JP5870772B2 - Developing device and image forming apparatus - Google Patents

Description

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

  For example, Patent Document 1 discloses a developing unit that develops an electrostatic latent image formed on a photosensitive drum with toner in an image forming apparatus to form a toner image. The developing unit is provided with a developing sleeve that rotates to convey the developer toward the photosensitive drum and develop the electrostatic latent image on the photosensitive drum. As the developing sleeve rotates, when the developer after development returns from the photosensitive drum into the housing, air contained in the developer flows into the housing. The developing unit of Patent Document 1 is provided with a pressure release hole for discharging the air in the housing and an electrostatic filter. Further, in the developing device of Patent Document 2, a meandering channel communicating with the outside is provided on the top plate of the casing in order to release the pressure of the casing.

JP 2006-3396 A JP 2010-54932 A

  An object of the present invention is to provide a developing device and an image forming apparatus that do not require a filter or a meandering flow path in a path for releasing pressure.

The developing device according to claim 1 is a center in the transport direction between a main space in which a first transport path for transporting a developer is formed in a lower portion and the first transport path arranged next to the first transport path. A part is partitioned and a second transport path for reciprocally transporting the developer in cooperation with the first transport path, and the developer in the second transport path is moved from the second transport path to the first transport path. Of the developer that continuously extends to the side end and is transported on the second transport path, and transports excess developer excluding the developer delivered to the first transport path to the outside. A container having a discharge path for discharging, and containing a developer;
A first stirring and conveying member arranged in the first conveying path for conveying the developer while stirring;
A second agitating and conveying member disposed in the second conveying path and conveying the developer in a direction opposite to the first agitating and conveying member while stirring the developer;
The developer in the main space by rotating and disposed on the opposite side of the first conveyance path to the second conveyance path and diagonally above the first conveyance path. A developer conveying member that conveys the toner to the developing object;
In the main space, disposed above the first stirring / conveying member, and rotated, the first developer is conveyed to the developer conveying member from the developing object and returned while stirring. A stirring member that drops onto one transport path,
The container further includes an air passage that opens into the main space above the stirring member and continues to the second conveyance path.

The developing device according to claim 2, wherein the developer conveying member is arranged side by side, and has two developing rolls rotating while holding the developer on the surface,
The opening of the air passage is an opening opened toward the flow path of the developer held on the upper developing roll of the two developing rolls and returning to the main space.

  In the developing device according to a third aspect, the discharge path has a step portion between the discharge path and the second transfer path, and is formed narrower than the second transfer path. It is characterized by being.

An image forming apparatus according to claim 4
A developing object on which an electrostatic latent image is formed and the electrostatic latent image is developed;
A developing device for developing the electrostatic latent image on the development target,
The developing device is
A central portion in the transport direction between the main space in which a first transport path for transporting a developer is formed in the lower portion and the first transport path is arranged next to the first transport path, and the first transport path is partitioned. A second conveying path for reciprocally conveying the developer in cooperation with the path, and a cylinder continuously to the end of the second conveying path on the side where the developer is moved from the second conveying path to the first conveying path. A discharge path that extends in a shape and transports excess developer excluding the developer delivered to the first transport path out of the developer transported on the second transport path, and discharges it to the outside. A container for containing a developer;
A first stirring and conveying member arranged in the first conveying path for conveying the developer while stirring;
A second agitating and conveying member disposed in the second conveying path and conveying the developer in a direction opposite to the first agitating and conveying member while stirring the developer;
The developer in the main space by rotating and disposed on the opposite side of the first conveyance path to the second conveyance path and diagonally above the first conveyance path. A developer conveying member that conveys the toner to the developing object;
In the main space, disposed above the first stirring / conveying member, and rotated, the first developer is conveyed to the developer conveying member from the developing object and returned while stirring. A stirring member that drops onto one transport path,
The container further includes an air passage that opens into the main space above the stirring member and continues to the second conveyance path.

  The developing device according to claim 1 and the image forming apparatus according to claim 4 do not require a filter or a meandering channel in the path for releasing the pressure.

  According to the developing device of the second aspect, the disturbance of the air flow from the upper developing roll having a relatively large air intake amount is suppressed as compared with the case where the present configuration is not provided.

