first portion 2A is provided with a toner inlet 5 at the top and a space through which the toner G1 passes. Further, a toner supply shutter 6 is provided in the vicinity of the toner inlet 5 inside the first portion 2A. The toner supply shutter 6 is a shutter that opens and closes the toner inlet 5 by rotating, and has a clutch (not shown) attached thereto. When the toner supply shutter 6 is opened, the toner G1 accommodated in the toner cartridge 3 is supplied into the first portion 2A. The toner G1 put into the first portion 2A from the toner cartridge 3 passes through the inside of the first portion 2A and is sent to the inside of the second portion 2B.

  The second portion 2B includes developer supply spiral members 10A and 10B, a developer transport spiral member 11, a photosensitive drum 12, a charging roller 13, an LED (Light Emitting Diode) head 14, and a developing sleeve 15. A doctor blade 16, a cleaning blade 17, and a toner concentration sensor 18. The second portion 2B accommodates a magnetic carrier G2 inside. The toner G1 sent from the first portion 2A to the inside of the second portion 2B is accommodated in the second portion 2B by the developer supply spiral members 10A and 10B and the developer transport spiral member 11. It is designed to be mixed with the magnetic carrier G2. The toner G1 includes, for example, a binder resin, a charge control agent as an internal additive, a release agent, a colorant, and an external additive. The magnetic carrier G2 is a magnetic powder or particle. Here, a mixture of the toner G1 and the magnetic carrier G2 is referred to as a developer G.

  The developer supply spiral members 10A and 10B and the developer transport spiral member 11 are members in which a spiral blade (referred to as a spiral blade) is provided on a shaft serving as a rotation shaft, and a drive transmission unit 62 described later is provided. It is rotated by the driving force transmitted through it. The developer supply spiral members 10A and 10B and the developer transport spiral member 11 are rotationally driven to mix and stir the toner G1 and the magnetic carrier G2 to form the developer G. The developing sleeve 15 is conveyed.

  The developer supply spiral members 10A and 10B are arranged around the development sleeve 15 along the circumferential direction of the development sleeve 15. The developer transport spiral member 11 is more developed than the developer supply spiral members 10A and 10B. It is arranged at a position away from 15. Note that the developer supply spiral member 10B is disposed on the downstream side in the rotation direction of the developing sleeve 15 when viewed from the developer supply spiral member 10A. In other words, the developer supply spiral member 10B is disposed at a position farther from a position where the developing sleeve 15 and the photosensitive drum 12 face each other than the developer supply spiral member 10A.

  The developer G is transported to the developer supply spiral members 10A and 10B by the developer transport spiral member 11, and further supplied to the developing sleeve 15 by the developer supply spiral members 10A and 10B.

  The photosensitive drum 12 is a cylindrical member and functions as an image carrier that carries an electrostatic latent image on the surface. The photosensitive drum 12 is composed of a conductive support and a photoconductive layer. Specifically, the photoreceptor drum 12 is an organic photoreceptor in which, for example, a charge generation layer as a photoconductive layer and a charge transport layer are sequentially laminated on the outer periphery of a metal pipe as a conductive support. It rotates by the driving force transmitted from the driving motor 61 via a driving gear (not shown).

  The charging roller 13 is a charging member that charges the surface of the photosensitive drum 12 and is disposed so as to be in contact with the surface of the photosensitive drum 12. The charging roller 13 is, for example, a metal shaft covered with a semiconductive rubber layer, and is rotated by a driving force transmitted via a drive transmission unit 62 described later. The LED head 14 is an exposure device that forms an electrostatic latent image on the surface of the photosensitive drum 12 by exposing the surface of the photosensitive drum 12, and is disposed to face the surface of the photosensitive drum 12. .

  The developing sleeve 15 is a cylindrical member, and functions as a developer carrying member that carries on the surface a developer G that develops the electrostatic latent image formed on the photosensitive drum 12. The developing sleeve 15 is disposed so as to face the surface of the photosensitive drum 12 so as to form a predetermined gap (for example, a gap of several hundred μm). For example, the developing sleeve 15 has a magnetic material arranged so that an appropriate magnetic flux density distribution is formed inside a metal pipe whose surface is blasted, and is transmitted via a drive transmission unit 62 described later. It is rotated by the driving force. The rotation axes of the developer supply spiral members 10 </ b> A and 10 </ b> B and the developer transport spiral member 11 are parallel to the rotation axis of the developing sleeve 15.

  The doctor blade 16 is a metal plate-like member that forms a thin layer of the developer G on the surface of the developing sleeve 15 and controls the amount of developer so that the thickness of the thin layer is constant. It is a regulating member. The doctor blade 16 is disposed so as to face the surface of the developing sleeve 15 so as to form a predetermined gap (for example, a gap of several hundred μm). The cleaning blade 17 is a rubber plate-like member, and cleans the surface of the photosensitive drum 12 by scraping and collecting the toner G1 remaining on the surface of the photosensitive drum 12. The cleaning blade 17 is disposed in contact with the surface of the photosensitive drum 12.

  The toner density sensor 18 is an element that detects the density of the toner G <b> 1 contained in the developer G, and is disposed, for example, in the vicinity of the developer transport spiral member 11. The configuration of the developing device 1 is as described above.

