JP2018205336A - Fixing device and image forming apparatus - Google Patents

Abstract

To provide a fixing device that can reduce the occurrence of a difference in glossiness level.SOLUTION: A fixing device 50 comprises: an endless fixing belt 51; a heating member 53 that heats the fixing belt 51; and a heat transfer sheet 55 that transfers heat generated by the heating member 53 to the fixing belt 51. The heating member 53 includes a contact surface 53a in contact with an inner peripheral surface of the fixing belt 51, and a non-contact surface 53b not in contact with the inner peripheral surface of the fixing belt 51; the heat transfer sheet 55 includes a connection part 541 in contact with the non-contact surface 53b, and a contact part 542 in contact with the inner peripheral surface of the fixing belt 51 in a portion different from the inner peripheral surface of the fixing belt 51 with which the heating member 53 is in contact.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a fixing device that fixes a toner image on a recording medium and an image forming apparatus including the same.

  As a document disclosing a conventional fixing device, for example, Japanese Patent Laying-Open No. 2006-161849 (Patent Document 1) is cited.

  In the fixing device disclosed in Japanese Patent Application Laid-Open No. H10-228707, the heating member is disposed between the fixing member and the heating member disposed inside the fixing belt so as to face the pressure member that forms the fixing nip portion with the fixing belt. A heat transfer member that transfers heat to the fixing belt is disposed.

JP 2006-161849 A

  In recent years, there has been a demand for improvement in the quality of toner images fixed on a recording medium, and there has been a demand for suppressing the occurrence of a gloss level difference that becomes image noise. Such a gloss level difference is caused when the toner image is fixed on the recording medium by fixing the heat of the fixing belt when the toner image is fixed on the recording medium at the fixing nip portion. This occurs when the temperature of the fixing belt fluctuates every round, such as the first and second rounds.

  The heat transfer member used in the fixing device disclosed in Patent Document 1 is a metal plate made of copper or aluminum. The thermal conductivities of copper and aluminum are as low as about 377 W / mK and 206 W / mK, respectively. For this reason, the heat supply from the heating member to the fixing belt is slow, and the fixing belt cannot be heated sufficiently until the fixing belt transitions to the next circumference. For this reason, it was difficult to suppress the occurrence of a gloss level difference.

  The present invention has been made in view of the above problems, and an object of the present invention is to provide a fixing device and an image forming apparatus that can suppress the occurrence of a gloss level difference.

  The fixing device according to the present invention includes an endless fixing belt that is rotatably provided, a heating member that heats the fixing belt, and a heat transfer sheet that conducts heat generated by the heating member to the fixing belt. . The heating member includes a contact surface that contacts the inner peripheral surface of the fixing belt and a non-contact surface that does not contact the inner peripheral surface of the fixing belt.

  The heat transfer sheet includes a connection portion that is in contact with the non-contact surface and a contact portion that is in contact with the inner peripheral surface of the fixing belt that is different from the inner peripheral surface of the fixing belt that is in contact with the heating member. , Fixing device.

  The fixing device according to the present invention preferably includes a pressure member that is disposed outside the fixing belt and that presses the fixing belt to form a fixing nip portion. In this case, it is preferable that the contact portion contacts the fixing belt on the upstream side of the fixing nip portion in the rotation direction of the fixing belt.

  The fixing device according to the present invention preferably includes a holding member that holds the heating member. In this case, in the fixing device, the holding member is positioned upstream of the fixing nip portion in the rotation direction of the fixing belt, and a guide portion that guides the fixing belt to the fixing nip portion. Preferably, the guide part has a curved surface that slides on the inner peripheral surface of the fixing belt.

  In the fixing device according to the present invention, it is preferable that the curvature of the curved surface decreases as the fixing nip portion is approached.

  In the fixing device according to the present invention, it is preferable that a sheet member having a lower coefficient of friction than the curved surface is provided between the curved surface and the fixing belt.

  The fixing device according to the present invention preferably includes a holding member that holds the heating member. In this case, in the fixing device, it is preferable that the contact portion of the heat transfer sheet extends along a circumferential direction of the fixing belt, and the holding member includes the contact portion. It is preferable to have a pressing portion that presses against the fixing belt.

  In the fixing device according to the present invention, the pressing portion has a curved shape that curves along the circumferential direction of the fixing belt, and the thickness decreases toward the upstream side in the rotation direction of the fixing belt. It is preferable to become.

  In the fixing device according to the present invention, the thermal conductivity of the heat transfer sheet is preferably 700 W / mK or more.

  In the fixing device according to the present invention, the thickness of the heat transfer sheet is preferably 40 μm or more and 100 μm or less.

  In the fixing device according to the present invention, the heat transfer sheet is preferably a graphite sheet.

  An image forming apparatus according to the present invention fixes an image forming unit that forms a toner image on a recording medium transported along a transport path, and fixes the toner image on the recording medium transported along the transport path. And a fixing device.

