Image forming apparatus

Abstract

To reduce an amount of fine particles generated from an image forming apparatus without increasing the number of components.SOLUTION: An image forming apparatus comprises a fixing device 20 that fixes an image to a recording medium P, and the fixing device 20 has a pair of rotating bodies 21, 22 that forms a nip part N for passing the recording medium P, and a heat source 2 that heats at least one of the pair of rotating bodies 21, 22. The image forming apparatus sets output of the heat source 23 within three minutes from when the first recording medium P is ejected to the outside of the apparatus to be lower than a preset reference value on the basis of image information of the recording medium P ejected within three minutes from when the first recording medium P is ejected to the outside of the apparatus during printing.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to an image forming apparatus. [Background technology]

[0002] 2. Description of the Related Art Techniques for removing foreign matter such as fine particles contained in exhaust gas from image forming apparatuses such as copiers and printers are known.

[0003] In recent years, with the growing awareness of environmental issues, measures to suppress the generation of fine particles emitted from products are desired, and there is a demand for the development of products that generate fewer fine particles in image forming devices using electrophotographic processes, such as copiers, multifunction devices, and printers. In particular, in Europe, there is a high interest in the environment, and there are various certification standards for volatile organic compounds (VOCs), ozone, dust, fine particles, etc., that are generated during image formation. For example, a German government research institute has an eco-label system called the "Blue Angel Mark," and only certified products and services are allowed to use the label. To be certified as a "Blue Angel Mark," various tests must be cleared, and the fine particle test is particularly strict. Specifically, when fine particles between 5.6 nm and 560 nm generated from an image forming device are measured using a particle measuring device FMPS (Fast Mobility Particle Sizer), the number of fine particles obtained is 3.5 × 10 11 The requirement is that the number of particles must be less than 10 per 10 minutes, and it is expected that the standard will become even stricter in the future.

[0004] As a technology for removing fine particles generated from an image forming apparatus, Patent Document 1 (JP 2016-85407 A) proposes a method of capturing fine particles by switching all filters to a state capable of capturing fine particles during periods when the number of fine particles increases sharply.

[0005] However, the method described in Patent Document 1 requires a duct and a fan for guiding fine particles to the filter in addition to the filter, which poses a problem of increased number of parts. Summary of the Invention [Problem to be solved by the invention]

[0006] SUMMARY OF THE PRESENT EMBODIMENT An object of the present invention is to reduce the amount of fine particles generated from an image forming apparatus without increasing the number of parts. [Means for solving the problem]

[0007] In order to solve the above problems, the present invention provides an image forming apparatus equipped with a fixing device that fixes an image onto a recording medium, the fixing device having a pair of rotating bodies that form a nip portion through which the recording medium passes, and a heat source that heats at least one of the pair of rotating bodies, and is characterized in that, based on image information of the recording medium that is discharged within three minutes after the first sheet of the recording medium is discharged outside the apparatus during printing, the output of the heat source within three minutes after the first sheet of the recording medium is discharged outside the apparatus is set to be lower than a preset reference value. Effect of the Invention

[0008] According to the present invention, the amount of fine particles generated from an image forming apparatus can be reduced without increasing the number of parts. [Brief description of the drawings]

[0009] [Figure 1] 1 is a schematic configuration diagram of an image forming apparatus according to a first embodiment of the present invention. [Diagram 2] 1 is a schematic configuration diagram of a fixing device according to a first embodiment of the present invention. [Diagram 3] 1 is a perspective view of a fixing device according to a first embodiment of the present invention. [Figure 4] FIG. 11 is a diagram showing the generation speed of FP / UFP generated from toner when continuous printing is performed. [Diagram 5] FIG. 11 is a diagram showing the energization duty of a halogen heater during continuous printing. [Figure 6] FIG. 2 is a block diagram showing a configuration of a control unit according to the first embodiment of the present invention. [Figure 7] 4 is a flowchart showing a method for controlling a current supply duty according to the first embodiment of the present invention. [Figure 8] FIG. 11 is a reference diagram for explaining an image area ratio. [Figure 9] 11A and 11B are diagrams illustrating an example of a case where the image area ratio is large and a case where the image area ratio is small. [Figure 10] 1A and 1B are diagrams illustrating an example of a toner overlap rate that is large and a small. [Figure 11] FIG. 13 is a diagram showing an example in which an image is formed within a heating area of ​​an end heater. [Figure 12] FIG. 13 is a diagram showing an example in which an image is formed across both the heating area of ​​the central heater and the heating area of ​​the end heater. [Figure 13] FIG. 13 is a diagram showing an example in which an image is formed within the heating area of ​​a central heater. [Figure 14] FIG. 11 is a reference diagram for explaining the width of a margin. [Figure 15] FIG. 4 is a schematic configuration diagram of a fixing device according to a second embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] The present invention will be described below with reference to the accompanying drawings. In each drawing for explaining the present invention, components such as members and components having the same function or shape are given the same reference numerals as far as they can be distinguished, and the description thereof will be omitted after it has been described once.

[0011] <Overall configuration of image forming apparatus> FIG. 1 is a schematic diagram of an image forming apparatus according to a first embodiment of the present invention. In this specification, the term "image forming apparatus" includes a printer, a copier, a facsimile, a printing machine, or a multifunction machine that combines two or more of these. In the following description, "printing" is synonymous with "image formation." Furthermore, "image formation" includes not only the formation of images that have meaning such as characters and figures, but also the formation of images that have no meaning such as patterns. First, the overall configuration and operation of the image forming apparatus according to the first embodiment of the present invention will be described with reference to FIG. 1.

[0012] As shown in FIG. 1, an image forming apparatus 1000 according to the first embodiment of the present invention includes an image forming section 100, a fixing section 200, a recording medium supply section 300, and a recording medium discharge section 400.

[0013] (Image forming section) The image forming section 100 is a section that forms an image on a sheet-like recording medium such as paper. The image forming section 100 is provided with four imaging units 1Y, 1M, 1C, and 1Bk, an exposure device 6, and a transfer device 8.