[2. Configuration of image forming apparatus]
Next, the configuration of the image forming apparatus 20 including the above-described developing device 1 will be described with reference to FIGS. 2 and 3. FIG. 2 is a diagram illustrating a schematic configuration example of the image forming apparatus 20, and FIG. 3 is a block diagram illustrating a functional configuration example of a control system of the image forming apparatus 20.

  First, a schematic configuration of the image forming apparatus 20 will be described with reference to FIG. As shown in FIG. 2, the image forming apparatus 20 is an electrophotographic printer and has a substantially box-shaped housing 21. Here, the right side in the figure of the housing 21 is the front surface, the left surface in the figure is the rear surface, the direction from the front surface to the rear surface of the housing 21 is the rear direction, the direction from the rear surface to the front surface is the front direction, The direction from the lower side to the upper side of the casing 21 is the upward direction, the direction from the upper side to the lower side of the casing 21 is the downward direction, the direction from the back side to the near side in the figure of the casing 21 is the left direction, and the casing The direction from the near side to the far side in FIG.

  The housing 21 includes a developing device 1, a paper tray 22, a transport path 23, a paper feed roller 24, transport rollers 25 (25A and 25B) and 26 (26A and 26B), a transfer roller 27, and a fixing device 28. Is provided. The paper tray 22 is a member that accommodates paper P as a recording medium in a stacked state, and is detachably attached to the lower portion of the housing 21. The paper feed roller 24 takes out the paper P stored in the paper tray 22 one by one from the top and feeds it to the transport path 23. The conveyance rollers 25 and 26 are arranged so as to face each other with the conveyance path 23 interposed therebetween, and convey the paper P along the conveyance path 23 in the direction indicated by the arrow A.

  The developing device 1 is a device that forms a toner image using, for example, black toner G1 and is provided on the transport path 23. The transfer roller 27 is a member for transferring the toner image formed by the developing device 1 onto the paper P conveyed along the conveying path 23, and the developing device 1 with the conveying path 23 interposed therebetween. The photoconductive drum 12 is disposed so as to face the photosensitive drum 12. The transfer roller 27 is, for example, a metal shaft covered with a urethane sponge layer.

  The fixing device 28 is a device for fixing the toner image on the paper P by applying heat and pressure to the toner image transferred onto the paper P. For example, the toner forming the toner image on the paper P A heater for melting the toner, a temperature sensor for detecting the temperature of the fixing device 28, and a pressure roller for pressing the toner image on the paper P. The fixing device 28 is provided on the conveyance path 23 located downstream of the developing device 1 in the conveyance direction. The schematic configuration of the image forming apparatus 20 is as described above.

  Next, the functional configuration of the image forming apparatus 20 will be described with reference to FIG. As shown in FIG. 3, the image forming apparatus 20 includes a control unit 30, a reception memory 31, an image data editing memory 32, an operation unit 33, a sensor group 34, and a power supply circuit 35. The control unit 30 includes an interface control unit 40, a print control unit 41, a high-voltage power supply control unit 42, a toner supply shutter drive control unit 43, a head drive control unit 44, a fixing control unit 45, a carry motor control unit 46, and a drive control unit 47. have. The power supply circuit 35 includes a charging voltage power supply 50, a developing sleeve voltage power supply 51, a doctor blade voltage power supply 52, and a transfer voltage power supply 53.

  Further, the image forming apparatus 20 includes a paper conveyance motor 60 that rotates the paper feed roller 24 and the conveyance rollers 25 and 26, a drive motor 61 that rotates the photosensitive drum 12, and a drive transmission unit 62. The drive transmission unit 62 transmits the driving force of the drive motor 61 to the charging roller 13, the developing sleeve 15, the transfer roller 27, the developer supply spiral members 10A and 10B, and the developer transport spiral member 11, and rotates them. Is.

  The interface control unit 40 receives print data and control commands transmitted from a host device (not shown) such as a personal computer, and transmits information indicating the state of the image forming apparatus 20 to the host device. .

  The print control unit 41 includes a microprocessor, a ROM, a RAM, an input / output port, a timer, and the like. The print control unit 41 receives print data and control commands received by the interface control unit 40 from the interface control unit 40, and controls the entire image forming apparatus 20 based on these data to perform a printing operation. .

  The reception memory 31 is a memory that temporarily stores print data received by the interface control unit 40. The image data editing memory 32 is a memory that receives print data stored in the reception memory 31 and stores image data (that is, image data) obtained by editing the print data.

  The operation unit 33 includes a display unit (an LED lamp or a display) that displays the state of the image forming apparatus 20 and an input unit (such as a button or a touch panel) for a user to input an instruction to the image forming apparatus 20. Yes. The sensor group 34 includes various sensors (for example, a paper position detection sensor, a temperature / humidity sensor, a print density sensor, and a toner remaining amount detection sensor) for monitoring the operation state of the image forming apparatus 20.

  The high voltage power supply control unit 42 controls each of the charging voltage power supply 50, the developing sleeve voltage power supply 51, the doctor blade voltage power supply 52, and the transfer voltage power supply 53 based on an instruction from the print control unit 41. The charging voltage power supply 50 applies a voltage instructed by the high voltage power supply control unit 42 to the charging roller 13. The developing sleeve voltage power supply 51 applies a voltage instructed by the high voltage power supply control unit 42 to the developing sleeve 15. The doctor blade voltage power source 52 applies a voltage instructed by the high voltage power source control unit 42 to the doctor blade 16. The transfer voltage power supply 53 applies a voltage instructed by the high voltage power supply control unit 42 to the transfer roller 27.

