JP2008009002A - Fixing roller, fixing device, and image forming apparatus - Google Patents

Abstract

To provide a fixing roller, a fixing device, and an image forming apparatus in which a nip amount in a fixing nip portion is sufficiently secured, fixing property is good, temperature rising efficiency is good, and a fixing sleeve is not displaced. To do.
A fixing sleeve 21 having a heat generating layer 21c heated by magnetic flux generated by a magnetic flux generating means, and a fixing auxiliary roller 22 having a heat insulating layer 23 on the outer peripheral surface and inserted in the fixing sleeve 21. Prepare. The inner peripheral surface of the fixing sleeve 21 and the outer peripheral surface of the fixing auxiliary roller 22 are bonded to each other only in the width direction both ends M by the adhesive 40.
[Selection] Figure 3

Description

  BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus such as a copying machine, a printer, a facsimile, or a complex machine thereof, and a fixing roller and a fixing device installed therein, and in particular, a fixing roller and a fixing device using an electromagnetic induction heating method And an image forming apparatus.

  2. Description of the Related Art Conventionally, in image forming apparatuses such as copiers and printers, a technique using an electromagnetic induction heating type fixing device is widely known for the purpose of reducing the start-up time of the apparatus and saving energy (for example, (See Patent Document 1).

  In Patent Document 1, etc., an electromagnetic induction heating type fixing device includes a fixing roller having a heat generating layer, a magnetic flux generating means (external heating means) facing the fixing roller, a pressure roller in pressure contact with the fixing roller, and the like. . The magnetic flux generation means is configured by a coil portion (coil) or the like that extends in the width direction (a direction orthogonal to the conveyance direction of the recording medium).

  The fixing roller (heat generation layer) is heated at a position facing the magnetic flux generation means. The heated fixing roller heats and fixes the toner image on the recording medium transported to the contact position (the fixing nip portion) with the pressure roller. Specifically, by passing a high-frequency alternating current through the coil portion, an alternating magnetic field is formed around the coil portion, and an eddy current is generated in the heat generating layer of the fixing roller. When an eddy current is generated in the heat generating layer, Joule heat is generated by the electric resistance of the heat generating layer. The entire fixing roller is heated by this Joule heat.

  On the other hand, Patent Document 2 discloses a fixing device of an electromagnetic induction heating system, which includes a fixing sleeve (metal sleeve) having a heat generation layer, a fixing auxiliary roller (internal pressure member) inserted in the fixing sleeve, and a fixing sleeve. And a pressure member (external pressure member) that presses against a fixing auxiliary roller via a fixing sleeve, and the like are disclosed.

  The fixing sleeve (heat generation layer) is heated at a position facing the magnetic flux generation means. The heated fixing sleeve heats and fixes the toner image on the recording medium conveyed to the contact position (the fixing nip portion) with the pressure roller. Specifically, by passing a high-frequency alternating current through the coil portion, an alternating magnetic field is formed around the coil portion, and an eddy current is generated in the heat generation layer of the fixing sleeve. When an eddy current is generated in the heat generating layer, Joule heat is generated by the electric resistance of the heat generating layer. The entire fixing sleeve is heated by the Joule heat.

  These electromagnetic induction heating type fixing devices have high heat conversion efficiency compared to other types such as a heat roller type (heater lamp heating type) because the heat generating layer is directly heated by electromagnetic induction, It is known that the surface temperature (fixing temperature) of the fixing roller can be raised to a desired temperature with a small energy consumption and a short start-up time.

  On the other hand, Patent Document 3 discloses an electromagnetic induction heating type fixing device between a heating layer and a heat insulating layer of a fixing roller (heating roller) for the purpose of lowering heat capacity, improving strength, ease of manufacture, and the like. A technique for regulating the thickness of an adhesive layer interposed between the two is disclosed. Patent Document 3 and the like also disclose an embodiment in which an adhesive layer interposed between a heating layer and a heat insulating layer is formed only at both ends in the axial direction.

JP 2001-31168 A JP 10-740007 A JP 2002-367766 A

  The difference in configuration between the electromagnetic induction heating type fixing device in Patent Document 1 and the like described above and the electromagnetic induction heating type fixing device in Patent Document 2 or the like is that the heat generating layer (fixing sleeve) is a heat insulating layer (fixing assist). Whether or not it is integrated with the roller. Specifically, in the former, the heat generating layer is integrated with the heat insulating layer by adhesion with a primer or the like. On the other hand, in the latter, the inner diameter of the fixing sleeve is formed larger than the outer diameter of the auxiliary fixing roller, and the heat generating layer (fixing sleeve) is not integrated with the heat insulating layer (fixing auxiliary roller).

  There are mainly three problems with the former. The first problem is that the deformation of the heat insulating layer (fixing auxiliary roller) made of an elastic material is limited by the heat generating layer (fixing sleeve), so that the nip amount of the fixing nip portion cannot be secured sufficiently. It is a point that fixing property is lowered. The second problem is that since the entire inner peripheral surface of the heat generating layer (fixing sleeve) is in contact with the outer peripheral surface of the heat insulating layer (fixing auxiliary roller), the amount of heat conducted to the heat insulating layer increases, and the device It is a point that the rise of is delayed. A third problem is that the temperature rise efficiency is lowered by the heat conduction of the adhesive applied over the entire inner peripheral surface of the heat generating layer.

