JP4359464B2 - Fixing device - Google Patents

Description

  The present invention relates to a fixing roller and a fixing device used in an apparatus using an electrophotographic process such as an electrophotographic copying machine, a facsimile machine, and a printer.

  An electromagnetic induction heating type fixing roller is known as a fixing roller used in an image forming apparatus using an electrophotographic process such as an electrophotographic copying machine, a facsimile machine, and a printer, for shortening a heating time and increasing a thermal efficiency. It has been.

Conventionally, as this electromagnetic induction heating type fixing roller, those disclosed in Japanese Patent Application Laid-Open Nos. 2000-214702, 2000-214713, and 2000-214714 are known. In these fixing rollers, an endless belt having a thickness of 0.1 mm as an electromagnetic induction heat generating layer is used.
JP 2000-214702 A JP 2000-214713 A JP 2000-214714 A

  However, if an attempt is made to form a nip by deforming the fixing roller side in order to improve the separability of the recording material, the endless belt having a thin electromagnetic induction heat generating layer thickness of 0.1 mm is integrated into a single piece, so that it is rigid. The nip width did not come out as expected. That is, as shown in FIG. 8, since the nip width N is narrow, there has been a problem that fixing failure occurs.

  SUMMARY OF THE INVENTION An object of the present invention is to provide a fixing roller and a fixing device that have a sufficient nip width and can prevent fixing failure.

The fixing device according to the present invention is, in order from the inside to the outside, a fixing roller composed of at least five layers of a support layer, a sponge layer, an electromagnetic induction heat generating layer, an elastic layer, and a release layer, and is pressed against the fixing roller. The electromagnetic induction heat generating layer provided on the fixing roller is heated by the magnetic flux generated by the magnetic flux generating means from the outside of the fixing roller, and is undecided at the pressure nip portion between the fixing roller and the pressure roller. In an electromagnetic induction heating type fixing device that sandwiches and conveys a recording material carrying an image and melts and fixes an unfixed image on the recording material,
A part of the electromagnetic induction exothermic layer in the thickness direction is divided into at least three in the circumferential direction ,
The electromagnetic induction exothermic layer is thicker at the center than at both ends, and
The sponge layer has a hardness difference such that a hardness of a portion corresponding to a central portion of the electromagnetic induction heat generating layer is lower than a hardness of a portion corresponding to an end portion of the electromagnetic induction heat generating layer. .

The fixing device according to a second aspect of the present invention is the fixing device according to the first aspect, wherein the sponge layer has a thickness at a central portion in accordance with a change in thickness of the electromagnetic induction heat-generating layer. Is thicker than the wall thickness at the end.

According to the fixing device of the present invention , since the electromagnetic induction heat generating layer is divided into three or more in the circumferential direction, the rigidity of the fixing roller is weaker than that of the conventional one, and the pressure roller Therefore, even if the same pressure is applied as before, the nip width can be increased to prevent the problem of fixing failure.

Furthermore , according to the fixing device of the present invention, the thickness of the central portion of the electromagnetic induction heat-generating layer is thicker than the thickness of both end portions. Since the edge temperature can be increased by that amount, the temperature distribution is improved and fixing failure at the edge can be prevented.

Furthermore , according to the fixing device of the present invention, since the sponge layer has the hardness changed in accordance with the change in the thickness of the electromagnetic induction heat generating layer, the change in the nip width due to the difference in thickness can be prevented. Fixing failure, which is a characteristic, can be prevented.

According to the fixing device of claim 2, since the thickness of the sponge layer is changed in accordance with the change of the thickness of the electromagnetic induction heat-generating layer, the processing time is shorter than the case where the hardness is changed by changing the foam diameter. The cost can be reduced.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a cross-sectional view of a fixing roller of a first embodiment as an embodiment according to the present invention.
As shown in FIG. 1, the fixing roller 1 includes at least a support layer 11, a sponge layer 12, an electromagnetic induction exothermic layer 13, an elastic layer 14, and a release layer 15 in order from the inner side (center side) to the outer side. It has 5 layers in order. In this embodiment, the diameter of the fixing roller 1 is 20 to 40 mm.

  The release layer 15 is composed of PFA (perfluoroalkoxy), PTFE (polytetrafluoroethylene), or a mixture of PFA and PTFE. The release layer 15 has a thickness of 10 to 30 μm, and a primer is applied between the release layer 15 and the elastic layer 14 for adhesion.

