JP4645270B2 - Fixing apparatus and image forming apparatus - Google Patents

Description

  The present invention relates to a belt fixing device, and more particularly to a fixing device that prevents the belt from being offset or meandered.

  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 a recording material, and then the toner image transferred onto the recording material 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 the primary transfer onto the intermediate transfer member composed of a belt, the toner image is transferred onto the recording material and then the toner image transferred onto the recording material is fixed and discharged.

  As a fixing device for fixing a toner image in this way, a heating roller incorporating a halogen heater and the like, an endless fixing belt stretched between the fixing roller, a pressure roller for pressing the fixing roller through the fixing belt, and There is a belt-fixing type fixing device that heats and presses a recording material onto which a toner image is transferred at a nip portion formed by a fixing belt and a pressure roller. Since the heat capacity of the fixing belt is small, the belt fixing device has an advantage of shortening the warm-up time and saving energy.

  However, strictly speaking, in the belt fixing device, due to manufacturing errors, the heating roller and the fixing roller are not always formed in the same outer diameter dimension in the longitudinal direction, and they are accurately arranged in parallel. Not necessarily. Further, the fixing belt is not always formed with the same circumferential length and thickness at the same position in the width direction. For this reason, the fixing belt may be shifted to the left or right or meandering on the roller.

  In order to prevent the fixing belt from being displaced, a flange is conventionally provided at the end of the roller. However, if the flange is small, the end of the fixing belt may ride on the flange. In addition, when the flange is enlarged, the end of the fixing belt continues to be in sliding contact with the flange, so that the end of the fixing belt is worn and the durability performance is deteriorated or smooth circulation drive cannot be performed. To do. In addition, the end of the fixing belt may be wrinkled, which may cause wrinkles on the recording paper or uneven fixing.

Therefore, a belt fixing device that pressurizes the heating roller with an endless belt stretched between a plurality of rollers, and heats and pressurizes the recording material onto which the toner image is transferred at a nip portion formed between the endless belt and the heating roller. There is a belt fixing device in which a steering roller is disposed as one of rollers for stretching an endless belt (see Patent Documents 1 and 2). According to this, since the steering roller is provided, when the endless belt is offset, the endless belt can be corrected by moving the endless belt in the reverse direction by tilting one roller shaft by the motor.
Japanese Patent Laid-Open No. 10-203684 Japanese Patent Laid-Open No. 11-024460

  In the belt fixing device, when a steering roller is used as described in Patent Documents 1 and 2 in order to prevent the belt from being displaced, a sensor for detecting the end of the belt, a motor for tilting the roller shaft, and a sensor A controller or the like for controlling the motor based on the information detected by is provided. Accordingly, a large number of mechanical parts and electric parts are required, which is complicated, large and expensive, and also requires electric power for controlling the steering roller. Therefore, since the energy is not saved, the significance of using the belt fixing device is halved.

  SUMMARY OF THE INVENTION The present invention has been made in view of such a problem. A fixing device capable of preventing belt deviation and meandering without requiring special power without being complicated and large-sized, and the fixing device. An object of the present invention is to propose an image forming apparatus provided.

  The above object can be achieved by any of the following configurations.

  [1] It has at least an endless fixing belt that is circulated and driven around a heating roller and a fixing roller, and a pressure roller that presses the fixing roller through the fixing belt. In a fixing device that heats and pressurizes a toner image on a recording material at a nip portion formed between the heated fixing belt and the pressure roller, the roller is divided in the longitudinal direction and a plurality of divided bodies Formed in parallel in the circumferential direction, and provided with a meandering prevention roller that pivotally supports each of the plurality of divided bodies in a seesaw shape in the longitudinal direction, and the fixing belt is stretched around the meandering prevention roller. A fixing device.

  [2] The fixing device according to [1], wherein the meandering prevention roller is disposed at a position where the pressure roller does not press the meandering prevention roller via the fixing belt.

  [3] A nip portion formed between a pressure roller and an endless pressure belt that is stretched around at least two rollers and driven to circulate, and is heated by a predetermined heating means. In the fixing device for fixing the toner image on the recording material by heating and pressurizing, the roller is divided in the longitudinal direction to form a plurality of divided bodies, which are arranged side by side in the circumferential direction. A fixing device comprising a meandering prevention roller pivotally supported in a seesaw-like manner so that the pressure belt is stretched around the meandering prevention roller.

  [4] The fixing device according to [3], wherein the meandering prevention roller is disposed at a position where the heating roller is not pressed via the pressure belt.

  [5] An image forming apparatus comprising the fixing device according to any one of [1 to 4].

  According to the fixing device and the image forming apparatus of the present invention, since the meandering prevention roller is disposed on one of the rollers for stretching the fixing belt or the pressure belt, it is possible to reliably prevent the belt from being offset or meandered. . In particular, the end of the fixing belt does not wear due to the flange at the end of the tension roller and the durability performance is not lowered, or smooth circulation drive cannot be performed, and the end of the fixing belt is wrinkled, There will be no wrinkles or uneven fixing on the recording paper. Further, unlike the case where a steering roller is used, it does not become complicated and large-sized and does not require special power.

