JP2011128278A - Fixing device and image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fixing device capable of maintaining the distribution of pressure for pressing a fixing belt adjusted by a pressing member and stabilizing fixing performance while suppressing the generation of electrostatic noise and the generation of image noise, and an image forming apparatus. <P>SOLUTION: The fixing device 130 includes: a heating roller 131 and a fixing belt 132 that are mutually circumscribed so as to form a nip N; a rubber pressing member 135: a resin pressing member 136; a slide sheet 134; and a conductive sheet 137 disposed between the slide sheet 134, and the rubber pressing member 135 and an abutting part 136a of the resin pressing member 136. The conductive sheet 137 is disposed in a specific area R that, in relation to the conveyance direction of a paper sheet S, corresponds to a part of an area occupied by the rubber pressing member 135 and the abutting part 136a of the resin pressing member 136, and also corresponds to a part other than the section upstream of the nip N of the area occupied by the slide sheet 134. <P>COPYRIGHT: (C)2011,JPO&amp;INPIT

Description

  The present invention relates to a fixing device used in, for example, an electrophotographic copying machine, a printer, a facsimile, and the like, and an image forming apparatus having the fixing device.

  Conventionally, this type of fixing device includes a heating roller and a fixing belt that rotate together in contact with each other, a heater that heats the heating roller, and an inner surface of the fixing belt disposed inside the fixing belt. Some include a pressing member that presses against the heating roller, and a sliding sheet that is interposed between the fixing belt and the pressing member to reduce the sliding resistance of the fixing belt.

  Here, the fixing belt and the sliding sheet are easily charged by friction, and in the charged state, electrostatic noise and image noise are generated. For this reason, the said sliding sheet is provided with the electroconductive surface layer and the electroconductive layer which has the electroconductivity distribute | arranged to the lower layer of the said surface layer. The conductive layer includes a base material layer including a heat-resistant woven fabric and a back surface layer including a heat-resistant resin, and at least one of the base material layer and the back surface layer is conductive (for example, Patent Document 1: JP 2008-275927 A, FIG. 3).

Japanese Patent Laid-Open No. 2008-275927, FIG.

  However, in the conventional sliding sheet, since the conductive layer is provided in the entire area of the sliding sheet, the sliding sheet becomes thicker and harder as a whole, and the fixing member adjusted by the pressing member is used. There is a problem in that the pressure distribution for pressing the belt changes and the fixing performance deteriorates.

  Accordingly, an object of the present invention is to maintain the pressure distribution for pressing the fixing belt adjusted by the pressing member and to stabilize the fixing performance while suppressing the generation of electrostatic noise and image noise. An object of the present invention is to provide a fixing device and an image forming apparatus.

In order to solve the above-described problem, the fixing device of the present invention includes:
A cylindrical roller and an annular endless belt circumscribed with each other so as to form a nip portion for fixing;
A heating source for heating at least one of the cylindrical roller and the endless belt to a temperature for fixing;
A pressing member that presses the inner peripheral surface of the endless belt toward the cylindrical roller;
In order to reduce friction with respect to the pressing member when the endless belt rotates in the circumferential direction, at least the pressing from the upstream side of the nip with respect to the transport direction of the recording material that is nipped and transported by the nip. A sliding sheet disposed over the entire area between the member and the endless belt pressed by the pressing member;
A conductive sheet disposed between the sliding sheet and the pressing member;
The conductive sheet corresponds to at least a part of the area occupied by the pressing member in the conveyance direction of the recording material, and is a part of the area occupied by the sliding sheet excluding the upstream side of the nip portion. It is characterized by being arranged in a corresponding specific area.

  In the fixing device of the present invention, the recording material to be conveyed while being nipped by the nip portion is less than the nip portion so as to reduce friction with respect to the pressing member when the endless belt rotates in the circumferential direction. From the upstream side, a sliding sheet is disposed over the entire region between at least the endless belt pressed by the pressing member and the pressing member. Therefore, the sliding resistance of the endless belt can be reduced. A conductive sheet is disposed between the sliding sheet and the pressing member. Therefore, according to the fixing device of the present invention, generation of electrostatic noise and image noise can be suppressed (data will be described and described in the embodiments described later).