  On the other hand, the latter problem is that since the fixing sleeve and the auxiliary fixing roller are not integrated, the fixing sleeve is displaced (moved in the axial direction) during operation of the apparatus. Is a point. In order to suppress such a shift of the fixing sleeve, a measure for installing a restricting member for restricting the movement of the fixing sleeve at both ends of the auxiliary fixing roller may be considered. However, in this case, another problem arises that the number of parts increases and the assembly of the fixing roller becomes complicated.

  On the other hand, the technique disclosed in Patent Document 3 regulates the thickness and range of the adhesive layer interposed between the heating layer and the heat insulating layer to ensure the adhesive strength between the heating layer and the heat insulating layer, while maintaining the entire fixing roller. However, it does not directly solve the above-described problem that the nip amount of the fixing nip portion cannot be sufficiently secured.

  The present invention has been made to solve the above-described problems, and the nip amount of the fixing nip portion is sufficiently secured, the fixing property is good, the temperature rise efficiency is good, and the fixing sleeve is shifted. It is an object of the present invention to provide a fixing roller, a fixing device, and an image forming apparatus that are free from defects.

  The fixing roller according to the first aspect of the present invention has a heat generating layer heated by the magnetic flux generated by the magnetic flux generating means, a fixing sleeve for melting the toner image and fixing it on the recording medium, and an outer peripheral surface. And a fixing auxiliary roller inserted into the fixing sleeve, and the inner peripheral surface of the fixing sleeve and the outer peripheral surface of the fixing auxiliary roller are bonded only at both ends in the width direction. .

  The fixing roller according to a second aspect of the present invention is the fixing roller according to the first aspect, wherein the heat insulating layer is made of an elastic foam material, and the outer circumferential surface of the auxiliary fixing roller has both ends in the width direction. It is formed so as to be the skin surface of the elastic foam material, and is formed so that the central portion in the width direction is the foam surface of the elastic foam material.

  A fixing roller according to a third aspect of the present invention is the fixing roller according to the second aspect, wherein the inner peripheral surface of the fixing sleeve and the outer peripheral surface of the auxiliary fixing roller are arranged such that the skin surface is an adhesive surface. Are bonded.

  A fixing roller according to a fourth aspect of the present invention is the fixing roller according to any one of the first to third aspects, wherein the both ends in the width direction are outside the maximum sheet passing area of the recording medium that can be fixed. It is what.

  The fixing roller according to a fifth aspect of the present invention is the fixing roller according to any one of the first to fourth aspects, wherein the fixing sleeve includes a base layer on an inner peripheral surface, and the base layer and the fixing roller A heat insulating layer is bonded at both ends in the width direction.

  The fixing roller according to a sixth aspect of the present invention is the fixing roller according to the fifth aspect, wherein the fixing sleeve further includes a release layer and an elastic layer.

  The fixing roller according to a seventh aspect of the present invention is the fixing roller according to any one of the first to sixth aspects, wherein the fixing auxiliary roller has an outer diameter of a region serving as an adhesive surface in the fixing sleeve. It is formed so as to be smaller than the inner diameter of the region to be the bonding surface.

  The fixing roller according to an eighth aspect of the present invention is the fixing roller according to any one of the first to seventh aspects, wherein the fixing auxiliary roller has a non-adhesive surface having an outer diameter in a region to be an adhesive surface. It is formed so as to be smaller than the outer diameter of the region.

  A fixing roller according to a ninth aspect of the present invention is the fixing roller according to any one of the first to eighth aspects, wherein the both ends in the width direction after the auxiliary fixing roller is inserted into the fixing sleeve. Are formed by bonding.

  According to a tenth aspect of the present invention, there is provided a fixing device according to any one of the first to ninth aspects, a pressure member that is in pressure contact with the fixing roller, and the magnetic flux generating means. , With.

  An image forming apparatus according to an eleventh aspect of the present invention includes the fixing device according to the tenth aspect.

  In the present invention, the inner peripheral surface of the fixing sleeve having the heat generating layer heated by electromagnetic induction and the outer peripheral surface of the auxiliary fixing roller having the heat insulating layer on the outer peripheral surface are bonded only at both ends in the width direction. As a result, a fixing roller, a fixing device, and an image forming apparatus are provided in which the nip amount of the fixing nip portion is sufficiently secured, the fixing property is good, the temperature rise efficiency is good, and the fixing sleeve is not displaced. can do.

  Hereinafter, the best mode for carrying out the present invention will be described in detail with reference to the drawings. In addition, in each figure, the same code | symbol is attached | subjected to the part which is the same or it corresponds, The duplication description is simplified or abbreviate | omitted suitably.

