JP2019158951A - Image formation device - Google Patents

Abstract

To provide an image formation device capable of efficiently discharging a toner inside a development apparatus.SOLUTION: An image formation device comprises: an image carrier body in which an image formation area and a non-image formation area different from the image formation area are set; a plurality of development sections which supply toners of respective colors to the image formation area at the time of printing, and discharge the toners to the non-image formation device; and a control section which performs control, within the range of an allowable discharge amount representing the total amount of the toners of respective colors allowed to be discharged from the development sections to the non-image formation area, so as to discharge a toner of a color at a lower printing rate of an image among the toners of respective colors supplied to the image formation area prior to a toner of a color at a higher printing rate from the development sections to the non-image formation area.SELECTED DRAWING: Figure 3

Description

  The present invention relates to an image forming apparatus.

  In general, an image forming apparatus using an electrophotographic process technology forms an electrostatic latent image by irradiating a charged photoconductor with laser light based on image data. Then, by supplying toner from the developing device to the photoconductor 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 to the paper, it is fixed by heating and pressurizing to form an image on the paper.

  In such an image forming apparatus, when image formation with low coverage (low printing rate) is continuously performed, the toner inside the developing device is not consumed, but is deteriorated due to mechanical stress due to circulation. To do. In order to prevent this, in the non-image forming area of the photoconductor (the area between the image forming areas where the toner image to be transferred onto one sheet is formed, generally referred to as “inter-paper”). There has been proposed a method for efficiently discharging toner inside the developing device by periodically forming refresh patches (RFP) (see, for example, Patent Document 1).

  FIG. 1A is a diagram illustrating an RFP of each color formed between sheets in a conventional image forming apparatus. FIG. 1A shows RFPs of Y (yellow), M (magenta), C (cyan), and K (black) colors that have been subjected to different hatching. In the image forming apparatus shown in FIG. 1A, the amount of toner discharged between each color of toner discharged as RFP between paper when white solid paper is passed is 5% when represented by coverage. In addition, the inter-paper discharge amount of the toner for the four colors is 20% (= 5% × 4).

JP 2009-25614 A

  By the way, the printing speed of the image forming apparatus is increasing year by year. In order to increase the printing speed, it is necessary to increase the speed of the developing device, the photosensitive unit, and the like, and it is also necessary to shorten the interval between sheets.

  FIG. 1B is a diagram illustrating RFPs of the respective colors formed between sheets in the image forming apparatus that has been speeded up. In the image forming apparatus shown in FIG. 1B, when the white solid is passed, the toner discharge amount of each color discharged as RFP between the papers is 2.25% when represented by coverage. Further, the discharge amount between the four colors of toner is 9% (= 2.25% × 4).

  As shown in FIG. 1A and FIG. 1B, when the interval between sheets is shortened by increasing the speed of the image forming apparatus, the region for forming the RFP becomes narrower. For this reason, for example, the discharge amount between the papers of the respective color toners shown in FIG. 1A is reduced from 5% to 2.25%. Thus, the conventional image forming apparatus can efficiently discharge the toner, but there is a problem that the image forming apparatus at high speed may not be able to discharge the toner.

  An object of the present invention is to provide an image forming apparatus capable of efficiently discharging toner inside a developing device.

In order to achieve the above object, an image forming apparatus according to the present invention includes:
An image carrier on which an image forming area and a non-image forming area different from the image forming area are set;
A plurality of developing units that respectively store toner of each color, supply the toner of each color to the image forming area during printing, and discharge the toner to the non-image forming area;
Among the toners of the respective colors supplied to the image forming area, the image is within the allowable discharge amount range indicating the total discharge amount of the respective color toners allowed to be discharged from the developing unit to the non-image forming area. A control unit that performs control to discharge toner having a low printing rate from the developing unit to the non-image forming region in preference to the toner having a high printing rate;
Is provided.

  According to the present invention, the toner inside the developing device can be efficiently discharged.

The figure which shows RFP of each color formed between the paper in the conventional image forming apparatus. The figure which shows RFP of each color formed between the papers in the image forming apparatus accelerated. 1 schematically shows an overall configuration of an image forming apparatus according to an embodiment of the present invention. 1 is a diagram illustrating a main part of a control system of an image forming apparatus according to an embodiment of the present invention. The figure which shows an example of the toner of each color discharged | emitted as RFP between paper, the discharge amount of toner between paper, etc. The figure which shows other examples, such as the toner of each color discharged | emitted as RFP between paper, and the discharge amount of toner between paper 7 is a flowchart showing toner discharge processing in the image forming apparatus according to the embodiment of the present invention. The figure which shows the evaluation with respect to the charge amount of the toner of each color when passing a predetermined sheet with a predetermined coverage Diagram showing the average charge amount of yellow toner that changes according to the number of prints

  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 the embodiment of the present invention. FIG. 3 is a diagram illustrating a main part of a control system of the image forming apparatus 1 according to the present embodiment. An image forming apparatus 1 shown in FIGS. 2 and 3 is an intermediate transfer type color image forming apparatus using an electrophotographic process technology. That is, the image forming apparatus 1 primarily transfers the Y (yellow), M (magenta), C (cyan), and K (black) toner images formed on the photosensitive drum 413 to the intermediate transfer belt 421. After the toner images of four colors are superimposed on the intermediate transfer belt 421, an image is formed by secondary transfer onto the paper S (recording medium).

