JP2006256708A - Sheet carrier device and image forming device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To certainly prevent creases of a double sheet to be carried. <P>SOLUTION: The double sheet 28 is carried by circular motion of angular speed equal to that of a heating roller 32 along an outer periphery of the heating roller 32 when the double sheet 28 is carried by making it contact with the heating roller 32 and a pressure roller 34. A carrier radius of curvature is larger on the sheet 28B on the remote side than on the sheet 28A on the close side to the heating roller 32 and the angular speed of both of the sheets A, B is equal to that of the heating roller 32, and consequently, carrier speed becomes higher on the sheet 28B on the remote side than on the sheet 28A on the close side to the heating roller 32. However, a load to reduce the speed of the sheet 28B on the remote side from the heating roller 32 is applied by reducing peripheral speed of the pressure roller 34 by applying a predetermined rotational load on the pressure roller 34 by a brake roller 42. Consequently, it is possible to make the speed of the double sheet 28 roughly the same and it is possible to eliminate slippage of the double sheet 28 and to prevent the creases of the double sheet 28. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a sheet conveying apparatus that conveys a sheet by pressing a pair of rollers, and an image forming apparatus using the sheet conveying apparatus.

  As a sheet conveying device that conveys a sheet while being pressed against a pair of rollers, there is a fixing device constituted by a pair of rollers of a driving heating roller and a pressure roller driven by the heating roller. In this fixing device, a metal heating roller passes a sheet through a pressure contact portion that is inserted into and pressed against a pressure roller having an elastic layer formed on the outer peripheral surface, and the transferred toner image is thermocompression bonded to the sheet. Then, the sheet is conveyed while fixing the toner image.

  It is known that when an envelope is conveyed with such a fixing device, wrinkles peculiar to the envelope are generated. The envelope has a structure in which at least two sheets of paper are overlapped and the two sheets are fixed to each other at the outer edge, and a deviation occurs between the upper and lower papers, and the upper and lower edges at the outer edge of the envelope. Distortion caused by paper misalignment cannot be eliminated, leading to wrinkles. The deviation between the upper and lower papers in the double paper such as an envelope occurs due to the following causes.

  In the pressure contact portion, the double sheet is conveyed along the outer periphery of the driving heating roller by a circular motion at an angular speed equal to that of the heating roller. The radius of curvature of conveyance at the pressure contact section is larger for the paper farther than the paper near the heating roller, and the angular speed of both papers is equal to that of the heating roller. However, the conveyance speed is increased. The cause of the paper misalignment of the double paper that occurs at the press contact portion is due to the difference in the transport speed.

  In order to prevent wrinkling of double sheets such as envelopes, an elastic body similar to the pressure roller is used for the outer layer of the heating roller, and when the press contact portion is formed, the outer layer of the heating roller is also deformed. Therefore, a method of forming a pressure contact portion with a small curvature is known. However, in order to obtain this effect, it is necessary to make the elastic body of the outer layer of the heating roller much thicker than a normal heating roller and to have a thickness close to the elastic layer of the pressure roller. Thereby, the thermal resistance of the heating roller increases and the thermal efficiency decreases. For this reason, this method is effective for extremely low-speed printing, but at higher printing speeds, the heat required for fixing the toner cannot be obtained. As a result, fixing failure occurs and it is difficult to put it to practical use. . For this reason, in order to increase the heating time of the heating roller, it is necessary to increase the diameter of the roller and extend the time for melting and holding (so-called “duel time”), resulting in a problem of increasing the size of the apparatus.

  Also, a fixing device is disclosed in which a driving force is applied not only to a heating roller but also to a pressure roller to convey a sheet (for example, Patent Document 1).

