JP5578434B2 - Image forming apparatus - Google Patents

Description

  The present invention relates to an image forming apparatus such as a copying machine, a printer, and a facsimile machine. Specifically, a toner image obtained by developing a latent image on a latent image carrier with a two-component developer is finally formed on a recording material. The present invention relates to an image forming apparatus that performs image formation by transferring to the above.

  When toner in a two-component developer (hereinafter simply referred to as “developer”) that is circulated and conveyed along the developer circulation conveyance path in the developing device (developing means) is consumed by image formation, The toner is supplied to the developer by the toner supply means. The following methods are known as conventional toner replenishing methods employed for this toner replenishment. For example, toner consumption expected to be consumed by developing the latent image from pixel writing information (image information) used when the exposure device (latent image forming means) forms the latent image on the latent image carrier. Is calculated. In this method, the developer corresponding to the calculated toner consumption amount is supplied to the developer all at once or at regular intervals. Further, a toner density sensor (toner density detecting means) is provided at a predetermined position (predetermined detection position) on a conveying screw (developer conveying means) for circulating and conveying the developer in the developing device. Then, the toner density sensor measures the toner density at the predetermined detection location, and supplies the developer to the developer all at once or at regular intervals so that the toner density becomes the target toner density. There is also.

  However, although any toner replenishing method can maintain the toner concentration in the developer in the entire developing device at a desired toner concentration, the toner in the circulation direction of the developer circulated through the developing device can be maintained. There is a problem that density unevenness (hereinafter simply referred to as “toner density unevenness”) is likely to occur. This is because the toner is replenished to the developer at a timing that has nothing to do with the position of the developer where the toner is consumed by the development.

  As an image forming apparatus capable of reducing this problem, an image forming apparatus disclosed in Patent Document 1 is known. The image forming apparatus predicts a toner consumption amount expected to be consumed by developing a latent image corresponding to the pixel writing information from the pixel writing information (image information), and develops the developer from the predicted toner consumption amount. Prediction data indicating a change with time in the toner density of the developer at a specific location in the circulation conveyance path is calculated. Based on the prediction data, replenishment control is performed so as to eliminate the temporal change in the toner density of the developer passing through the specific location. This specific portion is more developer than the developer supply / conveyance path (conveyance path for conveying the developer in the direction of the rotation axis of the developer carrying member while being supplied to the developer carrying member) constituting a part of the developer circulation conveying path. It is located upstream in the circulation direction and downstream in the developer circulation direction from a predetermined supply location. Therefore, according to this image forming apparatus, the developer from which the toner density unevenness has been eliminated can be sent to the developer supply conveyance path, and the developer from which the toner density unevenness has been eliminated is supplied to the developer carrying member for development. Can be used.

FIG. 25 is an explanatory view schematically showing a configuration example of a developing device that can eliminate uneven toner density by the toner replenishing method adopted by the image forming apparatus described in Patent Document 1.
This developing device employs an integrated supply / recovery system in which the developed developer on the developing roll 12 that has consumed toner in the developing region is returned to the developer supply / conveyance path 14 again. In this developing device, the developer transported in the developer supply transport path 14 by a transport member (transport screw or the like) (not shown) is sequentially pumped to the developing roll 12 as indicated by a white arrow (upward) in the figure. As the developing roll 12 rotates, it is conveyed to the developing area. Then, the developed developer that has contributed to development after passing through the development region is separated from the developing roll 12 and collected in the developer supply conveyance path 14 as indicated by a white arrow (downward) in the drawing. The developer conveyed to the downstream end of the developer supply conveyance path 14 moves to the upstream end of the developer agitation conveyance path 9 and is conveyed in the developer agitation conveyance path 9 by a conveyance member (such as a conveyance screw) not shown. The A toner replenishing port 17 is opened above the upstream end of the developer agitating / conveying path 9, and toner for replenishment is dropped from the toner replenishing port 17 to perform toner replenishment. Then, the replenished toner is conveyed by a conveying member (not shown) in the developer agitating / conveying path 9 together with the developer moved from the developer supply / conveying path 14 (in a state where the toner density is low). Mixed and dispersed in developer. The developer transported to the downstream end of the developer agitation transport path 9 moves to the upstream end of the developer supply transport path 14 and is transported again in the developer agitation transport path 9.

  In this way, the developing device has only one circulation path A shown in FIG. 25, and all the developed developer recovered from the developing roll 12 is from the downstream end of the developer supply conveyance path 14. The toner can reach the upstream end of the developer agitating / conveying path 9 and receive toner supply from the toner supply port 17. Therefore, based on the prediction data predicted from the pixel writing information (image information), the portion of the developed developer that has consumed toner corresponding to the toner consumption grasped by this reaches the position facing the toner supply port 17. The toner density unevenness can be eliminated by specifying the timing of the toner replenishment and supplying the toner corresponding to the toner consumption amount at the timing.

However, the toner replenishing method employed by the image forming apparatus described in Patent Document 1 has a problem that the toner density unevenness may not be eliminated by a developing apparatus having the following configuration.
FIG. 26 is an explanatory view schematically showing a configuration example of a developing device in which toner density unevenness cannot be solved by the toner replenishment method employed by the image forming apparatus described in Patent Document 1.
This developing device adopts an integrated supply and recovery system similarly to the developing device shown in FIG. 25. However, a plurality of (not shown) partition members 22 that partition the developer supply transport path 14 and the developer stirring transport path 9 are shown. Then, four communication holes are provided. As a result, the developer supply conveyance path 14 and the developer agitation conveyance path 9 are in communication with each other not only at both ends of each conveyance path but also at each communication hole of the partition member 22. . Therefore, a part of the developer transported in the developer supply transport path 14 is not transported to the downstream end of the developer supply transport path 14, and the developer stirring transport path from each communication hole of the partition member 22. It is conveyed to 9. Therefore, as shown in FIG. 26, the developing device circulation path is transported from the upstream end to the downstream end of the developer supply transport path 14 and then transported from the upstream end to the downstream end of the developer stirring transport path 9. In addition to the circulation path B, there are also circulation paths C to F that are conveyed from the middle of the developer supply conveyance path 14 to the developer agitation conveyance path 9 via the communication holes of the partition member 22.

  The developer conveyed along such circulation paths C to F does not pass through a position (predetermined replenishment location) facing the toner replenishment port 17 provided at the upstream end of the developer agitation conveyance path 9. Therefore, even if the toner consumption amount of the developed developer conveyed along the circulation paths C to F can be grasped in advance, the toner corresponding to the toner consumption amount is directly supplied to the developed developer. I can't do it.

  On the other hand, it is possible to grasp in advance the toner consumption amount of the developed developer conveyed along the circulation paths C to F, for example, from pixel writing information (image information). Therefore, the developer in the developer agitation transport path 9 that reaches the location of the communication hole at the timing when the developed developer passes through the communication hole of the partition member 22 and is transported into the developer agitation transport path 9. On the other hand, a replenishment method in which toner corresponding to the toner consumption amount of the developed developer is replenished in advance can be employed. According to this replenishment method, the developed developer that has passed through the communication hole is merged with the developer to which toner has been replenished in advance (the toner concentration is excessive) at a junction in the developer agitation transport path 9. Then, the toner concentration of the combined developer including the developed developer is restored to the target toner concentration. Therefore, when such a replenishing method is employed, the developing device has a configuration including circulation paths C to F in which the developer circulates without passing through a portion facing the toner replenishing port 17 as shown in FIG. However, for example, by grasping the toner consumption amount and passage timing of the developed developer passing through each circulation path from the pixel writing information (image information), it is possible to eliminate toner density unevenness.

  However, at the fastest replenishment start timing (fastest replenishment timing) at which toner replenishment can be started based on the result of grasping the toner consumption amount and passage timing of the developed developer passing through each circulation path from the pixel writing information (image information). Even when the toner supply is started, the developer that has received the toner supply causes the developed developer corresponding to the pixel writing information to enter the developer stirring and conveying path 9 via the communication hole of the partition member 22. By the time of coming, the location of the communication hole may not be reached. For example, if the developer passes through the circulation path F closest to the toner replenishing port 17, the developer replenished in advance based on the prediction data can be merged from the toner replenishing port 17. In the developer passing through the most distant circulation path C, the developer replenished with the toner in advance may not be able to join. In such a developing device in which there is a developer that does not supply the preceding toner in time (developer that cannot be replenished in advance), the toner is included in the developer portion that includes the developer that cannot be replenished in the developing device. Density drops, causing uneven toner density.

  This problem is not limited to the case where the toner consumption amount and passage timing of the developed developer are grasped from the pixel writing information (image information). For example, when grasping the toner consumption amount and passage timing of the developed developer from the detection result of the toner density detection means arranged at a predetermined position in the circulation path, the preceding toner supply based on the detection result is not in time. In some cases, a non-replenishable developer may be present, and in such a case, the above problem may occur as well.

  The present invention has been made in view of the above problems, and an object of the present invention is to quickly eliminate toner density unevenness that occurs in a configuration in which a developer that cannot be replenished in advance cannot be supplied in time. An image forming apparatus is provided.

