JP4810255B2 - Image heating device - Google Patents

Description

  The present invention relates to an image heating apparatus that is used in an image forming apparatus such as a copying machine, a printer, or a facsimile, and heats an image on a recording material.

  Examples of the image heating device include an image heating and fixing device that fixes an unfixed image on a recording material, and a gloss increasing device that increases the glossiness of an image by heating the image fixed on the recording material.

  An image forming apparatus such as a copying machine or a printer includes an image forming unit and an image heating fixing device (hereinafter referred to as a fixing device) that heats and fixes an unfixed toner image formed on the recording material by the image forming unit on the recording material. And).

  As a fixing device, for example, a toner image is placed on a recording material by applying heat and pressure while nipping and conveying the recording material at a pressure contact portion (fixing nip portion) between a fixing roller and a pressure roller that are in pressure contact with each other and rotating. A heat roller fixing system that melts and fixes the toner is known.

  As a heat source for such a heat roller fixing system, a configuration in which a halogen heater is used and the fixing roller is heated by the radiant heat of the halogen heater is widely known.

  Also, in a high-speed printing apparatus with a high printing speed per hour, both the heating roller and the pressure roller have built-in heaters such as halogens, and each heater is turned on to enable high power heating. Realizes the fixing of mass printing.

  However, in the fixing device having the above-described configuration, each roller needs to have a sufficient heat capacity in order to prevent a temperature drop of the roller at the time of fixing. Transmission efficiency is poor. Therefore, it takes a long wait time to heat the roller.

  Therefore, as another method capable of shortening the wait time, a high-frequency fixing device for fixing by irradiating a high-frequency electromagnetic wave has been devised. Among them, there has been proposed a technique in which a toner image is melted and fixed by directly irradiating a toner image with an electromagnetic wave from a high frequency generator without using a heating or pressing roller (Patent Document 1). Furthermore, a technique has been proposed in which high frequency is guided by a comb-shaped waveguide and is directly irradiated onto a toner image (Patent Document 2).

  In this method, a material having good electromagnetic wave absorption characteristics must be used for the toner material, and there is a problem that the coloring property and the technology for realizing it are difficult. On the other hand, when the electromagnetic wave absorptivity is sacrificed, the heat generation efficiency for heating the toner image is poor, and it is necessary to irradiate electromagnetic waves with a very strong electric field. For this reason, there is a problem that the apparatus becomes large, or there is a problem that the wait time cannot be shortened with a normal electric field. In addition, even if the toner is melted and fixed, the surface of the melted toner remains uneven, so that the fixed image can be uneven, non-glossy and inferior in quality. There was a problem such as.

A configuration that can solve such a problem is not to directly irradiate the toner image with high frequency, but to irradiate the high frequency to a roller sealed with liquid, and pressurize the toner image while fusing the liquid with a roller that generates heat. A fixing device (Patent Document 3) for fixing the toner image has been proposed. However, in this system, the volume of the liquid changes significantly because the liquid generates heat. Therefore, it is difficult to realize a container that stably keeps such a high temperature material in a roller shape, and it is difficult to realize the durability of such a container to the extent that it conforms to the service life of the device. There was a problem.
JP 2003-280421 A Japanese Patent Publication No.61-6386 JP-A-3-293691

  In the fixing device as described above, the size of the device is increased, the thermal efficiency is lowered, the image quality is lowered, the wait time is increased, the durability does not satisfy the device life, and further, There is a problem that it is difficult to realize the apparatus.

  Accordingly, an object of the present invention is to realize an image heating apparatus of an electromagnetic wave (high frequency) heating system that is highly efficient, has a short wait time, and can satisfy the apparatus life.

In order to achieve the above object, a typical configuration of an image forming apparatus according to the present invention is configured to generate an electromagnetic wave by a first rotating body and a second rotating body that heat an image on a recording material at a nip portion. In the image heating apparatus having the electromagnetic wave generator, the shield box that shields the electromagnetic wave, the waveguide that guides the electromagnetic wave generated by the electromagnetic wave generator into the shield box, and the electromagnetic wave guided into the shield box And electromagnetic wave reflecting means for reflecting toward the first rotating body and the second rotating body .

  According to the above apparatus configuration, it is possible to realize an electromagnetic heating type image heating apparatus that is highly efficient, has a short wait time, and can satisfy the apparatus life.

(Reference Example 1)

(1) Image Forming Unit FIG. 1 is a longitudinal sectional view showing a schematic configuration of an electrophotographic full-color copying machine which is an example of an image forming apparatus equipped with an image heating apparatus according to the present invention as a fixing device. First, an outline of the image forming unit will be described.

  Reference numeral 1 denotes an image reading unit (digital color image reader unit), which scans and exposes an image of a color image original O placed on a platen glass 1a by a moving optical system 1b, and performs color separation by a full color sensor (CCD) 1c. Photoelectric reading is performed as an image signal (electrical signal). The color separation image signal is subjected to predetermined image processing by the image processing unit 1 d and then sent to the control unit 100 of the image output unit (digital color image printer unit) 2. Reference numeral 1e denotes a document pressing plate or an automatic document feeder (ADF, RDF).

