JP5471979B2 - Developing device and image forming apparatus - Google Patents

Description

  The present invention relates to a developing device and an image forming apparatus provided with the device, and in particular, when using a two-component system that replenishes toner and a carrier independently, a developer stored inside and a new replenishment Relates to a technique for promoting mixing with a prepared carrier.

In an electrophotographic image forming apparatus, in order to develop (develop) an electrostatic latent image formed on the surface of a photoreceptor, the developing apparatus uses a two-component developer containing toner and a carrier. It is known to use a one-component developer containing no carrier.
When using a two-component developer, first, the toner and carrier are stirred and mixed to charge the toner, and then only the toner is supplied to the surface of the photosensitive member to develop an electrostatic latent image (development). ) Therefore, only the toner is consumed by the development of the electrostatic latent image, and the carrier is not consumed. Therefore, a system in which only the toner is replenished with the carrier as it is can be considered.

  However, if the image formation is repeated, the toner adheres to the carrier surface and the performance of charging the toner decreases. Therefore, in order to extend the life of the developing device, the carrier with a deteriorated charging performance is discarded little by little. A trickle system for replenishing new carriers was developed. According to the trickle method, a new carrier is replenished as needed, so that the charging performance of the carrier can be maintained.

In this trickle system, in order to simplify the apparatus configuration, a system in which toner and carrier are supplied at the same time by supplying from a developer cartridge containing a developer in which toner and carrier are mixed at a fixed ratio can be considered. ing.
However, the toner consumption per recording sheet (hereinafter simply referred to as “toner consumption”) varies greatly depending on the image to be formed. For example, text documents tend to consume less toner, while photographic images tend to increase toner consumption. On the other hand, the deterioration of the carrier depends on the number of times of stirring in the developing device, that is, the number of times of image formation (number of recording sheets) regardless of the toner consumption.

  Therefore, depending on the amount of toner consumed, if a developer in which toner and carrier are mixed at a constant ratio is replenished, if the amount of toner consumed is large, a large amount of toner must be replenished. And the carrier is wasted. On the contrary, when the toner consumption is small, it is not necessary to replenish the toner so much, so that the replenishment of the carrier is also reduced, so that the metabolism of the carrier is lowered and the charging performance may be deteriorated.

  For this reason, a technique for replenishing toner and carrier separately without mixing them in advance has been proposed (see Patent Documents 1 and 2).

JP 2001-183893 A JP 2003-337469 A

However, since the specific gravity of the carrier is 5 to 10 times larger than that of the toner, it is difficult to mix if the toner is not mixed in advance and the toner is sufficiently mixed even if the toner and the carrier are not mixed well. There is a problem that it is difficult to charge.
The present invention has been made in view of the above-described problems, and in the case of using a two-component development system in which toner and a carrier are supplied independently, the development stored in the developing device is stored. It is an object of the present invention to provide a developing device and an image forming apparatus that can promote mixing of an agent and a newly replenished carrier.

  In order to achieve the above object, a developing device according to the present invention is a developing device for agitating a two-component developer comprising a toner and a carrier while circulating it in a developer tank, and for developing an electrostatic latent image. The developer tank is disposed at a position higher than the first tank in the direction of gravity and the first tank transports the developer in the first transport direction while stirring the developer. A second tank that transports in the opposite second transport direction, and a first communication port that communicates with the upstream side in the developer transport direction of the second tank on the downstream side in the developer transport direction of the first tank, and the second tank And a second communication port that communicates with the upstream side of the developer conveyance direction of the first tank, and is provided from the first tank to the second tank via the first communication port. Communicating with the lifting path when lifting the developer to the A carrier supply tank, and a toner supply tank that communicates with the dropping path when the developer is dropped from the second tank to the first tank via the second communication port, and receives toner supply from above in the direction of gravity. It is characterized by providing.