The thickness of the paper transported by the fixing device usually varies about 50 to 300 μm, and the transport speed difference between the upper and lower papers changes in proportion to this thickness. Therefore, the fixing device drives the pressure roller. In order to eliminate the conveyance speed of the upper and lower sheets when the double sheet is conveyed, it is necessary to change the rotation speed of the pressure roller according to the thickness of the sheet. However, since the thickness of the paper is often unknown, the rotational speed of the pressure roller cannot be set accurately, and wrinkles occur on the double paper.
JP-A-2-291589

  In view of the above-described facts, an object of the present invention is to reliably prevent wrinkles of a conveyed double sheet.

  In the sheet conveying apparatus according to claim 1 of the present invention, when conveying a double sheet in a sheet conveying apparatus that conveys a sheet by press contact with a driving roller to be driven and a driven roller driven by the driving roller, It is characterized by having a speed adjusting means for making the conveyance speed of one sheet and the other sheet substantially the same by reducing the peripheral speed of the driven roller.

  In this configuration, the driving roller and the driven roller convey the paper while being pressed against each other. When the double sheet is conveyed in pressure contact, the double sheet is conveyed along the outer periphery of the drive roller by a circular motion at an angular speed equal to that of the drive roller. The radius of curvature of conveyance is larger on the paper farther than the paper closer to the drive roller, and the angular speed of both papers is equal to that of the drive roller, so the paper farther than the side closer to the drive roller is transported. Speed increases.

  However, in the configuration of claim 1, the speed adjusting means slows down the peripheral speed of the driven roller, so that the paper contacting the driven roller, that is, the paper far from the drive roller (paper near the driven roller), A load that slows the conveyance speed is applied, and the conveyance speed of the sheet on the side close to the drive roller is made substantially the same. This eliminates misalignment of the double paper and prevents wrinkles.

  According to a second aspect of the present invention, there is provided the sheet conveying apparatus according to the first aspect, wherein the speed adjusting means is provided on the outer peripheral surface of the non-sheet passing portion of the driven roller and abuts on the outer peripheral surface of the driving roller. And a transmission means for directly transmitting the driving force of the driving roller to the driven roller.

  In this configuration, the transmission means provided on the outer peripheral surface of the non-sheet passing portion of the driven roller is in contact with the outer peripheral surface of the driving roller and directly transmits the driving force of the driving roller to the driven roller.

  As a result, the non-sheet passing portion of the driven roller rotates in accordance with the surface of the driving roller, and therefore, the sheet of the paper does not rotate in comparison with the case of rotating in accordance with the paper farther from the driving roller (paper closer to the driven roller). Thickness dividing speed becomes slow.

  Since the radius of curvature of the driven roller of the driven roller that rotates through the double paper is reduced by the thickness of the paper, the peripheral speed of the driven roller of the driven roller is higher than that of the non-sheet passing portion of the driven roller. It is possible to give a load that further slows down the thickness and slows down the speed of the sheet farther from the drive roller. For this reason, since the conveyance speed of the double paper can be made substantially the same, the deviation of the double paper is eliminated and wrinkles of the double paper are prevented.

  Also, as the thickness of the double sheet increases, the speed difference between the two sheets increases, but the peripheral speed of the driven roller's sheet passing portion decreases as the sheet increases in thickness because the radius of curvature decreases. The load on the side far from the driving roller is reduced. For this reason, the speed of the double paper can be made substantially the same without depending on the thickness of the paper.

  According to a third aspect of the present invention, there is provided the sheet conveying apparatus according to the first aspect, wherein the speed adjusting means is a brake that applies a predetermined rotational load to the driven roller.

  In this configuration, a predetermined rotational load is applied to the driven roller by the brake, and the peripheral speed of the driven roller is slower than the speed of the paper far from the driving roller, and the speed of the paper far from the driving roller is slowed down. Can be given a load. For this reason, since the speed of the double paper can be made substantially the same, the deviation of the double paper is eliminated and the wrinkle of the double paper is prevented.

