JP5171058B2 - Image forming apparatus and fixing device - Google Patents

Description

  The present invention relates to a belt driving device and a fixing device in an image forming apparatus such as a copying machine, a printer, a facsimile, and a composite machine using the electrophotographic method using the belt driving device, and in particular, the surface layer is an elastic layer. A belt having a belt guide for axial movement restriction provided on a surface in contact with the outer surface of the roller on the axial end side, which is stretched between a pressure roller and a tension roller that are in pressure contact with the pressed roller. The present invention relates to a belt driving device and a fixing device in an image forming apparatus using the belt driving device.

  In an image forming apparatus such as a copying machine, a printer, a facsimile machine, or a composite machine using an electrophotographic system, it includes a plurality of rollers and a cylindrical belt member (hereinafter also simply referred to as a belt) that is rotatably supported by these rollers. A belt driving device is used for an intermediate transfer member, a transfer member, a fixing device, and the like.

  In such a belt driving device, the deviation of the belt occurs due to the parallelism of the roller supporting the belt and other factors. For example, in the intermediate transfer member or the transfer member, the formed toner images are superimposed. When the toner image is shifted, color unevenness occurs, and image noise occurs in the fixing device. Also, when transporting paper, the paper is sent out of the transport path and may cause jams.

  Therefore, conventionally, in order to prevent the deviation of the belt in such a belt driving device, for example, Patent Document 1 discloses a belt conveyance provided with a fixed guide member that abuts the belt end surface and restricts the movement of the belt in the width direction. The device is shown. Further, Patent Document 2 discloses an image forming apparatus in which a shift guide is provided on a surface of the both ends of the intermediate transfer belt that is in contact with the outer surface of the roller, and the shift guide contacts the end of the roller to drive the belt. It is shown.

JP-A-8-225180 JP 2006-154330 A

  Currently, there is a demand for downsizing, speeding up, and price reduction of image forming apparatuses. For this reason, fixing rollers and the like having a small diameter are used, and the conveyance speed of paper is increasing. In order to increase the speed, it is necessary to speed up the warm-up, so that the elastic layer of the heat roller is also made thin. In this way, the diameter of the heat roller is reduced and the elastic layer is made thin, When the transport speed is increased, the time during which the transported paper is heated is shortened.

  For this reason, a pressure roller using an elastic layer such as silicon rubber is pressed against a fixing roller with a built-in heater to increase the nip area, and a belt is stretched between the pressure roller and the tension roller. There has been proposed a fixing device using a belt driving device in which a region is formed to cope with shortening of the heating time of the conveyed paper and the paper is sufficiently heated.

  However, even in the fixing device using such a belt driving device, the above-described deviation of the belt occurs, and it is necessary to prevent this deviation by some method. However, in the belt conveyance device disclosed in Patent Document 1, since the fixed guide member that regulates the movement of the belt in the width direction comes into contact with the belt end, the belt end tends to be painful and the belt may be damaged.

  Further, in the image forming apparatus disclosed in Patent Document 2, a shift guide is provided on the surface of the both ends of the intermediate transfer belt that contacts the outer surface of the roller, and the shift guide contacts the end of the roller to regulate the shift of the belt. When a pressure roller using an elastic layer is in pressure contact with the fixing roller described above, the frictional force increases when this side guide and the elastic layer of the pressure roller come into contact with each other. The slip guide may be damaged.

  Therefore, in the present invention, the surface layer is made of an elastic layer such as silicon rubber, and the pressure roller and the tension roller that are pressed against a pressure roller such as a fixing roller are axially aligned with the surface in contact with the outer surface of the roller on the axial end side. In a belt drive device that stretches and drives a belt provided with a belt guide for movement restriction, the elastic layer and belt on the surface of the pressure roller, and the belt guide for movement restriction in the axial direction are not damaged. It is an object to provide a belt driving device and a fixing device in an image forming apparatus using the belt driving device which can regulate axial movement.

