JP6203901B1 - Fixing apparatus and fixing method - Google Patents

Abstract

An object of the present invention is to provide a fixing device and a fixing method capable of preventing toner scattering by separating a heating portion and a pressure portion so that the toner can be heated immediately after the transfer of the toner. . An insulating substrate 5 is provided continuously over the whole of a heating unit 1 and a pressure conveying unit 2, and is a surface facing the recording medium 41 of the insulating substrate 5 and corresponds to a transfer unit 3. The transfer electrode 39 is provided in the part to be heated, the heating resistors 12a to 12c for heating are provided in the part corresponding to the heating part 1, and the pressure of the pressure roller 21 is applied to the part corresponding to the pressure conveying part 2. It is formed as a cradle 22 that can be received. As a result, the toner 42 is heated immediately after the toner 42 is transferred to the recording medium 41, and the fine powder is prevented from being scattered. [Selection] Figure 1A

Description

  The present invention relates to an image forming apparatus such as a copying machine, a laser printer, and an LED printer, and a fixing device that forms an image by transferring a resin-based toner that forms an image onto a recording medium such as paper and sticking it to the recording medium. The present invention relates to a fixing method. More specifically, in order to prevent the toner fine powder from scattering in the air, the unfixed toner image transferred to the recording medium is immediately softened and adhered to the recording medium, thereby preventing the toner fine powder from scattering. The present invention relates to a fixing device and a fixing method capable of fixing toner in a short time.

  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 member by charging, exposing, and developing on the 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 fluidized by heating with a heat and pressure roller, whereby stickiness is produced and the toner is adhered to the recording medium while being adhered. As a result, the toner does not move freely. In short, softening, fluidization, and sticking occur, and the image is fixed on the recording medium by being pressed in the sticking state.

  As a method for transferring toner from the photosensitive member to a recording medium, for example, a corona discharge method, a roller transfer method, and the like are known (for example, see Non-Patent Document 1). As shown in FIG. 5A, the corona discharge method is configured by providing a transfer charger 82 and a separation charger 83 that are arranged to face the photoconductor 81 with the recording medium 80 interposed therebetween. With this configuration, the charging unit 84 uniformly charges the entire surface of the photoconductor 81, and irradiates the photoconductor 81 charged with a print data pattern with a light source 85 such as a laser beam or an LED, so that an electric latent image (reverse image) is obtained. Invisible image) is formed on the surface of the photoreceptor 81. The developer unit 86 adheres the toner to the latent image formed on the surface of the photoconductor 81 while stirring, thereby forming a visible image on the surface of the photoconductor 81 (development process). Thereafter, the toner on the photosensitive member 81 is transferred onto the recording medium 80 by applying a charge having a polarity opposite to that of the toner to the back surface of the recording medium 80 by corona discharge of the transfer charger 82. The separation charger 83 is applied with a weaker electric field than the transfer charger 82 so that the recording medium 80 is not attracted to the photoreceptor 81 and wound around the photoreceptor 81. That is, the transfer unit is formed as a transfer device in which the photoconductor 81 and the separation charger 82 are independently paired. In the roller transfer method, as shown in FIG. 5B, a transfer roller 87 provided opposite to the photosensitive member 81 and the recording medium 80 is pressed against the photosensitive member 81 with an appropriate contact pressure, so that the recording medium 80 is pressed. The toner image is transferred to the recording medium 80 by being conveyed and by applying a charge having a polarity opposite to that of the toner to the back surface of the recording medium 80 via the transfer roller 87.

  On the other hand, the heating and pressing unit is not shown in the drawing, but presses the recording medium on which the toner is transferred, for example, with a heating and pressing roller heated by incorporating a halogen lamp inside and a rotating roller on the opposite side. A method of conveying is known. That is, heating and pressurization are performed simultaneously. As described above, the surface of the toner is hardly rubbed by conveying the recording medium onto which the toner has been transferred while rotating the heating and pressing roller and the rotating roller. However, since the toner is pressurized while being heated, it is pressed by the heat and pressure roller in a fluidized state. Moreover, since the toner is heated from the surface and is pressed by the pressure roller in a state where the toner is not sufficiently heated to the recording medium side, the fluidized toner tends to adhere to the surface of the heat and pressure roller. As a result, the toner may be partially removed from the surface of the recording medium. In addition, 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 to raise the temperature of the heating and pressing roller after the switch is turned on. In order to solve this problem, it is necessary to preheat. For this reason, the power consumption is further reduced, and the demand for energy saving cannot be sufficiently met.

  Furthermore, there has been proposed a method using a so-called ceramic heater in which a heating resistor is formed on the surface of a ceramic substrate without using a halogen lamp. However, in this method, in order to effectively use the heat of the ceramic heater, an attempt is made to heat and press the portion of the recording medium to which the toner is transferred on the heater surface side. Therefore, it is necessary to prevent the surface of the ceramic heater and the surface of the recording medium onto which the toner has been transferred from being rubbed. 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, Patent Document 1).

JP-A-5-273879

“Electrophotography”, edited by the Japan Imaging Society, published by the Tokyo Denki University Press, June 20, 2008, pp. 67-69

  As described above, when the transfer unit and the heating and pressing unit are formed separately and independently, after the toner is transferred by the transfer unit, the toner is transferred onto the recording medium until reaching the heating and pressing roller. The process proceeds only when the toner powder adheres with a weak electrostatic force. The toner powder is coated with an external additive. For this reason, there is a problem that the fine powder of the toner and the external additive is likely to be scattered before reaching the heating and pressing roller, and the dust is likely to cause pollution due to floating in the air.

  Further, if the heating unit and the pressure unit are simultaneously performed at the same place, the toner in the fluid state is pressed by the pressure roller, so that the toner is likely to adhere to the pressure roller, and the toner image is likely to be damaged. There's a problem.

  Furthermore, if heating and pressurization are performed simultaneously, heating and pressurization must be performed between the width (nip width) of the contact portion between the heating and pressurizing roller and the rotating roller. If the speed is increased, sufficient fixing cannot be performed, and printing speed is limited.

