JP4918886B2 - Belt fixing device and image forming apparatus - Google Patents

Description

  The present invention relates to a belt fixing device that fixes a toner image on a recording material by heating and pressing, and an image forming apparatus including the belt fixing device.

  2. Description of the Related Art In an electrophotographic image forming apparatus such as a copying machine, a printer, a facsimile machine, and a multifunction machine having these functions, a latent image corresponding to an original is formed on a photosensitive member, and toner is applied to the latent image. Thus, the visualized toner image is transferred onto the recording paper, and then the toner image transferred onto the recording paper is fixed and discharged.

  When a color image is formed, Y, M, C, and K latent images corresponding to the original color are formed on four photosensitive drums, and the visualized four color toner images are endless. After primary transfer to an intermediate transfer member composed of a belt, secondary transfer is performed on recording paper, and the toner image transferred onto the recording paper is fixed and discharged.

  As a fixing device for fixing a toner image in this manner, an endless fixing belt stretched around a heating roller having a heating means such as a halogen heater and a pressure roller, and circulated and driven via the fixing belt. Belt fixing that has an external pressure roller that pressurizes the pressure roller, and that heats and presses while holding and transporting the recording paper onto which the toner image is transferred at the nip formed by the fixing belt and the external pressure roller There is a fixing device of the type, and such a belt fixing device has an advantage that the warming-up time is shortened and the energy is saved because the heat capacity of the heating roller of the fixing belt is small.

  In such a belt fixing device, it is necessary to increase the width of the nip portion in order to enable fixing at a higher speed. In order to improve the separation performance from the fixing belt, it is necessary to increase the curvature of the separation portion in the fixing belt. In any case, it is effective to make the elastic layer of the pressure roller have a lower hardness.

  Sponge can be easily obtained with a low hardness, but if it is used in the elastic layer of a pressure roller, the pressure in the nip portion becomes non-uniform because of the roughness, resulting in minute uneven glossiness and image quality. Further, a roller using a sponge has poor durability performance.

  Solid rubber provides uniform pressure, and there is no such deterioration in image quality or lack of durability. However, when rubber with low hardness is used, there is a problem of tackiness, and the adhesiveness is high and the state is similar to adhesion. . In the nip portion, the solid rubber layer is crushed by a high load, and the surface of the solid rubber is temporarily contracted before entering the nip, and is gradually extended as the pressure in the nip portion increases, and the reverse course is followed after the maximum pressure region has elapsed.

  On the other hand, the belt base is formed of a metal such as nickel electroforming or a high-strength heat-resistant resin such as polyimide, has a larger elastic modulus than a rubber, and hardly expands or contracts. Therefore, the inner surface of the fixing belt and the surface of the pressure roller need to slide in the nip portion. However, if the tackiness is high, the fixing belt cannot slide easily. This causes problems such as wrinkles on the fixing belt.

  In order to avoid this, it is possible to polish the surface of the solid rubber of the pressure roller to an appropriate roughness and make it slippery. However, with low-hardness rubber, the rubber tends to become large lumps when it is torn off by a grindstone, and in order to achieve an appropriate roughness, the management of the polishing conditions must be very strict, and the polishing powder and torn off The immediate part is likely to remain on the surface. After being incorporated in the fixing device, these abrasive powders and broken pieces cause uneven pressure distribution in the nip portion. Further, the abrasive powder or the like is transferred to the fixing belt or the heating roller, so that the heat conduction from the heating roller becomes non-uniform, and as a result, the temperature of the fixing belt becomes non-uniform. These nonuniform pressures and temperatures result in image defects such as uneven brightness. In addition, since the surface is made of low-hardness rubber, there is no change in tackiness, and some tackiness remains. Even if the fixing belt and the pressure roller can be driven, the pressure roller is attached to the inner surface of the fixing belt when the fixing device is assembled. As a result, the assemblability is significantly impaired. Also, if the assembly is forced, the fixing belt will be damaged immediately.

  Therefore, in order to prevent tackiness of the pressure roller surface, the surface of the solid rubber provided on the pressure roller is covered with a low friction resin PFA (perfluoroalkoxy) or PTFE (polytetrafluoroethylene) tube. Or coating. If comprised in this way, a slip property with a fixing belt will improve with a resin layer.

  A fixing device in which a silicone rubber layer of a pressure roller is covered with a PFA tube or the like is known (for example, see Patent Document 1).