  According to a fourth aspect of the present invention, there is provided the sheet conveying apparatus according to the third aspect, wherein the brake is a brake roller that contacts the driven roller, and a generator that generates electric power by the rotational force of the brake roller is provided. And

  In this configuration, power is generated by the generator using the rotational force of the brake roller that contacts the driven roller. By using this generated electric power as a power source for the drive roller, the energy lost by applying the brake can be reduced.

  5. The sheet conveying device according to claim 1, wherein the driving roller is a heating roller, and the driven roller is a pressure roller having an elastic layer having a hardness lower than that of the heating roller. It may be a fixing device.

  According to a sixth aspect of the present invention, there is provided an image forming apparatus comprising the paper conveying device according to any one of the first to fifth aspects.

  Since the present invention has the above-described configuration, wrinkles of the conveyed double paper can be reliably prevented.

Hereinafter, an embodiment according to a paper conveying apparatus of the present invention will be described with reference to the drawings.
(First embodiment)
First, a first embodiment according to the present invention will be described. As shown in FIG. 1, the image forming apparatus 10 according to the first embodiment includes a photosensitive drum 12 that rotates in one direction (A direction in FIG. 1). On the outer periphery of the photosensitive drum 12, a charger 14, an exposure device 16, a developing device 18, a transfer device 20, a static elimination light source 22, and a cleaning 24 are arranged in this order from the upstream side in the rotation direction.

  The photosensitive drum 12 is charged by a charger 14 while rotating, and an exposure according to image information is performed by an exposure device 16 to form an electrostatic latent image. The surface of the photosensitive drum 12 on which the electrostatic latent image is formed is supplied with toner by the developing device 18 so that the toner adheres to the charged portion and is developed. This reaches the transfer device 20 and reaches the moving belt 26. The image is transferred onto the double paper 28 that has been sent over. After the transfer, the photosensitive drum 12 further rotates, receives the light from the static elimination light source 22, loses residual charge, and is further cleaned by a cleaning 24. Such processing is sequentially repeated as the photosensitive drum 12 rotates. The double paper 28 onto which the toner image has been transferred through the transfer device 20 passes through a fixing device 30 as a paper transport device, and the transferred toner is melted and fixed.

  Next, the fixing device 30 will be described. As shown in FIG. 2, the fixing device 30 includes a heating roller 32 that is driven and a pressure roller 34 that is driven by the heating roller 32. The double paper 28 to which the toner image has been transferred is guided by a paper guide 38 to a pressure contact portion where the heating roller 32 and the pressure roller 34 are in pressure contact, and the toner image is thermocompression bonded to the double paper 28 at this pressure contact portion. Thus, the double paper 28 is conveyed while fixing the toner image, and is peeled off from the heating roller 32 by the peeling guide 40.

  The heating roller 32 is an iron hollow roller having an outer diameter of 30 mm, a thickness of 1 mm, and a length of 350 mm, and a fluororesin 32B is formed on the surface thereof as a release layer to a thickness of about 30 μm. A halogen lamp 32A is built in the heating roller 32, and is detected by a detecting means (not shown) for detecting the surface temperature of the heating roller 32 and a control means (not shown) for controlling the amount of heat generated by the halogen lamp 32A. The surface temperature of the heating roller 32 is set to a temperature of about 180 ° C. The heating roller 32 is rotationally driven in the direction A in FIG. 2 by a drive source (not shown), and its peripheral speed is about 200 mm / sec.

  The pressure roller 34 has an iron shaft 34A having an outer diameter of 15 mm and a length of 350 mm. A silicon rubber 34B having a thickness of 7.5 mm is molded around it, and fluorine is used as a release layer on the outermost periphery. The resin 34C is molded with a thickness of about 30 μm. However, this release layer is not coated on the non-sheet passing portions at both ends of the pressure roller 34.