  Next, silicone rubber is generally used as the material of the elastic layer 14, but heat-resistant rubber such as fluorine rubber may be used otherwise. Further, the elastic layer 14 is formed to have a thickness of 0.1 to 0.5 mm, and it is better to disperse and mix materials such as an oxidizing material and silica in order to increase the thermal conductivity in the rubber. .

  In this embodiment, the electromagnetic induction exothermic layer 13 uses an endless nickel electroformed belt layer having a thickness of 0.1 mm as in the prior art, but other materials such as magnetic stainless steel are used. A magnetic material can be used, and the thickness is preferably 0.03 to 1.0 mm.

  Further, the sponge layer 12 is composed of a silicone rubber sponge layer, the thickness thereof is set to 1 to 10 mm, and the hardness is preferably 40 degrees or less by an Asker hardness meter. The support layer 11 inside the sponge layer 12 is made of a metal material such as aluminum, iron, or copper, and its thickness is preferably 0.5 to 3 mm.

  The power supply to the magnetic flux generating means for generating the magnetic flux that generates heat from the electromagnetic induction heat generating layer 13 may be a machine body or a capacitor installed in the machine body.

  2A is a development view of the electromagnetic induction heat generating layer provided in the fixing roller of FIG. 1, FIG. 2B is a side view thereof, and FIG. 3 is a diagram showing a nip width when the fixing roller of FIG. 1 is used. It is.

  The feature of the present invention is that, as shown in FIG. 2 (A), the electromagnetic induction heat-generating layer 13 is divided into three or more in the circumferential direction. As shown in FIG. 2B, for example, as shown in FIG. 2B, the cut line 13c is inserted from the outer peripheral side to a part of the thickness of the electromagnetic induction heat generating layer 13, for example, to a depth of 1/2. The depth of the cut line 13c is 1/2 in this embodiment, but may be 1/4, 1/3, 2/3, 3/4, etc. from the outer periphery. It is set as appropriate according to the required flexibility.

  Instead of the cut line 13c, embossing may be performed in a dotted line along a line corresponding to the cut line 13c in FIG. In addition, it is preferable that dividing lines, such as the cut line 13c, are equidistant.

  In this embodiment, three or more divisions of the electromagnetic induction heat generating layer 13 are divided into ten portions (about 30 mm in width). As described above, since the electromagnetic induction heat generating layer 13 is divided into three or more to reduce the rigidity, a sufficient nip width N is obtained as shown in FIG. Note that the number of divisions can be set as appropriate so that necessary low rigidity can be obtained in consideration of the material, thickness, diameter, and the like of the electromagnetic induction heat-generating layer 13.

  FIG. 4 is a cross-sectional view of a fixing roller according to a second embodiment as an embodiment of the present invention, and FIG. 5 is a diagram showing an axial temperature distribution of the fixing roller shown in FIG.

  As shown in FIG. 4, the electromagnetic induction heat generating layer 13 provided in the fixing roller of this embodiment has a thick central portion 13 a in the axial direction and a thick central portion 13 a at both end portions 13 b in the axial direction. It is thinner than the wall thickness.

  In this embodiment, the A4 longitudinal paper width of 216 mm has a thickness of 0.2 mm and the other thickness is 0.1 mm. Therefore, the edge temperature is set to the extent that the heat capacity difference due to the thickness difference occurs and the rise of the central portion is delayed. Can be raised. Therefore, when the center portion reaches the fixing guarantee temperature, the end portion can also be set to the fixing compensation temperature, so that the end portion does not become defective in fixing. Specifically, as shown in FIG. 5, when the temperature distribution 120 by the conventional fixing roller and the temperature distribution 20 by the fixing roller of the present embodiment are compared, according to the fixing roller of the present embodiment, the central portion and the end The temperature difference with the part is greatly reduced and the temperature distribution is improved. Here, the thickness difference and width between the central portion and the end portion may be appropriately set according to the necessary temperature difference between the central portion and the end portion, and thus are not particularly defined here.

  FIG. 6 is a cross-sectional view of a fixing roller of a third embodiment as an embodiment according to the present invention.

