JP2011039482A - Fixing device and image forming apparatus - Google Patents

Abstract

A fixing device that prevents local overheating of a heating rotator with a simple mechanism without complicating the device.
[Solution]
A region having a metal conductive layer and having a first width in contact with a direction perpendicular to the direction in which the recording paper S is conveyed and a direction perpendicular to the direction in which the recording paper S is conveyed A heating rotator 202 having a hole in a metal conductive layer in a region different from a region in contact with a second recording paper having a second width, and a direction perpendicular to the conveyance direction of the recording paper S, The fixing device includes a heating member 210 that is provided to face the heating rotator 202 and heats the metal conductive layer.
[Selection] Figure 2

Description

  The present invention relates to a fixing device and an image forming apparatus including the fixing device.

  In an image forming apparatus such as a copying machine or a printer, a toner image formed on an image carrier such as a photosensitive drum is transferred to a sheet used as a recording medium, and the recording sheet is heated by a heating rotary member (a heating roller or a roller). A fixing device is used in which the toner is conveyed while being pressed against a heating belt, and is heated to fix the transferred toner image on a recording sheet. Conventionally, the heating rotator is heated by the induction heating coil over its entire length in the axial direction, and when the recording sheet comes into contact with the surface of the heating rotator, the sheet is deprived of heat. There are A3 (large) size paper and B5 (small) size paper to be fixed. With this type of fixing device, when a small size recording paper of the same width is continuously fixed, There is a problem that the temperature of the portion where the heat is not taken away by the recording paper is easily overheated. Excessive temperature rise may deteriorate the heating rotator and cause damage or the like.

  In view of the above problems, Patent Document 1 discloses that a demagnetizing coil is arranged so as to overlap with an induction heating coil in a portion through which a recording sheet does not pass when fixing to a recording sheet having a small width with a heating rotator. It is shown. In such a fixing device, a current that cancels the change in magnetic flux caused by the induction heating coil flows through the degaussing coil, and the magnetic field at the end where the recording paper does not pass is attenuated, so that the heating value of the heating rotator is partially increased. Can be reduced.

  Further, Patent Document 2 shows that a plurality of induction heating coils are provided in the direction of the rotation axis of the heating rotator, and each induction heating coil is energized appropriately according to the size of the supplied recording paper. . By providing a plurality of induction heating coils in this way, overheating can be prevented by controlling the induction heating coil provided for heating the area through which the recording paper does not pass so as not to energize. it can.

  However, in the fixing device of Patent Document 1, since it is necessary to provide a demagnetizing coil in addition to the normal fixing device, the number of components increases, which causes the device to be complicated and costly. Similarly, the fixing device disclosed in Patent Document 2 also requires a circuit for controlling energization of a plurality of coils, which may increase the cost.

  The present invention has been made to solve the above-described problems, and has a simple configuration without increasing the number of components, and the local area of the heating rotator that is generated by supplying recording sheets of different sizes to the heating rotator. A fixing device and an image forming apparatus that can prevent excessive overheating are provided.

  In order to solve the above problem, a fixing device according to the present invention has a metal conductive layer, and an area where a first recording sheet having a first width in a direction perpendicular to a direction in which the recording sheet is conveyed contacts. A heating rotator in which a hole is formed in a metal conductive layer in a difference area between a second recording sheet having a second width in a direction perpendicular to a direction in which the recording sheet is conveyed, and the recording sheet And a heating member that is provided to face the heating rotator along a direction orthogonal to the conveying direction and heats the metal conductive layer.

  The image forming apparatus according to the present invention further includes a paper supply unit that supplies recording paper, an image forming unit that forms an image on the recording paper, and a metal conductive layer in a direction in which the recording paper is conveyed. An area where a first recording sheet having a first width in a direction orthogonal to the area contacts an area where a second recording sheet having a second width contacts in a direction orthogonal to the direction in which the recording sheet is conveyed A heating rotator that provides holes in the metal conductive layer in the difference region, and a heating member that is provided facing the heating rotator along a direction perpendicular to the conveyance direction of the recording paper and that heats the metal conductive layer And a fixing device having

  According to the present invention, it is possible to prevent local overheating from occurring in the heating rotator with a simple configuration without complicating the apparatus.

Perspective view of image forming apparatus Sectional drawing which shows one Embodiment of the fixing device of this invention The perspective view which shows the positional relationship of the heating roller and induction heating coil of FIG. Relationship diagram of contact area to heating roller of recording paper with different paper sizes Side view of a heating roller provided with slits in the metal conductive layer shown in FIG. The figure which shows the modification of the metal conductive layer of FIG. The figure which shows the other Example of the fixing device of this invention. The figure which shows the fixing belt of the fixing device shown in FIG.

