JP4933174B2 - Image heating apparatus and image forming apparatus - Google Patents

Description

The present invention is used in an image forming apparatus that employs an electrophotographic process, an electrostatic recording process, or the like, typified by a copying machine, a printer, a facsimile, or a complex machine thereof, and heats an image on a recording material. The present invention relates to an induction heating type image heating apparatus .

Examples of the image heating device include a fixing device that heats and fixes an unfixed image formed on a recording material as a fixed image, and a glossiness increasing device that increases the glossiness of an image by heating the image fixed on the recording material. Can be mentioned.

An electrophotographic image forming apparatus comprises a heating device for heating and fixing an unfixed toner image is formed and held on the sheet-like recording material on a material to be heated as a solid Chakugazo.

  This heating device generally includes a rotary heating element that heats and melts the toner on the recording material, and a pressurizing unit that presses the recording material and sandwiches the recording material.

  The rotary heating element is, for example, a heating roller or an endless belt, and is directly or indirectly heated from the inside or the outside by the heating element. Examples of the heating element include a halogen heater and a resistance heating element.

  In recent years, since the emphasis has been on achieving energy savings in image forming devices and improving user operability (quick printing, shortening warm-up time), the induction heating method with high heat generation efficiency was used. A heating device has been proposed.

  This induction heating device generates an induction current (eddy current) in the rotating heating element by applying a high-frequency current to an exciting coil that generates a magnetic field, and the rotating heating element itself generates Joule heat by the skin resistance of the rotating heating element itself. Let

  According to this induction heating type heating apparatus, the heat generation efficiency is extremely improved, and therefore it is possible to shorten the warm-up time.

As an arrangement of the exciting coil in such an induction heating device, as shown in FIG.
(A) When the winding direction of the exciting coil is parallel to the rotating direction of the rotating heating element (b) The winding direction of the exciting coil can be broadly divided into a case where the winding direction makes an angle with the rotating direction of the rotating heating element.

  In the arrangement method (a), since the magnetic flux generated by the exciting coil leaks outside the rotating heating element, the periphery of the rotating heating element may be heated. Moreover, in order to prevent leakage of magnetic flux, a member for shielding the magnetic flux is required. For this reason, the arrangement method of (b) is advantageous because the heating device becomes large.

  However, in the arrangement method of (b), as shown in FIG. 23, when the winding center part of the exciting coil is tightly wound, a current in the opposite direction flows in the adjacent windings. Each acts in the direction of cancellation. For this reason, the amount of heat generation is reduced at the portion of the rotating heating element that faces the winding center of the exciting coil.

On the other hand, even when the winding center portion of the exciting coil is loosely wound, the amount of heat generation is reduced because the amount of magnetic flux generated in the winding center portion is small. Thus, the arrangement method of (b), with respect to the rotational direction of the rotary heat generator, Ru difficult der be uniformly heated.

  Examples of the arrangement method (b) include Patent Documents 1 to 5 and the like. For example, in Patent Document 1, the exciting coil is wound along the curved surface of the rotating heating element at the upstream portion of the fixing nip of the rotating heating element, and is wound around the ferrite core at the downstream portion of the fixing nip, thereby The heat distribution is different. According to this configuration, heat generation is concentrated on the upstream portion of the fixing nip, so that heat necessary for heating the recording material is generated immediately before the nip. Improves sex. Further, since the fixing nip and the recording material can be intensively heated, the separability can be improved.

  However, in the configuration of Patent Document 1, since heat generation is concentrated before and after the fixing nip portion, temperature unevenness occurs in the rotation direction of the rotary heating element. That is, if heat generation is simply concentrated before and after the fixing nip portion, temperature unevenness occurs in the rotation direction of the rotating heating element at the start of the apparatus. The same applies to Patent Document 2.

  Therefore, in order to improve the temperature unevenness, at the start of the heating operation, the rotary heating element must be idled for a while, so that the quick print performance is inferior.

  In addition, a method of improving the temperature unevenness in the rotation direction of the rotating heat generating element by rotating the rotating heat generating element continuously or intermittently during standby without performing the fixing operation is also conceivable. However, in this case, there are problems such as noise during standby and an increase in power consumption.

Therefore, as in Patent Documents 3 and 4, a configuration is provided in which coils are arranged in substantially the entire region in the rotation direction of the heat generating roller so that the heat generating roller generates heat substantially uniformly in the circumferential direction and temperature unevenness in the circumferential direction of the heat generating roller is prevented. Are known. According to this configuration, it is not necessary to spend time for eliminating the temperature unevenness, so that the warm-up time can be shortened.
Japanese Patent Laid-Open No. 9-281821 JP 2002-158084 A JP 2001-228771 A JP 2002-328550 A JP-A-9-152798

  However, in the case of the configuration as in Patent Documents 3 and 4, since the configuration in which the circumferential direction of the roller generates heat uniformly, the temperature unevenness can be reduced, but the configuration in which heat is efficiently applied to the recording material. is not. Therefore, there was room for improvement in terms of energy efficiency.

  The reason is that the time required to reach the nip portion after heating is longer on the downstream side than on the upstream side of the nip portion. For this reason, the amount of heat released from the downstream side of the nip is greater than that of the upstream side, and if the same amount of heat is applied, it is more energy efficient to heat the upstream side than the downstream side of the nip. It is.

  Therefore, according to the present invention, in the configuration in which the coil is extended in the direction of the rotation axis of the rotating heating element, energy is used while preventing image defects due to temperature unevenness in the rotating direction of the rotating heating element without idling. An object of the present invention is to provide an induction heating type image heating apparatus with high efficiency.

