JP2017211635A - Developing device, image forming apparatus and process cartridge - Google Patents

Abstract

PROBLEM TO BE SOLVED: To satisfactorily suppress toner scattering due to an increase in internal pressure of a developer storage part while suppressing an influence due to a magnetic force around a magnet.SOLUTION: A developing device 12 comprises: a developer storage part, such as a development casing 121 for storing a developer consisting of toner and a magnetic carrier; a developer carrier, such as developing roller 12a for conveying the developer to a development region facing the surface of a latent image carrier, such as a photoreceptor 10 by performing surface migration while carrying the developer in the developer storage part; a toner conveying path, such as a supply toner conveying path 123 connected to a communicating hole 123a provided in a wall part constituting the developer storage part; and a cylindrical magnet, such as a cylindrical magnet 130 in which the line of magnetic poles is in a direction parallel to the cylinder central axis direction passing through a cylinder. The cylindrical magnet is provided such that a portion surrounded by the inner peripheral surface of the cylindrical magnet overlaps the communicating hole with each other when viewed from the cylinder central axis direction of the cylindrical magnet.SELECTED DRAWING: Figure 19

Description

  The present invention relates to a developing device, an image forming apparatus, and a process cartridge.

  Conventionally, an opening for allowing a part of the outer peripheral surface of a developing roller, which is a developer carrying member having a magnet roller, to face a photosensitive member, which is a latent image carrying member, is provided in the developer containing portion. 2. Description of the Related Art There is known a developing device that develops a latent image formed on a photoconductor using powder toner carried on a partially exposed developing roller.

  For example, Patent Document 1 discloses a developing device in which a communication hole that communicates a toner conveyance path for conveying new toner and a developer accommodating portion is provided in a wall portion that constitutes the developer accommodating portion. An apparatus is disclosed. In the developing device, a rod-shaped magnet is provided in the vicinity of the communication hole in the developer accommodating portion, and the magnetic rod of the developer formed by the magnet closes the opening of the communication hole. As a result, even if the internal pressure of the developer accommodating portion rises due to the suction airflow flowing into the developer accommodating portion as the developing roller rotates, the toner leaks from the junction between the toner conveyance path and the new toner bottle. Suppressed.

Usually, the farther away from the magnet, the smaller the magnetic force of the magnet.
According to the developing device disclosed in Patent Document 1, the portion of the opening of the communication hole far from the magnet has less developer of magnetic spikes than the portion near the magnet, and the shielding by the developer becomes insufficient. As a result, the leakage of toner from the joint portion may occur due to the increase in the internal pressure of the developer accommodating portion, and the toner scattering may not be sufficiently suppressed.

  In order to solve the above-described problems, the present invention provides a developer containing portion that contains a developer composed of toner and a magnetic carrier, and a surface of the developer containing the developer contained in the developer containing portion. In a developing device, comprising: a developer carrying member for carrying a developer to a developing region facing the surface of the image carrying member; and a toner carrying path connected to a communication hole provided in a wall portion constituting the developer containing portion. A cylindrical magnet whose magnetic poles are parallel to the cylinder central axis direction passing through the cylinder, the cylindrical magnet having a portion surrounded by the inner peripheral surface of the cylindrical magnet. It is provided so that it may mutually overlap with the said communicating hole seeing from the cylinder center axis direction.

  According to the present invention, it is possible to obtain a specific effect that toner scattering due to an increase in the internal pressure of the developer accommodating portion can be satisfactorily suppressed while suppressing the influence of the magnetic force on the periphery of the magnet.

1 is a diagram illustrating an outline of an image forming apparatus. (A) is a perspective view of a process cartridge, (b) is a sectional view of the process cartridge. The perspective view which shows the external appearance of a developing device. The perspective view of the state which removed the upper casing and the developing roller so that the inside of the developer accommodating part of a developing device can be visually recognized. FIG. 3 is a diagram schematically illustrating a developer circulation path in a developing device. FIG. 3 is a perspective view of a toner conveying device. FIG. 3 is a cross-sectional perspective view of the toner conveying device. FIG. 3 is an enlarged perspective view of a main part of the toner conveying device. FIG. 3 is a cross-sectional front view of the toner conveying device. AA sectional drawing of FIG. FIG. The perspective view which shows the back side of a process cartridge. The perspective view explaining a mode that a process cartridge is attached to an apparatus main part. FIG. 6 is a perspective view illustrating toner conveyance of the toner conveyance device. (A) is a sectional perspective view of the vicinity of a collected toner receiving port when the collected toner is conveyed to a waste toner bottle, (b) is a sectional front view when the collected toner is conveyed to a waste toner bottle, and (c) is a sectional view. BB sectional drawing of (b). (A) is a cross-sectional perspective view around the collected toner receiving port when the collected toner is conveyed to the developing device, (b) is a sectional front view when the collected toner is conveyed to the developing device, and (c) is CC sectional drawing of (b). FIG. 2 is a block diagram showing a part of an electric circuit of the image forming apparatus. The flowchart of the opening / closing control of a shutter member. The perspective view which shows the characteristic part of this embodiment. The cross-sectional front view which shows the characteristic part of this embodiment. (A) is a front view of a cylindrical magnet, (b) is the sectional view on the AA line of (a), (c) is a figure explaining the magnetic force line of a cylindrical magnet. Sectional front view which shows another example of a 1st conveyance screw. Sectional perspective view which shows another example of a 1st conveyance screw. FIG. 24 is a cross-sectional front view of FIG. 23. The figure explaining the dimension of a cylindrical magnet and a 1st conveyance screw.

FIG. 1 is a diagram showing an outline of an image forming apparatus according to an embodiment of the present invention.
An image reading apparatus 200 is attached to the upper part of the apparatus main body 100 of the copying machine as an image forming apparatus.

A process cartridge 1 is provided inside the apparatus main body 100.
FIG. 2A is a perspective view of the process cartridge, and FIG. 2B is a cross-sectional view of the process cartridge.
As shown in FIG. 2B, the process cartridge 1 includes a photosensitive member 10 that is a latent image carrier, a charging device 11 that is disposed around the photosensitive member 10 and that acts on the photosensitive member 10, and a developing device. 12 and a cleaning device 14. The process cartridge 1 is detachably attached to the apparatus main body 100. Since the photosensitive member 10, the charging device 11, the developing device 12, and the cleaning device 14 are unitized as the process cartridge 1, replacement and maintenance work is facilitated. Further, it is possible to maintain the positional accuracy between the members with high accuracy, and to improve the quality of the formed image.

