JP7413732B2 - Developing device and image forming device - Google Patents

Description

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

In an image forming apparatus, a developing device therein includes a circulation tank for circulating developer and a collection tank for collecting developer not used for development, and the collection tank is disposed above the circulation tank. Some have a two-story structure.

In the developing device having such a configuration, the circulation tank includes a stirring screw and a supply screw, the stirring screw and the supply screw circulate the developer, and the supply screw supplies the developer to the developing roller. The collection tank has a collection roller and a collection screw, the collection roller collects unused developer from the developing roller, and the collection screw returns the collected developer to the downstream side of the supply screw in the conveyance direction. It has a circulating configuration (see Patent Document 1).

Further, there is also a developing device that is provided with a discharge mechanism that discharges a portion of the developer on the downstream extension of the supply screw in the conveyance direction. In this case, the developer flow branches at the boundary between the supply screw and the discharge mechanism, with most of the developer being conveyed to the stirring screw side and a portion of the developer being conveyed to the discharge mechanism side. The discharge mechanism has a reverse winding screw and a discharge screw, the reverse winding screw pushes the developer back toward the supply screw side, and the discharge screw discharges the developer that has passed over the reverse winding screw to the outside of the developing device.

Japanese Patent Application Publication No. 2008-116651

Incidentally, since the developer deteriorates depending on usage conditions and environmental conditions, the developer that has deteriorated (hereinafter referred to as "degraded developer") and the developer that has not deteriorated (hereinafter referred to as "non-degraded developer") are mixed together. The discharge mechanism configured as described above only discharges a portion of the developer in which degraded developer and non-degraded developer are mixed, and cannot selectively discharge deteriorated developer. Therefore, non-degraded developer is discharged at a constant rate, and degraded developer remains at a constant rate in the circulation tank.

In such a state, the developer containing the degraded developer is circulated in the circulation tank, and the developer containing the degraded developer is used for development. When a developer containing degraded developer is used for development, it becomes a cause of image defects such as white streaks and speckled noise during printing. Further, when the carrier contained in the deteriorated developer adheres to the photoreceptor drum, the photoreceptor drum is worn out and becomes scratched, which causes image defects such as white streaks. Therefore, it is desirable to prevent image defects by reducing the proportion of degraded developer in the developer while suppressing the discharge amount of non-degraded developer.

An object of the present invention is to provide a developing device and an image forming apparatus that can prevent the occurrence of image defects.

The developing device according to the present invention includes:
a first storage section that stores developer;
a second storage section that stores developer;
a third storage section that stores developer;
a distribution unit that distributes the developer stored in the third storage unit to the first storage unit and the second storage unit according to the deterioration state of the developer;
a vibrating section that vibrates the distribution section;
Equipped with
The vibrating section changes the vibration conditions of the distributing section according to an image forming history based on a developing operation .
The developing device according to the present invention includes:
a first storage section that stores developer;
a second storage section that stores developer;
a third storage section that stores developer;
a distribution unit that distributes the developer stored in the third storage unit to the first storage unit and the second storage unit according to the deterioration state of the developer;
Equipped with
The second storage part is provided on an extension of the first storage part in the conveying direction of the developer stored in the first storage part,
The third accommodating part is provided above the first accommodating part.

Further, the image forming apparatus according to the present invention includes:
the developing device;
an image carrier that carries an image developed by the developing device;
Equipped with.

According to the present invention, it is possible to reduce the proportion of degraded developer in the developer while suppressing the amount of discharged non-degraded developer, thereby preventing image defects.

1 is a diagram schematically showing the overall configuration of an image forming apparatus according to an embodiment of the present invention. 1 is a diagram showing main parts of a control system of an image forming apparatus according to an embodiment of the present invention. 1 is a diagram showing main parts of a developing device according to an embodiment of the present invention. 3A is a diagram illustrating a distribution section in the developing device shown in FIG. 3A. FIG. 1 is a diagram schematically showing the inside of a developing device according to an embodiment of the present invention, and is a diagram showing a stirring tank, a supply tank, and a recovery tank. FIG. 1 is a diagram schematically showing the inside of a developing device according to an embodiment of the present invention, and is a diagram showing a stirring tank, a collection tank, and a discharge tank. FIG. It is a figure explaining the effect by the distribution part shown in FIG. 3B. FIG. 7 is a diagram showing main parts of a developing device according to another embodiment of the present invention. 6A is a diagram illustrating a distribution section in the developing device shown in FIG. 6A. FIG. FIG. 3 is a diagram schematically showing the inside of a developing device according to another embodiment of the present invention, and is a diagram showing a stirring tank, a supply tank, and a recovery tank. FIG. 3 is a diagram schematically showing the inside of a developing device according to another embodiment of the present invention, and is a diagram showing a stirring tank, a collection tank, and a discharge tank. 7 is a graph showing an example of vibration frequency control with respect to printing rate for a vibrating unit. 7 is a graph illustrating an example of amplitude control with respect to printing rate for a vibrating section. 7 is a graph showing an example of frequency control of the vibrating unit with respect to the cumulative number of printed sheets. 7 is a graph showing an example of amplitude control with respect to the cumulative number of printed sheets for the vibrating section. It is a figure explaining the effect by a vibrating part.

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

FIG. 1 is a diagram schematically showing the overall configuration of an image forming apparatus 1 according to the present embodiment. FIG. 2 is a diagram showing the main parts of the control system of the image forming apparatus 1 according to the present embodiment.

