KR20080070162A - Fusing Unit of Image Forming Device - Google Patents

Abstract

The fixing unit of the disclosed image forming apparatus according to the present invention has a fixing nip through which a printing medium passes between a heating roller and a heating roller that generates heat to apply heat and pressure to a printing medium on which a visible image formed by a developer is transferred. It is characterized in that it comprises a pressure roller which is pressed toward the heating roller so that the nip) is formed, and the auxiliary heating device is installed in contact with the pressure roller surface to heat the surface of the pressure roller. According to the present invention, in addition to the heating roller, the pressing roller also heats the print medium to which the visible image is transferred, thereby improving fixability.

Description

Fusing unit for image forming apparatus

1 is a side cross-sectional view schematically showing an image forming apparatus equipped with a fixing unit according to an embodiment of the present invention.

Figure 2 is a side cross-sectional view schematically showing a fixing unit according to an embodiment of the present invention.

3 is a side sectional view schematically showing a fixing unit of the image forming apparatus according to another embodiment of the present invention.

Figure 4 is a front sectional view showing a part of the configuration of the fixing unit according to another embodiment of the present invention.

<Description of Signs of Major Parts of Drawings>

20, 60 fixing unit 21, 61 heating roller

23,63.Heat lamp 25,65 ... Pressure roller

40, 70 Auxiliary heating device 41 Abrasion resistant member

42,71.Heating elements 72 ... Protective film

73.Electric heating wire 74 ... Pressure member

The present invention relates to an image forming apparatus, and more particularly, to a fixing unit for fixing a visible image in a powder form formed by a developer under heat and pressure to a print medium in an image forming apparatus for forming an image in an electrophotographic manner. It is about.

In general, an image forming apparatus is a device for developing a black and white image or a color image on a print medium such as paper according to an image signal, and includes a laser printer, an ink jet printer, a copying machine, a multifunction printer, a facsimile, and the like. The image forming method of the various image forming apparatuses includes an electrophotographic method of scanning a beam on a photosensitive member to form an electrostatic latent image, and attaching a developer thereon to a printing medium, and applying liquid ink on the surface of the printing medium according to an image signal. The inkjet method of spraying is typical.

Among these, an electrophotographic image forming apparatus scans a photosensitive member charged at a constant potential to form an electrostatic latent image on the surface thereof, and attaches a developer to the electrostatic latent image to produce a visible image, and then the visible image. Is a device that transfers the print media to the print media.

Such an electrophotographic image forming apparatus transfers a visible image formed by a developer on a surface of a photosensitive member to a print medium, and then fixes the visible image on the surface of the print medium by applying heat and pressure to the print medium on which the visible image is transferred. The process is necessary. To this end, a fixing unit is installed before the discharge part through which the print medium inside the main body of the image forming apparatus is discharged.

The fixing unit includes a heating roller that generates high heat, and a pressure roller installed in close contact with the heating roller. The heating roller is composed of a lamp that generates high heat, an aluminum roller surrounding the lamp, and a release layer provided on the surface of the aluminum roller. Then, the pressure roller is provided with an elastic layer on its outer surface, it is in close contact with the heating roller by the pressure spring. The print medium on which the visible image is transferred during printing is subjected to heat and pressure while passing through a fixing nip formed between the heating roller and the pressure roller to fix the visible image on the surface thereof.

In general, in the mono image forming apparatus for black and white printing, the print medium passes between the heating roller and the pressure roller while the image forming surface on which the visible image is transferred is in contact with the heating roller.

However, in the case of a color image forming apparatus in which a plurality of developers having different colors overlap each other to form a color visible image, the developer layer transferred to the print medium is thick, so that when the print medium passes through the fixing unit, the print medium is heated. There is a lot of wrap jam (stick jam) to stick to. In order to prevent such rap jams, a guide claw is installed near the heating roller to separate the print media from the heating roller, which is attached to the heating roller.However, the print media is separated from the heating roller. The image forming surface of the film may be scratched by the guide claw, resulting in a problem of poor image quality.

In order to prevent the deterioration of the image quality caused by the guide claw, a method in which the print medium passes through the fixing unit while the image forming surface is in contact with the pressure roller is also considered. There is a problem of lack of social settlement.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and provides a fixing unit of an image forming apparatus capable of stably fixing a visible image on the surface of a printing medium while preventing a print jam from sticking to the heating roller. have.

The fixing unit of the image forming apparatus according to the present invention for achieving the above object is a printing medium between the heating roller and the heating roller for generating heat to apply heat and pressure to the printing medium transferred to the visible image formed by the developer It is characterized in that it comprises a pressure roller which is pressed toward the heating roller to form a fixing nip (nip) is passed through, and the auxiliary heating device is installed in contact with the surface of the pressure roller to heat the surface of the pressure roller.

