JP2015022088A - Developing device, and process cartridge and image forming apparatus using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a developing device employing a supply-recovery integrated system, which can suppress generation of an abnormal image such as uneven image density due to re-pumping or retention of a developer, and to provide a process cartridge and an image forming apparatus using the developing device.SOLUTION: A developing device 3 is configured to allow a developer supplied from a first conveyance passage 35 to a developing roller 32 to pass through a developing region and to be recovered into the first conveyance passage 35. The device includes a partition plate 41 that separates a space opposing to a supply position where the developer is supplied from within the first conveyance passage 35 to the developing roller 32, from a space opposing to a departing position where the developer having passed through the developing region departs from the developing roller 32. Thereby, a movement passage is formed where the developer in the space opposing to the departing position can move to a second conveyance passage 36 in accordance with a developer surface height in the space opposing to the departing position.

Description

  The present invention relates to a developing device, and a process cartridge using the same, and an image forming apparatus such as a copying machine, a facsimile, and a printer.

  This type of developing device is generally a two-component developer (hereinafter referred to as a developer) that is transported in a developer transport path extending along the rotation axis direction (hereinafter referred to as the longitudinal direction) of the developer carrying member. Is carried on the surface of the developer carrying member, and is supplied to the developing region which is the opposite portion of the latent image carrying member by moving the surface of the developer carrying member. In the development area, the latent image formed on the latent image carrier is developed and visualized as a toner image. The developed developer used for development in the development area and consuming the toner is collected from the surface of the developer carrying member, mixed and stirred with the replenished toner, and used again for development.

  As the configuration of the developing device described above, a supply / recovery integrated method and a supply / recovery separation method are known. The integrated supply / recovery system has both the action of supplying the developer to the developer carrying body and the action of collecting the developer from the developer carrying body by the first developer conveying path disposed opposite to the developer carrying body. To proceed simultaneously. The developer supplied from the first developer conveyance path to the developer carrying member passes through the development area and is collected in the first developer conveyance path. The developer collected in the first developer transport path is transported to the second developer transport path communicating with the first developer transport path via the agent delivery section at both longitudinal ends. Are mixed and stirred, and then returned to the first developer conveyance path. However, the developed developer that has passed through the development region and separated from the developer carrier may be immediately pumped up to the developer carrier without being agitated with the developer in the first developer conveyance path. is there. Hereinafter, this problem is referred to as “re-pumping”. This re-pumping occurs when the developed developer separated from the developer carrier is mixed with the developer supplied to the developer carrier from the first developer conveyance path. The developed developer consumes toner and has a low toner concentration (ratio of toner weight to developer weight). For this reason, when a developer having a lowered toner density is supplied to the development area, an abnormal image such as density unevenness in which the image density locally decreases in the longitudinal direction occurs.

  On the other hand, in the supply / recovery separation method, both the developer supply conveyance path for supplying the developer to the developer carrier and the developer recovery conveyance path for recovering the developer from the developer carrier are provided on the developer carrier. (See, for example, Patent Document 1). In a developing device employing a supply / recovery separation method, the developer in the developer supply transport path is supplied to the developer carrier, and the developed developer that has consumed toner in the development area is recovered in the developer recovery transport path. Is done. Then, after the toner is newly replenished and stirred in the developer collection conveyance path, the developer in the developer collection conveyance path returns to the developer supply conveyance path and is supplied to the developer carrier. Repeat action. Therefore, the supply / recovery separation type developing device is unlikely to cause density unevenness in the longitudinal direction, unlike the supply / recovery integrated type developing device.

  In the developing device adopting the above-described supply / recovery integrated method, the following method can be considered as a method for preventing re-pumping. For example, the space facing the supply position where the developer is supplied to the developer carrier from the first developer conveyance path, and the separation position where the developed developer that has passed through the development region is separated from the developer carrier. It is the method of installing the partition plate which partitions off the space to do. By this partition plate, the supply path of the developer supplied from the first developer conveyance path to the supply position and the separation path through which the developer separated from the separation position moves into the first developer conveyance path are partitioned. become. Thereby, the separated developed developer can be prevented from being mixed with the developer that is immediately supplied to the supply position.

