JP2005031517A - Fixing device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fixing device which can suppress the difference in the gloss of a fixed image due to the difference in the residual amount of releasing oil applied to the outer circumferential surface of a fixing belt. <P>SOLUTION: The fixing device is provided with: heating means (20 and 21) to heat the fixing belt (10); pressing rotary bodies (30 and 31) to bring recording paper (P) carrying the toner image (T) of a fixing object into press-contact with the surface of the fixing belt heated by the heating means; and an oil supply device (50) to apply the releasing oil to the outer circumferential surface of the fixing belt. The recording paper is peeled after being transported for a specified distance in the state of coming into close contact with the outer circumferential surface of the fixing belt even after the recording paper passes the fixing pressing parts of the pressing rotary bodies. The oil supply device further possesses an applying area changeover means (60) to switch the area of the fixing belt where the releasing oil is applied in accordance with the size and the transport direction of the recording paper. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a fixing device of a type in which a recording sheet carrying a toner image to be fixed is conveyed while being in close contact with a heated and rotating endless fixing belt, and in particular, a fixing device of the fixing belt. The present invention relates to a fixing device capable of suppressing a difference in gloss of a fixed image caused by a difference in a residual amount of releasable oil applied to an outer peripheral surface.

  In recent years, as a fixing device used in an image forming apparatus such as a printer, a copying machine, or a multi-function printer using an electrophotographic method, an electrostatic recording method, etc., a rotating and tensioning fixing belt is used. A recording sheet carrying an unfixed toner image is pressed against the surface of the belt while heating, transported while cooling while in close contact with the fixing belt, and finally peeled off from the fixing belt. A belt fixing device of a type that performs fixing has been proposed (Patent Documents 1 and 2).

  According to the fixing device of this type, the toner image on the recording paper is peeled off from the fixing belt after being cooled and solidified in a smooth surface following the smooth surface of the fixing belt, and thus fixing with particularly excellent glossiness. An image can be obtained. Further, since the recording paper is peeled off from the fixing belt after the toner is cooled and solidified, there is an advantage that an offset in which the toner is transferred and adhered to the fixing belt is hardly generated.

  By the way, in such a fixing device using a fixing belt, in order to prevent foreign matters such as toner from adhering to the fixing belt, releasable oil such as silicone oil is supplied to the outer peripheral surface of the fixing belt. It is applied by an apparatus to reduce the adhesion force of the fixing belt to the toner (hereinafter referred to as “toner adhesion force”). Also in the belt fixing device described above, an oil application roller is used as the oil supply device, and the oil application is performed by bringing the oil application roller into contact with the fixing belt (Patent Documents 1 and 2).

Japanese Patent Laid-Open No. 7-5781 (paragraph 0015, FIG. 3, etc.) JP-A-7-219366 (paragraph 0015, FIG. 2, etc.) JP-A-11-212379 (Claims 5 to 10, FIG. 5 and the like)

  However, the releasable oil applied to the fixing belt is usually almost removed by absorbing and adhering to the recording paper that is pressed against and contacts the fixing belt during fixing. On the other hand, the contact area between the fixing belt and the recording paper differs depending on the size of the recording paper and the feeding direction (vertical feed, horizontal feed).

  For this reason, on the outer peripheral surface of the fixing belt, there may be a region where a large amount of recording paper is in contact and a region where it is not. In this case, the releasable oil is successively removed by the paper in the belt region where a large amount of recording paper is in contact, and the residual amount of the oil is relatively small, while in the belt region where the recording paper is not very in contact. Mold oil is hardly removed by the paper, and the residual amount of oil tends to increase.

  For this reason, the remaining amount of the releasable oil applied to the outer peripheral surface of the fixing belt varies depending on the belt region, and then the recording is performed across the different regions with respect to the fixing belt in such a state. When the fixing is performed by pressing the paper, the adhesion of the recording paper (strictly, the toner image) to the fixing belt changes depending on the presence or absence of the oil, and the glossiness of the fixed image also changes accordingly. There is a problem that.

  Incidentally, the present applicant has also proposed an image forming apparatus in which the oil supply member is devised so as to supply an appropriate amount of silicone oil to the intermediate transfer belt (Patent Document 3). However, this proposed image forming apparatus merely shows that the oil supply member is configured to contact with and separate from the intermediate transfer belt at a predetermined timing. I don't teach anything about how to solve it.

  The present invention has been made to solve such problems of the prior art, and the main object of the present invention is to provide a difference in the residual amount of releasable oil applied to the outer peripheral surface of the fixing belt. It is an object of the present invention to provide a fixing device capable of suppressing a difference in gloss of a fixed image generated due to the above.

  The fixing device of the present invention (first invention) includes an endless fixing belt that rotates in a fixed direction, a heating unit that heats the fixing belt, and an outer peripheral surface of the fixing belt heated by the heating unit. A pressure rotator for press-contacting the recording paper carrying the toner image, and an oil supply device for applying releasable oil to the outer peripheral surface of the fixing belt, and a fixing pressure unit by the pressure rotator is provided. The oil supply device applies the releasable oil on the premise of a fixing device that, after passing, transports the recording paper for a predetermined distance in close contact with the outer peripheral surface of the fixing belt and then peels it off. An application area switching means for switching the area of the fixing belt according to the size and feeding direction of the recording paper is provided.

  Here, the oil supply device may be a roll type in which an elastic layer is impregnated with a releasable oil. However, the surface of the roll is soiled due to adhesion of toner and the oil supply amount is not sufficient. From the viewpoint of avoiding stabilization, it is preferable that the web-type oil supply device feeds out and winds up the web impregnated with the releasable oil. A web is a cloth-like sheet, and is composed of, for example, a nonwoven fabric. In addition to this, as the oil supply device, it is also possible to apply a spray type device in which the releasable oil protrudes from the nozzle.

  The application area switching means has different areas in contact with the recording paper of the fixing belt depending on the size of the recording paper to be fixed and the feed direction (vertical feed, horizontal feed), and the area in which the recording paper can contact (paper contact area) There are areas that do not come into contact with the paper (paper non-contact areas), so the fixing belt area to which the releasable oil is applied is divided in advance based on the contact area and the non-contact area. Any coating area may be used as long as the application area can be appropriately selected and switched.

  The switching of the oil application area is usually performed so as to stop or suppress the oil supply to the non-contact area of the fixing belt where the recording paper does not contact. Information on the size and feed direction of the recording paper can be obtained by taking in input information and detection information from the image forming apparatus main body side to which the fixing device is applied. The switching is performed, for example, before fixing the corresponding recording paper. In addition, when the above-mentioned spray type is adopted as the oil supply device, the oil protruding port of the nozzle is formed so as to be distributed corresponding to the contact area and the non-contact area, and the oil protrudes. What is necessary is just to comprise so that oil may be protruded only from the nozzle of the area | region which should be.