As shown in FIG. 1, an image forming apparatus 1 is an intermediate transfer type color image forming apparatus using electrophotographic process technology. That is, the image forming apparatus 1 primarily transfers each color toner image of C (cyan), M (magenta), Y (yellow), and K (black) formed on a photoreceptor to an intermediate transfer member. An image is formed by superimposing the four-color toner images on the paper and then performing secondary transfer onto the paper.

In addition, the image forming apparatus 1 employs a tandem system in which photoreceptors corresponding to the four colors of CMYK are arranged in series in the running direction of the intermediate transfer body, and toner images of each color are sequentially transferred to the intermediate transfer body in one step. has been done.

The image forming apparatus 1 shown in FIGS. 1 and 2 includes an image reading section 10, an operation display section 20, an image processing section 30, an image forming section 40, a paper transport section 50, a fixing section 60, a control section 100, and the like. The image forming apparatus 1 also includes a vibrating section 81 .

The control unit 100 includes a CPU (Central Processing Unit) 101, a ROM (Read Only Memory) 102, a RAM (Random Access Memory) 103, and the like. The CPU 101 reads a program according to the processing content from the ROM 102, loads it into the RAM 103, and centrally controls the operation of each block of the image forming apparatus 1 in cooperation with the loaded program. At this time, various data such as an LUT (Look Up Table) stored in the storage unit 72 are referred to. The storage unit 72 includes, for example, a nonvolatile semiconductor memory (so-called flash memory) or a hard disk drive.

The control unit 100 transmits and receives various data to and from an external device (for example, a personal computer) connected to a communication network such as a LAN (Local Area Network) or a WAN (Wide Area Network) via the communication unit 71. I do. For example, the control unit 100 receives image data transmitted from an external device, and forms an image on paper based on this image data (input image data). The communication unit 71 is composed of, for example, a communication control card such as a LAN card.

The image reading unit 10 includes an automatic document feeding device 11 called an ADF (Auto Document Feeder), a document image scanning device 12 (scanner), and the like.

The automatic document feeder 11 uses a conveyance mechanism to convey the document D placed on the document tray and sends it to the document image scanning device 12 . The automatic document feeder 11 can continuously read images (including both sides) of a large number of documents D placed on a document tray at one time.

The document image scanning device 12 optically scans the document conveyed onto the contact glass from the automatic document feeder 11 or the document placed on the contact glass, and converts light reflected from the document into a CCD (Charge Coupled Device). ) The image is formed on the sensor 12a and the original image is read. The image reading unit 10 generates input image data based on the reading result by the original image scanning device 12. This input image data is subjected to predetermined image processing in the image processing section 30.

The operation display unit 20 is configured with, for example, a liquid crystal display (LCD) with a touch panel, and functions as a display unit 21 and an operation unit 22. The display unit 21 displays various operation screens, image status display, operating status of each function, etc. in accordance with display control signals input from the control unit 100. The operation unit 22 includes various operation keys such as a numeric keypad and a start key, receives various input operations from the user, and outputs operation signals to the control unit 100.

The image processing unit 30 includes a circuit that performs image processing on input image data according to initial settings or user settings. The image forming section 40 is controlled based on the image data that has been subjected to image processing.

The image forming section 40 includes image forming units 41Y, 41M, 41C, and 41K for forming images using colored toners of Y component, M component, C component, and K component based on image data from the image processing section 30. , an intermediate transfer unit 42, and the like.

Image forming units 41Y, 41M, 41C, and 41K for Y component, M component, C component, and K component have similar configurations. Therefore, in FIG. 1, only the constituent elements of the image forming unit 41Y for the Y component are labeled, and the constituent elements of the other image forming units 41M, 41C, and 41K are omitted.

The image forming unit 41 includes an exposure device 411, a developing device 412, a photosensitive drum 413 (image carrier), a charging device 414, a drum cleaning unit (hereinafter referred to as a cleaning unit) 415, and the like.

The exposure device 411 is composed of, for example, a semiconductor laser, and irradiates the photosensitive drum 413 with laser light corresponding to an image of each color component. When positive charges are generated in the charge generation layer of the photoreceptor drum 413 by laser light irradiation and are transported to the surface of the charge transport layer, the surface charges (negative charges) of the photoreceptor drum 413 are neutralized. As a result, electrostatic latent images of each color component are formed on the surface of the photoreceptor drum 413 due to potential differences with the surroundings.

The developing device 412 is a two-component developing device, and by attaching toner of each color component to the surface of the photoreceptor drum 413, the electrostatic latent image is visualized and a toner image is formed. The configuration of this developing device 412 will be described later with reference to FIGS. 3A to 4B.

The photosensitive drum 413 includes, for example, a conductive cylinder made of aluminum (an aluminum tube), an undercoat layer (UCL), a charge generation layer (CGL), and a charge transport layer (CTL). transport layer), etc. The photoreceptor drum 413 is a photoreceptor having photoconductivity and is constructed by sequentially laminating an undercoat layer, a charge generation layer, and a charge transport layer on the circumferential surface of a conductive cylinder, and is, for example, a negatively charged type photoreceptor. It is an organic photoconductor (OPC). The photosensitive drum 413 is rotated at a constant circumferential speed (linear speed) by the control unit 100 controlling a drive current supplied to a drive motor (not shown).

