JP6729296B2 - Developing device and image forming device - Google Patents

Description

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

In general, an image forming apparatus (printer, copier, facsimile, etc.) using electrophotographic process technology irradiates (exposes) a laser beam based on image data onto a charged photosensitive drum (image carrier). To form an electrostatic latent image. Then, by supplying toner from the developing device to the photosensitive drum on which the electrostatic latent image is formed, the electrostatic latent image is visualized to form a toner image. Further, after the toner image is directly or indirectly transferred onto the sheet, the toner image is formed on the sheet by heating and pressing at the fixing nip to fix the toner image.

The developing device is provided with a stirring member for stirring the developer in the developing device. It is known that the agitating member agitates the developer so that the developer moves in the axial direction of the developing sleeve. In such a configuration, for example, when the size of the developing device is increased in order to accommodate a sheet that is long in the axial direction, such as the B1 size, the toner is mixed from the upstream side in the moving direction of the developer, so that the toner is mixed in the axial direction. There arises a problem that the deviation of the toner density tends to be large.

In order to address this problem, for example, Japanese Patent Application Laid-Open No. 2004-242242 discloses a configuration in which the developer is circulated in each of the half regions on the one side and the other side in the axial direction within the developing device. FIG. 1 is a diagram simply showing a developing device in a conventional example.

As shown in FIG. 1, the developing device 412 has a developing sleeve 412A and a developer housing 412B. The developer casing 412B has a first stirring member 412C and a second stirring member 412D that stir the developer in the developer casing 412B.

Each of the first stirring member 412C and the second stirring member 412D has a wing direction in one side of the first region B1 and the other side of the second region B2 with respect to the axial center of the developing sleeve 412A. It is configured to be reversed. By rotating the first stirring member 412C and the second stirring member 412D, the developer circulates in each of the first region B1 and the second region B2 along the flow of arrows B10 and B20.

Further, in Patent Document 2, at the boundary between the first region B1 and the second region B2, the developer is positively flowed to both sides of the first region B1 and the second region B2, so that the first region B1 There is disclosed a configuration capable of suppressing a difference in toner density between the second area B2 and the second area B2.

Japanese Utility Model Publication No. 50-27333 JP-A-3-260678

However, in the configuration disclosed in Patent Document 1, for example, an image in which the amount of toner in the portion corresponding to one of the first region B1 and the second region B2 is extremely larger than that in the portion corresponding to the other is continuously formed. In this case, only the toner density in the portion corresponding to one side is extremely lowered, and there arises a problem that the state of the developer in the first area B1 and the second area B2 is not uniform.

Further, in the configuration described in Patent Document 2, when the above images are continuously formed, the toner density of either one of the first area B1 and the second area B2 is extremely reduced, and thus the toner density of one of the areas is reduced. As a result, the density of the other toner decreases. As a result, since the toner density of the entire developing device decreases from the initial stage of the image forming process of the image, it takes time to recover the toner density of the entire developing device. That is, it takes time for the developer in the first region B1 and the second region B2 to be uniform in state.

Further, when the first region B1 and the second region B2 are partitioned by a partition, due to deterioration of the developer (spent, external addition, lubricant transfer amount, etc.) that occurs when continuously forming low coverage images. The charge amount of the toner decreases, and the toner charge amount and the bulk density deviate between the first region B1 and the second region B2. Therefore, if these deviations occur, it becomes difficult to make the state of the developer in the first region B1 and the second region B2 uniform in the entire axial direction of the developing device.

An object of the present invention is to provide a developing device and an image forming apparatus capable of efficiently uniformizing the state of the developer in the entire axial direction of the developing device.

The developing device according to the present invention,
A developer carrying member carrying a developer,
A developer housing that contains the developer supplied to the developer carrier and has a first region on one side and a second region on the other side in the axial direction of the developer carrier,
Of the first area and the second area, the developer in the area having the higher developer bulk density moves to the area having the lower developer bulk density, and the developer bulk density is A path forming portion that forms a second path in which the developer in the lower area moves to the area in which the developer bulk density is high;
A controller that controls the path forming unit to form the first path and the second path according to the developer bulk density of the first area and the second area;
Equipped with.

The image forming apparatus according to the present invention,
A developer carrying member carrying a developer,
A developer housing which contains the developer supplied to the developer carrier and has a first region on one side and a second region on the other side in the axial direction of the developer carrier,
Of the first area and the second area, the developer in the area having the higher developer bulk density moves to the area having the lower developer bulk density, and the developer bulk density is A path forming portion that forms a second path in which the developer in the lower area moves to the area in which the developer bulk density is high;
A control unit that controls the path forming unit to form the first path and the second path according to the developer bulk density of the first area and the second area;
Equipped with.

According to the present invention, the state of the developer in the entire axial direction of the developing device can be efficiently made uniform.

It is a figure which shows the developing device in a prior art example simply. FIG. 1 is a diagram schematically showing an overall configuration of an image forming apparatus according to this embodiment. FIG. 3 is a diagram showing a main part of a control system of the image forming apparatus according to the present embodiment. FIG. 3 is a view of the developing device as seen from above, and is a view when the path forming portion is in a closed state. FIG. 6 is a view of the developing device as viewed from above, showing the path forming portion in an open state. FIG. 6 is a perspective view schematically showing a path forming portion in a closed state in the developer housing. FIG. 6 is a perspective view schematically showing a path forming portion in an open state in the developer housing. FIG. 6 is a diagram showing a sheet on which a toner image having a large coverage difference between a portion corresponding to the first area and a portion corresponding to the second area is formed. FIG. 6 is a diagram for explaining how the developers in the respective areas are mixed when the first area and the second area are communicated with each other. FIG. 6 is a diagram showing a change in the charge amount of a developer with respect to the number of printed sheets. It is a figure which shows the change of the developer bulk density with respect to the printing number. It is an enlarged view of a route formation part. It is an enlarged view of a route formation part. 7 is a flowchart illustrating an example of an operation example of developer path change control in the image forming apparatus. FIG. 9 is a cross-sectional view of a vicinity of a path forming portion in a developer housing according to a modification.