A typical configuration of the image heating apparatus according to the present invention for achieving the above object includes a rotatable image heating member that generates heat by the action of magnetic flux and heats an image on a recording material, and the image heating member . wound is extended in the rotation axis direction, a first coil that produces a magnetic flux which causes acting on said image heating member, downstream of the nip an upstream side of the first coil in the rotation direction of the image heating member A second coil disposed on the side, electrically connected in series with the first coil, extended in a rotation axis direction of the image heating member and wound to generate a magnetic flux acting on the image heating member, and the image has a pressing body forming a heating member and nip and said image heating member includes a facing portion that generates heat so as to face the respective coils, and a non-facing portion other than the opposing section, wherein in the rotational direction of the length of the facing portion Meter is 1/2 or more relative to the circumferential length of the image heating member, the maximum length of the non-opposing portions in the rotational direction is 1/3 or less relative to the circumferential length of the image heating member image In the heating device, the facing portion of the first coil and the facing portion of the second coil each have two exothermic peak portions in a region facing the coil bundle wire, and two points in the facing portion of the first coil. The calorific value of the exothermic peak portion is larger than the calorific value of the two exothermic peak portions at the opposing portion of the second coil, and the calorific value of the minimum exothermic portion between the two exothermic peak portions at the opposing portion of the first coil. Is larger than the heat generation amount of the minimum heat generation portion between two heat generation peak portions in the facing portion of the second coil .

According to the onset bright, it is possible to circumferential direction of the temperature variations of the rotatable image heating member while improving, efficiently obtained image heating apparatus having high energy efficiency for heating the recording material.

(1) Image Forming Unit FIG. 1 is a schematic configuration diagram of an image forming apparatus in this embodiment. This image forming apparatus is an electrophotographic full-color image forming apparatus (composite machine) having a copying machine function, a printer function, and a facsimile function, in which an induction heating type fixing device is mounted as an image heating apparatus .

  Reference numeral 1 denotes a digital color image reader unit. A color image original O is placed on the original platen glass 2 of the reader unit 1 with the image surface facing downward according to a predetermined placement standard, and the original cover 2a is placed thereon. When the copy start key is pressed, the moving optical system 1a is moved, the original surface is optically scanned, and the original image is photoelectrically read by the full color sensor (CCD) 3 as a color separation image signal. The image signal is processed by the image processing unit 4 and then sent to the controller unit (control circuit unit) 17 of the digital color image printer unit 5. An original document feeder (ADF, RDF) may be mounted on the document table glass 2 to automatically feed the document O onto the document table glass 2.

  In the printer unit 5, UY, UM, UC, and UK are first to fourth image forming units arranged in tandem. Each image forming unit is an electrophotographic process mechanism using a laser scanning exposure unit 18. Based on the image signal sent from the reader unit 1 to the controller unit 17, a yellow toner image is formed on the photosensitive drum surface of the first image forming unit UY at a predetermined control timing. A magenta toner image is formed on the photosensitive drum surface of the second image forming unit UM at a predetermined control timing. A cyan toner image is formed on the photosensitive drum surface of the third image forming unit UC at a predetermined control timing. A black toner image is formed at a predetermined control timing on the photosensitive drum surface of the fourth image forming unit UK.

The color toner images formed on the photosensitive drum surfaces of the image forming units UY, UM, UC, and UK are sequentially superimposed and transferred onto the surface of the intermediate transfer belt 7 by the primary transfer unit 6, respectively. As a result, an unfixed full-color toner image is synthesized and formed on the surface of the intermediate transfer belt 7 by superimposing the four color toner images. The full-color toner image is separated and fed by the secondary transfer unit 8 from the multi-stage cassette paper feed mechanism unit 9, the deck paper feed unit 10, or the MP tray (multi-purpose tray ) 11 at a predetermined control timing. Secondary transfer is performed on the surface of the recording material P in a batch. The above is the image forming means for forming and supporting an unfixed image on the recording material.

The recording material P is separated from the surface of the intermediate transfer belt 7 and introduced into the fixing device 12, and is nipped and conveyed at the fixing nip portion. The full-color toner image unfixed in a sandwich conveying process is fixed as a solid Chakugazo full color on the surface of the recording material P are melted mixed by heat and pressure. The recording material P exiting the fixing device 12 is selectively discharged to the face-up discharge tray 14 or the face-down discharge tray 15 by the path switching control by the flapper 13.

  When the double-sided printing mode is selected, the first-side printed recording material P that has exited the fixing device 12 is sent by the flapper 13 to a sheet path that once leads to the face-down paper discharge tray 15. Then, the recording material P is switch-back conveyed, introduced into the re-conveying sheet path 16, turned upside down, and re-introduced into the secondary transfer unit 8. As a result, a toner image is secondarily transferred and formed on the second surface of the recording material P. Thereafter, the recording material P is introduced into the fixing device 12 as in the case of the first side printing, and the recording material that has been printed on both sides is discharged to the face-up discharge tray 14 or the face-down discharge tray 15.

  The above is the case of the copying machine mode. In the printer mode, an image information signal is input to the controller unit 17 from an external host device 19 such as a personal computer or image reader. The controller unit 17 outputs the image information signal to the laser scanner 18 and causes the image forming apparatus to perform an image forming operation as a printer. In the facsimile reception mode, an image information signal is input to the controller unit 17 from the counterpart facsimile machine 19 as an external device. The controller unit 17 outputs the image information signal to the laser scanner 18 to cause the image forming apparatus to perform an image forming operation as a facsimile receiving apparatus. In the facsimile transmission mode, the controller unit 17 transmits the document image information photoelectrically read by the reader unit 1 to the counterpart facsimile receiving device 19.