  According to the developing device of the third aspect, the clogging of the path by the developer is suppressed as compared with the case where the ventilation groove is not formed.

1 is a configuration diagram illustrating an embodiment of an image forming apparatus of the present invention. It is a perspective view which shows the developing device shown in FIG. FIG. 3 is a longitudinal sectional view of the developing device shown in FIG. 2. It is a plane block diagram which shows schematic structure of a developing device. It is a cross-sectional perspective view which shows the state which cut | disconnected the developing device horizontally. FIG. 6 is a cross-sectional perspective view showing a cross section taken along line 6-6 of the developing device shown in FIG. It is a longitudinal cross-sectional view explaining the schematic structure of the discharge path part of a developing device.

  Embodiments of the present invention will be described below with reference to the drawings.

  FIG. 1 is a configuration diagram showing an embodiment of an image forming apparatus of the present invention.

  The image forming apparatus 1 shown in FIG. 1 has image forming units 10Y, 10M, 10C, and 10K arranged in parallel for each color of yellow (Y), magenta (M), cyan (C), and black (K). The tandem type color printer can print a single color image and can print a full color image composed of four color toner images. The toner cartridges 18Y, 18M, 18C, and 18K contain YMCK color toners.

  Since the four image forming units 10Y, 10M, 10C, and 10K have substantially the same configuration, the image forming unit 10Y corresponding to yellow will be described as a representative example. The image forming unit 10Y includes a photoreceptor drum 11Y, a charger 12Y, an exposure device 13Y, a developing device 20Y, a primary transfer device 15Y, and a photoreceptor cleaner 16Y. The developing device 20Y is an embodiment of the developing device of the present invention, and the photosensitive drum 11Y corresponds to an example of the developing target according to the present invention.

  The photoconductive drum 11Y is provided with a photoconductive layer on the surface of a cylindrical substrate, and holds an image formed on the surface and rotates in the direction of arrow A around the axis of the cylinder. The charger 12Y, the exposure device 13Y, the developing device 20Y, the primary transfer device 15Y, and the photoconductor cleaner 16Y are arranged in the order of the arrow A around the photoconductor drum 11Y.

  The charger 12Y is a device that charges the surface of the photosensitive drum 11Y. The charger 12Y is a charging roll that comes into contact with the surface of the photosensitive drum 11Y. A voltage having the same polarity as that of the toner in the developing device 20Y is applied to the charger 12Y, and the surface of the photosensitive drum 11Y in contact with the charger 12Y is charged. The exposure device 13Y is a device that exposes the surface of the photosensitive drum 11Y by exposing it to exposure light. The exposure device 13Y emits a laser beam corresponding to an image signal supplied from the outside of the image forming apparatus 1, and scans the photosensitive drum 11Y with the laser beam. The developing device 20Y develops the surface of the photosensitive drum 11Y using a developer. Toner is supplied from the toner cartridge 18Y to the developing device 20Y. The developing device 20Y charges the toner and the magnetic carrier by stirring the developer in which the magnetic carrier and the toner are mixed, and develops the surface of the photoreceptor drum 11Y with the charged toner. The primary transfer unit 15Y is a roll that faces the photosensitive drum 11Y with the intermediate transfer belt 30 interposed therebetween. The primary transfer unit 15Y transfers a toner image on the photosensitive drum 11Y to the intermediate transfer belt 30 by applying a voltage to the photosensitive drum 11Y. The photoreceptor cleaner 16Y cleans the surface of the photoreceptor drum 11Y by removing unnecessary materials such as toner remaining on the portion of the surface of the photoreceptor drum 11Y that has been transferred by the primary transfer unit 15Y.

  The image forming apparatus 1 also includes an intermediate transfer belt 30, a fixing device 60, a paper transport unit 80, and a control unit 1A. The intermediate transfer belt 30 is an endless belt that is stretched between belt support rolls 31 to 35. The intermediate transfer belt 30 circulates in the direction of arrow B passing through the image forming units 10Y, 10M, 10C, and 10K and the secondary transfer unit 50. The toner images of the respective colors are transferred to the intermediate transfer belt 30 from the image forming units 10Y, 10M, 10C, and 10K. The intermediate transfer belt 30 moves while holding the toner images of these colors.