Further, the surface of an elastic roller used in a copying machine or the like is required to have a surface roughness according to the application in order to ensure friction with the recording paper. However, when the diameter of the elastic roller is reduced, the thickness of the elastic layer is also reduced, so the hardness of the elastic layer needs to be lowered. When forming such an elastic roller, it is not possible to uniformly form fine irregularities on the surface by conventional grinding or electric discharge machining, etc. A roller is disclosed in the patent publication. In addition, formation of a fine groove | channel is performed by forming a metal mold | die from the mother die manufactured by grinding of the grindstone, and performing injection molding using this metal mold | die (refer patent document 2).
JP 2004-94079 A Japanese Patent Laid-Open No. 10-156841

  If a resin layer made of PFA or PTFE is formed on the surface of the pressure roller, the slipperiness with the fixing belt is improved, and no abnormality occurs in the rotation of the fixing belt. It does not occur, and there is no problem that the working efficiency of assembling the fixing device is lowered.

  However, as described above, when pressure is applied in the nip portion, the low hardness solid rubber of the pressure roller is crushed and the surface tends to expand and contract. In order to obtain a wide nip portion and a high separation curvature, the solid rubber is greatly deformed, and if there is no resin layer, the expansion / contraction ratio is about 10%. In the initial state, the resin layer is in a state of preventing and supporting this deformation, but the resin layer is formed so thin as 10 to 50 μm so as not to impair the softness of the pressure roller. I can't. Since the resin layer does not have elasticity like rubber, the resin layer is gradually extended while repeatedly passing through the nip portion, and cracks are generated when it is eventually extended. Since there is no support by the resin layer in the cracked portion, deformation concentrates on the rubber layer in that portion, and the crack progresses not only in the resin layer but also in the rubber layer. In this case, the fixing pressure is not sufficiently applied at the cracked portion, resulting in uneven gloss and poor fixing. In the worst case, the rubber layer of the pressure roller is broken.

  The present invention has been made in view of such a problem. Even when the elastic layer of the pressure roller in the belt fixing device is covered with a resin layer made of PFA or PTFE, the resin layer or the elastic layer is pressed by the pressure at the nip portion. An object of the present invention is to propose a belt fixing device that does not cause cracks and an image forming apparatus including the belt fixing device.

  Note that Patent Document 1 does not describe a problem that the PFA tube or the silicone rubber layer is torn, and further does not describe any countermeasures to such a problem.

  Further, in Patent Document 2, the elastic roller only forms an elastic layer on the outer periphery of the core material, and forms fine grooves in order to make the surface roughness of the elastic layer uniform. Accordingly, there is no description of a configuration in which the elastic layer is further covered with a resin layer, and there is no description at all about a problem that a crack occurs in the elastic layer and a countermeasure for this.

The object is achieved by the invention described below.
1. An endless fixing belt,
A pressure roller disposed inside the fixing belt;
A pressure member that presses the fixing belt against the pressure roller,
In a belt fixing device for fixing a toner image on a recording material at a nip portion formed between the fixing belt and the pressure member,
The pressure roller has an elastic layer made of solid rubber, the elastic layer is covered with a resin layer, and a plurality of cuts are formed side by side in the circumferential direction of the resin layer. Belt fixing device.
2. 2. The belt fixing device according to 1, wherein the fixing belt is wound around a heating roller heated by a heating unit and the pressure roller.
3. 3. The belt fixing apparatus according to 1 or 2, wherein the fixing belt has at least a heat resistant resin layer.
4). The belt fixing apparatus according to any one of 1 to 3, wherein the fixing belt has at least a metal layer.
5. The belt fixing device according to any one of claims 1 to 4, wherein the plurality of cuts are formed at substantially equal intervals in the circumferential direction of the resin layer.
6). The belt fixing device according to any one of claims 1 to 5, wherein the cut is formed in a groove having a gap on an outer surface of the resin layer.
7). The belt fixing device according to any one of claims 1 to 5, wherein the cut is in close contact with the outer surface of the resin layer without a gap when the pressure roller is not deformed.
8). The belt fixing device according to any one of 1 to 7, wherein the cut is formed continuously from one end to the other end in the axial direction of the pressure roller.
9. Any of 1-7, wherein the cut is formed discontinuously from one end to the other end in the axial direction when the pressure roller is not used, and becomes a continuous cut when the pressure roller is used. The belt fixing device according to claim 1.
10. The belt fixing device according to any one of 1 to 9, wherein the cut is formed substantially parallel to an axial direction of the pressure roller.
11. The cut is formed on one side and the other side of a central portion in the axial direction by a plurality of spirals turning in the direction of the central portion along the rotation direction of the fixing belt. The belt fixing device according to any one of 1 to 9.
12 The belt fixing device according to 10 or 11, wherein the resin layer is further formed with a plurality of cuts along a rotation direction.
13. A plurality of cuts formed in the resin layer are formed by a plurality of spirals turning in one direction and a plurality of spirals turning in the other direction. The belt fixing device as described.
14 The belt fixing device according to any one of 1 to 13, wherein the resin layer is formed by covering a tube of heat resistant resin.
15. The belt fixing device according to any one of 1 to 13, wherein the resin layer is formed by coating a heat resistant resin.
16. An image forming apparatus comprising the belt fixing device according to any one of 16.1 to 15.

