JP2019028189A - Image forming apparatus - Google Patents

Abstract

To solve the problem in which: when an elastic body is included as a constituent member of a heating roller, if a larger amount of electrical power is supplied to control difference in glossiness, the elastic body is increased in temperature and thermally degraded, and thereby the life of the heating roller is reduced.SOLUTION: An image forming apparatus changes a fixing condition, such as to increase the temperature of a heating member only when an image is formed before and behind and over a position with a length of one cycle of the heating member from a leading end of a sheet.SELECTED DRAWING: Figure 9

Description

  The present invention relates to an image forming apparatus.

  In an electrophotographic image forming apparatus, a fixing device is provided. The fixing device is transported from the paper feed tray and fixed by applying heat and pressure to the paper on which the toner image formed by the image forming unit is transferred. The fixing device is generally composed of a heating roller for applying heat and a pressure roller for applying pressure.

  The heating roller is provided with heating means such as a heater, and the heating roller is heated to a predetermined temperature by the heater. The amount of heat of the heater is transmitted to the sheet via the heating roller in a nipping part (nip part) that nipping the sheet between the heating roller and the pressure roller. When heat is transferred to the paper, the temperature of the portion of the heating roller that contacts the paper decreases. The temperature of the corresponding portion is heated again by the heater and rises until the heating roller rotates once and returns to the position of the nip portion.

  However, even if it is heated again, paying attention to the corresponding part of the heating roller, the temperature differs between immediately before the heating roller passes the paper and when it reaches the position just before the nip after passing through the paper. become. That is, a temperature step occurs on the boundary between the contact portion and the non-contact portion with the sheet on the heating roller.

  This temperature difference causes a difference in glossiness in the toner image on the paper in the fixing process, and this difference in glossiness causes a difference in density in the toner image, which causes a reduction in image quality. Hereinafter, this difference in glossiness is referred to as a gloss level difference.

  On the other hand, in Patent Document 1 below, in a fixing device having a heating coil, a contact portion and a non-contact portion with a sheet are detected, and the electric power supplied to the heating coil is changed at these boundary portions to thereby change the power on the heating roller. The temperature is made uniform.

JP 2010-26493 A

  In the technique proposed in Patent Document 1, an elastic body may be included as a constituent member of the heating roller. At that time, if the power supply is increased in order to suppress the gloss level difference, the temperature of the elastic body increases and the thermal deterioration progresses. As a result, there is a problem that the life of the heating roller is shortened.

  The present invention has been made in view of the above problems, and an object of the present invention is to provide an image forming apparatus capable of suppressing adverse effects such as a short life of a heating roller while suppressing deterioration in image quality due to a gloss level difference.

In order to achieve the above object, an image forming apparatus according to the present invention includes:
An image forming unit for forming an unfixed image on a recording material;
A heating member that is an endless rotating body, and a pressure member that forms a nip portion together with the heating member;
A fixing unit configured to heat the recording material carrying an unfixed toner image at the nip portion while conveying the recording material and to fix the unfixed toner image on the recording material;
Temperature detecting means for detecting the temperature of the heating member or the pressure member;
Based on the detection result of the temperature detection means, a temperature control unit for controlling the temperature of the heating member,
The print information acquisition means (211) for acquiring print information for each area divided in a direction perpendicular to the conveyance direction of the recording material of the unfixed toner image formed by the image forming unit;
In an image forming apparatus comprising:
When printing based on the information acquired by the print information acquisition means,
From the print information, it has a print position determination means (212) for determining whether an image is straddling before and after the position of the length of the heating member from the front end of the recording material,
The operating condition of the fixing unit is changed based on the determination by the print position determining unit.

  According to the image forming apparatus of the present invention, it is possible to suppress the gloss level difference and the adverse effect of shortening the life of the heating roller.

