KR101188799B1 - Fixing Unit for Image Forming Apparatus - Google Patents

Abstract

The present invention relates to a fixing unit for an image forming apparatus such as a copying machine, a printer, and the like. The fixing unit includes a heat roller made of a Teflon coated heat pipe, an induction coil installed under the heat pipe, and a first insulating layer. The induction coil has an enamel coating on its entire surface, and the insulating layer is bonded with a thermosetting adhesive.

Such a fixing unit is capable of instantaneous heating and has excellent thermal conductivity, so that the warm-up time can be shortened within a few seconds at the time of initial start-up or standby mode, which is suitable for a high-performance image forming apparatus in the future.

Image forming apparatus, fixing unit, fixing unit, teflon, enamel

Description

Fixing Unit for Image Forming Apparatus}

1 is a schematic configuration diagram of a general image forming apparatus.

Figure 2 is a longitudinal sectional view of a conventional fixing unit applying the lamp heating method.

3 is a longitudinal sectional view of a conventional fixing unit applying the induction heating method.

FIG. 4 is a heat roller mounted on the fixing unit of FIG. 3, FIG. 4A is a cross-sectional view and FIG. 4B is a detail view "A" of FIG. 4A.

5 is a longitudinal sectional view of a fixing unit according to the present invention.

Figure 6 is a heat roller of the fixing unit according to the present invention, Figure 6a is a cross-sectional view and Figure 6b is a detail view "B" of Figure 6a.

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

1. Fixing unit

10. heat roller

11. Induction coil

12. heat pipe

13. Insulation layer

14. Thermosetting adhesive

15. Insulation coating layer

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus such as a copying machine, a printer, and more particularly, to a fixing unit for an image forming apparatus having an improved heat roller capable of instantaneous heating and good thermal conductivity. It is about.

1 illustrates a schematic configuration of a general image forming apparatus. In a typical image forming apparatus, such as a laser beam printer, as shown in FIG. 1, the laser light 2a adjusted according to the image forming data is transferred from the laser scanning unit 2 to the photosensitive drum. The photosensitive drum 3 is irradiated, and a latent image is formed on the surface of the photosensitive drum 2 by the irradiated laser light. The latent image is developed into a toner image by a plurality of developing units 4, and the toner image is transferred to a recording medium M through a transferring unit 5. The toner image passing through the fixing unit 100 is fixed on the recording medium.

Various fixing apparatuses for thermally fixing the toner image to the surface of the recording medium after the toner image on the recording medium are formed. As a representative example, FIG. 2 shows a schematic configuration of a fixing unit to which a lamp heating system is applied. In the fixing unit 100, as shown in FIG. 2, a heat roller 110 that rotates in a clockwise direction in a direction in which the recording medium M on which the toner image t is formed is discharged, that is, in the drawing, And a pressing roller 120 which is installed to face the heat roller 110 with the recording medium M therebetween and rotates in a counterclockwise direction while contacting the heat roller 110. In the fixing unit 100, the heat roller 110 is heated by radiant heat generated from the lamp 130, for example, a halogen lamp, and the recording passes between the pressure roller 120 facing the heat roller. The toner image t on the medium M is fused to the surface of the recording medium while being heated and pressurized. At this time, the thermistor 140 of the fixing unit 100 measures the surface temperature of the heat roller 110 and transmits the electric signal to the controller 150. The controller controls the amount of electricity supplied to the halogen lamp according to the measured temperature to maintain the surface temperature of the heat roller 110 within a given range. In addition, the switching element 160 is turned on / off when the temperature of the heat roller 110 by the thermistor 140 and the controller 150 is higher than the threshold setting value to turn on the power flowing to the halogen lamp. Block it.

However, a conventional fixing unit using such a lamp as a heat source consumes a lot of power, and requires a particularly long warm up time when the power is turned off and then turned on again for image formation. This warm up time takes tens of seconds to several minutes. Therefore, the lamp heating method is not suitable as an image forming apparatus for high speed copying or printing.

Recently, an electromagnetic induction heating method for directly heating a heat roller by applying an electromagnetic inductive coil has been widely used as a fixing unit to improve the lamp heating method (US Pat. No. 6,643,491; Korean Patent No. 385997; Korean Made. 458880). Fixing units using induction heating can achieve high thermal efficiency or good fixing as compared to fixing units using the lamp heating method.

Figure 3 is a longitudinal sectional view of a fixing unit applying this induction heating method, Figure 4a is a cross-sectional view showing the structure of the heat roller shown in Figure 3, Figure 4b is a detail view "A" of Figure 4a.

