JP2021026193A - Image forming apparatus - Google Patents

Abstract

To solve the problem in which since detection temperature of a temperature detection element is decreased due to heat loss occurring in a melting process of a toner image near a temperature detection element part in a fixing device of an image forming apparatus, heating of a heater may be encouraged, an excessive heat quantity may be generated as a whole heater, and wasted power may be dissipated.SOLUTION: An image forming apparatus that forms an image by means of an electro-photographic process analyzes image data received by receiving means using a local area unit having predetermined magnitude to calculate a toner applied amount associated with each local area, corrects the toner applied amount associated with the local area on the basis of weight which is determined by a main scanning position of the local area and a positional relation of temperature detecting means, and sets fixing temperature of fixing means according to a peak value of the toner applied amount of each local area after the correction.SELECTED DRAWING: Figure 6

Description

The present invention relates to fixing temperature control of an image forming apparatus.

Conventionally, in an image forming apparatus that heat-fixes a toner image formed by an electrophotographic method on a recording material (recording paper) to form an image, a film heating type heating device has been put into practical use as a fixing device. A typical example of this fuser has a heater, which is a heating member having a resistance heating element on a ceramic substrate, and a fixing film, which is a film-shaped fixing member that rotates in contact with the heater. It also has a pressurizing roller, which is a rotatable pressurizing member that is pressed against the heater via the fixing film. The recording material that supports the unfixed image (hereinafter referred to as the unfixed toner image or the toner image) is a pressure contact portion (fixing nip) formed by pressing a pressure roller against the heater via the fixing film. It is heated while being sandwiched between parts).

As a result, the toner image on the recording material is heated and fixed to the recording material as a fixed image. This film heating type fuser has an advantage that the time required to start energizing the heater and raise the temperature to a fixable temperature is short. Therefore, the image forming apparatus equipped with this fuser consumes less power while waiting for the print instruction, and can shorten the time from the print instruction to the output of the first image.

Such a film heating type fuser is temperature-controlled based on the detection result of a temperature detecting element (thermistor or the like) provided on the back surface of the heater or the inner surface of the fixing film. That is, when the detection temperature of the temperature detection element is lower than the predetermined set temperature (hereinafter referred to as the temperature control temperature), the temperature of the heater is raised, and conversely, when the temperature is higher, the temperature of the fuser is lowered. It is kept constant. Here, the temperature control temperature is determined according to the amount of color material (toner loading amount) per unit area to be loaded on the recording material, and usually, the maximum amount of color material to be loaded per unit area of the recording material is determined in advance. It is controlled so that the transferred image can be reliably fixed with the maximum amount of color material.

In addition to this, various methods have been proposed in which the printed image data is analyzed and the temperature control temperature is controlled according to the toner loading characteristic of the image data. Patent Document 1 describes a method of finely controlling the temperature control temperature according to the image area of the toner loading amount portion of a predetermined amount or more. Further, Patent Document 2 describes a method of controlling the temperature control temperature according to the presence or absence of an image region having a toner loading amount within a predetermined range.

Japanese Unexamined Patent Publication No. 2014-074894 JP-A-2017-201385

However, when the temperature control temperature is controlled by the method of the prior art disclosed in Patent Documents 1 and 2 described above, the temperature control is uniformly the same regardless of the drawing position in the page of the image area that matches the predetermined toner loading amount condition. The fuser is controlled by temperature.

Generally, when a recording material carrying a toner image is introduced into a fixing nip portion and sandwiched and conveyed, the amount of toner loaded at a position on the recording material corresponding to the position of the temperature detection element portion in the longitudinal direction of the heater is If it is high, the temperature of the entire heater tends to rise. This is because when a region having a high toner loading amount exists on the recording material, it is necessary to apply more heat to melt the toner, and the heat of the peripheral members of the temperature detection element portion is taken away. That is, the toner image close to the temperature detection element takes heat from the temperature detection element, and as a result, the temperature detected by the temperature detection element is lowered, so that the heater heats up, and the heater as a whole becomes excessive in heat, resulting in wasteful power consumption. It will be consumed.