  The secondary transfer device 50 is a roll that rotates with the intermediate transfer belt 30 and the paper P interposed between the backup roll 34 that is one of the belt support rolls 31 to 35. The secondary transfer device 50 transfers the toner image on the intermediate transfer belt 30 onto the paper P by applying a voltage having a polarity opposite to the charging polarity of the toner.

  The fixing device 60 is a device that fixes the toner image on the paper P. The fixing device 60 includes a heating roll 61 and a pressure roll 62, and a heater is disposed in the heating roll 61. The heating roll 61 and the pressure roll 62 sandwich and pass the paper P on which the toner image before fixing is formed to heat and press the toner, thereby fixing the toner image on the paper P.

  The paper transport unit 80 includes a take-out roll 81 that takes out the paper P stored in the paper container T, a transport roll 82 that transports the paper P, a registration roll 84 that transports the paper P to the secondary transfer device 50, and a paper A discharge roll 86 for discharging P to the outside is provided. The paper transport unit 80 transports the paper P along a paper transport path R that passes through the secondary transfer device 50 and the fixing device 60.

  The basic operation of the image forming apparatus 1 shown in FIG. 1 will be described. In the yellow image forming unit 10Y, the photosensitive drum 11Y is rotationally driven in the direction of arrow A, and the surface of the photosensitive drum 11Y is charged by the charger 12Y. The exposure device 13Y irradiates the photosensitive drum 11Y with exposure light corresponding to data corresponding to each color in the image signal. The exposure device 13Y irradiates the surface of the photosensitive drum 11Y with exposure light based on the image signal corresponding to yellow among the image signals supplied from the outside, thereby forming an electrostatic latent image on the surface of the photosensitive drum 11Y. Form. Yellow toner is supplied from the toner cartridge 18Y to the developing device 20Y. The developing device 20Y forms a toner image by developing the electrostatic latent image on the photosensitive drum 11Y with toner. The photosensitive drum 11Y rotates while holding a yellow toner image formed on the surface. The toner image formed on the surface of the photoreceptor drum 11Y is transferred to the intermediate transfer belt 30 by the primary transfer unit 15Y. After the transfer, the toner remaining on the photoconductive drum 11Y is removed by the photoconductive cleaner 16Y.

  The intermediate transfer belt 30 is cyclically moved in the arrow B direction. Similar to the image forming unit 10Y, the image forming units 10M, 10C, and 10K corresponding to colors other than yellow form toner images corresponding to the respective colors and transferred to the intermediate transfer belt 30 by the image forming unit 10Y. The toner image of each color is transferred so as to be superimposed on the toner image.

  The paper P is taken out from the paper container T by the take-out roll 81. The paper P is transported along the paper transport path R in the direction of arrow C toward the secondary transfer device 50 by the transport roll 83 and the registration roll 84. The registration roll 84 sends the paper P to the secondary transfer device 50 based on the timing at which the toner image is transferred onto the intermediate transfer belt 30. The secondary transfer unit 50 transfers the toner image on the intermediate transfer belt 30 onto the paper P. The paper P onto which the toner image has been transferred is conveyed from the secondary transfer device 50 to the fixing device 60, and the toner image transferred onto the paper P is fixed. In this way, an image is formed on the paper P. The paper P on which the image is formed is discharged to the outside of the image forming apparatus 1 by a discharge roll 86. The toner remaining on the intermediate transfer belt 30 after the transfer by the secondary transfer device 50 is removed by the belt cleaner 70.

[Developer]
FIG. 2 is a perspective view showing the developing device shown in FIG. FIG. 3 is a longitudinal sectional view of the developing device shown in FIG. FIG. 4 is a plan configuration diagram showing a schematic structure of the developing device. Since the configurations shown in these drawings are common to each color of YMCK, hereinafter, the reference numeral of the developing device is simply 20.

  The developing device 20 includes a container 21, a first developing roll 22, a second developing roll 24, a first stirring and conveying member 25, a second stirring and conveying member 26, and a paddle member 27. Here, the combination of the first developing roll 22 and the second developing roll 24 corresponds to an example of the developer transport body referred to in the present invention. The paddle member 27 corresponds to an example of the stirring member referred to in the present invention.

