JP5916448B2 - Fixing apparatus, image forming apparatus, and fixing roller - Google Patents

Description

  The present invention relates to an external heating type fixing device that can be applied to an image forming apparatus that forms an image by electrophotography, electrostatic recording, a magnetic photographic method, and the like, an image forming apparatus including the fixing device, and a fixing roller.

  An external heating type fixing device generally includes a rotating fixing roller, an external heating unit that heats the fixing roller from the outside, and a pressure roller that rotates with the rotation of the fixing roller while being pressed by the fixing roller. The unfixed image (specifically, unfixed toner) is fixed to the recording sheet while the recording sheet is conveyed to a fixing nip portion formed between the pressure roller and the fixing roller.

  In such a fixing device, from the viewpoint of improving the fixability of an unfixed image to a recording sheet, in order to increase the area of the fixing nip portion, in the fixing roller, a base (specifically, a cylindrical shape such as stainless steel) is used. There is known a configuration in which an elastic layer (for example, a foamed rubber layer) of an elastic porous material (specifically, a foamed resin material) is provided on a core metal, and a release layer is provided on the surface layer.

  In such a fixing device, the area of the fixing nip portion can be increased, thereby improving the fixing property of the unfixed image to the recording sheet, while the air bubble portion of the porous member in the fixing nip portion. And other portions are not uniform in fixing characteristics (amount of heat applied to the recording sheet or / and fixing pressure), so the fixing characteristics (heat is applied to the recording sheet) between the bubble portion of the porous member and the portions other than the bubble portions. An image defect (so-called glossy unevenness like a satin) may occur due to a difference in the amount to be added and the fixing pressure.

  Further, in a conventional fixing device, a configuration in which an elastic layer (for example, a silicone rubber layer) having elasticity is provided on a base in a fixing roller has been proposed (see, for example, Patent Document 1).

JP 2011-22207 A

  However, in the conventional fixing device in which the elastic layer is provided on the substrate, the fixing characteristics in the fixing nip portion can be made uniform, thereby suppressing the occurrence of image defects (so-called glossy unevenness like a satin), An elastic layer (for example, a silicone rubber layer) usually has a larger heat capacity than an elastic layer (for example, a foamed rubber layer), so that heat is easily taken away (especially easily taken through an inner substrate), and fixing by an external heating means is performed. Heating efficiency to the roller tends to decrease.

  Therefore, the present invention can make the fixing characteristics to the recording sheet uniform in the fixing nip portion, thereby suppressing the occurrence of image defects (so-called glossy unevenness like a satin) and fixing by an external heating means. It is an object of the present invention to provide a fixing device capable of improving the heating efficiency of the roller, an image forming apparatus including the fixing device, and a fixing roller.

  In order to solve the above problems, the present invention provides the following fixing device, image forming apparatus, and fixing roller.

(1) Fixing device, comprising: a rotating fixing roller; an external heating unit that heats the fixing roller from the outside; and a pressure roller that rotates together with the rotation of the fixing roller while being pressed by the fixing roller, A fixing device for fixing an unfixed image to the recording sheet while conveying the recording sheet to a fixing nip portion formed between a pressure roller and the fixing roller, wherein the fixing roller includes a base and a mold release A release layer having elasticity, an elastic layer having elasticity, and an elastic heat insulation layer having elasticity and heat insulation properties, and the release layer, the elastic layer, and the elastic heat insulation layer are formed on the surface from the surface. It is provided in this order toward the inside, a base material is provided between the elastic layer and the elastic heat insulating layer, the base material is made of polyimide, and the elastic layer is made of silicone rubber, Elasticity break A fixing device, wherein a cylindrical member in which the elastic layer made of the silicone rubber is formed on the base material made of the polyimide is provided on the thermal layer .

(2) Image forming apparatus An image forming apparatus comprising the fixing device according to the present invention.

(3) Fixing roller, comprising: a rotating fixing roller; an external heating means for heating the fixing roller from the outside; and a pressure roller rotating with the rotation of the fixing roller while being pressed by the fixing roller, A fixing roller provided in a fixing device for fixing an unfixed image on a recording sheet while conveying the recording sheet to a fixing nip formed between a pressure roller and the fixing roller, the substrate, and a mold release A release layer having elasticity, an elastic layer having elasticity, and an elastic heat insulation layer having elasticity and heat insulation properties, and the release layer, the elastic layer, and the elastic heat insulation layer are formed on the surface from the surface. It is provided in this order toward the inside, a base material is provided between the elastic layer and the elastic heat insulating layer, the base material is made of polyimide, and the elastic layer is made of silicone rubber, Above A fixing roller having a cylindrical member in which the elastic layer made of the silicone rubber is formed on the base made of the polyimide on the elastic heat insulating layer .

According to the present invention, the fixing roller has the release layer having releasability, the elastic layer having elasticity, and the elastic heat insulation layer having elasticity and heat insulation on the base. Because of the elasticity of the elastic layer provided inside the release layer and the elasticity of the elastic heat insulating layer provided inside the elastic layer, the fixing nip portion The area can be increased, whereby the fixability of the unfixed image to the recording sheet can be improved. In addition, by providing the elastic layer outside the elastic heat insulating layer, the fixing characteristics (the amount of heat applied to the recording sheet or / and the fixing pressure) to the recording sheet in the fixing nip portion can be made uniform. Thus, it is possible to suppress the occurrence of image defects (so-called glossy unevenness like a satin). And even if the heat capacity of the elastic layer becomes large, heat can be made difficult to be taken away by the heat insulating property of the elastic heat insulating layer provided inside the elastic layer. Furthermore, since the elastic layer is formed on the elastic heat insulating layer via the base material, the elastic layer having desired elasticity can be easily obtained.
Furthermore, a cylindrical member widely used as a fixing belt (specifically, a cylindrical member in which silicone rubber is formed on a base material made of polyimide, a so-called polyimide belt) is provided on the elastic heat insulating layer ( Specifically, the fixing roller can be manufactured inexpensively and easily by using it as the substrate and the elastic layer.

  In the present invention, the external heating means includes a heating roller disposed in contact with the fixing roller and a heat source for heating the heating roller, and the fixing is performed so that the heating roller forms a heating nip portion. The aspect made into the structure pressed by a roller can be illustrated.

  In this specific matter, the heat from the heating roller heated by the heat source can be easily transmitted to the fixing roller with a simple configuration.

  In the present invention, it is possible to exemplify an embodiment in which the fixing roller has a surface hardness smaller than the surface hardness of the substrate, and the heating roller has a surface hardness equivalent to the surface hardness of the substrate.

  In this specific matter, the fixing roller has a surface hardness smaller than the surface hardness of the substrate, and the heating roller has a surface hardness equivalent to the surface hardness of the substrate. The heating nip portion between the roller and the fixing roller can be reliably formed.

  In the present invention, the external heating means includes a plurality of heating rollers spaced apart from each other, a heat source for heating at least one of the plurality of heating rollers, and a heating belt wound around the plurality of heating rollers. And a configuration in which two adjacent two of the plurality of heating rollers are pressed against the fixing roller so as to form a heating nip portion via the heating belt.

  In this specific matter, the heat from the heating roller heated by the heat source can be efficiently transmitted to the fixing roller via the heating belt.