In order to solve the above problems, the image forming apparatus according to the present invention is
An image forming apparatus for forming an image by an electrophotographic process, which comprises a receiving means for receiving image data, an image forming means for forming a toner image on a recording material based on the image data received by the receiving means, and an image forming means. A fixing means for thermally fixing the toner image formed by the image forming means to the recording material, a temperature detecting means for detecting the temperature of the fixing means, and a fixing temperature for heat fixing by the fixing means are set. The fixing temperature control means has a fixing temperature control means for controlling the temperature of the fixing means so as to have the set fixing temperature, and the fixing temperature control means locally receives image data received by the receiving means to a predetermined size. The area-by-region analysis is performed to calculate the amount of toner loaded on the recording material for each local region, and the amount of toner loaded on the local region is the main scanning position when the local region is drawn on the recording material. It is characterized in that the fixing temperature of the fixing means is set according to the peak value of the toner loading amount in each local region corrected by the weighting, which is corrected by the weighting determined by the positional relationship of the temperature detecting means.

According to the image forming apparatus according to the present invention, whether or not the main scanning position when each local region of the printed image data is drawn on the recording material corresponds to the position of the temperature detecting element portion in the longitudinal direction of the heater. By weighting the toner loading amount of the local region and controlling the temperature control temperature of the fuser based on the toner loading amount information of each local region corrected by using the weighting, the toner loading of the image data is performed. It is possible to realize good fixability with the minimum amount of heat required according to the quantity characteristics.

It is a figure which shows the system block diagram of an image forming apparatus. It is a figure which shows the structure of the printer part of an image forming apparatus. It is a figure which shows the schematic cross section of the fixing unit. It is a block diagram explaining the functional structure of an image processing unit. It is a flowchart explaining a series of image processing by an image processing unit. It is a flowchart explaining image analysis processing by an image analysis unit. It is a flowchart explaining the toner loading amount calculation process in the local area unit. (A) It is a figure which shows an example of the gradation correction table. (B) It is a figure which shows an example of the halftone dot ratio table. (C) It is a figure which shows an example of the toner loading amount conversion table. It is a figure explaining the outline of the process of obtaining the toner loading amount information for fixing temperature control. It is a flowchart explaining the fixing temperature control of an image forming apparatus. It is a figure which shows an example of the correspondence relation between the toner loading amount information and a target fixing temperature. (A) It is a rear schematic diagram of a heater. (B) It is a front schematic diagram of a part cutout of a heater. (C) is a schematic cross-sectional view of a heater and a diagram showing an example of an energization control circuit of the heater. It is a figure which shows the relationship between the position of the thermistor and the print area on a paper P.

Hereinafter, embodiments for carrying out the present invention will be described with reference to the drawings.

FIG. 1 is a diagram showing a system configuration diagram of an image forming apparatus according to an embodiment of the present invention.

The image forming apparatus is, for example, an electrophotographic color or monochrome image forming apparatus using toner such as a digital copier, a laser printer, or a facsimile.

The image forming apparatus includes a controller 0101 and modules (operation unit 0121, printer unit 0122, external storage device 0123) outside the controller 0101.

The controller 0101 includes a ROM 0102, a CPU 0103, a RAM 0104, an image processing unit 0105, and a compression / decompression unit 0106. The CPU 0103 is a central processing unit (processor) that controls the entire device and performs arithmetic processing, and performs each process described later based on a program stored in the ROM 0102. The ROM 0102 is a read-only memory, which is a storage area for a system startup program, a program for controlling the printer unit 0122, character data, character code information, and the like. RAM0104 is a random access memory and is a data storage area having no usage restrictions. The RAM 0104 is used as a storage area for font data additionally registered by downloading, or as an execution area for programs and data for each of various processes. The RAM 0104 can also be used as a data storage area for the received image file. The image processing unit 0105 performs image data generation processing. The compression / decompression unit 0106 compresses and decompresses the image data.

The operation unit 0121 displays, for example, by a liquid crystal display, and is used for displaying the setting state of the device, the current processing inside the device, the error state, and the like. It is also used to change or reset print settings. The printer unit 0122 is a part that controls each device (fixing unit, etc.) of the printer engine, and the external storage device 0123 is a storage medium (for example, HDD), and is a data spool, a program, various information files, and image data. It is used for storage, work area, etc.

The controller 0101 further includes various interfaces (I / F) and a system bus 0111. The operation unit I / F 0112 is connected to the operation unit 0121. The printer I / F 0113 performs data supply control and the like with the printer unit 0122. The Network I / F 0114 connects the present device to a network (for example, LAN) via the I / F. The device I / F 0115 is connected to the external storage device 0123. System bus 0111 serves as a data passage between the structural elements described above.

Next, the configuration of the printer unit 0122 described above will be described with reference to FIG.

