JP5977103B2 - Fixing device and image forming apparatus having the same - Google Patents

Description

  The present invention relates to a fixing device for fixing toner and an image forming apparatus including the same.

  An electrophotographic image forming apparatus (hereinafter simply referred to as “image forming apparatus”) that forms an image based on an electrophotographic method can easily form an image having good image quality. Widely used in facsimile machines and multifunction machines.

  A fixing device, which is one component of the image forming apparatus, fixes a toner image on a recording medium to the recording medium, and includes a heat roller fixing method and a belt fixing method. Generally, a heat roller fixing type fixing device is a roller pair in which a fixing roller and a pressure roller are in pressure contact with each other, and a halogen lamp is provided as a heat source inside at least one of the two rollers.

  The fixing device of this heat roller fixing system is a recording medium such as a sheet on which an unfixed toner image is formed after a halogen lamp heats a roller pair to a predetermined temperature required for fixing (hereinafter referred to as “fixing temperature”). Is supplied to the pressure contact portion (fixing nip portion) between the fixing roller and the pressure roller, and fixes the unfixed toner image on the recording medium by the heat transmitted to the fixing nip portion and the pressure of the fixing nip portion.

  In recent years, an image forming apparatus capable of full color printing is required to have a high process speed. In order to cope with this, it is necessary to widen the width (nip width) in the recording medium conveyance direction in the fixing nip portion. As means for increasing the nip width, there are two methods of increasing the elastic layer of the fixing roller (elastic roller) or increasing the diameter of the elastic roller.

  However, the thermal conductivity of the elastic layer (silicone rubber) of the elastic roller is very low, so if there is a heat source inside the elastic roller, if the elastic layer of the elastic roller is thickened, the process speed will be increased. The roller temperature cannot follow the fixing temperature. Further, when the diameter of the elastic roller is increased, the warm-up time becomes longer and the power consumption of the heating means increases.

  In order to solve the above problems, a sponge roller with excellent heat insulation is used for the fixing roller and pressure roller, and proposals aiming for miniaturization, weight reduction, energy saving, and solutions for problems specific to the sponge roller have been made. (For example, refer to Patent Document 1).

  On the other hand, the belt fixing type fixing device includes a fixing roller, a pressure roller, and a fixing belt, and the fixing belt is stretched between the fixing roller and a heating roller including a heater for heating, There has been proposed an apparatus in which a fixing nip portion is formed by pressing a fixing roller and a pressure roller through a fixing belt.

  In this type of belt fixing system, the fixing belt is formed on a belt base material made of polyimide or the like, a belt elastic layer made of silicone rubber or the like formed on the surface of the belt base material, and a surface of the belt elastic layer. And a belt release layer made of a fluororesin or the like, and the fixing roller uses a sponge roller having excellent heat insulating properties as an elastic layer, so that heat of the fixing belt is not taken away by the fixing roller. Therefore, only the fixing belt having a small heat capacity can be efficiently heated, so that the warm-up time can be shortened.

  Further, in Patent Document 2, a fixing nip portion necessary for toner fixing is provided by providing a lamp and a pressure contact member inside a thin fixing roller, and deforming the pressure contact member and the fixing roller by a pressure roller facing the pressure contact member. A belt-fixing type fixing device has been proposed. In the fixing device disclosed in Patent Document 2, the energy saving is further improved as compared with the conventional belt fixing method because the heating roller is omitted.

JP 2005-309188 A JP-A-9-114296

  However, in Patent Document 2, the pressure contact member provided in the thin fixing roller is a pad fixed to the fixing roller or a metal roller coated with a surface rubber. In the case of a pad on which the pressure contact member is fixed, the surface pressure of the fixing nip cannot be increased to maintain the slidability of the pad and the fixing roller, the unevenness of the recording medium cannot be followed, and fine gloss unevenness occurs. When the recording medium is embossed paper, fixing failure may occur in the concave portion of the embossed paper.

  Further, in the case where the pressure roller is a metal roller coated with a surface layer rubber, when the metal roller is thick, deformation is insufficient, a necessary nip width cannot be obtained, and toner fixing is insufficient. In addition, when the metal roller is thin, even if the metal roller is deformed, the surface pressure of the fixing nip portion becomes low, and it is impossible to follow the unevenness of the recording medium (paper), and fine gloss unevenness occurs. There may be a case where a fixing defect corresponding to the concave portion occurs.

  As described above, in the nip formation by the deformation of the metal roller, it is very difficult to achieve both the width of the fixing nip and the load, and it is difficult to obtain a sufficient fixing property. In addition, a rubber layer is provided on the surface layer of the metal roller to make it difficult for heat from the halogen lamp or the like to be transmitted to the metal layer. However, compared to metal, the rubber layer emits infrared radiation from the lamp. Since it is easily absorbed, the heat necessary for heating the fixing roller is originally taken away by the rubber layer, and conversely, the heating efficiency is lowered and the energy saving performance is lowered.