The charging device 414 uniformly charges the surface of the photoconductive drum 413 to a negative polarity.

The cleaning unit 415 includes a drum cleaning blade (hereinafter referred to as a cleaning blade) as a cleaning member that comes into sliding contact with the surface of the photoreceptor drum 413. The cleaning unit 415 uses a cleaning blade to remove transfer residual toner remaining on the surface of the photoreceptor drum 413 after the primary transfer.

The intermediate transfer unit 42 includes an intermediate transfer belt 421, a primary transfer roller 422, a plurality of support rollers 423 including a drive roller 423A, a backup roller 423B, etc., a secondary transfer roller 424, a belt cleaning device 426, and the like.

The intermediate transfer belt 421 is stretched around a plurality of support rollers 423 in a loop shape, and as the driving roller 423A rotates, the intermediate transfer belt 421 runs at a constant speed in the direction of arrow A. The primary transfer roller 422 presses the intermediate transfer belt 421 against the photoreceptor drum 413, thereby transferring the toner image from the photoreceptor drum 413 to the intermediate transfer belt 421. The secondary transfer roller 424 is in pressure contact with the backup roller 423B with the intermediate transfer belt 421 in between, thereby transferring the toner image from the intermediate transfer belt 421 to the paper S. The paper S onto which the toner image has been transferred is conveyed toward the fixing section 60. Note that instead of the secondary transfer roller 424, a belt-type secondary transfer unit in which a secondary transfer belt is stretched around a plurality of support rollers in a loop shape may be employed.

The belt cleaning device 426 has a belt cleaning blade etc. that slides on the surface of the intermediate transfer belt 421, and removes transfer residual toner remaining on the surface of the intermediate transfer belt 421 after the secondary transfer.

The paper transport section 50 includes a paper feed section 51, a paper discharge section 52, a transport path section 53, and the like. The three paper feed tray units 51a to 51c constituting the paper feed section 51 accommodate sheets S (standard paper, special paper) that are identified based on basis weight, size, etc., according to preset types. . The conveyance path section 53 includes a plurality of conveyance roller pairs such as a registration roller pair 53a.

The sheets S stored in the paper feed tray units 51a to 51c are fed out one by one from the top and conveyed to the image forming section 40 by the conveyance path section 53. At this time, the inclination of the fed sheet S is corrected and the conveyance timing is adjusted by the registration roller section in which the registration roller pair 53a is disposed. Then, the sheet S on which the image has been formed after passing through the image forming section 40 and the fixing section 60 is discharged to the outside of the machine by a sheet discharging section 52 equipped with a sheet discharging roller 52a.

The fixing unit 60 fixes the toner image onto the paper S by heating and pressurizing the paper S to which the toner image has been secondarily transferred and being conveyed using a fixing nip. The fixing unit 60 includes a fixing belt 61, a heating roller 62, a fixing roller 63, a pressure roller 64, and the like. The fixing belt 61 is stretched between a heating roller 62 and a fixing roller 63. The pressure roller 64 and the fixing belt 61 form a fixing nip in which the paper S is conveyed while being held therebetween.

The vibrating section 81 vibrates mesh members 313 and 333, which will be described later. As the vibrating part 81, for example, a solid vibrator such as a piezoelectric ceramic that vibrates by itself by applying an alternating voltage is used. Note that other configurations may be used as long as the mesh members 313 and 333 can be vibrated, such as a configuration using a motor or the like.

Next, the configuration of the developing device 412 will be described with reference to FIGS. 3A to 4B. Note that in FIGS. 3A, 4A, and 4B, black arrows indicate the movement of the developer, and white arrows indicate the rotation direction of the rollers and screws described later.

The developing device 412 forms a toner image on the photosensitive drum 413 by developing an electrostatic latent image formed on the photosensitive drum 413 using a developer containing toner and a magnetic carrier. be.

The developing device 412 includes a developer tank 210 (first storage section) that stores developer, a recovery tank 250 (second storage section), and a discharge tank 260 (third storage section). The developer tank 210 includes a stirring tank 220 (stirring section) and a supply tank 230 (supply section), and is partitioned by a partition wall 211. The developer tank 210 includes a stirring screw 221 , a supply screw 231 , a folding paddle 232 , and a developing roller 240 . Further, the recovery tank 250 includes a recovery roller 251 and a recovery screw 252. Further, the discharge tank 260 includes a reverse winding screw 261, a discharge screw 262, and a discharge port 263.

The stirring tank 220 is supplied with developer from a developer supply unit (not shown) through a supply port (not shown) provided in the stirring tank 220 on the upstream side (left side in FIG. 3A) in the developer transport direction.

The stirring screw 221 and the supply screw 231 are housed in the stirring tank 220 and the supply tank 230, respectively. The stirring screw 221 and the supply screw 231 are spiral screw members, and have a role as a conveying member that conveys the developer while stirring it. Furthermore, a communication port 212 for cyclically conveying the developer between the stirring tank 220 and the supply tank 230 is formed in the partition wall 211 between the stirring tank 220 and the supply tank 230 . Therefore, by rotating, the stirring screw 221 and the supply screw 231 transport the developer in the axial direction while stirring the developer, and circulate the developer between the stirring tank 220 and the supply tank 230. Stirring.

The supply tank 230 supplies the developer conveyed from the stirring screw 221 of the stirring tank 220 to the developing roller 240 as the supply screw 231 rotates.