As shown in the figure, the printer unit 0122 has the following devices as main components.
(1) Cassette tray 0201
(2) Cassette paper feed roller 0202
(3) Transfer belt drive roller 0203
(4) Transfer belt 0204
(5) Photosensitive drum 0205-0208 (latent image carrier)
(6) Transfer roller 0209-0212 (transfer means)
(7) Cartridges 0213 to 0216 (described later)
(8) Optical units 0217 to 0220 (described later)
(9) Fixing unit 0221 (fixing device)
(10) Printer controller 0223
In the printer unit 0122, an electrophotographic process is used to superimpose and transfer toner images of each color of Y (yellow), M (magenta), C (cyan), and K (black) on a recording material. Then, the fixing unit 0221 heats the recording material at a predetermined temperature and pressurizes the recording material to fix the toner image on the recording material. The optical units 0217 to 0220 of each color are configured to expose and scan the surface of each photosensitive drum 0205 to 0208 with a laser beam to form a latent image. The series of image forming operations is controlled by scanning in synchronization so that the image is transferred from a predetermined position on the recorded material to be conveyed.

The latent image formed on the surface of each photosensitive drum 0205 to 0208 is visualized as a toner image by a toner as a developer of each color by a developing device (not shown) provided in the cartridges 0213 to 0216. Further, the printer unit 0122 includes various motors. The paper feed motor (not shown) is for feeding and transporting the recording material. The transfer belt drive motor (not shown) is for driving the transfer belt drive roller 0203. The photosensitive drum drive motor (not shown) is for driving each color photosensitive drum 0205 to 0208 and a transfer roller. Further, the printer unit 0122 is provided with various sensors. The cassette tray sensor (not shown) is for detecting the detached (open / closed) state of the cassette tray 0201. The recording material remaining amount sensor (not shown) is for detecting the remaining amount of the recording material stored in the cassette tray 0201.

The series of image forming operations by the printer unit 0122 described above are controlled by the printer controller 0223 according to the print instruction and the image data received from the controller 0101 via the printer I / F 0108 of FIG. Further, it is assumed that the various sensors described above are connected to the printer controller 0223, and various information detected / determined by the printer controller 0223 is notified to the controller 0101 via the I / F 0108.

FIG. 3 is a diagram illustrating a schematic cross section of the fixing unit 0221 according to the embodiment of the present invention.

The fixing unit 0221 is a film heating type and a pressure roller drive type fixing device, and is roughly classified into a heating unit 0310 as a heating means and an opposing member (pressurizing) forming the heating unit 0310 and a fixing nip portion N. It has an elastic pressure roller 0320 as a means) and a device housing (not shown) incorporating these.

The ceramic heater (hereinafter referred to as a heater) 0330 is horizontally long in the direction perpendicular to the paper surface in FIG. 3, has a low heat capacity as a whole, and raises the temperature quickly and responsively in response to ON / OFF of energization. To lower the temperature. The film guide member (hereinafter referred to as stay) 0311 is also a horizontally long member whose length is perpendicular to the paper surface in FIG. It is desirable that the stay 0311 is a rigid material having heat resistance and electrical insulation and capable of withstanding a high load. For example, it is composed of PPS (polyphenylene sulfide), PAI (polyamideimide), PI (polyimide), PEEK (polyetheretherketone) and the like.

The heater 0330 is fixedly supported by being fitted into a groove provided along the length of the stay in a substantially central portion of the lower surface of the stay 0311 with the surface side facing outward. The heat-resistant film (hereinafter referred to as a fixing film) 0312 is, for example, a heat-resistant film having a thickness of about 30 μm to 250 μm and having flexibility as a whole, and stay 0311 on which the heater 0330 is fixedly supported as described above. It is loosely fitted on the outside.

The fixing film 0312 is preferably a single-layer film made of a material such as PTFE, PFA or PPS, or a composite layer film in which the surface of a base layer made of a material such as PI, PAI or PEEK is coated with PTFE, PFA or the like as a release layer. .. Further, it is also preferable that a pure metal such as SUS, AI, Ni, Cu, Zn or the like having high thermal conductivity, an alloy or the like is used as a base layer, and the release layer is coated with the above-mentioned coating treatment and a fluororesin tube. ..

The elastic pressure roller (hereinafter referred to as a pressure roller) 0320 includes a core metal 0321, a roller layer 0322 made of an elastic / heat resistant material such as silicon rubber concentrically provided on the core metal, and a surface layer 0323. ing. Both ends of the core metal 0321 are rotatably supported between the front side and the back side chassis side plates (not shown) of the apparatus housing, respectively, via bearings.