In this way, in the lifting path, the developer is conveyed upward in the direction of gravity, while the carrier has a greater specific gravity than the developer, and thus tends to sink into the developer. For this reason, the carrier replenished on the lifting path is stirred and mixed with the developer while being conveyed more slowly than the developer upward in the direction of gravity.
In the dropping path, the developer drops one after another from the second tank to the first tank, so that the developer continues to fall on the toner supplied to the toner supply tank. Since the specific gravity of the toner is smaller than that of the developer, the toner tends to float in the developer falling from above in the direction of gravity. For this reason, the toner replenished on the dropping path is stirred and mixed with the developer while being conveyed more slowly than the developer downward in the direction of gravity.

  On the other hand, in the developing device according to Patent Document 1, as shown in FIG. 11, a pair of developer stirring screws 1134 are arranged at the same height in the direction of gravity in the developing device 13 (Y). A developer supply path 1135 disposed above one developer stirring screw 1134 is provided. The toner replenished from the replenishment toner storage unit 1131 (Y) and the carrier replenished from the replenishment carrier storage unit 1133 are replenished from the developer replenishment path 1135 independently of each other.

For this reason, the replenished toner tends to stay on the developer, and the carrier tends to sink into the developer, so that stirring and mixing with the developer are difficult to proceed.
Also in the developing device according to Patent Document 2, as shown in FIG. 12, both the toner and the carrier fall into the developing device 7Y from the opening 1207Y1. In the developing device 7Y, a pair of agitation supply rollers 1207Y3 are also arranged at the same height in the direction of gravity, so that the toner that has fallen onto the developer via the opening 1207Y1 has a low specific gravity and therefore rises. I tend to. In addition, since the carrier tends to sink into the developer, it is difficult for the carrier to stir and mix with the developer.

  On the other hand, in the present invention, as described above, the first tank and the second tank are arranged at different heights in the direction of gravity, and development is performed between the first tank and the second tank. When moving the developer, the developer is lifted or dropped. Since the carrier and toner are replenished in accordance with the lifting and dropping, the stirring and mixing of the carrier, toner and developer can be promoted to prevent image quality deterioration due to toner charging failure.

In this case, the carrier supply tank preferably includes a paddle for stirring the carrier and the developer supplied from outside the developer tank. In this way, stirring and mixing of the carrier and the developer can be further promoted.
In addition, if a discharge port for discharging the developer to the outside of the developer tank is provided downstream of the second communication port in the second transport direction, the newly replenished toner has to go through the developer tank at least once. Since the toner does not reach the discharge port, it is possible to prevent the newly supplied toner from being immediately discarded from the discharge port and wasting the toner.

  An image forming apparatus according to the present invention includes the developing device according to the present invention. In this way, the effect of the developing device according to the present invention can be obtained as it is.

1 is a diagram illustrating a main configuration of an image forming apparatus according to an embodiment of the present invention. 3 is a diagram illustrating a main configuration of an image forming unit 111. FIG. 2 is a diagram illustrating a main configuration of a developing device 200. FIG. FIG. 3 is a cross-sectional view of the developing device 200 as viewed from the rotation axis direction of the stirring and conveying screws 201 and 202. FIG. 10 is a diagram illustrating a main configuration of a developing device 200 according to a modification of the present invention, and is a diagram illustrating a paddle 500 built in a carrier replenishment unit 301. FIG. 10 is a diagram showing a main configuration of a developing device 200 according to a modification of the present invention, and is a diagram showing the developing device 200 provided with a carrier replenishment section 301 at substantially the same height as a partition wall 304. It is a figure which shows the main structures of the developing device 200 which concerns on the modification of this invention, Comprising: It is a figure which shows the developing device 200 provided with the carrier replenishment part 301 at the substantially same height as the 2nd tank 300b. It is a figure which shows the main structures of the developing device 200 which concerns on the modification of this invention, Comprising: It is a figure which shows the developing device 200 which replenishes a carrier to the raising part 330 from the upper direction of the 2nd tank 300b. FIG. 6 is a cross-sectional view of a developer tank 300 according to a modification of the present invention as viewed from the direction of the rotation axis of stirring and conveying screws 201 and 202. It is a figure which shows the developer tank 300 which concerns on the modification of this invention, Comprising: (a) is a side view, (b) is a front view. It is a figure which shows the structure of the developing device which concerns on a prior art. It is a figure which shows the structure of the image development apparatus concerning another prior art.

