JP5908150B1 - Fixing apparatus and fixing method - Google Patents

Abstract

Fixing capable of obtaining a clear fixed image without interposing a heat resistant film between a toner transferred to a recording medium and a heating substrate, and without causing damage to the transferred toner. An apparatus and a fixing method thereof are provided. A transfer unit 3 on which an image of a photoreceptor 31 is transferred to a recording medium 41, and heating that is provided on the moving direction side of the recording medium 41 from the transfer unit 3 and heats toner 42 transferred by the transfer unit 3. 1 and a pressure conveying unit 2 that conveys the recording medium 41 while pressing the surface of the recording medium 41 on which the toner 41 is provided with the pressing roller 21. It is equipped with. [Selection] Figure 1

Description

  The present invention relates to a fixing device and a fixing method for forming an image on a recording medium by heating and melting resin-based toner for forming an image in an image forming apparatus such as a copying machine, a laser printer, and an LED printer. More particularly, the present invention relates to a toner fixing device and a fixing method for performing heat fixing processing as a permanently fixed image on a recording medium without degrading (damaging) an unfixed toner image transferred to the recording medium and saving power.

  Electrophotographic recording is widely used in copying machines, printers and the like. This electrophotographic recording is performed as follows. That is, the toner is electrostatically attached to the photosensitive drum by charging, exposing and developing on a photosensitive member (photosensitive drum, belt-like photosensitive member, plate-like photosensitive member, etc.), and the toner is electrostatically attracted to the recording medium. Transfer and transfer toner. Then, the toner is softened by heating with a heat and pressure roller, whereby stickiness is produced and the toners adhere to the recording medium. As a result, the toner does not move freely. In short, softening, adhesion, and melting occur, and the image is fixed on the recording medium by being pressurized immediately after melting.

  As a fixing method, there is known a method in which a recording medium on which toner is transferred is conveyed while being pressed by a heated roller with a halogen lamp incorporated therein, for example. In this way, by transporting the recording medium onto which the toner has been transferred while rotating the pressure roller, the surface of the toner is hardly rubbed, so that the toner is baked and transported without causing a missing portion of the toner. Can do. However, it is necessary to incorporate a halogen lamp inside the roller. For this reason, there is a problem that power consumption is severe and it takes time for the temperature of the pressure roller to rise after the switch is turned on. In order to solve this problem, it is necessary to preheat. Therefore, further power consumption is required, and it is not possible to sufficiently meet the demand for energy saving.

  On the other hand, a method using a so-called ceramic heater in which a heating resistor is formed on a ceramic surface without using a halogen lamp has also been proposed. However, in this method, in order to effectively use the heat of the ceramic heater, the heater surface is brought into contact with the toner-transferred portion of the recording medium and heated and pressurized. Moreover, the ceramic heater cannot be rotated like a roller. For this reason, the surface of the ceramic heater and the surface of the recording medium on which the toner is transferred are conveyed while being rubbed. As a result, all of the toner is easily damaged before fixing. Therefore, a method is adopted in which a heat-resistant film (sheet) made of polyimide or the like is interposed between the ceramic heater and the recording medium, and the heat-resistant film is conveyed in synchronization with the conveying speed of the recording medium (for example, (See Patent Document 1 and Non-Patent Document 1).

JP-A-5-273879

"SURF and ODF" (The Imaging Society of Japan, Vol. 48, No. 5, pp. 411-416, 2009)

  As described above, heating and pressurizing the toner transferred through the heat resistant film results in indirect heating through the heat resistant film, and thus requires a large amount of heat. As a result, there is a problem that even if a corner ceramic heater is used, the power consumption cannot be sufficiently reduced. Furthermore, it is necessary to move the heat-resistant film in accordance with the recording medium conveyance speed, and there is a problem that the structure is complicated in terms of mechanism.

  The present invention has been made to solve such a problem, and without damaging the transferred toner without interposing a heat-resistant film or the like between the toner transferred to the recording medium and the heating substrate. It is an object of the present invention to provide a fixing device and a fixing method thereof capable of obtaining a clear fixed image without causing the above.

  Another object of the present invention is to provide a heating substrate and a recording medium that can save power and can be quick-started by forming a heating resistor on the surface of the substrate by making the heating unit and the pressure unit different. It is an object of the present invention to provide a fixing device and a fixing method capable of fixing without directly sliding the transferred toner surface.

  Yet another object of the present invention is to heat (preheat) the upstream toner transferred to the recording medium, which generates heat in the heating unit or pressurizing unit and cannot be used for heating the toner transferred to the recording medium. It is an object of the present invention to provide a fixing method that can be used effectively for effective use of heat as a whole.

The fixing device of the present invention is provided with a transfer unit that develops an electrostatic latent image formed on a photosensitive member and transfers toner adhered thereto to a recording medium, and is provided on the traveling direction side of the recording medium from the transfer unit. A heating unit that heats the toner transferred by the transfer unit, and the recording unit that is provided on the recording medium traveling direction side from the heating unit and presses the surface of the recording medium on which the toner is provided with a pressure roller. A pressure conveyance unit that conveys the medium, and a heater of the heating unit heats the recording medium from a surface opposite to the surface on which the toner is transferred, and / or the recording medium. Formed by a second heating substrate provided apart from the recording medium from the surface side to which the toner has been transferred, and the heating unit is heated until the toner transferred to the recording medium is melted, and the pressure conveying unit Then said Was photographed toner is pressurized at a temperature that does not melt, at a position facing each other across the recording medium and the pressure roller of the pressure conveying unit, in the first heating substrate is extended, or the first heating substrate differs fifth heating substrate provided with said pressure roller and said first heating substrate or the fifth heating substrate and by said recording medium Ru is pressed.