  In the present invention, the elastic heat insulating layer has a surface hardness smaller than that of the surface of the substrate, and the elastic layer has a surface hardness equal to or lower than the surface hardness of the substrate, and the elastic heat insulating layer. The aspect which is larger than the hardness of the surface of can be illustrated.

  In this specific matter, the elastic heat insulating layer has a surface hardness smaller than the surface hardness of the substrate, and the elastic layer has a surface hardness equal to or lower than the surface hardness of the substrate, and the elastic heat insulating layer. Since the hardness of the surface of the layer is larger, the fixing nip portion can be reliably formed.

  In the present invention, the pressure roller includes a base, a release layer having releasability, and an elastic heat insulating layer having elasticity and heat insulation, and the release layer and the elastic heat insulation are provided on the base. A mode in which the layers are provided in this order from the surface toward the inside can be exemplified.

  In this specific matter, the pressure roller is provided with the release layer having releasability and the elastic heat insulation layer having elasticity and heat insulation on the base in this order from the surface to the inside. Therefore, the area of the fixing nip portion can be further increased by the elasticity of the elastic heat insulating layer provided inside the release layer, thereby fixing the unfixed image to the recording sheet. The property can be further improved. In addition, the heat applied to the pressure roller can be made difficult to be taken away by the heat insulating property of the elastic heat insulating layer provided inside the release layer.

  In the present invention, the pressure roller may have an aspect in which the surface hardness is equal to or greater than the surface hardness of the fixing roller.

  In this specific matter, since the surface hardness of the pressure roller is equal to or higher than the surface hardness of the fixing roller, the fixing nip portion can be reliably formed.

  As described above, according to the present invention, the fixing characteristics to the recording sheet in the fixing nip portion can be made uniform, thereby suppressing the occurrence of image defects (so-called glossy unevenness like a satin). In addition, the heating efficiency of the fixing roller by the external heating means can be improved.

1 is a front view illustrating a schematic configuration of an image forming apparatus according to an embodiment of the present invention. FIG. 3 is a schematic cross-sectional view of an external heating device, a fixing roller, and a pressure roller portion in the external heating type fixing device according to the first embodiment when viewed from the front. FIG. 5 is a schematic cross-sectional view of an external heating device, a fixing roller, and a pressure roller portion in a fixing device of an external heating system according to a second embodiment when viewed from the front. It is a figure which shows the state which the external heating apparatus is pressing the fixing roller from the outside, Comprising: (a) is a schematic sectional drawing which looked at the external heating apparatus and the fixing roller from the front, (b) is external heating FIG. 3 is a schematic cross-sectional view of the apparatus and the fixing roller as viewed from the plane side. FIG. 4 is a cross-sectional view schematically showing the structure of each layer in the fixing roller of the first example applicable to the first embodiment and the second embodiment. It is sectional drawing which shows typically the structure of each layer in the fixing roller of the 2nd Example applicable to 1st Embodiment and 2nd Embodiment. It is sectional drawing which shows typically the structure of each layer in the pressure roller of the 1st Example applicable to 1st Embodiment and 2nd Embodiment. It is sectional drawing which shows typically the structure of each layer in the pressure roller of the 2nd Example applicable to 1st Embodiment and 2nd Embodiment. Release layer, elastic layer, elastic heat insulating layer and substrate of fixing roller in first embodiment and second embodiment, release layer of elastic roller, elastic layer and elastic heat insulating layer, and heating roller in first embodiment It is the graph which put together the physical-property value of each layer etc. with a mold release layer.

  Embodiments according to the present invention will be described below with reference to the drawings. The following embodiment is an example embodying the present invention, and does not limit the technical scope of the present invention.

  FIG. 1 is a front view showing a schematic configuration of an image forming apparatus 1 according to an embodiment of the present invention.

  An image forming apparatus 1 shown in FIG. 1 records and forms an image of a document read by a document reading device (not shown) or an image indicated by image data received from outside on a recording sheet P such as paper in color or single color. An image forming unit 10 is provided.

  The image forming unit 10 includes an exposure device 11, developing devices 12 to 12, photosensitive drums 13 to 13 acting as an image carrier, cleaner devices 14 to 14, chargers 15 to 15, and an intermediate transfer roller 24 acting as a transfer unit. To 24, an intermediate transfer belt device 16, a fixing device 40, a paper feed tray 18 that functions as a paper feed unit, a paper discharge tray 19 that functions as a paper discharge unit, and a sheet conveying device 20.

  The image data handled in the image forming unit 10 corresponds to a color image using each color of black (K), cyan (C), magenta (M), yellow (Y), or a single color (for example, black). This corresponds to the monochrome image used. Accordingly, the developing devices 12 to 12, the photosensitive drums 13 to 13, the cleaner devices 14 to 14, the chargers 15 to 15, and the intermediate transfer rollers 24 to 24 are each four so as to form four types of images corresponding to the respective colors. It is provided one by one.

The photoconductor drums 13 to 13 are disposed at substantially the center in the vertical direction of the main body 1 a of the image forming apparatus 1. The chargers 15 to 15 are charging means for uniformly charging the surfaces of the photosensitive drums 13 to 13 to a predetermined potential. Here, the exposure device 11 is a laser scanning unit including a laser diode and a reflection mirror, and exposes the charged surfaces of the photosensitive drums 13 to 13 according to image data, and converts the surface to image data. A corresponding electrostatic latent image is formed. The developing devices 12 to 12 develop the electrostatic latent images formed on the photosensitive drums 13 to 13 with (K, C, M, Y) toner. The cleaners 14 to 14 remove and collect toner remaining on the surfaces of the photosensitive drums 13 to 13 after development and image transfer.

  The intermediate transfer belt device 16 disposed above the photosensitive drums 13 to 13 includes an intermediate transfer belt 21, an intermediate transfer belt driving roller 22, a driven roller 23, and an intermediate transfer belt cleaning in addition to the intermediate transfer rollers 24 to 24. A device 25 and a tension roller 26 are provided.

  The intermediate transfer belt drive roller 22, the driven roller 23, the intermediate transfer rollers 24 to 24, and the tension roller 26 stretch and support the intermediate transfer belt 21, and the intermediate transfer belt 21 is supported in a predetermined sheet conveyance direction (arrow C in the figure). Direction). The intermediate transfer rollers 24 to 24 are rotatably supported inside the intermediate transfer belt 21 and are pressed against the photosensitive drums 13 to 13 via the intermediate transfer belt 21. The intermediate transfer belt 21 is provided so as to be in contact with each of the photosensitive drums 13 to 13, and the toner image on the surface of each of the photosensitive drums 13 to 13 is sequentially transferred to the intermediate transfer belt 21 to transfer the color. A toner image (a toner image of each color) is formed. Transfer of the toner image from the photosensitive drums 13 to 13 to the intermediate transfer belt 21 is performed by intermediate transfer rollers 24 to 24 that are in pressure contact with the inner side (back surface) of the intermediate transfer belt 21. A high-voltage transfer bias (for example, a high voltage having a polarity (+) opposite to the toner charging polarity (-)) is applied to the intermediate transfer rollers 24 to 24 in order to transfer the toner image.

