JP2005292295A - Heating apparatus and image forming apparatus - Google Patents

Abstract

An object of the present invention is to suppress the temperature rise of a non-sheet passing portion of a heating device and to prevent electrostatic offset.
The fixing speed when the recording material passes through the fixing nip is Vp, and the fixing speed when the recording material does not pass through the fixing nip is Vi, depending on the temperature of the non-sheet passing portion. , Vi> Vp.
[Selection] Figure 2

Description

  The present invention relates to a heating device as a fixing device such as a copying machine, a printer, and a fax machine using an electrophotographic system, and an electrophotographic apparatus equipped with the heating device.

  In an image forming apparatus, a recording material (transfer sheet, electrofax sheet, electrostatic recording paper, OHP sheet, printing paper, format, etc.) in an appropriate image forming process means such as an electrophotographic process, an electrostatic recording process, and a magnetic recording process As a fixing device that heats and fixes an unfixed image (toner image) of image information formed and carried on a transfer method or a direct method on paper or the like as a permanently fixed image on a recording material surface, a heat roller type device is widely used. It was done.

  In recent years, a film heating method has been put into practical use from the viewpoint of quick start and energy saving. An electromagnetic induction heating type device has also been proposed.

a) Film Heating System A film heating system fixing device (fixing device) is proposed in, for example, Patent Documents 1 to 4 and the like.

  That is, a fixing nip portion is formed by sandwiching a heat resistant film (fixing film, fixing belt) between a ceramic heater as a heating body and a pressure roller as a pressure member, and the fixing film of the fixing nip portion is formed. The recording material on which an unfixed toner image is formed and supported is introduced between the pressure roller and the pressure roller, and is nipped and conveyed together with the fixing film, so that the heat of the ceramic heater is received through the fixing film at the fixing nip portion. This is applied to the recording material, and further, the unfixed toner image is fixed on the surface of the recording material by the pressing force of the fixing nip portion.

  This film heating type fixing apparatus can be configured as an on-demand type apparatus using a ceramic heater and a low heat capacity member as a fixing film. That is, it is only necessary to energize a ceramic heater as a heat source to generate heat at a predetermined fixing temperature only when image forming of the image forming apparatus is executed, and a waiting time from power-on of the image forming apparatus to an image forming executable state There are advantages such as short (quick start) and significantly low power consumption during standby (power saving).

b) Film heating method using electromagnetic induction Patent Document 5 proposes a heating device that generates eddy currents in the fixing film itself or a conductive member close to the fixing film and generates heat by Joule heat at that time. . In this film heating method using electromagnetic induction, the heat generation area can be brought close to the material to be heated, so that further improvement in the efficiency of energy consumption can be achieved compared to the film heating method using a ceramic heater.

In a film heating system or a film heating system fixing apparatus using electromagnetic induction, as a driving method of a cylindrical or endless film fixing film as a rotating body, a film guide member (film support member) for guiding the inner peripheral surface of the fixing film ) And the pressure roller are driven by rotating the pressure film by the rotation of the pressure roller (pressure roller drive system), or conversely, an endless film-like fixing stretched by the drive roller and tension roller. For example, a pressure roller is driven to rotate by driving a film.
JP-A-63-313182 Japanese Patent Laid-Open No. 2-157878 JP-A-4-44075 JP-A-4-204980 JP-A-7-114276

  However, in each of the conventional examples described above, when a recording material such as small-size paper having a width narrower than the fixing nip width is passed (conveyed), the recording material is heated by the recording material (conveyance area). In contrast, the non-sheet passing portion (non-conveying area) is not deprived of heat, so the temperature of the non-sheet passing portion rises. If a large-sized recording material is passed while the temperature of the non-sheet passing part is raised, the temperature of the part that hits the non-passing part of the small-size paper that has been passed previously is too high, so hot offset occurs. Occur. In addition, when the temperature of the non-sheet passing portion exceeds the heat resistance temperature of the constituent member, the constituent member may be deteriorated and durability may be deteriorated or destroyed. For this reason, the temperature at which the above problem does not occur when the temperature of the non-sheet passing portion is suspended until the temperature of the non-sheet passing portion falls below the temperature at which the hot offset occurs or the space between the recording materials (paper interval) is widened. Therefore, there is a problem that throughput is lowered and print productivity is lowered.