  The toner supply shutter drive controller 43 controls the opening / closing operation of the toner supply shutter 6. Specifically, the toner supply shutter drive control unit 43 controls the opening / closing operation of the toner supply shutter 6, and thereby the toner cartridge is based on the density of the toner G 1 in the developer G detected by the toner density sensor 18. 3 to supply toner G1 to the main body 2.

  The head drive control unit 44 sends the image data stored in the image data editing memory 32 to the LED head 14 and controls the drive of the LED head 14. The fixing control unit 45 controls the voltage applied to the fixing device 28. Specifically, the fixing controller 45 energizes the heater of the fixing device 28 based on the temperature of the fixing device 28 detected by the temperature sensor of the fixing device 28 so that the temperature of the fixing device 28 becomes constant. To control.

  The transport motor control unit 46 controls driving of the paper transport motor 60 that operates the paper feed roller 24 and the transport rollers 25 and 26. Specifically, the transport motor control unit 46 starts or stops transporting the paper P at a predetermined timing by driving the paper transport motor 60 based on an instruction from the print control unit 41.

  The drive control unit 47 controls the drive of the drive motor 61 that operates the photosensitive drum 12. The driving force by the driving motor 61 is transmitted via the photosensitive drum 12 by the driving transmission unit 62 configured by a gear train or the like, the charging roller 13, the developing sleeve 15, the transfer roller 27, the developer supply spiral members 10A, 10B, It is transmitted to the developer conveying spiral member 11. The functional configuration of the image forming apparatus 20 is as described above.

[3. Printing operation of image forming apparatus]
Next, a printing operation of the image forming apparatus 20 will be briefly described. When a print command is input from a host device (not shown) via the interface control unit 40, the print control unit 41 of the image forming apparatus 20 starts a printing operation in cooperation with the drive control unit 47 and the like.

  The drive control unit 47 drives the drive motor 61 based on an instruction from the print control unit 41 to rotate the photosensitive drum 12 in the clockwise direction in FIG. 1 at a constant peripheral speed. When the photosensitive drum 12 rotates, the power is transmitted to the charging roller 13, the developing sleeve 15, the transfer roller 27, the developer supply spiral members 10 </ b> A and 10 </ b> B, and the developer transport spiral member 11 by the drive transmission unit 62. Thus, the developing sleeve 15 is counterclockwise in FIG. 1, the developer supply spiral members 10A and 10B are both counterclockwise in FIG. 1, the developer transporting spiral member 11 is clockwise in FIG. 1 rotates counterclockwise in FIG. 1, and the transfer roller 27 rotates counterclockwise in FIG. Further, the high voltage power supply control unit 42 applies a voltage from the charging voltage power supply 50 to the charging roller 13 based on an instruction from the printing control unit 41. As a result, the surface of the photosensitive drum 12 is uniformly and uniformly charged.

  Next, the head drive control unit 44 drives the LED head 14 based on an instruction from the print control unit 41 to irradiate the photoconductive drum 12 with light corresponding to an image signal based on the print command, so that the photoconductor An electrostatic latent image is formed on the surface of the drum 12. Here, the electrostatic latent image formed on the surface of the photosensitive drum 12 is developed with the toner G1 by a developing operation described later by the developing device 1.

  On the other hand, the transport motor control unit 46 drives the paper transport motor 60 based on an instruction from the print control unit 41 to rotate the paper feed roller 24 and the transport rollers 25 and 26. As a result, the paper P stored in the paper tray 22 is fed out from the paper tray 22 and conveyed to a location where the photosensitive drum 12 and the transfer roller 27 face each other (referred to as a transfer portion). Here, the high voltage power supply control unit 42 applies a voltage from the transfer voltage power supply 53 to the transfer roller 27 based on an instruction from the print control unit 41. As a result, the toner image formed on the surface of the photosensitive drum 12 is transferred to the paper P conveyed to the transfer unit.

  The sheet P on which the toner image is transferred in this way is conveyed to the fixing device 28. The fixing device 28 fixes the toner image transferred onto the paper P onto the paper P by heat and pressure. Then, the paper P is discharged to the outside of the image forming apparatus 20 by the transport roller 26. As described above, the image forming apparatus 20 forms (i.e., prints) an image on the paper P in accordance with a print command from the host apparatus and discharges it.

  The toner G1 that has not been transferred to the paper P may remain slightly on the photosensitive drum 12, but the remaining toner G1 is removed by the cleaning blade 17. By doing so, the photosensitive drum 12 can continuously form images.

[4. Configuration of developer supplying spiral member, developer conveying spiral member and developing operation]
Next, the configuration of the developer supply spiral members 10A and 10B and the developer transport spiral member 11 and the developing operation by the developing device 1 will be described. First, the configuration of the developer transport spiral member 11 will be described with reference to FIGS. 4 and 6. FIG. 4 is a view of the developer transport spiral member 11 as viewed from a direction orthogonal to the rotation axis direction, and is a simplified view of a part (the back side of the spiral blade 71 in FIG. 4). FIG. 6 is a view of the developing sleeve 15, the developer supply spiral members 10 </ b> A and 10 </ b> B, and the developer transport spiral member 11 as viewed from the front of the developing device 1.