To achieve the above object, the invention of claim 1 includes a latent image carrier, latent image forming means for forming a latent image on the latent image carrier based on image information, toner and a carrier. In addition, the two-component developer is circulated and conveyed along the developer circulation path, and the two-component developer conveyed in the developer supply and conveyance path that bears a part of the developer circulation path is transferred to the surface of the developer carrier. The two-component developer carried on the surface of the developer carrying member is conveyed to the developing region by the rotation of the developer carrying member, and the toner in the two-component developer is carried on the latent image carrying member in the developing region. A developing device that adheres to the latent image on the surface of the body and develops the latent image; and a toner replenishing unit that replenishes toner to the two-component developer in the developing device at a predetermined replenishment location on the developer circulation path. The latent image carrier is provided by being developed by the developing device. In the image forming apparatus for forming an image by finally transferring the toner image formed on the recording material, the developer circulation path passes through the development region and is separated from the developer carrier. At least a part of the developer is transported without passing through the predetermined replenishment location, and is more downstream than the predetermined replenishment location in the developer circulation direction and more than the upstream end of the developer supply transport path. It has a path where it joins with the two-component developer that has passed through the predetermined replenishment point at the merge point located on the upstream side in the circulation direction, and is located further downstream in the developer circulation direction than the merge point or the merge point. When the two-component developer without toner replenishment passes through a specific position on the developer circulation path, which is a position located upstream of the upstream end of the developer supply conveyance path in the developer circulation direction. Of toner concentration A prediction data calculation means for calculating prediction data of the inter-change, and the toner based on the prediction data calculated by the prediction data calculation means so as to eliminate the temporal change in the toner concentration of the two-component developer passing through the specific location. A replenishment control unit for controlling a replenishment operation of the replenishment unit, wherein the replenishment control unit is a fastest replenishment capable of causing the toner replenishment unit to perform a replenishment operation based on the prediction data calculated by the prediction data calculation unit. To restore the toner concentration to the target toner concentration for the developer that cannot be replenished before the two-component developer when toner is replenished at a certain time passes through the joining location before reaching the joining location. A necessary toner replenishment amount is calculated from the predicted data, and the toner replenishment procedure is performed so that at least a part of the calculated toner replenishment amount is additionally replenished at the fastest replenishment timing. The replenishment operation of the stage is controlled.
According to a second aspect of the present invention, in the image forming apparatus of the first aspect, the replenishment control unit uses the predicted data calculated by the predicted data calculation unit as the first predicted data for the developer that cannot be replenished in advance. The two-component developer when the toner is replenished at the fastest replenishment timing is divided into second predicted data for the preceding replenishable developer that will pass through the joining location after reaching the joining location. A toner replenishment amount required to restore the toner concentration of the developer that cannot be replenished in advance to the target toner concentration is calculated from one prediction data, and at least a part of the calculated toner replenishment amount is additionally replenished at the fastest replenishment timing. In this way, the toner supply means controls the replenishment operation, and after the fastest replenishment timing, the toner of the developer that can be replenished before passing the specific location based on the second predicted data. And is characterized in controlling the replenishment operation of the toner replenishing means so that the time variation of the time is eliminated.
According to a third aspect of the present invention, in the image forming apparatus according to the first or second aspect, the predicted data calculating means calculates the predicted data based on the image information.
According to a fourth aspect of the present invention, in the image forming apparatus according to the first aspect, the prediction data calculating means includes the image information, the preceding replenishment impossible area information developed by the preceding replenishment impossible developer, and the fastest replenishment. The two-component developer when the toner is replenished at the time is divided into the preceding replenishable area information developed by the preceding replenishable developer that passes through the merged location after reaching the merged location, For the non-supplementable area information, the amount of toner consumed by the preceding non-suppliable area information is calculated without calculating the predictive data, and the predictive data is calculated for the preceding replenishable area information. Means that the toner is additionally replenished at the fastest replenishment timing at least a part of the toner amount consumed by the preceding replenishable area information calculated by the prediction data calculating means. -Controls the replenishing operation of the replenishing means, and after the fastest replenishment time, based on the predicted data calculated by the predicted data calculating means, the change in the toner concentration of the preceding replenishable developer passing through the specific location is eliminated. The toner supply means controls the supply operation.
According to a fifth aspect of the present invention, in the image forming apparatus according to any one of the first to fourth aspects, the toner concentration of the two-component developer passing through a predetermined detection location on the developer circulation path is detected. A toner concentration detecting means for controlling the replenishing operation of the toner replenishing means in consideration of not only the prediction data but also a detection result of the toner density detecting means. It is.
According to a sixth aspect of the present invention, there is provided a two-component developer comprising a latent image carrier, a latent image forming means for forming a latent image on the latent image carrier based on image information, and a toner and a carrier. The developer is circulated and conveyed along the developer circulation path, and the two-component developer conveyed in the developer supply / conveyance path, which is a part of the developer circulation path, is supplied to the surface of the developer carrier, and the development is performed. The two-component developer carried on the surface of the developer carrier is transported to the development area by rotation of the developer carrier, and the toner in the two-component developer is transferred to the latent image on the surface of the latent image carrier in the development area. A developing device for developing the latent image by attaching to the toner, and a toner replenishing means for replenishing toner to the two-component developer in the developing device at a predetermined replenishment location on the developer circulation path. Toner formed on the latent image carrier by being developed by the apparatus In the image forming apparatus for forming an image by finally transferring an image onto a recording material, the developer circulation path is at least a part of the developed developer that has passed through the development region and separated from the developer carrier. Is transported without passing through the predetermined replenishment location, and is located downstream of the predetermined replenishment location in the developer circulation direction and upstream of the upstream end of the developer supply conveyance path. The developed developer transported to the merging point without passing through the predetermined replenishment point, and having a path for merging with the two-component developer that has passed the predetermined replenishment point. Detecting means for detecting a timing of passing through the joining point and a toner consumption amount of the developed developer, and supplying toner corresponding to a toner replenishing amount calculated from a detection result of the detecting means to the toner replenishing means. Possible Necessary to restore the toner concentration of the developed developer that passes through the merged portion before the toner is replenished at the fastest replenishment time to the target toner concentration. A toner replenishing amount is calculated from the detection result of the detecting means, and the replenishing operation of the toner replenishing means is controlled so that at least a part of the calculated toner replenishing amount is additionally replenished at the fastest replenishment timing. Is.
The image forming apparatus according to claim 7 is an image forming apparatus according to claim 6, wherein the detection means contributes to development by the developed developer transported to the joining location without passing through the predetermined supply location. The timing at which the developed developer passes through the joining portion and the toner consumption amount of the developed developer are calculated based on the image information regarding the above.

In the invention according to claim 1, based on the prediction data of the temporal change in toner density when the two-component developer that has not been replenished with toner passes through the specific location, the two-component developer that passes through the specific location The toner replenishing operation is controlled so that the change in toner density with time is eliminated. Here, when the toner is replenished at a predetermined toner replenishment location at the fastest replenishment timing at which the toner replenishment operation can be performed, the two-component developer passes through the joining location before reaching the joining location. For the two-component developer (developer that cannot be replenished in advance), the developer that has been replenished with toner cannot be merged, so that the toner concentration is the target toner concentration. The toner density cannot be recovered and toner density unevenness occurs. In the invention according to the first aspect, for the developer that cannot be replenished in advance, the toner replenishment amount required to restore the toner concentration to the target toner concentration is calculated from the predicted data. Then, at least a part of the calculated toner supply amount is additionally supplied at the fastest supply time.
In the invention according to claim 6, the toner replenishing operation is performed based on the detection result of the merged portion passage timing and the toner consumption of the developed developer conveyed to the merged location without passing through the predetermined replenished location. Two-component developer containing developed developer that will pass through the junction before the two-component developer reaches the merge location when toner is replenished at the fastest replenishment time possible For the developer, it is not possible to join the developer that has been previously replenished with toner. Therefore, the toner density of the developer that cannot be replenished in advance cannot be restored to the target toner density, and toner density unevenness occurs. According to the sixth aspect of the present invention, the toner replenishment necessary for recovering the toner density of the developed developer contained therein to the target toner density with respect to the developer that cannot be replenished in advance as described above, in which the preceding toner replenishment is not in time. The amount is calculated from the detection result of the detecting means, and at least a part of the calculated toner supply amount is additionally supplied at the fastest supply time.
In any case, in the present invention, at least a part of the toner that should be replenished with respect to the developer that cannot be replenished in advance cannot be replenished in advance, and is replenished additionally at the fastest replenishment time. When such additional toner replenishment is performed, the toner concentration of the two-component developer portion that has undergone the additional toner replenishment temporarily, even after passing the junction where the developed developer is merged, It becomes an excessive state exceeding the toner density. However, the over-concentrated developer that has undergone additional toner replenishment at the fastest replenishment timing is positioned in the developer circulation path closest to the developer that cannot be replenished in advance, which is not in time for replenishing the preceding toner. Therefore, the excess toner in the excessive concentration developer can be diffused most efficiently to the developer that cannot be replenished in advance by the stirring action while the developer circulation path is being conveyed. As a result, with respect to the developer that cannot be replenished in advance with the toner concentration being low, the toner concentration quickly recovers toward the target toner concentration. On the other hand, the toner density of a developer with a high toner density is quickly recovered toward the target toner density. As a result, it is possible to quickly eliminate toner density unevenness of the developer that is circulated and conveyed in the developing device.

  As described above, the present invention has an excellent effect that toner density unevenness that occurs in a configuration in which a developer that cannot be replenished in advance cannot be supplied in time can be quickly eliminated.

1 is a schematic configuration diagram illustrating a printer according to a first embodiment. FIG. 3 is a schematic diagram illustrating a configuration of a process unit for generating a Y toner image in the printer. It is a perspective view which shows the external appearance of the process unit. FIG. 3 is an explanatory diagram showing a development unit configuration around a developer circulation conveyance path in which the developer circulates in the development unit in the process unit. 6 is a graph showing a relationship between toner supply and toner density unevenness when toner is supplied to a developer all at once. 6 is a graph showing a relationship between toner supply and toner density unevenness when toner is supplied to a developer intermittently at regular intervals. FIG. 6 is an explanatory diagram showing a relationship between a situation in which a latent image is unevenly distributed on a photoconductor and a state of toner density unevenness. FIG. 5 is an explanatory diagram showing in more detail the relationship between the position of a latent image on a photoconductor and the state of toner density unevenness. 3 is a functional block diagram of a mechanism that performs toner supply control in Embodiment 1. FIG. 4 is a graph showing a basic supply pattern of a toner supply device in the printer. 6 is a graph showing a unit consumption waveform at a toner density detection location in the developing unit and a unit supply waveform for canceling toner density unevenness due to the unit consumption waveform. It is a graph which shows the arbitrary consumption waveform when arbitrary images are formed, and the replenishment waveform which cancels the toner density nonuniformity by the arbitrary consumption waveform. In the case where the shortcut circulation path exists, the arbitrary consumption waveform S when the same image as the graph shown in FIG. 12 is formed is the arbitrary consumption waveform S0 shown in FIG. 12 and the replenishment waveform H0 that cancels the toner density unevenness due to this. It is the graph represented together. 4 is a flowchart of toner replenishment control according to the first exemplary embodiment. It is the graph which decomposed | disassembled the arbitrary consumption waveform in Embodiment 1 into the several unit consumption waveform, ie, the graph which shows the content of prediction data. The arbitrary consumption waveform described in the upper part of the figure and the four unit consumption waveforms obtained by disassembling the waveform, the unit supply waveform and the additional supply waveform when the toner supply control of the first embodiment is performed, and the supply waveform H obtained by synthesizing these are shown. It is a graph to show. It is a graph which shows the arbitrary consumption waveform described in the upper part in the figure, the four unit consumption waveforms which decomposed | disassembled this, the unit supply waveform when the toner supply control of a comparative example was performed, and the supply waveform H1 which synthesize | combined these. 6 is a graph showing a change over time in the toner density of a developer passing through a toner density detection portion when toner supply control is performed in a comparative example. 6 is a graph showing a change over time in the toner concentration of a developer passing through a toner concentration detection portion when toner replenishment control is performed in the first embodiment. 10 is a flowchart of toner supply control in a modified example. It is explanatory drawing which shows four area | regions 1-4 on one image formed on one recording paper. (A)-(d) is a graph which shows the consumption waveform for every four area | regions on the image shown in FIG. 6 is a schematic cross-sectional view illustrating an example of a developing unit according to Embodiment 2. FIG. FIG. 24 is an explanatory diagram illustrating a developer circulation path in the developing unit when the developing unit is viewed from the direction of arrow F in FIG. 23. FIG. 10 is an explanatory diagram schematically illustrating a configuration example of a developing device that can eliminate toner density unevenness by a toner replenishment method employed by a conventional image forming apparatus described in Patent Document 1. FIG. 10 is an explanatory diagram schematically illustrating a configuration example of a developing device that cannot solve toner density unevenness by a toner replenishment method employed by a conventional image forming apparatus described in Patent Document 1.

Embodiment 1
Hereinafter, an embodiment (hereinafter, this embodiment is referred to as “embodiment 1”) in which the present invention is applied to an electrophotographic printer (hereinafter simply referred to as “printer”) as an image forming apparatus will be described. .
First, the basic configuration of the printer according to the first embodiment will be described.
FIG. 1 is a schematic configuration diagram illustrating a printer according to the first embodiment.
This printer includes four process units 1Y, 1C, 1M, and 1K for yellow, magenta, cyan, and black (hereinafter referred to as Y, C, M, and K). These use Y, C, M, and K toners of different colors as image forming substances for forming an image, but the other configurations are the same.

FIG. 2 is a schematic diagram showing a configuration of a process unit 1Y for generating a Y toner image.
FIG. 3 is a perspective view showing an appearance of the process unit 1Y.
The process unit 1Y includes a photoreceptor unit 2Y and a developing unit 7Y. As shown in FIG. 3, the photoconductor unit 2Y and the developing unit 7Y are configured to be detachably attached to the printer body as a process unit 1Y. However, in a state where it is detached from the printer main body, the developing unit 7Y can be attached to and detached from a photosensitive unit (not shown).