The heating unit 0310 is arranged substantially in parallel on the upper side of the pressurizing roller 0320 with the side of the heater 0330 facing downward. Then, the stay 031 has a fixing film 0612 sandwiched between the heater 0330 and the pressure roller 0320 by an urging means (not shown) to resist the elasticity of the roller layer 0322 against the upper surface of the pressure roller 0320. It is held in a state of being pressed together with a predetermined pressing force. As a result, the fixing film 0612 is sandwiched between the lower surface of the heater 0330 and the upper surface of the pressure roller 0320, and a fixing nip portion (nip portion) N having a predetermined width is formed in the paper transport direction (recording material transport direction) D. ..

The pressurizing roller 0320 is rotationally driven by a motor (drive source: not shown) at a predetermined peripheral speed in the counterclockwise direction of arrow R0320 in FIG. The rotational force of the pressure roller 0320 acts on the fixing film 0312 through the pressure contact friction force at the fixing nip portion N. Therefore, the fixing film 0312 rotates in the clockwise direction of the arrow R0310 while its inner surface slides in close contact with the lower surface of the heater 0330 at the fixing nip portion N.

The stay 031 serves as a film guide for holding the heater 0330 and for ensuring transport safety during rotation of the fixing film 0312. In order to improve the rotational slidability with the fixing film 0312, a lubricant such as durable grease is interposed between the fixing film 031 and the outer peripheral surfaces of the heater 0330 and the stay 0311.

When the heater 0330 is energized, the fixing nip portion N rises to a predetermined temperature due to the heat generated by the heater 0330, and when the temperature is adjusted, the paper P carrying the unfixed toner image t on the fixing nip portion N is formed. be introduced. In the fixing nip portion N, the toner image-supporting surface side of the paper P is in close contact with the outer surface of the fixing film 0312 and is sandwiched and conveyed. In this sandwiching and transporting process, the heat of the heater 0330 is applied to the paper P via the fixing film 0312, and the unfixed toner image t on the paper P is fixed by heating and pressurizing.

FIG. 12 is a diagram showing an outline of the configuration of the heater 0330 in the present embodiment. (A) is a schematic rear view (back side) of the heater 0330, (b) is a schematic front view (front side) of a partial notch of the heater 0330, and (c) is cc of the heater 0330 of (b). It is a cross-sectional schematic diagram and the figure which shows an example of the energization control circuit (energization control part) used for the heater 0330.

The heater 0330 has an elongated heat-resistant, insulating, and good thermal conductive substrate (insulating base material) 1201. A resistance heating element 1202 that generates heat by energization provided along the longitudinal direction (heater width direction) of the substrate 1201 is provided on the surface (hereinafter referred to as the surface) of the substrate 1201 on the fixing nip portion N side. Further, it is a heating member having a connecting electric circuit 1203, feeding electrodes 1204 and 1205, and a heat-resistant overcoat layer 1206 as a whole having a low heat capacity.

The substrate 1201 is, for example, a ceramic material substrate made of _{alumina (aluminum oxide, Al 2} O _3). Resistance heating element 1202 may be, for example, silver-palladium (Ag / Pb), electrical resistance material paste such as Ta 2 _N (resistance paste) along the substrate length on the heater board surface pattern applied by screen printing or the like, baked It was formed by the fact.

The power feeding electrodes 1204 and 1205 are provided side by side on the longitudinal end side of the surface of the substrate 1201, and one power feeding electrode portion 1204 is electrically conductive to one end of the resistance heating element 1202 via the conductive extension portion 1204a. I'm letting you. The other power feeding electrode portion 1205 is electrically conducted to the other end portion of the resistance heating element 1202 via a connecting electric circuit 1203 provided on the surface of the substrate 1201 in parallel with the resistance heating element 1202. As described above, a series electric circuit (AC line) of the feeding electrode portion 1204 → the resistance heating element 1202 → the connecting electric circuit 1203 → the feeding electrode portion 1205 is configured. The overcoat layer 1206 is formed on the surface of the substrate 1201 so as to cover the resistance heating element 1202 and the connecting electric circuit 1203, except for the feeding electrode portions 1204 and 1205.

Further, the heater 0330 has a temperature detection element 0337 on the back surface of the substrate 1201 (the surface opposite to the fixing nip portion N). The temperature detection element (thermistor) 0337 is provided to detect the temperature of the heater 0330. In this embodiment, an external contact type thermistor separated from the heater 0330 is used as the temperature detection element.

The thermistor 0337 is obtained by providing a heat insulating layer on a support and fixing an element of the chip thermistor on the heat insulating layer, and pressurizing the element toward the back surface of the substrate 1201 by a predetermined pressing force to support the support. Is attached to the back surface of the substrate 1201. In this example, a highly heat-resistant liquid crystal polymer was used as the support, and a ceramic paper was laminated as the heat insulating layer. The external contact type thermistor 0337 is arranged in the minimum size paper passing region through which the paper P of a predetermined size introduced into the fixing nip portion N always passes.