  SUMMARY OF THE INVENTION In view of the above, an object of the present invention is to provide a fixing device that improves the toner fixing performance of a recording medium and has excellent energy saving performance, and an image forming apparatus including the same.

To achieve the above object, a fixing device according to the present invention, radiation and fixing roller formed on the roller shape, and endless fixing belt, a pressure member, an infrared ray is disposed inside the fixing belt and a heat source for the fixing roller in the inside of the fixing belt is disposed, said pressure member is pressed against the fixing roller via the fixing belt, between the fixing belt and the pressure member A fixing device of a belt fixing type provided with a fixing nip portion through which a recording medium passes, wherein the fixing roller includes a fixing elastic layer, and has a metal layer as an infrared reflecting layer for reflecting infrared rays on a surface layer side thereof .

According to the above configuration, provided an infrared reflecting layer on the surface layer of the fixing roller is a fixing member, the radiant heat generated from the heat source inside the fixing belt, since the reflected infrared reflective layer of the fixing roller, inside the fixing roller The provided elastic layer can be prevented from directly receiving radiant heat, and overheat damage to the elastic layer can be prevented.

  In this case, the infrared reflection layer can be formed of various materials, but it is desirable to provide a fixing device having a high reflection efficiency by using a metal having a high infrared reflectance.

Here, it is preferable to set the reflectance of the surface of the fixing roller to be higher than the reflectance of the inner surface of the fixing roller as a fixing member and the inner surface of the base material of the fixing belt.

Because, by increasing the infrared reflectivity of the surface layer of the fixing roller, even fixing roller is subjected to radiant heat from a heating source such as a halogen lamp is reflected without being absorbed, heating the fixing belt by the reflection of the infrared There is an effect. By providing, for example, an infrared absorption layer inside the fixing belt and suppressing the reflectance, infrared rays that have once reached the inside of the fixing belt are hardly reflected and can contribute to heating of the fixing belt. .

As described above, since the infrared reflectance of the fixing roller surface layer is higher than the reflectance inside the fixing belt, the radiant heat from the heat source can be efficiently used for heating the fixing belt. An excellent fixing device can be provided.

Examples of the fixing roller include a fixing roller composed of four layers of a cored bar layer, a fixing elastic layer, a base material layer, and an infrared reflecting layer, which are sequentially arranged outward from the central axis.

  According to the above configuration, since the fixing elastic layer is formed on the surface side of the core metal layer, the fixing nip width can be widened by press contact with the pressing member. Moreover, when rubber | gum, such as silicone rubber, is employ | adopted as a fixing elastic layer, it can prevent that silicone rubber receives a direct radiant heat by an infrared reflective layer.

  The fixing roller can employ a configuration in which the outer periphery of the two-layer structure of the core metal layer and the fixing elastic layer is covered with a two-layer sleeve including a base material layer and an infrared reflection layer.

  According to the above configuration, since the sleeve having the infrared reflecting layer laminated on the surface side of the base material is used, the infrared reflecting layer can be made thin. When the infrared reflecting layer is made thinner, the infrared reflecting layer is a metal layer. Further, deformation at the fixing nip portion of the fixing elastic layer of the fixing roller can be further facilitated, and a sufficient nip width can be ensured.

  Further, the fixing roller has a structure in which an outer surface of the fixing elastic layer is covered with a sleeve having one or more layers in which an infrared reflecting layer is formed, and an inner diameter of the sleeve is larger than an outer diameter of the fixing elastic layer. can do.

  A sleeve intended for infrared reflection is heated by absorption of infrared rays, and the heat of the heated sleeve moves to the fixing elastic layer. However, since the outer diameter of the fixing elastic layer is smaller than that of the sleeve provided with the infrared reflecting layer, the sleeve and the fixing elastic layer inside thereof are separated, and heat transfer from the sleeve to the fixing elastic layer can be reduced. . Since the sleeve comes into contact with the elastic layer and the fixing belt only in the vicinity of the fixing nip portion, more heat from the sleeve can be applied to the fixing belt. Therefore, the heating efficiency of the fixing belt is improved.

  Further, it is possible to employ a configuration in which a belt guide as a fixing member that slides and guides the fixing belt is provided inside the fixing belt.

  By providing the belt guide, the contact between the fixing belt and a heat source such as a halogen lamp can be prevented, and the risk of thermal damage to the fixing belt can be reduced. In addition, due to uneven infrared radiation from the halogen lamp, there is a risk that the fixing belt is locally thermally expanded and distorted, and further, the distortion of the fixing belt causes contact with the halogen lamp or meandering. By providing the belt guide, these risks can be reduced.

