JP3731031B2 - Fixing device and image forming apparatus using the same - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a fixing device and an image forming apparatus using the same, and more particularly to an apparatus for fixing an unfixed image carried on a recording medium using a belt.
[0002]
[Prior art]
In an image forming apparatus such as a copying machine, a facsimile machine, a printer, or a printing machine, an unfixed image that is transferred and carried on a recording medium such as paper may be fixed to obtain a copy or a printed output.
[0003]
An apparatus used for fixing has a configuration in which a pair of rollers are arranged to face each other, one roller is used as a heating roller, and the other roller is used as a pressure roller for a recording medium. In this configuration, the unfixed image is fused and fixed by the heat from the heating roller while the recording medium is nipped and conveyed in the nip portion between the heating roller and the pressure roller.
[0004]
In addition to the above-described configuration, the apparatus used for fixing has a configuration in which a roller and a belt are combined.
[0005]
In this configuration, instead of the heating roller, a belt wound around a pair of rollers is used, and a pressure roller is opposed to one of the rollers.
[0006]
Of the pair of rollers, the roller that drives the belt in cooperation with the roller on the side facing the pressure roller is provided with a heat source for heating from the back side of the belt. A heat source is provided for heating. Since the belt has a smaller volume and a smaller heat capacity than the roller, the temperature can be increased in a short time, and the temperature rise at the start-up is faster than the configuration using only the heating roller and the pressure roller described above. There is an advantage. Moreover, the temperature rise on both the front and back sides of the belt can be accelerated by applying a heat source at the pressure roller.
[0007]
When aluminum having a high thermal conductivity is used for each roller as a constitution of the belt, stainless steel is used as a base in contact with the roller surface, and a belt body made of a release layer made of silicon rubber or fluorine resin is arranged on the surface 2. There is a layer structure.
[0008]
[Problems to be solved by the invention]
The belt has a very thin stainless steel substrate of about 50 μm, and the belt body is joined to maintain the strength of the belt. However, there are the following problems.
[0009]
First, due to the thinness, the edge along the axial direction of the roller has a sharp edge. For this reason, it may be dangerous if a hand or a finger touches the exposed end.
[0010]
Secondly, when the axis of the roller being laid is inclined, there is a risk that a deviation in the axial direction occurs and the fixing range is shifted. As a result, a copy or recorded matter in which a fixing failure occurs in a part of the image is obtained.
[0011]
In view of the problems in the conventional fixing device and the image forming apparatus using the same, an object of the present invention is to eliminate a risk during handling and to prevent a fixing defect from occurring, and to form an image using the fixing device. To provide an apparatus.
[0012]
[Means for Solving the Problems]
The invention according to claim 1 is an apparatus including a belt for fixing an unfixed image carried on a recording medium, wherein the belt is a metal wound around a heating roller and a pressure roller facing and abutting the belt. And a block body that covers at least the end surface of the base body is integrated with the end portion in the width direction of the belt. The block body includes a slope surface that is inclined so as to move away from the end surface of the heating roller as it goes from the end surface of the heating roller toward the radial center .
[0013]
According to a second aspect of the present invention, in the fixing device according to the first aspect, the block body is set to a thickness that does not protrude from the surface of the elastic body on the base .
[0014]
According to a third aspect of the present invention, in the fixing device according to the first or second aspect, the end of the belt in the width direction approaches the end surface of the heating roller as the inclination angle (θ) of the inclined surface. It is characterized in that the inclined surface is set at an angle that does not contact the end surface of the heating roller when it is bent and deformed in the direction .
[0015]
According to a fourth aspect of the present invention, in the fixing device according to any one of the first to third aspects, an inclination angle (θ) of the gradient surface is selected such that 10 ° <θ <45 °. It is a feature.
[0016]
According to a fifth aspect of the present invention, in the fixing device according to any one of the third to fourth aspects,
The inclination angle (θ) of the inclined surface is characterized by being set smaller than when the block body is made of metal and non-metallic .
[0017]
A sixth aspect of the invention is characterized in that the fixing device according to one of the first to fifth aspects is used in an image forming apparatus.