The folded paddle 232 is a blade-shaped member that is disposed downstream of the supply screw 231 in the supply tank 230 and is provided on the rotating shaft of the supply screw 231. Unlike the spiral supply screw 231, the folded paddle 232 has a flat plate shape, and is provided so that its plane portion is oriented along the axial direction of the rotating shaft. Therefore, the folded paddle 232 pushes the developer from the supply tank 230 to the stirring tank 220 via the communication port 212 as the rotating shaft rotates. The folded paddle 232 causes most of the developer in the supply tank 230 to be returned from the supply tank 230 to the stirring tank 220 and circulated between the supply tank 230 and the stirring tank 220. On the other hand, some of the developer branches off at the folded paddle 232 and proceeds to the discharge tank 260 side.

The developing roller 240 (developer carrier) is capable of carrying a developer, and is disposed facing the photosensitive drum 413. The developing roller 240 carries the developer in the supply tank 230 and supplies the carried developer to the photoreceptor drum 413 .

The developer layer carried on the developing roller 240 comes into contact with the surface of the photoreceptor drum 413, and the toner is electrostatically transferred to the electrostatic latent image formed on the surface of the photoreceptor drum 413. In this way, the developing device 412 visualizes the electrostatic latent image on the photoreceptor drum 413 using toner. Note that although the developing device 412 having one developing roller 240 is illustrated here, the developing device 412 may have a configuration having a plurality of developing rollers 240.

Recovery tank 250 is arranged above supply tank 230. In other words, the developing device 412 has a two-story structure. The recovery tank 250 is provided with a recovery roller 251 and a recovery screw 252. The recovery roller 251 is arranged to face the developing roller 240, and the recovery screw 252 is housed in the recovery tank 250. The collection tank 250 collects the developer on the developing roller 240 using a collection roller 251 . The collected developer is distributed (separated) by a distribution section described later, most of it is returned to the supply tank 230 (one-circulation configuration), and a part of it is transported to the discharge tank 260. .

As shown in FIG. 3A, the discharge tank 260 is provided on the downstream side (left side in the figure) of the supply tank 230, and is provided as an extension of the developer in the transport direction. The discharge tank 260 discharges a portion of the developer to the outside of the developing device 412 . The discharge tank 260 includes a reverse winding screw 261, a discharge screw 262, and a discharge port 263 through which the developer from the downstream side of the discharge tank 260 is discharged. In the developing device 412, the stirring screw 221, the supply screw 231, the reverse winding screw 261, and the discharge screw 262 are rotated in conjunction with each other by one driving source.

The rotation of the counterclockwise screw 261 generates a flow that moves the developer from the discharge tank 260 into the supply tank 230 . This prevents the developer in the supply tank 230 from entering the discharge tank 260. On the other hand, for example, when the developer is supplied into the developer tank 210 and exceeds the amount of developer that can be stored in the developer tank 210, the developer passes over the reverse winding screw 261 and moves from the supply tank 230 to the discharge tank 260. do. The developer that has passed through the reverse winding screw 261 is conveyed to a discharge port 263 by a discharge screw 262, and is discharged from the discharge port 263 to the outside of the developing device 412.

Here, the developing roller 240 and the collecting roller 251 will be supplementally explained. Although not shown, the developing roller 240 and the collection roller 251 each include a rotatable sleeve and a magnet roll disposed inside the sleeve. A plurality of magnetic poles that generate a magnetic field are arranged inside the magnet roll, and the magnetic field generated by the magnetic poles carries the developer on the outer circumferential surface of the sleeve, and as the sleeve rotates, the developer is transported. It turns out. The developer is supplied and collected based on this principle.

In the developing device 412 described above, developer is supplied to the stirring tank 220 from a supply port (not shown). The developer in the stirring tank 220 is conveyed in the direction of arrow C1 shown in FIG. 3A as the stirring screw 221 rotates, and flows from the stirring tank 220 into the supply tank 230 through a communication port (not shown). The developer in the supply tank 230 is conveyed in the direction of arrow C2 shown in FIG. 3A as the supply screw 231 rotates. Most of the transported developer is supplied to the developing roller 240, a portion passes through the communication port 212 and is returned from the supply tank 230 to the stirring tank 220, and the other part reaches the discharge tank 260. . The developer that has reached the discharge tank 260 is discharged to the outside of the developing device 412 through the discharge port 263.

In this way, in the developing device 412, new developer is supplied to the stirring tank 220 through the replenishment port, and a portion of the developer stored in the developing device 412 is discharged from the device through the discharge port 263. . This reduces the amount of deteriorated carrier in the developing device 412 and maintains the amount of carrier contained in the developing device 412 and the charging ability. In the image forming apparatus 1 using such trickle development method, the image quality of the output image can be stabilized.

By the way, the conventional developer discharge mechanism only discharges a portion of the developer in which degraded developer and non-degraded developer are mixed, and cannot selectively discharge degraded developer. Therefore, non-degraded developer is discharged at a constant rate, and degraded developer remains at a constant rate in the circulation tank. In such a situation, the developer containing the degraded developer is circulated in the circulation tank, and the developer containing the degraded developer is used for development, and the use of the developer containing the degraded developer is prohibited. , which causes image defects.