  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 respective color toner images are sequentially transferred to the intermediate transfer belt 421 in one step. Tandem system is adopted.

  As shown in FIG. 3, 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 paper transport 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 a program corresponding to the processing content from the ROM 102 and develops it in the RAM 103, and centrally controls the operation of each block of the image forming apparatus 1 in cooperation with the developed program. At this time, various data stored in the storage unit 72 is referred to. The storage unit 72 includes, for example, a nonvolatile semiconductor memory (so-called flash memory) or a hard disk drive.

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

  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 transports the document D placed on the document tray by a transport mechanism and sends it out to the document image scanning device 12. The automatic document feeder 11 can continuously read images (including both sides) of a large number of documents D placed on the document tray all at once.

  The document image scanning device 12 optically scans a document conveyed on the contact glass from the automatic document feeder 11 or a document placed on the contact glass, and reflects light from the document to a CCD (Charge Coupled Device). ) An image is formed on the light receiving surface of the sensor 12a, and an original image is read. The image reading unit 10 generates input image data based on the reading result by the document 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 configured by, for example, a liquid crystal display (LCD) with a touch panel, and functions as a display unit 21 and an operation unit 22. The display unit 21 displays various operation screens, an image status display, an operation status of each function, and the like in accordance with 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 an operation signal 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 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 processes such as color correction and shading correction, a compression process, 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 subjected to these processes.

  The image forming unit 40 is based on the input image data, and image forming units 41Y, 41M, 41C, 41K, and an intermediate transfer unit 42 for forming an image using colored toners of Y component, M component, C component, and K component. Etc.

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

  The image forming unit 41 includes an exposure device 411, a developing device 412 (corresponding to the “developing unit” of the present invention), a photosensitive drum 413 (corresponding to the “image carrier” of the present invention), a charging device 414, and a drum cleaning device. 415 and the like.

  The photosensitive drum 413 has an undercoat layer (UCL) and a charge generation layer (CGL) on the peripheral surface of an aluminum conductive cylinder (aluminum tube) having a drum diameter of 80 mm, for example. It is a negatively charged organic photoconductor (OPC) in which a generation layer (CTL) and a charge transport layer (CTL) are sequentially stacked. The charge generation layer is made of an organic semiconductor in which a charge generation material (for example, phthalocyanine pigment) is dispersed in a resin binder (for example, polycarbonate), and generates a pair of positive charges and negative charges by exposure by the exposure device 411. The charge transport layer consists of a material in which a hole transport material (electron donating nitrogen-containing compound) is dispersed in a resin binder (for example, polycarbonate resin), and transports positive charges generated in the charge generation layer to the surface of the charge transport layer. To do.

  The control unit 100 controls the drive current supplied to a drive motor (not shown) that rotates the photosensitive drum 413 to rotate the photosensitive drum 413 at a constant peripheral speed.

  The charging device 414 uniformly charges the surface of the photoconductive drum 413 to a negative polarity. The exposure device 411 is composed of, for example, a semiconductor laser, and irradiates the photosensitive drum 413 with laser light corresponding to the image of each color component. A positive charge is generated in the charge generation layer of the photosensitive drum 413 and is transported to the surface of the charge transport layer, whereby the surface charge (negative charge) of the photosensitive drum 413 is neutralized. An electrostatic latent image of each color component is formed on the surface of the photosensitive drum 413 due to a potential difference from the surroundings.

  As the charging device 414, a corona discharger that uniformly charges the surface of the photosensitive drum 413 to a negative polarity by corona discharge is used. The charging device 414 has a charging wire and a shield electrode. The charging wire is disposed along the width direction (longitudinal direction) of the photosensitive drum 413. By supplying a high voltage to the charging wire, a corona discharge is generated between the charging wire and the shield electrode surrounding the charging wire, and the surface of the photosensitive drum 413 arranged to face the shield electrode is made uniform. To charge.

  The developing device 412 is a two-component developing type developing device, and attaches toner of each color component to an image forming area on the surface of the photosensitive drum 413 to visualize the electrostatic latent image and form a toner image. Further, the developing device 412 forms an RFP in a non-image forming area on the surface of the photosensitive drum 413. The RFP may be referred to as a refresh patch or a paper patch. Here, the “image forming area” is an area used for forming an image transferred from the photosensitive drum 413 to a transfer material (for example, the intermediate transfer belt 421). In addition, the “non-image forming area” is an area between the image forming areas, and is also referred to as “paper gap”.

  The drum cleaning device 415 includes a drum cleaning blade that is slidably contacted with the surface of the photosensitive drum 413, and removes transfer residual toner remaining on the surface of the photosensitive drum 413 after 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 shape. At least one of the plurality of support rollers 423 is configured by a driving roller, and the other is configured by a driven roller. For example, it is preferable that the roller 423A disposed downstream of the K component primary transfer roller 422 in the belt traveling direction is a drive roller. This makes it easy to keep the belt running speed constant in the primary transfer portion. As the driving roller 423A rotates, the intermediate transfer belt 421 travels in the direction of arrow A at a constant speed.