Embodiment 1 FIG.
A first embodiment of the present invention will be described in detail with reference to FIGS.
First, the configuration and operation of the entire image forming apparatus will be described with reference to FIG.
In FIG. 1, reference numeral 1 denotes an apparatus main body of a tandem color copier as an image forming apparatus, 2 a writing unit that emits laser light based on input image information, and 3 an original conveying unit that conveys an original D to an original reading unit 4. 4 is a document reading unit that reads image information of the document D, 7 is a paper feeding unit that accommodates a recording medium P such as transfer paper, 9 is a registration roller that adjusts the conveyance timing of the recording medium P, and 11Y, 11M, and 11C. , 11BK are photosensitive drums on which toner images of respective colors (yellow, magenta, cyan, and black) are formed, 12 is a charging unit that charges the photosensitive drums 11Y, 11M, 11C, and 11BK, and 13 is each photosensitive drum. A developing unit that develops electrostatic latent images formed on 11Y, 11M, 11C, and 11BK, and a toner image formed on each of the photosensitive drums 11Y, 11M, 11C, and 11BK Transfer bias roller for transferring superimposed on the recording medium P, 15 denotes each of the photosensitive drums 11Y, 11M, 11C, cleaning unit for collecting the untransferred toner on 11BK, a.

  Reference numeral 16 denotes a transfer belt cleaning unit that cleans the transfer belt 17, reference numeral 17 denotes a transfer belt that conveys the recording medium P so that toner images of a plurality of colors are carried on the recording medium P, and reference numeral 19 denotes the recording medium P. 1 shows an electromagnetic induction heating type fixing device that fixes a toner image (unfixed image) of the toner.

Hereinafter, an operation during normal color image formation in the image forming apparatus will be described.
First, the document D is transported from the document table in the direction of the arrow in the drawing by the transport rollers of the document transport unit 3 and placed on the contact glass 5 of the document reading unit 4. Then, the document reading unit 4 optically reads the image information of the document D placed on the contact glass 5.

  Specifically, the document reading unit 4 scans the image of the document D on the contact glass 5 while irradiating light emitted from an illumination lamp. Then, the light reflected by the document D is imaged on the color sensor via the mirror group and the lens. The color image information of the document D is read for each RGB (red, green, blue) color separation light by the color sensor, and then converted into an electrical image signal. Further, color conversion processing, color correction processing, spatial frequency correction processing, and the like are performed by the image processing unit based on the RGB color separation image signals to obtain yellow, magenta, cyan, and black color image information.

  Then, the image information of each color of yellow, magenta, cyan, and black is transmitted to the writing unit 2. The writing unit 2 emits laser light (exposure light) based on the image information of each color toward the corresponding photosensitive drums 11Y, 11M, 11C, and 11BK.

On the other hand, the four photosensitive drums 11Y, 11M, 11C, and 11BK are rotated clockwise in FIG. First, the surfaces of the photoconductor drums 11Y, 11M, 11C, and 11BK are uniformly charged at a portion facing the charging unit 12 (this is a charging process). Thus, a charged potential is formed on the photosensitive drums 11Y, 11M, 11C, and 11BK. Thereafter, the charged surfaces of the photosensitive drums 11Y, 11M, 11C, and 11BK reach the irradiation positions of the respective laser beams.
In the writing unit 2, laser light corresponding to the image signal is emitted from the four light sources corresponding to each color. Each laser beam passes through a separate optical path for each of the yellow, magenta, cyan, and black color components (this is an exposure process).

  Laser light corresponding to the yellow component is irradiated on the surface of the first photosensitive drum 11Y from the left side of the drawing. At this time, the yellow component laser light is scanned in the rotation axis direction (main scanning direction) of the photosensitive drum 11Y by a polygon mirror that rotates at high speed. Thus, an electrostatic latent image corresponding to the yellow component is formed on the photosensitive drum 11Y charged by the charging unit 12.

  Similarly, the laser beam corresponding to the magenta component is irradiated onto the surface of the second photosensitive drum 11M from the left side of the paper, and an electrostatic latent image corresponding to the magenta component is formed. The cyan component laser light is applied to the surface of the third photosensitive drum 11C from the left side of the paper, and an electrostatic latent image of the cyan component is formed. The black component laser beam is applied to the surface of the fourth photosensitive drum 11BK from the left side of the paper, and an electrostatic latent image of the black component is formed.

Thereafter, the surfaces of the photoconductive drums 11Y, 11M, 11C, and 11BK on which the electrostatic latent images of the respective colors are formed reach positions facing the developing unit 13, respectively. Then, the respective color toners are supplied from the developing units 13 onto the photosensitive drums 11Y, 11M, 11C, and 11BK, and the latent images on the photosensitive drums 11Y, 11M, 11C, and 11BK are developed (development process). .)
Thereafter, the surfaces of the photosensitive drums 11Y, 11M, 11C, and 11BK after the development process reach the facing portions of the transfer belt 17, respectively. Here, a transfer bias roller 14 is installed at each facing portion so as to contact the inner peripheral surface of the transfer belt 17. Then, the toner images of the respective colors formed on the photoconductive drums 11Y, 11M, 11C, and 11BK are sequentially superimposed and transferred onto the recording medium P on the transfer belt 17 at the position of the transfer bias roller 14 (transfer process). .)