In order to solve the above problems, a belt driving device according to the present invention is provided.
A pressure roller and a tension roller that are in pressure contact with the pressure roller using the surface layer as an elastic layer are provided on a surface that is stretched between the pressure roller and the tension roller and in contact with the outer surface of the roller on the axial end side. A belt driving device for driving a belt having a first belt guide for axial movement restriction,
The pressure roller is the length that axial length is not in contact with the first belt guide, at a distance from the roller end, a larger diameter than the contacting pressure roller diameter in the axial direction end portion of the belt And a second belt guide that is rotatable on the shaft of the pressure roller, the tension roller has a length in contact with the first belt guide at an axial end, and the pressure roller is The diameter of the position corresponding to the second belt guide is a diameter that does not contact the second belt guide.
The tension roller comes into contact with the belt guide from the inside at both axial ends, and the pressure roller comes into contact with the belt from the outside through a second belt guide, so that both the axial ends of the tension roller and the second By restricting the belt from both sides by the belt guide, it is possible to prevent the belt from moving in the axial direction.

Further, the fixing device in the image forming apparatus using this belt driving device is:
A fixing device provided in an image forming apparatus, which heats and pressurizes a sheet carrying a toner image formed by an electrophotographic method,
The fixing device includes a heat roller as a pressure roller, a pressure roller pressed against the heat roller and having a surface layer as an elastic layer, and stretched between the pressure roller and the tension roller. In a fixing device in an image forming apparatus using a belt driving device that drives a belt having a first belt guide for axial movement restriction provided on a surface in contact with an outer surface of a roller on the side,
The pressure roller is the length that axial length is not in contact with the first belt guide, at a distance from the roller end, a larger diameter than the contacting pressure roller diameter in the axial direction end portion of the belt And a second belt guide rotatable on the axis of the pressure roller is provided,
The tension roller has an axial end that is in contact with the first belt guide, and the heat roller has a diameter that does not contact the second belt guide at a position corresponding to the second belt guide. As
The tension roller comes into contact with the belt guide from the inside at both axial ends, and the pressure roller comes into contact with the belt from the outside through a second belt guide, so that both the axial ends of the tension roller and the second A belt driving device that prevents the belt from moving in the axial direction by restricting the belt from both sides by the belt guide is used.

  Thus, the pressure roller having the elastic layer as the surface layer that may be damaged and the first belt guide have such a length that the pressure roller does not contact the first belt guide, and the distance from the end of the roller. And providing a second belt guide having a diameter larger than the pressure roller diameter that contacts the axial end of the belt, thereby preventing damage to the elastic layer of the pressure roller and the first belt guide, The movement of the belt in the axial direction can be restricted.

  Also, the tension roller is usually made of a member with little friction between the belt and the first belt guide, and there is no particular problem, but the second belt guide has a diameter larger than the pressure roller diameter. Therefore, there is a possibility of coming into contact with the pressed roller. However, as described above, since the diameter of the position corresponding to the second belt guide in the roller to be pressed is a diameter that does not contact the second belt guide, such a problem does not occur. It is possible to provide a belt driving device capable of restricting movement and a fixing device in an image forming apparatus using the belt driving device.

  The tension roller is a metal roller, and the pressed roller can be more effectively regulated in the axial movement of the belt by making the axial length shorter than the axial length of the belt.

  Further, the belt end surface side position in the second belt guide is provided on the pressure roller so as to coincide with the belt end surface position, so that the belt axial movement can be more effectively regulated. .

  As described above, according to the present invention, for example, the pressure roller and the first belt guide in which the surface layer which may be damaged when contacted is made of an elastic layer such as silicon rubber can be adjusted by adjusting the length of the pressure roller. Since the axial movement is restricted by the second belt guide while avoiding contact, damage to the elastic layer of the pressure roller and the first belt guide can be prevented. Furthermore, for the second belt guide having a diameter larger than the pressure roller diameter, the diameter of the pressed roller at the position corresponding to the second belt guide is set so as not to contact the second belt guide. Therefore, the problem due to the second belt guide can be avoided, and the belt driving device capable of effectively regulating the axial movement of the belt and the fixing device in the image forming apparatus using the belt driving device can be provided.

  Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the drawings. However, the dimensions, materials, shapes, relative arrangements, and the like of the components described in this embodiment are not intended to limit the scope of the present invention unless otherwise specified, but are merely illustrative examples. Not too much.

  First, the outline of the present invention will be briefly described. The present invention includes an axial end portion between a pressure roller and a tension roller that are pressed against a pressure-receiving roller such as a fixing roller using a surface layer as an elastic layer such as silicon rubber. In a belt driving device that stretches and drives a belt provided with a belt guide for axial movement restriction on the surface in contact with the outer surface of the roller on the side, the pressure roller and belt having an elastic layer as a surface layer that may be damaged The guide has a length that does not contact the belt guide so as to avoid contact between the pressure roller and the belt guide. Further, the elastic movement of the pressure roller is achieved by providing a second belt guide having a hook shape at a distance from the end of the pressure roller, for example, by providing a second belt guide that regulates the axial movement of the belt. And the belt guide are prevented from being damaged, and axial movement is also prevented.

  In addition, the tension roller is usually made of a member with little friction between the belt and the belt guide, and there is no particular problem, but the second belt guide has a diameter larger than the pressure roller diameter. There is a possibility of coming into contact with a pressed roller such as a heat roller. Therefore, by setting the diameter of the position corresponding to the second belt guide in the roller to be pressed to a diameter that does not contact the second belt guide, such a problem is prevented and the axial movement of the belt is effectively restricted. The fixing device is a belt driving device and an image forming apparatus using the belt driving device.

  FIG. 5 is a cross-sectional view of an example of an image forming apparatus in which the belt driving device according to the present invention is applied to a fixing device. The image forming apparatus shown in FIG. 5 has a plurality of 10M, 10C, 10Y, and 10K provided corresponding to each color of magenta (M), cyan (C), yellow (Y), and black (K). Is a tandem type color image forming apparatus in which the photosensitive member is arranged in the running direction of the intermediate transfer belt 12.

  In the following description, the case where the present invention is applied to the fixing device of the tandem type color image forming apparatus shown in FIG. 5 will be described as an example. However, the present invention is applicable to any type of image forming apparatus. In addition to the fixing device, it can be applied not only to a fixing device but also to an intermediate transfer member or a transfer member between a pressure roller and a tension roller that are pressed against a pressure-receiving roller as a surface layer of an elastic layer such as silicon rubber. Obviously, it can be applied to any device as long as it is a belt drive device that drives a belt that is provided with a belt guide for axial movement restriction on a surface that is mounted on an axial end portion and in contact with the outer surface of the roller. is there.

  In the tandem color image forming apparatus shown in FIG. 5, the intermediate transfer belt 12 is stretched around a driving roller 13 and a backup roller 15, and is driven to rotate by driving of the driving roller 13. The photoconductors 10M, 10C, 10Y, and 10K are sequentially arranged in this order from the upstream side in the conveyance direction of the intermediate transfer belt 12, and each of the photoconductors includes a charging device 18M, 18C, 18Y, and 18K, a developing device 19M, 19C, 19Y, and 19K, photoconductor cleaning devices 9M, 9C, 9Y, and 9K, a neutralization device (not shown), and the like are provided correspondingly.

  When this image forming apparatus is a printer, for example, image forming data sent from an external computer is a control device including a CPU (not shown) and each color of magenta (M), cyan (C), yellow (Y), and black (K) Data. After that, the surfaces of the photoconductors 10M, 10C, 10Y, and 10K are uniformly charged by the charging devices 18M, 18C, 18Y, and 18K, and the light exposure indicated by 20 is performed based on the image formation data divided into the respective colors. The photosensitive drums 10M, 10C, 10Y, and 10K are exposed by the apparatus to form an electrostatic latent image.