Hereinafter, the present embodiment will be described in detail with reference to the drawings. FIG. 2 is a diagram schematically showing the overall configuration of the image forming apparatus 1 according to this embodiment. FIG. 3 is a diagram showing a main part of a control system of the image forming apparatus 1 according to this embodiment.

The image forming apparatus 1 shown in FIGS. 2 and 3 is an intermediate transfer type color image forming apparatus utilizing an electrophotographic process technique. That is, the image forming apparatus 1 primarily transfers the toner images of Y (yellow), M (magenta), C (cyan), and K (black) formed on the photosensitive drum 413 to the intermediate transfer belt 421. An image is formed by superimposing toner images of four colors on the intermediate transfer belt 421 and then secondarily transferring the toner images to the paper S.

Further, in the image forming apparatus 1, the photosensitive drums 413 corresponding to the four colors of YMCK are arranged in series in the running direction of the intermediate transfer belt 421, and the toner images of the respective colors are sequentially transferred to the intermediate transfer belt 421 by one procedure. The tandem system is adopted.

The image forming apparatus 1 includes an image reading unit 10, an operation display unit 20, an image processing unit 30, an image forming unit 40, a sheet conveying unit 50, a fixing unit 60, and a control unit 100.

The control unit 100 includes a CPU (Central Processing Unit) 101, a ROM (Read Only Memory) 102, a RAM (Random Access Memory) 103, and the like. The CPU 101 reads out a program corresponding to the processing content from the ROM 102, expands it in the RAM 103, and centrally controls the operation of each block of the image forming apparatus 1 in cooperation with the expanded program. At this time, various data stored in the storage unit 72 is referred to. The storage unit 72 is composed of, for example, a nonvolatile semiconductor memory (so-called flash memory) or a hard disk drive.

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

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

The automatic document feeder 11 conveys the document D placed on the document tray by a conveyance mechanism and sends it to the document image scanning device 12. With the automatic document feeder 11, it is possible to continuously read the images (including both sides) of a large number of documents D placed on the document tray all at once.

The document image scanning device 12 optically scans a document conveyed from the automatic document feeding device 11 onto the contact glass or a document placed on the contact glass, and reflects light from the document on a CCD (Charge Coupled Device). ) The original image is read by forming an image on the light receiving surface of the sensor 12a. The image reading unit 10 generates input image data based on the reading result of the original image scanning device 12. The input image data is subjected to predetermined image processing in the image processing unit 30.

The operation display unit 20 is composed of, for example, a liquid crystal display (LCD: Liquid Crystal Display) with a touch panel, and functions as a display unit 21 and an operation unit 22. The display unit 21 displays various operation screens, image states, operating states of functions, information inside the image forming apparatus 1, and the like according to a display control signal input from the control unit 100. The operation unit 22 includes various operation keys such as a numeric keypad and a start key, receives various input operations by the user, and outputs operation signals to the control unit 100.

The image processing unit 30 includes a circuit that performs digital image processing on input image data according to initial settings or user settings. For example, the image processing unit 30 performs the gradation correction based on the gradation correction data (gradation correction table) under the control of the control unit 100. Further, the image processing unit 30 performs various correction processing such as color correction and shading correction, compression processing, and the like on the input image data in addition to the gradation correction. The image forming unit 40 is controlled based on the image data that has been subjected to these processes.

The image forming section 40 includes image forming units 41Y, 41M, 41C, 41K and an intermediate transfer unit 42 for forming an image with color toners of Y component, M component, C component, and K component based on the input image data. And so on.

The image forming units 41Y, 41M, 41C, and 41K for the Y component, the M component, the C component, and the K component have the same configuration. For convenience of illustration and description, common components are denoted by the same reference numerals, and when distinguishing from each other, reference numerals are appended with Y, M, C, or K. In FIG. 2, reference numerals are given only to the components of the image forming unit 41Y for the Y component, and reference numerals are omitted to the components of the other image forming units 41M, 41C and 41K.

The image forming unit 41 includes an exposure device 411, a developing device 200, a photosensitive drum 413, a charging device 414, a drum cleaning device 415, and the like.

The photoconductor drum 413 includes, for example, an undercoat layer (UCL: Under Coat Layer), a charge generation layer (CGL: Charge Generation Layer), a charge transport layer (on a peripheral surface of a conductive cylinder (aluminum tube) made of aluminum. It is a negative charging type organic photoconductor (OPC) in which CTL (Charge Transport Layer) is sequentially laminated.

The charging device 414 uniformly charges the surface of the photoconductor drum 413 having photoconductivity to a negative polarity by generating corona discharge.

The exposure device 411 is composed of, for example, a semiconductor laser, and irradiates the photoconductor drum 413 with laser light corresponding to an image of each color component. Positive charges are generated in the charge generation layer of the photoconductor drum 413 and are transported to the surface of the charge transport layer, whereby the surface charges (negative charges) of the photoconductor drum 413 are neutralized. An electrostatic latent image of each color component is formed on the surface of the photoconductor drum 413 due to the potential difference with the surroundings.

The developing device 200 is a two-component reversal type developing device, and visualizes an electrostatic latent image by forming toner images by attaching toners of respective color components to the surface of the photosensitive drum 413. The developing device 200 supplies toner contained in the developer to the photoconductor drum 413 to form a toner image on the surface of the photoconductor drum 413.

The drum cleaning device 415 has a drum cleaning blade or the like that is in sliding contact with the surface of the photoconductor drum 413, and removes transfer residual toner remaining on the surface of the photoconductor drum 413 after the primary transfer.

