JP2008151858A - Heating device and image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To safely shorten first print-out time without affecting durable lifetime, in a heating device that partially heats the heating rotational body and an image forming apparatus having the heating device. <P>SOLUTION: In a print standby state, the heating rotational body and a pressure member are separated from each other, thereby maintaining the heating rotational body at a fixable temperature or above. A heating position is arranged outside a nip area. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a heating apparatus that pressurizes and heats a material to be heated, and an electrophotographic apparatus / electrostatic recording provided as an image heating apparatus that heats and fixes an unfixed image formed and supported on the recording material. The present invention relates to an image forming apparatus such as an apparatus.

  In image forming apparatuses such as printers and copiers using toner, recording materials (transfer sheets, electrofax sheets, electrostatics, etc.) are used in appropriate image forming process means such as electrophotographic processes, electrostatic recording processes, and magnetic recording processes. A fixing device that heats and fixes an unfixed image (toner image) of image information formed and supported on a recording sheet, an OHP sheet, a printing sheet, a format sheet, or the like by a transfer method or a direct method on a recording material surface as a permanently fixed image. As such, a heat roller type heating device is widely used.

Also, a heating device that locally electromagnetically heats the nip portion of the heating roller, and in order to shorten the warm-up time, the heating device that separates the heating rotator from the pressure member until the temperature reaches a fixable temperature. (For example, refer to Patent Document 1).
Japanese Patent Laid-Open No. 11-202652

  As described in Japanese Patent Application Laid-Open No. 11-202652, in the heating device using local heating, the warm-up time can be shortened, but the time from the print standby state until one recording material is discharged When trying to shorten the first printout time (FPOT), depending on the temperature state of the pressure roller, the heat of the heating roller is taken away by the pressure member immediately after contacting the heating rotator and the pressure member. As a result, after the contact, the temperature of the heating rotator is lower than the fixable temperature, and fixing failure may occur. Further, in order to avoid this fixing failure, there is a problem that the FPOT cannot be shortened when waiting for the temperature of the heating rotator to rise again to the fixing possible temperature.

  Furthermore, when the heating rotator such as a color printer or high-speed printer has an elastic layer such as silicone rubber, the heat transfer rate of the elastic layer is slower than that of the metal, so the speed at which heat is transferred from the heat source to the surface of the heating rotator is high. Become slow. For this reason, the temperature drop amount of the heating roller immediately after contacting the heating rotator and the pressure member is further increased, and fixing failure is more likely to occur. In addition, there is a problem that a longer FPOT is required in order to avoid this fixing failure.

  In addition, by heating the nip part by local heating, if a failure occurs while the material to be heated stays in the nip part and the heating operation does not stop, local heating is performed. Therefore, since the energy density of the nip portion is high and the temperature rising rate of the nip portion is high, there is a possibility that ignition or smoke generation may occur.

  Therefore, it is an object of the present invention to solve the above problems without affecting the durability life in a heating device that performs local heating.

(1) A heating device that includes a heating rotator and a pressure member, and pressurizes and heats the material to be heated in a nip formed by contact between the heating rotator and the pressure member. In
A heat source that heats a part of the region other than the nip portion in the circumferential direction of the heating rotator, the heating rotator and the pressure member can be contacted and separated, and the material to be heated can be heated; A heating apparatus, wherein the heating rotator and the pressure member are separated from each other in a standby state to rotate the heating rotator.

(2) A heating apparatus that includes a heating rotator and a pressure member, and pressurizes and heats the material to be heated in a nip formed by contact between the heating rotator and the pressure member. And a heat source that heats a part of the region other than the nip portion in the circumferential direction of the heating rotator, the heating rotator and the pressure member can be brought into contact with and separated from each other, and the heated material is heated. In a heating device that separates the heating rotator and the pressure member in a possible standby state and rotates the heating rotator,
The heating apparatus characterized in that the rotation speed of the heating rotator is slower than the maximum conveyance speed of the material to be heated.

  (3) The heating apparatus according to any one of (1) to (2), wherein the heating rotator includes an elastic layer.

  (4) The heated material is an unfixed image or a recording material on which the unfixed image is formed and supported, and the temperature of the heating rotator in a standby state is set to be equal to or higher than a temperature at which the unfixed image can be fixed. The heating apparatus according to any one of (1) to (3), wherein:

  (5) The heating apparatus according to any one of (1) to (4), wherein the heating rotator includes a conductive layer, and is a heat source that generates heat by electromagnetic induction heating.

  (6) The heating apparatus according to any one of (1) to (4), wherein the heat source is a heat source that generates radiant heat.

  (7) The heating apparatus according to any one of (1) to (6), wherein the pressure member includes a heat source.

  (8) At the time of the separation, the heating rotator and the pressurizing member come into contact with each other in the region outside the conveyance region of the heated material in the rotation axis direction, so that the heating rotator and the pressurizing member are both The heating device according to any one of (1) to (7), wherein the heating device rotates.

  (9) The heated material is an unfixed image or a recording material on which the unfixed image is formed and supported, and the apparatus is a heat fixing device that heat-fixes the unfixed image on the recorded material. (1) The heating apparatus according to any one of (8).