  In the fixing device of the present invention, the conductive sheet corresponds to at least a part of the area occupied by the pressing member in the conveyance direction of the recording material, and the nip of the area occupied by the sliding sheet. It is arranged in a specific area corresponding to a portion excluding the upstream side of the portion. That is, the area occupied by the conductive sheet is smaller in the conveyance direction of the recording material than in the case where a conductive layer is provided over the entire sliding sheet as in the conventional example (Patent Document 1). For this reason, the pressure distribution in which the pressing member presses the sliding sheet with respect to the transport direction is not easily lost. Therefore, according to this fixing device, it is possible to maintain the pressure distribution for pressing the endless belt adjusted by the pressing member and stabilize the fixing performance while suppressing the generation of electrostatic noise and image noise. it can.

  In the fixing device according to an embodiment, the pressing member includes a first pressing member made of rubber disposed upstream with respect to the transport direction, and a resin harder than the rubber disposed downstream with respect to the transport direction. The specific area in which the conductive sheet is arranged is an area corresponding to a part of the area occupied by the second pressing member.

  In this fixing device, the second pressing member made of resin is harder than the first pressing member made of rubber. Therefore, the recording material that has been fixed can be peeled off favorably from the roller and the endless belt. Moreover, the area | region corresponding to a part of area | region which the said press member in which the said electrically conductive sheet is arrange | positioned is an area | region corresponding to a part of area | region which the said 2nd press member occupies. Therefore, the conductive sheet has less influence on the pressure distribution than when the conductive sheet is not disposed in a region corresponding to a part of the region occupied by the second pressing member. As a result, the fixing performance can be more easily stabilized.

  In the fixing device according to an embodiment, the conductive sheet is a conductor made of any of metal, conductive resin, and conductive rubber.

  In this fixing device, since the conductive sheet is a conductor made of any one of metal, conductive resin, and conductive rubber, the conductive sheet can be made conductive.

  In the fixing device of one embodiment, at least a part of the conductive sheet has a slit shape, a hole shape, or a net-like structure.

  In this fixing device, at least a part of the conductive sheet has a slit shape, a hole shape, or a net-like structure, and therefore, for example, compared to a case where the conductive sheet is provided in a continuous layer shape as in the conventional example (Patent Document 1). Thus, the conductive sheet is soft. Accordingly, since the influence of the conductive sheet on the pressure distribution is small, the fixing performance can be more easily stabilized.

  In the fixing device of one embodiment, the conductive sheet is grounded.

  In this fixing device, since the conductive sheet is grounded, generation of electrostatic noise and image noise can be suppressed more reliably (data will be described and described in an embodiment described later).

  An image forming apparatus according to the present invention includes the above-described fixing device.

  According to the image forming apparatus of the present invention, it is possible to maintain the pressure distribution for pressing the fixing belt adjusted by the pressing member and stabilize the fixing performance while suppressing the generation of electrostatic noise and image noise. Can do.

  According to the fixing device of the present invention, it is possible to maintain the pressure distribution for pressing the fixing belt adjusted by the pressing member and stabilize the fixing performance while suppressing the generation of electrostatic noise and image noise. it can.

  According to the image forming apparatus of the present invention, since the fixing device described above is provided, the pressure distribution for pressing the fixing belt adjusted by the pressing member is maintained while suppressing generation of electrostatic noise and image noise. Thus, the fixing performance can be stabilized.

1 is a diagram illustrating a cross-sectional structure of an image forming apparatus including a fixing device according to an embodiment of the present invention. It is a figure for demonstrating the structure of the principal part of the said fixing apparatus. FIG. 3 is a cross-sectional view illustrating a configuration of a fixing belt (insulating belt) forming a part of the fixing device. It is sectional drawing which shows the structure of the electrically conductive belt used for the comparison with the said fixing belt. It is a figure which shows the measurement result of the electrostatic noise of the image forming apparatus provided with the said fixing device. FIG. 6 is a diagram illustrating a measurement result of electrostatic noise when an electrically conductive sheet is not used in an image forming apparatus including the fixing device. FIG. 6 is a diagram illustrating a measurement result of electrostatic noise when a conductive belt is used instead of an insulating belt and a conductive sheet is not used in the image forming apparatus including the fixing device. FIG. 6 is a diagram illustrating a measurement result of electrostatic noise when the conductive sheet is not grounded in the image forming apparatus including the fixing device. It is a figure which shows the measurement result of the pressure distribution in the nip part of the said fixing device compared with a prior art example (patent document 1). It is a figure which shows the pattern shape of the modification of the said electrically conductive sheet. It is a figure which shows the other example of the pattern shape for the said electrically conductive sheets. It is a figure which shows the further another example of the pattern shape for the said electrically conductive sheets.