  The image forming unit 10 further includes a secondary transfer device 27 including a transfer roller 27a that functions as a transfer unit. The transfer roller 27 a is in contact with the outside of the intermediate transfer belt 21. As described above, the toner images on the surfaces of the photosensitive drums 13 to 13 are stacked on the intermediate transfer belt 21 to become a color toner image indicated by the image data. The stacked toner images of the respective colors are transported together with the intermediate transfer belt 21 and transferred onto the recording sheet P by the secondary transfer device 27. The intermediate transfer belt 21 and the transfer roller 27a of the secondary transfer device 27 are pressed against each other to form a transfer nip region (transfer nip portion). The transfer roller 27a of the secondary transfer device 27 has a voltage (for example, a polarity (+) opposite to the charging polarity (−) of the toner) for transferring the toner image of each color on the intermediate transfer belt 21 to the recording sheet P. )) Is applied.

  The intermediate transfer belt cleaning device 25 removes and collects residual toner on the intermediate transfer belt 21. The intermediate transfer belt cleaning device 25 is provided with, for example, a cleaning blade that contacts the intermediate transfer belt 21 as a cleaning member, and residual toner can be removed and collected by this cleaning blade.

  The paper feed tray 18 is a tray for storing the recording sheets P, and is provided below the image forming unit 10 in the main body 1 a of the image forming apparatus 1. A paper discharge tray 19 provided on the upper side of the image forming unit 10 is a tray for placing printed recording sheets P face down.

  Further, the main body 1 a of the image forming apparatus 1 is provided with a sheet conveying device 20 for sending the recording sheet P of the paper feed tray 18 to the paper discharge tray 19 via the secondary transfer device 27 and the fixing device 40. Yes. The sheet conveying device 20 has an S-shaped sheet conveying path S, and along the sheet conveying path S, a pickup roller 31, a pair of separation rollers 31a and 31b, a registration roller 32, a pre-registration roller 33, and a fixing device. 40 and a paper discharge roller 34 are arranged.

  The pickup roller 31 is a draw-in roller that is provided at the downstream end of the sheet feeding tray 18 in the sheet conveying direction and supplies the recording sheets P from the sheet feeding tray 18 one by one to the sheet conveying path S. One separation roller 31a passes the recording sheet P between the other separation roller 31b and conveys it to the sheet conveyance path S while separating the recording sheets one by one. In the stopped state, the registration roller 32 abuts the leading end of the recording sheet P that has been conveyed, aligns the leading end of the recording sheet P, and in the transfer nip region between the intermediate transfer belt 21 and the secondary transfer device 27. The recording sheet P is conveyed with good timing in synchronization with the toner image formed on the intermediate transfer belt 21 so that the toner image on the intermediate transfer belt 21 is transferred to the recording sheet P. The pre-registration roller 33 is a small roller for promoting and assisting the conveyance of the recording sheet P.

  The fixing device 40 receives the recording sheet P on which an unfixed toner image is formed, conveys the recording sheet P between the fixing roller 41 and the pressure roller 42, and transfers the unfixed toner image to the recording sheet P. To settle. The recording sheet P after fixing the toner images of the respective colors is discharged onto the paper discharge tray 19 by the paper discharge roller 34. In FIG. 1, a fixing device 40 according to a first embodiment to be described later is shown. The fixing device 40 will be described in detail later.

In the image forming apparatus 1 described above, the recording sheet P fed from the paper feeding tray 18 is formed on the recording sheet P by the photosensitive drums 13 to 13 while being conveyed along the sheet conveying path S. Then, the toner image conveyed to the intermediate transfer belt 21 is transferred by the secondary transfer device 27 and further fixed by the fixing device 40 to perform the printing process.

Specifically, the photosensitive drums 13 to 13 are rotationally driven in one direction, and after the surfaces neutralized by a neutralizing device (not shown) are cleaned by the cleaner devices 14 to 14, they are uniformly distributed by the chargers 15 to 15. Charged. The exposure device 11 repeatedly scans the surfaces of the photosensitive drums 13 to 13 in the main scanning direction with laser light modulated based on the image data, and forms electrostatic latent images on the surfaces of the photosensitive drums 13 to 13. The developing devices 12 to 12 supply toner to the surfaces of the photosensitive drums 13 to 13 to develop (develop) the electrostatic latent images, and form toner images on the surfaces of the photosensitive drums 13 to 13. The intermediate transfer belt device 16 transfers the toner image formed on the photosensitive drums 13 to 13 to the intermediate transfer belt 21. The secondary transfer device 27 is transferred onto the recording sheet P passing between the toner image formed on the intermediate transfer belt 21 and the intermediate transfer belt 21 and the transfer roller 27a. The fixing device 40 heats and pressurizes the recording sheet P on which the toner image is formed, and fixes the toner image on the recording sheet P to the recording sheet P. Thus, the image forming apparatus 1 completes a series of printing operations.

  It is also possible to form a monochrome image using at least one of the four image forming stations and transfer the monochrome image to the intermediate transfer belt 21 of the intermediate transfer belt device 16. This monochrome image is also transferred from the intermediate transfer belt 21 to the recording sheet P and fixed on the recording sheet P, similarly to the color image.

(About fixing device)
In the present embodiment, the fixing device 40 is an external heating type fixing device, and a fixing roller 41 that is rotationally driven and an external heating device 50 that heats the fixing roller 41 from the outside (an example of an external heating unit). And a pressure roller 42 that rotates together with the rotation of the fixing roller 41 while being pressed by the fixing roller 41.

  The fixing device 40 is configured to fix an unfixed toner image on the recording sheet P while conveying the recording sheet P to a fixing nip region (fixing nip portion) N formed between the pressure roller 42 and the fixing roller 41. It is said that.

(First embodiment)
FIG. 2 is a schematic cross-sectional view of the external heating device 50 (50a), the fixing roller 41, and the pressure roller 42 in the external heating type fixing device 40 (40a) according to the first embodiment as viewed from the front. Note that the rear view of the fixing device 40 (40a) is substantially the same as the front view, but the left and right sides are reversed. Therefore, only the front side is shown in FIG. 2, and the rear side is not shown. .

As shown in FIG. 2, the fixing device 40 (40 a) according to the first embodiment performs recording between the fixing roller 41 and the pressure roller 42 with the pressure roller 42 being in pressure contact with the fixing roller 41. A fixing nip region N that sandwiches the sheet P is formed, and the recording sheet P is passed through the fixing nip region N while the fixing roller 41 is driven to rotate in the rotational direction E1 and the pressure roller 42 is driven to rotate in the rotational direction E2. The toner image (unfixed toner T 1 ) on the recording sheet P is melted, mixed, and pressed to be thermally fixed to the recording sheet P.

  The fixing device 40 (40 a) further includes a pressing device 70 that acts as a pressing unit that presses the pressure roller 42 toward the fixing roller 41.

  The pressing device 70 includes a pressure frame 71 and an urging member (here, a coil spring 72).

The pressure frame 71 pivotally supports the pressure roller 42, and is swingable with respect to the fixing roller 41 in the pressure contact direction and the direction in which the pressure contact is released. Specifically, the pressure frame 71 supports the rotation shaft of the pressure roller 42 so as to be rotatable about an axis via a bearing (not shown), and the shaft of the pressure roller 42 with respect to the fixing device 40 (40a) main body. direction is (axially) supporting pivot shaft 71a freely (more specifically pivot shaft 71a is supported by the body frame (not shown) of the fixing device 40 (40a) is) swinging around along. The fixing roller 41 is pivotally supported by a main body frame (not shown) of the fixing device 40 (40a) so as to be rotatable about its axis, and the rotational driving force from the driving mechanism on the main body 1a side of the image forming apparatus 1 is not shown. It is transmitted through the gears to rotate.