  Further, when heated from the surface side of the transferred toner, even if the toner surface side is in a fluid state, the fluidization on the contact surface side with the recording medium is delayed, and thus the adhesiveness to the recording medium is poor. It tends to be enough. Further, when the recording medium has a hygroscopic property such as paper, the temperature rise of the recording medium is the slowest, so that the moisture hardly evaporates, and the moisture evaporates after the toner is in a fluid state. As a result, there is a problem that concave portions called so-called blisters are formed on the surface of the toner, unevenness is easily formed on the surface of the toner, and the finished state of the printed surface becomes unclear.

  The present invention has been made to solve such problems, and prevents the scattering of the toner by separating the heating portion and the pressure portion so that the toner can be heated immediately after the transfer of the toner. It is an object of the present invention to provide a fixing device and a fixing method that can be used.

  Another object of the present invention is to provide a fixing device and a fixing method capable of fixing toner on a recording medium at a high speed without damaging the surface of the toner.

  Still another object of the present invention is to provide a fixing device and a fixing method capable of preventing a toner image from becoming unclear due to evaporation of water even when the recording medium is a hygroscopic recording medium such as paper. is there.

  Still another object of the present invention is to immediately heat the transferred toner to prevent the fine powder from scattering, and to allow the toner to adhere to the recording medium without being in a fluid state (melted state) in the pressure conveying section. Another object of the present invention is to provide a fixing device and a fixing method capable of lowering the toner temperature.

  The fixing device of the present invention includes 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 downstream side of the transfer unit of the recording medium. A heating section for heating the toner transferred by the printing section; and the recording medium provided on the downstream side of the heating section of the recording medium while pressing the surface of the recording medium on which the toner is provided with a pressure roller. A pressure conveyance unit that conveys the toner, and the transfer unit, the heating unit, and the pressure conveyance unit. A transfer electrode provided on a portion of the insulating substrate facing the recording medium and corresponding to the transfer portion, and heating a portion corresponding to the heating portion. And a heating resistor for Portion corresponding to the conveying unit is formed as a cradle capable of receiving the pressure of the pressure roller, the toner immediately after the toner has been transferred to the recording medium is formed so as to be heated.

  Here, “downstream side” means the front side of the recording medium in the traveling direction, that is, the discharge side in the case of a recording medium, and conversely “upstream side” means the supply side in the case of a recording medium. Means. Further, “continuously” means that the recording medium 41 may be connected by an adhesive or the like so that heat conduction is easily performed along the traveling direction of the recording medium 41 even if it is not completely integrated. is there. A structure in which a plurality of recording media are provided apart from each other in the direction perpendicular to the traveling direction of the recording medium may be employed.

  A plurality of heating resistors provided in the heating unit are provided in parallel along the traveling direction of the recording medium, and the temperature on the transfer unit side increases between the transfer unit side and the pressure conveying unit side. Thus, it is preferable that the heating resistor or the applied voltage is formed differently.

  The fixing method of the present invention is provided with a transfer unit that transfers toner matched to an image to one surface of the recording medium by an electrophotographic process, and from the other surface side opposite to the one surface of the recording medium while transporting the recording medium. A heating unit that heats the transferred toner, and a pressure conveying unit that conveys the recording medium while applying pressure to the pressure roller from the one surface side of the recording medium and a cradle on the other surface side. Providing an insulating substrate continuously over the transfer unit, the heating unit, and the pressure conveying unit so as to contact the surface opposite to the surface to which the toner is transferred of the recording medium, A transfer electrode for transferring at the transfer portion and a heating resistor for heating at the heating portion are provided on the surface of the insulating substrate, respectively, and a pedestal of the pressure conveying portion is extended from the insulating substrate. Characterized by forming in parts .

Before SL heating unit, provided a plurality of heating resistors along the direction of travel of the recording medium, the transfer portion side is high, the pressure conveying unit side by a temperature gradient to be lower in the heating unit It is preferable to perform heating.

  According to the fixing device and the fixing method of the present invention, the insulating substrate provided with the heating resistor on the surface is continuously formed from at least the transfer portion to the pressure conveying portion. Therefore, even in the transfer portion where the heat generating resistor is not provided on the insulating substrate, the temperature of the insulating substrate and thus the recording medium is slightly increased, and the toner is heated to some extent from the time of transfer. However, since it is better not to raise the temperature so much from the viewpoint of life, the heat sensitive body is designed so as to suppress the heat generation of the heating resistor provided upstream thereof and to suppress the temperature rise. Further, since the heating resistor can be formed in the vicinity of the transfer electrode, the toner is heated in earnest immediately after the transfer. As a result, it is possible to shorten the time until the toner is in a softened state or a fluidized state (melted state), and to reliably suppress toner scattering. In addition, since this insulating substrate is provided on the opposite side (back side) of the surface of the recording medium to which the toner is transferred, and a heating resistor is formed on the surface of the insulating substrate, it is heated from the back side of the recording medium. Will be. As a result, the toner is also softened from the recording medium side to be in a fluid state. That is, the adhesion between the recording medium and the toner becomes very good. Accordingly, when the pressure is applied by the pressure conveying unit, the toner is easily adhered to the recording medium even if the temperature is lowered and the surface of the toner is not in a fluid state.

  The softened state is a viscoelastic property of the toner, and means a state where the viscoelasticity is lower than that of the solid region in the temperature range of the rubber region and easily deforms when an external force is applied, but has elasticity. The term “toner” means a state in which the toner can flow in a liquid state. Of course, even in the rubber region, the higher the temperature, the lower the viscoelasticity and the closer to the fluid state. Even if the fluid state is the same, the fluidity increases as the temperature increases.

  Furthermore, since the heating unit is separated from the pressure unit, the pressure conveying unit does not need to be in a fluid state (melted state), and the temperature on the pressure roller side can be lowered. Even if pressed by the toner, the toner hardly adheres to the pressure roller. Therefore, the risk of damaging the toner image is reduced, and a clear toner image can be obtained. Further, in the conventional method in which heating and pressurization are performed simultaneously, the fluidization and press-contact of the toner are performed only at the contact portion (nip portion) between the heat and pressure roller and the rotating roller. Therefore, the passage time of the nip part is short, and fine adjustment is necessary for the temperature and pressure of the pressurization. Nevertheless, with the conventional apparatus of 40 sheets per minute, the passage time of the nip part 5 mm is 200 mm per second. It is about 25 ms. However, since the present invention separates the heating unit and the pressure unit and the pressure roller only needs to be pressed, the recording medium can be conveyed in a very short time, for example, about 10 ms. Double the speed up. That is, the printing speed can be greatly improved. In addition, regarding the fluidization of the toner by the heating unit, even if the recording medium is transported at a high speed, the printing speed can be improved by increasing the distance.