(2) Fixing device 12
2A is a schematic front view of the fixing device 12, FIG. 2B is a schematic vertical front view thereof, and FIG. 3 is a schematic cross-sectional side view of a main part of the fixing device and a block diagram of a power supply control system.

Reference numeral 21 denotes a fixing roller as a rotary heating element (rotatable image heating member) , and 22 denotes a pressure roller as a pressure body. The fixing roller 21 and the pressure roller 22 are arranged in parallel vertically between the left and right side plates 32 and 32 of the apparatus frame 31 so as to be rotatably supported, and pressed to form a fixing nip portion N.

  The fixing roller 21 is a hollow roller whose base is a metal conductor layer having a thickness of, for example, about 0.1 mm to 1.5 mm. Examples of metals include conductive magnetic materials such as iron, nickel, and SUS430, and alloys thereof. A heat-resistant release layer made of fluororesin or the like is formed on the outer peripheral surface of the metal conductor layer. In order to improve the quality of the color image, a heat-resistant elastic layer such as silicone rubber or fluorine rubber may be provided between the metal conductor layer and the release layer. The fixing roller 21 is disposed such that both left and right end portions are rotatably supported between the left and right side plates 32 and 32 of the apparatus frame 31 via bearing members 33 and 33.

  The pressure roller 22 has a metal pipe material as a metal core 22a, an outer surface thereof provided with a heat-resistant elastic layer 22b made of silicone rubber and the like, and a release layer 22c made of a fluororesin or the like on the surface of the heat-resistant elastic layer. Laura. The pressure roller 22 is also disposed such that the left and right ends of the cored bar 22a are rotatably supported between the left and right side plates 32 and 32 of the apparatus frame 31 via bearing members 34 and 34, respectively. Then, the bearing members 34 and 34 are pushed up by a biasing member (not shown), and the pressure roller 22 is pressed against the lower surface of the fixing roller 21 with a predetermined pressing force against the elasticity of the elastic layer 22b. A fixing nip portion N having a predetermined nip length is formed in the fixing roller rotation direction.

  A fixing roller driving gear G is concentrically fixed to one end of the fixing roller 21. When the driving force of the driving motor M is transmitted to the driving gear G via a power transmission system (not shown), the fixing roller 21 is rotationally driven at a predetermined speed in the clockwise direction of the arrow a in FIG. Is done. The pressure roller 22 rotates in the counterclockwise direction indicated by the arrow b by following the rotational driving of the fixing roller 21 by the frictional force with the fixing roller 21 in the fixing nip N.

23 is a coil assembly which is arranged by being inserted into a fixing roller (are extended in the direction of the rotation axis of the rotatable image heating member is wound, the magnetic flux generating means having a coil to produce a magnetic flux to be applied to the image heating member) . The coil assembly 23 includes a cylindrical coil holder 24 having a length longer than that of the fixing roller 21 and first and second exciting coils 25A serving as magnetic flux generating means disposed on the outer surface of the coil holder 24. (First coil) and 25B (second coil) . FIG. 4 is an exploded perspective schematic view of the coil holder 24 of the coil assembly 23 and the first and second exciting coils 25A and 25B.

  The coil holder 24 is made of heat-resistant and electrically insulating engineering plastic or the like. The first and second exciting coils 25 </ b> A and 25 </ b> B each have a flat sheet-like shape that is long along the longitudinal direction of the fixing roller 21 by using an electric wire in which a litz wire having a heat-resistant insulating coating is wound and bundled. It is wound around a spiral coil. Then, the first and second exciting coils 25A and 25B are copied to the outer surface of the coil holder 24 with the coil longitudinal direction substantially parallel to the coil holder longitudinal direction at positions approximately opposite to the coil holder circumferential surface by 180 °. These are fixedly arranged. In the present embodiment, the coils 25A and 25B are fixed to the outer surface of the coil holder 24 by pressing with a heat-shrinkable tube. Other fixing means such as attachment with an adhesive can be used.

  In this embodiment, the first and second exciting coils 25A and 25B are connected in series, the first exciting coil 25A is wound by 12 turns, and the second exciting coil 25B is wound by 10 turns.

  The coil assembly 23 is inserted into the fixing roller 21, and the left and right ends of the coil holder 24 protrude outward from the left and right ends of the fixing roller 21, respectively. The protruding left end portion is fitted into and supported by the fitting hole 35a of the left bracket 35 disposed on the left plate 32 side of the apparatus frame 31, and the right end portion of the right bracket 36 disposed on the right plate 32 side. A fitting hole 36a is fitted and supported. In the present embodiment, the right end portion is a D-shaped portion (D-shaped cut end portion), and the fitting hole 36a of the right bracket 36 is also a D-shaped hole corresponding to the fitting portion 36a. As a result, the coil assembly 23 is supported between the left and right brackets 35 and 36 in a non-rotating manner, and in the fixing roller 21, the gap between the inner surface of the fixing roller and the excitation coil is maintained uniformly. .

  In the present embodiment, as shown in FIG. 3, the first excitation coil 25A is positioned upstream of the fixing nip portion N with respect to the fixing nip N, and the second excitation coil 25B is positioned downstream. The coil assembly 23 is supported between the left and right brackets 35 and 36. Hereinafter, the first excitation coil 25A is referred to as an upstream coil, and the second excitation coil 25B is referred to as a downstream coil.