  The developer transport spiral member 11 includes a shaft 70 serving as a rotation shaft and a spiral blade 71 provided so as to be spirally wound around the shaft 70. The spiral blades 71 have different spiral pitches (intervals at the peaks of adjacent peaks in the rotational axis direction) at both ends in the rotational axis direction and at portions other than both ends. It is constant (for example, the interval p1). The outer diameter (outermost diameter) of the spiral blade 71 is constant throughout. Further, both end portions in the rotation axis direction of the developer conveying spiral member 11 are positioned outside the developer carrier region on the developing sleeve 15, for example.

  The developer conveying spiral member 11 is oriented so that when the shaft 70 rotates in the clockwise direction in FIG. 1, the spiral traveling direction of the spiral blade 71 (the direction in which the spiral appears to travel) is the direction of arrow B in FIG. It is attached to the developing device 1. The developer conveying spiral member 11 mixes the toner G1 and the magnetic carrier G2 entering the valley between the peaks of the spiral blade 71 by rotating in the clockwise direction in FIG. The developer G is conveyed in the spiral traveling direction while stirring. As shown in FIG. 6, when the developer G transported by the developer transport spiral member 11 is transported to the tip in the spiral traveling direction of the spiral blade 71, the developer G is pushed out from the trough at the tip, The developer supply spiral members 10A and 10B are supplied.

  Further, the developer transport spiral member 11 is configured so that the developer G returning from the developer supply spiral members 10A and 10B is supplied to the trough at the tip of the spiral blade 71 in the direction opposite to the spiral traveling direction. The developer G is circulated between the developer supply spiral members 10A and 10B. The configuration of the developer conveying spiral member 11 is as described above.

  Next, the configuration of the developer supply spiral members 10A and 10B will be described. Since the developer supply spiral members 10A and 10B have the same shape and the same size, the developer supply spiral member 10A will be described with reference to FIGS. FIG. 5 is a view of the developer supply spiral member 10A as viewed from a direction orthogonal to the rotation axis direction, and a part (the back side of the spiral blade 81 in FIG. 5) is simplified. .

  The developer supply spiral member 10 </ b> A is composed of a shaft 80 serving as a rotation shaft and a spiral blade 81 provided so as to be spirally wound around the shaft 80, as in the developer transport spiral member 11. The spiral blade 81 has different spiral pitches at both ends in the rotation axis direction and at portions other than both ends, and the spiral pitch is constant at portions other than both ends (for example, the same interval p1 as the developer transport spiral member 11). ). The outer diameter (outermost diameter) of the spiral blade 81 is constant as a whole and is about half of the outer diameter of the spiral blade 71 of the developer conveying spiral member 11. Further, both ends of the developer supply spiral member 10 </ b> A in the rotation axis direction are positioned outside the developer carrier area on the developing sleeve 15, for example.

  In this developer supply spiral member 10A, when the shaft 80 rotates counterclockwise in FIG. 1, the spiral travel direction of the spiral blade 81 is the direction indicated by the arrow C in FIG. 5 (the spiral travel direction of the developer transport spiral member 11). Is attached to the developing device 1 in the opposite direction. The developer supply spiral member 10A is supplied from the developer transport spiral member 11 by rotating counterclockwise in FIG. 1 and has a trough at the tip opposite to the spiral traveling direction of the spiral blade 81. Incoming developer G is conveyed in the spiral traveling direction. Note that the developer supply spiral member 10A has an outer diameter of the spiral blade 81 that is about half that of the developer transport spiral member 11, so that the developer G transport capability is also about half.

  Here, the developer G is pumped up to the developing sleeve 15 by the magnetic force of the developing sleeve 15 facing the developer supplying spiral member 10A while being conveyed in the spiral traveling direction by the developer supplying spiral member 10A. That is, the developer supply spiral member 10A supplies the developer G to the developing sleeve 15 while conveying the developer G in the spiral traveling direction (the rotation axis direction of the developing sleeve 15).

  Further, as shown in FIG. 6, the developer G that is not pumped up to the developing sleeve 15 and is transported to the tip of the spiral blade 81 in the spiral traveling direction is pushed out from the trough at the tip, and the developer transport spiral member 11. It is supposed to be returned to. The configuration of the developer supply spiral member 10A is as described above.

  The developer supply spiral member 10B also has the same configuration, and rotates in the same direction as the developer supply spiral member 10A, so that the developer G supplied from the developer transport spiral member 11 is converted into the developer supply spiral member 10A. The developer is supplied to the developing sleeve 15 while being conveyed in the same direction.

  Here, the developing operation by the developing device 1 will be described. The developer G that is supplied to the developing sleeve 15 by the developer supplying spiral members 10 </ b> A and 10 </ b> B and pumped up to the developing sleeve 15 generates magnetic spikes that stand on the developing sleeve 15 by the magnetic flux density distributed on the developing sleeve 15. Form. The magnetic ear is a magnetic carrier G2 to which the toner G1 is attached linked in a chain by magnetic force.

  The magnetic spikes formed on the developing sleeve 15 move as the developing sleeve 15 rotates, and are cut (cut) into an appropriate length by the doctor blade 16. Thereby, a thin layer of the developer G is formed on the developing sleeve 15. At this time, for example, a voltage of −500 V is applied to the developing sleeve 15 and the doctor blade 16 from the developing sleeve voltage power source 51 and the doctor blade voltage power source 52 controlled by the high-voltage power source control unit 42, respectively, so as to have the same potential. Has been. A voltage may be applied to the developing sleeve 15 and the doctor blade 16 so that a potential difference is generated.