  According to the present invention, it is possible to provide a fixing device and an image forming apparatus capable of suppressing the occurrence of a gloss level difference.

1 is a schematic diagram illustrating an image forming apparatus according to Embodiment 1. FIG. 1 is a cross-sectional view of a fixing device according to Embodiment 1. FIG. 6 is a cross-sectional view of a fixing device according to Embodiment 2. FIG. FIG. 6 is a cross-sectional view illustrating a configuration around a fixing nip portion in a fixing device according to a third embodiment. FIG. 6 is a cross-sectional view illustrating a configuration around a fixing nip portion in a fixing device according to a fourth embodiment. FIG. 10 is a cross-sectional view illustrating a configuration around a fixing nip portion in a fixing device according to a fifth embodiment. It is a figure which shows the conditions and result of a 1st verification experiment performed in order to confirm the effect of embodiment. It is a figure which shows the conditions and result of a 2nd verification experiment performed in order to confirm the effect of embodiment. It is a figure which shows the conditions and result of a 3rd verification experiment performed in order to confirm the effect of embodiment.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In the following embodiments, the same or common parts are denoted by the same reference numerals in the drawings, and description thereof will not be repeated.

(Embodiment 1)
(Image forming device)
With reference to FIG. 1, an image forming apparatus 100 in which the above-described fixing device 50 is mounted will be described. FIG. 1 is a diagram illustrating an example of the internal structure of the image forming apparatus 100.

  FIG. 1 shows an image forming apparatus 100 as a color printer. Hereinafter, the image forming apparatus 100 as a color printer will be described, but the image forming apparatus 100 is not limited to a color printer. For example, the image forming apparatus 100 may be a monochrome printer, a fax machine, or a multifunction printer (MFP: Multi-Functional Peripheral) of a monochrome printer, a color printer, and a fax machine.

  The image forming apparatus 100 includes image forming units 1Y, 1M, 1C, and 1K, an intermediate transfer belt 30, a primary transfer roller 31, a secondary transfer roller 33, a cassette 37, a driven roller 38, and a drive roller 39. A timing roller 40, a fixing device 50, a housing 80, and a control device 101.

  The housing 80 defines an outer shell of the image forming apparatus 100. The casing 80 includes an image forming unit 1Y, 1M, 1C, 1K, an intermediate transfer belt 30, a primary transfer roller 31, a secondary transfer roller 33, a cassette 37, a driven roller 38, and a driving roller. 39, the timing roller 40, the fixing device 50, and the control device 101 are accommodated.

  The image forming units 1Y, 1M, 1C, and 1K, the intermediate transfer belt 30, the primary transfer roller 31, the secondary transfer roller 33, the cassette 37, the driven roller 38, the drive roller 39, and the timing roller 40 An image forming unit is configured. The image forming unit forms a toner image on a sheet S as a recording medium conveyed along a conveyance path 41 described later.

  The image forming units 1Y, 1M, 1C, and 1K are arranged in order along the intermediate transfer belt 30. The image forming unit 1Y receives toner from the toner bottle 15Y and forms a yellow (Y) toner image. The image forming unit 1M receives the supply of toner from the toner bottle 15M and forms a magenta (M) toner image. The image forming unit 1C receives toner from the toner bottle 15C and forms a cyan (C) toner image. The image forming unit 1K receives toner from the toner bottle 15K and forms a black (BK) toner image.

  The image forming units 1Y, 1M, 1C, and 1K are arranged along the intermediate transfer belt 30 in the rotation direction of the intermediate transfer belt 30, respectively. Each of the image forming units 1Y, 1M, 1C, and 1K includes a photoconductor 10, a charging device 11, an exposure device 12, a developing device 13, and a cleaning device 17.

  The charging device 11 uniformly charges the surface of the photoconductor 10. The exposure device 12 irradiates the photoconductor 10 with laser light in accordance with a control signal from the control device 101, and exposes the surface of the photoconductor 10 according to the input image pattern. Thereby, an electrostatic latent image corresponding to the input image is formed on the photoreceptor 10.

  The developing device 13 applies a developing bias to the developing roller 14 while rotating the developing roller 14, and causes the toner to adhere to the surface of the developing roller 14. As a result, the toner is transferred from the developing roller 14 to the photoreceptor 10, and a toner image corresponding to the electrostatic latent image is developed on the surface of the photoreceptor 10.

  The photoconductor 10 and the intermediate transfer belt 30 are in contact with each other at a portion where the primary transfer roller 31 is provided. The primary transfer roller 31 has a roller shape and is configured to be rotatable. A transfer voltage having a polarity opposite to that of the toner image is applied to the primary transfer roller 31, whereby the toner image is transferred from the photoreceptor 10 to the intermediate transfer belt 30. A yellow (Y) toner image, a magenta (M) toner image, a cyan (C) toner image, and a black (BK) toner image are sequentially superimposed and transferred from the photoreceptor 10 to the intermediate transfer belt 30. As a result, a color toner image is formed on the intermediate transfer belt 30.

