JP2009204924A - Fixing device and image forming apparatus equipped with the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fixing device and an image forming apparatus that are able to maintain a stable pressing state, without the displacement of a pressing section or a sliding sheet, when a fixing belt unit is brought into pressure-contact with a fixing roller. <P>SOLUTION: The fixing device includes: a heat roller; an endless belt rotated while being brought into contact with the heat roller; a sliding sheet disposed on the inside of the belt member; a pressing means disposed on the inside of the sliding sheet and pressing the sliding sheet and the belt member against the heat roller; a holding member that holds the sliding sheet and pressing means; a positioning member that positions the sliding sheet to the holding member; a pressure-contact/pressure-contact releasing means that brings the heat roller into pressure-contact with the belt member or releases the pressure-contact of the heat roller with the belt member. In the fixing device, the positioning member fixes the leading and trailing ends of the sliding sheet in the rotating direction of the belt member, thereby positioning the sliding sheet to the predetermined part of the holding member. The image forming apparatus is also disclosed. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a fixing device using a belt nip system and an image forming apparatus including the same.

  In an electrophotographic image forming apparatus such as a copying machine, a printer, a facsimile machine, and a multifunction machine having these functions, there are various configurations of fixing devices used. In recent years, due to demands for higher speed and shorter warm-up time, a fixing roller, an endless belt in contact with the fixing roller, and a non-rotating pressing portion inside the endless belt are arranged to secure a nip width during fixing. A nip method has been proposed.

  In this belt nip method, the pressing portion is pressed against the fixing roller across the endless belt, but if the belt is stopped for a long time after the image is formed, the fixing roller is dented or the fixing belt is deformed, resulting in uneven rotation. And cause uneven fixing.

As a countermeasure against this problem, a technique is disclosed in which the endless belt portion is separated from the fixing roller after the end of the image forming job (see, for example, Patent Document 1).
JP 2006-126536 A

  However, in the configuration of Patent Document 1, the position of the sliding sheet disposed for the purpose of reducing the frictional resistance between the pressing portion and the endless belt and the position of the pressing portion are easily shifted at the time of re-pressing after separation. There is a problem that it is difficult to maintain a stable pressing state in the nip portion. If a stable pressing state is not maintained at the nip portion, defects such as unevenness in image density and misalignment tend to occur.

  The object of the present invention is to solve the above-described problems, and when the pressing portion presses the fixing roller with the endless belt and the sliding sheet sandwiched therebetween, the pressing portion and the sliding sheet are not displaced and the stable pressing state is achieved. And a fixing device capable of maintaining the above, and an image forming apparatus including the same.

  The object of the present invention can be achieved by using a fixing device having the following configuration and an image forming apparatus having the same.

That is,
1. A heating roller; an endless belt member that rotates while contacting the heating roller; a sliding sheet disposed inside the belt member; and the sliding sheet disposed inside the sliding sheet. And a pressing means for pressing the belt member against the heating roller, a holding member for holding the sliding sheet and the pressing means, a positioning member for positioning the sliding sheet at a predetermined position of the holding member, In the fixing device having a pressure contact / pressure contact release means for pressing or releasing the pressure contact between the heating roller and the belt member, the positioning member fixes the front end portion and the rear end portion of the sliding sheet in the belt member rotation direction. A fixing device, wherein the sliding sheet is positioned at a predetermined position of the holding member,
as well as,
An image forming apparatus comprising the fixing device according to 2.1,
It is.

  When the configuration according to the present invention is used, when the pressing portion presses the fixing roller with the endless belt interposed therebetween, the fixing device can maintain a stable pressing state in which the position of the pressing portion and the sliding sheet does not shift, And an image forming apparatus including the same. As a result, it is possible to suppress the occurrence of defects such as image density unevenness and deviation.

  The present invention will be described based on the illustrated embodiment, but the present invention is not limited to the embodiment.

  FIG. 1 is a schematic configuration diagram for explaining an embodiment of an image forming apparatus according to the present invention.

  The image forming apparatus includes an image forming apparatus main body GH and an image reading apparatus YS.

  The image forming apparatus main body GH is called a tandem type color image forming apparatus, and a plurality of sets of image forming units 10Y, 10M, 10C, and 10K, a belt-like intermediate transfer member 6, a sheet feeding and conveying unit, a fixing device 9, and the like. Consists of.