  The control unit 100 plays a role of driving each load in the image forming apparatus, collecting and analyzing information of sensors, exchanging data with an operation unit, that is, a user interface, and the like. Is controlled by

  In the image output unit 2, UK, UM, UC, and UY are first to fourth image forming units, and are arranged in tandem in the image output unit 2 from the left to the right in the drawing. Each image forming unit is a laser exposure type electrophotographic process mechanism, and has the same configuration.

  That is, in each of the image forming units UK, UM, UC, and UY, 3 is a drum-type electrophotographic photosensitive member (hereinafter referred to as a drum), which is driven to rotate counterclockwise as indicated by an arrow. 4 is a primary charger that uniformly charges the outer peripheral surface of the drum 3, and 5 is a laser that scans and exposes the uniformly charged surface of the drum 3 with laser light L to form an electrostatic latent image based on a color separation image signal. It is an exposure device. A developing device 6 visualizes the electrostatic latent image on the drum surface as a toner image. The developing device 6 of the first image forming unit UK contains black toner as a developer. The developing device 6 of the second image forming unit UM contains magenta toner. The developing device 6 of the third image forming unit UC contains cyan toner. The developing device 6 of the fourth image forming unit UY contains yellow toner.

  Then, based on the color separation image signal sent from the image processing unit 1 d of the image reading unit 1 to the control unit 100 of the image output unit 2, the first image forming unit UK puts a black toner image on the surface of the drum 3. It is controlled to form at a predetermined control timing. The second image forming unit UM is controlled to form a magenta toner image on the surface of the drum 3 at a predetermined control timing. The third image forming unit UC is controlled to form a cyan toner image on the surface of the drum 3 at a predetermined control timing. The fourth image forming unit UY is controlled to form a yellow toner image on the surface of the drum 3 at a predetermined control timing.

  The toner images formed on the drum surface of each image forming unit are sequentially transferred to the surface of an endless and flexible intermediate transfer belt (hereinafter referred to as a belt) 8 that is rotationally driven by the primary transfer unit 7. Is superimposed and transferred. As a result, an unfixed full-color toner image is synthesized and formed on the surface of the belt 8 by superimposing the four toner images. In each image forming unit, the toner remaining on the drum 3 without being transferred to the belt 8 is removed by the cleaning device 9.

  The belt 8 is stretched between a driving roller 10, a driven roller 11 that also serves as a tension roller, and a secondary transfer counter roller 12. The belt 8 is substantially equal to the rotational speed of the drum 3 in the clockwise direction of the arrow. Driven at the same speed. The primary transfer portion 7 is formed by causing the belt portion between the driving roller 10 and the driven roller 11 to face or contact the lower surface of the drum 3 of each image forming unit. Reference numeral 13 denotes a primary transfer charger disposed on the back side of the belt 8 at the position of each primary transfer portion 7, and a predetermined voltage is applied during the primary transfer of the toner image.

  The unfixed full-color toner image synthesized and formed on the surface of the belt 8 reaches the secondary transfer portion 14 by the subsequent rotation of the belt 8. The secondary transfer portion 14 is formed by pressing the secondary transfer roller 15 with the belt 8 sandwiched between the secondary transfer counter roller 12. A nip portion between the secondary transfer roller 15 and the belt 8 is a secondary transfer portion 14. A sheet-like recording material (transfer material) P is fed to the secondary transfer portion 14 from the paper supply unit 16 side at a predetermined control timing, so that the surface of the belt 8 is placed on the surface of the recording material P. Unfixed full-color toner images are secondarily transferred together in sequence. A predetermined voltage is applied to the secondary transfer roller 15 during the secondary transfer of the toner image.

  The paper feed unit 16 has a plurality of stages of paper feed cassettes 17, 18, and 19, and the single sheet feeding operation of the recording material P from the paper feed cassette of the level selected according to the recording material size or the like is a predetermined control timing Is executed. The fed recording material P is conveyed to the registration roller 21 by the sheet path 20. At that time, the registration roller 21 is stopped, and the leading edge of the recording material P hits the nip portion. Thereafter, the rotation of the registration roller 21 is started in accordance with the timing at which the image forming units UK, UM, UC, and UY start image formation. The rotation start timing of the registration roller 21 is set so that the recording material P and the toner image primarily transferred from the image forming unit onto the belt 8 coincide with each other in the secondary transfer unit 14.

  The recording material P that has undergone the secondary transfer of the toner image from the belt 8 through the secondary transfer portion 14 is separated from the belt surface, and accurately conveyed to the fixing nip portion N of the fixing device (fixing unit) 40 by the conveyance guide 22. Guided. The recording material P is nipped and conveyed at the fixing nip portion N, and the toner image is fixed on the surface of the recording material P by heat and pressure during the conveyance process. The recording material P that has exited the fixing nip N of the fixing device 40 is transported by the internal and external paper discharge rollers 23 and 24 and stacked on the paper discharge tray 25.