  The developer G that has been cut off further moves as the developing sleeve 15 rotates, and reaches a location where the developing sleeve 15 and the photosensitive drum 12 face each other. Here, the negatively charged toner G1 contained in the developer G which has been cut off is formed on the photosensitive drum 12 by moving to the photosensitive drum 12 by leaving the developing sleeve 15 by Coulomb force. The electrostatic latent image is developed. As a result, a toner image obtained by developing the electrostatic latent image with the toner G1 is formed on the photosensitive drum 12.

  At this time, the magnetic carrier G2 contained in the developer G that has been cut off is not moved to the photosensitive drum 12 but remains on the developing sleeve 15 as it is. After the magnetic carrier G2 passes through a portion where the photosensitive drum 12 and the developing sleeve 15 face each other, the magnetic carrier G2 is separated from the developing sleeve 15 by the magnetic force distributed on the developing sleeve 15 to the developer supply spiral members 10A and 10B. Then, the toner G1 is stirred again with the toner G1. As described above, the developing device 1 develops using the toner G1 contained in the developer G, while the magnetic carrier G2 contained in the developer G has the developer supply spiral members 10A and 10B, the developer transport spiral. It is used repeatedly by circulating between the member 11 and the developing sleeve 15.

  As described above, the developer conveying spiral member 11 has a developer conveying capability that is about twice that of the developer supplying spiral members 10A and 10B, and the developer G conveyed by the developer conveying spiral member 11 is About half of each is supplied to each of the developer supply spiral members 10A and 10B. For this reason, the amount of the developer G conveyed by each of the developer supply spiral members 10A and 10B is approximately the same, and the developer G supplied to the developing sleeve 15 from each of the developer supply spiral members 10A and 10B. The amount is about the same. The developing operation by the developing device 1 is as described above.

  By the way, in the developer supply spiral members 10A and 10B, as shown in FIG. 6, when the amount of the developer G to be supplied is less than the maximum transportable amount, the developer supply spiral members 10A and 10B are located between the peak portions and the peak portions (valley portions). The developer G that has entered approaches the peak portion on the side opposite to the spiral traveling direction (the right side in FIG. 6), and the developer G that is being conveyed is densely connected to the sparse portion (low density portion) 82. (Parts having a high density) 83 appear alternately in the spiral traveling direction.

  This is a configuration in which the developer supply spiral members 10 </ b> A and 10 </ b> B convey the developer G in such a manner that the developer G is pushed out in the spiral traveling direction by the inclined surface on the spiral traveling direction side (left side in the drawing) of the peak portion constituting the spiral blade 81. This is because the developer G transport efficiency is lower on the side opposite to the spiral traveling direction of the peak than on the spiral traveling direction side of the peak.

  Therefore, in the developer supply spiral members 10A and 10B, when the amount of the developer G supplied is small, a sparse portion 82 and a dense portion 83 appear in the developer G for each spiral pitch, and these sparse portions as a whole. 82 and dense portions 83 appear alternately in the spiral direction. That is, in the developer supply spiral members 10A and 10B, when the developer G is transported, periodic transport unevenness in the spiral traveling direction (that is, the rotation axis direction) corresponding to the spiral pitch (interval p1) occurs. There is a case.

  As described above, when the developer supply spiral members 10A and 10B transport the developer G when the transport unevenness occurs, the developer supply spiral members 10A and 10B cause the developer G to be applied to the developing sleeve 15. At the time of supply, a portion where the supply amount of the developer G is large and a portion where the supply amount is small appear for each spiral pitch, and a portion where the supply amount is large and a portion where the supply amount is small appear alternately in the rotation axis direction. That is, in the developer supply spiral members 10A and 10B, periodic supply unevenness in the rotation axis direction may occur in accordance with the spiral pitch (interval p1).

  Due to such supply unevenness, there are portions that are sparse with the developer G pumped up on the developing sleeve 15 (portions where the supply amount of the developer G is small) and dense portions (portions where the supply amount of the developer G is large). When appearing alternately in the direction of the rotation axis, the sparse and dense portions remain in the developer G on the developing sleeve 15 even if the doctor blade 16 cuts off the magnetic spikes and regulates the layer thickness of the developer G. May end up. In this case, a sparse portion and a dense portion appear alternately in the rotation axis direction in the toner image developed on the photosensitive drum 12 by the toner G1 supplied from the developing sleeve 15, and finally, Then, density unevenness occurs in the toner image transferred from the photosensitive drum 12 to the paper P.

  Therefore, in the developing device 1 of the present embodiment, supply unevenness when the developer G is supplied from the developer supply spiral member 10A to the developing sleeve 15, and the developer G from the developer supply spiral member 10B to the developing sleeve 15 are supplied. A phase difference between the developer supply from the developer supply spiral member 10A to the developing sleeve 15 and the developer supply from the developer supply spiral member 10B to the developing sleeve 15 so that the supply unevenness at the time of supply cancels each other. It has come to have.

  Here, it demonstrates more easily using FIG. FIG. 7 is a schematic diagram (conceptual diagram) that imitates the surface of the developing sleeve 15 in order to make it easy to understand the state of the developer G carried on the developing sleeve 15. In the surface of the developing sleeve 15 shown in FIG. 7, the vertical direction in FIG. 7 is the circumferential direction, and the horizontal direction is the rotational axis direction.

