JP3987345B2 - Fixing apparatus and image forming apparatus - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a pressure roller that abuts against a rotating member such as a fixing belt and a heating roller and rotates in the same direction as the rotating member in a nip portion that is a pressure contact area with the rotating member, and the width of the nip portion. The present invention relates to a fixing device including a pressure roller having a sufficient heat capacity and a low heat capacity, and an image forming apparatus such as a copying machine, a facsimile, and a printer having the same.
[0002]
[Prior art]
Image forming apparatuses such as copying machines, facsimile machines, and printers generally have a fixing device for fixing a toner image on a sheet-like medium on which a toner image that is an unfixed image as a fixed image is formed. .
[0003]
As a fixing device, a heating roller as a rotating member heated by a heater as a heating unit, and a pressure that contacts the heating roller and rotates in the same direction as the heating roller at a nip portion that is in contact with the heating roller. A heat roller that uses a pressure roller or the like as a member as a component, and transports and passes a sheet-like medium on which toner is fixed to the nip portion by rotation of both rollers, and heats and pressurizes the sheet medium. A twin type fixing device is known.
[0004]
Further, as the fixing device, an endless fixing belt as a rotating member for conveying a sheet-like medium heated and fixed by a heater as a heating unit, a heating roller and a fixing roller around which the fixing belt is wound, A pressure roller or the like as a pressure member disposed opposite to the fixing roller via the fixing belt is a constituent element, and these nip portions are contact areas formed by the fixing belt and the pressure roller. There is known a so-called belt fixing device of a type that conveys and passes a sheet-like medium on which toner is fixed by rotation and fixes the toner image by heating and pressing.
[0005]
In any type of fixing device, the toner image is fixed on the sheet-like medium conveyed by the rotation of the rotating member by melting at a predetermined temperature and by a predetermined pressure, thereby including the fixing device. The fixing process, which is one process of image formation in the image forming apparatus, is performed.
[0006]
Therefore, after the image forming apparatus is turned on, or after the image forming apparatus returns from the standby mode such as the energy saving mode to the image forming mode, the fixing apparatus can be started up early in order to complete the start up quickly. It is necessary to let For this reason, conventionally, rotating members such as a heating roller and a fixing belt have been made thin to reduce the heat capacity.
[0007]
On the other hand, in order to perform the fixing satisfactorily, it is necessary to secure the width of the nip portion, that is, the length of the contact portion with the pressure roller in the rotation direction of the rotating member. Has an elastic body layer such as a rubber layer having a thickness of about 5 mm on the metal core, and the rotating member and the pressure roller are pressed against each other with a predetermined pressure.
[0008]
However, when the rotating member and the pressure roller are brought into pressure contact with each other, the rotating member is thinned, and thus the bending of the rotating member increases, and there is a problem that the sheet-like medium is wrinkled during fixing. In addition, even though the rotating member is thin, the pressure roller has a cored bar and an elastic layer, and the heat capacity of the pressure roller is increased. At times, the heat of the rotating member is absorbed by the pressure roller, and it is difficult to stabilize the rotating member in a relatively high temperature range suitable for fixing.
[0009]
The latter problem is particularly noticeable when the power is turned on when the image forming apparatus is used in a low temperature environment, and becomes more likely to occur as the heat capacity of the rotating member is reduced in order to shorten the rise of the fixing device. It was a major obstacle to achieving a quick rise.
[0010]
[Problems to be solved by the invention]
Therefore, Japanese Patent Laid-Open No. 10-84453 proposes a fixing device using a belt as a pressure member in place of the conventional pressure roller as described above. There are problems that the configuration is very complicated, the cost is high, the compactness is difficult, and the apparatus is enlarged.
[0011]
An object of the present invention is to provide a fixing device including a pressure roller that secures a sufficient width of a nip portion and performs good fixing and realizes a quick start-up by low heat capacity, and an image forming apparatus having the same. Objective.
[0012]
[Means for Solving the Problems]
  In order to achieve the above object, the invention described in claim 1 is directed to a rotating member heated by a heating means and abutting against the rotating member.DoIn a fixing device having a pressure roller,The rotating member is longer in the axial direction than the pressure roller,The rotating member includes a plurality of ribs on an inner peripheral surface, and the interval between the plurality of ribs is configured to increase as the distance from the axial center of the rotating member increases, and the rotation from the inside of the pressure roller. A pressure contact member that presses the member;The press contact member has a curved surface along the rotating member via the pressure roller.It is characterized by that.
[0013]
  According to a second aspect of the present invention, in the fixing device according to the first aspect,The thickness of the rotating member is 0.2 to 0.5 mm.It is characterized by that.
[0014]
  The invention of claim 3 is claimed in claim1 or2. The fixing device according to 2,The thickness of the pressure roller is 40 to 80 μm.It is characterized by that.