Therefore, in this embodiment, distribution units 310 and 320 are provided to distribute the developer collected in the collection tank 250 to the developer tank 210 and the discharge tank 260 according to the state of deterioration. The distribution units 310 and 320 will be described in detail below with reference to FIGS. 3A to 10.

[First embodiment]
This embodiment will be described with reference to FIGS. 3A to 5. In this embodiment, the collection tank 250 is arranged above the supply tank 230, but its downstream end in the transport direction does not extend to the downstream end of the supply tank 230 in the transport direction, but rather to the discharge tank. It has been extended to 260. That is, the recovery screw 252 of the recovery tank 250 and the conveyance path 253 through which the developer is conveyed extend to a position above the discharge tank 260.

The sorting unit 310 includes a mesh member having a first opening 311, a second opening 312 (second passage port), and a plurality of holes (first passage port) in the conveyance path 253 of the collection tank 250. 313. The first opening 311 and the second opening 312 are provided on the bottom surface of the conveyance path 253, and the mesh member 313 is provided in the first opening 311.

In the transport path 253, the first opening 311 is located on the upstream side in the developer transport direction, and the second opening 312 is located on the downstream side, and are spaced apart from each other. The first opening 311 is arranged to communicate with the supply tank 230, and the second opening 312 is arranged so as to communicate with the discharge tank 260. More specifically, the first opening 311 is located at the downstream end of the supply tank 230 in the conveyance direction and at a position immediately in front of the folding paddle 232 . Further, the second opening 312 is arranged at the position of the reverse winding screw 261 of the discharge tank 260. Note that the second opening 312 may be arranged at the position of the discharge screw 262.

As described above, the developer deteriorates depending on usage conditions and environmental conditions. Degraded developer has poor fluidity and is more likely to aggregate than non-degraded developer. Therefore, the degraded developer forms aggregates and has a particle size larger than that of the non-degraded developer. In this embodiment, attention is paid to such properties of the developer, and the developer is distributed according to the particle size of the developer depending on the state of deterioration. To this end, a mesh member 313 is provided at the first opening 311 that selects the non-deteriorating developer to be passed to the supply tank 230, and this is located on the upstream side. On the other hand, the second opening 312 through which the deteriorated developer passes into the discharge tank 260 is simply an opening, and is located on the downstream side. Through the first opening 311 and the second opening 312, the developer is distributed according to the state of deterioration.

According to the findings of the inventors, the particle size R of aggregates formed by deterioration of the developer is more than three times the particle size r of the developer containing toner and magnetic carrier before use. I know it. For example, when the particle size r of the developer before use is 50 μm, the particle size R of the aggregate is 150 μm or more. Therefore, the mesh diameter (opening) d, which indicates the size of the holes in the mesh member 313, is set such that 2r≦d<3R, taking into consideration such changes in particle size. By setting the mesh diameter d to 2r or more, the non-deteriorating developer can easily pass through the holes of the mesh member 313. By setting the mesh diameter d to be less than 3R, the passage of aggregates of deteriorated developer through the holes of the mesh member 313 is prevented. The mesh member 313 having such a mesh diameter d makes it possible to sort (separate) the non-degraded developer and the degraded developer.

Therefore, from the first opening 311 provided with the mesh member 313, non-degraded developer passes to the supply tank 230 side, and from the second opening 312, the developer that has deteriorated and did not pass through the first opening 311 passes through the second opening 312. The developer will pass to the discharge tank 260 side. As a result, the deteriorated developer is preferentially discharged from the discharge port 263 of the discharge tank 260.

Here, the mesh member 313 having a plurality of holes is exemplified as a configuration for selecting the non-degraded developer to be passed to the supply tank 230, but the particle size of the non-degraded developer to be passed to the supply tank 230 Other configurations may be used as long as they have holes of corresponding sizes. For example, instead of providing the first opening 311 and the mesh member 313 on the bottom surface of the transport path 253, a plurality of holes large enough to allow the non-deteriorating developer to pass through may be provided on the bottom surface of the transport path 253 itself. Alternatively, a non-degradable developer may be selected to be passed through. In this case as well, if the size (for example, diameter) of the hole is d, then the above-mentioned 2r≦d<3R may be satisfied.

Further, although the second opening 312 is illustrated here as a configuration for allowing the deteriorated developer to pass through the discharge tank 260, other configurations may be used as long as the configuration allows the deteriorated developer to pass through the discharge tank 260. . For example, instead of providing the second opening 312 on the bottom surface of the conveyance path 253, the end of the conveyance path 253 on the discharge tank 260 side is cut out, and the open end (second passage port) opens to the discharge tank 260. may be provided.

In this way, the proportion of degraded developer in the developer is reduced while suppressing the discharge amount of non-degraded developer. FIG. 5 shows the results of comparing white streaks, speckled noise, and magnetic carrier adhesion with the conventional configuration at the time of printing 1000 kp. In FIG. 5, ○ indicates that white streaks, spotty noise, and magnetic carrier adhesion problems did not occur, and △ indicates that white lines, spotty noise, and magnetic carrier adhesion problems occurred. It shows. As can be seen from FIG. 5, compared to the conventional configuration, this embodiment can suppress the occurrence of white streaks and speckled noise, and can prevent the adhesion of magnetic carriers to the photoreceptor drum 413. As a result, it is possible to prevent image defects from occurring in the developing device 412 and, by extension, in the image forming apparatus 1.