Schematic diagram of image forming apparatus Cross section of fixing device in short direction Longitudinal sectional view of the fixing device Block diagram of control unit FIG. 6 is a diagram illustrating a method for dividing an image area according to the first embodiment. The figure which shows the example of the image area division | segmentation in Example 1. The figure which shows the image count specific example in Example 1. FIG. The figure which shows the positional relationship of the image dividing area | region in Example 1, and one rotation of fixing film from the paper leading edge. FIG. 4 is a diagram for explaining a contact position between paper and a fixing film when a gloss level difference is generated in the first embodiment. FIG. 5 is a diagram illustrating the fixing film surface temperature and the paper position corresponding to the temperature in Example 1. The graph showing the relationship between the fixing film surface temperature and gloss in Example 1 The graph showing the temperature relationship between the first and second rounds of the fixing film in Example 1 The graph showing the relationship between the fixing film temperature control temperature and fixing film lifetime in Example 1 FIG. 3 is a block diagram illustrating the operation of the fixing device according to the first exemplary embodiment. The graph showing the relationship between the fixing film surface temperature and gloss in Example 2 Graph showing the temperature relationship between the first and second rounds of the fixing film in Example 2 FIG. 7 is a block diagram illustrating the operation of the fixing device according to the second embodiment.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

<Image forming apparatus>
FIG. 1 is a diagram showing an example of the overall configuration of the image forming apparatus of the present invention.

  When the image forming apparatus 1 is connected to a network (for example, a LAN) and receives a print instruction from an external terminal device (not shown) or an operation panel having a display unit (not shown), yellow, magenta, cyan, and cyan are received based on the instruction. A black toner image is formed, and these are multiplex-transferred onto a recording sheet to form a full-color image, thereby executing a printing process on the recording sheet. Hereinafter, the reproduction colors of yellow, magenta, cyan, and black are expressed as Y, M, C, and K, and Y, M, C, and K are added as subscripts to the numbers of the components related to the reproduction colors.

  The image processing unit 3 includes image forming units 3Y, 3M, 3C, and 3K, an intermediate transfer belt 11, primary transfer rollers 35Y, 35M, 35C, and 35K, a secondary transfer roller 47, and the like. Since the image forming units 3Y, 3M, 3C, and 3K have the same configuration, the configuration of the image forming unit 3Y will be mainly described below.

  The image forming unit 3Y includes a photosensitive drum 31Y, a developing device 32Y, a charger 33Y, a cleaner 34Y for cleaning the photosensitive drum 31Y, an exposure device 10Y, and the like disposed around the photosensitive drum 31Y. A Y-color toner image is formed on the body drum 31Y. The developing device 32Y faces the photosensitive drum 31Y and conveys charged toner to the photosensitive drum 31Y. The intermediate transfer belt 11 is an endless belt, is stretched around a driving roller 12 and a driven roller 13, and is driven to rotate in the direction of arrow C. The exposure device 10Y includes a light emitting element such as a laser diode, emits laser light for image formation, and performs exposure scanning of the photosensitive drum 31Y. By this exposure scanning, an electrostatic latent image is formed on the photosensitive drum 31Y charged by the charger 33Y. Similarly, electrostatic latent images are formed on the photosensitive drums 31M, 31C, and 31K of the image forming units 3M, 3C, and 3K.

  The electrostatic latent images formed on the photosensitive drums (photosensitive drums 31Y, 31M, 31C, and 31K) are developed by developing units (developing units 32Y, 32M, 32C, and 3K) of the image forming units 3Y, 3M, 3C, and 3K. 32K), a corresponding color toner image (unfixed image) is formed on each photosensitive drum. The formed unfixed image is superimposed at the same position on the intermediate transfer belt 11 by the primary transfer rollers (primary transfer rollers 35Y, 35M, 35C, and 35K) corresponding to the image forming units 3Y, 3M, 3C, and 3K. As described above, after primary transfer is sequentially performed on the intermediate transfer belt 11 at different timings, unfixed images on the intermediate transfer belt 11 are collectively transferred onto the recording sheet by the action of electrostatic force by the secondary transfer roller 47. Next transfer (electrostatic transfer) is performed. The secondary transfer roller 47 is applied with a transfer voltage having a polarity opposite to the polarity of the toner (here, for example, the polarity of the toner is negative).

The recording sheet on which the unfixed image has been electrostatically transferred is further conveyed to the fixing device 40, and the unfixed image on the recording sheet is heated and pressed by the fixing device 40 and thermally fixed to the recording sheet.
Thereafter, the recording sheet is conveyed to a secondary transfer position 46 via a timing roller 45, and an unfixed image is electrostatically transferred to the second surface of the recording sheet by the secondary transfer roller 47. Further, the recording sheet Then, after being transported to the fixing device 40 and thermally fixed, it is discharged out of the apparatus by a discharge roller 71.

  As a result, the unfixed image can be electrostatically transferred and thermally fixed to the other surface where the unfixed image is not electrostatically transferred.