The photoreceptor unit 2Y includes a drum-shaped photoreceptor 3Y as a latent image carrier, a drum cleaning device 4Y, a static eliminator (not shown), a charging device 5Y, and the like.
The charging device 5Y, which is a charging unit, uniformly charges the surface of the photoreceptor 3Y, which is driven to rotate clockwise in FIG. 2 by a driving unit (not shown), by the charging roller 6Y. Specifically, a charging bias is applied from a power source (not shown) to the charging roller 6Y that is driven to rotate counterclockwise in FIG. 2, and the charging roller 6Y is brought close to or in contact with the photosensitive member 3Y, whereby the photosensitive member 3Y. Is uniformly charged. Instead of the charging roller 6Y, another charging member such as a charging brush may be used in proximity or contact. Further, a charger that uniformly charges the photosensitive member 3Y by a charger method, such as a scorotron charger, may be used. The surface of the photoreceptor 3Y uniformly charged by the charging device 5Y is exposed and scanned by a laser beam emitted from an optical writing unit 20 serving as a latent image forming unit, which will be described later, and carries an electrostatic latent image for Y.

FIG. 4 is an explanatory diagram showing the configuration of the developing unit around the developer circulation conveyance path through which the developer circulates in the developing unit.
As shown in FIGS. 2 and 4, the developing unit 7 </ b> Y that is a developing device is provided with a first conveying screw 8 </ b> Y as a developer conveying means in a developer stirring and conveying path 9 </ b> Y. Further, a second conveying screw 11Y as a developer conveying means is disposed in the developer supply conveying path 14Y. Further, the developing unit 7Y includes a toner concentration sensor 10Y including a magnetic permeability sensor as a toner concentration detecting unit, a second conveying screw 11Y as a developer conveying unit, a developing roll 12Y as a developer carrying member, and a developer regulating member. The doctor blade 13Y is also provided. In these two transport paths, a Y developer (not shown) that is a two-component developer composed of a magnetic carrier and a negatively chargeable Y toner is accommodated.

  The first conveying screw 8Y is rotationally driven by a driving means (not shown) to convey the Y developer in the developer stirring and conveying path 9Y to the near side in FIG. 2 (in the direction of arrow A in FIG. 4). The Y developer in the middle of conveyance is replenished by a toner concentration sensor 10Y fixed on the first conveyance screw 8Y, facing the toner replenishing port 17Y in the developer agitation conveyance path 9Y (in this embodiment, developer agitation conveyance). The toner concentration of the Y developer passing through a predetermined detection position (near the downstream end of the developer agitation transport path 9Y in the first embodiment) is detected from the vicinity of the upstream end of the path 9Y. Is done. Then, the Y developer conveyed to the downstream end of the developer agitation conveyance path 9Y by the first conveyance screw 8Y enters the upstream end of the developer supply conveyance path 14Y from the end communication port 18Y.

  The second transport screw 11Y in the developer supply transport path 14Y is rotationally driven by a driving unit (not shown) to transport the Y developer to the back side in FIG. 2 (in the direction of arrow A in FIG. 4). In this way, the developing roll 12Y is arranged in a posture parallel to the second conveying screw 11Y above the second conveying screw 11Y that conveys the Y developer in FIG. The developing roll 12Y has a configuration in which a fixedly arranged magnet roller 16Y is included in a developing sleeve 15Y as a developer carrying member made of a non-magnetic sleeve that is driven to rotate counterclockwise in FIG. . A part of the Y developer conveyed by the second conveying screw 11Y is pumped up to the surface of the developing sleeve 15Y by the magnetic force generated by the magnet roller 16Y. Then, after the layer thickness is regulated by a doctor blade 13Y disposed so as to maintain a predetermined gap from the surface of the developing sleeve 15Y, the layer is conveyed to a developing region facing the photosensitive member 3Y, and is transferred onto the photosensitive member 3Y. Y toner is adhered to the electrostatic latent image for Y. This adhesion forms a Y toner image on the photoreceptor 3Y. The Y developer that has consumed Y toner by the development is returned onto the second conveying screw 11Y as the developing sleeve 15Y rotates. Then, the Y developer transported to the downstream end of the developer supply transport path 14Y by the second transport screw 11Y returns to the upstream end of the developer stirring transport path 9Y through the end communication port 19Y. In this way, the Y developer is circulated and conveyed in the developing unit.

  Further, in the developing unit 7Y of Embodiment 1, four communication holes 22a, 22b, 22c, and 22d are provided in the partition member 22 that partitions the developer supply transport path 14Y and the developer stirring transport path 9Y. The first embodiment is an example in which four of these communication holes 22a, 22b, 22c, and 22d are arranged along the developer conveyance direction of the conveyance paths 9Y and 14Y, but the position and number thereof can be set as appropriate. is there. By providing such communication holes 22a, 22b, 22c, and 22d in the middle of the transport paths 9Y and 14Y, a part of the developer transported in the developer supply transport path 14Y is downstream of the developer supply transport path 14Y. Before reaching the end, the toner is transferred to the developer stirring and conveying path 9Y via the communication holes 22a, 22b, 22c, and 22d. When such communication holes 22a, 22b, 22c, and 22d are not provided, the developer flowing in the developer circulation path is stirred in the developer circulation direction between the developers adjacent to each other in the developer circulation direction. Only occurs. On the other hand, when the communication holes 22a, 22b, 22c, and 22d are provided in the middle of the transport paths 9Y and 14Y as in the first embodiment, a part of the developer flowing through the developer supply transport path 14Y is communicated with the communication holes 22a. , 22b, 22c, and 22d, and merged with the developer flowing from the upstream side of the developer stirring and conveying path 9Y and stirred. Therefore, stirring in the developer circulation direction is promoted, and toner density unevenness of the entire developer circulating in the developer circulation path can be eliminated at an early stage.

  The Y toner image formed on the photoreceptor 3Y is intermediately transferred to an intermediate transfer belt 41 that is an intermediate transfer body. The drum cleaning device 4Y of the photoreceptor unit 2Y removes toner remaining on the surface of the photoreceptor 3Y after the intermediate transfer process. As a result, the surface of the photoreceptor 3Y subjected to the cleaning process is neutralized by a neutralizing device (not shown). By this charge removal, the surface of the photoreceptor 3Y is initialized and prepared for the next image formation. Similarly, in the process units 1C, 1M, and 1K for other colors, C toner images, M toner images, and K toner images are formed on the photoreceptors 3C, 3M, and 3K, and the intermediate transfer belt 41 is subjected to intermediate transfer. Is done.

  An optical writing unit 20 is disposed below the process units 1Y, 1C, 1M, and 1K in FIG. The optical writing unit 20 irradiates the photoconductors 3Y, 3C, 3M, and 3K of the process units 1Y, 1C, 1M, and 1K with the laser light L emitted based on the image information. As a result, electrostatic latent images for Y, C, M, and K are formed on the photoreceptors 3Y, 3C, 3M, and 3K, respectively. The optical writing unit 20 deflects the laser light L emitted from the light source by the polygon mirror 21 that is rotationally driven by a motor, and passes through the photoreceptors 3Y, 3C, 3M, and 3K via a plurality of optical lenses and mirrors. Is irradiated. Instead of such a configuration, an LED array may be used.

  A first paper feed cassette 31 and a second paper feed cassette 32 are disposed below the optical writing unit 20 so as to overlap in the vertical direction. In each of these paper feed cassettes, a plurality of recording papers P, which are recording materials, are stored in a stack of recording papers, and a first paper feed roller is placed on the top recording paper P. 31a and the second paper feed roller 32a are in contact with each other. When the first paper feed roller 31a is driven to rotate counterclockwise in FIG. 1 by driving means (not shown), the uppermost recording paper P in the first paper feed cassette 31 is vertically oriented on the right side of the cassette in FIG. The paper is discharged toward the paper feed path 33 arranged so as to extend. When the second paper feed roller 32a is rotated counterclockwise in FIG. 1 by driving means (not shown), the uppermost recording paper P in the second paper feed cassette 32 is discharged toward the paper feed path 33. The A plurality of transport roller pairs 34 are arranged in the paper feed path 33, and the recording paper P fed into the paper feed path 33 is sandwiched between the rollers of the transport roller pair 34 while being fed between the paper feed paths 33. 1 is conveyed from the lower side to the upper side in FIG. A registration roller pair 35 is disposed at the end of the paper feed path 33. The registration roller pair 35 temporarily stops the rotation of both rollers as soon as the recording paper P sent from the conveyance roller pair 34 is sandwiched between the rollers. Then, the recording paper P is sent out toward a later-described secondary transfer nip at an appropriate timing.

  Above each process unit 1Y, 1C, 1M, and 1K in FIG. 1, a transfer unit 40 is disposed to endlessly move the intermediate transfer belt 41 counterclockwise in FIG. In addition to the intermediate transfer belt 41, the transfer unit 40 includes a belt cleaning unit 42, a first bracket 43, a second bracket 44, and the like. Also provided are four primary transfer rollers 45Y, 45C, 45M, 45K, a secondary transfer backup roller 46, a drive roller 47, an auxiliary roller 48, a tension roller 49, and the like. The intermediate transfer belt 41 is endlessly moved counterclockwise in FIG. 1 by the rotational driving of the driving roller 47 while being stretched around these rollers. The four primary transfer rollers 45Y, 45C, 45M, and 45K sandwich the intermediate transfer belt 41 that moves endlessly between the photoreceptors 3Y, 3C, 3M, and 3K to form primary transfer nips, respectively. Yes. Then, a transfer bias having a polarity opposite to that of the toner (plus polarity in the first embodiment) is applied to the inner peripheral surface of the intermediate transfer belt 41. The intermediate transfer belt 41 sequentially passes through the primary transfer nips for Y, C, M, and K along with the endless movement thereof, and the photoreceptors 3Y, 3C, 3M, and 3K are disposed on the outer peripheral surface thereof. The upper color toner images are primarily transferred so as to overlap each other. As a result, a four-color superimposed toner image (hereinafter referred to as “four-color toner image”) is formed on the intermediate transfer belt 41.

  The secondary transfer backup roller 46 sandwiches the intermediate transfer belt 41 with the secondary transfer roller 50 disposed outside the loop of the intermediate transfer belt 41 to form a secondary transfer nip. The registration roller pair 35 described above feeds the recording paper P sandwiched between the rollers toward the secondary transfer nip at a timing at which the recording paper P can be synchronized with the four-color toner image on the intermediate transfer belt 41. The four-color toner image on the intermediate transfer belt 41 is affected by the secondary transfer electric field formed between the secondary transfer roller 50 to which the secondary transfer bias is applied and the secondary transfer backup roller 46, and the influence of the nip pressure. The secondary transfer is batch-transferred onto the recording paper P in the secondary transfer nip. Then, combined with the white color of the recording paper P, a full color toner image is obtained.

  Untransferred toner that has not been transferred to the recording paper P adheres to the intermediate transfer belt 41 after passing through the secondary transfer nip. This is cleaned by the belt cleaning unit 42. In the belt cleaning unit 42, the cleaning blade 42a is brought into contact with the front surface of the intermediate transfer belt 41, whereby the transfer residual toner on the belt is scraped off and removed.