  The application area switching means may be, for example, a position where the oil supply section of the oil supply device applies the releasable oil and the fixing belt and enters or is positioned away from the fixing belt. An oil application blocking member that can move and a control unit that moves the oil application blocking member forward and backward can be employed.

  In this case, the oil application blocking member is usually composed of a plurality of blocking members that are divided in the width direction of the fixing belt based on the paper contact area and the non-contact area. Also, from the standpoint of avoiding damage or wear of the blocking member that is in direct contact with the fixing belt, the oil supply device is not a type in which the oil application portion directly contacts the outer peripheral surface of the fixing belt. It is preferable that the coating unit is installed so as to indirectly contact the outer peripheral surface of the fixing belt via a heating roll or the like. In this case, the releasable oil is supplied from the oil application part to the fixing belt via a heating roll or the like, and a blocking member is inserted between the oil application part and the heating roll or the like so as to be interposed. become.

  Further, as the application region switching means, a plurality of oil application units that apply releasable oil by contacting directly or indirectly to different regions in the width direction of the outer peripheral surface of the fixing belt, and this It is possible to employ one constituted by a control means for bringing a predetermined one of the oil application portions into contact with and separating from the fixing belt.

  In this case, indirect contact with the outer peripheral surface of the fixing belt refers to a form in which the oil application portion contacts the outer peripheral surface of the fixing belt via a heating roll or the like as described above.

  On the other hand, according to the present invention (second invention), in the fixing device based on the first invention, in order to make the contact area between the fixing belt and the recording paper different, at least one of the fixing belt and the recording paper is A mechanism for relatively shifting according to the size and feeding direction of the recording paper is provided.

  As in the case of the application area switching means, the shifting mechanism is configured to grasp the contact area and the non-contact area between the fixing belt and the recording paper in advance and reduce the non-contact area. The recording sheet may be adjusted so that the recording sheet comes out of contact with the entire fixing belt by relatively shifting at least one of the recording sheets.

  As the mechanism for shifting the recording paper, for example, in a paper (introduction) transport path before the recording paper is brought into pressure contact with the fixing belt, a paper transport roll so as to shift a predetermined amount in the width direction of the fixing belt on which the recording paper is fixedly arranged. In addition, a mechanism for displacing a sheet conveying unit such as a sheet conveying belt or a sheet conveying guide can be employed. Further, as a mechanism for shifting the fixing belt, for example, a belt steering mechanism for forcibly displacing the fixing belt by a predetermined amount in the width direction with respect to a recording sheet introduced with a fixed position reference, or a fixing belt It is possible to employ a mechanism that displaces the entire fixing belt system that is stretched and rotated so as to be shifted by a predetermined amount in the belt width direction. Such a mechanism for shifting the recording paper and a mechanism for shifting the fixing belt can be provided side by side. In addition, even when providing each said shifting mechanism, you may employ | adopt the oil supply apparatus which has the said application | coating area | region switching means as needed.

  And in the said 1st invention and 2nd invention, although the thing of the roll form arrange | positioned facing is preferable, the pressurization rotary body is not specifically limited to the thing of the form. The fixing pressure unit in the pressure rotator may be any unit that can at least apply pressure necessary for fixing to the recording paper carrying the toner image to be fixed. The recording paper is not limited to ordinary paper or coated paper as long as the toner image can be fixed by being conveyed through the fixing device, and includes members such as an OHP sheet, a postcard, and an envelope. The toner constituting the toner image is a fine powder made of a binder resin containing a colorant or the like, and is generally used as a one-component or two-component developer.

  According to the fixing device of the first invention, the application region switching means of the oil supply device can appropriately switch the application region of the releasable oil according to the size and feeding direction of the recording paper, so that the recording on the fixing belt is possible. It is less likely that the residual amount of releasable oil differs between a contact area where a large amount of paper contacts and a non-contact area where the paper does not contact.

  As a result, even when the recording paper is fixed while being in contact with the contact area and the non-contact area of the fixing belt, the fixing belt for the recording paper is caused by the difference in the residual amount of the release oil. It is reduced that the adhesiveness changes. As a result, at the time of fixing, the recording sheet comes into close contact with the fixing belt almost uniformly, and the glossiness of the fixed image is good with little difference.

  Further, according to the fixing device of the second invention, the contact area between the fixing belt and the recording paper is made different by using a mechanism that relatively shifts at least one of the fixing belt and the recording paper, thereby avoiding shifting to one area. Therefore, it is difficult for the fixing belt to have a contact area where a large amount of recording paper is in contact and a non-contact area where the recording paper is not in contact, and the residual amount of releasable oil varies depending on whether the fixing belt is in contact with the paper. Less.

  As a result, the recording paper is not contacted and fixed in a state of straddling the contact area and the non-contact area of the fixing belt, and the difference between the remaining amount of release oil and the fixing belt of the recording paper It is also possible to reduce the change in the adhesiveness. As a result, the recording sheet comes into close contact with the fixing belt almost evenly during fixing, and the glossiness of the fixed image is good with little difference.

  Hereinafter, embodiments of the present invention will be described with reference to examples.

  FIG. 1 is a schematic configuration diagram illustrating a main part of a fixing device according to a first embodiment of the present invention. The fixing device 1 is used as a fixing unit in an image forming apparatus such as a printer or a copying machine. Solid arrows in the figure indicate the rotation directions of the main rotating parts.

  The fixing device 1 includes an endless fixing belt 10 that rotates in the direction of an arrow, heating rolls 20 and 21 that heat the fixing belt, and a fixing belt 10 that is heated by the heating rolls 20 and 21. The fixing belt 10 is supported by a pair of pressure rolls 30 and 31 disposed in pressure contact with each other and the second pressure roll 31 disposed on the outer peripheral surface side of the fixing belt 10 among the pair of pressure rolls. And a pressure belt 35 rotating so as to move in the same direction by contacting with a predetermined distance, and an inner peripheral surface side of the fixing belt 10 after passing through the pressure rolls 30 and 31. A heat circulator 40 as a cooling device for cooling the fixing belt and the like, a web-type oil supply device 50, and the like are provided. In the figure, symbol P denotes a recording sheet, and T denotes a toner image carried on the recording sheet. Also, the dashed dotted line indicates the conveyance path of the recording paper P.

  The fixing belt 10 is formed on a belt substrate made of polyimide containing carbon black and the like having a thickness of about 50 μm, an elastic layer made of a silicone copolymer having a thickness of about 60 μm, and a surface separation made of fluorine rubber. It has a three-layer structure in which mold layers are laminated in this order. The fixing belt 10 is stretched around a first heating roll 20, a second heating roll 21, a first pressure roll 30, a plurality of belt support rolls 15 to 18, and the like, and is also used as a driving roll. The roll 30 rotates in the direction of arrow A.

