JP2014092618A - Image forming apparatus and image forming method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image forming apparatus that reduces an error in the amount of toner consumed from a toner container even when a sensor is not arranged to the toner container.SOLUTION: An image forming apparatus includes: a developer container 22 that accommodates a developer; developer supply means 51 for supplying a developer from the developer container to a developing unit 2; means for detecting the amount of the developer in the developing unit 52 for detecting the amount of the developer in the developing unit; consumption calculation means 39 for calculating the consumption amount of the developer in association with the development from image data to calculate a cumulative developer consumption amount obtained by accumulating the amounts of the developer; storage means 37 for storing the cumulative developer consumption amount; developer residual amount estimating means 551 for estimating an estimated residual amount of the developer in the developer container from the supply speed of the developer by the developer supply means; and consumption correcting means 55 for correcting the cumulative developer consumption amount stored in the storage means according to a difference between an estimated developer cumulative consumption amount obtained by subtracting the estimated residual amount of developer from an initial value and the cumulative developer consumption amount stored in the storage means.

Description

  The present invention relates to an image forming apparatus for transferring and fixing an image formed on a photoreceptor with a developer onto a recording medium.

  An electrophotographic image forming apparatus forms an image by fixing toner onto a sheet, so that the toner becomes a consumable item. When the toner runs out, the user generally replaces the toner container (toner cartridge) containing the toner. Since a period during which printing cannot be performed by preparing the toner container after the toner has completely disappeared may occur, the image forming apparatus has a function of detecting and displaying the remaining amount of toner in the toner container. As a result, the user can predict the replacement timing of the toner container to some extent.

  Conventionally, the remaining amount of toner in the toner container has been detected by a sensor disposed in the toner container. However, in order to reduce costs, a sensor for detecting the remaining amount of toner is not disposed in the toner container. Has been calculated. In this case, the toner remaining amount measured last is stored in the nonvolatile memory of the toner container. For example, there is a method of calculating toner consumption from image data of a print image (see, for example, Patent Document 1). Patent Document 1 discloses a first prediction unit that calculates a predicted value of toner usage based on an integrated value of replenishment time during which toner is replenished from a toner container, and the number of pixels of an image formed using toner. And a second prediction unit that calculates a predicted value of toner usage based on the integrated value of the first prediction until the predicted value calculated by the first prediction unit reaches the first reference value. An image forming apparatus that applies a predicted value calculated by the second prediction unit and calculates a remaining amount of toner by applying the predicted value calculated by the second prediction unit after the predicted value reaches the first reference value Is disclosed.

  However, in the method of calculating the toner consumption from the image data of the printed image as in Patent Document 1, the remaining amount of toner becomes inaccurate when the toner container is refilled with toner itself or when the toner is extracted. There is a problem. That is, an error occurs between the remaining amount of toner recorded in the non-volatile memory and the actual remaining amount of toner due to refilling or removing of the toner from the toner container, making it difficult to accurately grasp the remaining amount of toner.

  In view of the above-described problems, the present invention provides the remaining amount of toner recorded in the non-volatile memory of the toner container and the actual remaining amount of toner in the toner container (or the accumulated toner consumption and actual An object of the present invention is to provide an image forming apparatus capable of reducing an error in cumulative toner consumption.

  The present invention relates to an exposure unit that exposes a photoconductor based on image data, a developing unit that develops the photoconductor with a developer, and an image formed on the photoconductor with a developer is transferred to a recording medium and fixed. An image forming apparatus, a developer container containing a developer, a developer supplying means for supplying the developer from the developer container to the developing unit, and a developer in the developing unit Developer amount detection means in the developing unit for detecting the amount, developer consumption amount due to development is calculated from image data, and cumulative developer consumption amount obtained by accumulating the developer consumption amount or remaining developer amount in the developer container A consumption amount calculating means for calculating the remaining amount of the developer by subtracting the developer consumption amount from the initial value, a storage means for storing the accumulated developer consumption amount or the remaining developer amount, and the developer supply means. Developer supplement A developer remaining amount estimating means for estimating an estimated developer remaining amount of the developer container from the speed; an estimated developer cumulative consumption amount obtained by subtracting the estimated developer remaining amount from the initial value; and the storage means The accumulated developer consumption amount or the remaining developer amount in the storage unit is corrected according to a difference in accumulated developer consumption amount or a difference between the estimated remaining developer amount and the remaining developer amount in the storage unit. Consumption amount correcting means.

  Even when no sensor is installed in the toner container, the error between the remaining amount of toner recorded in the non-volatile memory of the toner container and the actual remaining amount of toner in the toner container (or accumulated toner consumption and actual accumulated toner consumption) is reduced. An image forming apparatus can be provided.

It is an example of the figure explaining the schematic characteristic of this embodiment. 1 is an example of a schematic configuration diagram of an image forming apparatus. 1 is an example of a hardware configuration diagram of an image forming apparatus. 1 is an example of a functional block diagram of an image forming apparatus. FIG. 6 is an example of a diagram illustrating how to obtain a toner consumption amount by an image processing IC. FIG. 10 is an example of a diagram illustrating calculation of toner consumption and skew correction. FIG. 6 is an example of a diagram illustrating a remaining amount of toner in a developing unit. FIG. 10 is an example of a diagram illustrating detection signals in a state where the remaining amount of toner in the developing unit is low and in a high state. It is an example of a diagram showing a sensor duty / toner amount conversion table. FIG. 6 is an example of a diagram illustrating cumulative toner consumption and error determination. An example of the flowchart figure which shows the procedure which performs the error determination of accumulated toner consumption is shown.

  Hereinafter, embodiments for carrying out the present invention will be described with reference to the drawings. However, the technical scope of the present invention is not limited to this embodiment.

  FIG. 1 is an example of a diagram illustrating schematic features of the present embodiment. A developing unit is provided below the toner container. The toner in the toner container is replenished to the developing unit by an appropriate amount, and the toner is attached to the photosensitive member from the developing unit to develop the image.