[0023]
DETAILED DESCRIPTION OF THE INVENTION
The embodiments of the present invention will be described below with reference to the illustrated examples.
[0024]
FIG. 1 is a view showing one of image forming apparatuses to which a fixing device according to an embodiment of the present invention is applied. The image forming apparatus shown in FIG. 1 is a copier or printer capable of forming a full-color image. In addition to this, there is a facsimile apparatus capable of performing the same image forming process as the above-described copying machine and printer based on a received image signal. Note that the image forming apparatus includes not only the above-described color image but also an apparatus that targets a single color image.
[0025]
The image forming apparatus 20 shown in FIG. 1 sequentially transfers images for each color separation to the same intermediate transfer member, and collectively transfers the images superimposed on the intermediate transfer member onto a sheet-like recording medium such as paper. The method is used.
[0026]
In FIG. 1, an image forming apparatus 20 includes the following apparatuses.
Image forming devices 21C, 21Y, 21M, and 21BK that form images of respective colors according to the original image, transfer devices 22 that are disposed to face the image forming devices 21C, 21Y, 21M, and 21BK, and the respective image forming devices Manual feed tray 23, sheet feeding cassettes 24, 24, manual feed tray 23, paper feed as a sheet-like medium feeding means for feeding various sheet-like media to the transfer area where the devices 21C, 21Y, 21M, 21BK and the transfer device 22 face each other. A registration roller 30 that supplies the sheet medium conveyed from the paper cassettes 24 and 24 in accordance with the timing of image formation by the image forming apparatuses 21C, 21Y, 21M, and 21BK, and fixing of the sheet medium after transfer in the transfer region. The fixing device 1 performs the above.
[0027]
The image forming apparatus 20 includes plain paper (hereinafter simply referred to as plain paper) generally used for copying, 90K paper such as an OHP sheet, a card, and a postcard, thick paper having a basis weight of about 100 g / m ² or more, an envelope, and the like. Any so-called special sheet (hereinafter simply referred to as a special sheet) having a heat capacity larger than that of the paper can be used as the sheet-like medium.
[0028]
Each of the image forming devices 21C, 21Y, 21M, and 21BK develops each color of cyan, yellow, magenta, and black, and uses different toner colors, but the configuration is the same. The configuration of 21C will be described as a representative of the image forming devices 21C, 21Y, 21M, and 21BK.
[0029]
The image forming device 21C includes a photosensitive drum 25C as an electrostatic latent image carrier, a charging device 27C, a developing device 26C, and a cleaning device 28C that are sequentially arranged along the rotation direction A of the photosensitive drum 25C. A well-known configuration for receiving the exposure light 29C between the charging device 27C and the developing device 26C is used. In addition to the drum shape, the electrostatic latent image carrier may have a belt shape. The image forming apparatus 20 shown in FIG. 1 has a configuration in which the transfer device 22 extends in the horizontal direction. However, the image forming apparatus 20 is not limited to this configuration, and can be extended obliquely. The space occupied by the transfer device 22 in the horizontal direction can be reduced.
[0030]
In FIG. 2, a fixing device 1 includes an endless fixing belt 2 for conveying a sheet-like medium on which toner is fixed, a heating roller 3 and a fixing roller 4 that are stretched around the fixing belt 2 and drive the fixing belt 2. , A pressure roller 5 disposed opposite to the fixing roller 4 via the fixing belt 2, a heating roller 3, heaters 6 and 7 provided in the pressure roller 5, and heating via the fixing belt 2. The thermistor 8 is disposed opposite to the roller 3 to detect the temperature of the fixing belt 2 as temperature detecting means 8.
[0031]
The heating roller 3 is biased in a direction away from the fixing roller 4 by an elastic body (not shown) such as a spring, as indicated by an arrow P1, thereby applying an appropriate predetermined tension to the fixing belt 2. ing.
The fixing roller 4 includes a cored bar 9 and a heat-resistant porous elastic body layer 10 that covers the cored bar 9, and the cored bar 9 is rotationally driven by a driving unit (not shown) by the end shaft 11. Thus, the fixing roller 4 is rotationally driven, and the fixing belt 2 is driven by the driven rotation of the heating roller 3.