  Reference numeral 26 denotes a cleaning unit for cleaning the image forming surface of the belt 8. In the secondary transfer portion 14, toner remaining on the belt 8 without being transferred to the recording material P is removed by the cleaning unit 26.

(2) Fixing device 40
FIG. 2 is a cross-sectional side view showing a schematic configuration of a fixing device 40 as an image heating device in this reference example , and FIG. 3 is a longitudinal front view taken along line (3)-(3) of FIG.

  Here, with respect to the fixing device, the longitudinal direction is the axial direction of the heating / pressure roller. With respect to the fixing device, the front side is the recording material carry-in port side. Regarding the fixing device, left and right are left and right when the fixing device is viewed from the front.

  Reference numerals 41 and 42 denote a pair of a first rotating body and a second rotation for heating and pressurizing the recording material P (image on the recording material) on which the toner image t is formed, which is conveyed to the fixing device 40. A heating / pressure roller as a body (hereinafter referred to as first and second fixing rollers). The first and second fixing rollers 41 and 42 are arranged to press each other and form a fixing nip portion N for nipping and conveying the recording material P.

  The first and second fixing rollers 41 and 42 serve as a casing of the fixing device 40 and have a horizontally long box-shaped shield having six front plates 44a to 44f on the front surface, the rear surface, the upper surface, the lower surface, the left surface, and the right surface. In the box 44, they are arranged substantially in parallel in the vertical direction and in pressure contact with each other.

  The shield box 44 (hereinafter referred to as a box) is made of a metal plate such as aluminum, copper, and stainless steel that has an effect of reflecting and shielding electromagnetic waves (high frequencies such as microwaves: hereinafter referred to as microwaves). . That is, the box 44 is configured to surround the first and second fixing rollers 41 and 42 and the microwave w irradiated into the box 44 as will be described later. I try not to leak outside.

  In the first fixing roller 41, the left and right end portions of the central shaft 41a are rotatably supported via bearing members 50 between the left and right side plates 44e and 44f of the box 44, respectively. The second fixing roller 42 is also rotatably supported at both left and right end portions of the central shaft 42a between the left and right side plates 44e and 44f of the box 44 via a bearing member 51, respectively. Then, the first and second fixing rollers 41 and 42 are pressed against the elasticity of the elastic layers 41e and 42e of both rollers by an urging means (not shown) so as to be predetermined in the recording material conveyance direction a. A fixing nip N having a width is formed.

  The left end portion of the central shaft 41a of the first fixing roller 41 protrudes from the bearing member 50 to the outside of the box, and a gear G1 is fixed to the shaft end portion. Further, the left end portion of the center shaft 42a of the second fixing roller 42 is also projected out of the box from the bearing member 51, and the gear G2 is fixed to the shaft end portion. The gear G1 and the gear G2 are meshed. When the rotational force of the fixing rotation motor M is transmitted to the gear G1 via a gear train (not shown), the first fixing roller 41 is rotationally driven in the clockwise direction indicated by an arrow in FIG. In conjunction with this, the second fixing roller 42 is driven to rotate counterclockwise as indicated by the arrow in FIG. The gear ratio between the gear G1 and the gear G2 is set so that the rotational peripheral speeds at the fixing nip portion N of the first and second fixing rollers 41 and 42 are substantially the same.

  In the box 44, the front plate 44a is provided with a slit-shaped recording material carry-in port 44g along the longitudinal direction (left and right direction) at a substantially central portion. The rear plate 44b is provided with a slit-shaped recording material outlet 44h along the longitudinal direction at a substantially central portion.

  On the outer surface side of the upper surface plate 44c and the lower surface plate 44d, upper and lower waveguides (waveguides) 45 and 46 are provided along the length of the outer surface, respectively. Both the waveguides 45 and 46 are made of a metal such as aluminum, copper, and stainless steel that has the effect of reflecting and shielding a high frequency wave, like the box 44. The left end portions 45a and 46a of the waveguides 45 and 46 are closed. The right end portions of the waveguides 45 and 46 are extended and communicated with the outer surface side of the right side plate 44f. A microwave generator 43 as electromagnetic wave generating means is disposed outside the box 44 in the middle of the extended waveguide.

A plurality of openings (a plurality of openings) for irradiating the microwave w from the upper waveguide 45 into the box 44 along the waveguide 45 are formed on the surface portion of the upper surface plate 44c where the upper waveguide 45 is located. Small holes) 44i. A plurality of openings 44j for irradiating the microwave w into the box 44 along the waveguide 46 are provided on the surface portion where the lower waveguide 46 of the lower surface plate 44d is located.
That is, in the fixing device 40, the first and second fixing rollers 41 and 42 are disposed in the shield box, and the microwave generator (electromagnetic wave generator) 43 is disposed outside the shield box. The microwave generator 43 is connected to the first fixing roller 41 and the second fixing roller 42 by the waveguides 45 and 46.