  The belt support roll 17 supports the fixing belt 10 so that the fixing belt 10 moves while being bent sharply, and thereby the recording paper P conveyed in close contact with the fixing belt 10 is peeled off by its own strength. It functions as a peeling roll that plays the role of The second heating roll 21 also functions as a steering roll that corrects the meandering travel of the fixing belt 10 by displacing one end side of the rotation shaft thereof.

  The first heating roll 20 has a structure in which a heating source 22 such as a halogen lamp is disposed inside a cylindrical metal (aluminum or the like) roll, and heats the fixing belt 10 from the inner peripheral surface side. The second heating roll 21 has a structure in which a heating source 23 such as a halogen lamp is disposed inside a cylindrical metal roll, and heats the fixing belt 10 from the outer peripheral surface side.

  The pressure belt 35 has a three-layer structure in which an elastic layer made of silicone rubber or the like and a surface release layer made of silicone resin or the like are laminated in this order on a belt base material such as polyimide. The pressure belt 35 is stretched between the second pressure roll 31, the drive roll 36, and a plurality of belt support rolls 37 to 39, and between the first pressure roll 30 and the second pressure roll 31. When the rotational power of the first heating roll 30 is transmitted between the two, it rotates in the direction of arrow B. The pressure belt 40 rotates and moves in the same direction in contact with the outer peripheral surface of the fixing belt 10 in a predetermined section between the second pressure roll 31 and the belt support roll 39. The steering roll 36 is configured to correct the meandering travel of the pressure belt 35 by displacing one end side of the rotation shaft in a predetermined direction by a predetermined amount.

Each of the pressure rolls 30 and 31 has a structure in which a heat-resistant elastic layer having a thickness of about 6 mm made of silicone rubber or the like is formed on a cylindrical metal (aluminum or the like) roll base, and is predetermined by a pressure mechanism (not shown). With a pressing force (for example, a pressure at which the nip pressure is about 3.5 × 10 ⁵ Pa), and the nip width is about 20 mm. Further, in the pressure rolls 30 and 31, a heating source such as a halogen lamp is arranged in the internal space, and heating is performed only during the so-called warm-up for raising the roll to the temperature during the fixing operation (heating during the fixing operation). Do not).

  The heat circulator 40 includes a first metal plate 41 that is in contact with the inner peripheral surface of the fixing belt 10 between the first pressure roll 30 and the belt support roll 17, and between the belt support roll 18 and the first heating roll 20. The second metal plate 42 in contact with the inner peripheral surface of the fixing belt 10, and the first metal plate 41 and the second metal plate 42 are coupled to the second metal plate 42 to move the heat of the first metal plate 41 to the second metal plate 42 and circulate. It is comprised with the heat transport body 43 to be made.

  Each of the metal plates 41 and 42 is a plate-shaped member made of a metal such as aluminum, and the belt contact surface protrudes at least outward and is formed into a curved surface that is gently curved in the belt running direction. Yes. As the heat transport body 43, a plurality of heat pipes are used in which a liquid is decompressed and sealed in a tube, and the heat resistance is very small, and a large amount of heat can be transported to a low temperature side even at a small temperature difference. Yes. The heat pipe is used by being assembled into a quadrangular annular shape so as to circulate between the plates while touching and passing the inner surfaces of the metal plates 41 and 42.

  When the heat circulator 40 takes heat from the fixing belt 10 in a state where the first metal plate 41 is heated, the heat is transferred to the first metal plate 41 by the heat conduction action of the heat pipe as the heat transport body 43. Is transmitted to the second metal plate 42 in a low temperature state. As a result, the fixing belt portion in contact with the first metal plate 41 absorbs heat and is cooled to a predetermined temperature, while the fixing belt portion in contact with the second metal plate 42 is heated to a predetermined temperature. The heat circulator 40 is provided with a cooling device (for example, a heat radiating member such as a heat sink) on the inner peripheral surface between the belt support rolls 17 and 18 of the fixing belt 10 from the viewpoint of enhancing the effect of the heat circulation. To increase the temperature gradient between the first metal plate 41 and the second metal plate 42.

  The web-type oil supply device 50 feeds the web 51 impregnated with releasable oil at a predetermined low speed by a feed roll 52 and feeds the web 51 to the second heating roll 21 by a pressing roll 53 such as a sponge roll. After being brought into pressure contact with the surface of the sheet, the sheet is wound up by a winding roll 54. As a result, the releasable oil contained in the web 51 is applied to the heating roll 21 and then supplied to the outer peripheral surface of the fixing belt 10. The oil supply amount can be adjusted to an appropriate amount by changing the feed speed of the web 51, the amount of oil impregnation, and the like.

As the web 51, a cloth-like sheet made of a non-woven fabric having substantially the same width as the width of the fixing belt 10 is used. The feeding speed of the web 51 is set to about 1 to 4 mm / min. Further, as the releasable oil, dimethyl silicone oil or the like is used, and the web 51 is impregnated by an amount of 25 g / m ² .

  In such a fixing device 1, the following fixing is performed on the recording paper P onto which the toner image T has been transferred on the image forming unit side of the image forming apparatus.

  That is, first, the recording paper P onto which the toner image T has been transferred is in a posture in which the toner image carrying surface is brought into contact with the fixing belt 10 through a paper conveyance belt, a conveyance guide (not shown), and the like. Is introduced into the fixing nip portion N, which is between the pressure rolls 30 and 31 while starting to run while overlapping each other.

  At this time, the fixing belt 10 in the fixing device 1 is rotated and moved sequentially from the inner peripheral surface side and the outer peripheral surface side when passing mainly through the first heating roll 20 and the second heating roll 21. The fixing conditions at this time are, for example, that the first heating roll 20 is 180 ° C., the second heating roll 21 is 185 ° C., the first pressure roll 30 is 145 ° C., and the second pressure roll 31 is 90 ° C. Each is heated. In addition, the fixing belt 10 is rotated at a speed of 355 mm / sec, and is cooled to a temperature at which the peeling belt support roll 17 reaches 70 ° C. by the cooling device 40.

  The recording paper P carrying the toner image T introduced into the fixing nip N is heated by the heated fixing belt 10 and simultaneously pressurized by the pressure rolls 30 and 31.

  Subsequently, the recording sheet P is sandwiched between the fixing belt 10 and the pressure belt 35 and conveyed while being in close contact with the fixing belt 10, and the first metal plate from which heat is removed by the heat circulation of the heat circulator 40. When passing through 41, the toner image and the toner image are cooled to a predetermined temperature or lower. This cooling solidifies the toner image. The recording paper P that has passed through the first metal plate 41 of the heat circulator 40 is peeled off from the fixing belt 10 together with the toner image by the strength of the paper itself at the peeling portion where the belt support roll 17 is provided. The peeled recording paper P is discharged out of the apparatus.