  However, the partition plate described above is inclined so that the developer separated from the developer carrying member is dropped not into the space facing the supply position but into the space facing the separation position. Specifically, the horizontal position with respect to the rotation axis of the developer carrying member is hung from the upper end facing the developer carrying member to the lower end facing the developer carrying member in the first developer carrying path. Inclined to leave. When the toner density of the developer in the developing device increases and the height of the developer surface in the space facing the separation position in the first developer transport path rises to the height of the lower end of the partition plate, The developed developer separated from the body accumulates on the partition plate. In such a case, the developed developer accumulated on the partition plate moves between the upper end of the partition plate and the developing roller to a space facing the supply position, and is re-pumped to the developer carrier. There is a risk that. Alternatively, if the developed developer accumulates on the partition plate, the developed developer may be transported to the development area without being separated from the developer carrier. Even when the partition plate does not have an inclination, a space facing the separation position, that is, one surface on the space side facing the separation position in the partition plate, and an inner wall constituting the first developer conveyance path, The developed developer separated from the developer carrying member is accumulated in the space surrounded by, and there is a possibility that the same problem occurs.

  The supply / recovery separation type developing device disclosed in Patent Document 1 is provided with a communication port through which only the developer exceeding a predetermined developer surface height in the developer recovery transport path passes through the developer supply transport path. ing. This communication port is similar to the “communication port” in “Means for Solving the Problems” described later in that the height of the developer surface in the developer transport path is lowered. However, as described above, in the supply / recovery integrated developing device in “Means for Solving the Problems” and the supply / recovery separation developing device disclosed in Patent Document 1, there is a place where the developed developer is recovered. It is a different configuration. In addition, the supply / collection separation type developing device needs to transport the developer in the developer transport path at a higher speed than the supply / collection integrated type developing device, which increases the size of the device and reduces the size of the device. There are difficulties.

  The present invention has been made in view of the above problems. An object of the present invention is to provide a supply / collection-integrated developing device capable of suppressing the occurrence of abnormal images such as image density unevenness due to re-pumping or developer accumulation, and a process cartridge and an image forming apparatus using the same. .

  In order to solve the above-mentioned problem, the invention of claim 1 comprises a developer carrying member that carries a two-component developer composed of toner and a carrier and conveys it to a development region that is opposite to the latent image carrier, A first developer conveying member that conveys the developer in the axial direction of the developer carrying member facing the developer carrying member and is provided with a first developer conveying member that supplies the developer to the developer carrying member. A second developer conveying member that communicates with the path, the first developer conveying path, and both ends in the axial direction of the developer carrying member, and conveys the developer in a direction opposite to the first developer conveying member. And a developer supplied to the developer carrier from the first developer transport path passes through the development region and is collected in the first developer transport path. In the developing device, the developer is supplied to the developer carrier from the first developer transport path. A partition plate that partitions the space facing the supply position and the space facing the separation position where the developer that has passed through the development area is separated from the developer carrier, and the developer surface in the space facing the separation position According to the height, a moving path is formed in which the developer in the space facing the separated position can move to the second developer transport path.

  The present invention has an excellent effect of being able to suppress the occurrence of abnormal images such as image density unevenness due to re-pumping or developer accumulation.

1 is a configuration diagram illustrating an overall configuration of a printer. FIG. 2 is a configuration diagram illustrating an image forming unit of the printer. FIG. 3 is a configuration diagram illustrating a configuration of a developing device of the image forming unit. FIG. 3 is a schematic diagram illustrating a developer flow in the developing device. FIG. 3 is a configuration diagram illustrating the behavior of the developer when the developer in the developing device has a high toner concentration. The block diagram which shows the structure of the conventional image development apparatus.

  Hereinafter, an embodiment of an electrophotographic image forming apparatus (hereinafter referred to as a printer) to which the present invention is applied will be described. First, the configuration and operation of the entire printer will be described. FIG. 1 is a configuration diagram illustrating the overall configuration of the printer, and FIG. 2 is a configuration diagram illustrating an image forming unit of the printer. As shown in FIG. 1, four image forming units 10Y that form toner images of yellow (Y), magenta (M), cyan (C), and black (K) are formed at the center of the printer. 10M, 10C, 10K are arranged. Each of the image forming units 10 (Y, M, C, K) includes photoconductors 1Y, 1M, 1C, and 1K that are drum-shaped latent image carriers.