[0032]
The pressure roller 5 is urged by an elastic body (not shown) such as a spring so as to be in pressure contact with the fixing roller 4 as indicated by an arrow P2. The pressure roller 5 has two straight lines connecting the axis of the fixing roller 4 and the axis of the heating roller 3, and the axis of the heating roller 3 and the axis of the pressure roller 5, with the axis of the fixing roller 4 as the apex. Are in contact with the fixing roller 4 so that the angle between them forms an acute angle. As a result, the first fixing portion A that contacts only the fixing belt 2 at a portion where the pressure roller 5 does not face the fixing roller 4, and the second that the pressure roller 5 contacts the fixing roller 4 via the fixing belt 2. The fixing portion B is formed, and a range for sandwiching and heating the sheet-like medium is configured. Reference numeral 12 denotes a guide for guiding the sheet-like medium to be fixed toward the first fixing unit A.
[0033]
In FIG. 3, the fixing belt 2 is made up of a base body 13 having a thickness of 50 to 100 μm using a metal body such as nickel or stainless steel, and an elastic body made of 200 μm silicon rubber laminated on the base body 13. The mold layer 14 includes a small heat capacity and good thermal response.
[0034]
The substrate 13 may be made of resin such as polyimide instead of the metal described above, and the thickness may be about 30 to 150 μm in consideration of flexibility. The release layer 14 desirably has a thickness of about 50 to 300 when silicon rubber is used, and desirably has a thickness of about 10 to 50 μm when a fluororesin system is used. Further, the release layer 14 may have a configuration in which a fluororesin system is stacked on silicon rubber. The fixing belt 2 is desired to have a property that the belt surface is self-cooled in the fixing region to such an extent that it is instantaneously heated and does not cause hot offset. On the other hand, the toner is sufficiently melted and fixed in the fixing region. Must have the necessary heat capacity. The material and thickness of the fixing belt 2 satisfy this condition. The self-cooling in this case refers to a phenomenon in which the belt cools in the fixing process because there is no heating source on the unfixed image side of the sheet-like medium in the fixing region.
[0035]
The fixing belt 2 is given a tension of 3 kgf / one side by the heating roller 3 being urged in the direction of the arrow P1. This tension can be set by adjusting the urging force in the direction of the arrow P1, and is preferably set in the range of 1 kgf (9.8 N) to 3 kgf (29.4 N) for good fixing.
Each of the heating roller 3 and the pressure roller 5 is made of a thin cylindrical cored bar to reduce the heat capacity. The diameter of the core metal of the heating roller 3 is 20 mm or more and 30 mm or less, the thickness of the core metal is 0.3 mm or more and 2.0 mm or less, and the diameter of the core metal of the pressure roller 5 is 30 mm or more and 50 mm or less. The thickness of the core metal is 0.3 mm or more and 1.5 mm or less. Thereby, the heat capacity of the heating roller 3 is 26 cal / ° C. or less, and the heat capacity of the pressure roller 5 is 36 cal / ° C. or less.
[0036]
In the present embodiment, the cored bar of the heating roller 3 is made of iron and has a diameter of 20 mm and a wall thickness of 0.7 mm. The material preferably has a small specific heat and a high thermal conductivity, and other metals such as aluminum, copper, and stainless steel can be used. In addition, when the roller diameter is 20 mm made of iron, the thickness ranges from 0.7 mm to 1.4 mm. When the roller diameter is 30 mm made of iron, the thickness ranges from 0.3 mm to 0.9 mm, made of aluminum. When the roller diameter is 30 mm, the wall thickness can be set in the range of 0.6 mm to 1.4 mm. The reason why the wall thickness decreases as the diameter increases is that the bending of the roller in the axial direction is taken into consideration.
[0037]
The fixing belt 2 is provided with a structure for preventing a phenomenon in which the position of the fixing belt 2 is displaced in the axial direction of the roller, that is, so-called deviation in the axial direction, and preventing a fixing defect from occurring in a part of the image. .
In FIG. 3, a block body 20 that can cover the end surface is disposed at the side end of the base 13 in the width direction of the fixing belt 2. The block body 20 faces the end surfaces of the heating roller 3 and the fixing roller 4 around which the fixing belt 2 is wound, and is provided for restricting displacement in the width direction of the roller by abutting against the end surfaces of the rollers. .