The protective element 1208 is arranged in contact with the back surface of the substrate 1201 as a safety element that shuts off energization when the heater 0330 rises abnormally. In this embodiment, as the protection element 1208, a thermal fuse that reacts with heat to cut off the energization of the electrode 1204 is used.

The printer controller 0223 turns on the triac 0223a, which is a means for controlling energization of the heater 0330. As a result, the electrodes 1204 and 1205 of the heater 0330 are energized from the AC power supply AC through the protection element 1208.

When the resistance heating element 1202 is energized through the electrodes 1204-1205, the heater 0330 generates heat in its effective overall length, and the heat generation region of the heater 0330 rises in temperature. The width of the heat generating region of the heater 0330 corresponds to the effective overall length of the resistance heating element 1202. Further, the width of the heat generating region of the heater 0330 substantially corresponds to the width of the maximum size paper passing region. The thermistor 0337 detects the temperature of the substrate 1201 that is heated in response to the temperature rise.

The printer controller 0223 captures the output (detection temperature information) of the thermistor 0337 by A / D conversion. Then, the printer controller 0223 controls the temperature of the heater 0330 by controlling the electric power energized to the heater 0330 by the triac 0223a by phase control, wave number control, or the like based on the output from the thermistor 0337. That is, the printer controller 0223 atriac 0223a raises the heater 0330 when the detection temperature of the thermistor 0337 is lower than the predetermined set temperature (temperature control temperature) and lowers the heater 0330 when the detection temperature is higher than the set temperature. To control. As a result, the temperature of the heater 0330 is kept constant. In this embodiment, the output is changed from 0 to 100% in 21 steps in 5% increments by phase control. The output of 100% indicates the output when the heater 0330 is fully energized.

FIG. 13 is a diagram showing the relationship between the position of the thermistor 0337 in the longitudinal direction of the heater 0330 and the printing area on the paper P in the embodiment of the present invention.

In the figure, the region T is a region where the toner image t introduced into the fixing nip portion N and sandwiched and conveyed affects the detection temperature of the thermistor 0337. That is, it is a region on the paper including a region corresponding to the arrangement position of the thermistor 0337 when the paper P is sandwiched and conveyed by the fixing nip portion N of the fixing unit 0221 with respect to the image formed on the paper P.

In the present embodiment, the width of the region T is 20 mm, which is 5 mm extending from the 10 mm region where the thermistor 0337 and the substrate 1201 come into contact with each other in the paper width direction. Further, the length of the region T is the length from the front end Ia to the rear end Ib of the image forming region I excluding the margins Pa and Pb of the front end portion and the rear end portion of the paper P in the paper transport direction.

Next, regarding the configuration of the image processing unit 0105 that performs image processing on the image data included in the input print data when the image forming apparatus in the present embodiment forms (prints) an image using the printer unit 0122. explain.

FIG. 4 is a block diagram illustrating a functional configuration of the image processing unit 0105 of the image forming apparatus according to the present embodiment.

The image processing unit 0105 includes an input unit 0401, a color conversion unit 0402, a rendering processing unit 0403, a gradation correction processing unit 0404, an image forming processing unit 0405, an image analysis unit 0406, and an output unit 0407. The input unit 0401 receives, for example, image data described in PDL (page description language) included in the print data input by the network I / F unit 0114. The color conversion processing unit 0402 performs color conversion from RGB to CMYK, for example.

The rendering processing unit 0403 renders the PDL data and converts it into image data. The gradation correction processing unit 0404 corrects the gradation of the image data. The image forming processing unit 0405 creates information of each color necessary for image forming from the converted image data. The image analysis unit 0406 analyzes the CMYK data after the image formation process and detects the amount of toner loaded in the region in units of local regions of a predetermined size.

The image data processed by the image processing unit 0105 is transferred to the compression / decompression unit 0106 via the output unit 0407, compressed by a predetermined compression method, and then stored in the RAM 0104.

Next, a process of detecting the amount of toner loaded in a predetermined size of a local region unit from the image data by the image analysis unit 0406 will be described with reference to FIG.

FIG. 5 is a flowchart illustrating an image analysis process by the image processing unit 0406.

Here, an example will be described in which CPU 0103 of the controller 0101 controls each unit of the image processing unit 0105 according to a program.

