JP5380942B2 - Developing device and image forming apparatus - Google Patents

Description

  The present invention relates to a developing device used in an image forming apparatus such as a copying machine, a facsimile machine, and a printer, and an image forming apparatus equipped with the developing device.

Conventionally, an image forming apparatus including a developing device using a two-component developer including toner and a magnetic carrier has been widely used. As this type of two-component developing device, for example, a developing container, a developing roller containing a magnet disposed at the opening of the developing container so as to face the latent image carrier, and a surface of the developing roller are supported. A doctor blade that regulates the developer layer thickness, first and second conveying screws that circulate and convey the developer in the developer container, a replenisher that replenishes the toner in the developer container, and toner A device including a toner density sensor for detecting density has been proposed (see, for example, Patent Documents 1 to 3).
In such a conventional developing device, a partition is provided between the first and second transporting screws in the longitudinal direction of the developing roller, and the developer is the first portion at the portion where the partitioning at both ends of the screw is interrupted. And passed between the second conveying screws and circulated in one direction. As the developing roller rotates, the developer in the conveyance path is collected after being supplied to the developing roller and circulates in the developing device.
Since the developer supplied to the developing roller is used for developing the electrostatic latent image on the latent image carrier, the toner density decreases. In order to recover the toner density, it is necessary to supply toner to the developing device. At this time, if the replenished toner is not sufficiently dispersed by being agitated with the developer before being supplied to the developing roller, it may cause image density unevenness due to insufficient charge amount of the toner or uneven distribution of the toner. In order to prevent such image density unevenness, various means for improving the stirring performance are used in the developing device, and one of such means is a change in the developer conveyance path.

The developing device described in Patent Document 1 includes two developer screws and a developer circulation path provided with a partition in the longitudinal direction between the two conveying screws in the same manner as the developing device described above. In this technique, the sub-circulation path having a small cycle is provided outside the image area to improve the agitation of the replenishment toner.
According to this technique, the screw outer peripheral portion with high stirring performance is buried in the developer by regulating the amount of the developer flowing in by the regulating member provided at the entrance portion where the agent flows from the main circulation path to the sub circulation path. Therefore, the toner replenished to the secondary circulation path is efficiently stirred with the developer. Further, since the developer having a high toner concentration in the secondary circulation path flows into the farthest place from the developing roller in the main circulation path, the developer is further stirred in the main circulation path before being supplied to the development roller.
The developing device described in Patent Document 2 includes two developer screws and a developer circulation path provided with a partition in the longitudinal direction between them as in the above-described developing device. In this technique, an opening that can be opened and closed is provided in the partition between the transport paths, the speed of the transport screw is made variable, and these speeds are controlled according to the signal from the toner density sensor and the output image. Improves toner density dispersibility.
The developing device described in Patent Document 3 has a plurality of developer transport paths to increase the developer capacity and improve the dispersibility of the developer. In a typical view of this technique, a developer conveyance path provided with three screws and two partitions between them is shown. In this configuration, the developer life is increased and the dispersibility is improved by increasing the developer capacity for a single conveying path as compared with the conventional developing device.

FIG. 16 is a schematic diagram illustrating a developer circulation path through which a developer moves in a conventional developing device. FIG. 17 is a schematic diagram for explaining the flow of the developer in the conventional developing device having one sub-developer circulation path.
Referring to FIGS. 16 and 17, the partition walls 511 for isolating the agitating / conveying screw (not shown) provided in the developing device casing 510 are provided at both ends of the developing device casing 510 in the longitudinal direction. A developer circulation path 500 (FIG. 16A) indicated by an arrow is provided at intervals from the inner wall.
In such a developer circulation path 500, the developer 503 (FIG. 16B) is not dispersed in the developer circulation path 500 by elements other than the dispersing function by the screw, and therefore, the dispersibility is not good. Even if it is conveyed as shown in c), it is conveyed as a lump similar to FIG.
Even if the opening 501 is provided as shown in FIG. 17A in order to branch off the developer circulation path 500, in this case, the cycle of developer circulation between the flow path of the opening 501 and the flow path of the opening 502. 17 is equal to 1: 2, the developer 503 shown in FIG. 17B is divided into a and b as shown in FIG. 17 (d), 17 (e), and 17 (f), the developer 503a and 503b are merged with the same developer 503 again as shown in FIG. 17 (g). By changing the flow of the developer that hinders such dispersion, the developer history in the developing device is prevented from being biased, and the toner dispersibility and the developer life are improved. provide.
JP 2005-215383 A JP 2007-148182 A JP 2003-316158 A