  In addition, in the case of a fixing device that enables a quick start using a fixing film as a fixing rotator, the fixing film is thinner than the heat roller (fixing roller) and has a smaller heat capacity, so the heat conduction in the longitudinal direction deteriorates. To do. For this reason, in the fixing device using the fixing film, the temperature rise in the non-sheet passing portion is more severe, and in order to suppress the temperature of the non-sheet passing portion to the temperature or lower as described above, the gap between the sheets is larger than the fixing device using the heat roller. There is a problem in that throughput needs to be further expanded and throughput is further reduced.

  As another problem, in the above-described fixing device, toner on the recording material is electrostatically transferred to the fixing member, so that a so-called electrostatic offset is generated, which stains the subsequent image.

  The invention according to the present application aims to suppress the temperature rise of these non-sheet passing portions and prevent electrostatic offset.

  The present invention can solve the above problems by providing the following configuration.

  (1) In a heating device for fixing a toner image on the recording material by nipping and conveying the recording material in a nip portion composed of a fixing rotator and a pressure rotator, the recording material passes through the nip portion. A heating apparatus characterized in that Vi> Vp, where Vp is a conveying speed when the sheet is being transported and Vi is a conveying speed when the sheet is not passing.

  (2) P (n) is the nth recording material continuously conveyed to the heating device, P (n + 1) is the n + 1th recording material {n = 1, 2, 3,... }, The conveying speed between P (n) and P (n + 1) satisfies Vi> Vp. (1).

  (3) When the temperature of the fixing rotator when the recording material passes through the nip portion is Tp and the temperature when the recording material does not pass is Ti, Ti <Tp. The heating device according to (1) or (2).

  (4) In the longitudinal direction of the fixing rotator or the pressure rotator, the transport speed is set to Vi> Vp according to the temperature of the non-transport area of the recording material. The heating device according to any one of (3).

  (5) In the longitudinal direction of the fixing rotating body or the pressure rotating body, the transport speed Vi is increased or decreased according to the temperature of the non-transport area of the recording material. Heating device.

  (6) In the longitudinal direction of the fixing rotator or the pressure rotator, the timing at which the leading end of the recording material enters the nip portion is changed according to the temperature of the non-conveying area of the recording material. The heating device according to (4) or (5).

  (7) The heating apparatus according to any one of (1) to (6), wherein the fixing rotator is a flexible film-like rotator.

  (8) The heating apparatus according to any one of (1) to (7), wherein the fixing rotator of the fixing unit is induction-heated.

  (9) The fixing rotating body is a flexible film-shaped rotating body, and rotates around the linear heating element in contact with the fixing rotating body, according to any one of (1) to (6), Heating device.

  (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, which is the heating apparatus according to any one of the above.

  According to the present invention, when the transport speed when the recording material passes through the nip portion is Vp and the transport speed when the recording material does not pass is Vi, Vi> Vp, so that the non-sheet passing portion. Temperature rise can be suppressed. Further, since the ability to recover the surface potential of the fixing member between the recording materials is increased, electrostatic offset can be prevented.

  Hereinafter, the best mode for carrying out the present invention will be described in detail with reference to examples.

<First Embodiment>
(1) Image Forming Apparatus FIG. 10 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 a second color separation component image (for example, a magenta component image, the magenta developer 104M is activated) of a target full color image, and a 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, thereby outputting a double-sided image print.

  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 device. 2 is a cross-sectional side view of the main part of the heating device 100 of this example, FIG. 3 is a front view of the main part, and FIG. 4 is a longitudinal front 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.

  An excitation circuit (not shown) is connected to the exciting portions 18a and 18b of the exciting coil 18, and 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 an alternating current (high-frequency current) supplied from an exciting circuit.