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

The intermediate transfer belt 421 is an endless belt and is stretched around a plurality of support rollers 423 in a loop. At least one of the plurality of support rollers 423 is a driving roller, and the others are driven rollers. The rotation of the drive roller causes the intermediate transfer belt 421 to travel in the A direction at a constant speed. The intermediate transfer belt 421 is a belt having conductivity and elasticity, and is rotationally driven by a control signal from the control unit 100.

The primary transfer roller 422 is arranged on the inner peripheral surface side of the intermediate transfer belt 421 so as to face the photoconductor drums 413 of the respective color components. The primary transfer roller 422 is pressed against the photoconductor drum 413 with the intermediate transfer belt 421 sandwiched therebetween, so that a primary transfer nip for transferring a toner image from the photoconductor drum 413 to the intermediate transfer belt 421 is formed.

The secondary transfer roller 424 is arranged on the outer peripheral surface side of the intermediate transfer belt 421, facing the backup roller 423B arranged on the downstream side of the driving roller 423A in the belt traveling direction. The secondary transfer roller 424 is pressed against the backup roller 423B with the intermediate transfer belt 421 interposed therebetween to form a secondary transfer nip for transferring the toner image from the intermediate transfer belt 421 to the sheet S.

The belt cleaning device 426 removes transfer residual toner remaining on the surface of the intermediate transfer belt 421 after the secondary transfer.

When the intermediate transfer belt 421 passes through the primary transfer nip, the toner images on the photoconductor drum 413 are sequentially primary-transferred on the intermediate transfer belt 421 in an overlapping manner. Specifically, a primary transfer bias is applied to the primary transfer roller 422, and a charge having a polarity opposite to that of the toner is applied to the back surface side of the intermediate transfer belt 421, that is, the side in contact with the primary transfer roller 422, to thereby obtain a toner image. Are electrostatically transferred onto the intermediate transfer belt 421.

After that, when the sheet S passes through the secondary transfer nip, the toner image on the intermediate transfer belt 421 is secondarily transferred to the sheet S. Specifically, a secondary transfer bias is applied to the backup roller 423B, and a charge of the same polarity as the toner is applied to the surface side of the sheet S, that is, the side in contact with the intermediate transfer belt 421. It is electrostatically transferred to S.

The fixing unit 60 includes an upper fixing unit 60A having a fixing surface side member disposed on the surface of the sheet S on which the toner image is formed, and a fixing unit 60 on the opposite side of the fixing surface that is the back side of the sheet S. The lower fixing unit 60B and the like having the rear surface side supporting member arranged is provided. When the back surface side support member is pressed against the fixing surface side member, a fixing nip for sandwiching and conveying the sheet S is formed.

The fixing unit 60 fixes the toner image on the paper S by heating and pressurizing the paper S that has been secondarily transferred with the toner image and conveyed at the fixing nip.

The upper fixing unit 60A has an endless fixing belt 61 which is a fixing surface side member, a heating roller 62, and a fixing roller 63. The fixing belt 61 is stretched around a heating roller 62 and a fixing roller 63.

The lower fixing unit 60B has a pressure roller 64 that is a back surface side supporting member. The pressure roller 64 forms a fixing nip for nipping and conveying the sheet S with the fixing belt 61.

The paper transport unit 50 includes a paper feed unit 51, a paper discharge unit 52, a transport path unit 53, and the like. The paper S (standard paper, special paper) identified on the basis of the basis weight, the size, and the like is stored in each of the three types of paper feed tray units 51a to 51c that configure the paper feed unit 51 for each preset type. ..

The transport path portion 53 has a plurality of transport roller pairs such as a registration roller pair 53a. The sheets S stored in the sheet feed tray units 51a to 51c are sent out one by one from the top, and are conveyed to the image forming section 40 by the conveyance path section 53. At this time, the registration roller unit provided with the registration roller pair 53a corrects the inclination of the fed paper S and adjusts the conveyance timing. Then, in the image forming unit 40, the toner images on the intermediate transfer belt 421 are secondarily transferred to one surface of the sheet S at one time, and the fixing unit 60 performs a fixing process. The sheet S on which the image is formed is ejected to the outside of the machine by the sheet ejection section 52 including the sheet ejection roller 52a.

Next, the details of the developing device 200 will be described. FIG. 4A is a view of the developing device 200 as seen from above, and is a view when the path forming portion 240 is in a closed state. FIG. 4B is a view of the developing device 200 as seen from above, and is a view when the path forming unit 240 is in an open state.

As shown in FIGS. 4A and 4B, the developing device 200 has a size that can accommodate a sheet that is long in the axial direction, such as the B1 size, and includes a developing sleeve 210, a developer housing 220, and a developer discharging unit. 230 and. The developing sleeve 210 is a developer carrier that carries a developer, and has a length corresponding to a sheet having a long axial direction. The developing sleeve 210 in this embodiment has a diameter of 25 mm.

The developer housing 220 stores the developer supplied to the developing sleeve 210. The developer housing 220 has a first region 221A, which is a region on one side of a portion corresponding to the central portion of the developing sleeve 210 in the axial direction, and a portion corresponding to the central portion of the developing sleeve 210 in the axial direction. On the other hand, the path forming part 240 is provided between the second area 221B which is the area on the other side. The path forming unit 240 partitions the first area 221A and the second area 221B. In this embodiment, the amount of developer that can be stored in the developer housing 220 is 1200 g.

Further, a first stirring member 222, a second stirring member 223, a toner concentration detection unit 224, and a toner replenishment unit 225 are provided in each of the first region 221A and the second region 221B of the developer housing 220. Has been.

The first stirring member 222 is provided in a portion of the first region 221A and the second region 221B that is farther from the developing sleeve 210 than the second stirring member 223.