1. When replenishing toner to the developing unit, the image forming apparatus detects the amount of toner in the developing unit before and after replenishment using a detection signal detected by a sensor in the developing unit.
2. From the toner amount before and after the replenishment, the replenishment amount and the time taken for the replenishment are measured. Thereby, the replenishment speed can be calculated.
3. The remaining amount of toner is estimated using knowledge (table) that the replenishment speed is affected by the remaining amount of toner in the toner container.
4). From the above, the estimated cumulative toner consumption can be obtained.
4. Estimated cumulative toner consumption = toner toner full toner amount−estimated toner remaining amount The toner container is provided with an NVRAM (nonvolatile memory) that stores the accumulated toner consumption calculated and accumulated from the image data. The image forming apparatus compares the estimated accumulated toner consumption amount with the NVRAM accumulated toner consumption amount, and if the error is large, replaces the NVRAM accumulated toner consumption amount with the estimated accumulated toner consumption amount.

  Therefore, the error between the cumulative toner consumption actually consumed from the toner container (calculated from the image data) and the cumulative toner consumption stored in NVRAM is reduced, and the detection accuracy of the toner remaining amount in the toner container is increased. be able to. For example, even when the toner container is replenished or withdrawn, the detection accuracy of the remaining amount of toner in the toner container can be improved.

[Configuration example]
FIG. 2 shows an example of a schematic configuration diagram of the image forming apparatus. The image forming apparatus 100 includes, as main components, an exposure device 7, toner containers 22 </ b> A to 22 </ b> D, developing units 2 </ b> A to 2 </ b> D, a transfer belt 12, a waste toner box 23, a paper feed tray 14, a paper transport mechanism 24, and a fixing device 18. And a paper discharge tray 25.

  The exposure device 7 irradiates the photoconductors 5A to 5D with light to form an electrostatic latent image on the photoconductor. The exposure device 7 mainly has a method using a combination of a laser light source and a polycon mirror and a method using an LED array, but any exposure method may be used. In the figure, the exposure unit 7 can irradiate four laser beams so that a color image can be formed. However, the exposure unit 7 may form only a single color image.

  The exposure device 7 irradiates the irradiation position determined based on, for example, image data of each color of cyan, magenta, yellow, and black, removes the charging of the photoconductors 5A to 5D, and determines the toner adhesion position. .

  The toner containers 22 </ b> A to 22 </ b> D have a longitudinal direction at the back of the paper surface, and contain toner supplied to the developing units 2 </ b> A to 2 </ b> D. The toner containers 22 </ b> A to 22 </ b> D are detachably attached to the image forming apparatus 100. The toner containers 22A to 22D have agitators 28A to 28D, screws 29A to 29D, and toner supply clutches 42A to 42D. The agitators 28A to 28D are stirring members or loosening members that rotate about the depth direction of the paper surface. The screws 29 </ b> A to 29 </ b> D transport the toner toward a toner supply port closed by the toner supply clutch 42. The toner supply clutch 42 opens and closes the replenishing ports of the developing units 2A to 2D and the toner containers 22A to 22D to switch between the communication state and the separation state. In the communication state, the screws 29A to 29D rotate to supply toner to the developing units 2A to 2D.

  The developing units 2A to 2D are developing devices that store toner and attach the toner to the photoreceptors 5A to 5D. The developing units 2A to 2D have three supply rollers 15A to 15C. Since the surface distance between the developing rollers 8A to 8D and the supply rollers 15A to 15C is about a few millimeters, the toner stored in the developing units 2A to 2D is conveyed from the supply rollers 15A to 15C to the developing rollers 8A to 8D. It is. One or two supply rollers 15A to 15C may be provided, and a stirring member may be provided instead of the supply roller. The surfaces of the developing rollers 8A to 8D are made of, for example, conductive urethane rubber or silicone rubber, and the surfaces of the supply rollers 15A to 15C are made of sponge rollers such as foamed polyurethane.

  A developing blade is disposed at a predetermined interval from the surface along the axial direction of the developing rollers 8A to 8D. The developing blade regulates the layer thickness of the toner conveyed from the supply rollers 15A to 15C onto the surfaces of the developing rollers 8A to 8D to a predetermined amount.

  Around the photoreceptors 5A to 5D, charging rollers 6A to 6D, developing rollers 8A to 8D, cleaning devices 9A to 9D, and transfer units 11A to 11D are arranged. The charging rollers 6A to 6D charge the photoreceptors 5A to 5D to a uniform high potential, and the charged photoreceptors 5A to 5D are irradiated with laser light from the exposure unit 7. The portion irradiated with the laser light becomes an electrostatic latent image of a low potential portion, and toner is attached from the developing rollers 8A to 8D. The toner on the photoconductors 5 </ b> A to 5 </ b> D is transferred to the transfer belt 12. The remaining toner transferred to the transfer belt 12 is removed by the cleaning devices 9A to 9D. The cleaning devices 9A to 9D include a blade, a toner collecting unit, and a conveying screw, and the blade writes the toner remaining on the photoreceptors 5A to 5D and collects it in the toner collecting unit. The conveying screw conveys the toner in the toner collecting unit to the waste toner box 23.

  The transfer belt 12 is an endless belt wound around a secondary transfer drive roller 3 and a transfer belt tension roller 4 that are rotationally driven. On each of the photoconductors 5A to 5D, transfer devices 11A to 11D are arranged to face each other via a transfer belt 12. Each of the transfer machines 11A to 11D is brought into contact with the inner peripheral surface of the transfer belt 12, and brings the transfer belt 12 into contact with the surface of each of the photoreceptors 5A to 5D. When a voltage is applied to the transfer machines 11A to 11D, an electric field is generated, and the toner on the photoreceptors 5A to 5D is transferred to the transfer belt 12.

