JP6361285B2 - Image forming apparatus - Google Patents

Description

  The present invention relates to an image forming apparatus, and more particularly to estimation of the amount of toner consumed by an electrophotographic image forming apparatus.

  An electrophotographic image forming apparatus generally has a function of estimating toner consumption from image data. The purpose of this function is mainly to display the remaining amount of toner or the toner cartridge replacement request on the operation panel or the like, or automatically the amount of toner to be replenished from the toner cartridge to the developing unit or the timing of replenishment thereof. It is to decide.

  The toner consumption is estimated from the image data as follows. (For example, refer to Patent Documents 1 and 2.) First, gradation values of pixels included in one region on the sheet are read from the image data. Since the toner amount to be attached to one pixel is determined by the gradation value of the pixel, the total amount of toner consumed by the attachment to the entire area is estimated from the read gradation value.

  The functional relationship between the gradation value and the toner consumption depends on various conditions. For example, in the techniques disclosed in Patent Documents 2 and 3, it is considered that toner adheres more easily to the edge of the toner image than other parts, and the above functional relationship is corrected according to the number of pixels belonging to the edge. Is done.

JP 2009-282947 A JP 2003-122205 A JP 2013-020076 A

  In recent years, with the improvement of offset printing technology, printing designs that can be handled by image forming apparatuses have been diversified. These designs include, for example, one-point or partial color printing, color photographs or partial insertion of computer graphics (CG) images.

  Furthermore, technically, image forming apparatuses that receive FOGRA authentication, Japan Color authentication, or the like are increasing for the purpose of stabilizing print quality. In these devices, the color reproducibility is further enhanced for the purpose of achieving compliance with international standards required by the certification system.

  The diversification of design and the improvement of color reproducibility cause a large variation in toner consumption for each sheet. As a result, in the business of leasing an image forming apparatus to an office or the like, there is an increasing number of cases where it is more reasonable to charge the usage fee of the apparatus based on the amount of toner consumed than the number of printed sheets.

  However, in order to realize a charge for the usage fee based on the toner consumption at a practical level, the conventional estimation technique mainly for displaying the remaining amount of toner has insufficient accuracy. In particular, when parameters that affect the image density among the parameters that define the operating conditions of an electrophotographic process (also simply referred to as “process”) are adjusted according to the user's operation, the adjustment is performed in the conventional technology. The change in the functional relationship between the gradation value and the toner consumption accompanying the above is not reflected in the estimation. As a result, it is difficult to improve the accuracy of estimation.

  An object of the present invention is to solve the above-described problems, and in particular, to provide an image forming apparatus capable of improving the estimation accuracy of toner consumption without being hindered by parameter adjustment by a user.

An image forming apparatus according to an aspect of the present invention shows an image forming unit that forms an image with toner on a sheet based on image data, and an average line width when a line drawing portion of the image is drawn with toner. When an image is formed from a receiving unit that receives an index value from a user, an adjustment unit that controls the image forming unit based on the index value to adjust the density of the image, and a tone value of a pixel indicated by the image data Is a functional unit that estimates the amount of toner consumed by the printer, and includes an estimation unit that corrects the relationship between the gradation value and the toner consumption amount according to the index value . The image forming unit is a chargeable member, and an image carrier whose charge amount changes in a portion illuminated with light, and a light of a pattern based on the image data is irradiated to the image carrier to statically adhere to the image carrier. It has an exposure part for forming an electrostatic latent image, a developing part for attaching toner to the electrostatic latent image and converting it into an image, and a transfer part for transferring the image from the image carrier to a sheet . The adjustment unit controls the exposure unit based on the index value to adjust the amount of light that illuminates the image carrier.

The estimation unit may store a plurality of tables representing the relationship between gradation values and toner consumption. The plurality of tables differ from each other according to the index value.
The relationship between the gradation value and the toner consumption amount may differ depending on the toner amount constituting the edge of the image and the toner amount constituting another region of the image. Further, the relationship between the gradation value and the toner consumption amount may vary depending on the resolution of the image.

  The estimation unit may transmit the estimated toner consumption amount to an external charging server. The image forming apparatus may further include a replenishing unit that accumulates the toner consumption estimated by the estimating unit and replenishes the image forming unit with an amount of toner based on the accumulated value.

  In the image forming apparatus according to the above aspect of the present invention, when the value of the parameter affecting the image density is adjusted according to the user's operation, the gradation value and the toner consumption amount according to the index value indicating the degree of the adjustment. To correct the relationship between. Thus, this image forming apparatus improves the estimation accuracy of the toner consumption amount without being hindered by the parameter adjustment by the user.

1 is a schematic front view illustrating a structure of an image forming apparatus according to an embodiment of the present invention. (A) is a cross-sectional view of the image forming unit shown in FIG. 1, and (b) and (c) are a top view and a cross-sectional view, respectively, of a developing unit built in the unit. FIG. 2 is a block diagram illustrating a configuration of an electronic control system of the image forming apparatus illustrated in FIG. 1. FIG. 1 is a schematic diagram showing an input screen for parameters displayed on the operation panel of the image forming apparatus shown in FIG. 1, and a change in control amount according to the values of these parameters gives toner consumption per dot. It is a graph showing an influence. (A) is an input screen for the maximum density of an image, and (b) shows an example of the influence of a change in the developing bias according to the value of the maximum density on the toner consumption per dot. (C) is an input screen for character reproducibility, and (d) shows an example of the influence of the change in the amount of light emitted from the exposure unit according to the degree of reproducibility on the toner consumption per dot. 6 is a graph showing a functional relationship between a gradation value of a pixel and a toner consumption amount in the image forming apparatus. (A) represents the change in the functional relationship according to the index value with respect to the maximum density of the image, and (b) represents the change in the functional relationship according to the index value with respect to the character reproducibility. FIG. 1 shows the correspondence between the toner consumption for each job sent from the image forming apparatus shown in FIG. 1 to the accounting server shown in FIG. 3 and the usage fee determined by the accounting server. It is a table. 2 is a flowchart of processing in which the image forming apparatus shown in FIG. 1 estimates toner consumption from image data in one job. 2 is a flowchart of a process in which the image forming apparatus illustrated in FIG. 1 supplies toner to a developing unit.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
[Outline of structure of image forming apparatus]

