JP2006154413A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming apparatus for improving control accuracy of a fixing temperature corresponding to the layer thickness of toner. <P>SOLUTION: The image forming apparatus comprises a scanner part 11 or the like for acquiring image data, an image forming part 23 for forming toner images at each color by arranging dots on the basis of the image data acquired by the scanner part 11 or the like, a transfer part 24 for transferring to overlay the toner images at each color on recording paper, and a fixing part 25 for forming color images by heating, melting and fixing the toner images transferred on the recording paper by the transfer part 24. In addition, the image forming apparatus comprises an overlapping dot counting part 411 for counting the number of a part where dots of a plurality of colors are overlapped as an overlapping dot number when the image data are expressed by arranging the dots every color and a temperature control part 412 for increasing and decreasing the temperature of a thermal roller 209 in response to the increase and decrease of the overlapping dot number counted by the overlapping dot counting part 411. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an image forming apparatus that forms a color image by fixing a toner image.

  The so-called electrophotographic process in which a toner image is heated and melted and fixed to form an image includes charging, exposure, development, transfer, and fixing. When forming a color image, after transferring toner images of four basic colors such as black, magenta, yellow, and cyan on a recording sheet, the toner image is heated and melted and fixed. Thus, a color image is formed. In this case, a basic color in a color image, for example, magenta or yellow dots, is composed only of toner of that color. On the other hand, dots of colors other than the basic color are configured by superposing a plurality of basic color toners. Therefore, the basic color dots have a thin layer thickness of the toner that constitutes the dots, and the dots of colors different from the basic color have a plurality of basic color dots superimposed, so the toner layer thickness increases. Therefore, the layer thickness of the toner constituting the dot differs. Therefore, if the thickness of the toner is not taken into consideration when fixing the toner image, the heating becomes insufficient and the toner image cannot be sufficiently melted, resulting in a fixing failure and the toner peeling or heating. May waste power and generate paper wrinkles.

Therefore, the number of basic color dots transferred to the recording paper is counted for each line of the image, and if the number is large, the probability of dot overlap is high, so the toner layer thickness is large, and if the number is small, the probability of dot overlap. Therefore, an image forming apparatus is known in which the fixing temperature is controlled based on the number of transferred basic color dots by estimating that the toner layer thickness is small because of low toner (see, for example, Patent Document 1). ).
JP-A-1-239578

  By the way, when the fixing temperature is controlled based on the number of transferred basic color dots, the increase or decrease in the number of transferred basic color dots does not necessarily match the number of overlapping dots. There is a disadvantage in that the fixing temperature does not match and the fixing temperature suitable for the toner layer thickness cannot be controlled.

  SUMMARY An advantage of some aspects of the invention is that it provides an image forming apparatus capable of improving the control accuracy of a fixing temperature in accordance with a toner layer thickness.

  In order to achieve the above-described object, the invention according to claim 1 is an image forming apparatus, wherein an image acquisition unit that acquires image data, and dots are arranged based on the image data acquired by the image acquisition unit An image forming unit for forming a toner image for each color, a transfer unit for transferring the toner images for each color formed by the image forming unit on the recording paper, and a transfer unit for transferring the toner image on the recording paper. When the transferred toner image is heated and melted and fixed to form a color image, and the image data acquired by the image acquisition unit is represented by arranging dots for each color, a plurality of colors The overlapping dot counting unit that counts the number of overlapping dots as the number of overlapping dots, and the temperature of the fixing unit is increased or decreased according to the increase or decrease of the number of overlapping dots counted by the overlapping dot counting unit. It is characterized by comprising a temperature control unit.