Hereinafter, embodiments of a developing device and an image forming apparatus according to the present invention will be described with reference to the drawings.
[1] Configuration of Image Forming Apparatus First, the configuration of the image forming apparatus according to the present embodiment will be described.
FIG. 1 is a diagram illustrating a main configuration of the image forming apparatus according to the present embodiment. As shown in FIG. 1, the image forming apparatus 1 includes a document reading unit 100, an image forming unit 110, and a paper feeding unit 120. The document reading unit 100 optically reads a document placed on a platen tray with an automatic document feeder (ADF) and generates image data. The image data is stored in the control unit 112 described later.

The image forming unit 110 includes image forming units 111Y to 111K, a control unit 112, an intermediate transfer belt 113, a secondary transfer roller pair 114, a fixing device 115, a paper discharge roller pair 116, a paper discharge tray 117, a cleaner 118, and a timing roller pair 119. It has.
The image forming units 111Y to 111K form toner images of Y (yellow), M (magenta), C (cyan), and K (black), respectively, under the control of the control unit 112, so that the toner images of the respective colors overlap. Then, electrostatic transfer (primary transfer) is performed on the intermediate transfer belt 113. The intermediate transfer belt 113 is an endless rotator, and rotates in the direction of arrow A to convey the primary transferred toner image to the secondary transfer roller pair 114.

  The paper feeding unit 120 includes a paper feeding cassette 121 that stores the recording paper P for each paper size, and supplies the recording paper P to the image forming unit 110. The supplied recording paper P is unloaded in parallel with the intermediate transfer belt 113 conveying the toner image, and is conveyed to the secondary transfer roller pair 114 via the timing roller pair 119. The timing roller pair 119 includes a pair of rollers, and adjusts the timing at which the recording paper P reaches the secondary transfer roller pair 114.

  The secondary transfer roller pair 114 is composed of a pair of rollers having a potential difference, and these roller pairs are pressed against each other to form a transfer NIP portion. In the transfer NIP portion, the toner image on the intermediate transfer belt 113 is electrostatically transferred (secondary transfer) onto the recording paper P. The recording paper P to which the toner image has been transferred is conveyed to the fixing device 115. Further, the residual toner remaining on the intermediate transfer belt 113 after the secondary transfer is further conveyed in the direction of arrow A, and then scraped off by the cleaner 118 and discarded.

  The fixing device 115 is an electromagnetic induction heating type fixing device, and heats and melts the toner image and presses the toner image on the recording paper P. The recording paper P to which the toner image has been fused is discharged onto the paper discharge tray 117 by the paper discharge roller pair 116. The control unit 112 controls the operation of the image forming apparatus 1 including the above. The control unit 112 also transmits / receives image data to / from other devices such as a personal computer (PC) and accepts print jobs.

[2] Configuration of Image Creating Unit 111 Next, the configuration of the image creating unit 111 will be described. Since the image forming units 111Y to 111K all have the same configuration, the following description is applicable to all.
FIG. 2 is a diagram illustrating a main configuration of the image forming unit 111. As shown in FIG. 2, the image forming unit 111 includes a photosensitive drum 210, a charging device 211, an exposure device 212, a developing device 200, a primary transfer roller 213, and a cleaner 214.