  According to the belt fixing device and the image forming apparatus of the present invention, the fixing belt is damaged or flawed, abnormal noise is generated when the fixing belt is driven, the assembling property of the fixing device is deteriorated, uneven gloss, a crack on the pressure roller surface, or the like. In this way, it is possible to realize a wide nip width and high separation performance corresponding to high-speed fixing, while preventing problems such as defective images and breakage of the pressure roller.

  Embodiments of the image forming apparatus according to the present invention will be described below with reference to the drawings.

  First, an example of an image forming apparatus will be described based on the configuration diagram of FIG.

  The image forming apparatus includes an image forming apparatus main body GH and an image reading apparatus YS.

  The image forming apparatus main body GH is called a tandem type color image forming apparatus, and a plurality of sets of image forming units 10Y, 10M, 10C, and 10K, a belt-like intermediate transfer member 6, a sheet feeding and conveying unit, a fixing device 9, and the like. Consists of.

  An image reading device YS including an automatic document feeder 201 and a document image scanning exposure device 202 is installed on the upper part of the image forming apparatus main body GH. The document d placed on the document table of the automatic document feeder 201 is transported by a transport unit, and an image on one or both sides of the document is scanned and exposed by the optical system of the document image scanning exposure device 202, and the line image sensor CCD is scanned. Is read.

  A signal formed by photoelectric conversion by the line image sensor CCD is subjected to analog processing, A / D conversion, shading correction, image compression processing, and the like in an image processing unit, and then exposure means 3Y, 3M, 3C, 3K. Sent to.

  In the image forming unit 10Y that forms a yellow (Y) image, a charging unit 2Y, an exposure unit 3Y, a developing device 4Y, and a cleaning unit 8Y are arranged around the photosensitive drum 1Y. In the image forming unit 10M that forms a magenta (M) color image, a charging unit 2M, an exposure unit 3M, a developing device 4M, and a cleaning unit 8M are arranged around the photosensitive drum 1M. In the image forming unit 10C that forms a cyan (C) color image, a charging unit 2C, an exposure unit 3C, a developing device 4C, and a cleaning unit 8C are arranged around the photosensitive drum 1C. In the image forming unit 10K that forms a black (K) image, a charging unit 2K, an exposure unit 3K, a developing device 4K, and a cleaning unit 8K are arranged around the photosensitive drum 1K. The charging unit 2Y and the exposure unit 3Y, the charging unit 2M and the exposure unit 3M, the charging unit 2C and the exposure device 3C, and the charging unit 2K and the exposure device 3K constitute a latent image forming unit.

  The developing devices 4Y, 4M, 4C, and 4K include a two-component developer including yellow (Y), magenta (M), cyan (C), and black (K) toner having a small particle diameter and a carrier.

  The intermediate transfer member 6 is wound around a plurality of rollers and is circulated.

  The fixing device 9 includes an endless fixing belt 91 that is stretched around a heating roller 92 and a pressure roller 93, and an external pressure roller 94 that presses the pressure roller 93 via the fixing belt 91. The toner image on the recording material (recording paper) P is heated and pressed at a nip portion formed between the fixing belt 91 and the external pressure roller 94 to be fixed.

  Thus, each color image formed by the image forming units 10Y, 10M, 10C, and 10K is sequentially transferred onto the rotating intermediate transfer body 6 by the transfer means 7Y, 7M, 7C, and 7K (primary transfer). A toner image synthesized with a color image is formed. The recording material P accommodated in the paper feeding cassette 20 is fed by the paper feeding means 21 and is conveyed to the transfer means 7A via the paper feeding rollers 22A, 22B, 22C, 22D, the registration rollers 23, etc. A color image is transferred onto P (secondary transfer). The recording material P to which the color image has been transferred is heated and pressurized by the fixing device 9 and the color toner image on the recording material P is fixed. Thereafter, the sheet is sandwiched between the sheet discharge rollers 24 and placed on the sheet discharge tray 25 outside the apparatus.

  On the other hand, after the color image is transferred to the recording material P by the transfer means 7A, the residual toner is removed by the cleaning means 8A from the intermediate transfer body 6 from which the recording material P is separated by curvature.

  Although the above is an image forming apparatus that forms a color image, the present invention can also be applied to an image forming apparatus that forms a monochrome image.

  Next, the belt fixing device according to the present invention will be described with reference to the sectional view of FIG.

  The fixing belt 91 is formed in an endless shape. For example, PI (polyimide) with a thickness of 70 μm or nickel electroforming with a thickness of 40 μm is used as a base, and heat-resistant silicon with a thickness of 200 μm with an outer peripheral surface of the base as an elastic layer. It is covered with rubber (hardness JIS-A 30 °) and further covered with a resin layer of a PFA (perfluoroalkoxy) tube having a thickness of 30 μm. The inner diameter is 80 mm, for example.