Said first heating substrate by the toner is provided in contact with the surface opposite transferred surface Rukoto of the recording medium, power saving, and is heated on demand (operation immediately switched on) This is preferable.

  The third heating substrate is provided in contact with the recording medium on the upstream side of the pressure contact roller of the pressure conveying unit, so that the pressure roller is not only heated and pressed but also heated. Therefore, it can be fixed more reliably.

The heating substrate according to claim 4, wherein the third heating substrate is provided so that a surface of the third heating substrate provided with the heating resistor is parallel to the recording medium, and the insulating substrate Since the third heating substrate is shared with the second heating substrate by providing the side surface in contact with the pressing roller, the toner can be heated and melted and the pressing roller can be heated by one heating substrate. The amount of heat can be used more effectively.

First heating the substrate or the second heating substrate described above, the third heating the substrate before mentioned, or the fifth heating the substrate at least one of an insulating substrate, it is formed on one surface of the insulating substrate, heating the insulating substrate A temperature measurement formed on the insulating substrate along the heating resistor in the vicinity of the heating resistor, and at least a pair of electrodes that can pass a current in the longitudinal direction of the heating resistor, And a structure including at least a pair of measurement terminals for measuring an electrical resistance between a predetermined length of the temperature measurement resistor, the start-up is very fast, In addition, it is possible to form a power-saving heating unit that is small and can be sufficiently heated.

  Since the second heating substrate has a heat radiation member formed on the surface side of the heating resistor, the second heating substrate is excellent in heat radiation and can effectively heat the toner on the recording medium with less power.

In the fixing method of the present invention, the toner matched to the image is transferred to a recording medium by an electrophotographic process, and heated while being separated from the recording medium from the surface side on which the toner is transferred while transporting the recording medium. The toner is melted by heating from the side opposite to the surface on which the toner is transferred, and the recording medium in which the toner is melted is removed from the toner side of the recording medium at a temperature at which the toner does not melt. The first heating substrate is extended at a position facing the recording medium with a pressure roller , or a fifth heating substrate separate from the first heating substrate is provided and pressed, and the recording medium is pressed. It is characterized by conveying.

By increasing the temperature of the pressing roller to a temperature at which the toner does not melt , fixing can be performed more reliably by performing both pressing and heating.

  The portion to which the toner is transferred is made higher in the vertical direction than the portion to which pressure is transferred by the pressure roller, and the portion to which pressure is transferred from the transfer is covered with a cover. The toner transferred to the recording medium can be preheated by effectively raising the heat of the heating substrate that heats the rollers of the roller, which is preferable from the viewpoint of the total effective use of the heat amount.

  According to the fixing device of the present invention, the portion where the transferred toner is heated and melted and the portion where the transferred toner is conveyed while being pressed and pressed are performed in different portions, whereby the heating portion of the heating substrate and the toner are transferred. The recording medium is not slid. For this reason, the toner melts and adheres to the recording medium in the heating unit, and the toner is fixed without being damaged even when pressed by the press roller in the pressure conveying unit. As a result, in the heating unit, the recording medium is conveyed while being rotated by the pressure contact roller while being heated by an on-demand heating substrate formed of a heating resistor on the ceramic substrate having a high response speed. be able to. In this case, even if the pressure roller is indirectly heated to raise the temperature to melt the toner, it can be completely fixed by increasing the temperature and pressing.

  According to the fixing method of the present invention, the portion that heats and melts the toner and the pressure contact portion that presses and fixes the toner on the recording paper are configured separately, so that the pressure contact is achieved without sliding the recording medium. can do. On the other hand, the heating unit can be heated by a heating substrate formed of an exothermic resistor on an insulating substrate, so the heat capacity is small and the response is very good, so it can be fixed immediately by turning on the switch when necessary. In addition to being able to do a quick start on demand, the power consumption is very small, greatly contributing to power saving. In addition, it is possible to further heat on demand by generating only part of the heating resistor as necessary.

FIG. 2 is an explanatory diagram illustrating an outline of a fixing device according to an embodiment of the present invention. FIG. 8 is an explanatory diagram illustrating a modification of the fixing device in FIG. 1. FIG. 10 is an explanatory diagram showing still another modification of the fixing device in FIG. 1. It is a top view explaining one Embodiment of a heating substrate. It is a figure explaining the BB cross section of FIG. 4A. It is sectional drawing explaining other embodiment of a heating board | substrate. It is a top view of Drawing 5A. It is a figure which shows the example of a drive circuit which controls the insulated substrate of a heating board | substrate to predetermined temperature. It is a circuit diagram which shows an example of substrate temperature control.

  Next, the fixing device and fixing method of the present invention will be described with reference to the drawings. FIG. 1 shows a schematic diagram of a fixing device according to an embodiment of the present invention. As shown in FIG. 1, the fixing device of the present invention is a recording medium in which toner adhered by developing an electrostatic latent image formed on a photosensitive drum 31 is recorded. The transfer unit 3 transferred to 41, the heating unit 1 provided on the moving direction side of the recording medium 41 from the transfer unit 3 and heating the toner 42 transferred by the transfer unit 3, and the recording unit 41 from the heating unit 1 And a pressure conveying unit 2 that conveys the recording medium 41 while pressing the surface of the recording medium 41 on which the toner 41 is provided with the pressure roller 21.