  An image reading device YS including an automatic document feeder 201 and a document image scanning exposure device 202 is installed on the upper part of the image forming apparatus main body GH. The document d placed on the document table of the automatic document feeder 201 is transported by a transport unit, and an image on one or both sides of the document is scanned and exposed by the optical system of the document image scanning exposure device 202, and the line image sensor CCD is scanned. Is read.

  A signal formed by photoelectric conversion by the line image sensor CCD is subjected to analog processing, A / D conversion, shading correction, image compression processing, and the like in an image processing unit, and then exposure means 3Y, 3M, 3C, 3K. Sent to.

  In the image forming unit 10Y that forms a yellow (Y) image, a charging unit 2Y, an exposure unit 3Y, a developing unit 4Y, and a cleaning unit 8Y are arranged around the photosensitive drum 1Y. The image forming unit 10M that forms a magenta (M) color image includes a charging unit 2M, an exposure unit 3M, a developing unit 4M, and a cleaning unit 8M around the photosensitive drum 1M. In the image forming unit 10C that forms a cyan (C) color image, a charging unit 2C, an exposure unit 3C, a developing unit 4C, and a cleaning unit 8C are arranged around the photosensitive drum 1C. In the image forming unit 10K that forms a black (K) image, a charging unit 2K, an exposure unit 3K, a developing unit 4K, and a cleaning unit 8K are arranged around the photosensitive drum 1K. The charging unit 2Y and the exposure unit 3Y, the charging unit 2M and the exposure unit 3M, the charging unit 2C and the exposure device 3C, and the charging unit 2K and the exposure device 3K constitute a latent image forming unit.

  The developing units 4Y, 4M, 4C, and 4K include a two-component developer composed of a toner having a small particle size of yellow (Y), magenta (M), cyan (C), and black (K) and a carrier.

  The intermediate transfer body 6 is wound around a plurality of rollers and is rotatably supported.

  The fixing device 100 heats and presses the toner image on the recording paper (recording material) P at a nip portion formed between the heated fixing roller 101 and the fixing belt 102a to fix the toner image.

  Thus, each color image formed by the image forming units 10Y, 10M, 10C, and 10K is sequentially transferred onto the rotating intermediate transfer body 6 by the transfer means 7Y, 7M, 7C, and 7K (primary transfer). A toner image synthesized with a color image is formed.

  The recording paper P, which is a recording medium accommodated in the paper feeding cassette 20, is fed by the paper feeding means 21 and conveyed to the transfer means 7A via the paper feeding rollers 22A, 22B, 22C, 22D, the registration rollers 23, and the like. Then, a color image is transferred onto the recording paper P (secondary transfer).

  The recording paper P to which the color image has been transferred is heated and pressurized by the fixing device 100, and the color toner image on the recording paper P is fixed. Thereafter, the sheet is sandwiched between the sheet discharge rollers 24 and placed on the sheet discharge tray 25 outside the apparatus.

  On the other hand, after the color image is transferred to the recording paper P by the transfer means 7A, the residual toner is removed by the cleaning means 8A from the intermediate transfer body 6 from which the recording paper P is separated by curvature.

  The image forming apparatus for forming a color image has been described above. However, an image forming apparatus for forming a monochrome image may be used, or an intermediate transfer member may or may not be used.

  Next, an embodiment of the main configuration of the fixing device 100 of the present invention will be described with reference to FIGS.

  FIG. 2 is a cross-sectional view for explaining the first embodiment of the main configuration of the fixing device 100 of the present invention, and is orthogonal to the width direction (direction perpendicular to the rotation direction) of the fixing belt 102a. Represents a cross section.

  3 and 4 are partially enlarged views for explaining a fitting state between a hole formed in the front end portion or the rear end portion of the sliding sheet in FIG. 2 and a stepped screw fitted to the hole, 3 shows a case where the hole is a round hole, and FIG. 4 shows a case where the hole is a long hole. Here, the front end portion of the sliding sheet 111 refers to the upstream end portion of the sliding sheet 111 with respect to the rotation direction of the fixing belt 102a, and the rear end portion refers to the downstream end portion.

  A fixing roller 101 as a heating roller includes a halogen lamp (heating means) H in the center, a cylindrical cored bar 101A formed of iron or the like, an elastic layer 101B covering the cylindrical cored bar 101A, and an elastic layer And a release layer 101C covering 101B. The elastic layer 101B that covers the cylindrical cored bar 101A is formed of silicone rubber or the like having high heat resistance. The release layer 101C that covers the elastic layer 101B is formed of a fluororesin such as PFA (perfluoroalkoxy) or PTFE (polytetrafluoroethylene).