  Then, the electrostatic latent images on the photoconductors 10M, 10C, 10Y, and 10K are developed by the developing devices 19M, 19C, 19Y, and 19K, respectively, and a magenta (M) toner image, a cyan (C) toner image, and a yellow (Y ) A toner image and a black (K) toner image are formed.

  On the other hand, the primary transfer rollers 11M, 11C, 11Y, and 11K are opposed to the photoconductors 10M, 10C, 10Y, and 10K with the intermediate transfer belt 12 interposed therebetween, and the photoconductor drums 10M, 10C, 10Y, and 10K are opposed to each other. The upper color toner images are sequentially transferred to the intermediate transfer belt 12 by the primary transfer rollers 11M, 11C, 11Y, and 11K, and a color toner image is formed on the intermediate transfer belt 12.

  Then, a CPU (not shown) instructs the paper take-out roller 27 to take out the paper from the paper feeding device 26, and the paper is conveyed to the registration roller pair 17 through the paper conveyance path. Then, the registration roller pair 17 transports the sheet of the toner image on the intermediate transfer belt 12 at the timing when the toner image reaches the secondary transfer position where the secondary transfer roller 16 is located.

  The secondary transfer roller 16 at the secondary transfer position is disposed at a position facing the backup roller 15 with the intermediate transfer belt 12 interposed therebetween, and the toner image on the intermediate transfer belt 12 is secondarily transferred to the conveyed paper. . Then, the sheet on which the toner image is transferred is sent to the fixing device 21, where the toner image on the sheet is fixed and discharged to the discharge tray. After the secondary transfer, the intermediate transfer belt 12 is cleaned by the cleaning device 14, and the remaining toner is also removed by the photoconductor cleaning devices 9M, 9C, 9Y, and 9K in the photoconductors 10M, 10C, 10Y, and 10K. For image formation.

  FIG. 4 shows the fixing roller 22 including the heater 221 and the first belt guide 251 except for the bearing 223, the second belt guide 233, and the tension roller bearing portion 243, which constitute the belt driving device according to the present invention. It is a schematic side view showing a pressure roller 23 and a tension roller 24 that stretch a belt 25 having the belt 25. First, the fixing roller 22 includes a heat roller 222 having a heater 221 at the center. The pressure roller 23 is formed with a metal pressure roller base portion 231 around an axis 234 and an elastic layer 232 made of, for example, silicon rubber. The tension roller 24 is entirely made of metal, and the roller portion 241 is integrated with the roller shaft 242.

  The belt 25 is provided with a first belt guide 251 for axial movement restriction on the axial end side of the surface in contact with the outer surfaces of the pressure roller 23 and the tension roller 24. In addition, as described above, the tension applied to the belt 25 by the tension roller 24 is adjusted to reduce the heating time of the conveyed paper accompanying the increase in the speed of the image forming apparatus, and the roller / roller nip region 257, the roller / belt nip region are adjusted. 258, a preheating effect region 259 is formed so that the paper is sufficiently heated.

  FIG. 1 is a perspective view of a fixing device 21 using the belt driving device according to the present invention whose cross section is shown in FIG. In the figure, 22 is a fixing roller as described above, 24 is a tension roller, and the pressure roller 23 is covered with a belt 25 and cannot be seen. In addition, 223 is a bearing for driving the fixing roller 25, 233 is a second belt guide provided on the pressure roller 23, 243 is a tension roller bearing portion, and 251 is a first belt guide.

  FIG. 2 is an enlarged view illustrating a part of the fixing device shown in FIG. 1 except for the tension roller bearing portion 243. As described above, the belt 25 is stretched between the pressure roller 23 and the tension roller 24, and the first surface for restricting the axial movement is provided on the surface in contact with the outer surface of the pressure roller 23 and the tension roller 24 on the axial end side. The belt guide 251 is provided. For this belt guide 251, for example, rubber, elastomer, and the like typified by polyurethane are often used. However, the present invention is not limited to these materials.