  In other words, as described above, in the conventional fixing device, in order to save power without using a halogen lamp, a heat resistant film is interposed between the ceramic heater and the surface of the recording medium on which the toner is transferred. Thus, the surface on which the toner is fixed must be made so as not to be rubbed directly with the ceramic heater. Therefore, there is a problem that the heat of the ceramic heater is not directly transferred to the surface of the toner, and the heat is wasted. Furthermore, the heat resistant film must be transported in synchronism with the recording medium, which is complicated mechanically. However, in the present invention, the conventional idea of simultaneously performing heat melting and pressure welding of toner is changed, and the heating unit 1 that heats and melts the toner transferred to the recording medium and the pressure that presses the heat and melted toner 42 are pressed. By separately configuring the transport unit 2, the heating substrate 10 mainly including a ceramic heater is used, and the recording medium 41 is transported while being pressed by a rotating roller (pressing roller 21). As a result, even if the toner 42 is heated and melted by the heating unit 1 to adhere to the recording medium 41 and is pressed and conveyed by the pressure roller 21 by the pressure conveying unit 2, the toner 42 is not damaged at all.

  The temperature of the toner 42 is decreasing for higher speed. In addition, it is necessary to consider not only the text but also the fixing of the entire image. For example, if an acrylic / styrene resin is used, the heat quantity required on the toner side is 17.6 J / 100 ° C. with a thickness of 2 μm, a specific heat of 1.4, and 0.126 g per A4 size sheet. On the other hand, ordinary copy paper is 9 μm thick, has a specific heat of 1.25, 4.5 g per A4 size sheet, and the required amount of heat on the paper side is 5,600 J / 100 ° C. Therefore, it becomes 2,800 J / 50 degreeC as 50 degreeC. Accordingly, in order to fix an image on one A4 size sheet, a heat amount of 2,820 J is required (a part is radiated to the outside). Also from this point, it is very effective to incline the apparatus itself in the fixing method of the present invention and effectively use the amount of heat. Further, by increasing the number of heating substrates, it is possible to fix 60 sheets or more per minute.

  In the example shown in FIG. 1, the heating unit 1 includes a first heating substrate 10 a provided on the back surface (the surface opposite to the surface on which the toner has been transferred) of the recording medium 41, and the surface of the recording medium 41 (the toner 42 is transferred). The second heating substrate 10b provided on the surface side is separated from the recording medium 41 and is heated. However, it is not necessary to provide a heating substrate in both, and it is sufficient to provide it in only one of them. The first heating substrate 10 a is provided to such an extent that the surface on which a protective film 17 described later is formed contacts the back surface of the recording medium 41. Since the first heating substrate 10a is fixed and the recording medium 41 is sequentially conveyed, it slides when in contact, but is not in pressure contact but is in contact with the recording medium 41. The surface is the back surface opposite to the surface on which the toner 42 is transferred, and the toner 42 is not attached, so there is no problem.

  The second heating substrate 10b is provided apart from the recording medium 41 on the surface side of the recording medium 41 of the heating unit 1 where the toner 42 is provided. That is, the toner 42 can be heated without contacting the toner 42 transferred to the recording medium 41. That is, the second heating substrate 10b is not heated in contact with the recording medium 41, but is heated by radiant heat (radiant heat) from the second heating substrate 10b. Accordingly, the surface of the recording medium 41 to which the toner 42 is transferred is not rubbed by the second heating substrate 10b, and a part of the unfixed toner 42 is not peeled off. From this viewpoint, the second heating substrate 10b preferably has a structure that easily radiates heat from the surface thereof. For example, as shown in FIG. 5A and FIG. 5B, a heat radiation layer 18 made of a material excellent in heat radiation is formed on the surface, or irregularities 18a are formed on the surface, thereby making it easy to emit heat. Preferably there is.

  Further, in the example shown in FIG. 1, the third heating substrate 10 c that heats the pressure roller 21 is also used as the second heating substrate 10 b. In the example shown in FIG. 1, the third heating substrate 10c is provided also as the second heating 10b. The third heating substrate 10c is provided with its end surface obliquely cut so that the side surface of the insulating substrate 11 is pressed against the peripheral surface 21a of the pressure roller 21. Therefore, the heat of the third heating substrate 10c is transmitted to the peripheral surface 21a of the pressure roller 21, and the toner 42 of the recording medium 41 can be pressed against the peripheral surface 21a of the pressure roller 21 whose temperature has increased. For this reason, the toner 42 heated and melted by the heating unit 1 approaches the press roller 21 and the temperature rapidly decreases and is not pressed in a solidified state. The toner 42 is pressed in a melted state. it can. As a result, the fixing can be further reliably performed. As shown in FIG. 1, the end surface of the insulating substrate 11 of the third heating substrate 10 c is cut obliquely so that the press roller 21 can be heated immediately before the recording medium 41 is pressed, Heat can be used effectively. However, the third heating substrate 10c is not essential. The main parts of the first heating substrate 10a, the second heating substrate 10b, and the third heating substrate 10c have substantially the same structure as a so-called ceramic heater in which a heating resistor is formed on one surface of a conventional ceramic substrate. Therefore, an example of the common heating substrate 10 will be described with reference to FIGS.

  The heating substrate 10 has the same structure as a conventional heating head used for recording or erasing on a card or the like. For example, the heating substrate 10 in which the protective film (sheet) 17 is removed in FIGS. The plan view and the BB cross-sectional view thereof are configured to show the state in which the protective film 17 is formed. That is, the heating resistor 12, the temperature measuring resistor 13 (13a, 13b), the electrode 14 (14a, 14b, 14c), the temperature measuring terminal 15 (15a to 15e), etc. formed on the insulating substrate 11 are formed. A protective film 17 is formed thereon. The heating resistor 12 and the temperature measuring resistor 13 are connected to the electrode 14 and the measuring terminal 15 by conductors 16, respectively. A lead 19 is connected to the electrode 14 and the measurement terminal 15 as shown in FIG. 5A.