  The toner image on the transfer belt 12 is transferred to a sheet P (corresponding to a recording medium in claims) by a secondary transfer roller 13. A cleaning device 121 is disposed on the right side of the transfer belt 12 in the drawing, and the toner remaining on the transfer belt 12 is collected and conveyed to a waste toner box 23.

  The paper feed tray 14 is a paper feed unit on which the paper P to be supplied to the secondary transfer portion formed by the secondary transfer roller 13 and the secondary transfer drive roller 3 is stacked, and is provided in the paper feed tray 14. The paper feed roller 16 feeds the paper P and separates it one by one by a friction pad. The paper P is transported to the secondary transfer roller 13, the fixing device 18, and the paper discharge tray 25 by the paper transport mechanism 24. The paper P conveyed by the paper feed roller 16 is detected by the registration sensor 27 and held by the registration roller 17 until the timing when the toner image reaches the secondary transfer portion.

  The registration roller 17 sends the sandwiched paper P to the secondary transfer unit at a predetermined timing. The secondary transfer roller 13 is disposed to face the secondary transfer driving roller 3. The secondary transfer roller 13 is separated from the secondary transfer driving roller 3 except for printing (or may be always in contact), and the secondary transfer roller 13 is brought into contact with the transfer belt 12 during printing and is A next transfer electric field is generated. As a result, the full color image is collectively transferred onto the paper P by the secondary transfer unit.

  The fixing device 18 fixes the full color image formed on the paper P to the paper P by heat and pressure. In the case of single-sided printing, the paper is discharged to the paper discharge tray 25 as it is. In the case of double-sided printing, when the paper discharge sensor 21 detects that the end of the paper P has passed, the paper discharge roller 19 rotates in the reverse direction, and the paper P is reversed to the top so that the double-sided printing paper feed path 241 is reversed. It is conveyed to. When the paper P is detected by the double-side sensor 26, the paper P is transported through the double-sided printing paper feed path 241 by the double-sided roller 20, and is transported again to the secondary transfer unit. .

  Each developing unit 2A, 2B, 2C, 2D is provided with a sensor (described later) for detecting toner, and this sensor detects whether or not the toner in the developing unit has become a certain amount or less. . When the amount is less than a certain amount, a substantially constant amount of toner is supplied from the toner containers 22A, 22B, 22C, 22D to the developing units 2A, 2B, 2C, 2D.

  The image forming apparatus shown in FIG. 2 is a so-called tandem type. However, the four-cycle method (after transferring the four color toner images sequentially on the intermediate transfer member and transferring the four color toner images on the intermediate transfer member once. In other words, the image forming apparatus may be an image forming apparatus that transfers to paper. Further, an image forming apparatus that forms a toner image directly on the paper P without transferring a full-color image onto the transfer belt 12 may be used.

  FIG. 3 shows an example of a hardware configuration diagram of the image forming apparatus 100. In FIG. 3, the configuration that is not characteristic of the present embodiment is omitted. The image forming apparatus 100 includes an external I / F 31, a CPU 32, a ROM 33, a RAM 34, an operation panel I / F 35, an NVRAM 37, an I / O 38, and an image processing IC 39 connected to the system bus 30.

  The CPU 32 comprehensively controls access to various devices connected to the system bus 30 based on a control program stored in the ROM 33. That is, it controls input / output of electrical components such as the toner supply motor 41, the developing unit toner detection sensor 43, and the toner supply clutch 42 connected via the I / O 38. That is, the ROM 33 stores a program for the image forming apparatus 100 to realize processing as shown in a flowchart described later. The program may be stored not in the ROM 33 but in an HDD (Hard Disk Drive) (not shown).

  In addition to executing the program stored in the ROM 33, the CPU 32 can communicate with an external device (not shown) such as a host computer via the external I / F 31.

  The RAM 34 is a random access memory that functions as a main memory, work area, and the like for the CPU 32, and is used as a recording data development area, an environment data storage area, and the like.

  The NVRAM 37 is prepared for each color, and the NVRAM (K) 37 is mounted on the black toner container 22A. Similarly, the NVRAM (C) 37 is mounted on the cyan toner container 22B, the NVRAM (M) is mounted on the magenta toner container 22C, and the NVRAM (Y) 37 is mounted on the yellow toner container 22D. The NVRAM 37 stores at least one of the cumulative toner consumption amount and the remaining toner amount of each color toner.

  The operation panel I / F 35 is an interface between the operation panel 36 and the CPU 32. Soft keys and setting conditions are displayed on the operation panel 36, input by the user to the operation panel 36 is accepted, and display contents are updated. Also, the CPU 32 is notified of the setting conditions.

  The I / O 38 is an input / output interface and can connect various peripheral devices. Although there are a plurality of I / O 38, the illustration is omitted, or a peripheral device is connected to the I / O 38 via a multiplexer. To the I / O 38, a toner supply motor 41, a toner supply clutch 42 for each color, and a development unit toner detection sensor 43 of each color development unit 2A to 2D are connected.

  When the CPU 32 drives the toner supply motor 41, the agitators 28A to 28D and the screws 29A to 29D are rotated. In addition, the CPU 32 selectively turns the toner supply clutch 42 ON to selectively connect the toner containers 22A to 22D and the developing units 2A to 2D. Further, the CPU 32 causes the developing unit toner detection sensor 43 to detect and monitor the amount of toner in the developing unit.

  The image processing IC 39 receives the image data from the controller 40 and transmits the image data to the exposure unit 7. The controller 40 is connected to a PC (Personal Computer) via a network card or the like, receives PDL (Page Description Language) data from the PC, performs general image processing, and converts it into raster data in units of pages. In other words, characters, graphics and images (photographs) described in PDL are separated, color conversion (RGB → CMYK) is performed, and color conversion and screen (characters and graphics are resolution and images are high gradation) suitable for each. Convert to raster data. Further, the controller 40 acquires image data from a scanner (not shown), performs processing such as editing, and then sends it to the image processing IC 39.