[0015]
  According to a fourth aspect of the present invention, in the fixing device according to any one of the first to third aspects,The pressure contact member has a heat-resistant nonwoven fabric in contact with the pressure roller on the curved surface.It is characterized by that.
[0016]
  The invention of claim 5The fixing device according to claim 4, wherein the nonwoven fabric has a height of 2 to 3 mm..
[0017]
  The invention of claim 66. The fixing device according to claim 1, further comprising a sliding bearing that receives and supports both ends of the pressure roller at a half or more of the circumference of the pressure roller.It is characterized by that.
  A seventh aspect of the invention is characterized by having the fixing device according to any one of the first to sixth aspects.
  According to an eighth aspect of the present invention, in the image forming apparatus according to the seventh aspect, heating by the heating means is stopped at the end of image formation or within one minute after the end of image formation.
[0018]
【Example】
FIG. 1 shows an outline of an image forming apparatus to which the present invention is applied. The image forming apparatus may be any known apparatus such as a copying machine, a facsimile machine, or a printer, but the image forming apparatus in this embodiment is a printer that forms a single color image. The image forming apparatus 20 includes plain paper generally used for copying and the like, 90K paper such as an OHP sheet, a card, and a postcard, and a basis weight of about 100 g / m.²Any of so-called special sheets having a larger heat capacity than plain paper, such as considerably thicker paper or envelopes, can be used as the sheet-like medium.
[0019]
The image forming apparatus 20 includes an image forming apparatus 21 that forms an image, that is, a toner image according to a document image, a transfer apparatus 22 that is disposed opposite to the image forming apparatus 21, and a transfer apparatus 22 and an image forming apparatus. The sheet feeding cassettes 23 and 24 serving as sheet-like medium feeding means for feeding various sheet-like media to the transfer area, which is the area facing the image device 21, are transported from the sheet feeding cassettes 23 and 24 by sheet feeding rollers 56 and 58, respectively. It has a registration roller 30 that supplies the sheet-like medium that has been supplied in accordance with the timing of image formation by the image forming apparatus 21.
[0020]
The image forming apparatus 20 also has a cleaning device 28 as a cleaning unit that cleans the belt 61 after the toner image is transferred to the sheet-like medium by the transfer device 22, and the toner image is transferred and carried on the transfer region. A fixing device 1 for fixing the sheet-like medium, a discharge roller 13 for discharging the fixed sheet-like medium discharged from the fixing device 1 to the outside of the main body of the image forming apparatus 20, and a sheet shape discharged by the discharge roller 13. And a sheet discharge tray 14 as a sheet stacking unit disposed on the main body of the image forming apparatus 20 on which the medium is stacked.
[0021]
The image forming device 21 includes a photosensitive belt 25 as an electrostatic latent image carrier, rollers 62 and 63 around which the photosensitive belt 25 is wound, and a charging charger that is sequentially arranged in the rotation direction A of the photosensitive belt 25. And a developing device 26 as a developing device, and receives exposure light 29 from an exposure device 19 as a laser optical system between the charging device 27 and the developing device 26.
[0022]
The photosensitive belt 25 is negatively charged by the charging device 27, and the portion receiving the exposure light 29 is reversely developed with the negatively charged toner. The charging device 27 is of a type such as corotron or scorotron, which generates a charge by corona discharge and disperses it on the surface of the photoreceptor belt 25. The sheet-like medium after the toner image is transferred is separated from the photosensitive belt 25 by the curvature of the roller 62.
[0023]
After the sheet-like medium is separated, the photosensitive belt 25 is neutralized by a neutralizing device (not shown) before being cleaned by the cleaning device 28. The developing device 26 has a developing roller 61 disposed so as to face the roller 63, and the photosensitive belt 25 is developed at a position on the roller 63 so that the latent image is visualized. It has become.
[0024]
The photoreceptor belt 25 has photoconductivity and is an organic photoreceptor, but may be an inorganic photoreceptor. The electrostatic latent image carrier may be a drum instead of a belt. The exposure device 19 performs optical writing by irradiating the photosensitive belt 25 with exposure light 29 in accordance with write image data input from the outside of the image forming device 20. The toner used in the image forming apparatus 20 contains at least a binder resin, a colorant, and a wax, and contains 5 to 20 parts by weight of either wax represented by carnauba or oil represented by dimethylsiloxane. It contains.
[0025]
As shown in FIG. 2, the fixing device 1 includes a heating roller 59 that is a fixing roller as a rotating member for conveying a sheet-like medium P on which toner is fixed, and a heating roller 59 that is in contact with the heating roller 59. The fixing unit 16 as a nip portion which is a contact area has a pressure roller 60 as a pressure member that rotates in the same direction C as the rotation direction B of the heating roller 59. For the convenience of illustration, the heating roller 59 and the pressure roller 60 are illustrated with their wall thicknesses thicker than actual.