  More specifically, as shown in FIG. 4A, for example, a heating resistor 12 and a temperature measuring resistor 13 (13a, 13b) are provided on one surface of an insulating substrate 11 made of ceramics such as alumina. It has become. In the example shown in FIG. 4A, for example, a linear and strip-shaped heating resistor 12 is formed along one side of the rectangular insulating substrate 11 in the longitudinal direction. The length of the insulating substrate 11 in the longitudinal direction is formed to be 50 mm or more, for example, according to the width of the recording medium 41 (dimension in the direction perpendicular to the paper surface of the recording medium 41 in FIG. 1). When the recording medium 41 is large, the insulating substrate 11 is lengthened, or a plurality of heating substrates 10 are arranged in the longitudinal direction so as to match the width of the recording medium 41. Further, when the heating substrate 10 is formed of a single long insulating substrate 11, a plurality of electrodes 14 and measuring terminals 15 are formed in the middle of the heating resistor 12 and the temperature measuring resistor 13, The voltage can be applied in a divided manner, or the temperature can be set for each region of the insulating substrate 11, so that the temperature is always controlled to be uniform throughout the insulating substrate 11. In the example shown in FIG. 4A, two temperature measuring resistors 13a and 13b are formed. If the temperature of the insulating substrate 11 is too low, the toner 42 transferred onto the recording medium 41 will not melt and will not be sufficiently fixed. If it is too high, the toner 42 will melt too much and the toner will be applied to the pressure roller 21. Since the toner offset phenomenon occurs due to adhesion, the temperature of the insulating substrate 11 needs to be accurately controlled according to each region. Therefore, it is preferable that the number of temperature measurement resistors 13 and the number of measurement terminals 15 be as large as possible.

  As the insulating substrate 11, an insulating substrate made of alumina or the like and having excellent thermal conductivity is used. The shape is preferably rectangular, but is not limited thereto. The length is preferably equal to the width of the recording medium 41, but even if it is smaller than that, there is no problem by arranging the plurality of heating substrates 10 as described above. The width of the insulating substrate 11 (the dimension in the direction perpendicular to the direction in which the heating resistor 12 in FIG. 4A extends) is, for example, about 12 mm. For example, an alumina substrate having a thickness of about 0.6 mm is used.

The heating resistor 12 is printed in a paste form, for example, by selecting and mixing Ag, Pd, RuO ₂ , Pt, metal oxide, glass powder, etc. so that the temperature coefficient, resistance value, etc. are optimized. It is formed by firing. The sheet resistance value of the resistance film formed by firing is changed depending on the amount of the solid insulating powder. The resistance value and the temperature coefficient can be changed according to the ratio of the two. In addition, as a material used as the conductor (electrode 14, measurement terminal 15, and connection conductor 16), the same paste-like material in which the ratio of Ag is increased and Pd is reduced is used. It can be formed by printing in the same manner as the body 12. In some cases, it may be necessary to change depending on the operating temperature due to the connection of the terminal, and the resistance value can be lowered as the amount of Ag increases. It is preferable that the temperature coefficient is positively high, and it is particularly preferable to use a material having a temperature of 1000 to 3500 ppm / ° C. Although not shown, the electrode is placed at an appropriate position along the direction of current flow of the heating resistor 12. By being provided, a voltage can be applied partially, and the temperature can be changed depending on the location.

  The fact that the temperature coefficient of resistance is positively large means that the resistance value increases greatly when the temperature rises. Therefore, it is easy to detect the actual heat generation temperature due to deviation from the reference resistance value by measuring the resistance value in the heated state. It is easy to correct the deviation from the desired heat generation temperature by adjusting the applied voltage or adjusting the duty of the applied pulse. Also, since the temperature coefficient of resistance is positive, if the temperature rises too much, the resistance value increases, the current value decreases, and the amount of heat generated by the resistance decreases, so the temperature becomes saturated sooner, This is because it has excellent temperature stability and can prevent overheating due to thermal runaway. Note that the width of the standard portion of the heating resistor 12 is also set to a predetermined temperature according to the application, and a plurality of heating resistors 12 may be arranged in parallel.

  Further, electrodes 14 made of a good conductor such as a silver / palladium alloy or an Ag—Pt alloy with a reduced palladium ratio are formed on both ends of the heating resistor 12 by printing or the like. As shown in FIG. 5A, the electrode 14 has a structure in which a lead 19 is connected, a power source is connected, and the heating resistor 12 is energized. This power source may be a direct current, an alternating current, or a pulse voltage. If it is a pulse voltage, the applied power can be controlled by changing its duty. Further, in FIG. 4A, a wide heating resistor 12 having a width of about 4 mm is formed by one, but the width and the number of the heating resistors are not limited to this example. Formed to be.

  In the vicinity of the heating resistor 12, a temperature measuring resistor 13 is formed on the surface of the insulating substrate 11 in the same manner as the heating resistor 12. The temperature measuring resistor 13 is preferably formed along the heating resistor 12 as shown in FIG. 4A, for example. In the example shown in FIG. 4A, two pieces having slightly different lengths are formed at intervals. Then, both ends are connected to a pair of measurement terminals 15a and 15b. The measurement terminals 15a and 15b are also formed of a highly conductive material, like the electrode 14 described above. The temperature measuring resistor 13 is provided with a measuring terminal 15e not only at the pair of measuring terminals 15a and 15b at both ends but also at the center thereof. A pair of measurement terminals 15c and 15d are also formed at both ends of the second temperature measurement resistor 13b, and are also connected to the measurement terminal 15e at the center.