As the block body 20, an elastic body such as rubber having a hardness of 80 HS (JIS) or less and higher than the hardness of the surface layer portion of the fixing belt 2 is used. It is formed in an angled shape that is orthogonally folded back to the back surface of the base body 13 and can prevent peeling from the end surface that can occur when bonded only to the end surface.
[0038]
The position of the other end of the substrate 13 that is folded back is the roller around which the fixing belt 2 is wound, in this embodiment, as shown in FIG. 3, the axial end surfaces of each of the heating roller 3 and the fixing roller 4. It is positioned at a position where it can be opposed to. As a result, the fixing belt 2 in which the block body 20 is integrated can be brought close to each other in a state of being opposed to both end surfaces in the axial direction of the rollers 3 and 4 when being wound around the heating roller 3 and the fixing roller 4. When the fixing belt 2 is biased in the axial direction of the roller, the folded end portion on the biased side comes into contact with the axial end surface of the roller.
[0039]
The block body 20 is integrally joined to the side end surface and the back surface of the base body 13 by a heat-resistant adhesive (not shown) so that the block body 20 is not peeled off from the side end surface of the base body 13. The adhesive is not limited to heat resistance as long as it does not deteriorate with the temperature of the fixing belt 2.
[0040]
When the block body 20 is installed on the fixing belt 2, the upper end surface of the block body 20 is joined so as not to protrude upward from the surface layer portion of the fixing belt 2, and the recording medium moving on the belt surface layer portion is connected. It does not inhibit progress.
[0041]
Since the present embodiment is configured as described above, when the fixing belt 2 is manufactured, the block body 20 is also joined to the side end surface and the back surface of the base body 13 of the fixing belt 2 and integrated with the fixing belt 2.
Since the block body 20 integrated with the fixing belt 2 covers the side end surface of the base body 13, human hands and fingers do not directly touch the base body 13. As a result, it is possible to prevent harm from being caused by the base 13 of the fixing belt 2 when the fixing belt 2 is assembled or maintained.
[0042]
When the fixing belt 2 is wound around the heating roller 3 and the fixing roller 4, the folded end portion of the block body 20 is opposed to and close to the axial end surfaces of the rollers 3 and 4. The block body 20 can abut against the roller end surface. As a result, when the fixing belt 2 hits the end surface of the roller, further movement in the axial direction is prevented, so that the opposing positional relationship between the fixing belt 2 and the recording medium does not become inappropriate. Heat transfer for an unfixed image on the recording medium can be prevented from deteriorating. In addition, the block body 20 does not protrude upward from the surface layer portion of the fixing belt 2, and further, since the hardness is set higher than that of the surface layer portion of the fixing belt, movement of the recording medium is not hindered. At the same time, even when the fixing belt 2 moves in the axial direction of the roller and abuts against the end surface of the roller, a state in which the fixing belt 2 is not inadvertently deformed can be maintained. Thus, even when the fixing belt 2 is biased in one direction in the axial direction of the roller, the deformation of the block body 20 is prevented when the block body 20 abuts against the roller end surface, thereby minimizing the bias of the fixing belt 20. Can be suppressed.
[0043]
Next, another embodiment of the present invention will be described.
The embodiment shown in FIG. 4 is characterized in that a block portion 13A having the same function as the block body 20 is integrally formed on a base body 13 which is one of the members constituting the fixing belt 2.
In this case, the base 13 is made of a resin such as polyimide, which is one of the materials used as the base 13, and the block portion 13 </ b> A is integrally formed with the base 13.
[0044]
According to this embodiment, unlike the configuration shown in FIG. 3, it is not necessary to retrofit the fixing belt 2 with the block portion 21 serving as a block body, so that the processing cost can be reduced.
[0045]
Next, another embodiment of the present invention will be described.
The embodiment shown in FIG. 5 is characterized in that a block body 21 provided with an inclined surface 21A is provided instead of the block body 20 shown in FIG.