The second stirring member 223 is provided in a portion of the first area 221A and the second area 221B that faces the developing sleeve 210.

The first stirring member 222 and the second stirring member 223 in the present embodiment have a diameter of 25 mm and a rotation speed of 450 rpm.

Further, in each of the first region 221A and the second region 221B, the region of the first stirring member 222 and the region of the second stirring member 223 are partitioned by the partition plate 227. By being partitioned by the partition plate 227, the regions of the first stirring member 222 and the second stirring member 223 in the first region 221A and the second region 221B are the end portions of the first stirring member 222 and the second stirring member 223. Are connected by the part corresponding to.

Therefore, as the first stirring member 222 and the second stirring member 223 rotate, the developer moves in the first area 221A and the second area 221B in the directions of the arrows X1 and X2, and eventually the first area 221A. And the developer in the second area 221B is agitated.

The toner concentration detection unit 224 detects the toner concentrations of the first area 221A and the second area 221B. The toner replenishing unit 225 replenishes the toner to each of the first area 221A and the second area 221B. The control unit 100 controls the toner replenishment amount in the toner replenishment unit 225 based on the detection result detected by the toner concentration detection unit 224.

The developer discharging portion 230 is a portion for discharging the developer in the developer housing 220, and is provided in a portion of the developer housing 220 corresponding to the second region 221B. The developer discharging portion 230 has a passage portion 231, a screw member 232, and a discharging portion 233.

The passage portion 231 is a portion that communicates with the developer housing 220 and the discharge portion 233. The screw member 232 is arranged in the passage portion 231 and is coaxial with the first stirring member 222. The screw member 232 generates a flow for moving the developer from the passage portion 231 toward the inside of the developer housing 220 by rotating. The screw member 232 prevents the developer in the developer housing 220 from entering the passage portion 231.

Then, of the developers in the developer housing 220, for example, when a carrier is deteriorated, the carrier is replenished in the developer housing 220 by a carrier replenishing unit (not shown), and the developer can be stored in the developer housing 220. When the amount is exceeded, the developer moves from the developer housing 220 to the passage portion 231 and is discharged from the discharge portion 233.

Next, details of the path forming unit 240 will be described. FIG. 5A is a perspective view schematically showing the path forming portion 240 in the closed state in the developer housing 220. FIG. 5B is a perspective view schematically showing the path forming portion 240 in the opened state inside the developer housing 220.

As shown in FIGS. 5A and 5B, the path forming portion 240 is located at the boundary between the first area 221A and the second area 221B in the developer housing 220, and has the first door 241 and the second door 242. And a supporting member 243. The support member 243 is located at a position corresponding to the first stirring member 222 and the second stirring member 223, respectively.

The first door 241 and the second door 242 are rotatably supported by a support member 243 that supports the first stirring member 222. When the first door 241 and the second door 242 are positioned so as to be parallel to the support member 243, they are in a closed state that closes the first region 221A and the second region 221B (see FIG. 5A). That is, when the first door 241 and the second door 242 are in the closed state, the path forming unit 240 uses the first door 241, the second door 242, and the two support members 243 to generate the first area 221A and the second area. It has a role of a partition member that partitions the 221B.

The 1st door 241 and the 2nd door 242 will be in an open state which opens the 1st field 221A and the 2nd field 221B by rotating to the 1st field 221A side or the 2nd field 221B side (the figure). 5B).

When the first door 241 is opened, a portion corresponding to the first door 241 in the vertical direction forms a first path for the developer to move between the first area 221A and the second area 221B. To be done. In addition, the first door 241 is in the closed state, so that the first path is not formed.

By opening the second door 242, a portion corresponding to the second door 242 in the vertical direction, that is, a portion below the first door 241 is developed between the first area 221A and the second area 221B. A second path is formed for the agent to move. In addition, the second door 242 is in the closed state, so that the second path is not formed.

By the way, when images having a large difference between the toner amount of the portion corresponding to the first region 221A and the toner amount of the portion corresponding to the second region 221B are continuously formed, the volume density of the developer in the first region 221A is , And the bulk density of the developer in the second area 221B causes a difference.

For example, as shown in FIG. 6, when the toner image T in the portion S1 corresponding to the first area 221A is extremely smaller than the toner amount in the portion S2 corresponding to the second area 221B, the toner image T is continuously formed. As shown in FIG. 7, since the toner is not used in the first area 221A, the developer T1 in the first area 221A is easily deteriorated, and the bulk density of the developer T1 is increased. Further, since the new developer is replenished by using the toner in the second area 221B, the bulk density of the developer T2 in the second area 221B becomes low.

Since the developer T1 having a high bulk density has a larger specific gravity than the developer T2 having a low bulk density, when the first region 221A and the second region 221B in the developer housing 220 communicate with each other, the developer having a high bulk density is used. T1 sunk below the developer T2 having a low bulk density. Therefore, the developer in the first area 221A and the developer in the second area 221B are double-layered by the developer T1 having a high bulk density and the developer T2 having a low bulk density, and are developed in the first area 221A and the second area 221B. Agents do not mix efficiently.

In particular, the greater the number of printed sheets, the greater the amount of deterioration of the developer on the area where the amount of toner used is small. For example, as shown in FIG. 8, when the toner image T shown in FIG. 6 is continuously printed, and the number of printed sheets is a predetermined number M (for example, 10K sheets), new developer is replenished in the second area 221B. Therefore, the first charge amount Q1 at the start of printing (eg, 50 μc/g) hardly changes. On the other hand, in the first area 221A, the charge amount of the developer decreases, and when the predetermined number M of sheets, the charge amount decreases to the second charge amount Q2 (for example, 40 μc/g).