FIG. 1 is a schematic front view showing the structure of an image forming apparatus according to an embodiment of the present invention. In FIG. 1, elements inside the image forming apparatus 100 are depicted as if they were seen through the front surface of the housing.
Referring to FIG. 1, an image forming apparatus 100 is a multi-function peripheral (MFP), for example, and includes an image forming unit, an operation unit 50, and a control unit 60. The image forming unit is a part that forms a toner image on a sheet based on image data, and includes a feeding unit 10, an image forming unit 20, a fixing unit 30, and a paper discharge unit 40.

The feeding unit 10 feeds the sheets SHT one by one to the image forming unit 20. The image forming unit 20 forms a toner image on the sheet SH2 sent from the feeding unit 10. The fixing unit 30 thermally fixes the toner image. The paper discharge unit 40 stacks the sheet SH3 on which the toner image is fixed on the paper discharge tray 44. The operation unit 50 receives a print request (hereinafter referred to as a job) and image data to be printed through a user operation or communication with an external electronic device, and transmits them to the control unit 60. The control unit 60 is an electronic circuit mounted on a single substrate, and controls the operation of other elements in the image forming apparatus 100 based on information from the operation unit 50.
[Feeding department]

Referring to FIG. 1, the feeding unit 10 includes a storage tray 11, a feed roller 12, a transport roller 13, and a timing roller 14. The storage tray 11 is built in the lower part of the image forming apparatus 100 and can store a plurality of sheets SHT. The material of the sheet SHT is paper or resin, and the size is A3, A4, A5, B4, or the like. The feeding roller 12 feeds the uppermost sheet SH1 among the sheets SHT in the storage tray 11 toward the transport roller 13. The sheet SH <b> 1 is further conveyed to the timing roller 14 by the conveyance roller 13. The timing roller 14 is generally stopped at the start of the conveyance, and starts rotating in response to a drive signal from the control unit 60. Thereby, the sheet SH2 sent from the transport roller 13 is sent out from the timing roller 14 to the image forming unit 20 at the timing indicated by the drive signal.
[Image creation part]

  Referring to FIG. 1, the image forming unit 20 includes four image forming units (also referred to as process units) 21Y, 21M, 21C, 21K, four primary transfer rollers 22Y, 22M, 22C, 22K, and an intermediate transfer belt. 23, a secondary transfer roller 24, and an exposure unit 25. The image forming units 21Y,..., 21K are arranged at predetermined intervals along the horizontal direction. The primary transfer rollers 22Y,..., 22K are arranged so as to face one of the image forming units 21Y,. The intermediate transfer belt 23 is stretched around the two rollers 23L and 23R, and rotates with the rotation thereof. A portion of the intermediate transfer belt 23 that is stretched in the horizontal direction passes between the image forming units 21Y,..., 21K and the primary transfer rollers 22Y,. When the intermediate transfer belt 23 rotates, each part of the surface contacts the primary transfer rollers 22Y,. The secondary transfer roller 24 is installed in parallel with one of the two rollers 23R around which the intermediate transfer belt 23 is stretched, and the intermediate transfer belt 23 is sandwiched between the rollers 23R. The sheet SH2 fed from the timing roller 14 is passed through a contact portion between the intermediate transfer belt 23 and the secondary transfer roller 24, that is, a nip. The exposure unit 25 is installed under the four image forming units 21Y, 21M, 21C, and 21K and irradiates each unit with laser light.

  FIG. 2A is a cross-sectional view of one of the four image forming units 21Y, 21M, 21C, and 21K. The four image forming units sequentially form toner images of respective colors of yellow (Y), magenta (M), cyan (C), and black (K) based on the image data. Each of the image forming units has the same configuration as that shown in FIG. 2A, and includes a photosensitive drum 211, a charger 212, an exposure port 213, a developing unit 214, a cleaner 215, an eraser lamp ( 2), and supply parts 216 and 217.

  The photosensitive drum 211 is a cylindrical image carrier, and the outer periphery thereof is covered with the photosensitive member. The photosensitive member can be charged, and the exposed portion is neutralized when exposed to external light. The photosensitive drum 211 can rotate around the central axis, and by rotating the photosensitive drum 211, the respective parts on the outer peripheral surface are made to face each other in the order of the charger 212, the exposure port 213, the developing unit 214, the intermediate transfer belt 23, and the cleaner 215.

  The charger 212 generates a discharge in the vicinity of the opposed portion of the outer peripheral surface of the photosensitive drum 211, or injects a charge directly into that portion. Thereby, the portion of the photosensitive drum 211 is uniformly charged.

  The exposure port 213 introduces the laser beam from the exposure unit 25 into the image forming unit, and irradiates the opposite portion of the charged region on the outer peripheral surface of the photosensitive drum 211. At that time, the exposed portion is neutralized, and an electrostatic latent image is formed in that portion.

The developing unit 214 takes in toner from the replenishing units 216 and 217. Further, when the developing unit 214 is opposed to a portion where the electrostatic latent image is formed on the outer peripheral surface of the photosensitive drum 211, the developing unit 214 puts toner on the portion. As a result, the toner adheres to the electrostatic latent image, and the electrostatic latent image becomes visible as a toner image.
2B and 2C are a top view and a cross-sectional view of the developing unit 214, respectively. 2B and 2C, the developing unit 214 includes a housing 240, a stirring shaft 241, a supply shaft 242, and a developing roller 243.