  The first bracket 43 of the transfer unit 40 swings at a predetermined rotation angle about the rotation axis of the auxiliary roller 48 as the solenoid (not shown) is turned on / off. In the case of forming a monochrome image, the printer of the first embodiment rotates the first bracket 43 a little counterclockwise in the drawing by driving the solenoid described above. By this rotation, the Y, C, and M primary transfer rollers 45Y, 45C, and 45M are revolved counterclockwise in the drawing around the rotation axis of the auxiliary roller 48, whereby the intermediate transfer belt 41 is moved to the Y direction. , C and M photoconductors 3Y, 3C and 3M. Of the four process units 1Y, 1C, 1M, and 1K, only the K process unit 1K is driven to form a monochrome image. Accordingly, it is possible to avoid exhaustion of the process units due to wastefully driving the process units for Y, C, and M during monochrome image formation.

  A fixing unit 60 as a fixing unit is disposed above the secondary transfer nip in the figure. The fixing unit 60 includes a pressure heating roller 61 that includes a heat source such as a halogen lamp, and a fixing belt unit 62. The fixing belt unit 62 includes a fixing belt 64, a heating roller 63 containing a heat source such as a halogen lamp, a tension roller 65, a driving roller 66, a temperature sensor (not shown), and the like. Then, the endless fixing belt 64 is endlessly moved in the counterclockwise direction in FIG. 1 while being stretched by the heating roller 63, the tension roller 65, and the driving roller 66. In the process of endless movement, the fixing belt 64 is heated from the back side by the heating roller 63. A pressure heating roller 61 that is driven to rotate in the clockwise direction in FIG. 1 is in contact with the surface of the fixing belt 64 that is heated in this manner. Thereby, a fixing nip where the pressure heating roller 61 and the fixing belt 64 abut is formed.

  Outside the loop of the fixing belt 64, a temperature sensor (not shown) is disposed so as to face the front surface of the fixing belt 64 with a predetermined gap, and the fixing belt 64 just before entering the fixing nip. Detect surface temperature. This detection result is sent to a fixing power supply circuit (not shown). The fixing power supply circuit performs on / off control of power supply to the heat generation source included in the heating roller 63 and the heat generation source included in the pressure heating roller 61 based on the detection result of the temperature sensor. As a result, the surface temperature of the fixing belt 64 is maintained at about 140.degree. The recording paper P that has passed through the secondary transfer nip is separated from the intermediate transfer belt 41 and then fed into the fixing unit 60. Then, in the process of being conveyed from the lower side to the upper side in the drawing while being sandwiched by the fixing nip in the fixing unit 60, the full-color toner image is applied to the recording paper P by being heated or pressed by the fixing belt 64. To settle.

  The recording paper P subjected to the fixing process in this manner is discharged outside the apparatus after passing between the rollers of the paper discharge roller pair 67. A stack unit 68 is formed on the upper surface of the housing of the printer main body, and the recording paper P discharged to the outside by the discharge roller pair 67 is sequentially stacked on the stack unit 68.

  Above the transfer unit 40, toner cartridges 72Y, 72C, 72M, and 72K, which are four toner containers that respectively store Y toner, C toner, M toner, and K toner, are disposed. The color toners in the toner cartridges 72Y, 72C, 72M, and 72K are appropriately supplied to the developing units 7Y, 7C, 7M, and 7K of the process units 1Y, 1C, 1M, and 1K by the toner replenishing device 70, respectively. The toner cartridges 72Y, 72C, 72M, and 72K are detachable from the printer main body independently of the process units 1Y, 1C, 1M, and 1K.

Hereinafter, toner replenishment control, which is a characteristic part of the present invention, will be described by taking a developing unit having a general configuration in which the communication holes 22a, 22b, 22c, and 22d are not provided in the partition member 22 as an example.
Since the contents of the toner replenishment control are the same for each color, the Y toner replenishment control will be described below as an example.
FIG. 5 is a graph showing the relationship between toner supply and toner density unevenness when toner is supplied to the developer all at once.
FIG. 6 is a graph showing the relationship between toner replenishment and toner density unevenness when toner is replenished to the developer at regular intervals.
In these graphs, the waveform (consumption waveform) indicated by a thin solid line indicates that the toner density sensor is not replenished with respect to the developer after developing a predetermined latent image using a developer having no toner density unevenness. 4 is a waveform showing the result of measuring the toner density by means of FIG. That is, this consumption waveform shows an example of toner density unevenness that occurs after development.
The waveform indicated by the dotted line (replenishment waveform) is the result of measuring the toner concentration with the toner concentration sensor for the developer after toner replenishment is performed for each developer in a state where there is no toner density unevenness. It is a waveform which shows. Each waveform indicated by a two-dot chain line in FIG. 6 represents an individual supply waveform of each toner supply performed intermittently. A waveform obtained by combining the waveforms indicated by the two-dot chain line is a supply waveform indicated by a dotted line. Become.
The waveform indicated by the thick solid line is a composite of the consumption waveform and the replenishment waveform, and the toner density unevenness after the toner replenishment by each replenishment method for the developer after developing a predetermined latent image. It is shown.

As shown by thick solid lines in FIGS. 5 and 6, in a conventional method of supplying toner to the developer in a lump manner or a method of supplying toner to the developer intermittently at regular intervals. It can be seen that there is toner density unevenness in the developer after toner replenishment.
In particular, the consumption waveform in actual image formation is not constant because it varies depending on the image to be formed, specifically, the position, area, potential, etc. of the latent image to be developed. Therefore, as in the conventional replenishment method, when toner is replenished at a constant timing and a constant speed regardless of the difference in consumption waveform, the toner density unevenness of the developer after toner replenishment is eliminated. I can't.

  Explaining this point, the developer conveyed by the second conveying screw 11Y is conveyed in the developer supply conveying path 14Y, and is sequentially carried on the surface of the developing roll 12 during the conveyance and conveyed to the developing region. . Then, after contributing to development in the development area, the developer is again returned into the developer supply transport path 14Y and transported by the second transport screw 11Y. If the position of the latent image is unevenly distributed on the photoreceptor 3Y, the developer after development includes a portion that consumes a lot of toner and a portion that consumes little toner, and the developer in such a state Is returned to the developer supply transport path 14Y. In this case, toner density unevenness occurs in the developer after returning to the developer supply conveyance path 14Y. In addition, the state of toner density unevenness varies depending on the uneven distribution of latent images on the photoreceptor 3Y.

FIG. 7 is an explanatory diagram showing the relationship between the uneven distribution of the latent image on the photoreceptor 3Y and the toner density unevenness state. In the figure, an arrow A indicates the developer conveyance direction by the second conveyance screw 11Y, and an arrow C in the figure indicates the surface movement direction of the photoreceptor 3Y.
The upper part of FIG. 7 shows three image patterns formed on the recording paper P, and the lower part of FIG. 7 shows latent images corresponding to the respective image patterns. A graph showing a measurement result (consumption waveform) when a toner density is measured by the toner density sensor 10Y without replenishing toner for a developer after an image is developed using a developer having no toner density unevenness. It is.
As shown in FIG. 7, it can be seen that the consumption waveform, that is, the state of toner density unevenness changes depending on the uneven distribution of the latent image on the photoreceptor 3Y. In addition, when the image pattern drawn on the left in the figure is compared with the image pattern drawn on the right in the figure, the latter has a broader consumption waveform than the former. This is because the latter has a longer developer transport distance from the position where the part of the developer that has consumed the toner is returned to the developer supply transport path 14Y to the toner density detection location (specific location) B by the toner density sensor 10Y. This is a difference due to receiving a lot of stirring action by the conveying screw. That is, in the latter, since the developer portion that has consumed the toner is more agitated by the conveying screw until it is conveyed to the toner concentration detection portion of the toner concentration sensor 10Y, the toner concentration unevenness is more than that of the former. As a result of some cancellation, the consumption waveform becomes broad.

FIG. 8 is an explanatory diagram showing in more detail the relationship between the position of the latent image on the photoreceptor 3Y and the state of toner density unevenness.
FIG. 8 shows three image patterns in which latent images are formed at three different positions in the developer conveying direction by the second conveying screw, and latent images are formed at two different positions in the photosensitive member surface movement direction. Two image patterns are drawn. Note that some image patterns overlap. All image patterns have the same image area.
Further, FIG. 8 shows the toner after developing the latent image corresponding to each of the three image patterns in the developer conveying direction by the second conveying screw 11Y with the developer having no toner density unevenness. A graph showing the measurement result (consumption waveform) when the toner density is measured by the toner density sensor 10Y without replenishment is shown in the lower part of the figure. Further, the toner density sensor described above is used without replenishing toner for the developer after developing the latent image corresponding to each of the two image patterns related to the moving direction of the surface of the photoreceptor 3Y with the developer having no toner density unevenness. A graph showing the measurement result (consumption waveform) when the toner density is measured with 10Y is shown in the left part of the figure.

  When latent images of the same area are formed at different positions in the developer conveying direction by the second conveying screw 11Y, the consumption waveform corresponding to each image pattern has its peak time and half width as shown in the lower part of FIG. (Broad state) and minimum toner density are different. As described above, this is due to the difference in developer transport distance from the position where the portion of the developer that has consumed the toner is returned to the developer supply transport path 14Y to the toner density detection location by the toner density sensor 10Y. Specifically, the difference in peak time is simply due to the difference in time until the portion of the developer that has consumed the toner reaches the toner density detection location by the toner density sensor. Further, the difference between the half-value width (broad state) and the minimum toner density is due to the difference in the amount of agitation received until the part of the developer that has consumed the toner reaches the toner density detection position by the toner density sensor 10Y. .

  On the other hand, when latent images of the same area are formed at different positions in the photosensitive member surface movement direction, the consumption waveforms corresponding to each image pattern have different peak times as shown in the left part of FIG. There is no difference in the half width (broad state) and the minimum toner density. This is because each image pattern has the same position at which the portion of the developer that has consumed toner is returned to the developer supply transport path 14Y, and therefore the developer transport distance to the toner density detection location by the toner density sensor. There is no difference, and therefore there is no difference in the amount of agitation received before reaching the toner density detection location by the toner density sensor. Therefore, there is no difference in the half width (broad state) and the minimum toner density. However, since the timing at which the portion of the developer that has consumed the toner is returned to the developer circulation conveyance path is different, the peak timing is different.

  As described above, the consumption waveform varies depending not only on the size of the latent image on the photoreceptor 3Y but also on the position of the latent image, and thus does not become constant in actual image formation. For this reason, in the conventional general replenishment method, the average toner concentration of the entire developer present in the developing device can be maintained at the target toner concentration, but the toner concentration unevenness of the developer cannot be eliminated.

FIG. 9 is a functional block diagram of a mechanism that performs toner supply control according to the first exemplary embodiment.
In the first embodiment, the control unit 100 is provided with an image information acquisition unit 103 as an image information acquisition unit that acquires image data (image information) from a personal computer or an image reading apparatus. The control unit 100 includes a CPU (Central Processing Unit) as a calculation means, a RAM (Random Access Memory) as a data storage means, a ROM (Read Only Memory), and the like, and executes various calculation processes and control programs. It can be carried out. The image information acquisition unit 103 sends a necessary part of the acquired image data to the prediction data calculation unit 101 as a prediction data calculation unit. The predicted data calculation unit 101 develops a latent image based on the image data from the received data, and develops a toner density at a later-described toner density detection location (specific location) B generated in the developed developer that has consumed the toner. Time change (predicted data) is calculated. In the first embodiment, information obtained by counting the number of laser beams (number of dots) emitted from the optical writing unit 20 is used as image information, and prediction data is calculated based on the image information. Image data from the image reading apparatus may be used as image information, and prediction data may be calculated based on the image information.