  TH is a temperature sensor that detects the temperature of the fixing roller 21, and is, for example, a thermistor. This temperature sensor TH detects the temperature by being elastically pressed against the outer surface or the inner surface of the fixing roller 21 or disposed close to the non-contact.

  Thus, the drive motor M is turned on by the control sequence signal of the controller unit (control circuit unit) 17 and the power supply terminals d · of the upstream and downstream coils 25A and 25B connected in series from the high frequency power supply 41 are connected. A high frequency current is applied between e. Thereby, a high frequency magnetic field (an alternating magnetic field, an alternating magnetic flux) is generated in each of the upstream and downstream coils 25A and 25B. Due to this high-frequency magnetic field, the metal conductor layer of the rotation-driven fixing roller 21 is inductively heated to heat the fixing roller 21. That is, an eddy current is induced in the metal conductor layer by the action of the high-frequency magnetic field, generating Joule heat, and the fixing roller 21 is heated. The temperature of the fixing roller 21 is detected by the temperature sensor TH, and electrical information related to the temperature of the fixing roller 21 is input to the controller unit 17 via the A / D conversion circuit 42. The controller unit 17 controls the high-frequency current supplied from the high-frequency power supply 41 to the coils 25A and 25B so that the temperature detected by the temperature sensor TH becomes a predetermined optimum temperature and is maintained.

Then, the recording material (heated material) P on which the unfixed toner image T is formed is conveyed from the image forming mechanism side to the fixing device 12. An arrow c is the conveyance direction of the recording material P. The recording material P faces the heated fixing roller 21 on the toner image carrying surface, enters the fixing nip portion N and is nipped and conveyed, and the toner image carrying surface is pressed against the heated fixing roller 21. Thereby, the unfixed toner image T (image on the recording material) is fused as a solid Chakugazo the surface of the recording material P is melted by heat and pressure. The recording material P that has passed through the fixing nip N is separated from the surface of the fixing roller 21 and discharged and conveyed.

  A is the width of the fixing roller effective heating area by excitation of the coils 25A and 25B, B is the maximum sheet passing portion width, and A ≧ B.

  Next, the heat generation distribution in the circumferential direction of the fixing roller 21 will be described with reference to FIG.

As shown in FIG. 5, with respect to the circumferential direction of the fixing roller 21 of this embodiment, the place where the fixing roller 21 and the upstream and downstream coils 25 </ b> A and 25 </ b> B face each other is the facing portion X, and the place where they do not face each other. Is a non-opposing part ( non-opposing part other than the opposing part) .

  The opposed part X has more eddy currents induced than the non-opposed part Y, and generates more heat. On the other hand, since the eddy current induced in the non-opposing portion Y is small, the heat generation amount is small.

  Therefore, if the non-opposing portion Y is too large, a difference in the amount of heat generated in the circumferential direction of the fixing roller 21 will cause temperature unevenness, resulting in poor fixing and uneven gloss due to temperature difference. Further, when a plurality of facing portions X and non-facing portions Y exist in the circumferential direction of the fixing roller, the maximum non-facing portion Y having the largest interval (angle) becomes a problem. On the other hand, when the non-opposing portion Y is small, it is heated by heat conduction from the adjacent opposing portions X and X, so that there is no problem due to temperature unevenness.

  Here, after the fixing roller 21 is stopped and maintained at a predetermined temperature for 1 minute, the A3 image is fixed at a process speed of 300 mm / sec by shaking the sum of the angles of the facing portion X and the angle of the non-facing portion Y. The results obtained are shown in FIG.

  According to FIG. 6, if the total of the facing portions X is 180 ° or more, preferably 210 ° or more and the angle of the maximum non-facing portion Y is 120 ° or less, preferably 90 ° or less, the circumference of the fixing roller 21 is increased. It can be seen that the temperature unevenness in the direction is improved.

  In other words, the total length of the facing portions X is not less than ½ of the circumferential length of the fixing roller 21, desirably 7/12 or more. Further, if the length of the maximum non-facing portion Y is 1/3 or less of the circumference of the fixing roller 21, preferably 1/4 or less, temperature unevenness in the circumferential direction of the fixing roller can be improved.

  Also, during continuous fixing operation, heat is concentrated from the fixing nip N to the upstream region in the fixing roller rotation direction in anticipation of heat being removed from the fixing nip N to the recording material P that is a heated material. By doing so, a good fixed image can be obtained.

In this embodiment, as shown in FIG. 7, the upstream coil 25A is wound 12 turns as a heat generation peak portion in the upstream direction of the fixing roller rotation of the fixing nip portion N, and downstream of the fixing roller rotation of the fixing nip portion N. Wound 10 turns of the downstream coil 25B. That is, the upstream side of the nip portion of the fixing roller 21 has more coil turns than the downstream side. Further, the total angle of the facing portion X was 290 °, and the angle of the maximum non-facing portion Y was 30 °.

A distribution of the heat generation amount in the circumferential direction of the fixing roller 21 at this time is shown in FIG. When the same high frequency current is applied to the coils 25A and 25B, the eddy current induced in the fixing roller 21 has a larger amount of magnetic flux guided into the fixing roller 21 as the number of turns of the coil is larger. The amount of induced eddy current increases and the amount of heat generation increases. That is, the maximum heat generating portion is provided in the upper half of the nip portion of the fixing roller 21. Therefore, it is possible to make a difference in the amount of heat generated between the heat generation peak portion and the other facing portion. That is, it is possible to make a difference in heat generation between the upstream portion and the downstream portion of the nip.