  The intermediate transfer belt 30 is stretched around a driven roller 38 and a driving roller 39. The drive roller 39 is rotationally driven by, for example, a motor (not shown). The intermediate transfer belt 30 and the driven roller 38 rotate in conjunction with the driving roller 39. As a result, the toner image on the intermediate transfer belt 30 is conveyed to the secondary transfer roller 33.

  The cleaning device 17 is in pressure contact with the photoreceptor 10. The cleaning device 17 collects the toner remaining on the surface of the photoreceptor 10 after the toner image is transferred.

  A sheet S is set in the cassette 37. The sheets S are sent one by one from the cassette 37 to the secondary transfer roller 33 along the transport path 41 by the timing roller 40. The secondary transfer roller 33 has a roller shape and is configured to be rotatable. The secondary transfer roller 33 applies a transfer voltage having a polarity opposite to that of the toner image to the sheet S being conveyed. As a result, the toner image is attracted from the intermediate transfer belt 30 to the secondary transfer roller 33, and the toner image on the intermediate transfer belt 30 is transferred. The conveyance timing of the sheet S to the secondary transfer roller 33 is adjusted by the timing roller 40 in accordance with the position of the toner image on the intermediate transfer belt 30. The toner image on the intermediate transfer belt 30 is transferred to an appropriate position on the paper S by the timing roller 40.

  The fixing device 50 pressurizes and heats the paper S passing through the fixing device 50. As a result, the toner image is fixed on the paper S. As described above, the fixing device 50 fixes the toner image on the sheet S conveyed along the conveyance path 41. The sheet S on which the toner image is fixed is discharged to the tray 48.

  In the above description, the image forming apparatus 100 adopting the tandem method as the printing method has been described. However, the printing method of the image forming apparatus 100 is not limited to the tandem method. The arrangement of the components in the image forming apparatus 100 can be changed as appropriate according to the employed printing method. As a printing method of the image forming apparatus 100, a rotary method or a direct transfer method may be employed. In the case of the rotary system, the image forming apparatus 100 includes a single photoconductor 10 and a plurality of developing devices 13 configured to be coaxially rotatable. At the time of printing, the image forming apparatus 100 guides each developing device 13 to the photoreceptor 10 in order to develop each color toner image. In the case of the direct transfer method, the image forming apparatus 100 directly transfers the toner image formed on the photoreceptor 10 onto the paper S.

  FIG. 2 is a cross-sectional view of the fixing device according to the first embodiment. With reference to FIG. 2, the fixing device 50 according to the first embodiment will be described.

  As shown in FIG. 2, the fixing device 50 includes an endless fixing belt 51, a pressure roller 52 as a pressure member, a heating member 53, a holding member 54, and a heat transfer sheet 55.

  The endless fixing belt 51 is wound around the heating member 53 so that the heating member 53 is positioned inside. The fixing belt 51 is configured to be rotatable. The fixing belt 51 includes, for example, a base layer, an elastic layer, and a release layer. A base layer, an elastic layer, and a release layer are sequentially arranged from the inside to the outside of the fixing belt 51.

  The base layer of the fixing belt 51 is made of, for example, a polyimide film. The inner diameter of the base layer is 40 mm. The thickness of the base layer is 50 μm or more and 70 μm or less. The elastic layer of the fixing belt 51 is made of silicone rubber. The thickness of the elastic layer is, for example, 120 μm or more and 190 μm or less. The release layer of the fixing belt 51 is made of a fluorine resin such as PFA or PTFE. The thickness of the release layer is, for example, 12 μm or more and 15 μm or less.

  A pressure roller 52 as a pressure member is disposed outside the fixing belt 51. The pressure roller 52 is disposed to face the heating member 53. The pressure roller 52 presses the heating member 53 with the fixing belt 51 interposed therebetween. In this way, the pressure roller 52 forms a fixing nip portion by being pressed against the fixing belt 51.

  The pressure roller 52 is composed of, for example, a cored bar and a surface layer. The cored bar is made of aluminum or iron and has a pipe shape. The surface layer includes an elastic layer and a release layer. The elastic layer and the release layer are sequentially arranged from the inside toward the outside. The elastic layer is made of, for example, silicone rubber. The thickness of the elastic layer is, for example, about 6 mm. The release layer is made of, for example, a fluorine resin such as PFA. The thickness of the release layer is, for example, about 30 μm.

  The heating member 53 is disposed so as to sandwich the fixing belt 51 between the pressure roller 52 and heats the fixing belt 51. The heating member 53 has a plate shape and extends along a direction parallel to the rotation axis of the fixing belt 51. The heating member 53 contacts the inner peripheral surface of the fixing belt 51 in the fixing nip portion.