  The photosensitive drum 210 is a cylindrical member having a photosensitive layer formed on the outer peripheral surface of a conductive substrate, and is driven to rotate in the direction of arrow B. The charging device 211 uniformly charges the outer peripheral surface of the photosensitive drum 210 by, for example, scorotron discharge. The exposure device 212 includes a laser diode. Under the control of the control unit 112, the outer peripheral surface of the photosensitive drum 210 is exposed to form an electrostatic latent image while modulating the light emitted from the laser diode.

  The developing device 200 is a developing device using a two-component developer, and includes stirring and conveying screws 201 and 202 and a developing roller 203. The developing roller 203 has a cylindrical shape, and the rotation axis is parallel to the photosensitive drum 210. The developing device 200 uses the developing roller 203 to supply toner onto the outer peripheral surface of the photosensitive drum 210 to develop the electrostatic latent image into a toner image (visualized image).

  The primary transfer roller 213 is in pressure contact with the photosensitive drum 210 via the intermediate transfer belt 113, and the toner formed on the outer peripheral surface of the photosensitive drum 210 is provided with a potential difference between the primary transfer roller 213 and the photosensitive drum 210. The image is electrostatically transferred onto the intermediate transfer belt 113. The cleaner 214 scrapes and discards the toner remaining on the outer peripheral surface of the photosensitive drum 210 after the primary transfer. Thereafter, a static eliminator (not shown) irradiates a laser beam having a wavelength of 500 to 800 nm to remove charges remaining on the outer peripheral surface of the photosensitive drum 210. As a result, the surface potential of the photosensitive drum 210 can be stabilized. Note that light of other wavelengths may be used as long as residual charges on the outer peripheral surface of the photosensitive drum 210 can be removed.

[3] Configuration of Developing Device 200 Next, the configuration of the developing device 200 will be described with particular attention to carrier and toner replenishment.
FIG. 3 is a diagram showing a main configuration of the developing device 200, in which the developing roller 203 is omitted. As shown in FIG. 3, the developing device 200 includes a developer tank 300, a carrier supply unit 301, a toner supply unit 302, and a developer discharge unit 303, and the developer tank 300 is separated by a partition wall 304 in the direction of gravity. Are divided into a first tank 300a located on the lower side and a second tank 300b located on the upper side.

  The first tank 300a is provided with a stirring and conveying screw 201, and conveys the developer 320 in the direction of arrow C while stirring. The second tank 300b is provided with a stirring and conveying screw 202, and conveys the developer 320 in the arrow D direction while stirring. At both ends of the developer tank 300 in the transport direction of the developer 320, communication ports are provided for communicating the first tank 300a and the second tank 300b.

The developer 320 is transported in the direction of arrow E from the first tank 300a toward the second tank 300b at the communication port on the downstream side in the transport direction (arrow C direction) of the developer 320 in the first tank 300a. Since the arrow E direction is opposite to the direction of gravity, the developer 320 is lifted up toward the second tank 300b.
The developer 320 is conveyed in the direction of arrow F from the second tank 300b toward the first tank 300a at the downstream communication port (direction of arrow D) of the developer 320 in the second tank 300b. Since the arrow F direction is the same direction as the gravity direction, the developer 320 falls toward the first tank 300a.

  The downstream end of the first tank 300a in the developer conveyance direction (arrow C direction) communicates with the carrier replenishment unit 301. The agitating and conveying screw 201 reaches the inside of the carrier replenishing portion 301 and conveys the developer 320 flowing from the first tank 300a toward the lifting path 330 in the direction of arrow G. In the vicinity of the lifting path 330 of the developer 320, the developer 320 is transported in the direction of arrow C from the first tank 300a, and the developer 320 is transported in the direction of arrow G from the carrier replenishment unit 301. The powder pressure of the developer 320 is high, and the density of the developer 320 is high.