  The image processing IC 39 calculates the toner consumption amount per page from the image data received from the controller 40, and notifies the CPU 32 of the calculated toner consumption amount via the system bus 30. Thereby, the CPU 32 can update the accumulated toner consumption amount or the remaining toner amount of the NVRAM.

[Function block diagram]
FIG. 4 shows an example of a functional block diagram of the image forming apparatus 100. The CPU 32 executes the program stored in the ROM 33 to realize the function shown in the figure. The functions shown in the figure are functions relating to detection of the remaining amount of toner in the toner containers 22A to 22D, and other functions are omitted. The image forming apparatus 100 includes a toner replenishing unit 51, a developing unit toner detection unit 52, a cumulative consumption calculation unit 53, a remaining toner calculation unit 54, a toner consumption correction unit 55, and a storage unit 56. . The storage unit 56 has, for example, an NVRAM 37 as an entity.

  The cumulative consumption amount calculation unit 53 receives the toner consumption amount for one page from the image processing IC 39, and updates the cumulative toner consumption amount of the toner containers 22A to 22D. That is, the calculated toner consumption amount is added to the accumulated toner consumption amount in the storage unit 56 and replaced with the accumulated toner consumption amount already stored. The calculation of the toner consumption will be described with reference to FIG.

  Further, since the toner amount (toner toner amount at full time = initial value) of the toner containers 22A to 22D immediately after the replacement is determined in advance, the remaining toner amount calculation unit 54 can obtain the remaining toner amount from the accumulated toner consumption amount. .

  The toner consumption correction unit 55 determines whether or not there is an error between the cumulative toner consumption recorded in the storage unit 56 and the cumulative toner consumption actually consumed from the toner container. If there is, correct it. The error determination and correction of the toner consumption amount will be described in detail with reference to FIGS.

  The development unit toner detection unit 52 uses the development unit toner detection sensor 43 to detect whether the toner in the development unit is less than a certain value. For example, the development unit toner detection sensor 43 is caused to detect the toner amount in the development unit at a predetermined timing such as every time when one job is finished, every certain time, or every printing of a certain number of pages.

  When the development unit toner detection sensor 43 detects that the development unit toner detection sensor is OFF, the development unit toner detection unit 52 notifies the toner supply unit 51 of this.

  The toner replenishing unit 51 controls the toner supply motor 41 and each toner supply clutch 42 to supply toner from the toner containers 22A to 22D to the developing units 2A to 2D, and from the toner containers 22A to 22D to the developing unit 2A. Replenish toner to ~ 2D. The toner replenishment amount is controlled mainly by the rotation duration of the screws 29A to 29D in the communication state. The rotational speed of the screws 29A to 29D is substantially constant during one replenishment (except during acceleration / deceleration), but the rotational speed itself can be changed by changing the rotational speed of the toner supply motor 41.

  In addition, the toner consumption correction unit 55 includes a toner remaining amount estimation unit 551 that estimates the remaining amount of toner in the toner container. The toner remaining amount estimation unit estimates the toner remaining amount in the toner container from the detection signal of the toner detection unit 52 in the developing unit.

[How to determine toner consumption]
FIG. 5 is an example of a diagram for explaining how to obtain the toner consumption amount by the image processing IC 39. The image processing IC 39 reads image data from its own line memory, and calculates the toner consumption for each pixel.

  As shown in the figure, 5 × 5 matrix data is generated around the pixel of interest A. That is, the density of 5 pixels in the main scanning direction and 5 pixels in the sub-scanning direction is extracted from the image data read from the line memory, and attention is paid to the center pixel A. It should be noted that the γ conversion of the density data is performed in advance according to the characteristics of the exposure means (laser or LED array).

  In addition, the weighting coefficient is set for each of the target pixel A, the reference pixels B to I adjacent to the target pixel A, and the reference pixels J to Y adjacent to each other, and the total light amount of the target pixel A is calculated. To do. This amount of light is the size of the laser beam at the time of exposure. The visual density of the toner is affected by the amount of light, and therefore may have the same meaning as the density of the toner. Density and weight are expressed in [a: b]. For example, [3: 0] means a 4-bit numerical value from 0 to 3 bits as a whole. Therefore, the larger the number on the left, the greater the weight.

The weighting factors are reference pixels having point symmetry with respect to the target pixel A (for example, B and F, C and G, D and H, E and I, J and R, K and S, L and T, M and U, N and V, etc.) use a common value. The weighting coefficient of the target pixel A is represented by main, and the weighting coefficient of the reference pixel is represented by ref1_n or ref2_n (n is an identification number). ref1_n> ref2_n. Further, the alphabet for identifying a pixel represents the density of the pixel as it is.
Light intensity of target pixel A = A * main + (C + G) * ref1_1 + (E + I) * ref1_2 + (B + D + F + H) * ref1_3 + (L + T) * ref2_1 + (P + X ) * ref2_2 + (K + M + S + U) * ref2_3 + (O + Q + W + Y) * ref2_4 + (J + N + R + V) * ref2_5… (1)
The reason why the density of the reference pixel as well as the density of the target pixel A is taken into account is that exposure to the target pixel affects surrounding pixels. Further, since the influence is larger as it is closer to the pixel of interest A, and is the same at a point-symmetrical position, it can be calculated as in the above equation (1). Therefore, the toner consumption amount can be accurately calculated by considering the light amount of the reference pixel as well as the target pixel A in this way. Note that the 5 × 5 pixel is used as a reference pixel, and is determined in consideration of the range of pixels affected by exposure and the calculation load.