  According to the above configuration, the toner images for the respective colors formed by arranging dots based on the image data acquired by the image acquisition unit are superimposed and transferred onto the recording paper, and the toner image transferred onto the recording paper is transferred. A color image is formed by being heated and melted and fixed by the fixing unit. In addition, when the image data acquired by the image acquisition unit is represented by arranging dots for each color, the number of places where dots of a plurality of colors overlap is counted as the number of overlapping dots, and the number of overlapping dots is increased or decreased. Accordingly, the temperature of the fixing unit is increased or decreased. As a result, the temperature of the fixing unit is increased / decreased according to the number of locations where dots of multiple colors overlap, that is, the number of locations where the toner layer thickness increases, thus improving the control accuracy of the fixing temperature according to the toner layer thickness. can do.

  The invention according to claim 2 is the image forming apparatus according to claim 1, wherein the overlapping dot counting unit counts the number of overlapping dots for each number of colors with which the dots overlap, and the temperature control unit includes: The temperature of the fixing unit is changed based on the number of overlapping dots counted by the overlapping dot counting unit.

  According to the above configuration, the number of overlapping dots is counted for each number of colors with which dots overlap, and the temperature of the fixing unit is changed based on the number of overlapping dots for each number of colors with which dots overlap. In this case, an increase / decrease in the number of colors in which dots overlap, that is, an increase / decrease in the layer thickness of the dots is reflected in the temperature of the fixing unit, so that the control accuracy of the fixing temperature according to the toner layer thickness can be further improved.

  A second aspect of the present invention is the image forming apparatus according to the first or second aspect, wherein the overlapping dot counting unit divides the image data acquired by the image acquiring unit into a plurality of regions and the plurality of the plurality of regions. The temperature control unit counts the number of overlapping dots for each of the regions, and the temperature control unit fixes the toner image corresponding to each region by the fixing unit when the toner image corresponding to the region is counted by the overlapping dot counting unit. The temperature of the fixing unit is changed based on the number of overlapping dots.

  According to the above configuration, the image data acquired by the image acquisition unit is divided into a plurality of regions, the number of overlapping dots is counted for each of the plurality of regions, and the toner image corresponding to each region is fixed by the fixing unit. In this case, the temperature of the fixing unit is changed based on the number of overlapping dots for each region. As a result, even when the dot overlap is different depending on the area of the image data, that is, when the toner layer thickness is different, the fixing temperature is changed according to the toner layer thickness in each area, and the fixing temperature according to the toner layer thickness is changed. The control accuracy can be improved.

  As described above, according to the present invention, the control accuracy of the fixing temperature according to the toner layer thickness can be improved.

  Embodiments according to the present invention will be described below with reference to the drawings. In addition, the structure which attached | subjected the same code | symbol in each figure shows that it is the same structure, The description is abbreviate | omitted. FIG. 1 is an example of a schematic side sectional view mainly showing a mechanical configuration of a digital copying machine as an embodiment of an image forming apparatus according to the present invention. The digital copying machine 1 includes a main body unit 200, a sheet post-processing unit 300 disposed on the left side of the main body unit 200, an operation unit 400 for a user to input various operation commands and the like, and an upper part of the main body unit 200. The document reading unit 500 disposed on the document reading unit 500 and the document feeding unit 600 disposed above the document reading unit 500.

  The operation unit 400 includes a touch panel 401, a start key 402, a numeric keypad 403, and the like. The touch panel 401 displays various operation screens and various operation buttons for the user to input various operation commands. The start key 402 is used for the user to input a print execution command and the like, and the ten key 403 is used for inputting the number of copies to be printed.

  The document feeding unit 600 includes a document placement unit 601, a document discharge unit 602, a paper feed roller 603, a document transport unit 604, and the like, and the document reading unit 500 includes a scanner 501 and the like. The paper feed roller 603 feeds out the original set on the original placement unit 601, and the original transport unit 604 transports the fed originals one by one on the scanner 501. The scanner 501 sequentially reads the conveyed document, and the read document is discharged to the document discharge unit 602.

  The main body 200 includes a plurality of paper feed cassettes 201, a plurality of paper feed rollers 202, a transfer roller 203, an intermediate transfer body roller 204, a photosensitive drum 205, an exposure device 206, and development for each color of yellow, magenta, cyan, and black. Apparatuses 207Y, 207M, 207C, and 207K, a fixing unit 25, a discharge port 210, and a discharge tray 211 are provided.