  Further, since the insulating substrate extends upstream from the transfer portion, the recording medium is preheated before transfer, and further, a heating resistor is also provided in the extension portion, so that the recording medium from before transfer is provided. When the toner is heated, the transferred toner tends to be softened immediately, and the water contained in the recording medium evaporates before transfer or even if it has not completely evaporated, Can be easily kicked out. Therefore, it is possible to prevent irregularities due to bubbles on the surface of the toner by increasing the temperature of the recording medium simultaneously with the heating for making the conventional toner flow. As a result, it can be fixed with a very glossy and clean image. However, as described above, from the viewpoint of suppressing the temperature rise of the heat sensitive body, it is preferable that the temperature of the recording medium does not increase so much before the transfer. Furthermore, since the temperature of the recording medium has risen to some extent at the time of transfer, the toner is likely to be softened simultaneously with the transfer, and the scattering of fine powder of toner and external additive can be further prevented. In particular, in the case of color printing, for example, a four-color toner image is often transferred in a belt-like manner and fixed at the end, and in such a case, toners of different colors are transferred in an overlapping manner. If the temperature of the medium is increased, it is easy to prevent the scattering and the deterioration of the image, which is very effective.

1 is an explanatory diagram of a cross section showing an outline of a fixing device according to an embodiment of the present invention. It is explanatory drawing which shows the outline of the surface of the insulated substrate of FIG. 1A. It is explanatory drawing which shows the modification of FIG. 1B. It is explanatory drawing which shows the ID-ID cross section of FIG. 1C. It is explanatory drawing which shows the example of formation of an electrode etc. when there is one heating resistor. It is explanatory drawing which shows the structural example of the cross section of FIG. 2A. It is explanatory drawing which shows other examples of formation, such as an electrode when there is one heating resistor. 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 figure which shows the other example of the drive circuit which controls the insulated substrate of a heating board | substrate to predetermined temperature. It is a figure explaining an example of the conventional transfer apparatus. It is a figure explaining the other example of the conventional transfer apparatus.

  Next, the fixing device and fixing method of the present invention will be described with reference to the drawings. 1A shows a schematic diagram of a fixing device according to an embodiment of the present invention, the fixing device of the present invention develops an electrostatic latent image formed on a photoreceptor 31 and records toner 42a attached thereto. A transfer unit 3 that transfers to the medium 41, a heating unit 1 that is provided downstream of the transfer unit 3 of the recording medium 41 and heats the toner 42 transferred by the transfer unit 3, and a downstream of the heating unit 1 of the recording medium 41. A pressure conveying unit 2 that conveys the recording medium 41 while pressing the surface of the recording medium 41 on which the toner 42 is provided by the pressure roller 21, and a surface to which the toner 42 of the recording medium 41 is transferred. And an insulating substrate 5 that is continuously provided over the whole of the transfer unit 3, the heating unit 1, and the pressure conveyance unit 2. A transfer electrode 39 is provided on the surface of the insulating substrate 5 facing the recording medium 41 and corresponding to the transfer portion 3, and the heating resistor 12 (12 a) is provided on the portion corresponding to the heating portion 1. 12b, 12c, 12d), and a portion corresponding to the pressure conveying unit 2 is formed as a pedestal 22 capable of receiving the pressure of the pressure roller 21.

  That is, according to the present invention, the heating unit 1 and the pressure conveyance unit 2 are separated, heating is performed by the heating unit 1, and pressure is applied by the pressure conveyance unit 2, and the transfer unit 3 is separated from the conventional photoreceptor. Rather than being independent as a transfer device having a charger or a transfer roller, an insulating substrate 5 on which a heating resistor heated by the heating unit 1 is formed (this portion can also be referred to as a heating substrate) continues to the transfer unit 3. The transfer portion 3 is formed by providing the transfer electrode 39 on the surface of the insulating substrate 5. Then, the toner 42 a developed on the photoconductor 31 by the high electric field applied to the transfer electrode 39 is attracted to the recording medium 41 side and transferred to the recording medium 41. In other words, the transfer device is not provided independently, but the transfer electrode 39 is formed on the surface of the extended portion of the insulating substrate 5 as the heating substrate. The insulating substrate 5 is formed separately with a portion to be a heating substrate of the heating unit 1, a portion to be a pedestal for the pressure conveying unit 2, and a portion where the transfer electrode 39 of the transfer unit 3 is formed. Even if it is, it is only necessary to be connected so that heat conduction is possible.

  In other words, the insulating substrate 5 of the heating substrate used for heating the heating unit 1 is extended to the transfer unit 3, and the transfer electrode 39 is formed on the surface of the insulating substrate 5. Then, the other end portion of the insulating substrate 5 is continuously formed (including the case where it is connected) to the pressure conveying unit 2, and is used as the receiving unit 22 of the pressure roller 21. Since the insulating substrate 5 is continuously formed from the heating unit 1 to both the transfer unit 3 and the pressure conveying unit 2, the heat generated by the heating unit 1 is transferred through the insulating substrate 5. The recording medium 41 on the transfer electrode 39 and the recording medium 42 on the receiving part 22 of the pressure conveying unit 2 are also heated. As a result, the transferred toner 42 is immediately preheated for heating, and the pressurizing and conveying unit 2 pressurizes and records without rapidly decreasing the temperature of the heated toner 42. The medium 42 can be adhered. That is, it is heated before being heated by the heating unit 1, and even if it does not reach the softened state before the heating unit 1, it is sufficiently preheated and is heated by the heating unit 1. As a result, a softened state or a fluidized state is immediately obtained. Further, in the pressure conveying unit 2, the toner 42 is pressed in a softened state without suddenly lowering the temperature, and a part of the toner 42 does not adhere to the pressure roller 21 or the like, that is, the toner 42 is damaged. Without sticking to the recording medium 42.