  (10) Image forming means for forming and supporting an unfixed image on a recording material; and fixing means for fixing an unfixed image formed and supported on the recording material. The fixing means includes (1) to (9) An image forming apparatus comprising the heating device according to any one of the above.

  As described above, according to the present invention, even when a part of the region other than the nip portion is heated in the circumferential direction of the heating rotator by the heating device according to claim 1, the heating rotator during print standby The temperature unevenness in the circumferential direction can be reduced. Since the heating rotator and the pressure member are rotated without being brought into contact with each other, even if the heating rotator is rotated, no deformation occurs in the nip portion, so that the life is not affected. In addition, by heating the parts other than the nip part by local heating, the nip part is heated even if a failure occurs when the material to be heated stays in the nip part and the heating operation does not stop. It will not cause fire or smoke.

  Since the heating rotator and the pressure member are rotated without being brought into contact with each other, even if the heating rotator is rotated, no deformation occurs in the nip portion, so that the idle rotation can be performed without affecting the life.

  In the heating apparatus according to the second aspect, by reducing the rotation speed from the maximum conveyance speed, it is possible to reduce the load on the motor and reduce power consumption. In addition, by reducing the rotation speed, the rotation sound of the motor can be reduced, and the noise can be reduced even if the rotation is performed during printing standby.

  In the heating device according to claim 3, even when the heating rotator such as a high-speed printer or a color printer has an elastic layer such as silicone rubber, the nip portion is separated, so that the elastic layer is not repeatedly deformed and thus is durable. The temperature of the heating rotator can be maintained at a fixable temperature without affecting the life.

  In the heating device according to claim 4, regardless of the temperature state of the pressure roller, even if the heat of the heating roller is taken away by the pressure member immediately after contacting the heating rotator and the pressure member, fixing failure is caused. This makes it possible to obtain a good fixed image without causing any problems. In addition, the FPOT can be shortened.

  In the heating apparatus according to the fifth aspect, the above effect can be achieved by a heating apparatus that performs electromagnetic induction heating.

  In the heating apparatus according to the sixth aspect, the above effect can be achieved by a heating apparatus that performs electromagnetic induction heating.

  In the heating device according to claim 7, since the pressure member has a heat source, the heating rotator and the pressure member are maintained by maintaining the pressure member at a fixing temperature necessary for the pressure member. FPOT can be shortened without causing a temperature drop of the heating rotator when abutting.

  In the heating device according to claim 8, the heating rotator and the pressurizing member are in contact with each other in the region outside the conveyance region of the heated material in the rotation axis direction at the time of separation. Since the pressurizing members can be rotated together, the heating rotator can be rotated even when the driving means cannot be provided directly on the heating rotator. Moreover, even if the heat source of the pressurizing member is a heat source that performs local heating like a heating rotator, temperature unevenness in the circumferential direction of the pressurizing member can be reduced.

  The heating apparatus according to claim 9, wherein the heated material is an unfixed image or a recording material on which the unfixed image is formed and supported, and the apparatus can heat-fix the unfixed image on the recorded material. .

  11. The image forming apparatus according to claim 10, further comprising: an image forming unit that forms and supports an unfixed image on a recording material; and a heating unit as a fixing unit that fixes an unfixed image formed and supported on the recording material. Thus, an image forming apparatus having a fast warm-up time and a fast FPOT, a safe and long durability life can be obtained.

(Example 1)
(1) Image Forming Apparatus FIG. 12 is a schematic configuration diagram of an example of an image forming apparatus. The image forming apparatus of this example is an electrophotographic color printer.

  Reference numeral 101 denotes a photosensitive drum (image carrier) made of an organic photosensitive member or an amorphous silicon photosensitive member, which is rotationally driven in a counterclockwise direction indicated by an arrow at a predetermined process speed (circumferential speed).

  The photosensitive drum 101 is uniformly charged with a predetermined polarity and potential by a charging device 102 such as a charging roller during its rotation.

  Next, the charged surface is subjected to a scanning exposure process of target image information by a laser beam 103 output from a laser optical box (laser scanner) 110. The laser optical box 110 outputs a laser beam 103 modulated (on / off) corresponding to a time-series electric digital pixel signal of target image information from an image signal generation device such as an image reading device (not shown) to rotate the photoconductor. An electrostatic latent image corresponding to target image information scanned and exposed on the surface of the drum 101 is formed. Reference numeral 109 denotes a mirror that deflects the output laser light from the laser optical box 110 to the exposure position of the photosensitive drum 101.

  In the case of full-color image formation, scanning exposure / latent image formation is performed on a first color separation component image of a target full-color image, for example, a yellow component image, and the latent image is subjected to yellow development in the four-color developing device 104. The yellow toner image is developed by the operation of the device 104Y. The yellow toner image is transferred to the surface of the intermediate transfer drum 105 at the primary transfer portion T1 which is a contact portion (or proximity portion) between the photosensitive drum 101 and the intermediate transfer drum 105. The surface of the rotating photosensitive drum 101 after the transfer of the toner image to the surface of the intermediate transfer drum 105 is cleaned by the cleaner 107 after removal of adhesion residues such as transfer residual toner.