[0014] Each of the imaging units 1Y, 1M, 1C, and 1Bk has basically the same configuration, except that it contains toner (developer) of a different color, such as yellow, magenta, cyan, or black, which corresponds to the color separation components of a color image. Specifically, each of the imaging units 1Y, 1M, 1C, and 1Bk includes an electrostatic latent image carrier 2, a charging member 3, a developing device 4, a cleaning member 5, and the like.

[0015] The electrostatic latent image carrier 2 is a rotating body that carries an electrostatic latent image on its surface. As the electrostatic latent image carrier 2, a drum-shaped photoconductor as shown in FIG. 1, an endless belt-shaped photoconductor, etc. may be used.

[0016] The charging member 3 is a member that charges the surface of the electrostatic latent image carrier 2. There are no particular limitations on the charging member 3 as long as it can apply a voltage to the surface of the electrostatic latent image carrier 2 to uniformly charge it, and it can be appropriately selected depending on the purpose. Specific examples of the charging member 3 include contact-type charging members such as conductive or semiconductive charging rollers, magnetic brushes, fur brushes, films, and rubber blades, as well as non-contact-type charging members that utilize corona discharge.

[0017] The developing device 4 is a device that forms a toner image by supplying toner as a developer to the electrostatic latent image on the electrostatic latent image carrier 2. The developing device 4 includes a toner carrier that is disposed in contact with or close to the electrostatic latent image carrier 2. The toner carrier rotates while carrying toner on its surface, whereby the toner is supplied from the toner carrier to the electrostatic latent image carrier 2.

[0018] The cleaning member 5 is a member that removes toner and other foreign matter remaining on the electrostatic latent image carrier 2. As the cleaning member 5, for example, a cleaning blade that is arranged so as to come into contact with the surface of the electrostatic latent image carrier 2 is used. When the electrostatic latent image carrier 2 rotates, the residual toner and foreign matter remaining on the electrostatic latent image carrier 2 is removed by the cleaning member 5.

[0019] The exposure device 6 is a device that forms an electrostatic latent image by exposing the charged surface of the electrostatic latent image carrier 2. The exposure device 6 is not particularly limited as long as it can expose the charged surface of the electrostatic latent image carrier 2, and can be appropriately selected depending on the purpose. Specific examples of the exposure device include various exposure devices such as a copying optical system, a rod lens array system, a laser optical system, a liquid crystal shutter optical system, and an LED optical system.

[0020] The transfer device 8 is a device that transfers an image onto a recording medium. The transfer device 8 includes an intermediate transfer belt 11, a primary transfer roller 12, and a secondary transfer roller 13. The intermediate transfer belt 11 is an endless belt member, and is stretched by a plurality of support rollers. Four primary transfer rollers 12 are provided inside the intermediate transfer belt 11. Each primary transfer roller 12 contacts each electrostatic latent image carrier 2 via the intermediate transfer belt 11, thereby forming a primary transfer nip between the intermediate transfer belt 11 and each electrostatic latent image carrier 2. The secondary transfer roller 13 contacts the outer peripheral surface of the intermediate transfer belt 11, forming a secondary transfer nip.

[0021] (Fixing part) The fixing section 200 is a section that fixes an image onto a recording medium. The fixing section 200 is provided with a fixing device 20 that fixes the image. The fixing device 20 includes a pair of rotating bodies 19A and 19B that convey the recording medium while applying heat and pressure thereto.

[0022] (Recording Media Supply Unit) The recording medium supply unit 300 is a part that supplies a recording medium to the image forming unit 100. The recording medium supply unit 300 is provided with a paper feed cassette 14 that stores paper P as a recording medium, and a paper feed roller 15 that supplies paper P from the paper feed cassette 14 to the image forming unit 100. Hereinafter, the "recording medium" will be described as "paper", but the "recording medium" is not limited to paper (paper). The "recording medium" includes not only paper (paper) but also overhead projector sheets or fabrics, metal sheets, plastic films, or prepreg sheets in which carbon fibers are pre-impregnated with resin. In addition to plain paper, the "paper" also includes cardboard, postcards, envelopes, thin paper, coated paper (coated paper, art paper, etc.), tracing paper, etc.

[0023] (Recording medium ejection section) The recording medium ejection section 400 is a section that ejects paper P (recording medium) to the outside of the image forming apparatus. The recording medium ejection section 400 is provided with a pair of ejection rollers 17 that ejects paper P, and an ejection tray 18 on which the ejected paper P is placed.

[0024] <Image formation operation> Next, the image forming operation of the image forming apparatus 1000 according to this embodiment will be described with reference to FIG.

[0025] When the image forming operation is started, the electrostatic latent image carriers 2 of the imaging units 1Y, 1M, 1C, and 1Bk and the intermediate transfer belt 11 of the transfer device 8 start to rotate. Also, the paper feed roller 15 starts to rotate, and the paper P is fed out from the paper feed cassette 14. The fed paper P comes into contact with a pair of timing rollers 16 and stops, and the transport of the paper P is temporarily stopped until the image to be transferred to the paper P is formed.

[0026] In each of the imaging units 1Y, 1M, 1C, and 1Bk, the surface of the electrostatic latent image carrier 2 is first charged to a uniform high potential by the charging member 3. Next, the exposure device 6 exposes the surface (charged surface) of each electrostatic latent image carrier 2 based on the image information of the document read by the document reading device or the print image information instructed to be printed from the terminal. This reduces the potential of the exposed portion, forming an electrostatic latent image on the surface of each electrostatic latent image carrier 2. Then, the developing device 4 supplies toner to this electrostatic latent image, so that the electrostatic latent image is developed into a toner image. After that, the toner image on each electrostatic latent image carrier 2 reaches the primary transfer nip (the position of the primary transfer roller 12) as the electrostatic latent image carrier 2 rotates, and is transferred to the rotating intermediate transfer belt 11 so as to be overlapped in sequence. Thus, a full-color toner image is formed on the intermediate transfer belt 11. The image formation is not limited to forming a full-color image using all four imaging units 1Y, 1M, 1C, and 1Bk, but it is also possible to form a monochromatic image using any one of the imaging units 1Y, 1M, 1C, and 1Bk, or to form a two-color or three-color image using any two or three of the imaging units. After the toner image is transferred, the surface of the electrostatic latent image carrier 2 is cleaned by a cleaning member 5. This removes foreign matter such as residual toner on the electrostatic latent image carrier 2.

