JP5446181B2 - Fixing apparatus and image forming apparatus - Google Patents

Description

  The present invention has a pair of rotating fixing members, a fixing device for fixing a toner image on the sheet by passing a sheet carrying the toner image between the nips thereof, and an image formation having the fixing device Relates to the device. More specifically, the present invention relates to a fixing device and an image forming apparatus in which one of a pair of fixing members has a cylindrical belt member.

2. Description of the Related Art Conventionally, an electrophotographic image forming apparatus has a fixing device for fixing a toner image on a sheet. As a fixing device, for example, there is a fixing device including a heating roller and an endless belt-like fixing belt that is pressed against the heating roller (see, for example, Patent Document 1). In the apparatus disclosed in this document, a fixing nip is formed by pressing a pressure contact member disposed inside a fixing belt toward a heating roller. In particular, a member using a rubber material pad member held by a rigid member is disclosed as a pressure contact member.
JP 2003-5553 A

  However, in the conventional fixing device described above, the size of the nip is limited by the diameter of the heating roller. That is, in order to make the nip larger, it is necessary to make the heating roller larger in diameter. Increasing the diameter of the heating roller has problems such as increasing the heat capacity, increasing the time required for warm-up, and increasing the size and energy consumption of the device.

  The present invention has been made to solve the problems of the conventional fixing device described above. That is, an object of the present invention is to provide a fixing device and an image forming apparatus that can obtain a larger nip width without increasing the diameter of the heating roller.

The fixing device of solving the present invention made for the purpose of this exercise is, hand in together when both rotation has a pair of fixing members Ru Oh the heating roller and the other Ri beltlike der has an elastic layer, the toner image A fixing device that fixes a toner image on a sheet by passing the sheet carrying the toner between a pair of fixing members, and is disposed in contact with the back surface of the belt-shaped fixing member. The fixing member includes a pressing member that presses the fixing member toward the heating roller . The pressing member is positioned upstream of the first pressing member and the first pressing member in the sheet conveyance direction, and is more than the first pressing member. also provided sticking out toward the heating roller, and a softer first pressing member second pressing member, the surface facing the heat roller of the second pressing member, and extending to the downstream side in the conveying direction of the sheet Face and pressure contact member The angle between the direction to be pressed toward the heating roller is intended to be within the scope of 95 ° or more 105 ° or less.

According to the fixing device of the present invention, the belt-shaped fixing member is pressed against the heating roller by the pressing member, so that a fixing nip is formed between them. Here, the pressure contact member has a relatively hard first pressure contact member and a softer second pressure contact member. The second pressure contact member is positioned upstream of the first pressure contact member in the sheet conveyance direction. Therefore, it is possible to obtain a good separation property by the first pressure contact member while obtaining a large nip width by the second pressure contact member. Here, the surface of the heating roller facing the second pressure contact member is slightly larger than a right angle with respect to the direction in which the pressure contact member is pressed toward the heating roller . In the present invention, the contact area between the second pressure contact member and the heating roller can be increased by providing the second pressure contact member so as to be inclined within a range of 95 ° to 105 °. Thereby, a larger nip width can be obtained without increasing the diameter of the heating roller.

Further, in the present invention, the first pressing member has a flat portion on a surface opposed to the heating roller, the angle between the surface facing the heat roller of the planar portion and a second pressing member, 10 ° or 20 ° Within the following range.
Thus, the sheet that has passed through the nip between the second pressure contact member and the heating roller is smoothly guided to the nip between the first pressure contact member and the heating roller, and the exit from the nip. Properly separated.