  The process cycle of charging, scanning exposure, development, primary transfer, and cleaning as described above includes the second color separation component image of the target full-color image (for example, the magenta component image, the magenta developer 104M is activated), the third color An intermediate transfer body is sequentially executed for each color separation component image of the separation component image (for example, cyan component image, cyan developing device 104C is activated) and the fourth color separation component image (for example, black component image, black developing device 104BK is activated). Four color toner images of a yellow toner image, a magenta toner image, a cyan toner image, and a black toner image are sequentially superimposed and transferred onto the surface of the drum 105, and a color toner image corresponding to the target full-color image is synthesized and formed.

  The intermediate transfer drum 105 has a middle-resistance elastic layer and a high-resistance surface layer on a metal drum. The intermediate transfer drum 105 is in contact with or close to the photosensitive drum 101 at the same peripheral speed as that of the photosensitive drum 101. , And a bias potential is applied to the metal drum of the intermediate transfer drum 105 to transfer the toner image on the photosensitive drum 101 side to the surface of the intermediate transfer drum 105 by the potential difference with the photosensitive drum 101. .

  The color toner image synthesized and formed on the surface of the rotary intermediate transfer drum 105 is transferred to the secondary transfer portion T2 in the secondary transfer portion T2 which is a contact nip portion between the rotary intermediate transfer drum 105 and the transfer roller 106. Are transferred onto the surface of the recording material P fed at a predetermined timing from a paper feeding unit (not shown). The transfer roller 106 supplies a charge having a polarity opposite to that of the toner from the back surface of the recording material P, thereby sequentially transferring the combined color toner images sequentially from the surface of the intermediate transfer drum 105 to the recording material P side.

  The recording material P that has passed through the secondary transfer portion T2 is separated from the surface of the intermediate transfer drum 105 and introduced into the image heating apparatus 100, and is subjected to a heat-fixing process for an unfixed toner image as a color image forming product. Are discharged to a paper discharge tray (not shown). The heating device 100 will be described in detail in the next section (2).

  After the color toner image has been transferred to the recording material P, the rotating intermediate transfer drum 105 is cleaned by the cleaner 108 after removal of adhering residues such as transfer residual toner and paper dust. The cleaner 108 is always held in a non-contact state with the intermediate transfer drum 105 and is in contact with the intermediate transfer drum 105 during the secondary transfer of the color toner image from the intermediate transfer drum 105 to the recording material P. Retained.

  Also, the transfer roller 106 is always held in a non-contact state with the intermediate transfer drum 105, and the intermediate transfer drum 105 is covered with the intermediate transfer drum 105 during the secondary transfer of the color toner image from the intermediate transfer drum 105 to the recording material P. The recording material P is held in contact.

  This example apparatus can also execute a mono-color image print mode such as a monochrome image. A double-sided image print mode or a multiple image print mode can also be executed.

  In the double-sided image print mode, the recording material P on which the first-side image has been printed out of the heating device 100 is turned upside down via a recirculation conveyance mechanism (not shown) and sent again to the secondary transfer portion T2. Upon receipt of the toner image transfer to the surface, the toner image is again introduced into the heating device 100 and undergoes toner image fixing processing on the two surfaces, whereby a double-sided image print is output.

  In the multiple image print mode, the recording material P that has been printed on the first image from the heating device 100 is sent to the secondary transfer portion T2 again without being turned upside down via a recirculation conveyance mechanism (not shown). A second toner image transfer is received on the surface on which the first image has been printed, and the image is again introduced into the heating device 100 and undergoes a second toner image fixing process, whereby a multiple image print is output.

(2) Heating device 100
In this example, the heating device 100 is an electromagnetic induction heating type heating device. FIG. 1 is a cross-sectional side view of the main part of the heating apparatus 100 of this example, and FIG. 2 is a front model view of the main part.

  The magnetic field generating means includes magnetic cores 17a, 17b, and 17c and an excitation coil 18.

  The magnetic cores 17a, 17b, and 17c are members having high magnetic permeability, and are preferably made of a material used for a transformer core such as ferrite or permalloy, and more preferably ferrite having a low loss even at 100 kHz or more.

  As shown in FIG. 3, an excitation circuit 27 is connected to the power feeding sections 18a and 18b of the excitation coil 18, so that a high frequency of 20 kHz to 500 kHz can be generated by a switching power supply.

  The exciting coil 18 generates an alternating magnetic flux by the alternating current (high-frequency current) supplied from the exciting circuit 27.

  Reference numeral 16 denotes a saddle-shaped holder having a substantially semicircular cross section, and holds magnetic cores 17a, 17b, and 17c as magnetic field generating means and an exciting coil 18 inside.

  A fixing roller 10, which is a cylindrical electromagnetic induction heat generating rotator, is rotatably disposed outside the holder 16 with a gap.

