JP2005062654A - Fixing device and image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fixing device which can enhance the mechanical strength of a core bar without using a special reinforcing member without sacrificing the startup time of the device and an image forming apparatus equipped with the fixing device. <P>SOLUTION: The fixing device is equipped with a fixing roller 12 and a pressure roller 13. The pressure roller 13 has the cylindrical core bar 21 and is provided with a plurality of projections 27 on the inner peripheral surface of the core bar 21. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a fixing device and an image forming apparatus used in an image forming apparatus or the like.

  In an image forming apparatus such as a copying machine, a printer, or a facsimile machine, after a toner image on a photoconductor is transferred to a transfer paper, the toner image is fixed by heating and pressing the transfer paper with a fixing device. Yes. The fixing device includes a fixing roller having a heat source such as a heater therein, and a pressure roller pressed against the peripheral surface of the fixing roller. Recently, in order to shorten the rise time of the fixing device and to save power, the core bar of the pressure roller has been formed into a thin pipe shape. If the core of the pressure roller is thin, the heat capacity of the pressure roller is reduced. As a result, the amount of heat that the pressure roller takes from the fixing roller when the fixing device is started up can be reduced, and the rise time of the fixing device is shortened. On the other hand, since the mechanical strength of the pressure roller is reduced, the pressure roller bends in the axial direction, and there is a difference in the transfer force of the transfer paper between the both ends (pressure part) and the center part of the pressure roller. There arises a problem that paper is wrinkled or a fixing failure occurs.

  In order to solve this problem, there has been known one that reinforces the peripheral surface of the pressure roller from the inside by inserting an annular pressing member inside the pressure roller (see, for example, Patent Document 1).

Japanese Patent No. 2871662 (page 2, FIG. 1)

  However, in the invention described in Patent Document 1, since an annular pressing member that is a separate member from the pressure roller is used, an increase in the number of parts and an increase in the number of assembling steps result in an increase in cost and a decrease in productivity. In other words, the heat capacity of the pressure roller is increased by the amount of the annular pressing member, and the rise time of the fixing device becomes longer.

  The present invention has been made in view of such problems, and a fixing device capable of suppressing the deflection of the core metal without sacrificing the rise time of the device and without using a special reinforcing member. It is an object of the present invention to provide an image forming apparatus including the fixing device.

  In order to solve the above-described problem, the invention according to claim 1 is a fixing device including a fixing roller and a pressure roller, wherein the pressure roller includes a cylindrical cored bar, A plurality of protrusions or recesses are provided on the inner peripheral surface.

  According to a second aspect of the present invention, in the fixing device according to the first aspect, the protrusion or the recess is formed along an axial direction of the cored bar.

  According to a third aspect of the present invention, in the fixing device according to the second aspect, the protrusions or recesses are ridges or grooves formed at predetermined intervals in the circumferential direction of the cored bar. Features.

  According to a fourth aspect of the present invention, in the fixing device according to the first aspect, the protrusions or recesses are formed along an axial direction and a circumferential direction of the cored bar.

  The invention according to claim 5 is characterized in that the protrusions or recesses according to claim 4 are ridges or grooves formed at predetermined intervals in the circumferential direction and the axial direction of the cored bar. This is a fixing device.

  According to a sixth aspect of the present invention, in the fixing device according to the second aspect, the protrusion is a protrusion having a hollow inside, and the protrusion is predetermined in the circumferential direction of the inner peripheral surface of the cored bar. It is characterized by being formed with an interval of.

  A seventh aspect of the invention is an image forming apparatus comprising the fixing device according to any one of the first to sixth aspects.

  According to the first to sixth aspects of the present invention, it is possible to suppress the bending of the core metal without sacrificing the rise time of the fixing device and without using a special reinforcing member. According to the seventh aspect of the present invention, an image forming apparatus including the fixing device as described above can be provided.

  The best mode for carrying out the present invention will be described below with reference to the drawings.

  FIG. 1 is an overall schematic side view showing an apparatus configuration of an image forming apparatus provided with a fixing device according to the present embodiment, and FIG. 2 is an enlarged side view of a main part of the fixing device in FIG.

  The image forming apparatus shown in the figure is a copying machine, but is not limited thereto, and can be a printer, a facsimile machine, or a printing machine.