  The first developing roll 22 and the second developing roll 24 are cylindrical members, and are arranged side by side so that the circumferential surface faces the photosensitive drum 11 (see FIG. 1). Here, the extending direction of the first developing roll 22 and the second developing roll 24 is referred to as an axial direction Y. The first developing roller 22 is disposed downstream of the second developing roller 24 in the direction in which the circumferential surface of the photosensitive drum 11 rotating in the direction of arrow A moves. The developing device 20 is adapted to increase the image forming speed by increasing the developing ability by the two developing rolls 22 and 24.

  The container 21 supports each part of the developing device 20 and houses a developer. As shown in FIG. 3, the container 21 is provided with a main space 210 in which the first developing roll 22 and the second developing roll 24 are arranged. A paddle member 27 is also disposed in the main space 210. The paddle member 27 has a structure in which a plate-like paddle is erected on a rotating shaft extending in the axial direction Y. The paddle member 27 rotates clockwise in FIG. A first transport path 211 for transporting the developer is formed below the main space 210. The first developing roller 22 and the second developing roller 24 are disposed on the opposite side of the main space 210 to the second conveying path 212 across the first conveying path 211 and obliquely above the first conveying path 211. ing. A second transport path 212 is provided side by side next to the first transport path 211.

  The first stirring and conveying member 25 and the second stirring and conveying member 26 are members that convey the developer in the container 21 while stirring. The first agitation transport member 25 is disposed in the first transport path 211, and the second agitation transport member 26 is disposed in the second transport path 212. As shown in FIG. 4, each of the first agitation transport member 25 and the second agitation transport member 26 has a structure in which spiral blades are provided around a rotation shaft extending in the axial direction Y. The first agitating and conveying member 25 and the second agitating and conveying member 26 are arranged side by side, and the first agitating and conveying member 25 is adjacent to the first developing roll 22. The paddle member 27 is disposed above the first stirring / conveying member 25. In the first conveyance path 211 and the second conveyance path 212 in which the first agitation conveyance member 25 and the second agitation conveyance member 26 are arranged, the central portion in the axial direction Y that is the conveyance direction of the developer is partitioned by the partition part 213. ing. Communication ports 213a and 213b are provided at both ends in the axial direction Y of the partition portion 213. The developer is reciprocated along the first conveyance path 211 and the second conveyance path 212 by the first agitation conveyance member 25 and the second agitation conveyance member 26, and is delivered to the opposite conveyance path through the communication ports 213a and 213b. The first agitating and conveying member 25 conveys the developer in the direction of arrow F in FIG. 4, and the second agitating and conveying member 26 conveys the developer in the direction of arrow G opposite to the first agitating and conveying member 25.

  A toner supply unit 215 is provided in a portion of the first transport path 211 adjacent to the communication port 213a. Toner 21 is supplied with toner from toner cartridges 18 to 18K (see FIG. 1) via toner supply unit 215. The developer mixed with the toner is agitated by the first agitating and conveying member 25 and the second agitating and conveying member 26, whereby the toner of the developer and the magnetic carrier are charged.

  The container 21 is provided with a discharge path 214 for discharging the developer. The discharge path 214 extends in a cylindrical shape continuously to the end of the second transport path 212 on the side where the developer is moved from the second transport path 212 to the first transport path 211. The discharge path 214 transports and discharges the excess developer excluding the developer delivered to the first transport path 211 through the communication port 213a among the developers transported through the second transport path 212. The developer is discharged to the outside of the developing device 20 through a discharge port 214h provided at the bottom of the discharge path 214. The amount of developer discharged from the discharge path 214 is very small compared to the amount delivered to the first transport path 211. The developer discharged from the discharge path 214 contains a magnetic carrier. From the toner cartridges 18 to 18K (see FIG. 1), in addition to the toner, a magnetic carrier corresponding to the amount discharged is supplied. Therefore, the magnetic carrier in the container 21 is gradually replaced with a new one.

  FIG. 5 is a cross-sectional perspective view showing a state in which the developing device is cut horizontally. FIG. 6 is a cross-sectional perspective view showing a cross section taken along line 6-6 of the developing device shown in FIG. FIG. 7 is a longitudinal sectional view illustrating a schematic structure of a discharge path portion of the developing device. FIG. 7 also shows a collection container 9 that accommodates the developer discharged from the discharge path 214.