  The temperature measuring resistor 13 may be formed of the same material as that of the heat generating resistor 12, but it is preferable that the absolute value (%) of the temperature coefficient is as large as possible. This temperature measuring resistor 13 does not generate heat, but detects the temperature of the insulating substrate 21 so as to reach the melting temperature of the modeling material. For example, the resistor 13 for measuring temperature is 0.5 mm wide than the heating resistor 12. It is formed with a slightly shorter length. Further, the applied voltage is kept low so that the temperature measuring resistor 13 itself does not generate heat, and, for example, about 5 V is applied. That is, since the temperature measuring resistor 13 is directly provided on the insulating substrate 11, both temperatures are almost the same. By measuring the resistance value of the temperature measuring resistor 13, the surface of the insulating substrate 11 is measured. This is because the temperature, and thus the temperature of the modeling material that is in close contact with the back surface of the insulating substrate 11, is known, and the temperature is made equal to or higher than the melting temperature. That is, since the resistance value of the resistor material generally changes as the temperature changes, the temperature is measured by measuring the change in the resistance value. Although the temperature detection means will be described later, the resistance value of the temperature measurement resistor 13 is detected by detecting a voltage change at both ends of the temperature measurement resistor 13, and the resistance value and the temperature measurement resistor 13 are detected. The temperature is detected from the temperature coefficient (which is known by the material), and the larger the temperature coefficient, the smaller the measurement error. In this case, the temperature coefficient may be positive or negative.

  The temperature measuring resistor 13 is not limited to the same material as the heating resistor 12, and is formed by printing or the like depending on the application. That is, when a very small temperature difference is required, it is possible to change the mixing ratio of Ag and Pd or use a completely different material having a large temperature coefficient. The measurement terminals 15a and 15b of the temperature measuring resistor 13 are also formed of a highly conductive material in which Ag is increased and Pd is decreased, like the electrode 14 of the heating resistor 12. The formation of the temperature measurement terminals 15 a and 15 b is not necessarily provided at the end of the temperature measurement resistor 13. For example, as shown in FIG. 4A, a measurement terminal 15e may be provided at the center, or may be formed at each midpoint divided into two. The temperature measuring resistor 13 is set in accordance with the size or purpose of the insulating substrate 11 and the position of the measurement terminal 15.

  In FIG. 4A, only the outer peripheral portion is shown by a two-dot chain line, but as shown in the sectional view in FIG. 4B, the heating resistor 12, the temperature measuring resistor 13, and the connection conductor 16 is covered with a protective film 17. The protective film 17 preferably has a high thermal conductivity, and is formed of, for example, a polyimide film. However, in the case where the surface opposite to the insulating substrate 11 as shown in FIG. 3 to be described later comes into contact with the pressure roller 21 or the like to heat the roller or the like, a thin ceramic about half the thickness of the insulating substrate 11 is used. A cover substrate made of a plate or the like may be provided instead. Note that the electrode 14 and the measurement terminal 15 are not covered and exposed, and the lead 19 is connected as shown in FIG. 5A.

  The example shown in FIG. 5A is an example of a heating substrate suitable for the second heating substrate 10b described above, in which a heat radiation layer 18 is formed instead of the protective film 17 provided on the surface of the heating resistor 12 or the like. is there. The configurations of the insulating substrate 11 and the heating resistor 12 are the same as those described above, and a description thereof will be omitted.

  That is, the heat radiation layer 18 is coated with a material that easily radiates heat, rather than dissipating heat by heat conduction, like the protective film 17 described above. Therefore, a material having a high emissivity of electromagnetic waves that move heat is used as the material. The emissivity is generally 0 to 1.0 (graphite: graphite). Metals have a low emissivity, and black oxide systems have a high emissivity. Glass and quartz also have high emissivity. From the viewpoint of emissivity, graphite (1.0), black alumite, glass, rubber, etc. (0.9), black lacquer (0.9), black paint (0.85), epoxy glass, paper phenol, Of polytetrafluoroethylene glass (0.8), a material that has high heat resistance and hardly changes in quality can be used. Furthermore, it is preferable that the surface of the heat radiation layer 18 is formed in an uneven surface or a curved surface (wave shape) and has a large surface area. In the example shown in FIGS. 5A to 5B, an example in which regular irregularities are formed in the longitudinal direction and the vertical direction thereof is shown, but there is no need to make regular irregularities in this way. However, the unevenness as shown in FIG. 5B, for example, has a width of about 10 to 50 μm and a depth of about 10 to 50 μm, but may be formed by pressing a mesh of that degree, Further, it may be formed on a rough surface having a depth of about 10 μm. It is preferable that the unevenness and the curved surface are formed in a dot shape because the surface area can be doubled.

More specifically, the main component of the mixture of ruthenium oxide (RuO ₂ ) and alumina (Al ₂ O ₃ ) is the same as that of the heating resistor 12 (in the heating resistor 2, Ag is further mixed to adjust the resistance value. ) Paste is applied by printing or the like and sintered. Therefore, by pressing the aforementioned mesh or the like before being completely cured, irregularities are formed on the surface, and a desired rough surface can be formed.