  The pressure roller 34 is pressed against the heating roller 32 with a force of 42 kgf, and the silicon rubber 34B of the pressure roller 34 is deformed by this load, whereby a nip having a width of about 6 mm is obtained. At this time, the silicon rubber 34B of the non-sheet passing portion at both ends of the pressure roller 34 is exposed on the surface and is always in direct pressure contact with the heating roller 32. Note that the silicone rubber 34B that is in direct pressure contact with the heating roller 32 corresponds to the transmitting means.

  Next, the operation of the first embodiment will be described.

  When the double paper 28 is conveyed in pressure contact with the fixing device 30 according to the first embodiment, the double paper 28 is moved along the outer circumference of the heating roller 32 by circular motion at the same angular speed as the heating roller 32. Be transported. The conveyance radius of curvature is larger on the paper 28B farther from the heating roller 32 than on the paper 28A closer to the heating roller 32, and the angular speed of both papers is equal to that of the heating roller 32. The paper 28B farther from the heating roller 32 than 28A has a higher conveyance speed.

  However, in the first embodiment, as described below, a load that slows down the speed of the paper 28 </ b> B on the side far from the heating roller 32 is applied, and the conveyance speed of the double paper 28 is substantially the same.

  In the first embodiment, the silicon rubber 34 </ b> B exposed on the outer peripheral surface of the non-sheet passing portion of the pressure roller 34 abuts on the outer peripheral surface of the heating roller 32, and the driving force of the heating roller 32 is directly applied to the pressure roller 34. introduce.

  As a result, the non-sheet passing portion of the pressure roller 34 rotates in accordance with the surface of the heating roller 32, and therefore rotates in accordance with the paper 28 </ b> B far from the heating roller 32 (paper near the pressure roller 34) 28 </ b> B. The speed of dividing the sheet thickness (surface speed) is slower than that of the case.

  Since the radius of curvature of the sheet passing portion of the pressure roller 34 that rotates via the double sheet 28 is reduced by the thickness of the sheet, the peripheral speed of the sheet passing portion of the pressure roller 34 is the non-pressure of the pressure roller 34. It is slower than the peripheral speed of the sheet passing portion by the thickness of the sheet, and a load can be applied to reduce the speed of the sheet 28B far from the heating roller 32. For this reason, since the conveyance speed of the double paper 28 can be made substantially the same, the deviation of the double paper 28 is eliminated, and the wrinkle of the double paper 28 is prevented.

  Further, as the thickness of the double paper 28 increases, the speed difference between the two papers 28A and 28B increases. However, the peripheral speed of the sheet passing portion of the pressure roller 34 increases as the double paper 28 increases in thickness. Is reduced, the peripheral speed is reduced, and a load is applied to reduce the speed of the paper 28B on the side far from the heating roller 32. For this reason, the speed of the double paper 28 can be made substantially the same without depending on the thickness of the double paper 28.

In the configuration of the first embodiment, no additional drive source is required to apply a load to the paper 28B on the side far from the heating roller 32, so there is no energy loss and no accessory parts are required. The number of parts does not increase.
(Second Embodiment)
Next, a second embodiment according to the present invention will be described. Note that the overall configuration of the image forming apparatus is the same as that of the first embodiment, and a description thereof will be omitted.

  First, the fixing device will be described. In addition, the same code | symbol is attached | subjected to the part same as 1st Embodiment, and description is abbreviate | omitted suitably.

  As shown in FIG. 3, the fixing device 31 according to the second embodiment includes a brake roller 42 that presses against the surface of the pressure roller 34. A generator 44 is rotationally coupled to the brake roller 42, and the generator 44 brakes the rotation of the brake roller 42, thereby applying a load torque of, for example, about 13 kgf · cm to the pressure roller 34. The generator 44 generates electric power by the rotational force applied from the brake roller 42, and the generated electric power is converted into a predetermined waveform or voltage by a converter (not shown), and the fixing device 31 according to the second embodiment. It can be used as a part of the power of the driving source or a part of the power for driving the image forming apparatus on which the fixing device 31 is mounted. Thereby, a part of the load energy of the drive source of the heating roller 32 generated by applying a rotational load to the pressure roller 34 is reduced.