  The photosensitive drum 205 is uniformly charged by a charging device (not shown) while rotating in the direction of the arrow. The exposure device 206 converts a modulation signal generated based on image data such as a document read by the document reading unit 500 into a laser beam and outputs it, and forms an electrostatic latent image on the photosensitive drum 205 for each color. . The developing devices 207Y, 207M, 207C, and 207K supply each color developer to the photosensitive drum 205 to form a toner image for each color. The intermediate transfer roller 204 is transferred by superimposing the toner images of each color from the photosensitive drum 205, and a color toner image is formed on the intermediate transfer roller 204.

  On the other hand, the paper feeding roller 202 pulls out the recording paper from the paper feeding cassette 201 in which the recording paper is stored, and feeds the recording paper to the transfer roller 203. The transfer roller 203 transfers the toner image on the intermediate transfer roller 204 to the conveyed recording paper. The fixing unit 25 includes a pressure roller 208 and a heat roller 209, and presses and heats the recording paper on which the toner image has been transferred by the pressure roller 208 and the heat roller 209, whereby the toner image is applied to the recording paper. Let it settle. Thereafter, the recording paper is carried into the paper post-processing unit 300 from the discharge port 210 of the main body unit 200. The recording paper is also discharged to the discharge tray 211 as necessary.

  FIG. 2 is a perspective view showing a detailed configuration of the fixing unit 25. The fixing unit 25 shown in FIG. 2 is configured such that a pressure roller 208 having an elastic body made of, for example, silicon rubber or the like on the surface and a heat roller 209 having an induction coil unit 220 inside, for example, face each other. In FIG. 2, the heat roller 209 is seen through. The heat roller 209 is made of a cylindrical metal conductor. The induction coil unit 220 includes, for example, a plurality of induction coils 221, 222, 223, 224, and 225. The induction coils 221, 222, 223, 224, and 225 are arranged in a line in the longitudinal direction (main scanning direction) of the heat roller 209 at a position close to the inner surface of the heat roller 209 that faces the pressure roller 208. A so-called IH (Induction Heating) type heating device is configured to induce and heat the heat roller 209 by generating an induced eddy current in the heat roller 209.

  Further, in the vicinity of the induction coils 221, 222, 223, 224, and 225, temperature sensors 231 including, for example, thermistors for detecting the temperature of the heat roller 209 at positions facing the induction coils 221, 222, 223, 224, and 225. 232, 233, 234, and 235 are disposed close to the inner surface of the heat roller 209.

  Returning to FIG. 1, the paper post-processing unit 300 includes a carry-in port 301, a recording paper transport unit 302, a carry-out port 303, a stack tray 304, and the like. The recording paper transport unit 302 sequentially transports the recording paper carried into the carry-in port 301 from the discharge port 210 and finally ejects the recording paper from the carry-out port 303 to the stack tray 304. The stack tray 304 is configured to move up and down in the direction of the arrow in accordance with the number of recording sheets stacked from the carry-out port 303.

  FIG. 3 is an example of a block diagram mainly showing an electrical configuration of the digital copying machine 1 shown in FIG. The digital copying machine 1 includes a scanner unit 11, a printer unit 21, an operation panel unit 31, a control unit 41, a parallel I / F unit 52, a serial I / F unit 51, and an HDD (hard disk drive) 53.

  The scanner unit 11 includes an illumination light source 12 and an image sensor 13 that constitute the scanner 501 shown in FIG. The image sensor 13 includes, for example, a CCD (charge coupled device). The scanner unit 11 irradiates the document with the illumination light source 12 and receives the reflected light for each color with the image sensor 13, thereby reading the image from the document and controlling the image data of each color corresponding to the read image with the control unit. 41 is output.