[0026]
In the fixing device 1, the sheet-like medium P carrying the toner image conveyed from the main body side of the image forming apparatus 20 is heated between the heating roller 59 and the pressure roller 60 heated by the heater 6 in the fixing unit 16. The toner image is melted and fixed on the sheet-like medium P by heating and pressurizing.
[0027]
The fixing device 1 is also disposed inside the pressure roller 60 and presses the pressure roller 60 against the heating roller 59 from the inside, and the pressure member 71 faces the inner peripheral surface of the pressure roller 60. It has a spring 73 that is a pressure member as a biasing means having one end engaged with the immovable member 72 and the other end engaged with the pressure contact member 71 for biasing.
[0028]
The fixing device 1 also includes a 700 W to 800 W heater 6 that is a halogen heater as a heating unit provided inside the heating roller 59, a thermistor (not shown) as a temperature detection unit that detects the temperature of the heating roller 59, and the thermistor. 7 includes a control unit (not shown) that blinks the heater 6 in accordance with the temperature of the heating roller 59 detected by the motor, and a gear 64 shown in FIG.
[0029]
The fixing device 1 also separates, from the heating roller 59, the entrance guide plate 52 as guide means for guiding the sheet-like medium P carrying the toner image toward the fixing unit 16, and the sheet-like medium that has passed through the fixing unit 16. A separation member 70, and an outlet guide plate 28 for guiding the sheet-like medium P separated from the heating roller 59 by the separation member 70 toward the outside of the fixing device 1 main body.
[0030]
The heating roller 59 has a core metal 65 as a base material made of an aluminum alloy having an outer diameter, in other words, a diameter φ of 30 mm, in other words, a radius of curvature of 15 mm, and a wall thickness of 0.3 mm. The length is 365 mm, but can be set between 350 and 410 mm. The diameter φ can be set between 20 and 40 mm, and the wall thickness can be set between 0.2 and 0.5 mm. The aluminum alloy as the base material is an A5052 or 3000 series alloy.
[0031]
As shown in FIGS. 3 and 4, the heating roller 59 has a shape obtained by cutting a normal pipe, but a plurality of ribs 51 are formed on the inner peripheral surface in order to increase the strength. As shown in FIG. 3, the rib 51 is disposed on a center O as a paper center that is the center of the paper passing area X, and symmetrically around the center O, L1, L2, L3, and L4, respectively. It is arranged with a distance of. L1 is 8 to 12 mm, L2 is 10 to 15 mm, L3 is 35 to 45 mm, and L4 is 60 to 80 mm, and has a relationship of L1 <L2 <L3 <L4.
[0032]
3, reference numeral 31 indicates a bearing of the heating roller 59, reference numeral 11 indicates a U-groove that engages with the gear 64 and is driven by the gear 64, and reference numeral 12 indicates the thickness of both ends of the heating roller 59. The reference numeral 15 indicates a thin portion in the sheet passing region X, the reference numeral 17 indicates a portion having a length of 5 to 10 mm outside the one bearing 31, and the reference numeral 50 indicates the other portion. A portion of the bearing 31 having a length of 12 to 16 mm is shown. The thickness of the thin portion 15 is set to mm.
[0033]
As shown in FIG. 5, the width d of the rib 51 is 1.5 to 3 mm, the thickness t of the rib 51 is 0.5 mm, and all the ribs 51 have the same shape. ing. The cored bar 65 can also be formed of aluminum. In this case, the wall thickness t is preferably 0.4 mm. By providing the ribs 51 in this manner, the strength is increased, the thickness can be reduced, the heat capacity can be reduced, and the warm-up time is very effective. Therefore, when not in use, the heater 6 is turned off to contribute to energy saving.
[0034]
Here, as shown in FIGS. 17 and 18, the conventional pressure roller generally has a metal shaft 67 and a rubber layer 68 having a thickness of about 5 mm disposed on the peripheral surface of the metal shaft 67. It was the target. Accordingly, in order to sufficiently secure the nip, that is, the width of the fixing portion 16 in this embodiment, it is necessary to press the heat roller toward the heating roller with a strong force of 70N to 120N on one side.
[0035]
Therefore, there is a problem in that bending and crushing increase during fixing, and the pressure tends to decrease particularly in the vicinity of the center of the pressure roller, which tends to cause fixing failure and to cause wrinkling of the sheet-like medium. In addition, such a pressure roller configuration has a large heat capacity, especially when the pressure roller is cold at low temperatures, and when the heating roller and pressure roller both start rotating during fixing, the heating roller usually becomes thin. Since the heat capacity is reduced, there is a problem that the temperature of the heating roller is remarkably lowered, resulting in poor fixing.