  The inside of the housing 240 is partitioned into a stirring tank TK1 and a supply layer TK2 by a partition wall PRT. The stirring tank TK1 and a part of the supply layer TK2 are immersed in the developer DVL. This developer DVL contains two components of toner and carrier. The toner is a non-magnetic fine powder having conductivity, and is colored in one of four colors Y, M, C, and K. The carrier is a magnetic insulator powder having a particle size larger than that of the toner, and adsorbs a large amount of the toner powder on the surface.

  The agitation shaft 241 is built in the agitation tank TK1 and can rotate around the central axis. A screw SC1 is formed on the outer peripheral surface of the stirring shaft 241, and the developer DVL is moved in one direction while stirring the stirring shaft 241 (see the arrow AR1 shown in FIG. 2B). ). The supply shaft 242 is built in a portion of the supply tank TK2 that is immersed in the developer DVL, and can rotate around the central axis. A screw SC2 is formed on the outer peripheral surface of the supply shaft 242, and the developer DVL is agitated with the rotation of the supply shaft 242 and is moved in the opposite direction to the screw SC1 of the stirring shaft 241 ((b in FIG. 2). ) (See arrow AR2). Since the partitions PRT are provided with openings OP1 and OP2, the developer DVL circulates between the agitation tank TK1 and the supply tank TK2 (see arrows AR3 and 4 shown in FIG. 2B). ). As described above, the toner is charged by friction with the carrier while the developer DVL circulates.

  The developing roller 243 is installed above the portion of the supply tank TK2 that is immersed in the developer DVL, and is rotatable about the central axis. The developing roller 243 has a built-in magnet, and the carrier in the developer DVL is attracted to the outer peripheral surface by the magnetic force. This outer peripheral surface is opposed to the outer peripheral surface of the photosensitive drum 211 with a predetermined distance. Since a bias voltage (hereinafter referred to as “development bias”) is applied between the developing roller 243 and the photosensitive drum 211, it is attracted to the outer peripheral surface of the developing roller 243 by an electrostatic force due to the voltage. The toner moves from the surface of the carrier to the outer peripheral surface of the photosensitive drum 211 and adheres.

  Further referring to FIG. 2 (b), a magnetic permeability sensor (toner-carrier ratio sensor: TCR sensor) 245 is installed at the bottom of the stirring tank TK1. The TCR sensor 245 measures the magnetic permeability of the developer DVL that moves inside the stirring tank TK1. Unlike the carrier, the toner does not have magnetism, so the higher the magnetic permeability of the developer DVL, the lower the ratio of the toner to the carrier. Using this, the control unit 60 detects the mixing ratio of the toner and the carrier in the developer DVL from the measured value of the TCR sensor 245, and determines the amount of toner to be replenished to the developing unit 214 based on the detected value. To do.

  The supply unit includes a toner supply tube 216 and a toner cartridge 217. The toner supply pipe 216 is connected to the stirring tank TK1 through the toner supply port 244. The toner supply port 244 includes a motor for supplying toner. The toner cartridge 217 stores toner of the color assigned to the corresponding image forming unit. The replenishing unit drives the motor of the toner replenishing port 244 in accordance with a drive signal from the control unit 60 to supply the toner to be replenished to the developer DVL inside the agitation tank TK1.

  Referring again to FIG. 2A, the cleaner 215 removes the remaining toner from the portion of the outer peripheral surface of the photosensitive drum 211 immediately after contacting the intermediate transfer belt 23. The eraser lamp discharges electricity by uniformly irradiating light to the opposed portion of the outer peripheral surface of the photosensitive drum 211.

  Referring again to FIG. 1, since the primary transfer voltage is applied to the primary transfer rollers 22Y,..., 22K, the primary transfer rollers 22Y facing each other with the intermediate transfer belt 23 therebetween. ..., an electric field is generated between 22K and the photosensitive drum 211. This electric field transfers the toner image from the photosensitive drum 211 to the surface of the intermediate transfer belt 23. The four image forming units 21Y,..., 21K shift the timing of each image forming operation in accordance with the rotation of the intermediate transfer belt 23. As a result, from the photosensitive drums 211 of the image forming units 21Y,..., 21K, the respective color toner images are sequentially transferred and overlapped at the same position on the surface of the intermediate transfer belt 23. Thus, a color toner image is formed on the surface of the intermediate transfer belt 23.

  Since a secondary transfer voltage is applied to the secondary transfer roller 24, an electric field is generated between the secondary transfer roller 24 and the intermediate transfer belt 23. When the sheet SH2 is passed through the nip between the intermediate transfer belt 23 and the secondary transfer roller 24, this electric field transfers the color toner image from the intermediate transfer belt 23 to the surface of the sheet SH2. Thereafter, the secondary transfer roller 24 sends the sheet SH <b> 2 to the fixing unit 30.

The exposure unit 25 includes a light emitting element 251 and four mirrors 252. The light emitting element 251 is a laser diode, for example. The light emitting element 251 changes the emission pattern of the laser light according to the drive signal from the control unit 60. The mirrors 252 are installed one by one under one of the four image forming units 21Y,..., 21K, and reflect the laser light emitted from the light emitting element 251 to irradiate the image forming unit thereon.
[Fixing part]

Referring to FIG. 1, the fixing unit 30 includes a fixing roller 31 and a pressure roller 32. These rollers 31 and 32 are arranged in parallel with each other and are in contact with each other. The sheet SH2 sent out from the image forming unit 20 is passed through a contact portion between them, that is, a fixing nip. As the fixing roller 31 rotates, the fixing roller 31 comes into contact with the surface of the sheet SH2 to be passed through the fixing nip. The fixing roller 31 incorporates a heater such as a halogen lamp, and transfers heat released from the heater to a portion of the sheet SH2 that is in contact with the side surface thereof. The pressure roller 32 applies pressure to the portion of the sheet SH2 and presses it against the fixing roller 31. When a portion of the sheet SH2 on which the toner image is formed by the image forming unit 20 is passed through the fixing nip, the toner image is changed to a sheet by heat from the fixing roller 31 and pressure from the pressure roller 32. Fix on the surface of SH2.
[Output section]