  Since the tension roller 24 is made of metal, the end in the axial direction has a length that contacts the first belt guide 251 so that the axial movement of the belt 25 does not occur at the end. The pressure roller 23 has a length that does not contact the first belt guide 251, avoids contact between the pressure roller 23 made of an elastic layer 232 such as silicon rubber and the first belt guide 251, and damages to both. To prevent it from happening.

  However, since the axial movement of the belt 25 occurs at the pressure roller 23 portion in this way, in order to prevent this, the distance from the end of the pressure roller 23 is set, and the pressure roller 23 is, for example, shaped like a bowl. A second belt guide 233 having a diameter larger than that of the first roller guide 233 is provided to restrict the end of the belt 25 so that axial movement does not occur, so that the elastic layer 232 of the pressure roller 23 and the first belt guide 251 In addition to preventing breakage due to contact, axial movement is also prevented.

  The fixing roller 22 makes the axial length of the portion of the heat roller 222 shorter than the axial length of the belt 25, and sets the diameter of the position 224 corresponding to the second belt guide 233 to the second belt guide 233. The second belt guide 233 having a diameter larger than that of the pressure roller 23 is prevented from coming into contact with the fixing roller 22 as a diameter that does not come into contact.

  The second belt guide 233 is provided on the pressure roller 23 so that the position of the end face side of the belt 25 coincides with the end face position of the belt 25, thereby effectively restricting the axial movement of the belt 25. In addition, the second belt guide 233 can be rotated on the shaft 234 of the pressure roller 23 to reduce rubbing with the end face of the belt 25, thereby increasing durability, and a more preferable embodiment. It becomes.

  FIG. 3 illustrates the pressure roller 23 and the tension roller 24 described above, and the first belt guide 251 provided on the surface in contact with the outer surface of the pressure roller 23 and the tension roller 24 on the axial end side. It is a partially expanded perspective view for showing this relationship in more detail.

  As is apparent from FIG. 3, since the tension roller 24 is made of metal as described above, the axial end of the tension roller 24 contacts the first belt guide 251 and the axial movement of the belt 25 does not occur at the end. I am doing so. In addition, the pressure roller 23 is configured such that the end portion of the pressure roller elastic layer 232 does not come into contact with the first belt guide, and avoids damage to the elastic layer 232 such as silicon rubber and the first belt guide 251. Yes.

  The fixing roller 22 makes the axial length of the portion of the heat roller 222 shorter than the axial length of the belt 25, and sets the diameter of the position 224 corresponding to the second belt guide 233 to the second belt guide 233. The diameter does not contact.

  As described above, according to the present invention, the pressure roller 23 and the first belt guide 251 having the elastic layer 232 as the surface layer that may be damaged do not contact the pressure roller 23 with the first belt guide 251. By providing a second belt guide 233 having a diameter larger than the diameter of the pressure roller 23 abutting on the axial end of the belt 25 at a distance from the end of the pressure roller 23, the length is increased. While preventing the elastic layer 232 of the pressure roller 23 and the first belt guide 251 from being damaged, the axial movement of the belt 25 can be restricted.

  Further, since the tension roller 24 is made of metal and there is little friction between the belt 25 and the first belt guide 251, there is no problem even if it comes into contact with the belt guide 251, but the second belt guide 233 is Since the diameter is larger than the diameter of the pressure roller 23, there is a possibility of coming into contact with the fixing roller 22. However, since the diameter of the position 224 corresponding to the second belt guide 233 in the fixing roller 22 is set to a diameter that does not contact the second belt guide 233 as described above, such a problem does not occur. A belt driving device capable of regulating the axial movement of the image forming apparatus and a fixing device in an image forming apparatus using the belt driving device can be provided.