  The fixing belt 102a as a belt member includes a base formed of a material such as polyimide having a thickness of about 100 μm and a release layer formed of PFA or PTFE having a thickness of about 25 μm covering the outer surface of the base. And endlessly formed.

  The pressing pad 103 is formed of silicone rubber having a hardness of about 10 ° JISA, and is held by a holder 113 formed of a heat resistant resin together with a base metal plate 104 made of stainless steel and a base member 105 formed of a heat resistant resin. A compression spring 106 is disposed on the back surface of the base member 105. The compression spring 106 presses the pressing pad 103, the base metal plate 104, and the base member 105, and fixes the fixing belt 102a and a sliding sheet 111 described later to the fixing roller 101. It is pressing in the direction of pressing.

  Here, the pressing pad 103, the base sheet metal 104, the base member 105, and the compression spring 106 are collectively referred to as pressing means.

  The separation member 107 is a member arranged on the downstream side of the pressing pad 103 in the rotation direction of the belt member in order to improve the separation property of the fixed recording paper P, and locally deforms the elastic layer 101B of the fixing roller 101. As a result, the separation of the recording paper P is improved. The separation member 107 is made of a heat-resistant resin or a metal such as aluminum and has a tip formed in an arc having a large curvature and is held by holders 109 and 113 and a frame 110 as holding members. An elastic member 114 made of urethane rubber or the like is disposed on the back surface of the separating member 107.

  The holders 108, 109, 113 as holding members made of heat-resistant resin are held by metal frames 110 arranged at the center.

  The sliding sheet 111 is formed of a Teflon (registered trademark) -coated glass fiber sheet or PTFE sheet. The sliding sheet 111 is formed between the inner peripheral surface of the fixing belt 102 a and the pressing pad 103 and between the inner peripheral surface of the fixing belt 102 a and the separating member 107. The both ends are held by the frame 110.

  That is, the sliding sheet 111 has round holes 111a and 111b at the front end portion and the rear end portion, and the respective round holes 111a and 111b are fitted by stepped screws 115a and 115b, and the holder 108, 109 and the frame 110 are positioned and held.

  The sliding sheet 111 includes round holes 111a and 111b as positioning holes formed at the front end portion and the rear end portion of the sliding sheet 111, and stepped screws 115a and 115b as positioning members fitted thereto. The holders 108 and 109 are positioned at predetermined positions. A plurality of round holes 111a and 111b and stepped screws 115a and 115b fitted to the round holes 111a and 111b may be provided.

  The oil pad 112 is formed of sponge or the like and contains a lubricant made of silicone oil or the like. The oil pad 112 is held by the holder 109 and pressed against the inner peripheral surface of the fixing belt 102a.

  When the fixing belt 102a rotates, the holder 113 guides the fixing belt 102a via the sliding sheet 111, and the holders 108 and 109 also function as guide members that directly guide the fixing belt 102a.

  Here, the fixing belt 102a and the sliding sheet 111, the pressing means, the frame 110, the holders 108, 109, 113, the separating member 107, the oil pad 112, and the like disposed inside the fixing belt 102a are collectively referred to. The fixing belt unit 102 is referred to.

  In the fixing device 100 configured as described above, the fixing roller 101 heated by the halogen lamp H and driven by a driving unit (not shown) rotates in the clockwise direction. The pressing pad 103 is pressed by the compression spring 106 through the base metal plate 104 and the base member 105, and the pressing pad 103 presses the fixing belt 102 a against the fixing roller 101 through the sliding sheet 111. Further, the separating member 107 presses the sliding sheet 111 and the fixing belt 102 a against the fixing roller 101.

  Accordingly, the fixing belt 102 a rotates counterclockwise with the rotation of the fixing roller 101, is pressed against the fixing roller 101 by the pressing pad 103, and is elastically deformed, and the fixing belt 102 a is fixed between the fixing belt 102 a and the fixing roller 101. A wide nip portion NP is formed. The unfixed toner on the conveyed recording paper P is heated and pressurized at the nip portion NP and fixed.