  Thus, the insulating substrate 5 needs to be formed continuously from the heating unit 1. “Consecutively” does not necessarily have to be integrated as described above, and is formed separately by the heating unit 1, the transfer unit 3, and the pressure conveying unit 2, and then connected by an adhesive or the like. Or may be in close contact. In other words, it is only necessary that they are connected so that sufficient heat conduction is obtained. The insulating substrate 5 does not need to be entirely made of an insulator, and at least the surface on which the heating resistor 12 and the transfer electrode 39 are provided needs to be an insulator. Accordingly, an insulating film may be formed on the surface of the metal plate. With such a configuration, the insulating substrate 5 is excellent in heat conduction.

  However, the insulating substrate 5 may be used as an insulating substrate for the heating substrate used in the heating unit 1. That is, for example, an insulating substrate having excellent thermal conductivity made of alumina or the like can be used. However, it is not limited to this. The shape is preferably rectangular, but is not limited thereto. The width W (see FIG. 1B; the length in the direction perpendicular to the paper surface of FIG. 1A) is preferably equal to the width of the recording medium 41. However, even if it is smaller, the plurality of insulating substrates 5 are in the width W direction. There is no problem by being arranged. The length L of the insulating substrate 5 (see FIG. 1B; the length in the direction of travel of the recording medium in FIG. 1A) is, for example, about 5 cm. In the figure, the size relationship between the dimension of the width W and the dimension of the length L is reversed, but the change in the width direction is constant while the change in the surface in the length direction is emphasized. Therefore, the direction of the length L is enlarged. For example, an alumina substrate having a thickness of about 0.6 mm can be used. The insulating substrate 5 is formed so as to extend from the heating unit 1 to the transfer unit 3 and the pressure conveying unit 2, and is provided on the back side of the recording medium 41. However, as described above, it is not necessary to be completely integrated. For example, the heating unit 1, the transfer unit 3, and the pressure conveying unit 2 may be separately formed and connected to each other with an adhesive or the like. In short, it should be continuous and have sufficient heat conduction.

  As will be described later, a heating resistor 12 and the like are formed on the surface of the insulating substrate 5, and a protective film 17 such as a cover substrate is formed on the surface. A suction through hole 19a and a suction groove 19b are formed in the insulating substrate 5 and the protective film 17 on the surface thereof, and the recording medium 42 is sucked, whereby the contact pressure at the convex portion is increased, and the heating resistance is further increased. Heat conduction from the body 12 can be improved. For example, as shown in FIG. 1D, which will be described later, the unevenness (not shown) is formed by the height of the portion of the heating resistor of about 0.2 mm to 0.3 mm per 50 mm length (L) of the insulating substrate 5. It is formed in a swell (a bowl shape). As a method for forming such irregularities, the surface of the insulating substrate 5 itself is formed in a bowl-shaped arc, or is formed by connecting a plurality of bowl-shaped substrates with a substrate having a short length L, or insulating. When forming a glaze layer (heat insulating layer) (not shown) before forming the heating resistor 12 on the substrate 5, the central portion is thickened, or the thickness of the heating resistor 12 and the surface of the protective film 17 are raised. Can be formed. Further, as an adsorption method, an electrostatic chuck method in which an electrode is formed and charged and adsorbed can be used instead of the suction method. In any case, it is preferable that irregularities for raising the portion of the heating resistor 12 are formed.

  In the transfer unit 3, a transfer electrode 39 is formed on the surface of the insulating substrate 5. The transfer electrode 39 is made of, for example, a stainless alloy bonded with an elastic adhesive, and is a component having a thickness of about 30 to 50 μm and a smooth finish on the surface and corners of a metal film having a width of about 8 mm. A voltage opposite to that of the charged toner 42 a, for example, a voltage of about 500 to 1000 V, is applied via an electrode (not shown), and the recording medium 41 is charged to transfer the charged toner 42 a from the surface of the photoreceptor 31. . If the potential of the transfer electrode 39 is too high, the transferred toner 42 is charged to the opposite potential, and is attracted to the potential of the photoconductor 31 when leaving the transfer portion 3, and the recording medium 41 is A4, B5, or the like. If the cut paper is not continuous paper, the recording medium 41 is wound around the photosensitive member 31, so that the recording medium 41 cannot be wound around the photosensitive member while the toner 42 is pulled away from the photosensitive member 31. It is necessary to set the potential. The transfer electrode 39 can be fixed to the surface of the insulating substrate 5 by extending the width of the transfer electrode 39 to the upstream side of the transfer portion 3 or by connecting it. In the case where a fifth heating resistor 12e described later is provided, it can be provided on the surface via an insulating layer.

  In the present invention, the substrate on which the transfer electrode 39 of the transfer unit 3 is formed extends the insulating substrate 5 on which the heating resistor 12 of the heating unit 1 is formed or is connected to the insulating substrate of the heating unit 1. Is formed. For this reason, the temperature of the insulating substrate 5 also rises in the transfer unit 3 and the recording medium 41 is also heated. As a result, since the transferred toner 41 is immediately heated, the toner 42 is easily attached to the recording medium 41, and scattering of fine powder of the toner 42, image deterioration, and winding around the photoreceptor 31 are suppressed, and the toner 42 is reduced to the softened or fluidized state. The transfer electrodes 39 of the transfer unit 3 may be formed in two as shown in FIG. 1C described later. In this case, if the voltage is changed between the two, the downstream electrode 29b can be used as a winding prevention for the recording medium 41 around the photosensitive member 31, that is, as a separate charge electrode. It is preferable that an elastic body is provided on the surface. Alternatively, the upstream end of the insulating substrate 5 can be lifted with a spring so that it can be rotated about the pressurizing and conveying unit 2 as a fulcrum, so that the photosensitive member 31 can be lightly contacted. The structure of the transfer unit 3 on the photoconductor 31 side is as described above.

  The structure of the transfer unit 3 on the photoconductor 31 side is the same as that of a normal electrophotographic printer, but includes a cleaning unit 32, a charge eliminating unit 33, a charging unit 34, an exposure (optical writing) unit 35, and a developing unit 36. While the photosensitive drum 31 as an example of the photosensitive member is rotated so as to pass, the exposure unit 35 performs optical writing using a laser beam or LED light to form an electrostatic latent image on the photosensitive drum 31, and a developing unit At 36, the toner 43a is adhered to the photosensitive drum 31 and developed to form a visible image. Then, the toner 42 a is transferred from the photosensitive drum 31 to the recording medium 41 by electric force at the transfer electrode 39, 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, black (K), cyan (C), magenta (M), and yellow (Y) color toners 42 are sequentially transferred to transfer a plurality of color toners. The process is long, and there is a possibility of scattering and image deterioration.