  Microwaves generated from the microwave generator 43 are divided into two directions, ie, upper and lower waveguides 45 and 46, and are guided to the upper surface plate 44c side and the lower surface plate 44d side of the box 44. The microwave guided to the upper surface plate 44c enters the box 44 through the opening 44i, and mainly irradiates the first fixing roller 41 from the outside of the roller. The microwave guided to the lower surface plate 44c side enters the box 44 through the opening 44j, and mainly irradiates the second fixing roller 42 from the outside of the roller.

The microwave generator 43 can generate microwaves in an ISM frequency band that can be used for industrial, scientific, and medical radio frequency devices, so-called ISM devices, defined by international treaties. In this reference example , a magnetron capable of generating a microwave having a frequency of 2.45 GHz is used.

The first and second fixing rollers 41 and 42 in the present reference example are composite layers in which the following first to fourth layers are adhered in order from the metal central shafts 41a and 42a to the outside. It is a cylindrical roller having a structure. The first layer is a heat insulating layer 41b / 42b, the second layer is a heat generating layer 41c / 42c, the third layer is a heat conducting layer 41d / 42d, and the fourth layer is an elastic layer 41e / 42e.

  The heating layers 41c and 42c (first and second heating elements) are made of microwave absorbers that absorb microwaves and generate heat. The first and second fixing rollers 41 and 42 are heated by the heat generation layers 41c and 42c absorbing the microwave w irradiated from the outside and generating heat.

In this reference example , the following ceramics are used as the heat generating layers 41c and 42c. That is, the shape of the rotating body is adjusted so that a raw material obtained by mixing powders such as SiC (silicon carbide) or ferrite and a small amount of SiN (silicon nitride) matches the shapes of the first and second fixing rollers 41 and 42. It is a ceramic that has been pressed and sintered. As the material of the heating element, a material having a high dielectric loss coefficient is convenient. For example, SiC (silicon carbide) has a dielectric loss coefficient of 0.33 or more. In practice, if the dielectric loss coefficient is 0.2 or more, a heat quantity sufficient to fix the toner image can be generated without reducing the recording material conveyance speed of the image forming apparatus in which the fixing device is incorporated. I can do things.

  As a material that absorbs high frequencies and generates heat, liquids such as water and alcohol have heat generation characteristics that can be used as a fixing device. However, to absorb high frequency efficiently, a certain capacity or more is required, which is not suitable for realizing a small-sized device, cannot reach a temperature higher than the boiling point of the liquid, or seals the liquid. It is difficult to configure the container to be used. In addition, if the container is damaged or the like, liquid leaks and affects the surrounding mechanisms and devices. Therefore, the heating element is preferably in a solid state (solid) having no fluidity at least within a temperature range for fixing a toner image from room temperature.

The heat insulating layers 41b and 42b between the central shafts 41a and 42a and the heat generating layers 41c and 42c prevent the heat of the heat generating layer from conducting through the central shaft and escaping to the outside. The heat insulating layers 41b and 42b are made of, for example, a heat insulating material that hardly absorbs microwaves, such as quartz wool or alumina (Al ₂ O ₃ ).

  The heat conductive layers 41d and 42d (first and second heat conductive members) are configured uniformly, and the heat generating layers 41c and 42c are uniformly disposed on the inner surface thereof. The heat conductive layers 41d and 42d are material layers having a dielectric loss coefficient smaller than that of the heat generating layers 41c and 42c and having a higher thermal conductivity than that of the heat generating layers 41c and 42c. The purpose of disposing the heat conductive layers 41d and 42d outside the heat generating layers 41c and 42c is to efficiently diffuse the heat generated in the heat generating layers 41c and 42c so that the length of the elastic layers 41e and 42e in contact with the recording material P is longer. The surface temperature distribution in the direction and circumferential direction is made uniform. That is, the temperature distribution in the longitudinal direction and the circumferential direction of the first and second fixing rollers 41 and 42 is made uniform. The heat conductive layers 41d and 42d are brought into close contact with the outer surfaces of the heat generating layers 41c and 42c, and the heat generating layers are covered with the heat conductive layers. Thereby, the heat conductive layers 41d and 42d act efficiently so as to make the variation in the temperature distribution of the heat generating layers 41c and 42c uniform and transmit them to the elastic layers 41e and 42e, thereby enhancing the above effect.

In this reference example , silicon rubber is used for the heat conductive layers 41d and 42d. Silicone rubber is difficult to absorb microwaves and has high thermal conductivity. By disposing silicon rubber as the heat conductive layers 41d and 42d on the sheet passing surface side of the heat generating layers 41c and 42c, the temperature distribution can be made uniform effectively without loss of microwave energy. .

  Silicon rubber has a thermal conductivity of 168 W / (m · K). For this reason, even in a mode in which temperature unevenness (temperature increase of the non-sheet passing portion) is likely to occur in the heating roller 41 and the pressure roller 42 such as continuously passing a small size recording material, the temperature unevenness is 40 ° C. It is suppressed to a range of about, and good fixing becomes possible.