  In the toner replenishment control according to the first exemplary embodiment, an amount of Y toner necessary for maintaining the toner concentration of the Y developer within the target toner concentration range is replenished from the toner replenishing port 17Y. However, in the first exemplary embodiment, the amount of Y toner is supplied from a location facing the toner supply port 17Y (supply location) to a location where the Y developer is supplied to the developing roll 12Y (developer supply conveyance path 14Y). More specifically, there is a change with time in the toner concentration of the Y developer passing through a toner density detection point, which will be described later, which is an arbitrary point (specific point) located between the replenishment point and the upstream end of the developer supply conveyance path 14Y. The toner replenishment amount at the replenishment point is adjusted so as to be eliminated. As shown in FIG. 9, the adjustment of the toner replenishment amount at the replenishment location is performed by driving a drive source 71Y that drives the toner replenishment member of the toner replenishing device 70 by the replenishment control unit 102 of the control unit 100 functioning as a replenishment control unit. This is done by controlling timing, driving time, driving speed, and the like. Any known toner replenishing member can be used as long as it can adjust the toner supply from the toner replenishing port 17Y to the Y developer by the driving force of the drive source 71Y.

  The replenishment control unit 102 controls one drive source 71Y of the toner replenishing device 70 based on the prediction data calculated by the prediction data calculation unit 101 that functions as a prediction data calculation unit. Here, based on the image data, the prediction data calculation unit 101 calculates prediction data of the temporal change in the toner concentration of the Y developer at the toner concentration detection location using a calculation program or calculation table stored in the ROM. . Then, the replenishment control unit 102 functioning as a replenishment control unit performs drive control of one drive source 71Y with a combination of various unit replenishment patterns described later based on the prediction data calculated by the prediction data calculation unit 101. Toner density unevenness is eliminated.

The unit supply pattern can be obtained by conducting an experiment or the like in advance. Hereinafter, a specific procedure for creating a unit supply pattern will be described.
First, the toner density of the Y developer that passes through the toner density detection portion is measured by the toner density sensor 10Y, and a basic pattern of toner supply operation by the toner supply device 70 (hereinafter referred to as “replenishment basic pattern”) is measured.

FIG. 10 is a graph illustrating a basic supply pattern of the toner supply device 70 according to the first exemplary embodiment.
The waveforms H1, H2, H3, H4, and H5 indicate the amount of toner that is replenished by a single drive operation of the drive source 71Y (hereinafter referred to as “replenishment operation”) for the Y developer in a state where there is no toner density unevenness. (Hereinafter referred to as “unit replenishment amount”) A waveform (shown as a result of detecting a change in toner density over time at a toner density detection location by the toner density sensor 10Y when toner is replenished with five different replenishment patterns. Hereinafter referred to as “replenishment basic waveform”). The unit replenishment amount increases in the order of the replenishment basic waveforms H1, H2, H3, H4, and H5. The unit replenishment amount can be varied by changing the drive time and drive speed of the drive source 71Y in one replenishment operation.

  On the other hand, without using toner replenishment after printing a unit image corresponding to the unit area for toner density detection on the recording paper P using Y developer without toner density unevenness and consuming Y toner. A waveform indicating a detection result when the toner concentration sensor 10Y detects a change in toner concentration with time is defined as a unit consumption waveform. As a unit area for toner density detection when determining a unit consumption waveform, one dot area of image information is ideal, but in reality, the resolution of the toner density sensor 10Y, the influence of noise, or the toner replenishing device 70. Therefore, it is preferable to determine a unit area for toner density detection that can be set as small as possible in consideration of these factors.

Next, a unit supply waveform for canceling the toner density unevenness due to the unit consumption waveform is obtained.
FIG. 11 is a graph showing a unit consumption waveform and a unit supply waveform that cancels toner density unevenness due to the unit consumption waveform.
From the unit consumption waveform at the toner density detection location and each supply basic waveform H1, H2, H3, H4, H5, a unit supply waveform H ′ that cancels the unit consumption waveform S ′ is represented by each supply basic waveform H1, H2, and so on. Created by combining H3, H4 and H5. Here, the unit consumption waveform S ′ indicates a change in toner density with time when the Y developer after developing a latent image corresponding to a unit area for toner density detection passes through the toner density detection portion. On the other hand, each of the basic supply waveforms H1, H2, H3, H4, and H5 is such that when a replenishment operation with different unit replenishment amounts is performed only once, the Y developer that has received the toner replenishment passes through the toner density detection portion. The change in toner density over time is shown. Therefore, as shown in FIG. 11, the unit supply waveform H ′ obtained by appropriately combining the supply basic waveforms H1, H2, H3, H4, and H5 is a waveform close to a waveform corresponding to the opposite phase of the unit consumption waveform S ′. If the toner replenishing operation is performed, the toner density unevenness of the Y developer after passing through at least the toner density detection portion can be eliminated. That is, the toner density unevenness can be eliminated before the Y developer, which has developed the latent image corresponding to the unit area for toner density detection, is conveyed again to the developer supply conveyance path 14Y and contributes to development.

  When the unit supply waveform H 'is obtained in this way, the toner supply operation corresponding to the combination of the basic supply waveforms H1, H2, H3, H4, and H5 constituting the unit supply waveform H' becomes the unit supply pattern. In the graph shown in FIG. 11, toner replenishment is performed in which the replenishment operation of the second replenishment basic waveform H2 is performed, the replenishment operation of the third replenishment basic waveform H3 is performed, and finally the replenishment operation of the second replenishment basic waveform H2 is performed. By performing the operation, the unit supply waveform H ′ obtained by synthesizing these supply basic waveforms becomes a waveform close to a waveform corresponding to the opposite phase of the unit consumption waveform S ′. That is, this toner replenishment operation becomes the unit replenishment pattern in the first embodiment.

FIG. 12 is a graph showing an arbitrary consumption waveform S0 when an arbitrary image is formed (for example, when an image based on a user's desire is formed) and a replenishment waveform that cancels toner density unevenness due to the arbitrary consumption waveform S0. .
When an arbitrary image is formed during actual image formation, the image data is sent to the prediction data calculation unit 101 of the control unit 100. The predicted data calculation unit 101 can obtain an arbitrary consumption waveform corresponding to the latent image based on the image data, that is, an arbitrary consumption waveform S0 indicating a change in toner density over time at a toner density detection location. Then, the arbitrary consumption waveform S0 obtained in this way is sequentially decomposed into unit consumption waveforms S ′ shown in FIG. Therefore, the arbitrary consumption waveform S0 obtained by synthesizing these unit consumption waveforms S ′ is obtained when the toner concentration of the Y developer having toner density unevenness indicating the arbitrary consumption waveform S0 is detected at the toner concentration detection portion. It becomes a waveform (predicted value) approximated to a waveform showing the time change of

  In the first embodiment, the prediction data calculation unit 101 executes a predetermined calculation program, and based on the above-described mechanism, the developer that develops the latent image based on the image data from the image data is detected by the toner density detection portion. Prediction data (arbitrary consumption waveform S0), which is a change over time in the toner density when passing through, is calculated. Specifically, a combination of a plurality of unit consumption waveforms S ′ obtained by decomposing this arbitrary consumption waveform S0 is calculated as prediction data.

  The prediction data (the combination data of the plurality of unit consumption waveforms S ′) calculated by the prediction data calculation unit 101 in this way is sent to the supply control unit 102. Here, by combining a plurality of unit supply waveforms H ′ respectively corresponding to these unit consumption waveforms S ′, as shown in FIG. 12, a supply waveform H0 that cancels the toner density unevenness indicated by the arbitrary consumption waveform S0, That is, it is possible to create a replenishment waveform H0 that is close to a waveform that is opposite in phase to the arbitrary consumption waveform S0. Therefore, the replenishment control unit 102 obtains a combination of unit replenishment waveforms H ′ corresponding to the combination of the plurality of unit consumption waveforms S ′ based on the prediction data. Next, a toner supply operation corresponding to the prediction data is determined by combining a plurality of unit supply patterns stored in the RAM in advance so as to correspond to the obtained combination of unit supply waveforms H ′. Then, drive control of the drive source 71Y is performed by the determined toner supply operation. Since the replenishment waveform obtained by such a toner replenishment operation is a combination of the unit replenishment waveforms H ′ according to the unit replenishment patterns, the replenishment waveform H0 shown in FIG. 12 is obtained. Therefore, the toner density unevenness indicated by the arbitrary consumption waveform S0 is sufficiently eliminated by the toner replenishment control at the toner density detection portion as shown by the thick solid line in FIG.

  The above description is of a general configuration in which the partition member 22 is not provided with the communication holes 22a, 22b, 22c, and 22d. However, the developing unit of the first embodiment has the communication hole 22a, 22b, 22c, and 22d are provided. Therefore, as shown in FIG. 26, the developer circulation path of the developing unit of Embodiment 1 is the upstream end of the developer agitating / conveying path 9Y after being transported from the upstream end to the downstream end of the developer supply / conveying path 14Y. In addition to the circulation path (hereinafter referred to as “main circulation path”) B that is conveyed to the downstream end from the middle of the developer supply conveyance path 14Y, it passes through the communication holes 22a, 22b, 22c, and 22d of the partition member 22. There are also four circulation paths (hereinafter referred to as “shortcut circulation paths”) C to F conveyed to the developer agitation conveyance path 9Y.

  The developer (shortcut developer) transported along the shortcut circulation paths C to F does not pass through a position (supplementing location) facing the toner replenishing port 17Y provided at the upstream end of the developer stirring and transporting path 9Y. For such a shortcut developer, the shortcut developer passes through the communication holes 22a, 22b, 22c, and 22d of the partition member 22 and is conveyed into the developer stirring and conveying path 9Y at the timing of the communication hole 22a. A replenishing method is adopted in which the developer flowing through the main circulation path that reaches the location is replenished in advance with the amount of toner consumed by the developed developer contained in the shortcut developer. As a result, the shortcut developer merges with the developer to which toner has been replenished in advance (in a state where the toner density is excessive) at the merge point in the developer agitating and conveying path 9Y, so that the merge including the shortcut developer is performed. The toner density of the subsequent developer can be restored to the target toner density. Therefore, even in the developing unit having the shortcut circulation paths C to F that do not pass through the replenishment location, it is possible to eliminate toner density unevenness.

13 cancels the arbitrary consumption waveform S0 shown in FIG. 12 and the toner density unevenness caused by the arbitrary consumption waveform S when the same image as the graph shown in FIG. 12 is formed when the shortcut circulation path exists. It is a graph represented with the supply waveform H0.
In the present embodiment, the circulation path through which the part of the developer that has been first removed from the developing roll 12Y reaches the toner density detection point is the first shortcut circulation located at the uppermost stream of the developer supply transport path 14Y. Path C. The next fastest is the second shortcut circulation path D, and in the following order, the third shortcut circulation path E and the fourth shortcut circulation path F. And it arrives the latest when it passes through the main circulation path B. Accordingly, the developed development from when the developed developer via the first shortcut circulation path C reaches the toner density detection location until the developed developer via the main circulation path B reaches the toner density detection location. The agent reaches the toner density detection portion earlier than the developed developer in the example shown in FIG. 12 in which the developer circulation path is only the main circulation path B. As a result, the arbitrary consumption waveform S shown in FIG. 13 becomes broader than the arbitrary consumption waveform S0 shown in FIG. However, since both are consumption waveforms when the same image is formed, the integrated value (toner consumption) is the same.