  The charging device 11 serving as a charging unit applies a charging bias to apply a charge to the surface of the photoconductor 10 to uniformly charge the photoconductor 10, and an adhering material such as toner attached to the surface of the charging roller 11a. And a removing roller 11b to be removed.

  The developing device 12 as developing means has a first agent storage chamber V1 in which blades of a first conveying screw 12b as developer conveying means are disposed. Further, it also has a second agent storage chamber V2 in which a second conveying screw 12c as a developer conveying means, a developing roller 12a as a developer carrying member, a doctor blade 12d as a developer regulating member, and the like are disposed. .

  In these two agent storage chambers V1 and V2, a developer which is a two-component developer including a magnetic carrier and a negatively chargeable toner is included. The first transport screw 12b is rotationally driven by a driving unit to transport the developer in the first agent storage chamber V1 to the front side in the drawing. Then, the developer transported to the front side end portion of the first agent storage chamber V1 in the drawing by the first transport screw 12b enters the second agent storage chamber V2.

  The 2nd conveyance screw 12c in the 2nd agent storage chamber V2 is rotated by a drive means, and conveys a developer to the back side in the figure. In this manner, the developing roller 12a is disposed in a posture parallel to the second conveying screw 12c above the second conveying screw 12c that conveys the developer. The developing roller 12a includes a magnet roller fixedly disposed in a developing sleeve made of a non-magnetic sleeve that is rotationally driven.

  A part of the developer conveyed by the second conveying screw 12c is pumped up to the surface of the developing roller 12a by the magnetic force generated by the magnet roller in the developing roller 12a. Then, after the layer thickness is regulated by a doctor blade 12d arranged so as to maintain a predetermined gap from the surface of the developing roller 12a, the layer thickness is regulated and conveyed to a developing region facing the photoconductor 10, and on the photoconductor 10 Toner is attached to the electrostatic latent image. By this adhesion, a toner image is formed on the photoreceptor 10. The developer that has consumed toner by development is returned to the second conveying screw 12c as the surface of the developing roller 12a moves. Then, the developer transported to the end of the second agent storage chamber V2 by the second transport screw 12c returns to the first agent storage chamber V1. In this way, the developer is circulated and conveyed in the developing device.

  Further, the developing device 12 includes a toner concentration sensor 124 (see FIG. 5) that detects the toner concentration of the developer in the first agent storage chamber V1. The toner concentration sensor 124 measures the toner concentration of the developer from the magnetic permeability of the developer. When the toner concentration is lowered, the magnetic carrier is concentrated, so that the magnetic permeability is increased. When the value measured by the toner density sensor 124 exceeds the target value (threshold value), toner is supplied from the toner bottle 20 shown in FIG. 1, and the toner density is controlled to a constant density. The target value is determined based on the detection result obtained by detecting the toner adhesion amount of the toner pattern formed on the photoconductor 10 with an optical sensor.

  By such an operation, the control is performed so that the density of the reference pattern (toner pattern) on the photoconductor is kept constant. However, when the toner in the toner bottle 20 runs out, the density reduction cannot be suppressed. In such a situation, the detection result of the toner pattern by the optical sensor is not improved despite the operation of supplying the toner from the toner bottle 20 for a predetermined period. Therefore, when the toner pattern detection result by the optical sensor is not improved despite the operation of replenishing the toner from the toner bottle 20, the determination means determines that the toner has run out (toner end) (or Estimate).

  In addition, after the toner end is determined, the toner bottle 20 is replaced, and when the toner end recovery for supplying the toner in the replaced toner bottle 20 to the developing device 12 is performed, the following operation is performed. That is, in order to mix the replenished toner and the developer well, the developing roller 12a and the conveying screws 12b and 12c in FIG. 2B are rotated. At this time, in order to prevent the developer on the developing roller 12a from sliding unevenly, the photosensitive member 10 is also driven to rotate.

  The cleaning device 14 serving as a cleaning unit includes a cleaning blade 14 a that contacts the surface of the photoconductor 10 and scrapes off transfer residual toner attached to the photoconductor 10. In addition, a toner collection coil 14b is provided that conveys the collected toner collected in the collection unit W and collected by the cleaning blade 14a. The recovered toner transported by the toner recovery coil 14b is transported to the developing device 12 or the waste toner bottle 41 (see FIG. 1) by a toner transport device 50 described later in FIG.

  A transfer device 17 as a transfer unit shown in FIG. 1 includes a transfer roller 16, and the transfer roller 16 is pressed against and brought into contact with the peripheral surface of the photoconductor 10. Further, a thermal fixing device 24 as a fixing unit is provided above the transfer device 17. The thermal fixing device 24 includes a heating roller 25 and a pressure roller 26. Further, the apparatus main body 100 is provided with a laser writing device 21 as latent image forming means. The laser writing device 21 includes a laser light source, a scanning rotary polygon mirror, a polygon motor, an fθ lens, and the like. Further, the apparatus main body is provided with a plurality of sheet cassettes 22 for storing sheets S such as transfer paper and OHP film.

  When copying using the apparatus configured as described above, the user presses the start switch. Then, first, the contents of the original set on the image reading apparatus 200 are read. At the same time, the photosensitive member 10 is rotated by the photosensitive member driving motor, and the surface of the photosensitive member 10 is uniformly charged by the charging device 11 (see FIG. 2) using the charging roller 11a. Next, a writing process is executed using the laser writing device 21 by irradiating laser light according to the content of the original read by the image reading device 200. Then, after forming an electrostatic latent image on the surface of the photoconductor 10, toner is attached using the developing device 12 (see FIG. 2) to visualize (develop) the electrostatic latent image.

  At the same time as the user presses the start switch, the selected sheet S is sent out by the calling roller 27 from the multistage sheet cassette 22. Next, the sheet is separated one by one by the supply roller 28 and the separation roller 29 and sent to the supply path R1. The sheet S sent to the supply path R <b> 1 is conveyed by the sheet conveyance roller 30 and is abutted against the registration roller 23 and stopped. The transfer roller 16 is sent to a transfer nip formed in contact with the photoconductor 10 in accordance with the rotation timing of the toner image that is visualized on the photoconductor 10.