However, in the technique of Patent Document 1, since the amount of developer in the secondary circulation path is very small compared to the main circulation path, improvement in local stirring performance can be expected, but the toner density deviation in the entire developing device is improved. The effect is not expected.
In addition, a complicated configuration like the technique of Patent Document 2 is expensive and causes an increase in failure rate due to an increase in the number of parts. Furthermore, since the periods of the two types of conveyance paths are synchronized, the developer having substantially the same history is mixed at the joining portion of the conveyance paths, and the effect of improving the dispersibility is small. In the configuration of Patent Document 3, as in Patent Document 2, a mechanism for preventing the developers having the same history from being mixed is not employed.
As described with reference to FIGS. 16 and 17, in the conventional technology, the flow of the developer hinders dispersion, and the history of the developer in the developing device is biased, which adversely affects the toner dispersibility and the developer life. It was.
Accordingly, an object of the present invention is to prevent the history of the developer in the developing device from being biased by low-cost means with a small number of parts, and to improve the toner dispersibility and the developer life in consideration of the above situation. Another object of the present invention is to provide a developing device having a stable image quality and an image forming apparatus equipped with the developing device.

In order to solve the above problems, the invention described in claim 1 is characterized in that the developer is carried on the surface and rotated to form a latent image on the surface of the latent image carrier at a position facing the latent image carrier. A developer carrier for supplying and developing toner, and a developer supply region for supplying the developer to the developer carrier, and supplying the developer while supplying the developer to the developer carrier Receiving the developer through a first opening from a transport path, a recovery transport path for recovering the developer from the developer carrying member, transporting the recovered developer, and a downstream side of the recovery transport path; And a stirring and conveying path for delivering the developer through a second opening to the upstream side of the supply and conveying path, wherein the recovery conveying path and the stirring and conveying path are separate from the first opening. A communication opening that communicates with the communication opening, The developer is provided on the upstream side of the collection conveyance path with respect to one opening, and passes from the supply conveyance path to the supply conveyance path through the developer carrying member, the collection conveyance path, and the stirring conveyance path. Of the developer by a circulation conveyance path through which the developer circulates, and a circulation conveyance path through which the developer circulates through the first opening and the communication opening between the recovery conveyance path and the stirring conveyance path. circulation, it said developing device time period of each other is a non-integer multiple.
According to a second aspect of the present invention, there is provided at least one latent image carrier, charging means for charging the surface of the latent image carrier, and forming an electrostatic latent image on the latent image carrier. a latent image forming means, in an image forming apparatus having the developing means for toners Zoka to develop the electrostatic latent image, a developing means, the image formation using a developing apparatus according to claim 1 Symbol placement Features the device .

  According to the present invention, since the plurality of developer circulation paths have a non-integer multiple cycle, when the developers divided into each developer circulation path merge, developers having different histories are mixed together. It becomes possible to make it. Thereby, the history of the amount of toner replenished to the developer is dispersed, and the toner dispersibility in the developing device is improved. Further, since the history of stress applied to the developer is also dispersed, the life of the developer can be improved.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. As an image forming apparatus to which the present invention is applied, one embodiment (hereinafter simply referred to as “implementation”) of a tandem type color laser copying machine (hereinafter simply referred to as “copier”) in which a plurality of photoconductors are arranged in parallel. Form)).
FIG. 1 is a schematic configuration diagram of a copying machine according to an embodiment of the present invention. The copier includes a printer unit 100, a paper feeding device 200 on which the printer unit 100 is placed, a scanner 300 fixed on the printer unit 100, and the like. An automatic document feeder 400 fixed on the scanner 300 is also provided.
The printer unit 100 includes an image forming unit including four sets of process cartridges 18Y, 18M, 18C, and 18K for forming images of each color of yellow (Y), magenta (M), cyan (C), and black (K). 20 is provided. “Y”, “M”, “C”, and “K” added after the numerals indicate the members for yellow, cyan, magenta, and black (the same applies hereinafter).
In addition to the process cartridges 18Y, 18M, 18C, and 18K, an optical writing unit 21, an intermediate transfer unit 17, a secondary transfer device 22, a resist roller pair 49, a belt fixing type fixing device 25, and the like are disposed.
The optical writing unit 21 includes a light source, a polygon mirror, an f-θ lens, a reflection mirror, and the like (not shown), and irradiates the surface of a photoconductor described later with laser light based on image data. The process cartridges 18Y, 18M, 18C, and 18K include a drum-shaped photosensitive member 1, a charger (not shown), a developing device 4, a drum cleaning device, a static eliminator, and the like.