  As a result, the toner image is fixed on the recording paper. The fixed image at this time is obtained as an image rich in glossiness that is smoothed especially in accordance with the smooth surface of the fixing belt 10.

  In such fixing, the oil supply device 50 supplies the releasable oil to the outer peripheral surface of the fixing belt 10 via the second heating roll 21. As a result, the fixing belt 10 is placed in a state where it is difficult for foreign matters such as toner to adhere to the outer peripheral surface thereof.

  By the way, in such a fixing device 1, as shown in FIGS. 2 and 3, the recording paper P contacts the fixing belt 10 depending on the size of the recording paper P carrying the toner image T to be fixed and its feeding direction. A sheet contact area D and a sheet non-contact area E where the recording sheet P does not contact occur.

  FIG. 2 shows a case where A4 size recording paper P is fed vertically. In this case, the recording paper P can come into contact with a region D1 corresponding to the entire effective region of the fixing belt 10. FIG. 3 shows a case where the A4-size recording paper P is laterally fed. In this case, the recording paper P contacts only a part (D2) of the effective area of the fixing belt 10, and the recording paper P does not contact the remaining area (E). Note that the fixing belt 10 in the drawing shows a belt portion between the fixing nip portion N and the belt support roll 17 which is also a peeling roll for convenience.

  Of these, as illustrated in FIG. 3, when fixing is performed continuously such that the sheet contact area D <b> 2 and the sheet non-contact area E coexist on the fixing belt 10, oil is supplied in the sheet contact area D <b> 2. The releasable oil supplied by the apparatus 50 is absorbed and adhered to the recording paper P and removed, while the same releasable oil remains in the paper non-contact area E without being removed by the recording paper P. . As a result, the problem described in the problem of the prior art may occur.

  That is, after the fixing (FIG. 3) is performed, the recording paper P (for example, the same A4 printing paper or the B5 printing paper having the same size and feeding direction as to come into contact with the paper contact area D2) There is no problem when fixing is performed by (transverse feed). However, the fixing is performed by the recording paper P (for example, the same A4 size paper or B5 size paper) that has a size and a feeding direction condition extending over the paper contact area D2 and the paper non-contact area E. In particular, the sheet portion located in the sheet non-contact region E (actually, the toner image T portion to be fixed) is more adhesive to the fixing belt 10 due to the releasable oil remaining than the sheet contact region D2. It becomes inferior, and it becomes easy to peel off (float) from the fixing belt 10 at the time of fixing.

  In view of such a phenomenon, the adhesion force of the fixing belt 10 to the toner was examined.

  First, the adhesion force of the fixing belt 10 to the toner will be described. FIG. 4 is an explanatory cross-sectional view schematically showing a state when the molten toner Ta heated by the fixing belt 10 is fixed on the recording paper P. In such a state, an adhesive force F1 generated between the molten toner Ta and the recording paper P, an adhesive force F2 generated between the fixing belt 10 and the molten toner Ta, and an aggregating force F3 inside the molten toner Ta. Three forces are working. The toner is fixed by peeling off the recording toner P at the boundary with the fixing belt 10 without being divided when the recording paper P is peeled off from the fixing belt 10. It is necessary that the adhesion force F1 has a large force relationship with respect to the adhesion force F2 and the cohesion force F3 inside the molten toner. Accordingly, by measuring the force required when the recording paper P is peeled off from the fixing belt 10 in the above-described state, the gap between the fixing belt 10 and the molten toner Ta corresponding to the adhesion force of the fixing belt 10 to the toner is measured. Can be known.

  From this point of view, the adhesion force of the fixing belt 10 to the toner was measured using an adhesion force measuring apparatus 100 as schematically shown in FIG.

  This adhesive force measuring device 100 is a simplified device of the fixing device 1, and pressure rolls 101 and 102 and belt support rolls 103 and 104 are installed in the state shown in the figure, and each of the rolls 101 and 103 is installed. 104, the fixing belt 10 is wound around, and the pressure roll 102 is arranged in a state of being pressed against the pressure roll 101 with the fixing belt 10 interposed therebetween. In addition, the adhesive force measuring apparatus 100 is provided with a heating plate 25 in contact with the inner peripheral surface of the fixing belt 10 between the pressure roll 102 and the support roll 103. Each of the pressure rolls 101 and 102 is formed by forming a silicone rubber layer (hardness: 30 Hs) on a metal roll used in the pressure roll 30 or the like, and installing an electric heater inside the metal roll. , And a pressure load of 600 N. The pressure roll 101 is connected to a rotational drive source and used as a drive roll. Further, the adhesive force measuring device 100 pulls the recording paper PX for measurement conveyed by the belt 10 upward (in the direction of the arrow) on the outer peripheral surface side of the fixing belt 10 on the heating plate 25 to pull the belt 10. And a tensile tester 120 that can measure the peeling force at that time.

And the measurement by this adhesive force measuring apparatus 100 is performed as follows. First, after the fixing belt 10 to be measured is wound and the apparatus is set, the driving and pressure roll 101 is heated to 152 ° C., the pressure roll 102 is heated to 157 ° C., and the heating plate 25 is heated to 115 ° C. The fixing belt 10 is rotated in the direction of the arrow at a speed of 30 mm / sec. Next, the recording paper PX for measurement is inserted between the fixing belt 10 and the pressure roll 102 of the working adhesion measuring apparatus 100. As shown in FIG. 6, the recording paper PX for measurement has a cyan toner layer (density of 3. mm) on the entire front end area of 25 mm from the front end PXa of coated paper (Fuji Xerox: J coated paper) having a size of 15 mm × 60 mm. 5 g / m ² ) Ta is formed. The toner image Ta was formed by an image forming apparatus equipped with a function from the formation of the toner image on the photoreceptor to the transfer to the recording paper.

  Subsequently, when the recording paper PX for measurement inserted between the fixing belt 10 and the pressure roll 102 reaches the heating plate 25, the rotation of the fixing belt 10 is stopped, and heating is left at that position for 1 minute. A hook of a tensile testing machine 120 is attached to the rear end PXb of the recording paper PX and pulled upward (in the direction of the arrow) at a speed of 5 mm / sec. At this time, an average tensile force until the recording paper PX was completely peeled off from the fixing belt 10 was measured, and the value was defined as a toner adhesion force of the fixing belt 10.

  Next, after the fixing device 1 was operated under the following conditions, each fixing belt 10 was attached to the adhesion measuring device 100, and the toner adhesion for each condition was measured.