  Reference numeral 19 denotes an insulating member for insulating the magnetic cores 17 a, 17 b, and 17 c and the exciting coil 18 from the holding stay 22. The holding stay 22 can be made of a metal material such as iron, aluminum, stainless steel, or nonmagnetic stainless steel. Further, it is sufficient if the holder 16 can be held, and a heat resistant resin can be substituted.

  An alternating magnetic flux is generated by the magnetic field generating means. A magnetic flux C represents a part of the generated alternating magnetic flux. The magnetic flux C guided to the magnetic cores 17a, 17b, and 17c generates eddy currents in the heat generating layer 1 of the fixing roller 10 between the magnetic cores 17a and 17b and between the magnetic cores 17a and 17c. Let This eddy current causes Joule heat (eddy current loss) to be generated in the heat generating layer 1 by the specific resistance of the heat generating layer 1.

  The calorific value Q is determined by the density of the magnetic flux C passing through the heat generating layer 1, and shows a distribution as shown in the graph of FIG. The vertical axis of the graph represents the position in the circumferential direction of the fixing film 10 expressed by an angle θ with the center of the magnetic core 17 a being 0, and the horizontal axis represents the heat generation amount Q in the heat generating layer 1 of the fixing roller 10. Here, the heat generation region H is defined as a region where the maximum heat generation amount is Q and the heat generation amount is Q / e or more (e is the base of the natural logarithm). This is a region where the amount of heat generated for the fixing process can be obtained.

  FIG. 4 is a model diagram of the layer structure of the fixing roller 10 in this embodiment.

  The fixing roller 10 of the present embodiment has a composite structure of a heat generating layer 1 made of an electromagnetic induction heat generating metal or the like serving as a core, an elastic layer 2 laminated on the outer surface, and a release layer 3 laminated on the outer surface. belongs to.

  For adhesion between the heat generating layer 1 and the elastic layer 2 and adhesion between the elastic layer 2 and the release layer 3, a primer layer (not shown) may be provided between the respective layers.

  In the fixing roller 10, the heat generating layer 1 is on the inner surface side, and the release layer 3 is on the outer surface side in contact with the pressure roller or the recording material (heated material).

  When the above-described alternating magnetic flux acts on the heat generating layer 1, an eddy current is generated in the heat generating layer 1, and the heat generating layer 1 generates heat. This heat is transmitted to the elastic layer 2 and the release layer 3 so that the entire fixing roller 10 is heated, and the recording material P that is passed through the fixing nip portion N is heated to heat and fix the toner t image. .

  As the heat generating layer 1, magnetic and nonmagnetic metals can be used, but magnetic metals are preferably used. As such a magnetic metal, a ferromagnetic metal such as nickel, iron, ferromagnetic stainless steel, nickel-cobalt alloy or permalloy is preferably used. Further, in order to prevent metal fatigue due to repeated bending stress received when the fixing film 10 rotates, a member in which manganese is added to nickel may be used.

  The thickness of the heat generating layer 1 is preferably greater than the skin depth δ [m] represented by the following formula and 1 mm or less. If the thickness of the heat generating layer 1 is within this range, the heat generating layer 1 can efficiently absorb electromagnetic waves, and therefore heat can be generated efficiently.

ここで、ｆは励磁回路の周波数［Ｈｚ］、μは発熱層１の透磁率、κは発熱層１の導電率である。

Here, f is the frequency [Hz] of the excitation circuit, μ is the magnetic permeability of the heat generating layer 1, and κ is the conductivity of the heat generating layer 1.

  This skin depth δ indicates the depth of absorption of electromagnetic waves used for electromagnetic induction, and the intensity of the electromagnetic waves is 1 / e or less deeper than this. Conversely, most of the energy is absorbed up to this depth (see the relationship between the heat generation layer depth and the electromagnetic wave intensity shown in FIG. 6).

  The thickness of the heat generating layer 1 is more preferably 0.2 to 0.8 mm. When the thickness of the heat generating layer 1 is thinner than the above range, the efficiency is deteriorated because most of the electromagnetic energy cannot be absorbed. On the other hand, when the heat generating layer 1 is thicker than the above range, the heat capacity is increased and the rate of temperature increase is decreased.

  The elastic layer 2 is preferably made of a material having good heat resistance and thermal conductivity, such as silicone rubber, fluorine rubber, and fluorosilicone rubber.

  The thickness of the elastic layer 2 is preferably 0.05 to 3 mm in order to guarantee the fixed image quality. When a color image is printed, a solid image is formed over a large area on the recording material P, particularly in a photographic image. In this case, if the heating surface (release layer 3) cannot follow the unevenness of the recording material P or the unevenness of the toner layer t, uneven heating occurs, and uneven gloss occurs in the image where the heat transfer amount is large and small. . That is, the glossiness is high in the portion where the heat transfer amount is large, and the glossiness is low in the portion where the heat transfer amount is small. When the thickness of the elastic layer 2 is smaller than the above range, the release layer 3 cannot follow the unevenness of the recording material P or the toner layer t, and image gloss unevenness occurs. On the other hand, when the elastic layer 2 is too larger than the above range, the thermal resistance of the elastic layer 2 becomes too large, making it difficult to realize a quick start. The thickness of the elastic layer 2 is more preferably 0.1 to 2 mm.