Looking at this as the bulk density of the developer, as shown in FIG. 9, in the second region 221B, when the number of printed sheets is a predetermined number M, the first bulk density G1 at the start of printing (for example, 1. Almost no change from 6 g/CC). On the other hand, in the first region 221A, the bulk density of the developer increases, and when the predetermined number M of sheets, the second bulk density G2 (for example, 1.9 g/CC) rises. As described above, when a difference in bulk density occurs between the first area 221A and the second area 221B, a difference in image quality occurs between the portion corresponding to the first area 221A and the portion corresponding to the second area 221B. I will end up.

Therefore, in the present embodiment, the control unit 100 controls the path forming unit 240 according to the developer bulk density of the first area 221A and the second area 221B. By controlling in this way, even if there is a difference in developer bulk density between the first area 221A and the second area 221B, the developers in the first area 221A and the second area 221B can be efficiently mixed. You can The control of the path forming unit 240 will be described below. 10 and 11, the case where the first area 221A is the area having the lower developer bulk density and the second area 221B is the area having the higher developer bulk density will be described.

As shown in FIGS. 10 and 11, in the control unit 100, the developer in the region (first region 221A) having the higher developer bulk density of the first region 221A and the second region 221B has the first path. The path forming unit 240 is controlled so as to move to a region (second region 221B) having a lower bulk density of the developer.

Specifically, the control unit 100 rotates the first door 241 toward the second region 221B, which has a lower developer bulk density. In other words, the control unit 100 rotates the first door 241 toward the second area 221B when moving the developer in the first area 221A to the second area 221B by the first path.

In the control unit 100, the developer in a region (second region 221B) of the first region 221A and the second region 221B having a lower developer bulk density passes through the second path and has a higher developer bulk density. The path forming unit 240 is controlled to move to the area (first area 221A).

Specifically, the control unit 100 rotates the second door 242 to the side of the first area 221A on the side where the bulk density of the developer is high. In other words, the control unit 100 rotates the second door 242 toward the first area 221A when moving the developer in the second area 221B to the first area 221A by the second path.

In this way, each of the first door 241 and the second door 242 rotates so as to be located on the different region side. By doing so, the developers having different bulk densities move between the first region 221A and the second region 221B without interfering with each other. Hereinafter, the movement between the first region 221A and the second region 221B in each of the developer having high bulk density and the developer having low bulk density will be specifically described.

First, the movement of the developer having a high bulk density will be described.
As shown in FIG. 10, the developer having a high bulk density moves in the counterclockwise direction (arrow X1 in FIG. 4A) in the first region 221A. When the developer having a high bulk density moves to the position of the path forming portion 240, the developer located in the portion corresponding to the first door 241 in the vertical direction passes through the first path above the second door 242 to the second area. Move to 221B (see arrow X3). Further, the developer located in the portion corresponding to the second door 242 in the vertical direction collides with the second door 242 and stops in the first area 221A (see arrow X4).

Next, the movement of the developer having a low bulk density will be described.
As shown in FIG. 11, the developer having a low bulk density moves in the clockwise direction (arrow X2 in FIG. 4A) in the second region 221B. When the developer having a low bulk density moves to the position of the path forming portion 240, the developer located in a portion corresponding to the second door 242 in the vertical direction passes through the second path below the first door 241 to pass through the first area. Move to 221A (see arrow X5). Further, the developer located in the portion corresponding to the first door 241 in the vertical direction collides with the first door 241 and stops in the second area 221B (see arrow X6).

In this way, the path forming portion 240 forms the first path and the second path, whereby the developer having a high bulk density and the developer having a low bulk density do not interfere with each other, and the first region 221A and the second region 221A. It moves to and from 221B. Thereby, the developer bulk density between the first area 221A and the second area 221B can be easily made uniform.

Further, since the developer having a high bulk density has a larger specific gravity and is heavier than the developer having a low bulk density, the developer moves from the first route, which is above the second route, to the region having the low bulk density. For this reason, the transferred developer having a high bulk density sinks from above the developer having a low bulk density, so that the developer having a high bulk density and the developer having a low bulk density can be easily mixed with each other.

The bulk density of the developer is, for example, the first coverage K1 of the toner image supplied from the first area 221A to the developing sleeve 210 and the second coverage K2 of the toner image supplied from the second area 221B to the developing sleeve 210. The determination is made by the control unit 100 based on the difference between and. And the control part 100 determines the rotation direction of the 1st door 241 and the 2nd door 242 according to the difference of the 1st coverage K1 and the 2nd coverage K2, and determines the 1st door 241 and the 2nd door 242 according to the said difference. The opening amount of the 2 door 242 is determined.

The opening amounts of the first door 241 and the second door 242 include the opening angles of the first door 241 and the second door 242 with respect to the boundary between the first region 221A and the second region 221B.

For example, when the difference between the first coverage K1 and the second coverage K2 is 30% or more and less than 50%, the opening angles of the first door 241 and the second door 242 are set to 30°, and the first coverage K1 and the second coverage K2 are set. When the difference from the coverage K2 is 50% or more, the opening angles of the first door 241 and the second door 242 are set to 45°.

In addition, the control unit 100 may perform control so as to determine the rotation direction and the opening amount of the first door 241 and the second door 242 according to the toner concentration of the developer in the first area 221A and the second area 221B. good.

For example, when the difference between the toner density in the first area 221A and the toner density in the second area 221B is 0.5%, the opening angles of the first door 241 and the second door 242 are set to 30°, and the first area is set to 30°. When the difference between the toner density in 221A and the toner density in second area 221B is 1.0%, the opening angles of first door 241 and second door 242 are set to 45°.

Next, an operation example of the developer path change control in the image forming apparatus 1 will be described. FIG. 12 is a flowchart showing an example of an operation example of the developer path change control in the image forming apparatus 1. The process in FIG. 12 is appropriately executed during the print job.