  Here, even if the toner supply is started at the fastest supply start time (the fastest supply time) at which the toner supply can be started by the toner supply control based on the prediction data described above, the developer that has received the toner supply remains in the shortcut circulation path C. Before reaching the junction with the shortcut developer via ~ F, some shortcut developers pass through the junction. That is, in the graph shown in FIG. 13, before the time corresponding to the illustrated fastest replenishment time in the arbitrary consumption waveform S (the time for the developer replenished with toner at the fastest replenishment time to reach the toner density detection location) (FIG. 13). As for the arbitrary consumption waveform portion (left side of 13), even when toner is replenished in advance, the preceding toner replenishment according to the consumption waveform is not in time. For this reason, the toner density of the developer portion that cannot be supplied in time with the preceding toner is not recovered, which causes uneven toner density.

Next, specific contents of toner replenishment control in the first exemplary embodiment will be described.
FIG. 14 is a flowchart of toner supply control according to the first exemplary embodiment.
When an arbitrary image is formed during actual image formation, the prediction data calculation unit 101 sequentially acquires image data (S1). Then, from the acquired image data, an arbitrary consumption waveform S indicating a change in the toner density over time at the toner density detection location is sequentially generated, and this is sequentially decomposed into the unit consumption waveform S ′ shown in FIG. A combination of a plurality of unit consumption waveforms S ′ obtained by decomposing the waveform S is calculated as prediction data (S2).

FIG. 15 is a graph in which the arbitrary consumption waveform S in the first embodiment is decomposed into a plurality of unit consumption waveforms S ′, that is, a graph showing the contents of the prediction data.
If the prediction data as shown in FIG. 15 which is a combination of unit consumption waveforms S1 ′, S2 ′, S3 ′, S4 ′ (here, only four unit consumption waveforms are illustrated) is calculated, then the prediction is performed. The replenishment control unit 102 that has received the data determines whether or not the preceding toner replenishment for canceling the unit consumption waveform is in time for each of the unit consumption waveforms S1 ′, S2 ′, S3 ′, and S4 ′ (S3). For the first unit consumption waveforms S1 ′ and S2 ′ indicated by the dotted lines in FIG. 15, the preceding toner supply is not in time. That is, the unit consumption waveform S1 including a portion (left side in FIG. 15) before the time corresponding to the illustrated fastest replenishment time (the time for the developer replenished with toner at the fastest replenishment time to reach the toner density detection location). For “, S2”, it is determined that the preceding toner supply is not in time (No in S3). In this way, the toner amount necessary to cancel each of the unit consumption waveforms S1 ′ and S2 ′ determined not to be in time for the preceding toner supply is calculated, and the total amount is calculated as the additional supply amount (S4).

  On the other hand, the unit consumption waveforms S3 ′ and S4 ′ indicated by the solid lines in FIG. 15 do not include a portion before the time corresponding to the illustrated fastest replenishment time (left side in FIG. 15), so that the preceding toner replenishment is in time. (Yes in S3). For these unit consumption waveforms S3 ′ and S4 ′, for each unit consumption waveform S3 ′ and S4 ′, the toner amount (replenishment amount) necessary to cancel this is calculated (S5) and the correction timing thereof is calculated. (S6).

  It should be noted that, based on the difference value between the toner density detection result obtained from the toner density sensor 10Y and the target toner density, the additional supply amount for the unit consumption waveforms S1 ′ and S2 ′ described above and the unit consumption waveform S3 ′ described above. , S4 ′ is preferably corrected. In this case, the toner density unevenness can be eliminated while the toner density is close to the target toner density.

  First, the replenishment control unit 102 combines a plurality of unit replenishment patterns stored in the RAM in advance based on the replenishment amounts and the correction timings for the unit consumption waveforms S3 ′ and S4 ′ in time for the preceding toner replenishment. Of the arbitrary consumption waveform S, the toner for the portion obtained by synthesizing these unit consumption waveforms S3 ′ and S4 ′, that is, the portion after the time corresponding to the illustrated fastest replenishment time (part of the predicted data) Determine the replenishment action. On the other hand, the replenishment control unit 102 also determines a toner replenishment operation in which the additional replenishment amount for the unit consumption waveforms S1 'and S2' that are not in time for the preceding toner replenishment is replenished at once at the fastest replenishment timing. Based on these toner supply operations, drive control of the drive source 71Y is performed (S7).

FIG. 16 shows an arbitrary consumption waveform S described in the upper part of the figure and four unit consumption waveforms S1 ′, S2 ′, S3 ′, S4 ′ obtained by disassembling the same, and toner supply control according to the first embodiment. 6 is a graph showing a unit supply waveform H ′, an additional supply waveform H ″, and a supply waveform H obtained by synthesizing these.
When performing the drive control of the drive source 71Y, the replenishment control unit 102 first performs an additional replenishment operation for replenishing the additional replenishment amount at a time when the fastest replenishment time comes. The replenishment waveform thus obtained is as shown in the additional replenishment waveform H ″ shown in FIG. By the additional replenishment operation indicated by this additional replenishment waveform H ″, the toner to be replenished is supplied to the unit consumption waveforms S1 ′ and S2 ′ that are not in time for the preceding toner replenishment. However, the amount of toner to be replenished by this additional replenishment operation does not have to be the total amount of toner to be replenished in the unit consumption waveforms S1 ′ and S2 ′ that are not in time for the preceding toner replenishment, and may be a partial amount thereof. . After such additional replenishment operation, when the toner replenishment timing corresponding to the unit consumption waveforms S3 ′ and S4 ′ in time for the preceding toner replenishment arrives, these unit consumption waveforms S3 ′ and S4 ′ are displayed as shown in FIG. A toner replenishing operation for generating unit replenishment waveforms H3 ′ and H4 ′ to be canceled is performed.

  Since the replenishment waveform obtained by the toner replenishment operation as described above is a combination of the additional replenishment waveform H ″ and the unit replenishment waveforms H3 ′ and H4 ′, the replenishment waveform H shown in FIG. Among such replenishment waveforms H, the waveform portion where the additional replenishment waveform H ″ is not superimposed, that is, the waveform portion formed only by the unit replenishment waveforms H3 ′ and H4 ′, the arbitrary consumption waveform of the corresponding portion. The toner density unevenness indicated by S is sufficiently eliminated at the toner density detection location. On the other hand, in the portion of the replenishment waveform H where the additional replenishment waveform H ″ is superimposed, the toner is in an excessive state by the amount of toner consumption of the unit consumption waveforms S1 ′ and S2 ′ in which the preceding toner replenishment is not in time. Therefore, the toner density is locally high at the toner density detection location. However, such a developer having a high toner density (over-concentrated developer) flows through the developer circulation path at a position closest to the developer that cannot be in time for preceding toner replenishment (developer that cannot be replenished in advance). Go. Therefore, the excess toner in the excessive concentration developer rapidly diffuses to the developer that cannot be replenished in advance due to the stirring action while transporting the developer circulation path. As a result, for the developer that cannot be replenished in advance with a low toner concentration (that is, the developer corresponding to the unit consumption waveforms S1 ′ and S2 ′), the toner concentration quickly recovers toward the target toner concentration, In addition, the toner concentration of a toner with a high toner density (that is, the developer corresponding to the additional supply waveform H ″) is quickly recovered toward the target toner density. As a result, the toner density unevenness that has occurred at the location of the excessive density developer or the developer that cannot be replenished in advance can be quickly resolved.

  In particular, in the present embodiment, as shown in FIG. 4, the developer conveyed to the downstream end of the developer agitating / conveying path 9Y by the first conveying screw 8Y is moved in the conveying direction by the downstream end wall surface. Be blocked. Then, the developer is sequentially pushed by the developer conveyed later by the first conveying screw 8Y, so that the conveying direction is bent by 90 ° and enters the upstream end of the developer supply conveying path 14Y from the end communication port 18Y. . Due to the movement of the developer at the downstream end of the developer agitating / conveying path 9Y, the mixing of the adjacent portions of the developer in the developer circulation direction is promoted. Therefore, the developer that cannot be replenished in advance, which is not in time for replenishment of the preceding toner, and the over-concentrated developer that is adjacent in the developer circulation direction are mixed at the downstream end of the developer agitating / conveying path 9Y, and the toner concentration is increased. Recovers rapidly. Therefore, the toner density unevenness that has occurred at the location of the excessive density developer or the developer that cannot be replenished in advance is substantially eliminated when the toner is conveyed from the upstream end of the developer supply conveyance path 14Y.

Here, as a comparative example, instead of performing the additional supply operation as in the present embodiment, the unit consumption waveforms S1 ′ and S2 ′ are followed by the unit supply waveforms H3 ′ and H4 ′ that cancel the unit consumption waveforms S3 ′ and S4 ′. An example in which the replenishment operation of the unit replenishment waveforms H1 ′ and H2 ′ corresponding to is performed will be described.
FIG. 17 shows an arbitrary consumption waveform S described in the upper part of the figure and four unit consumption waveforms S1 ′, S2 ′, S3 ′, S4 ′ obtained by disassembling the unit, and a unit when toner supply control of this comparative example is performed. It is a graph which shows supply waveform H1 ', H2', H3 ', H4' and the supply waveform H1 which synthesize | combined these.
FIG. 18 is a graph showing the change over time in the toner concentration of the developer passing through the toner concentration detection portion when the toner replenishment control is performed in this comparative example.
According to this comparative example, the toner density unevenness with respect to the unit consumption waveforms S3 ′ and S4 ′ in time for the preceding toner supply can be eliminated by the unit supply waveforms H3 ′ and H4 ′. However, the toner density unevenness cannot be solved for the unit consumption waveforms S1 ′ and S2 ′ in which the preceding toner supply is not in time. In this comparative example, since the toner density is normal at the locations corresponding to the unit supply waveforms H1 ′ and H2 ′, the toner density at the locations is obtained by performing the supply operation of the unit supply waveforms H1 ′ and H2 ′. Will be in excess. As a result, according to this comparative example, toner density unevenness as shown in FIG. However, also in this comparative example, the toner corresponding to the toner consumption amount in the unit consumption waveforms S1 ′ and S2 ′ that cannot be supplied in advance is supplied by the unit supply waveforms H1 ′ and H2 ′. The toner density (average value) in the whole is kept constant.

FIG. 19 is a graph showing the change over time of the toner concentration of the developer passing through the toner concentration detection portion when the toner replenishment control in the first embodiment is performed. In this graph, the graph of the comparative example shown in FIG. 18 is also indicated by a dotted line.
In the first embodiment, the toner corresponding to the toner consumption amount of the unit consumption waveforms S1 ′ and S2 ′ that cannot be supplied in time with the preceding toner supply is canceled at the timing of the fastest replenishment timing, and the toner that cancels the consumption waveforms of the unit consumption waveforms S3 ′ and S4 ′. Supply in addition to the supply operation. Accordingly, the toner density unevenness in the consumption waveform portion after the additional supply is eliminated by the toner supply operation of the unit consumption waveforms H3 ′ and H4 ′. As a result, according to the first embodiment, toner density unevenness as shown by the solid line in FIG.

As shown in FIG. 19, according to the present embodiment, the peak value of toner density unevenness is suppressed by ΔVt1 smaller than that of the comparative example even at the toner density detection location. This is because the developer cannot be replenished in advance and the additional replenishment waveform H ″ corresponding to the unit consumption waveforms S1 ′ and S2 ′, in which the replenishment of the preceding toner is not in time during the transport to the toner density detection point even though the transport distance is short. This is due to the progress of stirring with the corresponding excessive density developer.
As shown in FIG. 19, according to the present embodiment, the range in which toner density unevenness occurs at the toner density detection location (the length in the developer conveyance direction) is suppressed to be narrower by ΔT2 than in the comparative example. The narrower the range in which toner density unevenness occurs, the faster the toner density unevenness is eliminated by the stirring action during developer conveyance. Therefore, according to the present embodiment, even when there is a developer that cannot be replenished in advance, the toner density unevenness due to the developer that cannot be replenished in advance is present, compared with the case where the toner replenishment control of the comparative example is performed. It can be solved quickly.