  As shown in FIG. 2, in the image forming unit 10Y, for example, a charging device 2Y that uniformly charges the surface of the photoreceptor 1Y around the photoreceptor 1Y, and an electrostatic latent image on the photoreceptor 1Y is developed with toner. A developing device 3Y, a cleaning device 4Y for cleaning residual toner on the photoreceptor 1, and the like are disposed. Then, as will be described later, an image forming process (charging process, exposure process, developing process, transfer process, cleaning process) is performed on the photoreceptor 1Y, and a yellow image is formed on the photoreceptor 1Y. .

  The image forming unit 1Y is a process cartridge in which the photosensitive member 1Y and the charging device 2Y, the developing device 3Y, and the cleaning device 4Y disposed around the photosensitive member 1Y are supported as a single unit on a common support. It is comprised and can be attached or detached with respect to a printer main body. In the image forming unit 10Y, the charging device 2Y, the developing device 3Y, and the cleaning device 4Y can be easily replaced, and the maintainability can be improved. The other image forming units 10M, 10C, and 10K have substantially the same configuration as the image forming unit 10Y except that the color of the toner used is different.

  Further, below the image forming unit 10 (Y, M, C, K) of the printer, an optical writing unit 5 for forming an electrostatic latent image on each of the photoconductors 1Y, 1M, 1C, 1K is provided. The optical writing unit 5 has a laser diode, a polygon mirror, various lenses, etc., and drives the laser diode based on image information read by a scanner outside the printer or image information sent from a personal computer. To do. Specifically, the optical writing unit 5 irradiates the uniformly charged photoreceptor 1 (Y, M, C, K) while deflecting the laser light in the direction of the rotation axis. An optical scanning process is performed.

  Above the image forming unit 10 (Y, M, C, K) of the printer, an intermediate transfer belt 11 to which a toner image formed by the image forming unit 10 (Y, M, C, K) is transferred is provided. ing. The intermediate transfer belt 11 is stretched and supported by a plurality of rollers 12, 13, and 14, and is endlessly moved in the direction of the arrow in FIG. 1 by the rotational drive of one roller. Primary transfer rollers 6Y, 6C, 6M, and 6K that perform primary transfer are disposed inside the intermediate transfer belt 11 at positions where the photoconductors 1Y, 1C, 1M, and 1K are in contact with each other. The primary transfer rollers 6 (Y, M, C, K) sandwich the intermediate transfer belt 11 with the photoreceptor 1 to form a primary transfer nip portion. Further, the intermediate transfer belt 11 is provided with a secondary transfer roller 15 that performs secondary transfer at a portion facing the roller (secondary transfer backup roller) 12. A roller (secondary transfer backup roller) 12 sandwiches the intermediate transfer belt 11 between the secondary transfer roller 15 and forms a secondary transfer nip portion. A belt cleaning device 16 that cleans the surface of the intermediate transfer belt 11 is disposed at a portion facing the roller 13.

  Above the secondary transfer nip portion of the printer, a fixing device 20 for fixing the toner image on the transfer paper P as a recording medium is disposed. The fixing device 20 fixes the color image transferred onto the transfer paper P by heat and pressure generated by the fixing belt and the pressure roller.

  In addition, toner bottles 30Y, 30C, 30M, and 30K that store replenishing toner are installed at the top of the printer. As will be described later, these toner bottles 30 (Y, M, C, K) and the developing device 3 (Y, M, C, K) are connected by a supply pipe (not shown). Then, toner to be supplied in the toner bottle 30 (Y, M, C, K) is supplied to the developing device 3 (Y, M, C, K) as necessary by a toner supply device (not shown). Note that the toner bottles 30 (Y, M, C, K) are detachably attached to the printer main body, and the replenishment toner in the toner bottles 30 (Y, M, C, K) is insufficient. Replaced with a new toner bottle.

  On the other hand, below the optical writing unit 5 of the printer, paper feed cassettes 21 and 22 for storing transfer paper P to be fed to the secondary transfer nip portion are arranged. The paper feed cassettes 21 and 22 are provided with paper feed rollers 23 and 24 for sending the uppermost transfer paper P in the paper feed cassettes 21 and 22 to the paper feed path 25.