  The carrier supply unit 301 receives the carrier 310 from the upper side in the direction of gravity. For this reason, the replenished carrier 310 falls on the developer 320 staying in the carrier replenishment section 301. Since the carrier 310 has a specific gravity greater than that of the developer 320, the carrier 310 sinks into the developer 320 due to gravity, and thus is easily stirred in the developer 320. When the carrier 310 is transported to the lifting path 330 in a state of being well stirred in the developer 320, the carrier 310 can easily get on the circulation of the developer 320. On the other hand, when the stirring is insufficient, the carrier 310 is difficult to circulate the developer 320 and tends to stay at the bottom of the lifting path 330.

  Since the developer powder pressure is high in the lifting path 330, the carrier transport speed in the arrow G direction from the carrier replenishment unit 301 to the lifting path 330 is another transport speed, for example, developer transport in the arrow D direction. Although there is a tendency to be slower than the speed or the like, there is no problem because the carrier supply does not require quick response as compared with the toner supply whose shortage immediately affects the image quality.

  The upstream end of the first tank 300 a in the developer transport direction (arrow C direction) communicates with the toner replenishing unit 302. The agitating and conveying screw 201 reaches the inside of the toner replenishing unit 302 and conveys the replenished toner 311 in the arrow H direction. At a location near the communicating portion with the toner replenishing portion 302 of the first tank 300a, the developer 320 falls from the second tank 300b, while the developer is conveyed in the direction of arrow C. The powder pressure is not so high.

  For this reason, the developer 320 does not flow so much into the toner replenishing portion 302, and the replenished toner 311 once falls to near the bottom surface of the toner replenishing portion 302 and then conveyed in the direction of arrow H by the agitating and conveying screw 201. . Then, when the developer 320 in the second tank falls on the toner 311, the toner 311 has a lighter specific gravity than the developer 320, so that even if the toner 311 is buried under the developer, it easily floats. Easily mixed and stirred.

  The downstream side of the second tank 300b in the developer conveyance direction (arrow D direction) communicates with the developer discharge portion 303. The agitating and conveying screw 202 reaches the developer discharge portion 303 and conveys the developer flowing into the developer discharge portion 303 in the direction of arrow I. A discharge port is provided at the upstream end of the developer discharge portion 303 in the direction of arrow I, and the developer 320 is gradually discharged out of the developer tank 300. As a result, the carrier deteriorated with time is discarded. The toner 311 that has been replenished by the toner replenishing unit 302 cannot reach the developer discharging unit 303 unless it goes around the developer tank 300 along the arrows C and D. Immediate disposal is prevented.

  FIG. 4 is a cross-sectional view of the developing device 200 as viewed from the direction of the rotation axis of the stirring and conveying screws 201 and 202. As shown in FIG. 4, in the developing device 200, the rotation axes of the agitating and conveying screws 201 and 202 are parallel to each other, while the agitating and conveying screw 202 is displaced from directly above in the gravity direction of the agitating and conveying screw 201. It is arranged at the position. For this reason, the toner replenishing unit 302 and the developer discharging unit 303 are disposed at positions shifted from each other in the horizontal direction perpendicular to the rotation shafts of the stirring and conveying screws 201 and 202.

  For this reason, there is a portion where there is no toner replenishment portion 302 below the developer discharge portion 303 in the gravity direction, and there is a portion where there is no developer discharge portion 303 in the information of the toner replenishment portion 302. The developer discharge unit 303 includes a developer discharge port 401 at a location where the toner replenishment unit 302 is not provided below, and discharges the developer 312 downward (in the direction of arrow L). In addition, the toner replenishing unit 302 includes a toner replenishing port 402 at a location where the developer discharging unit 303 is not present above, and receives replenishment of toner 311 that falls in the direction of arrow K from above.

  As described above, according to the present embodiment, gravity is applied to the developer 320 that has flowed into the carrier replenishment unit 301 that communicates with the lifting path 330 that lifts the developer 320 from the first tank 300a to the second tank 300b. Since the carrier 310 is replenished from above in the direction, the carrier 310 having a high specific gravity sinks into the developer 320 due to gravity, and the stirring and mixing of the carrier 310 and the developer 320 are promoted.