  As shown in FIGS. 5 and 7, the discharge path 214 extends linearly following the second transport path 212. As shown in FIG. 7, the discharge path 214 is formed narrower than the second transport path 212, and a step portion 214 s is provided between the discharge path 214 and the second transport path 212. The second agitating and conveying member 26 extends into the discharge path 214, but the front portion of the discharge path 214 has a reverse blade 26 f whose spiral direction is opposite to that of the remaining portion. The reverse blade 26f conveys the developer conveyed in the direction of arrow G back through the second conveyance path 212, thereby conveying the developer from the communication port 213b to the first conveyance path 211. The amount of the developer that enters the discharge path 214 is limited by the reverse blade 26f and the step portion 214s of the discharge path 214. As shown in FIGS. 5 and 6, a ventilation groove 214 g following the second conveyance path 212 is formed in the upper part of the discharge path 214.

  The description will be continued with reference to FIG. 3 again. A first magnet 221 is disposed inside the first developing roll 22 and attracts the developer to the first developing roll 22. A second magnet 241 is disposed inside the second developing roll 24 and attracts the developer to the second developing roll 24. Each of the first developing roller 22 and the second developing roller 24 rotates to convey the developer in the main space 210 to the surface of the photosensitive drum 11. In the present embodiment, the first developing roll 22 rotates in the direction of arrow D, and the second developing roll 24 rotates in the direction of arrow E, which is the opposite direction to the first developing roll 22. That is, the first developing roll 22 and the second developing roll 24 rotate so that the circumferential surfaces facing each other move in the same direction. The first developing roll 22 moves in the same direction as the movement direction of the circumferential surface of the photosensitive drum 11 in the first developing area d1 facing the photosensitive drum 11. In the second developing roll 24, the circumferential surface facing the photosensitive drum 11 in the second developing area d2 moves in the direction opposite to the moving direction of the circumferential surface of the photosensitive drum 11.

  The main space 210 is provided with a layer regulating member 281 and a guide member 282. The layer regulating member 281 is a plate-like member having an edge directed toward the first developing roll 22, and the developer layer on the first developing roll 22 is formed by a gap between the layer regulating member 281 and the first developing roll 22. Thickness is regulated. The guide member 282 is a plate-like member passed between the second developing roll 24 and the paddle member 27, and guides the developer conveyed back to the second developing roll 24 to the paddle member 27.

  The container 21 is provided with a ventilation path 29 that connects the main space 210 and the second transport path 212. The air passage 29 is provided on the opposite side of the first developing roll 22 and the second developing roll 24 with the paddle member 27 interposed therebetween, and is a horizontally long cavity extending in the axial direction Y. One end of the air passage 29 opens to the upper part of the second transport path 212, and the opposite end opens to the main space 210 at the upper part of the paddle member 27. The wall that defines the air passage 29 is formed by the upper part of the partition part 213 extending above the first stirring and conveying member 25 and the second stirring and conveying member 26 and extending to the upper part of the paddle member 27. The opening of the air passage 29 opens toward the upper part of the upper second developing roll 24 of the two developing rolls 22 and 24. When the second developing roll 24 rotates in the direction of arrow E, the developer held on the second developing roll 24 returns to the main space 210 through the upper part of the second developing roll 24, but the opening of the air passage 29 is , And open toward the flow path returning to the developer main space 210.

[Developer operation]
The operation of the developing device 20 will be described. As shown in FIG. 4, the developer is transported through the first transport path 211 and the second transport path 212 while the developer is stirred as the first stirring transport member 25 and the second stirring transport member 26 rotate. The magnetic carrier and toner of the developer are charged by stirring. The developer is delivered between the first conveyance path 211 and the second conveyance path 212 via the connection ports 213a and 213b. A part of the developer is transported through the discharge path 214 and discharged from the developing device 20. This developer is collected in a collection container 9.

  As shown in FIG. 3, the developer conveyed by the first agitating / conveying member 25 is attracted to the first developing roll 22 by the first magnet 221 and forms a spike on the first developing roll 22. The developer is supported on the first developing roll 22 and moves in the direction of arrow D. Part of the developer moves to the second developing roll 24 after the thickness is regulated by the layer regulating member 205. The developer transferred onto the second developing roll 24 is conveyed by the second developing roll 24 to the second developing area d2 facing the photosensitive drum 11. The developer remaining on the first developing roll 22 is conveyed to the first developing area d1 facing the photosensitive drum 11.