  Since this risk is reduced, a highly flexible material such as a polyimide resin can be used for the base material of the fixing belt. As a result, the flexibility of the fixing belt is increased, and the deterioration of the peelability of the recording medium caused by the deformation of the elastic layer of the fixing roller at the fixing nip portion being hindered by the rigidity of the fixing belt can be prevented.

  Moreover, it is preferable to employ a configuration in which an infrared absorption layer that absorbs infrared rays emitted from the heat source is formed on the inner surface of the belt guide. As a result, by suppressing the reflectance by the infrared absorption layer inside the belt guide, the infrared rays that have once reached the inside of the belt guide are hardly reflected and contribute to the heating of the belt guide. The belt guide thus heated heats the contacting fixing belt by heat conduction.

  In addition, it is preferable that the infrared reflectance of the infrared reflecting layer of the fixing roller is set higher than the infrared reflectance of the belt guide. According to the above configuration, the infrared rays radiated from the heat generation source are reflected by the infrared reflection layer of the fixing roller and are directed to the infrared absorption layer inside the belt guide, so that the heat efficiency transferred to the fixing belt is further improved. can do.

The fixing belt employs a configuration including a belt base material in contact with the fixing roller , a belt elastic layer formed on the surface thereof, and a belt release layer formed on the surface and in contact with the toner image on the recording medium. can do.

  As a result, the flexibility of the fixing belt is increased, the deformation of the elastic layer of the fixing roller in the fixing nip portion can be prevented from being hindered by the rigidity of the fixing belt, and the deterioration of the peelability of the recording medium can be prevented. it can.

  Such a fixing device is excellent in fixability and energy saving performance when fixing a toner image on a recording medium, and an image forming apparatus equipped with these has an image excellent in peelability of the recording medium and excellent in energy saving performance. Can be formed.

As described above, since the surface layer of the fixing roller is a metal layer reflects radiant heat from the heat source such as a halogen lamp, a fixing elastic layer of the fixing roller can be prevented from undergoing radiant heat directly fixing the elastic layer Can prevent overheating damage.

1 is a schematic configuration diagram of an image forming apparatus of the present invention. 1 is a cross-sectional configuration diagram of a fixing device according to a first embodiment of the present invention. It is a sectional view of a fixing roller in the same manner. FIG. 6 is a cross-sectional view of a fixing roller in a second embodiment of the present invention. It is a cross-sectional block diagram of the fixing apparatus in the 3rd Embodiment of this invention. It is a cross-sectional block diagram of the fixing device in the 4th Embodiment of this invention.

  Hereinafter, an image forming apparatus according to an embodiment of the present invention and a fixing device mounted thereon will be described with reference to the drawings. In the following description, in the forms preceding each form, portions corresponding to the matters already described may be denoted by the same reference numerals, and overlapping descriptions may be omitted. Further, in each embodiment, when only a part of the configuration is described, the other parts of the configuration are the same as those described in advance. Furthermore, not only the combination of the parts specifically described in each embodiment, but also the embodiments may be partially combined if there is no problem in combining them. Furthermore, each embodiment is illustrated in order to embody the technology according to the present invention, and does not limit the technical scope of the present invention. The technical contents according to the present invention can be variously modified within the technical scope described in the claims.

(About image forming device)
FIG. 1 is a schematic diagram schematically showing a configuration of an image forming apparatus 100 according to an embodiment of the present invention. The image forming apparatus 100 is an apparatus that forms a multicolor or single color image on a recording medium such as a sheet based on image data of a read original or image data transmitted via a network.

  The image forming apparatus 100 includes an exposure unit 1, photosensitive drums 3a to 3d, developing devices 2a to 2d, chargers 5a to 5d, cleaning units 4a to 4d, an intermediate transfer belt unit 8, primary transfer rollers 6a to 6d, and a secondary. A transfer roller 11, a fixing device 12, recording medium conveyance paths S <b> 1 to S <b> 3, a paper feed cassette 10, a manual paper feed tray 20 and a paper discharge tray 15 are provided.

  The image forming apparatus 100 corresponds to the hues of four colors of cyan (C), magenta (M), and yellow (Y), which are three subtractive primary colors obtained by color separation of black (K) and a color image. Image formation is performed in each image forming unit corresponding to each hue using the image data.

  Each image forming unit has the same configuration. For example, the black (K) image forming unit includes a photosensitive drum 3a, a developing device 2a, a charging device 5a, a primary transfer roller 6a, a cleaning unit 4a, and the like. . The cyan (C) image forming unit includes a photosensitive drum 3b, a developing device 2b, a charging device 5b, a primary transfer roller 6b, a cleaning unit 4b, and the like. The magenta (M) image forming unit includes a photosensitive drum 3c, a developing device 2c, a charging device 5c, a primary transfer roller 6c, and a cleaning unit 4c. The yellow (Y) image forming unit includes a photosensitive drum 3d, a developing device 2d, a charging device 5d, a primary transfer roller 6d, a cleaning unit 4d, and the like.