The appropriate thermal conductivity range of the heat conductive layers 41d and 42d is slightly different depending on the method of irradiating the heat generating layer 41c with microwaves, the electric field distribution of microwaves, and the like. However, in the fixing device configuration of this reference example , if the material has a thermal conductivity exceeding about 60 W / (m · K), the temperature unevenness of the heating roller is suppressed within 40 ° C. in use, and the toner image is displayed. Fixing can be performed with almost no unevenness when fixed.

  The elastic layers 41e and 42e (first and second elastic members) are uniformly disposed on the heat conductive layers 41d and 42d. The elastic layers 41e and 42e serve to ensure good fixability, image glossiness, and the like by causing the roller heating surface to closely follow the unevenness of the recording material P and the unevenness of the toner image and closely contacting the recording material surface. Yes. The elastic layers 41e and 42e are made of rubber or the like that has heat resistance and exhibits a property of transmitting microwaves well. The higher the transmittance with respect to the microwave, the more microwaves are applied to the inner heat generating layers 41c and 42c, and heat can be generated efficiently.

In addition, as another reference example , the heat conductive layers 41d and 42d make the temperature distribution of the heat generating layers uniform by arranging heat pipes or the like in close contact with the inside of the heat generating layers 41c and 42c. be able to. At this time, the heat conductive layer also functions as a reflecting member for reflecting the microwaves irradiated from the outside to the first and second fixing rollers 41 and 42. That is, by covering the inner peripheral surfaces of the heat generating layers 41c and 42c, the microwave transmitted through the heat generating layer can be reflected and sent to the heat generating layer again, and the heat generation efficiency can be further increased.

  The first and second fixing rollers 41 and 42 may be further provided with a releasable layer made of fluorine resin or the like as the outermost surface layer.

  Thus, the microwave generated when the microwave generator 43 is turned on is branched into two directions, the upper waveguide 45 and the lower waveguide 46, and the upper surface plate 44 c side and the lower surface plate of the box 44. It is led to the 44d side. The microwave guided to the upper surface plate 44c enters the box 44 through the opening 44i, and mainly irradiates the first fixing roller 41 from the outside of the roller. The microwave guided to the lower surface plate 44c side enters the box 44 through the opening 44j, and mainly irradiates the second fixing roller 42 from the outside of the roller. The first and second fixing rollers 41 and 42 are heated by the heat generation layers 41c and 42c respectively generating heat by absorbing the microwaves transmitted through the elastic layers 41e and 42e and the heat conduction layers 41d and 42d. The With this configuration, it is possible to improve the deviation of the amount of microwave irradiation with respect to the first and second fixing rollers 41 and 42.

  The shafts 41a and 42a of the first and second fixing rollers 41 and 42 are exposed at least from the roller portion in the shield box 44 in order to prevent a discharge phenomenon from occurring due to the microwave irradiation. The shaft portion is provided with insulating coatings 41f and 42f. The insulating coating is a heat-resistant resin or rubber.

  Electrical information regarding the surface temperature of the first fixing roller 41 detected by a temperature sensor TH (not shown) is input to the control unit 100, and the temperatures of the first and second fixing rollers 41 and 42 become predetermined temperatures. The microwave generator 43 is on / off controlled so as to be maintained. That is, the fixing device 40 is temperature-controlled.

  The fixing device 40 is controlled by the control unit 100 when an image forming operation start signal is issued. FIG. 4 is an operation flow showing the operation of the fixing device 40. FIG. 5 is a block diagram of a temperature control system of the fixing device 40.

  Referring to FIG. 4, when the image forming apparatus is activated, control unit 100 turns on microwave generator 43 of fixing apparatus 40 to start temperature adjustment of fixing apparatus 40 (S101). Subsequently, driving of the fixing rotation motor M is also started (S102). When the temperature of the fixing device 40 reaches a predetermined temperature, a printing operation is performed (S104). Even during the printing operation, the temperature control is continued so that the temperature of the fixing device is maintained at a predetermined temperature. When the copying or printing operation of the job set in the image forming apparatus is finished, the temperature of the fixing device 40 is stopped by turning off the microwave generator 43 (S105), and the driving of the fixing rotation motor M is also stopped (S105). S106).

Referring to FIG. 5, control unit 100 is equipped with a CPU 100a. Similarly, the CPU 100a executes various sequences based on a predetermined image forming sequence by a program stored in the ROM 100b mounted on the control unit 100. At that time, the RAM 100c is also mounted to store rewritable data that needs to be stored temporarily or permanently. The control unit 100 includes a microwave control unit 100 d that controls the microwave generator (magnetron) 43 and a motor control unit 100 e that controls the fixing rotation motor M. The microwave control unit 100d includes a high voltage control circuit and a filament voltage control circuit necessary for the operation of the microwave generator 43. The control units 100d and 100e are controlled by the CPU 100a.
Then, electrical information regarding the surface temperature of the first fixing roller 41 detected by a temperature sensor TH (not shown) is input to the CPU 100a via the A / D converter 100d. That is, the analog value output from the temperature sensor TH according to the temperature change of the first fixing roller 41 is input to the CPU 100a of the control unit 100 by the A / D converter 100d as a digital value. Based on this temperature data, the CPU 100a controls the microwave control unit 100d and turns on / off the microwave generator 43, whereby the first and second fixing rollers 41 and 42, that is, the temperature of the fixing device. Tones.