  Next, an image forming operation in the printer having the above configuration will be described. When the transfer paper P fed from one of the paper feed cassettes 21 and 22 by the paper feed rollers 23 and 24 reaches the registration roller pair 26, the transfer paper P is temporarily stopped and stopped in order to match the timing of image formation. The photoreceptor 1 (Y, M, C, K) is rotationally driven in the clockwise direction in the figure by a drive motor (not shown), and is uniformly charged by the charging device 2 (Y, M, C, K) (charging). Process). The uniformly charged photoreceptor 1 (Y, M, C, K) is exposed and scanned with laser light by the optical writing unit 5 to form an electrostatic latent image (exposure process). Each electrostatic latent image is supplied with toner by the developing device 3 (Y, M, C, K) for each color, and yellow, magenta, cyan, and cyan are respectively applied to the surface of the photoreceptor 1 (Y, M, C, K). A black toner image is formed (development process). Next, a transfer bias opposite to the polarity of the toner is applied to the primary transfer roller 6 (Y, M, C, K), and the toner image on the photoreceptor 1 (Y, M, C, K) at the primary transfer nip portion. Are sequentially transferred onto the intermediate transfer belt 11 (primary transfer step). At this time, the image forming operation for each color is executed with the timing shifted from the upstream side toward the downstream side so that the toner image is transferred to the same position on the intermediate transfer belt 11. The surface of the photoreceptor 1 (Y, M, C, K) after the toner image is transferred is mechanically removed by the cleaning blade 4a of the cleaning device 4 (Y, M, C, K), and the next static Prepared for formation of an electrostatic latent image (cleaning step).

  The toner image transferred onto the intermediate transfer belt 11 is transported to the secondary transfer nip portion, and transferred to the transfer paper P transported to the secondary transfer nip portion at this timing. Thereafter, the transfer paper P onto which the toner image has been transferred is conveyed to the fixing device 20 and thermally fixed, and the transfer paper P after the fixing is discharged from the paper discharge roller 27 to the outside of the apparatus. On the other hand, the residual toner is removed from the intermediate transfer belt 11 after the transfer of the toner image by the belt cleaning device 16 to prepare for the image formation by the image forming unit 10 again.

  Next, the developing device 3 will be described in detail. The developing devices 3Y, 3M, 3C, and 3K use toners of different colors as image forming substances, but have the same configuration except for the above. For this reason, the subscripts Y, M, C, and K are omitted as appropriate. FIG. 3 is a configuration diagram showing the configuration of the developing device. FIG. 4 is a schematic diagram illustrating the flow of the developer in the developing device. FIG. 3 is a configuration diagram showing the configuration at the cross-sectional line indicated by X in FIG. In the figure, the flow of the developer is indicated by a dotted line.

  As shown in FIG. 3, the developing device 3 stores a developer G containing toner and a magnetic carrier in a developing container 31. The developing container 31 of the developing device 3 has an opening at a position facing the photoreceptor 1 (not shown in FIG. 3), and a part of the developing roller 32 that is a developer carrying member is exposed from the opening. , A development area is formed. The developing roller 32 is fixedly attached with a magnet (not shown) that radiates a magnetic field radially in a predetermined direction at the center thereof, and is cylindrically driven around the magnet in the direction of arrow A by a drive motor or the like. A developing sleeve (not shown) is rotatably attached.

  Further, an agent regulation that regulates the amount of developer held on the developing roller 32 on the upstream side in the surface movement direction of the developing roller 32 from the developing region so as to form a part of the opening of the developing container 31. A member 33 is provided. A magnetic plate 34 is attached to the agent regulating member 33. The base of the magnetic plate 34 is supported on the upstream side surface in the developer transport direction of the agent regulating member 33, the distal end side is bent substantially horizontally, and faces the developing roller 32 on the upstream side of the agent regulating member 33. The opposing surface is formed.

  A first conveyance path 35 as a first developer conveyance path and a second conveyance path 36 as a second developer conveyance path are formed at the bottom of the developer container 31 side by side with a partition wall 39 therebetween. Two agent delivery portions 39a and 39b are formed at both ends in the longitudinal direction of the partition wall 39, and the first transport path 35 and the second transport path 36 communicate with each other. The first developer path 35 rotates in the direction of arrow B (counterclockwise) in FIG. 3 and transports the developer G in the direction of arrow D in FIG. 4 along the axial direction of the developing roller 32. A first screw 37 as a member is provided. The second developing path 36 rotates in the direction of arrow C (clockwise) in FIG. 2 and conveys the developer G in the direction of arrow E in the figure, which is opposite to the direction of conveyance by the first screw 37. The 2nd screw 38 which is an agent conveyance member is provided.