  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 body 6 is wound around a plurality of rollers and is rotatably supported.

  The fixing device 9 includes an endless fixing belt 91 that is stretched around a heating roller 92, a fixing roller 93, and a meandering prevention roller 94, and a pressure roller 95 that presses the fixing roller 93 via the fixing belt 91. The toner image on the recording paper (recording material) P is heated and pressed at a nip portion formed between the fixing belt 91 and the pressure roller 95 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 paper (recording material) P stored in the paper feeding cassette 20 is fed by the paper feeding means 21 and conveyed to the transfer means 7A via the paper feeding rollers 22A, 22B, 22C, 22D, the registration rollers 23, and the like. Then, a color image is transferred onto the recording paper P (secondary transfer). The recording paper 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 paper 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 paper 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 paper 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 in detail with reference to the sectional view of FIG.

  The fixing belt 91 is formed in an endless shape, and is stretched around the heating roller 92, the fixing roller 93, and the meandering prevention roller 94, and is driven to circulate. The fixing belt 91 uses, for example, a heat-resistant resin belt made of PI (polyimide) having a thickness of 70 μm as a base, and a heat-resistant silicon rubber having a thickness of 200 μm with an outer peripheral surface of the base as an elastic layer (hardness JIS-A30). And a PFA (perfluoroalkoxy) tube having a thickness of 30 μm as a release layer.

  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 hollow rotating body 92B having a thickness of 2 mm formed of aluminum or the like is formed on a heat-resistant PFA. It is covered with a tube 92C and configured as a hard roller.

  The fixing roller 93 is configured as a soft roller, for example, by covering a solid core metal 93A formed of a metal such as iron with a heat-resistant silicon sponge 93B having a thickness of 10 mm.

  The meandering prevention roller 94 divides the roller in the longitudinal direction to form a plurality of divided bodies 941 that are arranged side by side in the circumferential direction, and each of the divided bodies 941 is supported so as to be tiltable in a seesaw shape in the longitudinal direction. Yes. Details will be described later.

  The pressure roller 95 incorporates a halogen lamp 95A as a heating means for heating the fixing belt 91. For example, the outer peripheral surface of a cylindrical hollow rotating body 95B having a thickness of 3 mm made of aluminum or the like is formed on the outer peripheral surface of the thickness 3 mm. It is covered with a heat-resistant silicone rubber 95C (hardness JIS-A 30 °), and further is covered with a PFA (perfluoroalkoxy) tube 95D having a thickness of 50 μm as a release layer to constitute a hard roller.

  Further, a temperature sensor S <b> 1 that detects the temperature of the heating roller 92 and a temperature sensor S <b> 2 that detects the temperature of the pressure roller 95 are provided via the fixing belt 91.

  Note that any heating means may be used as a heating means for heating the fixing belt 91, for example, an induction heating heating element using an excitation 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.

  In the above configuration, when the fixing roller 93 is rotated clockwise by a driving means (not shown), the fixing belt 91, the heating roller 92, and the meandering prevention roller 94 are also rotated clockwise, and the pressure roller 95 is counterclockwise. Rotate. Further, the fixing belt 91 in contact with the heating roller 92 is heated by the halogen lamp 92A, and the pressure roller 95 is also heated by the halogen lamp 95A. Since the pressure roller 95 is urged in the direction of the fixing roller 93 by an urging means (not shown), the nip portion N between the fixing belt 91 wound around the fixing roller 93 and the pressure roller 95. Thus, the fed recording paper P is heated and pressurized, and the toner image on the recording paper P is fixed.

  Even if the fixing belt 91 is displaced in the width direction or meanders for some reason, it is eliminated by the characteristics of the meandering prevention roller 94 described later. Etc. does not occur.

  Next, the meandering prevention roller 94 will be described in detail with reference to FIGS. 3 is a perspective view of the meandering prevention roller 94, and FIG. 4 is a cross-sectional view of the meandering prevention roller 94. As shown in FIG.

  In both figures, the meandering prevention roller 94 has four divided bodies 941 obtained by equally dividing a roller having an outer surface formed in a substantially drum shape in the longitudinal direction. The divided bodies 941 are arranged side by side with a predetermined gap in the circumferential direction.

  The rotation shaft 942 of the meandering prevention roller 94 has a support portion 943 in the center, and each support portion 943 has a recess 943A and a pair of attachment portions 943B standing from the edge of the recess 943A at positions spaced by 90 degrees. ing.

  On the other hand, each of the divided bodies 941 has a convex portion 941A protruding to the inner surface side, and after inserting the convex portion 941A into the concave portion 943A of the support portion 943, the support pin 944 is inserted from the hole provided in one mounting portion 943B. Then, the hole provided in the convex portion 941A is penetrated and inserted into the hole provided in the other mounting portion 943B. Accordingly, the divided body 941 can be tilted in a seesaw shape in the longitudinal direction around the support pin 944.