The present invention includes an image forming unit, hand in together when both rotated along with the other Ri beltlike der has a pair of fixing members Ru Oh a heating roller having an elastic layer, the toner applied by the image forming section An image forming apparatus having a fixing device that fixes a toner image on a sheet by passing a sheet carrying an image between a pair of fixing members. The pressure contact member is disposed in contact with the back surface of the fixing member and presses the belt-shaped fixing member toward the heating roller . The pressure contact member conveys the sheet more than the first pressure contact member and the first pressure contact member. A second pressure contact member that is located upstream of the first pressure contact member and protrudes toward the heating roller from the first pressure contact member and is softer than the first pressure contact member. The first pressure contact member faces the heat roller . Do To have a flat portion, the surface facing the heat roller of the second pressing member, the angle of the surface which is extended to the downstream side in the conveying direction of the sheet, the direction in which the pressing member is pressed toward the heating roller However, in an image forming apparatus in which the angle between the plane portion and the surface of the second pressure contact member facing the heating roller is in the range of 10 ° to 20 °. It also extends.

  According to the fixing device and the image forming apparatus of the present invention, a larger nip width can be obtained without increasing the diameter of the heating roller.

  DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the best mode for embodying the present invention will be described in detail with reference to the accompanying drawings. In this embodiment, the present invention is applied to an electrophotographic image forming apparatus.

  As shown in FIG. 1, the color printer 1 of the present embodiment has process units 10Y, 10M, 10C, and 10K for each color of yellow (Y), magenta (M), cyan (C), and black (K). Are arranged along the intermediate transfer belt 11 and are of a so-called tandem type. The color printer 1 further includes a paper feed cassette 12, a secondary transfer unit 13, a fixing unit 14, a paper discharge roller 15, and the like. Each of the process units 10Y, 10M, 10C, and 10K is a general unit for forming an image. 25, a cleaning device 26, and the like.

  At the time of image formation, the surface of the photoreceptor 21 is uniformly charged by the charging device 22. Thereafter, an electrostatic latent image based on the image data is formed by the exposure device 23. Further, a developer image is formed on the photosensitive member 21 by supplying a developer to the electrostatic latent image by the developing device 24. The developer images of the respective colors formed on the respective photoreceptors 21 of the process units 10 of the respective colors are sequentially transferred to the intermediate transfer belt 11 and superimposed. The developer remaining on the photoreceptor 21 after the transfer is removed by the cleaning device 26.

  On the other hand, sheets are fed from the sheet feeding cassette 12 one by one. Then, the developer image superimposed on the intermediate transfer belt 11 is transferred to the paper in the secondary transfer unit 13. The sheet on which the developer image is transferred is guided to the fixing unit 14. Further, the developer image is fixed on the sheet by being pressurized and heated in the fixing unit 14. The sheet on which the image is fixed is discharged to the outside by a discharge roller 15.

  As shown in FIG. 2, the fixing unit 14 of this embodiment includes a heating roller 31 and a pressure belt 32. A heater 33 such as a halogen lamp is disposed inside the heating roller 31. Thereby, the surface of the heating roller 31 is maintained at an appropriate temperature during the fixing process. The pressure belt 32 is a flexible endless belt-like member. A pressing member 34 that presses the pressure belt 32 toward the heating roller 31 is disposed inside the pressure belt 32. By this pressing member 34, a fixing nip is formed between the heating roller 31 and the pressure belt 32.

  During the fixing process, the sheet is conveyed upward from below in the figure with the surface carrying the developer directed toward the heating roller 31. The toner image is fixed at the fixing nip between the heating roller 31 and the pressure belt 32, and is further conveyed upward in the drawing.

  The heating roller 31 includes a core metal 35, an outer peripheral side intermediate layer 36, and an outer peripheral side surface layer 37. In this embodiment, the outer diameter of the heating roller 31 is preferably about 20 to 50 mm. The core metal 35 is a pipe-shaped member made of metal such as aluminum or iron. The thickness of the core metal 35 is about 0.1 to 5 mm.

  The intermediate layer 36 of the heating roller 31 is formed of a material having both elasticity and heat resistance, such as silicone rubber and fluorine rubber. The thickness of the intermediate layer 36 is preferably in the range of 0.05 to 5 mm. The surface layer 37 may be formed of a fluororesin tube having excellent releasability. Alternatively, a fluororesin coating may be used instead of the tube. The thickness of the surface layer 37 is preferably about 5 to 100 μm.