  According to the present invention, it is possible to provide a belt driving device that can effectively regulate the movement of the belt 25 in the axial direction and contribute to downsizing of the fixing device in the image forming apparatus and, consequently, speeding up of the image forming apparatus.

FIG. 3 is a perspective view when the belt driving device according to the present invention is applied to a fixing device in an image forming apparatus. FIG. 3 is an enlarged perspective view of a part of the belt driving device according to the present invention. It is the partially expanded perspective view which showed the relationship between a pressure roller, a tension roller, and the 1st belt guide provided in the surface which contact | connects the roller outer surface in the axial direction edge part side. FIG. 3 is a schematic side view showing a fixing roller 22 having a built-in heater 221 and a pressure roller 23 and a tension roller 24 that stretch a belt 25, which constitute a belt driving device. 1 is a cross-sectional view of an example of an image forming apparatus in which a belt driving device according to the present invention is applied to a fixing device.

Explanation of symbols

21 fixing device 22 fixing roller 221 heater 222 heat roller 223 bearing 224 position 23 corresponding to second belt guide 233 pressure roller 231 pressure roller base 232 pressure roller elastic layer 233 second belt guide 234 pressure roller shaft 24 Tension roller 241 Roller portion 242 Tension roller shaft 243 Tension roller bearing portion 25 Belt 251 First belt guide

Claims (5)

A pressure roller and a tension roller that are in pressure contact with the pressure roller using the surface layer as an elastic layer are provided on a surface that is stretched between the pressure roller and the tension roller and in contact with the outer surface of the roller on the axial end side. A belt driving device for driving a belt having a first belt guide for axial movement restriction,
The pressure roller has an axial length that does not contact the first belt guide, and has a diameter larger than the diameter of the pressure roller that contacts the axial end of the belt at a distance from the roller end. And a second belt guide that is rotatable on the shaft of the pressure roller, the tension roller has a length in contact with the first belt guide at an axial end, and the pressure roller is The diameter of the position corresponding to the second belt guide is a diameter that does not contact the second belt guide.
The tension roller comes into contact with the belt guide from the inside at both axial ends, and the pressure roller comes into contact with the belt from the outside through a second belt guide, so that both the axial ends of the tension roller and the second A belt driving device that prevents the belt from moving in the axial direction by restricting the belt from both sides by a belt guide. A fixing device provided in an image forming apparatus, which heats and pressurizes a sheet carrying a toner image formed by an electrophotographic method,
The fixing device includes a heat roller as a pressure roller, a pressure roller pressed against the heat roller and having a surface layer as an elastic layer, and stretched between the pressure roller and the tension roller. In a fixing device in an image forming apparatus using a belt driving device that drives a belt having a first belt guide for axial movement restriction provided on a surface in contact with an outer surface of a roller on the side,
The pressure roller has an axial length that does not contact the first belt guide, and has a diameter larger than the diameter of the pressure roller that contacts the axial end of the belt at a distance from the roller end. And a second belt guide rotatable on the axis of the pressure roller is provided,
The tension roller has an axial end that is in contact with the first belt guide, and the heat roller has a diameter that does not contact the second belt guide at a position corresponding to the second belt guide. As
The tension roller comes into contact with the belt guide from the inside at both axial ends, and the pressure roller comes into contact with the belt from the outside through a second belt guide, so that both the axial ends of the tension roller and the second A fixing device in an image forming apparatus using a belt driving device that prevents the belt from moving in the axial direction by restricting the belt from both sides by a belt guide. The belt driving device according to claim 1 , wherein the tension roller is a metal roller. The belt driving device according to claim 1 , wherein the pressed roller has an axial length shorter than an axial length of the belt . 2. The belt driving device according to claim 1 , wherein the belt end surface side position in the second belt guide is provided on the pressure roller so as to coincide with the belt end surface position.

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