  Hereinafter, the present invention will be described in detail with reference to illustrated embodiments.

  FIG. 1 shows a cross-sectional structure of a color tandem type image forming apparatus 100 including a fixing device 130 according to an embodiment of the present invention. The image forming apparatus 100 includes an intermediate transfer belt 108 as an annular image carrier that moves in a circumferential direction and is wound around three rollers 102, 104, and 106, approximately at the center in the main body casing 101. . Of the three rollers, two rollers 102 and 104 are arranged vertically apart from each other on the left side in the figure, and the remaining rollers 106 are arranged on the right side in the figure. The intermediate transfer belt 108 is supported by these rollers 102, 104, and 106 and is driven to rotate in the arrow X direction.

  Below the intermediate transfer belt 108, in order from the left side in the figure, an image forming unit 110Y as an image forming unit corresponding to each color toner of yellow (Y), magenta (M), cyan (C), and black (K), 110M, 110C, and 110K are arranged side by side.

  The image forming units 110Y, 110M, 110C, and 110K are configured in exactly the same manner except for the difference in the toner colors that they handle. Specifically, for example, the yellow image forming unit 110 </ b> Y includes a photosensitive drum 190, a charging device 191, an exposure device 192, a developing device 193 that performs development using toner, and a cleaner device 195. It is configured. A primary transfer roller 194 is provided at a position facing the photosensitive drum 190 with the intermediate transfer belt 108 interposed therebetween. At the time of image formation, the surface of the photosensitive drum 190 is first uniformly charged by the charging device 191. Subsequently, the surface of the photosensitive drum 190 is changed by the exposure device 192 in accordance with an image signal input from an external device (not shown). When exposed, a latent image is formed there. Next, the latent image on the surface of the photosensitive drum 190 is developed by the developing device 193 to become a toner image. This toner image is transferred to the intermediate transfer belt 108 by applying a voltage between the photosensitive drum 190 and the primary transfer roller 194. The transfer residual toner on the surface of the photosensitive drum 190 is cleaned by a cleaner device 195.

  As the intermediate transfer belt 108 moves in the arrow X direction, four color toner images are superimposed on the intermediate transfer belt 108 by the image forming units 110Y, 110M, 110C, and 110K.

  On the left side of the intermediate transfer belt 108, a cleaning device 125 that removes residual toner from the surface of the intermediate transfer belt 108 and a toner collection box 126 that is removed by the cleaning device 125 are provided. A secondary transfer roller 112 is provided on the right side of the intermediate transfer belt 108 with a conveyance path 124 for a sheet S as a recording material interposed therebetween. A fixing device 130 for fixing the toner to the paper S is provided at the upper right portion in the main body casing 101.

  When the sheet S on which the toner image is transferred passes through the fixing device 130, the toner image is fixed on the sheet S. In addition, a paper feed cassette 116 that stores paper S as a recording medium is provided at a lower portion of the main body casing 101.

  At the time of image formation, the paper S is sent one by one from the paper feed cassette 116 to the transport path 124 by the paper feed roller 118, and sent to the toner transfer position between the intermediate transfer belt 108 and the secondary transfer roller 112 by the transport roller 120. It is. On the other hand, as described above, four color toner images are formed on the intermediate transfer belt 108 by the image forming units 110Y, 110M, 110C, and 110K. The four-color toner images on the intermediate transfer belt 108 are transferred by the secondary transfer roller 112 to the sheet S sent to the toner transfer position described above. The sheet S on which the toner image is transferred is fixed on the sheet S by the fixing device 130. Then, the paper S on which the toner image is fixed is discharged by a paper discharge roller 121 to a paper discharge tray portion 122 provided on the upper surface of the main body casing 101.