Note that in order to reduce the proportion of deteriorated developer in the developer, there is a method of increasing the proportion of magnetic carrier in the replenishing developer, but this method increases the cost of the developer. On the other hand, in this embodiment, the proportion of degraded developer in the developer is reduced while suppressing the discharge amount of non-degraded developer, so there is no need to increase the proportion of magnetic carrier in the developer, and There is no increase in the cost of drugs.

[Second embodiment]
This embodiment will be described with reference to FIGS. 6A to 7B. Note that in FIGS. 6A, 7A, and 7B, black arrows indicate the movement of the developer, and white arrows indicate the rotation direction of the rollers and screws. In this embodiment as well, the recovery tank 250 is arranged above the supply tank 230, but the downstream end in the transport direction does not extend to the downstream end of the supply tank 230 in the transport direction. It extends to tank 260. That is, the recovery screw 252 of the recovery tank 250 and the conveyance path 253 through which the developer is conveyed extend to a position above the discharge tank 260.

This conveyance path 253 is provided with an opening 254 at the end thereof on the downstream side in the conveyance direction and on the side surface on the stirring tank 220 side adjacent to the bottom surface thereof. Further, in this embodiment, the sorting section 320 includes a conveyance tray 321 that is a conveyance path different from the conveyance path 253. The developer collected in the collection tank 250 passes through the opening 254 and is transported to the transport tray 321. The transport tray 321 has wall surfaces at the ends except for the downstream end, so that the developer transported to the transport tray 321 does not spill around.

Furthermore, the transport tray 321 is inclined with respect to the vertical direction. For example, the angle of inclination is 45°, but this angle of inclination can be changed as appropriate depending on the properties of the developer. Moreover, the conveyance tray 321 is arranged so as to straddle between the stirring tank 220 and the discharge tank 260. At this time, the upper side of the inclined transport tray 321 is located above the stirring tank 220, and the lower side thereof is located above the discharge tank 260. That is, in the transport tray 321, the upstream side in the transport direction of the developer that moves due to its own weight is arranged above the stirring tank 220, and the downstream side thereof is arranged above the discharge tank 260, and they are arranged apart from each other. has been done.

Then, in the transport tray 321, the distribution unit 320 has a first opening 331, a second opening 332 (second passage port), and a plurality of holes (first a mesh member 333 having a passage opening). The first opening 331 and the second opening 332 are provided on the bottom surface of the transport tray 321, and the mesh member 333 is provided in the first opening 331.

In the transport tray 321, the first opening 331 is arranged on the upstream side in the developer transport direction, and the second opening 332 is arranged on the downstream side. The first opening 331 is arranged to communicate with the stirring tank 220, and the second opening 332 is arranged so as to communicate with the discharge tank 260. More specifically, the first opening 331 is disposed on the upstream side of the stirring tank 220 in the conveying direction and immediately after the replenishment port (not shown). Further, the second opening 332 is arranged at the position of the reverse winding screw 261 of the discharge tank 260. Note that the second opening 332 may be arranged at the position of the discharge screw 262.

Also in this embodiment, as in the first embodiment, the developer is distributed according to the particle size of the developer depending on the state of deterioration. For this purpose, a mesh member 333 is provided at the first opening 331 for selecting the non-deteriorating developer to be passed into the stirring tank 220, and this is located on the upstream side. On the other hand, the second opening 332 through which the deteriorated developer passes into the discharge tank 260 is simply an opening, and is located on the downstream side. Through the first opening 331 and the second opening 332, the developer is distributed according to the state of deterioration. Furthermore, as described in the first embodiment, the mesh diameter d indicating the size of the holes in the mesh member 333 is relative to the particle diameter r of the developer before use and the particle diameter R of the aggregate of the deteriorated developer. is set such that 2r≦d<3R.

Note that although the mesh member 333 having a plurality of holes is exemplified here as a configuration for selecting the non-degraded developer to be passed to the stirring tank 220, the particle size of the non-degraded developer to be passed to the stirring tank 220 is Other configurations may be used as long as they have holes of corresponding sizes. For example, instead of providing the first opening 331 and the mesh member 333 on the bottom of the transport tray 321, the bottom of the transport tray 321 itself is provided with a plurality of holes large enough to allow the non-deteriorating developer to pass through, and the stirring tank 221 Alternatively, a non-degradable developer may be selected to be passed through. In this case as well, if the size (for example, diameter) of the hole is d, then the above-mentioned 2r≦d<3R may be satisfied.

Further, although the second opening 332 is illustrated here as a configuration for allowing the deteriorated developer to pass through the discharge tank 260, other configurations may be used as long as the configuration allows the deteriorated developer to pass through the discharge tank 260. . For example, instead of providing the second opening 332 on the bottom surface of the transport tray 321, the end of the transport tray 321 on the discharge tank 260 side is cut out, and the open end (second passage port) opens to the discharge tank 260. may be provided.

In this way, by setting the mesh diameter d to 2r or more, the non-deteriorating developer can easily pass through the mesh member 333. By setting the mesh diameter d to be less than 3R, the passage of aggregates of deteriorated developer through the mesh member 333 is prevented. The mesh member 333 having such a mesh diameter d makes it possible to sort the non-degraded developer and the degraded developer.

Therefore, the non-degraded developer passes from the first opening 331 provided with the mesh member 333 to the stirring tank 220 side, and the degraded developer passes from the second opening 332 to the discharge tank 260 side. Become. As a result, the deteriorated developer is preferentially discharged from the discharge port 263 of the discharge tank 260.