  As shown in FIG. 6, the fixing roller of the third embodiment is different from the fixing roller shown in FIG. 4 only in the sponge layer 12, and the other configuration is the same as that of the fixing roller shown in FIG. That is, the foam diameter of the sponge layer 12 is changed between the center part and the end part, and the sponge layer is composed of the sponge layer end part 12b and the sponge layer center part 12a having a larger foam diameter than the sponge layer end part 12b. The hardness of the central part is lower than the hardness of.

  Usually, in order to foam silicone rubber, foaming is performed by adding a foaming agent to silicone rubber before vulcanization and vulcanizing at a temperature of about 200 ° C. for several hours. In order to change the foam diameter of the sponge layer 12, the foam diameter of the center part is vulcanized by adding more foaming agent to the center part than the end part (adding less foaming agent to the end part than the center part). Can be increased. As another method, the amount of the foaming agent is made the same at the center and the end (with the same density of the foaming agent), and the vulcanization time at the end is made shorter than the vulcanization time at the center. You may do it.

  Since the hardness of the sponge layer 12 in the central portion is reduced, the necessary nip width can be obtained even with the conventional pressure and the end portion of the electromagnetic induction heat-generating layer 13 is increased even if the thickness is increased. Similarly, the necessary nip width can be secured also in the central portion.

  In this processing method, first, a rubber material blended for increasing the foam diameter is poured into the center portion to cause foaming, and then a conventional foaming rubber material is poured into the center portion for foaming.

  FIG. 7 is a cross-sectional view of a fixing roller according to a fourth embodiment as an embodiment of the present invention.

  As shown in FIG. 7, the fixing roller of the fourth embodiment is different from the fixing roller shown in FIG. 4 only in the sponge layer 12 and the support layer 11, and the other configuration is the same as that of the fixing roller shown in FIG. It is the same. That is, the apparent hardness can be lowered by making the thickness of the sponge layer 12 thicker at the central portion 12a than at the end portion 12b. As shown in FIG. 7, this can be achieved by changing the thickness of the support layer 11 so that the central portion 11a is thinner than the end portion 11b, and the central portion 12a of the sponge layer 12 is thicker. As a result, the apparent hardness decreases and the necessary nip width can be secured.

  The present invention is not limited to the above embodiment. That is, various modifications can be made without departing from the scope of the present invention.

1 is a cross-sectional view of a fixing roller of a first embodiment as an embodiment according to the present invention. (A) is a development view of an electromagnetic induction heat generating layer provided in the fixing roller of FIG. 1, and (B) is a side view of the same. It is a figure which shows the nip width at the time of using the fixing roller of FIG. It is a cross-sectional view of the fixing roller of the second embodiment as one embodiment according to the present invention. FIG. 5 is a diagram showing an axial temperature distribution of the fixing roller shown in FIG. 4. It is a cross-sectional view of the fixing roller of the third embodiment as an embodiment according to the present invention. It is a cross-sectional view of the fixing roller of the fourth embodiment as one embodiment according to the present invention. It is a figure which shows the nip width | variety of the conventional fixing roller.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Fixing roller 11 Support layer 12 Sponge layer 12a Sponge layer center part 12b Sponge layer edge part 13 Electromagnetic induction heat-generating layer 13a Center part 13b End part 13c Cut line 14 Elastic layer 15 Release layer

Claims (2)

In order from the inside to the outside, there are a fixing roller composed of at least five layers of a support layer, a sponge layer, an electromagnetic induction heat generating layer, an elastic layer, and a release layer, and a pressure roller that is in pressure contact with the fixing roller. Then, the electromagnetic induction heat generating layer provided on the fixing roller is heated by the magnetic flux generated by the magnetic flux generating means from the outside of the fixing roller, and a recording material carrying an unfixed image at the pressure nip portion between the fixing roller and the pressure roller is formed. In an electromagnetic induction heating type fixing device that sandwiches and conveys and fixes an unfixed image on a recording material,
A part of the electromagnetic induction exothermic layer in the thickness direction is divided into at least three in the circumferential direction ,
The electromagnetic induction exothermic layer is thicker at the center than at both ends, and
The sponge layer has a hardness difference so that a hardness of a portion corresponding to a central portion of the electromagnetic induction heat generating layer is lower than a hardness of a portion corresponding to an end portion of the electromagnetic induction heat generating layer. A fixing device characterized by the above. 2. The fixing device according to claim 1, wherein the sponge layer has a thickness at a center portion larger than a thickness at an end portion in accordance with a change in thickness of the electromagnetic induction heat generating layer .

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