  Reference numerals 16a and 16b are saddle-shaped film guide members having a substantially semicircular arc shape in cross section, which form a substantially cylindrical body with the opening sides facing each other, and loosely fix the fixing film 10 which is a cylindrical electromagnetic induction heating film on the outside. It is fitted outside.

  The film guide member 16a holds magnetic cores 17a, 17b, and 17c as magnetic field generating means and an excitation coil 18 inside.

  Further, on the film guide member 16 a, a sliding member 40 is disposed inside the fixing film 10 on the side of the nip portion N facing the pressure roller 30.

  Reference numeral 22 denotes a laterally long pressurizing rigid stay disposed in contact with the inner surface flat portion of the film guide member 16b.

  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 pressurizing rigid stay 22.

  FIG. 5 is a model diagram of the layer structure of the fixing film 10 in this embodiment.

  The fixing film 10 of this embodiment is a composite of a heat generating layer 1 made of an electromagnetic induction heat generating metal film or the like as a base layer, an elastic layer 2 laminated on the outer surface, and a release layer 3 laminated on the outer surface. Of structure.

  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 film 10 having a substantially cylindrical shape, the heat generating layer 1 is on the inner surface side in contact with the sliding member 40, and the release layer 3 is on the outer surface side in contact with the pressure roller or the recording material (heated material).

  In addition, the heat insulation layer 4 can also be provided like FIG.

  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 film 10 is heated, and the recording material P passed through the fixing nip portion N is heated to fix the toner t image by heat. .

  The flange members 23a and 23b are fitted around the left and right ends of the assembly of the film guide members 16a and 16b, and are attached to the left and right positions while being fixed by the regulating members 24a and 24b, so that the fixing film 10 rotates. It receives the end of 10 and serves to regulate the movement of the fixing film along the length of the film guide member.

  As materials of the flange members 23a and 23b, phenol resin, polyimide resin, polyamide resin, polyamideimide resin, PEEK resin, PES resin, PPS resin, fluorine resin (PFA, PTFE, FEP, etc.), LCP (Liquid Crystal Polymer): liquid crystal Polymer) resin and those having a thickness of 0.5 to 3 mm made of a heat-resistant material such as a mixed resin thereof are preferable. For imparting conductivity, for example, carbon black such as ketjen black, aluminum, etc. Metal powder can be used.

  A pressure roller 30 as a pressure rotating body includes a core metal 30a, a heat-resistant / elastic material layer 30b such as silicone rubber, fluororubber, and fluororesin that is concentrically formed and coated around the core metal in a roller shape. The release layer 30c is provided on the surface layer. In order to ensure conductivity of the pressure roller 30, the elastic layer 30b and the release layer 30c use conductive materials. For example, the release layer 30c can be made of a material having good release properties and heat resistance such as fluororesin, silicone resin, fluorosilicone rubber, fluororubber, silicone rubber, PFA, PTFE, FEP. The elastic layer 30b is preferably made of silicone rubber, fluorine rubber, fluorosilicone rubber, or the like that has good heat resistance and good thermal conductivity. The release layer and the elastic layer can be provided with conductivity by mixing carbon powder such as ketjen black or metal powder such as aluminum.

  Both ends of the core metal 30a are disposed between chassis metal plates (not shown) of the apparatus so as to be freely rotatable via conductive bearings.

  By pressing the pressure springs 25a and 25b between the both ends of the pressure rigid stay 22 and the spring receiving members 29a and 29b on the apparatus chassis side, a pressing force is applied to the pressure component stay 22. As a result, the lower surface of the film guide member 16a and the upper surface of the pressure roller 30 are pressed against each other with the fixing film 10 interposed therebetween to form a fixing nip portion N having a predetermined width.