<Fixing device>
Next, the fixing device 40 will be described.

  2 is a cross-sectional view in the short-side direction of the fixing device 40, and FIG. 3 is a view for explaining a cross-sectional view in the longitudinal direction of the fixing device 40.

  The film unit 60 that heats the image on the recording material P has a configuration in which a thin fixing film 603 having flexibility is heated by a heater 600 that contacts the inner surface.

  As shown in FIG. 2, the fixing film 603 has a nip portion N formed by the pressure of the heater 600 and the pressure roller 700, and sandwiches and conveys the recording material P fed to the nip portion N. At this time, the heat generated by the heater 600 is applied to the recording material P via the fixing film 603, and the toner image T on the recording material P is fixed to the recording material P.

  The film unit 60 is a unit for heating and pressing an image on the recording material P, and is provided in parallel with the pressure roller. The film unit 60 includes a heater 600, a heater holder 601, a support stay 602, and a fixing film 603.

  The heater 600 presses the fixing film 603 toward the pressure roller 700 so that the nip portion N has a desired width. The heater 600 includes a substrate 610 and resistance heating elements 701 and 702 on the substrate 610, and is fixed to a recess on the lower surface of the heater holder 601. In this embodiment, the heating elements 701 and 702 are provided on the back side of the substrate 610 (the side not in contact with the fixing film 603). However, the present invention is not limited to this. You may provide in the side which touches.

  A polyimide layer having a thickness of about 10 μm is provided as a sliding layer on the surface side of the substrate 610, and by reducing the frictional resistance between the fixing film 603 and the heater 600, wear on the inner surface of the fixing film 603 is suppressed. It can be done. Further, a lubricant such as grease may be applied to the inner surface of the fixing film 603 in order to reduce the rubbing resistance.

  The fixing film 603 is a cylindrical film for heating and pressurizing the toner image on the recording material at the nip portion N. In this embodiment, a substrate provided with an elastic layer 603b and a release layer 603c on a base material 603a is used.

  Specifically, a cylindrical member made of a nickel alloy having an outer diameter of 30 mm, a length of 340 mm, and a thickness of 30 μm is used as the base material 603a. Furthermore, a silicone rubber layer having a thickness of 400 μm is formed as an elastic layer 603b on the base material 603a, and a fluororesin tube having a thickness of about 20 μm is coated as a release layer 603c on the elastic layer 603b.

  The heater holder 601 (hereinafter referred to as the holder 601) is a member that holds the heater 600 in a state of being pressed toward the fixing film 603. In addition, the heater holder 601 has a semicircular cross-sectional shape and has a function of regulating the rotation trajectory of the fixing film 603. The heater holder 601 is made of highly heat-resistant resin or the like, and in this embodiment, Zenite 7755 (trade name) manufactured by DuPont is used.

  The support stay 602 is a member that supports the heater 600 via the heater holder 601. The support stay 602 is desirably made of a material that is not easily bent even when a large load is applied. In this embodiment, SUS304 (stainless steel) is used.

  As shown in FIG. 3, the support stay 602 is supported by the flanges 411a and 411b at both ends in the longitudinal direction. The flanges 411a and 411b are collectively referred to as a flange 411. The flange 411 regulates the movement of the fixing film 603 in the longitudinal direction and the shape in the circumferential direction. A heat-resistant resin or the like is used for the flange 411, and PPS (polyphenylene sulfide) is used in this embodiment. A pressure spring 415 is provided between the flange 411 and the pressure arm 414 in a contracted state. With the above configuration, the elastic force of the pressure spring 415 is transmitted to the heater 600 via the flange 411 and the support stay 602. Then, the fixing film 603 is pressed against the pressure roller 700 with a predetermined pressing force, and a nip portion N having a predetermined width is formed. The pressing force to the pressure arm 414 is controlled by the engine controller 250 operating the motor M2 from the I / O unit 256. In this embodiment, the applied pressure is about 156.8 N (16 kgf) at one end, and the total applied pressure is about 313.6 N (32 kgf).

  The connector 500 is a power supply member that is electrically connected to the heater 600 in order to apply a voltage to the heater 600, and is detachably attached to one end in the longitudinal direction of the heater 600.