  Next, the fixing device 130 will be described in detail.

  FIG. 2 shows a specific configuration example of the fixing device 130. FIG. 2 is a cross-sectional view of the sheet S conveyed through the nip portion N as viewed along the width direction.

  In the configuration example of the fixing device 130, as shown in FIG. 2, the fixing device 130 includes a heating roller 131 as a cylindrical roller and an annular fixing belt 132 as an endless belt circumscribing the heating roller 131. ing. The heating roller 131 is supported on the main body casing 101 via a frame (not shown), and is rotated around its own central axis by a drive motor (not shown).

  Inside the heating roller 131, a heater 133 is provided as a heating source for heating the heating roller 131 to a temperature for fixing.

  Inside the fixing belt 132, as a pressing member, a rubber pressing member 135 as a first pressing member is disposed on the upstream side with respect to the transport direction of the paper S, and as a second pressing member on the downstream side with respect to the transport direction. A resin pressing member 136 is disposed. The rubber pressing member 135 and the resin pressing member 136 are supported by the support member 138 and press the inner peripheral surface of the fixing belt 132 toward the heating roller 131. The support member 138 is supported by the main body casing 101 by a frame (not shown). As a result, the fixing belt 132 is pressed against the heating roller 131, and a nip portion N for fixing is formed. In this example, the shape of the nip portion N is such that the heating roller 131 is convex with respect to the fixing belt 132.

  The heating roller 131 has a two-layer structure of a core bar 131A and a surface layer 131B. The core bar 131A is preferably made of a metal material such as aluminum or iron so as to have mechanical strength. The core bar 131A has a pipe shape, and in this example, the thickness is about 0.1 mm to 5 mm. The surface layer 131B is a tube made of a fluororesin such as PFA (tetrafluoroethylene perfluoroalkyl vinyl ether copolymer), PTFE (polytetrafluoroethylene), ETFE (ethylene tetrafluoroethylene) or the like so as to have releasability on the surface. It is formed by the coating which consists of the same fluororesin. The thickness of the surface layer 131B is desirably about 5 μm to 100 μm. Examples of fluorine-based tubes include PFA350-J, 451HP-J, and 951HP Plus manufactured by Mitsui DuPont Fluorochemical Co., Ltd.

  As shown in FIG. 3A, the fixing belt 132 has a three-layer structure of the base material 10, the primer layer 20, and the surface layer 30 in this example. The substrate 10 is made of polyimide. The surface layer 30 is made of PFA so that the surface 30a has releasability. The primer layer 20 between the surface layer 30 and the base material 10 is preferably made of a material having elasticity and high heat resistance such as silicone rubber and fluororubber. The fixing belt 132 is an insulating belt and has a thickness of 150 μm.

  The rubber pressing member 135 shown in FIG. 2 is made of silicone rubber. The thickness of the rubber pressing member 135 is arbitrary, but is preferably about 0.1 mm to 10 mm. The rubber pressing member 135 may be integrally attached to a metal plate such as SUS (stainless steel), aluminum, or iron from the viewpoint of assembling property, productivity, and the like.

  The resin pressing member 136 is made of a heat resistant resin that is harder than the rubber pressing member 135 and has a substantially L-shaped cross section. Therefore, the sheet S that has been fixed can be peeled off favorably from the heating roller 131 and the fixing belt 132.

  Further, the short side of L of the resin pressing member 136 constitutes a contact portion 136 a that contacts the sliding sheet 134, and the long side of L of the resin pressing member 136 constitutes a base portion 136 b that supports the rubber pressing member 135. is doing. The rubber pressing member 135 described above is accommodated in an L-shaped depression of the resin pressing member 136.

  Further, a sliding sheet 134 is provided over the entire area between the fixing belt 132 and the contact portion 136a of the rubber pressing member 135 and the resin pressing member 136 from the upstream side of the nip portion N with respect to the transport direction. Yes. The upstream portion 134 a of the sliding sheet 134 is sandwiched between the base portion 136 b of the resin pressing member 136 and the support member 138 and is indirectly fixed to the main body casing 101. Therefore, the sliding sheet 134 can reduce the friction with respect to the contact part 136a of the rubber pressing member 135 and the resin pressing member 136 when the fixing belt 132 rotates in the circumferential direction.