  The pressure roller 30 is rotationally driven by the driving means M in the counterclockwise direction indicated by the arrow. A rotational force acts on the fixing film 10 by a frictional force between the pressure roller 30 and the outer surface of the fixing film 10 due to the rotational driving of the pressure roller 30, and the inner surface of the fixing film 10 is a sliding member in the fixing nip N. The outer periphery of the film guide members 16a and 16b is rotated in a clockwise direction indicated by an arrow while rotating in close contact with the lower surface of the film 40 at a peripheral speed substantially corresponding to the rotational peripheral speed of the pressure roller 30.

  In this case, in order to reduce the mutual sliding frictional force between the lower surface of the sliding member 40 and the inner surface of the fixing film 10 in the fixing nip portion N, the lower surface of the sliding member 40 and the inner surface of the fixing film 10 in the fixing nip portion N A lubricant such as heat-resistant grease can be interposed between the two.

  The temperature of the fixing film 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 the state where the fixing film 10 rotates, the fixing film 10 generates electromagnetic induction heat by feeding power from the exciting circuit to the exciting coil 18, and the fixing film 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 section is introduced into the fixing nip portion N with the image surface facing upward, that is, facing the fixing film surface. The fixing nip portion N is nipped and conveyed together with the fixing film 10 in close contact with the outer surface of the fixing film 10. In the process in which the recording material P is nipped and conveyed together with the fixing film 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 film 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.

(3) Fixing speed control Here, the fixing speed while the recording material P passes through the fixing nip portion N is set to Vp, and is set to be substantially equal to the conveying speed of the transfer portion T2. The speed when the recording material P does not pass through the fixing nip portion N (fixing speed between sheets) is Vi. In addition, for the recording material P that is continuously passed, the nth recording material is P (n) (n = 1, 2, 3,...).

  In this example, the fixing speed is set to Vi> Vp between the recording materials P (n) and P (n + 1) to be continuously passed. FIG. 1 is a graph showing the temperature of the non-sheet passing portion of the fixing film with respect to the fixing speed between sheets. The three lines indicating the non-sheet passing portion temperature on the graph are the temperature when Vi = 1.5 × Vp and Vi = 2 × Vp as an example of Vi> Vp, and when Vi = Vp as a comparative example. Indicates temperature. Further, the temperature drop between papers when Vi = Vp is ΔT0, the temperature drop between papers when Vi = 1.5 × Vp is ΔT1, and the temperature drop between papers when Vi = 2 × Vp. If ΔT2 is set, ΔT0 <ΔT1 <ΔT2 is obtained because the temperature drop between the papers increases as Vi is accelerated. Therefore, it can be seen that by setting Vi> Vp, the temperature rise curve of the non-sheet passing portion becomes gentle and the saturation temperature of the non-sheet passing portion decreases.

  This is because the number of contact between the pressure roller and the fixing roller per unit time is increased by making the fixing speed between the recording materials faster than the fixing speed when the recording material P passes through the nip portion N. By doing. When the number of times of contact increases, the number of times the heat of the non-sheet passing portion is transmitted from the fixing film to the pressure roller increases, so that heat transfer from the fixing film to the pressure roller is promoted. The heat transmitted to the pressure roller can diffuse the heat of the non-sheet passing portion to the sheet portion or the end surface of the pressure roller using heat conduction in the longitudinal direction of the pressure roller. The temperature rise can be alleviated. Further, when the rotation speed of the fixing film and the pressure roller is increased, stirring of the atmosphere (air) staying around the fixing film and the pressure roller is promoted. Get higher. For this reason, it is possible to suppress the temperature rise of the non-sheet passing portion.

As an actual example, with a fixing temperature (sheet passing portion temperature) of 180 ° C., a recording material P of A5 size (148 × 210 mm) paper (paper width L _P = 148 mm) with respect to the fixing film length L _F = 250 mm The results shown in the table below were obtained when 80 mm continuous paper was passed between the papers.

(4) Grounding Form Next, FIG. 3 shows a grounding form of the fixing film 10 and the pressure roller 30. In this example, negative toner that is negatively charged will be described.

  The conductive heat generating layer 1 of the fixing film 10 is grounded through conductive flange members 23a and 23b and conductive regulating members 24a and 24b.