  As shown in FIG. 7, a sparse part of the developer G that is supplied from one developer supply spiral member 10 (for example, the developer supply spiral member 10A) to the development sleeve 15 and carried on the development sleeve 15 ( For the portion 90 with a small supply amount) 90, the supply amount is increased when the developing sleeve 15 is supplied from the other developer supply spiral member 10 (for example, the developer supply spiral member 10B), and one development is performed. For the dense portion (the portion with a large supply amount) 91 of the developer G that is supplied from the developer supply spiral member 10 to the developing sleeve 15 and carried on the developing sleeve 15, the other developer supply spiral member 10. The developer supply from the developer supply spiral member 10A to the development sleeve 15 is reduced so that the supply amount is reduced when the development sleeve 15 is supplied from the developer sleeve 15. If, so as to have a phase difference from the developer supply spiral member 10B to the rotation axis direction and the developer supply to the developing sleeve 15.

  As a specific example, in the developing device 1, the phase difference between the developer supply from the developer supply spiral member 10A to the development sleeve 15 and the developer supply from the developer supply spiral member 10B to the development sleeve 15 (that is, the developer supply spiral member 10B). The developer supply spiral members 10A and 10B are rotated so that the deviation in the rotation axis direction on the developing sleeve 15 has an opposite phase (a phase difference of about 1/2 of the spiral pitch and a phase difference of about 180 °). It is supposed to let you. Here, a phase difference in a range including an error of about 10% of the spiral pitch in a half phase difference of the spiral pitch is assumed to be an opposite phase.

  In other words, a predetermined phase difference is generated between the developer supply from the developer supply spiral member 10A to the development sleeve 15 and the developer supply from the developer supply spiral member 10B to the development sleeve 15. (I.e., so that a phase difference having an opposite phase occurs), the positions of the peaks and valleys of the spiral blade 81 facing the developing sleeve 15 in the developer supply spiral member 10A, and the developer supply spiral member 10B. The crests and troughs of the spiral blade 81 facing the developing sleeve 15 are displaced in the rotation axis direction.

  The rotation angles when the developer supply spiral members 10A and 10B are attached to the second portion 2B are adjusted so that the phase difference of the developer supply to the developing sleeve 15 is opposite. Therefore, in the developing device 1, only by rotating the developer supply spiral members 10A and 10B in the same direction at the same timing, the phase difference of the developer supply to the developing sleeve 15 by the developer supply spiral members 10A and 10B is reversed. It becomes a phase.

  By doing so, in the developing device 1, the supply unevenness when the developer G is supplied from the developer supply spiral member 10A to the developing sleeve 15 and the developer G is supplied from the developer supply spiral member 10B to the developing sleeve 15. The uneven supply will cancel out each other. As a result, the developer G pumped up from the developer supply spiral members 10A and 10B onto the developing sleeve 15 becomes a state having no sparse / dense portion before being cut off by the doctor blade 16, and in this state the doctor blade Therefore, the developer G after passing through the doctor blade 16 has a constant layer thickness without a dense portion.

  For this reason, the toner image developed on the photosensitive drum 12 by the toner G1 supplied from the developing sleeve 15 is also in a state having no sparse / dense portion, and as a result, as shown in FIG. The transferred toner image 92 is a high-quality image without density unevenness.

  In this embodiment, the phase difference of the developer supply to the developing sleeve 15 by the developer supply spiral members 10A and 10B is set to the opposite phase (about 180 °), but this is an example, and the phase difference is In the range of 120 ° to 240 ° (1/3 to 2/3 phase difference of the spiral pitch), a high-quality image could be obtained as compared with the conventional case. Actually, depending on the degree of deviation of the developer G entering the valley of the spiral blade 81, it is better to make the phase difference larger or smaller than 180 ° within the range of 120 ° to 240 °. In some cases, an image can be obtained. The phase difference range is more preferably 150 ° to 210 ° (5/12 to 7/12 phase difference of the spiral pitch). If the phase difference is set within this range, a sufficiently high-quality image can be obtained. be able to.

[5. Summary and Effect]
As described so far, in this embodiment, the developing device 1 is provided with the two developer supply spiral members 10A and 10B, and the developer supply spiral member 10A supplies the developer G to the developing sleeve 15. The periodic supply unevenness in the rotation axis direction according to the spiral pitch generated at the time, and the rotation axis direction according to the spiral pitch generated when the developer supply spiral member 10B supplies the developer G to the developing sleeve 15 The developer supply spiral member 10 </ b> A rotates to the developer sleeve 15 and the developer supply spiral member 10 </ b> B to the developer sleeve 15 so that the periodic supply unevenness cancels each other. The developer supply spiral members 10A and 10B are rotated in the same direction in a state where a phase difference in the axial direction is generated.

  In other words, the phase of the supply unevenness when the developer supply spiral member 10A supplies the developer G to the developing sleeve 15 in the rotation axis direction, and the developer supply spiral member 10B to the developing sleeve 15 is the developer G. The developer supply spiral members 10A and 10B are rotated in the same direction so that the supply unevenness when supplying the toner is out of phase with the rotation axis direction (that is, in the opposite phase).

  By doing so, in the developing device 1, even if periodic supply unevenness in the rotation axis direction corresponding to the spiral pitch occurs in each of the developer supply spiral members 10A and 10B, each supply unevenness is in an opposite phase. Therefore, the developer G can be carried on the developing sleeve 15 without any sparse / dense portion. Thus, in the image forming apparatus 20 having such a developing device 1, it is possible to avoid the occurrence of density unevenness in the toner image transferred to the paper P and to obtain a high-quality image.