  Further, the inner peripheral surface of the fixing belt 102a is rubbed with the sliding sheet 111 during rotation, but since the sliding sheet 111 has a small friction coefficient, the sliding resistance between the two is small. Furthermore, since silicone oil as a lubricant is supplied from the oil pad 112 to the inner peripheral surface of the fixing belt 102a, the sliding resistance is further reduced.

  When the rotation of the fixing roller 101 is stopped for a long time, the pressure contact between the fixing belt unit 102 and the fixing roller 101 is released by using a pressure contact releasing unit described later in order to prevent deformation of the fixing belt 102a.

  Next, in the first embodiment according to the present invention, fitting between the round holes 111a and 111b formed in the front end portion or the rear end portion of the sliding sheet 111 and the stepped screws 115a and 115b fitted therein. The state will be described with reference to FIG.

  In FIG. 3, arrow F represents the rotation direction of the fixing belt 102 a, reference numeral 111 a is a round hole formed in the front end of the sliding sheet 111, and reference numeral 111 b is formed in the rear end of the sliding sheet 111. A round hole is shown. Reference numeral 115a denotes a stepped screw that fits into the round hole 111a, and reference numeral 115b denotes a stepped screw that fits into the round hole 111b.

  FIG. 3A shows a fitting state between the stepped screw 115a and the round hole 111a when the pressure contact between the fixing belt unit 102 and the fixing roller 101 is released by a pressure release unit described later. b) is a diagram showing a fitting state of the stepped screw 115b and the round hole 111b. FIG. 3C is a diagram showing a fitting state between the stepped screws 115a and 115b and the round holes 111a and 111b when the fixing belt unit 102 presses the fixing roller 101 for fixing.

  In FIG. 3A showing the pressure release state, the stepped screw 115a is fitted in the round hole 111a at the front end of the sliding sheet 111, and the upstream side of the round hole 111a with respect to the rotation direction F of the fixing belt 102a. Abutting at the end, positioning of the sliding sheet 111 to the holder 108 is performed. Similarly, in FIG. 3 (b) showing the pressure contact released state, the stepped screw 115b is fitted into the round hole 111b at the rear end portion of the sliding sheet 111 and is brought into contact with the downstream end portion of the round hole 111b. The positioning of the sliding sheet 111 to the holder 109 is performed.

  The symbol d in FIG. 3A or 3B represents the gap between the stepped screw 115a or 115b that contacts the round hole 111a or 111b and the round hole 111a or 111b. The gap d is a predetermined amount set in advance, and corresponds to a dimensional difference between the inner diameter of the round holes 111a and 111b and the outer diameter of the stepped portions of the stepped screws 115a and 115b.

  The reason why the contact positions of the round holes 111a and 111b and the stepped screws 115a and 115b are different between the front end portion and the rear end portion of the sliding sheet 111 will be described below.

  When the pressure contact is released, due to the separation between the fixing roller 101 and the fixing belt unit 102, the compression spring 106 pressing the pressing pad 103 pushes up the pressing pad 103, and the sliding sheet 111 and the fixing belt 102a are lifted. By this operation, the round hole 111a at the front end portion of the sliding sheet 111 positioned on the upstream side of the position of the pressing pad 103 is pulled in the direction of the pressing pad 103 positioned on the downstream side. On the other hand, the round hole 111b at the rear end is pulled in the direction of the pressing pad 103 located on the upstream side. Therefore, the round hole 111a at the front end abuts the stepped screw 115a at the upstream end of the round hole 111a, and the round hole 111b at the rear end abuts the stepped screw 115b at the downstream end of the round hole 111b. It will be.

  At the time of fixing, since the fixing belt unit 102 is pressed against the fixing roller 101, the pressing pad 103 is pushed back, and the tension state of the sliding sheet 111 is eliminated. Therefore, the sliding sheet 111 moves to the upstream side at the front end portion located upstream of the position of the pressing pad 103 of the sliding sheet 111, and the sliding sheet 111 at the rear end portion positioned downstream of the position of the pressing pad 103. Moves further downstream. Accordingly, as shown in FIG. 3C, the round hole 111a at the front end and the round hole 111b at the rear end are in a state of being separated from the contact portions with the stepped screws 115a and 115b.

  The value of the gap d described above is a value that should be set in accordance with the moving distance of the fixing belt unit 102 when the fixing belt unit 102 and the fixing roller 101 are pressed against each other and when the pressure contact is released. The value of the gap d is set to 1 mm for a moving distance of 3 mm.