  A density detection sensor 40 for detecting the toner density of the developer G is provided on the bottom surface of the second transport path 36. When the density detection sensor 40 detects that the toner density is insufficient, a toner supply device (not shown) is driven, and toner is supplied from the toner bottle 30 into the second conveyance path 36 through the toner supply port 36a.

  In the developing device 3 configured as described above, the developer G in the developing container 31 circulates as follows. The toner contained in the toner bottle 30 is replenished into the second transport path 36 via the toner replenishing port 36a by a toner replenishing device (not shown) according to the consumption of the toner in the developing device 3, and the second screw 38. Stir with the carrier. The developer G composed of toner and carrier in the second transport path 36 is transported in the longitudinal direction while being stirred by the second screw 38, and the developer G that has reached the downstream end in the transport direction passes through the end of the partition wall 39. Passes through the first agent delivery section 39 b and moves to the first transport path 35. The developer G in the first conveyance path 35 is conveyed in the opposite direction to the developer G in the second conveyance path 36 while being stirred by the first screw 37. Then, when reaching the downstream end of the first transport path 35 in the transport direction, the first transport path 35 passes through the agent delivery section 39a of the partition wall 39 and moves to the second transport path 36. As described above, the developer G is circulated in the developing container 31 including the first conveyance path 35 and the second conveyance path 36 by the first screw 37 and the second screw 38. In addition, the installation height of the first screw 37 and the second screw 38 and the developer circulation speed are set so that the developer surface height of the first transport path 35 is higher than the developer surface height of the second transport path. It has been adjusted.

  Here, as shown in FIG. 3, the first screw 37 in the first transport path 35 rotates in the direction of the arrow B so that the surface of the developer G rises to the right, that is, in the first transport path 35. The developer G is unevenly distributed on the developing roller 32 (agent regulating member 33) side. The second screw 38 in the second transport path 36 rotates in the direction of arrow C, so that the surface of the developer G rises to the left, that is, the developer G in the second transport path 36 is removed from the developing roller. 32 is unevenly distributed on the side away from 32.

  Of the developer G stirred and conveyed by the first screw 37 in the first conveying path 35, the developer G attracted by the magnetic force of the magnet roller of the developing roller 32 is carried on the surface of the developing sleeve (hereinafter referred to as “developing sleeve”). This position is called the supply position). The toner in the developer G is attracted to the carrier by frictional charging with the carrier, and is carried on the developing roller (developing sleeve) 32 together with the carrier. The layer thickness of the developer G carried on the developing roller (developing sleeve) 32 is regulated by passing through the gap between the developing roller 32 and the agent regulating member 33. The stirring function of the agent restricting member 33 is improved by the action of the opposing surface of the magnetic plate 34 provided on the upstream side of the agent restricting member 33.

  When the developer on the developing roller 32 that has passed through the agent regulating member 33 is transported to the developing area facing the photoreceptor 1, the developer is brought up on the developing sleeve by the magnetic force of the magnet roller. The carrier spiked on the developing roller (developing sleeve) 32 supplies the toner adhering to the carrier surface to the surface of the photosensitive member 1 while rubbing the surface of the photosensitive member 1. At this time, a developing bias is applied to the developing roller (developing sleeve) 32 from a power source (not shown), whereby a developing electric field is formed in the developing region.

  Then, between the electrostatic latent image on the photoreceptor 1 and the developing roller (developing sleeve) 32, an electrostatic force toward the electrostatic latent image side acts on the toner on the developing roller 32. As a result, the toner on the developing roller 32 adheres to the electrostatic latent image on the photoreceptor 1. By this adhesion, the electrostatic latent image on the photoreceptor 1 is developed into a corresponding color toner image. Thereafter, the developed developer that has consumed the toner on the developing roller 32 reaches the upper portion of the developing container 31 as the developing sleeve rotates, and the magnetic force from the magnet roller is released, whereby the developing roller (developing sleeve) 32 is released. (Hereinafter, this position is referred to as a separated position). The separated developer falls on a partition plate 41 described later and is collected in the first transport path 35.