Then, the surfaces of the photosensitive drums 11Y, 11M, 11C, and 11BK after the transfer process reach positions facing the cleaning unit 15, respectively. Then, the untransferred toner remaining on the photosensitive drums 11Y, 11M, 11C, and 11BK is collected by the cleaning unit 15 (this is a cleaning process).
Thereafter, the surfaces of the photoconductive drums 11Y, 11M, 11C, and 11BK pass through a neutralization unit (not shown), and a series of image forming processes on the photoconductive drums 11Y, 11M, 11C, and 11BK is completed.

On the other hand, the recording medium P on which the toners of the respective colors on the photosensitive drums 11Y, 11M, 11C, and 11BK are transferred (carrying) is run in the direction of the arrow in the drawing and reaches a position facing the separation charger 18. . Then, the charge accumulated in the recording medium P is neutralized at a position facing the separation charger 18, and the recording medium P is separated from the transfer belt 17 without causing toner dust or the like.
Thereafter, the surface of the transfer belt 17 reaches the position of the transfer belt cleaning unit 16. Then, the deposit adhered on the transfer belt 17 is collected by the transfer belt cleaning unit 16.

Here, the recording medium P transported onto the transfer belt 17 is transported from the paper feeding unit 7 via the registration rollers 9 and the like.
Specifically, the recording medium P fed by the paper feeding roller 8 from the paper feeding unit 7 that stores the recording medium P passes through a conveyance guide (not shown) and is guided to the registration roller 9. The recording medium P that has reached the registration roller 9 is conveyed toward the position of the transfer belt 17 in time.

The recording medium P to which the full color image has been transferred is separated from the transfer belt 17 and then guided to the fixing device 19. In the fixing device 19, the color image (toner) is fixed on the recording medium P at the nip between the fixing roller and the pressure roller.
Then, the recording medium P after the fixing step is discharged as an output image outside the apparatus main body 1 by a discharge roller (not shown), and a series of image forming processes is completed.

Next, the configuration and operation of the fixing device 19 installed in the image forming apparatus main body 1 will be described in detail.
FIG. 2 is a cross-sectional view showing the fixing device, and FIG. 3 is a cross-sectional view showing the configuration of the fixing roller 20. 3 shows one width direction end portion of the fixing roller 20, the other width direction end portion is configured similarly.
As shown in FIG. 2, the fixing device 19 includes an induction heating unit 25 as a magnetic flux generation unit, a fixing roller 20 facing the induction heating unit 25, a pressure roller 30 as a pressure member in pressure contact with the fixing roller 20, and the like. Consists of. The fixing roller 20 includes a fixing sleeve 21 and a fixing auxiliary roller 22.

Here, referring to FIG. 3, the fixing sleeve 21 is a multilayer structure in which a base layer 21d, a heat generating layer 21c, an elastic layer 21b, a release layer 21a and the like are sequentially laminated from the inner peripheral surface side.
As the base layer 21d of the fixing sleeve 21, a resin material such as polyimide can be used. The layer thickness of the base layer 21d is 30 to 100 μm.
As the heat generating layer 21c of the fixing sleeve 21, a good conductor such as copper, silver, or aluminum can be used. The layer thickness of the heat generating layer 21c is 5 to 20 μm, and can be formed on the base layer 21d by plating. The heat generating layer 21c of the fixing sleeve 21 is electromagnetically heated by the magnetic flux generated from the induction heating unit 25 (magnetic flux generating means).

The elastic layer 21b of the fixing sleeve 21 has a layer thickness of 30 to 200 μm and is formed of silicone rubber or the like. Providing the elastic layer 21b on the fixing sleeve 21 prevents the occurrence of uneven fixing, particularly in a color image forming apparatus.
The release layer 21 a of the fixing sleeve 21 has a layer thickness of 20 to 50 μm and is formed of a fluorine compound such as PFA. The release layer 21a is for enhancing the toner release property on the surface of the fixing sleeve 21 with which the toner image (toner) T is in direct contact, and a tube material can be used.

In the first embodiment, the base layer 21d is provided on the inner peripheral surface side with respect to the heat generating layer 21c. However, the inner peripheral surface may be formed as the heat generating layer 21c without providing the base layer. . In that case, as the heat generating layer 21c, a magnetic metal material such as iron, cobalt, nickel, or an alloy thereof, or a nonmagnetic metal material such as SUS304 or SUS316 can be used. Further, the heat generating layer 21c may have a two-layer structure of a first nonmagnetic layer and a second nonmagnetic layer having different volume resistivity.
In addition, when the above-described magnetic metal material or nonmagnetic metal material is used as the heat generating layer 21c, a nickel layer or the like can be provided as the base layer 21d in order to enhance rust prevention.

The fixing auxiliary roller 22 is formed by forming a heat insulating layer 23 having heat resistance on a cored bar 24 made of stainless steel.
The heat insulating layer 23 of the fixing auxiliary roller 22 has a layer thickness of 2 to 10 mm and an Asker hardness of 15 to 50 degrees (Hs). As a material of the heat insulation layer 23, an elastic foam material such as foamed silicone rubber or an elastic material such as silicone rubber can be used. As described above, since the heat insulating layer 23 of the auxiliary fixing roller 22 is made of an elastic foam material (or elastic material), the outer diameter of the auxiliary fixing roller 22 becomes larger than the inner diameter of the fixing sleeve 21 due to thermal expansion. However, no great stress is generated on the fixing sleeve 21. In the first embodiment, an elastic foam material is used as the material of the heat insulating layer 23 in order to make it difficult for the heat of the fixing sleeve 21 to escape to the heat insulating layer 23 side.
Here, although the auxiliary fixing roller 22 is inserted into the fixing sleeve 21, only the both ends M in the width direction of the auxiliary auxiliary roller 22 and the fixing sleeve 21 are bonded by the adhesive 40. This will be described in detail later.