  The photosensitive drum 11 is in contact with the developer at two locations facing the first developing roll 22 and the second developing roll 24. The toner in the developer adheres to the electrostatic latent image on the photosensitive drum 11 to form a toner image. Of the developer supported by the first developing roll 22, the developer other than that adhering to the photosensitive drum 11 is transported to the first developing roll 22 and returns to the first agitation transport member 25. Further, of the developer supported on the second developing roll 24, the developer other than that adhering to the photosensitive drum 11 is conveyed to the second developing roll 24 and then guided on the guide member 282 to be padded 27. To. The developer is stirred by the paddle member 27 and falls onto the first stirring and conveying member 25.

  The stand-up developer supported by the second developing roll 24 contains air, and when this developer passes through the photosensitive drum 11 and returns to the container 21, air is also contained in the container 21. It is captured. Air is also taken in when the developer on the first developing roll 22 returns into the container 21. However, since the lower portion of the first developing roller 22 of this embodiment is in contact with the developer in the first transport path 211, the amount of air taken in is smaller than that of the second developing roller 24. That is, the second developing roll 24 takes in more air than the first developing roll 22.

  The air taken in by the second developing roll 24 is taken into the air passage 29 that opens to the main space 210 at the upper part of the paddle member 27, and is sent to the second transport passage 212 through the air passage 29. Since the air passage 29 is open at the top of the paddle member 27, air is taken into the upper air passage 29 and the developer is taken into the lower paddle member 27. Therefore, for example, the amount of developer mixed in the air passage 29 can be suppressed as compared with a case where the air passage opens to a position lower than the upper portion of the paddle member. The opening of the air passage 29 is open toward the flow path that returns to the developer main space 210 held by the second developing roll 24. For this reason, the turbulence of the air flow between the second developing roll 24 and the air passage 29 is suppressed, and the amount of the developer mixed in the air passage 29 is suppressed.

  The air sent to the second conveyance path 212 flows through the second conveyance path 212. Since the developer is transported in the lower portion of the second transport path 212, air flows above the developer. From the air passage 29, the developer floating in the air also enters the second transport path 212, and this developer falls while passing through the second transport path 212 and is separated from the developer in the second transport path 212. Mixed. Air enters the discharge path 214 from the second transport path 212.

  As shown in FIG. 7, the discharge path 214 is formed narrower than the second transport path 212, and the developer transported to the second agitation transport member 26 rises in a portion corresponding to the communication port 213a. The upper part of the discharge path 214 may be reached. Even in this case, the air enters the discharge path 214 through the ventilation groove 214g provided in the upper part of the discharge path 214, and is discharged from the discharge port 214h through the upper part of the discharge path 214. The discharge path 214 is for discharging in order to gradually replace the developer in the container 21, and the discharge amount in the normal operation state is very small. Accordingly, although the discharge port 214h of the discharge path 214 is provided at the bottom, the discharge port 214h is not blocked by the developer and there is a gap through which air flows out. The air that flows out from the discharge port 214h of the discharge path 214 is discharged from the hole 9h provided in the collection container 9.

  Since the developing device 20 discharges air using the developer outlet 214h, it is not necessary to provide a hole for discharging the air. Further, the developing device 20 discharges the air taken in by the second developing roll 24 to the outside of the container 21 through the ventilation path 29, the second transport path 212, and the discharge path 214. The developer in the air falls and separates while passing through this path. Therefore, for example, the amount of developer leakage is reduced compared to a configuration in which a discharge port leading to the outside is formed near the developing roll of the container. Therefore, a filter or a meandering flow path in the air discharge path is unnecessary, and even when a filter is provided in the hole of the collection container, for example, the filter is not clogged.

  In the above-described embodiment, two rolls of the first developing roll 22 and the second developing roll 24 are shown as the developer conveying member. However, the present invention is not limited to this, and the developer conveying member may be a single roll.