  The pressure roller 30 is composed of a conductive member as described above, and the surface potential of the pressure roller becomes approximately 0 V by grounding the cored bar.

  Since the fixing film is rotated following the pressure roller, the surface of the release layer is negatively charged by rubbing. The fixing film is charged to about −500 V from the start of the pre-rotation until the recording material P reaches the fixing nip. However, depending on the paper type, the surface potential of the fixing film is lowered by passing the paper. The reduction rate of the surface potential varies depending on the paper type, but may decrease to about 0 V by continuous paper feeding.

  In the present invention, by setting the fixing speed to Vi> Vp, it is possible to increase the number of rubbing times between the pressure roller and the fixing film between the sheets. For this reason, recharging by rubbing between the pressure roller and the fixing film between papers is promoted, and the surface potential of the fixing film can be kept at about minus -100 V even when continuous paper is passed. Therefore, it is possible to obtain a good fixed image without electrostatic offset.

  In the present invention, Vi> Vp may be satisfied even during the pre-rotation before P (1) which is the first sheet of the recording material reaches the fixing nip portion N. Thereby, the surface potential of the fixing film can be made lower than that in the case of Vi = Vp, which is effective in preventing electrostatic offset. Therefore, it is possible to satisfy Vi> Vp as necessary during the pre-rotation.

  As described above, by setting Vi> Vp between the sheets according to the present invention, it is possible to suppress the temperature rise of the non-sheet passing portion by passing small size paper or the like. Even if the paper is passed, hot offset does not occur at the portion corresponding to the non-passage portion of the small size paper. In addition, since the throughput is not reduced, print productivity can be improved. Further, since the ability to recover the surface potential of the fixing film, which is a fixing rotator, between recording materials is increased, electrostatic offset can be prevented.

<Second Embodiment>
In addition to the first embodiment, in this example, when the recording material P passes through the fixing nip N, the fixing temperature is Tp, and when the recording material P does not pass through the fixing nip N ( When the fixing temperature between papers is Ti, the fixing temperature between papers is Ti <Tp. In this example, the temperature drop between the sheets can be further increased as compared with the first embodiment, and the saturation temperature of the non-sheet passing portion can be further lowered.

<Third Embodiment>
In this example, as shown in FIG. 3, when the temperature detected by the temperature sensor 27 disposed in the non-sheet passing portion detects a predetermined temperature, the fixing speed Vi> Vp between the recording materials (between sheets) is set. . Other configurations are the same as those in the first or second embodiment, and the description thereof is omitted here.

  FIG. 7 is a graph showing switching of the temperature of a non-sheet passing portion and the fixing speed between sheets in continuous sheet passing. Since the predetermined temperature Td is detected at the non-sheet passing portion while the third continuous sheet P (3) passes through the fixing nip N, the fixing speed between the subsequent sheets is set to Vi = 2 × Vp. As a result, it can be seen that the temperature drop of the non-sheet passing portion increases between the sheets after P (3), and the temperature of the non-sheet passing portion can be maintained below the predetermined temperature Te. Incidentally, the dotted line in the graph shows the case where the fixing speed Vi = Vp between papers, and the temperature of the non-sheet passing portion can be lowered by setting the fixing speed between papers Vi> Vp.

  In this example, since the fixing speed between the recording materials can be increased only when necessary according to the temperature rise state of the non-sheet passing portion, the fixing film and the pressure roller are compared with the first or second embodiment. This is effective when the durability life is important.

<Fourth Embodiment>
In this example, the fixing speed Vi between the recording materials (between sheets) is increased or decreased according to the temperature detected by the temperature sensor disposed in the non-sheet passing portion. Other configurations are the same as those of the third embodiment, and the description thereof is omitted here.

  In this example, control is performed such that the fixing speed Vi between the sheets is faster when the temperature of the non-sheet passing portion is higher than the predetermined temperature, and Vi is decreased when the temperature is lower. In this control, the fixing speed Vi is increased by the necessary amount according to the temperature of the non-sheet passing portion, so that the fixing speed Vi can be finely controlled. Compared with the third embodiment. As a result, the number of rotations of the fixing film and the pressure roller can be reduced. Therefore, it is possible to extend the durability life of the fixing device as compared with the third embodiment.