  The toner image on the photoreceptor 10 is transferred to the sheet S fed to the transfer nip by the transfer device 17. The residual toner on the photoconductor 10 after image transfer is removed and cleaned by a cleaning device 14 (see FIG. 2), and the residual potential on the photoconductor 10 from which the residual toner has been removed is removed by a static eliminator. In preparation for the next image formation starting from the charging device 11 (see FIG. 2).

  On the other hand, the sheet S after the image has been transferred is guided to the heat fixing device 24, passed between the heating roller 25 and the pressure roller 26, and conveyed to these rollers while applying heat and pressure to the toner. The image is fixed. Thereafter, the sheet S on which the image has been fixed is discharged onto the discharge stack unit 32 by the discharge roller 31 and stacked.

Next, the configuration and operation of the developing device 12 in FIG. 2 will be described in more detail.
FIG. 3 is a perspective view showing the appearance of the developing device 12.
FIG. 4 is a perspective view of a state in which the upper casing and the developing roller 12a are removed so that the inside of the developer accommodating portion of the developing device 12 can be visually recognized.
FIG. 5 is a diagram schematically showing a developer circulation path in the developing device 12. The broken arrow in FIG. 5 indicates the flow of the developer, and the solid arrow in FIG. 5 is replenished from the toner replenishing port 12e (see FIG. 4) at the end in the axial direction upstream of the first conveying screw 12b. The flow of toner is shown.

  A developer accommodating portion is formed inside the developing device 12 by the developing casing 121 of FIG. The developer accommodating portion has a partition wall 122 that partitions the first agent accommodating chamber V1 and the second agent accommodating chamber V2. A first transport screw 12b and a second transport screw 12c are provided in the first agent storage chamber V1 and the second agent storage chamber V2, respectively. The first agent storage chamber V <b> 1 and the second agent storage chamber V <b> 2 communicate with each other through the transfer openings 121 a and 121 b at the end of the partition wall 122.

  The developer transported to the downstream end of the second agent storage chamber V2 by the second transport screw 12c passes through the transfer opening 121a at the end of the partition wall 122 and moves to the first agent storage chamber V1. The developer in the first agent storage chamber V1 is conveyed in the opposite direction to the developer G in the second agent storage chamber V2 while being agitated by the first conveyance screw 12b. When reaching the downstream end of the first agent storage chamber V1 in the transport direction, the first agent storage chamber V1 moves to the second agent storage chamber V2 through the transfer opening 121b at the end of the partition wall 122. As described above, the developer is contained in the developer accommodating portion partitioned by the partition wall 122 by the first conveying screw 12b and the second conveying screw 12c provided in the first agent accommodating chamber V1 and the second agent accommodating chamber V2, respectively. Is circulating.

  Further, a replenishment toner transport path 123 is connected to the upstream end of the developer transport in the first agent storage chamber V1. A toner replenishing port 12e is provided in the replenishing toner transport path 123, and new toner and recovered toner collected by the cleaning device 14 are replenished from the toner replenishing port 12e as described later. The first transport screw 12 b provided in the first agent storage chamber V <b> 1 extends to the replenishment toner transport path 123. The toner replenished from the toner replenishing port 12e is conveyed through the replenishment toner conveyance path 123 by the toner conveyance blades of the first conveyance screw 12b, and then communicates between the replenishment toner conveyance path 123 and the first agent storage chamber V1. It passes to the 1st agent storage chamber V1 through the hole 123a. The toner concentration sensor 124 (see FIG. 5) is a sensor that detects the toner concentration of the developer, and is installed below the first agent storage chamber V1 of the developing casing 121.

Next, the toner recycling mechanism will be described with reference to FIGS.
FIG. 6 is a perspective view of the toner conveying device 50. FIG. 7 is a cross-sectional perspective view of the toner conveying device 50, and FIG. 8 is an enlarged perspective view of a main part of the toner conveying device 50. 9 is a cross-sectional front view of the toner conveying device 50, and FIG. 10 is a cross-sectional view taken along line AA of FIG.
6 selects the toner collected from the cleaning device 14 (see FIG. 2B) as either the developing device 12 or the waste toner bottle 41 (see FIG. 1). And a collected toner conveying section 150 for conveying the image. The collected toner conveyance unit 150 has a collected toner receiving port 51 that receives the collected toner from the cleaning device 14. The collected toner receiving port 51 is connected to the upstream end of the collected toner conveyance path 55 in the toner moving direction as shown in FIG. A collected toner conveyance coil 53 is provided in the collected toner conveyance path 55. A waste toner communication path 56 for connecting the collected toner to the waste toner bottle 41 (see FIG. 1) is connected to the downstream end of the collected toner conveyance path 55 in the toner conveyance direction.

  Further, as shown in FIG. 8, the collected toner conveyance path 55 is provided with a collected toner supply path 52 for supplying the collected toner to the developing device 12 on the downstream side in the conveyance direction where the collected toner receiving port 51 is connected. It has been. Further, the collected toner conveyance unit 150 is provided with a shutter member 54 as a path selection unit that opens and closes between the collected toner conveyance path 55 and the collected toner supply path 52. The shutter member 54 is fixed to one end of the drive shaft 54a, and the other end of the drive shaft 54a is connected to an opening / closing motor 54b (see FIG. 15B). By opening and closing the shutter member 54, the collected toner is selectively guided to a path to a waste toner bottle on the downstream side of the collected toner conveyance path 55 or a path to a developing device below the collected toner supply path 52.

  Further, the toner conveying device 50 has a new toner communication path 57 as shown in FIGS. The new toner communication path 57 communicates the new toner transport path for transporting new toner in the toner bottle 20 (see FIG. 1) and the toner replenishing port 12e of the developing device 12.

FIG. 11 is a cross-sectional perspective view of the process cartridge 1 attached to and detached from the image forming apparatus main body.
The transfer residual toner on the photoreceptor 10 is blocked by the cleaning blade 14a and removed from the photoreceptor. The transfer residual toner blocked by the cleaning blade 14a is pushed by the subsequent transfer residual toner and moves to the upper side of the cleaning blade 14a. Then, the untransferred toner is further pushed and moved to the collection unit W. The transfer residual toner (collected toner) that has moved to the collection unit W is transported toward the back side end (one axial end) of the process cartridge 1 by the toner collection coil 14b.