  As shown in FIG. 2, the pressure roller 700 is a member that forms the nip portion N by being pressed by the fixing film unit 60. The pressure roller 700 has a multilayer structure in which an elastic layer 711 is provided on a metal core 710 and a release layer 712 is provided on the elastic layer 711.

  As the metal core 710, stainless steel, SUM (sulfur and sulfur composite free-cutting steel), and aluminum can be used. As the elastic layer 711, silicone rubber, sponge rubber layer, or elastic foam rubber can be used. As the release layer 712, a fluororesin material can be used.

  The pressure roller 700 of the present embodiment is composed of a stainless steel core bar 710, an elastic layer 711 of foamed silicone rubber, and a release layer 712 of a fluororesin tube. The outer diameter is about 25 mm and the longitudinal length of the elastic layer is 330 mm.

  As shown in FIG. 3, the cored bar 710 of the pressure roller 700 is rotatably held via the side plate 410 and the bearings 420a and 420b, and a gear G is provided at one end of the cored bar 710 so that the motor The driving force of M1 is transmitted to the cored bar 710. As shown in FIG. 2, the pressure roller 700 driven by the motor M <b> 1 is rotationally driven in the direction of the arrow, and the driving force is transmitted to the fixing film 603 at the nip portion N to be driven to rotate. In this embodiment, the motor M1 is controlled by the I / O unit 256 of the engine controller 250 so that the surface speed of the pressure roller 700 (hereinafter referred to as the fixing rotation speed) is 200 mm / sec. A thermistor (TH) 630 which is a temperature detection means shown in FIG. 2 is a temperature sensor that is provided on the back side of the heater 600 and detects the temperature of the heater 600.

  FIG. 4 is a block diagram showing the overall control block configuration of the image forming apparatus 1.

  In FIG. 4, the fixing control unit shown in the lower right in particular is described with reference to this figure to explain the power control method.

  The thermistor 630 is connected to the temperature detection unit 35 of the fixing control unit via an A / D converter (not shown), and transmits an output corresponding to the detected temperature to the control circuit unit 92. The control circuit unit 92 links the power control unit 352 and the power supply device 91 so as to control energization of the power source. Further, the control circuit unit 92 controls the power control unit 352 that controls the power supplied to the heater 600 by reflecting the temperature information acquired from the thermistor 630 in the power supply energization control. In this embodiment, a method of adjusting the amount of heat generated by the heater 600 by performing wave number control or phase control on the power output is used. When fixing the toner on the recording material, the heater 600 is kept at a predetermined temperature. Maintained.

  The heater 600 is obtained by applying an Ag / Pd resistance material with a thickness of about 10 μm on an aluminum nitride substrate (insulating substrate) and patterning heating elements 701 and 702. (Detailed description of each heating element will be described later.) Further, glass (not shown) is coated on the heating elements 701 and 702 to keep insulation from the electric member such as the thermistor and the surface of the fixing film. Next, each heating element will be described. The heating elements 701 and 702 use a heating element having a longitudinal width of 322 mm as the heating element. The heater is energized through the electrodes and generates heat on the substrate 610.

<Control block diagram>
FIG. 4 is a block diagram showing the overall configuration of the control block of the image forming apparatus 1, and is roughly divided into a video controller unit 200 and an engine controller unit 250.

  In the video controller unit 200, a CPU 201 is a CPU (central processing unit) that gives instructions to each unit constituting the video controller unit 200, and a ROM 202 is a boot ROM (read-only memory) that stores a startup program. A unit 206 is a hard disk drive that stores a control program of the video controller unit 200, input image data, and the like. A RAM 203 is a random access memory that stores work data of the control program of the video controller unit 200.

  The network IF unit 207 is a LAN card that exchanges image data with an external computer (not shown), and the option IF unit 208 is connected to a document image reading device (not shown) or a FAX line (not shown). An interface for transferring image data between them, and includes a lattice connector connected to the document image reading apparatus, a modem connected to a public line, and the like. It is assumed that the resolution of the image data in this embodiment is 1200 dpi.

Image data input via the network IF unit 207 or the option IF unit 208 is compressed in the image compression / decompression unit 209 and stored in the nonvolatile storage unit 206.
At this time, if the image data is a page description language (PDL) input via the network IF, the RIP unit 210 as a raster image processor expands the PDL code into raster image data. Once done, compress.

  The image processing unit 204 performs image processing according to the characteristics of the image forming apparatus on the input image data.