  The printer unit 21 includes a sheet conveying unit 22 including the sheet feeding cassette 201 and the sheet feeding roller 202 shown in FIG. 1, the intermediate transfer member roller 204, the photosensitive drum 205, the exposure device 206, and the developing device 207Y shown in FIG. , 207M, 207C, 207K, and the like, a transfer unit 24 including the transfer roller 203 shown in FIG. 1, and a fixing unit 25 shown in FIG. Specifically, the paper transport unit 22 transports the recording paper to the image forming unit 23, the image forming unit 23 forms a toner image corresponding to the image data, and the transfer unit 24 transfers the toner image to the recording paper. Then, the fixing unit 25 fixes the toner image on the recording paper to form an image.

  The fixing unit 25 supplies the pressure roller 208, the heat roller 209, the induction coil unit 220, the temperature sensors 231, 232, 233, 234, and 235, and a high-frequency current to the induction coil unit 220 to induce and heat the heat roller 209. A control unit 240 is provided. The IH control unit 240 is configured using, for example, an inverter circuit, and outputs a high-frequency current to the induction coils 221, 222, 223, 224, and 225 in accordance with a control signal from the control unit 41, and each of the heat rollers 209 By generating an induced eddy current at a position facing the induction coils 221, 222, 223, 224, and 225, a predetermined position on the heat roller 209 is heated.

  The operation panel unit 31 includes a touch panel unit 32 including the touch panel 401 shown in FIG. 1 and an operation key unit 33 including the start key 402 and the numeric keypad 403 shown in FIG. The operation panel unit 31 is used for a user to perform an operation related to the copy function, and gives an operation command or the like by the user to the control unit 41. The touch panel unit 32 includes a touch panel unit that combines a touch panel and an LCD (Liquid Crystal Display). The touch panel unit 32 displays information on various operation screens, for example, enlargement / reduction ratio setting, and the user touches the part. Thus, an operation button or the like for inputting various operation commands to the control unit 41 is displayed. The operation key unit 33 is used by the user to input a print execution command or the like.

  The control unit 41 controls the operation of the entire apparatus. For example, the program for controlling the copying operation of the digital copying machine 1 and the image data acquired by the document reading unit 500 are arranged by arranging dots for each color. In this case, a counting program for counting the number of overlapping portions of a plurality of color dots as the number of overlapping dots, a temperature control program for increasing / decreasing the temperature of the fixing unit 25 in accordance with the increase / decrease in the number of overlapping dots, and the like are stored. ROM (Read Only Memory), RAM (Random Access Memory) that temporarily stores data, a CPU (Central Processing Unit) that reads and executes control programs from the ROM, and a dedicated hardware circuit, etc. ing.

  The control unit 41 functions as the overlapping dot counting unit 411 by reading and executing the counting program from the ROM, and functions as the temperature control unit 412 by reading and executing the temperature control program from the ROM.

  The HDD 53 stores image data read by the scanner unit 11. Note that the writing of image data to the HDD 53 and the reading of image data from the HDD 53 are executed in accordance with instructions from the control unit 41. The parallel I / F unit 52, the serial I / F unit 51, and a network interface unit (not shown) such as a wireless LAN perform data input / output with an information processing apparatus such as a personal computer connected to the outside. Interface.

  The image forming apparatus shown in FIGS. 1 and 3 is configured as a digital color copying machine as described above. In general, an image forming apparatus widely includes not only a copying machine but also a printer, a facsimile machine, or a multi-function machine having both of them, and a device for inputting and outputting an image or image data. Therefore, in general, an image forming apparatus is provided with an image acquisition unit that captures image data, an image output unit that outputs an image or image data, and a control unit that controls them. The image acquisition unit includes a scanner unit (for example, the scanner unit 11) that reads an image from a recording sheet on which an image is recorded, and an image data reception unit (for example, a parallel I / F unit 52, a serial I / F unit 51, And an image output unit includes an image printing unit (for example, the printer unit 21) for recording an image on a recording paper and an image data transmission unit (for transmitting image data). For example, at least one of a parallel I / F unit 52, a serial I / F unit 51, and a network interface unit (not shown) is included. For example, an image data receiving unit and a printing unit are provided for a printer, and a scanner unit and an image data transmitting unit are provided for a facsimile apparatus.