  As shown in FIG. 12, which shows the process cartridge 1 of FIG. 11 from the back side, on the back side surface of the process cartridge 1, there is a collection unit W and a toner transport device that is in the apparatus body when mounted on the image forming apparatus body. There is a recovered toner connecting portion 14c that connects 50 recovered toner receiving ports 51 (see FIG. 6). The collected toner transported to the back end of the process cartridge 1 by the toner collecting coil 14b is transferred to the collected toner connecting portion 14c, and freely falls within the collected toner connecting portion 14c, and is recovered by the toner transport device 50. Move to the receiving port 51.

FIG. 13 is a perspective view for explaining how the process cartridge 1 is mounted on the toner conveying device 50 in the apparatus main body.
As shown in FIG. 13, the toner conveying device 50 is attached to a side plate on the back side of the apparatus main body 100 in the process cartridge mounting direction. When the process cartridge 1 is attached to the apparatus main body 100 as shown in FIG. 13B, as shown in FIG. 9, the collected toner connecting portion 14c receives the collected toner of the toner conveying device 50 in the apparatus main body. Connected to the mouth 51. As shown in FIG. 10, the toner supply port 12 e of the developing device 12 is connected to a new toner communication path 57 of the toner transport device 50. Further, the toner supply port 12 e is connected to the collected toner supply path 52.

FIG. 14 is a perspective view illustrating toner conveyance of new toner and recovered toner of the toner conveyance device 50.
When the value measured by the toner density sensor 124 shown in FIG. 5 exceeds the target value (threshold value), that is, when the toner density in the developing device 12 becomes thin, the toner bottle shown in FIG. The new toner is conveyed from the toner 20 to the new toner communication path 57 as shown by an arrow A2 in FIG. The new toner conveyed to the new toner communication path 57 falls freely in the new toner communication path 57 and is supplied to the developing device 12 from the toner replenishing port 12e of the developing device 12 as indicated by an arrow A3 in the figure.

  Further, the toner collected by the cleaning device 14 freely falls within the collected toner connecting portion 14c (see FIG. 12), and as shown by an arrow A1 in the figure, to the collected toner receiving port 51 of the toner conveying device 50. Moving. Then, when the collected toner is reused by the shutter member 54 (see FIG. 9), it is supplied to the developing device 12 from the toner replenishing port 12e of the developing device 12 as indicated by an arrow A3 in FIG. On the other hand, when discarding the collected toner, the collected toner is conveyed through the collected toner conveyance path 55 to the waste toner communication path 56, and freely falls in the waste toner communication path 56 as indicated by an arrow A4 in the figure. It is sent to the waste toner bottle 41 (see FIG. 1).

Here, the conveyance of the collected toner by the movement of the shutter member 54 will be described with reference to FIGS. 15 and 16.
FIG. 15 is a diagram for explaining the conveyance of the collected toner to the waste toner bottle 41.
FIG. 15A is a cross-sectional perspective view around the collected toner receiving port 51 when the collected toner is conveyed to the waste toner bottle 41. FIG. 15B is a sectional front view when the collected toner is conveyed to the waste toner bottle 41, and FIG. 15C is a sectional view taken along line BB in FIG.
When transporting the collected toner to the waste toner bottle 41, the open / close motor 54b (see FIG. 15B) is driven to rotate the drive shaft 54a in FIG. 15C clockwise by a predetermined angle. Then, the shutter member 54 fixed to one end of the drive shaft 54a is rotated by a predetermined angle in the clockwise direction of FIG. 15C around the fixed portion with the drive shaft 54a. As a result, as shown in FIGS. 15A and 15C, the shutter member 54 closes the connecting portion between the collected toner conveyance path 55 and the collected toner supply path 52. Accordingly, in this case, as shown in FIG. 15B, the collected toner supplied from the collected toner connecting portion 14c (see FIG. 12) to the collected toner receiving port 51 is transported by the collected toner transport coil 53. It is conveyed in the path 55. Then, after the collected toner is conveyed to the downstream end of the collected toner conveyance path 55, the collected toner freely falls in the waste toner communication path 56 and moves to the lower waste toner bottle 41.

On the other hand, FIG. 16 is a diagram illustrating the conveyance of the collected toner to the developing device 12.
FIG. 16A is a cross-sectional perspective view around the collected toner receiving port 51 when the collected toner is conveyed to the developing device 12. FIG. 16B is a cross-sectional front view when the collected toner is conveyed to the developing device 12, and FIG. 16C is a cross-sectional view taken along the line CC in FIG.
When transporting the collected toner to the developing device 12, the opening / closing motor 54b (see FIG. 16B) is driven in the opposite direction to that when the shutter member 54 is closed, and the drive shaft 54a is moved in the direction opposite to that shown in FIG. Rotate clockwise by a predetermined angle. Then, the shutter member 54 fixed to one end of the drive shaft 54a rotates by a predetermined angle in the counterclockwise direction of FIG. 16C around the fixed portion with the drive shaft 54a. As a result, as shown in FIGS. 16A and 16C, the shutter member 54 is retracted from the communication portion between the collected toner conveyance path 55 and the collected toner supply path 52, and the collected toner conveyance path 55 and the collected toner are collected. Communication with the toner supply path 52 is established. Thus, the collected toner supplied from the collected toner connecting portion 14 c to the collected toner receiving port 51 falls to the collected toner supply path 52 on the way to the waste toner communication path 56 by the collected toner conveying coil 53. Then, the toner is supplied from the toner supply port 12e of the developing device to the developing device 12.

  FIG. 17 is a block diagram showing a part of an electric circuit in the image forming apparatus. In the figure, a control unit 60 as control means has a CPU (Central Processing Unit) as calculation means. In addition, it has storage means such as RAM (Random Access Memory) and ROM (Read Only Memory). Although various devices and sensors are connected to the control unit 60 that controls the entire apparatus, only the main devices used for the supply control of the collected toner are shown in FIG.

  The control unit 60 controls each means based on a control program stored in the RAM or ROM. Then, the image area ratio is calculated based on the image data. The control unit 60 controls the opening and closing of the shutter member 54 based on the calculated image area ratio.