  The outer surface of the heating member 53 includes a contact surface 53 a that contacts the inner peripheral surface of the fixing belt 51 and a non-contact surface 53 b that does not contact the inner peripheral surface of the fixing belt 51. The contact surface 53a is a main surface located on the pressure roller 52 side of two main surfaces facing each other in the direction in which the heating member 53 and the pressure roller 52 are arranged.

  The non-contact surface 53b includes a main surface located on the opposite side to the pressure roller 52 side of the two main surfaces facing each other in the direction in which the heating member 53 and the pressure roller 52 are arranged, and the two main surfaces. It is comprised by the surrounding surface which connects.

  The thickness of the heating member in the direction in which the heating member 53 and the pressure roller 52 are arranged is about 1.2 mm. The width of the heating member 53 along the paper transport direction is about 10 mm. The length of the heating member in the direction parallel to the rotation axis of the fixing belt 51 is about 300 mm.

The heating member 53 includes a base material and a resistance heating layer. The substrate is made of a composite material such as alumina. The resistance heating layer is provided on the surface of the base material, for example. The resistance heating layer is made of an electric resistance material layer such as Ag / Pd, RuO ₂ , and Ta ₂ N, for example.

  The resistance heating layer is provided, for example, at the center of the surface of the substrate so that both ends of the substrate are exposed in the width direction of the heating member 53. The width of the resistance heating layer is about 6 mm to 8 mm. The resistance heating layer is applied by printing, for example.

  A power feeding portion is provided on the base material exposed from the resistance heating layer. The heating member 53 generates heat by energizing the resistance heating layer through the power feeding unit.

  The holding member 54 holds the heating member 53. The holding member 54 includes a covering portion 541 and a pressing portion 542. The covering portion 541 is provided so as to cover the heating member 53 from the side opposite to the contact surface 53 a of the heating member 53. That is, the covering portion 541 is provided so as to cover the non-contact surface 53 b of the heating member 53.

  The pressing portion 542 has a curved shape that curves from the covering portion 541 along the circumferential direction of the fixing belt 51. The pressing portion 542 presses a contact portion 552 of a heat transfer sheet 55 described later toward the inner peripheral surface of the fixing belt 51. Thereby, the adhesion between the heat transfer sheet 55 and the fixing belt 51 can be enhanced. As a result, heat from the heat transfer sheet 55 can be effectively conducted to the fixing belt 51.

  The pressing unit 542 may press the heat transfer sheet 55 toward the fixing belt 51 by pressing the pressing unit 542 toward the fixing belt 51 by a not-shown pressing mechanism. Further, the pressing portion 542 is formed so that the front end side of the pressing portion 542 is urged toward the outside, so that the pressing portion 542 directs the heat transfer sheet 55 toward the fixing belt 51 using the urging force. May be pressed. When the heat transfer sheet 55 is pressed toward the fixing belt 51 using the urging force of the pressing portion 542 itself, the pressing mechanism can be omitted, and the number of parts can be reduced.

  The holding member 54 is supported by a support member (not shown) provided in the housing 80 of the image forming apparatus 100. The holding member 54 holds the heating member 53 so that the heating member 53 is not deformed by the pressure received from the pressure roller 52. Thereby, a uniform nip width is obtained in the longitudinal direction parallel to the rotation axis of the fixing belt 51.

  The holding member 54 is made of a resin material having high heat resistance such as LCP (liquid crystal polymer). Thereby, it is possible to prevent the holding member 54 from being deformed by the heat from the heating member 53.

  The heat transfer sheet 55 conducts the heat generated by the heating member 53 to the fixing belt 51. The heat transfer sheet 55 is made of, for example, a graphite sheet. The thermal conductivity of the heat transfer sheet 55 is preferably 700 W / mK or more. Moreover, it is preferable that the heat conductivity of a heat-transfer sheet | seat is 1350 W / mK or less. Since the heat transfer sheet 55 has such a thermal conductivity, the heat generated by the heating member 53 can be quickly conducted to the fixing belt 51.

  The thickness of the heat transfer sheet 55 is preferably 40 μm or more and 100 μm or less. By setting the thickness of the heat transfer sheet 55 to 40 μm or more, sufficient wear resistance can be ensured. Thereby, even when the heat transfer sheet 55 is slid on the inner peripheral surface of the fixing belt 51, it is possible to suppress the generation of foreign matter due to wear. By setting the thickness of the heat transfer sheet 55 to 100 μm or less, sufficient thermal conductivity can be ensured.

  The heat transfer sheet 55 includes a connection portion 551 and a contact portion 552. The connection portion 551 is connected to the non-contact surface 53 b of the heating member 53. The connecting portion 551 is interposed between the holding member 54 and the heating member 53.