Here, the auxiliary heating device is installed in close contact with the inner surface of the friction preventing member to generate heat and pressurize the friction preventing member to the pressure roller surface and the cylindrical friction preventing member to rotate in contact with the pressure roller surface. It may include a heating element.

In addition, the auxiliary heating device may include a cylindrical heating element that generates heat and rotates in contact with the pressure roller surface.

Here, the pressing member for pressing the heating element to the surface of the pressing roller may be installed inside the heating element.

The heating element may include a cylindrical protective film which rotates in contact with the pressure roller, and a heat transfer member which is integrally coupled to the protective film and generates heat by receiving power.

In addition, the pressure roller may be disposed on the image forming surface side of the print medium such that the image forming surface on which the visible image of the print medium passing through the fixing nip is formed is in contact with the surface thereof.

In addition, the auxiliary heating device may be installed in front of the fixing nip to heat the image forming surface of the print medium entering the fixing nip.

Hereinafter, a fixing unit of an image forming apparatus according to an embodiment of the present invention will be described with reference to the accompanying drawings.

As shown in FIG. 1, the fixing unit 20 of the image forming apparatus according to an embodiment of the present invention includes a plurality of developing units 14a, 14b, 14c, and 14d each provided with a developer of different colors. It is installed in the color image forming apparatus including a. The fixing unit 20 is installed between the transfer unit 17 and the print medium discharging device 18 on the print medium moving path provided inside the image forming apparatus main body 11 to print medium 20 (see FIG. 2). The visible image existing in the form of developer powder on the surface is fixed to the surface of the print medium 20.

When the image forming apparatus starts to print, the pickup roller 13 rotates to pick up the print media loaded in the print medium feeder 12 in a single sheet, and thus, a plurality of developing units 14a, 14b, 14c and 14d. To the) side. The plurality of developing units 14a, 14b, 14c and 14d are provided with a developer of four different colors (for example, yellow, magenta, cyan and black), and each optical scanning device 16a according to an image signal. Each color developer is attached to an electrostatic latent image formed on the surface of each photosensitive member 15a, 15b, 15c, or 15d by the beams scanned by the beams 16b, 16c, and 16d. Form an image. Each color formed in each of the developing units 14a, 14b, 14c, and 14d when the picked up print medium 50 is passed through each of the developing units 14a, 14b, 14c, and 14d. The visible image of is superimposed on the surface of the print medium 50 while being sequentially transferred by the transfer unit 17. When the print medium 50 formed with the color visible images 52 (see FIG. 2) in which the four colors of the visible images overlap, passes through the fixing unit 20, the fixing unit 20 applies heat and pressure to the printing medium 50. In addition, the visible image 52 is fixed to the surface of the print medium 50, and the print medium 50 having been fixed is discharged to the outside of the image forming apparatus main body 21 by the print medium discharge device 18.

As shown in detail in FIG. 2, the fixing unit 20 includes a fixing nip (N, N) through which the printing medium 50 can pass between the heating roller 21 that generates heat and the heating roller 21. Press roller 25 is installed in close contact with the surface of the heating roller 21 to form a), and the auxiliary heating device 40 is installed to contact the surface of the pressure roller 25 to heat the surface of the pressure roller 25 It includes.

The heating roller 21 is a hollow cylindrical roller body 22, a heating lamp 23 is installed in the center of the roller body 22 to generate a high heat, and the release is provided on the outer surface of the roller body 22 Layer 24. The heating roller 21 heats the print medium 50 while rotating to transfer the print medium 50 passing through the transfer nip N toward the print medium discharge device 18 (see FIG. 1). Heat generated from the heating lamp 23 is transferred to the roller body 22 and to the print medium 50 passing through the transfer nip N through the release layer 24.

The pressure roller 25 includes a roller body 26 and an elastic layer 27 provided on the outer surface of the roller body 26. The pressure roller 25 is installed to be in close contact with the heating roller 21 toward the image forming surface 51 on which the visible image 52 of the printing medium 50 is formed so that the printing medium 50 can pass through the fixing nip N. At this time, the print medium 50 is pressed while rotating in contact with the image forming surface 51 of the print medium 50.

The auxiliary heating device 40 is installed in front of the fixing nip N into which the print medium enters the fixing nip N so as to contact the pressure roller 25. The auxiliary heating device 40 is friction prevented so as to be in close contact with the surface of the pressure roller 25 with the cylindrical friction preventing member 41 rotating in contact with the surface of the pressure roller 25 and the friction preventing member 41 therebetween. And a heat generating element 42 provided inside the member 41.