The pressure frame 71 is urged by a coil spring 72 in a direction in which the pressure roller 42 is pressed against the fixing roller 41. Specifically, both ends of the hook 72a of the locking portion 73 and the coil spring 72 and the locking portion 74 of the body frame F is located radially outward around the pivot shaft 71a of the pressure frame 71, 72a is hooked respectively, the locking portion 73 of the pressing frame 71 by the coil spring 72 is attracted toward the locking portion 74 of the body frame F, thereby, the pressure frame 71 fixing roller 41 side around the pivot shaft 71a The pressure roller 42 is pressed against the fixing roller 41.

[External heating device]
Next, the external heating device 50 (50a) in the fixing device 40 (40a) of the first embodiment will be described.

  The fixing device 40 (40a) further includes an external heating device 50 (50a) for heating the fixing roller 41 from the outside by the heating roller 51.

  The external heating device 50 (50 a) includes a heating roller 51 and a heat source (here, a halogen heater lamp) 51 h provided inside the heating roller 51, and the heating roller 51 is pressed against the fixing roller 41. In this state, a heating nip region (heating nip portion) H (for example, a length of 15 mm in the rotation direction) is formed between the fixing roller 41 and the heating roller 51.

  The external heating device 50 (50a) heats the fixing roller 41 by pressing the heating roller 51 heated by the heat source 51h in a state where the heating roller 51 is in contact with a part of the outer peripheral surface of the fixing roller 41. Yes. Although not shown, the external heating device 50 (50a) further includes a pressing device that acts as a pressing unit that presses the heating roller 51 toward the fixing roller 41. This pressing device may have a conventionally known configuration similar to that for pressing the pressure roller 42 toward the fixing roller 41, and the description thereof is omitted here.

  Specifically, the heating roller 51 is brought into contact with the outer peripheral surface of the rotation-driven fixing roller 41 so as to follow the fixing roller 41 and rotate in the rotation direction E2.

  Further, a heat source 51h that generates heat when power is supplied is provided inside the heating roller 51. The heating roller 51 is heated by a heat source 51h, and the temperature is controlled to a predetermined temperature (for example, 200 ° C.). The heating roller 51 heats the outer peripheral surface of the fixing roller 41 through a contact portion that contacts the outer peripheral surface of the fixing roller 41.

  The heating roller 51 is provided with a release layer 511 having releasability on the outer surface of a base (specifically, a metal core 512). That is, the heating roller 51 is a roller in which a release layer 511 is formed on a core metal 512.

  The core metal 512 is made of a hollow cylindrical metal core material (element tube) made of aluminum, iron-based material, or the like. As the release layer 511, for example, a fluorine-based resin such as PFA (a copolymer of tetrafluoroethylene and perfluoroalkyl vinyl ether) or PTFE (polytetrafluoroethylene) can be used. Here, the release layer 511 is made of PFA.

  The fixing device 40 (40a) further includes a first temperature sensor 43 and a second temperature sensor 44 that function as temperature detection means such as a thermistor.

  The first temperature sensor 43 detects the temperature of the surface 51 f of the heating roller 51. The first temperature sensor 43 may be a contact type temperature sensor or a non-contact type temperature sensor. Here, the first temperature sensor 43 is provided on the surface 51f of the heating roller 51 in contact with the heating roller 51 via a support member (not shown) in the main body of the fixing device 40 (40a).

  The second temperature sensor 44 detects the temperature of the surface 41 f of the fixing roller 41. The second temperature sensor 44 may be a contact type temperature sensor or a non-contact type temperature sensor. Here, the second temperature sensor 44 is provided on the surface 41f of the fixing roller 41 in contact with the fixing roller 41 via a support member (not shown) in the main body of the fixing device 40 (40a).

  The heat source 51h is a predetermined predetermined value based on a temperature (for example, an average value) detected by the first temperature sensor 43 and the second temperature sensor 44 under the instruction of a control unit (not shown) that functions as a temperature control means. Energization control (temperature control) is performed so that the reference temperature is reached. Specifically, when the heat source 51h is energized from a control unit (not shown), the heat source 51h emits light and radiates infrared rays. Thereby, the inner peripheral surface of the heating roller 51 is heated, and the heating roller 51 is heated.

  The fixing device 40 (40a) may further include a heat source (here, a halogen heater lamp) 42h provided inside the pressure roller 42.

  The fixing device 40 (40a) may further include a third temperature sensor 45 that functions as temperature detection means such as a thermistor.

  The third temperature sensor 45 detects the temperature of the surface 42 f of the pressure roller 42. The third temperature sensor 45 may be a contact type temperature sensor or a non-contact type temperature sensor. When the fixing device 40 (40a) includes the third temperature sensor 45, for example, the third temperature sensor 45 is illustrated in contact with the pressure roller 42 on the surface 42f of the pressure roller 42. The main body is provided via a support member (not shown). In this case, the heat source 51h and the heat source 42h are based on temperatures (for example, average values) detected by the first temperature sensor 43, the second temperature sensor 44, and the third temperature sensor 45 under the instruction of a control unit (not shown). Then, energization control (temperature control) is performed so as to obtain a predetermined reference temperature. FIG. 2 of the first embodiment and FIG. 3 of the second embodiment to be described later show an example in which the fixing device 40 (40a) includes a heat source 42h and a third temperature sensor 45.

  2 and the detailed structure of the fixing roller 41 such as the release layer 411, the elastic layer 412, the elastic heat insulating layer 413, and the cored bar 414 shown in FIGS. 3 and 4 to be described later, and the release layer 421, the elastic layer 422, and the like. The detailed structure of the pressure roller 42 such as the cored bar 423 will be described collectively after the description of the second embodiment.

(Second Embodiment)
FIG. 3 is a schematic sectional view of the external heating device 50 (50b), the fixing roller 41, and the pressure roller 42 in the external heating type fixing device 40 (40b) according to the second embodiment viewed from the front.

  FIG. 4 is a diagram illustrating a state in which the external heating device 50 (50b) presses the fixing roller 41 from the outside. 4A is a schematic cross-sectional view of the external heating device 50 (50b) and the fixing roller 41 as viewed from the front. FIG. 4B is a schematic cross-sectional view of the external heating device 50 (50b) and the fixing roller 41 viewed from the plane side.

  In FIG. 3, the pressing device 55 shown in FIG. 4 in the external heating device 50 (50b) is not shown. In FIG. 4A, the third temperature sensor 45 is not shown. Further, since the rear view of the fixing device 40 (40b) is substantially the same as the front view, only the right and left sides are reversed. Therefore, only the front side is shown in FIGS. 3 and 4, and the rear side is not shown. doing.

  The fixing device 40 (40b) of the second embodiment is substantially the same as the fixing device 40 (40a) of the first embodiment except that an external heating device 50 (50b) is provided instead of the external heating device 50 (50a). The same configuration. Therefore, in the second embodiment, the same components as those in the first embodiment are denoted by the same reference numerals, and description thereof is omitted.