As illustrated in FIG. 12, the control unit 100 acquires image formation information of the first area 221A and the second area 221B (step S101). Next, the control unit 100 calculates the difference between the first coverage K1 and the second coverage K2 from the acquired image formation information (step S102). Next, the control unit 100 determines whether or not the absolute value of the difference between the first coverage K1 and the second coverage K2 is 30% or more (step S103).

As a result of the determination, when the absolute value of the difference between the first coverage K1 and the second coverage K2 is less than 30% (step S103, NO), the process transitions to step S112. On the other hand, if the absolute value of the difference between the first coverage K1 and the second coverage K2 is 30% or more (step S103, YES), the control unit 100 determines that the absolute value of the difference between the first coverage K1 and the second coverage K2 is It is determined whether it is 50% or more (step S104).

As a result of the determination, when the absolute value of the difference between the first coverage K1 and the second coverage K2 is 50% or more (YES in step S104), the control unit 100 determines the opening angles of the first door 241 and the second door 242. It is set to 45° (step S105). On the other hand, when the absolute value of the difference between the first coverage K1 and the second coverage K2 is less than 50% (step S104, NO), the control unit 100 sets the opening angles of the first door 241 and the second door 242 to 30°. (Step S106).

After steps S105 and S106, the control unit 100 determines whether the first coverage K1 is larger than the second coverage K2 (step S107). As a result of the determination, when the first coverage K1 is larger than the second coverage K2 (step S107, YES), the control unit 100 sets the route forming unit 240 to the first open state to set the route forming unit 240 to the first state. 1 is set to the open state (step S108). The first open state is a case where the developer bulk density in the first area 221A is lower than the developer bulk density in the second area 221B. That is, in the first open state, the first door 241 is located on the first region 221A side and the second door 242 is located on the second region 221B side.

On the other hand, when the first coverage K1 is less than or equal to the second coverage K2 (step S107, NO), the control unit 100 sets the route forming unit 240 to the second open state, thereby setting the route forming unit 240 to the second open state. (Step S109). The second open state is a case where the developer bulk density in the first area 221A is higher than the developer bulk density in the second area 221B. That is, in the second opened state, the first door 241 is located on the second region 221B side and the second door 242 is located on the first region 221A side.

After steps S108 and S109, the control unit 100 performs the stirring operation by the first stirring member 222 and the second stirring member 223 in the developer housing 220 for 1 minute (step S110).

Next, the control unit 100 sets the route forming unit 240 to the closed state, thereby closing the route forming unit 240 (step S111). Next, the control unit 100 starts the image forming operation (step S112). Then, this control is ended.

According to the present embodiment configured as described above, since the path forming portion 240 forms the first path and the second path, the developer having a high bulk density and the developer having a low bulk density interfere with each other. Instead, it moves between the first area 221A and the second area 221B. Thereby, the developer bulk density between the first area 221A and the second area 221B can be efficiently made uniform.

Further, since the developer having a high bulk density has a larger specific gravity than the developer having a low bulk density, the developer moves from the first path, which is above the second path, to a region having a low bulk density. For this reason, since the transferred high-bulk density developer sinks from above the low-bulk density developer, it is possible to easily mix the high-bulk density developer and the low-bulk density developer with each other. The bulk density of the developer between the first area 221A and the second area 221B can be quickly made uniform.

Further, by providing the first door 241 and the second door 242 in the part that divides the first area 221A and the second area 221B in the developer housing 220, the first area 221A and the second area 221B are opened and closed. Therefore, the bulk density of the developer can be made uniform between the first area 221A and the second area 221B with a simple configuration.

Next, the path forming unit 250 according to the modification will be described. FIG. 13 is a cross-sectional view of the vicinity of the path forming portion 250 in the developer housing 220 according to the modification. The first stirring member 222 and the second stirring member 223 in the developer housing 220 in FIG. 13 are not shown.

As shown in FIG. 13, the developer housing 220 according to the modified example has a partition part 260 that partitions the first region 221A and the second region 221B. The partition part 260 has an opening 261 in the central portion in the vertical direction. The path forming unit 250 is provided in the opening 261.

The path forming section 250 has a rotating shaft 251 and a pair of plate sections 252. The rotary shaft 251 is located at the center of the opening 261 of the partition 260 in the vertical direction. Each plate portion 252 extends from the rotary shaft 251, and is configured to be able to close the openings 261 above and below the rotary shaft 251.

The path forming unit 250 rotates about the rotation shaft 251 and communicates the first region 221A and the second region 221B when the pair of plate units 252 separates from the opening 261. Two paths are formed.

Specifically, each of the pair of rotating plate portions 252 conveys the developer in the first area 221A and the second area 221B to the opening 261 so as to be pushed out. With respect to the rotation direction of the path forming unit 250, the developer T1 having a high bulk density passes through the opening 261A (first path) above the rotating shaft 251 and the developer T2 having a low bulk density is on the rotating shaft 251. The rotation direction is such that it passes through the lower opening 261B (second path).

For example, when the developer in the first area 221A has a higher bulk density than the developer in the second area 221B, the plate portion 252 located on the first area 221A side is rotated from bottom to top. Further, the plate portion 252 located on the second region 221B side rotates so as to face downward.

As a result, the developer T1 having a high bulk density in the first area 221A moves to the second area 221B through the opening 261A above the rotating shaft 251, that is, the first path. Further, the developer T2 having a low bulk density in the second area 221B moves to the first area 221A through the opening 261B below the rotating shaft 251, that is, the second path.

The rotation direction of the path forming unit 250 is determined according to the difference between the first coverage K1 of the toner image corresponding to the first area 221A and the second coverage K2 of the toner image corresponding to the second area 221B. Then, the rotation speed of the path forming unit 250 is determined according to the difference.