  The contact portion 552 extends from the connection portion 551 along the circumferential direction of the fixing belt 51, and contacts the inner peripheral surface of the fixing belt 51 that is different from the inner peripheral surface of the fixing belt 51 with which the heating member 53 contacts. . The contact portion 552 is provided to guide the fixing belt 51 to the fixing nip portion.

  Specifically, the contact portion 552 extends toward the upstream side in the rotation direction of the fixing belt 51 from the connection portion 551 in the portion located upstream of the fixing nip portion in the transport direction. The contact portion 552 contacts the inner peripheral surface of the fixing belt 51 on the upstream side of the fixing nip portion. The contact length of the contact portion 552 along the circumferential direction of the fixing belt 51 is, for example, 30 mm or more.

  Generally, when the toner image is fixed on the paper S in the fixing nip portion, the heat of the fixing belt 51 is taken away by the paper S. As a result, the temperature of the fixing belt 51 is likely to fluctuate before the fixing belt 51 transits to the next circumference, such as the first and second rounds.

  Here, in the fixing device 50 according to Embodiment 1, the heat transfer sheet 55 extends along the circumferential direction of the fixing belt 51 from the connection portion 551 that contacts the non-contact surface 53b. And a contact portion 552 that comes into contact with the inner peripheral surface of the fixing belt 51 at a portion different from the inner peripheral surface of the fixing belt 51 with which the heating member 53 contacts. As a result, the heating member 53 not only applies heat to the fixing belt 51 from the contact surface 53a, but also allows heat radiated from the non-contact surface 53b side to be conducted to the fixing belt 51 by the heat transfer sheet 55.

  For this reason, the heat generated by the heating member 53 can be effectively conducted to the fixing belt 51, and the heat taken away by the paper S when fixing the toner image on the paper S in the fixing nip portion is effective. Can be replenished. Accordingly, the fixing belt 51 can be sufficiently heated until the fixing belt 51 transits to the next circumference, and fluctuations in the temperature of the fixing belt 51 can be suppressed. As a result, in the fixing device 50 according to the first embodiment, it is possible to suppress the occurrence of a gloss level difference.

  Further, the contact portion 552 of the heat transfer sheet 55 contacts the fixing belt 51 on the upstream side in the rotation direction of the fixing belt 51 with respect to the fixing nip portion, so that the fixing belt 51 is heated immediately before being guided to the fixing nip portion. Can do. Thereby, when the fixing belt 51 rotates, it is possible to suppress the release of heat from the fixing belt 51. As a result, the fixing belt 51 can be heated more effectively.

(Embodiment 2)
FIG. 3 is a cross-sectional view of the fixing device according to the second embodiment. A fixing device 50A according to the second embodiment will be described with reference to FIG.

  As shown in FIG. 3, the fixing device 50 </ b> A according to the second embodiment is mainly different in the shape of the holding member 54 </ b> A when compared with the fixing device 50 according to the first embodiment. Other configurations are almost the same.

  The holding member 54A has a guide portion 543 that is positioned upstream of the fixing nip portion in the rotation direction of the fixing belt 51 and guides the fixing belt 51 to the fixing belt. The guide part 543 is integrally formed with the covering part 541 and the pressing part 542 by injection molding or the like. The guide portion 543 has a curved surface 543 a that slides on the inner peripheral surface of the fixing belt 51.

  The connecting portion 551 of the heat transfer sheet 55 is connected to a main surface located on the opposite side of the two main surfaces facing each other in the direction in which the heating member 53 and the pressure roller 52 are arranged, opposite to the pressure roller 52 side. Yes. The contact portion 552 of the heat transfer sheet 55 is folded from the upstream end side of the connection portion 551 toward the upstream in the rotation direction of the fixing belt 51 so as to be continuous with the curved surface 543a.

  Even in this case, the fixing device 50A according to the second embodiment can obtain substantially the same effect as that of the first embodiment.

  By providing the guide portion 543 as described above, it is possible to prevent the fixing belt 51 from being deformed when the fixing belt 51 is pulled into the fixing nip portion. Further, by integrally forming the covering portion 541, the pressing portion 542, and the guide portion 543, it is possible to improve the assembling accuracy in the image forming apparatus 100 as compared to the case where these are constituted by separate members. . Thereby, sufficient adhesion between the fixing belt 51 and the heat transfer sheet 55 can be ensured.

(Embodiment 3)
FIG. 4 is a cross-sectional view illustrating a configuration around the fixing nip portion in the fixing device according to the third embodiment. In FIG. 4, for convenience, the heating member 53, the holding member 54 </ b> A, the heat transfer sheet 55, and a later-described sheet member 56 of the fixing device 50 </ b> B are illustrated. A fixing device 50B according to the third embodiment will be described with reference to FIG.