[External heating device]
The fixing device 40 (40b) of the second embodiment further includes an external heating device 50 (50b) that heats the fixing roller 41 from the outside by the heating belt 54.

  The external heating device 50 (50b) includes a plurality of (here, two) heating rollers 52 and 53 that are spaced apart from each other and arranged around the fixing roller 41, and at least one of the plurality of heating rollers 52 and 53 ( Here, heat sources (here, halogen heater lamps) 52 h and 53 h provided on both sides, a heating belt 54 stretched around the heating rollers 52 and 53, and the heating rollers 52 and 53 are directed toward the fixing roller 41. And a pressing device 55 (see FIG. 4A) that acts as a pressing means for pressing, and the heating belt 54 is in pressure contact with the fixing roller 41 and between the fixing roller 41 and the heating belt 54. A heating nip region (heating nip portion) H is formed in

  The external heating device 50 (50b) makes the heating belt 54 heated by the heat sources 52h and 53h through the heating rollers 52 and 53 abut on a part of the outer peripheral surface of the fixing roller 41, and the pressing device 55 The fixing roller 41 is heated by pressing.

  Specifically, the heating belt 54 is endless, and the back surface (inner peripheral surface) side is stretched around the outer peripheral surfaces of the heating rollers 52 and 53. The heating rollers 52 and 53 are pressed against the fixing roller 41 with a predetermined pressing force predetermined by the pressing device 55 with the heating belt 54 interposed therebetween.

  Further, the heating belt 54 abuts on the outer peripheral surface of the fixing roller 41 that is driven to rotate, and moves around the belt following the fixing roller 41. Thereby, the heating rollers 52 and 53 rotate in the rotation direction E2.

  Specifically, the heating belt 54 is in contact with the surface 41 f of the fixing roller 41 while being heated to a predetermined temperature (for example, 200 ° C.), and heats the surface 41 f of the fixing roller 41.

  The heating rollers 52 and 53 are pressed against the outer peripheral surface of the fixing roller 41 via the heating belt 54 by a pressing device 55 (see FIG. 4).

The pressing device 55 supports a side frame 551 that rotatably supports the heating rollers 52 and 53, a side frame 551 that swings around a pivot shaft 552 along the axial direction of the fixing roller 41, and An arm 554 rotatably supported around a pivot shaft 553 along the axial direction of the fixing roller 41 with respect to the main body (specifically, the main body frame F) of the fixing device 40 (40b), and the arm 554 as the fixing roller. 4 biasing urges the first member and a 555 (coil spring in this case).

  More specifically, the side frame 551 is configured such that deviation regulating members 52b and 53b (see FIG. 4B) provided at both ends of the heating rollers 52 and 53 are respectively inserted into bearings 556a and 556b (see FIG. 4B). And is supported rotatably. The deviation regulating members 52b and 53b are members that regulate the movement of the heating belt 54 in the axial direction accompanying the rotation of the heating belt 54 (occurrence of meandering or deviation). The deviation regulating members 52b and 53b have a diameter larger than the diameter of the heating rollers 52 and 53, and are provided coaxially with the heating rollers 52 and 53. Further, the bearings 556a and 556b are arranged in the side frame 551 so as to have a predetermined inter-axis distance D so that the parallelism of the heating rollers 52 and 53 is ensured.

  Specifically, the heating rollers 52 and 53 suspending the heating belt 54 are rotatably supported by bearings 556a and 556b attached to the side frames 551, respectively. Since the bearings 556a and 556b are fixed to the side frame 551 at a predetermined inter-axis distance D, the parallelism between the heating rollers 52 and 53 is ensured. In the second embodiment, the parallelism tolerance of the heating rollers 52 and 53 is 100 μm or less.

  The side frame 551 is supported so as to be swingable about a pivot shaft 552 provided on the arm 554. The arm 554 is supported so as to be rotatable about a pivot shaft 553 provided in the main body frame F of the fixing device 40 (40b). The coil spring 555 has one end connected to the arm 554 and the other end connected to the main body (specifically, the main body frame F) of the fixing device 40 (40b) so that the arm 554 is biased toward the fixing roller 41. Has been.

  Specifically, the side frame 551 is pivotally supported about the pivot shaft 552 with respect to the arm 554, and the arm 554 is configured to be rotatable about the pivot shaft 553. Yes.

  A coil spring 555 is attached to the arm end opposite to the pivot shaft 553 with the pivot shaft 552 in between, and a load is applied to the arm end portion by the coil spring 555, so that the arm 554 The attached side frame 551 is biased in the direction of the fixing roller 41, and as a result, the heating rollers 52 and 53 pivotally supported on the side frame 551 are configured to be in pressure contact with the fixing roller 41 with an equal load. .

  Further, heat sources 52h and 53h that generate heat when power is supplied are provided inside the heating rollers 52 and 53, respectively. The heating belt 54 is heated from the heat sources 52h and 53h through the heating rollers 52 and 53, and the temperature is controlled to a predetermined temperature. The heating belt 54 heats the outer peripheral surface of the fixing roller 41 through a contact portion that contacts the outer peripheral surface of the fixing roller 41.

  The heating belt 54 is provided on the upstream side of the fixing nip region N of the fixing roller 41 in the rotation direction E1, and is pressed against the fixing roller 41 with a predetermined pressing force (40N in this case). A heating nip region H (for example, a length of 20 mm in the rotation direction) is formed between the fixing roller 41 and the fixing roller 41.

  The heating belt 54 has a two-layer structure in which a synthetic resin material (for example, a fluorine resin such as PFA or PTFE) having excellent heat resistance and releasability is formed as a release layer on the surface of a hollow cylindrical base. It has become. Further, in order to reduce the shifting force of the heating belt 54, the inner surface of the belt base material may be coated with a fluorine resin or the like.

  The heating rollers 52 and 53 are made of a hollow cylindrical metal core made of aluminum or iron-based material. In addition, in order to reduce the biasing force of the heating belt 54, the surface of the metal core material may be coated with a fluorine resin or the like.

  Next, the internal configuration of the fixing roller 41 and the pressure roller 42 will be described below with reference to FIGS.

(Fixing roller of the first embodiment)
FIG. 5 is a cross-sectional view schematically showing the structure of each layer in the fixing roller 41 (41a) of the first example applicable to the first embodiment and the second embodiment.

  In the fixing device 40 (40a, 40b) of the first embodiment and the second embodiment, the fixing roller 41 (41a) of the first example has releasability from the base (specifically, the cored bar 414). A release layer 411, an elastic layer 412 having elasticity, and an elastic heat insulating layer 413 having elasticity and heat insulating properties are provided. In the fixing roller 41, a release layer 411, an elastic layer 412 and an elastic heat insulating layer 413 are provided on a cored bar 414 in this order from the surface 41f to the inside.

  Specifically, the fixing roller 41 (41 a) is provided with an elastic heat insulating layer 413 on the outer surface of the core metal 414, an elastic layer 412 having a uniform surface property on the elastic heat insulating layer 413, and further an elastic layer 412. A release layer 411 is provided thereon. That is, the fixing roller 41 (41a) is a four-layered roller in which a resilient heat insulating layer 413, an elastic layer 412 and a release layer 411 are formed in this order on a cored bar 414.