  If the elastic layer 2 is too hard, it cannot follow the unevenness of the recording material P or the toner layer t, and image gloss unevenness occurs. Therefore, the hardness of the elastic layer 2 is 60 ° (JIS-A) or less, more preferably 45 ° (JIS-A) or less.

The thermal conductivity λ of the elastic layer 2 is preferably 2.5 × 10 ^{−1 to} 8.4 × 10 ⁻¹ W / m · K. When the thermal conductivity λ is smaller than the above range, the thermal resistance is too large, and the temperature rise in the surface layer (release layer 3) of the fixing film 10 is delayed. When the thermal conductivity λ is larger than the above range, the hardness of the elastic layer 2 becomes too high or compression set tends to occur. More preferably, it is 3.3 × 10 ^{−1 to} 6.3 × 10 ⁻¹ W / m · K.

  The release layer 3 is preferably made of a material having good release properties and heat resistance such as fluororesin, silicone resin, fluorosilicone rubber, fluororubber, silicone rubber, PFA, PTFE, and FEP.

  The thickness of the release layer 3 is preferably 1 to 100 μm. If the thickness of the release layer 3 is thinner than the above range, uneven coating of the coating film occurs, causing a problem that a part having poor release property is generated or durability is insufficient. Moreover, when the thickness of the release layer 3 is thicker than the above range, the heat conduction is deteriorated. In particular, when a resin material is used for the release layer 3, the hardness of the release layer 3 becomes too high and the effect of the elastic layer 2 is lost.

  The pressure roller 30 as a pressure member includes a cored bar 30a and a heat-resistant / elastic material layer 30b such as silicone rubber, fluororubber, or fluororesin that is concentrically and integrally molded around the cored bar. The release layer 30c is provided on the surface layer.

  The fixing roller 10 is rotatably supported by the fixing frame 50 via a bearing 41. The pressure roller 30 is rotatably supported by a pressure frame 51 as a swing member via a bearing 42. The pressure frame 51 is swingably supported by a support shaft 52 fixed to the fixing frame 50, and is urged so that the pressure roller 30 is pressed against the fixing roller 10 by a pressure spring 53 as pressure means. ing.

  As shown in FIG. 2, a gear 43 is attached to one end of the fixing roller 10 so as to rotate integrally with the fixing roller 10. Further, the fixing roller 10 is rotationally driven by the driving means M in the clockwise direction indicated by the arrow.

  Reference numerals 44 denote cams as pressure release means, which are respectively fixed to both sides of a cam shaft 45 rotatably supported by the fixing frame 50, and rotate integrally with the cam shaft 45. . A gear 46 is attached to one end of the cam shaft 45 so as to rotate integrally with the cam shaft 45. The cam shaft 45 is rotationally driven by the driving means M2. The heating device 100 is configured to contact / separate the fixing roller 10 and the pressure roller by swinging the pressure frame 51 against the pressure force of the pressure spring 53 by the rotation of the cam 44. Yes.

  The contact and separation between the fixing roller 10 and the pressure roller 30 are selectively switched based on the determination of a CPU (not shown) as a control means.

  As shown in FIG. 5A, the contact is made when the pressure frame 51 is pressed by the pressure spring 53 and the pressure roller 30 is pressed by the fixing roller 10 during image formation. A nip N is formed at the contact portion of the pressure roller 30.

  The fixing roller 10 is rotationally driven by the driving means M in the counterclockwise direction indicated by the arrow. A rotational force acts on the pressure roller 30 by the frictional force between the fixing roller 10 and the outer surface of the pressure roller 30 due to the rotation of the fixing roller 10, and the fixing roller 10 and the pressure roller 30 move in the direction of the arrow. The rotating state is achieved at a peripheral speed substantially corresponding to the rotational peripheral speed.

  The temperature of the fixing roller 10 is controlled so that a predetermined temperature is maintained by controlling the current supply to the exciting coil 18 by a temperature control system (not shown) including the temperature detecting means 26. The temperature detection means 26 is a temperature sensor such as a thermistor.

  Thus, in a state where the fixing roller 10 rotates, the fixing roller 10 generates electromagnetic induction heat by feeding power from the exciting circuit to the exciting coil 18, and the fixing roller 10 rises to a predetermined temperature and is temperature-controlled, the image forming means. The recording material P on which the unfixed toner image t conveyed from the image forming portion is introduced into the fixing nip portion N with the image surface facing upward, that is, facing the fixing roller surface. The fixing nip portion N is nipped and conveyed together with the fixing roller 10 in close contact with the outer surface of the fixing roller 10. In the process in which the recording material P is nipped and conveyed together with the fixing roller 10 through the fixing nip N, the unfixed toner image t on the recording material P is heated and fixed. When the recording material P passes through the fixing nip portion N, it is separated from the outer surface of the fixing roller 10 and discharged and conveyed. The heat-fixed toner image on the recording material is cooled to a permanently fixed image after passing through the fixing nip.