  The pressure belt 32 has a base layer 38 on the inner surface side and a surface layer 39 on the outer surface side. It is desirable that the pressure belt 32 has a size such that the outer diameter when it is cylindrical is in the range of 20 to 100 mm. The base layer 38 is formed using a heat-resistant resin such as polyimide, polyamide, or polyimideamide, or a metal material such as aluminum, stainless steel, or nickel. The surface layer 39 is provided with releasability by a fluorine-based tube or a fluorine-based coating. The surface layer 39 may further have conductivity. The thickness of the surface layer 39 is desirably about 5 to 100 μm.

  Next, the pressing member 34 will be described. As shown in FIG. 2, the pressing member 34 includes a rigid pad 41 and an elastic pad 42, which are held by a holding frame 43. The rigid pad 41 and the elastic pad 42 are members that are uniform in the sheet width direction (depth direction in the figure). Alternatively, for example, the size may be different between the center and the end in the width direction of the sheet. The holding frame 43 is formed of a metal drawing material or extrusion material such as aluminum or iron, or a sheet metal. The rigid pad 41 and the elastic pad 42 will be described later.

  Further, the holding frame 43 is pressed by the arm member 44 at both ends in the width direction. The arm member 44 is provided so as to be rotatable about a rotation shaft 45, receives the pressing force P0 at the upper part in the figure, and presses the pressing member 34 leftward in the figure. Here, the force with which the pressing member 34 is pressed by the pressing force P0 is defined as the pressing force P. A heat source may be disposed on the pressing member 34, or a rotating body such as a roller may be disposed on the inner side of the pressure belt 32 for bridging the pressure belt 32.

  Next, the rigid pad 41 and the elastic pad 42 of the pressing member 34 will be described with reference to FIG. FIG. 3 shows the main part extracted from FIG. As shown in FIG. 3, the rigid pad 41 is a member that holds the elastic pad 42, and is a substantially rod-shaped member that has a width at least equal to the fixing width of the heating roller 31 in the depth direction in the drawing. If the heating roller 31 has a full width equal to or greater than the fixing width, the rigid pad 41 may be shorter than the full width of the heating roller 31. The rigid pad 41 is formed of a harder material than the pressure belt 32 and the elastic pad 42. In this embodiment, for example, a resin such as polyphenylene sulfide, polyimide, liquid crystal polymer, a metal such as aluminum, iron, and stainless steel, or a ceramic is suitable.

  In this embodiment, the back surface 41a, to which the rigid pad 41 receives the pressing force P via the holding frame 43 (see FIG. 2), is a surface substantially perpendicular to the pressing force P and is a surface parallel to the axis of the heating roller 31. is there. Further, on the surface of the rigid pad 41 that is disposed on the heating roller 31 side, a planar front pressing portion 41b parallel to the back surface 41a and a groove portion 41c to which the elastic pad 42 is fixed are formed. The front pressing portion 41b is pressed against the heating roller 31 with the pressure belt 32 interposed therebetween.

  The elastic pad 42 has a prismatic shape that is long in the depth direction in FIG. The front surface 42a on the upper left side of the elastic pad 42 is almost entirely pressed against the heating roller 31 with the pressure belt 32 interposed therebetween. The portion pressed against the heating roller 31 by the elastic pad 42 is lower in the drawing than the portion pressed by the front pressing portion 41b of the rigid pad 41, and is upstream in the paper transport direction. The elastic pad 42 is formed of a material having elasticity and heat resistance, such as silicone rubber and fluorine rubber. The hardness of the elastic pad 42 is preferably about 15 to 30 in terms of Asker C hardness. The thickness of the elastic pad 42 (the size in the left-right direction in the figure) is preferably about 0.1 to 10 mm.