  The above condition is an area in which a fixed amount of releasable oil (a supply amount of about 0.05 μl per A4 size sheet) is supplied to the fixing belt 10 by the oil supply device 50 (the sheet does not contact). And a region where the recording paper P is contacted while supplying a certain amount of the oil and a region where only the recording paper P is contacted without supplying the oil, and when the fixing belt is rotated a predetermined number of times, The toner adhesion was measured. The measurement result at this time is shown in FIG.

  As is apparent from the results of FIG. 7, the toner adhesion force of the fixing belt 10 tends to gradually increase according to the rotation speed of the fixing belt when the sheet is brought into contact without supplying the releasable oil. In addition, when the paper is brought into contact with a constant amount of releasable oil, a stable tendency is exhibited. Further, when a certain amount of oil is supplied without contacting the paper (specifically, standby oil is supplied) Show a tendency to gradually decrease according to the rotation speed of the fixing belt.

  Further, from the experiments by the present inventors, when the toner adhesion force of the fixing belt 10 exceeds 0.4 N, as shown in FIG. 7, the separation failure of the recording paper from the fixing belt 10 occurs and the fixing is performed. It has been confirmed that foreign matters such as toner and paper dust easily adhere to the belt 10. Further, when the toner adhesion force becomes less than 0.02 N, the fixing belt 10 and the toner image are not sufficiently adhered to each other, and air enters a part between them, The heat capacity differs from the other portions, and the toner image is not uniformly melted at the time of fixing, and minute gloss unevenness due to uneven fixing tends to occur. In addition, in the fixing nip portion N formed between the pressure rolls 30 and 31, the recording paper is heated to a high temperature by the fixing belt 10 heated to 100 ° C. or higher, so that moisture contained in the paper is contained. Vaporization generates water vapor, and the vapor pressure tends to induce a phenomenon called blistering in which the paper (toner image) is peeled off from the fixing belt 10.

  From the above results, it has been found that the fixing device 1 needs to be controlled so that the toner adhesion force of the fixing belt 10 falls within the range of 0.02 to 0.4N.

  In the fixing device 1, from the above knowledge, as shown in FIGS. 1 and 8, the region of the fixing belt 10 to which the release oil of the oil supply device 50 is applied is arranged in the size and the feeding direction of the recording paper P. A coating area switching means 60 for switching according to the above is provided.

  As shown in FIGS. 8 and 9, the application region switching means 60 enters between the web 51 portion (oil application portion) pressed by the pressing roll 53 of the oil supply device 50 and the second heating roll 21. The shutter plates 61 and 62 that can move to positions where they intervene or move away from them, retract mechanisms 63 and 64 that individually move the shutter plates 61 and 62 forward and backward, and the retract mechanisms 63 and 64 It is comprised with the control apparatus 69 which controls operation | movement etc.

  Each of the shutter plates 61 and 62 is a metal thin plate made of a stainless thin plate or the like, and as illustrated in FIG. 3, a rectangular first shutter plate 61 having the same width as the paper contact region D <b> 2 of the fixing belt 10. The rectangular second shutter plate 62 having the same width as the paper non-contact area E is formed. Further, both the shutter plates 61 and 62 are formed in a curved surface shape so that the lower end portions (entrance portions 61 a and 62 a) thereof are close to the curvature of the pressing roll 53. In this way, when the lower end of the plate is not curved but left flat, the entry directions (the up and down movement directions J and K) for entering and interposing the shutter plates 61 and 62 are extremely limited. It will be within the specified range, and it will be difficult to design the installation.

  The retract mechanisms 63 and 64 are for moving the shutter plates 61 and 62 in the directions of arrows J and K in the figure, and a holder 68 at the tip of the moving support member 67 that moves in the directions of arrows J and K. Holds the upper end of each plate. As a drive mechanism of the retract mechanism, a known solenoid, cam mechanism, pinion / rack mechanism, wire winding mechanism, or the like is appropriately selected and used. The shutter plates 61 and 62 are configured to move in the directions of arrows J and K when their both ends and the like are guided by a moving guide member (not shown).

  The control device 69 is constituted by a microcomputer or the like, and controls the operation of the retract mechanisms 63 and 64 according to a predetermined control program so that the shutter plates 61 and 62 are moved at the predetermined timings with the arrows J and J. It is moved in the K direction. Information on the size and feed direction of the recording paper P and information on the number of recording papers P (the count value of the number of fixing sheets) are input to the control device 69 from the image forming apparatus that uses the fixing device 1. It is like that. Such a control device 69 may be installed on the fixing device 1 side or on the image forming device side. The control device 69 is set to shut down the oil supply by lowering both shutter plates 61 and 62 in the arrow J direction when the fixing device 1 is warmed up or in standby. Further, during the actual fixing operation, the oil supply state varies depending on the size of the recording paper P, the feeding direction and the number of sheets, so that the shutter plates 61 and 62 are set to move through the control procedure shown in FIG. Yes.

  Next, the operation of the oil supply apparatus 50 provided with the application region switching means 60 composed of such shutter plates 61 and 62 will be described.

  First, when the fixing device 1 is warmed up or in a standby state, as shown in FIGS. 8 and 11, the control device 69 operates the retract mechanisms 63 and 64 to move both the shutter plates 61 and 62 by a predetermined amount in the arrow J direction. Only descend.

  Accordingly, the lower end portions 61 a and 62 a of the shutter plates 61 and 62 enter and interpose between the web 51 portion (oil application portion) pressed by the pressing roll 53 and the second heating roll 21. As a result, the supply of the releasable oil from the web 51 to the second heating roll 21 is blocked on the whole area due to the presence of the shutter plates 61 and 62, so that the oil supply to the fixing belt 10 via the heating roll 21 is performed. Is completely blocked.

  Accordingly, it is possible to avoid a decrease in toner adhesion force (FIG. 7) of the fixing belt 10 due to unnecessary oil supply during warm-up or standby and the remaining oil. By operating the application region switching means 60 in this way, the toner adhesion force of the fixing belt 10 can be satisfied within the above-mentioned preferable range (0.02 to 0.4 N), and the fixing operation performed thereafter is performed. In this case, it is possible to ensure good adhesion of the recording paper to the fixing belt 10, and to suppress the occurrence of a gloss difference in the fixed image due to such poor adhesion. Before the fixing operation is performed, the shutter plates 61 and 62 are both lifted in the direction of the arrow K, separated from the web 51 portion (oil application portion) and the second heating roll 21, and retracted. (The state of the shutter plates 61 and 62 shown by the solid line in FIG. 8).

  Subsequently, when the fixing operation is executed, first, as shown in FIG. 10, information on the size and feeding direction of the recording paper P used for fixing is input to the control device 69 (step 10: S10). In the control device 69, the number of times the recording paper P has contacted is calculated for each of the areas A and B (FIG. 9) divided according to the paper contact area D2 and the paper non-contact area E (see FIG. 3) of the fixing belt 10. (S11). The number of times of sheet contact for each region is obtained based on information on the size and feed direction of the recording sheet to be used and the number of sheets used for fixing.