  In the separation, the driving means M2 is rotated at a predetermined timing during non-image formation, and the cam 44 is rotated by about 180 ° as shown in FIG. Push down against. As a result, the fixing roller 10 and the pressure roller 30 are separated from each other, and the formation of the nip N is released.

  Next, the operation of the heating device 100 in the operation of the image forming apparatus will be described.

  Usually, when the power of the image forming apparatus is turned off, the fixing roller and the pressure roller are separated from each other. As shown in FIG. 7, heating of the heating device 100 is started when the power is turned on, and warming up is performed until the fixing is possible. The pressure roller is brought into contact when the temperature of the fixing roller rises to a predetermined temperature (180 ° C.) while rotating the fixing roller. Thereafter, it is determined that printing is possible when the temperature reaches a fixable temperature (180 ° C. in this example). In this state, the printer enters a print standby state at a fixing possible temperature.

  If a print signal is received, the printing operation is performed as it is, and the toner image on the recording material is fixed.

  After the print operation is completed or when no print signal is received, the print standby state is entered. After a predetermined time has elapsed since entering the print standby state, the fixing roller and the pressure roller are separated from each other to bring the fixing roller and the pressure roller into a non-contact state. At this time, the rotation of the fixing roller is temporarily stopped and the separation operation is performed. The separation operation may be performed while rotating.

  Next, the print standby state will be described. In this example, the fixing roller and the pressure roller are separated from each other during printing standby, and the fixing roller is rotated.

  FIG. 8 is a graph comparing the state of the surface temperature of the fixing roller when the fixing roller is stopped at a temperature of 180 ° C. and when the fixing roller is rotating. The temperature increases from the center toward the outside, and the outermost periphery is 180 ° C. The arrangement of the magnetic field generating means corresponds to the arrangement shown in FIG. The rotation direction of the fixing roller is clockwise.

  In this example, the fixing roller and the pressure roller are rotated apart in a print standby state. Thereby, even if a part of the fixing roller in the circumferential direction is heated, the temperature unevenness in the circumferential direction can be reduced. Specifically, as shown by the solid line in FIG. 8, when rotating while adjusting the temperature to 180 ° C. in the heat generating region where the temperature detecting element 26 is disposed, the surface of the fixing roller 10 passes from the heat generating layer 1 through the elastic layer 2. Since it takes time to transfer heat to the nip, the maximum temperature reaches 182 ° C. near the nip position (just below the graph). After that, the heat is radiated and the temperature decreases most at 176 ° C. in the vicinity of the reheating region, and returns to 180 ° C. while returning to the position of the temperature detecting element 26 again. In this example, the fixable temperature is set to 180 ° C., and the printing operation can be performed immediately after receiving the print signal.

  On the other hand, a state where the fixing roller is stopped is shown by a broken line in FIG. 7 as a comparative example. In the stopped state, if the temperature of the heat generating area where the temperature detecting element 26 is arranged is adjusted to 180 ° C., the temperature can be maintained only at about 90 ° C. at the lowest temperature in the non-heat generating area. For this reason, it is necessary to perform front multiple rotations from the print standby state to the fixing ready state to eliminate temperature unevenness in the circumferential direction of the fixing roller. This pre-multi-rotation time is disadvantageous for shortening the first printout time because it takes time until temperature unevenness is eliminated.

  Furthermore, when the fixing roller has a rubber layer, it takes time to transfer heat from the heat generating layer to the surface of the fixing roller. As can be seen from the graph of FIG. 7, since the heat generation area and the area reaching the maximum temperature are different during rotation, the heating temperature is arranged on the upstream side of the nip portion in consideration of the heat transfer time. The area reaching the nip portion can be a nip portion, and power consumption can be reduced unnecessarily.

  When local heating is performed on the fixing roller, energy is concentrated on a part of the fixing roller, so that the temperature of the heat generating area rises quickly. For this reason, it was effective in shortening the warm-up time. However, when the nip part is heated, if the device stops due to a failure of the device and the device stops, and if the heating does not stop, the recording material may ignite or cause smoke. There is a risk of doing. Therefore, in addition to the above heat transfer time, in the present invention, the heat generating area is arranged outside the nip portion. By disposing the heat generation area other than the nip part as in this example, by heating other than the nip part by local heating, a failure occurs in the state where the heated material stays in the nip part. Even when the heating operation is not stopped, the nip portion is not heated, and therefore, ignition or smoke generation does not occur. Furthermore, the temperature detecting element 28 as a safety device can be disposed opposite to the heat generating area as shown in FIG. 1, and the device can be safely stopped even if a failure occurs.

  Further, according to the present invention, even if a part of the region other than the nip portion is heated in the circumferential direction of the heating rotator by rotating the heating rotator, the temperature in the circumferential direction of the heating rotator during printing standby Unevenness can be reduced. Since the heating rotator and the pressure member are rotated without being brought into contact with each other, even if the heating rotator is rotated, the elastic layer is not compressed and deformed at the nip portion, so that the life is not affected. Further, the surface layer is not damaged by the rotation.

  As described above, the heating apparatus has a fast warm-up time and FPOT, is safe and has a long durability life, and can be an image forming apparatus.