  These image forming units are arranged in a line in the moving direction B of the intermediate transfer belt 7 of the intermediate transfer belt unit 8. The intermediate transfer belt 7 is stretched between a pair of rollers 71 and 72 above the four image forming units.

  In such an image forming apparatus 100, the recording medium stored in the paper feed cassette 10 is transferred to the paper discharge tray 15 between the secondary transfer roller 11 and the intermediate transfer belt 7 and via the fixing device 12. A first recording medium conveyance path S1 extending in a substantially vertical direction for feeding is provided.

  In the first recording medium transport path S1, a pickup roller 161 that feeds the recording medium in the paper feed cassette 10 one by one into the paper transport path S1, a transport roller 251 that transports the fed recording medium upward, A registration roller 14 for guiding the conveyed recording medium between the secondary transfer roller 11 and the intermediate transfer belt 7 at a predetermined timing, a conveying roller 252 for conveying the recording medium after passing through the fixing device 12, and a recording A paper discharge roller 253 that discharges the medium to the paper discharge tray 15 is disposed.

  Inside the image forming apparatus 100, a second recording medium conveyance path S <b> 2 in which a pickup roller 162 and conveyance rollers 254, 255, and 256 are arranged is formed between the manual paper feed tray 20 and the registration rollers 14. . Further, a third recording medium conveyance path S3 is formed between the discharge roller 253 and the upstream side of the registration roller 14 in the first recording medium conveyance path S1.

  The paper discharge roller 253 is rotatable in both forward and reverse directions, and is formed on the second surface during single-sided image formation for forming an image on one side of the recording medium and double-sided image formation for forming an image on both sides of the recording medium. When the image is formed, the recording medium is driven in the forward rotation direction and discharged to the paper discharge tray 15.

  On the other hand, at the time of image formation on the first side in double-sided image formation, the paper discharge roller 253 is driven in the normal rotation direction until the rear end of the paper passes through the fixing device 12, and then sandwiches the rear end of the recording medium. In this state, the recording medium is driven in the reverse direction to guide the recording medium into the third recording medium conveyance path S3 in which the conveyance rollers 257 and 258 are arranged. As a result, the recording medium on which the image is formed only on one side at the time of double-sided image formation is guided to the first recording medium conveyance path S1 with the front and back sides and the front and rear ends reversed.

(About fixing device)
FIG. 2 is a cross-sectional view schematically showing the configuration of the fixing device 12 according to the first embodiment of the present invention. FIG. 3 is an enlarged sectional view of the fixing roller.

  The fixing device 12 includes a fixing roller 21 that is a fixing member, a pressure roller 22 that is a pressure member, and an endless fixing belt 23. The fixing roller 21 is disposed inside the fixing belt 23, and the pressure roller 22 is disposed so as to face the fixing roller 21 through the fixing belt 23.

  In the fixing device 12, a heat source 24 composed of a halogen lamp is provided inside the fixing belt 23, and the fixing belt 23 is heated by radiant heat radiated from the heat source 24, and the fixing belt 23 and the pressure roller 33. A belt for fixing an unfixed toner image carried on a recording medium by heating and pressurizing the recording medium when the recording medium passes through the fixing nip portion A formed at a predetermined fixing speed and a copying speed. Adopt fixing method.

  The belt fixing type fixing device 12 of this example has a configuration in which the fixing belt 23 having a small heat capacity is heated by a heat source such as a halogen lamp, so that the warm-up time is short and the increase in power consumption is suppressed to save energy. Can be achieved.

  The unfixed toner image may be a developer (toner) such as a non-magnetic one-component developer (non-magnetic toner), a non-magnetic two-component developer (non-magnetic toner and carrier), or a magnetic developer (magnetic toner). ). The fixing speed is a so-called process speed, and the copying speed is the number of copies per minute. Further, when the recording medium passes through the fixing nip portion A, the fixing belt 23 comes into contact with the toner image carrying surface of the recording medium.

  The fixing roller 21 is a roller-like member having a substantially cylindrical shape, and is a fixing core metal 25 and a fixing elastic layer 26 from the substantially cylindrical central axis toward the outer periphery, and a metal layer as an infrared reflecting layer on the outermost layer. 27 is formed in a three-layer structure.

  For the fixing metal core 25, a metal such as iron, stainless steel, aluminum or copper, or an alloy thereof is used. A rubber material having heat resistance such as silicone rubber or fluorine rubber is suitable for the fixing elastic layer 26. The fixing elastic layer 26 preferably has an Asker C (ASKER C) hardness of 20 to 40 degrees. The metal layer 27, which is an infrared reflecting layer, is preferably made of a material having a relatively high infrared reflectance such as stainless steel, copper, or Ni (nickel) and hardly changed by oxidation.