  The intermediate transfer belt 421 is a belt having conductivity and elasticity, and has a high resistance layer having a volume resistivity of 8 to 11 [log Ω · cm] on the surface. The intermediate transfer belt 421 is rotationally driven by a control signal from the control unit 100. Note that the material, thickness, and hardness of the intermediate transfer belt 421 are not limited as long as they have conductivity and elasticity.

  Specifically, the intermediate transfer belt 421 has a laminated structure including a base material layer and a surface layer. The base material layer is made of a synthetic resin in which a conductive material or the like is dispersed. The base material layer may have a single layer structure or a multi-layer structure of two or more layers.

  The primary transfer roller 422 is disposed on the inner peripheral surface side of the intermediate transfer belt 421 so as to face the photosensitive drum 413 of each color component. The primary transfer roller 422 is pressed against the photosensitive drum 413 with the intermediate transfer belt 421 interposed therebetween, thereby forming a primary transfer nip for transferring a toner image from the photosensitive drum 413 to the intermediate transfer belt 421.

  The secondary transfer roller 424 is disposed on the outer peripheral surface side of the intermediate transfer belt 421 so as to face the backup roller 423B disposed on the downstream side in the belt traveling direction of the drive roller 423A. The secondary transfer roller 424 is pressed against the backup roller 423B with the intermediate transfer belt 421 interposed therebetween, thereby forming a secondary transfer nip for transferring the toner image from the intermediate transfer belt 421 to the paper S. A secondary transfer belt is looped around a plurality of support rollers including the secondary transfer roller 424.

  When the intermediate transfer belt 421 passes through the primary transfer nip, the toner images on the photoconductive drum 413 are primarily transferred onto the intermediate transfer belt 421 in sequence. Specifically, a primary transfer bias is applied to the primary transfer roller 422, and an electric charge having a polarity opposite to that of the toner is applied to the back side of the intermediate transfer belt 421 (the side in contact with the primary transfer roller 422). It is electrostatically transferred to the intermediate transfer belt 421.

  Thereafter, 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 toner image is applied by applying a secondary transfer bias to the secondary transfer roller 424 and applying a charge having a polarity opposite to that of the toner to the back side of the paper S (the side in contact with the secondary transfer roller 424). Is electrostatically transferred to the paper S. The sheet S to which the toner image is transferred is conveyed toward the fixing unit 60.

  The belt cleaning device 426 includes a belt cleaning blade that is in sliding contact with the surface of the intermediate transfer belt 421 and removes transfer residual toner remaining on the surface of the intermediate transfer belt 421 after the secondary transfer.

  The fixing unit 60 includes a fixing belt 61, a heating roller 62, an upper pressure roller 63 disposed on the fixing surface (surface on which the toner image is formed) of the paper S, and the back surface of the paper S (the surface opposite to the fixing surface). ) Side lower pressure roller 65, heating source 60C and the like. The heating roller 62 includes a heating source 60 </ b> C that heats the fixing belt 61. When the lower pressure roller 65 is brought into pressure contact with the upper pressure roller 63, a fixing nip for nipping and transporting the paper S is formed.

  The fixing unit 60 fixes the toner image on the paper S by heating and pressurizing the paper S on which the toner image is secondarily transferred and conveyed at the fixing nip. The fixing unit 60 is disposed in the fixing device F as a unit.

  The paper transport unit 50 includes a paper feed unit 51, a paper discharge unit 52, a transport path unit 53, and the like. In the three paper feed tray units 51a to 51c constituting the paper feed unit 51, paper S (standard paper, special paper) identified based on basis weight, size, etc. is stored for each preset type. . The conveyance path unit 53 includes a plurality of conveyance roller pairs including a registration roller pair 53a.

  The sheets S stored in the sheet feed tray units 51 a to 51 c are sent one by one from the top and are conveyed to the image forming unit 40 by the conveyance path unit 53. At this time, the registration roller portion provided with the registration roller pair 53a corrects the inclination of the fed paper S and adjusts the conveyance timing. In the image forming unit 40, the toner image on the intermediate transfer belt 421 is secondarily transferred onto one side of the sheet S at a time, and a fixing process is performed in the fixing unit 60. The sheet S on which the image has been formed is discharged out of the apparatus by a discharge unit 52 having a discharge roller 52a.

  By the way, in the image forming apparatus 1, toner is discharged as RFP from the developing device 412 between the sheets of the photosensitive drum 413 (non-image forming area). Thus, even when image formation with a low coverage (low printing rate) is continuously performed, the toner inside the developing device 412 can be discharged, so that the toner inside the developing device 412 is subjected to mechanical stress due to circulation. It is prevented from receiving.

  In recent years, as one of measures for increasing the speed of the image forming apparatus 1, shortening the interval between sheets has been performed. However, since the amount of toner discharged as RFP between papers decreases by shortening the paper interval, it is difficult to efficiently discharge the toner inside the developing device 412.