  The cored bar 414 is made of a cylindrical (solid) metal core. As the core metal 414, for example, a material such as a free-cutting steel material (SUM material), a stainless steel material (SUS material), aluminum, iron, copper, or an alloy thereof can be used. Here, the core metal 414 is made of a free-cutting steel material (SUM material).

  As the elastic heat insulation layer 413, for example, a porous resin material or a foamed resin material can be used. Typical examples of the foamed resin material include foamed rubber such as urethane rubber (foamed urethane) and silicone rubber (foamed silicone). Here, the elastic heat insulating layer 413 is made of foamed urethane.

  As the elastic layer 412, a rubber member, typically silicone rubber can be exemplified. Here, the elastic layer 412 is made of silicone rubber.

  As the release layer 411, for example, a fluorine-based resin such as PFA (a copolymer of tetrafluoroethylene and perfluoroalkyl vinyl ether) or PTFE (polytetrafluoroethylene) can be used. Here, the release layer 411 is made of PFA. In the configuration of the fixing roller 41 (41a) of the first embodiment, since the elastic heat insulating layer 413 has heat insulating properties, it is preferable not to provide a heat source inside the fixing roller 41 (41a).

(Fixing roller of the second embodiment)
FIG. 6 is a cross-sectional view schematically showing the structure of each layer in the fixing roller 41 (41b) of the second example applicable to the first embodiment and the second embodiment.

  By the way, when the elastic layer 412 is formed directly on the elastic heat insulating layer 413 as in the fixing roller 41 (41a) of the first embodiment shown in FIG. 5, the elastic layer 412 tends to be thin for manufacturing convenience. It is difficult to obtain the elastic layer 412 having desired elasticity.

  Therefore, as shown in FIG. 6, in the fixing roller 41 (41a) shown in FIG. 5, a base 415 made of a resin material such as polyimide (PI) is provided between the elastic layer 412 and the elastic heat insulating layer 413. The configuration of the fixing roller 41 (41b) of the second embodiment is preferable. By doing so, for example, on the foamed resin material (elastic heat insulating layer 413) of the cored bar 414 provided with the foamed resin material (specifically foamed rubber) (specifically bonded) on the outer peripheral surface, A cylindrical member widely used as a fixing belt (specifically, a cylindrical member in which silicone rubber is formed on a base material made of polyimide, a so-called polyimide belt) is provided (specifically, bonded). By using as the material 415 and the elastic layer 412, the fixing roller 41 (41b) can be easily manufactured at low cost. In the configuration of the fixing roller 41 (41b) of the second embodiment, the elastic heat insulating layer 413 has a heat insulating property similarly to the fixing roller 41 (41a) of the first embodiment. ) Is preferably not provided with a heat source.

(Pressure roller of the first embodiment)
FIG. 7 is a cross-sectional view schematically showing the structure of each layer in the pressure roller 42 (42a) of the first example applicable to the first embodiment and the second embodiment.

  In the fixing device 40 (40a, 40b) of the first embodiment and the second embodiment, the pressure roller 42 (42a) of the first example is releasable from the base (specifically, the cored bar 423). A release layer 421 having elasticity and an elastic layer 422 having elasticity are provided. In the pressure roller 42 (42 a), a release layer 421 and an elastic layer 422 are provided in this order from the surface 42 f to the inside on the core metal 423.

  Specifically, the pressure roller 42 (42 a) is provided with an elastic layer 422 on the outer surface of the core metal 423, and a release layer 421 is provided on the elastic layer 422. That is, the pressure roller 42 (42 a) is a three-layer roller in which an elastic layer 422 and a release layer 421 are formed in this order on a core metal 423.

  The core metal 423 is made of a hollow cylindrical metal core material. As the metal core 423, a material similar to that of the fixing roller 41, for example, a material such as a free-cutting steel material (SUM material), a stainless steel material (SUS material), aluminum, iron, copper, or an alloy thereof may be used. it can. Here, the core metal 423 is made of a free-cutting steel material (SUM material).

  The elastic layer 422 can be made of the same material (specifically, a rubber member) as that of the fixing roller 41, and typically, silicone rubber can be exemplified. Here, the elastic layer 422 is made of silicone rubber.

  The release layer 421 is made of the same material as the fixing roller 41, that is, a rubber member, for example, a fluorine-based material such as PFA (a copolymer of tetrafluoroethylene and perfluoroalkyl vinyl ether) or PTFE (polytetrafluoroethylene). Resin can be used. Here, the release layer 411 is made of PFA. In the configuration of the pressure roller 42 (42a) of the first embodiment, the heat source 42h may or may not be provided inside the pressure roller 42 (42a).

(Pressure roller of the second embodiment)
FIG. 8 is a cross-sectional view schematically showing the structure of each layer in the pressure roller 42 (42b) of the second example applicable to the first embodiment and the second embodiment.

  By the way, if an elastic layer 422 having a relatively large heat capacity is provided like the pressure roller 42 (42a) of the first embodiment shown in FIG. 7, heat is easily taken away (especially through the inner metal core 423). The heating efficiency to the fixing roller 41 by the external heating device 50 (50a, 50b) is likely to decrease.

  Therefore, as shown in FIG. 8, in the pressure roller 42 (42a) shown in FIG. 5, instead of the elastic layer 422, a pressure heat insulating layer 424 having elasticity and heat insulation is provided. 42 (42b) is preferable. By doing so, it is difficult for heat to be taken away (particularly, via the inner cored bar 423), and it is possible to effectively prevent a reduction in heating efficiency to the fixing roller 41 by the external heating device 50 (50a, 50b). . In the configuration of the pressure roller 42 (42b) of the second embodiment, it is preferable not to provide the heat source 42h inside the pressure roller 42 (42b) because the elastic heat insulating layer 424 has a heat insulating property. .

(About physical properties of each layer)
9 shows the release layer 411, the elastic layer 412, the elastic heat insulating layer 413 and the base material 415 of the fixing roller 41 (41a, 41b) in the first embodiment and the second embodiment, and the pressure roller 42 (42a, 42b). 3 is a table in which physical property values of the release layer 421, the elastic layer 422, the elastic heat insulation layer 424, and the release layer 511 of the heating roller 51 in the first embodiment are combined into one.

  In the first embodiment and the second embodiment, the thickness of the release layer 411 (for example, PFA) of the fixing roller 41 (41a, 41b) in the first and second examples may be 20 μm to 70 μm. The thickness of the release layer 411 is preferably as small as possible from the viewpoint of reducing the heat capacity, but if it is too small, it becomes difficult to maintain the release property.

  In the first embodiment and the second embodiment, the thickness of the elastic layer 412 (for example, silicone rubber) of the fixing roller 41 (41a, 41b) of the first and second examples is 10 μm to 1 mm, preferably 20 μm. ˜200 μm can be exemplified. The thickness of the elastic layer 412 is preferably as small as possible from the viewpoint of reducing the heat capacity, but if it is too small, it is difficult to maintain the uniformity of the fixing characteristics. Examples of the hardness (Asker C hardness) of the elastic layer 412 include 70 degrees to 90 degrees. The hardness of the elastic layer 412 can be set to a value that can obtain a desired fixing pressure.