  When the first and second fixing rollers 41 and 42 are driven to rotate and the fixing device is heated to a predetermined fixing temperature, an unfixed toner image t is formed on the surface from the secondary transfer unit 14 side. The recording material P thus introduced is introduced into the fixing device 40 from the recording material carry-in port 41g. Then, the toner enters the fixing nip portion N which is a pressure contact portion between the first and second fixing rollers 41 and 42 and is nipped and conveyed through the fixing nip portion N. The first fixing roller 41 contacts the recording material surface side of the recording material P, which is the unfixed toner image carrying surface side, and the second fixing roller 42 contacts the recording material rear surface side on the opposite side.

  In the process in which the recording material P is nipped and conveyed through the fixing nip portion N, the unfixed toner image t on the recording material P is heated by the heat of the first and second fixing rollers 41 and 42 and the pressure of the fixing nip portion N. It is fixed to the surface of the recording material P by heat and pressure. By fixing the toner image by melting and simultaneously pressurizing the toner with the heated first and second fixing rollers 41 and 42, it is possible to realize fixing with glossy and high image quality. The recording material P that has exited the fixing nip N is separated from the surfaces of the first and second fixing rollers 41 and 42 and is sent out of the fixing device through the recording material carry-out port 44h. WP is the maximum sheet passing width of the recording material with respect to the fixing device 40.

  As described above, the first and second fixing rollers 41 and 42 as the counter rollers are provided with the heat generating layers 41c and 42c by the microwave absorber. Both rollers 41 and 42 are arranged in a common shield box 44. Then, the microwave from the common microwave generator 43 is branched in two directions using the conductive paths 45 and 46 so as to irradiate both the rollers 41 and 42 arranged in the shield box 44 respectively. And configured to be heated equally. With this configuration, the first and second fixing rollers 41 and 42 that are the pair of rollers can be heated uniformly, and the fixing device for high-speed printing is highly efficient by using microwaves effectively. It can be realized at high speed. That is, a fixing device for high-speed printing that heats the pair of rollers 41 and 42 at the same time can be realized by using an efficient microwave heating method.

  Further, according to the present configuration, the start-up time can be shortened, and at the same time, the conventional configuration in which the pressure is applied between the pair of rollers 41 and 42 to be fixed can be followed. Accordingly, the above-described effects can be obtained, and at the same time, high image quality can be realized by heating and pressure fixing.

  Further, the heat conductive layers 41d and 42d are disposed inside the elastic layers 41e and 42e, and the heat generating layers 41c and 42c are disposed in close contact with the inner surfaces of the heat conductive layers 41d and 42d. With this configuration, temperature unevenness generated in the heat generating layers 41c and 42c is diffused in the heat conductive layers 41d and 42d, and the temperature distribution on the surfaces of the elastic layers 41e and 42e that directly heat the recording material P can be made uniform. For this reason, it is possible to obtain an effect that it is possible to realize a higher-quality fixed image without uneven fixing.

In the above reference example , the microwaves emitted from the common microwave generator 43 are branched in two directions using the waveguides 45 and 46. The configuration in which microwaves are irradiated from the respective directions corresponding to the two first and second fixing rollers 41 and 42 arranged vertically in the shield box 44 from the vertical direction of the fixing unit 40 has been described. However, it is not limited to this . That is, the microwaves are branched in a plurality of directions, and the branched microwaves are irradiated in correspondence with the first and second fixing rollers 41 and 42 disposed in the fixing unit 40, respectively. Just do it. Therefore, for example, in addition to the up and down direction, the first and second fixing rollers disposed in the shield box 44 are guided from each of the added directions by introducing the microwave in the direction of the recording material carry-in port 44g and the recording material carry-out port 44h. This includes the case of irradiating microwaves corresponding to 41 and 42. Further, the member to be heated and the number of the members are not limited to the pair of rollers, but include a case where microwaves are guided and irradiated to the added heating member.

In the fixing device 40 described above, a magnetron capable of generating a microwave with a frequency of 2.45 GHz is used as the microwave generator 43 which is a high-frequency generating means. However, the present invention is not limited to this. It is not a thing. For example, an oscillator capable of generating a high frequency of about 30 GHz called a millimeter wave may be used as the high frequency generation means.
(Reference Example 2)

FIG. 6 is a longitudinal front view showing a schematic configuration of the fixing device 40 in this reference example . Constituent members / portions common to the fixing device 40 of Reference Example 1 are denoted by the same reference numerals, and description thereof is omitted.