The yellow process cartridge 18Y will be described below. The surface of the photoreceptor 1Y is uniformly charged by a charger that is a charging unit. The surface of the photoreceptor 1 </ b> Y that has been subjected to the charging process is irradiated with laser light modulated and deflected by the optical writing unit 21.
Then, the potential of the irradiation part (exposure part) is attenuated. By this attenuation, an electrostatic latent image for Y is formed on the surface of the photoreceptor 1Y. The formed electrostatic latent image for Y is developed by a developing device 4Y which is a developing unit to become a Y toner image.
The Y toner image formed on the Y photoreceptor 1Y is primarily transferred to an intermediate transfer belt 110 described later. The surface of the photoreceptor 1Y after the primary transfer is cleaned of the transfer residual toner by a drum cleaning device.
In the Y process cartridge 18Y, the photoconductor 1Y cleaned by the drum cleaning device is discharged by the charge eliminator. The photoreceptor 1Y is uniformly charged by the charger and returns to the initial state. The series of processes as described above is the same for the other process cartridges 18M, 18C, and 18K.

Next, the intermediate transfer unit will be described. The intermediate transfer unit 17 includes an intermediate transfer belt 110, a belt cleaning device 90, and the like. Further, the tension roller 14, the driving roller 15, the secondary transfer backup roller 16, four primary transfer bias rollers 62Y, 62M, 62C, and 62K are also provided.
The intermediate transfer belt 110 is stretched by a plurality of rollers including the stretching roller 14. Then, it is endlessly moved clockwise in the drawing by the rotation of the driving roller 15 driven by a belt driving motor (not shown).
The four primary transfer bias rollers 62Y, 62M, 62C, and 62K are disposed so as to be in contact with the inner peripheral surface side of the intermediate transfer belt 110, respectively, and receive a primary transfer bias from a power source (not shown). Further, the intermediate transfer belt 110 is pressed toward the photoreceptors 1Y, 1M, 1C, and 1K from the inner peripheral surface side to form primary transfer nips, respectively. In each primary transfer nip, a primary transfer electric field is formed between the photosensitive member and the primary transfer bias roller due to the influence of the primary transfer bias.
The above-described Y toner image formed on the Y photoreceptor 1Y is primarily transferred onto the intermediate transfer belt 110 due to the influence of the primary transfer electric field and nip pressure. On the Y toner image, the M, C, and K toner images formed on the M, C, and K photoconductors 1M, 1C, and 1K are sequentially superimposed and primarily transferred. By this primary transfer of superposition, a four-color superposed toner image (hereinafter referred to as a four-color toner image) that is a multiple toner image is formed on the intermediate transfer belt 110.
The four-color toner image superimposed and transferred on the intermediate transfer belt 110 is secondarily transferred onto a transfer sheet, which is a recording medium (not shown), at a secondary transfer nip described later. Transfer residual toner remaining on the surface of the intermediate transfer belt 110 after passing through the secondary transfer nip is cleaned by a belt cleaning device 90 that sandwiches the belt with the driving roller 15 on the left side in the drawing.

Next, the secondary transfer device 22 will be described. Below the intermediate transfer unit 17 in the figure, a secondary transfer device 22 is disposed in which a paper conveying belt 24 is stretched by two stretching rollers 23. The paper transport belt 24 is moved endlessly in the counterclockwise direction in the drawing in accordance with the rotational drive of at least one of the stretching rollers 23. One of the two stretching rollers 23 arranged on the right side in the drawing sandwiches the intermediate transfer belt 110 and the paper transport belt 24 between the secondary transfer backup roller 16 of the intermediate transfer unit 17. It is out.
By this sandwiching, a secondary transfer nip is formed in which the intermediate transfer belt 110 of the intermediate transfer unit 17 and the paper transport belt 24 of the secondary transfer device 22 are in contact with each other. Then, a secondary transfer bias having a polarity opposite to that of the toner is applied to the one stretching roller 23 by a power source (not shown). By applying the secondary transfer bias, the four-color toner image on the intermediate transfer belt 110 of the intermediate transfer unit 17 is electrostatically moved from the belt side toward the one stretching roller 23 side in the secondary transfer nip 2. A next transfer electric field is formed.
The transfer paper fed into the secondary transfer nip so as to be synchronized with the four-color toner image on the intermediate transfer belt 110 by a registration roller pair 49 described later has four colors affected by the secondary transfer electric field and nip pressure. The toner image is secondarily transferred. Instead of the secondary transfer method in which the secondary transfer bias is applied to one of the stretching rollers 23 as described above, a charger for charging the transfer paper in a non-contact manner may be provided.