[0027] Thereafter, the toner image on the intermediate transfer belt 11 is transported to the secondary transfer nip (the position of the secondary transfer roller 13) as the intermediate transfer belt 11 rotates, and is transferred onto the paper P that has been transported thereto by the timing roller 16. The paper P is then transported to the fixing device 20, where it is heated and pressurized by a pair of rotating bodies 19A, 19B. This causes the toner image on the paper P to be fixed to the paper P. The paper P is then discharged outside the device by the paper discharge roller 17, and the paper P is placed on the paper discharge tray 18, completing the series of image forming operations.

[0028] <Basic structure of the fixing device> Next, the configuration of the fixing device 20 according to the first embodiment of the present invention will be described.

[0029] As shown in FIG. 2, the fixing device 20 according to the first embodiment of the present invention includes, in addition to a pair of rotating bodies 19A, 19B, a halogen heater 23, a nip forming member 24, a support member 25, a reflecting member 26, a shielding member 27, a rotating body holding member 28, and a temperature sensor 29.

[0030] The pair of rotating bodies 19A, 19B is composed of a fixing belt 21 as the first rotating body 19A that is arranged on the unfixed image carrying surface side (toner image T side) of the paper P, and a pressure roller 22 as the second rotating body 19B that is arranged opposite the outer peripheral surface of the first rotating body 19A.

[0031] The fixing belt 21 is an endless belt, and includes, from the inside, a base material, an elastic layer, a release layer, and the like. The base material has a layer thickness of, for example, 30 to 50 μm, and is made of a metal material such as nickel or stainless steel, or a resin material such as polyimide. The elastic layer has a layer thickness of 100 to 300 μm, and is made of a rubber material such as silicone rubber, foamed silicone rubber, or fluororubber. Since the fixing belt 21 has an elastic layer, minute irregularities are unlikely to be formed on the surface of the fixing belt 21, and heat is easily transferred uniformly to the toner image T on the paper P. The release layer has a layer thickness of 10 to 50 μm, and is made of a material such as PFA (tetrafluoroethylene-perfluoroalkylvinylether copolymer), PTFE (polytetrafluoroethylene), polyimide, polyetherimide, or PES (polyether sulfide). Since the fixing belt 21 has a release layer, the release property for the toner image T on the paper P is ensured. Furthermore, in order to achieve a compact size and low heat capacity, it is preferable that the overall thickness of the fixing belt 21 is 1 mm or less and the diameter is 30 mm or less.

[0032] The pressure roller 22 has a cylindrical or columnar core, an elastic layer provided on the outer circumferential surface of the core, and a release layer provided on the outer circumferential surface of the elastic layer. The core is made of a metal material such as iron. Examples of materials for the elastic layer include silicone rubber, foamed silicone rubber, and fluororubber. The release layer is made of a fluororesin such as PFA or PTFE.

[0033] The halogen heater 23 is a radiant heat type heating source that radiates infrared rays (infrared light) and heats an object by the radiant heat of the infrared rays. In this embodiment, two halogen heaters 23 are arranged inside the fixing belt 21. When the halogen heaters 23 radiate infrared rays, the fixing belt 21 is heated from the inside by the radiant heat. Note that, in addition to the halogen heaters, other radiant heat type heaters such as carbon heaters may be used as the heating source. It is also possible to use an electromagnetic induction heating (IH) type heating source in which a metal layer is provided on the fixing belt 21 and the metal layer is heated by electromagnetic induction. The number of heating sources is not limited to two, and may be one or three or more.

[0034] The nip forming member 24 is a member disposed inside the fixing belt 21, and sandwiches the fixing belt 21 between the pressing roller 22 to form the nip portion N. The nip forming member 24 is preferably made of a heat-resistant member having a heat-resistant temperature of 200° C. or higher. Examples of materials for the nip forming member 24 include general heat-resistant resins such as polyethersulfone (PES), polyphenylene sulfide (PPS), liquid crystal polymer (LCP), polyethernitrile (PEN), polyamideimide (PAI), and polyetheretherketone (PEEK). By using such a heat-resistant material, it is possible to prevent the nip forming member 24 from being deformed by heat, and to stabilize the shape of the nip portion N. The shape of the nip portion N may be a flat shape as shown in FIG. 2, a curved shape, or any other shape.

[0035] The support member 25 is a member that supports the nip forming member 24. The support member 25 supports the nip forming member 24 from the side opposite to the pressure roller 22 side, thereby suppressing bending of the nip forming member 24 due to the pressure force from the pressure roller 22, and forming a nip portion N of uniform width. The material of the support member 25 is preferably an iron-based metal material such as SUS or SECC in order to ensure rigidity.

[0036] The reflecting member 26 is a member that reflects the radiant heat of the halogen heater 23 toward the fixing belt 21. The reflecting member 26 is disposed so as to face the halogen heater 23 on the inner side of the fixing belt 21 in order to reflect the radiant heat. When the radiant heat of the halogen heater 23 is reflected toward the fixing belt 21 by the reflecting member 26, the fixing belt 21 is effectively heated by the reflected radiant heat. In addition, in this embodiment, since the reflecting member 26 is disposed between the halogen heater 23 and the supporting member 25, the application of unnecessary radiant heat to the supporting member 25 is also suppressed, thereby achieving energy saving.

[0037] The shielding member 27 is a member interposed between the halogen heater 23 and the fixing belt 21, and shields the radiant heat from the halogen heater 23 to the fixing belt 21. The shielding member 27 is, for example, made of a metal plate with a thickness of 0.1 mm to 1.0 mm formed in an arc shape following the inner peripheral surface of the fixing belt 21. The material of the shielding member 27 may be any material capable of shielding the radiant heat, and is preferably, for example, a metal material such as aluminum, iron, or stainless steel, or a heat-resistant material such as ceramic. The shielding member 27 may completely shield the radiant heat, or may shield only a part of the radiant heat.

[0038] The rotating body holding member 28 is a member that rotatably holds the fixing belt 21. The rotating body holding member 28 is inserted inside the fixing belt 21, so that the inner peripheral surface of the fixing belt 21 is rotatably supported by the rotating body holding member 28.