First, in step S0501, the CPU 0103 inputs the print data received by the network I / F 0114 to the input unit 0401 of the image processing unit 0105.

Next, the process proceeds to step S0502, and the rendering processing unit 0403 converts the input print data into raster image data, and supplies the raster image data to the color conversion processing unit 0402 to execute the color conversion processing. At this time, the CPU 0103 controls the rendering processing unit 0403 to determine the characteristics (characters / figures / photographs, etc.) of each pixel from the PDL data. Then, attribute data such as Text (text), Graphics (graphics), Image (image), SmallText, ThinLine (thin line) is generated. Then, the generated attribute data is passed to the color conversion processing unit 0402.

Next, in step S0503, the CPU 0103 color-converts the RGB data generated by the color conversion processing unit 0402 into CMYK data to generate raster image data, and passes it to the gradation correction processing unit 0404. Further, the CPU 0103 also passes the attribute data received from the color conversion processing unit 0402 to the gradation correction processing unit 0404 to execute the gradation correction processing. In the color conversion from RGB data to CMYK data, the printer unit 0122 converts so as not to exceed the maximum amount of toner that can be printed (for example, 200%). In this way, in step S0503, the CPU 0103 controls the gradation correction processing unit 0404 to perform gradation correction processing on the CMYK data in consideration of the gradation characteristics of the printer unit 0122 of the image forming apparatus, and obtains the processed image data. It is passed to the image forming processing unit 0405. Further, the CPU 0103 controls the gradation correction processing unit 0404 so that the attribute data is also passed to the image forming processing unit 0405.

Next, in step S0504, the CPU 0103 controls the image forming processing unit 0405 to perform processing such as error diffusion processing and screen processing on the CMYK data after gradation correction, and the image analysis unit 0406 and the output unit 0407 hand off.

Next, in step S0505, the CPU 0103 controls the image analysis unit 0406 to analyze the CMYK data after the above-mentioned processing, and detects the amount of toner loaded in the region in units of local regions of a predetermined size. The toner loading amount information detected here is aggregated as toner loading amount information of each print page by a predetermined algorithm and used for fixing temperature control of the printer unit 0122 (details will be described later), and is output from the output unit 0407. It is stored in RAM 0102 in association with the CMYK data to be printed. The CMYK data output via the output unit 0407 is transferred to the compression / decompression unit 0106, compressed by a predetermined compression method, and then stored in the RAM 0104. Then, the CPU 0103 decompresses the compressed data stored in the RAM 0104 by using the compression / decompression unit 0106, transfers the decompression data and the toner loading amount information to the printer unit 0122 via the printer I / F 0113, and executes printing. Let me.

Next, with reference to FIG. 6, the analysis process in which the image analysis unit 0406 analyzes the CMYK data for which the image formation process has been performed in step S0505 of FIG. 5 to calculate the fixing temperature control toner loading amount information will be described.

As described above, the image forming apparatus of the present embodiment uses a film heating type fixing unit, and when the recording material carrying the toner image is introduced into the fixing nip part and is sandwiched and conveyed, the temperature detection element unit is used. A toner image close to is deprived of heat from the temperature detecting element, and as a result, the temperature detected by the temperature detecting element is lowered, so that heat generation of the heater is promoted, and the amount of heat of the heater as a whole becomes excessive. Therefore, it is necessary to set the fixing temperature in consideration of the heat loss due to the melting of the toner in the vicinity of the temperature detecting element portion.

In this embodiment, the position of each local region when drawing the printed image data on the recording material is mapped to the coordinate system (fixer coordinates) of the fixing film of the fixing unit, and each main scanning position of the fixing device coordinates is used. The integrated value of the toner loading amount is counted at the sub-scanning position. At this time, the toner loading amount for each local region is weighted and corrected according to whether or not the main scanning position is at the position of the temperature detection element unit. Then, the peak value from the integrated values is adopted as the fixing temperature control toner loading amount information, the fixing temperature is determined according to the fixing temperature control toner loading amount information, and the temperature control of the fixing unit is controlled.

FIG. 6 is a flowchart illustrating an image analysis process by the image analysis unit 0406 of the image forming apparatus according to the present embodiment.

Here, it is assumed that the process shown in this flowchart is realized by the CPU 0103 expanding the program stored in the ROM 0102 to the RAM 0103 and executing the expanded program.