The friction preventing member 41 is fixed to the surface of the pressure roller 25 and the surface of the heating element 42 when the heating element 42 fixedly installed is in direct contact with the surface of the pressure roller 25 and the pressure roller 25 rotates. It is to prevent wear or breakage by friction, and is made in the form of a thin cylindrical film. As the material of the anti-friction member 41, polyimide (Pi) having high mechanical strength, high impact strength, and good electrical insulation and abrasion resistance may be used. The friction preventing member 41 may be made of various other materials that can be deformed and heat resistant in addition to the polyimide. When the surface of the friction preventing member 41 is in close contact with the surface of the pressure roller 25 and the pressure roller 25 rotates, the friction preventing member 41 rotates in the opposite direction to the pressure roller 25 by friction with the pressure roller 25. The inner surface of the friction preventing member 41 may be coated with a lubricating material for reducing friction between the inner surface of the friction preventing member 41 and the contact surface 43 of the heating element 42.

The heating element 42 presses the friction preventing member 41 so that the generated heat can be transferred to the surface of the pressing roller 25 so that the surface of the friction preventing member 41 is in close contact with the surface of the pressing roller 25. The contact surface 43 is also in close contact with the inner surface of the friction preventing member 41. The heating element 42 has a length corresponding to the length of the pressure roller 25 so that heat can be evenly applied to the entire surface of the pressure roller 25. The heating element 42 may be flat as shown, the contact surface 43 in contact with the inner surface of the friction preventing member 41, may be convex to correspond to the inner surface of the friction preventing member 41, the pressure roller ( It may be recessed to correspond to the surface of 25). The heating element 42 may be configured in the form of a thermal conductor that receives heat from an external heat source and applies heat or may be configured in the form of a heating element that generates heat by receiving power.

The fixing unit 20 of the image forming apparatus according to the present invention has a heating roller so that the print medium 50 to which the visible image 52 is transferred can be transferred toward the print medium discharging device 18 when the image forming apparatus is operated. 21 and the pressure roller 25 rotate in the opposite direction in close contact with each other. At this time, the heating lamp 23 and the heating element 42 of the auxiliary heating device 40 operates to generate heat, and the friction preventing member 41 of the auxiliary heating device 40 is pressurized while being in close contact with the pressure roller 25. It rotates in the opposite direction to the roller 25. The surface of the heating roller 21 is heated by the heat generated by the heating lamp 23, and the surface of the pressure roller 25 is also heated by the heat generated by the heat generator 42.

When the print medium 50 to which the visible image 52 has been transferred passes through the transfer unit 17 (see FIG. 1) and enters into the fixing nip N between the heating roller 21 and the pressure roller 25. The image forming surface 51 of 50 is heated by heat generated by the auxiliary heating device 40. Then, the heated printing medium 50 passes through the fixing nip N, and both surfaces thereof are pressurized by the heating roller 21 and the pressure roller 25 and heated at the same time. Thus, the visible image 52 in the form of a developer powder of the image forming surface 51 is melted and fixed to the image forming surface 51.

Here, the print medium 50 is preheated by the auxiliary heating device 40 before entering the fixing nip N, and the image forming surface 51 does not come into contact with the high temperature heating roller 21 and is heated. Since it passes through the fixing nip N in contact with the surface of the pressure roller 25 heated by the apparatus 40, it does not stick to the heating roller 21 while exiting the fixing nip N.

In the present invention, a heat source may be used instead of the heating lamp 23 as a heat source of the heating roller 21, the structure of the heating roller 21 and the pressure roller 25 is made of another known structure. Can be.

3 shows a fixing unit of the image forming apparatus according to another embodiment of the present invention.

As shown in FIG. 3, the fixing unit 60 of the image forming apparatus according to another embodiment of the present invention is a heating roller having a heating lamp 63, like the fixing unit 60 according to the embodiment. 61, a pressure roller 65 having a roller body 66 and an elastic layer 67, and an auxiliary heating device installed to contact the surface of the pressure roller 65 in order to heat the surface of the pressure roller 65 ( 70).

Here, the structure and arrangement of the heating roller 61 and the pressure roller 65 is the same as the fixing unit 60 according to the embodiment, the auxiliary heating device 70 is rotated in contact with the surface of the pressure roller 65 It comprises a cylindrical heating element 71 and a pressing member 74 for pressing the heating element 71 to the surface of the pressure roller (65).

The cylindrical heating element 71 is installed to be in contact with the surface of the pressure roller 65, when the pressure roller 65 rotates while rotating in the opposite direction to the pressure roller 65 by friction with the pressure roller 65, the pressure roller ( Heat the surface of 65). The heating element 71 has a size substantially equal to the length of the pressure roller 65 so as to evenly heat the entire surface of the pressure roller 65 in contact with the printing medium 50. The heating element 71 includes a cylindrical protective film 72 (see FIG. 4) and a heating wire 73 (see FIG. 4) wound inside the protective film 72.