In the folded paddle 232, the developer may accumulate, but in this embodiment, the non-deteriorating development is carried out from the first opening 331 provided with the mesh member 333 to the stirring tank 220 side instead of the supply tank 230 side. The drug is being returned. Therefore, the recovered non-degraded developer can be circulated without staying in the folded paddle 232 portion.

In this way, the proportion of degraded developer in the developer is reduced while suppressing the discharge amount of non-degraded developer. For this reason, as shown in FIG. 5 described in the first embodiment, compared to the conventional configuration, the generation of white streaks and speckled noise is suppressed, and the adhesion of magnetic carriers to the photoreceptor drum 413 is prevented. be able to. As a result, it is possible to prevent image defects from occurring in the developing device 412 and, by extension, in the image forming apparatus 1.

Also, in this embodiment, the proportion of degraded developer in the developer is reduced while suppressing the discharge amount of non-degraded developer, so there is no need to increase the proportion of magnetic carrier in the developer, and the amount of the developer is reduced. Costs will not increase.

[Third embodiment]
This embodiment will be described with reference to FIGS. 8A to 10. In the first and second embodiments described above, there is a possibility that the mesh members 313 and 333 may be clogged with developer. Therefore, in this embodiment, a vibrating section 81 that vibrates the mesh members 313 and 333 is provided. Note that the transport path 253 having the mesh member 313 and the transport tray 321 having the mesh member 333 may be vibrated by the vibrating section 81.

For example, when the mesh member 313 is to be vibrated, the mesh member 313 is attached to the first opening 311 via an elastic member such as rubber so that it can vibrate, one end of the vibrating part 81 is fixed to the conveyance path 253 side, and other The end is fixed to the mesh member 313 side. In addition, when the mesh member 313 is vibrated together with the conveying path 253, the conveying path 253 is attached to the housing of the developing device 412 so that it can vibrate via an elastic member such as rubber, and one end of the vibrating portion 81 is connected to the developing device 412. It is fixed to the housing side, and the other end is fixed to the conveyance path 253 side. When the vibrating section 81 is made of piezoelectric ceramics, for example, the vibrating section 81 is vibrated by applying an alternating current voltage, and the mesh member 313 or the conveyance path 253 is vibrated. Even when the mesh member 333 and the transport tray 321 shown in the second embodiment are vibrated, the above-mentioned configuration may be used.

By applying vibration by the vibrating section 81, the developer that is caught in the mesh despite having a particle size that can pass through the mesh is moved by the vibration, and the developer is encouraged to pass through the mesh. Furthermore, even if degraded developer with a particle size that cannot pass through the mesh is caught in the mesh, the degraded developer is moved by vibration so as to be removed from the mesh.

When the mesh members 313 and 333 are vibrated, the frequency of vibration by the vibrating section 81 is controlled in the range of 10 to 100 Hz, and the amplitude is controlled in the range of 0.1 to 1.0 mm.

The amount of deteriorated developer in the developer varies depending on the image formation history based on the developing operation of the developing device 412, that is, the amount of the image formed based on the developing operation of the developing device 412. changes. The amount of image formation is, for example, the printing rate (ratio of character area to paper area) or the cumulative number of printed sheets, and as the printing rate increases or the cumulative number of printed sheets increases, the amount of deteriorated developer increases. As the amount of deteriorated developer increases, the possibility that it gets caught in the meshes of the mesh members 313 and 333 and causes clogging increases. Therefore, in this embodiment, the deteriorated developer is moved by changing the vibration conditions such as the frequency and amplitude within the above-mentioned range according to the amount of image formation such as the printing rate and the cumulative number of printed sheets. , the distribution of non-degraded developer and degraded developer is maintained. The amount of image formation may include at least one of the printing rate and the cumulative number of printed sheets, and the vibration condition may include at least one of the frequency and amplitude.

For example, FIGS. 8A and 8B are graphs showing examples of controlling the frequency and amplitude of the printing rate. As described above, as the printing rate increases, the amount of deteriorated developer increases, and the possibility that it gets caught in the meshes of the mesh members 313 and 333 and causes clogging increases. Therefore, as shown in FIG. 8A, as the printing rate increases, the vibration frequency is increased to move the deteriorated developer caught in the mesh more strongly. Further, as shown in FIG. 8B, as the printing rate increases, the amplitude is increased to move the deteriorated developer caught in the mesh more strongly. Such a change in vibration conditions may be performed by the control unit 100 in real time based on the printing rate of the image to be formed, or may be performed by referring to the average printing rate between jobs.

Further, FIGS. 9A and 9B are graphs showing examples of controlling the frequency and amplitude of the vibration with respect to the cumulative number of printed sheets. As described above, as the cumulative number of printed sheets increases, the amount of deteriorated developer increases, and the possibility that it gets caught in the meshes of the mesh members 313 and 333 and causes clogging increases. Therefore, as shown in FIG. 9A, as the cumulative number of printed sheets increases, the vibration frequency is increased to move the deteriorated developer caught in the mesh more strongly. Further, as shown in FIG. 9B, as the cumulative number of printed sheets increases, the amplitude is increased to move the deteriorated developer caught in the mesh more strongly. Such a change in vibration conditions may be performed by the control unit 100 in real time based on the cumulative number of printed sheets, or may be performed by referring to the number of printed sheets between jobs.