  In the control device 69, the sheet contact number Na in the belt area A corresponding to the sheet contact area D2 is a predetermined number (for example, 100 sheets) than the sheet contact number Nb in the belt area B corresponding to the sheet non-contact area E. It is determined whether or not there are more (S12).

  At this time, when it is determined that the sheet contact number Na in the region A is 100 sheets more than the contact number Nb in the region B, it is considered that the releasable oil remaining in the region B of the fixing belt is increased and is in an excessive state. The control device 69 operates the retract mechanism 64 to lower only the second shutter plate 62 by a predetermined amount in the arrow J direction (S13). Accordingly, as shown in FIGS. 9, 12, and 13, the lower end portion 62 a of the second shutter plate 62 is between the web 51 portion (oil application portion) pressed by the pressing roll 53 and the second heating roll 21. It enters and becomes intervened. As a result, the releasable oil is supplied from the web 51 to the second heating roll 21 in the area where the shutter plate 62 does not exist, but is blocked in the area where the shutter plate 62 exists. The oil is supplied to the fixing belt 10 via the belt region A only and is blocked from the belt region B.

  Therefore, when the fixing is performed continuously such that the sheet contact area D2 and the sheet non-contact area E (see FIG. 3) are generated on the fixing belt 10 depending on the size and feeding direction of the recording sheet P, the sheet comes into contact. In the belt area B (sheet non-contact area E) where the toner does not remain, the release oil does not accumulate excessively and does not become excessive, and a decrease in toner adhesion force in the area B (FIG. 7) can be avoided. it can.

  As a result, the toner in the areas A and B of the fixing belt 10 even when the fixing is performed on the recording paper P extending over the paper contact area D2 and the paper non-contact area E after the fixing. Since the adhesive force is maintained under substantially the same condition (balanced state), it is possible to ensure good adhesion of the recording paper P to the fixing belt 10 and to fix the fixed image due to such poor adhesion. Generation of a gloss difference can be suppressed. When the standby operation is completed after the series of fixing operations (one job) is completed, both the shutter plates 61 and 62 are lowered as described above, and the web 51 portion (oil application portion) and the second heating roll 21 are moved. It will intervene in between.

  On the other hand, if it is not determined in step S12 that the sheet contact number Na in the region A is 100 sheets more than the contact number Nb in the region B, the difference in the residual amount of the release oil between the regions A and B of the fixing belt 10 is determined. Assuming that the level is still low, the control device 69 operates the retract mechanisms 63 and 64 to lower both shutter plates 61 and 62 by a predetermined amount in the direction of arrow J while interlocking when necessary (S14). In this case, the timing when both shutter plates 61 and 62 are lowered in conjunction with each other is, for example, the timing when the A4 size paper is continuously fed vertically.

  In the first embodiment, the oil supply device 50 is installed around the second heating roll 21. However, in the case of a fixing device without the second heating roll 21, a dedicated heating roll in contact with the outer peripheral surface of the fixing belt 10. Are arranged separately, and the oil supply device 50 is installed around the heating roll (so that the web 51 abuts), or the oil supply device 50 is installed without installing the dedicated heating roll. Can be installed on the outer peripheral surface side of the fixing belt 10 (so that the web 51 is in direct contact).

  In the fixing device 1 according to the first embodiment, the provision of the pressure belt 35 may be omitted. In this case, the rolls 36 to 39 for stretching and rotating the pressure belt 35 are also unnecessary. Further, as a means for heating the fixing belt 10, other heating means such as a heating plate may be applied instead of the heating rolls 20 and 21.

  FIG. 14 is a schematic configuration diagram illustrating a main part of the fixing device according to the second embodiment of the present invention. The fixing device 1 has the same configuration as that of the fixing device 1 according to the first embodiment except that a different application area switching unit 60 is applied as the oil supply device 50. For this reason, in FIG. 14 etc., the same code | symbol and arrow are attached | subjected to the component which is common in the fixing device of Example 1, and those description is abbreviate | omitted.

  In the second embodiment, as shown in FIG. 15, two oil supply devices 50 </ b> A and 50 </ b> B having different web 51 widths as the oil supply device 50 and the oil supply devices 50 </ b> A and 50 </ b> B are connected to the second heating roll 21. The retraction mechanisms 71 and 72 are moved toward and away from each other and a control device 79 that controls the operation of the retraction mechanisms 71 and 72 and the like.

  The two oil supply devices 50A and 50B are both of the web type having basically the same configuration as the oil supply device 50 in the first embodiment, and are different only in that the width of the web 51 is different. . That is, the web 51A in the first oil supply device 50A is set to have a width equal to or greater than the paper contact area D2 of the fixing belt 10 as illustrated in FIG. 3, and the web 51B in the second oil supply device 50B The width is set equal to or larger than the paper non-contact area E.

  The retract mechanisms 71 and 72 are for moving the first oil supply device 50A and the second oil supply device 50B in the directions of arrows Q and R in the drawing, respectively. The web 51 portion (oil application portion) pressed by the pressing roll 53 can be brought into and out of contact with the second heating roll 21. As a drive type of the retract mechanism, a known solenoid, cam mechanism, pinion / rack mechanism, wire winding mechanism or the like is appropriately selected and used. Each of the oil supply devices 50A and 50B moves in the directions of arrows Q and R by being guided and supported by a moving guide member (not shown) as a whole (if necessary, only the pressing roll 53 and the web 51 portion supported thereby). It is structured.

  The control device 79 has the same configuration as that of the control device 69 in the first embodiment described above, and controls the operation of the retract mechanisms 71 and 72 in accordance with a predetermined control program, thereby providing two oil supply devices 50A, 50B is moved in the directions of arrows Q and R at a predetermined timing. The control device 79 is also set to shut off the oil supply by moving both of the oil supply devices 50A and 50B in the arrow R direction when the fixing device 1 is warmed up or on standby. Further, during the actual fixing operation, the oil supply state varies depending on the size of the recording paper P, the feeding direction and the number of sheets, so that the oil supply devices 50A and 50B are connected to the shutter plate 61, through the control procedure shown in FIG. It is set to move with almost the same content as 62.

  Next, the operation of the oil supply apparatus provided with the application region switching means 60 composed of the two oil supply apparatuses 50A and 50B will be described.

  First, when the fixing device 1 is warmed up or in a standby state, as in the case of the first embodiment, the control device 79 operates the retract mechanisms 71 and 72 so that both the oil supply devices 50A and 50B are set in a predetermined amount in the arrow R direction. Just move.