The protective film 72 may be made of the same polyimide (Pi) as the material of the anti-friction member 41 of the fixing unit 20 according to the above embodiment. It may be made of another material having good insulation.

In addition, the heating wire 73 generates heat by receiving power, as shown in FIG. 4, and is uniformly wound on the inside of the protective film 72 to be evenly disposed on the entire protective film 72. Therefore, even if the contact portion of the heating roller 71 and the heating element 71 in contact with the pressing roller 65 is continuously changed by the rotation of the pressure roller 65, the heat generated from the heating element 71 is constant on the surface of the pressure roller 65. Is applied.

The pressing member 74 presses the inner surface of the heating element 71 toward the pressing roller 65 so that heat generated from the heating element 71 can be effectively transmitted to the surface of the pressing roller 65. To the pressure roller 65. Since the friction member is generated between the pressing member 74 and the heating element 71 when the heating element 71 rotates, the contact surface 75 has a convex shape to reduce the friction. In addition, in order to reduce friction between the inner surface of the heating element 71 and the contact surface 75 of the pressing member 74, a lubricating material may be applied to the inner surface of the heating element 71 or the contact surface 75 of the pressing member 74. Can be.

The auxiliary heating device 70 having such a configuration is installed in front of the fixing nip N into which the print medium 50 enters the fixing nip N, like the fixing unit 60 according to the embodiment. Therefore, the auxiliary heating device 70 not only heats the surface of the pressure roller 65 but also heats the image forming surface 51 of the print medium 50 entering the transfer nip N.

In the fixing unit 60 according to another embodiment of the present invention as described above, when the print medium 50 to which the visible image 52 is transferred is transferred, the auxiliary heating apparatus 70 forms an image forming surface of the print medium 50 ( 51 is first heated, and then, when the print medium 50 enters the fixing nip N, the heating roller 61 and the pressure roller 65 apply heat and pressure to the print medium 50. Here, the pressure roller 65 is in direct contact with the image forming surface 51 of the print medium 50 to press the print medium 50 and at the same time using the heat transferred to the auxiliary heating device 70 The formation surface 51 is heated. Accordingly, the visible image 52 in the form of developer powder is melted by the pressure between the heating roller 61 and the pressure roller 65 and the heat transmitted from the heating roller 61 and the pressure roller 65 to form an image forming surface ( 51).

According to the present invention described above, since the auxiliary heating device installed in contact with the surface of the pressure roller heats the surface of the pressure roller in contact with the surface of the printing medium, the printing medium to which the visible image has been transferred, together with the heat of the heating roller, Heat is added. Therefore, fixability is improved.

In addition, according to the present invention, since the press roller having a lower surface temperature than the heating roller is disposed on the image forming surface on which the visible image is transferred, the printing medium exiting the fixing nip between the heating roller and the pressing roller is heated roller as in the prior art. There is no problem with sticking to.

Further, according to the present invention, since the auxiliary heating device for heating the press roller preheats the image forming surface of the print medium entering the fixing nip, fixing performance is further improved.

The present invention described above is not limited to the configuration and operation as illustrated and described. That is, the present invention is capable of various changes and modifications within the spirit and scope of the appended claims.

Claims (7)

The visible image formed by the developer is pressed toward the heating roller to form a fixing nip through which the printing medium passes between the heating roller which generates heat to apply heat and pressure to the transferred printing medium. In the fixing unit of the image forming apparatus including a pressure roller, The fixing unit of the image forming apparatus, characterized in that it further comprises an auxiliary heating device which is installed to contact the surface of the pressure roller to heat the surface of the pressure roller. The method of claim 1, The auxiliary heating device includes a cylindrical anti-friction member that rotates in contact with the pressure roller surface, and a heating element that is installed in close contact with the inner surface of the anti-friction member to generate heat and pressurize the anti-friction member to the pressure roller surface. A fixing unit of the image forming apparatus, characterized in that. The method of claim 1, The auxiliary heating device is a fixing unit of the image forming apparatus, characterized in that it comprises a cylindrical heating element for generating heat and rotating in contact with the surface of the pressure roller. The method of claim 3, wherein A fixing unit of the image forming apparatus, characterized in that the pressing member for pressing the heating element to the surface of the pressing roller is installed inside the heating element. The method of claim 3, wherein The heating element is a fixing unit of the image forming apparatus, characterized in that it comprises a cylindrical protective film that rotates in contact with the pressure roller, and a heat transfer member integrally coupled to the protective film and applied with power. The method of claim 1, And the pressure roller is disposed on the image forming surface side of the printing medium such that the image forming surface on which the visible image of the printing medium passing through the fixing nip is formed is in contact with the surface of the pressing roller. The method of claim 6, And the auxiliary heating device is installed in front of the fixing nip so as to heat the image forming surface of the printing medium entering the fixing nip.

Images