[0036]
Therefore, the pressure roller 60 to which the present invention is applied has a pipe 77 which is a thin seamless pipe as shown in FIG. The pipe 77 has a diameter φ of 30 mm, in other words, a curvature radius of 15 mm. The thickness of the pipe 77 is 40 μm to 80 μm. The length is 314 mm to 328 mm. The material is nickel or manganese containing a small amount of nickel or manganese, and a seamless pipe 77 is formed by electroforming. Alternatively, a SUS (stainless steel) pipe may be extruded and drawn.
[0037]
As shown in FIGS. 7, 8, and 9, the fixing device 1 has a bearing 74 that is a sliding bearing that receives and supports both ends of the pressure roller 60. The bearing 74 is made of a heat-resistant material PPS resin. As shown in FIG. 8 and FIG. 9, the bearing 74 has an arc shape, and a bearing portion 75 that supports both ends of the pressure roller 60 from below in a part of the circumference of the pressure roller 60 or more, The bearing portion 75 is integral with a seat portion 76 for fixing the bearing 74 at a predetermined position.
[0038]
The bearing 74 is fixed to a hole 78 formed in the seat portion 76 by screwing to a stationary member 79 shown in FIG. The distance between the two bearing portions 75 is determined so that the positioning in the longitudinal direction of the pressure roller 60, in other words, the thrust direction can be favorably performed so that the rotational friction of the pressure roller 60 is reduced. In FIG. 7, reference numeral 83 indicates a stationary member that supports the bearing 31 of the heating roller 59.
[0039]
As shown in FIGS. 6, 9, 10, and 11, the pressure contact member 71 is a curved surface for giving the fixing unit 16 a predetermined width at a position facing the inner peripheral surface of the pipe 77 in the pressure roller 60. 82. The curved surface 82 has a radius of curvature of 18 to 20 mm. The curved surface length f shown in FIG. 11 is set such that the width of the fixing portion 16, that is, the nip width is sufficient for fixing. The pressure contact member 71 is formed by bending a sheet metal having a thickness of 0.8 mm to 2 mm.
[0040]
As shown in FIGS. 6, 7, 9, 10, and 11, on the curved surface 82, a heat-resistant non-woven fabric 80 that contacts the inner peripheral surface of the pipe 77 in the pressure roller 60 is disposed. . The thickness e of the nonwoven fabric is set to 2 mm to 3 mm. This prevents abnormal noise when both the rollers 59 and 60 rotate, and also ensures sliding performance between the pipe 77 and the pressure contact member 71, thereby rotating the pressure roller 60 evenly and preventing jitter. is doing.
[0041]
In order to improve the slidability between the nonwoven fabric 80 and the pipe 77, the nonwoven fabric 80 is impregnated with silicone oil having a viscosity of 1000 CS to 3000 CS. As shown in FIG. 12, a film such as a polyimide film having a thickness of 25 μm to 50 μm or a fluororesin film (PTFE film) having a thickness of 50 μm to 120 μm is formed on the nonwoven fabric 80 in order to improve the slidability with the pipe 77. 81 may be covered.
[0042]
The urging force, that is, the pressing force applied to the pressure contact member 71 by the spring 73 depends on the characteristics of the toner. Generally, when the nip length of the fixing unit 16 is 316 mm, the pressure is 10 N to 20 N per nip width of 1 mm. The area of the fixing unit 16 is 1 mm²It is set to be 30 mN to 60 mN.
[0043]
As described above, since the pressure roller 60 is based on the ultra-thin seamless pipe 77, the pressure roller 60 has a low heat capacity. The temperature drop of the heating roller 59 due to the start of rotation of the rollers 59 and 60 is suppressed, and the press contact member 71 is provided, so that a necessary and sufficient pressure is applied for fixing and the fixing property is good. In addition, since the pipe 77 is seamless and has no seam, there is no problem that the pressurization is non-uniform due to breakage from the seam, or the pressurization is concentrated at the seam, resulting in non-uniform fixability. .
[0044]
Conventionally, if the applied pressure is the pressure necessary to fix the toner, the nip width becomes too small, resulting in poor fixing, and if the applied pressure is increased to obtain the required nip width, the toner is fixed. There is a contradictory relationship between the applied pressure and the nip width, such as applying a pressure higher than the pressure necessary to do this.
[0045]
However, in the fixing device 1, the pipe 77 is thin and a pressure is generated by the pressure contact member 71. The pressure contact member 71 has a curved surface 82, and the curved surface length f has a necessary nip width. Since the length is obtained and the nip width is mainly determined by the curved surface 82, the required nip width is obtained by pressing the pressure contact member 71 having the curved surface 82 against the pipe 77 to improve the fixing property. .