  Further, a conductive sheet 137 is disposed between the sliding sheet 134 and the contact portion 136a of the rubber pressing member 135 and the resin pressing member 136. The conductive sheet 137 corresponds to a part of the region occupied by the contact portion 136a of the rubber pressing member 135 and the resin pressing member 136 with respect to the conveying direction, and from the nip portion N in the region occupied by the sliding sheet 134. Are also arranged in the specific region R corresponding to the portion excluding the upstream side.

  The conductive sheet 137 is made of an aluminum plate member having a thickness of 30 μm, a width of 260 mm, and a length of 8 mm, and has conductivity.

  Regarding the conveyance direction of the paper S, the length of the nip portion N is 7 mm. Similarly, the length of the nip portion corresponding to the rubber pressing member 135 is 5.5 mm, and the length of the nip portion corresponding to the contact portion 136a of the resin pressing member 136 is 1.5 mm.

  In this example, the sheet S to which the toner 91 is attached is sent to a nip portion N formed by the heating roller 131 and the fixing belt 132 as shown in FIG. Here, the heating roller 131 is previously heated to a predetermined target temperature (fixing temperature) by a heater 133 together with a portion corresponding to the nip portion N of the fixing belt 132. Therefore, as the sheet S is conveyed through the nip portion N, the toner 91 is melted by being pressurized and heated. As a result, the image is fixed on the paper S. The sheet S on which the image is fixed is discharged through the nip portion N in this example.

  Next, electrostatic noise of the fixing device will be described.

  Specifically, EMI (Electro Magnetic) for the image forming apparatus 100 including the fixing device 130 (hereinafter referred to as “Example 1”) and Comparative Example 1, Comparative Example 2, and Example 2 shown below as objects of comparison. The level of electrostatic noise is measured according to EN55022 CLASS B, one of the standards.

  Table 1 shows the main configuration of each fixing device of the comparative example 1, the comparative example 2 and the comparative example 2 as compared with the configuration of the practical example 1.

  Here, Comparative Example 1 differs from Example 1 only in that there is no conductive sheet 137. Further, Comparative Example 2 is different from Example 1 only in that there is no conductive sheet 137 and the fixing belt 132 is the conductive belt 132A. Here, as shown in FIG. 3B, the conductive belt 132 </ b> A has a three-layer structure of the base material 10, the conductive primer layer 21, and the surface layer 30. The substrate 10 is made of polyimide. The surface layer 30 is made of PFA so that the surface 30a has releasability. The conductive primer layer 21 between the surface layer 30 and the base material 10 is made of a material having conductivity and high heat resistance by dispersing a conductive material such as carbon. In this comparative example 2, since conductive materials such as carbon are dispersed, there are drawbacks that manufacturing becomes difficult and cost increases. Furthermore, the second embodiment is different from the first embodiment only in that the conductive sheet 137 has no ground.

  4A to 4D show the results of measuring the level of electrostatic noise for Example 1, Comparative Example 1, Comparative Example 2, and Example 2, together with the limit value of EN55022 CLASS B. FIG.

  The vertical axis in FIGS. 4A to 4D represents the level of electrostatic noise (unit: dB (μV / m)), and the horizontal axis represents frequency (unit: MHz). Moreover, the thick line L10 in FIG. 4A-FIG. 4D represents the limit value (converted value) of EN55022 CLASS B. Here, the limit value (converted value) is defined in the EN55022 CLASS B as the limit value of “when measured at a protection distance of 10 m from the measurement target”, whereas Since it was performed at a protective distance of 6 m from the measurement object, it means a value obtained by converting the limit value in the case of 10 m in accordance with 6 m. According to EN55022 CLASS B, the limit value of “when measured at a protection distance of 10 m from the object to be measured” is that the level of electrostatic noise is 30 dB from a frequency of 30 MHz to 230 MHz, and the frequency is from 230 MHz to 1000 MHz. The level of electrostatic noise is 37 dB.