For example, when the difference between the first coverage K1 and the second coverage K2 is 30% or more and less than 50%, the rotation speed of the path forming unit 250 is set to 450 rpm, and the difference between the first coverage K1 and the second coverage K2 is When it is 50% or more, the rotation speed of the path forming unit 250 is set to 600 rpm.

The rotation direction and the rotation speed of the path forming unit 250 may be determined according to the toner concentration of the developer in the first area 221A and the second area 221B.

Alternatively, the rotation time of the path forming unit 250 may be determined according to the difference between the first coverage K1 and the second coverage K2 and the toner concentration of the developer in the first area 221A and the second area 221B. good.

In addition, each of the above-described embodiments is merely an example of the embodiment in carrying out the present invention, and the technical scope of the present invention should not be limitedly interpreted by these. That is, the present invention can be implemented in various forms without departing from the gist or the main features thereof.

The present invention can be applied to an image forming system including a plurality of units including an image forming apparatus. The plurality of units include external devices such as a post-processing device and a network-connected control device.

Finally, an evaluation experiment of the developing device 200 according to this embodiment will be described. In the following evaluation experiment, the image forming apparatus 1 shown in FIG. 1 is used.

First, 1000 sheets of a toner image having a large difference in toner amount between the portion S1 corresponding to the first area 221A and the portion S2 corresponding to the second area 221B as shown in FIG. Paper and evaluate the image quality after passing. Then, the stirring operation in the first stirring member 222 and the second stirring member 223 is performed, and the image quality after that is evaluated. In this experiment, the toner image coverage of the portion S1 corresponding to the first region 221A was set to 1%, and the toner image coverage of the portion S2 corresponding to the second region 221B was set to 30%.

Example 1 has a configuration having the route forming section 240 shown in FIGS. 4A, 4B, 5A and 5B, and Example 2 has a configuration having the route forming section 250 shown in FIG. 13. Further, Comparative Example 1 has a configuration in which the first region 221A and the second region 221B are partitioned, and Comparative Example 2 has a configuration in which the first region 221A and the second region 221B communicate with each other. Table 1 shows the experimental results in Examples 1 and 2 and Comparative Examples 1 and 2.

“◯” in Table 1 indicates that a good image was obtained in which there was no difference between the amount of toner supplied from the first area 221A and the amount of toner supplied from the second area 221B. “Δ” indicates that an image having a practically no problem level was obtained, and “x” indicates that an image defect occurred. The same applies to Tables 2 to 4 below.

According to Table 1, it was confirmed that an image defect occurred in any of the sheets after passing 10,000 sheets. When the stirring operation was performed, it was confirmed that in Comparative Example 1 and Comparative Example 2, an image defect occurred when the stirring operation was performed for 1 minute. Further, when the stirring operation was performed for 2 minutes, the image quality was improved to some extent in Comparative Example 2, but it was confirmed that the image defect still occurred in Comparative Example 1.

On the other hand, in Example 1, it was confirmed that good images were obtained both when the stirring operation was performed for 1 minute and when the stirring operation was performed for 2 minutes. Further, in Example 2, it was confirmed that a good image was obtained when the stirring operation was performed for 2 minutes, and an image having a practically no problem level was obtained even when the stirring operation was performed for 1 minute. That is, by applying the present invention, it was confirmed that the developers in the first area 221A and the second area 221B were quickly mixed.

Next, as shown in FIG. 6, a toner image having a large difference in toner amount between the portion S1 corresponding to the first area 221A and the portion S2 corresponding to the second area 221B is printed on 1000 sheets of A3 size paper S. Paper is passed and the image quality after passing is evaluated. Then, the opening angles of the first door 241 and the second door 242 of the path forming unit 240 in the above-described first embodiment are changed to 0°, 15°, 30°, and 45° to change the first stirring member 222 and the second stirring member. The stirring operation in the member 223 is performed, and the image quality after that is evaluated.

In this experiment, the toner image coverage of the portion S1 corresponding to the first region 221A was set to 1%, and the toner image coverage of the portion S2 corresponding to the second region 221B was set to 30%. Table 2 shows the experimental results for each opening angle.

According to Table 2, when the stirring time is 30 seconds, the image defect occurs at any opening angle, but when the stirring time is 60 seconds, the image defect occurs when the opening angle is 0° and 15°. Although it occurred, when the opening angle was 30°, an image having a practically no problem level was obtained, and when the opening angle was 45°, a good image was obtained. Therefore, it was confirmed that the developers in the first region 221A and the second region 221B were quickly mixed by setting the opening angle to 30° or more.

Further, when the stirring time was 90 seconds, when the opening angle was 15°, an image having a practically no problem level was obtained, and when the opening angle was 30°, a good image was obtained. That is, it was confirmed that the image quality was improved by increasing the stirring time.

Next, a toner image obtained by changing the coverage difference between the toner image of the portion S1 corresponding to the first area 221A and the toner image of the portion S2 corresponding to the second area 221B as shown in FIG. Each of the sheets S is passed through 1000 sheets, and the image quality after passing is evaluated. Then, the opening angle of the first door 241 and the second door 242 of the path forming unit 240 in the above-described first embodiment is set to 45°, and the stirring operation is performed in the first stirring member 222 and the second stirring member 223, The subsequent image quality is evaluated. Table 3 shows the experimental results for each coverage difference.

According to Table 3, it was confirmed that when the stirring time was 30 seconds and the difference in coverage was 50% or more, an image defect occurred. However, it was confirmed that when the stirring time was 60 seconds or more, a good image was obtained in any coverage. Therefore, it was confirmed that the stirring time was required to be 60 seconds (1 minute) or more.