Furthermore, it is known that the amount of thermal radiation of an object is proportional to (emissivity) × (the fourth power of the absolute temperature of the object surface (K ⁴ )). Therefore, it is preferable to increase the surface temperature of the heat radiation layer 18 in order to increase the amount of heat radiation. From this point of view, it is preferable that the heat generated in the heating resistor 12 is concentrated on the heat radiation layer 18 without escaping as much as possible. Therefore, as described above, a heat insulating layer (not shown) is formed between the heating resistor 12 and the insulating substrate 11 so that the heat generated in the heating resistor 12 is not transmitted to the insulating substrate 11 as much as possible. It is preferable. However, as described above, in the case where the third heating substrate 10c is also used, it is necessary to transfer heat to the insulating substrate 11 side, and it is not preferable to interpose a heat insulating layer.

  In the example shown in FIG. 1, the pressure conveying unit 2 rotates the rollers 21 and 22 while the recording medium 41 is in pressure contact with the pressure roller (upper roller) 21 and the rotating roller (lower roller) 22. Thus, the recording medium 41 is transported. Although the names are shown separately for the pressure roller 21 and the rotary roller 22, it goes without saying that the rollers 21 and 22 are used for pressure contact only for convenience. The heating and pressure roller used in a normal fixing device is made of a material that can be easily heated, such as a rubber roller. However, in the present invention, since it is not intended for heating, it is rather bonded to the toner 42 while being pressed. However, it is preferably formed of a releasable material that can be easily separated. Specifically, a relatively hard heat insulating material such as plastic having a fluororesin coating film for preventing adhesion on the outer surface 21a is used. The lower rotating roller 22 is also made of a heat insulating material (such as sponge or balloon (air capsule) mixed plastic). Note that the heating of the pressure roller 21 does not require the amount of heat for melting the toner 42. As described above, the heating is auxiliary heating at the time of fixing, and thus it is not necessary to raise the temperature so much. As shown in FIG. 1, heat through the insulating substrate 11 of the heating substrate 10 is sufficient. However, as shown in FIG. 2 described later, when the heating substrate 10c is used exclusively for heating the pressure roller 21, it can be provided so that the protective film 17 side is in contact with the insulating substrate 11 side. .

  The purpose of the pressure roller 21 is to impregnate the recording medium 41 by pressing the toner 42 melted by the heating unit 1 on the recording medium 41, but the recording sheet 41 sent to the pressure conveying unit 2. If the temperature of the upper toner 42 is drastically lowered, there may be a case where the recording medium 41 cannot be sufficiently infiltrated only by the pressure contact. Considering such a case, it is preferable that the pressure roller 21 is also at a certain high temperature so that the temperature of the toner 42 does not drop suddenly. Therefore, in the example shown in FIG. 1, the third heating substrate 10 c (also used as the second heating substrate 10 b in the example shown in FIG. 1) contacts the peripheral portion 21 a of the pressure roller 21 on the side surface of the insulating substrate 11. It is pressed to do. The contact portion between the pressure roller 21 and the third heating substrate 10c is an upstream portion as close as possible to a portion where the pressure roller 21 contacts the recording medium 41 (a position where the pressure contact roller 21 reaches the pressure contact as soon as possible by rotation of the pressure roller 21). It is preferable. This is because it is preferable to contact the recording medium 41 before the heat conducted from the third heating substrate 10c escapes. However, in order to share with the second heating substrate, it is determined by the relationship with the arrangement position of the second heating substrate 10b.

  In the example shown in FIG. 1, a rotating roller 22 is provided via a pressure roller 21 and a recording medium 41. By synchronizing the rotation of the rotating roller 22 with the rotation of the pressure roller 21, the recording medium 41 can be conveyed from both sides, which is preferable. However, the back side of the recording medium 41 may not be a rotating roller but may be a normal flat plate. Any material that can withstand the pressure of the pressure roller 21 may be used. Although it slides with the recording medium 41 conveyed, since it slides on the back side of the recording medium 41, there is no influence.

  Further, when the rotating roller (lower roller) 22 is used on the lower side (the side opposite to the toner surface), although not shown, the fourth heating substrate is also provided in contact with the periphery of the rotating roller 22. As in the case of the press roller 21, it is desirable that reliable fixing can be easily performed without rapidly decreasing the temperature of the recording medium 41. However, in the case of the rotating roller 22, the effect is small and not essential because it contacts the back surface of the recording medium 41. Further, when a flat plate is provided instead of the rotating roller 22, the heating substrate 10 described above may be provided instead of the flat plate. In this manner, the toner 42 that has been melted and pressed by the pressure conveying unit 3 is pressed and brought into contact with the toner 43, thereby forming a fixed toner 43.

  That is, when the transferred toner 42 is heated, it sticks, melts and fluidizes beyond the softening point, and when this is pressurized, it becomes difficult to enter between the fibers of the paper and peel off. At around 100 ° C., the surface of the toner 42 begins to unravel, and the toner and the paper start to adhere to each other, so that they do not move freely as particles. Eventually, the whole is melted and then pressed, and is flattened to penetrate into the paper and fix.