  As shown in FIG. 4, the fixing device 50B according to the third embodiment is different from the fixing device 50A according to the second embodiment in that the sheet member 56 is provided and the guide portion 543B of the holding member 54. The shape is different. Other configurations are almost the same.

  The curvature of the curved surface 543a of the guide portion 543B is provided so as to decrease as it approaches the fixing nip portion. That is, the curvature radii R1, R2, and R3 of the curved surface 543a increase as the distance from the fixing nip portion approaches. The sheet member 56 is provided between the curved surface 543 a and the fixing belt 51. The friction coefficient of the sheet member 56 is smaller than the friction coefficient of the curved surface 543a.

  Even when configured as described above, the fixing device 50B according to the third embodiment can obtain substantially the same effect as the fixing device 50A according to the second embodiment.

  Further, as described above, the curvature of the curved surface 543a decreases as it approaches the fixing nip portion, so that the curvature of the fixing belt 51 can be reduced as it approaches the fixing nip portion near the entrance of the fixing nip portion. . As a result, fatigue of the fixing belt due to repeated pulling of the fixing belt into the fixing nip portion can be prevented. As a result, the life of the fixing belt can be extended.

  Further, by providing the sheet member 56 having a low friction coefficient, the frictional force acting on the fixing belt 51 can be reduced. As a result, it is possible to suppress a decrease in the conveyance speed of the fixing belt 51 and to suppress the occurrence of image misalignment.

(Embodiment 4)
FIG. 5 is a cross-sectional view showing a configuration around the fixing nip portion in the fixing device according to the fourth embodiment. 5, for the sake of convenience, the heating member 53, the holding member 54C, the heat transfer sheet 55, and the sheet member 56 of the fixing device 50C are illustrated. A fixing device 50C according to the fourth embodiment will be described with reference to FIG.

  As shown in FIG. 5, the fixing device 50C according to the fourth embodiment is different in the shape of the pressing portion 542C of the holding member 54 when compared with the fixing device 50B according to the third embodiment. Other configurations are almost the same.

  As shown in FIG. 5, the pressing portion 542 </ b> C is provided so that the thickness becomes thinner toward the upstream side in the rotation direction of the fixing belt 51.

  Even in this case, the fixing device 50C according to the fourth embodiment can obtain substantially the same effect as the fixing device 50B according to the third embodiment. In addition, when the pressing portion 542C has the shape as described above, the flexibility of the pressing portion 542C is increased. Accordingly, the pressing portion 542C is bent and deformed following the deformation of the fixing belt 51 accompanying the rotation operation of the fixing belt 51. As a result, the adhesion between the fixing belt 51 and the heat transfer sheet 55 can be further improved. Further, the fixing belt 51 can be prevented from meandering by the bending of the pressing portion 542C following the deformation of the fixing belt 51.

(Embodiment 5)
FIG. 6 is a cross-sectional view showing a configuration around the fixing nip portion in the fixing device according to the fifth embodiment. 6, for the sake of convenience, the heating member 53, the holding member 54D, the heat transfer sheet 55, and the fixing belt 51 of the fixing device 50D are illustrated. A fixing device 50D according to the fifth embodiment will be described with reference to FIG.

  As shown in FIG. 6, the fixing device 50D according to the fifth embodiment is different in the configuration of the holding member 54D from the fixing device 50 according to the first embodiment. Other configurations are almost the same.

  The covering portion 541 and the pressing portion 542 of the holding member 54 are configured by different members. Even in this case, the fixing device 50D according to the fifth embodiment can obtain substantially the same effect as the fixing device 50 according to the first embodiment.

(Verification experiment)
FIG. 7 is a diagram illustrating conditions and results of a first verification experiment performed to confirm the effect of the embodiment. With reference to FIG. 7, the 1st verification experiment performed in order to confirm the effect of embodiment is demonstrated.

  In the first verification experiment, toner images were fixed on a plurality of sheets using the fixing devices according to Examples 1 to 3 and the fixing devices according to Comparative Examples 1 and 2. At this time, the toner image fixed on the first turn of the fixing belt 51 and the toner image fixed on the second turn of the fixing belt 51 are visually observed to determine whether or not the difference in glossiness is noticeable. evaluated. Those that allowed a difference in glossiness by visual inspection were judged good, good, and excellent. Here, “good”, “good” and “excellent” indicate judgment criteria, and “excellent” has a light intensity difference reduced more than good, and “good” has a light intensity difference reduced more than good. Moreover, it was judged that the thing whose glossiness difference cannot be accept | permitted visually is improper.

  As fixing conditions, a fixing temperature was set to 180 ° C. by a temperature detection device and a temperature control device provided in the fixing nip portion, a process speed was set to 220 mm / sec, and a pressure contact force in the fixing nip portion was set to 450 N.

A3 size paper was used, and a color toner was laminated on a paper basis weight of 80 g / m ² to form a brown toner image. At this time, the toner adhesion amount on the paper was 10 g / m ^2, and an unfixed toner image was fixed using each fixing device.