  When a high-frequency current was applied to the fixing device shown in this example at a predetermined power and continuously fixed at a process speed of 300 mm / sec, a good fixed image was obtained. Further, even if the rotation of the fixing roller 21 was stopped during standby, no temperature unevenness occurred in the circumferential direction.

  Further, as Comparative Example 1 with Example 1, as shown in FIG. 9, a fixing device in which the total of the facing portions X is 170 ° and the angle of the maximum non-facing portion Y is approximately 180 ° is prepared. did.

  Further, as Comparative Example 2, as shown in FIG. 10, the fixing roller circumferential direction in which the total of the facing portions X is 240 ° and the angle of the maximum non-facing portion Y is 30 ° is heated almost uniformly. A fixing device was prepared.

  The fixing devices of Comparative Examples 1 and 2 were verified in the same manner as in Example 1.

  As a result, in the fixing device of Comparative Example 1 shown in FIG. 9, a good fixed image was obtained in the continuous fixing operation. However, the temperature unevenness in the circumferential direction of the fixing roller 21 occurs, and idling is necessary during standby.

  On the other hand, in the fixing device of Comparative Example 2 shown in FIG. 10, since the circumferential direction of the fixing roller is heated almost uniformly, there is no need for idling during standby without causing temperature unevenness. However, the recording material cannot be heated efficiently because the upstream side of the nip portion that contributes to fixing is not intensively heated, resulting in a reduction in energy efficiency.

As described above, the total length of the facing portions X having a large heat generation amount is ½ or more, preferably 7/12 or more of the circumferential length of the fixing roller 21 (rotary heating body circumferential length) , and The length of the maximum non-opposing portion Y that generates a small amount of heat (the maximum length of the non-opposing portion in the rotation direction of the rotating heating element) is 1/3 or less of the circumference of the fixing roller 21, preferably 1/4 or less. As a result, the temperature unevenness in the circumferential direction of the fixing roller 21 is improved, so that the fixing roller 21 can be stopped during standby. Here, in standby mode, the temperature adjustment temperature of the fixing roller is set to the predetermined temperature when the image heating start signal is not received for a predetermined time from the state in which the heating process can be performed when the fixing roller temperature reaches the predetermined target temperature. It means when you are waiting for a lowering.

Further, the calorific value of the fixing roller 21 includes the total calorific value in the upstream half area (the upstream half area of the nip portion of the rotary heating element) from the fixing nip N and the downstream half area (nip). The total heat generation amount in the upstream half area) is larger in the upstream half area than in the downstream half area. The facing portion X has a heat generation peak portion, and the heat generation peak portion is arranged in the upstream direction of rotation of the fixing nip portion. Accordingly, the upstream portion of the fixing nip can be efficiently heated, and a good fixed image can be obtained even during the continuous fixing operation.

  That is, the fixing roller 21 which is a rotary heating body has a merit of both local heating and full circumference heating by adopting a pseudo full circumference heating configuration. That is, since the heat generation can be concentrated immediately before the nip portion even though the heating is almost the entire circumference, it is advantageous for speeding up, and the idle power is not required even during standby, so the power consumption is reduced.

  The configuration of the first embodiment described above is not described in order to limit the present invention, and various changes can be made according to the heat fixing apparatus to be applied.

  For example, the fixing roller 21 is exemplified as the rotating heat generating member in the configuration of the first embodiment described above, but the rotating heat generating member can be applied to a flexible metal endless belt 21A such as nickel as shown in FIG. is there. The endless belt 21 </ b> A is suspended and driven between the first and second rollers 26 and 27. The first roller 26 is an elastic roller, and the pressure roller 22 is a metal roller. The pressure roller 22 is pressed against the first roller 26 with the belt 21 </ b> A interposed therebetween, and a fixing nip portion N is formed between the belt 21 </ b> A and the pressure roller 22.

  In the first embodiment, there are two exothermic peak portions, but the number of exothermic peak portions is not limited, and there may be one exothermic peak portion depending on how the exciting coil is wound.

  Furthermore, the number of turns of the exciting coil, the angle between the facing portion X and the non-facing portion Y, and the like may be changed to an optimal configuration in a timely manner.

  Further, in the configuration of the first embodiment, the coils 25A and 25B are arranged inside the fixing roller 21 which is a rotating heating element, but can also be arranged close to the outside of the fixing roller 21 as shown in FIG. It is.

  According to the configuration of the present invention, image defects due to temperature unevenness of the fixing roller can be prevented and heat can be efficiently applied to the recording material without idling for eliminating temperature unevenness. Further, in this embodiment, the configuration is such that the fixing roller is rotated during warm-up, but a configuration in which it does not rotate may be used.

  FIG. 13 is a cross-sectional view schematically showing an induction heating type fixing device according to the second embodiment of the present invention.

  If the gap between the fixing roller 21 serving as a rotating heating element and the exciting coil is large, the magnetic flux guided to the opposing fixing roller portion is reduced. Therefore, eddy currents induced in the fixing roller portion are reduced, and Joule heat generation is also reduced.

  Therefore, in the second embodiment shown in FIG. 13, both the upstream coil 25A and the downstream coil 25B are wound by 10 turns, and the gap with the fixing roller 21 is 1.0 mm for the upstream coil 25A and the downstream side. The coil 25B was set to 3.0 mm.