  Although not shown, a thermistor is in contact with the surface of the fixing sleeve 21. The thermistor is a temperature sensitive element with high thermal responsiveness, and detects the temperature on the fixing sleeve 21 (fixing temperature). And based on the detection result by a thermistor, the heating amount by the induction heating part 25 is adjusted.

  Referring to FIG. 2, a pressure roller 30 as a pressure member is formed on a cylindrical member 32 made of aluminum, copper or the like, an elastic layer 31 made of silicone rubber or the like, a release layer made of PFA or the like (not shown). Is formed). The elastic layer 31 of the pressure roller 30 is formed to have a thickness of 1 to 5 mm. The release layer of the pressure roller 30 is formed so that the layer thickness is 20 to 50 μm. The pressure roller 30 is in pressure contact with the fixing roller 20. Then, the recording medium P is conveyed to a pressure contact portion (a fixing nip portion) between the fixing roller 20 and the pressure roller 30.

The induction heating unit 25 as a magnetic flux generating means includes a coil unit 26 (excitation coil), a core unit 27 (excitation coil core), a coil guide 28, a cover member 29, and the like. The coil portion 26 is wound around a coil guide 28 arranged so as to cover a part of the outer peripheral surface of the fixing sleeve 21, and a litz wire bundled with thin wires is wound in the width direction (in the direction perpendicular to the paper surface of FIG. 2). It is extended. The coil guide 28 is made of a heat-resistant resin material or the like, and holds the coil portion 26 on the side facing the fixing sleeve 21. The core portion 27 is made of a ferromagnetic material such as ferrite (having a relative permeability of about 2500), and is provided with a center core and a side core to form an efficient magnetic flux toward the heat generating layer of the fixing sleeve 21. ing. The core part 27 is installed so as to face the coil part 26 extended in the width direction. The cover member 29 is configured to cover the coil portion 26, the core portion 27, and the coil guide 28.
An internal core (core) made of a ferromagnetic material such as ferrite can be installed inside the fixing roller 20, or a magnetic flux shielding member that covers a part of the outer periphery of the internal core can also be installed.

The fixing device 19 configured as described above operates as follows.
The fixing roller 20 is rotated in the clockwise direction in FIG. 2 by a drive motor (not shown), and the pressure roller 30 is rotated in the counterclockwise direction. The fixing sleeve 21 is heated by a magnetic flux generated from the induction heating unit 25 at a position facing the induction heating unit 25 (opposed surface).

  Specifically, the oscillation circuit causes a high frequency alternating current of 10 kHz to 1 MHz (preferably, 20 kHz to 800 kHz) to flow from the coil unit 26 to a coil unit 26 from a power supply unit (not shown) whose frequency is variable. The lines of magnetic force are formed so as to alternately switch in both directions toward the heat generating layer 21 c of the fixing sleeve 21. By forming an alternating magnetic field in this manner, an eddy current is generated in the heat generating layer 21c of the fixing sleeve 21, and the heat generating layer 21c is inductively heated by generating Joule heat due to its electric resistance. Thus, the fixing sleeve 21 (fixing roller 20) is heated by induction heating of the heat generating layer 21c of itself.

Thereafter, the surface of the fixing sleeve 21 (fixing roller 20) heated by the induction heating unit 25 reaches a contact portion with the pressure roller 30. Then, the toner image T (toner) on the conveyed recording medium P is heated and melted.
Specifically, the recording medium P carrying the toner image T through the image forming process described above is fed between the fixing roller 20 and the pressure roller 30 while being guided by a guide plate (not shown) (arrow). Y1 movement in the transport direction.) The toner image T is fixed to the recording medium P by the heat received from the fixing roller 20 and the pressure received from the pressure roller 30, and the recording medium P is sent from between the fixing roller 20 and the pressure roller 30.

The surface of the fixing roller 20 that has passed through the fixing position then reaches the position facing the induction heating unit 25 again.
Such a series of operations is continuously repeated to complete the fixing step in the image forming process.

Hereinafter, the characteristic configuration and operation of the fixing roller 20 according to the first embodiment will be described.
Referring to FIG. 3, in fixing roller 20 according to the first exemplary embodiment, the outer peripheral surface of fixing auxiliary roller 22 and the inner peripheral surface of fixing sleeve 21 are bonded to each other at both ends M in the width direction by adhesive 40. (The central portion L in the width direction is not adhered). Specifically, the heat insulating layer 23 provided on the outer peripheral surface side of the fixing auxiliary roller 22 and the base layer 21 d provided on the inner peripheral surface side of the fixing sleeve 21 are formed by the adhesive 40 only at both ends M in the width direction. It is glued.