  In this example, the diameter of the fixing roller 21 is 30 mm. The fixing core 25 is made of stainless steel having a diameter of 15 mm, and the fixing elastic layer 26 is made of silicone sponge rubber having an Asker C hardness of 25 degrees and a thickness of 7.5 mm. The metal layer 27 is covered with the fixing elastic layer 26 using a stainless steel tube belt having a thickness of 0.05 mm. The metal layer 27 can prevent the surface layer of the fixing elastic layer 26 that is a sponge roller from directly receiving radiant heat by the action of reflecting the radiant heat from the halogen lamp 24, and can prevent the fixing elastic layer 26 from being overheated. There is.

  The fixing roller 21 is provided so as to be rotatable about a substantially cylindrical central axis, and is rotated by the rotation of the pressure roller 22 that is a pressure member. When the fixing roller 21 is in pressure contact with the pressure roller 22 via the fixing belt 23, a fixing nip portion A that is a portion where the fixing roller 21 and the pressure roller 22 are in contact with each other via the fixing belt 23 is formed. Is done.

  As shown in FIG. 2, the pressure roller 22 is a roller-shaped member having a substantially cylindrical shape, and a pressure cored bar 28 and a pressure elastic layer 29 from the substantially cylindrical central axis toward the outer periphery. And a three-layer structure in which the pressure release layer 30 is formed.

  A metal such as iron, stainless steel, aluminum, copper, or an alloy thereof is used for the pressure core 28. For the pressure elastic layer 29, a rubber material having heat resistance such as silicone rubber or fluorine rubber is suitable. A fluororesin such as PFA (a copolymer of tetrafluoroethylene and perfluoroalkyl vinyl ether) or PTFE (polytetrafluoroethylene) is suitable for the pressure release layer 30.

  In this example, the diameter of the pressure roller 22 is 30 mm. For the pressure core 28, iron (STKM: carbon steel pipe for machine structure) having a diameter of 46 mm and a thickness of 1 mm is used. For the pressure elastic layer 29, a silicone solid rubber having Asker C hardness of 60 degrees and a thickness of 2 mm is used. For the pressure release layer 30, a PFA tube having a thickness of 50 μm is used.

  Inside the pressure roller 22, a pressure roller heater lamp 31 as a heating source is arranged. The pressure roller heater lamp 31 heats the pressure roller 22. When a control circuit (not shown) supplies power to the pressure roller heater lamp 31 from a power supply circuit (not shown), the pressure roller heater lamp 31 emits light and infrared light is emitted from the pressure roller heater lamp 31. Is done. The entire pressure roller 22 is heated by absorbing the infrared rays emitted from the pressure roller heater lamp 31 inside the pressure roller 22. In this example, a heater roller lamp with a rated power of 300 W is used.

  The pressure roller 22 is provided to be rotatable about a substantially cylindrical central axis. The pressure roller 22 is a roller-like member that is rotationally driven by a drive motor that is a drive means (not shown). The fixing roller 21 presses against the pressure roller 22 via the fixing belt 23 to form the fixing nip portion A, and simultaneously conveys the fixing belt 23 by being driven to rotate.

  The fixing roller 21 and the pressure roller 22 are pressed against each other with a predetermined load, for example, 700N. When the fixing roller 21 and the pressure roller 22 are pressed against each other, a fixing nip portion A is formed. In this example, the width of the fixing nip portion A in the recording medium conveyance direction (hereinafter referred to as “fixing nip width”) is 7 mm. A recording medium carrying an unfixed toner image T is fed to the fixing nip portion A. As the recording medium P passes through the fixing nip portion A, the toner image is fixed on the recording medium P. When the recording medium P passes through the fixing nip A, the fixing belt 23 comes into contact with the toner image carrying surface of the recording medium P, and the pressure roller 22 is on the surface of the recording medium opposite to the toner image carrying surface. Abut.

  The fixing belt 23 has a diameter of 40 mm. As shown in FIG. 2, the fixing belt 23 includes a belt base material 33, a belt elastic layer 34 formed on the surface of the belt base material 33, and a belt release layer 35 formed on the surface of the belt elastic layer. And a four-layer structure in which an infrared absorption layer 36 is provided inside the fixing belt 23.

  As a material for forming the belt base material 33 of the fixing belt 23, a heat-resistant synthetic resin excellent in heat resistance and durability, or a metal material such as stainless steel and nickel is used. Of the heat resistant synthetic resins, polyimide (PI) is preferable. The thickness of the belt base material 33 is preferably 50 to 90 μm when a resin material such as polyimide is used, and preferably 30 to 70 μm when a metal material is used. In this example, nickel is used as the belt base material 33, and the thickness thereof is 40 μm.