  Next, the operation of the digital copying machine 1 configured as described above will be described. FIG. 4 is a flowchart showing an example of the operation of the digital copying machine 1. First, for example, image data representing a color image is transmitted to the serial I / F unit 51 from a personal computer (not shown) connected to the outside of the serial I / F unit 51. The image data received by the serial I / F unit 51 is transmitted from the serial I / F unit 51 to the control unit 41 and stored in the HDD 53 by the control unit 41 (step S1).

  Next, the overlapping dot counting unit 411 divides the image data stored in the HDD 53 into a plurality of areas (step S2). FIG. 5 is an explanatory diagram showing an example of a state in which the image data 531 stored in the HDD 53 is divided into a plurality of areas. The image data 531 shown in FIG. 5 is divided into, for example, the same five regions as the number of induction coils in the induction coil unit 220 in the main scanning direction. For example, one side is the number of dots in one region in the main scanning direction in the sub-scanning direction. Are divided so as to correspond to the same number of dots. Each area is given a number of m = 1 to 5 in the main scanning direction and n = 1 to 5 in the sub-scanning direction, for example. It is expressed by orthogonal coordinates with the scanning direction. Hereinafter, an area having the number m in the main scanning direction and the number n in the sub scanning direction is referred to as Dmn.

  Next, the overlapping dot counting unit 411 generates dot arrangement data indicating dot arrangements of basic colors, for example, four colors of black, magenta, yellow, and cyan, for each of the regions D11 to D55 from the image data 531 ( Step S3). FIGS. 6A, 6B, 6C, and 6D are explanatory diagrams for explaining dot arrangement data generated for, for example, black, magenta, yellow, and cyan in the region D23. In FIG. 6, the area D23 illustrates image data of 8 dots in the main scanning direction and 8 dots in the sub-scanning direction for the sake of simplicity of explanation, and 1 の in each figure corresponds to 1 dot. Further, in FIG. 6, the positions where the dots of the respective colors are arranged are indicated by hatching. Further, the overlapping dot counting unit 411 generates similar dot arrangement data for other regions other than the region D23.

  Next, based on the dot arrangement data generated for each region by the overlapping dot counting unit 411, the number of overlapping dots N1, which is the number of dots of only one color for each region, and the number of dots overlapping two colors. The number of overlapping dots N2, the number of overlapping dots N3, which is the number of dots overlapping three colors, and the number of overlapping dots N4, which is the number of dots overlapping four colors, are counted (step S4). FIG. 6E is an explanatory diagram showing the number of colors in which the dots in the region D23 overlap based on the dot arrangement data shown in FIGS. 6A, 6B, 6C, and 6D. In FIG. 6E, the overlapping dot counter 411 causes the number of overlapping dots “1” to be the number of overlapping dots N1 in the region D23 and the number of overlapping colors “2” to be the number of overlapping in the region D23. The number of dots N2, the number of overlapping dots of “3” is counted as the number of overlapping dots N3 in the region D23, and the number of overlapping dots of “4” is counted as the number of overlapping dots N4 in the region D23. Further, the overlapping dot counting unit 411 similarly counts the number of overlapping dots N1, N2, N3, and N4 for other regions other than the region D23.

  Next, based on the overlapping dot numbers N1, N2, N3, and N4 counted for each region by the overlapping dot counting unit 411, the temperature control unit 412 calculates the target fixing temperature T for each region (step S5). ). Specifically, the target fixing temperature T is calculated based on the following formula (1), for example.