[0046]
Further, the pressing member 71 is pressed against the pipe 77 with a small pressure, specifically, the pressure necessary for fixing the toner described above, so that the deflection of the heating roller 59 is small even though the heating roller 59 is thin. This realizes a high-quality fixing device that prevents generation of wrinkles. Further, since the pressing force is generated by the pressure contact member 71, it is not necessary to pressurize the bearing 74. Therefore, unnecessary deformation of the pressing roller, which has occurred in the conventional configuration in which the pressing force is generated by the bearing, is prevented. Thus, a fixing device that does not jam and maintains good transportability is realized.
[0047]
As shown in FIG. 13, the pressure roller 60 may have a silicone rubber layer 84 with a thickness of 80 μm to 250 μm on the surface of the pipe 77. If the metal pipe 77 is exposed on the surface of the pressure roller 60, the silicone rubber layer 84 may cause problems such as damage to the heating roller 59 or a decrease in the conveyance force of the sheet-like medium. This is provided to prevent this.
[0048]
The silicone rubber layer 84 needs to cover the pipe 77 in a range larger than the range of the paper passing region X. The silicone rubber layer 84 can cover the entire pipe 77. In this case, particularly, the heating roller 59 can be completely prevented from being damaged. Since the silicone rubber layer 84 has a large frictional resistance, the sheet-like medium is improved in the conveyance force of the sheet-like medium by rotating with the heating roller 59 outside the sheet passing area X even during passage of the sheet-like medium. This also contributes to good transportability.
[0049]
As shown in FIG. 14, the pressure roller 60 may have a fluororesin layer 85 having a thickness of 20 μm to 50 μm on the surface of the pipe 77. The fluororesin layer 85 is used for fixing when image formation is performed on the back surface of a sheet-like medium once image-formed, such as when the image forming apparatus including the fixing device 1 can perform double-sided image formation. If the surface of the sheet-like medium on which the image has already been formed comes into contact with the pressure roller 60 and the surface of the pressure roller 60 has low releasability, there is a possibility that the toner may adhere to the surface and become dirty. If the surface of the pressure roller 60 becomes dirty, the toner is retransferred to the sheet-like medium to cause the sheet-like medium to become dirty. In the worst case, the sheet-like medium may be wound around the pressure roller 60 and cause jamming. This is provided to prevent this.
[0050]
The fluororesin layer 85 needs to cover the pipe 77 in a range larger than the range of the image region (not shown) included in the paper passing region X. The fluororesin layer 85 can be formed by covering a pipe 77 with a fluororesin tube. When the electrostatic polarity of the toner is negative, the fluororesin layer 85 has some conductivity, and has a surface resistance of 1 × 10.⁸Ω ～ 1 × 10¹²When the electrostatic polarity of the toner is positive, the surface resistance is 1 × 10¹⁴It shall have high insulation properties of Ω or higher.
[0051]
Since the fluororesin has a good releasability and the resistance can be easily changed according to the polarity of the toner, unnecessary toner hardly adheres to the pressure roller 60, and the pressure roller 60 can be prevented from being soiled. Thus, it is possible to prevent the sheet-like medium from being soiled or jammed during the backside image formation, that is, the double-sided image formation, thereby contributing to a fixing device capable of obtaining a high-quality fixed image with high safety.
[0052]
As shown in FIG. 15, the above-mentioned silicone rubber layer 84 may be formed on the surface of the pipe 77, and the above-mentioned fluororesin layer 85 may be formed on this silicone rubber layer 84. The effects of the silicone rubber layer 84 and the fluororesin layer 85 described with reference to FIGS. 13 and 14 can be achieved simultaneously.
[0053]
When a conventional pressure roller having a thick rubber layer 68 as shown in FIGS. 17 and 18 is used, when continuous fixing is performed, the outer diameter increases due to thermal expansion, the rubber hardness becomes soft, and the nip is reduced. However, when the pressure roller 60 is configured as described above, the rubber layer is not used or is used. However, since it is very thin, there is almost no thermal expansion even when continuous fixing is performed, and the nip width does not change regardless of the initial and continuous fixing, preventing curling of the sheet-like medium, and high-quality fixing This contributes to a fixing device for obtaining a product.
[0054]
In addition, since the heating roller 59 and the pressure roller 60 are each formed into a thin cylindrical shape, the heat capacity is reduced, and the pressure roller 60 does not heat the heating roller 59 even if both rollers 59 and 60 rotate. This prevents the fixing device 1 from being adversely affected and prevents the rise time from being prolonged, and the warm-up time of the fixing device 1 is shortened. Specifically, the image forming apparatus 20 is used in the fixing device 1 in which the diameter φ of the heating roller 59 is 30 mm and the heater 6 is 700 W to 800 W, and the warm-up time is very short, 5 seconds to 14 seconds. Selfishness is very good.