  The heating roller 92 incorporates a halogen lamp 92A as a heating means for heating the fixing belt 91. For example, the outer peripheral surface of a cylindrical metal core 92B having a thickness of 2 mm formed of aluminum or the like is heat-resistant to a thickness of 30 μm. It is covered with a resin layer 92c coated with PFA which is a functional resin. The outer diameter is 52 mm, for example.

  Further, as the halogen lamp 92A, in order to correspond to the recording materials P having different widths, for example, portions of 930 W and 600 W are provided in the axial direction to have different heat generation distributions.

  The pressure roller 93 covers a solid core metal 93A formed of a metal such as iron with silicon rubber (hardness JIS-A 10 °) which is a heat-resistant solid rubber having a thickness of 7 mm as an elastic layer 93B. Further, it is covered with a resin layer 93C coated with PFA which is a heat-resistant resin having a thickness of 30 μm and a low friction. In addition, an outer diameter dimension is 40 mm, for example.

  The external pressure roller (pressure member) 94 incorporates a halogen lamp 94A as a heating means for heating the fixing belt 91, and the outer peripheral surface of a cylindrical metal core 94B having a thickness of 2 mm formed of aluminum or the like is provided. The elastic layer 94C is covered with heat-resistant silicon rubber (hardness JIS-A20 °) having a thickness of 2 mm, and further covered with a resin layer 94D of a PFA tube having a thickness of 30 μm. In addition, an outer diameter dimension is 50 mm, for example.

  The external pressure roller 94 presses the fixing belt 91 against the pressure roller 93 by an urging means (not shown).

  The halogen lamp 94A has a uniform heat generation distribution in the axial direction at 530 W, for example.

  Furthermore, a temperature sensor S1 that detects the temperature at the winding portion of the fixing belt 91, a temperature sensor S2 that detects the temperature of the fixing belt 91 just before the nip portion, and a temperature sensor S3 that detects the temperature of the external pressure roller 94. Is provided.

  The resin layers 92C, 93C, and 94D may be formed by covering or coating a tube of a heat-resistant, high-release resin such as PTFE (polytetrafluoroethylene).

  Further, any heating means may be used as the heating means for heating the fixing belt 91, for example, an induction heating heating element using an exciting coil may be used. Further, the heating means is not necessarily arranged in the heating roller 92 or the like, and may be arranged anywhere.

  Further, a fixing device provided with a tension roller for pressing the fixing belt may be used.

  In the above configuration, when the pressure roller 93 is rotated clockwise by a driving unit (not shown), the fixing belt 91 and the heating roller 92 are also rotated clockwise, and the external pressure roller 94 is rotated counterclockwise. The external pressure roller 94 may be driven. Further, the fixing belt 91 in contact with the heating roller 92 is heated by the halogen lamp 92A, and the external pressure roller 94 is also heated by the halogen lamp 94A. Since the external pressure roller 94 is urged in the direction of the pressure roller 93 by an urging means (not shown), the gap between the fixing belt 91 wound around the pressure roller 93 and the external pressure roller 94 is In this nip portion N, the fed recording material P is heated and pressurized, and the toner image on the recording material P is fixed.

  In the fixing device shown in FIG. 2, the heating roller 92 is directly above the pressure roller 93 and the nip portion N is formed on a straight line passing through the center of each other. However, the present invention is not limited to this. Instead, the heating roller 92 may be in the lateral direction of the pressure roller 93, and the nip portion N may be formed in a portion that is not on the straight line.

  In the belt fixing device described above, when the elastic layer 93B of the pressure roller 93 is coated with the resin layer 93C made of PFA or PTFE, the resin layer 93C or the elastic layer 93B is deformed and cracked by the pressure at the nip portion N. May occur.

  Therefore, as shown in FIG. 3, a plurality of cuts 93C1 along the axial direction are provided in at least the resin layer 93C of the pressure roller 93. Thereby, when the nip portion N is pressurized, the cut 93C1 spreads in the circumferential direction.

  In the present embodiment, the width of the nip portion N is about 12 mm, and the cuts 93C1 are provided at intervals of 0.5 mm in the circumferential direction, so that there are 20 or more cuts 93C1 at the nip portion N. The cut 93C1 spreads as the elastic layer 93B of the pressure roller 93 is deformed at the nip portion N. In the case where there is no cut 93C1, if an unintended crack occurs in the resin layer 93C, the surrounding deformation concentrates on that first crack, but in this configuration, it is dispersed over 20 or more cuts 93C1. become. For this reason, the spread of each cut 93C1 is small, and the cut 93C1 does not expand even if it passes through the nip portion N repeatedly. In addition, the depth of the cut 93C1 is extremely small, about the thickness of the resin layer, and even if an unfixed image is pressed via the fixing belt 91, the image is not affected.