The image processing IC 39 has a conversion formula f (A light amount) for obtaining the toner consumption amount from the light amount. The conversion formula f is a linear expression for the amount of A light.
Toner consumption conversion value = f (light quantity of A)
By the way, the amount of toner developed (the amount attached to the paper) is proportional to the amount of light of the laser or LED that exposes the photoconductors 5A to 5D, but is saturated at a certain light amount level (upper limit), and the amount of light beyond that is saturated. The development amount does not change even if it is increased. Therefore, a saturation process is performed on the calculated A light quantity.
If the amount of A light ≤ the upper limit value → Conversion value of toner consumption = f (light amount of A)
If the light quantity of A> upper limit value → converted value of toner consumption = f (upper limit value)
Further, the toner consumption amount calculated from the light amount of the target pixel A is subtracted by an amount corresponding to a certain amount of offset value of the light amount of the target pixel A. This is in consideration of the relationship between the light amount of the target pixel A and the developing amount of the toner, and can be brought close to the developing amount at which the toner is actually developed by the offset. If the subtraction result is negative, the result is zero.

From the above, the converted value of the toner consumption is obtained as follows.
(i) The amount of A is calculated using equation (1).
(ii) Perform saturation processing and obtain a conversion value of toner consumption per pixel using the conversion formula f.
(iii) Calculate “Conversion value of toner amount−offset value” The image processing IC 39 performs the above calculation for all pixels of one page. For example, after the target pixel A, the process is performed for E adjacent to the right, and then performed for P. Since one page is decomposed into CMYK, the process is performed for all pixels in one page for each CMYK. By summing the converted values of toner consumption for each CMYK, a total of converted toner consumption values for one page is obtained for each CMYK. When the peripheral pixel is outside the image area, the peripheral pixel is treated as a pixel with zero light quantity.

<Necessity for consideration of skew correction>
Since the above calculation method is optimized according to the exposure means, it is possible to calculate the toner consumption with high accuracy by changing according to the exposure means.

  When the exposure unit 7 is a scanning type using a laser and a rotating body (polygon mirror), the consumption can be calculated with high accuracy by calculating the consumption using the density. On the other hand, when the exposure device 7 is a line type exposure means (line head) employing LEDs, the light emitting elements 47 arranged on the line are wavy. For this reason, in the case of a line type exposure means, skew correction is often performed.

  FIG. 6A shows an example of a schematic perspective view of the line head 71. In the line heads 71A to 71D, LEDs are arranged in a line in the main scanning direction. FIG. 6B is an example of a diagram schematically showing image data to be printed. In the figure, the horizontal direction is the main scanning direction, and the vertical direction is the sub-scanning direction. If the image data in FIG. 6B is printed without skew correction, the image is skewed because the line head is skewed. FIG. 6C shows an image printed without skew correction.

  In order to correct such image skew, in the skew correction, as shown in FIG. 6D, the order of image data read from the line memory is one pixel in the sub-scanning direction with respect to one pixel in the main scanning direction. Shifted (instead of reading 1 next to pixel 1, instead of 1, then 6, then 2, then 11). The number of pixels that are shifted by one pixel in the sub-scanning direction depends on the degree of skew of the line head.

  By performing the skew correction, when the image data of FIG. 6D is printed, the image becomes an image that is not skewed. FIG. 6E shows an image printed after skew correction.

  Here, when attention is paid to the pixel 13 of the skew-corrected image data in FIG. 6D, the density of the pixels in the frame shown in FIG. 6F is used for calculating the toner consumption. However, since the actually printed image is the image of FIG. 6E, the pixel adjacent to the pixel 13 is changed between FIG. 6F and FIG. 6E. For example, in FIG. 6F, the reference pixels adjacent to the target pixel 13 are the pixels 12, 8, 4, 9, 14, 18, 22, and 17, whereas in FIG. 6E, the reference pixels are 7, 8, 9 , 14, 19, 18, 17, 12.

  As described above, since the arrangement of pixels to be actually printed is the same as the image data before skew correction in FIG. 6E, when the image forming apparatus is a line-type exposure unit, the image before skew correction is performed. It is preferable to calculate the toner consumption for the data. Thereby, even when the exposure device 7 is an LED array, it is possible to suppress a decrease in the accuracy of toner consumption.

[Remaining amount of toner in development unit]
7 to 9 are examples of diagrams for explaining detection of the toner amount in the developing unit using the optical developing unit toner detection sensor 43. FIG. FIG. 7 is a view showing the toner container 22 and the developing unit 2 extracted from FIG. 2, and only the main constituent elements will be described with the same reference numerals.

  Inside the developing units 2A, 2B, 2C, and 2D, a light emitting element 47 and a light receiving element 48 are attached, respectively, and the light emitted from the light emitting element 47 passes through the inside of the developing unit and is received by the light receiving element 48. Yes. With this configuration, light is transmitted when there is no toner on the optical path, and light is blocked when there is toner on the optical path, so it is possible to determine whether the toner is present or absent.

  In addition, the toner in the developing unit has a density near the photosensitive member 5 of deteriorated toner (old toner: easy to accumulate in the lower part) and new toner (short time elapsed after being replenished from the toner container). For the purpose of making it uniform, it is constantly stirred. For this reason, the toner between the light emitting element 47 and the light receiving element 48 repeatedly moves, and the detection signal (voltage) by the developing unit toner detection sensor shows a periodic waveform as shown in FIGS. .

  FIG. 8A shows a detection signal when the toner amount in the developing unit is small, and FIG. 8B shows a detection signal when the toner amount in the developing unit is large. When the amount of toner is large, the time period during which the detection signal is large becomes long. The toner detection unit 52 in the development unit sets a threshold for this detection signal, and detects the toner amount in the development unit from the ratio between the number of times of detection without toner and the number of times of detection with toner. This ratio is called a sensor duty.

  FIG. 9 shows an example of a sensor duty / toner amount conversion table 552 showing the relationship between the toner amount in the developing unit and the sensor duty. In a region where the toner amount in the developing unit is small, the toner amount in the developing unit and the sensor duty are substantially proportional. As the amount of toner in the developing unit increases, even if the amount of toner in the developing unit increases, the increase in sensor duty becomes moderate. If the amount of toner in the developing unit is sufficiently large, the sensor duty is less affected. For this reason, if the manufacturer of the image forming apparatus checks the toner amount in the developing unit and the sensor duty, the toner amount in the developing unit can be estimated from the sensor duty.