  As a result, the webs 51 </ b> A and 51 </ b> B (oil application portions) pressed by the respective pressing rolls 53 in the oil supply devices 50 </ b> A and 50 </ b> B are both separated from the second heating roll 21. As a result, since the supply of the releasable oil from the webs 51A and 51B to the second heating roll 21 is completely cut off, the oil supply to the fixing belt 10 via the heating roll 21 is also cut off completely. The Thereby, the same effect as the case of Example 1 is acquired.

  Subsequently, when the fixing operation is executed, first, as shown in FIG. 10, information on the size and feeding direction of the recording paper P used for fixing is input to the control device 79 (S10), and the control device 79 is also operated. In step S11, the number of times the recording paper P has contacted is calculated for each of the areas A and B (FIG. 9) that are divided in accordance with the paper contact area D2 and the paper non-contact area E (see FIG. 3) of the fixing belt 10 (S11). ). In the control device 79, the sheet contact number Na in the belt area A corresponding to the sheet contact area D2 is a predetermined number (for example, 100 sheets) than the sheet contact number Nb in the belt area B corresponding to the sheet non-contact area E. It is determined whether or not there are more (S12).

  At this time, when it is determined that the sheet contact number Na in the area A is 100 sheets more than the contact number Nb in the area B, it is regarded as in the case of the first embodiment, and the control device 79 operates the retract mechanism 71 to perform the first. The oil supply device 50A is moved in the arrow Q direction by a predetermined amount. As a result, the web 51 </ b> A comes into contact with the second heating roll 21 to supply oil, so that oil is supplied to the region A of the fixing belt 10 via the heating roll 21. On the other hand, the control device 79 operates the retract mechanism 72 to move the second oil supply device 50B in the arrow R direction by a predetermined amount. As a result, the web 51B is separated from the second heating roll 21 and the oil supply is shut off, so that the oil supply to the region B of the fixing belt 10 via the heating roll 21 is also shut off.

  Therefore, when the fixing is performed continuously such that the sheet contact area D2 and the sheet non-contact area E (see FIG. 3) are generated on the fixing belt 10 depending on the size and feeding direction of the recording sheet P, the sheet comes into contact. In the belt area B (sheet non-contact area E) where the toner does not remain, the release oil does not accumulate excessively and does not become excessive, and a decrease in toner adhesion force in the area B (FIG. 7) can be avoided. it can. As a result, even when the fixing is performed on the recording paper P across the paper contact area D2 and the paper non-contact area E after such fixing is performed, the same effect as in the first embodiment is obtained. Is obtained. Note that when the standby operation is performed after the series of fixing operations (one job) is completed, the first oil supply device 50A also moves away from the second heating roll 21 as described above.

  On the other hand, if it is not determined in step S12 that the sheet contact number Na in the area A is 100 sheets greater than the contact number Nb in the area B, the control device 79 regards the retract mechanisms 71 and 72 as in the case of the first embodiment. The oil supply devices 50A and 50B are actuated and moved by a predetermined amount in the direction of arrow Q in an interlocked state when necessary. The timing at which both of the oil supply devices 50A and 50B are brought into contact with the second heating roll 21 in this case is the same as in the first embodiment.

  FIG. 18 is a schematic configuration diagram illustrating a main part of the fixing device according to the third embodiment of the present invention. In this fixing device, a sheet conveying belt device 80 for introducing a recording sheet P carrying a toner image T to be fixed into a fixing nip N of the fixing belt 10 is arranged in a direction perpendicular to the sheet feeding direction (of the fixing belt 10). The width direction is substantially the same as that of the fixing device 1 according to the first embodiment except that a displacement device 85 that shifts a predetermined amount in G and H is provided. For this reason, in FIG. 18 etc., the same code | symbol and arrow are attached | subjected to the same component as the fixing device of Example 1, and the description is abbreviate | omitted unless there is particular notice. The oil application device 50 may employ a configuration in which the application region switching unit 60 in the first embodiment is provided, but may employ a configuration in which the application region switching unit 60 is omitted.

  In the third embodiment, as shown in FIGS. 18 and 19, the paper conveying belt device 80 is displaced in the directions of arrows G and H by the displacement device 85, and the operation of the displacement device 85 is controlled by the control device 89. It has become. The paper transport belt device 80 is configured such that a plurality of paper transport belts 81 arranged in parallel along the transport direction of the recording paper P are stretched around a drive roll 82 and a driven roll 83 and rotated in the direction of the arrow. Reference numeral 84 in the figure denotes a device frame, and this device frame 84 is supported by a slide rail or the like so as to be displaced in the directions of arrows G and H. Reference numeral S denotes a conveyance reference line that serves as a reference position during normal conveyance of the recording paper P.

  Incidentally, in order to shift the relative position of the recording paper P with respect to the fixing belt 10 by the displacement of the paper transport belt device 80, the recording paper P transported by the paper transport belt device 80 accompanies the displacement of the device 80. Need to be displaced together. For this reason, the paper conveyance belt device 80 has a size that can hold the entire conveyance direction region of the recording paper P to be conveyed, or even if the size is smaller than that size, recording is performed at the front and rear positions of the device 80 in the conveyance direction. It is necessary to configure so that there is no other position-fixed type paper transport roll or the like that prevents the displacement of the paper P.

  The displacing device 85 displaces the sheet conveying belt device 80 by a predetermined amount in the directions of arrows G and H, thereby making it possible to vary the contact area between the recording paper P fed for fixing and the fixing belt 10. Yes. As a drive type of the displacement device 85, a known cam mechanism, pinion / rack mechanism, wire winding mechanism, or the like is appropriately selected and used.

  The control device 89 has the same configuration as that of the control device 69 in the first embodiment, and controls the operation of the displacement device 85 in accordance with a predetermined control program so that the sheet transport belt device 80 is moved to an arrow at a predetermined timing. It is displaced in the G and H directions. The control device 89 prevents the contact area between the fixing belt 10 and the recording sheet from being shifted to a partial area depending on the size, feeding direction, and number of recording sheets P to be fixed during the fixing operation. Therefore, for example, as shown in FIG. 20, the recording paper P is set to be shifted from the conveyance reference line S by a predetermined amount m in the arrow G direction.

  Next, the operation of the fixing device 1 having the paper conveying belt device 80 provided with such a displacement mechanism 85 will be described.

  When the fixing operation is executed, first, as shown in FIG. 10, information on the size and the feeding direction of the recording paper P used for fixing is input to the control device 89 (S10), and the fixing belt is used in the control device 89. The number of times the recording paper P has come into contact is calculated for each of the areas A and B (FIG. 9) that are divided according to the ten paper contact areas D2 and the non-paper contact area E (see FIG. 3) (S11). Then, in the control device 89, the displacement mechanism 85 is operated so that the fixed sheet non-contact area E does not occur on the fixing belt 10, and the sheet conveying belt device 80 is moved from the conveying reference line S in the direction of arrow G by a predetermined amount m1 to m3. Just shift. The shifting timing is shifted in a plurality of stages within a series of fixing operations (one job), or when a job and a job with the same recording paper conditions (size and feeding direction) are executed.