Referring to FIG. 1, the paper discharge unit 40 includes a guide plate 41, a discharge port 42, a pair of discharge rollers 43, and a paper discharge tray 44. The guide plate 41 guides the sheet SH2 discharged from the upper part of the fixing unit 30 toward the discharge port 42. The discharge port 42 is a slit that is elongated in the horizontal direction and is opened in the housing of the image forming apparatus 100. The pair of discharge rollers 43 are disposed horizontally along the discharge port 42 inside the discharge port 42 and contact each other's side surfaces. The sheet SH3 guided by the guide plate 41 is passed through the nip between them. The discharge roller 43 rotates and feeds the sheet SH3 passed through the nip from the discharge port 42 to the discharge tray 44 on its side surface. The paper discharge tray 44 is installed outside the housing of the image forming apparatus 100 and stacks the sheets SH3 discharged from the discharge port 42.
[Electronic control system]

  FIG. 3 is a block diagram illustrating a configuration of an electronic control system of the image forming apparatus 100. Referring to FIG. 3, in this system, the operation unit 50, the control unit 60, and the image forming unit 70, that is, the feeding unit 10, the image forming unit 20, and the fixing unit 30 are communicably connected to each other through a bus 90. Has been.

  The control unit 60 includes a CPU 61, a RAM 62, and a ROM 63. The CPU 61 controls the other elements 50 and 70 connected to the bus 90 according to the firmware. The RAM 62 provides a work area when the firmware is executed by the CPU 61 to the CPU 61 and stores image data IMG to be printed received by the operation unit 50. The ROM 63 includes a non-writable semiconductor memory device and a rewritable semiconductor memory device such as an EEPROM. The former stores firmware, and the latter provides the CPU 61 with a storage area for environment variables and the like. In particular, the ROM 63 stores a plurality of types of tables TBL representing the functional relationship between the gradation value of the pixel and the toner consumption. The ROM 63 also stores a parameter PRM value that affects the image density.

Hereinafter, for convenience of explanation, the table TBL stored in the ROM 63 is referred to as a “toner consumption table”, and the parameter PRM is referred to as an “image density adjustment variable”. The image density adjustment variable includes, for example, a maximum density for each color of the image, or a parameter representing the reproducibility of line drawings such as characters, that is, the width of a line drawn with toner.
[Operation section]

The operation unit 50 includes an operation panel 51, a scanner 52, a memory interface (I / F) 53, and a LAN I / F 54.
Operation panel 51 includes a push button, a touch panel, and a display. The operation panel 51 displays a GUI screen such as an operation screen and an input screen for various parameters on the display in accordance with a drive signal from the control unit 60. The operation panel 51 also identifies the position of the push button or touch panel operated by the user, and transmits information related to the identification to the control unit 60 as operation information.

  The operation panel 51 particularly includes a reception unit 511. The accepting unit 511 displays an image density adjustment variable input screen on the display of the operation panel 51 in accordance with a user operation, and accepts an index value from the user through the input screen. This index value indicates the target value of the image density adjustment variable, that is, the degree of adjustment for the image density. The receiving unit 511 further transmits the received index value to the control unit 60.

The scanner 52 uses a built-in optical device to irradiate light on the surface of the document, reads characters, designs, or photographs from the intensity distribution of the reflected light and converts them into image data IMG.
The memory I / F 53 directly captures image data IMG from an external storage device such as a USB memory or a hard disk drive (HDD) through a video input terminal such as a USB port or a memory card slot.
The LAN I / F 54 is connected to an external network NTW by wire or wirelessly and communicates with other electronic devices connected to the network NTW. The LAN I / F 54 receives an instruction from the user, in particular, a job and image data IMG to be printed from those electronic devices. These electronic devices in particular include a billing server SRV. The accounting server SRV receives the toner consumption amount from the control unit 60, and determines the usage fee of the image forming apparatus 100 based on the amount.
[Control unit]

  The control unit 60 transmits a drive signal to other elements in the image forming apparatus 100 based on the operation information from the operation unit 50. Thereby, the control unit 60 instructs the operation modes such as the operation mode, the standby mode, and the sleep mode to the elements, and causes each element to execute a process according to the operation mode.

  The control unit 60 displays an operation screen on the operation unit 50 and accepts an operation by the user. When the operation unit 50 receives a job from the user, the control unit 60 causes the operation unit 50 to transfer the image data IMG to be printed to the RAM 62. The control unit 60 further designates the type of sheet to be fed and the timing of the feeding to the feeding unit 10 according to the printing conditions indicated by the job, and forms the forming for the image forming unit 20. Image data IMG representing a toner image to be provided is provided. In particular, the control unit 60 causes the light emitting element 251 of the exposure unit 25 to change the laser light emission pattern based on the image data IMG. The control unit 60 also causes the fixing unit 30 to maintain the surface temperature of the fixing roller 31 at a value suitable for thermal fixing of the toner image.

  When the control unit 60 provides the image data IMG to the image forming unit 20, the image data IMG is subjected to image processing such as color correction processing, gradation correction processing, screen processing, and error extension processing (hereinafter, RIP ( raster-image processor) process), and the resulting raster data is passed to the image forming unit 20. Particularly, by screen processing, the image data IMG represents the gradation value of each pixel by the density of “points” (hereinafter referred to as “dots”) drawn with toner of each color on that pixel.