In the paper feeding device 200 provided at the lower part of the copying machine main body, a paper feeding cassette 44 that forms a paper bank 43 in which a plurality of transfer sheets can be stacked and accommodated in a bundle of paper is provided in the vertical direction. It is arranged so as to overlap a plurality. Each paper feed cassette 44 presses the paper feed roller 42 against the uppermost transfer paper in the paper bundle. Then, by rotating the paper feed roller 42, the uppermost transfer paper is sent out toward the paper feed path 46.
The paper feed path 46 that receives the transfer paper fed from the paper feed cassette 44 has a plurality of transport roller pairs 47 and a registration roller pair 49 provided near the end in the path. Then, the transfer paper is conveyed toward the registration roller pair 49. The transfer sheet conveyed toward the registration roller pair 49 is sandwiched between the rollers of the registration roller pair 49.
On the other hand, in the intermediate transfer unit 17, the four-color toner image formed on the intermediate transfer belt 110 enters the secondary transfer nip as the belt moves endlessly. The registration roller pair 49 sends out the transfer paper sandwiched between the rollers at a timing at which the transfer paper can be brought into close contact with the four-color toner image at the secondary transfer nip.
As a result, at the secondary transfer nip, the four-color toner image on the intermediate transfer belt 110 is in close contact with the transfer paper. Then, it is secondarily transferred onto the transfer paper and becomes a full color image on the white transfer paper. The transfer paper on which a full-color image is formed in this way exits the secondary transfer nip as the paper transport belt 24 moves endlessly, and is then sent from the paper transport belt 24 to the fixing device 25.

The fixing device 25 includes a belt unit that moves the fixing belt 26 endlessly while being stretched by two rollers, and a pressure roller 27 that is pressed toward the fixing belt 26 of the belt unit. The fixing belt 26 and the pressure roller 27 are in contact with each other to form a fixing nip, and the transfer paper received from the paper transport belt 24 is sandwiched between the fixing nips.
Of the two rollers in the belt unit, the large-diameter roller in the drawing has a heat source (not shown) inside, and the fixing belt 26 is applied by the pressure roller 27 in contact with the heat generated by the heat source. Press. The pressed fixing belt 26 heats the transfer paper sandwiched in the fixing nip. The full color image is fixed on the transfer paper by the influence of the heating and the nip pressure.
The transfer paper subjected to the fixing process in the fixing device 25 passes through the paper discharge roller 56 and is stacked on the stack portion 57 provided on the outer side of the left side plate in the drawing of the printer housing or on the other surface. Also, it is returned to the above-mentioned secondary transfer nip to form a toner image.

When a copy of a document (not shown) is taken, for example, a bundle of sheet documents is set on the document table 30 of the automatic document feeder 400. However, when the original is a single-sided original that is closed in a main form, it is set on the contact glass 32. Prior to this setting, the automatic document feeder 400 is opened with respect to the copying machine main body, and the contact glass 32 of the scanner 300 is exposed. Thereafter, the single-bound original is pressed by the closed automatic document feeder 400.
When a copy start switch (not shown) is pressed after the original is set in this way, the original reading operation by the scanner 300 is started. However, when a sheet document is set on the automatic document feeder 400, the automatic document feeder 400 automatically moves the sheet document to the contact glass 32 prior to the document reading operation.
In the document reading operation, first, the first traveling body 33 and the second traveling body 34 start traveling together, and light is emitted from a light source provided in the first traveling body 33. Then, the reflected light from the document surface is reflected by a mirror provided in the second traveling body 34, passes through the imaging lens 35, and then enters the reading sensor 36. The reading sensor 36 constructs image information based on the incident light.
In parallel with the original reading operation, each device in each of the process cartridges 18Y, 18M, 18C, and 18K, the intermediate transfer unit 17, the secondary transfer device 22, and the fixing device 25 start driving. Based on the image information constructed by the reading sensor 36, the optical writing unit 21 is driven and controlled, and Y, M, C, and K toner images are formed on the photoreceptors 1Y, 1M, 1C, and 1K. The These toner images become four-color toner images superimposed and transferred on the intermediate transfer belt 110.

Further, almost simultaneously with the start of the document reading operation, the paper feeding operation is started in the paper feeding device 200. In this paper feeding operation, one of the paper feeding rollers 42 is selectively rotated, and the transfer paper is sent out from one of the paper feeding cassettes 44 accommodated in the paper bank 43 in multiple stages. The fed transfer sheets are separated one by one by the separation roller 45 and enter the reverse feeding path 46, and then conveyed toward the secondary transfer nip by the conveyance roller pair 47.
In some cases, paper feeding from the manual feed tray 51 is performed instead of such paper feeding from the paper feeding cassette 44. In this case, after the manual paper feed roller 50 is rotated by the selected enemy and the transfer paper on the manual tray 51 is sent out, the separation roller 52 separates the transfer paper one by one, and the manual paper feed path 53 of the printer unit 100. Feed the paper.
In the case of forming a multi-color image composed of two or more colors of toner, the copying machine stretches the intermediate transfer belt 110 so that the upper stretched surface is almost horizontal, Photoconductors 1Y, 1M, 1C, and 1K.