  In the present embodiment, the control unit 100 allows an allowable discharge amount Vt (see FIG. 4) indicating the total discharge amount of toner of each color that is allowed to be discharged from the developing device 412 between the sheets of the photosensitive drum 413. In the range of), control is performed so that toner of a color with a low image printing rate out of toners of each color supplied to the image forming area is discharged from the developing device 412 to the sheet with priority over toner with a color with a high printing rate. I do. Here, “the toner having a color with a low image printing rate is discharged from the developing device 412 between papers in preference to the toner with a color having a high printing rate” is not necessarily a printing rate discharged between papers. The inter-paper discharge amount Vf of low-color toner (corresponding to the “non-image forming region discharge amount” of the present invention, see FIG. 4) does not mean that the inter-paper discharge amount Vf of high-color toner is high. .

  With respect to the toner carry-over amount Vc (see FIG. 4) that has been carried forward without being discharged between papers at the time of the previous paper discharge, the color toner carry-over amount Vc with a high print rate is carried over to the color toner with a low print rate. When the amount is larger than the amount Vc, the inter-paper discharge amount Vf of the toner with a color having a high printing rate may be larger than the inter-paper discharge amount Vf of the toner with a color having a low printing rate.

  It should be noted that in the current toner discharge amount Vb (see FIG. 4) that is required to be discharged between papers in this paper discharge, the required discharge amount Vb of the color toner having a low print rate is the print rate. Is larger than the required discharge amount Vb of the high color toner. The required discharge amount Vb is a quantity obtained by subtracting the on-paper consumption amount Va (corresponding to the “image forming area consumption amount” of the present invention, see FIG. 4) from a predetermined fixed discharge amount. The on-paper consumption Va is the quantity of toner supplied on the paper and is a quantity corresponding to the printing rate. Therefore, the on-paper consumption amount Va of the toner having a low printing rate is smaller than the on-paper consumption amount Va of the toner having a high printing rate. The required discharge amount Vb of the toner with a low printing rate is larger than the required discharge amount Vb of the toner with a high printing rate by a small amount. That is, in the required discharge amount Vb, the toner with a color with a low printing rate is preferentially increased over the toner with a high printing rate. “Preferentially” has the above meaning.

  Specifically, the control unit 100 determines the allowable discharge amount Vt indicating the total discharge amount of the toner of each color, and the discharge amount of the toner of each color discharged from the developing device 412 to the space between the sheets of the photosensitive drum 413. Based on the ratio of Vf, control is performed to discharge toner as RFP from the developing device 412 to the space between the sheets of the photosensitive drum 413.

  The control unit 100 functions as a calculation unit that calculates the ratio of the inter-sheet discharge amount Vf of the toner of each color based on the planned discharge amount Vd (see FIG. 4) of the toner that is scheduled to be discharged between the sheets. have. Hereinafter, the calculation unit will be described as the control unit 100.

  Next, a specific example of calculating the ratio of the inter-sheet discharge amount Vf of toner will be described with reference to FIG. FIG. 4 is a diagram illustrating an example of toner discharged as an RFP between paper sheets, a toner paper discharge amount Vf, and the like. FIG. 4 shows Y (yellow), M (magenta), C (cyan), and K (black) toners discharged as RPF between sheets. Further, FIG. 4 shows the inter-paper discharge amount Vf, the carry-over amount Vc, the fixed discharge amount, the required discharge amount Vb, the on-paper consumption Va, the planned discharge amount Vd, the allowable discharge amount Vt, and the allowable individual discharge amount. Vi is represented by coverage (%), respectively.

  In the present embodiment, the carry-over amount Vc refers to the amount of toner of each color that has been carried forward without being discharged between papers at the time of previous paper discharge. Further, the fixed discharge amount is the amount of toner that is planned to be fixedly discharged between papers each time paper is discharged. Here, the fixed discharge amount is, for example, 5%. The on-paper consumption amount Va is the amount of toner of each color supplied to the image forming area before the current paper discharge.

  The required discharge amount Vb refers to the amount of toner of each color that is required to be discharged between papers during the current paper discharge. Specifically, the control unit 100 calculates the necessary discharge amount Vb by subtracting the on-paper consumption amount Va from the fixed discharge amount (5%). The reason for calculating the required discharge amount Vb in consideration of the on-paper consumption amount Va is that more toner can be discharged by the amount of the on-paper consumption amount Va than when there is no on-paper consumption amount Va. This is because even if the on-paper consumption amount Va is subtracted from the required discharge amount Vb, the toner discharge efficiency is not lowered. Further, the control unit 100 calculates the scheduled discharge amount Vd based on the carry-over amount Vc and the necessary discharge amount Vb. In the present embodiment, the planned discharge amount Vd is a total amount of the carry-over amount Vc and the required discharge amount Vb. Further, the allowable discharge amount Vt is, for example, 9%. The allowable individual discharge amount Vi is the discharge amount of toner for each color that is allowed to be discharged from the developing device 412 to between the sheets, and is 5% here. Accordingly, the control unit 100 limits the inter-sheet discharge amount Vf to be equal to or less than the allowable individual discharge amount Vi (= 5%).