In this reference example , each of the first and second fixing rollers 41 and 42 has a three-layer laminated structure of heat generation layers 41c and 42c, heat conduction layers 41d and 42d, and elastic layers 41e and 42e in order from the inside to the outside. It is a cylindrical roller.

  The heat conductive layers 41d and 42d (first and second heat conductive members) are configured uniformly. The heat generating layers 41c and 42c (first and second heat generating elements) are uniformly and closely arranged on the inner surfaces of the heat conductive layers 41d and 42d. The elastic layers 41e and 42e (first and second elastic members) are uniformly disposed on the heat conductive layers 41d and 42d.

  Disc-shaped microwave shielding plates 41g and 42g are joined to the left end portions of the first and second fixing rollers 41 and 42, respectively, to close the left opening portion of the cylindrical roller. The shielding plates 41g and 42g prevent or suppress the microwave irradiated to the inner space 41i of the first and second fixing rollers 41 and 42 from leaking to the outside from the left opening of the cylindrical roller, respectively. To do. Further, ring-shaped microwave shielding plates (roller-side shielding plates) 41h and 42h are joined to the right end portions of the first and second fixing rollers 41 and 42, respectively.

  The first and second fixing rollers 41 and 42 are arranged substantially in parallel in the vertical direction, and are rotatably supported between support members (not shown). Further, the rollers 41 and 42 are pressed against the elasticity of the elastic layers 41e and 42e by a biasing means (not shown) to form a fixing nip portion N having a predetermined width in the recording material conveyance direction. The first and second fixing rollers 41 and 42 are rotationally driven in a recording material nipping and conveying direction by a fixing rotation motor (not shown).

A waveguide 47 is provided with a microwave generator (magnetron) 43. The waveguide 47 is branched in two directions, the upper branch waveguide 47a from the opening of the ring-shaped microwave shielding plate 41h at the right end of the first fixing roller 41, and the inside of the first fixing roller 41. It faces the empty space 41i. Further, the lower branching waveguide 47 b faces the inner space 42 i of the second fixing roller 42 from the opening of the ring-shaped microwave shielding plate 42 h at the right end of the second fixing roller 42. Reference numerals 47c and 47d denote waveguide-side shielding plates, and the waveguide-side shielding plate 47c is disposed close to the ring-shaped microwave shielding plate 41h at the right end on the first fixing roller 41 side. The waveguide-side shielding plate 47d is disposed close to the ring-shaped microwave shielding plate 42h at the right end portion on the second fixing roller 42 side. The shielding plate 41h and the shielding plate 47c prevent or suppress the microwave irradiated to the inner space 41i of the first fixing roller 41 from leaking to the outside from the right opening of the cylindrical roller. The shielding plate 42h and the shielding plate 47d prevent or suppress the microwaves irradiated to the inner space 42i of the second fixing roller 42 from leaking to the outside from the right opening of the cylindrical roller. The shielding plates 41g, 42g, 41h, 42h, 47c, 47d are made of a metal plate such as aluminum, copper, and stainless steel that reflects and shields microwaves.

  The microwave generated from the microwave generator 43 is divided into two directions, that is, an upper waveguide 47a and a lower waveguide 47b of the waveguide 47, and the microwave branched in the upper direction is the inner space of the first fixing roller 41. Guided to part 41i. Further, the microwave branched in the downward direction is guided to the inner space 42 i of the second fixing roller 42.

  The microwave w guided to the inner space 41 i of the first fixing roller 41 is absorbed by the heat generation layer 41 c that forms the inner wall of the fixing roller 41 and generates heat by absorbing the microwave. The heat generating layer 41c generates heat. The heat generated in the heat generating layer 41c is diffused in the heat conductive layer 41d disposed in close contact with the outside. Thereby, temperature unevenness caused by unevenness of microwave irradiation and unevenness of loss factor (εr * tanδ) of the heating element is reduced, and the temperature distribution on the surface of the elastic layer 41e is made uniform.

  The microwave w guided to the inner space 42 i of the second fixing roller 42 is absorbed by the heat generation layer 42 c that forms the inner wall of the fixing roller 42 and generates heat by absorbing the microwave. The heat generating layer 42c generates heat. The heat generated in the heat generating layer 42c is diffused in the heat conductive layer 42d disposed in close contact with the outside. Thus, temperature unevenness caused by unevenness of microwave irradiation and unevenness of the loss factor (εr * tanδ) of the heating element is reduced, and the temperature distribution on the surface of the elastic layer 42e is made uniform.

Since the control including the temperature control of the fixing device 40 is the same as that of the fixing device 40 of Reference Example 1 , the description thereof is omitted.

  The pressurization between the first and second fixing rollers 41 and 42 is performed by a mechanical pressure (not shown) (for example, pressurization by a spring force), for example, the first and second fixing rollers 41 and 42. The two fixing rollers 41 and 42 are added to both or one of the rotation shafts 41a and 42a. The same pressure is also applied to the other ends of the first and second fixing rollers 41 and 42, but this is configured to be applied from the outer wall or the inner wall of the roller.