  The material constituting the belt elastic layer 34 of the fixing belt 23 is not particularly limited as long as it has rubber elasticity, but is preferably excellent in heat resistance. For example, silicone rubber, fluorine rubber, fluorosilicon rubber, and the like are used, and among these, silicone rubber that is particularly excellent in rubber elasticity is preferable.

  The thickness of the belt elastic layer 34 of the fixing belt 23 is preferably 150 to 300 μm. Within this thickness range, the heat insulating property can be kept low while maintaining the elastic effect of the belt elastic layer 34, so that the energy saving effect is exhibited. The belt elastic layer 34 has a JIS-A hardness of 30 degrees or less. In this example, a silicone rubber having a JIS-A hardness of 25 degrees and a thickness of 200 μm is used as the belt elastic layer 34.

  The belt release layer 35 of the fixing belt 23 is a layer made of a fluororesin such as PFA or PTFE, and has a thickness of 10 to 50 μm. In this example, a 30 μm thick PFA tube is used as the belt release layer 35.

  A heater lamp 24 is disposed inside the fixing belt 23 as a heat source. When a control circuit (not shown) supplies (energizes) power to the heater lamp from a power supply circuit (not shown), the heater lamp emits light and infrared rays are emitted from the heater lamp 24. The fixing belt 23 is heated by the infrared absorbing layer 36 inside the fixing belt 23 absorbing the infrared rays emitted from the heater lamp 24. In this example, a heater lamp with a rated power of 1200 W is used.

  In the above configuration, when silicone rubber is used as the fixing elastic layer 26 of the fixing roller 21, the infrared absorption rate of the silicone rubber is 90% or more and the infrared radiation radiant heat is absorbed so that the temperature easily rises. Since the surface layer of the roller 21 is a metal layer 27 and has a function of reflecting radiant heat from a heat source such as the halogen lamp 24, the silicone rubber that is an elastic layer of the fixing roller 21 can be prevented from receiving radiant heat directly. Overheating damage of the silicone rubber surface layer can be prevented.

  Further, in a fixing roller used in a conventional belt fixing type fixing device, a fixing elastic layer made of a rubber material is coated on a surface layer of a metal roller (core metal), and heat insulation of the fixing elastic layer causes the metal roller Although it prevents heating, the rubber material has a lower infrared reflectance than metal materials, and when it receives the radiant heat of a halogen lamp, it absorbs as it is, so the heating efficiency inside the fixing belt in contact with the fixing roller decreases. There are challenges.

  Further, in a fixing roller used in a conventional belt fixing type fixing device, when the metal layer of the metal roller is thick, the fixing roller is not sufficiently deformed, and a necessary nip width cannot be obtained, resulting in insufficient fixing. There are challenges. Conversely, if the metal layer of the metal roller is thin, the surface pressure of the fixing nip will be low even if it is deformed, and it will not be able to follow the unevenness of the recording medium, causing fine gloss unevenness, In the case of embossed paper, there has been a problem that poor fixing of the concave portion of the embossed paper occurs. As described above, the fixing roller used in the conventional belt-fixing type fixing device has a problem that it is difficult to ensure both the nip width and the surface pressure.

  On the other hand, the fixing roller 21 used in the fixing device 12 of the present example is coated with the metal layer 27 that is an infrared reflecting layer on the surface layer, and has a high infrared reflectance on the surface layer. Even when radiant heat from the halogen lamp 24 is received, it is reflected without being absorbed and the fixing belt is heated. Even if the surface metal layer 27 is heated by radiant heat or heat conduction from the fixing belt 23 in the fixing nip portion A, the heat insulating action of the inner sponge layer (elastic layer) of the metal layer 27 causes the fixing roller 21 to There is an effect that heat is not easily transmitted to the inside. Further, the infrared rays that have once reached the inside of the fixing belt 23 by the infrared absorbing layer 36 inside the fixing belt 23 contribute to heating the fixing belt 23 with almost no reflection.

  As the metal layer 27, a material having a high infrared reflectance such as aluminum, silver, or gold, or a material having a high mechanical strength such as nickel or steel having an infrared reflectance higher than the absorptivity is suitable. In this example, a steel belt having a thickness of 50 μm and an inner diameter φ30.25 mm covered with a fixing elastic layer having an outer diameter φ30 mm is used.

  As described above, the surface layer of the fixing roller 21 has a higher infrared reflectance than that of the inner side of the fixing belt 23, so that the radiant heat from the halogen lamp, which is a heat generation source, is efficiently used to heat the fixing belt 23. Since it can be used, the fixing device 12 excellent in energy saving performance can be provided.