  Next, the current (first) toner discharge between sheets shown in FIG. 4 will be described. Each color toner carry-over amount Vc is 0%. The consumption amount Va of each color toner on the paper is 0%. The required discharge amount Vb of each color toner obtained by subtracting the on-paper consumption amount Va (= 0%) from the fixed discharge amount (5%) is 5% (= 5% -0%).

  The controller 100 adds the carry-over amount Vc (= 0%) and the required discharge amount Vb (= 5%) when the on-paper consumption amount Va of each color toner is equal to or less than a predetermined amount (5%). Then, the estimated discharge amount Vd (= 5%) of each color toner is obtained. The control unit 100 calculates the ratio of the inter-sheet discharge amount Vf of the toner of each color based on the planned discharge amount Vd (5%, 5%, 5%, 5%) of YMCK toner. The ratio of the inter-sheet discharge amount Vf of the toner of each color is (5: 5: 5: 5). The control unit 100 performs control to discharge the toner of each color into the space based on the ratio of the discharge amount Vf of the toner of each color and the allowable discharge amount Vt (= 9%). The inter-paper discharge amount Vf of each color toner is 2.25% (= 9% * (5/20)).

  Next, the current (second) toner discharge between sheets shown in FIG. 4 will be described. The carry-over amount Vc of the toner of each color is 2.75% (= 5% -2.25%). The on-paper consumption Va of toner of Y (yellow), M (magenta), C (cyan), and K (black) is 0%, 0%, 3%, and 5%, and all are 5% or less. . The required discharge amount Vb of YMCK toner is 5% (= 5% -0%), 5% (= 5% -0%), 2% (= 5% -3%), 0% (= 5%- 5%).

  When the on-paper consumption amount Va of the toner of each color is equal to or less than a predetermined amount (5%), the control unit 100 adds the carry-over amount Vc and the necessary discharge amount Vb to obtain the planned discharge amount Vd of the toner of each color. Ask. According to the above calculation result, the expected discharge amount Vd of YMCK toner is 7.75% (= 2.75% + 5%), 7.75% (= 2.75% + 5%), 4.75%. (= 2.75% + 2%) and 2.75% (= 2.75% + 0%). The control unit 100 determines the ratio of the inter-sheet discharge amount Vf of each color toner based on the planned discharge amount Vd (7.75%, 7.75%, 4.75%, 2.75%) of YMCK toner. calculate. The ratio of the inter-paper discharge amount Vf of the toner of each color is (7.75: 7.75: 4.75: 2.75). The control unit 100 performs control to discharge the toner of each color into the space based on the ratio of the paper discharge amount Vf and the allowable discharge amount Vt (= 9%). YMCK inter-sheet discharge amount Vf is 3.03% (≈9% * (7.75 / 23)), 3.03% (≈9% * (7.75% / 23)), 1.86% (≈9% * (4.75% / 23)), 1.08% (≈9% * (2.75% / 23)).

  Next, the current (third) toner discharge between sheets shown in FIG. 4 will be described. YCCK toner carry-over amount Vc is 4.72% (= 7.75% -3.03%), 4.72% (= 7.75% -3.03%), 2.89% (= 4). .75% -1.86%) and 1.67% (= 2.75% -1.08%). The consumption amount Va of YMCK toner on paper is 8%, 2%, 2%, and 2%. When the on-paper consumption amount Va exceeds a predetermined amount (5%), the amount exceeding 5% is referred to as surplus on-paper consumption amount Ve. Here, the consumption amount Ve on surplus paper is 3% (= 8% -5%). The required discharge amount Vb of YMCK toner is 0% (= 5% -5%), 3% (= 5% -2%), 3% (= 5% -2%), 3% (= 5%- 2%).

  When the on-paper consumption amount Va of the toner of each color is equal to or less than a predetermined amount (5%), the control unit 100 adds the carry-over amount Vc and the necessary discharge amount Vb to obtain the planned discharge amount Vd of the toner of each color. Ask. When the on-paper consumption amount Va of the toner of each color exceeds a predetermined amount (5%) (when there is an excess paper consumption amount Ve), the control unit 100 uses the estimated discharge amount Vd of the toner of each color to the excess paper consumption amount. Subtract Ve. The reason for subtracting the surplus paper consumption amount Ve from the planned discharge amount Vd is that more toner is discharged by the surplus paper consumption amount Ve, so even if the surplus paper consumption amount Ve is subtracted from the planned discharge amount Vd. This is because the toner discharge is not hindered.