In this way, the outer peripheral surface of the auxiliary fixing roller 22 and the inner peripheral surface of the fixing sleeve 21 are bonded to each other at both ends M in the width direction, thereby fixing the fixing nip at the center portion L in the width direction as shown in FIG. The nip amount N1 of the portion is sufficiently ensured, and the fixability is improved.
Specifically, if the outer peripheral surface of the auxiliary fixing roller 22 and the inner peripheral surface of the fixing sleeve 21 are bonded over the entire width direction, as shown in FIG. 4B, the heat insulating layer 23 ( Since the deformation of the fixing auxiliary roller 22) is limited by the fixing sleeve 21 (because it becomes the shape of the fixing sleeve 21), a sufficient nip amount N2 of the fixing nip portion at the center portion L in the width direction can be secured. It will disappear.
On the other hand, in the first embodiment, since the outer peripheral surface of the auxiliary fixing roller 22 and the inner peripheral surface of the fixing sleeve 21 are not bonded at the center L in the width direction, as shown in FIG. Further, the heat insulating layer 23 (fixing auxiliary roller 22) is deformed without being restricted by the fixing sleeve 21. As a result, a sufficient nip amount N1 in the widthwise central portion L can be secured (N1> N2). Note that the fixing nip portion is in a state as shown in FIG. 4B at both ends M in the width direction with the adhesive 40 interposed therebetween, but this range M is a region that hardly contributes to the fixability in the fixing step. For this reason, the above-described effect is surely achieved.

In the first exemplary embodiment, the fixing auxiliary roller 22 and the fixing sleeve 21 are bonded to each other at both ends M in the width direction. Therefore, the fixing sleeve 21 is moved closer (moved in the width direction) during operation of the fixing device. ) Is also prevented.
Further, since the adhesive 40 is not interposed between the auxiliary fixing roller 22 and the fixing sleeve 21 in the center portion L in the width direction, it is possible to suppress a decrease in temperature rise efficiency due to heat conduction of the adhesive 40.

Here, in the first embodiment, the range in which the adhesive 40 is applied (the above-described width direction both end portions M) is outside the maximum sheet passing area of the recording medium P that can be fixed. For example, in the image forming apparatus according to the first embodiment, it is assumed that the maximum sheet passing area (the width direction size) of the recording medium P that can be passed is the A3 vertical size (the size in the A3 short direction). The width direction central portion L that becomes the non-adhesive surface is A3 vertical size, and the width direction both end portions M that become the adhesive surface are outside the A3 vertical size region (non-sheet passing region).
With such a configuration, the above-described effects on the fixing property and the temperature rise efficiency are ensured.

Here, it is preferable to form the outer diameter of the region M serving as the bonding surface in the fixing auxiliary roller 22 to be smaller than the inner diameter of the region M serving as the bonding surface in the fixing sleeve 21. In the first embodiment, the outer diameter of the auxiliary fixing roller 22 is formed to be smaller than the inner diameter of the fixing sleeve 21 over the entire width direction in a normal temperature environment. Thereby, in the manufacturing process of the fixing roller 20, the auxiliary fixing roller 22 can be easily inserted into the fixing sleeve 21.
3 shows the fixing roller 20 at the time of assembly (or at normal temperature), and there is a gap between the fixing sleeve 21 and the auxiliary fixing roller 22 in the center portion L in the width direction. On the other hand, during the fixing process (at the time of temperature increase), the gap between the fixing sleeve 21 and the auxiliary fixing roller 22 in the widthwise central portion L disappears due to thermal expansion, and the inner peripheral surface of the fixing sleeve and the auxiliary fixing roller The outer peripheral surface is in close contact.

  The fixing roller 20 according to the first embodiment is formed by injecting (applying) the adhesive 40 to both ends M in the width direction after the auxiliary fixing roller 22 is inserted into the fixing sleeve 21. As a result, the problem that the adhesive 40 is applied to the widthwise central portion L (paper passing region) is suppressed, and the above-described effects on the fixing property and the temperature rise efficiency are ensured.

Next, FIG. 5 demonstrates the experiment which this inventor conducted in order to confirm the effect mentioned above.
In this experiment, (1) a fixing roller (conventional one) in which the fixing sleeve 21 and the fixing auxiliary roller 22 are not bonded to each other, and (2) the fixing sleeve 21 and the fixing auxiliary roller 22 are arranged at both ends in the width direction. A fixing roller in which only M is bonded (this is the first embodiment), and (3) a fixing roller in which the fixing sleeve 21 and the auxiliary fixing roller 22 are bonded over the entire width direction (conventional one). Are used to check the warm-up time (rise time) until the desired fixing temperature (160 ° C.) is reached, the nip width (nip amount) of the central portion L in the width direction, and the degree of deviation of the fixing sleeve 21. It is a thing.
In the fixing rollers (1) to (3), the length in the width direction (L + M × 2) is 330 mm, the inner diameter of the fixing sleeve 21 (at room temperature) is 40 mm, and the outer diameter of the auxiliary fixing roller 22 (at room temperature). Was set to 39.8 mm. In the fixing rollers (2) and (3), a silicone adhesive was used as the adhesive 40, and the thickness of the adhesive 40 was set to 200 μm. In the fixing roller (2), the adhesive range M of the adhesive 40 was set to 15 mm.