FIG. 18 is a flowchart of opening / closing control of the shutter member.
As shown in FIG. 18, the control unit 60 counts the cumulative print area of the output image and the travel distance of the developing device (developing roller), and when a certain number of pages is output (Yes in S1). ), The image area ratio per unit distance is calculated from the cumulative image printing area and the travel distance of the developing roller. It is checked whether the image area ratio per unit distance is equal to or greater than a threshold value (S2). In the present embodiment, the threshold is set to 3%.

  The “predetermined number of pages” refers to the number of pages required for the toner removed by the cleaning blade 14a to reach the position where the collected toner conveyance path 55 branches to the path to the waste toner bottle and the path to the developing device. It is. That is, when an image forming operation for a predetermined number of pages is performed, the collected toner removed by the cleaning blade at the time of printing the first sheet reaches the branch. In the image forming apparatus according to the present embodiment, as illustrated in FIG. 2, the collection unit W is located above the contact portion between the cleaning blade 14 a and the photoconductor 10. Therefore, as described above, the transfer residual toner cleaned by the cleaning blade does not immediately go to the collection unit W but continues to be dammed by the cleaning blade. Then, the toner is pushed by the subsequent transfer residual toner, gradually moves upward, and is collected by the collecting unit W. For this reason, a “predetermined number of pages” is reached until the collected transfer residual toner (collected toner) reaches a position where the collected toner conveyance path 55 branches into the path to the waste toner bottle and the path to the developing device. Is required.

The smaller the image area ratio, the larger the contact area between the photoconductor 10 and the sheet S, and the higher the possibility that paper dust or the like will adhere to the photoconductor 10. Therefore, when the image area ratio per unit distance is less than the threshold (No in S2), it can be determined that a large amount of paper dust is mixed in the collected toner. Therefore, at this time, the shutter member 54 is closed, and the collected toner is transported to the waste toner bottle 41 and discarded (S4). As a result, it is expected that the collected toner collected by the printing operation of “a certain number of pages” has a large amount of paper dust, and is transported to the waste toner bottle 41 and discarded.
On the other hand, when the image area ratio per unit distance is equal to or greater than the threshold value (Yes in S2), it can be determined that the collected toner collected by the printing operation of “a certain number of pages” contains little paper dust. Accordingly, at this time, the shutter member 54 is opened and the collected toner is supplied to the developing device 12 (S3).

  In the above description, the opening / closing of the shutter member 54 is controlled based on the image area ratio per unit distance. However, this is merely an example. For example, the opening / closing of the shutter member 54 is performed based on the image area ratio per page. You may control. Specifically, when a predetermined number of pages is output, an image area ratio per page is calculated from the cumulative print area of the image and the number of pages, and the shutter is based on the image area ratio per page. The opening and closing of the member 54 is controlled. The image area ratio per page can be conveyed to the waste toner bottle 41 when the collected toner contains a large amount of paper dust, and can be conveyed to the developing device when the collected toner contains a small amount of paper dust. .

Next, features of the present embodiment will be described. As the photoconductor 10 in the process cartridge 1 in FIG. 2 and the developing roller 12 a in the developing device 12 rotate, an airflow flows into the developing device 12. Due to this air flow, the internal pressure in the developing device 12 increases. When the internal pressure in the developing device 12 rises, the pressure passes through the communication hole 123a and the replenishment toner conveyance path 123 in FIG. 5 and the collected toner conveyance path 55 (see FIG. 9) of the toner conveyance apparatus 50 shown in FIG. The pressure in the new toner communication path 57 (see FIG. 10) is increased. Further, the internal pressure of the toner bottle 20 is increased via the waste toner bottle 41 and the new toner communication path 57 via the collected toner conveyance path 55. When the internal pressure of the collected toner conveyance path 55 and the internal pressure of the waste toner bottle 41 increase, air leaks from the joint portion with the toner conveyance device 50. Specifically, the junction between the toner replenishing port 12e and the collected toner supply path 52, the junction between the waste toner bottle 41 and the waste toner communication path 56, and the junction between the collected toner receiving port 51 and the collected toner connecting portion 14c. It is. Further, a junction between the toner supply port 12e and the new toner communication path 57, and a junction between the new toner communication path 57 and the new toner conveyance path.
If air leaks from these joints, the toner in the toner transport device and the waste toner bottle scatters to the outside of the toner transport device together with the leaked air, causing the inside of the image forming apparatus to become dirty.

  Therefore, in this embodiment, the developer in the developer accommodating portion is used to satisfactorily close the opening on the first agent accommodating chamber V1 side of the communication hole 123a with the developer, and the internal pressure of the developing device 12 is applied to the toner conveying device 50. I tried not to reach. Below, the characteristic part of this embodiment is demonstrated concretely.

FIG. 19 is a perspective view showing a characteristic part of the present embodiment. FIG. 20 is a cross-sectional front view showing the characteristic part of the present embodiment. FIG. 21 is a schematic diagram showing a cylindrical magnet. FIG. 21A is a front view, FIG. 21B is a cross-sectional view taken along line AA in FIG. 21A, and FIG. 21C is a diagram for explaining magnetic lines of force of a cylindrical magnet.
In the present embodiment, as shown in FIGS. 19 and 20, a cylindrical magnet 130 is provided. The cylindrical magnet 130 is provided on the inner wall surface of the communication hole 123a on the first agent storage chamber V1 side, and the shaft of the first conveying screw 12b passes through the portion surrounded by the inner peripheral surface of the cylindrical magnet 130. ing. As shown in FIGS. 19 and 21, the cylindrical magnet 130 has a cylindrical (ring) shape when viewed from the cylindrical central axis direction. The shape of the shaft is not limited to a flat washer or a cylindrical cylinder (annulus) having a ring-shaped axial cross section, but may be a donut or a ring-shaped circular ring-shaped axial section or a polygonal axial section. Further, the arrangement of the magnetic poles is a direction parallel to the cylindrical central axis direction as shown in FIG. This is formed by magnetizing a cylindrical mineral that is not magnetized from one surface side to the other surface of the perforated planes facing each other in the cylinder central axis direction. That is, in this embodiment, the first agent storage chamber V1 side is the S pole and the opposite side is the N pole in a direction parallel to the cylindrical central axis direction, and the magnetic poles of the cylindrical magnet 130 are arranged in this thickness direction.