  The cut 93C1 of the pressure roller 93 may be a groove having a gap on the outer surface of the V-shaped or U-shaped resin layer 93C. When the pressure roller 93 is not deformed, the cut 93C1 is the resin layer. You may contact | adhere so that there may be no gap | interval in the outer surface of 93C.

  Thus, as an example of a processing method for providing a number of cuts 93C1 in the pressure roller 93, there is a processing method using a jig as shown in FIG.

  4A is a diagram of the jig J viewed from the direction in which the pressure roller 93 is inserted and removed, and FIG. 4B is an enlarged development view of the inner peripheral surface of the jig J.

  The jig J has a plurality of blades J2 on the inner peripheral surface of a cylindrical support member J1. The inner diameter of the inner peripheral surface of the support member J1 is slightly smaller than the outer diameter of the pressure roller 93, and is, for example, −50 μm to −300 μm.

  A plurality of blades J2 protrude from the inner peripheral surface of the support member J1 in the circumferential direction at a predetermined interval. When the pressure roller 93 is inserted from one side of the jig J and removed from the other side, In the resin layer 93C of the pressure roller 93, a plurality of cuts 93C1 are formed along the axial direction as shown in FIG.

  When the cuts 93C1 are formed in the circumferential direction at intervals of 0.5 mm, for example, it is difficult to arrange the blades J2 on the inner peripheral surface of the support member J1 at intervals of 0.5 mm. Therefore, as shown in FIG. 4B, the blades J2 are arranged in four groups in the axial direction, the first group of blades J21, the second group of blades J22, the third group of blades J23, and the fourth group of blades. The blades J24 are arranged at equal intervals of 2 mm in the circumferential direction. Further, the second group of blades J22 is arranged with a phase shift of 0.5 mm in the circumferential direction with respect to the first group of blades J21. The same applies to the third group of blades J23 for the second group of blades J22 and the fourth group of blades J24 for the third group of blades J23. By arranging the blades J2 in this way, the cuts 93C1 are formed at equal intervals of 0.5 mm in the circumferential direction.

  The circumferential interval between the cuts 93C1 is preferably 0.1 mm to 2 mm, and more preferably 0.3 mm to 0.5 mm. That is, if the interval is narrow, it is difficult to arrange the blade J2, and it is difficult to process. Moreover, if the interval is wide, stress concentrates at the cut 93C1, and the cut 93C1 may be enlarged.

  In addition, if the interval between the cuts 93C1 is not very uniform, stress concentration may occur or the elastic layer 93B may have insufficient strength.

  Further, as shown in FIG. 5A, the cut 93C1 may not completely cut the resin layer 93C. When the pressure roller 93 is pressed at the nip portion N, the resin layer 93C is divided. Is sufficient. On the other hand, as shown in FIG. 5B, even if the cut 93C1 penetrates the resin layer 93C and the elastic layer 93B is cut, there is no problem as long as the amount is shallow. However, if the elastic layer 93B is cut deeply, the cut 93C1 grows due to deformation caused by pressurization at the nip portion N, and the elastic layer 93B may be broken.

  Accordingly, the depth of the cut 93C1 is desirably −10 μm to +100 μm, and more desirably 0 μm to 30 μm, based on the boundary surface 93D between the resin layer 93C and the elastic layer 93B. The numerical value “−” corresponds to a state where the cut 93C1 does not reach the boundary surface 93D, and the numerical value “+” corresponds to a state where the cut 93C1 reaches a position deeper than the boundary surface 93D.

  The resin layer 93C is preferably a low friction resin, but may be a heat resistant resin such as polyimide or polyamideimide. Moreover, you may form by coating instead of coating | cover of a tube. On the other hand, as the elastic layer 93B, fluorine rubber can be used in addition to silicon rubber.

  In other words, when the tube is used as the resin layer 93C, the tube is bonded to the elastic layer 93B, and therefore the resin layer 93C does not peel even if the resin layer 93C is completely cut at the cut 93C1. .

  Furthermore, using the fixing device 9 described with reference to FIG. 2, the resin layer was provided with the cut 93C1 as described above, and continuous feeding was performed.

The experimental conditions of the fixing device 92 are as follows.
・ Fixing load: 700N
・ Fixing belt tension: 42N
・ Paper feed speed: 150 to 300 mm / s
Fixing belt control temperature: 150 to 210 ° C
・ External pressure roller control temperature: 120 ~ 160 ℃
-Number of sheets passed: 600,000 sheets As a result of this experiment, no problem occurred.

  As described above, by providing the cut 93 </ b> C <b> 1 in the pressure roller 93, a minute slip is possible when the resin layer 93 </ b> C of the pressure roller 93 contacts the fixing belt 91 at the nip portion N, and the fixing belt 91 is damaged. No abnormal noise is generated. Moreover, since the break 93C1 is extremely small and there are many, the enlargement of the break 93C1 is dispersed. Therefore, there is no occurrence of a break that occurs as in the conventional case leading to destruction of the elastic layer 93B.