[Modification]
Next, a modified example of the toner replenishment control of the first embodiment will be described.
FIG. 20 is a flowchart of toner replenishment control in this modification.
When an arbitrary image is formed during actual image formation, the prediction data calculation unit 101 sequentially acquires image data (S11). In the first embodiment, prediction data is created from the acquired image data, and thereafter, the unit consumption waveforms S1 ′ and S2 ′ in which the preceding toner supply is not in time and the unit consumption waveforms S3 ′ and S4 ′ in which the preceding toner supply is in time are obtained. Separated and processed differently. On the other hand, in the present modified example, before the prediction data is created, an image area that cannot be supplied in advance is divided into an image area that cannot be supplied in advance and an image area that can be supplied in advance that can be supplied in advance. Does not calculate prediction data.

FIG. 21 is an explanatory diagram showing four regions 1 to 4 on one image formed on one recording sheet.
22A to 22D are graphs showing consumption waveforms for each of the four regions on the image shown in FIG.
In the developing unit of the first embodiment, the arrangement of the shortcut circulation paths C to F arranged along the rotation axis direction (left and right direction in FIG. 21) of the developing roll 12, the position of the toner replenishment location in the developer circulation path, and the like. Therefore, an image area where the preceding toner replenishment is in time and an image area where it is not in time are generated due to a difference in position on one image.

For example, the relationship between the consumption waveform in region 1 shown in FIG. 21 and the fastest replenishment time is as shown in FIG. Since this area 1 is developed at a location corresponding to the upstream side of the developer supply conveyance path 14Y, most of the developed developer passes through the first shortcut circulation path C and the second shortcut circulation path D. It is conveyed to the toner density detection location. Therefore, the rising of the consumption waveform for the region 1 is earlier than the fastest replenishment time, so that the preceding toner replenishment is not in time.
Further, the relationship between the consumption waveform and the fastest replenishment time in the region 2 where the position on the image is shifted to the downstream side of the developer supply transport path from the region 1 is as shown in FIG. Since this area 2 is developed at a location corresponding to the downstream side of the developer supply conveyance path 14Y, most of the developed developer passes through the third shortcut circulation path E and the fourth shortcut circulation path F. It is conveyed to the toner density detection location. Therefore, the consumption waveform for region 2 is delayed from the consumption waveform for region 1. However, the consumption waveform for region 2 also rises earlier than the fastest replenishment time, so that the preceding toner replenishment is not in time.

Further, the relationship between the consumption waveform and the fastest replenishment time in the region 3 where the position on the image is shifted to the downstream side in the paper conveyance direction (photoconductor surface movement direction) from the region 1 is as shown in FIG. It will be a thing. The area 3 is developed at a location corresponding to the upstream side of the developer supply transport path 14Y as in the area 1, but the development is performed later than the area 1. As a result, the consumption waveform for the region 3 is delayed with respect to the consumption waveform for the region 1, and its rise is delayed from the fastest supply time. Therefore, for the region 3, the preceding toner supply is in time.
Similarly, the relationship between the consumption waveform and the fastest replenishment time in the region 4 where the position on the image is shifted to the downstream side in the paper transport direction (photosensitive member surface movement direction) from the region 2 is as shown in FIG. In addition, the rise is delayed from the fastest supply time. Therefore, the preceding toner supply is in time for the region 4 as well.

  From the above results, the positions on the image of the image area X where the preceding toner supply is not in time and the image area Y where the preceding toner supply is not in time are as shown in FIG. In the present modification, based on this result, the prediction data calculation unit 101 divides the acquired image data into an image region X portion where the preceding toner supply is not in time and an image region Y portion where the preceding toner supply is in time. (S12). For the image data portion that is determined not to be in time for the preceding toner supply (No in S12), the amount of toner consumed for the image data portion is calculated, and this is calculated as the additional supply amount (S13). On the other hand, for the image data portion determined to be in time for the preceding toner supply (Yes in S12), the prediction data is calculated in the same manner as in the above-described embodiment (S14), and the consumption waveform obtained from the prediction data is canceled. The toner amount (replenishment amount) necessary for the correction is calculated (S15), and the correction timing is calculated (S16).

  Thereafter, the replenishment control unit 102 performs drive control of the drive source 71Y, and first performs an additional replenishment operation for replenishing the additional replenishment amount at a time when the fastest replenishment time has come, and the preceding toner replenishment is not in time. Additional toner is replenished in the image area X. Of course, the amount of toner to be replenished by this additional replenishment operation need not be the total amount of toner consumed in the image area X for which the preceding toner replenishment is not in time, but may be a partial amount thereof. After such additional replenishment operation, when the toner replenishment timing corresponding to the unit consumption waveform for the image area Y in time for the preceding toner replenishment has arrived, the toner replenishment operation for generating the unit replenishment waveform that cancels those unit consumption waveforms is performed.

[Embodiment 2]
Next, as in the case of the first embodiment, another embodiment in which the present invention is applied to a printer (hereinafter, this embodiment is referred to as “second embodiment”) will be described.
The configuration and operation of the second embodiment are the same as those of the first embodiment described above except that the developer circulation path in the developing unit is different. Therefore, only the differences will be described below, and other descriptions will be given. Is omitted.

FIG. 23 is a schematic cross-sectional view illustrating an example of the developing unit 107Y according to the second embodiment.
FIG. 24 is an explanatory diagram for explaining the developer circulation path in the developing unit 107Y when the main developing unit 107Y is viewed from the direction of arrow F in FIG.
In the developing unit 107Y of Embodiment 2, a developer supply transport path 114Y and a developer recovery transport path 109Y are formed vertically with a partition plate 122 in between. Openings are provided at both ends of the partition plate 122. Specifically, the opening 118Y communicates between the upstream side of the developer supply transport path 114Y in the developer transport direction and the downstream side of the developer recovery transport path 109Y in the developer transport direction. The opening 119Y provided on the upstream side in the developer transport direction of the developer recovery transport path 109Y communicates with the end of the developer supply transport path 114Y on the downstream side in the developer transport direction. A toner replenishing port 117Y for replenishing replenished toner is disposed above the opening 119Y.

  The developing unit 107Y according to the second exemplary embodiment collects the developed developer on the developing roll 12 that has consumed the toner in the developing area, to a developer collecting and conveying path 109Y that is a conveying path different from the developer supply and conveying path 114Y. A supply recovery separation system is adopted. Therefore, as shown in FIG. 24, the developer circulation path of the developing unit of Embodiment 2 is the upstream end of the developer recovery transport path 109Y after being transported from the upstream end to the downstream end of the developer supply transport path 114Y. In addition to the circulation path (hereinafter referred to as “main circulation path”) B ′, the developer is transported from the developer supply / conveyance path 114Y to the developing roll 112Y, passes through the development region, and passes through the developer recovery conveyance path. There is also a circulation path (shortcut circulation path) C ′ that is recovered to 109Y.

  The developer (shortcut developer) conveyed along the shortcut circulation path C ′ does not pass through the position (replenishment location) facing the toner supply port 117 </ b> Y provided at the upstream end of the developer recovery conveyance path 109 </ b> Y. With respect to such a shortcut developer, the shortcut developer arrives at the joining point in the developer recovery transport path 109Y at the timing when the shortcut developer is transported into the developer recovery transport path 109Y via the developing roll 12. A replenishment method is adopted in which the developer flowing through the main circulation path is replenished with toner corresponding to the amount of toner consumed by the shortcut developer (developed developer) in advance. As a result, the shortcut developer joins the developer that has been replenished with the toner (the toner density is excessive) at the joining location in the developer collection conveyance path 109Y, and the merged containing the shortcut developer. It is possible to restore the toner density of the subsequent developer to the target toner density.

  The arbitrary consumption waveform when an arbitrary image is formed using such a developing unit is the same as the arbitrary consumption waveform S shown in FIG. 13 in the first embodiment. For this reason, there is a portion where advance toner replenishment is not in time, and this causes toner density unevenness. Such toner density unevenness also performs toner replenishment control in the first embodiment (including the above-described modification). Can be solved in the same way.

As described above, the printer as the image forming apparatus according to the first and second embodiments described above is a photosensitive member 3 as a latent image carrier and a latent image forming unit that forms a latent image on the photosensitive member based on image information. The optical writing unit 20 and the two-component developer containing toner and carrier are circulated and conveyed along the developer circulation path, and in the developer supply and conveyance paths 14 and 114 that play a part of the developer circulation path. The two-component developer being conveyed is supplied to the surfaces of the developing rolls 12 and 112 as developer carriers, and the two-component developer carried on the surfaces of the developing rolls 12 and 112 is moved to the development region by the rotation of the developing rolls. And developing units 7 and 107 as developing devices for transporting and developing the latent image by adhering the toner in the two-component developer to the latent image on the surface of the photosensitive member in the developing area, and a predetermined path on the developer circulation path At the replenishment point And a toner replenishing device 70 as toner replenishing means for replenishing toner to the two-component developer in the image units 7 and 107, and the toner formed on the photosensitive member by being developed by the developing units 7 and 107. The image is finally transferred onto the recording paper P as a recording material to form an image. The developer circulation path of the developing unit is such that at least a part of the developed developer that has passed through the developing region and separated from the developing rolls 12 and 112 is transported without passing through the predetermined replenishment location. A two-component developer that has passed through the predetermined replenishment point at a confluence point located downstream of the developer circulation direction and further upstream of the upstream ends of the developer supply transport paths 14 and 114 than the upstream side of the developer supply direction. It has shortcut circulation paths C to F, C ′ that merge. The developing units 7 and 107 are set as specific locations that are located downstream of the joining location in the developer circulation direction and upstream of the upstream ends of the developer supply transport paths 14 and 114. A prediction data calculation unit 101 as prediction data calculation means for calculating prediction data of a temporal change in toner concentration when the two-component developer without toner replenishment passes through the toner density detection portion, and the toner Replenishment as a replenishment control means for controlling the replenishment operation of the toner replenishing device 70 based on the prediction data calculated by the prediction data calculation unit 101 so as to eliminate the temporal change in the toner concentration of the two-component developer passing through the density detection location. The replenishment control unit 102 performs a replenishment operation based on the prediction data calculated by the prediction data calculation unit 101. The toner concentration of the developer that cannot be replenished in advance is determined so that the two-component developer when the toner is replenished at the fastest replenishment timing that can be performed passes through the junction before the two-component developer reaches the junction. The toner replenishment amount required to recover the target toner density is calculated from the predicted data, and the replenishment operation of the toner replenishing device 70 is controlled so that at least a part of the calculated toner replenishment amount is additionally replenished at the fastest replenishment timing. To do. As a result, the developer additionally supplied with toner in this manner is in an excessively high toner state, so that the toner concentration is locally high at the toner concentration detection location. However, such a developer with a high toner concentration (over-concentrated developer) flows through the developer circulation path at a position closest to the developer that cannot be replenished in advance, which cannot replenish the preceding toner. Therefore, the excess toner in the excessive concentration developer rapidly diffuses to the developer that cannot be replenished in advance due to the stirring action while transporting the developer circulation path. As a result, for a developer that cannot be replenished in advance with a low toner concentration, the toner concentration quickly recovers toward the target toner concentration, and for an over-concentrated developer that has a high toner concentration, The toner density quickly recovers toward the target toner density. As a result, the toner density unevenness that has occurred at the location of the excessive density developer or the developer that cannot be replenished in advance can be quickly resolved.
In particular, in the first embodiment (excluding the above-described modification) and 2, the replenishment control unit 102 uses the predicted data calculated by the predicted data calculation unit 101 as the first predicted data for the developer that cannot be replenished in advance, and the fastest. The two-component developer when the toner is replenished at the replenishment time is divided into second prediction data for the preceding replenishable developer that will pass through the joining location after reaching the joining location, and the first prediction data. Toner replenishment device that calculates the toner replenishment amount required to restore the toner concentration of the developer that cannot be replenished to the target toner concentration from the toner and replenishes at least a part of the calculated toner replenishment amount at the fastest replenishment time 70 is controlled, and after the fastest replenishment timing, the time variation of the toner concentration of the developer that can be replenished before passing through the toner concentration detection location based on the second prediction data. It controls the supply operation of the toner supply device 70 as eliminated. As a result, it is possible to appropriately eliminate the toner density unevenness of the developer that can be replenished in advance, while eliminating the toner density unevenness due to the developer that cannot be replenished in advance.
Further, for example, the prediction data can be calculated from the detection result by providing a toner concentration detection means for continuously or intermittently detecting the toner concentration of the developer passing through the merged portion. However, in this case, since it is necessary to provide a toner density detecting means, the number of parts increases, leading to an increase in cost. Therefore, in the present embodiment, prediction data is calculated based on image data. As a result, the prediction data can be calculated without providing the toner density detecting means, and the cost can be suppressed.
Further, in the above modification, the image information includes the information on the image area X, which is the preceding replenishment impossible area information developed by the preceding replenishment impossible developer, and the two-component developer when the toner is replenished at the fastest replenishment timing. The information is divided into information on the image area Y, which is the preceding replenishable area information developed by the preceding replenishable developer that will pass through the merged place after reaching the merged place, and the preceding replenishment impossible area information is predicted. The amount of toner consumed in the preceding replenishment impossible area information is calculated without calculating data, and prediction data is calculated for the preceding replenishment possible area information. Then, the replenishment operation of the toner replenishing device 70 is controlled so that at least a part of the amount of toner consumed in the calculated preceding replenishable area information is additionally replenished at the fastest replenishment time, and the predicted data calculated after the fastest replenishment time is used. Based on the control, the replenishment operation of the toner replenishing device 70 is controlled so that the temporal change in the toner concentration of the developer that can be replenished in advance that passes through the toner density detection point is eliminated. Thereby, the processing load of the calculation process of prediction data can be reduced.
In addition, as described above, the toner concentration sensor 10 is provided as a toner concentration detection means for detecting the toner concentration of the two-component developer that passes through the toner concentration detection portion that is a predetermined detection portion on the developer circulation path. If the replenishment operation of the toner replenishing device 70 is controlled in consideration of not only the data but also the detection result of the toner concentration sensor 10, not only the toner density unevenness is eliminated, but also the toner in the entire developer in the developing unit. The density (average value) can also be maintained at the target toner density.