  By providing a dimensional difference (corresponding to the gap d) between the inner diameter of the round holes 111a and 111b and the outer diameter of the stepped portions of the stepped screws 115a and 115b, the fixing belt unit 102 and the fixing roller 101 are pressed against each other. The sliding sheet 111 can be smoothly moved when switching to release.

  Next, in the first embodiment according to the present invention, a configuration in which holes formed in the front end portion or the rear end portion of the sliding sheet 111 and fitted to the stepped screws 115a and 115b are elongated holes 111c and 111d. This will be described with reference to FIG.

  In FIG. 4, arrow F indicates the rotation direction of the fixing belt 102 a, and reference numeral 111 c indicates an elongated hole formed in the front end portion of the sliding sheet 111. Reference numeral 111 d denotes a long hole formed in the rear end portion of the sliding sheet 111. Reference numeral 115a denotes a stepped screw that fits into the elongated hole 111c, and reference numeral 115b denotes a stepped screw that fits into the elongated hole 111d.

  FIG. 4A shows a fitting state between the stepped screw 115a and the elongated hole 111c when the pressure contact between the fixing belt unit 102 and the fixing roller 101 is released by a pressure release unit described later. b) is a diagram showing a fitting state of the stepped screw 115b and the elongated hole 111d. FIG. 4C is a diagram showing a fitting state between the stepped screws 115a and 115b and the long holes 111c and 111d when the fixing belt unit 102 presses the fixing roller 101 for fixing.

  In FIG. 4A showing the pressure release state, the stepped screw 115a that fits into the elongated hole 111c at the front end of the sliding sheet 111 is located upstream of the elongated hole 111c with respect to the rotation direction F of the fixing belt 102a. Contact at the end. Similarly, in FIG. 4 (b) showing the pressure contact released state, the stepped screw 115b fitted into the elongated hole 111d at the rear end of the sliding sheet 111 is long with respect to the rotation direction F of the fixing belt 102a. It abuts at the downstream end of the hole 111c. The symbol d is a predetermined amount set in advance and represents the gap between the elongated hole 111c or 111d and the stepped screw 115a or 115b.

  The reason why the contact positions between the long holes 111c and 111d and the stepped screws 115a and 115b are different between the front end portion and the rear end portion of the sliding sheet 111 is already described in FIG.

  At the time of fixing, the fixing belt unit 102 is pressed against the fixing roller 101, and as shown in FIG. 4C, the long hole 111c at the front end and the long hole 111d at the rear end are respectively connected to the stepped screws 115a and 115b. It will be in the state separated from the contact part.

  The first embodiment of the main configuration according to the fixing device 100 of the present invention is used to position the front end portion and the rear end portion of the sliding sheet 111, so that the fixing belt unit 102 re-presses the fixing roller 101. The displacement of the positions of the pressing pad 103 and the sliding sheet 111 can be prevented. That is, since the movement of the sliding sheet 111 is restricted to the range of the dimensional difference (predetermined amount d) between the round hole or the long hole and the stepped screw, the pressing pad 103 and the sliding sheet 111 are not easily displaced, The position of the pressing pad 103 and the sliding sheet 111 at the time can be reproduced within a certain range.

  By preventing the displacement of the positions of the pressing pad 103 and the sliding sheet 111, a stable pressing state can be maintained, and occurrence of defects such as image density unevenness and image misalignment can be suppressed.

  Further, by using this embodiment, there is an advantage that the sliding sheet 111 can be positioned and held with a simple configuration using only the long holes formed in the sliding sheet 111 and the stepped screws 115a and 115b. .

  FIG. 5 is a cross-sectional view for explaining a second embodiment of the main configuration of the fixing device according to the present invention, and shows a cross section orthogonal to the width direction of the fixing belt 102a and the like.

  FIG. 6 is a partially enlarged view for explaining a fitting state between a square hole formed in the front end portion of the sliding sheet in FIG. 5 and a protruding member serving as a positioning member fitted thereto. Note that the rear end portion of the sliding sheet 111 is configured to fit the stepped screw 115b and the round hole as in the first embodiment shown in FIGS. .

  Further, the second embodiment of the fixing device 100 shown in FIG. 5 is similar to the first embodiment of the fixing device 100 shown in FIGS. 2 and 3, and the same reference numerals are used for members having the same configuration. No description will be given because they are numbered, and only different configurations will be described.