  Then, on one holed surface of the cylindrical magnet 130, using a double-sided tape 131, as shown in FIGS. 19 and 20, the space inside the cylinder overlaps the space of the opening of the communication hole 123a. A perforated surface is bonded to the inner wall surface of the first agent storage chamber V1 provided with the communication hole 123a. In the case of an annular shape, a part of the annular surface may be processed into a flat surface to provide an adhesive surface for the double-sided tape 131. Cylindrical magnet 130 has an N-pole on the side bonded to the developing casing and an S-pole on the opposite side. By adopting such a magnetic pole arrangement, as shown in FIG. 21C, the lines of magnetic force are engulfed and concentrated inside the cylinder of the cylindrical magnet 130. As a result, even if the magnetic force of the cylindrical magnet itself is relatively weak compared to the conventional configuration in which a rod-shaped magnet is used as a magnet for forming a magnetic field that closes the communication hole 123a with a magnetic head of developer, a sufficient amount of development is performed. The communication hole 123a is closed with an agent. Thereby, the magnetic force of the cylindrical magnet itself may be weak in order to form a magnetic field having a magnetic flux density that satisfactorily closes the communication hole 123a. When the magnetic force is strong, a developer pool is generated around the magnet, and conveyance failure due to rotation failure of the first conveyance screw 12b, developer reverse flow to the second conveyance screw 12c side, and toner reattachment to the development roller side. Wake up and be affected by magnetic force. However, since the magnetic force may be weak in this embodiment, the influence of the magnetic force on the periphery of the magnet can be reduced as compared with the conventional configuration. Therefore, the developer can satisfactorily close the clearance (interval) between the first conveying screw 12b and the developing casing (case) around it while suppressing the influence of the magnetic force on the periphery of the magnet. It is possible to satisfactorily prevent air from leaking out from the junction with the waste toner bottle and the developing device. The cylindrical magnet 130 has a portion (space) surrounded by the inner peripheral surface of the cylindrical magnet other than the inner wall surface on the first agent storage chamber V1 side of the communication hole 123a as shown in FIGS. What is necessary is just to be provided so that it may mutually overlap with the communicating hole 123a of the 1st agent storage chamber V1 in the cylindrical center axis direction. Specifically, the cylindrical magnet 130 may be inserted into the inner peripheral wall portion of the communication hole 123a or may be provided on the inner wall surface of the communication hole 123a on the replenishment toner transport path 123 side.

  In the present embodiment, when the shaft diameter of the first transport screw 12b is thin, the developer adsorbed on the inner peripheral surface of the cylindrical magnet does not reach the shaft surface of the first transport screw 12b, and the first transport screw 12b and its The clearance with surrounding cases cannot be sufficiently blocked. Accordingly, it is conceivable to reduce the distance between the shaft of the first conveying screw 12b and the inside of the cylindrical magnet to some extent. However, if the shaft diameter is increased in order to narrow it, the blades become shorter and the transportability of the toner replenished from the replenishing port is lowered at the arrangement portion of the cylindrical magnet, and toner clogging occurs in the replenishment toner transport path. Thus, dimensional accuracy is important in the shaft diameter, but it is difficult to maintain the accuracy. Therefore, in the present embodiment, the material of the shaft of the first conveying screw 12b is a magnetic metal material (for example, SUS416). As a result, the shaft portion of the first conveying screw 12b facing the cylindrical magnet is magnetized by the influence of the magnetic field, and the developer is adsorbed on the magnetized first conveying screw 12b. As a result, the gap between the shaft of the first transport screw 12b and the cylindrical magnet can be reduced even if the shaft diameter of the first transport screw 12b is made thinner than when the material of the shaft of the first transport screw 12b is a non-magnetic material. It can be well blocked with a developer. Therefore, the shaft diameter of the first transport screw 12b can be made thinner and the blades can be made longer than when the material of the shaft of the first transport screw 12b is made of a non-magnetic material.

  The magnetic material has a higher component cost as the shaft diameter of the first conveying screw 12b becomes larger. Therefore, as shown in FIG. 22, the shaft core is thinned to such an extent that the magnetizing ability of the magnetic material can be maintained, and the periphery of the shaft core 12b1 of the first conveying screw 12b of the magnetic material is covered with a resin material coating 12b2 by insert molding. It would be even better if the configuration is different. Thereby, the diameter of the shaft core 12b1 of the relatively inexpensive first conveying screw 12b having a thin shaft core can be adjusted by the thickness of the coating 12b2 of the resin material. As a result, compared with the case of only the shaft of the first transport screw 12b made of a magnetic material, the shaft diameter of the first transport screw 12b can be reduced by reducing the shaft diameter of the first transport screw 12b and the cylindrical magnet. It can be well blocked with a developer.

  Moreover, although the shaft diameter can be reduced by using a magnetic material for the shaft of the first transport screw 12b, the blades of the first transport screw 12b in the first agent storage chamber V1 are further provided in the case of developer characteristics with low transportability. There was a need to lengthen. Therefore, as shown in FIGS. 23 and 24, the shaft diameter of the portion of the first transport screw 12b of the first agent storage chamber V1 on the side facing the cylindrical magnet 130 is changed. Specifically, as shown in FIG. 25, the shaft diameter of the thin portion (first portion) 132 of the first conveying screw 12b having the shaft as a resin portion made of a non-magnetic material is D1, and the shaft diameter is large. The shaft diameter of the portion (second portion) 133 is D2, and the inner diameter of the cylindrical magnet 130 is D3. Further, the axial distance between the cylindrical magnet 130 and the end portion on the cylindrical magnet 130 side in the axial direction of the first conveying screw 12b in the thick shaft portion 133 is set to L1, and the length of the thick shaft portion 133 is set to the length. The taper angle of the taper portion connecting the portion having L2 and the shaft diameter D1 and the portion having the shaft diameter D2 is defined as θ1. An experiment was conducted to check for air leakage when each parameter was shaken.

The pass / fail judgment of the experimental result was evaluated by ○ and ×. ○ indicates that there is no air leakage from the replenishing port and there is no toner clogging in the replenishing toner conveyance path, and x indicates that there is air leakage from the replenishing port or toner clogging in the replenishing toner conveyance path.
The experimental results are shown in Table 1 below. D1 was fixed at 6 [mm], D3 was fixed at 13 [mm], L2 was fixed at 20 [mm], and θ1 was fixed at 30 [°]. From the experimental results, it was found that when D2 = 11 [mm], L1 = 2 [mm] or less, and when D2 = 9 [mm], L1 = 0 [mm] or less can suppress air leakage satisfactorily. . It should be noted that air leakage could not be sufficiently suppressed when D2 = 7 [mm] or less. From the above, when D1 is 6 [mm] and D2 is 11 [mm], it is understood that air leakage from the replenishing port can be satisfactorily suppressed by setting L1 to 0 to 2 [mm]. It was.