T = T0 + K1 * N1 + K2 * N2 + K3 * N3 + K4 * N4 (1)
However, T0 is a basic fixing temperature when, for example, the thickness of the toner is not taken into consideration. The coefficients K1, K2, K3, and K4 are constants stored in advance in a storage unit such as the HDD 53. For example, experimentally obtained numerical values are stored in the HDD 53 as coefficients K1, K2, K3, and K4. ing. Note that the coefficients K1, K2, K3, and K4 are set, for example, having a relationship represented by the following equation (2).

0 <K1 <K2 <K3 <K4 (2)
Further, the coefficients K1, K2, K3, and K4 may be set so as to increase exponentially as shown in FIG. 7, for example. Alternatively, a data table obtained by experimentally obtaining the relationship between the target fixing temperature T and the number of overlapping dots N1, N2, N3, and N4 in advance is stored in advance in the HDD 53, for example, and the temperature control unit 412 The target fixing temperature T may be obtained from the number of overlapping dots N1, N2, N3, and N4 by referring to this data table.

  Next, a toner image is formed on the recording paper based on the image data 531 (step S6). Specifically, the photosensitive drum 205 is uniformly charged by a charging device (not shown) while rotating in the direction of the arrow in accordance with a control signal from the control unit 41, and is stored in the HDD 53 by the exposure device 206. A modulation signal generated based on the image data 531 is converted into a laser beam and output, and an electrostatic latent image for each color is formed on the photosensitive drum 205. Next, in accordance with a control signal from the control unit 41, each color developer is supplied to the photosensitive drum 205 by the developing devices 207Y, 207M, 207C, and 207K, and a toner image for each color is formed. The toner image is transferred from the photosensitive drum 205 to the intermediate transfer roller 204 so that a color toner image is formed on the intermediate transfer roller 204.

  On the other hand, in response to a control signal from the control unit 41, the recording paper is pulled out from the paper feeding cassette 201 by the paper feeding roller 202, fed to the transfer roller 203, and transferred onto the intermediate transfer body roller 204. A color toner image is transferred and conveyed to the fixing unit 25.

  Next, in response to a control signal from the temperature control unit 412, the IH control unit 240 applies pressure and heat while the recording paper nipped by the pressure roller 208 and the heat roller 209 is conveyed in the fixing unit 25. The high-frequency current is output to the induction coils 221, 222, 223, 224, and 225 at positions corresponding to the respective regions in order to set the fixing temperature to the target fixing temperature T of each region in the image data 531 in synchronization with the temperature sensor 231. , 232, 233, 234, and 235 are output to the induction coils 221, 222, 223, 224, and 225 in order to match the temperature of the heat roller 209 at the position corresponding to each area detected with the target fixing temperature T at that position. The high frequency current is controlled (step S7).

  Specifically, for example, the position of the recording paper on which the toner image having the number n in the sub-scanning direction in the image data 531 is “1” is nipped by the pressure roller 208 and the heat roller 209. In this case, in response to a control signal from the temperature control unit 412, the IH control unit 240 sets the temperature at the position corresponding to each region of the heat roller 209 to the target fixing temperature T of the regions D11, D12, D13, D14, and D15. High-frequency currents are output to the induction coils 221, 222, 223, 224, and 225, respectively, and the toner image in each region is heated and melted and fixed at the target fixing temperature T in that region. Thereafter, as the recording paper is conveyed by the pressure roller 208 and the heat roller 209, the toner image in each area in contact with the heat roller 209 is heated and melted and fixed at the target fixing temperature T in the area.

  As described above, by the operation of steps S1 to S7, the overlapping dot counting unit 411 counts the number of overlapping dots N1, N2, N3, and N4 for each number of colors that the dots overlap, and the temperature control unit 412 calculates the number of colors that the dots overlap. Since the fixing temperature is changed based on the number of overlapping dots counted in the above, even when the toner layer thickness varies due to the overlap of multiple color toners, the control accuracy of the fixing temperature according to the toner layer thickness is improved. can do.