First, in step S0601, the CPU 0103 determines the weighting coefficient W of the toner loading amount with respect to the local region from the main scanning position in the page of the local region (KPx, KPy) to be analyzed.
W = 1 (0 ≦ KPx <KPT0, KPT1 ≦ KPx)
W = 2 (KPT0 ≤ KPx <KPT1)
Here, KP _T0 corresponds to the left end position of the region T described in FIG. 13 in which the toner image t introduced into the fixing nip portion N and sandwiched and conveyed affects the detection temperature of the thermistor 0337. Further, KPT1 corresponds to the right end position of the same region T. According to the above weighting condition, when the local region to be analyzed is in the range of the region T, it is weighted by W = 2, and when it is outside the range of the region T, it is weighted by W = 1.

Next, in step S0602, the CPU 0103 analyzes the CMYK data after the image forming process received in step S0505 of FIG. 5 to calculate the toner loading amount (TnrSum) in units of local regions. (Details will be described later) Next, in step S0603, the CPU 0103 obtains the toner loading amount correction value (WTnrSum) by multiplying the toner loading amount in the local region calculated in step S0602 by the weighting coefficient W obtained in step S0601.

Next, in step S0604, the CPU 0103 calculates the fuser coordinates (FPx, FPy) with respect to the local region currently being analyzed.

Next, in step S0605, the CPU 0103 adds the toner loading amount correction value (WTnrSum) calculated in step S0603 to the toner loading amount integrated value (σWTnrSum, initial value 0) related to the fuser coordinates (FPx, FPy).

Next, in step S0606, the CPU 0103 shifts the analysis position in the main scanning direction in order to switch the local region to be analyzed.

Then, in step S0607, the CPU 0103 determines whether or not the analysis position in the main scanning direction has reached the right end of the image, and if it reaches the right end of the image, the process proceeds to step S0608. The process of step S06067 is continued.

In step S0608, the CPU 0103 shifts the analysis position in the sub-scanning direction.

Then, in step S0609, the CPU 0103 determines whether or not the analysis position in the sub-scanning direction has reached the lower end of the image. If it reaches the lower end of the image, the process proceeds to step S0610. If not, the process returns to step S0601 and steps S0601 to The process of step S0609 is repeatedly executed.

In step S0610, the CPU 0103 determines the peak value from the integrated toner loading amount values at each main scanning position.

In step S0611, the CPU 0103 stores the peak value determined in step S0610 in the RAM 0103 in association with the image data as toner loading amount information for fixing temperature control related to the printed image data, and ends a series of processes.

FIG. 7 is a flowchart illustrating a process of calculating the toner loading amount (TnrSum) in a local region unit in step S0602 of FIG.

In the image forming apparatus of the present embodiment, since the image analysis is performed in step S0505 of FIG. 5, the CMYK data (each color loading amount information) after the color conversion is subjected to the gradation correction processing and the image forming processing. The image is represented by area gradation. Therefore, the halftone dot ratio per unit area is analyzed, and the amount of toner loaded is calculated back from that.

First, in step S0701, the CPU 0103 calculates the amount of load in the local region from the CMYK data after image formation received by the image analysis unit 0406 in step S0505 of FIG. 5, so that a predetermined region unit corresponding to the local region ( For example, the image data is cut out to a size of 10 mm × 10 mm).

Next, the process proceeds to step S0702, and the CPU 0103 counts the number of pixels included in the image data in the area.

Next, the process proceeds to step S0703, and the CPU 0103 obtains the halftone dot ratio from the number of pixels with respect to the area of the area. That is, the halftone dot ratio is calculated assuming that the area is filled with a solid solid color as 100%.

Next, the process proceeds to step S0704, and the CPU 0103 generates a table that reversely converts the halftone dot ratio obtained in step S0703 into the toner loading amount, and calculates the toner loading amount from the halftone dot ratio.

By executing the processes of steps S0701 to S0704 on each of the CMYK data in this way, the amount of toner loaded on each of the CMYK data is calculated.

Then, the process proceeds to step S0705, and the CPU 0103 calculates the total amount of toner corresponding to the CMYK data in the local region from the amount of toner loaded in the CMYK data obtained in step S0704, and ends the process.

FIG. 8 is a diagram showing an example of each of a gradation correction table, a halftone dot ratio table, and a toner loading amount conversion table used in the image processing in the present embodiment.

FIG. 8A shows an example of a gradation correction table, which is a table used in the gradation correction processing of step S0503 of FIG. 5, and is a table of the printer unit 0122 which varies depending on the environment, durability, variation of the machine body, and the like. The gradation characteristics are corrected.

FIG. 8B shows an example of the halftone dot ratio table, and the input multi-value signal and the unit area in the conversion from the multi-value (10-bit) gradation expression to the area gradation by the image formation process in step S050 of FIG. The relationship between the halftone dot ratios is shown. In FIG. 8B, the halftone dot ratios corresponding to the multi-valued signals of each color have a substantially linear relationship.

