KR20060023767A - Fixing Roller of Image Forming Device - Google Patents

Abstract

A fixing roller of an image forming apparatus is disclosed. The fixing roller of the disclosed image forming apparatus includes: a roller body rotatably disposed on a transfer path of a printing medium on which an image is transferred; And a heater installed inside the roller body to generate heat when a voltage is applied to the roller body, wherein the roller body extends from the center of rotation to the outer circumferential surface of the roller body to reduce the density difference of the magnetic field generated by the heater. The radial distance of is uneven in the longitudinal direction of the roller body. As a result, it is possible to provide a uniform fixing temperature by compensating for the density variation of the magnetic field generated at both ends and the central portion of the roller body.

Image forming apparatus, induction coil, fixing, roller, magnetic field, heater, heat generation, density.

Description

Image fixing roller of image forming apparatus

1 is a longitudinal sectional view schematically showing a fixing roller of a general image forming apparatus;

2 is a cross-sectional view schematically showing a fixing roller of an image forming apparatus according to an embodiment of the present invention;

3 is a cross-sectional view schematically showing a fixing roller of an image forming apparatus according to another embodiment of the present invention, and

4 is a cross-sectional view schematically showing a fixing roller of the image forming apparatus according to another embodiment of the present invention.

<Description of the symbols for the main parts of the drawings>

110, 210, 310: roller body 120, 220, 320: heater

130, 230, 330: insulator 140, 240, 340: coating layer

250, 350: magnetic core

The present invention relates to an image forming apparatus, and more particularly, to a fixing roller of an image forming apparatus for fixing an image transferred to a printing medium by heating and pressing.                         

In general, an image forming apparatus such as a copier, a printer, a facsimile, or a multifunction printer incorporating these functions into one device to implement a combination thereof has a function of printing an input image signal on a print medium.

The image forming apparatus includes a developing unit, a transfer unit, a fixing unit, and the like. The fixing unit applies heat and pressure to the image transferred from the transfer unit to the print medium so that the toner image is fused to the print medium. An example of a fixing unit is shown in FIG. 1.

Referring to FIG. 1, the fixing unit includes a first fixing roller 10 and a second fixing roller 20, which have predetermined fixing nips and are in contact with each other.

The halogen lamp 11 is installed inside the first fixing roller 10. The halogen lamp 11 heats the first fixing roller 10 to a predetermined fixing temperature so that the first fixing roller 10 maintains a constant temperature. As a result, the toner image transferred to the printing medium P passing between these rollers 10 and 20 is heated to a temperature necessary for fusion.

The second fixing roller 20 is pressurized by the elastic body 21 toward the first fixing roller 10, whereby the toner image on the printing medium P heated by the first fixing roller 10 to a predetermined temperature. It is made to be fused to this printing medium (P).

However, in the fixing unit of the general image forming apparatus as described above, heat generated from the halogen lamp 11 installed in the inner central portion of the first fixing roller 10 is transferred to the first fixing roller 10 in a radiant heat transfer method. And the first fixing roller 10 is heated. Therefore, there is a problem that heat loss is generated by heating up to an unnecessary portion of the first fixing roller 10 (for example, a portion which is not in contact with the print medium). In addition, since the first fixing roller 10 is preheated in a non-contact manner, the preheating time to the fixing temperature is long, and thus, the warm-up time is long.

In order to remedy this problem, a method of shortening the warm-up time by heating the first fixing roller 10 by induction heat caused by a magnetic field generated by an induction coil and resistance heat caused by a resistance load of the induction coil is applied. It is actively being researched and developed.

However, when the first fixing roller 10 is heated using the induction coil, the magnetic field generated in the induction coil is concentrated at both ends of the first fixing roller 10. For this reason, the density difference between the magnetic field of the center part and the both ends of the 1st fixing roller 10 generate | occur | produces, and there exists a problem that a fixing temperature becomes nonuniform.

The present invention has been made in view of the above, and an object thereof is to provide a fixing roller of an image forming apparatus having an improved structure to uniformly control the fixing temperature.

The fixing roller of the image forming apparatus according to the present invention for achieving the above object, the roller body is rotatably disposed on the transfer path of the printing medium is transferred image; And a heater installed inside the roller body to generate heat when voltage is applied, and to heat the roller body, wherein the roller body is configured to reduce the density difference of the magnetic field generated by the heater from the rotation center. The radial distance to the outer circumferential surface of the roller body is uneven in the longitudinal direction of the roller body.