  Further, a toner replenishing unit 302 is provided in communication with the first tank 300a at a location where the developer 320 falls from the second tank 300b to the first tank 300a, and the replenished toner 311 is once dropped to the bottom of the toner replenishing unit 302. After that, the developer 320 flows into the toner 311. Therefore, the toner 311 having a low specific gravity floats up in the developer 320 by gravity, so that the toner 311 and the developer 320 are agitated and mixed. Promoted.

  Further, at the end on the same side in the rotation axis direction of the agitating and conveying screws 201 and 202, a toner replenishing unit 302 is provided in communication with the first tank 300a, and a developer discharging unit 303 is provided in communication with the second tank 300b. Thus, the toner 311 replenished to the toner replenishing unit 302 is not discharged from the developer discharging unit 303 until the developer tank 300 makes a round, and thus it is possible to prevent the toner 311 from being wasted.

[4] Modifications Although the present invention has been described based on the embodiments, it is needless to say that the present invention is not limited to the above-described embodiments, and the following modifications can be implemented. .
(1) In the above embodiment, the case where the carrier 310 and the developer 320 are agitated and conveyed by the agitating / conveying screw 201 in the carrier replenishment unit 301 has been described, but it goes without saying that the present invention is not limited to this. In addition, the following may be used.

  FIG. 5 is a diagram showing a main configuration of the developing device 200 according to this modification. As shown in FIG. 5, a paddle 500 is provided in a portion of the agitating and conveying screw 201 located in the carrier replenishing portion 301. The paddle 500 is a flat member attached to the rotating shaft of the stirring and conveying screw 201. The paddle 500 rotates according to the rotation of the stirring and conveying screw 201, and stirs and mixes the carrier 310 and the developer 320 of the carrier supply unit 301. Thus, if the paddle 500 is provided, stirring and mixing of the carrier 310 and the developer 320 can be further promoted.

  In the case where the paddle 500 is provided, the transport speed of the developer 320 in the carrier replenishing unit 301 may be slightly reduced as compared with the case where the paddle 500 is not provided, but the electrostatic latent image is developed. Unlike the toner that is consumed every time, the carrier is not likely to be consumed rapidly, so that the carrier replenishment is not required to be responsive. Therefore, even if the conveyance tank speed of the developer 320 in the carrier replenishing section 301 is somewhat reduced, there is no practical problem.

(2) In the above-described embodiment, the case where the carrier replenishment unit 301 communicates with the first tank 300a has been described. However, it goes without saying that the present invention is not limited to this, and is replaced with the following. May be.
FIG. 6 is a diagram showing a main configuration of the developing device 200 according to this modification. As shown in FIG. 6, in the developing device 200 according to this modification, the carrier replenishment unit 301 is disposed at a position facing the partition wall 304 that partitions the first tank 300a and the second tank 300 in the direction of gravity. It is installed. The developer 320 having a high powder pressure flows into the carrier replenishment section 301 from the lifting path 330, and the carrier 310 drops and is replenished thereon.

  In the carrier replenishing unit 301, a stirring and conveying screw 601 is provided, and the carrier 310 and the developer 320 are conveyed in the direction of arrow G while being stirred and mixed. Even in this case, similarly to the above-described embodiment, the carrier 310 is submerged from the liquid surface of the developer 320 by gravity, so that the stirring and mixing of the developer 320 and the carrier 310 can be promoted.

  FIG. 7 is a diagram showing a configuration of a developing device 200 according to another modification of the present invention. As shown in FIG. 7, in the developing device 200 according to this modification, the carrier replenishment unit 301 communicates with the upstream end of the second tank 300b in the developer transport direction (arrow D direction). Further, the agitating / conveying screw 202 reaches the inside of the carrier replenishing unit 301, while stirring and mixing the carrier 310 dropped and replenished from above the carrier replenishing unit 301 and the developer 320 flowing from the lifting path 330. It is conveyed in the direction of arrow G toward the second tank 300b. Even in this case, stirring and mixing of the developer 320 and the carrier 310 can be promoted by dropping the carrier 310 onto the developer 320 whose powder pressure is high in the lifting path 330.