  Also in this case, as in the first embodiment, the temperature unevenness in the circumferential direction of the fixing roller 21 which is a rotating heating element was improved, and the fixing roller 21 could be stopped even during standby.

  Further, the heat generation amount of the fixing roller 21 is larger in the upstream half region with respect to the rotation direction of the fixing roller 21 from the fixing nip portion N than in the downstream half region. The portion is arranged in the upstream direction of rotation of the fixing nip portion. With this configuration, the upstream portion of the fixing nip can be efficiently heated, so that a good fixed image can be obtained even during the continuous fixing operation.

  The configuration of the second embodiment described above is not described to limit the present invention. For example, the gap between the fixing roller and the excitation coil is variously changed according to the heat fixing apparatus to be applied. It is possible. Also, the second embodiment can be combined with the configuration of the first embodiment described above.

  FIG. 14 is a cross-sectional view schematically showing an induction heating type fixing device according to the third embodiment of the present invention.

  In the exciting coil, if the spacing between adjacent winding lines is large, the magnetic flux density guided to the opposing fixing roller portion is reduced, so that the eddy current induced in the fixing roller portion is reduced and Joule heat generation is reduced.

Therefore, in the third embodiment shown in FIG. 14, the gap with the fixing roller 21 is held at 1.0 mm for both the upstream coil 25A and the downstream coil 25B. The upstream coil 25A was wound by 8 turns so as not to leave a space between the winding lines, and the downstream coil 25B was wound by 8 turns while keeping the spacing of the winding lines at 1.5 mm. That is, in the upstream half area of the nip portion of the fixing roller 21, the interval between adjacent winding lines of the coil is narrower than the downstream half area of the nip portion of the fixing roller 21.

  Also in this case, the temperature unevenness in the circumferential direction of the fixing roller 21 which is a rotating heating element was improved, and the fixing roller 21 could be stopped even during standby.

  Further, the heat generation amount of the fixing roller 21 is larger in the upstream half region with respect to the rotation direction of the fixing roller 21 from the fixing nip portion N than in the downstream half region. The portion is arranged in the upstream direction of rotation of the fixing nip portion. With this configuration, the upstream portion of the fixing nip can be efficiently heated, so that a good fixed image can be obtained even during the continuous fixing operation.

  The configuration of the third embodiment described above is not described to limit the present invention. For example, the intervals between the winding lines of the exciting coil are variously changed depending on the heat fixing apparatus to be applied. It is possible. In addition, the third embodiment can be combined with the configurations of the first and second embodiments described above.

  FIG. 15 is a cross-sectional view schematically showing an induction heating type fixing device according to a mode of Example 4 of the present invention.

  In the fixing device of FIG. 15, the magnetic flux generated in the upstream and downstream coils 25 </ b> A and 25 </ b> B is guided to the magnetic core 28 disposed in the vicinity of the coil, and induces eddy currents in the metal conductor layer of the fixing roller 21. The core 28 is preferably made of a material having a high magnetic permeability and a small self-loss. For example, ferrite, permalloy, sendust, silicon steel plate and the like are suitable.

  Here, if the gap between the core 28 and the fixing roller 21 is large, the magnetic flux guided to the fixing roller 21 is reduced, so that the eddy current induced to the fixing roller is reduced and Joule heat generation is also reduced.

  Therefore, in Example 4 shown in FIG. 15, the gap between the fixing roller 21 and the core 28 is set to 0.5 mm in the upstream portion of the fixing nip portion N in the fixing roller rotation direction and 3.0 mm in the downstream portion. The number of windings of the upstream and downstream coils 25A and 25B was 12 turns, and the gap from the fixing roller 21 was 1.0 mm for both the upstream and downstream coils 25A and 25B.

  Also in this case, the temperature unevenness in the circumferential direction of the fixing roller 21 which is a rotating heating element was improved, and the fixing roller 21 could be stopped even during standby.

  Further, the heat generation amount of the fixing roller 21 is larger in the upstream half region with respect to the rotation direction of the fixing roller 21 from the fixing nip portion N than in the downstream half region. The portion is arranged in the upstream direction of rotation of the fixing nip portion. With this configuration, the upstream portion of the fixing nip can be efficiently heated, so that a good fixed image can be obtained even during the continuous fixing operation.

  The configuration of the fourth embodiment described above is not described to limit the present invention. For example, the number and arrangement of the magnetic cores may be variously changed according to the heat fixing device to be applied. Is possible.

  Further, as shown in FIG. 16, the magnetic core 28 may be disposed only in the vicinity of the first heat generation peak portion where the heat generation amount is large.

  Furthermore, as shown in FIG. 17, the fourth embodiment can be similarly applied to a configuration in which the rotary heating element 21 is disposed between the excitation coil 25 and the magnetic core 28. For example, when the rotary heating element 21 is a thin magnetic belt, the magnetic flux generated by the excitation coil passes through the magnetic belt, and the heat generation efficiency of the magnetic belt is reduced. A configuration shown in FIG. 16 in which the rotary heating element 21 is disposed is suitable.

  Furthermore, the fourth embodiment can be combined with the configurations of the first to third embodiments described above.

  FIG. 18 is a cross-sectional view schematically showing an induction heating type fixing device according to a fifth embodiment of the present invention.

  In the fixing device of FIG. 18, the magnetic fluxes generated by the upstream and downstream coils 25A and 25B are guided to the first magnetic core 28A and the second magnetic core 28B arranged near the coils, respectively. An eddy current is induced in the metal conductor layer of the fixing roller 21.