  The elastic pad 42 may be formed integrally with a metal plate such as stainless steel, aluminum, or iron in order to improve assembly and productivity. When the elastic pad 42 integrated with the metal plate is used as described above, the metal plate is disposed on the side in contact with the inner surface of the groove 41c of the rigid pad 41.

  Next, the mounting angle with respect to the pressing force P of the front surface pressing portion 41b of the rigid pad 41 and the front surface 42a of the elastic pad 42 in the pressing member 34 of this embodiment will be described. In this embodiment, only the two places are pressed against the heating roller 31 via the pressure belt 32, and a fixing nip is formed by these two places. In order to increase the speed of the fixing unit 14, it is desirable to increase the fixing nip.

In this embodiment, by setting the angle θ formed by the front surface 42a of the elastic pad 42 and the pressing force P to an angle within an appropriate range, a larger fixing nip can be obtained for the heating roller 31 having the same diameter as the conventional one. Succeeded. That is, in the present embodiment, the angle θ is set to an angle slightly larger than the right angle, specifically within the following range.
95 ° ≦ θ ≦ 105 °
In FIG. 3, the alternate long and short dash line indicating the right end of the range θ is an extension line of the front surface 42a of the elastic pad 42 downstream in the transport direction.

  The front surface 42a of the elastic pad 42 is disposed on the upstream side in the paper transport direction from the front surface pressing portion 41b, and slightly protrudes toward the heating roller 31 side from the front surface pressing portion 41b. Therefore, when the pressing force P is set according to the degree of pressure contact between the front pressing portion 41 b and the heating roller 31, the protruding portion of the front surface 42 a is pressed against the heating roller 31. Furthermore, by setting the angle θ within the above range, it is possible to ensure a fairly wide range of the front surface 42a that is pressed against the heating roller 31. Note that it is preferable that the length of the front surface 42a in the paper conveyance direction is increased within a range that does not hinder the rotation of the pressure belt 32.

Further, as shown in FIG. 3, the rigid pad 41 is pressed by the heating roller 31 only on the flat front pressing portion 41 b. In the present embodiment, the front pressing portion 41b is a flat surface, and the upper portion in the drawing is a slope that slightly approaches the heating roller 31 side. For example, it is preferable to form it inclined forward by about 5 ° from the surface perpendicular to the pressing force P. That is, the angle φ formed by the front surface 42a of the elastic pad 42 and the front surface pressing portion 41b of the rigid pad 41 is ((θ−90 °) + 5 °) and is within the following range.
10 ° ≦ φ ≦ 20 °
In the figure, the alternate long and short dash line indicating the left end of the range of φ is an extension of the front pressing portion 41b of the rigid pad 41.

  Thus, by making the front pressing portion 41b a slightly inclined plane, it is possible to obtain an appropriate sheet separation property and it is preferable from the viewpoint of the durability of the heating roller 31. That is, the intermediate layer 36 of the heating roller 31 is appropriately deformed at the nip exit, and the sheet can be easily separated by the restoring force. The above θ and φ are angles at the time of attachment, and may actually be slightly different from those shown in the figure due to deformation of each part due to attachment.

  In addition, it is not preferable that the front pressing portion 41b is a curved surface instead of a flat surface for the following reason. If the front pressing portion 41 b is convex toward the heating roller 31, the deformation amount of the intermediate layer 36 is large, which is not preferable for the durability of the heating roller 31. On the other hand, if it is concave on the heating roller 31 side, the deformation amount of the intermediate layer 36 is too small, and there is a possibility that a paper separation defect will occur.

  Next, FIG. 4 shows the result of examining the change in the nip width by changing the angle θ formed by the front surface 42a of the elastic pad 42 and the pressing force P. The nip width here is a width obtained by combining the rigid pad 41 and the elastic pad 42. Here, the heating roller 31 having an outer diameter of 26 mmφ was used. Within the range of this figure, it was confirmed that the nip width increases as the angle increases.