  FIG. 8 is a diagram showing a configuration of a developing device 200 according to still another modified example of the present invention. As shown in FIG. 8, in the developing device 200 according to this modification, the carrier 310 is dropped from the upper side in the gravity direction of the lifting path 330 in the second tank 300b, so that the developer 320 having a high powder pressure The carrier 310 falls on the top, and the stirring and mixing of the developer 320 and the carrier 310 are promoted.

In any case, if a paddle is provided in the same manner as in the modification (1), the stirring and mixing of the carrier 310 and the developer 320 can be further promoted.
(3) In the above embodiment, the case where the second tank 300b is disposed obliquely above the first tank 300a of the developer tank 300 has been described, but it is needless to say that the present invention is not referred to this. Alternatively, the second tank 300b may be disposed almost directly above the first tank 300a in the direction of gravity. FIG. 9 is a view of the developer tank 300 according to this modification as viewed from the rotation axis direction of the agitating and conveying screws 201 and 202.

  As shown in FIG. 9, the second tank 300b is disposed almost directly above the first tank 300a in the direction of gravity, and as a result, the toner replenishing section 302 communicating with the first tank 300a is substantially in the direction of gravity. A developer discharge portion 303 communicating with the second tank 300b is located directly above. Therefore, the developer discharge unit 303 extends the developer discharge pipe 401 obliquely downward avoiding the toner replenishment section 302 and discharges the developer 312 via the developer discharge pipe 401.

  In addition, the toner supply unit 302 extends the toner supply pipe 402 obliquely upward, and receives the supply of the toner 311 through the toner supply pipe 402. In this way, even when the second tank 300b is disposed directly above the first tank 300a, the toner 311 can be replenished and the developer 312 can be discharged. Needless to say, the direction in which the developer discharge pipe 401 and the toner supply pipe 402 are extended is not limited to the direction shown in FIG. 9, but may be extended in other directions. If the developer discharge pipe 401 and the toner supply pipe 402 do not interfere with each other, the effect of the present invention can be obtained by extending the developer discharging pipe 401 and the image forming apparatus 1 in an appropriate direction according to the device configuration.

(4) In the above-described embodiment, the case where the carrier replenishment unit 301 is disposed at the end of the developer tank 300 in the rotation axis direction of the stirring and conveying screws 201 and 202 has been described, but the present invention is not limited to this. Needless to say, the following may be used instead.
10A and 10B are diagrams showing a developer tank 300 according to this modification, in which FIG. 10A is a side view and FIG. 10B is a front view. As shown in FIG. 10A, in the present modification, a second tank 300b is disposed obliquely above the first tank 300a. As a result, there is a portion where the second tank 300b is not provided in the upper portion of the first tank 300a, and the carrier replenishment unit 301 is provided at the location, and the carrier 310 passes through the carrier replenishment unit 301 and the first tank 300a. It falls on the developer 320 inside.

  As shown in FIG. 10B, the carrier replenishment unit 301 is provided with a partition wall 304 that partitions the first tank 300a and the second tank 300b in the direction of the rotation axis of the stirring and conveying screws 201 and 202. It is arranged. If the carrier replenishment unit 301 is disposed at such a position, the carrier 310 is dropped on the developer 320 in the first tank 300a, so that the carrier 310 sinks into the developer 320 due to the difference in specific gravity, and the carrier Agitation and mixing of 310 and developer 320 can be promoted.