  The difference between the second embodiment and the first embodiment is the difference in the configuration for positioning the tip of the sliding sheet 111. In the first embodiment, the sliding sheet 111 is positioned on the holder 109 by fitting the round hole 111a at the tip and the stepped screw 115a, but in the second embodiment, the square hole 111e at the tip and the positioning member are positioned. It is positioned by fitting with the protruding member 116 as. That is, in the second embodiment, the sliding sheet 111 is positioned by fitting the square hole 111a formed at the tip portion with the protruding member 116, and the holding hole formed at a position closer to the tip than the square hole 111a. Are held on the frame 110 with screws 117 using the round holes.

  FIG. 6 is a partially enlarged view for explaining a fitting state between the square hole 111a and the protruding member 116 in the second embodiment.

  In FIG. 6, the arrow F indicates the rotation direction of the fixing belt 102a, the reference numeral 111e is a square hole as a positioning hole formed in the front end portion of the sliding sheet 111, and the reference numeral 116 is fitted in the square hole 111c. The protrusion member which consists of a convex (rectangular prism) -shaped member as a positioning member to match is shown.

  The sliding sheet 111 is positioned at predetermined positions of the holders 108 and 109 by fitting the square hole 111e and the round hole 111b of the sliding sheet 111 with the protruding member 116 and the stepped screw 115b.

  FIG. 6A shows a fitting state between the protruding member 116 and the square hole 111e when the pressure contact between the fixing belt unit 102 and the fixing roller 101 is released by a pressure release unit described later. ) Is a diagram showing a fitting state between the protruding member 116 and the square hole 111e during pressure contact.

  In FIG. 6A showing the pressure contact release state, the protruding member 116 fitted into the square hole 111e at the front end portion of the sliding sheet 111 is at the upstream end portion of the square hole 111e with respect to the rotation direction F of the fixing belt 102a. The front end of the sliding sheet 111 is positioned on the holder 108 by abutting. The symbol d is a predetermined amount that is set in advance as in the first embodiment, and represents the difference between the inner diameter dimension of the square hole 111e and the outer dimension dimension of the protruding member 116.

  About positioning of the rear-end part of the sliding sheet 111, since a structure is the same as 1st Embodiment, description is abbreviate | omitted.

  At the time of fixing, since the fixing belt unit 102 is pressed against the fixing roller 101, the pressing pad 103 is pushed back, and the tension state of the sliding sheet 111 is eliminated. Therefore, the sliding sheet 111 moves further upstream at the front end portion located upstream from the position of the pressing pad 103 of the sliding sheet 111. Therefore, as shown in FIG. 6B, the square hole 111 e at the front end is in a state of being separated from the contact portion with the protruding member 116.

  In the present embodiment, the rear end portion of the sliding sheet 111 is positioned and held using the stepped screw 115b. However, like the front end portion, the protruding member 116 and the screw 117 are also formed at the rear end portion. It is good also as a structure using.

  Further, the projecting member 116 for positioning the front end portion of the sliding sheet 111 is a prismatic member, and the hole fitted to the projecting member 116 is a square hole 111e. However, the shape of the projecting member 116 is a column or a corner other than a square. It is good also as columnar shape and it is good also as a shape which matched the hole to fit to the shape of the projection member 116. FIG.

  By using the second embodiment of the main configuration of the fixing device 100 of the present invention and positioning and holding the front end portion and the rear end portion of the sliding sheet 111, the pressing pad 103 represses the fixing roller 101. The displacement of the positions of the pressing pad 103 and the sliding sheet 111 can be prevented. Therefore, a stable pressing state can be maintained between the pressing pad 103 and the fixing roller 101, and occurrence of defects such as image density unevenness and image misalignment can be suppressed.

  Further, by using this embodiment, there is an advantage that the operability when positioning the sliding sheet 111 is good and the sliding sheet 111 can be easily attached.

  FIG. 7 is a cross-sectional view for explaining a third embodiment of the main configuration of the fixing device 100 according to the present invention, and shows a cross section orthogonal to the width direction of the fixing belt 102a and the like.

  The third embodiment of the fixing device 100 shown in FIG. 7 is similar to the second embodiment of the fixing device 100 shown in FIG. 5, and members having the same configuration are denoted by the same reference numerals. Therefore, a description thereof is omitted, and only a different configuration will be described.