In this reference example , the shield box 44 is omitted. This is because the fixing device of this configuration irradiates the inside of the roller with the microwave w, so that the microwave is absorbed almost 100% by the material and the configuration of the heat generating layers 41c and 42c in the roller. Further, the configuration of the shielding plates 41g and 42g, 41h and 47c, and 42h and 47d can suppress the leakage of microwaves to the outside of the first and second fixing rollers 41 and 42 to almost 0 [mW / Cm ² ]. It depends. Therefore, if the leakage cannot be suppressed, the present invention is not limited to this, and it is necessary to place the fixing unit in a shield box.

According to the fixing device 40 of the above reference example , in addition to the effect of the fixing device 40 of the reference example 1, the following effect can be obtained. That is, since the microwaves are irradiated to the inside of each of the rollers 41 and 42, microwave leakage can be easily reduced by increasing the microwave absorption efficiency of the heating element disposed in each roller. The effect that the shield box 44 is unnecessary can be obtained.
(Example)

  FIG. 7 shows the fixing device 40 of the system in which the upper and lower first and second fixing rollers 41 and 42 are heated by irradiating microwaves from the outside of the rollers. The structure which compensates the dispersion | variation in microwave irradiation amount is shown. The configurations of the first and second fixing rollers 41 and 42 are the same as those of the first and second fixing rollers 41 and 42 of the first embodiment.

  Reference numeral 48 denotes a microwave reflection plate (electromagnetic wave reflection means) disposed in the shield box 44. The waveguide 45 is constructed and arranged to irradiate the microwave w into the shield box 44 from the upper part of the fixing device 40 and from the entrance 44g of the recording material P. A microwave generator (not shown) as electromagnetic wave generating means is disposed outside the shield box 44. The waveguide 45 guides the microwave generated from the microwave generator to the above position.

  The microwave w irradiated from the waveguide 45 hits the reflection plate 48. The reflection plate 48 uniformly irradiates the upper first fixing roller 41 and the lower second fixing roller 42 with the microwave w irradiated from the waveguide 45.

  In order to perform the function, the reflecting plate 48 has an upper roller irradiation surface 48 a that reflects microwaves to the first fixing roller 41, and a lower roller irradiation surface 48 b that reflects microwaves to the second fixing roller 42. It is comprised.

  With the above configuration, the first and second fixing rollers 41 and 42 having the heat generating layers 41c and 42c in the inside generate heat in substantially the same manner, and heat of the heat generating layer is provided in the heat conductive layer 41d disposed inside each roller. -Diffused and uniformized by 42d. Thereby, it is possible to obtain a uniform fixed image by uniformly heating the total surface of the elastic layers 41e and 42e provided on the outer circumferences of the rollers 41 and 42.

  Since the upper and lower first and second fixing rollers 41 and 42 are similarly heated by this configuration, it is possible to make the heating temperature rise time from the normal temperature to the fixing temperature uniform. Furthermore, it is possible to control the temperatures of the rollers 41 and 42 substantially the same while using one microwave generator 43 in common.

  The fixing device 40 of this embodiment guides the electromagnetic wave w into the shield box 44 by a simple waveguide 45 having one path. Then, the electromagnetic wave w guided into the shield box 44 is used to uniformly irradiate the pair of first and second fixing rollers 41 and 42 using the reflector 48 disposed in the shield box 44. Configured. As a result, the pair of rollers 41 and 42 can be heated equally, so that an effect image can be obtained that enables efficient electromagnetic wave heating with a simple configuration.

A longitudinal sectional view showing a schematic configuration of the image forming apparatus in Reference Example 1 . Cross-sectional side view showing schematic configuration of fixing device Longitudinal front view along line (3)-(3) in FIG. Operation flow showing the operation of the fixing device Block diagram of temperature control system for fixing device Longitudinal front view showing a schematic configuration of the fixing device in Reference Example 2 . Cross-sectional side view showing a schematic configuration of the fixing device in the embodiment

  DESCRIPTION OF SYMBOLS 40 ... Fixing unit (fixing apparatus), 41 ... 1st heating and pressure roller, 42 ... 2nd heating and pressure roller, 43 ... Microwave generator, 44 ... Shield box, 45, 46 ... Waveguide, 41a, 42a ... roller rotation shaft, 41b, 42b ... heat insulation layer, 41c, 42c ... heat generation layer, 41d, 42d ... heat conduction layer, 41e, 42e ... elastic layer, 44g ... recording material carry-in port, 44 ... recording material carry-out port

Claims (1)

In an image heating apparatus having a first rotating body and a second rotating body that heat an image on a recording material at a nip portion, and an electromagnetic wave generator that generates an electromagnetic wave,
A shield box that shields electromagnetic waves, a waveguide that guides electromagnetic waves from the electromagnetic wave generator into the shield box, and electromagnetic waves guided into the shield box to the first rotating body and the second rotating body. An image heating apparatus comprising: an electromagnetic wave reflecting means that reflects toward the screen.

Images