[0039] The temperature sensor 29 is a temperature detection member that detects the temperature of the fixing belt 21. In this embodiment, a non-contact type temperature sensor that is arranged in a non-contact manner with respect to the outer circumferential surface of the fixing belt 21 is used as the temperature detection member. Note that the temperature detection member may be a contact type temperature sensor that detects the surface temperature by contacting the surface of the fixing belt 21, in addition to the non-contact type temperature sensor.

[0040] FIG. 3 is a perspective view of the fixing device 20 according to the first embodiment of the present invention.

[0041] As shown in FIG. 3, the shielding member 27 is disposed in a non-paper passing area (non-passing area) W2 outside a maximum paper passing area (maximum recording medium passing area) W1 through which a maximum width paper P passes.

[0042] Due to its characteristics, the heat generation intensity of the heat generation portion of the halogen heater 23 tends to decrease toward the end of the heat generation portion. Therefore, if the heat generation portion of the halogen heater 23 is arranged in the same range as the maximum paper passing area W1, there is a risk that the temperature of the fixing belt 21 will decrease at the end of the maximum paper passing area W1. Therefore, in the past, a measure was taken to extend the length of the heat generation portion to a length exceeding the maximum paper passing area W1 so that the heat generation intensity in the maximum paper passing area W1 is constant, thereby eliminating the temperature decrease at the end of the maximum paper passing area W1. However, if the length of the heat generation portion is extended to a length exceeding the maximum paper passing area W1, infrared rays are irradiated from the end of the heat generation portion in the non-paper passing area W2, so that there is a risk that the temperature of the non-paper passing area W2 of the fixing belt 21 will excessively increase during continuous paper passing. Therefore, in this embodiment, the shielding member 27 is arranged in the non-paper passing area W2. By disposing the shielding member 27 in the non-paper passing region W2, irradiation of infrared rays in the non-paper passing region W2 is blocked, so that excessive temperature rise of the fixing belt 21 during continuous paper passing can be suppressed. On the other hand, in the paper passing region W1 where the shielding member 27 is not disposed, the fixing belt 21 is heated well with a constant heat generation intensity.

[0043] 3, fixing belt 21 is rotatably held by a pair of rotating body holding members 28 arranged on both ends of fixing belt 21 in its longitudinal direction X. Note that the "longitudinal direction" here means a direction perpendicular to the rotation direction of fixing belt 21 and along the outer circumferential surface of fixing belt 21. In other words, the "longitudinal direction" is the direction indicated by arrow X in FIG. 3, and is the same as the longitudinal direction or rotation axis direction of pressure roller 22, or the width direction of a paper sheet passing through nip portion N (a direction intersecting the paper conveyance direction).

[0044] The rotating body holding member 28 has a holding portion 28a having a C-shaped cross section, a regulating portion 28b, and a fixing portion 28c. The holding portion 28a is a portion that is inserted into the end of the fixing belt 21. The holding portion 28a is inserted into the fixing belt 21, so that the fixing belt 21 is rotatably held by the holding portion 28a. The regulating portion 28b is a portion that regulates the deviation of the fixing belt 21 in the longitudinal direction X. That is, when the fixing belt 21 is deviated in the longitudinal direction X, the end of the fixing belt 21 abuts against the regulating portion 28b having a larger diameter than the holding portion 28a, so that the deviation of the fixing belt 21 in the longitudinal direction X is regulated. The fixing portion 28c is a portion that is fixed to a frame member such as a side plate of the fixing device 20. The fixing portion 28c is fixed to the frame member, so that the fixing belt 21 is rotatably held via the rotating body holding member 28.

[0045] The fixing device 20 according to the first embodiment of the present invention operates as follows.

[0046] When the image forming operation is started, the pressure roller 22 starts to rotate in the direction of the arrow in Fig. 2, and the fixing belt 21 is rotated accordingly. Also, the halogen heater 23 starts to be energized, and the fixing belt 21 is heated by infrared rays emitted from the halogen heater 23. Then, when the temperature of the fixing belt 21 reaches a predetermined target temperature, the paper P carrying an unfixed image (toner image T) is transported between the fixing belt 21 and the pressure roller 22 (nip portion N), where the paper P is heated and pressurized. As a result, the unfixed image is fixed to the paper P. The paper P is then discharged outside the apparatus.

[0047] <Mechanism of particle generation> Here, we will explain the mechanism of fine particle generation in image forming devices. In this specification, "fine particles" refers to fine particles and ultrafine particles with a particle size of 5.6 nm to 560 nm, measured using equipment and conditions that comply with the Blue Angel fine particle standard. Hereinafter, "fine particles" will be referred to as "FP / UFP."

[0048] One of the causes of FP / UFP is the wax contained in the toner. When the paper with the toner image transferred thereon is conveyed to the fixing device, the paper and the toner image are heated and pressurized in the fixing device, so that the toner image is fixed to the paper. When the toner is heated at this time, the wax in the toner rises in temperature and volatilizes, and then the wax cools and solidifies, generating FP / UFP.

[0049] <FP / UFP generation during continuous printing> Figure 4 shows the generation rate of FP / UFP generated from toner when continuous printing is performed. In Figure 4, the horizontal axis shows the elapsed time after the first sheet of paper is discharged from the image forming device, and the vertical axis shows the generation rate of FP / UFP over time (number of FPs generated per second).

[0050] In the measurement test of the FP / UFP generation rate shown in Figure 4, the image forming apparatus was placed in a test room conforming to Blue Angel DE-UZ219, and continuous printing was performed for about 9 minutes by a method conforming to Blue Angel DE-UZ219. The FP / UFP generation rate during continuous printing was then measured using a high-speed response particle sizer FMPS (Fast Mobility Particle Sizer).

[0051] In addition, in order to limit the FP / UFP measured to only those generated by toner, FP / UFP generation factors other than toner were excluded. FP / UFP are generated not only from toner but also from liquid or semi-solid lubricants used for purposes such as improving the sliding properties of the fixing belt. For this reason, in this test, no lubricants were used in the fixing device.