  In the first embodiment and the second embodiment, the thickness of the elastic heat insulating layer 413 (for example, foamed rubber) of the fixing roller 41 (41a, 41b) in the first and second examples can be 4 to 15 mm. . The thickness of the elastic heat insulating layer 413 is such that a desired nip region (a fixing nip region N and a heating nip region H in the first embodiment, and a fixing nip region N in the second embodiment) from the viewpoint of maintaining elasticity and heat insulating properties. It is preferable to make it as large as possible. Examples of the hardness (Asker C hardness) of the elastic heat insulation layer 413 include 30 degrees to 50 degrees. The hardness of the elastic heat insulating layer 413 can be set to a value capable of obtaining a desired fixing pressure.

  In 1st Embodiment and 2nd Embodiment, 10 micrometers-15 micrometers can be illustrated as thickness of the base material 415 (for example, PI) of the fixing roller 41 (41b) of 2nd Example. The thickness of the base material 415 is preferably as small as possible from the viewpoint of reducing the heat capacity, but if it is too small, it is difficult to maintain the role as the base material.

  In 1st Embodiment and 2nd Embodiment, 20 micrometers-70 micrometers can be illustrated as thickness of the release layer 421 (for example, PFA) of the pressure roller 42 (42a, 42b) of 1st Example and 2nd Example. . The thickness of the release layer 421 is preferably as small as possible from the viewpoint of reducing the heat capacity, but if it is too small, it becomes difficult to maintain the release property.

  In 1st Embodiment and 2nd Embodiment, 2 mm-3 mm can be illustrated as thickness of the elastic layer 422 (for example, silicone rubber) of the pressure roller 42 (42a) of 1st Example. From the viewpoint of reducing the heat capacity, the thickness of the elastic layer 422 is preferably as small as possible so that the desired fixing nip region N can be obtained. Examples of the hardness (Asker C hardness) of the elastic layer 422 include 70 degrees to 90 degrees. The hardness of the elastic layer 422 can be appropriately set according to the hardness of the fixing roller 41 (41a, 41b).

  In 1st Embodiment and 2nd Embodiment, 5 mm-6 mm can be illustrated as thickness of the elastic heat insulation layer 424 (for example, foamed rubber) of the pressure roller 42 (42b) of 2nd Example. The thickness of the elastic heat insulating layer 424 is preferably as large as possible to obtain a desired fixing nip region N from the viewpoint of maintaining elasticity and heat insulating properties. Examples of the hardness (Asker C hardness) of the elastic heat insulating layer 424 include 30 degrees to 50 degrees. The hardness of the elastic heat insulating layer 424 can be appropriately set according to the hardness of the fixing roller 41 (41a, 41b).

  In 1st Embodiment, 5 micrometers-50 micrometers can be illustrated as thickness of the mold release layer 511 (for example, PFA) of the heating roller 51. FIG. The thickness of the release layer 421 is preferably as small as possible from the viewpoint of reducing the heat capacity, but if it is too small, it becomes difficult to maintain the release property.

  In the first embodiment and the second embodiment, the core metal 414 of the fixing roller 41 (41a, 41b) of the first and second examples, the core metal 423 of the pressure roller 42 (42a, 42b), And in 1st Embodiment, 90 degree | times or more can be illustrated as hardness (Asker C hardness) of the metal core 512 of the heating roller 51. FIG. In the first embodiment and the second embodiment, the diameters of the fixing roller 41 (41a, 41b) and the pressure roller 42 (42a, 42b) of the first and second examples may be 30 mm to 40 mm. . Moreover, in 1st Embodiment, as a diameter of the heating roller 51, 20 mm can be illustrated.

  In the first embodiment and the second embodiment, the hardness of the surface 41f of the fixing roller 41 (41a, 41b) in the first and second examples is smaller than the hardness of the surface of the cored bar 414. .

  Further, in the first embodiment, the hardness of the surface 51f of the heating roller 51 and the hardness of the surface of the cored bar 414 in the fixing roller 41 (41a, 41b) of the first and second examples are equal (is the same? Or substantially the same). For example, in the heating roller 51 in which the release layer 511 is formed on the cored bar 512, the surface hardness of the heating roller 51 is equal to (same or substantially the same as the surface hardness of the cored bar 414 in the fixing roller 41 (41a, 41b). The release layer 511 can be formed to be the same.

  In the first embodiment and the second embodiment, the surface hardness of the elastic heat insulating layer 413 in the fixing roller 41 (41a, 41b) of the first and second examples is more than the surface hardness of the core metal 414. Is also getting smaller. The surface hardness of the elastic layer 412 in the fixing roller 41 (41a, 41b) is equal to or lower than the surface hardness of the cored bar 414 and larger than the surface hardness of the elastic heat insulating layer 413.

  In the first embodiment and the second embodiment, the hardness of the surface 42f of the pressure roller 42 (42a, 42b) of the first and second examples is the same as that of the fixing of the first and second examples. The hardness of the surface 41f of the roller 41 (41a, 41b) is equal to or higher than the hardness (same or substantially the same). For example, the hardness of the surface 42f of the pressure roller 42 (42a, 42b) is such that the hardness of the surface 41f of the fixing roller 41 (41a, 41b) is 10 degrees to 20 degrees, 10 degrees to 30 degrees, 10 degrees to 40 degrees, In the case of 10 degrees to 50 degrees, 10 degrees to 60 degrees, 10 degrees to 70 degrees, and 10 degrees to 80 degrees, 20 degrees to 90 degrees, 30 degrees to 90 degrees, 40 degrees to 90 degrees, and 50 degrees, respectively. ˜90 degrees, 60 degrees to 90 degrees, 70 degrees to 90 degrees, and 80 degrees to 90 degrees.

  In addition, Asker C (ASKER C) is a value indicating the hardness defined in the Japan Rubber Association Standard (SRIS0101).

(About this embodiment)
According to the first embodiment and the second embodiment of the present embodiment, the fixing roller 41 (41a, 41b) of the first and second examples includes the release layer 411, the elastic layer on the cored bar 414. By providing the layer 412 and the elastic heat insulating layer 413 in this order from the surface 41f toward the inside, the elasticity of the elastic layer 412 provided inside the release layer 411 and the elasticity provided inside the elastic layer 412 The area of the fixing nip region N can be increased by the elasticity (cushioning property, flexibility) of the heat insulating layer 413, and thereby the fixing property of the unfixed toner T to the recording sheet P can be improved. In addition, since the elastic layer 412 having a uniform surface property is provided outside the elastic heat insulating layer 413, the fixing characteristics (the amount of heat applied to the recording sheet and the fixing pressure) to the recording sheet P in the fixing nip region N are uniform. Accordingly, it is possible to suppress the occurrence of image defects (so-called glossy unevenness such as satin). Even if the heat capacity of the elastic layer 412 increases (especially even if the thickness of the elastic layer 412 increases and the heat capacity increases), the heat insulating property of the elastic heat insulating layer 413 provided inside the elastic layer 412. Thus, it is possible to make it difficult for heat to be taken away (particularly, it is hard to be taken away via the inner core metal 414). Further, due to the releasability of the release layer 411 provided on the surface 41f, adhesion of unfixed toner T to the surface 41f of the fixing roller 41 (41a, 41b) can be suppressed.

  Thus, in the fixing device 40 (40a, 40b), the fixing roller 41 (41a, 41b) can be heated with a low heat capacity even if a low-cost halogen heater lamp is used, and the warm-up time can be shortened accordingly. It can be realized.