  As shown in FIGS. 1A to 1B, the heating unit 1 of the present invention is formed by providing a heating resistor 12 on the surface of the insulating substrate 5 facing the recording medium 41. That is, the heating resistor 12 is formed so as to be heated from the back side of the recording medium 41. However, the heating is not limited to the case where the recording medium 41 is heated from the back surface side, and although not shown, heating from the surface (front surface) side to which the toner 42 of the recording medium 41 is transferred can be used in combination. In this case, the recording medium 41 is provided a few millimeters away from the surface to which the toner 42 is transferred. However, the heating unit 1 heats the recording medium 41 by the heating resistor 12 formed on the surface of the insulating substrate 5. In the example shown in FIGS. 1A to 1B, the first to third heating resistors 12 a to 12 c are formed in the heating unit 1, and the fourth heating resistor 12 d is disposed upstream of the transfer unit 3 in the pressure conveyance unit 2. A fifth heating resistor 12e is provided on the side. However, the number of the heating resistors 12 (in the case of description as a common heating resistor, 12 is assigned) is not limited. In the vicinity of the heating resistor 12, a temperature measuring resistor 13 for confirming how much the temperature of the insulating substrate 5 has been raised by the heating resistor 12 is provided. Since the heating unit 1 of the present invention can be heated for a longer time than the conventional heating substrate, the current during temperature control can be reduced, and the influence of noise should be less than that of the conventional heating substrate. Can do. However, when a commercial AC power supply is used, the influence of noise on an external circuit such as a zero cross switch circuit can be reduced.

  The heating substrate provided on the surface side (toner 42 side) of the recording medium 41 is provided apart from the recording medium 41 on the surface side where the toner 42 of the recording medium 41 of the heating unit 1 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 (not shown) is not heated in contact with the recording medium 41, but is heated by radiant heat (radiant heat) from the second heating substrate. Accordingly, the surface of the recording medium 41 to which the toner 42 is transferred is not rubbed by the second heating substrate, and a part of the unfixed toner 42 is not peeled off. From this viewpoint, the second heating substrate preferably has a structure that easily radiates heat from its surface. For example, a heat radiation layer such as a material excellent in heat radiation such as black alumite or glass is formed on the surface, or irregularities with a width of about 10 to 50 μm and a depth of about 10 to 50 μm are formed on the surface. It is preferable that the structure has a large surface area and can easily increase the amount of heat radiation.

  In the example shown in FIG. 1B, an electrode connected to the heating resistor 12 or the like is omitted and not shown, but the relationship between the electrode and the heating resistor 12 or the temperature measurement resistor 13 is one. An example in which the heating resistor is formed as the heating substrate 10 formed on the insulating substrate 11 will be described later with reference to FIGS. The insulating substrate 5 may be a larger one of the insulating substrate 11 of the heating substrate 10.

  1C to 1D show another example of the shape of the surface of the insulating substrate 5 and an example in which the surface of the insulating substrate 5 is formed in a bowl shape. That is, the width and number of the heating resistors 12 and the number and location of the suction through holes 19a and the suction grooves 19b for the suction device can be freely set. Further, in this example, two transfer electrodes 39 are formed, and the downstream electrode 39b is formed as a separate charge electrode, so that the recording medium 41 is prevented from being wound around the photoreceptor 31. Further, in this example, as described above, a convex portion having a height of about 0.2 to 0.3 mm is formed with respect to a length of about 50 mm in the vicinity of the center portion, and is formed in a bowl shape. (See FIG. 1D). By adopting such a shape, the adhesion between the recording medium 41 and the heating resistor is improved. This idea may be a structure in which each substrate is formed in a bowl shape and the projections and depressions are repeated even when a plurality of insulating substrates 5 are not formed but connected. By forming the through-hole 19a for suction of the suction device in the recessed portion, the adhesiveness with the recording medium 41 is further improved, but by forming irregularities without the suction device, Adhesion is improved. In addition, the bowl shape is not limited to the insulating substrate 5, and a heating substrate 10 described later may be formed in such a bowl shape, and a plurality of them may be arranged. 1C to 1D, the same parts as those in FIG. 1B are denoted by the same reference numerals, and the description thereof is omitted.

  The heating substrate 10 has the same structure as a conventional heating head used for recording or erasing a card or the like. For example, FIG. 2A is a plan view illustrating an example of the heating resistor 12, the temperature measuring resistor 13, and the electrodes 14 to 16 on the basic insulating substrate 11 from which the protective film (cover substrate) 17 is removed. FIG. 2A is a cross-sectional view taken along the line BB in FIG. 2A and shows a state where 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 (not shown) is connected to the electrode 14 and the measurement terminal 15.

  More specifically, as shown in FIG. 2A, 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. (In this example, two temperature measuring resistors 13 are formed for one heating resistor 12, but the larger the number, the more accurately the temperature of the insulating substrate 11 can be grasped. But the number is not limited). In addition, these shapes, arrangement | positioning, etc. can be formed arbitrarily. In the example shown in FIG. 2A, 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 (width) W in the longitudinal direction of the insulating substrate 11 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 width W of the insulating substrate 11 is increased, or a plurality of heating substrates 10 are arranged in the longitudinal direction so as to be matched to the width of the recording medium 41. Further, when a single heating substrate is formed by the long insulating substrate 11, a plurality of electrodes 14 and measurement terminals 15 are formed in the middle of the heating resistor 12 and the temperature measurement resistor 13, and divided. Thus, the voltage can be applied, or the temperature can be determined 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. 2A, two temperature measurement resistors 13a and 13b are formed, but the structure is not limited to this. If the temperature of the insulating substrate 11 is too low, the toner 42 transferred onto the recording medium 41 will not be softened or flowed, and will not be sufficiently fixed. If it is too high, the toner 42 will flow too much. Then, the toner adheres to the pressure roller 21 and a toner offset phenomenon occurs. Therefore, 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.