  As a method of changing Vi, there are a plurality of fixing speeds between sheets, and a method of changing between fixing speeds stepwise, or changing Vi continuously based on the rate of increase / decrease in the non-sheet passing portion temperature. A method is possible.

  Further, even when the temperature of the non-sheet passing portion is lower than the predetermined temperature even between the sheets, Vi = Vp can be set.

<Fifth Embodiment>
In addition to the third or fourth embodiment, the fixing speed between sheets is set to Vi> Vp according to the temperature of the non-sheet passing portion, and the interval between the leading end of the recording material P entering the nip portion N is widened. Take control. This control is performed by widening the supply interval of the recording material P using a control system (not shown).

  According to this example, when the temperature increase of the non-sheet passing portion is insufficient even in the above-described embodiment, the temperature of the non-sheet passing portion is set to a predetermined temperature in the passing of, for example, a narrow long paper or a small size thick paper. It is effective to maintain below the temperature of. Even in this case, by setting the fixing speed Vi> Vp between the recording materials, it is possible to shorten the paper feeding interval as compared with the case of Vi = Vp, and to improve the print productivity.

<Other embodiment examples>
(1) Even if a linear resistance heating element and a fixing film are used as the heating device 100 as shown in FIG. 8, the same effect as in the above embodiment can be obtained. In addition, description here is abbreviate | omitted about the structure similar to 1st Embodiment.

  The fixing device of this example uses a heat-resistant film provided with a release layer as the fixing film 11, and a ceramic heater or electromagnetic induction heat generation is provided on the surface portion corresponding to the fixing nip portion N on the lower surface of the film guide member 16. A heating body 41 such as a member is disposed. The fixing film 11 can also have the same configuration as the fixing film 10 of the first embodiment.

  The temperature of the heating body 41 is controlled so that a predetermined temperature is maintained by controlling power feeding from the power source by a temperature control system (not shown) including the temperature detection means 26. The temperature detection means 26 is a temperature sensor such as a thermistor. Further, although not shown in the drawing, a temperature sensor can be provided in the non-sheet passing portion as in the above embodiment.

  A recording material P on which an unfixed toner image is formed and supported is introduced into a fixing nip portion N between the fixing film 11 and the pressure roller 30 and is nipped and conveyed together with the fixing film 11 to thereby fix the fixing nip portion. In N, the heat of the heating body 41 is applied to the recording material via the fixing film 11 to fix the unfixed toner image on the surface of the recording material.

  (2) Even if a heating roller fixing device is used as the heating device 100 as shown in FIG. 9, the same effect as in the above embodiment can be obtained. In addition, description here is abbreviate | omitted about the structure similar to 1st Embodiment.

  In the fixing device of this example, the fixing roller 50 as a fixing rotator is formed of a hollow cored bar 50a and a heat resistant material such as silicone rubber, fluororubber, or fluororesin that is concentrically molded and coated around the cored bar. The release layer 50c is provided on the surface layer. A halogen heater 51 is disposed in the fixing roller, and generates heat by supplying power from a power source (not shown).

  The temperature of the fixing roller 50 is controlled so that a predetermined temperature is maintained by controlling power supply to the halogen heater 51 by a temperature control system (not shown) including the temperature detection unit 26. The temperature detection means 26 is a temperature sensor such as a thermistor. Further, although not shown in the drawing, a temperature sensor can be provided in the non-sheet passing portion as in the above embodiment. In this case, like the temperature sensor 26, it is preferably disposed on the outer surface side of the fixing roller 50.

  At both ends of the cored bar of the fixing roller and the pressure roller, the chassis side sheet metal (not shown) of the apparatus is rotatably held via a bearing. Then, the fixing roller 50 and the pressure roller 30 are pressed to form a fixing nip portion N having a predetermined width.