  Reference numeral 1 denotes a copying machine. The copying machine 1 includes a belt-like photosensitive member 2 as an image carrier, a charging charger 3 for charging the photosensitive member 2, and optical image information is written on the photosensitive member 2 to electrostatic latent images. A laser optical system 4 for forming the toner, a developing device 5 for supplying toner to the electrostatic latent image and developing it, a transfer charger 6 for transferring the toner image on the photosensitive member 2 to the transfer paper, and remaining on the photosensitive member 2 after the transfer. A cleaning device 7 for removing toner, a paper feed cassette 8 containing transfer paper, a registration roller pair 9 for feeding transfer paper fed from the paper feed cassette 8 to a transfer position at a predetermined timing, and holding a toner image A fixing device 10 for fixing the transfer paper, a paper discharge roller 11 for discharging the fixed transfer paper, and a paper discharge tray 11a for stacking the discharged transfer paper are provided.

  The fixing device 10 is means for fixing the toner image on the transfer paper by applying at least heat and pressure to the toner image on the transfer paper. As shown in FIG. 2, the fixing device 10 includes a fixing roller 12 that is rotationally driven with a heat source 19 such as a halogen heater therein, a pressure roller 13 that is in pressure contact with the peripheral surface of the fixing roller 12, and a tip. A separation claw 15 for separating the transfer paper by bringing it close to the peripheral surface of the fixing roller 12, a pressure spring 16 for pressing the pressure roller 13 against the fixing roller 12 via a lever 16a, a fixing inlet guide plate 17, The driving mechanism includes a gear (not shown) that transmits a rotational driving force to the fixing roller 12, a bearing for the fixing roller 12, a thermistor, and the like. P is transfer paper.

  The fixing roller 12 is formed in a hollow cylindrical shape. In this embodiment, the base material is iron (STKM12), the total length is 365 mm, the outer diameter is 30 mmφ, and the thickness of the paper passing portion is 0.25 mm.

  The total length of the fixing roller 12 is about 410 mm at the maximum, and the total length can be adjusted to the maximum size of the transfer paper used in the copying machine 1. Further, the outer diameter can be set within a range of 16 to 40 mmφ in consideration of the structure of the copying machine 1 and the like. In addition to iron (STKM11, STKM12), an aluminum alloy (A5052 or 3000 series alloy) can be used as the base material. Further, the thickness of the fixing roller 12 differs depending on the outer diameter of the roller, and the amount of bending when the transfer paper is nipped and conveyed differs. Even if the thickness is the same, the amount of bending increases as the roller outer diameter increases. The thickness / outer diameter is preferably in the range of 7/1000 to 20/1000, and in the present embodiment, the thickness / outer diameter is set to 8/1000. If the thickness of the fixing roller 12 is less than 7/1000, the amount of bending when the transfer paper P is nipped and conveyed increases, and the transfer paper P is likely to be wrinkled. A thickness larger than 20/1000 is not preferable because it takes a long time from when the power is turned on until the fixing roller 12 reaches the fixing temperature. When an aluminum alloy (A5052) having an outer diameter of 30 mmφ is used as the base material of the fixing roller 12, the thickness / outer diameter is set to 11 by setting the thickness of the sheet passing portion of the fixing roller 12 to 0.4 mm. / 1000.

  FIG. 3 is a perspective view of the pressure roller, and FIG. 4 is an enlarged vertical side view of the same. The pressure roller 13 is formed by integrally forming a heat-resistant rubber layer 23 on the outer periphery of a hollow cylindrical cored bar 21. A metal lid 25 having a rotation shaft 25a is fitted into both ends of the core bar 21, and the pressure roller 13 is supported at both ends of the rotation shaft 25a by levers 16a. As the heat-resistant rubber layer 23, a sponge type containing a large number of bubbles inside is adopted to reduce the heat capacity, and the upper layer of the heat-resistant rubber layer 23 is covered with a coating layer of a heat-resistant resin such as a fluororesin. ing.

  Referring to FIG. 4, a plurality of reinforcing protrusions are provided on the inner peripheral surface of the core metal 21 of the pressure roller 13. This protrusion is a ridge 27 formed from one end opening of the core metal 21 to the other end opening along the axial direction of the core metal 21, and this protrusion 27 is the circumferential direction of the inner peripheral surface of the core metal 21. A total of eight lines are formed at predetermined intervals (45 ° intervals) and facing the center direction.

  In this embodiment, the pressure roller 13 has a core metal 21 whose base material is iron (STKM12), has a total length of 365 mm, an outer diameter of the core metal 21 of 18 mm, and a thickness of the core metal 21 of 1.2 mm. . The heat resistant rubber layer 23 has a length of 316 mm, a thickness of 6 mm, and a coating layer covering the heat resistant rubber layer 23 having a thickness of 50 μm.