  The pixel count unit 211 integrates the density value of each pixel constituting the image data of each color for each of Y, M, C, and K color components with respect to the input image data (hereinafter, this value is referred to as a pixel value). Called). In this embodiment, the density value of each pixel has a gradation of 8 bits (0 to 255). As an example, if the density value of the first pixel of the Y image data is 100 and the density value of the second pixel is 50, the pixel value of the first pixel and the second pixel is 150. Such integration of pixel values is performed for all color components for all pixels in a predetermined area. The pixel value calculated by the pixel count unit 211 is stored in a register (not shown) inside the pixel count unit 211. When the pixel count unit 211 finishes counting pixels in a specified area, it sends an interrupt signal to the CPU 201. To do.

  In the controller unit 200, with the interrupt signal as a trigger, the CPU 201 reads out this register based on the control program, whereby the pixel value at that time can be acquired. The video controller unit 200 reads image data stored in the non-volatile storage unit 206 in accordance with an instruction from the CPU 201 based on the control program, and performs decompression by the compression / decompression unit 209 in synchronization with the operation of the image forming apparatus main body. After performing image processing by the processing unit 204 and pixel counting by the pixel counting unit 211, an image signal is sent to the PWM output unit 254 of the engine controller unit 250.

  In the engine controller unit 250, a CPU 251 is a CPU (central processing unit) that instructs each unit constituting the engine controller unit 250, a ROM 252 is a ROM (read only memory) that stores firmware as a control program, and a RAM 253. Is a random access memory for storing work data of the control program of the engine controller unit 250.

  The PWM output unit 254 is connected to the image processing unit 204 of the video controller unit 200, and generates a PWM (Pulse Width Modulation) signal based on the image signal transmitted from the image processing unit 204.

  The I / O unit 256 is connected to various actuators and sensors (not shown) provided in the image forming apparatus 1, and the engine controller unit 250 drives each unit of the image forming apparatus 1 according to instructions of the CPU 251 based on the control program. Print by electrophotographic process method. The motor M2 for controlling the pressure and the motor M1 for controlling the fixing rotation speed are also connected to the I / O unit 256.

  The video controller unit 200 and the engine controller unit 250 include three-wire serial communication IFs 205 and 255, respectively, and the CPU 201 and the CPU 251 transmit and receive data via these.

  From the video controller unit 200 to the engine controller unit 250, notification of information relating to a print job such as the size and resolution of input image data, the type of recording material to be used (plain paper, cardboard, etc.), and pixel values. Is done.

  Further, based on the notified information, the engine controller unit 250 controls the power control unit 352 so that the detected temperature input from the thermistor 630 in the control circuit unit 92 of the fixing control unit 350 is maintained at a predetermined target temperature (fixing temperature). The electric power input to the heater 600 is controlled.

<Mechanism of gross level difference>
In the case where the recording material is heated at the nip portion, the heat of the fixing roller is taken away by the passage of paper, and there is a possibility that a gloss level difference occurs in the fixed image. This point will be described with reference to FIGS.

  FIG. 9 is a schematic diagram for explaining an operation of fixing an unfixed toner image formed on the paper P at a nip portion formed by a fixing film and a pressure roller to obtain a fixed image.

  When the paper P passes through the nip portion, the amount of heat is taken from the surface of the fixing film, so that the temperature of the portion of the surface of the fixing film 603 where the recording material comes into contact decreases. In FIG. 9A, the paper front end position is P1, and the fixing film position in contact with the paper front end is P1 '. FIG. 9B shows a state in which the paper has advanced, and the position P2 on the paper and the fixing film position P2 ′ are in contact with each other. Further, in FIG. 9 (3), the fixing film goes around once, and the fixing film position P1 ′ that was initially in contact with the leading edge of the paper comes into contact with the position P3 on the paper. In FIG. 9 (4), the paper further advances, and the position P4 on the paper and the fixing film position P4 ′ are in contact with each other. Further, the roller surface temperature described in FIG. 10 is measured at a temperature detection position shown in FIG. 9 in the vicinity of the nip of the fixing film.

  FIG. 10 shows the temperature on the film surface corresponding to the position on the paper shown in FIG.