  From the results of FIG. 5, it can be seen that according to the configuration of the first embodiment, the temperature raising efficiency is high and the nip amount can be secured as compared with the case of using the fixing roller (3) in which the entire width direction is bonded. . Furthermore, according to the configuration of the first embodiment, it can be seen that the fixing sleeve 21 is less likely to be displaced as compared with the case of using the fixing roller (1) in which the entire width direction is not bonded.

  As described above, in the first embodiment, the inner peripheral surface of the fixing sleeve 21 having the heat generating layer 21c heated by electromagnetic induction and the outer peripheral surface of the auxiliary fixing roller 22 having the heat insulating layer 23 on the outer peripheral surface are provided. Only the width direction both ends M are bonded. Thereby, the nip amount N1 of the fixing nip portion is sufficiently secured, the fixing property is good, the temperature raising efficiency is good, and the occurrence of the deviation of the fixing sleeve 21 can be suppressed.

Embodiment 2. FIG.
A second embodiment of the present invention will be described in detail with reference to FIG.
FIG. 6 is a cross-sectional view showing the fixing roller in the second embodiment, and corresponds to FIG. 3 in the first embodiment. The fixing roller according to the second embodiment is different from that according to the first embodiment in that the skin surface of the elastic layer of the auxiliary fixing roller is an adhesive surface.

  As shown in FIG. 6, in the fixing roller 20 in the second embodiment, the outer peripheral surface of the auxiliary fixing roller 22 and the inner peripheral surface of the fixing sleeve 21 are both end portions in the width direction as in the first embodiment. Only M is bonded by the adhesive 40. The heat insulating layer 23 of the fixing auxiliary roller 22 is formed of an elastic foam material such as foamed silicone rubber.

In the second embodiment, the outer peripheral surface of the auxiliary fixing roller 22 is formed such that both end portions M in the width direction become skin surfaces 23a of the elastic foam material, and the central portion L in the width direction is the foam surface of the elastic foam material. 23b is formed. That is, the fixing auxiliary roller 22 and the fixing sleeve 21 are bonded so that the skin surface 23a of the elastic foam material becomes an adhesive surface and the foam surface 23b of the elastic foam material becomes a non-adhesive surface.
Here, the skin surface 23a of the elastic foam material is a smooth surface free from pores due to foaming. In contrast, the foaming surface 23b of the elastic foam material is an uneven surface having pores due to foaming. Normally, when an elastic foam material is injected into a mold, the surface in contact with the mold and its vicinity become a skin surface, and the inside becomes a foam surface (foamed portion). Therefore, in order to make the outer peripheral surface a foamed surface, the skin surface of the elastic foam material taken out from the mold is removed by polishing or the like. In addition, after forming an elastic layer using the metal mold | die with a level | step difference in a diameter part, only the center part L is grind | polished, as shown in FIG. Diameter).

Thus, by using the skin surface 23a of the elastic foam material as an adhesive surface, it is possible to suppress a decrease in adhesiveness due to the adhesive 40 soaking into the pores. That is, the fixing sleeve 21 and the elastic layer 23 of the auxiliary fixing roller 22 can be securely bonded at both ends M in the width direction.
Further, by setting the foaming surface 23b of the elastic foam material as a non-adhesive surface (paper passing region), the heat of the fixing sleeve 21 becomes difficult to escape to the heat insulating layer 23 side, and the temperature raising efficiency of the fixing roller 20 is improved.

  As described above, also in the second embodiment, as in the first embodiment, the fixing having the heat insulating layer 23 on the inner peripheral surface of the fixing sleeve 21 having the heat generating layer 21c heated by electromagnetic induction and the outer peripheral surface. Only the width direction both ends M are bonded to the outer peripheral surface of the auxiliary roller 22. Thereby, the nip amount N1 of the fixing nip portion is sufficiently secured, the fixing property is good, the temperature raising efficiency is good, and the occurrence of the deviation of the fixing sleeve 21 can be suppressed.

Embodiment 3 FIG.
A third embodiment of the present invention will be described in detail with reference to FIG.
FIG. 7 is a cross-sectional view showing the fixing roller in the third embodiment, and corresponds to FIG. 3 in the first embodiment. The fixing roller according to the third embodiment is different from that according to the first embodiment in that the outer diameter of the region serving as the adhesive surface in the elastic layer of the auxiliary fixing roller is reduced.

  As shown in FIG. 7, in the fixing roller 20 according to the third embodiment, the outer peripheral surface of the auxiliary fixing roller 22 and the inner peripheral surface of the fixing sleeve 21 are both end portions in the width direction, as in the above embodiments. Only M is bonded by the adhesive 40.

  In the fixing auxiliary roller 22 according to the third exemplary embodiment, the outer diameter D2 of the region serving as the bonding surface (the width direction end portions M) is the region serving as the non-bonding surface (the width direction central portion L). ) Is smaller than the outer diameter D1 (D1> D2). Specifically, in the third embodiment, the outer diameter D2 of both ends M in the width direction of the auxiliary fixing roller 22 at room temperature is set to 39.8 mm, and the inner diameters of both ends M in the width direction of the fixing sleeve 21 at room temperature. Is set to 40.3 mm (approximately the same size as the outer diameter D1 of the auxiliary fixing roller 22). In the manufacturing process of the fixing roller 20, after the auxiliary fixing roller 22 is inserted into the fixing sleeve 21, the adhesive 40 is injected (applied) into the gap between the two.