  Here, in the developing device 5 according to this embodiment, as shown in FIG. 3, a partition plate 41 is disposed in the space between the developing roller 32 and the first screw 37. The partition plate 41 partitions the space facing the supply position on the developing roller 32 and the space facing the separation position on the developing roller 32 over the entire area in the longitudinal direction of the developing roller 32. The partition plate 41 opposes the upper end portion with a predetermined distance between the supply position and the separation position on the surface of the developing roller 32, and the lower end portion opposes the first screw 37 with a predetermined distance. doing. The partition plate 41 is inclined so that the horizontal position is away from the developing roller 32 from the upper end to the lower end. As a result, the supply path through which the developer in the first transport path 35 is supplied to the developing roller 32 and the recovery path from which the developed developer separated from the developing roller 32 is collected in the first transport path 35 are separated. It will be partitioned by the plate 41. The developer G in the first conveyance path 35 is supplied to the surface of the developing roller 32 through the supply path, and the developed developer separated at the separation position on the development roller 32 passes through the collection path to the first conveyance path 35. It will be collected inside.

  The developed developer separated from the developing roller 32 determines whether it is agitated with another developer by the first screw 37 or is pumped up again to the developing roller 32 with insufficient agitation depending on the dropping position. For example, as shown in FIG. 6, in the developing device that does not have the partition plate 41, there is a possibility that a part of the developed developer separated from the developing roller 32 may be re-pumped with insufficient stirring. In particular, when the image area ratio of the output image is high, the toner concentration of the developed developer after passing through the development region is low, and the toner concentration with the developer G on the first screw 37 is low. The difference is big. Therefore, when outputting an image with a high image area ratio, the developed developer having a lowered toner density is mixed with the developer G supplied to the supply position and re-pumped, so that the image density is locally increased. An abnormal image that becomes thinner may occur.

  On the other hand, in the developing device 3 according to this embodiment, the developed developer separated from the developing roller 32 falls along the partition plate 41, and the developing roller 32 is bordered on the screw shaft of the first screw 37. To the blade portion of the first screw 37 on the far side. The developed developer transported onto the first screw 37 is agitated with the developer G in the first transport path 35 by the rotation of the first screw 37 and then pumped up to the developing roller 32. In other words, the developed developer that has passed through the development region is sufficiently sprayed and agitated with the developer G on the first screw 37 in the first transport path 35 and then supplied to the developing roller 32. It is hard to generate an image.

  Depending on the inclination of the partition plate 41, the developed developer dropped from the partition plate 41 falls to the side closer to the developing roller 32 with the screw shaft of the first screw 37 as a boundary, and is stirred by the first screw 37. There is a risk of being re-pumped before Therefore, the partition plate 41 is inclined so as to drop the developed developer dropped from the partition plate 41 to the side farther from the developing roller with the screw shaft of the first screw 37 as a boundary.

  Next, the characteristic part of the developing device 5 according to the present embodiment will be described. The developing container 31 in the developing device 5 according to the present embodiment is formed with a communication port 42 that communicates the first transport path 35 and the second transport path 36 over the entire area in the longitudinal direction above the partition wall 39. ing. As shown in FIG. 3, the communication port 42 is formed so that the lower opening portion is lower than the lowermost portion of the partition plate 41 and higher than the uppermost portion of the second screw 38. . Here, the lower opening portion of the communication port 42 is a position H <b> 1 at the lowermost position in the vertical direction of the communication port 42, and is also the position of the upper end portion of the partition wall 39. The lowermost part of the partition plate 41 refers to the lowest position H2 in the vertical direction where the developer is restricted from moving. The uppermost portion of the second screw 38 refers to the uppermost position H3 in the vertical direction of the screw blade.

  In the developing device 3 provided with the communication port 42 in this way, as shown in FIG. 5, even if the toner concentration of the developer G in the developer container 31 increases and the volume of the developer increases, the first transport path 35 Therefore, the developer surface height of the developer G in the space facing the separated position is not excessively high. Even when the developer surface height of the developer G in the space opposite to the separation position is increased, the developed developer separated from the developing roller 32 does not accumulate on the partition plate 41 and passes through the communication port 42. Can move into the second conveyance path 36 (movement path). Thereby, it is possible to prevent the developed developer on the developing roller 32 from losing its place and being re-pumped between the developing roller 32 and the partition plate 41. Further, the developed developer on the developing roller 32 cannot be separated from the developing roller 32 and can be prevented from entering the developing region as it is.