[0052] In the test results shown in Figure 4, the rate at which FPs / UFPs occur suddenly increases from the time the first sheet of paper is ejected until 3 minutes have passed, and then gradually decreases after 3 minutes have passed. This shows that FPs / UFPs occur most frequently, especially during the first 3 minutes after the start of printing.

[0053] <Relationship between halogen heater power duty and amount of FP / UFP generated> FIG. 5 shows the power supply duty of the halogen heater during continuous printing.

[0054] The output of the halogen heater provided in the fixing device is determined by controlling the energization duty of the power supplied to the halogen heater. The "energization duty" is the ratio of energization time per unit time. The energization duty is usually controlled based on temperature information of the fixing belt. For example, when the temperature of the fixing belt is significantly lower than the target temperature, the energization duty is increased to increase the output of the halogen heater and increase the amount of heat applied to the fixing belt. Conversely, when the temperature of the fixing belt is close to the target temperature, the energization duty is reduced to decrease the output of the halogen heater, so that the temperature of the fixing belt does not significantly exceed the target temperature.

[0055] As shown in Fig. 5, the energization duty is relatively large until 60 seconds have passed since the first sheet of paper was discharged from the image forming apparatus, and then the energization duty gradually decreases. Then, after 240 seconds have passed since the first sheet of paper was discharged, the energization duty stabilized at a relatively small value. The reason why the energization duty is large in the initial stage after the start of printing and then decreases is due to the following control.

[0056] Immediately after the warm-up operation is completed and printing starts, the fixing belt has reached the specified target temperature, but the pressure roller has not accumulated much heat. Therefore, when printing starts, the temperature of the fixing belt tends to drop as paper passes through. Therefore, for 60 seconds after the first sheet of paper is ejected, the power duty is controlled to a large value so that the temperature of the fixing belt does not drop suddenly, and a large amount of heat is applied to the fixing belt.

[0057] In contrast, after a certain amount of time has passed since the start of printing, the amount of heat stored in the pressure roller increases, and the heat consumed by the fixing belt as the paper passes can be compensated for by the heat of the heating roller. Therefore, after 240 seconds have passed since the first sheet of paper was discharged, the drop in temperature of the fixing belt caused by paper passing can be suppressed without increasing the current duty, and the temperature of the fixing belt can be maintained at a specified temperature even with a relatively small current duty.

[0058] As mentioned above, in the initial stage after printing starts, the current duty of the halogen heater tends to be large, so the temperature of the heated unfixed toner also tends to be high. As a result, as shown in Figure 4, it is believed that the number of FPs / UFPs generated from the toner increased during the period up to 3 minutes after the first sheet of paper was ejected. On the other hand, after 3 minutes have passed since the first sheet of paper was ejected, the pressure roller has accumulated a certain amount of heat, so that the temperature of the fixing belt can be maintained at the target temperature even with a relatively small current duty, and the heating temperature of the unfixed toner is also suppressed, which is believed to have suppressed the generation of FPs / UFPs.

[0059] Therefore, from the results of this test, it can be said that in order to reduce FPs / UFPs that occur with image formation, it is effective to reduce the amount of FPs / UFPs that occur, particularly in the initial stage after printing starts. Therefore, in the first embodiment of the present invention, the current duty of the halogen heater is controlled as follows in order to suppress the occurrence of FPs / UFPs in the initial stage after printing starts. Below, the configuration of the control unit that controls the current duty of the halogen heater and the control of the current duty in the first embodiment of the present invention will be described.

[0060] <Control Unit Configuration> FIG. 6 is a block diagram showing the configuration of a control unit according to the first embodiment of the present invention.

[0061] As shown in FIG. 6, the control unit 600 has a CPU (Central Processing Unit) 61, a ROM (Read Only Memory) 62, a RAM (Random Access Memory) 63, an external device connection I / F 64, a network I / F 65, and an image information acquisition unit 66.

[0062] The CPU 61 controls the energization duty of the halogen heater as well as the overall operation of the image forming apparatus. That is, the CPU 61 controls various operations of the image forming unit 100, the fixing unit 200, the recording medium supply unit 300, and the recording medium discharge unit 400. The ROM 62 stores programs used to drive the CPU, such as the IPL. The RAM 63 is used as a work area for the CPU 61.

[0063] The external device connection I / F 64 is connected to a PC (Personal Computer) via a USB (Universal Serial Bus) cable or the like, and communicates control signals and image information for printing with the PC. The network I / F 65 is an interface for data communication using a communication network such as the Internet. The image information acquisition unit 66 acquires and stores image information for printing via the external device connection I / F 64.

[0064] <Current Duty Control> Next, the control of the current supply duty according to the first embodiment of the present invention will be described with reference to FIG.

[0065] When the printing operation is started, first, the image information acquisition unit 66 sends, from among the acquired image information, image information of a sheet of paper that will be discharged within three minutes after the first sheet of paper is discharged outside the image forming apparatus during printing to the CPU 61. Then, the CPU 61 controls the energization duty of the halogen heater within three minutes after the first sheet of paper is discharged based on the image information of the sheet of paper that will be discharged within three minutes after the first sheet of paper is discharged (Step 1 in FIG. 7).

[0066] Within 3 minutes after the first sheet is discharged, the pressure roller and other components do not store enough heat. Therefore, when an image that requires a large amount of heat for fixing is formed, the current duty of the halogen heater increases, and there is a risk of FP / UFP occurring. Therefore, the CPU 61 determines whether a large amount of heat for fixing is required based on image information, and if the current duty within 3 minutes after the first sheet is discharged is likely to be equal to or greater than a preset reference value, the current duty is set to a value lower than the reference value. Note that the "reference value" here refers to a current duty value at which the wax in the toner may volatilize in normal control in which the current duty is determined based on the temperature information of the fixing belt. The "reference value" in the following description has the same meaning. That is, if the current duty is likely to be equal to or greater than a preset reference value, the current duty is set to a value lower than the reference value so that the wax in the toner does not volatilize. On the other hand, if the current duty within 3 minutes after the first sheet is discharged is expected to be less than the reference value, the current duty is determined based on the temperature of the fixing belt detected by the temperature sensor.