Referring to FIG. 3, in the control unit 60, the CPU 61 functions as an adjustment unit 611 and an estimation unit 612 by executing corresponding firmware. The adjustment unit 611 causes the image forming unit 70 to adjust the image density based on the index value received from the user by the receiving unit 511 of the operation panel 51. The estimation unit 612 estimates from the image data IMG the amount of toner consumed when the image forming unit 70 forms a toner image on a sheet according to the image data IMG.
-Adjustment part-

  When the operation unit 50 receives a request for changing the image density adjustment variable from the user, the control unit 60 activates the adjustment unit 611 according to the operation information to that effect. First, the adjustment unit 611 displays an image density adjustment variable input screen on the reception unit 511 of the operation panel 51 to receive an index value from the user.

  FIG. 4 is a graph showing the input screen of the image density adjustment variable displayed on the operation panel 51 and the influence of the change in the control amount according to the value of the variable on the toner consumption per dot. The receiving unit 511 identifies an index value from a user operation on these input screens, and notifies the adjustment unit 611 of the index value. Based on the index value, the adjustment unit 611 changes the control amount for the process, such as the developing bias or the amount of light emitted from the light emitting element 251, corresponding to the image density adjustment variable. According to the change, the toner consumption amount per dot changes according to the graph shown in FIG. 4B or 4D.

  The adjustment unit 611 further causes the image forming unit 20 to execute a gradation correction operation. Specifically, for example, the adjustment unit 611 first determines a target value of image density that should correspond to the index value. Next, the adjustment unit 611 causes the image forming unit 20 to form a patch pattern on the intermediate transfer belt 23 and measures the density of the pattern with an optical sensor (image density control sensor: IDC sensor). The adjustment unit 611 compares the measured value with the target value of the image density, and confirms from the comparison result that the control amount after the change corresponds to the target value. When this confirmation is obtained, the adjustment unit 611 stores the index value PRM in the ROM 63.

  FIG. 4A shows an input screen for the maximum density of an image. Referring to FIG. 4A, in this input screen IP1, the maximum density of each color of C, M, Y, and K, that is, the index value for the image density associated with the maximum gradation value is the default value. Is represented by an integer from “−10” to “+10”. The larger the index value, the darker the maximum density color. The accepting unit 511 causes the user to operate the four cursors CSR displayed on the input screen IP1 to select the maximum density of toner of each color from index values from “−10” to “+10”. The receiving unit 511 further identifies the four selected index values from the user's operation, and notifies the adjusting unit 611 of these index values. The adjustment unit 611 changes the development bias according to the notified index value.

  FIG. 4B shows an example of the influence of the change in the developing bias on the toner consumption per dot. The higher the maximum density index value, the higher the development bias, and thus the toner consumption per dot increases.

  FIG. 4C shows a character reproducibility input screen. Referring to FIG. 4C, the input screen IP2 defaults to the reproducibility of line drawings such as characters drawn in C, M, Y, and K colors, that is, the index value for the average line width. The value is expressed as ± 10 levels in the order of “thin” → “medium thin” → “normal” → “middle thick” → “thick” with “normal” (= “0”). The accepting unit 511 causes the user to operate the four cursors PRV displayed on the input screen IP2, and to select the reproducibility of characters of each color from ± 10 index values. The operation unit 50 further identifies the selected four index values from the user's operation, and notifies the adjustment unit 611 of these index values. The adjustment unit 611 changes the amount of light emitted from the exposure unit 25 according to the notified index value.

FIG. 4D shows an example of the influence of the change in the amount of light emitted from the exposure unit 25 according to the degree of character reproducibility on the toner consumption per dot. The higher the index value, that is, the greater the line width, the greater the amount of emitted light, so the toner consumption per dot increases.
-Estimator-

  When the operation unit 50 receives a job request from the user, the control unit 60 activates the estimation unit 612 according to the operation information to that effect. The estimation unit 612 reads the gradation value of each pixel from the image data IMG that is the object of the job, and when the image forming unit 20 forms a toner image based on the image data IMG from these gradation values. Estimate the amount of toner consumed. The estimation unit 612 particularly corrects the functional relationship between the gradation value of the pixel and the toner consumption amount according to the index value PRM stored in the ROM 63 by the adjustment unit 611.

  Specifically, the estimation unit 612 first counts pixels indicating each gradation value for each page and each color based on the image data IMG after image processing, that is, raster data. In particular, the estimation unit 612 divides the count between pixels belonging to the edge portion of the toner image and pixels belonging to a portion other than the edge portion (hereinafter referred to as “dot portion”). Here, the “edge portion” of the toner image means a portion of the toner image in which the gradation value difference between two adjacent pixels, such as the contour of the image, is equal to or greater than a predetermined threshold value.

Next, the estimation unit 612 estimates the toner consumption for each page and each color based on the count for the edge portion of each page and the count for the dot portion.
Here, the functional relationship between the gradation value of a pixel, that is, the number of dots drawn on the pixel, and the amount of toner consumed for drawing the dots differs between the edge portion and the dot portion. Therefore, the toner consumption amount table TBL stored in the ROM 63 includes correction for the difference in the functional relationship between the edge portion and the dot portion. Specifically, the table for the pixels belonging to the edge portion (the toner consumption table for the edge portion) and the table for the pixels belonging to the dot portion (the toner consumption table for the dot portion) are defined for each gradation value. The amount of toner consumed per dot is different (see, for example, Patent Document 3).

  The estimation unit 612 multiplies the count of each gradation value pixel by the toner consumption amount of the gradation value pixel, and sums the obtained products for all gradation values. Here, the toner consumption value in the pixel of each gradation value is retrieved from the toner consumption table for the edge portion in the estimation for the pixel for the edge portion, and the toner consumption for the dot portion in the estimation for the pixel for the dot portion. Retrieved from the quantity table. As described above, the difference in functional relationship between the edge portion and the dot portion is corrected by properly using the two types of toner consumption amount tables for the edge portion and the dot portion.