  In Table 1 above, the shaft of the first conveying screw 12b is a resin part made of a non-magnetic material. However, as described above, the shaft is made of a magnetic material, or the shaft core of the magnetic material is covered with a resin material. Air leakage can be suppressed more satisfactorily by using the same shaft.

What was demonstrated above is an example, and there exists an effect peculiar for every following aspect.
(Aspect A)
A developer accommodating portion such as a developing casing 121 that accommodates a developer composed of toner and a magnetic carrier, and a latent image bearing member such as the photosensitive member 10 by carrying the developer in the developer accommodating portion and moving on the surface. A developer carrying member such as a developing roller 12a that conveys the developer to a developing region facing the surface of the toner, and a replenishing toner conveying path 123 that is connected to a communication hole 123a provided in a wall portion that constitutes the developer accommodating portion. The developing device 12 including the toner conveyance path includes a cylindrical magnet such as a cylindrical magnet 130 in which the magnetic poles are arranged in a direction parallel to the cylinder central axis direction passing through the cylinder. The portion surrounded by the inner peripheral surface of the cylindrical magnet is provided so as to overlap the communication hole when viewed from the cylindrical central axis direction of the cylindrical magnet.
In this embodiment, a cylindrical magnet is used as the magnet that closes the communication hole with the magnetic spike of the developer. In the cylindrical magnet, lines of magnetic force are trapped and concentrated inside the cylinder. Such a cylindrical magnet is provided so that the space inside the cylinder and the communication hole overlap each other when viewed from the cylinder central axis direction. As a result, even if the magnetic force of the cylindrical magnet itself is relatively weaker than the conventional configuration in which the communication hole is closed with a magnetic head of developer formed by a rod-shaped magnet, the communication hole can be closed with a sufficient amount of developer. it can. As a result, the magnetic force of the cylindrical magnet itself may be relatively weak to form a magnetic field having a magnetic flux density that satisfactorily closes the communication hole, so that the influence of the magnetic force on the periphery of the magnet is changed to the conventional configuration. It can be reduced in comparison.
As described above, it is possible to satisfactorily suppress toner scattering due to an increase in the internal pressure of the developer accommodating portion while suppressing the influence of the magnetic force on the periphery of the magnet.

(Aspect B)
In (Aspect A), the cylindrical magnet is provided on the wall portion on the developer accommodating portion side of the communication hole as viewed from the inside of the developer accommodating portion.
According to this aspect, the developer in the developer accommodating portion is uniformly collected throughout the entire cylinder by the action of the magnetic field formed by the magnetic lines of force drawn from the cylindrical inner side of the cylindrical magnet. Can be closed with a developer. Therefore, it is possible to satisfactorily suppress toner scattering due to an increase in the internal pressure of the developer accommodating portion.

(Aspect C)
In (Aspect A) or (Aspect B), the developer accommodating portion includes a conveying screw such as a first conveying screw 12b for agitating and conveying the developer, and the cylindrical magnet is an inner peripheral surface of the cylindrical magnet. Is provided so as to surround the conveying screw.
According to this aspect, the developer collected by the cylindrical magnet is magnetically restrained by the magnetic spikes formed in the gap between the cylindrical magnet and the shaft of the conveying screw. For this reason, the developer trapped by the cylindrical magnet is filled in the gap between the shaft of the conveying screw and the communication hole. In this state, the developer accommodating portion and the toner conveyance path connected to the communication hole are shielded, and air is prevented from leaking out of the developer accommodating portion through the communication hole. Therefore, it is possible to satisfactorily suppress toner scattering due to an increase in the internal pressure of the developer accommodating portion.

(Aspect D)
In (Aspect C), the shaft of the conveying screw is made of a magnetic material.
According to this aspect, since the material of the shaft of the transport screw is formed of a magnetic material, the shaft portion of the transport screw opposed to the cylindrical magnet is magnetized by the influence of the magnetic field, and the portion of the magnetized transport screw shaft is magnetized. The developer is adsorbed on the surface. This makes it possible to satisfactorily close the gap between the shaft of the transport screw and the cylindrical magnet with the developer even when the diameter of the transport screw is made thinner than when the material of the shaft of the transport screw is made of a non-magnetic material. .

(Aspect E)
In (Aspect C) or (Aspect D), the shaft of the conveying screw is composed of a magnetic material and a nonmagnetic material covering the periphery thereof.
According to this aspect, the shaft diameter of the conveying screw can be adjusted by the thickness of the resin portion at a relatively inexpensive part cost. Compared to the case of only the shaft of the transport screw made of a resin material, the gap between the shaft of the transport screw and the cylindrical magnet can be satisfactorily closed with the developer even if the shaft diameter of the transport screw is reduced.

(Aspect F)
In any one of (Aspect C) to (Aspect E), the conveying screw has two portions having different shaft diameters, and the shaft diameter of the first portion having the smaller shaft diameter is 6 [mm]. ] And the shaft diameter of the second portion having the larger shaft diameter of the two portions is 11 [mm], the shaft of the cylindrical magnet and the conveying screw on the cylindrical magnet side in the second portion. An interval in the axial direction of the conveying screw with respect to the direction end is set to 0 to 2 [mm].
According to this aspect, the developer can satisfactorily close the clearance between the conveying screw and the developer accommodating portion around it.

(Aspect G)
An image forming apparatus comprising: a latent image bearing member such as a photosensitive member 10 bearing a latent image; and a developing device 12 that develops a toner image by attaching toner to the latent image on the latent image bearing member. As the apparatus, any one of (Aspect A) to (Aspect F) is used.
According to this aspect, the inside of the image forming apparatus can be prevented from being stained with toner.