[0067] After that, when three minutes have passed since the first sheet was discharged (if "YES" is selected in Step 2 of FIG. 7), the control of the power supply duty of the halogen heater is changed from the control based on the image information to the normal control based on the temperature information of the fixing belt. That is, the CPU 61 controls the power supply duty of the halogen heater based on the temperature information of the fixing belt detected by the temperature sensor, not on the image information sent from the image information acquisition unit 66 (Step 3 of FIG. 7). After that, the normal control based on the temperature information of the fixing belt is performed in the same manner. Then, when printing on all the sheets is completed (if "YES" is selected in Step 4 of FIG. 7), the control of the power supply duty is also terminated.

[0068] As described above, in the first embodiment of the present invention, the amount of FP / UFP generated in the initial stage after the start of printing can be reduced by controlling the energization duty of the halogen heater within 3 minutes after the first sheet is discharged based on the image information of the sheet discharged within 3 minutes after the first sheet is discharged. In other words, if the image information of the sheet discharged within 3 minutes after the first sheet is an image that requires a large energization duty, the energization duty is set to a value lower than the reference value to prevent the temperature of the nip portion from becoming higher than the volatilization temperature of the wax in the toner. This makes it possible to prevent the wax in the toner from volatilizing in the initial stage after the start of printing, and to reduce the amount of FP / UFP generated by the image forming device.

[0069] Furthermore, according to the control according to the first embodiment of the present invention, it is possible to suppress the generation of FPs / UFPs simply by controlling the power supply duty. In other words, it is possible to reduce the amount of FPs / UFPs generated by the image forming apparatus without adding components such as filters for collecting FPs / UFPs, thereby reducing the number of components and achieving cost reduction.

[0070] Whether or not the image information of the sheets of paper discharged within three minutes of the first sheet of paper contains an image that will cause the energization duty to be large does not necessarily have to be determined based on the image information of all sheets of paper discharged within three minutes of the first sheet of paper being discharged. For example, if the image information of five sheets of paper selected at random contains three or more images whose energization duty is expected to be equal to or greater than a reference value, the energization duty may be set to a value lower than the reference value. Note that the number of sheets of paper selected at random and the number of images that are the criteria for determining the energization duty can be changed as appropriate.

[0071] Next, a specific example of control of the energization duty based on image information will be described.

[0072] <Control based on image area ratio> When controlling the energization duty based on the temperature information of the fixing belt, if the image area ratio of the paper passing through the nip portion differs, the energization duty also changes. The "image area ratio" here is the ratio of the area of ​​the portion where an image is actually formed to the area on the paper where an image can be formed. For example, in a specification where an image can be formed on the paper without margins, as shown in FIG. 8(a), when toner T adheres to half of the entire area of ​​one side of the paper P, the image area ratio is 50%. On the other hand, in a specification where margins are generated even when printing on the entire surface, as shown in FIG. 8(b), when toner T adheres to half of the area of ​​the dotted line portion excluding the margins of the paper, the image area ratio is 50%.

[0073] An image with a large image area ratio as shown in FIG. 9(a) requires a larger amount of heat to fix the image than an image with a small image area ratio as shown in FIG. 9(b). Therefore, in the case of normal control based on the temperature information of the fixing belt, if an image with a large image area ratio is included, especially in the initial stage after the start of printing, the current duty of the halogen heater becomes large, and there is a risk of FP / UFP occurring. Therefore, if a predetermined number or more of images with an image area ratio larger than a preset image area ratio are included among the images of the sheets discharged within three minutes after the first sheet is discharged, the current duty is set to a value lower than the reference value. This makes it possible to reduce the amount of FP / UFP occurring in the initial stage after the start of printing. The image area ratio is one of the image information acquired by the image information acquisition unit 66. Therefore, the CPU 61 controls the current duty of the halogen heater within three minutes after the first sheet is discharged based on the information on the image area ratio sent from the image information acquisition unit 66.

[0074] <Control based on toner overlap ratio> Further, the toner overlap ratio is an image information that affects the energization duty. The "toner overlap ratio" here means the overlap ratio of the portion where the most toner overlaps within the specified area of ​​the paper. For example, if the specified area includes a black monochrome character with a toner overlap ratio of 100% and a blue character with a toner overlap ratio of 200%, the toner overlap ratio in the specified area is 200% for the blue character. The toner overlap ratio can be calculated from the image information acquired by the image information acquisition unit 66. When four colors of toner, such as yellow, magenta, cyan, and black, are used, the maximum toner overlap ratio is 400%.

[0075] An image with a large overlap ratio of toner T (e.g., blue image 90L) as shown in FIG. 10(a) requires a larger amount of toner per unit area than an image with a small overlap ratio of toner T (e.g., black monochrome image 90K) as shown in FIG. 10(b), and therefore requires a larger amount of heat for fixing. For this reason, in the case of normal control based on the temperature information of the fixing belt, if an image with a large overlap ratio of toner is included, especially in the initial stage after the start of printing, the current duty of the halogen heater becomes large, and FP / UFP may occur. For this reason, if a predetermined number or more of images with a larger overlap ratio of toner than a preset toner overlap ratio are included among the images of the sheets discharged within three minutes after the first sheet is discharged, the CPU 61 sets the current duty of the halogen heater within three minutes after the first sheet is discharged to a value lower than the reference value. This makes it possible to reduce the amount of FP / UFP generated in the initial stage after the start of printing.

[0076] The energization duty may be controlled taking into account the image area ratio in addition to the toner overlap ratio. In other words, the energization duty may be set to be lower than the reference value when there is a risk of FP / UFP occurring, based on both the toner overlap ratio and the image area ratio of the image.

[0077] <Control based on margin size> 11 shows an example in which toner images 90 are formed on both ends of the width direction B perpendicular to the transport direction A of the paper P. Here, the two halogen heaters 23 provided in the fixing device are composed of a center heater 23A as a center heating source that heats the center of the fixing belt 21 in the longitudinal direction, and end heaters 23B as end heating sources that heat both end sides of the fixing belt 21 in the longitudinal direction.

[0078] The central heater 23A has a heat generating portion 231 that is arranged in a range toward the central portion, including the central portion in the width direction of the paper P. On the other hand, the end heater 23B has two heat generating portions 232 that are arranged closer to both ends in the width direction of the paper P than the heat generating portion 231 of the central heater 23A.