  The toner remaining amount estimating unit 551 uses the sensor duty / toner amount conversion table 552 to estimate the toner amount in the developing unit from the sensor duty detected by the toner detecting unit 52 in the developing unit.

  Although the light transmission type development unit toner detection sensor 43 has been described with reference to FIG. 7, any sensor may be used as long as it can detect the amount of toner in the development unit. For example, although there are a light reflection type and a piezoelectric type sensor, the present invention can be applied to this embodiment as long as the toner amount in the developing unit can be detected including the data processing method regardless of the detection principle.

[Error judgment of accumulated toner consumption]
FIG. 10 is an example of a diagram illustrating the error determination of the cumulative toner consumption amount. The toner consumption amount correction unit 55 estimates the toner consumption amount in the toner container from the time required to replenish a certain amount of toner, and compares the toner consumption amount recorded in the NVRAM to determine an error. As shown in FIGS. 10A and 10B, the replenishment speed from the toner container to the developing unit varies depending on the remaining amount of toner in the toner container, so that the remaining toner amount is estimated by the remaining toner amount estimation unit 551 measuring the replenishment speed. Can be estimated. Details will be described below.

Assuming that the time required to replenish the replenishment amount X (g) is the replenishment time T (s), the replenishment speed S (g / s) for replenishing toner from the toner container to the developing unit can be calculated by the following equation.
Supply speed S (g / s) = X ÷ T
The replenishment speed S varies depending on the remaining amount R (g) of the toner container. FIG. 10A is a graph showing the relationship between the replenishment speed S and the remaining amount R (g) of the toner container, and FIG. 10B is a diagram showing the same relationship numerically. FIG. 10B is a supply speed / toner remaining amount table 553. By experimentally obtaining such a graph or table (corresponding to the developer remaining amount estimation table in the claims), the toner remaining amount estimating unit 551 calculates the remaining amount R of the toner container from the replenishment speed S. It can be calculated. Actually, the replenishment speed / toner remaining amount table 553 shown in FIG. 10B is recorded in the ROM 33, and the linear interpolation is performed for the replenishment speed S that cannot be obtained directly from the replenishment speed / toner remaining amount table 553. The toner container remaining amount R is calculated.

The estimated cumulative toner consumption C (g) is calculated from the following formula using the toner amount M (g) when full and the toner container remaining amount R (g) obtained from the replenishment speed / toner remaining amount table 553. Is calculated by
Estimated cumulative toner consumption C (g) = M−R
The toner consumption correction unit 55 compares the calculated estimated cumulative toner consumption C with the cumulative toner consumption recorded in the NVRAM, and determines that there is an error if there is a difference greater than the threshold.

  When the toner consumption amount correction unit 55 determines that there is an error in the error determination of the toner consumption amount, the toner consumption amount correction unit 55 determines that the estimated cumulative toner consumption amount calculated from the toner replenishment time is more reliable, and the estimated cumulative toner consumption amount Is the cumulative toner consumption of NVRAM. If it is determined that there is no error, the cumulative toner consumption recorded in the NVRAM is used as the cumulative toner consumption (that is, not corrected).

  This will be described using a specific example. For example, the calculation of the cumulative toner consumption when the supply amount X = 7.5 (g) and the full toner amount M = 100 (g) will be described.

  When the toner of 7.5 (g) is supplied from the toner container to the developing unit, the amount of 7.5 g of toner has increased in the developing unit. This is because the toner remaining amount estimating unit 551 has the sensor duty / toner amount conversion table 552 in FIG. Can be obtained from That is, it can be determined that the sensor duty at the start of toner replenishment becomes the sensor duty corresponding to the amount of toner increased by 7.5 (g). Further, the time until 7.5 (g) increases is the replenishment time T.

  If the replenishment time does not increase by 7.5 g even after a certain time, the remaining toner amount estimation unit 551 determines that the estimated accumulated toner consumption is 100 g (that is, empty).

For example, when the replenishment time is 33 seconds, the replenishment speed S is 7.5 / 33 = 0.227.
Since the replenishment rate 0.227 is between 0.2259 and 0.2318 in the replenishment rate / toner remaining amount table 553 in FIG. 10B, the toner remaining amount estimating unit 551 performs linear interpolation to obtain the toner remaining amount R as follows.
R = 40 + (0.227-0.2259) x (50-40) ÷ (0.2318-0.2259) = 41.9 (g)
That is, the estimated cumulative toner consumption amount C is as follows.
C = 100-41.9 = 58.1 (g)
The toner replenishing unit 51 may replenish toner during image formation. In this case, the replenishment amount X does not coincide with the change amount of the toner amount in the developing unit (because the toner in the developing unit is consumed by image formation). Therefore, the replenishment amount X (g) includes the toner amount R0 (g) in the developing unit at the start of toner replenishment, the toner amount R1 (g) in the developing unit at the end of toner replenishment, and the toner consumption during replenishment. From Cs (g), the following formula is used.
X (g) = R1-R0 + Cs
Since the replenishment speed / toner remaining amount table 553 of FIG. 10B is stored in the ROM 33 for each toner color, even if there is a difference in replenishment speed due to a difference in color, the calculation accuracy of consumption can be improved.

  Further, it is known that the replenishment speed / toner remaining amount table 553 changes depending on the rotation speed of the toner supply motor 41. For this reason, the replenishment speed / toner remaining amount table 553 is prepared for each rotation speed of the toner supply motor 41 and is switched according to the rotation speed. The calculation accuracy can be improved.

  As described above, the error between the accumulated toner consumption amount stored in the NVRAM 37 and the actual toner consumption amount in the toner container can be reduced.