The functional relationship between the tone value of the pixel and the toner consumption varies depending on the index value for the image density adjustment variable as follows.
FIG. 5A is a graph showing the change in the functional relationship according to the index value with respect to the maximum density of the image. The solid line graph represents a functional relationship between the gradation values “0” to “255” and the toner consumption when the index value is the default value “0”. The one-dot chain line graph group represents a functional relationship between the gradation value and the toner consumption when the index value is higher than the default value “0”. A broken-line graph group represents a functional relationship between the gradation value and the toner consumption when the index value is lower than the default value “0”. Referring to FIG. 5A, in all gradation values “0” to “255”, the higher the index value, the larger the toner consumption per dot, and the lower the index value, the smaller the toner consumption. .

  FIG. 5B is a graph showing the change in the functional relationship according to the index value for the reproducibility of the line drawing. The solid line graph represents a functional relationship between the gradation values “0” to “255” and the toner consumption when the index value is the default value “normal”. The one-dot chain line graph group represents a functional relationship between the gradation value and the toner consumption when the index value is larger than the default value “normal”. A broken-line graph group represents a functional relationship between the gradation value and the toner consumption when the index value is smaller than the default value “normal”. Referring to FIG. 5B, in all gradation values “0” to “255”, the larger the index value, the larger the toner consumption per dot, and the smaller the index value, the smaller the toner consumption. .

The toner consumption table TBL stored in the ROM 63 to reflect the change in the functional relationship between the gradation value and the toner consumption according to the index value for the image density adjustment variable shown in FIG. Different corrections are included for each index value. Specifically, different types of toner consumption amount tables are assigned to different index values, and the toner consumption amount per dot defined for each gradation value differs between these tables. The estimation unit 612 refers to the index value PRM stored in the ROM 63, and searches the toner consumption amount in the pixel of each gradation value from the type of toner consumption table TBL corresponding to the index value PRM. In this way, by using different types of toner consumption tables for different index values, differences in functional relationships according to the index values are corrected.
-Determination of usage fee of image forming device by billing server-

The control unit 60 further aggregates the toner consumption estimated for each page by the estimation unit 612 for each job, and causes the LAN I / F 54 to transmit data indicating the aggregation result to the accounting server SRV on the external network NTW. .
FIG. 6 is a table showing a correspondence relationship between the toner consumption amount for each job sent from the control unit 60 to the charging server SRV and the usage fee of the image forming apparatus 100 determined by the charging server SRV. Referring to FIG. 6, the data sent from the control unit 60 to the accounting server SRV includes the size of the paper used for printing, the number of printed sheets, and the colors of C, M, Y, and K for each job identification number. Another toner consumption is shown. The billing server SRV determines the usage fee of the image forming apparatus 100 for each job based on the toner consumption indicated by this data in addition to or instead of the number of printed sheets indicated by this data.
-Toner replenishment based on estimated toner consumption-

The control unit 60 also uses the estimated toner consumption calculated by the estimation unit 612 to supply toner to the developing unit 214 as follows.
The control unit 60 monitors the mixing ratio of the toner and the carrier in the developer DVL through the measurement value of the TCR sensor 245, while the toner consumption calculated by the estimation unit 612 from the time when the toner is supplied to the developing unit 214 last time. Accumulate the estimated quantity. Thereby, the control unit 60 supplies toner to the developing unit 214 not only when the ratio of the toner to the carrier decreases to the allowable lower limit as the toner is consumed, but also when the integrated value of the toner consumption reaches the threshold value. Replenish. In particular, the control unit 60 determines the toner supply amount based on the integrated value of the toner consumption, calculates the rotation speed of the motor of the toner supply port 244 based on the supply amount, and supplies the image forming unit 20 with the drive signal. Tell the department. Thus, the replenishment amount of toner is supplied from the toner cartridge 217 to the stirring tank TK1 of the developing unit 214 through the toner supply tube 216 and the toner supply port 244.

The toner replenishment based on the toner consumption estimated from the image data is based on either the toner abundance ratio in the developer detected by the TCR sensor or the developer volume detected by the optical sensor. In comparison, it is advantageous in the following points. First, the estimation accuracy of toner consumption is high. Actually, in addition to the dot count error from the image data, the error including the functional relationship between the tone value of the pixel and the toner consumption is smaller than any measurement error of the existence ratio and the bulk of the developer. Second, toner supply can be performed at an appropriate timing. In fact, the estimation of the toner consumption based on the image data can be performed before the time when the amount of toner is actually consumed. On the other hand, changes in both the abundance ratio and the bulk of the developer can be detected only after a certain amount of time has elapsed since the toner was actually consumed. Third, less hardware is required for the estimation process. Actually, it is only necessary to have a CPU for toner consumption estimation based on image data, whereas a TCR sensor is necessary for estimation based on the existence ratio, and an optical sensor is necessary for estimation based on the bulk of the developer. is there.
-Flow chart of toner consumption estimation process-

  FIG. 7 is a flowchart of processing in which the estimation unit 612 estimates the toner consumption amount from the image data IMG in one job. This process is started when the control unit 60 receives operation information indicating a job request from the operation unit 50.

  In step S701, the control unit 50 activates the estimation unit 612 according to the operation information. First, the estimation unit 612 refers to the index value PRM for the image density adjustment variable stored in the ROM 63, and stores the types of toner consumption tables corresponding to the index value PRM in the plurality of types of tables TBL stored in the ROM 63. Choose from. The estimation unit 612 also secures a variable area in the RAM 62 that indicates the pixel count separately for each edge portion and each dot portion, for each color, and for each gradation value. Thereafter, the process proceeds to step S702.