  According to the above calculation results, the expected discharge amount Vd of YMCK toner is 1.72% (= 4.72 + 0% -3%), 7.72% (= 4.72% + 3%), 5.89. % (= 2.89% + 3%), 4.67% (= 1.67% + 3%). The control unit 100 determines the ratio of the inter-sheet discharge amount Vf of the toner of each color based on the planned discharge amount Vd (1.72%, 7.72%, 5.89%, 4.67%) of the toner of each color. calculate. The ratio of the inter-sheet discharge amount Vf of the toner of each color is (1.72: 7.72: 5.89: 4.67). The control unit 100 performs control to discharge the toner of each color into the space based on the ratio of the discharge amount Vf of the toner of each color and the allowable discharge amount Vt (= 9%). The YMCK inter-sheet discharge amount Vf is 0.77% (≈9% * (1.72 / 20)), 3.47% (≈9% * (7.72 / 20)), 2.65% ( ≈9% * (5.89 / 20)) and 2.10% (≈9% * (4.67 / 20)).

  Next, another specific example of calculating the ratio of the inter-sheet discharge amount Vf of toner will be described with reference to FIG. FIG. 5 is a diagram illustrating another example of toner discharged as an RFP between paper sheets and the amount of toner discharged between paper sheets Vf. In the specific example shown in FIG. 4, the control unit 100 calculates the ratio of the inter-paper discharge amount Vf of the toner of each color based on the planned discharge amount Vd of the toner that is expected to be discharged between the papers.

  On the other hand, in the specific example shown in FIG. 5, the control unit 100 further sets a predetermined upper limit value (for example, 5%) on the paper consumption amount Va of any color toner based on the scheduled discharge amount Vd. In the above case, the ratio of the inter-sheet discharge amount Vf in the toners of other colors excluding the color exceeding the upper limit value is calculated. The reason why the toner of the color exceeding the upper limit value is not discharged between the papers is that the toner of a certain color is consumed in a large amount as the consumption amount Va on the paper and the toner of the same color is discharged as the discharge amount Vf between the papers. Therefore, the print rate set by the user and the actual toner consumption amount deviate from each other. This may give the user an impression that the printer consumes excessive toner. This is to avoid such a situation.

  Next, the current (second time) toner discharge between sheets shown in FIG. 5 will be described. The expected discharge amounts Vd of toners of Y (yellow, M (magenta), C (cyan), and K (black) are 7.75%, 7.75%, 7.75%, and 2.75%. When the on-paper consumption amount Va of the previous K toner is 5%, the unit 100 calculates the ratio of the inter-paper discharge amount Vf of YMC toner, which is the other color except K. According to the calculation result, YMCK. The ratio of the inter-sheet discharge amount Vf of the toner is (7.75: 7.75: 7.75: 0) The ratio of the inter-sheet discharge amount Vf of the toner of each color and the allowable discharge amount Based on Vt (= 9%), control is performed to discharge the toner of each color between the sheets, and the YMCK toner discharge amount Vf is 3% (= 9% * (7.75 / 23.25), respectively. )) 3%, 3%, 0%.

  Next, the current (third) toner discharge between sheets shown in FIG. 5 will be described. The expected discharge amount Vd of the YMCK toner is 9.75%, 9.75%, 4.75%, 4.75%. When the on-paper consumption amount Va of the previous C toner is 5%, the control unit 100 calculates a ratio of the inter-paper discharge amount Vf of Y, M, and K toners other than C. According to the calculation result, the ratio of the YMCK toner sheet discharge amount Vf is 9.75: 9.75: 0: 4.75). The control unit 100 performs control to discharge the toner of each color into the space based on the ratio of the discharge amount Vf of the toner of each color and the allowable discharge amount Vt (= 9%). The discharge amount Vf between YMCK toners is 3.62% (≈9% * (9.75 / 24.25)), 3.62%, 0% (≈9% * (0 / 24.25) ) 1.76% (≈9% * (4.75 / 24.25)).

  When the printing operation is interrupted, the control unit 100 performs control to discharge the accumulation amount Vg obtained by subtracting the inter-sheet discharge amount Vf from the scheduled discharge amount Vd. Here, the interruption of the printing operation is, for example, in the case of job end, in the case where image stabilization control is performed to detect the density of a patch image output on paper in order for the image forming apparatus 1 to adjust the image density. The case where the post-processing machine connected to the downstream side of the apparatus 1 is interrupted. This is because the discharge of the accumulated amount Vg when the printing operation is interrupted does not give the user an impression of a decrease in the printing speed compared to the case where the printing operation is forcibly interrupted in order to discharge the accumulated amount Vg. .

  In addition, when the accumulation amount Vg exceeds a predetermined quantity, the control unit 100 performs control to forcibly discharge the toner having the accumulation amount Vg. Thereby, deterioration of the toner in the developing device 412 can be prevented. The predetermined quantity is determined based on the transfer residual toner recovery capability (cleaning capability) in a unit (here, the belt cleaning device 426) that recovers the toner discharged between the sheets. Note that the collection capacity is determined based on the life of the unit, the service life, the accumulated toner collection time, the accumulated toner collection amount, the accumulated drive time, and the like.

  Next, with reference to FIG. 6, the inter-paper discharge process for toner will be described. FIG. 6 is a flowchart showing the inter-sheet discharge process of toner. This flow is executed for each print job.

  In step S100, the control unit 100 analyzes the output chart at the start of printing, and calculates the consumption amount Va of the toner of each color on the paper.