According to a preferred embodiment of the present invention, the radial distance is preferably reduced in the central portion than both ends of the roller body.

In addition, a magnetic core for concentrating the magnetic field may be installed at the outer center portion of the roller body.

On the other hand, the outer peripheral surface of the roller body is preferably formed in a junk round shape.

On the other hand, the heater is coated with an insulator is in close contact with the inside of the roller body, and includes an induction coil for heating the roller body by the heat of induction by the magnetic field generated by the applied voltage and the resistance heat by the self-resistance load.

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

2 is a view schematically showing a fixing roller of an image forming apparatus according to an embodiment of the present invention. Referring to the drawings, the fixing roller 100 of the image forming apparatus includes a roller body 110, a heater 120, and an insulator 130. Here, reference numeral 140 denotes a coating layer coated with a predetermined material on the outer circumferential surface 111 of the roller body 110. The coating layer 140 may be formed of a material such as heat resistant Teflon.

The roller body 110 is rotatably disposed on a transfer path of the print medium on which the image is transferred, thereby heating and fixing the image of the print medium. Here, the roller body 110 is preferably formed of an alloy containing high thermal conductivity copper, aluminum, iron, nickel, etc. in order to receive the heat generated from the heater 120.                     

In addition, the roller body 110 is a hollow pipe, the end cap 112 is coupled to both ends. The end cap 112 is formed of an injection molded material made of an insulating material, and is provided with a terminal 113 electrically connected to the heater 120 to apply power to the heater 120 on the outside. Reference numeral 114 is an air vent (Air Bent) formed in the end cap 112 to prevent the expansion of the air pressure inside the heating roller (110).

The heater 120 is attached to the inner circumferential surface by means such as a high temperature adhesive to the roller body 110 is disposed to rotate with the roller body 110. Here, the heater 120 may include an induction coil driven by receiving an AC voltage from a high frequency isolation transformer (not shown). The induction coil generates induction heat due to a magnetic field generated by an applied AC voltage and resistance heat due to its own resistance load.

The induction coil may be formed by alloying at least one of materials such as copper, aluminum, iron, and nickel, which may generate the induction heat and the heat of resistance. In addition, the induction coil may have various shapes such as square, round, oval or ribbon.

The insulator 130 is formed to surround the outer circumferential surface of the heater 120 for electrical insulation between the roller body 110 and the heater 120. Therefore, the insulator 130 may suppress the loss of the magnetic field generated by the heater 120. Here, the insulator 130 may be formed by coating an outer surface of the heater 120 with an excellent insulating property such as an artificial microphone.

The roller body 110 has a radial distance (L) from the center of rotation (X) to the outer circumferential surface 111 is uniformly formed in the longitudinal direction of the roller body (110). That is, the roller body 110 is formed such that the radial distance (L) is gradually reduced in the central portion than both ends of the roller body (110).

Here, the outer peripheral surface 111 of the roller body 110 may be used in the crown processing method in order to form a radial distance (L) of the both ends and the central portion of the roller body 110 differently. In addition, the thickness difference between the both ends and the central portion of the roller body 110 is preferably formed to 50% to 99%. Therefore, as shown in FIG. 2, the outer circumferential surface 111 of the roller body 110 has a junk round shape.

As such, when the outer circumferential surface 111 of the roller body 110 is formed in a junk round shape, the density of the magnetic field generated by the heater 1200 can be suppressed from being shifted along the longitudinal direction of the roller body 1100. That is, It is possible to increase the magnetic field density at the central portion of the roller body 110. Therefore, it is possible to reduce the deviation of the induced heat due to the magnetic field along the longitudinal direction of the roller body 110.

3 is a view showing a fixing roller of the image forming apparatus according to another embodiment. As shown in FIG. 3, the fixing roller 200 of the image forming apparatus includes a roller body 210, a heater 220, an insulator 230, and a magnetic core 250.

Since the roller body 210 has the same configuration as the roller body 110 shown in FIG. 2, a detailed description thereof will be omitted, and the heater 220 and the insulator 230 are also the same as the configuration shown in FIG. 2. Is omitted.