[0046]
In FIG. 5, similarly to the block body 20 shown in FIG. 3, the block body 21 is a roller which is bent toward the back surface of the base body 13 continuously with the surface facing and close to the side end surface of the base body 13. An angle-shaped configuration having a surface facing and close to the axial end surface of the heating roller 3 (for convenience, the heating roller 3 is shown in FIG. 5) is used.
[0047]
A surface of the block body 21 that faces the end surface in the axial direction of the heating roller 3 is formed with a gradient surface 21A that inclines away from the end surface of the roller toward the radial center from the end surface of the roller.
[0048]
On the gradient surface 21A of the block body 21, the position closest to the axial end surface of the heating roller 3 is positioned so as to keep in contact with or close to the axial end surface of the heating roller 3.
[0049]
Since the present embodiment is configured as described above, the block body 21 is joined and integrated with the base 13 by a heat-resistant adhesive, similarly to the case shown in FIG.
[0050]
The gradient surface 21 </ b> A of the block body 21 is positioned so that the large-diameter portion is in close proximity to the axial end surface of the heating roller 3.
[0051]
When the fixing belt 2 is displaced to one side of the heating roller 3 in the axial direction, the end surface of the heating roller 3 abuts against the gradient surface 21A. When the end surface of the heating roller 3 abuts against the gradient surface 21A, the gradient surface 21A generates component forces F1 and F2 toward the axial direction and the center of the end surface of the heating roller 3 based on the contact force acting at right angles to the gradient surface 21A. To do. For this reason, the block body 21 is prevented from running on the outer peripheral surface from the end surface of the heating roller 3 by pressing the end surface of the heating roller 3 and generating a moving force toward the center of the end surface. As a result, it is possible to prevent the fixing belt 2 from running on the outer peripheral surface of the heating roller 3 when the fixing belt 2 is shifted to one side in the axial direction of the heating roller 3. It is prevented from coming off or causing a larger shift.
[0052]
According to this embodiment, even when the speed at which the fixing belt 2 is displaced changes depending on the rotation speed of the heating roller 3 and the collision force when the fixing belt 2 and the end surface of the heating roller 3 abut against each other due to the deviation speed, Since a component force corresponding to the strength of the collision force is generated, it is possible to reliably prevent the fixing belt 2 from running on the outer peripheral surface of the heating roller 3 or the fixing roller 4. In particular, when the fixing belt 2 is displaced when the fixing belt 2 is moved at a high speed and the heat transfer to the recording medium is accelerated at a high temperature in order to shorten the time required for image formation. However, in this embodiment, since the riding is prevented by the generation of the above-described component force, the fixing due to the bias of the fixing belt 2 is fixed. Defects can be reliably prevented.
[0053]
Next, still another embodiment of the present invention will be described.
FIG. 6 shows the fixing belt 2 provided with the gradient surface 21A shown in FIG. 5. In this embodiment, the inclination angle (θ) of the gradient surface 21A is set to 10 ° <θ <45 °. It has become so.
The inclination angle (θ) is determined for the following reason.
When the block body 21 is provided on the fixing belt 2, when the block body 21 is mounted in a state slightly separated from the end surface in the axial direction of the roller, the end portion in the width direction of the fixing belt 23 where the block body 21 is located is the roller. This means that the roller is displaced from the peripheral surface to the outside in the axial direction of the roller, and this portion is bent and deformed by tension. For this reason, when the block body 21 has the angle shape shown in FIG. 3, the frictional force generated when the block body 21 comes into contact with the end surface of the roller and the direction in which the tension acts may run on the peripheral surface of the roller. In this embodiment, in order to prevent such climbing, even if the end in the width direction of the fixing belt 2 is bent and deformed, the surface facing the roller end surface of the block body 21, that is, the inclined surface 21A is shown in FIG. As shown by the two-dot chain line, the inclination angle of the slope surface 21A is set so as not to contact the roller end surface.
The inclination angle (θ) of the inclined surface 21A can be selected depending on the material of the fixing belt 2, and in the case of a metal as described above, the inclination angle (θ is larger than that of a non-metal such as rubber or resin. ) Is made smaller. In the case of the non-metallic fixing belt 2, the inclination angle (θ) is set to be large in consideration of the fact that bending deformation is likely to occur compared to the case of the metallic belt.