[0055]
Therefore, the heating by the heater 6 may be performed for the minimum necessary time. Therefore, the control means for blinking the heater 6 is the end of image formation in the image forming apparatus 20, in other words, the end of fixing in the fixing apparatus 1, or Within one minute after completion of image formation, in other words, within one minute after completion of fixing in the fixing device 1, heating by the heater 6 is stopped, and the fixing device 1 is set to a standby mode.
[0056]
The image forming apparatus 20 has such a configuration, and forms an image at a linear speed of the sheet-like medium of 120 mm / s to 160 mm / s. However, such a 1000 speed is not limited to this range. Even if an image is formed while conveying a sheet-like medium at a higher speed, the present invention can be applied to form an appropriate nip, etc., so that a good image can be formed. It is something that can be done.
[0057]
In the present exemplary embodiment, the fixing device 1 is configured as described above when the power of the image forming apparatus 20 is turned on by a predetermined operation by the operator or when the operation state is changed from the standby state. As a result, the control unit controls to reach a predetermined set temperature at an early stage to complete the start-up and to enable image formation and fixing.
[0058]
When the operator performs a well-known operation for starting image formation, the photosensitive belt 25 is charged by the charging device 27 as the photosensitive belt 25 rotates in the direction A, and the exposure light 29 causes a static image corresponding to the original image. An electrostatic latent image is formed, the electrostatic latent image is developed by the developing device 26, and the toner image formed on the photosensitive belt 25 is transferred onto the sheet-like medium conveyed at a predetermined timing by the registration roller 30. Is done.
[0059]
After the toner image is transferred to the sheet-like medium, the sheet-like medium is separated from the photosensitive belt 25 by the curvature of the roller 62, enters the fixing device 1, and is guided to the fixing unit 16 by the guide plate 52. The sheet-like medium is conveyed by the rotation of the heating roller 59 and the rotation of the pressure roller 60 that rotates following the rotation of the heating roller 59, and the toner constituting the toner image is heated and pressed in the fixing unit 16 to be melted and fixed on the sheet-like medium. Is done.
[0060]
This is a case where the heating by the heater 6 and the reduction of the heat capacity of the pressure roller 60 do not cause a temperature drop to the extent that the fixing is disturbed even if the heating roller 59 starts to rotate, and continuous fixing is performed. However, it is not necessary to interrupt the fixing and perform reheating, and the sheet-like medium is not bent, wrinkled, curled, or contaminated with toner, and good fixing is performed. The sheet-like medium after fixing is conveyed by a paper discharge roller 13 and discharged to a paper discharge tray 14 located at the upper part of the main body of the image forming apparatus 20. After the image formation is completed, the image forming apparatus 20 enters the standby mode at an early stage to prepare for the next image formation while suppressing power consumption.
[0061]
The case where the present invention is applied to a heat roller pair type fixing device has been described above, but the present invention can also be applied to a belt fixing device as shown in FIG. Hereinafter, the same components as those in the above-described example are denoted by the same reference numerals, detailed description thereof is omitted, and different portions are mainly described. The illustration of the toner constituting the toner image is omitted.
[0062]
As shown in FIG. 16, the fixing device 1 includes an endless fixing belt 2 as a rotating member for conveying a sheet-like medium P on which toner is fixed, a heating roller 3 around which the fixing belt 2 is wound, and fixing. The roller 4 and the fixing roller 4 are arranged to face the fixing roller 4 with the fixing belt 2 interposed therebetween. In the fixing portion 16 as a nip portion that is a contact area with the fixing belt 2, the fixing belt 2 rotates in the same direction C as the rotation direction B. And a pressure roller 60 as a rotating pressure member.
[0063]
The fixing device 1 also includes a heater 6 as a heating unit provided inside the heating roller 3, a separation plate 70 as a separation member for separating the sheet-like medium that has passed through the fixing unit 16 from the fixing belt 2, and A guide plate 52 or the like is provided as guide means for guiding the sheet-like medium carrying the toner image toward the fixing unit 16. The heating roller 3 is urged away from the fixing roller 4 in order to give an appropriate predetermined tension to the fixing belt 2.
[0064]
The pressure roller 60 has the same configuration as that described with reference to FIGS. 2 and 6 to 15. In this example, the curved surface 82 provided with the pressure contact member 71 is a convex surface unlike the concave surface in the above example. As described above, the curved surface 82 can have various curved shapes depending on the shape of the fixing unit 16 to be formed.
[0065]
The fixing belt 2 is formed by forming a release layer made of 200 μm high release silicone rubber on the surface layer of a 100 μm-thick polyimide resin, which is a heat-resistant resin, and has a small heat capacity and thermal response. Have been good. As the heat-resistant resin, the substrate may be polyamide resin, polyetherketone (PEEK), or the like in addition to polyimide resin, and may be made of metal such as stainless steel or nickel, or rubber. In consideration of flexibility and the like, the thickness is desirably 100 μm or less.