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. 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 effective applied power. In the case of the fixing device, a commercial AC power source is often used as the power source for the heating resistor 12, and there are cases where the AC power source is used as it is, for example, half-wave rectification and full-parity rectification without DC conversion. Many. In this case, the effective value is controlled with the pulsating flow. However, a bidirectional thyristor (trade name Triac) is used for the control, and is controlled by an effective value. The temperature measurement is also performed with the effective value, and the temperature is controlled with a triac. 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. The electrode 14 has a structure in which a lead (not shown) 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. In FIG. 2A, a wide heating resistor 12 having a width of about 4 mm is formed by one. However, the width and 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. 2A, for example. In the example shown in FIG. 2A, 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 insulating substrate 11 that heats the recording medium 41, is known, and the temperature is set to the softened or fluidized state. 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. 3A, 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. 2A, only the outer peripheral portion is shown by a two-dot chain line, but as shown in the sectional view of FIG. 2B, 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 hard glass film having a smooth surface. However, the portion of the receiving portion 22 where the surface opposite to the insulating substrate 11 as shown in FIG. 1A, which will be described later, is pressed by the pressure roller 21 or the like is formed on the insulating substrate 11 so that it can withstand the pressure. A cover substrate 17a (see FIG. 1A) made of a thin ceramic plate having a thickness of about half may be bonded by a glass material 17b or the like. Durability is improved. The protective film 17 is also included in this case. However, even if such a cover substrate 17a is not provided or there is no wear-resistant layer, the surface of the insulating substrate 5 may be maintained. It is preferable that the surface is glass-coated. The protective film 17 is formed of a glass material or the like, and on the surface thereof, unevenness (a ridge-like bulge or curved shape) of 0.2 mm or more is formed along the traveling direction of the recording medium 41. Is preferable because the contact pressure between the insulating substrate 5 and the recording medium 41 can be increased. In particular, when the upper side of the heating resistor 12 is convex, a portion having a high temperature can easily come into contact with the recording medium 41. The electrode 14 and the measurement terminal 15 are not covered with the protective film 17 and are exposed, and leads (not shown) are connected. From the viewpoint of power saving, although not shown, it is preferable to insert a heat insulating layer having a low thermal conductivity such as a glaze layer between the heating resistor 12 and the insulating substrate 11.

  In the example shown in FIG. 2A, the electrodes and the measurement terminals are provided at the respective end portions. However, it is also possible to consolidate the electrodes and the measurement terminals on the narrower side edge by using one of them. An example is shown in FIG. 2C. That is, in the example shown in FIG. 2C, the heating resistor 12 and the temperature measuring resistor 13 are formed in parallel one by one, and the common conductor 18 is further formed. The common conductor 18 is formed to be connected to the other end portion of the heating resistor 12 and the other end portion of the temperature measuring resistor 13, and an electrode 14 whose one end portion is connected to one end portion of the heating resistor, And a measuring terminal 15 connected to one end of the temperature measuring resistor 13. The other structure is the same as that of FIG. 2A, and the same parts are denoted by the same reference numerals and description thereof is omitted.

  In the heating unit 1 shown in FIGS. 1A to 1B, the heating resistors 12 a to 12 c are formed on an insulating substrate 5. The number of the heating resistors 12 is not limited to this, and may be larger or smaller. In addition, the heating resistors 12 may not have the same heat generation amount, and the heating resistors 12 may be formed so that the temperatures thereof are different, or the voltage applied to the heating resistors 12 may be adjusted. As described above, it is preferable to heat immediately after transfer to a softened state or a fluidized state. From this point of view, the temperature of the first heating resistor 12a on the side close to the transfer unit 3 is likely to rise, and the temperature on the side of the third heating resistor 12c on the pressure conveying unit 2 side is lowered. Is preferred. However, the temperature setting is not limited to this example.

  In the heating unit 1, the toner 42 is heated until it becomes softened or fluidized. The toner is configured by mixing various components. For example, the main component is an acrylic-styrene copolymer, but the mixing ratio can be set variously. Besides, plastics, pigments, dyes, plasticizers (hardness control), waxes (softening state, onset of fluidized state) Etc.) are mixed. Further, external additives (small particles made of titanium oxide, silica, etc. of 1 μm or less that adhere to the outside of the toner particles so that the toner particles do not adhere to each other) are also mixed. For this reason, it is difficult to show the properties of the toner in general, but it is generally known that when the temperature is raised, the viscoelasticity is lowered. For example, PET, which is an example of plastic used as a toner, has a glass transition point of about 68 to 80 ° C., and an acrylic-styrene copolymer has a glass transition point of about 105 ° C., which changes from a solid region to a rubber region and softens. It becomes a state. At this glass transition point, the temperature changes from the solid region to the rubber region, but since the viscoelasticity does not drop so rapidly from the solid region, it is not sufficient to be immersed in a recording medium such as paper. Actually, it is sufficiently softened at a temperature about 20 to 50 ° C. higher than this temperature (glass transition point). Furthermore, when the temperature is raised, the viscoelasticity becomes a fluid state (melted state) in which the viscosity rapidly decreases (about 212 to 265 ° C. with the aforementioned PET, about 200 ° C. with the acrylic-styrene copolymer). However, the absolute values of these temperatures are not constant depending on the composition.

  In the case of color printing, it is necessary to sufficiently mix toners of different colors. For this reason, there are cases where it is not possible to obtain a beautiful printed matter with a normal toner particle size simply by being softened. However, when the temperature reaches a fluidized state, the toners are sufficiently mixed, and it is easy to obtain clean printing even in color printing. However, even in the case of color printing, there is no need to be in a fluid state, and there is no problem if the toner particles are small. Further, even in the case of monochrome printing, it can be performed in this flow state. Therefore, the heating unit 1 is heated until it becomes a softened state or a fluidized state depending on the type of printing.