  In the first and second embodiments, the developer that can be replenished in time for the replenishment of the preceding toner is performed with the toner replenishment operation using the prediction data so as to cancel the consumption waveform. A toner replenishing operation that does not use prediction data may be performed. In particular, as in the above modification, the detection means detects the timing at which the developed developer transported to the joining location without passing through the predetermined supply location passes through the joining location and the toner consumption amount of the developed developer. (For example, a means for detecting the timing and the toner consumption amount from the detection result of the toner density detection means and the image data), and before the two-component developer reaches the joining point when the toner is supplied at the fastest supply time. A toner replenishment amount required to restore the toner density of the developed developer that will pass through the merged portion to the target toner concentration is calculated from the detection result of the detection means, and at least a part of the calculated toner replenishment amount If the replenishment operation of the toner replenishing device 70 is controlled so that additional replenishment is performed at the fastest replenishment time, the preceding toner replenishment will be in time without using prediction data. Toner density unevenness according to the prior replenishment Call developer had quickly eliminate.

  In the first and second embodiments, the case where a single unit consumption waveform S ′ is used has been described. However, a plurality of different unit consumption waveforms S ′ are used, and a plurality of types of unit supply corresponding to each unit consumption waveform are used. The waveform H ′ may be used.

7, 107 Developing unit 8 First conveying screw 9 Developer agitation conveying path 10 Toner density sensor 11 Second conveying screw 12, 112 Developing rolls 14, 114 Developer supply conveying path 15 Developing sleeve 16 Magnet rollers 17, 117 Toner replenishing port 20 Optical writing units 22a, 22b, 22c, 22d Communication holes 22, 122 Partition member 41 Intermediate transfer belt 70 Toner supply device 100 Control unit 101 Prediction data calculation unit 102 Supply control unit 103 Image information acquisition unit 109 Developer collection conveyance path A Circulation path B Main circulation path C to F Short-cut circulation paths H ′, H1 ′, H2 ′, H3 ′, H4 ′ Unit supply waveform H ″ Additional supply waveform H, H0 Supply waveform H1, H2, H3, H4, H5 Replenishment basic waveform S ′, S1 ′, S2 ′, S3 ′, S4 ′ Unit consumption waveform S, S0 Arbitrary consumption waveform

JP 2008-299315 A

Claims (7)

A latent image carrier;
Latent image forming means for forming a latent image on the latent image carrier based on image information;
A two-component developer containing toner and a carrier is circulated and conveyed along the developer circulation path, and a two-component developer conveyed in a developer supply and conveyance path serving as a part of the developer circulation path. The two-component developer carried on the surface of the developer carrying member is conveyed to the developing area by the rotation of the developer carrying member, and the two-component developer contained in the two-component developer is developed in the developing area. A developing device for developing the latent image by attaching toner to the latent image on the surface of the latent image carrier;
A toner replenishing means for replenishing toner to the two-component developer in the developing device at a predetermined replenishment location on the developer circulation path;
In an image forming apparatus for forming an image by finally transferring a toner image formed on the latent image carrier by being developed by the developing device onto a recording material,
In the developer circulation path, at least a part of the developed developer that has passed through the development area and separated from the developer carrier is transported without passing through the predetermined replenishment location. And a path where the two-component developer that has passed through the predetermined replenishment point is merged at a merge point that is downstream of the developer circulation direction and upstream of the upstream side of the developer supply conveyance path. Having
The specific location on the developer circulation path, which is the downstream location in the developer circulation direction from the merge location or the upstream location in the developer circulation direction from the upstream end of the developer supply transport path. Prediction data calculation means for calculating prediction data of the temporal change in toner density when the two-component developer without toner replenishment passes,
Replenishment control means for controlling the replenishment operation of the toner replenishment means based on the prediction data calculated by the prediction data calculation means so as to eliminate the temporal change in the toner density of the two-component developer passing through the specific location. And
The replenishment control means includes the two-component developer when the toner is replenished at the fastest replenishment timing at which the toner replenishment means can perform a replenishment operation based on the prediction data calculated by the prediction data calculation means. The toner replenishment amount necessary to restore the toner concentration of the developer that cannot be replenished in advance to reach the target toner concentration before passing through the merged point before reaching the target toner concentration is calculated from the predicted data. An image forming apparatus, wherein the replenishment operation of the toner replenishing means is controlled so that at least a part of the replenishment amount is additionally replenished at the fastest replenishment timing. The image forming apparatus according to claim 1.
The replenishment control means uses the prediction data calculated by the prediction data calculation means, the first prediction data for the developer that cannot be replenished in advance, and the two-component developer when toner is replenished at the fastest replenishment timing. And the second predicted data for the preceding replenishable developer that will pass through the merged location after reaching the location, and the toner concentration of the developer that cannot be replenished from the first predicted data is set to the target toner concentration. The toner replenishment amount required for recovery is calculated, the replenishment operation of the toner replenishing means is controlled so that at least a part of the calculated toner replenishment amount is additionally replenished at the fastest replenishment time, and the fastest replenishment time Thereafter, the replenishment operation of the toner replenishing means is performed so that the temporal change in the toner concentration of the preceding replenishable developer passing through the specific location is eliminated based on the second prediction data. Image forming apparatus and controls. The image forming apparatus according to claim 1 or 2,
The image forming apparatus, wherein the prediction data calculation means calculates the prediction data based on the image information. The image forming apparatus according to claim 1.
The predictive data calculating means reaches the merge point when the image information includes the preceding replenishment impossible area information developed by the preceding replenishment impossible developer and the two-component developer when the toner is replenished at the fastest replenishment timing. And the preceding replenishable area information developed by the preceding replenishable developer that will pass through the joining location, and the preceding replenishment impossible area information without calculating the prediction data. The amount of toner consumed by the information is calculated, and the prediction data is calculated for the preceding replenishable area information.
The replenishment control means controls the replenishment operation of the toner replenishment means so as to additionally replenish at least a part of the toner amount consumed in the preceding replenishable area information calculated by the prediction data calculation means at the fastest replenishment timing. In addition, after the fastest replenishment time, the replenishment operation of the toner replenishing means is performed so that the temporal change in the toner concentration of the advance replenishable developer passing through the specific location is eliminated based on the prediction data calculated by the prediction data calculating means. An image forming apparatus that controls the image forming apparatus. The image forming apparatus according to any one of claims 1 to 4, wherein:
A toner concentration detection means for detecting the toner concentration of the two-component developer passing through a predetermined detection location on the developer circulation path;
The image forming apparatus, wherein the replenishment control unit controls a replenishment operation of the toner replenishment unit in consideration of not only the prediction data but also a detection result of the toner density detection unit. A latent image carrier;
Latent image forming means for forming a latent image on the latent image carrier based on image information;
A two-component developer containing toner and a carrier is circulated and conveyed along the developer circulation path, and a two-component developer conveyed in a developer supply and conveyance path serving as a part of the developer circulation path. The two-component developer carried on the surface of the developer carrying member is conveyed to the developing area by the rotation of the developer carrying member, and the two-component developer contained in the two-component developer is developed in the developing area. A developing device for developing the latent image by attaching toner to the latent image on the surface of the latent image carrier;
A toner replenishing means for replenishing toner to the two-component developer in the developing device at a predetermined replenishment location on the developer circulation path;
In an image forming apparatus for forming an image by finally transferring a toner image formed on the latent image carrier by being developed by the developing device onto a recording material,
In the developer circulation path, at least a part of the developed developer that has passed through the development area and separated from the developer carrier is transported without passing through the predetermined replenishment location. And a path where the two-component developer that has passed through the predetermined replenishment point is merged at a merge point that is downstream of the developer circulation direction and upstream of the upstream side of the developer supply conveyance path. Having
Detecting means for detecting a timing at which the developed developer conveyed to the joining location without passing through the predetermined replenishment location passes through the joining location and a toner consumption amount of the developed developer;
Before the two-component developer reaches the merging point when toner is replenished at the fastest replenishment timing at which the toner replenishment amount can be replenished by the toner replenishment amount calculated from the detection result of the detection means. The toner replenishment amount required to restore the toner concentration of the developed developer that will pass through the merged location to the target toner concentration is calculated from the detection result of the detecting means, and at least the calculated toner replenishment amount An image forming apparatus, wherein a replenishment operation of the toner replenishing means is controlled so that a part is additionally replenished at the fastest replenishment time. The image forming apparatus according to claim 6.
The detection means is configured to detect the developed developer on the basis of the image information about the image in which the developed developer transported to the joining location without passing through the predetermined replenishment location contributes to development. And an image forming apparatus for calculating a toner consumption amount of the developed developer.

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