  At the position on the paper, the fixing film surface temperature corresponding to P1 to P3 on the first round of the fixing film is substantially constant at T1 (first temperature on the fixing film). However, when entering the second turn of the fixing film at the position on the paper, the paper takes heat from the surface of the fixing film on the first turn of the fixing film and the heat supply from the heater is not in time, so it corresponds to the positions P3 to P4 on the paper. The fixing film temperature to be T2 (fixing film second turn temperature) lower than the first turn. Therefore, before and after the on-paper position P3, the temperature of the corresponding fixing film decreases from T1 to T2, so that the glossiness of the image changes at the on-paper position P3. It will be seen as a gross step.

<Gloss leveling suppression method>
As a method for suppressing the gloss level difference, a method of raising the temperature adjustment temperature of the fixing film is conceivable.

  In the configuration of this example, when passing 80 g / cm 2 of paper at a fixing film rotation speed of 321 mm / s, how much the gloss level difference is suppressed by increasing the temperature of the fixing film. This will be described below.

  In this embodiment, the relationship between the fixing film surface temperature and the gloss is as shown in FIG. It can be seen that the higher the temperature of the fixing film, the smaller the change in gloss with respect to the temperature change.

  In this example, as shown in FIG. 12, when the first-round temperature T1 of the fixing film was 163 ° C., the second-round temperature T2 was 162 ° C., which was about 2 ° lower. When the difference of 2 ° C. between 163 ° C. and 161 ° C. is converted into a gross difference using FIG. On the other hand, when the first round temperature T1 of the fixing film was increased to 190, the second round temperature T2 was 187 ° C., which was 3 ° C. lower. When this 3 ° C. difference between 190 ° C. and 187 ° C. is converted into a gross difference using FIG. 12, it becomes 0.3. As a result, it is understood that the gloss level difference can be suppressed by increasing the first-round temperature T1 of the first fixing film.

<Region division and pixel count>
The pixel counting method in this embodiment will be described in detail with reference to FIG.

  In FIG. 5, the hatched portion indicates a printable image area, and the direction orthogonal to the transport direction is called the main scanning direction, and the direction parallel to the transport direction is called the sub-scanning direction.

  In this embodiment, since it is necessary to know the toner amount distribution indicating how much density of the toner image is formed in which area of the image area, the image area is divided into a plurality of areas in the main scanning direction. The pixel value is counted. A large pixel value indicates that the amount of toner in that region is large.

  The width of the image area in the main scanning direction is equal to the maximum width of an image that can be printed by the image forming apparatus 100, and is 330 mm in this embodiment. In addition, since the image data in this embodiment is 1200 dpi, the number of pixels in the main scanning direction is 15600 pixels. This was divided into 10 areas indicated by X0 to X9. That is, the width of one area in the main scanning direction is 1560 pixels (33.0 mm).

  Next, in the sub-scanning direction, the width of one area is set to 4160 pixels (88.1 mm), and an area that can accommodate the recording material is prepared. Since the number of areas is variable, the area names Y0 to Yn are shown in the figure.

  As described above, the image area is divided into the main scanning direction and the sub-scanning direction, and the pixel value is calculated for each area. Each area is determined by combining area names in the main scanning direction and the sub-scanning direction, such as X0Y0 to X9Yn.

  An example of area division is shown in FIG. FIG. 6 shows an example in which the A3 size is used as the recording material, and P indicates the recording material. The main scanning direction is divided into 10 regions X0 to X9. On the other hand, in the sub-scanning direction, the length of the A3 size is 420 mm = 19842 pixels, and therefore, it falls within the five areas Y0 to Y4. It is divided into 50 areas of X0Y0 to X9Y4.

  The number of area divisions in the main scanning direction is not limited to this, and the number of divisions may be changed in accordance with the required toner amount distribution accuracy. Further, the area width and the division method in the sub-scanning direction are not limited to this, and a method in which the number of areas is determined in advance and the length of an image to be printed is equally divided by the number of areas may be used.

  An example of the pixel count is shown in FIG. In FIG. 7, P is an example of an image printed on A3 size paper, and the lower table shows an example of the pixel value of each region. In addition, description is abbreviate | omitted about the area | region where a pixel value is 0.

  In the regions X1Y3 and X2Y3, since a figure with a large amount of toner is formed, the pixel value is large. Since images of only characters are formed in the regions X1Y2, X7Y0, and X7Y1, the pixel values are small. Since no toner image is formed in other areas, the pixel value is zero.

<Fixing condition change method according to image position and its effect>
Next, a method for determining the temperature control temperature setting according to the image position will be described.