  In step S702, in parallel with the RIP processing on the image data IMG by the control unit 60, the estimation unit 612 selects one page from the image data IMG after the RIP processing, that is, raster data, and sets one page from the page. Extract pixel data. Thereafter, the process proceeds to step S703.

  In step S703, the estimation unit 612 analyzes the set of pixel data extracted in step S702 and determines whether the corresponding pixel belongs to the edge portion or the dot portion of the toner image. If the pixel belongs to the edge part, the process proceeds to step S704. If the pixel belongs to the dot part, the process proceeds to step S705.

  In step S704, the pixels belonging to the edge portion of the toner image correspond to the set of pixel data extracted in step S702. The estimation unit 612 reads the tone value of each color from the pixel data, and increments the count of the pixels belonging to the edge portion and indicating each read tone value by one. Thereafter, the process proceeds to step S706.

  In step S705, the pixels belonging to the dot portion of the toner image correspond to the set of pixel data extracted in step S702. The estimation unit 612 reads the gradation value of each color from the pixel data, and increments the count of pixels belonging to the dot portion and indicating each read gradation value by one. Thereafter, the process proceeds to step S706.

  In step S706, the estimation unit 612 checks whether there is pixel data different from the pixel data extracted in step S702 in one page selected in step S702. If there is another pixel data, the process is repeated from step S702, and if not, the process proceeds to step S707.

  In step S707, the estimating unit 612 first searches the toner consumption amount table TBL for each gradation value pixel from the toner consumption amount table TBL for the edge portion, and multiplies the count of pixels of each gradation value belonging to the edge portion. Next, the estimation unit 612 retrieves the toner consumption amount in each gradation value pixel from the toner consumption table TBL for the dot portion, and multiplies the count of the pixels of each gradation value belonging to the dot portion. Subsequently, the estimation unit 612 sums up the product obtained by the multiplication between all the gradation values and the edge portion and the dot portion, and the total result is an estimated value of toner consumption in the processing target page. Determine as. Thereafter, the process proceeds to step S708.

In step S708, the estimation unit 612 confirms whether or not an unprocessed page remains in the image data IMG after RIP processing. If an unprocessed page remains, the process is repeated from step S702, and if not, the process proceeds to step S709.
In step S709, the control unit 60 totals the estimated toner consumption value determined for each page in step S707 for each job, and causes the LAN I / F 54 to transmit the total result to the accounting server SRV. Thus, the process ends.
-Flow chart of toner supply process-

FIG. 8 is a flowchart of processing in which the control unit 60 causes the image forming unit 20 to supply toner to the developing unit 214. This process is started when the image forming unit 70 starts the job.
In step S <b> 801, the control unit 60 acquires an estimated value of toner consumption from the estimation unit 612 and integrates it. Thereafter, the process proceeds to step S802.
In step S802, the control unit 60 compares the integrated value calculated in step S801 with a threshold value. If the integrated value has reached the threshold value or more, the process proceeds to step S804, and if the accumulated value remains below the threshold value, the process proceeds to step S803.
In step S803, the control unit 60 calculates the abundance ratio of the toner in the developer DVL from the measurement value of the TCR sensor 245 and compares it with the allowable lower limit. If the existence ratio falls below the allowable lower limit, the process proceeds to step S804, and if it remains higher than the allowable lower limit, the process is repeated from step S801.

In step S804, the control unit 60 determines the toner replenishment amount based on the integrated value of the toner consumption amount. Thereafter, the process proceeds to step S805.
In step S805, the control unit 60 calculates the number of rotations of the motor of the toner supply port 244 based on the supply amount determined in step S804, and transmits it to the supply unit of the image forming unit 20 with a drive signal. By driving the motor of the toner supply port 244 in accordance with the drive signal, the supplied amount of toner is supplied from the toner supply port 244 to the agitation tank TK1 of the developing unit 214. Thereafter, the process proceeds to step S806.
In step S806, the control unit 60 confirms whether or not the job by the image forming unit 70 has been completed. If the job is finished, the process is finished. If the job is continued, the process is repeated from step S801.
[Advantages of the embodiment]

As described above, the image forming apparatus 100 according to the embodiment of the present invention estimates the amount of toner consumed when a toner image is formed from the gradation value of the pixel indicated by the image data. For this estimation, a toner consumption table TBL stored in the ROM 63, that is, a plurality of tables representing a functional relationship between the gradation value of the pixel and the toner consumption is used. In particular, these tables TBL include different corrections for each index value PRM for the image density adjustment variable, that is, for each degree of adjustment for the image density. The image forming apparatus 100 uses these tables TBL in accordance with the index value PRM, thereby correcting the change in the functional relationship between the gradation value of the pixel corresponding to the index value and the toner consumption amount. Thus, the image forming apparatus 100 improves the estimation accuracy of the toner consumption amount without being hindered by the user's parameter adjustment.
[Modification]

  (A) The image forming apparatus 100 shown in FIG. 1 is an MFP. In addition, the image forming apparatus according to the embodiment of the present invention may be any of a laser printer, an ink jet printer, a facsimile, a copier, and the like.

(B) The four image forming units 21Y,..., 21K shown in FIG. In addition, the sizes of the four image forming units may be uneven, such as the size of the image forming unit 21K to which the frequently used black toner is allocated is larger than that of the other colors.
(C) In the image forming unit 21 shown in FIG. 2, the photosensitive drum 211 functions as an image carrier. In addition, the image carrier may be a belt.

(D) The developing unit 214 shown in FIG. 2 uses a two-component developer DVL. In addition, the developing unit may be a one-component developer, that is, a developer containing only toner as a main component and no carrier.
(E) In the developing unit 214 shown in FIG. 2, the mixing ratio of the toner and the carrier in the developer DVL detected by the TCR sensor 245 is used for monitoring the amount of toner remaining in the developing unit 214. The In addition, the bulk of the developer DVL in the developing unit 214 detected by the optical sensor may be used for monitoring.