  Further, at the time of assembling the fixing device, the resin layer 93C comes into contact with the fixing belt 91 instead of the low-hardness elastic layer 93B. Therefore, the pressure roller 93 slides well inside the fixing belt 91 and can be easily assembled.

  Further, the cut provided in the pressure roller 93 is not limited to the cut provided in parallel to the axial direction as shown in FIG. 3, and various modifications can be considered. This is shown in FIG. FIG. 6 is a developed view of the outer peripheral surface of the pressure roller 93, and the horizontal direction is the axial direction.

  In FIG. 6A, the cut is inclined from the both ends in the axial direction of the pressure roller 93 toward the center, and is formed in a spiral shape on the circumference. In this drawing, the fixing belt 91 rotates in the direction of the arrow. Therefore, in addition to the above-described effects, the longitudinal deviation of the pressure roller 93 can be corrected.

  In FIG. 6B, a plurality of cuts perpendicular to the cuts provided in the axial direction are formed. Actually, the resin layer 93 </ b> C and the elastic layer 93 </ b> B of the pressure roller 93 are also deformed in the axial direction by pressing at the nip portion N. At this time, there is no problem at the central portion in the axial direction, but at the end portion in the axial direction, deformation that the elastic layer 93B escapes toward the end portion becomes large. Therefore, in addition to the above effects, the occurrence of cracks in the resin layer 93C and the like due to the deformation of the end portion in the axial direction can be prevented.

  In FIG. 6C, a plurality of cuts having different inclination directions are formed in a spiral shape. Therefore, as compared with the case where the cuts parallel to the axial direction are provided, the same effect as that obtained when the gaps are narrowed even when the gaps are coarse is produced.

  As a processing method for forming a spiral cut, the pressure roller 93 or the jig J may be moved in the axial direction while rotating. In this case, the positions of the blades of the first to fourth groups shown in FIG. 4B are corrected so as to rotate the jig so that they are equally spaced in the circumferential direction. Further, as a processing method for forming a cut perpendicular to the axial direction, a jig having a plurality of blades may be disposed in the axial direction, and the pressure roller 93 may be contacted and rotated.

  Furthermore, laser processing is mentioned as a processing method for forming a cut in the pressure roller 93, which will be described in detail.

  In this case, the resin layer 93C of the pressure roller 93 may be irradiated with laser light. However, in order to prevent the laser light passing through the resin layer 93C from excessively damaging the elastic layer 93B, for example, the resin layer 93C contains carbon black in a PFA tube, and the laser light is efficiently absorbed by the resin layer 93C. It is desirable to do so. In addition, it is preferable to contain 1-15% of carbon black. Further, as an additive for improving the absorption rate, various pigments may be used instead of carbon black. The pressure roller 93 is not required to be releasable as compared with the external pressure roller 94 that comes into contact with the toner image. Therefore, no problem occurs even if the above-mentioned additives are added.

  As a processing method using a laser, first, the outer peripheral surface is irradiated with laser light over the entire length of the pressure roller 93 while moving the pressure roller 93 in the axial direction. Subsequently, the pressure roller 93 is rotated, for example, by 0.5 mm to 2 mm around the central axis, and laser light is irradiated in the same manner as described above. If this is repeated, a plurality of cuts 93C1 along the axial direction of the pressure roller 93 are formed as shown in FIG.

  Further, the laser beam may be scanned by a polygon mirror or a galvanometer mirror without moving the pressure roller 93 in the axial direction.

  The laser output, irradiation beam diameter, and scanning speed are such that the resin layer 93C such as a PFA tube melts, the resin layer 93C spreads along the cut 93C1 when pressurizing the nip portion, and damage to the elastic layer 93B is minimized. Set as follows. The depth of the cut 93C1 formed in the elastic layer 93B is desirably 200 μm or less. Further, when the laser beam is irradiated, since the resin layer 93C of the resin is once melted by heat, it is difficult for the resin layer 93C and the elastic layer 93B to peel off at the cut 93C1, and the jig as described above. Compared to the case of cutting using J, the durability is superior.

  Also in this case, the resin layer 93C is desirably a low friction resin in terms of slipperiness, but may be a general heat resistant resin such as polyimide, polyamideimide, PTFE, or the like. Moreover, you may form by coating instead of coating | cover of a tube.

  On the other hand, as the elastic layer 93B, fluorine rubber is also suitable in addition to silicon rubber. When a fluororesin is used for the resin layer 93C, fluororubber is more preferable from the viewpoint of the adhesiveness between the resin layer 93C and the elastic layer 93B. For the purpose of improving thermal conductivity, rubber added with metal oxide or the like is often used. However, thermal conductivity is not indispensable for the pressure roller 93 of this configuration, but rather heat loss. In order to suppress this, low thermal conductivity is preferable.