  In the above-described embodiment, a configuration including a charging roll and a laser exposure device is shown as an example of the image forming apparatus according to the present invention. However, the image forming apparatus referred to in the present invention is not limited to this. For example, the image forming apparatus may include a corona discharger such as a corotron or a scorotron instead of a charging roll, and includes a plurality of light emitting diodes instead of a laser exposure unit. It may have an array. In addition, the image forming unit referred to in the present invention may be a unit that directly applies a potential corresponding to an image to an image holding member by an electrode array.

  In the embodiment described above, a tandem color printer is shown as an example of the image forming apparatus. However, the image forming apparatus referred to in the present invention is not limited to this, and may be a monochrome printer that does not have an intermediate transfer belt, for example.

  In the above-described embodiment, a printer is shown as an example of the image forming apparatus. However, the image forming apparatus referred to in the present invention is not limited to a printer, and may be, for example, a copying machine or a facsimile.

DESCRIPTION OF SYMBOLS 1 Image forming apparatus 10Y, 10M, 10C, 10K Image forming part 11 Photoconductor drum 20 Developing device 21 Container 22, 24 Developing roll 25 First stirring conveyance member 26 Second stirring conveyance member 27 Paddle member 29 Air passage 210 Main space 211 1st conveyance path 212 2nd conveyance path 214 Discharge path 214s Step part 214g Ventilation groove

Claims (4)

A central portion in the transport direction between the main space in which a first transport path for transporting developer is formed in the lower portion and the first transport path is arranged beside the first transport path, and the first transport path is partitioned. A second conveyance path for reciprocally conveying the developer in cooperation with the path, and a cylinder continuously to the end of the second conveyance path on the side where the developer is moved from the second conveyance path to the first conveyance path A discharge path extending in a shape and transporting excess developer excluding the developer delivered to the first transport path out of the developer transported on the second transport path and discharging it to the outside, A container for containing a developer;
A first agitating and conveying member arranged in the first conveying path for conveying the developer while stirring;
A second agitating and conveying member disposed in the second conveying path and conveying the developer in a direction opposite to the first agitating and conveying member while stirring the developer;
The developer in the main space by rotating and disposed on the opposite side of the main conveyance space to the second conveyance path across the first conveyance path and obliquely above the first conveyance path A developer conveying member that conveys the toner to the developing object;
In the main space, disposed above the first stirring / conveying member, by rotating, the first developer transported from the developing object to the developer conveying member and stirring the developer is returned to the first space. A stirring member that drops onto one transport path,
The developing device according to claim 1, wherein the container further includes a ventilation path that opens to the main space above the stirring member and continues to the second conveyance path. The developer conveying member is arranged side by side, and has two developing rolls that rotate while holding the developer on the surface,
The opening of the air passage is an opening opened toward a flow path of the developer held on the upper developing roll of the two developing rolls and returning to the main space. The developing device according to 1.   2. The discharge path has a step portion between the discharge path and the second transfer path, and is formed narrower than the second transfer path. Alternatively, the developing device according to 2. A developing object on which an electrostatic latent image is formed and the electrostatic latent image is developed;
A developing device that develops the electrostatic latent image on the developing object,
The developing device is
A central portion in the transport direction between the main space in which a first transport path for transporting developer is formed in the lower portion and the first transport path is arranged beside the first transport path, and the first transport path is partitioned. A second conveyance path for reciprocally conveying the developer in cooperation with the path, and a cylinder continuously to the end of the second conveyance path on the side where the developer is moved from the second conveyance path to the first conveyance path A discharge path extending in a shape and transporting excess developer excluding the developer delivered to the first transport path out of the developer transported on the second transport path and discharging it to the outside, A container for containing a developer;
A first agitating and conveying member arranged in the first conveying path for conveying the developer while stirring;
A second agitating and conveying member disposed in the second conveying path and conveying the developer in a direction opposite to the first agitating and conveying member while stirring the developer;
The developer in the main space by rotating and disposed on the opposite side of the main conveyance space to the second conveyance path across the first conveyance path and obliquely above the first conveyance path A developer conveying member that conveys the toner to the developing object;
In the main space, disposed above the first stirring / conveying member, by rotating, the first developer transported from the developing object to the developer conveying member and stirring the developer is returned to the first space. A stirring member that drops onto one transport path,
The image forming apparatus according to claim 1, wherein the container further includes a ventilation path that opens to the main space above the stirring member and continues to the second conveyance path.

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