Embodiments of the present invention will be described below with reference to the drawings.
(First embodiment)

  A first embodiment will be described with reference to FIGS.

  FIG. 1 is a perspective view of the image forming apparatus. The image forming apparatus 100 includes an image reading unit 102 that reads a document image and an image forming unit that forms the read image data as a toner image on an image carrier such as a photoconductor.

  In addition, the image forming apparatus 100 further transfers, fixes, and discharges the toner image onto a recording sheet, a paper feeding device 124, a conveyance path 126, a conveyance belt 128, a fixing device 130, a discharge roller 132, an electric board 134, A maintenance door 136 is provided.

  An operation panel 110 having a touch panel display unit 106 and various operation keys 108 is provided on the upper part of the image forming apparatus 100. The operation keys 108 of the operation panel 110 include, for example, a numeric keypad, a reset key, a stop key, and a start key. In the display unit 106, input of various processes such as paper size, number of copies, print density setting, and binding processing is performed.

  The detailed configuration and operation of each part of the image forming apparatus described above will be outlined below.

  The image forming unit includes a laser unit 112, a photoconductor 114, a charging device 115, a developing device 116, a transfer device 118, a cleaner 120, and a charge eliminating device 122. The charging device 115 charges the outer peripheral surface of the rotating photosensitive member 114. The laser unit 112 forms an electrostatic latent image on the outer peripheral surface of the charged photoconductor 114 based on the image data read by the image reading unit 102. The developing device 116 develops the electrostatic latent image into a toner image with toner. The transfer device 118 transfers the toner image on the photoconductor 114 onto the recording paper S conveyed from the paper supply device 124 through the conveyance path 126. The cleaner 120 removes toner remaining on the photoconductor 114 without being transferred. Further, the neutralizing device 122 neutralizes the outer peripheral surface of the photoreceptor 114.

  Next, the transport belt 128 transports the recording paper S, onto which the toner image D has been transferred in the image forming unit as described above, to the fixing device 130. The fixing device 130 fixes the toner image D on the recording paper S. Finally, the discharge roller 132 discharges the recording sheet S on which the toner image D is fixed from the image forming apparatus 100.

  FIG. 2 is a cross-sectional view of the fixing device 130.

  The fixing device 130 includes a heating roller 202 that is a heating rotator and a pressure roller 204. The heating roller 202 has a metal core, a foam rubber layer, a metal conductive layer, a solid rubber layer, and a release layer in order from the inside. For example, the thickness is 5 mm for the foam rubber layer, 50 μm for the metal conductive layer, 200 μm for the solid rubber layer, and 30 μm for the release layer. The metal conductive layer is formed of, for example, nickel, stainless steel, aluminum, a composite material of stainless steel and aluminum, or the like.

  On the other hand, the pressure roller 204 has a metal core, a rubber layer, and a release layer in order from the inside. For example, the rubber layer has a thickness of 1 mm and the release layer has a thickness of 30 μm.

  The diameters of the heating roller 202 and the pressure roller 204 are, for example, 40 mm. As shown in FIG. 2, a pressure mechanism 208 such as a spring presses the pressure roller 204 against the heating roller 202 to form a nip 206. The heating roller 202 is driven to rotate in the direction shown by a motor (not shown), and the pressure roller 204 is driven to rotate. Accordingly, the heating roller 202 conveys the recording sheet S conveyed to the nip 206 while sandwiching it with the pressure roller 204, and pressurizes and heats the surface on which the toner image D is transferred.

  The fixing device 130 further includes an induction heating coil 210 that is a heating member. The induction heating coil 210 faces the heating roller 202 through a space. The induction heating coil 210 has a magnetic core 214 and a litz wire 212 wound around the core 214. The litz wire 212 is, for example, a plurality of conductive wires that are insulated and bundled with each other by heat-resistant polyamideimide or the like. For example, the magnetic core 214 has a shape that is bent so as to surround the outer periphery of the heating roller 202.

  The induction heating coil 210 having the above configuration generates a magnetic flux when a high frequency current is applied. This magnetic flux generates a magnetic flux and an eddy current so as to prevent a change in the magnetic field in the metal conductive layer of the heating roller 202. Joule heat is generated by the eddy current and the resistance of the metal conductive layer, and the heating roller 202 is heated.

  FIG. 3 is a perspective view showing the positional relationship between the heating roller 202 and the induction heating coil.

  The induction heating coil 210 is disposed opposite to the entire area of the heating roller 202 in the rotation axis direction with a certain distance from the heating roller 202. The heating capacity of the entire area of the heating roller 202 in which the induction heating coil 210 is disposed to face each other is approximately uniform.