  Therefore, in order to minimize damage to the elastic layer 93B due to the laser light, reducing the additive to the rubber or eliminating the additive to make a transparent or translucent rubber, and dispersing the absorption of the laser light by the rubber, Damage to the elastic layer 93B can be minimized.

  Further, a cut 93C1 was formed in the resin layer 93C by laser processing, and 600,000 sheets were continuously fed under the same experimental conditions as when the cut 93C1 was formed by the jig J. As a result of this experiment, no problem occurred. Then, the same effect as that obtained when the cut 93C1 was formed by the jig J was obtained.

  Also, when the cut 93C1 is formed in the resin layer 93C by laser processing, in order to satisfy other functions in addition to the absorption of the deformation in the circumferential direction at the nip portion N, as shown in FIGS. 6A to 6C. You may process as follows.

  Furthermore, since arbitrary processing is possible in the case of laser processing, an arbitrary pattern of cuts such as continuous waveform cuts and continuous chevron cuts in the axial direction may be formed.

  It should be noted that the distribution pattern of cuts for obtaining the effects of the present invention is not limited to that exemplified above. When the surface of the pressure roller is scanned in the circumferential direction at an arbitrary position in the axial direction, it suffices if there are cuts having an appropriate depth at appropriate intervals. Further, even if the cut is not continuous from one axial end to the other axial end but is formed discontinuously, the cut may be continuous when the pressure roller is used.

  Further, even if the cuts and the distribution pattern thereof do not satisfy the above requirements at the time of processing, the same effect can be obtained as long as the above requirements are satisfied immediately when deformed at the nip portion. For example, a groove or perforation of an appropriate pattern is provided in the resin layer before coating the elastic layer of the pressure roller, and when the pressure roller is deformed by receiving a load at the nip portion, the groove or perforation The resin layer may be torn along. These grooves and perforations may be processed after the resin layer is coated on the elastic layer.

  The belt fixing apparatus shown in FIG. 2 is an upper belt system that uses a fixing belt on the image surface side. In order to increase the supply amount from the fixing belt from the viewpoint of thermal efficiency, it is necessary to increase the set temperature of the fixing belt. is there. Inevitably, the temperature of the pressure roller disposed inside the fixing belt increases, and the elastic modulus of the elastic layer decreases. For this reason, the deformation rate at the nip portion is increased, the problem of the present invention is further increased, and the effect is particularly remarkable.

  However, the belt fixing device that should form a plurality of cuts as described above in the pressure roller is not limited to the belt fixing device having the configuration shown in FIG. The same effect can be obtained. 7 to 10 show another embodiment of the belt fixing device.

  In the belt fixing device shown in FIG. 7, the fixing belt 191 is stretched around the guide member 195 in addition to the heating roller 192 and the pressure roller 193 having a predetermined thickness of an elastic layer and a resin layer. Supported, a load is applied to the external pressure roller (pressure member) 194. Further, the fixing belt belt 191 is pressed against the external pressure roller 194 from the inside of the fixing belt belt 191 by a pressure pad 196 made of silicone rubber disposed between the pressure roller 193 and the guide member 195. Thereby, the width of the nip portion N is further increased. The pressure roller 193 has a plurality of cuts as described above. A roller may be used instead of the pressing pad 196.

  In the belt fixing device shown in FIG. 8, the fixing belt 291 is wound around a pressure roller 293 having a predetermined thickness of an elastic layer and a resin layer, and two rollers 294 and 295, and the outer peripheral surface of the fixing belt 291 is heated around the heating roller 292. (Pressure member) is in pressure contact. A pressing pad 296 holds the inner peripheral surface of the fixing belt 291. Thereby, the width of the nip portion N is further increased. The pressure roller 293 has a plurality of cuts as described above. The pressure roller 293 acts as a separation roller for separating the recording material. Since the separation roller has a high load and a large deformation rate of the elastic layer, the effect when a plurality of cuts are formed as described above is great.

  In the belt fixing device shown in FIG. 9, a fixing belt 391 is stretched between a heating roller 392 and one pressure roller 393, and a pressure belt 396 is stretched along with two rollers 395 on the other pressure roller 394. . The pressure rollers 393 and 394 each have an elastic layer and a resin layer having a predetermined thickness. The pressure roller 394 presses the pressure roller 393 through the pressure belt 396 and the fixing belt 391. The unfixed image of the recording material P is held on the pressure belt 369 in front of the nip portion N and preheated, so that high fixability can be obtained, and the recording material P can be fixed to the pressure belt 369 even after passing through the nip portion N. Can be transported stably. In this case, the pressure roller 394 corresponds to a pressure member for the pressure roller 393. However, the pressure roller 393 may be a pressure member for the pressure roller 394, and both the pressure roller 393 and the pressure roller 394 are used. In addition, it is desirable to form a plurality of cuts as described above.