[Toner consumption correction procedure]
FIG. 11 shows an example of a flowchart showing a procedure for determining an error of the accumulated toner consumption. This procedure is performed, for example, before the start of toner supply. Image formation may or may not be performed.
S101: The remaining toner amount estimation unit 551 specifies the current toner amount R0 in the developing unit using the sensor duty / toner amount conversion table 552 of FIG.
S102: The toner remaining amount estimation unit 551 reads from the ROM 33 the toner amount R1 of the developing unit when the replenishment is finished. R1 is a fixed value. Alternatively, R1 may be calculated with the replenishment amount as a fixed value.
S103: The toner replenishing unit 51 starts toner replenishment.
S104: During toner replenishment, the toner replenishing unit 51 detects the toner amount R of the developing unit from the sensor duty detected by the toner detecting unit 52 in the developing unit using the sensor duty / toner amount conversion table 552 of FIG.
S105: The toner replenishing unit 51 determines whether the toner amount R detected in S104 is equal to or larger than the toner amount R1 in the developing unit for which replenishment is completed. If it is R1 or more (Y), the process proceeds to S108, and if it is less than R1 (N), the process proceeds to S106.
S106: Until the detected toner amount R becomes equal to or greater than the toner amount R1 in the developing unit for which replenishment is completed, the toner replenishing unit 51 determines whether or not the replenishment time T exceeds the threshold Te. If it exceeds (Y in S106), the process proceeds to S1061. If not exceeded (N in S106), the process proceeds to S107. In this determination, it is detected that the replenishment is not completed even after a lapse of a certain time, that is, that there is no toner in the toner container (empty).
S1061: Since the replenishment time T has exceeded the threshold Te even though the toner amount R does not exceed the toner amount R1 in the developing unit, the toner replenishing unit 51 turns on the empty flag to store that it is empty.
S107: When the replenishment time T does not exceed the threshold Te, the toner replenishment unit 51 determines whether or not the toner replenishment needs to be interrupted due to an event such as a paper jam or a cover open. If interrupted (Y in S107), the process proceeds to S108, and if not interrupted (N in S107), the process returns to S104.
S108: If it is determined as Y in any one of S105 to S107, the toner replenishing unit 51 stops toner replenishment.
S1081: The toner remaining amount estimation unit 551 determines whether or not the empty flag is ON. If it is ON (Y in S1081), the process proceeds to step S114. If it is not ON (N in S1181), the process proceeds to step S109.
S109: The toner remaining amount estimation unit 551 determines whether or not the replenishment time T exceeds the threshold Tj. If it has exceeded (Y in S109), the process proceeds to S110. If not (N in S109), the process in FIG. 11 ends. This determination is because the processing is interrupted when the toner replenishment time is short, since the error becomes large and it is difficult to accurately calculate the replenishment amount. In this case, the toner consumption is corrected at the next toner replenishment.
S110: The toner remaining amount estimating unit 551 calculates the replenishment amount X. That is, from the toner amount R0 (g) in the developing unit at the start of toner replenishment, the toner amount R (g) in the developing unit at the end of toner replenishment, and the toner consumption amount Cs (g) during replenishment, Calculate with The toner amount R (g) in the developing unit at the end of toner replenishment may be the toner replenishment remaining amount R1.
X (g) = R-R0 + Cs
S111: The toner consumption correction unit 55 calculates the estimated cumulative toner consumption C from the supply amount X and the supply time T. First, the toner remaining amount estimation unit 551 calculates the replenishment speed S (= X / T), and calculates the toner remaining amount from the replenishment speed / toner remaining amount table 553 of FIG. Next, the toner consumption correction unit 55 calculates an estimated cumulative toner consumption C by subtracting the remaining amount of toner from the full toner amount M.
S112: The toner consumption correction unit 55 determines whether the absolute value of the difference between the estimated cumulative toner consumption C calculated in step S111 and the cumulative toner consumption Cm recorded in NVRAM is greater than the threshold Ct. If larger (Y of S112), the process proceeds to S113. If it is smaller (N in S112), the process in FIG. 11 ends.
S113: When the absolute value of the difference is larger than the threshold value Ct, the toner consumption correction unit 55 rewrites the NVRAM cumulative toner consumption Cm with the estimated cumulative toner consumption C calculated in step S111. The NVRAM cumulative toner consumption is replaced with the estimated cumulative toner consumption. In this way, more reliable toner consumption can be held in NVRAM.
S114: When the empty flag is ON, the toner consumption correction unit 55 rewrites the NVRAM cumulative toner consumption Cm with “100%”. That is, it is recorded that the toner remaining amount in the toner container is zero.
As described above, the cumulative toner consumption amount of NVRAM can be corrected.

<When using the remaining amount of toner>
In the above, the cumulative toner consumption amount of NVRAM is corrected using the cumulative toner consumption amount, but the same can be corrected when the remaining amount of toner is stored in NVRAM. In this case, the remaining amount of toner calculated by subtracting the toner consumption amount received from the image processing IC 39 by the toner remaining amount calculation unit 54 from the toner consumption amount when full is stored in the NVRAM. The toner remaining amount is updated every time an image is formed.

  Similarly, the toner remaining amount estimation unit 551 calculates the replenishment amount X, calculates the replenishment speed S (= X / T) from the replenishment amount X and the replenishment time T, and the replenishment rate / toner remaining amount in FIG. The toner remaining amount is calculated from the table 553. Since the remaining amount of toner becomes an estimated value, the toner consumption correction unit 55 may determine whether the absolute value of the difference between the estimated remaining toner amount and the remaining toner amount recorded in NVRAM is greater than a threshold value. The process after the determination is the same.

  In this manner, the NVRAM cumulative toner consumption (toner remaining amount) can be corrected by using either the cumulative toner consumption or the toner remaining amount.

  As described above, the image forming apparatus according to the present exemplary embodiment can correct an error even if there is an error between the cumulative toner consumption of the toner container recorded in the NVRAM and the actual cumulative toner consumption of the toner container. it can. For example, the error can be corrected even when the toner container is replenished with toner or the toner container is extracted.