  The third embodiment is different from the second embodiment in the configuration of positioning the front end portion and the rear end portion of the sliding sheet 111. In the second embodiment, the front end portion of the sliding sheet 111 is positioned with a protruding member, and the rear end portion with a round hole and a stepped screw. However, in the third embodiment, the front end portion is fixed with a screw. Then, the rear end portion is connected to a tension spring that is a spring member as a positioning member, and is positioned by pulling. In other words, in the third embodiment, the sliding sheet 111 has its front end fixed by the screw 117, its rear end held by the grip 120, and one end of the tension spring 121 engaged with the grip 120 to pull it. It is positioned and held while being. The other end of the tension spring 121 is connected to a spring hooking portion (no reference numeral) that is a predetermined position of the frame 110 as a holding member. The grip 120 is constituted by a known shed-like gripping means.

  The sliding sheet 111 includes a hole (not shown) as a positioning hole into which a screw 117 for fixing the tip of the sliding sheet 111 is fitted, a screw 117 as a positioning member, and a tension spring 121, so that the holders 108 and 109 Positioned at a predetermined position.

  In the third embodiment, since the rear end portion is pulled by the tension spring, it is necessary to provide a predetermined amount of difference in size between the positioning member and the positioning hole in the first embodiment and the second embodiment. There is no.

  In the present embodiment, the tip of the sliding sheet 111 is positioned using the screw 117, but a configuration using a stepped screw 115a may be used as in the first embodiment.

  By using the third embodiment of the main configuration of the fixing device 100 of the present invention and positioning the front end portion and the rear end portion of the sliding sheet 111, the pressing pad 103 presses the fixing roller 101 again by pressing. The displacement of the positions of the pad 103 and the sliding sheet 111 can be prevented. Therefore, a stable pressing state can be maintained between the pressing pad 103 and the fixing roller 101, and occurrence of defects such as image density unevenness and image misalignment can be suppressed.

  Moreover, since the position of the sliding sheet 111 is determined by the tension spring 121 by using this embodiment, there is an advantage that it is always pressed at a fixed position.

  Next, the configuration of the end portion of the fixing belt unit 102 will be described with reference to the longitudinal sectional view of the fixing device shown in FIG. Although FIG. 8 shows only the right end of the fixing device, the left and right ends are symmetrical, and the same applies to the left end. The same members as those shown in FIGS. 2, 5, and 7 are denoted by the same reference numerals.

  In FIG. 8, the length in the width direction of the fixing belt 102 a is formed longer than all the members positioned inside the fixing belt 102 a except the frame 110. Then, both ends in the width direction of the fixing belt 102a are supported by a pair of support members 118 from the inner peripheral surface side. Further, both support members 118 are supported by a rotating member 119.

  The frame 110 is also formed longer in the width direction than all the members positioned inside the fixing belt 102a, and both end portions of the protruding frame 110 are respectively inserted and fixed to the pair of support members 118.

  In addition, the fixing belt unit 102 and the fixing roller 101 are pressed against and released to prevent deformation of the fixing roller and the fixing belt at the time of shipment, maintenance, jam processing, or when the fixing roller rotates for a long time. A pressure contact / pressure contact release means is provided.

  The configuration and operation of this pressure contact / pressure release means will be described with reference to FIG. FIG. 9A is a diagram of a state when the fixing device is used, and FIG. 9B is a diagram in which the pressure contact between the fixing belt unit 102 and the fixing roller 101 is released.

  In FIG. 9A, the rotation member 119 is pivotally supported by the support shaft 131 and can be rotated. Then, the end 119A of the rotating member 119 is pressed by the compression spring 132, and the rotating member 119 is biased counterclockwise. Accordingly, the fixing belt unit 102 also rotates through the support member 118, and the fixing belt unit 102 is in pressure contact with the fixing roller 101.

  When releasing the pressure contact between the fixing belt unit 102 and the fixing roller 101, the cam 133 is rotated as shown in FIG. When the cam 133 rotates, the bottom 119B of the rotating member 119 is pressed by the cam 133, and the rotating member 119 rotates clockwise against the urging force of the compression spring 132. Accordingly, the fixing belt unit 102 is also rotated via the support member 118, and the fixing belt unit 102 is retracted from the fixing roller 101, so that the pressure contact of the fixing belt 102a with the fixing roller 101 is released.