  In this modified example, when the carrier replenishment portion 301 is disposed at a position where the partition wall 304 is not provided, the lifting path 330 for lifting the developer from the first tank 300a to the second tank 300b, or the second The carrier replenishment unit 301 is disposed in a portion where the developer is dropped from the tank 300b to the first tank 300a. Among these, when the carrier replenishment unit 301 is provided in the lifting path 330, the developer 320 is lifted in a high powder pressure state, so the developer 320 having a high powder pressure enters the carrier replenishment unit 301, As a result of the carrier 310 being prevented from falling into the first tank 300a, the carrier 310 may be clogged in the carrier replenishment unit 301.

  In addition, when the carrier replenishment unit 301 is provided in the portion where the developer is dropped from the second tank 300b to the first tank 300a, the powder pressure of the developer 320 is low, so the carrier dropped via the carrier replenishment unit 301 301 quickly sinks into the developer 320 and reaches the bottom of the first tank 300a, and the carrier 301 and the developer 320 cannot be sufficiently stirred and mixed.

  In the developing device and the image forming apparatus according to the present invention, when a two-component system that replenishes toner and carrier independently is used, the developer stored inside is mixed with the newly replenished carrier. It is useful as a technology to promote.

1 …………………………………… Image forming apparatuses 111 </ b> Y to 111 </ b> K... ... Stirring conveying screw 203, 1207Y2 ..... Developing roller 300, 1207Y6 ........... Developer tank 300a ........... First tank 300b ......... …………………… Second tank 301 ………………………………… Carrier replenishment unit 302 ………………………………… Toner replenishment unit 303 ………… ……………………… Developer discharge unit 304 ………………………………… Partition wall 310 ………………………………… Carrier 311 …………… …………………… Toner 320 ………………………………… Developer 330 …………………………………… Lifting path 50 ………………………………… Paddle 601 ………………………………… Agitating and conveying screw 401 ………………………………… Developer discharge pipe 402 Toner supply tube 1110 ……………………………… Photosensitive drum 1131 (Y) ……………………… Supply toner storage portion 1132 (Y) ................ Toner replenishing means 1133... ……………… Opening 1207Y3 …………………… Stirring supply roller 1207Y7 …………………… Weir portion 1204Y …………………………… Photosensitive drum 11131 …………………………… Magnet body 11132 …………………………… Developer thickness regulating member 11133 Developer supply roller 11134 ... Developer stirring screw 11135 ... Developer supply path 11136 ... …………………… Housing 11136a ………………………… Hole 11136b ………………………… Waste Carrier Recovery Unit 11136c ………………………… Disposal Carrier recovery screw 11137 ......... …………………… Bias voltage 11138 …………………………… Protection resistance 11139 …………………………… Toner concentration detection sensor

Claims (4)

A developing device that agitates a two-component developer composed of a toner and a carrier while circulating in a developer tank and is used for developing an electrostatic latent image,
The developer tank is disposed at a position higher than the first tank in the direction of gravity while stirring the developer, and is opposite to the first transport direction while stirring the developer. A second tank to be conveyed in the second conveying direction,
On the downstream side of the developer conveyance direction of the first tank, the first communication port communicating with the upstream side of the developer conveyance direction of the second tank, and the developer conveyance of the first tank on the downstream side of the second tank in the developer conveyance direction. A second communication port communicating with the upstream side in the direction,
A carrier supply tank that communicates with the lifting path when the developer is lifted from the first tank to the second tank via the first communication port and receives the carrier from above in the direction of gravity;
And a toner supply tank that communicates with a dropping path when the developer is dropped from the second tank to the first tank via the second communication port and receives toner supply from above in the gravity direction. Development device. The developing device according to claim 1, wherein the carrier supply tank includes a paddle for stirring the carrier and the developer supplied from outside the developer tank. 2. The developing device according to claim 1, further comprising a discharge port for discharging the developer to the outside of the developer tank at a downstream side in the second transport direction from the second communication port. An image forming apparatus comprising the developing device according to claim 1.

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