FIG. 8C shows an example of a toner loading amount conversion table, which is a table for calculating the toner loading amount from the halftone dot ratio.

Here, since the halftone dot ratio can be obtained by multiplying the toner loading amount by the gradation correction table and the halftone dot ratio table, the gradation correction table and the halftone dot ratio table are combined and the inverse conversion thereof is obtained. This makes it possible to generate a table for obtaining the amount of toner loaded from the halftone dot ratio.

As described above, it is possible to calculate the amount of toner applied in each local region with respect to the image data after image processing. In this embodiment, it has been described that the image analysis process of step S0505 of FIG. 5 is performed after the image formation process of step S0504 of FIG. 5, but the present invention is not limited thereto. For example, the image analysis process of step S0505 may be performed after the color conversion process of step S0502 of FIG. In that case, since the image signal of the CMYK data after color conversion is the toner loading amount information, it is not necessary to back-calculate the toner loading amount from the halftone dot ratio, and the pixel value can be used as it is. good.

FIG. 9 is a diagram illustrating an outline of a process for obtaining toner loading amount information for fixing temperature control according to the flowchart of FIG. 6 in the present embodiment.

In FIG. 9, 0901 indicates a local region within the page, and 0902 maps it to the fuser coordinates.

FIG. 10 is a flowchart illustrating control of the fixing temperature of the image forming apparatus according to the present embodiment.

First, in step S1001, the CPU 0103 acquires the toner loading amount information for fixing temperature control related to the current page to be printed, which is stored in the above-mentioned S0611 from the RAM 0102.

Next, the process proceeds to step S1002, and the CPU 0103 determines the target fixing temperature based on the acquired toner loading amount information. Here, the target fixing temperature is determined by referring to, for example, a conversion table as shown in FIG. Here, the higher the fixing temperature is set as the value of the toner loading amount information (σWTnrSum) increases. Further, the correspondence between the toner loading amount information and the target fixing temperature shown in FIG. 11 is merely an example, and the present invention is not limited to this.

After that, in step S1003, the CPU 0103 performs temperature control control so that the temperature of the fuser rises to the target fixing temperature, and ends this process. Since it is necessary to improve the fixability of the image on a page-by-page basis in the temperature control of the fuser, the control is performed in real time.

As described above, according to the present embodiment, whether or not the main scanning position when each local region of the printed image data is drawn on the recording material corresponds to the position of the temperature detecting element portion in the longitudinal direction of the heater. By weighting the toner load amount in the local region and controlling the temperature control temperature of the fuser based on the toner load amount information in each local region corrected by using the weighting, the image data can be obtained. It is possible to realize good fixability with the minimum required amount of heat according to the toner loading characteristic.

101 image forming apparatus controller, 103 CPU,
105 image processing unit, 122 printer unit, 221 fixing unit,
310 heating unit, 320 elastic pressurizing roller, 406 image analyzer

Claims (3)

An image forming apparatus that forms an image by an electrophotographic process.
Receiving means for receiving image data and
An image forming means for forming a toner image on a recording material based on the image data received by the receiving means, and an image forming means.
A fixing means for thermally fixing the toner image formed by the image forming means to the recording material, and
A temperature detecting means for detecting the temperature of the fixing means and
A fixing temperature control means for setting a fixing temperature at the time of heat fixing by the fixing means and controlling the temperature of the fixing means so as to reach the set fixing temperature.
Have,
The fixing temperature control means
The image data received by the receiving means is analyzed in units of local regions having a predetermined size, and the amount of toner loaded on the recording material is calculated for each local region.
The amount of toner loaded on the local region is corrected by a weighting determined by the positional relationship between the main scanning position and the temperature detecting means when the local region is drawn on the recording material.
An image forming apparatus, characterized in that the fixing temperature of the fixing means is set according to the peak value of the toner loading amount in each local region corrected by the weighting. In the fixing temperature control means, when the main scanning position when the local region is drawn on the recording material is within the range of the position of the temperature detecting means, the main scanning position is the position of the temperature detecting means. The image forming apparatus according to claim 1, wherein the weighting is controlled to be higher than when the weight is out of the range. The fixing temperature control means integrates the toner loading amount after correction by the weighting at each position of the fixing device coordinates in which each local region of the image data is mapped to the fixing device, and integrates the toner loading amount after the correction. The image forming apparatus according to claim 1, wherein the fixing temperature of the fixing means is set according to a peak value of the value.