  The transfer unit 3 is an example of a photoconductor that passes through the cleaning unit 32, the charge removal unit 33, the charging unit 34, the exposure (light writing) unit 35, and the development unit 36 as in the case of a normal electrophotographic printer. While the photosensitive drum 31 is rotated, the exposure unit 35 performs optical writing using laser light or LED light to form an electrostatic latent image on the photosensitive drum 31, and the developing unit 36 applies toner 43 a to the photosensitive drum 31. Develop and make visible image. Then, the transfer tool 37 transfers the toner 42 a from the photosensitive drum 31 to the recording medium 41 by an electric force, whereby a photographic image is formed on the recording medium 41. The toner 42a is obtained by mixing various pigments with resin. The recording medium 41 is sequentially conveyed and passes through the heating unit 1 and the pressure conveying unit 2, whereby the transferred image of the toner 42 is fixed. In the case of color printing, a group from the transfer unit 3 to the heating unit 1 and the pressure conveying unit 2 is arranged in a tandem manner, and black (K), cyan (C), magenta (M), yellow (Y ) For color printing.

  The embodiment shown in FIG. 2 is different in that the second heating substrate 10 b is not provided in the heating unit 1 and the third heating substrate 10 c is provided exclusively for heating the pressure roller 21. In FIG. 2 and the next FIG. 3, the operation part of the photosensitive drum 31 is simplified and partially omitted, but has the same configuration as FIG. Thus, when the third heating substrate 10c is used exclusively for heating the pressure roller 21, it is not a heating substrate having a structure in which the above-described heat radiation layer is provided, but rather a protective film 17 with less heat radiation from the surface side. It is preferable to use a heating substrate 10 on which is formed. Furthermore, as shown in FIG. 2, it is preferable to bring the back surface of the insulating substrate 11 of the heating substrate 10 into contact with the pressure roller 21. Further, as described above, it is preferable to provide the rotating roller 22 with a structure in which the insulating substrate of the fourth heating substrate is pressed similarly to the pressure roller 21 side. As shown in FIG. 3 to be described later, the third heating substrate 10c is pressed so that the protective film 17 side is in contact with the pressure roller 21, so that the amount of heat generated is further transmitted to the pressure roller 21. Is preferable.

  In the embodiment shown in FIG. 3, the first heating substrate 10a is elongated or a fifth heating substrate 10e made of a similar heating substrate is provided side by side with the first heating substrate 10a. This portion is used as a cradle 23 for the pressure roller 21 instead of the rotating roller 22. That is, the recording medium 41 is pressed by the pressure roller 21 and the cradle 23 (the fifth heating substrate 10e). Even in this case, the recording medium 41 is conveyed on the toner surface to which the toner 42 of the recording medium 41 adheres by the rotation of the pressure roller 21. Therefore, the toner is not damaged, and the toner 42 can be reliably fixed by being heated from the back surface side of the recording medium 41 by the fifth heating substrate 10e. Further, as shown in FIG. 3, the third heating substrate 10 c has its protective film (cover substrate) 17 side pressed against the pressing roller 21, thereby efficiently transferring the heat amount of the third heating substrate 10 c to the pressing roller 21. can do. In this case, in order to reduce damage to the protective film 17 of the third heating substrate 10c, the cover substrate can be pressed against the pressure roller 21 as a cover substrate such as a thin ceramic substrate.

  Although not shown, it is preferable that the entire fixing device shown in FIGS. 1 to 3 is disposed obliquely so that the pressure conveyance unit 2 side is low (vertically below) and the transfer unit 3 side is high. This is to save energy by using as much as possible the amount of heat generated in the heating unit 1 and the pressure conveying unit 2 and emitted to the outside. That is, because heat escapes vertically upward, heat that is not absorbed by the heating unit 1 and the pressure conveying unit 2 of the toner 42 flows in the direction of the transfer unit 3 and is used as residual heat of the transferred toner 42. If the temperature of the toner 42 transferred in advance is increased by heating, the toner 42 can be melted by weak heating in the heating unit 1. Therefore, overall energy consumption can be reduced, and it can be a countermeasure against global warming. Note that it is preferable to cover the entire apparatus with a cover, since the amount of heat radiated can be used more effectively.

  As described above, if the temperature for heating the toner 42 is too low, the toner 42 cannot be melted and sufficient fixing cannot be performed. Further, even if it is too high, a part of the toner 42 adheres to the pressure contact roller 21 in the pressure conveying unit 2 and is not preferable. Therefore, it is necessary to accurately control the temperature of the heating substrate 10. FIG. 6 shows temperature control means (drive circuit) of the fixing device shown in FIG. That is, this drive circuit is an example of driving with a DC or AC power source 390. As the power source 390, a battery, a commercial power source, or a commercial power source 390 is adjusted with a transformer or the like to adjust the voltage and application time, thereby adjusting the applied power. Driving electric power is supplied to the electrode 14 (see FIG. 4A) connected to the heating resistor 12 via 370. As a result, the AC power supply can be used as it is, and the voltage supplied from the commercial AC power supply 390 is adjusted by the power adjustment unit 370 and adjusted to a desired temperature. For example, when power source 390 is AC, adjustment unit 370 uses AC power control means such as a triac or thyristor. As a result, no DC power supply is required, and no power supply cooling fan is required. However, a direct current power source using a battery can also be used. Although not shown, heating can also be performed by pulse driving in which a pulse is applied. In that case, the applied power can be adjusted by changing the duty cycle in addition to changing the voltage. Further, when a pulse is applied, the output can be changed by modulating the frequency (PFM). The temperature is determined by measuring the current supplied by the constant current circuit 350 with the current of the measurement power supply 310 kept constant and the voltage V across the temperature measurement resistor 24 using the temperature measurement resistor 13. Then, the resistance value of the temperature measuring resistor 13 at that time is known, and the temperature of the temperature measuring resistor 13, that is, the insulating substrate 11 (see FIG. 4A) is measured by the change in the resistance value. The adjustment unit 370 can adjust the applied voltage and the like. The adjustment unit 370 is particularly effective in making the temperature of each heating resistor 12 uniform or different when heating a plurality of heating resistors 12 side by side. Therefore, when a plurality of temperature measuring resistors 13 are provided, it is preferable that the temperature in the vicinity thereof is separately measured and the applied voltage and the like are adjusted by each heating resistor 12.