On the other hand, when forming a monochrome image consisting of only K toner, the intermediate transfer belt 110 is tilted to the lower left in the drawing by a mechanism (not shown) and the upper stretched surface is set to Y, M, C. The photoconductors 1Y, 1M, and 1C are separated.
Of the four photoconductors 1Y, 1M, 1C, and 1K, only the K photoconductor 1K is rotated counterclockwise in the drawing to form only the K toner image. At this time, for Y, M, and C, not only the photosensitive member 1 but also the developing device is stopped to prevent unnecessary consumption of the photosensitive member and the developer.
The copying machine includes a control unit (not shown) configured by a CPU or the like that controls the following devices in the copying machine, and an operation display unit (not shown) configured by a liquid crystal display, various key buttons, and the like.
The operator sends a command to the control unit by a key input operation on the operation display unit, so that one of the three modes is selected from the three-sided print mode, which is a mode for forming an image only on one side of the transfer paper. You can choose one. The three single-sided printing modes include a direct discharge mode, a reverse discharge mode, and a reverse decal discharge mode.

FIG. 2 is an enlarged configuration diagram showing a developing device and a photoreceptor provided in one of the four process cartridges. FIG. 2 shows the developing device 4 and the photoreceptor 1 provided in one of the four process cartridges 18Y, 18M, 18C, and 18K described above.
The four process cartridges 18Y, 18M, 18C, and 18K have substantially the same configuration except that the colors of the toners to be handled are different from each other. Therefore, the subscripts Y, M, C, and K attached to the reference numeral 4 in FIG. Is omitted.
As shown in FIG. 2, the surface of the photosensitive member 1 is charged by a charging device (not shown) while rotating in the direction of arrow G in the drawing. An electrostatic latent image is formed on the surface of the charged photoreceptor 1 by laser light emitted from an exposure device (not shown), and toner is supplied from the developing device 4 to the electrostatic latent image to form a toner image. To do.
The developing device 4 has a developing roller 5 as a developer carrier for supplying toner to the electrostatic latent image on the surface of the photosensitive member 1 and developing it while moving in the direction of arrow I in the drawing. Further, a supply / conveying screw 8 is provided as a supply / conveying member for conveying the developer in the depth direction of FIG. 2 while supplying the developer to the developing roller 5.
The supply / conveying screw 8 is a developer supply / conveying screw that includes a rotation shaft and a blade portion (not shown) provided on the rotation shaft and conveys the developer in the axial direction by rotating. The developing roller 5 facing the developer supply / conveying screw 8 is supplied to the developing roller 5 on the downstream side of the surface movement direction (above the developing roller 5 in FIG. 2) from the portion facing the developer supplying / conveying screw 8. A developing doctor 12 is provided as a developer regulating member for regulating the developer to a thickness suitable for development.

The developed developer that has passed through the developing unit is collected and collected on the downstream side in the surface movement direction (below the developing roller 5 in FIG. 2) from the developing unit, which is the part of the developing roller 5 facing the photoreceptor 1. A developer collecting and conveying screw 6 is provided as a developer collecting and conveying member that conveys the collected developer in the same direction as the developer supply and conveying screw 8. The developer supply / conveyance path 9 including the developer supply / conveying screw 8 is in the lateral direction of the developing roller 5, and the developer recovery / conveyance path 7 serving as the developer recovery / conveyance path including the developer recovery / conveying screw 6 is the developing roller 5 Are juxtaposed below.
The developing device 4 is provided with a developer stirring / conveying path 10 in parallel with the developer collecting / conveying path 7 below the developer supply / conveying path 9. The developer agitating / conveying path 10 includes a developer agitating / conveying screw 11 as an agitating / conveying member that conveys the developer to the front side in the figure, which is in the direction opposite to the developer supply / conveying screw 8 while stirring the developer.
The developer supply conveyance path 9 and the developer agitation conveyance path 10 are partitioned by a first partition wall 133 as a partition member in the developing device casing 4a. The first partition wall 133 divides the developer supply / conveyance path 9 and the developer agitation / conveyance path 10 at both ends on the front side and the back side in the drawing, and the developer supply / conveyance path 9 The developer stirring / conveying path 10 communicates.
Although the developer supply transport path 9 and the developer recovery transport path 7 are both partitioned by the first partition wall 133, the developer supply transport path 9 and the developer recovery transport path 7 of the first partition wall 133 are partitioned. There are no openings in the places.