  Next, a contact area between each recording sheet S and the heating roller 202 when a small recording sheet (for example, A4 size) and a large recording sheet (for example, A3 size) are conveyed to the fixing device will be described with reference to FIG. I will explain. FIG. 4 is a diagram illustrating a relationship between regions in which the heating roller 202 is in contact with the A4 size recording sheet S and the A3 size recording sheet S in the rotation axis direction of the heating roller 202. The short sides of the A4 size recording paper S and the short sides of the A3 size recording paper S are defined as the respective width directions. Further, the short side of the A4 size recording paper S is referred to as L1, and the short side of the A3 size recording paper S is referred to as L2. At this time, the relationship of L1 <L2 is established. The A3 size recording paper has a maximum width in which the recording paper contacts the heating roller 202.

  At both ends in the rotational axis direction of the heating roller 202, there is a region in the rotational direction where the A3 size recording paper S contacts but the A4 size recording paper S does not contact in the rotational direction when transporting the paper. This non-overlapping area (difference area) is an area in the rotational direction in which heat is not taken away by the recording paper as compared with the area of the width L1 when the A4 size recording paper S continues to pass. .

  FIG. 5 is a side view of the heating roller 202 according to the present embodiment as seen from the conveyance direction of the recording paper, that is, the direction of arrow A in FIG.

  When the A4 size recording paper S is passed and when the A3 size recording paper S is passed through the heating roller 202, the metal conductivity of the heating roller 202 is determined in the difference area between the passing areas of the recording paper of each size. A plurality of slit-like holes (hereinafter referred to as slits) 401 are provided in the layer.

  The magnetic field generated from the induction heating coil 210 provided so as to face the slit 401 is cut off by the slit 401 provided in the metal conductive layer. Therefore, the heat generation capability is weaker than that of the area of the heating roller 202 where the slit 401 is not provided.

  Here, when the slit 401 becomes large, the area of the cavity of the metal conductive layer of the heating roller 401 becomes large, and the strength of the heating roller 401 may be reduced. Therefore, the length of the slit 401 is about 5 mm, for example. Also, providing the slit 401 at a position very close to the end of the heating roller 202 leads to a decrease in strength of the heating roller 202. Therefore, for example, the slit 401 is provided 10 mm or more inside from the end of the heating roller 202.

  In addition, the slits 401 are arranged at equal intervals so that image unevenness does not occur in the rotation cycle of the heating roller 202. Further, the slit 401 is provided so as not to be parallel to the rotation axis direction of the heating roller 202. When the slit 401 is provided parallel to the rotation axis direction of the heating roller 202, a portion where the slit 401 is present and a portion where the slit 401 is not present are remarkably separated with respect to the rotation direction of the heating roller 202. That is, there is a possibility that temperature unevenness occurs in the rotation direction of the heating roller 202. When the slit 401 is provided so as to have an inclination with respect to the rotation axis direction of the heating roller 202, the portion having no slit 401 in the rotation direction of the heating roller 202 is reduced, and the rotation direction of the heating roller 202 in the region where the slit 401 is provided. The temperature is kept uniform.

  Further, both ends of the slit 401 are provided so as to have a round shape having no corners. This is because if the end of the slit 401 has a corner, the slit 401 may be avoided from the corner.

  The reason why the slit 401 is provided in the metal conductive layer instead of the release layer on the surface of the heating roller 202 is that the release layer is in contact with the recording paper. The image is not fixed well, and there is a risk of image failure. Therefore, the slit 401 is provided only in the metal conductive layer inside the release layer.

  As described above, according to the above embodiment, the slit 201 is provided in the metal conductive layer of the heating roller 202 without increasing the number of components of the apparatus, thereby fixing the small size recording paper and the large size recording paper. When paper is fed to the apparatus, especially when small-size recording paper is fed continuously, the heating roller 202 has a portion where the temperature rises due to different areas in contact with the heating roller 202. Can be prevented.

  In the above embodiment, the slit-shaped hole is provided in the difference area between the area contacting the heating roller when the A4 size sheet is passed and when the A3 size sheet is passed. The size of is not limited to this. If a hole is provided in a difference area between a small-sized sheet and a large-sized sheet that are frequently used and in contact with the heating roller, local overheating of the heating roller can be effectively prevented.

  In the above embodiment, the hole provided in the metal conductive layer of the heating rotator is slit-shaped, but the hole may have a round shape as shown in FIG.

  In the above embodiment, the heating roller is heated by an electromagnetic induction heating method using an induction heating coil as a heating member, but the heating method of the heating roller is not limited to this. For example, a filament coil may be used as the heating member. Even when a filament coil is used, heating is promoted in the heating roller as compared with a portion where the metal conductive layer is not present. For this reason, providing a hole in the metal conductive layer of the heating roller is effective in preventing local overheating of the heating roller not only in the induction heating method but also in other heating methods.