[0066]
The release layer is preferably excellent in heat resistance and durability in addition to releasability. Therefore, it is desirable that the release layer be a heat-resistant release layer using fluorine resin or the like in addition to high release silicone rubber. In the case of a fluororesin, the release layer is formed by coating the substrate surface by spraying or the like and then heat-sealing. Further, the high release silicone rubber layer is desirable as a condition for obtaining good fixability and thermal responsiveness when the rubber height is 25 to 65 degrees (JIS A hardness meter) and the thickness is in the range of 100 to 300 μm.
[0067]
On the surface of the fixing belt 2, an elastic layer such as silicon rubber is provided on the base, and a release layer such as a fluororesin and a PFA tube is provided on the elastic layer, whereby an OHP sheet is formed as a sheet-like medium. Transparency when used can be secured, and a good fixed image can be obtained by uniformly fixing.
[0068]
The fixing roller 4 has a diameter of 40 mm and a cored bar 9 as a base made of a steel metal pipe, and covers the cored bar 9 to make the width of the fixing unit 16 sufficiently wide. And an elastic layer 10. The elastic body layer 10 is made of heat-resistant porous foamed silicon rubber, and is soft and heat insulating.
[0069]
Since the material of the elastic body layer 10 is a heat-resistant porous elastic body having a low thermal conductivity and a heat insulating function, it reduces the heat loss of the belt, reduces the temperature drop after the start-up, and recovers the temperature. The pre-rotation time is shortened. Further, since the elastic layer 10 has a relatively low hardness, a sufficient nip width can be obtained even if the pressure contact force of the pressure roller 60 is small, and a good fixing performance can be obtained even under relatively low temperature and low pressure conditions. Obtainable.
[0070]
The heating roller 3 has a diameter of 50 mm, and the core metal is a thin-walled aluminum roller pipe having good thermal conductivity to prevent temperature unevenness in the longitudinal direction, and has a thickness of 5 mm. The core metal surface is anodized to prevent wear due to friction with the fixing belt 2. A heater 6 is built in the center of the cored bar. The core metal may be carbon steel, stainless steel, copper or the like.
[0071]
Since the heating roller 3 and the pressure roller 60 are each formed into a thin cylindrical shape, a reduction in heat capacity is achieved. By making the heating roller 3 and the pressure roller 60 have low heat capacities, even when the fixing belt 2 rotates, the heat is hardly taken away, and adverse effects on fixing and a rise time are prevented. The heater 6 heats the fixing belt 2 via the heating roller 3.
[0072]
Although the fixing device and the image forming apparatus to which the present invention is applied have been described above, the heater as the heating unit is not limited to the heating roller but may be disposed on the fixing roller. Regardless of the heater, the rotating member is directly or indirectly heated by the heater, so that the heater is heated. The image forming apparatus of the present embodiment forms a single color image, but may form a color image.
[0073]
【The invention's effect】
The present invention includes a rotating member that is heated by a heating unit, and a pressure roller that contacts the rotating member and rotates in the same direction as the rotating member in the contact region with the rotating member. In the fixing device that heats and presses the toner image through the sheet medium to fix the toner image on the sheet medium, the pressure roller has a thin seamless pipe and is disposed inside the pressure roller. Since the pressure roller has a pressure contact member that presses the pressure roller from the inside to the rotary member, the pressure roller has a low heat capacity, the rise of the pressure member is fast, and even when the environmental temperature is low, the rotation member and the pressure roller In addition to suppressing the temperature drop of the rotating member due to the start of rotation, the pressure contact member provides a necessary and sufficient nip width and pressing force for fixing, resulting in good fixability and seamless performance. There is no seam in the joint, so there is no problem that the pressure is uneven due to breakage from the seam, or the pressure is concentrated at the seam. By pressing against the seamless pipe with the applied pressure, even if the rotating member is thin, high-quality fixing can be performed with little deflection and the prevention of wrinkles, and the applied pressure is generated by the pressure contact member. Therefore, it is not necessary to apply pressure by the bearing of the pressure roller, so that unnecessary deformation of the pressure roller, which was generated in the conventional configuration in which pressure was generated by the bearing, is prevented, and there is no jamming. Therefore, it is possible to provide a fixing device that can maintain good transportability.
[0074]
If the pressure contact member has a curved surface for giving a predetermined width to the contact area at a position facing the pressure roller, the pressure roller has a thin seamless pipe, and the conventional method. If the applied pressure is the pressure required to fix the toner, the nip width becomes too small, resulting in poor fixing, and if the applied pressure is increased to obtain the required nip width, the toner is fixed. This solves the problem that there is a contradictory relationship between the applied pressure and the nip width, such as applying a pressure higher than the pressure required for the nip. It is possible to provide a fixing device that has a good width and a good fixing property.