  Although the image forming apparatus is described as a printer in FIG. 2, the error correction method according to the present exemplary embodiment is applied to an apparatus having an image forming function such as a copier, a FAX apparatus, or an MFP (Multi Function Printer) provided with the printer. Can be suitably applied.

2A to 2D Developing unit 5A to 5D Photoconductor 6A to 6D Charger 7 Exposure unit 8A to 8D Developing roller 9A to 9D Cleaning device 12 Conveying belt 18 Fixing device 22A to 22D Toner container 39 Image processing IC
42 toner supply clutch 43 development unit toner detection sensor 51 toner replenishment unit 52 development unit toner detection unit 53 cumulative consumption calculation unit 54 toner remaining amount calculation unit 55 toner consumption correction unit 100 image forming apparatus

Japanese Unexamined Patent Publication No. 2005-173088

Claims (10)

Exposure means for exposing the photoreceptor based on the image data;
A developing unit for developing the photoreceptor with a developer;
Transfer means for transferring an image formed on the photoreceptor by a developer to a recording medium;
An image forming apparatus having fixing means for fixing an image on a recording medium,
A developer container containing a developer;
Developer supplying means for supplying developer from the developer container to the developing unit;
A developer amount detecting means in the developing unit for detecting the developer amount in the developing unit;
The developer consumption by development is calculated from the image data, and the developer consumption is subtracted from the accumulated developer consumption by accumulating the developer goods consumption or the initial value of the developer remaining amount in the developer container. Consumption calculation means for calculating the remaining amount;
Storage means for storing the cumulative developer consumption or the developer remaining amount;
A developer remaining amount estimating means for estimating an estimated developer remaining amount in the developer container from a developer replenishing speed by the developer replenishing means;
The difference between the estimated developer accumulated consumption obtained by subtracting the estimated developer remaining amount from the initial value and the accumulated developer consumption amount of the storage unit, or the estimated developer remaining amount and the development of the storage unit An image forming apparatus comprising: the accumulated developer consumption amount of the storage unit or a consumption amount correcting unit that corrects the remaining developer amount according to a difference in the remaining amount of the developer. The developer remaining amount estimating means obtains the replenishment amount to be replenished by the developer replenishing means from the developer amount detected by the developer amount detecting means in the developing unit, and replenishes the replenishment time for the replenishment amount. Calculate the replenishment speed by dividing the amount,
The image forming apparatus according to claim 1. When the difference is larger than a predetermined value, the consumption amount correcting unit replaces the accumulated developer consumption amount in the storage unit with the estimated developer accumulated consumption amount, or the remaining developer amount in the storage unit is Replaced with estimated developer remaining,
When the difference is not greater than a predetermined value, the consumption amount correcting unit does not correct the accumulated developer consumption amount or the developer remaining amount of the storage unit.
The image forming apparatus according to claim 1, wherein the image forming apparatus includes: A developer remaining amount estimation table associating the replenishment speed with the estimated developer remaining amount of the developer container;
The developer remaining amount estimation means converts the replenishment speed into the estimated developer remaining amount using the developer remaining amount estimation table.
The image forming apparatus according to claim 1, wherein the image forming apparatus is an image forming apparatus. The developer remaining amount estimation table is provided for each developer color,
The developer remaining amount estimating means converts the replenishment speed into the estimated developer remaining amount for each color of the developer.
The image forming apparatus according to claim 4. The developer replenishing means is configured to replenish the developer from the developer container to the developing unit by rotationally driving an electric motor,
The developer remaining amount estimation table is provided for each rotation speed of the electric motor,
The developer remaining amount estimating means converts the replenishment speed into the estimated developer remaining amount using the developer remaining amount estimation table selected based on the rotation speed of an electric motor.
The image forming apparatus according to claim 4, wherein the image forming apparatus is an image forming apparatus. When the replenishment time during which the developer replenishing means replenishes the developer is less than or equal to a threshold value, the consumption amount correcting means does not correct the accumulated developer consumption amount or the remaining developer amount in the storage unit;
The image forming apparatus according to claim 1, wherein the image forming apparatus is an image forming apparatus. When the replenishment time exceeds a certain time while the developer replenishing means replenishes the developer, the consumption amount correcting means sets the accumulated developer consumption amount of the storage means to the initial value, or , Correct the remaining amount of developer in the storage means to zero,
The image forming apparatus according to claim 7. Even if the developer replenishing means detects an event that should stop developer replenishment,
If the replenishment time until the developer replenishing means interrupts developer replenishment is not less than or equal to the threshold, the consumption correction means corrects the accumulated developer consumption or the developer remaining amount in the storage means. ,
The image forming apparatus according to claim 7. An exposure means for exposing the photoreceptor based on the image data;
A developing unit developing the photoreceptor with a developer;
A transfer means for transferring an image formed on the photosensitive member by a developer to a recording medium;
A fixing unit fixing the image on the recording medium, and an image forming method comprising:
A step of supplying a developer from a developer container containing the developer to the developing unit;
A step of detecting a developer amount in the developing unit by a developer amount detecting means in the developing unit;
A consumption calculating means calculates a developer consumption amount due to development from image data, and calculates the developer consumption from an accumulated developer consumption amount obtained by accumulating the developer goods consumption amount or an initial value of a developer remaining amount in the developer container. Calculating the remaining amount of developer by reducing the amount;
Storing the accumulated developer consumption amount or the developer remaining amount in a storage unit;
A developer remaining amount estimating unit estimating an estimated developer remaining amount in the developer container from a developer replenishment speed by the developer replenishing unit;
A consumption amount correcting unit subtracts the estimated developer remaining amount from the initial value, and the difference between the estimated developer accumulated consumption amount and the accumulated developer consumption amount of the storage unit, or the estimated developer remaining amount Correcting the accumulated developer consumption amount or the developer remaining amount in the storage unit according to the difference in the developer remaining amount in the storage unit;
An image forming method comprising:

Images