Next, a second embodiment will be described with reference to FIGS.
(Second Embodiment)

  The fixing device in this embodiment has an endless belt as a heating rotator instead of the heating roller 202 of the fixing device of the first embodiment.

  FIG. 7 is a diagram illustrating a fixing device according to the second embodiment.

  The fixing device 130 includes an endless belt 704 that spans between the fixing roller 702 and the satellite roller 706, and a pressure roller 204 that is a nip forming member. A satellite roller 706 supports the belt 704 rotatably together with the heating roller 702. The satellite roller 706 rotates following the belt 704 driven by the heating roller 702.

  The fixing roller 702 is formed, for example, by covering a foamed rubber layer around a cored bar. The satellite roller 706 is made of ceramic, for example. The satellite roller 706 may be formed of, for example, iron, stainless steel, resin, or a heat pipe.

  The belt 704 has a coat layer, a metal conductive layer, an elastic layer, and a release layer in order from the inside, and generates Joule heat by the magnetic flux applied from the induction heating coil 210. The coat layer may be one in which mica is dispersed in a polyimide resin. The metal conductive layer is formed of, for example, nickel, stainless steel, aluminum, a composite material of stainless steel and aluminum, or the like. For example, the elastic layer may be silicon rubber or fluororubber, and the release layer may be fluororesin.

  The pressure roller 204 is pressed against the fixing roller 702 and the belt 704. A nip is formed between the belt 704 and the pressure roller 204 by the pressure contact of the pressure roller 204. The recording paper S is conveyed to the nip, and the toner image on the recording paper S is fixed.

  In such a fixing device, the slit 401 is provided in the metal conductive layer of the belt 704. FIG. 8 is a view showing the belt 704. Similarly to the hole provided in the heating roller 202 in the first embodiment, the hole provided in the belt is, for example, when the A4 size recording paper S is passed and when the A3 size recording paper S is passed. It is provided in the difference area of the passing area in the belt 704 of the size recording paper. In addition, both ends of the slit 401 have a round shape with no corners so as not to be parallel to the rotation axis.

  As shown in the above embodiment, even when a belt is used as the heating rotator, the same effect as that of the heating roller in the first embodiment can be obtained.

DESCRIPTION OF SYMBOLS 100 Image forming apparatus 102 Image reading part 104 Image forming part 106 Display part 108 Operation key 110 Operation panel 112 Laser unit 114 Photoconductor 115 Charging apparatus 116 Developing apparatus 118 Transfer apparatus 120 Cleaner 122 Static elimination lamp 124 Paper feed apparatus 126 Conveyance path 128 Conveyance Belt 202 Heating roller 204 Pressure roller 210 Induction heating coil 704 Belt 706 Satellite roller 401 Slit

JP 2005-108603 A JP 2001-235963 A

Claims (11)

A hole is formed in a non-overlapping difference area between a rotation direction area where a recording sheet having a first width contacts during conveyance and a rotation area area where a recording sheet having a second width different from the first width contacts. A heating rotator provided with
A heating member provided along the heating rotator and heating the heating rotator;
A fixing device.   The fixing device according to claim 1, wherein the heating rotator includes a metal conductive layer, and the hole is provided in the metal conductive layer.   The fixing device according to claim 2, wherein the heating member is an induction heating coil, and the induction heating coil generates electromagnetic induction heat in the metal conductive layer.   The fixing device according to claim 1, wherein a plurality of the holes are provided.   The fixing device according to claim 3, wherein the holes are arranged at equal intervals.   The fixing device according to claim 1, wherein the hole is formed in a slit shape.   The fixing device according to claim 6, wherein both ends of the hole provided in a slit shape are formed in an arc shape.   The fixing device according to claim 6, wherein the hole provided in a slit shape is provided at a predetermined angle with a rotation axis direction of the heating rotator.   The fixing device according to claim 1, wherein the heating rotator is an endless belt. A paper supply unit for supplying recording paper;
An image forming unit for forming an image on the recording paper;
A region having a metal conductive layer and having a first width in the direction perpendicular to the direction in which the recording paper is conveyed contacts the second region in the direction perpendicular to the direction in which the recording paper is conveyed. A heating rotator in which a hole is formed in a metal conductive layer in an area that is different from an area in contact with a second recording paper having a width of the second recording paper, and the heating rotator is provided along a direction orthogonal to the conveyance direction of the recording paper. A fixing device that is provided oppositely and has a heating member that heats the metal conductive layer;
An image forming apparatus comprising:   The image forming apparatus according to claim 10, wherein a plurality of the holes are provided.

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