  As the fixing devices according to Examples 1 to 3 and Comparative Example 2, the fixing device according to Embodiment 1 was used. In each fixing device, the thermal conductivity of the heat transfer sheet 55 was changed as shown in FIG. 7, and the length of the heat transfer sheet 55 along the circumferential direction of the fixing belt 51 was changed as shown in FIG.

  Specifically, in the fixing device according to Example 1, the heat conductivity of the heat transfer sheet 55 was set to 700 W / mK, and the length of the heat transfer sheet 55 was changed to 20 mm, 30 mm, 40 mm, and 50 mm. .

  In the fixing device according to Example 2, the heat conductivity of the heat transfer sheet 55 was 1000 W / mK, and the length of the heat transfer sheet 55 was changed to 20 mm, 30 mm, 40 mm, and 50 mm.

  In the fixing device according to Example 3, the heat conductivity of the heat transfer sheet 55 was 1350 W / mK, and the length of the heat transfer sheet 55 was changed to 20 mm, 30 mm, 40 mm, and 50 mm.

  In the fixing device according to Comparative Example 2, the heat conductivity of the heat transfer sheet 55 was 500 W / mK, and the length of the heat transfer sheet 55 was changed to 20 mm, 30 mm, 40 mm, and 50 mm.

  As the fixing device according to Comparative Example 1, the fixing device according to Embodiment 1 in which the heat transfer sheet 55 is omitted is used. That is, as the fixing device according to Comparative Example 1, one that does not include the heat transfer sheet 55 was used.

  As a result of the first verification experiment, in Example 1, a heat transfer sheet having a length of 20 mm was determined to be acceptable, a heat transfer sheet having a length of 30 mm was determined to be good, and the heat transfer sheet length was 40 mm and 50 mm were determined to be excellent.

  In Example 2, the heat transfer sheet having a length of 20 mm is determined to be acceptable, the heat transfer sheet having a length of 30 mm is determined to be good, and the heat transfer sheet has a length of 40 mm and 50 mm. The thing was judged as excellent.

  In Example 3, the heat transfer sheet having a length of 20 mm was determined to be good, and the heat transfer sheets having a length of 30 mm, 40 mm, and 50 mm were determined to be excellent.

  In Comparative Example 1, it was determined to be impossible. In Comparative Example 2, it was determined that the heat transfer sheet was impossible at any of 20 mm, 30 mm, 40 mm, and 50 mm.

  From the above results, by setting the thermal conductivity of the heat transfer sheet 55 to 700 W / mK or more, the heat generated by the heating member 53 can be quickly conducted to the fixing belt 51 and the occurrence of a gloss step is suppressed. It was confirmed experimentally that it was possible.

  The length of the heat transfer sheet 55 is preferably 20 mm or more, more preferably 30 mm or more, and more preferably 40 mm or more.

  FIG. 8 is a diagram illustrating conditions and results of a second verification experiment performed to confirm the effect of the embodiment. With reference to FIG. 8, the second verification experiment conducted to confirm the effect of the embodiment will be described.

  In the second verification experiment, whether or not the result of the visual observation in the first verification experiment was appropriate was confirmed using a glossiness measuring device. Specifically, in Examples 1 to 3 and Comparative Example 1 in the first verification experiment, the toner image fixed on the first round of the fixing belt 51 and the fixing belt 51 of 2 using the gloss measuring device. The glossiness of the toner image fixed on the periphery was measured, and the glossiness difference was calculated. As the glossiness measuring instrument, GMX-202 manufactured by Murakami Color Research Laboratory was used. The measurement result is as shown in FIG. 8, and a light intensity difference corresponding to the result of visual observation was obtained.

  FIG. 9 is a diagram illustrating conditions and results of a third verification experiment performed to confirm the effect of the embodiment. With reference to FIG. 9, the 3rd verification experiment performed in order to confirm the effect of embodiment is demonstrated.

  In the third verification experiment, 300,000 sheets and 600,000 sheets were printed using the fixing device according to Example 4 and Example 5, and the thickness of the fixing belt 51 was measured after each printing, whereby heat transfer The degree of wear of the sheet 55 was evaluated. As a measuring device for measuring the thickness of the fixing belt 51, a digital micrometer (manufactured by Mitutoyo Corporation) was used.

  As fixing conditions, a fixing temperature was set to 175 ° C. by a temperature detection device and a temperature control device provided in the fixing nip portion, a process speed was set to 220 mm / sec, and a pressure contact force in the fixing nip portion was set to 450 N.

As the paper, A4 size paper was used, a monochrome image having a printing rate of 6% was formed on a paper basis weight of 80 g / m ² , and an unfixed toner image was fixed using each fixing device.