  Further, instead of the pressure roller 394, a pressure pad may be used as the pressure member.

  In the belt fixing device shown in FIG. 10, the fixing belt 491 is stretched between a heating roller 492 and two pressure rollers 493 and 494, and the pressure belt 495 is another heating roller 496 and the other two pressure rollers 497 and 498. It is stretched around. The pressure rollers 493, 494, 497, and 498 each have an elastic layer and a resin layer having a predetermined thickness. The pressure roller 497 is in pressure contact with the pressure roller 493, and the pressure roller 498 is in pressure contact with the pressure roller 494 via the pressure belt 495 and the fixing belt 491, respectively. Thereby, the width | variety of the nip part N is securable. Further, the nip portion N achieves both high fixability and high separation performance. In this case, the pressure roller 497 corresponds to a pressure member for the pressure roller 493, and the pressure roller 498 corresponds to a pressure member for the pressure roller 494, but this may be reversed. It is desirable to form a plurality of cuts in 493, 494, 497, and 498 as described above.

  In the present invention, a roller group referred to as a pressure roller means a member for applying pressure to an image on a transfer material such as recording paper, and which member is actually fixed and which member is a spring or the like. There is no limitation on whether to apply a load to the opposing member by urging or to move the member in a configuration involving contact or separation.

  For example, in the fixing device of FIG. 2, the pressure roller 93 is fixed and the external pressure roller 94 is urged by a spring, or the external pressure roller 94 is fixed and the pressure roller 93 or the pressure roller. 93, the fixing belt 91, the heating roller 92, and the like are integrated and urged by a spring is not limited to either one in obtaining the effect of the present invention.

1 is a configuration diagram of an image forming apparatus. FIG. 3 is a cross-sectional view of a fixing device. It is a perspective view of the pressure roller in which the cut was formed. It is a figure of the jig | tool which forms a cut | interruption. It is a figure which shows the depth of a cut | interruption. It is a figure which shows the modification of a cut | interruption. It is sectional drawing of the belt fixing apparatus of another form. It is sectional drawing of the belt fixing apparatus of another form. It is sectional drawing of the belt fixing apparatus of another form. It is sectional drawing of the belt fixing apparatus of another form.

Explanation of symbols

91,191,291,391,491 Fixing belt 92,192,292,392,492 Heating roller 93,193,293,393,394,493,494,497,498 Pressure roller 93B Elastic layer 93C Resin layer 93C1 94 External pressure roller P Recording material N Nip part J Jig

Claims (16)

An endless fixing belt,
A pressure roller disposed inside the fixing belt;
A pressure member that presses the fixing belt against the pressure roller,
In a belt fixing device for fixing a toner image on a recording material at a nip portion formed between the fixing belt and the pressure member,
The pressure roller has an elastic layer made of solid rubber, the elastic layer is covered with a resin layer, and a plurality of cuts are formed side by side in the circumferential direction of the resin layer. Belt fixing device. The belt fixing device according to claim 1, wherein the fixing belt is wound around a heating roller heated by a heating unit and the pressure roller. The belt fixing device according to claim 1, wherein the fixing belt has at least a heat resistant resin layer. The belt fixing device according to claim 1, wherein the fixing belt has at least a metal layer. The belt fixing device according to claim 1, wherein the plurality of cuts are formed at substantially equal intervals in the circumferential direction of the resin layer. The belt fixing device according to claim 1, wherein the cut is formed in a groove having a gap on an outer surface of the resin layer. The belt fixing device according to any one of claims 1 to 5, wherein the cut is in close contact with the outer surface of the resin layer without a gap when the pressure roller is not deformed. . The belt fixing device according to claim 1, wherein the cut is formed continuously from one end to the other end in the axial direction of the pressure roller. The cut is formed discontinuously from one end to the other end in the axial direction when the pressure roller is not used, and becomes a continuous cut when the pressure roller is used. The belt fixing device according to any one of the above. The belt fixing device according to claim 1, wherein the cut is formed substantially parallel to an axial direction of the pressure roller. The cut is formed on one side and the other side of a central portion in the axial direction by a plurality of spirals turning in the direction of the central portion along the rotation direction of the fixing belt. The belt fixing device according to any one of claims 1 to 9. The belt fixing device according to claim 10, wherein a plurality of cuts along a rotation direction are further formed in the resin layer. The plurality of cuts formed in the resin layer are formed by a plurality of spirals turning in one direction and a plurality of spirals turning in the other direction. The belt fixing device according to Item. The belt fixing device according to claim 1, wherein the resin layer is formed by covering a tube of heat resistant resin. The belt fixing device according to claim 1, wherein the resin layer is formed by coating a heat resistant resin. An image forming apparatus comprising the belt fixing device according to claim 1.

Images