  In addition, the fixing temperature is changed by the temperature control unit 412 based on the number of overlapping dots counted for each number of colors in which dots overlap in each region obtained by dividing the image data into a plurality of parts by the overlapping dot counting unit 411. Even if the dot overlap depends on the image area, that is, the toner layer thickness varies, the fixing temperature changes according to the toner layer thickness in each area, and the fixing temperature control accuracy according to the toner layer thickness is improved. Can be improved.

  Although the example in which the image data is divided into a plurality of areas and the target fixing temperature T is calculated for each area has been shown, the entire image data is set as one area without dividing the image data into a plurality of areas. Processing of ~ S7 may be performed. In this case, the induction coil unit 220 may be composed of a single induction coil.

  In addition, although an example in which the number of overlapping dots N1, N2, N3, and N4 is counted for each number of overlapping colors has been shown, for example, the overlapping dot counting unit 411 is a place where multiple color dots overlap regardless of the number of overlapping colors. And the temperature control unit 412 may increase or decrease the target fixing temperature T in accordance with the increase or decrease of the number of overlapping dots Nx.

  Further, although the fixing unit 25 has shown an example in which the heat roller 209 is heated by induction heating by the induction coil unit 220, the heat roller 209 is heated by using other heating means such as a heating wire or a ceramic heater. May be.

1 is an example of a schematic side sectional view mainly showing a mechanical configuration of a digital copying machine as an embodiment of an image forming apparatus according to the present invention; FIG. 2 is a perspective view illustrating a detailed configuration of a fixing unit illustrated in FIG. 1. FIG. 2 is an example of a block diagram mainly showing an electrical configuration of the digital copying machine shown in FIG. 1. 2 is a flowchart showing an example of the operation of the digital copying machine shown in FIG. It is explanatory drawing which shows an example of the state by which image data was divided | segmented into the several area | region. (A) is black, (b) is magenta, (c) is yellow, (d) is explanatory drawing for demonstrating the dot arrangement data produced | generated about cyan, respectively. (E) is explanatory drawing which showed the number of colors with which a dot overlaps. It is explanatory drawing which shows an example of the coefficient K1, K2, K3, and K4.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Digital copier 21 Printer part 22 Paper conveyance part 23 Image formation part 24 Transfer part 25 Fixing part 41 Control part 51 Serial I / F part 52 Parallel I / F part 53 HDD
200 Main body 203 Transfer roller 204 Intermediate transfer roller 205 Photosensitive drum 206 Exposure device 207Y, 207M, 207C, 207K Development device 208 Pressure roller 209 Heat roller 220 Induction coil portions 221, 222, 223, 224, 225 Induction coil 231 232, 233, 234, 235 Temperature sensor 240 IH controller

Claims (3)

An image acquisition unit for acquiring image data;
An image forming unit that forms a toner image for each color by arranging dots based on the image data acquired by the image acquisition unit;
A transfer unit that superimposes and transfers a toner image for each color formed by the image forming unit on a recording paper;
A fixing unit that forms a color image by heating and melting and fixing the toner image transferred onto the recording paper by the transfer unit;
When the image data acquired by the image acquisition unit is represented by arranging dots for each color, an overlapping dot counting unit that counts the number of overlapping dots as the number of overlapping dots,
A temperature controller that increases or decreases the temperature of the fixing unit in accordance with an increase or decrease in the number of overlapping dots counted by the overlapping dot counting unit;
An image forming apparatus comprising: The overlapping dot counting unit counts the number of overlapping dots for each number of colors that the dots overlap,
The image forming apparatus according to claim 1, wherein the temperature control unit changes the temperature of the fixing unit based on the number of overlapping dots counted by the overlapping dot counting unit. The overlapping dot counting unit divides the image data acquired by the image acquisition unit into a plurality of regions and counts the number of overlapping dots for each of the plurality of regions,
When the toner image corresponding to each region is fixed by the fixing unit, the temperature control unit controls the temperature of the fixing unit based on the number of overlapping dots counted by the overlapping dot counting unit. The image forming apparatus according to claim 1, wherein the image forming apparatus is changed.

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