  As the material of the core metal 21, iron (STKM11, STKM12) or aluminum alloy (A5052 or 3000 series alloy) can be used in the same manner as the fixing roller 12. In addition, the thickness of the cored bar 21 can be determined in consideration of the outer diameter and material of the pressure roller 13 within a range of 1 to 1.6 mm. When the thickness of the cored bar 21 is smaller than 1 mm, the amount of bending of the pressure roller 13 when the transfer sheet P is nipped and conveyed increases, and the transfer sheet P is easily wrinkled. Is larger than 1.6 mm, it is not preferable because the heat capacity of the pressure roller 13 is increased. The outer diameter of the cored bar 21 can be determined in consideration of the cost of materials and the like within a range of 16 to 20 mmφ. In terms of cost, the standard product of 19.1 mmφ or 17.3 mmφ is most preferable. It is. The heat-resistant rubber layer 23 may be a solid type that does not contain bubbles inside, but the heat capacity of the pressure roller 13 is increased, so that the sponge type is more preferable. The thickness of the heat resistant rubber layer 23 is preferably in the range of 5 to 7 mm in consideration of the outer diameter of the fixing roller 12. The thickness of the coating layer is preferably in the range of 30 to 80 μm in consideration of durability.

  Further, the protrusion 27 provided along the axial direction on the inner peripheral surface of the cored bar 21 has a circumferential width t1 of 0.5 to 1.2 mm and a protruding height h1 of 1 to 5 mm. Is preferred. If the circumferential width t1 is less than 0.5 mm, the mechanical strength of the cored bar 21 is insufficient, and the amount of bending when the transfer paper is nipped and conveyed increases. Is larger than 1.2 mm, it is not preferable because the processing of the ridges 27 becomes difficult. Similarly, if the protrusion height h1 is less than 1 mm, the amount of bending of the core metal 21 is not preferable, and if the protrusion height h1 is greater than 5 mm, the protrusion 27 is difficult to process. Absent. The number of protrusions 27 may be any number and arrangement that can suppress the bending of the pressure roller 13 when the transfer paper is nipped and conveyed. It is preferable to arrange them at equal intervals in the circumferential direction.

  Next, the operation of this embodiment will be described. The transfer paper P transported from the paper feed cassette 8 is transported to a latent image carrier made up of the belt-shaped photoconductor 2 at a timing by the registration roller pair 9. The belt-like photoconductor 2 is driven to rotate in the clockwise direction. At that time, the surface is charged by the charging charger 3 and irradiated with laser light from the laser optical system 4 to form an electrostatic latent image on the photoconductor 2. . The latent image is visualized by toner when passing through the developing device 5, transferred to the transfer paper P conveyed to the photoconductor 2 by the transfer charger 6, and the transfer paper P that is in close contact with the photoconductor 2 depends on the curvature. To be separated. Thereafter, the transfer paper P is conveyed to the fixing device 10 and is heated and pressed by nipping and conveying the fixing portion where the fixing roller 12 and the pressure roller 13 are in pressure contact, whereby the toner image is fixed on the transfer paper. The paper is discharged to the paper discharge tray 11a. At this time, since the convex roller 27 is provided on the pressure roller 13, the pressure roller 13 can sandwich and convey the transfer paper without bending. On the other hand, after the unnecessary charge is removed from the photoreceptor 2 by the charge eliminating lamp, the residual toner is removed by the cleaning device 7 and collected.

  As described above, in this embodiment, the ridges 27 are formed on the inner peripheral surface of the hollow cylindrical cored bar 21 of the pressure roller 13 along the axial direction and at a predetermined interval in the circumferential direction of the inner peripheral surface. As a result, the mechanical strength of the pressure roller 13 can be increased, and the deflection of the pressure roller 13 when the transfer paper is nipped and conveyed can be made smaller than in the prior art. More specifically, the amount of bending of the pressure roller not provided with the ridges 27 during transfer of the transfer paper is 0.3 to 0.5 mm. By using the pressure roller 13 of this embodiment, the amount of bending is as follows. Can be made 0.2 mm or less.

  Further, the ridges 27 provided on the inner peripheral surface of the pressure roller 13 have a slight effect of increasing the heat capacity of the pressure roller 13, and a sponge type is adopted as the heat resistant rubber layer 23. The temperature drop of the heating roller 12 when the copying machine 1 is started up can be reduced. More specifically, when a solid type was used as the heat-resistant rubber layer and a rod was used as the core of the pressure roller 13, the temperature drop of the heating roller 12 when the apparatus was started up was 30 to 50 ° C. However, when the pressure roller 13 of the present embodiment is used, the temperature drop of the heating roller 12 is suppressed to 5 to 20 ° C. Thus, when the pressure roller 13 of this embodiment is used, the start-up of the copying machine can be completed in a short time.