(Aspect H)
In (Aspect G), a transfer unit such as a transfer device 17 that transfers a toner image on the latent image carrier to a transfer member, and a cleaning device 14 that removes deposits attached to the latent image carrier after transfer. And a toner replenishing unit such as a toner conveying device 50 that replenishes toner to the developing device. The toner replenishing unit has a collected toner conveying path 55 that conveys the collected toner removed by the cleaning unit. The collected toner conveyance path communicates with the waste toner bottle 41, communicates with a waste toner conveyance path for conveying the collected toner to the waste toner bottle, and a replenishment toner conveyance path of the developing device, and Branching to a recovered toner supply path for supplying recovered toner to the apparatus, the recovered toner in the recovered toner transport path is branched to the recovered toner supply path, and the recovered toner transporting path The recovered toner in the road, the recovery in one of the toner supply path and the waste toner conveyance path, and is characterized in that it comprises a path selection unit such as a shutter member 54 for selectively directing.
According to this aspect, when it is determined that a large amount of foreign matter such as paper dust is contained in the toner collected by the cleaning unit such as a cleaning device, the collected toner can be conveyed to the waste toner bottle 41. Thereby, it can suppress that paper dust mixes in a developing device. Further, when it is determined that there is little foreign matter such as paper dust in the collected toner, the toner consumption can be suppressed by transporting the collected toner to the developing device and reusing it.
Further, in this aspect, the developing device and the waste toner bottle are configured to communicate with each other via the collected toner conveyance path. However, since the communication hole is closed with the developer, the internal pressure of the developing device is It is possible to prevent the toner from reaching the waste toner bottle via the collected toner conveyance path. Accordingly, it is possible to prevent the toner in the waste toner bottle from leaking from the junction between the edge of the opening portion of the waste toner bottle and the collected toner conveyance path. Accordingly, it is possible to suppress the toner in the waste toner bottle from being scattered in the image forming apparatus and contaminating the image forming apparatus.

(Aspect I)
In an image forming apparatus comprising a latent image carrier that carries a latent image and a developing unit that develops the latent image on the latent image carrier, at least the latent image carrier and the developing unit are shared as one unit. In a process cartridge configured to be held by a holder and detachably integrated with the image forming apparatus main body, any one of the developing devices of (Aspect A) to (Aspect F) is used as the developing unit. It is what.
According to this aspect, it is possible to provide a process cartridge capable of suppressing the inside of the image forming apparatus from being stained with toner.

DESCRIPTION OF SYMBOLS 1 Process cartridge 10 Photoconductor 12 Developing device 12a Developing roller 12b 1st conveyance screw 12b1 Shaft 12b2 Cover 12c 2nd conveyance screw 12e Toner replenishing port 14 Cleaning device 14b Toner collection coil 14c Collected toner connection part 17 Transfer device 20 Toner bottle 41 Waste Toner bottle 50 Toner transport device 51 Collected toner receiving port 52 Collected toner supply path 53 Collected toner transport coil 54 Shutter member 55 Collected toner transport path 56 Waste toner communication path 57 New toner communication path 60 Control unit 121 Developing casing 121a, 121b Developer Delivery opening 122 Partition wall 123 Replenishment toner conveyance path 123a Communication hole 130 Cylindrical magnet 131 Double-sided tape 132 Thin shaft diameter portion 133 Large shaft diameter portion V1 First agent storage chamber V2 Second agent storage chamber W Osamubu

Japanese Patent Laying-Open No. 2015-215369

Claims (9)

A developer accommodating portion that accommodates a developer composed of toner and a magnetic carrier, and the developer in the developer accommodating portion is carried on the surface and moved to the developing region facing the surface of the latent image bearing member. A developing device comprising: a developer carrying member for conveying the toner; and a toner conveying path connected to a communication hole provided in a wall portion that constitutes the developer accommodating portion.
A cylindrical magnet in which the arrangement of magnetic poles is parallel to the cylinder central axis direction passing through the cylinder,
The developing device, wherein the cylindrical magnet is provided so that a portion surrounded by an inner peripheral surface of the cylindrical magnet overlaps the communication hole when viewed from the cylinder central axis direction of the cylindrical magnet. The developing device according to claim 1,
The cylindrical magnet is provided on the wall portion on the developer accommodating portion side of the communication hole as viewed from the inside of the developer accommodating portion. The developing device according to claim 1 or 2,
In the developer accommodating portion, provided with a conveying screw for agitating and conveying the developer,
The developing device, wherein the cylindrical magnet is provided so that an inner peripheral surface of the cylindrical magnet surrounds the conveying screw. The developing device according to claim 3.
The developing device characterized in that the shaft of the conveying screw is made of a magnetic material. The developing device according to claim 3 or 4,
The developing device characterized in that the shaft of the conveying screw is composed of a magnetic material and a non-magnetic material covering the periphery thereof. The developing device according to any one of claims 3 to 5,
The conveying screw has two portions having different shaft diameters, the shaft diameter of the first portion having the smaller shaft diameter of the two portions is 6 [mm], and the shaft diameter of the two portions. When the shaft diameter of the second part having a larger diameter is 11 [mm], the axis of the conveying screw between the cylindrical magnet and the axial end of the conveying screw on the cylindrical magnet side in the second part A developing device characterized in that the direction interval is 0 to 2 [mm]. An image forming apparatus comprising: a latent image carrier that carries a latent image; and a developing device that develops a toner image by attaching toner to the latent image on the latent image carrier.
An image forming apparatus using the developing device according to claim 1 as the developing device. The image forming apparatus according to claim 7.
A transfer unit that transfers the toner image on the latent image carrier to a transfer member, a cleaning unit that removes deposits attached to the latent image carrier after transfer, and a toner supply unit that supplies toner to the developing device And
The toner replenishing unit has a collected toner conveyance path for conveying the collected toner removed by the cleaning unit;
The collected toner conveyance path communicates with a waste toner bottle, communicates with a waste toner conveyance path for conveying the collected toner to the waste toner bottle, and a replenishment toner conveyance path of the developing device, and collects the collected toner with the developing device. The collected toner in the collected toner transport path is branched to the collected toner supply path.
An image forming apparatus comprising: a path selection unit that selectively guides the collected toner in the collected toner conveyance path to one of the collected toner supply path and the waste toner conveyance path. In an image forming apparatus comprising a latent image carrier that carries a latent image and a developing unit that develops the latent image on the latent image carrier, at least the latent image carrier and the developing unit are shared as one unit. In a process cartridge configured to be held in a holding body and detachable integrally with the image forming apparatus main body,
7. A process cartridge using the developing device according to claim 1 as the developing unit.

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