  First, when performing image processing, the pixel values X0Y0 to X9Yn are counted in accordance with the pixel counting method and stored in the calculation result storage unit 213.

  In FIG. 8, the relationship between the position of one rotation of the fixing film and the divided image area will be described. Since the fixing film in this embodiment has a diameter of 30 mm, there is a possibility that a gloss level difference may be formed at a position L1 that is a distance of 94.2 mm for one circumference of the fixing film.

  Therefore, when the pixel values are included in Y1X0 to Y1X9, the print position determining means (212) determines that there is a possibility that an image is created across the L1.

  In that case, the gloss level difference can be suppressed by adjusting the temperature adjustment temperature of the fixing film from 160 ° C. to 190 ° C. as described above.

  In the configuration of this example, when 80 g / cm 2 of paper is passed at a fixing film rotational speed of 321 mm / s, the life of the fixing film due to deterioration of the elastic material of the fixing film is 160 as shown in FIG. The temperature is adjusted to 500K and the temperature is adjusted to 190K and 100K. Therefore, in order to suppress the gloss level difference, the temperature is not always adjusted to 190 ° C., and when Y1X0 to Y1X9 do not include pixel value numbers, the temperature is adjusted to 160 ° C. to minimize the life of the fixing film. It becomes possible to limit to the limit.

<Sequence>
A flowchart of FIG. 14 shows a process executed by the CPU 251 of the engine controller unit in order to realize the above control.

  When the print job is started, the CPU 251 determines the first-side default temperature adjustment temperature X ° C. according to the paper type and basis weight of the recording material (S101). The type and basis weight of the recording material to be used are notified from the video controller unit 200 to the engine controller unit through serial communication IFs 205 and 255 at the start of the print job.

  In step S102, the pixel count unit 211 serving as the print information acquisition unit acquires the pixel value of each area. . That is, as in the example shown in FIG. 8, the pixel values of the respective areas X0Y0 to X9Yn are acquired.

  At this time, in S103, if the pixel value is included in the area Y1X0 to Y1X9 including the part of the fixing film from the leading edge of the paper, the temperature adjustment temperature is changed to X + α ° C. The changed temperature adjustment temperature X + α ° C. is notified to the fixing control unit 350, and the electric power input from the power supply device 91 to the heater 600 is controlled so that the temperature sensor TH is controlled to the temperature adjustment temperature corresponding to the temperature adjustment temperature X + α ° C. S104). If no pixel value is included in Y1X0 to Y1X9, the fixing operation is continued with the temperature controlled temperature X (S105). Next, in S106, it is determined whether there is a next job. If there is a job, the process returns to S102 and the fixing operation is continued. If there is no next job, printing is terminated.

  When the above sequence is applied to, for example, 80 sgm office paper A3 size, in this embodiment, X = 160 ° C. and α = 30 ° C. These values are not limited, and differ depending on the type of recording material, basis weight, paper size, and also depending on the fixing device configuration.

  Further, the division of the image area may be finer.

  Furthermore, since the gloss level difference becomes more conspicuous as the image has a larger area, the fixing temperature may be switched only when the number of pixels in each region becomes equal to or greater than a certain value.

  As described above, according to the present embodiment, it is possible to suppress the shortening of the life of the fixing film due to the temperature control temperature increase while suppressing the gloss level difference.

  The image forming apparatus and the fixing apparatus in the present embodiment are the same as those in the first embodiment, and the gloss level difference suppression method is different. Therefore, the suppression method and sequence will be described.

<Gloss leveling suppression method>
As a method for suppressing the gloss level difference, a method of reducing the rotation speed of the fixing film can be considered.

  In the configuration of this example, when passing 80 g / cm 2 of paper at a fixing film temperature control temperature of 160 ° C., how much the gloss level difference is suppressed by reducing the rotation speed of the fixing film. This will be described below.

  Further, in this embodiment, as shown in FIG. 15, by changing the rotation speed of the fixing film from 321 mm / s to 246 mm / s, the amount of change of the glass with respect to the change of the fixing film surface temperature becomes small.

  Next, as shown in FIG. 16, when the temperature of the first round of the fixing film is 163 ° C., the surface temperature of the fixing film of the second round is 161 at 2 ° C. and 264 mm / 1 ° C. at 321 mm / s. It has become. From the relationship between the temperature difference and the gloss relative to the fixing film surface temperature at each speed shown in FIG. 16, the glass step at 321 mm / s is 1, but at 264 mm / s, the glass level difference is suppressed to 0.2. Is possible.