[0054]
According to the present embodiment, the fixing belt 2 is detached from the roller so that the belt can be prevented from climbing when the block body 21 for preventing the bias of the belt is provided at the end of the fixing belt 2 in the width direction. It is possible to prevent unforeseen circumstances such as Thereby, fixing failure can be reliably prevented.
[0055]
【The invention's effect】
According to the invention of claim 1 Symbol placement, the since it is configured to tilt to the state away from the heating roller end face, the heating roller end faces inclined face according to the gradient surface of the block body is directed in the radial direction center side from the end surface of the heating roller It is possible to prevent a force from running on the end surface of the heating roller by generating a component force toward the axial direction of the end surface of the heating roller and the center of the end surface. It can be surely prevented from getting on .
[0056]
According to the second and third aspects of the present invention, even when the widthwise end of the fixing belt undergoes bending deformation due to the inclination angle of the gradient surface , the gradient surface positioned in the direction of bending deformation is the axial direction of the heating roller. It is possible to prevent the fixing belt from running on the outer peripheral surface of the heating roller by facing the end surface but not contacting the end surface .
[0057]
According to the fourth aspect of the present invention, in the case of using a metal base with respect to the inclination angle of the inclined surface, the inclination angle is made smaller than in the case of using a non-metallic base, in other words, a non-metal that is liable to bend and deform. In the case of using a base made of a substrate, it is possible to obtain the prevention of the belt from climbing when it is bent and deformed with a larger inclination angle than that of a metal base, regardless of the material of the base .
[0059]
According to the fifth aspect of the present invention, since the fixing belt does not run on the outer peripheral surface of the heating roller, it is possible to prevent the belt from falling off when it is run and to eliminate fixing failure .
[Brief description of the drawings]
FIG. 1 is a schematic diagram for explaining an example of an image forming apparatus to which a fixing device according to an embodiment of the invention is applied.
FIG. 2 is a schematic diagram for explaining an overall configuration of a fixing device according to an embodiment of the present invention.
FIG. 3 is a cross-sectional view for explaining a main part of the fixing device according to the embodiment of the present invention.
FIG. 4 is a partial cross-sectional view for explaining a main part of a fixing device according to another embodiment of the present invention.
FIG. 5 is a partial cross-sectional view for explaining a main part of a fixing device according to another embodiment of the present invention.
FIG. 6 is a partial cross-sectional view for explaining still another embodiment of the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Fixing device 2 Fixing belt 3 Heating roller 4 Fixing roller 5 Pressure roller 13 Fixing belt base 13A Block part 14 Fixing belt release layer 20, 21 Block body 21A Gradient surface F1, F2 Component force θ Inclination angle of gradient surface

Claims (6)

In an apparatus provided with a belt for fixing an unfixed image carried on a recording medium,
The belt is composed of a metal base wound around a heating roller and a pressure roller facing and abutting the belt, and an elastic body integrated with the base surface and having a release layer on the surface.
A block body covering at least the end surface of the base body is integrated with the end portion in the width direction of the belt ,
The fixing device according to claim 1, wherein the block body includes a slope surface that inclines away from the end surface of the heating roller toward the radial center from the end surface of the heating roller . The fixing device according to claim 1.
The fixing device according to claim 1, wherein the block body is set to a thickness that does not protrude from the surface of the elastic body on the base . The fixing device according to claim 1 or 2,
The block body has an inclination angle (θ) of the gradient surface, and the gradient surface does not contact the end surface of the heating roller when the widthwise end of the belt is bent and deformed in a direction approaching the end surface of the heating roller. A fixing device characterized by being set to an angle . The fixing device according to any one of claims 1 to 3,
The fixing device according to claim 1, wherein an inclination angle (θ) of the gradient surface is selected to be 10 ° <θ <45 ° . The fixing device according to any one of claims 1 to 4, wherein:
The fixing device according to claim 1, wherein the inclination angle (θ) of the inclined surface is set to be smaller than when the block body is made of metal and non-metallic . An image forming apparatus using the fixing device according to claim 1 .

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