  A recording material P on which an unfixed toner image is formed and supported is introduced into a fixing nip portion N between the fixing roller 51 and the pressure roller 30 and is nipped and conveyed together with the fixing roller 50, whereby the fixing nip portion At N, the heat of the halogen heater 51 is applied to the recording material via the fixing roller 50, and the unfixed toner image is fixed on the surface of the recording material.

  (3) In the above embodiment, since the toner containing the low softening material is used, the heating device 100 is not provided with an oil application mechanism for preventing offset, but the toner does not contain the low softening material. In the case where is used, an oil application mechanism may be provided. Further, a cooling unit may be provided after the fixing nip to perform cooling separation. Also, oil application or cooling separation may be performed when a toner containing a low softening substance is used. Although the four-color image forming apparatus has been described, the present invention may be applied to a monochrome or one-pass multi-color image forming apparatus or a quadruple tandem type image forming apparatus.

The figure which showed the relationship between the speed between recording materials of 1st Embodiment, and non-sheet passing part temperature FIG. 3 is a cross-sectional side view of a main part of the fixing device according to the first embodiment. Similarly, front view of the main part Similarly, a longitudinal front view of the main part Model diagram of layer structure of electromagnetic induction heat-generating fixing film (Part 1) Layer structure model diagram of electromagnetic induction heat-generating fixing film (Part 2) The figure which showed the relationship between the speed between recording materials of 3rd Embodiment, and a non-sheet passing part temperature. Cross-sectional side view of the main part of a fixing device using a fixing film Cross-sectional side view of the main part of the fixing device using a heat roller Schematic configuration model diagram of an image forming apparatus

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Heat generating layer 2 Elastic layer 3 Release layer 4 Heat insulation layer 10 and 11 Fixing film (heating member, cylindrical film)
16 Film guide member (support member)
17, 18, 27 Magnetic core, excitation coil, excitation circuit (magnetic field generating means)
26, 27 Temperature detection element 30 Pressure roller (pressure member)
40 Sliding member 41 Heating body 50 Fixing roller 100 Fixing device (heating device)
N Fixing nip (nip area)
P Recording material

Claims (10)

In a heating device for fixing a toner image on the recording material by nipping and conveying the recording material at a nip portion constituted by a fixing rotator and a pressure rotator,
A heating apparatus characterized in that Vi> Vp, where Vp is a conveyance speed when the recording material is passing through the nip portion and Vi is a conveyance speed when the recording material is not passing.   The nth recording material continuously conveyed to the heating device is P (n), and the n + 1th recording material is P (n + 1) {n = 1, 2, 3,. The heating apparatus according to claim 1, wherein the conveyance speed is set to Vi> Vp between P (n) and P (n + 1).   2. The temperature of the fixing rotating body when the recording material passes through the nip portion is Tp, and the temperature when Ti does not pass is Ti <Tp. Or the heating apparatus of Claim 2.   4. The conveying speed in the longitudinal direction of the fixing rotator or the pressure rotator is set such that Vi> Vp according to the temperature of the non-conveying area of the recording material. The heating device according to any one of the above.   5. The heating apparatus according to claim 4, wherein the transport speed Vi is increased or decreased according to a temperature of a non-transport area of the recording material in a longitudinal direction of the fixing rotator or the pressure rotator.   The timing at which the leading end of the recording material enters the nip portion is changed in the longitudinal direction of the fixing rotator or the pressure rotator according to the temperature of the non-conveying area of the recording material. The heating device according to claim 4 or 5.   The heating apparatus according to claim 1, wherein the fixing rotator is a flexible film-like rotator.   The heating apparatus according to claim 1, wherein the fixing rotator of the fixing unit is induction-heated.   7. The fixing rotating body according to claim 1, wherein the fixing rotating body is a flexible film-shaped rotating body, and the film-shaped rotating body is rotated in contact with the periphery of a linear heating element. The heating device described.   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 the recording material, wherein the fixing means is any one of claims 1 to 9. An image forming apparatus, which is the heating apparatus according to item 1.

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