  In step S110, when the on-paper consumption amount Va is equal to or smaller than a predetermined amount, the control unit 100 subtracts the on-paper consumption amount Va from a predetermined fixed discharge amount, thereby obtaining the required discharge amount Vb of each color toner. calculate. Note that when the on-paper consumption amount Va exceeds a predetermined amount, the control unit 100 subtracts a predetermined amount from a predetermined fixed discharge amount, so that the required discharge amount Vb of each color toner is obtained. Is calculated.

  In step S120, the control unit 100 calculates a carry-over amount Vc of toner of each color that could not be discharged by the previous print.

  In step S130, the control unit 100 calculates the planned toner discharge amount Vd for each color by adding the necessary discharge amount Vb and the carry-over amount Vc for each color toner.

  In step S140, the control unit 100 determines whether the on-paper consumption amount Va exceeds a predetermined quantity (5%). When the on-paper consumption amount Va exceeds the predetermined amount (step S140: YES), the process proceeds to step S150. If the on-paper consumption amount Va does not exceed the predetermined quantity (step S140: NO), the process proceeds to step S160.

  In step S150, the control unit 100 subtracts the surplus paper consumption amount Ve (= Va-5%) from the planned discharge amount Vd.

  In step S160, the control unit 100 calculates a ratio of the inter-sheet discharge amount Vf of the toner of each color based on the planned discharge amount Vd of the toner of each color. Further, the control unit 100 calculates the inter-paper discharge amount Vf based on the ratio of the inter-paper discharge amount Vf.

  In step S170, the control unit 100 calculates an accumulation amount Vg obtained by subtracting the inter-sheet discharge amount Vf from the planned discharge amount Vd.

  In step S180, the control unit 100 determines whether the printing operation is interrupted. If the printing operation is interrupted (step S180: YES), the process proceeds to step S190. If the print operation is not interrupted (step S180: NO), the process proceeds to step S200.

  In step S190, the control unit 100 performs control to discharge the accumulation amount Vg.

  In step S200, the control unit 100 determines whether or not the accumulated amount Vg exceeds a predetermined quantity (X%). When the accumulation amount Vg exceeds the predetermined amount (step S200: YES), the process proceeds to step S210. When the accumulation amount Vg does not exceed the predetermined amount (step S200: NO), the process proceeds to step S220.

  In step S210, the control unit 100 performs control to interrupt printing and discharge the accumulated amount Vg.

  In step S220, the control unit 100 carries the accumulated amount Vg over to the next print.

  According to the image forming apparatus 1 in the above-described embodiment, the control unit 100 includes the allowable discharge amount Vt that indicates the total discharge amount of each color toner that is allowed to be discharged from the developing device 412 to between the sheets, and Based on the ratio of the inter-sheet discharge amount Vf of the toner of each color discharged from the developing device 412 to the interval between the sheets, control is performed to discharge the toner of each color from the developing device 412 to the interval between the sheets. As a result, even when the sheet interval is shortened as the image forming apparatus 1 increases in speed, the toner may be consumed based on the ratio of the sheet discharge amount Vf under the limit of the allowable discharge amount Vt. Therefore, it is possible to efficiently discharge the toner of each color. As a result, a fresh developer state can be maintained, and an image with stable quality can be supplied.

  Further, the control unit 100 calculates the ratio of the inter-sheet discharge amount Vf of the toner of each color based on the planned discharge amount Vd of the toner that is scheduled to be discharged between the sheets. Thereby, the toner of each color can be consumed evenly.

  Further, based on the scheduled discharge amount Vd, the control unit 100 further selects a color greater than or equal to the upper limit value when the on-paper consumption amount Va of any color toner is greater than or equal to a predetermined upper limit value (for example, 5%). The ratio of the inter-sheet discharge amount Vf for the toners of other colors except the above is calculated. As a result, when the on-paper consumption amount Va of a certain color toner becomes relatively large, the toner of that color may be consumed in large quantities by not adding the inter-paper discharge amount Vf of that color toner. Is prevented. For this reason, it is possible to avoid giving the user an impression that the printer consumes excessive toner.

Next, an embodiment will be described with reference to FIGS.
FIG. 7 is a diagram showing an evaluation of the charge amount of each color toner when a predetermined sheet is passed with a predetermined coverage. As an actual machine, Bizhub (registered trademark) manufactured by Konica Minolta Business Technologies was used. The actual machine used was shorter than the conventional machine.

  In the embodiment, the ratio of the inter-paper discharge amount of the toner of each color is calculated based on the planned discharge amount of the toner of each color, and the control is performed to discharge the toner to the inter-paper based on the calculated inter-paper discharge amount. The coverage of Y (yellow), M (magenta), C (cyan), and K (black) was 0.5%, 1%, 1%, and 1%. The charge amount of each color toner when 50,000 sheets were passed was measured. The charge amount of each color toner was evaluated.

  As a result of the evaluation, the charge amount of Y with low coverage was within the practically usable range, like the charge amounts of the M, C, and K toners. As a result, it was possible to suppress the deterioration of Y toner having low coverage.