  Next, Example 2 will be described with reference to FIG. 5A is an enlarged vertical side view of the core of the pressure roller, FIG. 5B is a partially enlarged view thereof, and FIG. 5C is a further view of the core of the pressure roller according to the modification. It is a partially enlarged view corresponding to (B).

  Referring to FIGS. 5A and 5B, in the second embodiment, the inner circumferential surface of the pressure roller 13 is provided with a ridge 27a having a hollow inside. 1 and different. The circumferential width t2 of the ridge 27a is preferably 3 to 8 mm, the protruding height h2 thereof is 2 to 6 mm, and the wall thickness w of the ridge 27a is preferably 0.3 to 1.2 mm. By making the protrusions 27a have the dimensions as described above, it becomes possible to secure the mechanical strength of the cored bar 21 that only suppresses the bending of the pressure roller 13 when the transfer paper P is nipped and conveyed. The workability of the cored bar 21 is not impaired. The second embodiment has the same effects as the first embodiment and has a greater effect of mechanically reinforcing the pressure roller 13 than the first embodiment because the protrusions 27a are hollow. The cross-sectional shape of the hollow portion of the ridge 27a is not limited to the semicircular shape as shown in FIG. 5, and for example, the same is true even if the hollow portion of the ridge 27b is circular as shown in FIG. The effect of.

  FIG. 6 is a longitudinal front view of the core of the pressure roller according to the third embodiment. In Example 3, four protrusions 27, 27a, 27b are provided in the circumferential direction, and a plurality of reinforcing protrusions are provided on the inner peripheral surface of the cored bar 21 along the circumferential direction. Is different from the first and second embodiments. The protrusions are ridges 29 formed at predetermined intervals along the circumferential direction of the cored bar 21, and the ridges 29 are formed at predetermined intervals in the axial direction of the inner peripheral surface of the cored bar 21. ing.

  The third embodiment has the same effects as the first and second embodiments, and the mechanical strength of the core metal 21 is increased due to the presence of the ridges 29 provided along the circumferential direction of the core metal 21. It becomes possible to increase resistance to crushing.

  In the first to third embodiments, it has been described that the ridges 27, 27a, 27b are provided along the axial direction on the inner peripheral surface of the core bar 21, but here, the ridges 27, 27a, 27b When attention is paid to the groove between the adjacent ridges 27, 27a, 27b, it can be said that a recess along the axial direction of the core bar 21 is provided between the ridges 27, 27a, 27b. When a typical case is illustrated, a very large number of ridges 27 are provided on the inner peripheral surface of the core bar 21, and when the interval between a certain ridge 27 and the adjacent ridge 27 becomes narrow, the ridges 27, 27, it can be said that concave grooves formed along the axial direction of the cored bar 21 and at a predetermined interval in the circumferential direction of the inner peripheral surface of the cored bar 21 are provided.

1 is an overall schematic side view illustrating an apparatus configuration of an image forming apparatus including a fixing device according to Embodiment 1. FIG. It is a principal part enlarged side view of a fixing device same as the above. It is a perspective view of a pressure roller. It is an enlarged vertical side view same as the above. It is drawing explaining Example 2, (A) is an expansion vertical side view of the metal core of a pressure roller, (B) is a partially expanded view same as the above, (C) is a modification. It is a partially enlarged view corresponding to (B) of the cored bar of the pressure roller according to FIG. 6 is a longitudinal sectional view of a core bar of a pressure roller according to Embodiment 3. FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Copier 12 Fixing roller 13 Pressure roller 21 Core metal 23 Heat-resistant rubber layer 25 Metal lid bodies 27, 27a, 27b, 29

Claims (7)

In a fixing device including a fixing roller and a pressure roller,
The pressure roller has a cylindrical cored bar, and a plurality of protrusions or recesses are provided on the inner peripheral surface of the cored bar.   The fixing device according to claim 1, wherein the protrusion or the recess is formed along an axial direction of the cored bar.   The fixing device according to claim 2, wherein the protrusions or recesses are ridges or grooves formed at predetermined intervals in the circumferential direction of the cored bar.   The fixing device according to claim 1, wherein the protrusion or the recess is formed along an axial direction and a circumferential direction of the cored bar.   The fixing device according to claim 4, wherein the protrusions or recesses are ridges or grooves formed at predetermined intervals in a circumferential direction and an axial direction of the cored bar.   The said protrusion is a protruding item | line which the inside is hollow, and the said protruding item | line is formed at predetermined intervals in the circumferential direction of the inner peripheral surface of a metal core. Fixing device.   An image forming apparatus comprising the fixing device according to claim 1.

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