In addition, the two transport paths of the developer stirring transport path 10 and the developer recovery transport path 7 are partitioned by a second partition wall 134 as a partition member. The second partition wall 134 has an opening on the front side in the figure, and the developer agitation transport path 10 and the developer recovery transport path 7 communicate with each other.
The developer supply and transport screw 8, the developer recovery screw 6, and the developer agitation and transport screw 11, which are developer supply and transport members, are made of resin or metal screws, and each screw diameter is φ22 [mm], and the screw pitch. The supply screw is 50 [mm], the recovery screw 6 and the stirring screw 11 are 25 [mm], and the rotation speed is all set to about 600 [rpm].
The developer thinned by the developing doctor 12 made of stainless steel on the developing roller 5 is transported to a developing area which is a portion facing the photoreceptor 1 for development. The surface of the developing roller 5 is V-groove or sandblasted, and is made of an Al (aluminum) or SUS (stainless steel) tube having a diameter of 25 [mm], and the gap between the developing doctor 12 and the photoreceptor 1 is 0.3 [ mm].
The developer after the development is collected in the developer collection conveyance path 7 and conveyed to the front side of the cross section in FIG. 2, and the developer agitation is performed at the opening of the first partition wall 133 provided in the non-image area portion. The developer is transferred to the conveyance path 10. The developer agitation transport path 10 is connected to the developer agitation transport path 10 from a toner replenishing port provided on the upper side of the developer agitation transport path 10 in the vicinity of the opening of the first partition wall 133 on the upstream side in the developer transport direction in the developer agitation transport path 10. Toner is replenished.

FIG. 3 is a perspective view showing the flow of the developer in the main developer circulation path in the developing device. FIG. 4 is a simplified diagram showing the developer flow in the main developer circulation path. 3 and 4, the developer conveyed toward the back of the drawing in the developer agitating / conveying path 10 is pushed up at the end of the developer and directed toward the developer supplying / conveying path 9, and development is performed in the developer supplying / conveying path 9. The agent is fed to the developing roller 5 at the same time as it is transported forward.
The developer supplied to the developing roller 5 and used for development is collected in the developer collecting / conveying path 7 and conveyed toward the front in the figure, and at a front end (not shown) of the developer collecting / conveying screw 6. It is delivered to the developer stirring and conveying path 10. FIG. 4 shows the developer flow in the main developer circulation path 150 described above.
The thick arrow in the main developer circulation path 150 in the figure indicates the flow of the developer together with the main developer circulation path. The upper and lower parts in FIG. 4 show the arrangement of the upper and lower parts of the perspective view of FIG. 3 separately for easy explanation of the circulation path and the developer flow. Reference numerals 101 and 102 denote openings.

FIG. 5 is a simplified diagram showing the first sub-developer circulation path. In FIG. 5, the first sub-developer circulation path 151 circulates the developer between the developer supply conveyance path 9 and the developer agitation conveyance path 10. In the opening 102, the developer that has hit the dead end is pushed up by the conveying force of the screw, whereby the developer is transferred from the developer supply conveyance path 10 to the developer agitation conveyance path 9.
In the opening 103, the developer is transferred from the developer agitation transport path 9 to the developer supply transport path 10 by the potential energy due to the difference in height of the transport path. The period of the sub-developer circulation path 151 is about 78% of the period of the main developer circulation path 150.
Since the developer in the main developer circulation path 150 and the sub-developer circulation path 151 are synchronized with each other in the least common multiple cycle of the cycle of each developer circulation path, the developer passes through different conveyance paths until about 1950 laps. It continues to be mixed with the developer that has passed.
In practice, however, the mixing of the developer is further complicated by other dispersion mechanisms. Further, since the sub-developer circulation path 151 circulates a larger amount of developer than the other sub-developer circulation paths, there is an effect of dispersing the bias in the long-term developer history.

According to this embodiment, the developer hitting the dead end by the conveying force of the screw at the opening 102 is pushed up. Since the developer flow in the sub developer circulation path 151 is controlled by the potential energy of the developer, a plurality of developer circulation paths can be provided without using a special drive source.
That is, as shown in FIG. 4, since the original developing device is a vertical three-axis OD developing device, the developer obtains potential energy at the opening 102. However, by providing the opening 103 as shown in FIG. 5, it is possible to form the sub-developer circulation path without using any other power.
Here, the non-integer multiple cycle will be described. As described above, since the period of the sub-developer circuit 151 is about 78% of the period of the main developer circuit 150, the time period of the main developer circuit 150: the time of the sub-developer circuit 151 The period is 100: 78 = 50: 39, which is not an integral multiple of each other. Therefore, the developer circulation is performed at a non-integer multiple of each other.