The magnetic core 250 is installed to be laminated on the outer circumferential surface 211 of the roller body 210, it may be installed on the roller body 210 by means such as plasma spraying or electrolytic plating. In particular, the magnetic core 250 has a non-uniform thickness along the longitudinal direction of the roller body 210 in order to compensate for the difference in density of the magnetic field generated between the center and both ends of the roller body 210. To this end, the magnetic core 250 has an inner circumferential surface 251 of an inverse crown shape corresponding to the outer circumferential surface 211. Therefore, the magnetic core 250, the inner diameter (L1) from the center of rotation (X) to the inner peripheral surface 251 is the longest at both ends of the roller body 210, and gradually decreases toward the center. The outer diameter L2 of the magnetic core 250 from the outer circumferential surface 252, ie, the outer circumferential surface 252 in contact with the coating layer 240, to the center of rotation X has a constant value.

As such, when the magnetic core 250 is further installed on the outer side of the roller body 210, the density difference of the magnetic field generated along the longitudinal direction of the roller body 210 may be more effectively reduced. Therefore, the temperature of the roller body 210 can be precisely controlled, thereby improving the quality of printing.

On the other hand, Figure 4 shows another embodiment in which the magnetic core 350 is formed in the roller body 310. As shown in FIG. 4, the fixing roller 300 of the image forming apparatus includes a roller body 310, a heater 320, an insulator 330, a coating layer 340, and a magnetic core 350. Here, the heater 320, the insulator 330 and the coating layer 340 is the same as the configuration shown in Figures 2 and / or 3, so detailed description thereof will be omitted, and as a further embodiment according to Figure 4 Only in detail.

That is, the roller body 310 has a constant outer diameter, unlike the roller bodies 110 and 210 having an outer peripheral surface of the junk round shape as shown in FIGS. 2 and 3. However, the outer circumferential surface 311 of the central portion with respect to the longitudinal direction of the roller body 310 is provided with a recess 350a drawn in a predetermined depth. The depression 350a may be formed by cutting the outer circumferential surface 311. The magnetic core 350 is accommodated and installed in the recess 350a. The magnetic core 350 has a constant thickness in the longitudinal direction of the roller body 310. That is, the radial distance (L3) from the center of rotation (X) to the outer surface 352 of the magnetic core 350 is formed to have a constant value along the longitudinal direction of the roller body (310).

As such, when the recessed portion 350a is formed on the outer circumference of the roller body 310 to install the magnetic core 350, the magnetic core 350 can be easily installed and the roller body 310 can be easily processed. . In addition, by providing the magnetic core 350 in the center of the roller body 310, it is possible to suppress the magnetic field density at the center of the roller body 310 is lowered.

As described above, according to the fixing roller of the image forming apparatus according to the present invention, the roller body is heated by heat radiation by providing a heater arranged closely to the inner circumferential surface of the roller body. The heat transfer rate is further improved, whereby the preheating time can be shortened.

In addition, by forming a magnetic core to reduce the radial distance from the center of rotation of the roller body to the outer peripheral surface of the roller body at the central portion than the both ends of the roller body or to concentrate the magnetic field, both ends and the central portion of the roller body It is possible to compensate for the fixing temperature variation due to the magnetic field density difference. As a result, it is possible to provide a fixing roller of the image forming apparatus with improved fixing efficiency.

While the invention has been illustrated and described in connection with the preferred embodiments for illustrating the principles of the invention, the invention is not limited to the construction and operation as shown and described. Rather, those skilled in the art will appreciate that many modifications and variations of the present invention are possible without departing from the spirit and scope of the appended claims. Accordingly, all such suitable changes and modifications and equivalents should be considered to be within the scope of the present invention.

Claims (5)

A roller body rotatably disposed on a transfer path of a print medium to which an image is transferred; And A heater installed inside the roller body to generate heat when a voltage is applied to heat the roller body. And the roller body has a radial distance from the center of rotation to the outer circumferential surface of the roller body so as to reduce the difference in density of the magnetic field generated by the heater in the longitudinal direction of the roller body. The method of claim 1, The radial distance of the fixing roller of the image forming apparatus, characterized in that the reduction in the central portion than both ends of the roller body. The method of claim 2, A fixing roller of the image forming apparatus, characterized in that a magnetic core for concentrating the magnetic field is installed at the outer central portion of the roller body. The method of claim 1, Fixing roller of the image forming apparatus, characterized in that the outer circumferential surface of the roller body is formed in a junk round shape. The method according to any one of claims 1 to 4, The heater is coated by an insulator and is in close contact with the inside of the roller body, characterized in that it comprises an induction coil for heating the roller body by the heat of induction by the magnetic field generated by the applied voltage and the resistance heat by the self-resistance load. A fixing roller of the image forming apparatus.

Images