  i) A solid line L20 and a broken line L21 in FIG. 4A indicate the measurement results of the level of electrostatic noise in the vertical and horizontal directions in Example 1, respectively. As can be seen from FIG. 4A, the solid line L20 and the broken line L21 are at a lower level than the thick line L10 at any frequency. Thus, according to Example 1, it has confirmed that generation | occurrence | production of electrostatic noise was suppressed within the limit value of EN55022 CLASS B.

  ii) A solid line L22 and a broken line L23 in FIG. 4B indicate the measurement results of the level of electrostatic noise in the vertical and horizontal directions of Comparative Example 1, respectively. As can be seen from FIG. 4B, the solid line L22 and the broken line L23 are at a higher level than the thick line L10 depending on the frequency. Thus, it was confirmed that without the conductive sheet 137, the generation of electrostatic noise could not be suppressed within the limit value of EN55022 CLASS B.

  iii) A solid line L24 and a broken line L25 in FIG. 4C indicate the measurement results of the level of electrostatic noise in the vertical and horizontal directions of Comparative Example 2, respectively. As can be seen from FIG. 4C, at a frequency of about 180 MHz, the solid line L24 and the broken line L25 are lower than the thick line L10 at any frequency except that the solid line L24 is at a higher level than the thick line L10 at one location. It is a level. If the conductive belt 132A is used in this way, the generation of electrostatic noise can be substantially suppressed within the limit value of EN55022 CLASS B.

  iv) A solid line L26 and a broken line L27 in FIG. 4D indicate the measurement results of the level of electrostatic noise in the vertical and horizontal directions in Example 2, respectively. As can be seen from FIG. 4D, the solid line L26 and the broken line L27 are at a lower level than the thick line L10 at any frequency. Further, when the conductive sheet 137 has a ground (see FIG. 4A), when there is no ground (see FIG. 4D), the amount of noise generated is particularly large in the vicinity of the frequency of about 300 MHz. Thus, in this fixing device 130, since the conductive sheet 137 has a ground, the generation of electrostatic noise and image noise can be suppressed more reliably.

  Further, in the fixing device 130, generation of electrostatic noise can be suppressed within the limit value of EN55022 CLASS B without using the costly conductive belt 132A. Therefore, an inexpensive fixing device 130 can be provided.

  Next, the pressure distribution for pressing the fixing belt 132 adjusted by the rubber pressing member 135 and the resin pressing member 136 at the nip portion N of the fixing device 130 will be described based on actual measurement results.

  FIG. 5 shows the measurement result of the pressure distribution at the nip portion N of the fixing device 130 in comparison with the conventional example (Patent Document 1). The vertical axis in FIG. 5 represents the pressure distribution value, and the horizontal axis represents the pressure measurement position in the transport direction of the paper S. Here, a solid line L30 and a broken line L31 in FIG. 5 indicate the results of pressure measurement in Example 1 and Comparative Example 3 shown below, respectively. The pressure distribution value represents a value obtained by averaging the pressure measurement values at a plurality of pressure measurement positions provided in the width direction of the paper S (the pressure measurement positions in the transport direction are the same). As shown in the lower part of FIG. 5, the comparative example 3 does not have the conductive sheet 137 as compared with the example 1, and the resin sheet 134 </ b> A having a thickness of 25 μm in which the entire surface of the sliding sheet 134 is subjected to the conductive treatment. The only difference is that is provided.

  As a result of this pressure measurement, the pressure distribution value in the region corresponding to the region occupied by the rubber pressing member 135 is substantially constant in the pressure distribution L30 of the first embodiment, whereas it is large in the pressure distribution L31 of the third comparative example. It has fluctuated. Therefore, in Example 1, compared with Comparative Example 3, the area occupied by the conductive sheet 137 in the conveyance direction of the paper S is small, so that it was confirmed that the pressure distribution is not easily broken.

  In general, the peak value (target value is 125 or more) of the pressure distribution that presses the fixing belt 132 has the greatest influence on the fixing performance of this type of fixing device. Here, from the result of the pressure measurement shown in FIG. 5, the peak value in the pressure distribution L30 of Example 1 is 128, whereas the peak value in the pressure distribution L31 of Comparative Example 3 is 118. Therefore, in Example 1, the peak value of the pressure distribution in the resin pressing member exceeded the target value, and it was confirmed that fixing performance could be ensured.