With such a configuration, the adhesive 40 easily stays at both ends M in the width direction provided with a step, so that the intrusion of the adhesive into the center portion L in the width direction is suppressed.
In the third embodiment, in the manufacturing process of the fixing roller 20, after the auxiliary fixing roller 22 is inserted into the fixing sleeve 21, the adhesive 40 is injected into the gap between the two. On the other hand, the fixing auxiliary roller 22 carrying the adhesive 40 may be inserted into the fixing sleeve 21 after the adhesive 40 is applied to both ends M in the width direction of the fixing auxiliary roller 22 provided with a step in advance. Also in this case, the adhesive can be prevented from entering the central portion L in the width direction by the step of the adhesive surface.

  As described above, also in the third embodiment, as in each of the embodiments described above, the fixing having the inner peripheral surface of the fixing sleeve 21 having the heat generating layer 21c heated by electromagnetic induction and the heat insulating layer 23 on the outer peripheral surface. Only the width direction both ends M are bonded to the outer peripheral surface of the auxiliary roller 22. Thereby, the nip amount N1 of the fixing nip portion is sufficiently secured, the fixing property is good, the temperature raising efficiency is good, and the occurrence of the deviation of the fixing sleeve 21 can be suppressed.

  It should be noted that the present invention is not limited to the above-described embodiments, and within the scope of the technical idea of the present invention, the embodiments can be modified as appropriate in addition to those suggested in the embodiments. Is clear. In addition, the number, position, shape, and the like of the constituent members are not limited to the above embodiments, and can be set to a number, position, shape, and the like that are suitable for carrying out the present invention.

1 is an overall configuration diagram illustrating an image forming apparatus according to Embodiment 1 of the present invention. FIG. 3 is a cross-sectional view illustrating a fixing device. FIG. 3 is a cross-sectional view illustrating a configuration of a fixing roller. FIG. 3 is a schematic view showing the vicinity of a fixing nip portion. It is a table | surface figure which shows an experimental condition and an experimental result. It is sectional drawing which shows the fixing roller in Embodiment 2 of this invention. It is sectional drawing which shows the fixing roller in Embodiment 3 of this invention.

Explanation of symbols

1 image forming apparatus body (apparatus body),
19 fixing device,
20 fixing roller,
21 fixing sleeve,
21a release layer, 21b elastic layer, 21c heat generating layer, 21d base layer,
22 fixing auxiliary roller,
23 heat insulation layer, 23a skin surface, 23b foam surface,
24 Core,
25 induction heating part (magnetic flux generating means),
26 coil part, 27 core part,
28 coil guide, 29 cover member,
30 pressure roller (pressure member),
40 Adhesive.

Claims (11)

A fixing sleeve that has a heat generation layer heated by magnetic flux generated by the magnetic flux generation means, and that melts and fixes the toner image on the recording medium;
A fixing auxiliary roller inserted into the fixing sleeve and having a heat insulating layer on the outer peripheral surface;
A fixing roller, wherein an inner peripheral surface of the fixing sleeve and an outer peripheral surface of the auxiliary fixing roller are bonded only at both ends in the width direction. The heat insulating layer is made of an elastic foam material,
The outer peripheral surface of the fixing auxiliary roller is formed such that both end portions in the width direction are skin surfaces of the elastic foam material, and the center portion in the width direction is formed to be a foam surface of the elastic foam material. The fixing roller according to claim 1.   The fixing roller according to claim 2, wherein an inner peripheral surface of the fixing sleeve and an outer peripheral surface of the auxiliary fixing roller are bonded so that the skin surface becomes an adhesive surface.   4. The fixing roller according to claim 1, wherein both ends in the width direction are outside a maximum sheet-passing area of the recording medium that can be fixed. 5. The fixing sleeve includes a base layer on an inner peripheral surface,
The fixing roller according to claim 1, wherein the base layer and the heat insulating layer are bonded to each other at both ends in the width direction.   The fixing roller according to claim 5, wherein the fixing sleeve further includes a release layer and an elastic layer.   7. The fixing auxiliary roller is formed so that an outer diameter of a region serving as an adhesive surface is smaller than an inner diameter of a region serving as an adhesive surface in the fixing sleeve. The fixing roller described in 1.   8. The fixing auxiliary roller is formed so that an outer diameter of a region serving as an adhesive surface is smaller than an outer diameter of a region serving as a non-adhesive surface. Fixing roller.   The fixing roller according to claim 1, wherein the fixing auxiliary roller is formed by adhering both ends in the width direction after the fixing auxiliary roller is inserted into the fixing sleeve.   A fixing device comprising: the fixing roller according to claim 1; a pressure member that is in pressure contact with the fixing roller; and the magnetic flux generation unit. An image forming apparatus comprising the fixing device according to claim 10.

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