(Example 2)
In this example, the speed of rotating apart in the configuration of the first embodiment is rotated slower than the maximum sheet passing speed. As a result, the load on the rotating motor can be reduced, and the power consumption can be reduced. In addition, by reducing the rotation speed, the rotation sound of the motor can be reduced, and the noise can be reduced even if the rotation is performed during printing standby.

(Example 3)
In this example, the operation from the standby state in the configuration of Example 1 or Example 2 will be described.

  If the fixing roller and the pressure roller are separated from each other during printing standby, the heat of the fixing roller is not transferred to the pressure roller, so that the temperature of the pressure roller decreases. For this reason, when the printer receives a print signal, starts printing, and contacts the fixing roller and the pressure roller, heat is taken from the fixing roller to the pressure roller, and the temperature of the fixing roller decreases. appear.

  Therefore, in the graph of FIG. 9, the case where the temperature of the fixing roller is adjusted to 180 ° C. is indicated by a dotted line. In this case, since there is no heat source in the pressure roller, the temperature of the pressure roller may drop to near room temperature when the print standby time is increased. Time 0 in the graph of FIG. 9 starts with 0 sec when the pressure roller temperature drops to about 25 ° C., which is near room temperature. From this state, there is “fixable B” as the time for the fixing roller 10 to come into contact with the pressure roller 30 and the fixing roller temperature to return to the fixable temperature again. In this example, about 12 sec was required. Therefore, when waiting for printing at a fixing possible temperature of 180 ° C., if the time until the recording material is fed from the cassette of the image forming apparatus and reaches the nip portion N is 12 sec or less, printing is performed. It is preferable to set the time for the recording material to reach the nip portion after 12 seconds from receiving the signal.

  As described above, the temperature of the fixing roller is such that the pressure roller abuts, the temperature of the fixing roller is once lowered, and the material to be heated reaches the fixing nip N at the timing when the temperature reaches the fixable temperature again. It is good to set.

  Furthermore, in the graph of FIG. 9, the case where the temperature of the fixing roller is adjusted to 190 ° C. is indicated by a solid line. By setting the temperature of the fixing roller during printing standby to 190 ° C., the fixing roller and the pressure roller are brought into contact with each other, and even if heat is taken from the fixing roller to the pressure roller, the temperature of the fixing roller is the fixing temperature. Not lower than 180 ° C. Therefore, the time required for the fixing roller temperature to return to the fixable temperature again after contacting the fixing roller and the pressure roller can be set to about 3 sec until “fixable A”.

  As described above, when it is necessary to shorten the first printout time (FPOT), the temperature of the fixing roller in the standby state is set higher than the fixable temperature, and the pressure roller is brought into contact with the fixing roller. It is preferable to set so that the lowest temperature at which the temperature decreases is equal to or higher than the fixable temperature.

Example 4
In this example, the heat source is provided in the pressure roller in the configurations of the first to fourth embodiments. In addition, the same number is attached about the same component, and description for the second time is abbreviate | omitted.

  As shown in the graph of FIG. 10, the temperature of the fixing roller is adjusted at 180 ° C., and a halogen heater that radiates in the entire circumferential direction is disposed inside the pressure roller, and the temperature is adjusted at 170 ° C. The temperature indicated by the dotted line in the temperature of the fixing roller 10 is the surface temperature of the fixing roller when the pressure roller temperature is reduced to near room temperature when the pressure roller has no heat source as in the comparative example shown in the third embodiment. It shows a change. There is “fixable B” as the time for the fixing roller temperature to return to the fixable temperature again after contacting the fixing roller 10 and the pressure roller 30, and in this example, about 12 sec was required. On the other hand, in this example, a heat source is provided in the pressure roller 30 and the temperature is adjusted at 170 ° C. during printing standby, so that the fixing roller 10 and the pressure roller 30 come into contact with each other to reach the fixing temperature again. The time required for the temperature to recover was about 3 seconds until “fixable C”. Therefore, the time required for fixing can be shortened to about 1/4. Further, by adjusting the temperature of the pressure roller 30 at the same temperature as that of the fixing roller 10, even if the fixing roller 10 and the pressure roller 30 are brought into contact with each other, the temperature of the fixing roller 10 does not decrease, so that fixing is possible. The time to become 0 sec can be set.

  From the above, by providing a heat source in the pressure member and maintaining the pressure member at the fixing temperature required for the pressure member, the temperature of the heating rotator decreases when the heating rotator and the pressure member abut. FPOT can be shortened without causing any problems.

(Example 5)
In this example, in the configuration of the first to fourth embodiments, the fixing roller and the pressure roller are separated from each other in the rotation axis direction of the roller and in the region outside the conveyance region of the heated material, The outer diameter of the end of the pressure roller is increased so that the pressure member comes into contact. In addition, the same number is attached about the same component, and description for the second time is abbreviate | omitted. As shown in FIG. 11, the portions where the outer diameter is increased at both ends of the pressure roller 30 are defined as 30d. FIG. 11A shows a state where the heating rotator and the pressure member are in contact with each other, and FIG. 11B shows a state where the heating rotator and the pressure member are separated from each other. In this example, 30d is 0.2 mm larger in outer diameter over a width of 5 mm than the conveyance area of the recording material. Note that the conveyance area is set to 30 d from a position 2 mm outside the maximum recording material width in consideration of paper feeding errors. Thus, even in the separated state, the pressure roller end 30d and the fixing roller 10 are in contact with each other, and the pressure roller 30 rotates together.