  As described above in detail, according to the image forming apparatus 1 of this embodiment, the pressing member 34 has the rigid pad 41 and the elastic pad 42, and faces the heating roller 31 from the inner peripheral side of the pressure belt 32. Is pressed. Here, the surface of the elastic pad 42 that faces the heating roller 31 is a flat surface, and the angle θ between the surface and the direction of the pressing force is in the range of 95 ° ≦ θ ≦ 105 °. Thereby, most of the front surface 42 a of the elastic pad 42 can be pressed against the heating roller 31. Therefore, the image forming apparatus can obtain a larger nip width without increasing the diameter of the heating roller.

In addition, this form is only a mere illustration and does not limit this invention at all. Therefore, the present invention can naturally be improved and modified in various ways without departing from the gist thereof.
For example, the shapes of the rigid pad 41 and the elastic pad 42 other than the side pressed by the heating roller 31 are not limited to those illustrated. Further, the configuration for pressing the pressing member 34 toward the heating roller 31 is not limited to the above, and any configuration may be used. The present invention can be applied to an image forming apparatus such as a monochrome / color copying machine, a printer, a FAX, or a complex machine of these.

1 is a schematic configuration diagram illustrating an image forming apparatus according to an embodiment. 1 is a schematic configuration diagram illustrating a fixing device of the present embodiment. It is explanatory drawing which shows arrangement | positioning of a press member. It is a graph which shows the relationship between the attachment angle of an elastic body pad, and nip width.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Image forming apparatus 14 Fixing part 31 Heating roller 32 Pressure belt 34 Pressing member 36 Intermediate | middle layer 41 Rigid pad 42 Elastic body pad

Claims (2)

Both hand in together when rotating the belt-shaped der Ri other has a pair of fixing members Ru Oh a heating roller having an elastic layer, passing the sheet carrying the toner image between said pair of fixing members In the fixing device for fixing the toner image on the sheet,
A pressure contact member that is disposed in contact with the back surface of the belt-shaped fixing member and presses the belt-shaped fixing member toward the heating roller ;
The pressure contact member is:
A first pressure contact member;
A second pressure contact member that is located upstream of the first pressure contact member in the sheet conveying direction, protrudes toward the heating roller than the first pressure contact member, and is softer than the first pressure contact member; Have
The first pressure contact member has a flat portion on a surface facing the heating roller ;
An angle formed between a surface of the second pressure contact member that faces the heating roller and a surface that extends downstream in the sheet conveyance direction and a direction in which the pressure contact member is pressed toward the heating roller is 95. Within the range of not less than ° and not more than 105 °,
An angle formed by the plane portion and a surface of the second pressure contact member facing the heating roller is in a range of 10 ° to 20 °. An image forming unit, hand in together when both rotated along with the other Ri beltlike der has a pair of fixing members Ru Oh a heating roller having an elastic layer, carries the toner image provided by the image forming section An image forming apparatus having a fixing device that fixes a toner image on the sheet by passing the sheet between the pair of fixing members,
The fixing device includes:
A pressure contact member that is disposed in contact with the back surface of the belt-shaped fixing member and presses the belt-shaped fixing member toward the heating roller ;
The pressure contact member is:
A first pressure contact member;
A second pressure contact member that is located upstream of the first pressure contact member in the sheet conveying direction, protrudes toward the heating roller than the first pressure contact member, and is softer than the first pressure contact member; Have
The first pressure contact member has a flat portion on a surface facing the heating roller ;
An angle formed between a surface of the second pressure contact member that faces the heating roller and a surface that extends downstream in the sheet conveyance direction and a direction in which the pressure contact member is pressed toward the heating roller is 95. Within the range of not less than ° and not more than 105 °,
An image forming apparatus, wherein an angle formed by the plane portion and a surface of the second pressure contact member facing the heating roller is in a range of 10 ° to 20 °.

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