[0075]
If the pressure contact member has a heat-resistant non-woven fabric in contact with the pressure roller on the curved surface, the noise when the rotation member and the pressure roller rotate is prevented and the pressure roller and the pressure contact member are pressed against each other. By ensuring slidability with the member, the pressure roller can be rotated evenly and jitter can be prevented, so that a good fixing can be performed and a fixing device with high user reliability can be provided.
[0076]
If there is a slide bearing that receives and supports both ends of the pressure roller in more than half of the circumference of the pressure roller, even if the pressure roller is thin, deformation of the pressure roller more than necessary Therefore, it is possible to provide a fixing device with high reliability of the user, which has good transportability and prevents jamming.
[0077]
The present invention resides in an image forming apparatus having the fixing device according to any one of claims 1 to 4. Therefore, the image forming apparatus includes the fixing device that exhibits each of the above-described effects, and performs good fixing, whereby a good image is obtained. It is possible to provide an image forming apparatus that can perform formation, has a short warm-up time, and rises quickly.
[0078]
If the heating by the heating means is stopped at the end of image formation or within 1 minute after the end of image formation, the start-up is fast, so that the usability is not impaired and unnecessary power is not consumed. It is possible to provide an image forming apparatus which is excellent in consideration and highly reliable by the user.
[Brief description of the drawings]
FIG. 1 is a side view showing an outline of a fixing device to which the present invention is applied and an image forming apparatus having the same.
2 is a side view of a fixing device provided in the image forming apparatus shown in FIG.
3 is a front sectional view of a heating roller provided in the fixing device shown in FIG. 2. FIG.
4 is a perspective view of a heating roller provided in the fixing device shown in FIG. 2. FIG.
5 is a front sectional view showing a shape of a rib formed on an inner peripheral surface of a heating roller provided in the fixing device shown in FIG. 2; FIG.
6 is a sectional view taken along line VI-VI in FIG.
7 is a front view of the fixing device shown in FIG. 2. FIG.
8 is a perspective view showing a bearing of a pressure roller provided in the fixing device shown in FIG. 2. FIG.
9 is a cross-sectional view taken along the line IX-IX in FIG.
10 is an enlarged view showing a pressure contact member and a non-woven fabric provided in the fixing device shown in FIG. 2. FIG.
FIG. 11 is an enlarged view of the pressure contact member shown in FIG.
FIG. 12 is a perspective view showing an example in which a film is coated on the outside of a nonwoven fabric.
FIG. 13 is a front view of an example fixing device in which a pressure roller has a silicone rubber layer.
FIG. 14 is a front view of an example fixing device in which a pressure roller has a fluororesin layer.
FIG. 15 is a front view of an example fixing device in which a pressure roller has a silicone rubber layer and a fluororesin layer on the silicone rubber layer.
16 is a side view showing another example of the fixing device provided in the image forming apparatus shown in FIG. 1. FIG.
FIG. 17 is a side view of a conventional pressure roller.
FIG. 18 is a perspective view of a conventional pressure roller.
[Explanation of symbols]
1 Fixing device
2 Fixing belt as rotating member
6 Heating means
7 Heating means
16 Contact area between rotating member and pressure roller
20 Image forming apparatus
59 Heating roller as rotating member
60 Pressure roller
71 Pressure contact member
74 plain bearing
77 seamless pipe
80 Nonwoven fabric
82 Curved surface
B Rotation direction of rotating member

Claims (8)

A rotary member which is heated by the heating means, in a fixing device having a pressure roller which abuts on this rotating member,
The rotating member includes a plurality of ribs on the inner peripheral surface, and the interval between the plurality of ribs is configured to increase as the distance from the axial center of the rotating member increases.
A pressure contact member that presses the rotating member from the inside of the pressure roller;
The fixing device according to claim 1, wherein the pressure contact member has a curved surface along the rotation member via the pressure roller . The fixing device according to claim 1, wherein the rotating member has a thickness of 0.2 to 0.5 mm . 3. The fixing device according to claim 1, wherein the pressure roller has a thickness of 40 to 80 [mu] m . 4. The fixing device according to claim 1, wherein the pressing member includes a heat-resistant non-woven fabric in contact with the pressure roller on the curved surface . The fixing device according to claim 4, wherein the fixing device, wherein the height of the non-woven fabric is 2 to 3 mm. 6. The fixing device according to claim 1, further comprising a slide bearing that receives and supports both ends of the pressure roller at a half or more of the circumference of the pressure roller. Fixing device to do. An image forming apparatus comprising the fixing device according to claim 1 . 8. The image forming apparatus according to claim 7, wherein heating by the heating unit is stopped at the end of image formation or within 1 minute after the end of image formation.

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