  The brake roller 42 is configured so as to be separated from the pressure roller 34 so that the load torque does not act on the pressure roller 34 when the heating roller 32 and the pressure roller 34 convey one sheet. May be. Further, instead of the generator 44, a powder brake that applies a load torque of, for example, about 13 kgf · cm to the pressure roller 34 by braking the rotation of the brake roller 42 may be provided.

  Next, the operation of the second embodiment will be described.

  In the fixing device 31 according to the second embodiment, a rotational load torque of about 13 kgf · cm is applied to the pressure roller 34 by the brake roller 42 braked by the generator 44. When the double paper 28 is conveyed, the peripheral speed of the pressure roller 34 is slower than the speed of the paper 28B far from the heating roller 32, and the load that slows down the speed of the paper 28B far from the pressure roller 32. give. For this reason, the speed of the double paper 28 can be made substantially the same, and the deviation of the double paper 28 is eliminated.

  As shown in the table of FIG. 4, in the fixing device 31 of the second embodiment, when the envelope was conveyed, the amount of deviation of the upper and lower sheets when a rotational load was applied to the pressure roller 34 was measured. According to this, the paper displacement is reduced by gradually applying a load torque to the pressure roller 34, and the paper displacement amount is eliminated in a certain region (about 9 to 15 kgf · cm). This is because an ordinary envelope is bonded on three of the four sides, so that a slight shift amount does not cause a shift due to the strength of the bonded three sides.

  In the fixing device 31 of the second embodiment, when the unbonded double paper 28 is conveyed, the upper and lower paper sheets are not displaced when a rotational load of about 13 kgf · cm is applied to the pressure roller 34. It was.

  In the first and second embodiments, the fixing device has been described as the paper conveying device. However, the fixing device is not limited to this, and a paper conveying device having no toner fixing function may be used.

FIG. 1 is a schematic view of an image forming apparatus according to the first embodiment of the present invention. FIG. 2 is a diagram illustrating the fixing device according to the first embodiment. FIG. 3 is a diagram illustrating a fixing device according to the second embodiment. FIG. 4 is a table showing the amount of deviation of the upper and lower sheets when a rotational load is applied to the pressure roller when the envelope is conveyed in the fixing device according to the second embodiment.

Explanation of symbols

10 Image forming apparatus 30, 31 Fixing device 32 Heating roller (driving roller)
34 Pressure roller (driven roller)
34B Silicon rubber (transmission means, speed adjustment means)
42 Brake roller (speed adjustment means)
44 Generator (generator)

Claims (6)

In a paper conveying apparatus that conveys a paper by press contact with a driving roller to be driven and a driven roller driven by the driving roller,
A sheet conveying apparatus comprising speed adjusting means for making the conveying speed of one sheet and the other sheet substantially the same by decreasing the peripheral speed of the driven roller when conveying a double sheet. .   The speed adjusting means is a transmitting means that is provided on the outer peripheral surface of the non-sheet passing portion of the driven roller, is in contact with the outer peripheral surface of the driving roller, and directly transmits the driving force of the driving roller to the driven roller. The sheet conveying apparatus according to claim 1.   The sheet conveying apparatus according to claim 1, wherein the speed adjusting unit is a brake that applies a predetermined rotational load to the driven roller.   The sheet conveying device according to claim 3, wherein the brake is a brake roller that is in contact with the driven roller, and a generator that generates electric power by a rotational force of the brake roller is provided. The drive roller is a heating roller;
The driven roller is a pressure roller having an elastic layer having a hardness lower than that of at least the heating roller,
The sheet conveying apparatus according to claim 1, wherein the sheet conveying apparatus is a fixing device.   An image forming apparatus comprising the sheet conveying device according to claim 1.

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