  Further, a tension spring 945 is locked between the tip of the convex portion 941A and the bottom portion of the concave portion 943A, and the divided body 941 can be inclined in any of the longitudinal directions by the biasing force. When the divided body 941 is tilted in one direction, the tension spring 945 acts to restore the neutral position.

  In the meandering prevention roller 94 configured as described above, when the fixing belt 91 is shifted to one side for some reason, the support pins 944 are arranged so that the four divided bodies 941 are close to each other on the shifted side. Inclining to the center, the outer diameter of the four divided bodies 941 is reduced, and the outer diameter of the four divided bodies 941 is increased on the other side. Since the belt has the habit of moving to the thicker outer diameter side, the fixing belt 91 offset to the thinner outer diameter side moves to the thicker outer diameter side and is restored to its original position.

  Therefore, by using the meandering prevention roller 94, it is possible to easily correct the deviation of the fixing belt and the meandering, and it does not become large and does not require special power.

  The roller may be divided into six in the longitudinal direction to form six divided bodies.

  Further, instead of dividing a roller having an outer surface formed in a substantially drum shape, a plurality of divided bodies may be formed by dividing a roller having the same outer diameter in the longitudinal direction.

  Further, the fixing device using the meandering prevention roller is not limited to the fixing device as shown in FIG. 2, but may be a fixing device as shown in FIG. 5, for example.

  In FIG. 5, reference numeral 193 denotes a heating roller, which incorporates a halogen lamp 193A as a heating means, and covers the outer peripheral surface of a cylindrical hollow rotating body 193B made of aluminum or the like with a heat-resistant silicone rubber 193C. ing. A pressure belt 191 is stretched between a support roller 195, a pressure roller 196, and a meandering prevention roller 197. The pressure belt 191 located between the support roller 195 and the pressure roller 196 The nip portion N is formed by applying pressure. In the nip portion N, the fed recording paper P is heated and pressurized, and the toner image on the recording paper P is fixed.

  In this way, by providing the meandering prevention roller 197, the end of the pressure belt 191 is not worn, uneven fixing, or the like does not occur.

  As described above, examples of the two types of belt fixing devices using the meandering prevention roller have been shown. However, the belt fixing device is not limited to this and may take any form.

  However, since the plurality of divided bodies of the meandering prevention roller are arranged with a predetermined gap, it is desirable to arrange the meandering prevention roller at a position that does not contribute to the formation of the nip portion. In other words, in the belt fixing device shown in FIG. 2, it is desirable that the meandering prevention roller 94 is disposed at a position where the pressure roller 95 does not press the meandering prevention roller 94 via the fixing belt 91. Further, in the belt fixing device shown in FIG. 5, it is desirable that the meandering prevention roller 197 is disposed at a position where the heating roller 193 is not pressed via the pressure belt 191.

  Further, the meandering prevention roller for stretching the fixing belt or the pressure belt is not necessarily one, and may be a plurality.

1 is a configuration diagram of an image forming apparatus. It is sectional drawing of a belt fixing apparatus. It is a perspective view of a meandering prevention roller. It is sectional drawing of a meandering prevention roller. It is sectional drawing of the belt fixing apparatus of another form.

Explanation of symbols

91 Fixing belt 92, 193 Heating roller 93 Fixing roller 94, 197 Meander prevention roller 941 Divided body 95 Pressure roller 191 Pressure belt 195 Support roller 196 Pressure roller P Recording paper N Nip part

Claims (5)

An endless fixing belt stretched around at least a heating roller and a fixing roller and circulated and a pressure roller that pressurizes the fixing roller through the fixing belt, and is heated by a predetermined heating unit. In a fixing device for fixing a toner image on a recording material by heating and pressing at a nip portion formed between the fixing belt and the pressure roller,
The roller is divided in the longitudinal direction to form a plurality of divided bodies and arranged side by side in the circumferential direction, and each of the plurality of divided bodies is provided with a meandering prevention roller that is pivotably supported in a seesaw shape in the longitudinal direction,
The fixing device, wherein the fixing belt is stretched also on the meandering prevention roller. The fixing device according to claim 1, wherein the meandering prevention roller is disposed at a position where the pressure roller does not press the meandering prevention roller via the fixing belt. A recording material having an endless pressure belt stretched around at least two rollers and circulated and driven by a predetermined heating means and a nip formed between the pressure belt In a fixing device that heats and pressurizes the upper toner image,
The roller is divided in the longitudinal direction to form a plurality of divided bodies and arranged side by side in the circumferential direction, and each of the plurality of divided bodies is provided with a meandering prevention roller that is pivotably supported in a seesaw shape in the longitudinal direction,
The fixing device, wherein the pressure belt is stretched also on the meandering prevention roller. The fixing device according to claim 3, wherein the meandering prevention roller is disposed at a position where the heating roller is not pressed via the pressure belt. An image forming apparatus comprising the fixing device according to claim 1.

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