  In the example shown in FIGS. 1A to 1C, a through hole 19 a and a narrow groove 19 b are formed in the insulating substrate 5. The through-hole 19a is connected to a suction tool (not shown) that sucks from the back surface (the surface opposite to the recording medium 41) of the insulating substrate 5. Further, there may be no through hole, and both ends of the groove 19b may be extended to both ends of the insulating substrate 5 so as to be connected to a suction tool (not shown). By forming the suction device by the through hole 19a and / or the narrow groove 19b and the suction tool, the recording medium 41 on the surface is sucked, and the surface of the insulating substrate 5 and the recording medium 41 are in good contact with each other. The heat generated by the heating resistor 12 formed on the surface of the insulating substrate 5 is easily transferred efficiently to the recording medium 41. In this case, the contact pressure between the convex portion and the recording medium 41 is higher when the surface of the insulating substrate 5 is somewhat ridge-shaped uneven (curved portion) along the transport direction than when the surface is flat. The heat conduction is further improved. In this case, since the portion where the heating resistor 12 is formed is a convex portion, the heat conduction is further improved. Note that this suction device performs suction so as to be in a decompressed state, and does not perform suction that is strong enough to hinder the conveyance of the recording medium 41.

  The size of the through hole 19a is about 0.3 to 0.5 mm, the width of the groove 19b is about 0.3 to 0.5 mm, and the depth of the groove 19b is about 0.2 to 0.3 mm. It is. As the suction tool, a small blower, a small source pressure pump (a semiconductor wafer vacuum chuck), or the like can be used. The sucked heated air may be reused in the preheating part (preheating of the recording medium before and after transfer). Although not shown, it is preferable from the viewpoint of heat insulation and prevention of scattering of the powder of the toner 42 that a cover is formed on the surface side of the heating 1 with an interval of about 1 to 3 mm.

  In the pressurizing and conveying unit 2, the pressure of the toner that is softened and easily penetrates between fibers such as paper or the temperature of the toner that is in a fluidized state is decreased while being pressed to adhere to the recording medium 41. There is a special feature. Further, the insulating substrate 5 extends and a receiving part 22 is formed at a part of the pressure conveying part 2 facing the pressure roller 21. In the pressure conveying unit 2, the recording medium 41 is conveyed while being pressed by the receiving unit 22 of the insulating substrate 5 and the pressure roller 21. From this viewpoint, it is preferable that the outer peripheral surface of the pressure roller 21 has some elasticity. The pressurizing and conveying unit 2 is heated by heat conducted through the insulating substrate 5. In the pressure conveying unit 2, the toner 42 is not brought into a fluidized state (melted state). However, when the toner 42 in the fluidized state in the heating unit 1 is rapidly cooled, the recording medium can be sufficiently used even if the toner 42 is pressurized. Since it is necessary to maintain a certain degree of softening state, it is preferable to be heated to some extent. If necessary, the fourth heating resistor 12d may also be formed in the receiving portion 22. Even in that case, it is not necessary to raise the temperature as much as the heat generating resistors 12a to 12c in the heating unit 1, and therefore the temperature is adjusted to be lower by the fourth heat generating resistor 12d or an applied voltage. As a result of such a structure, not only can the amount of heat generated in the heating unit 1 be used effectively from the transfer unit 3 to the pressure conveyance unit 2, but the toner 42 is heated simultaneously with the transfer, The scattering of fine powder such as toner 42 is prevented.

  Furthermore, the conveyance speed of the recording medium 41 can be increased, and the number of processed sheets per minute can be increased. That is, since the pressure contact by the pressure roller 21 only needs to be pressed, it can be passed in a very short time, and the traveling speed of the recording medium 42 is not limited. Further, since heating is performed from the back side of the recording medium, the adhesion between the toner 42 and the recording medium 41 is greatly improved, moisture contained in the recording medium is easily evaporated, and the printing surface of the toner image is very clear. A beautiful printed image can be obtained.

  In the pressurizing and conveying unit 2, the fourth heating resistor 12d is not formed on the insulating substrate 5, or another heating substrate is brought into contact with the peripheral surface of the pressure roller 21 together with the fourth heating resistor 12d. It can also be heated. Therefore, the temperature of the pressure roller 21 of the pressure conveying unit 2 is set to a temperature equal to or lower than the temperature of the softened state or the flow state in the heating unit 1 and is lower than the flow state. In other words, pressure is applied at a temperature lower than the temperature heated by the heating unit 1. Therefore, when the temperature of the pressure roller 21 is excessively increased due to heat from the toner 42 in a softened or fluidized state due to continuous printing, cooling (air cooling) may be performed without heating. .

  Although not shown in the drawing, the wear-resistant layer made of smooth hard glass or the like is preferably formed on the surface of the protective film 17. That is, unlike the rotating roller, the receiving portion 22 facing the pressure roller 21 described above conveys the recording medium 41 pressed by the pressure roller 21 while being repelled, so that the recording medium 41 and the receiving portion 22 do not slide. Will move. Therefore, it is preferable that a wear-resistant layer that is smooth and not easily worn is formed so that the recording medium 41 moves smoothly and the surface of the insulating substrate 5 is not consumed. The receiving portion 22 may be a metal layer or an insulating layer without an abrasion resistant layer.

  In the example shown in FIG. 1, a fifth heating resistor 12 e is provided upstream from the transfer unit 3. The fifth heating resistor 12e immediately heats the thin recording medium 41 from the back side. As a result, when the recording medium 41 is paper or the like, it easily absorbs moisture, and even if it contains moisture, it is easy to dry before the toner 42 is transferred. It is easy to prevent the problem of unevenness on the surface. In FIG. 1, reference numeral 55 denotes a feeding roller for the recording medium 41. Even when the fifth heating resistor 12e is provided, as described above, the temperature generated by the fifth heating resistor 12e is set low so as not to raise the temperature of the photoconductor 31 so much.

  From the viewpoint of heating the recording medium 41 to evaporate water and effectively heating each heating unit, for example, heating to heat the fifth heating resistor 12e and the toner 42 is not shown. The sheet stacking unit (not shown) for stacking the unit 1, the pressure conveying unit 2, and the discharged recording medium 41 is integrated in a minimum space through the back side of the recording medium 41 of the transfer unit 3. An enclosing cover case (not shown) is formed, and it is preferable that the conveyance path of the recording medium 41 is inclined so that the transfer unit 3 side is higher than the pressure conveyance unit 2.

  The inclination of the fixing device is preferably as the angle with respect to the horizontal plane is larger from the viewpoint of effective use of heat. However, since the transferred toner 42 is only attached to the surface of the recording medium 41 such as paper, there is a possibility that the toner 42 is displaced if it is tilted too much. This also has the same danger when heated to the fluidized state in the heating unit 1. From that viewpoint, the smaller the inclination, the better. Considering the relationship between the two, 20 ° to 60 °, more preferably about 30 ° to 45 ° is preferable. By being surrounded and inclined by the cover case 7 in this manner, the recording medium 41 is dried even by weak heating by the recording medium heating unit 5 or the like, and the toner 42 is put into a softened state or a fluidized state in the heating unit 1. Can be heated. Therefore, overall energy consumption can be reduced, and it can be a countermeasure against global warming.