In the fixing unit 200 shown in FIG. 3, an AC voltage is applied from the outside to the induction coil 211 so that the heat roller 210, which is a heating element, is directly heated, and is disposed between the heat roller 210 and the pressure roller 220. The toner image t on the recording medium M passing through is fused to the surface of the recording medium. In such an induction heating method, an induction current must be generated in the heat roller 210, so that the object to be heated and the induction coil must be insulated at all times.

Figure 4 shows the cross-sectional structure of a conventional heat roller using an induction heating method in detail. In the conventional heat roller, as shown in FIG. 4, an induction coil 211 is mounted inside a heat pipe 212, and in order to prevent toner contamination on an outer surface of the heat pipe 212. Teflon coating 213 is formed. In addition, a first insulating layer 214 of polyimide or Kapton film is formed between the induction coil and the heat pipe. Although the induction coil of the heat roller is somewhat different depending on the safety standard requirements of each country, the inner and outer surfaces of the induction coil as the mica sheet (Mica sheet) as the second, It is essential to form the third insulating layers 215 and 215.

However, the mica sheet is resistant to insulation and breakdown pressure, but since its thickness is about 0.15 to 0.18 mm, the conventional heat roller has no choice but to have a thick insulation layer. For example, in the case of the conventional heat roller as shown in FIG. 4, the first insulating layer 214 of the polyimide film is about 25 μm, but the second mica sheets 215a to 215e are formed to have a minimum thickness. The third insulating layers 215 and 215 have a thickness of 0.75 to 0.90 mm. This increase in insulation thickness for strengthening the electrical insulation has a bad effect in terms of heat transfer. In other words, there is an opposite relationship between electrical insulation for safety and temperature rise rate. In addition, since the interlayer adhesion is reduced when the insulation thickness is increased, it is necessary to insert the expansion wires 216 into the heat roller 210 to increase the interlayer adhesion. Therefore, the conventional heat rollers are less suitable for high speed image forming apparatuses that require fast warm-up time because the adhesion between the insulating layers is lowered and the thermal conductivity is also lowered as the thickness of the insulating layer is increased.

The present invention improves the structure of the heat roller by the conventional induction heating method as described above, and its object is to generate heat efficiency of the heat roller so that the warm-up time can be shortened within a few seconds during the initial operation of the image forming apparatus or from the standby mode. It is to provide a fixing unit for an image forming apparatus having a heat roller that maximizes the quality and maintains good insulating properties.

In order to achieve the above object, the fixing unit for an image forming apparatus of the present invention includes a heat roller and a pressure roller facing the heat roller; The heat roller is a heat pipe; An induction coil installed on an inner surface of the heat pipe and having an entire surface coated with an insulation; And a first insulating layer insulated between the heat pipe and the induction coil, wherein the induction coil is adhered to the first insulating layer with a thermosetting adhesive.

Preferably, the induction coil further includes a second insulating layer adhered to the outer portion by a thermosetting adhesive.

The first and second insulating layers may be made of the same material, for example, a Teflon coating layer.

The heat pipe of the heat roller is preferably the outer surface is Teflon coated.

Preferably, the induction coil is enamel coated on the entire surface thereof.

In the fixing unit for an image forming apparatus according to the present invention, a method in which a high frequency AC power source using an inverter as an external power source is applied to both ends of the induction coil is suitable.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings.

5 is a longitudinal sectional view of a fixing unit according to the present invention. As shown in FIG. 5, the fixing unit for the image forming apparatus according to the present invention includes a heat roller 10 which is driven in contact with the pressing roller 20.

The heat roller 10 is provided with an induction coil 11 is installed spirally on the inner surface to generate an induction current.

The heat roller 10 is directly heated by applying a high frequency AC voltage to the induction coil 11 from the outside. As a result, the toner image t on the recording medium M passing between the heat roller 10 and the pressure roller 20 is fused to the surface of the recording medium.

Thermistor 40 measures the surface temperature of the heat roller 10 and transmits the electric signal measured by the control unit 50, the control unit controls the amount of electricity supplied to the induction coil in accordance with the measurement temperature of the heat roller 10 Is maintained at a given range, preferably from 160 to 190 ° C.

A feature of the present invention lies in the improved insulating layer structure of the heat roller 10, which has a very thin layer compared to the insulating layer structure of the conventional heat roller (see FIG. 4). 6 shows in detail such a cross-sectional structure of a heat roller 10 according to the invention. FIG. 6A is a cross-sectional view thereof and FIG. 6B is a detail view of the portion “B” of FIG. 6A.

Referring to FIG. 6, the heat roller 10 insulates a heat pipe 12 of a magnetic body constituting a body, an induction coil 11 positioned below the heat pipe 12, and between the heat pipe and the induction coil. One first insulating layer 13b is included. The induction coil may further include a second insulating layer 13c for insulating an outer portion thereof.