  Further, due to the deformation of the sponge layer (elastic layer) of the fixing roller 21, even when the metal layer 27 is present on the surface layer of the fixing roller 21, a sufficient fixing nip width A can be obtained and the surface pressure can be secured. It is possible to ensure both the width and the surface pressure.

(Second Embodiment)
FIG. 4 is a cross-sectional view of the fixing roller in the second embodiment. As shown in the figure, the fixing roller 21 is a two-layered fixing roller composed of a fixing metal core 25 and a fixing elastic layer 26 from the central axis toward the outer periphery, and a resin base material 27a with an infrared reflecting layer as a surface layer. A fixing roller having a four-layer structure is formed by covering a sleeve having a two-layer structure that is the metal layer 27.

  Since the resin base material 27a can play a role of maintaining the mechanical strength required for the sleeve, the metal layer 27 does not require mechanical strength, and a material having high infrared reflectance can be selected.

  The cylindrical base material 27a is made of a heat resistant synthetic resin having a thickness of about 50 to 90 μm and excellent in heat resistance and durability, for example, polyimide (PI), and the metal layer 27 is made of 5 to 50 μm aluminum. It has been.

  In the above configuration, since a sleeve having a two-layer configuration of the base material 27a and the metal layer 27 is used, the metal layer 27 is maintained while maintaining the action of reflecting the infrared rays of the halogen lamp as compared with the sleeve having a single metal layer. Can be thinned. When the metal layer 27 is thinned, the fixing elastic layer 26 (sponge layer) can be more easily deformed, and a sufficient fixing nip width can be secured. Therefore, the fixing temperature can be lowered, and the deformation and return of the fixing elastic layer (sponge layer) at the portion coming out from the fixing nip A can be accelerated, and the peelability of the recording medium can be improved.

(Third embodiment)
FIG. 5 is a cross-sectional view of the fixing device showing the third embodiment. As shown in the figure, the fixing roller 21 is a two-layered fixing roller composed of a fixing metal core 25 and a fixing elastic layer 26 from the central axis toward the outer periphery, and a single layer that is a metal layer 27 that is an infrared reflecting layer. A fixing roller having a three-layer structure is formed by covering the sleeve having the structure.

  Here, the inner diameter of the metal layer 27 is larger than the outer diameter of the fixing elastic layer 26 so that the metal layer 27 hardly adheres to the fixing elastic layer 26.

  According to the above configuration, when rubber such as silicone rubber is employed as the fixing elastic layer 26, heat transfer to the silicone rubber due to heat conduction from the metal layer 27 heated by infrared absorption can be reduced. The heat of the heated metal layer 27 is transmitted to the toner on the recording medium (paper) through the fixing belt 23 in the fixing nip portion.

  Thus, the heat of the metal layer 27 can be used for heating the toner on the recording medium (paper), and the heating efficiency is improved. For example, when the outer diameter of the two-layer fixing roller is φ27 mm and the inner diameter of the metal layer 27 is φ30 mm, even if the fixing elastic layer 26 is thermally expanded at the time of heating, the metal layer 27 is almost not in the fixing elastic layer 26. It can be made not to adhere.

(Fourth embodiment)
FIG. 6 is a cross-sectional view of the fixing device showing the fourth embodiment. In this example, a belt guide 38 is provided inside the fixing belt 23 as a fixing member for slidingly guiding the fixing belt 23. The belt guide 38 is disposed inside the fixing belt 23 except for the position where the fixing roller 21 is disposed, more specifically, the fixing nip portion A.

  Therefore, the belt guide 38 has a cross-sectional shape that is C-shaped with the fixing nip portion A open. The cross-sectional shape of the belt guide 38 is preferably a perfect circle in order to improve the slidability of the fixing belt 23, but is not limited to this, and may be an elliptical shape or other shapes.

  Inside the belt guide 38, a halogen lamp 24 as a heat source is disposed. The arrangement of the belt guide 38 has a function of preventing the fixing belt 23 from coming into contact with the halogen lamp 24.

  The material of the belt guide 38 is preferably a metal such as aluminum or stainless steel, and an infrared absorption layer 39 having a high absorptance with respect to infrared rays emitted from the halogen lamp 24 is provided inside the belt guide 38. The infrared absorption layer 39 can be formed by a known film or paint.

  In this example, since the infrared absorbing layer 39 is provided inside the belt guide 38 that slides and guides most of the inner surface side of the fixing belt 23, the fixing belt 23 includes the belt base material 33, the belt elastic layer 34, and the belt release. The layer 35 has a three-layer structure.

  When the infrared reflectances of the belt guide 38 and the fixing roller 21 are compared, the infrared reflectance of the metal layer 27 on the surface side of the fixing roller 21 is higher due to the infrared absorption layer 39 of the belt guide 38.