FIG. 10 shows the results of evaluating clogging in the mesh in the case of mesh only, the case of mesh + fixed vibration conditions, and the case of mesh + variable vibration conditions. In FIG. 10, ◎ indicates a state where there is no or very little clogging, ○ indicates a state where there is more clogging than ◎ but less than △, and △ indicates a state where there is more clogging than ○. .

As shown in FIG. 10, in the case of only mesh, clogging progresses as the cumulative number of printed sheets increases or the printing rate increases compared to the initial state. In the case of mesh + fixed vibration conditions, clogging progresses as the cumulative number of prints increases or printing rate increases compared to the initial state, but clogging is less than in the case of mesh only. It is. In the case of mesh + variable vibration conditions, even if the cumulative number of printed sheets increases or the printing rate increases, clogging remains close to the initial state, and clogging is more likely to occur than in the case of mesh + fixed vibration conditions. It is in a low state.

As described above, the distribution units 310 and 320 divide the developer collected in the collection tank 250 into the developer tank 210 (agitation tank 220 or supply tank 230) and discharge tank 260 according to the particle size according to the state of deterioration. It is divided into By distributing the non-degraded developer and the degraded developer by the distributing sections 310 and 320, it is possible to reduce the proportion of the degraded developer in the developer while suppressing the discharge amount of the non-degraded developer. As a result, it is possible to prevent image defects from occurring in the developing device 412 and, by extension, in the image forming apparatus 1.

Further, the vibrating section 81 applies vibration to the mesh members 313 and 333, thereby making it possible to prevent clogging of the developer in the meshes of the mesh members 313 and 333. In particular, when changing the vibration conditions according to the printing rate and cumulative number of printed sheets, it is possible to prevent clogging even when the printing rate and cumulative number of printed sheets increase, and this makes it possible to use non-deteriorating developer. The function of distributing deteriorated developer can be maintained.

Note that the above embodiments are merely examples of implementation of the present invention, and the technical scope of the present invention should not be construed to be limited by these embodiments. That is, the present invention can be implemented in various forms without departing from its gist or main features.

1 Image forming apparatus 10 Image reading section 20 Operation display section 30 Image processing section 40 Image forming section 50 Paper transport section 60 Fixing section 81 Vibration section 100 Control section 210 Developing tank 220 Stirring tank 221 Stirring screw 230 Supply tank 231 Supply screw 240 Development Roller 250 Collection tank 251 Collection roller 252 Collection screw 260 Discharge tank 261 Reverse winding screw 262 Discharge screw 263 Discharge port 310 Distribution section 311 First opening 312 Second opening 313 Mesh member 320 Distribution section 321 Transport tray 331 First opening Section 332 Second opening 333 Mesh member 412 Developing device 413 Photosensitive drum

Claims (14)

a first storage section that stores developer;
a second storage section that stores developer;
a third storage section that stores developer;
a distribution unit that distributes the developer stored in the third storage unit to the first storage unit and the second storage unit according to the deterioration state of the developer;
a vibrating section that vibrates the distribution section;
Equipped with
The vibrating unit changes vibration conditions of the distributing unit according to an image formation history based on a developing operation.
Developing device. a first storage section that stores developer;
a second storage section that stores developer;
a third storage section that stores developer;
a distribution unit that distributes the developer stored in the third storage unit to the first storage unit and the second storage unit according to the deterioration state of the developer;
Equipped with
The second storage part is provided on an extension of the first storage part in the conveying direction of the developer stored in the first storage part,
The third accommodating part is provided above the first accommodating part,
Developing device. comprising a vibrating section that vibrates the distribution section;
The developing device according to claim 2 . The vibrating unit changes the vibration conditions of the distributing unit according to an image formation history based on the developing operation of the developing device.
The developing device according to claim 3 . The image formation history is the amount of images formed based on the developing operation of the developing device.
The developing device according to claim 1 or 4 . The amount of the image formed includes at least one of the printing rate and the number of printed sheets of the formed image,
The developing device according to claim 5 . The vibration conditions include at least one of the frequency and amplitude of the distribution section,
The developing device according to any one of claims 1, 4, 5, and 6 . Equipped with a developer carrier capable of carrying a developer,
The first accommodating portion supplies the developer contained in the first accommodating portion to the developer carrier,
The second accommodating portion discharges the developer contained in the second accommodating portion to the outside of the developing device,
the third storage section collects the developer on the developer carrier;
The developing device according to any one of claims 1 to 7 . The deterioration state is the particle size of the developer,
The developing device according to any one of claims 1 to 8 . The sorting section is
a first passage port having a size corresponding to the particle size of the developer to be passed through and distributed to the first storage section;
The developing device according to claim 9 . The distribution section is arranged such that the developer that has not passed through the first passage port is passed through the second storage section and distributed through the second passage port in a direction in which the developer is conveyed in a conveyance path through which the developer is conveyed. provided on the downstream side of the first passage port,
The developing device according to claim 10 . The conveyance path is inclined with respect to the vertical direction.
The developing device according to claim 11 . The first storage section includes a stirring section that stirs the developer contained in the first storage section,
the first passage port allows the developer conveyed in the conveyance path to pass through to the stirring section;
The developing device according to claim 11 or 12 . The developing device according to any one of claims 1 to 13,
an image carrier that carries an image developed by the developing device;
An image forming apparatus comprising:

Images