  As described above, if the temperature for heating the toner 42 is too low, the toner 42 cannot be softened or fluidized, and sufficient fixing cannot be performed. Even if it is too high, a part of the toner 42 adheres to the pressure roller 21 in the pressure conveying unit 2 and is not preferable. Therefore, it is necessary to accurately control the temperature of the insulating substrate 5. FIG. 3 shows a temperature control means (drive circuit) of the fixing device shown in FIG. In other words, this drive circuit is an example of driving with a DC or AC power source 390. As the power source 390, the battery or the commercial power source 390 is pulse-driven, the voltage and application time are adjusted by a transformer, etc., and the applied power is adjusted. The driving power is supplied to the electrode 14 (see FIG. 2A) connected to the heating resistor 12 via the adjusting unit 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. By using a commercial power supply, a DC power supply is unnecessary and a power supply cooling fan is also unnecessary. 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 controlling the phase (PDM).

  The temperature is determined by measuring the current supplied by the constant current circuit 350 with the current of the measurement power source 310 kept constant by using the temperature measurement resistor 13 and the voltage V across 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. 2A) 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. Although an example of a DC power supply is shown here, temperature detection can be performed by effective value control even in AC.

  The principle of temperature measurement will be described in a little more detail. 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 the measurement power supply 310 formed of a DC power supply, and the voltage V across the temperature measurement resistor 13 is set to V If measured by the detector 340, the temperature detection means 330 divides the voltage by a constant current, whereby the resistance value of the temperature measuring resistor 13 at that time can be known, and the temperature is known in advance. The temperature can be calculated from the temperature coefficient of the measurement resistor 13 (determined by the material). In the case of alternating current, half-wave rectification is performed internally and triggered. 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 370. 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. 3, 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 across the measurement resistor 13 may be measured by the V detector 340. 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 5 Insulating board 10 Heating board 11 Insulating board 12 Heating resistor 12a-12e 1st heating resistor-5th heating resistor 13 Temperature measuring resistor 14 Electrode 15 Measurement terminal 16 Connecting conductor 17 Protective film 17a Sub-board 17b Glass material 19a Through hole 19b Groove 21 Pressure roller 22 Receiving part 31 Photosensitive drum 34 Charging part 35 Exposure part 36 Developing part 39 Transfer electrode 41 Recording medium 42a Developed toner 42 Unfixed Toner 43 Toner after fixing

Claims (13)

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 provided on the downstream side of the transfer unit of the recording medium and heating the toner transferred by the transfer unit;
A pressure conveying unit that is provided on the downstream side of the heating unit of the recording medium and conveys the recording medium while applying pressure to a surface side of the recording medium on which the toner is provided by a pressure roller;
An insulating substrate continuously provided so as to be in contact with a surface opposite to a surface to which the toner is transferred of the recording medium, over the entire transfer unit, the heating unit, and the pressure conveying unit;
A transfer electrode is provided on a surface of the insulating substrate facing the recording medium, corresponding to the transfer portion, and a heating heating resistor is provided on a portion corresponding to the heating portion. The portion corresponding to the pressure conveying portion is formed as a cradle that can receive the pressure of the pressure roller, and is formed so that the toner is heated immediately after the toner is transferred to the recording medium. A fixing device. 2. The heating substrate according to claim 1, wherein the insulating substrate extends upstream from the transfer portion, and a heating resistor that heats the recording medium is provided on a surface of the extending portion facing the recording medium. Fixing device. The fixing device according to claim 1, wherein the transfer electrode is formed of two, and the downstream electrode is used for separation charge. The fixing device according to claim 1, wherein a plurality of heating resistors provided in the heating unit are provided in parallel along a traveling direction of the recording medium. The fixing device according to claim 1, wherein a portion of the insulating substrate where the heating resistor is formed is formed in a convex shape. 2. The insulating substrate is formed by continuously forming a plurality of insulating substrates, and at least two of the plurality of insulating substrates are formed in a bowl shape with a cross-sectional shape along the traveling direction of the recording medium. The fixing device according to claim 5. The fixing device according to claim 1, wherein a wear-resistant layer and / or a heating resistor is formed on a portion of the insulating substrate corresponding to the pressure conveyance unit. The uneven part is formed in the advancing direction of the recording medium on the surface on the insulating substrate in the heating part, and the surface of the portion of the heating resistor is formed in a convex part. The fixing device according to Item 1. 9. The suction substrate according to claim 1, wherein a suction through hole or a suction groove is formed in communication with the insulating substrate and the surface thereof, and the recording medium can be sucked toward the insulating substrate. The fixing device according to 1. A transfer unit is provided for transferring the toner matched to the image by the electrophotographic process to one side of the recording medium,
A heating unit for heating the transferred toner from the other side opposite to the one side of the recording medium while conveying the recording medium;
A pressure conveying unit configured to convey the recording medium while applying pressure by the pressure roller from the one surface side of the recording medium and the cradle on the other surface side;
An insulating substrate is continuously provided over the transfer unit, the heating unit, and the pressurizing and conveying unit so as to be in contact with the surface opposite to the surface to which the toner is transferred of the recording medium. A transfer electrode for transferring at the transfer portion and a heating resistor for heating at the heating portion, respectively, and a pedestal for the pressurizing and conveying portion at an extended portion of the insulating substrate. A fixing method characterized by forming. The scattering of the fine powder of the toner is prevented by heating the toner transferred immediately after the transfer of the toner in the transfer unit by conduction of the heat heated by the heating unit in the insulating substrate. Fixing method. Before SL heating unit, provided a plurality of heating resistors along the direction of travel of the recording medium, the transfer portion side is high, the pressure conveying unit side by a temperature gradient to be lower in the heating unit The fixing method according to claim 10 or 11 , wherein the heating is performed. The fixing method according to claim 10, wherein the recording medium is smoothly moved by providing a wear-resistant layer on a surface of the pressure conveying unit facing the recording medium.

Images