<Fixing condition change method according to image position and its effect>
Next, a method for determining the temperature control temperature setting according to the image position will be described.

  First, when performing image processing, the pixel values X0Y0 to X9Yn are counted in accordance with the pixel counting method and stored in the calculation result storage unit 213.

  In FIG. 8, the relationship between the position of one rotation of the fixing film and the divided image area will be described. Since the fixing film in this embodiment has a diameter of 30 mm, there is a possibility that a gloss level difference may be formed at a position L1 that is a distance of 94.2 mm for one circumference of the fixing film.

  Therefore, when the pixel values are included in Y1X0 to Y1X9, the print position determining means (212) determines that there is a possibility that an image is created across the L1.

  In this case, the gloss level difference can be suppressed by changing the rotation speed of the fixing film from 321 mm / s to 264 mm / s as described above.

  Since the rotational speed of the fixing film is reduced only for an image that may cause a gloss level difference, it is possible to suppress the decrease in the number of sheets passed per unit time as much as possible.

<Sequence>
The process executed by the CPU 251 of the engine controller unit for realizing the above control is shown in the flowchart of FIG.

  When the print job is started, the CPU 251 determines the first-side default temperature adjustment temperature X ° C. according to the paper type and basis weight of the recording material (S101). The type and basis weight of the recording material to be used are notified from the video controller unit 200 to the engine controller unit through serial communication IFs 205 and 255 at the start of the print job.

  Next, proceeding to S102, the CPU 251 acquires the pixel value of each area of the image area. That is, as in the example shown in FIG. 8, the pixel values of the respective areas X0Y0 to X9Yn are acquired.

  At this time, in S103, when the pixel value is in the area Y1X0 to Y1X9 including the part of the fixing film from the leading edge of the paper, the fixing film rotation speed is changed to X / αmm / s. The changed temperature control temperature X / αmm / s is notified to the fixing control unit 350 and controlled so as to obtain a fixing film rotation speed corresponding thereto. (S104). If no pixel value is entered in Y1X0 to Y1X9, the fixing operation is continued with the fixing film rotation speed being Xmm / s (S105). Next, in S106, it is determined whether there is a next job. If there is a job, the process returns to S102 and the fixing operation is continued. If there is no next job, printing is terminated.

  When the above sequence is applied to, for example, 80 sgm office paper A3 size, in this embodiment, X = 321 mm / s and α = 321/264 = 1.21. These values are not limited, and differ depending on the type of recording material, basis weight, paper size, and also depending on the fixing device configuration.

  As described above, according to the present embodiment, it is possible to suppress as much as possible the decrease in the number of sheets passed per unit time by reducing the rotation speed of the fixing film while suppressing the gloss level difference.

603 fixing film, 700 pressure roller, 600 fixing film unit,
200 Video controller, 250 Engine controller, P paper

Claims (4)

An image forming unit for forming an unfixed image on a recording material;
The heating member, which is an endless rotating body, and a pressure member that forms a nip portion together with the heating member, are heated while transporting a recording material carrying an unfixed toner image at the nip portion, and Fixing means for fixing the toner image to the recording material;
Temperature detecting means for detecting the temperature of the heating member or the pressure member;
Based on the detection result of the temperature detection means, a temperature control unit for controlling the temperature of the heating member,
The print information acquisition means (211) for acquiring print information for each area divided in a direction perpendicular to the conveyance direction of the recording material of the unfixed toner image formed by the image forming unit;
In an image forming apparatus comprising:
When printing based on the information acquired by the print information acquisition means,
From the print information, it has a print position determination means (212) for determining whether an image is straddling before and after the position of the length of the heating member from the front end of the recording material,
An image forming apparatus characterized in that an operation condition of a fixing unit is changed based on a determination by a printing position determination unit. The image forming apparatus according to claim 1, wherein the operation condition of the fixing unit is to increase a temperature of the heating unit. 3. The image forming apparatus according to claim 1, wherein the operation condition of the fixing unit is to reduce the number of rotations of the heating member. When the printing position determining means determines that an image having a predetermined area or more is located before and after the position of the length of one heating member from the front end of the recording material, the operating condition of the fixing means is set. The image forming apparatus according to claim 1, wherein the image forming apparatus is changed.