  Further, when the toner concentration in the developing container 31 increases and the developer bulk in the second transport path 36 increases, there is a problem that it is difficult to take in the replenished toner. To solve this problem, when the second screw 38 rotates in the direction of arrow C (clockwise) in the figure, the developer moves to the left and the lighter specific toner moves to the right. Since the developed developer that has fallen from the partition plate 41 is conveyed into the second conveyance path 36 through the communication port 42, it falls on the toner T that is unevenly distributed to the right side of the screw shaft of the second screw 38. Become. Therefore, the installation of the communication port 42 has an effect of taking the unevenly distributed toner T into the developer G. If the replenishment toner is transported to the first conveyance path 35 without being taken in by the developer G, the replenishment toner is not sufficiently charged and is transported to the development region (unevenness in the replenishment toner portion is dark). End up. Thus, by providing the communication port 42, it is possible to suppress the occurrence of uneven image density due to poor replenishment toner dispersion at high toner density.

  As described above, the height of the developer surface in the first transport path 35 is higher than the height of the developer surface in the second transport path 36 so that the first screw 37 and the second screw 38 have a higher height. Installation height and developer circulation speed are adjusted. If the developer surface height of the first transport path 35 is lower than the developer surface of the second transport path 36, the developer G and toner in the second transport path 36 pass through the communication port 42 in the first transport path 35. Will move to. In such a case, an uncharged developer is liable to cause abnormal images such as toner scattering and background stains, which is not preferable.

Further, as described above, the communication port 42 described above has the following positional relationship in the vertical direction with respect to the partition plate 41 and the second screw 38.
(High) Lower part of partition plate> Lower part of communication port> Upper part of second screw (low)
When the lowermost part of the communication port 42 is lower than the uppermost part of the second screw 38, the developer G and toner in the second transport path 36 are transported to the first transport path 35 via the communication port 42. In such a case, an insufficiently charged developer that is not sufficiently agitated and mixed is conveyed to the development area, and abnormal images such as toner scattering and background contamination are likely to occur. Further, it is not preferable that the lowermost part of the partition plate 41 is located below the lowermost part of the communication port 42 because the developer that has dropped from the partition plate 41 tends to stay on the partition plate 41.

  By the way, although the above-mentioned communication port 42 may be attached to the whole longitudinal direction of the partition wall 39, even if it attaches to one part, the target function can be achieved. For example, the communication port 42 may be formed corresponding to a portion (for example, both end portions) where the developer surface height is increased in the first transport path 35.

What has been described above is merely an example, and the present invention has a specific effect for each of the following modes.
(Aspect A)
A developer carrying member such as a developing roller 32 carrying a two-component developer composed of toner and a carrier and transporting it to a developing region which is a facing portion of the latent image carrying member such as the photosensitive member 1, and the developer carrying member; A first transport in which a first developer transport member such as a first screw 37 for transporting the developer in the axial direction of the developer bearing member and supplying the developer to the developer bearing member is disposed. A first developer conveying path such as a path 35, the first developer conveying path and the developer carrying member in the axial direction communicate with each other at both ends, and the developer is in a direction opposite to the first developer conveying member. A second developer conveying path such as a second conveying path 36 on which a second developer conveying member such as a second screw 38 is disposed, and from the first developer conveying path to the developer carrying member. The supplied developer passes through the development area and is collected in the first developer transport path. In a developing device such as the device 3, a space opposite to a supply position where the developer is supplied from the first developer transport path to the developer carrier, and the developer that has passed through the development region is the developer carrier. A partition plate such as a partition plate 14 that partitions the space facing the separation position separated from the space, and development in the space facing the separation position according to the developer surface height in the space facing the separation position. A movement path in which the agent can move to the second developer conveyance path is formed.
According to this, as described in the above embodiment, even if the toner density of the developer in the developing device increases and the volume of the developer increases, the height of the developer surface in the first developer conveyance path increases. Never too much. Even when the developer surface height in the first developer conveyance path becomes high, the developed developer separated from the developer carrier does not collect on the partition plate, and the second development is performed via the communication port. It can move into the agent transport path (movement path). As a result, it is possible to prevent the developed developer on the developer carrier from losing its place and being re-pumped between the developer carrier and the partition plate. Further, it is possible to prevent the developed developer on the developer carrying member from entering the developing region without being separated from the developer carrying member.
(Aspect B)
In the developing device of (Aspect A), the first developer transport member rotates in a direction in which the developer in the first developer transport path is biased toward the developer carrier, and the second developer transport member is Then, the developer in the second developer transport path rotates in a direction biased to the side away from the developer carrier.
According to this, as described in the above embodiment, the developer is sufficiently present in the space facing the supply position in the first developer transport path as compared with the space facing the separation position. For this reason, the developer in the first developer conveyance path can be efficiently supplied to the developer carrier. In the second developer conveyance path, the developer is biased away from the developer carrier, and the toner having a low specific gravity is biased closer to the developer carrier. For this reason, in the second developer conveyance path, the developed developer falls on the toner through the communication port, so that the toner is easily taken into the developer. Therefore, it is possible to suppress the occurrence of uneven image density due to poor replenishment toner dispersion at a high toner density.
(Aspect C)
In the developing device of (Aspect A) or (Aspect B), the developer surface height in the first developer transport path is higher than the developer surface height in the second developer transport path.
According to this, as described in the above embodiment, it is possible to prevent the developer in the second developer transport path from moving into the first developer transport path via the communication port. Accordingly, it is possible to suppress the occurrence of abnormal images such as toner scattering due to insufficiently charged toner and background stains.
(Aspect D)
At least the latent image carrier in an image forming apparatus comprising a latent image carrier such as a photoreceptor 1 that carries a latent image and a developing unit such as a developing device 3 that develops the latent image on the latent image carrier, In the process cartridge in which the developing means is held on a common holding body as a unit and is detachable from the image forming apparatus main body, the developing device of (Aspect A), (Aspect B), or (Aspect C) is used.
According to this, as described in the above embodiment, it is possible to obtain a high-quality image with less occurrence of abnormal images such as image density unevenness and excellent maintainability.
(Aspect E)
At least an image carrier such as the photosensitive member 1, charging means such as a charging device 2 for charging the surface of the image carrier, and an optical writing unit 5 for forming an electrostatic latent image on the image carrier. In the image forming apparatus having a latent image forming means such as the above and a developing means such as the developing device 3 for developing the latent image on the image carrier to form a toner image, as the developing means, the mode A) ( The developing device of Aspect B) or (Aspect C) is used.
According to this, as described in the above embodiment, it is possible to obtain a high-quality image with less occurrence of abnormal images such as uneven image density.