  With the configuration as in this example, even if the heat source provided in the pressure roller 30 is a heat source that locally heats a part in the circumferential direction like the heat source provided in the fixing roller 10, By rotating the roller 30, the temperature unevenness in the circumferential direction of the pressure roller can be reduced to the same extent as the fixing roller.

  In the configuration in which the pressure roller 30 is driven, the fixing roller 10 can be rotated while the fixing roller 10 and the pressure roller 30 are separated from each other. This is particularly effective in a configuration in which the fixing roller 10 cannot be directly driven.

  The fixing roller 10 and the pressure roller 30 need only rotate together, and 30d can be realized by providing a similar function at the end of the fixing roller 10. The shape can also be realized by adopting a configuration in which the outer diameter gradually increases from the center toward the end, like a drum, regardless of the fixing roller or the pressure roller.

The cross-sectional side view model of the principal part of the heating apparatus concerning Example 1 of this invention, and the figure which showed heat_generation | fever distribution. The front model figure of the principal part. The perspective model figure of the holder of the right side which arrange | positioned and supported the magnetic field generation | occurrence | production means inside. FIG. 3 is a layer configuration model diagram of an electromagnetic induction heat-generating fixing roller. The figure which shows the (A) contact state in the a-a 'cross section, and the separated state. The graph which showed the relationship between the heat generating layer depth and electromagnetic wave intensity. A graph showing the temperature change of the fixing roller and the pressure roller (when warming up). The graph which showed the temperature distribution of the circumferential direction of a fixing roller. A graph showing temperature changes of the fixing roller and the pressure roller (when waiting for printing). The graph which showed the temperature change of a fixing roller and a pressure roller (at the time of pressure roller heating). (A) The figure which shows the contact state in the fixing roller and the pressure roller in the front model figure of the heating apparatus concerning Example 3, (B) The figure which shows a separation state. 1 is a schematic configuration model diagram of an image forming apparatus of the present invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Heat generation layer 2 Elastic layer 3 Release layer 4 Heat insulation layer 10 Fixing roller (heating rotating body)
16 Holder 17, 18, 27 Magnetic core, excitation coil, excitation circuit (magnetic field generating means)
26 Temperature sensing element 28 Temperature sensing element as safety element 30 Pressure roller (pressure member)
100 Fixing device (heating device)
N Fixing nip (nip area)
P Recording material

Claims (10)

In a heating apparatus that includes a heating rotator and a pressure member, and pressurizes and heats the material to be heated in a nip formed by contact between the heating rotator and the pressure member.
A heat source that heats a part of the region other than the nip portion in the circumferential direction of the heating rotator, the heating rotator and the pressure member can be contacted and separated, and the material to be heated can be heated; A heating apparatus, wherein the heating rotator and the pressure member are separated from each other in a standby state to rotate the heating rotator. A heating device that includes a heating rotator and a pressure member, and pressurizes and heats the material to be heated in a nip formed by contact between the heating rotator and the pressure member; A heat source that heats a part of the region other than the nip portion in the circumferential direction of the heating rotator, the heating rotator and the pressure member can be contacted and separated, and can be heated to heat the material to be heated. In the heating device that separates the heating rotator and the pressure member in a state and rotates the heating rotator,
The heating apparatus characterized in that the rotation speed of the heating rotator is slower than the maximum conveyance speed of the material to be heated.   The heating apparatus according to claim 1, wherein the heating rotator includes an elastic layer.   The heated material is an unfixed image or a recording material on which the unfixed image is formed and supported, and the temperature of the heating rotator in a standby state is set to be equal to or higher than a temperature at which the unfixed image can be fixed. The heating apparatus according to any one of claims 1 to 3, wherein the heating apparatus is characterized.   The heating device according to any one of claims 1 to 4, wherein the heating rotator includes a conductive layer, and is a heat source that generates heat by electromagnetic induction heating.   The heating apparatus according to claim 1, wherein the heat source is a heat source that generates radiant heat.   The heating apparatus according to claim 1, wherein the pressure member has a heat source.   At the time of the separation, the heating rotator and the pressure member rotate together when the heating rotator and the pressure member are in contact with each other in a region outside the conveyance region of the heated material in the rotation axis direction. The heating apparatus according to any one of claims 1 to 7, wherein   2. The heated material is an unfixed image or a recording material on which the unfixed image is formed and supported, and the apparatus is a heating and fixing device that heat-fixes the unfixed image on the recorded material. The heating apparatus according to any one of 1 to 8.   10. An image forming means for forming and carrying an unfixed image on a recording material; and a fixing means for fixing an unfixed image formed and supported on a recording material, wherein the fixing means is any one of claims 1 to 9. An image forming apparatus, which is the heating apparatus described in 1.

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