  As described above, according to the image forming apparatus 100, it was confirmed that the fixing performance can be stabilized while maintaining the pressure distribution while suppressing the generation of electrostatic noise and image noise.

  FIG. 6A shows a pattern shape of a conductive sheet 137A as a modification of the conductive sheet 137. The conductive sheet 137A is provided with a plurality of slits 137A1 each having a length of 6 mm. The slits 137 </ b> A <b> 1 are provided from one upstream side toward the downstream side in the transport direction of the paper S, and are provided at intervals of 3 mm in the width direction of the paper S.

  In the fixing device 130 of this modified example, the conductive sheet 137A is provided with a plurality of slits 137A1, so that the conductive sheet 137A is compared with the case where the conductive sheet 137A is provided in a continuous layer shape as in the conventional example (Patent Document 1). Constructed softly. Therefore, when this conductive sheet 137A is used, the influence on the pressure distribution is reduced and the fixing performance can be more easily stabilized.

  The conductive sheet may be, for example, a wire net having a wire diameter of 1 mm × 12 mesh as shown in FIG. 6B or a punch having a hole diameter of 1 mm as shown in FIG. A plate-like member having a hole 137C1 may be used. In these cases as well, the conductive sheet is configured softer than in the case where the layers are provided in a continuous layer as in the conventional example (Patent Document 1). Therefore, when these conductive sheets are used, the influence on the pressure distribution is reduced and the fixing performance can be more easily stabilized.

  The conductive sheet 137 and the conductive sheets 137A, 137B, and 137C of each of the above-described modifications are plate members made of aluminum, but are not limited thereto, and are made of other metals such as SUS and iron, conductive resins, conductive rubbers, and the like. A member made of a highly conductive material may be used.

  In the above embodiment, the core bar 131A of the heating roller 131 has a pipe shape. However, the core bar 131A may be solid or may have a cross-sectional shape such as a three-headed shape.

  The image forming apparatus may be a monochrome / color copying machine, a printer, a fax machine, or a multifunction machine.

  Moreover, the content given this time is an example, and a structure and material are not restricted to this. It may be changed in a timely manner according to the device.

DESCRIPTION OF SYMBOLS 100 Image forming apparatus 130 Fixing apparatus 131 Heating roller 132 Fixing belt 133 Heater 134 Sliding sheet 135 Rubber pressing member 136 Resin pressing member 137 Conductive sheet 137A Conductive sheet 137B Conductive sheet 137C Conductive sheet N Nip part R Specific area S Paper

Claims (6)

A cylindrical roller and an annular endless belt circumscribed with each other so as to form a nip portion for fixing;
A heating source for heating at least one of the cylindrical roller and the endless belt to a temperature for fixing;
A pressing member that presses the inner peripheral surface of the endless belt toward the cylindrical roller;
In order to reduce friction with respect to the pressing member when the endless belt rotates in the circumferential direction, at least the pressing from the upstream side of the nip with respect to the transport direction of the recording material that is nipped and transported by the nip. A sliding sheet disposed over the entire area between the member and the endless belt pressed by the pressing member;
A conductive sheet disposed between the sliding sheet and the pressing member;
The conductive sheet corresponds to at least a part of the area occupied by the pressing member in the conveyance direction of the recording material, and is a part of the area occupied by the sliding sheet excluding the upstream side of the nip portion. A fixing device which is arranged in a corresponding specific area. The fixing device according to claim 1,
The pressing member includes a first pressing member made of rubber disposed on the upstream side in the transport direction, and a second pressing member made of resin harder than the rubber disposed on the downstream side in the transport direction. Consists of
The fixing device, wherein the specific region in which the conductive sheet is disposed is a region corresponding to a part of a region occupied by the second pressing member. The fixing device according to claim 1 or 2,
The fixing device, wherein the conductive sheet is a conductor made of any of metal, conductive resin, and conductive rubber. In the fixing device according to any one of claims 1 to 3,
At least a part of the conductive sheet has a slit shape, a hole shape, or a net-like structure. In the fixing device according to any one of claims 1 to 4,
The fixing device, wherein the conductive sheet is grounded.   An image forming apparatus comprising the fixing device according to claim 1.

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