  In this example, the belt guide 38 is made of stainless steel having a thickness of 0.5 mm. Note that the surface layer of the belt guide 38 in contact with the fixing belt 23 may be coated with a fluororesin so as to improve the slidability.

  In the above configuration, the infrared rays emitted from the halogen lamp 24 are absorbed by the infrared absorption layer 39 inside the belt guide 38 to heat the belt guide 38. Therefore, the fixing belt 23 that slides in contact with the belt guide 38 is transferred and heated by heat conduction from the belt guide 38.

  At this time, by providing the belt guide 38, the contact between the fixing belt 23 and the halogen lamp 24 can be prevented, and thermal damage to the fixing belt 23 can be reduced. Further, the heating of the fixing belt 23 by infrared rays emitted from the halogen lamp 24 is once absorbed by the belt guide 38 and then transferred to the fixing belt 23 by heat conduction from the belt guide 38. Therefore, the risk of distortion occurring in the fixing belt 23 due to local thermal expansion of the fixing belt 23 due to uneven infrared radiation from the halogen lamp 24, or the risk of the fixing belt 23 meandering due to this distortion is reduced. be able to.

  Due to this risk reduction, the fixing belt 23 can use a highly flexible material, such as a polyimide resin, for the base material 33. Therefore, it is possible to prevent a decrease in the peelability of the recording medium P caused by the deformation of the fixing elastic layer 26 (sponge layer) of the fixing roller 21 in the fixing nip portion A being hindered by the rigidity of the fixing belt 23.

  Further, by increasing the infrared reflectance of the surface layer of the fixing roller 21, even if the fixing roller 21 receives infrared radiant heat from a heat source such as a halogen lamp 24, it is reflected without being absorbed. The belt 23 and the belt guide 38 can be efficiently heated.

  As described above, since the infrared reflectance of the surface layer of the fixing roller 21 is higher than the reflectance on the inner side of the fixing belt 23, the radiant heat from the heat source can be efficiently used for heating the fixing belt 23. A fixing device with excellent energy saving performance can be provided.

  The image forming apparatus 100 equipped with the fixing device 12 excellent in peelability and energy saving as described above can form an image excellent in peelability and energy saving performance.

DESCRIPTION OF SYMBOLS 12 Fixing device 21 Fixing roller 22 Pressure roller 23 Fixing belt 24 Heat source 25 which consists of halogen lamps Fixing core metal 26 Fixing elastic layer 27 Infrared reflective layer (metal layer)
28 pressure core metal 29 pressure elastic layer 30 pressure release layer 31 heater roller 33 for pressure roller belt base material 34 belt elastic layer 35 belt release layer 36 infrared absorption layer 38 belt guide

Claims (9)

Comprising a fixing roller formed roller-shaped, and endless fixing belt, a pressure member, and a heat source for emitting infrared rays is disposed inside the fixing belt, the fixing to the inside of the fixing belt rollers are disposed, said pressure member is pressed against the fixing roller via the fixing belt, the pressure member and the belt fixing system fixing nip portion is provided in which the recording medium passes between the fixing belt The fixing device according to claim 1, wherein the fixing roller includes a fixing elastic layer, and has a metal layer as an infrared reflecting layer that reflects infrared rays on a surface layer side thereof.   The fixing device according to claim 1, wherein the reflectance of the infrared reflection layer is higher than the reflectance of the base material on the inner surface side of the fixing belt in contact with the infrared reflection layer with respect to infrared rays. The fixing roller, are sequentially arranged outward from the central axis, the core metal layer, fixing the elastic layer is composed of four layers of the base layer and the infrared reflective layer, according to claim 1 or 2 Fixing device. The fixing roller, the outer circumference of the two-layer structure of the metal core layer and the fixing elastic layer, the sleeve having a two-layer structure consisting of the base layer and the infrared reflective layer is coated, according to claim 3 Fixing device. The fixing roller, on the outside of the fixing elastic layer, the sleeve of one or more layers comprising an infrared reflective layer is covered, greater claim than the outer diameter of the inner diameter of the sleeve fixing elastic layer The fixing device according to 3 or 4 . The fixing device according to claim 1 , wherein a belt guide as a fixing member that slides and guides the fixing belt is provided inside the fixing belt. The fixing device according to claim 6 , wherein an infrared reflectance of a metal layer as an infrared reflecting layer of the fixing roller is higher than an infrared reflectance on an inner surface side of the belt guide. The fixing belt includes: a belt base material in contact with the fixing roller ; a belt elastic layer on a surface side of the belt base material ; and a belt release layer in contact with a toner image on a recording medium on the surface side of the belt elastic layer. The fixing device according to claim 1, further comprising : An image forming apparatus comprising the fixing device according to claim 1 .

Images