FIG. 6 is a simplified diagram showing the second sub-developer circulation path. In FIG. 6, in the sub-developer circulation path 152, the opening 104 for delivering the developer from the developer supply transport path 9 to the developer stirring transport path 10 is elongated in the longitudinal direction.
The delivery of the developer in the opening 104 depends on the potential energy due to the difference in height between the developer supply transport path 9 and the developer agitation transport path 10. By providing the opening 104, a sub-developer circulation path is newly formed without using other power.
Since the opening 104 is long in the longitudinal direction, there is a time difference between the developer delivered upstream of the developer supply transport path 9 and the developer delivered downstream of the developer supply transport path 9. There is an effect that the bias of the developer history having a short cycle is extended and dispersed in the transport direction.
The auxiliary developer supply / conveyance path 9 circulates the developer from the upstream side to the downstream side of the main developer stirring / conveying path 10, thereby extending the time until the developer reaches the developing roller 5, thereby stirring and dispersing the developer. It is possible to perform sufficiently. As a result, a uniform developer can be stably supplied to the developing roller 5.
Development with different histories corresponding to the width of the developer exchange port is achieved because the main developer agitation transport path 10 and the sub-developer supply transport path 9 can exchange the developer over a wide area in the transport direction. It becomes possible to mix the agent.

FIG. 7 is a simplified diagram showing a third sub-developer circulation path. In FIG. 7, in the sub-developer circulation path 153, the developer in the developer agitation transport path 10 is transferred to the transport path 7 by the potential energy due to the difference in the height of the developer in the opening 105.
In order to control the developer flow in the sub-developer circulation path 153, it is possible to obtain the potential energy of the developer without using a special drive source by biasing the developer and creating a difference in its volume. Become. The developer flow in the sub developer circulation path 153 can be controlled by the potential energy thus obtained.
In other words, the developer rotates clockwise in the sub-developer circulation path 153. The auxiliary agent circulation path 153 is common to the main developer circulation path 150 of FIG. 4 except for the opening 105. Here, the opening 105 forms a sub-developer circulation path 153 by returning the developer to the upstream side of the main developer circulation path 150.
FIG. 8 is a simplified diagram showing a sub-developer circulation path due to developer bias. FIG. 9 is a schematic view showing a difference in developer height in the developing device. FIG. 10 is a schematic view showing the same height of the developer in the developing device. As shown in FIG. 8, the developer conveyed through the developer collection conveyance path 7 is the developer collected from the developing roller 5, and therefore the amount increases as it goes downstream of the developer collection conveyance path 7.
In other words, since the volume of the developer is low in the middle of the developer collection conveyance path 7, the height of the developer can be varied as shown in FIG. Therefore, it is possible to control the amount of developer flowing by providing the opening 105 and adjusting the height and width thereof.

In addition, even when there is no difference in the developer amount between the developer collection conveyance path 7 and the developer agitation conveyance path 10 as shown in FIG. It is also possible to form the sub-developer conveyance path by using the developer 210 jumping up by the agitation conveyance screw 11.
The developer delivered to the developer recovery transport path 7 is transported in the left direction in FIG. 8, pushed out at the dead end, and delivered to the developer agitation transport path 10. The period of the sub-developer circulation path 154 is about 30% of the main developer circulation path 150 (FIG. 4), which has an effect of dispersing the deviation of the developer history in the middle period.
The period of the secondary developer circulation path 154 is the same as that described with reference to FIG. 5. The time period of the main developer circulation path 150: The time period of the secondary developer circulation path 154 is 100: 30 = 10. : 3, which is not an integral multiple of each other. Therefore, again, the developer circulation is performed in non-integer multiples.
Developing without using a special drive source by controlling the flow of the developer in the sub-developer transport path using energy other than the transport direction given to the developer by the developer agitating and transporting screw 11 that is a developer transport member. It becomes possible to control the flow of the agent.
A mechanism in which the developer is dispersed by a plurality of circulation paths will be described by taking the main developer circulation path 150 and the sub developer circulation path 153 as an example. For the sake of simplicity, it is assumed here that the developer is not dispersed due to the conveying screw, the developing roller, the retention of the developer, and the like.

FIG. 11 is a simplified diagram showing a state in which the developer immediately after toner replenishment is located at the left end of the transport path. FIG. 12 is a simplified diagram showing the state of the conveyance path divided into two directions. FIG. 13 is a simplified diagram showing the state of the developer around the main developer circulation path. FIG. 14 is a simplified diagram showing a state when the developer reaches the opening again. FIG. 15 is a graph showing the bias of the dispersed developer such as stress and toner density.
In FIG. 11, the developer 201 immediately after toner replenishment is located at the left end of the developer agitation transport path 10. As shown in FIG. 12, the developer 201 conveyed toward the right of the developer agitation conveyance path 10 is divided into two directions a and b in the opening 105. As shown in FIG. 13, the developer 201 a that is conveyed as it is in the developer agitation conveyance path 10 becomes a developer that goes around the main developer circulation path 150.
In addition, the developer 201 b transferred to the developer recovery conveyance path 7 through the opening 105 becomes the developer 201 b that goes around the sub-developer circulation path 153. Since the period of the sub-developer circulation path 153 is about 30% of the main developer circulation path 150, when the developer 201 b reaches the opening 105 again as shown in FIG. 14, the developer 201 a is still in the main developer circulation path 150. Thus, 201a and 201b are not mixed.
Even after the developer 201b is divided into ba and bb at the opening 105, the developer 201ba and the developer 201bb are not mixed in the same manner, so that the developer is further dispersed. The developer divided into the main developer circulation path 150 and the sub-developer circulation path 153 is mixed again in the cycle of the least common multiple of the cycle of each circulation path. 201 is always mixed with a developer having a different history.