  In Example 4, the fixing device according to Embodiment 1 was used. At this time, the heat conductivity of the heat transfer sheet 55 was 700 W / mK, the length of the heat transfer sheet 55 was 40 mm, and the thickness of the heat transfer sheet 55 before printing was about 100 μm.

  In Example 5, the fixing device according to Embodiment 2 was used. At this time, the heat conductivity of the heat transfer sheet 55 was 700 W / mK, the length of the heat transfer sheet 55 was 40 mm, and the thickness of the heat transfer sheet 55 before printing was about 100 μm.

  As shown in FIG. 9, in Example 4, the initial thickness of the fixing belt 51 is 98 μm, and the thickness of the fixing belt 51 after printing 300,000 sheets is 83 μm, after printing 600,000 sheets. The thickness of the fixing belt 51 was 75 μm.

  In Example 5, the thickness of the initial fixing belt 51 is 97 μm, the thickness of the fixing belt 51 after printing 300,000 sheets is 92 μm, and the thickness of the fixing belt 51 after printing 600,000 sheets. Was 86 μm.

  Comparing the results of Examples 4 and 5, by providing the guide portion 543 as in the fixing device according to the second embodiment, the friction force acting when the fixing belt 51 is pulled into the fixing nip portion is reduced. 51 and the guide part 543 can be said to have been able to act. Thus, it was confirmed that the wear resistance of the heat transfer sheet can be improved by providing the guide portion 543 and reducing the frictional force acting on the heat transfer sheet 55.

  As described above, the embodiment invented this time is illustrative in all points and is not restrictive. The scope of the present invention is defined by the terms of the claims, and includes meanings equivalent to the terms of the claims and all modifications within the scope.

  1C, 1K, 1M, 1Y Image forming unit, 10 photoconductor, 11 charging device, 12 exposure device, 13 developing device, 14 developing roller, 15C, 15K, 15M, 15Y toner bottle, 17 cleaning device, 30 intermediate transfer belt, 31 Primary transfer roller, 33 Secondary transfer roller, 37 Cassette, 38 Driven roller, 39 Drive roller, 40 Timing roller, 41 Transport path, 48 Tray, 50, 50A, 50B, 50C, 50D Fixing device, 51 Fixing belt, 52 Pressure roller, 53 heating member, 53a contact surface, 53b non-contact surface, 54, 54A, 54D holding member, 55 heat transfer sheet, 56 sheet member, 80 housing, 100 image forming apparatus, 101 control device, 541 Covering part, 542, 542C Pressing part, 543, 54 B guiding portion, 543a curved surface, 551 connecting portion, 552 contact.

Claims (11)

An endless fixing belt provided rotatably;
A heating member for heating the fixing belt;
A heat transfer sheet that conducts heat generated by the heating member to the fixing belt,
The heating member includes a contact surface that contacts the inner peripheral surface of the fixing belt, and a non-contact surface that does not contact the inner peripheral surface of the fixing belt,
The heat transfer sheet includes a connecting portion that comes into contact with the non-contact surface and a contact portion that comes into contact with the inner peripheral surface of the fixing belt that is different from the inner peripheral surface of the fixing belt with which the heating member comes into contact. , Fixing device. A pressure member disposed outside the fixing belt and forming a fixing nip portion by pressing the fixing belt;
The fixing device according to claim 1, wherein the contact portion is in contact with the fixing belt on the upstream side in the rotation direction of the fixing belt with respect to the fixing nip portion. A holding member for holding the heating member;
The holding member includes a guide portion that is positioned upstream of the fixing nip portion in the rotation direction of the fixing belt and guides the fixing belt to the fixing nip portion.
The fixing device according to claim 2, wherein the guide portion has a curved surface that slides on an inner peripheral surface of the fixing belt.   The fixing device according to claim 3, wherein a curvature of the curved surface becomes smaller as approaching the fixing nip portion.   The fixing device according to claim 3, wherein a sheet member having a friction coefficient lower than that of the curved surface is provided between the curved surface and the fixing belt. A holding member for holding the heating member;
In the heat transfer sheet, the contact portion extends along a circumferential direction of the fixing belt,
The fixing device according to claim 1, wherein the holding member has a pressing portion that presses the contact portion toward the fixing belt.   The fixing device according to claim 6, wherein the pressing portion has a curved shape that curves along the circumferential direction of the fixing belt, and the thickness becomes thinner toward an upstream side in the rotation direction of the fixing belt.   The fixing device according to claim 1, wherein the heat transfer sheet has a thermal conductivity of 700 W / mK or more.   The fixing device according to claim 1, wherein a thickness of the heat transfer sheet is 40 μm or more and 100 μm or less.   The fixing device according to claim 1, wherein the heat transfer sheet is a graphite sheet. An image forming unit that forms a toner image on a recording medium conveyed along a conveying path;
An image forming apparatus comprising: a fixing device according to claim 1, which fixes a toner image on the recording medium transported along the transport path.

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