  Accordingly, as shown in FIG. 20, for example, when fixing is performed by laterally feeding a recording paper P of A4 size, if the recording paper P is normal (when the paper transport belt device 80 is not displaced), the recording paper P is transported. Since it is conveyed along the reference line S, it only contacts a partial area A0 (paper contact area D2 in FIG. 3) of the fixing belt 10. However, the relative position between the recording sheet P and the fixing belt 10 is changed by displacing the recording sheet P from the conveyance reference line S by a predetermined amount m1, m2, m3 by displacing the sheet conveying belt device 80. Since the sheet is conveyed, the contact area between the shifted recording paper P (the same size and the same feeding direction) and the fixing belt 10 are shifted from the contact area A0 in the direction of arrow G by m1, m2, and m3. The contact areas A1, A2 and A3 are changed. As a result, the recording paper P comes in contact with the entire area of the effective area of the fixing belt 10 in a well-balanced manner (without being offset), so that the releasable oil supplied from the oil supply device 50 to the fixing belt 10 is removed. In addition, the variation in the remaining amount of the releasable oil in the entire fixing belt 10 is reduced.

  Therefore, since the toner adhesion force in the entire area of the fixing belt 10 is maintained under substantially the same condition (balanced state), it is possible to ensure good adhesion of the recording paper P to the fixing belt 10, It is possible to suppress the occurrence of a gloss difference in a fixed image due to such poor adhesion. The displacement of the paper conveying belt device 80 is reviewed for each series of fixing operations.

  Further, when the application region switching means 60 is provided in the oil supply device 50 in the third embodiment, the two-plate shutter plate in the first embodiment is changed to the one-plate configuration, and the one shutter plate is moved back and forth. It is possible to adjust the supply amount of oil by moving it. In such a configuration, the shutter plate can be a simple one plate configuration.

1 is a schematic configuration diagram illustrating a main part of a fixing device according to Embodiment 1. FIG. FIG. 6 is an explanatory diagram illustrating an example of a relationship between contact areas of a recording sheet and a fixing belt. FIG. 10 is an explanatory diagram illustrating another example of a relationship between contact areas of a recording sheet and a fixing belt. FIG. 4 is an explanatory diagram schematically illustrating a force relationship between a fixing belt and a recording sheet when toner is present. FIG. 3 is a conceptual diagram illustrating an adhesion force measuring device that measures adhesion force of a fixing belt to toner. FIG. 6 is an explanatory plan view showing a recording sheet used for measurement by the measuring apparatus of FIG. 5 and a toner image formation state. 6 is a graph showing the correlation between the rotation speed of the fixing belt and the toner adhesion force with respect to the presence or absence of recording paper and releasable oil. It is a principal part enlarged view which shows the structure of the oil supply apparatus which provided the application | coating area | region switching means by a shutter plate. It is a schematic explanatory drawing which shows the structure of the application area | region switching means of FIG. 8, and its oil application area. It is a flowchart which shows the control procedure at the time of fixing execution of the application | coating area | region switching means of FIG. It is a principal part schematic perspective view which shows the structure of the application | coating area | region switching means by a shutter plate etc., and an operation state. It is a principal part schematic perspective view which shows the other operation state of the application area | region switching means by a shutter plate. It is principal part explanatory drawing which shows the operation state of the application area | region switching means by a shutter plate. FIG. 3 is a schematic configuration diagram illustrating a main part of a fixing device according to a second embodiment. It is a principal part enlarged view which shows the structure of the oil supply apparatus which provided the application | coating area | region switching means in Example 2. FIG. It is a principal part schematic perspective view which shows the structure of the web from which an oil application | coating area | region differs. It is a principal part schematic perspective view which shows the structure of the application area | region switching means of FIG. 15, and an oil application area | region. FIG. 10 is a schematic configuration diagram illustrating a main part of a fixing device according to a third embodiment. It is explanatory drawing which shows the structure of the paper conveyance belt apparatus provided with the displacement mechanism. FIG. 6 is an explanatory diagram illustrating a relationship between a contact area between a recording sheet displaced by a sheet conveying belt device and a fixing belt.

Explanation of symbols

  1: fixing device, 10: fixing belt, 20, 21: heating roll (heating means), 30, 31: pressure roll (pressure rotating body), 50: oil supply device, 60: coating area switching means, 61, 62: Shutter plate (oil application blocking member), 69: Control device, 50A, 50B: Oil supply device with different oil application regions, Control device 79, 80: Paper transport belt device, 85: Displacement device (shift mechanism), T : Toner image, P: Recording paper, N: Fixing nip part (fixing pressure part).

Claims (4)

An endless fixing belt rotating in a fixed direction, a heating means for heating the fixing belt, and a recording paper carrying a toner image to be fixed on the outer peripheral surface of the fixing belt heated by the heating means. A pressure rotator, and an oil supply device that applies releasable oil to an outer peripheral surface of the fixing belt, and the recording paper is placed on the fixing belt even after passing the fixing pressure unit by the pressure rotator. In a fixing device that peels after transporting a predetermined distance in close contact with the outer peripheral surface,
The fixing device according to claim 1, wherein the oil supply device includes an application region switching means for switching the region of the fixing belt to which the releasable oil is applied in accordance with the size and the feeding direction of the recording paper.   The application area switching means is an oil application that can move between an oil application part that applies releasable oil of the oil supply device and a position where the oil supply part enters and is interposed between the fixing belt and a position where the oil supply apparatus is moved away from the position. 2. The fixing device according to claim 1, comprising a blocking member and control means for moving the oil application blocking member forward and backward.   The application region switching means includes a plurality of oil application units that apply releasable oil in direct or indirect contact with different regions in the width direction of the outer peripheral surface of the fixing belt, and the oil application unit. The fixing device according to claim 1, further comprising a control unit that contacts and separates a predetermined one from the fixing belt. An endless fixing belt rotating in a fixed direction, a heating means for heating the fixing belt, and a recording paper carrying a toner image to be fixed on the outer peripheral surface of the fixing belt heated by the heating means. A pressure rotator, and an oil supply device that applies releasable oil to an outer peripheral surface of the fixing belt, and the recording paper is placed on the fixing belt even after passing the fixing pressure unit by the pressure rotator. In a fixing device that peels after transporting a predetermined distance in close contact with the outer peripheral surface,
In order to make the contact area between the fixing belt and the recording paper different, a mechanism for relatively shifting at least one of the fixing belt and the recording paper according to the size and feeding direction of the recording paper is provided. Fixing device.

Images