  Here, a specific comparative example will be described. For example, as shown in FIG. 9, in the case of the developing device 100 having the developer transport spiral member 11 and one developer supply spiral member 10, the developer When the supply spiral member 10 supplies the developer G to the developing sleeve 15, uneven supply may occur depending on the spiral pitch, and this causes a portion that is sparse to the developer G supplied onto the developing sleeve 15. A dense part appears. As a result, in the image forming apparatus having such a developing device 100, as shown in FIG. 10, for example, when the solid toner image 101 is transferred onto the paper P, the portion where the density of the toner G1 is high and the portion where the toner G1 is low Appear like a striped pattern, resulting in a low-quality image.

  On the other hand, in the case of the developing device 1 of the present embodiment having the developer transport spiral member 11 and the two developer supply spiral members 10A and 10B, as shown in FIG. 7, the developer supply spiral member When each of 10A and 10B supplies the developer G to the developing sleeve 15, even if supply unevenness corresponding to the spiral pitch occurs, the supply unevenness cancels each other. The developer G can be carried in the absence of the developer G. As a result, in the image forming apparatus 20 of the present embodiment, as shown in FIG. 8, for example, when the solid toner image 92 is transferred to the paper P, the density of the toner G1 becomes constant as a whole, Compared with the developing device 100, a high-quality image can be obtained.

  As described above, according to the developing device 1 and the image forming apparatus 20 of the present embodiment, it is possible to obtain a higher quality image as compared with the conventional case.

  By the way, the unevenness in the transport of the developer G by the developer supply spiral members 10A and 10B is that the amount of the developer G transported by the developer supply spiral members 10A and 10B can be transported by the developer supply spiral members 10A and 10B. This is a phenomenon that occurs when the maximum amount is reduced.

  Thus, the developer supply spiral members 10A and 10B and the developer transport spiral member 11 are arranged so that the amount of the developer G transported by the developer supply spiral members 10A and 10B is always about the maximum transportable amount. If the amount of the developer G circulated in is maintained at a certain level or more, uneven conveyance of the developer G by the developer supply spiral members 10A and 10B can be avoided, and accordingly, the developer supply spiral member 10A, Uneven supply of the developer G due to 10B can also be avoided.

  However, when the amount of the developer G circulated between the developer supply spiral members 10A and 10B and the developer transport spiral member 11 is increased as described above, the amount of the developer G supplied to the developing sleeve 15 also increases. As a result, when the amount of developer on the developing sleeve 15 is regulated by the doctor blade 16, the load on the developer G increases. As described above, when the load applied to the developer G increases, the developer G is likely to deteriorate. Eventually, such deterioration of the developer G causes a reduction in image quality.

  On the other hand, in the developing device 1 of the present embodiment, the developer generated when the amount of the developer G circulated between the developer supply spiral members 10A and 10B and the developer transport spiral member 11 is small. Since the uneven supply of the developer G by the supply spiral members 10A and 10B can be canceled, the amount of the developer G circulated between the developer supply spiral members 10A and 10B and the developer transport spiral member 11 is set to a certain level or more. It is not necessary to maintain the load, and the load applied to the developer G can be suppressed, so that the deterioration of the developer G can be suppressed. For this reason, the developing device 1 has high quality even under printing conditions in which toner consumption is high and the amount of the developer G circulated between the developer supply spiral members 10A and 10B and the developer transport spiral member 11 tends to decrease. An image can be obtained.

  Further, in the developing device 1, one developer supplying spiral member 10 is added to the conventional configuration, and the rotation angle when the two developer supplying spiral members 10A and 10B are attached is adjusted. The developer supply to the developing sleeve 15 has a phase difference. Therefore, the developing device 1 can execute the developing operation without adding a complicated mechanism to the conventional configuration and with almost the same control as the conventional one.

[6. Other Embodiments]
[6-1. Other Embodiment 1]
In the above-described embodiment, the two developer supply spiral members 10 </ b> A and 10 </ b> B are arranged around the developing sleeve 15 along the circumferential direction of the developing sleeve 15. Not limited to this, three or more developer supply spiral members 10 may be arranged around the developing sleeve 15 along the circumferential direction of the developing sleeve 15. For example, when supply unevenness occurs, the width (length in the rotation axis direction) of the dense portion 83 of the developer G that has entered the valley of the spiral blade 81 is about ½ of the spiral pitch (interval p1). In this case, two developer supply spiral members 10 are provided, and the phase difference of each developer supply is set to about ½ (about 180 °) of the spiral pitch, and the width of the dense portion 83 is set to the spiral pitch. In this case, three developer supply spiral members 10 may be provided, and the phase difference of each developer supply may be set to about 1/3 of the spiral pitch (about 120 °). . Alternatively, the number of developer supply spiral members 10 may be N, and the phase difference of each developer supply may be about 1 / N of the spiral pitch.