In this way, as shown in FIG. 15, biases such as developer stress and toner concentration are dispersed. That is, the developer divided into the main developer circulation path 150 and the sub-developer circulation path 153 is mixed again in the period of the least common multiple of the period of each developer circulation path. ), Biases such as developer stress and toner concentration are dispersed and reduced.
Thus, in the developing device of the present invention, the developer carrying member rotates with the developer carried on the surface thereof, and develops the electrostatic latent image formed on the latent image carrying member. The developer supplied to the developing carrier circulates in the circulation conveyance path while being agitated by the developer conveyance member. At this time, two or more developer circulation paths having different cycles are arranged so that a part or all of the circulation conveyance paths are shared or the conveyance paths cross each other, whereby the developer between the developer circulation paths is arranged. Exchange.

1 is a schematic configuration diagram of a copier according to an embodiment of the present invention. FIG. 4 is an enlarged configuration diagram illustrating a developing device and a photoconductor included in one of four process cartridges. FIG. 7 is a perspective view showing a developer flow in a main developer circulation path in the developing device. FIG. 6 is a simplified diagram illustrating a developer flow in a main developer circulation path. FIG. 6 is a simplified diagram showing a first sub-developer circulation path. FIG. 6 is a simplified diagram showing a second sub-developer circulation path. FIG. 10 is a simplified diagram showing a third sub-developer circulation path. FIG. 6 is a simplified diagram illustrating a sub-developer circulation path due to developer bias. It is the schematic which shows the difference in the height of the developer in a developing device. It is the schematic which shows the same height of the developer in a developing device. FIG. 10 is a simplified diagram illustrating a state in which the developer immediately after toner replenishment is positioned at the left end of the conveyance path. It is a simplification figure showing the state of the conveyance way divided into two directions. FIG. 6 is a simplified diagram illustrating a state of a developer that goes around a main developer circulation path. It is a simplified diagram showing a state when the developer reaches the opening again. FIG. 4 is a graph showing a bias of a dispersed developer such as stress and toner concentration. It is the schematic explaining the developer circulation path in which a developer moves in the conventional developing device. FIG. 10 is a schematic diagram illustrating a developer flow of a conventional developing device having one sub-developer circulation path.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Latent image carrier (photoconductor), 4 developing device, 4a developing device casing, 5 developer carrier (developing roller), 6 developer collection conveyance member (developer collection conveyance screw), 7 developer conveyance path (development) Developer transport path), 8 supply transport member (supply transport screw), 9 developer transport path (developer supply transport path), 10 developer transport path (developer stirring transport path), 11 developer stirring transport member (development) 18Y latent image forming means (process cartridge), 133 first partition wall, 134 second partition wall, 150 main developer circulation path, 151 sub developer circulation path, 152 sub developer circulation path, 153 Sub developer circuit, 154 Sub developer circuit

Claims (2)

  A developer carrying member that rotates by carrying a developer on the surface and supplies toner to the latent image on the surface of the latent image carrying member at a position facing the latent image carrying member;
  A supply conveyance path for conveying the developer while supplying the developer to the developer carrier in the developer supply region for supplying the developer to the developer carrier;
  A recovery transport path for recovering the developer from the developer carrier and transporting the recovered developer;
  An agitation transport path that receives the developer from the downstream side of the recovery transport path through a first opening and delivers the developer through a second opening to the upstream side of the supply transport path;
In a developing device comprising:
  In addition to the first opening, it has a communication opening that communicates the collection conveyance path and the stirring conveyance path, and the communication opening is upstream of the collection conveyance path from the first opening. It is provided in
  A circulation conveyance path through which the developer circulates from the supply conveyance path to the supply conveyance path through the developer carrier, the recovery conveyance path, and the stirring conveyance path;
  A circulation conveyance path through which the developer circulates between the recovery conveyance path and the stirring conveyance path through the first opening and the communication opening;
The developing device is characterized in that the circulation of the developer is a non-integer multiple of the time period of each other. At least one latent image carrier; charging means for charging the surface of the latent image carrier; latent image forming means for forming an electrostatic latent image on the latent image carrier; An image forming apparatus having a developing means for developing the image into a toner image,
  An image forming apparatus using the developing device according to claim 1 as the developing means.

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