In the first embodiment of the present embodiment, the heating roller 51 is disposed in contact with the fixing roller 41 (41a, 41b), whereby the elasticity of the elastic layer 412 provided inside the release layer 411 is obtained. Further, the area of the heating nip region H between the heating roller 51 and the fixing roller 41 (41a, 41b) can be increased by the elasticity (cushioning property, flexibility) of the elastic heat insulating layer 413 provided inside the elastic layer 412. Thus, heat from the heating roller 51 heated by the heat source 51h can be easily transmitted to the fixing roller 41 (41a, 41b). That is, in the first embodiment, although the heating roller 51 and the heat source 51h are used in a simple configuration, heat from the heating roller 51 heated by the heat source 51h is easily transmitted to the fixing roller 41 (41a, 41b). be able to. Moreover, the hardness of the surface 41f of the fixing roller 41 (41a, 41b) is smaller than the hardness of the surface of the cored bar 414, and the hardness of the surface 51f of the heating roller 51 is the cored bar in the fixing roller 41 (41a, 41b). By being equivalent to the hardness of the surface of 414, the heating nip region H between the heating roller 51 and the fixing roller 41 can be reliably formed.

  In the second embodiment of the present embodiment, heat from the heating rollers 52 and 53 heated by the heat sources 52h and 53h is supplied to the fixing roller 41 (41a and 41b) via the heating nip region H of the heating belt 54. Can be transmitted efficiently.

  In the first embodiment and the second embodiment of the present embodiment, the elastic layer 412 is formed on the elastic heat insulating layer 413 via the base material 415 in the fixing roller 41 (41b) of the second example. The elastic layer 412 having desired elasticity can be easily obtained.

  In the first and second embodiments of the present embodiment, the surface hardness of the elastic heat insulating layer 413 is smaller than the surface hardness of the cored bar 414 in the fixing roller 41 (41a, 41b). Since the hardness of the surface of the elastic layer 412 is equal to or lower than the hardness of the surface of the cored bar 414 and larger than the hardness of the surface of the elastic heat insulating layer 413, the fixing nip region N can be formed reliably.

  Further, in the first embodiment and the second embodiment of the present embodiment, the pressure roller 42 (42b) of the second example has the release layer 421 and the elastic heat insulating layer 424 on the core metal 423, the surface 42f. By providing in this order from the inner side to the inner side, the area of the fixing nip region N can be further increased by the elasticity (cushioning property, flexibility) of the elastic heat insulating layer 424 provided inside the release layer 421. Thereby, the fixing property of the unfixed toner T to the recording sheet P can be further improved. Moreover, due to the heat insulating property of the elastic heat insulating layer 424 provided on the inner side of the release layer 421, heat applied to the pressure roller 42 (42b) is difficult to be deprived (particularly difficult to be deprived via the inner metal core 423). )can do. Further, due to the releasability of the release layer 421 provided on the surface 42f, adhesion of unfixed toner T to the surface 42f of the pressure roller 42 (42b) can be suppressed.

  In the first and second embodiments of the present embodiment, the hardness of the surface 42f of the pressure roller 42 (42a, 42b) of the first and second examples is equal to that of the fixing roller 41 (41a, 41b). ), The fixing nip region N can be reliably formed.

40 (40a) Fixing device 40 (40b) Fixing device 41 (41a) Fixing roller 41 (41b) Fixing roller 41f Surface 42 (42a) Pressure roller 42 (42b) Pressure roller 42f Surface 50 (50a) External heating device ( Example of external heating means)
50 (50b) External heating device (other examples of external heating means)
51 Heating roller 51h Heat source 52, 53 Heating roller 52h, 53h Heat source 54 Heating belt 411 Release layer 412 Elastic layer 413 Resilient heat insulating layer 414 Core metal (example of substrate)
415 Base material 421 Release layer 422 Elastic layer 423 Core metal (example of substrate)
424 Elastic heat insulation layer H Heating nip area (heating nip part)
N Fixing nip area (fixing nip part)
P Recording sheet T Toner

Claims (9)

A fixing roller that is rotated; an external heating unit that heats the fixing roller from the outside; and a pressure roller that rotates with the rotation of the fixing roller while being pressed by the fixing roller. A fixing device for fixing an unfixed image to the recording sheet while conveying the recording sheet to a fixing nip formed between the fixing roller and the fixing roller;
The fixing roller includes a base, a release layer having releasability, an elastic layer having elasticity, and an elastic heat insulating layer having elasticity and heat insulation, and the release layer, The elastic layer and the elastic heat insulating layer are provided in this order from the surface to the inside ,
A base material is provided between the elastic layer and the elastic heat insulating layer,
The substrate is made of polyimide,
The elastic layer is made of silicone rubber,
On the elastic heat insulating layer, there is provided a fixing member provided with a cylindrical member in which the elastic layer made of the silicone rubber is formed on the base material made of the polyimide . The fixing device according to claim 1,
The external heating means includes a heating roller disposed in contact with the fixing roller, and a heat source for heating the heating roller, and the heating roller is pressed against the fixing roller so as to form a heating nip portion. A fixing device characterized by being configured as described above. The fixing device according to claim 2,
The fixing roller has a surface hardness smaller than the surface hardness of the substrate,
The fixing device according to claim 1, wherein a surface hardness of the heating roller is equal to a surface hardness of the substrate. The fixing device according to claim 1,
The external heating means includes a plurality of heating rollers disposed away from each other, a heat source for heating at least one of the plurality of heating rollers, and a heating belt wound around the plurality of heating rollers, A fixing device, wherein two adjacent ones of the plurality of heating rollers are pressed against the fixing roller so as to form a heating nip portion via the heating belt. A fixing device according to any one of claims 1 to 4 , wherein
The elastic heat insulating layer has a surface hardness smaller than the surface hardness of the substrate,
The fixing device according to claim 1, wherein the elastic layer has a surface hardness equal to or less than a surface hardness of the substrate and a surface hardness of the elastic heat insulating layer. A fixing device according to any one of claims 1 to 5 , wherein
The pressure roller includes a base, a release layer having releasability, and an elastic heat insulation layer having elasticity and heat insulation, and the release layer and the elastic heat insulation layer are formed on the surface from the surface. A fixing device provided in this order toward the inside. The fixing device according to claim 6 , wherein
The pressure roller has a surface hardness equal to or higher than a surface hardness of the fixing roller. An image forming apparatus comprising the fixing device according to any one of claims 1 to 7. A fixing roller that is rotated; an external heating unit that heats the fixing roller from the outside; and a pressure roller that rotates with the rotation of the fixing roller while being pressed by the fixing roller. A fixing roller provided in a fixing device for fixing an unfixed image on the recording sheet while conveying the recording sheet to a fixing nip portion formed between the fixing roller and the fixing roller;
A substrate, a release layer having releasability, an elastic layer having elasticity, and a resilient heat insulating layer having elasticity and heat insulation, and the release layer, the elastic layer, and the elasticity are provided on the substrate. Insulating layer is provided in this order from the surface to the inside ,
A base material is provided between the elastic layer and the elastic heat insulating layer,
The substrate is made of polyimide,
The elastic layer is made of silicone rubber,
A fixing roller having a cylindrical member on which the elastic layer made of the silicone rubber is formed on the base made of the polyimide is provided on the elastic heat insulating layer .

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