[6-2. Other Embodiment 2]
Further, in the above-described embodiment, the developer supply spiral member 10A and the development sleeve 15 are developed from the developer supply spiral member 10A by adjusting the rotation angle of the shaft 80 when the developer supply spiral members 10A and 10B are attached to the developing device 1. The developer supply and the developer supply from the developer supply spiral member 10 </ b> B to the developer sleeve 15 have a phase difference (shift in the rotation axis direction when the developer G is supplied to the developer sleeve 15). Not limited to this, development from the developer supply spiral member 10 </ b> A to the development sleeve 15 is performed by shifting the mounting position of the shaft 80 when the developer supply spiral members 10 </ b> A and 10 </ b> B are attached to the developing device 1 in the direction of the rotation axis. There may be a phase difference between the developer supply and the developer supply from the developer supply spiral member 10 </ b> B to the developing sleeve 15.

[6-3. Other Embodiment 3]
Furthermore, in the above-described embodiment, the present invention is applied to the image forming apparatus 20 that includes the single developing device 1 and can perform monochrome printing. The present invention is not limited to this, and the present invention can also be applied to an image forming apparatus capable of color printing that includes a plurality of developing devices 1. In the above-described embodiment, the present invention is applied to the direct transfer type image forming apparatus 20 that directly transfers the toner image formed on the photosensitive drum 12 to the paper P. However, the present invention is not limited to this. The present invention can also be applied to an intermediate transfer type image forming apparatus in which a toner image formed on the drum 12 is once transferred to an intermediate transfer member such as a belt and then transferred to a sheet P. Further, in the above-described embodiment, the present invention is applied to the image forming apparatus 20 that is an electrophotographic printer. However, the present invention is not limited to this, and other electrophotographic copying machines, facsimiles, and complex machines of these may be used. It can also be applied to an image forming apparatus.

  Furthermore, in the above-described embodiment, the present invention is applied to the developing device 1. However, the present invention is not limited to this, and the configuration other than the developing sleeve 15 and the developer supply spiral member 10 is applied to a developing device different from the developing device 1. You can also For example, the present invention can be applied to a developing device that uses an exposure method (for example, exposure with a laser) different from the developing device 1. In the above-described embodiment, the present invention is applied to the developing device 1 that develops using the developer G in which the toner G1 and the magnetic carrier G2 are mixed. However, the present invention is not limited thereto, and other developers are used. The present invention can also be applied to a developing device that develops images.

[6-4. Other Embodiment 4]
Furthermore, in the above-described embodiment, the developer supply spiral members 10A and 10B having a configuration in which the spiral pitch is different between the both ends in the rotation axis direction and the portions other than the both ends are used. Instead of the spiral members 10A and 10B, a developer supply spiral member having a constant spiral pitch in the entire rotation axis direction may be used. Further, a developer supply spiral member having a different configuration may be used. The same applies to the developer conveying spiral member 11. Further, in the above-described embodiment, the developing sleeve 15 is used as a specific example of the developer carrying member. However, the developing sleeve 15 is not limited to this, and the developing is different from the developing sleeve 15 as long as it is rotatable and carries the developer. An agent carrier may be used.

[6-5. Other Embodiment 5]
Furthermore, the present invention is not limited to the above-described embodiments. That is, the scope of application of the present invention extends to embodiments in which some or all of the above-described embodiments and other embodiments are arbitrarily combined, and embodiments in which some are extracted.

  The present invention can be widely used in a developing device that supplies a developer to a developer carrying member by a spiral member and an image forming apparatus having such a developing device.

  DESCRIPTION OF SYMBOLS 1,100 ... Developing apparatus, 10A, 10B ... Developer supply spiral member, 11 ... Developer conveying spiral member, 12 ... Photoconductor drum, 15 ... Developing sleeve, 16 ... Doctor blade, 20 ... Image forming apparatus, 70, 80... Shaft, 71, 81... Spiral blade, 82, 90 .. sparse part, 83, 91 .. dense part, 92, 101 .. toner image, P.

Claims (7)

A rotatable developer carrying member carrying the developer;
A plurality of developer supply spiral members that are arranged along the circumferential direction of the developer carrier, are rotatable, and supply the developer to the developer carrier while transporting the developer in the rotation axis direction. And
The plurality of developer supply spiral members are:
Each of the developing devices rotates in the same direction in a state where a phase difference in the rotation axis direction is generated in the supply of the developer to the developer carrying member. The plurality of developer supply spiral members are:
The spiral spiral blades provided so as to be wound around the rotation shaft, the pitches of the spiral blades being equal, and the spiral traveling directions when rotating in the same direction are the same. The developing device according to 1. The plurality of developer supply spiral members are:
3. The developing device according to claim 2, wherein each of the spiral blades facing the developer carrying member rotates in the same direction in a state where a peak portion and a valley portion of the spiral blade are shifted in a rotation axis direction. Two developer supply spiral members are provided,
The two developer supply spiral members are:
The position of the crest and trough of the spiral blade that faces the developer carrier in one developer supply spiral member, and the spiral that faces the developer carrier in the other developer supply spiral member. The developing device according to claim 3, wherein the developing device rotates in the same direction in a state in which the position of the peak portion and the valley portion of the blade is shifted in the rotation axis direction. The plurality of developer supply spiral members are:
5. The developing device according to claim 3, wherein each of the developing devices is attached at a rotation angle adjusted so as to generate a predetermined phase difference in supplying the developer to the developer carrying member. A developer conveying spiral member that is rotatable and feeds each of the plurality of developer supply spiral members while conveying the developer in a rotation axis direction;
The developer conveying spiral member is
The developing device according to claim 1, wherein the developer conveying ability is higher than that of the plurality of developer supply spiral members. An image forming apparatus comprising the developing device according to claim 1.

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