Finally, as shown in FIG. 6, 1000 sheets of A3 size sheet S of toner images having a large difference in toner amount between the portion S1 corresponding to the first area 221A and the portion S2 corresponding to the second area 221B are formed. Paper is passed and the image quality after passing is evaluated. Then, the rotation speed of the path forming unit 250 in the second embodiment is changed to 225 rpm, 450 rpm, and 600 rpm, the stirring operation is performed in the first stirring member 222 and the second stirring member 223, and the image quality after that is evaluated. In addition, as a comparative example, the first region 221A and the second region 221B are partitioned.

In this experiment, the toner image coverage of the portion S1 corresponding to the first region 221A was set to 1%, and the toner image coverage of the portion S2 corresponding to the second region 221B was set to 30%. Table 4 shows the experimental results for each rotation speed.

According to Table 4, in the comparative example, it was confirmed that the image defect occurred even when the stirring time was changed. On the other hand, when the rotation speed of the path forming unit 250 was changed, an image defect occurred at any rotation speed when the stirring time was 30 seconds, but when the stirring time was 60 seconds and the rotation speed was 450 rpm, It was confirmed that an image of a level practically no problem was obtained, and that a good image was obtained when the rotation speed was 600 rpm. That is, it has been confirmed that when the stirring time is 60 seconds (1 minute), it is desirable that the rotation speed of the path forming unit 250 be 450 rpm or more.

Further, it was confirmed that when the stirring time was 90 seconds, an image at a rotation speed of 225 rpm, which was at a level practically no problem, was obtained, and when the rotation speed was 450 rpm or more, a good image was obtained. That is, it was confirmed that the image quality was further improved by increasing the stirring time.

1 Image Forming Apparatus 100 Control Unit 200 Developing Device 210 Developing Sleeve 220 Developer Housing 240 Path Forming Unit 241 First Door 242 Second Door

Claims (15)

A developer carrying member carrying a developer,
A developer housing which contains the developer supplied to the developer carrier and has a first region on one side and a second region on the other side in the axial direction of the developer carrier,
Of the first area and the second area, the developer in the area having the higher developer bulk density moves to the area having the lower developer bulk density, and the developer bulk density is A path forming portion that forms a second path in which the developer in the lower area moves to the area in which the developer bulk density is high;
A control unit that controls the path forming unit to form the first path and the second path according to the developer bulk density of the first area and the second area;
Developing device. The path forming unit,
Partitioning the first region and the second region in the developer housing,
A first door that forms the first path by opening the first area and the second area, and does not form the first path by closing the first area and the second area;
Located below the first door, the second area is formed by opening the first area and the second area, and the second area is closed by closing the first area and the second area. A second door that does not form two paths,
Have
The control unit opens and closes the first door and the second door according to the developer bulk density of the first area and the second area,
The developing device according to claim 1. The first door and the second door are rotatable to the first region side and the second region side with respect to a boundary between the first region and the second region,
When the controller moves the developer in one of the first area and the second area to the other by either the first path or the second path, the control section may be the first door or the second door. To the other area side,
The developing device according to claim 2. The control unit may be configured to operate according to a difference between a coverage of a toner image supplied from the first area to the developer carrier and a coverage of a toner image supplied from the second area to the developer carrier. Determining the respective turning directions of the first door and the second door,
The developing device according to claim 3. The control unit may be configured to operate according to a difference between a coverage of a toner image supplied from the first area to the developer carrier and a coverage of a toner image supplied from the second area to the developer carrier. Determining the opening amount of the first door and the second door,
The developing device according to claim 4. A toner concentration detecting section for detecting the toner concentration of the developer in the first region and the second region,
The control unit determines a rotation direction of each of the first door and the second door according to the toner concentration detected by the toner concentration detection unit.
The developing device according to claim 3. The controller determines the opening amount of the first door and the second door according to the toner concentration detected by the toner concentration detector.
The developing device according to claim 6. A partition portion that partitions the first region and the second region in the developer housing and has an opening at the central portion in the up-down direction that connects the first region and the second region to each other;
The path forming unit,
A rotating shaft provided in the central portion of the opening in the vertical direction,
A pair of plate portions extending from the rotation shaft and capable of closing the opening;
Have
The control unit forms the first route and the second route by rotating the route forming unit,
The developing device according to claim 1. The control unit may be configured to operate according to a difference between a coverage of a toner image supplied from the first area to the developer carrier and a coverage of a toner image supplied from the second area to the developer carrier. Determines the direction of rotation of the path forming unit,
The developing device according to claim 8. The controller controls the path according to the difference between the coverage of the toner image supplied from the first area to the developer carrier and the coverage of the toner image supplied from the second area to the developer carrier. Determines the rotational speed of the forming part,
The developing device according to claim 9. The controller controls the path according to the difference between the coverage of the toner image supplied from the first area to the developer carrier and the coverage of the toner image supplied from the second area to the developer carrier. Determine the rotation time of the forming part,
The developing device according to claim 9 or 10. A toner concentration detecting section for detecting the toner concentration of the developer in the first region and the second region,
The control unit determines a rotation direction of the path forming unit according to the toner concentration detected by the toner concentration detection unit,
The developing device according to any one of claims 8 to 11. The control unit determines a rotation speed of the path forming unit according to the toner concentration detected by the toner concentration detection unit,
The developing device according to claim 12. The control unit determines a rotation time of the path forming unit according to the toner concentration detected by the toner concentration detecting unit,
The developing device according to claim 12 or 13. A developer carrying member carrying a developer,
A developer housing which contains the developer supplied to the developer carrier and has a first region on one side and a second region on the other side in the axial direction of the developer carrier,
Of the first area and the second area, the developer in the area having the higher developer bulk density moves to the area having the lower developer bulk density, and the developer bulk density is A path forming portion that forms a second path in which the developer in the lower area moves to the area in which the developer bulk density is high;
A control unit that controls the path forming unit to form the first path and the second path according to the developer bulk density of the first area and the second area;
An image forming apparatus including.

Images