(F) In the input screen shown in FIG. 5A, the maximum density of each color is an adjustment target. In addition, an image density associated with a gradation value different from the maximum gradation value may be an adjustment target.
(G) The estimation unit 612 counts all the pixels included in one page separately for each edge, each dot, each color, and each gradation value. In addition, the estimation unit 612 thins and counts the pixels included in the page by scanning one page every two or more lines, etc., and estimates the count of the entire page from the obtained count. The toner consumption may be estimated from the approximate result.
(H) The estimation unit 612 searches the toner consumption amount table TBL for the toner consumption amount at the pixel of each gradation value. In addition, the estimation unit 612 may calculate the toner consumption amount of a pixel from each gradation value of the pixel by using an operation based on a function between the gradation value and the toner consumption amount.

(I) The type of toner consumption table TBL differs between the edge portion and the dot portion, and also differs depending on the index value for the image density adjustment variable. In addition to these, the type of toner consumption table TBL differs depending on resolution, for example, between 600 dpi and 1200 dpi, or depending on the type of RIP processing for image data, for example, between error diffusion processing and screen (dither) processing. May be different.
Further, the toner consumption amount table TBL may be selectively used according to the environmental temperature and humidity of the image forming apparatus 100 or the integrated operation time. In this case, the estimation unit 612 monitors the measured values of the temperature / humidity sensor mounted on the image forming apparatus 100 or integrates the operating time of the image forming apparatus 100 and associates them with the measured values or the integrated values. Select the type of table specified.

  (J) The toner consumption value at each gradation value of the pixel differs between the toner consumption table for the edge portion and the one for the dot portion. In addition, the toner consumption amount table may define different values of the toner consumption amount per dot for each combination of the ratio of pixels belonging to the edge portion and the dot density in the dot portion (see, for example, Patent Document 2). . In this case, the estimation unit calculates the ratio of the pixels belonging to the edge part and the density of the dots in the dot part from the counts of the pixels belonging to the edge part and the dot part, and uses the combination thereof to calculate the toner consumption. The toner consumption per dot is retrieved from the amount table.

(K) The toner consumption table TBL defines the toner consumption value itself for each gradation value of the pixel. In addition, the toner consumption amount table may be divided into one indicating a reference value of toner consumption for each gradation value and one indicating a correction value for the reference value. In this case, the estimation unit selects a toner consumption amount table indicating an appropriate correction value according to the index value for the image density adjustment variable in addition to the edge portion and the dot portion, and the correction value retrieved from the table. Thus, the value retrieved from the table indicating the reference value of the toner consumption is corrected.
The estimation unit may further calculate the correction value from the reference value and the index value by using a mathematical expression in which the correction value is represented by the reference value and the index value, instead of the toner consumption table indicating the correction value.

  (L) The estimation unit 612 divides the pixel count between the edge portion and the dot portion. In addition, when the ratio of the edge part to the dot part is low or the degree of edge enhancement is weak, etc., and the toner consumption at the edge part is negligible than that at the dot part, the estimation part You may count a pixel, without distinguishing.

  The present invention relates to a technique for estimating toner consumption by an image forming apparatus. As described above, when estimating toner consumption from image data, a functional relationship between a pixel gradation value and toner consumption is calculated from a user. Correction is performed according to the received index value. Thus, the present invention is clearly industrially applicable.

DESCRIPTION OF SYMBOLS 100 Image forming apparatus 10 Feed part 20 Image forming part 25 Exposure part 214 Developing part 216/217 Replenishment part 30 Fixing part 40 Paper discharge part 50 Operation part 51 Operation panel 52 Scanner 53 Memory interface (I / F)
54 LAN I / F
60 control unit 61 CPU
611 Adjustment unit 612 Estimation unit 62 RAM
63 ROM
70 Image forming unit 90 Bus IMG Image data TBL Toner consumption table PRM Image density adjustment variable NTW External network SRV Billing server

Claims (6)

An image forming unit that forms an image with toner on a sheet based on image data;
A reception unit that receives an index value indicating an average line width when a line drawing portion of the image is drawn with toner;
An adjustment unit that controls the image forming unit based on the index value to adjust the density of the image;
A function unit that estimates a toner amount consumed when the image is formed from a gradation value of a pixel indicated by the image data, and a relationship between the gradation value and the toner consumption amount is set as the index value; and the estimation section is corrected in accordance
With
The image forming unit includes:
An image bearing member that is a chargeable member and changes its charge amount in a portion illuminated by light; and
An exposure unit that irradiates the image carrier with a pattern of light based on the image data to form an electrostatic latent image on the image carrier;
A developing unit for attaching toner to the electrostatic latent image and converting it into an image;
A transfer section for transferring the image from the image carrier to a sheet;
Have
The adjusting unit controls the exposure unit based on the index value to adjust the amount of light that illuminates the image carrier.
An image forming apparatus. The estimation unit stores a plurality of tables representing the relationship between the gradation value and the toner consumption amount,
The image forming apparatus according to claim 1, wherein the plurality of tables are different from each other according to the index value.   The relationship between the gradation value and the toner consumption amount differs depending on the toner amount constituting the edge of the image and the toner amount constituting another region of the image. The image forming apparatus described in 1.   4. The image forming apparatus according to claim 1, wherein the relationship between the gradation value and the toner consumption varies depending on the resolution of the image. 5. The image forming apparatus according to claim 1 , wherein the estimation unit transmits the estimated toner consumption amount to an external charging server. A replenishing unit that accumulates the toner consumption estimated by the estimating unit and replenishes the image forming unit with an amount of toner based on the accumulated value;
The image forming apparatus according to claim 1, further comprising:

Images