[0079] 11, image 90 is formed within heating region H2 of end heater 23B, and therefore image 90 can be heated and fixed by generating heat from end heater 23B. In this case, if end heater 23B generates heat within three minutes from the ejection of the first sheet after printing starts, the amount of FP / UFP generated can be reduced by setting the power supply duty of end heater 23B to a value lower than the reference value.

[0080] 11, no image is formed in the heating region H1 of the center heater 23A, but the center heater 23A may be heated when the end heater 23B is heated. However, since there is no risk of FP / UFP occurring due to the heat generated by the center heater 23A, the current duty of the center heater 23A is determined by normal control based on the temperature information of the fixing belt.

[0081] 12, when image 90 is formed across both heating area H1 of center heater 23A and heating area H2 of edge heater 23B, image 90 can be heated by heating both center heater 23A and edge heater 23B. In this case, if heat is generated by center heater 23A and edge heater 23B within three minutes after the first sheet is ejected, the amount of FP / UFP generated can be reduced by setting the current duty of center heater 23A and edge heater 23B to a value lower than the reference value.

[0082] 13, when the image 90 is formed only in the heating region H1 of the center heater 23A, the image 90 can be heated by only turning on the center heater 23A. The edge heater 23B does not have to be turned on. In this case, when the center heater 23A turns on within three minutes of the first sheet being ejected, the amount of FP / UFP generated can be reduced by setting the power duty of the center heater 23A to a value lower than the reference value.

[0083] In this way, when different heaters are used to generate heat depending on the position where image 90 is formed, it is possible to reduce the amount of FP / UFP generated by lowering the power duty of the heater that mainly heats image 90.

[0084] 14. The margin widths d1 and d2 can be obtained from the image information acquired by the image information acquisition unit 66. Therefore, the position of the image 90 on the paper P can be determined from the margin widths d1 and d2, and the CPU 61 can control the power supply duty of the heater that heats the image 90 based on the position of the image 90.

[0085] The energization duty may be controlled taking into account the toner overlap rate in addition to the image position. For example, the energization duty may be set as shown in Table 1 below.

[0086] [Table 1]

[0087] In Table 1, the reduction level of the energization duty of the center heater 23A and the end heater 23B is set individually for each heating region H1, H2 of the heaters 23A, 23B based on the position of the image and the overlapping ratio of the toner. Specifically, when the overlapping ratio of the toner in the heating region H1 of the center heater 23A is 150%, the reduction level of the energization duty of the center heater 23A is set to "Level 1", and as the overlapping ratio of the toner increases, the reduction level of the energization duty is increased to "Level 2" and "Level 3", so that the energization duty is greatly reduced. That is, in normal control based on the temperature information of the fixing belt, the energization duty increases as the overlapping ratio of the toner increases, so the reduction width from the reference value is increased so that the temperature of the nip portion does not become higher than the volatilization temperature of the wax in the toner. Similarly to the center heater 23A, the reduction width of the energization duty of the end heater 23B increases as the overlapping ratio of the toner in the heating region H2 increases. Also, in this example, even if the toner overlap rate is the same, the reduction level of the power duty of the end heater 23B is set higher than that of the central heater 23A, thereby effectively suppressing the occurrence of FP / UFP at both ends, where the temperature is more likely to rise than at the center of the paper width.

[0088] In this way, by controlling the power duty taking into account the toner overlap rate as well as the image position obtained from the margin information, it is possible to more effectively reduce the amount of FP / UFP generated by the image forming device.

[0089] The energization duty is not limited to being controlled based on the image position and the toner overlap ratio, but may be controlled based on the image position and the image area ratio in each of the heating regions H1 and H2. Furthermore, the energization duty may be controlled in consideration of the toner overlap ratio in addition to the image position and image area ratio.

[0090] <Preheat control> Incidentally, when control is performed to reduce the output of the halogen heater within 3 minutes after the first sheet is discharged, the occurrence of FP / UFP can be suppressed, but the fixability of the image may decrease. Therefore, when it is determined that it is necessary to reduce the output of the halogen heater within 3 minutes after the first sheet is discharged, it is preferable to increase the heat storage capacity of the fixing device in advance. For this purpose, it is preferable to control at least one of the preheating time and preheating temperature of the fixing device or components such as the pressure roller. The "preheating time" and "preheating temperature" referred to here are the heating time and heating temperature of the fixing device or components by the halogen heater from the start of heating of the halogen heater to the supply of the first sheet of paper to the nip portion of the fixing device.

[0091] When the output of the halogen heater is reduced within 3 minutes after the first sheet is discharged, the amount of heat stored in the components such as the fixing device and pressure roller can be increased by extending the preheating time compared to when the output is not reduced. The amount of heat stored can also be increased by increasing the preheating temperature.

[0092] In this way, by lengthening the preheating time or increasing the preheating temperature, the amount of heat stored in each component of the fixing device or pressure roller can be increased, making it possible to compensate for the lack of heat in the fixing belt. This makes it possible to suppress the deterioration of fixing performance due to the reduction in output of the halogen heater, and to obtain good fixing performance.

[0093] The first embodiment of the present invention has been described above.

[0094] As described above, in the first embodiment of the present invention, the output (power duty) of the halogen heater is controlled within 3 minutes of the first sheet being ejected based on the image information (image area ratio, toner overlap ratio, margin width, etc.) of the sheet being ejected within 3 minutes of the first sheet being ejected, thereby making it possible to reduce the amount of FP / UFP generated in the initial stage after the start of printing, thereby making it possible to provide an image forming apparatus that is environmentally friendly. Moreover, since the amount of FP / UFP can be reduced without adding components such as filters that collect FP / UFP, the number of components can be reduced, leading to lower costs.

[0095] The printing operation to which the control according to the present invention is applied can be applied not only to cases where printing continues for three minutes or more after the first sheet is discharged, but also to cases where printing is completed within three minutes after the first sheet is discharged. By applying the control according to the present invention even when printing is completed within three minutes, it is possible to reduce the number of FPs / UFPs occurring in the early stages when there is a tendency for many FPs / UFPs to occur.