The outer surface of the heat pipe 12 is Teflon coated 13a. When the first insulating layer 13b coated on the inner surface of the heat pipe 12 is formed by Teflon coating, the heat pipe 12 forms the same insulating layer on the inside and the outside, thereby facilitating the manufacture of the heat pipe. Can be. The heat pipe is preferably a magnetic material, particularly preferably an aluminum pipe.

Before the induction coil 11 is mounted on the heat pipe 12, the surfaces thereof are all coated with an insulation 15, thereby obtaining the same insulation characteristics as the conventional mica sheet. The surface-coated induction coil 11 is bonded to the first insulating layer 13b with a thermosetting adhesive 14a. Most preferably, the induction coil is enamel coated on its entire surface. That is, when the induction coil itself is enamel coated, the thickness of the insulating layer of the heat roller can be minimized while obtaining the same insulation effect as compared to using a conventional mica sheet.

In addition, the heat roller 10 of the present invention further prevents the flow of the induction coil 11 by forming a second insulating layer 13c on the outside of the induction coil 11 and the adhesion between the insulating layers of the heat roller 10. Can be further enhanced. In this case, the induction coil 11 is in close contact with the second insulating layer 13c by the thermosetting adhesive 14b to prevent flow.

The manufacturing process is simplified when both the outer surface of the heat pipe 12 and the first and second insulating layers are Teflon coated. That is, after Teflon coating the inner and outer surfaces of the heat pipe 12, the upper and lower surfaces of the enamel coated induction coil 11 is coated with a thermosetting adhesive, and the induction coil 11 inside the heat pipe 12 Insert and attach. Then, the induction coil 11 is coated with Teflon to form a second insulating layer 13c. The heat roller 10 completed through such a simple manufacturing process can have a very good insulation and a very thin thickness of the insulating layer as compared to using a conventional mica sheet.

Hereinafter, the effects of the fixing unit of the present invention will be described in detail with reference to the accompanying drawings.

In the fixing unit 1 of the present invention, when a high frequency AC current is applied to both ends of the induction coil 11 from a high frequency AC power source (not shown) using an inverter, a magnetic field is generated around the induction coil 11. An eddy current is generated in the heat pipe 12 by the counter electromotive force to cancel this magnetic field, and Joule heat is generated in the heat pipe 12 by the induced current. At the same time as the induction heating, the current flowing through the induction coil generates Joule heat due to the resistance load of the coil itself, and heat is transferred to the insulating coating layers 13 and 15. It is used for the settlement of (t).

Since the induction current is proportional to the magnetic field generated in the coil 11 by linking the heat pipe 12, the more induction current flows as the distance between the heat pipe and the induction coil is closer. Therefore, in the heat roller 10 of the present invention, since the thickness of the insulating layer is thinner than the conventional heat roller, heat conduction is easy with the heat pipe, and the time until the heat roller 10 of the fixing unit reaches the fixing temperature is greatly increased. In this case, the warm-up time can be shortened to 10 seconds or less during the initial operation of the image forming apparatus or from the standby mode.

As described above, the fixing unit according to the present invention can maximize the heat generation efficiency while maintaining good insulation characteristics of the heat roller, compared to the fixing unit by the conventional lamp heating method or induction heating method.

Furthermore, the fixing unit can shorten the warm-up time in a few seconds at the time of initial operation or from the standby mode, and thus will be very useful for a high-performance image forming apparatus to be developed in the future.

Although the present invention has been described with reference to one embodiment shown in the drawings, this is merely exemplary, and those skilled in the art will understand that various modifications and variations can be made therefrom. Therefore, the true technical protection scope of the present invention will be defined by the technical spirit of the appended claims.

Claims (5)

A heat roller; It includes a pressure roller facing the heat roller, The heat roller, Heat pipes; An induction coil installed on the inner surface of the heat pipe; An insulation coating formed on the entire surface of the induction coil; A first insulating layer insulating between the heat pipe and the induction coil; And A second insulating layer formed on an outer portion of the induction coil; And the insulating coating formed on the induction coil is adhered to the first insulating layer and the second insulating layer with a thermosetting adhesive. delete The method of claim 1, An outer surface of the heat pipe of the heat roller is Teflon coating (Teflon coating), and both the first and second insulating layer is a Teflon coating layer, the fixing unit for the image forming apparatus. The method of claim 1, Insulation coating of the induction coil is a fixing unit for an image forming apparatus, characterized in that the enamel coating (enamel coating) uniformly formed on the entire surface of the induction coil. The method of claim 1, The induction coil is a fixing unit for an image forming apparatus, characterized in that the high-frequency AC power using an inverter is applied to both ends.

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