  In the comparative example, the ratio of the discharge amount between the toners of the respective colors was made the same, and control was performed to discharge the toner to the interval between the papers based on the discharge amount between the papers. YMCK coverage was 0.5%, 1%, 1%, 1%. The charge amount of each color toner when 50,000 sheets were passed was measured. The charge amount of each color toner was evaluated.

  As a result of the evaluation, the charge amounts of the M, C, and K toners were within the actual usable range, but the charge amount [μC / g] of the Y toner with low coverage was 30, which was out of the allowable range. It became unusable.

  FIG. 8 is a diagram illustrating the average charge amount of Y (yellow) toner that changes according to the number of prints (number of sheets to be passed) in the above-described examples and comparative examples.

  In Examples, the average charge amount [μC / g] of Y toner when printing 0 sheet, 10000 sheet, 20000 sheet, 30000 sheet, 40000 sheet, and 50000 sheet is 43, 41, 39, 38, respectively. 37.5 and 37. The drop in the average charge amount of Y toner with low coverage was gradual. As a result, the deterioration rate of the Y toner could be lowered.

  In the comparative example, the average charge amount [μC / g] of Y (yellow) toner when printing 0 sheet, 10000 sheet, 20000 sheet, 30000 sheet, 40000 sheet, and 50000 sheet is 42, 40, and 36, respectively. , 35, 33, 30. The drop in the average charge amount of Y toner with low coverage was remarkable. As a result, the deterioration rate of the Y toner could not be lowered.

  In addition, each of the above-described embodiments is merely an example of a specific example for carrying out the present invention, and the technical scope of the present invention should not be construed as being limited thereto. That is, the present invention can be implemented in various forms without departing from the gist or the main features thereof.

Va Consumption amount on paper Vb Required discharge amount Vc Carry-over amount Vd Expected discharge amount Vf Discharge amount between papers Vi Allowable individual discharge amount Vt Allowable discharge amount 1 Image forming apparatus 100 Control unit

Claims (12)

An image carrier on which an image forming area and a non-image forming area different from the image forming area are set;
A plurality of developing units that respectively store toner of each color, supply the toner of each color to the image forming area during printing, and discharge the toner to the non-image forming area;
Among the toners of the respective colors supplied to the image forming area, the image is within the allowable discharge amount range indicating the total discharge amount of the respective color toners allowed to be discharged from the developing unit to the non-image forming area. A control unit that performs control to discharge toner having a low printing rate from the developing unit to the non-image forming region in preference to the toner having a high printing rate;
An image forming apparatus. The control unit calculates a ratio of the non-image forming area discharge amount of each color toner discharged from the developing unit to the non-image forming area based on the printing rate of each color toner, and calculates the calculated non-image formation Performing control to discharge the toner of the allowable discharge amount allocated based on the ratio of the region discharge amount from the developing unit to the non-image forming region;
The image forming apparatus according to claim 1. The control unit further removes toner from the developing unit based on an allowable individual discharge amount indicating a discharge amount of toner for each color that is allowed to be discharged from the developing unit to the non-image forming area. Control to eject to the image forming area,
The image forming apparatus according to claim 1. A calculating unit that calculates a ratio of a non-image forming area discharge amount of the toner of each color based on a planned discharge amount of toner that is scheduled to be discharged to the non-image forming area;
The image forming apparatus according to claim 1. The scheduled discharge amount includes a carry-over amount of toner of each color that has been carried forward without being discharged to the non-image formation region when toner was discharged to the previous non-image formation region.
The image forming apparatus according to claim 4. The scheduled discharge amount includes a required discharge amount of each color toner that is required to be discharged to the non-image forming area when discharging toner to the non-image forming area this time.
The image forming apparatus according to claim 4 or 5. When the consumption amount of the image forming area of the toner of at least one color of each color supplied to the image forming area exceeds a predetermined quantity, the calculation unit is configured to discharge the toner of the color exceeding the quantity. Subtract the excess quantity from
The image forming apparatus according to claim 4. When the consumption amount of the image forming area of any color toner supplied to the image forming area exceeds a predetermined upper limit value, the calculation unit determines the toner of other colors excluding the color exceeding the upper limit value. Calculating the ratio of the non-image forming area discharge amount in
The image forming apparatus according to claim 4. The control unit performs control to discharge an accumulated amount of toner indicating a quantity obtained by subtracting the non-image forming region discharge amount from the scheduled discharge amount when the image forming operation is interrupted.
The image forming apparatus according to claim 4. The control unit performs control for discharging the accumulated amount of toner when an accumulated amount indicating a quantity obtained by subtracting the non-image forming area discharged amount from the scheduled discharged amount exceeds a predetermined amount;
The image forming apparatus according to claim 4. The predetermined quantity is set based on a toner collecting capability in the unit that collects the discharged toner.
The image forming apparatus according to claim 10. The required discharge amount is the consumption amount of the image forming area of the toner supplied to the image forming area from the fixed discharge amount of the toner fixedly discharged to the non-image forming area each time the non-image forming area is discharged. The subtracted quantity,
The image forming apparatus according to claim 6.

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