  Here, if the relative permeability of the first and second cores 28A and 28B is large, the magnetic flux guided to the fixing roller 21 increases. Therefore, the eddy current induced to the fixing roller 21 increases, resulting in Joule heat generation. Will also increase.

  Therefore, in Example 5 shown in FIG. 18, a ferrite core having a relative magnetic permeability of 1800 is used for the first magnetic core 28 </ b> A arranged at the upstream portion of the fixing nip portion N in the fixing roller rotation direction. In addition, a ferrite core having a relative permeability of 1000 was used for the second magnetic core 28B disposed in the downstream portion.

  The number of windings of the upstream and downstream coils 25A and 25B was 12 turns, and the gap from the fixing roller 21 was 1.0 mm for both the upstream and downstream coils 25A and 25B.

  Also in this case, the temperature unevenness in the circumferential direction of the fixing roller 21 which is a rotating heating element was improved, and the fixing roller 21 could be stopped even during standby.

  Further, the heat generation amount of the fixing roller 21 is larger in the upstream half region with respect to the rotation direction of the fixing roller 21 from the fixing nip portion N than in the downstream half region. The portion is arranged in the upstream direction of rotation of the fixing nip portion. With this configuration, the upstream portion of the fixing nip can be efficiently heated, so that a good fixed image can be obtained even during the continuous fixing operation.

  The configuration of the fifth embodiment described above is not described in order to limit the present invention. For example, the relative permeability of the magnetic cores 28A and 28B can be variously changed depending on the fixing device to be applied. It is possible to add.

  Further, the fifth embodiment can be combined with the configurations of the first to fourth embodiments described above.

  FIG. 19 is a cross-sectional view schematically showing an induction heating type fixing device according to a mode of Example 6 of the present invention.

  Also in the fixing device according to the sixth embodiment, the magnetic flux generated in the upstream and downstream coils 25A and 25B is guided to the first magnetic core 28A and the second magnetic core 28B arranged near the coils, respectively. An eddy current is induced in the metal conductor layer of the fixing roller 21.

  Here, in the first and second cores 28A and 28B, if the width in the rotation direction of the fixing roller 21 is large, the magnetic flux guided to the fixing roller 21 increases. Therefore, the eddy current induced to the fixing roller 21 is large. As a result, Joule heat also increases.

  Therefore, in Example 6 shown in FIG. 19, the first and second cores 28 </ b> A and 28 </ b> B are both ferrite cores having a relative magnetic permeability of 1800, and the widths in the rotation direction of the fixing roller 21 are different. Specifically, the first core 28A disposed at the upstream portion of the fixing nip N in the fixing roller rotation direction has a width of 8.0 mm in the fixing roller rotation direction, and the second core 28A disposed at the downstream portion. The width of the core 28B in the fixing roller rotation direction is 5.0 mm.

  The number of windings of the upstream and downstream coils 25A and 25B was 12 turns, and the gap from the fixing roller 21 was 1.0 mm for both the upstream and downstream coils 25A and 25B.

  Also in this case, the temperature unevenness in the circumferential direction of the fixing roller 21 which is a rotating heating element was improved, and the fixing roller 21 could be stopped even during standby.

  Further, the heat generation amount of the fixing roller 21 is larger in the upstream half region with respect to the rotation direction of the fixing roller 21 from the fixing nip portion N than in the downstream half region. The portion is arranged in the upstream direction of rotation of the fixing nip portion. With this configuration, the upstream portion of the fixing nip can be efficiently heated, so that a good fixed image can be obtained even during the continuous fixing operation.

  The configuration of the sixth embodiment described above is not described to limit the present invention. For example, the rotation direction of the fixing rollers of the magnetic cores 28A and 28B can be variously changed depending on the fixing device to be applied. Can be added.

  In addition, the sixth embodiment can be combined with the configurations of the first to fifth embodiments described above.

  FIG. 20 is a cross-sectional view schematically showing an induction heating type fixing device according to a seventh embodiment of the present invention.

  In the fixing device according to the sixth embodiment, the upstream coil 25A and the downstream coil 25B are not connected in series, the upstream coil 25A is supplied with the first high frequency power supply 41A, and the downstream coil 25B is supplied with the second high frequency power supply 41B. Therefore, a configuration is adopted in which a high-frequency current flows. h and i are power supply terminals on the coil 25B side.

  The temperature sensor TH detects the surface temperature of the fixing roller 21. Based on this detection signal, the controller unit 17 applies a high-frequency current to the first high-frequency power source 41A for applying a high-frequency current to the upstream coil 25A and the downstream coil 25B so that the temperature of the fixing roller 21 is optimized. The second high frequency power supply 41B to be applied is controlled.

  Here, if the high frequency current applied to the upstream and downstream coils 25A and 25B has a large frequency, the amount of change in the magnetic flux guided to the fixing roller 21 increases. Increases, and Joule heat generation also increases.

  Therefore, in Example 7 shown in FIG. 20, the first high frequency power supply 41A applies a high frequency current of 40 kHz to the upstream coil 25A, and the second high frequency power supply 41B has a frequency of 20 kHz applied to the downstream coil 25B. A high frequency current was applied.

  The number of windings of the upstream and downstream coils 25A and 25B was 12 turns, and the gap from the fixing roller 21 was 1.0 mm for both the upstream and downstream coils 25A and 25B.