[0096] Furthermore, the printing operation to which the control according to the present invention is applied includes not only the printing operation that starts after the image forming apparatus is powered on, but also the printing operation that starts after the fixing device goes into a standby state after the power is turned on, etc. In other words, the control according to the present invention is applied when the halogen heater starts to generate heat and starts the printing operation from a state in which no paper is passing through the fixing device and the halogen heater is not generating heat.

[0097] Furthermore, the fixing device provided in the image forming apparatus according to the present invention is not limited to the fixing device 20 shown in Fig. 2. The present invention is also applicable to an image forming apparatus provided with, for example, the following fixing device.

[0098] FIG. 15 shows the configuration of a fixing device according to the second embodiment of the present invention.

[0099] The fixing device 30 shown in FIG. 15 includes a fixing roller 31 as a first rotating body 19A arranged on the unfixed image carrying surface side (toner image T side) of the paper P. The fixing roller 31 contacts a pressure roller 32 as a second rotating body 19B to form a nip portion N. The fixing roller 31 has, for example, a cylindrical core material, an elastic layer provided on the outer peripheral surface of the core material, and a release layer covering the elastic layer. A halogen heater 33 is arranged inside the core material of the fixing roller 31. As a result, when infrared rays are radiated from the halogen heater 33, the fixing roller 31 is heated from the inside by radiant heat. The output of the halogen heater 33 is controlled based on the temperature of the fixing roller 31 detected by a temperature sensor 34.

[0100] Even in a fixing device 30 equipped with such a fixing roller 31, if the energization duty of the halogen heater 33 becomes large in the initial stage after the start of printing, the wax in the toner heated in the nip portion N may volatilize, and FP / UFP may occur. Therefore, by applying the present invention, when there is a risk of FP / UFP occurring in the initial stage after the start of printing, the amount of FP / UFP generated can be reduced by reducing the energization duty of the halogen heater 33 within 3 minutes after the first sheet is discharged based on image information.

[0101] Furthermore, to summarize the aspects of the present invention, the present invention includes at least the following aspects.

[0102] [First aspect] The first aspect is an image forming apparatus equipped with a fixing device that fixes an image on a recording medium, the fixing device having a pair of rotating bodies that form a nip portion through which the recording medium passes, and a heating source that heats at least one of the pair of rotating bodies, and the image forming apparatus sets the output of the heating source within three minutes after the first sheet of the recording medium is discharged from the apparatus during printing to be lower than a predetermined reference value based on image information of the recording medium that is discharged within three minutes after the first sheet of the recording medium is discharged from the apparatus.

[0103] [Second aspect] A second aspect is an image forming apparatus according to the first aspect, wherein the image information is an image area ratio of an image formed on the recording medium.

[0104] [Third aspect] A third aspect is the image forming apparatus according to the first or second aspect, wherein the image information is a toner overlap ratio of an image formed on the recording medium.

[0105] [Fourth aspect] A fourth aspect is an image forming apparatus according to any one of the first to third aspects, wherein the image information is a margin width from both ends of the recording medium in a width direction to the image.

[0106] [Fifth aspect] A fifth aspect is an image forming apparatus in any one of the first to fourth aspects, which controls at least one of the preheating time and preheating temperature of the fixing device by the heating source from the start of heating of the heating source to the time when the first sheet of the recording medium is supplied to the nip portion, based on image information of the recording medium that is discharged within three minutes after the first sheet of the recording medium is discharged outside the apparatus during printing.

[0107] [Sixth aspect] A sixth aspect is an image forming device in which, in any one of the first to fourth aspects, one of the pair of rotating bodies is a first rotating body arranged on the unfixed image bearing surface side of the recording medium, and the other is a second rotating body arranged to face the outer peripheral surface of the first rotating body, and at least one of the preheating time and preheating temperature of the second rotating body by the heating source from the start of heating of the heating source to the time when the first sheet of the recording medium is supplied to the nip portion is controlled based on image information of the recording medium that is discharged within three minutes after the first sheet of the recording medium is discharged outside the device during printing. [Explanation of symbols]

[0108] 20 Fixing device 19A Rotating body (first rotating body) 19B Rotating body (second rotating body) 21 Fixing belt (first rotating body) 22 Pressure roller (second rotating body) 23 Halogen heater (heat source) 1000 Image forming device N Nip P Paper (recording medium) [Prior art documents] [Patent documents]

[0109] [Patent Document 1] JP 2016-85407 A

Claims

1. In an image forming apparatus having a fixing device for fixing an image on a recording medium, The fixing device is A pair of rotating bodies forming a nip portion through which the recording medium passes; A heat source that heats at least one of the pair of rotating bodies; having An image forming apparatus characterized in that, based on image information of the recording medium that is discharged within three minutes after the first sheet of the recording medium is discharged from the apparatus during printing, the output of the heating source within three minutes after the first sheet of the recording medium is discharged from the apparatus is set to a value lower than a preset reference value.

2. 2. The image forming apparatus according to claim 1, wherein the image information is an image area ratio of the image formed on the recording medium.

3. 2. The image forming apparatus according to claim 1, wherein the image information is a toner overlap ratio of the image formed on the recording medium.

4. 2. The image forming apparatus according to claim 1, wherein the image information is a margin width from each end of the recording medium in a width direction to the image.

5. 2. The image forming apparatus according to claim 1, wherein at least one of the preheating time and preheating temperature of the fixing device by the heating source from the start of heating of the heating source to the time when the first sheet of the recording medium is supplied to the nip portion is controlled based on image information of the recording medium that is discharged within three minutes after the first sheet of the recording medium is discharged outside the apparatus during printing.

6. one of the pair of rotating bodies is a first rotating body arranged on a side of the recording medium on which an unfixed image is carried, and the other is a second rotating body arranged to face an outer circumferential surface of the first rotating body, 2. The image forming apparatus according to claim 1, wherein at least one of the preheating time and preheating temperature of the second rotating body by the heating source from the start of heating of the heating source to the time when the first sheet of the recording medium is supplied to the nip portion is controlled based on image information of the recording medium that is discharged within three minutes after the first sheet of the recording medium is discharged outside the apparatus during printing.

Images