  The principle of this temperature measurement will be described with reference to FIG. For example, a constant current circuit CCR (current controlled regulator) 350 is connected in series with the temperature measurement resistor 13 at both ends of a measurement power supply 310 composed of a DC power supply, and the voltage V across the temperature measurement resistor 13 is measured. Then, by dividing the voltage by the constant current by the temperature detecting means 330, the resistance value of the temperature measuring resistor 13 at that time can be known, and the temperature measuring resistor 13 which is known in advance is known. The temperature can be calculated from the temperature coefficient (determined by the material). According to the detected temperature, the temperature of the insulating substrate 11 can be maintained at a predetermined temperature by controlling the power applied from the control unit 360 to both ends of the heating resistor 12 by the adjusting unit 37. As described above, the temperature control of the heating resistor 12 by the control means 360 may be performed by changing the duty cycle of the pulse by changing the applied voltage to a pulse or the voltage itself. In the example shown in FIG. 7, the constant current circuit 350 is provided. Instead, a reference resistor is provided in a place where the temperature does not change, and the voltage of the reference resistor is measured to obtain the current. The voltage at both ends of the temperature measuring resistor 13 may be measured. Further, the temperature measurement power supply 310 is not necessarily a DC power supply. A constant current can be obtained in a pulsed manner even with an alternating current.

DESCRIPTION OF SYMBOLS 1 Heating part 2 Pressurization conveyance part 3 Transfer part 10 Heating board 10a-10c 1st-3rd heating board 11 Insulating board 12 Heating resistor 13 Temperature measuring resistor 14 Electrode 15 Measuring terminal 16 Connection conductor 17 Protective film 18 Thermal radiation layer 19 Lead 21 Pressure roller 22 Rotating roller 31 Photosensitive drum 34 Charging unit 35 Exposure unit 36 Development unit 37 Transfer tool 41 Recording medium 42a Developed toner 42 Unfixed toner 43 Toner after fixing

Claims (9)

A transfer unit that develops the electrostatic latent image formed on the photoreceptor and transfers the toner adhered thereto to a recording medium;
A heating unit that is provided on the recording medium traveling direction side from the transfer unit and that heats the toner transferred by the transfer unit;
A pressure conveying unit that is provided closer to the recording medium in the advancing direction than the heating unit and conveys the recording medium while pressing a surface of the recording medium on which the toner is provided with a pressure roller;
Comprising
The heater of the heating unit heats the recording medium from the surface opposite to the surface to which the toner is transferred, and / or the recording medium is separated from the recording medium from the surface to which the toner is transferred. Formed by a second heating substrate provided,
The heating unit is heated until the toner transferred to the recording medium is melted, and the pressure conveying unit is pressed at a temperature at which the transferred toner is not melted ,
The first heating substrate is extended or a fifth heating substrate different from the first heating substrate is provided at a position facing the pressure contact roller of the pressure conveying unit across the recording medium, and the pressure contact is provided. the recording medium is Ru fixing device is pressed by the roller and the first heating substrate or the fifth heating substrate. The fixing device according to claim 1, wherein the first heating substrate is provided in contact with a surface of the recording medium opposite to a surface onto which the toner is transferred. The fixing device according to claim 1, wherein a third heating substrate is provided in contact with an upstream side of a contact portion of the pressure contact roller of the pressure conveying unit with the recording medium. First heating the substrate or the second heating substrate of claim 1, wherein the third heating substrate 請 Motomeko 3 wherein, or the fifth heating the substrate at least one,
An insulating substrate; a belt-like heating resistor formed on one surface of the insulating substrate for heating the insulating substrate; at least a pair of electrodes capable of passing a current in a longitudinal direction of the heating resistor; and the vicinity of the heating resistor A temperature measuring resistor formed on the insulating substrate along the heating resistor and at least a pair of measuring terminals for measuring an electrical resistance between the predetermined lengths of the temperature measuring resistor The fixing device according to claim 1, further comprising: The heating substrate according to claim 4, wherein the third heating substrate is provided so that a surface of the third heating substrate provided with the heating resistor is parallel to the recording medium, and the insulating substrate The fixing device according to claim 4, wherein the third heating substrate is shared with the second heating substrate by providing a side surface in contact with the pressure roller. The fixing device according to claim 4, wherein the second heating substrate has a heat radiation member formed on a surface side of the heating resistor. Transfer the toner matching the image to the recording medium by electrophotographic process,
While transporting the recording medium, the toner is heated away from the recording medium from the side to which the toner has been transferred and / or heated from the side opposite to the surface to which the toner has been transferred. West,
Extending the first heating substrate from the toner side of the recording medium at a temperature at which the toner has not melted to a position facing the recording medium with the pressing medium interposed therebetween, or A fixing method, wherein a fifth heating substrate separate from the first heating substrate is provided and pressed, and the recording medium is conveyed while being pressed . The fixing method according to claim 7 , wherein both the pressure contact and the heating are performed by raising the temperature of the pressure roller to a temperature at which the toner does not melt. A portion for transferring the toner, the higher the pressure roller in the vertical direction than the portion to pressurized transport, and method of fixing according to claim 7 or 8, wherein performing covers a portion of the pressure transferred from the transfer in the cover .

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