DESCRIPTION OF SYMBOLS 1 Photoconductor 2 Charging device 3 Developing device 4 Cleaning device 5 Optical writing unit 6 Primary transfer roller 10 Image forming part 31 Developing container 32 Developing roller 33 Agent regulating member 34 Magnetic plate 35 First transport path 36 Second transport path 37 First One screw 38 Second screw 39 Partition wall 40 Concentration detection sensor 41 Partition plate 42 Communication port

JP 2012-133119 A

Claims (5)

A developer carrier that carries a two-component developer composed of a toner and a carrier and conveys the developer to a development region that is opposite to the latent image carrier;
A first developer in which a first developer conveying member is arranged to convey the developer in the axial direction of the developer carrying body and to supply the developer to the developer carrying body facing the developer carrying body A transport path;
A second developer conveying member that communicates at both ends in the axial direction of the first developer conveying path with the developer carrying member and conveys the developer in a direction opposite to the first developer conveying member is disposed. A second developer transport path,
In the developing device in which the developer supplied to the developer carrying member from the first developer transport path passes through the development region and is collected in the first developer transport path.
The space facing the supply position where the developer is supplied to the developer carrier from the first developer conveyance path, and the separation position where the developer that has passed through the development region is separated from the developer carrier. A partition plate for partitioning the space is provided, and the developer in the space facing the separation position can move to the second developer conveyance path according to the height of the developer surface in the space facing the separation position. A developing device in which a movement path is formed. The developing device according to claim 1.
The first developer transport member rotates in a direction in which the developer in the first developer transport path is biased toward the developer carrier,
The developing device, wherein the second developer transport member rotates in a direction in which the developer in the second developer transport path is biased to a side away from the developer carrier. The developing device according to claim 1 or 2,
The developing device, wherein a developer surface height in the first developer transport path is higher than a developer surface height in the second developer transport path. A latent image carrier for carrying a latent image;
In an image forming apparatus comprising a developing unit that develops a latent image on the latent image carrier, at least the latent image carrier and the developing unit are held as a single unit on a common holder and are held in the main body of the image forming apparatus. In the removable process cartridge,
A process cartridge using the developing device according to claim 1, 2 or 3. At least an image carrier, a charging unit for charging the surface of the image carrier, a latent image forming unit for forming an electrostatic latent image on the image carrier, and a latent image on the image carrier. In an image forming apparatus having a developing means for developing and forming a toner image,
An image forming apparatus using the developing device according to claim 1, 2 or 3 as the developing means.

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