  Also in this case, the temperature unevenness in the circumferential direction of the fixing roller 21 which is a rotating heating element was improved, and the fixing roller 21 could be stopped even during standby.

  Further, the heat generation amount of the fixing roller 21 is larger in the upstream half region with respect to the rotation direction of the fixing roller 21 from the fixing nip portion N than in the downstream half region. The portion is arranged in the upstream direction of rotation of the fixing nip portion. With this configuration, the upstream portion of the fixing nip can be efficiently heated, so that a good fixed image can be obtained even during the continuous fixing operation.

  The configuration of the seventh embodiment described above is not described in order to limit the present invention. For example, the frequency of the high-frequency current applied to the respective excitation coils 25A and 25B depends on the fixing device to be applied. Various changes can be made. Similarly, the amount of current applied to each exciting coil 25A / 25B may be changed.

  Further, as shown in FIG. 21, the seventh embodiment can be applied even when both or one of the upstream coil 25 </ b> A and the downstream coil 25 </ b> B are arranged outside the rotating heat generator 21.

  Furthermore, the seventh embodiment can be combined with the configurations of the first to sixth embodiments described above.

1 is a schematic configuration diagram of an image forming apparatus according to a first embodiment. (A) is a schematic front view of the fixing device in Embodiment 1, and (b) is a schematic front sectional view thereof. Cross-sectional side view of the main part of the fixing device and block diagram of the power supply control system Exploded perspective schematic view of coil holder 24 and first and second exciting coils of coil assembly Schematic explaining the facing and non-facing parts FIG. 3 is a chart showing a temperature difference in the circumferential direction of the fixing roller in the first embodiment. The figure explaining the 1st exothermic peak part and the 2nd exothermic peak part in Example 1. The figure which shows the heat generation distribution of the circumferential direction of a fixing roller in Example 1. FIG. Schematic explaining the form of Comparative Example 1 Schematic explaining the form of Comparative Example 2 Schematic of another configuration of the fixing device of Example 1 (No. 1) Schematic of another configuration of the fixing device according to the first exemplary embodiment (part 2). Schematic explaining the fixing device form of Example 2 Schematic explaining the fixing device form of Example 3 Schematic explaining the fixing device form of Example 4 Schematic of the other configuration of the fixing device of Example 4 (Part 1) Schematic of another configuration of the fixing device of Example 4 (part 2) Schematic explaining the fixing device form of Example 5 Schematic explaining the fixing device form of Example 6 Schematic explaining the fixing device form of Example 7 Schematic of another configuration of the fixing device according to the seventh exemplary embodiment. Schematic explaining the arrangement of a general exciting coil and rotating heating element Schematic explaining the direction of the magnetic flux generated by the exciting coil and the calorific value distribution

Explanation of symbols

  17 .. Controller part (CPU), 21 .. Rotating heating element (fixing roller), 22 ..Pressurizing body (pressure roller), 23 .. Coil assembly, 24 .. Coil holder, 25 (25 A and 25 B) ..Excitation coil 28 (28A / 28B) Magnetic core 41 (41A / 41B) High frequency power supply TH Temperature sensor (temperature detection means) P Recording material T Unfixed toner Image, N ... fixing nip

Claims (7)

A rotatable image heating member that generates heat by the action of magnetic flux and heats an image on the recording material, and a first magnetic flux that is stretched and wound in the rotation axis direction of the image heating member to act on the image heating member . A coil and an image heating member disposed upstream of the first coil and downstream of the nip portion in the rotational direction of the image heating member, and electrically connected in series with the first coil; And a second coil that generates a magnetic flux that acts on the image heating member, and a pressure member that forms a nip portion with the image heating member. a facing portion that generates heat so as to face the respective coils, and a non-facing portion other than the opposing section, the total length of the facing portion in the direction of rotation, the circumferential length of the image heating member with respect to Te is 1/2 or more, in the rotational direction In the maximum length of kicking the non-facing portion image heating apparatus is less than one third the circumferential length of the image heating member,
The opposing portion of the first coil and the opposing portion of the second coil each have two exothermic peak portions in the region facing the coil bundle wire, and two exothermic peak portions in the opposing portion of the first coil. The calorific value is larger than the calorific value of the two exothermic peak parts at the opposing part of the second coil, and the calorific value of the minimum exothermic part between the two exothermic peak parts at the opposing part of the first coil is An image heating apparatus having a heat generation amount greater than a heat generation amount of a minimum heat generation portion between two heat generation peak portions at opposing portions of two coils . Claim 1, wherein the gross calorific value of region upstream half is greater than the total amount of heat generated region of the downstream half portion of the nip portion of said image heating member than the nip portion of said image heating member The image heating apparatus described in 1. 3. The image heating apparatus according to claim 1, wherein a maximum length of the non-opposing portion in the rotation direction is ¼ or less with respect to a circumferential length of the image heating member . The image heating apparatus according to any one of claims 1 to 3, further comprising a maximum heat generating portion in a region in the upstream half of the nip portion of the image heating member . Wherein the first coil is an image heating apparatus according to any one of claims 1 to 4, characterized in that a larger number of turns coils than said second coil. Wherein the first coil is an image heating apparatus according to any one of claims 1 to 5, wherein the narrow interval of twisted wire adjacent the coils than said second coil. 7. An image forming unit that forms and supports an unfixed image on a recording material, and a fixing unit that heat-fixes the unfixed image on the recording material, wherein the fixing unit is any one of claims 1 to 6. An image forming apparatus, which is the image heating apparatus described in 1.

Images