  Here, the support member 118, the rotation member 119, the support shaft 131, the compression spring 132, and the cam 133 are collectively referred to as pressure contact / pressure contact release means.

1 is a schematic configuration diagram for explaining an embodiment of an image forming apparatus according to the present invention. FIG. 3 is a cross-sectional view for explaining a first embodiment of a main configuration according to the fixing device 100 of the present invention. It is the elements on larger scale for demonstrating the fitting state of the hole formed in the front-end part or rear-end part of the sliding sheet | seat in FIG. 2, and the stepped screw fitted to it. It is the elements on larger scale for demonstrating the fitting state of the hole formed in the front-end part or rear-end part of the sliding sheet | seat in FIG. 2, and the stepped screw fitted to it. FIG. 6 is a cross-sectional view for explaining a second embodiment of the main configuration of the fixing device according to the present invention. It is the elements on larger scale for demonstrating the fitting state of the square hole formed in the front-end part of the sliding sheet | seat in FIG. 5, and the projection member fitted to it. FIG. 9 is a cross-sectional view for explaining a third embodiment of the main configuration of the fixing device according to the present invention. FIG. 4 is a cross-sectional view illustrating a configuration of an end portion of the fixing belt unit. It is the schematic for demonstrating the structure and operation | movement of a press-contact cancellation | release means.

Explanation of symbols

GH image forming apparatus main body YS image reading apparatus 100 fixing apparatus 101 fixing roller 102 fixing belt unit 102a fixing belt (belt member)
103 Press pad (pressing means)
104 Base sheet metal (pressing means)
105 Base member (pressing means)
106 Compression spring (pressing means)
107 Separating member 108, 109, 113 Holder 110 Frame 111 Sliding sheet 111a, 111b Round hole 111c, 111d Long hole 111e Square hole 114 Elastic member 115a, 115b Stepped screw 116 Projection member 118 Support member (pressure contact / pressure contact release means)
119 Rotating member (pressure contact / pressure release means)
131 Support shaft (pressure contact / pressure release means)
132 Compression spring (pressure contact / pressure release means)
133 cam (pressure contact / pressure release means)

Claims (8)

A heating roller;
An endless belt member that rotates while contacting the heating roller;
A sliding sheet disposed inside the belt member;
A pressing means disposed on the inside of the sliding sheet and pressing the sliding sheet and the belt member against the heating roller;
A holding member for holding the sliding sheet and the pressing means;
A positioning member for positioning the sliding sheet at a predetermined position of the holding member;
A fixing device having pressure contact / pressure contact release means for pressing or releasing the pressure contact between the heating roller and the belt member;
The fixing device is configured to position the sliding sheet at a predetermined position of the holding member by fixing a front end portion and a rear end portion of the sliding sheet in a rotation direction of the belt member. At least one positioning hole is formed in each of the front end portion and the rear end portion, and the same number of positioning members as the number of the positioning holes are arranged at positions corresponding to the sliding sheet in the holding member. Has been
The sliding sheet is positioned at a predetermined position of the holding member by fitting the positioning hole formed in the front end portion and the rear end portion with the positioning member. The fixing device according to 1. The fixing device according to claim 2, wherein an internal measurement dimension of the positioning hole in the rotation direction of the belt member is larger by a predetermined amount than an external dimension of the positioning member. At least one of the positioning members is a stepped screw;
The fixing device according to claim 3, wherein the positioning hole fitted therein is formed as a long hole or a round hole having a large dimension in the rotation direction of the belt member. The positioning member is a protruding member having a convex shape,
The sliding sheet has a holding hole for holding the sliding sheet on the holding member;
A screw hole for holding the sliding sheet is formed in the holding member,
The positioning of the sliding sheet to the holding member is performed by fitting the protruding member and the positioning hole of the sliding sheet,
The fixing device according to claim 3, wherein the sliding sheet is held on the holding member by screwing the holding hole and the screw hole together. The positioning member that holds the rear end is a spring member made of a tension spring;
The fixing device according to claim 1, wherein one end portion of the spring member is connected to the rear end portion, and the other end portion of the spring member is connected to a predetermined position of the holding member. . The fixing device according to claim 1, further comprising a separation member that presses the sliding sheet and the belt member against the heating roller and separates a recording medium from the heating roller. . An image forming apparatus comprising the fixing device according to claim 1.

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