JP2002072736A - Fixing apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a fixing apparatus realizing the reduction of power con sumed to attain specified heating temperature by warming up a fixing roll after supplying power by making the heat capacity of the roll small while keeping temperature distribution in the rotary shaft direction of the roll uniform. SOLUTION: In this fixing apparatus where a recording medium on whose surface an unfixed toner image is carried is nipped, heated and pressed so that the unfixed toner image may be fixed on the recording medium, at least either of a pair of rolls is a hollow roll. Then, the device is equipped with plural fixed heat sources and a reflector reflecting radiant heat from the plural respective heat sources going toward the other heat source toward the inner surface of the hollow roll on the inside of at least either hollow roll.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fixing device used in an electrophotographic image forming apparatus such as a copying machine or a printer, and more particularly, to a fixing device in which an unfixed toner image is heated and pressed to be fixed on a recording medium. Related to the device.

[0002]

2. Description of the Related Art An electrophotographic image forming apparatus such as a copying machine or a printer generally charges the surface of a photoconductive photosensitive drum and forms an electrostatic latent image by irradiating exposure light. Is visualized with toner to form a toner image, and the toner image is finally transferred to a recording medium and fixed by a fixing device.

Further, the fixing device includes a pair of rolls having a heat source inside at least one of the rolls, and presses the pair of rolls while rotating to form a nip portion, on which an unfixed toner image is formed. A method is often used in which the toner is passed through, heated and pressurized, and the melted toner is fixed on the fiber structure of the recording medium.

In this type of fixing device, it is necessary to warm up the roll surface to a temperature at which the surface of the roll can be fixed after the power is turned on. Further, when the sheet carrying the unfixed toner image passes through the nip portion, the roll is deprived of heat and the surface temperature drops, so it is necessary to recover this temperature drop. Therefore, the power consumption of the fixing device tends to increase, and reduction and power saving of the fixing device have been issues.

[0005] To solve this problem, see, for example, JP-A-8-2
Japanese Patent No. 54915 discloses a fixing device in which a reflecting member is arranged around a heat source inside a roll, and radiant heat from the heat source is reflected and concentrated on the upstream of the nip portion.

According to this fixing device, the portion where the roll is in contact with the recording paper is efficiently heated, so that there is an advantage that power consumption can be reduced and power consumption can be reduced.

[0007]

However, the fixing device disclosed in Japanese Patent Application Laid-Open No. 8-254915 is
It contributes to reducing power consumption to recover the temperature drop of the fixing roll during continuous fixing, but it is necessary to warm up the surface of the fixing roll after turning on the power until the temperature of the fixing roll rises to the feasible temperature. However, a relatively large reduction in power consumption cannot be expected.

Accordingly, it is necessary to reduce the heat capacity by reducing the thickness of the roll and to reduce the power consumed during the warm-up time after the power is turned on. Heat transfer in the direction of the rotation axis is impeded,
There is a disadvantage that the temperature distribution in the axial direction of the roll is deteriorated. If a single heat source is simply disposed inside the roll, when the recording medium passes, only the portion where the recording medium has passed loses heat to the recording medium. Since the temperature distribution in the direction of the rotation axis of the roll becomes non-uniform and recording media of various sizes can be used in general, the heating method differs depending on each part of the recording medium, and uniform heating and fixing are performed. The problem arises that it is not possible.

In order to solve this problem, it is conceivable to arrange a plurality of heat sources having different heat generation distributions in the rotation axis direction inside the roll and to change the heating amount of each portion in the rotation axis direction of the roll. The heat capacity of the heat source relative to the heat capacity of the roll becomes a nonnegligible amount.

That is, since one heat source consumes electric power also for heating another heat source, the power consumption is not reduced as a result.

SUMMARY OF THE INVENTION In view of the above circumstances, it is an object of the present invention to provide a fixing device in which a relatively large amount of electric power consumed during a warm-up time of a roll after turning on a power supply is reduced.

[0012]

A fixing device according to the present invention that achieves the above object has a heat source inside at least one of the fixing devices.
A pair of rolls that rotate while forming a nip portion by contacting each other, and heat and press the recording medium carrying an unfixed toner image on its surface conveyed to the nip portion and heat and press the In the fixing device for fixing the toner image to the recording medium, at least one of the pair of rolls is a hollow roll, inside the at least one hollow roll, a plurality of heat sources fixed, A reflector that reflects radiant heat from each of the plurality of heat sources toward another heat source toward the inner wall surface of the hollow roll.

A hollow fixing roll having a heat source therein and rotating in a predetermined direction; and a belt moving with the rotation of the fixing roll while forming a predetermined nip portion between the fixing roll and the fixing roll. Conveyed to the nip,
In a fixing device for fixing the unfixed toner image to the recording medium by heating and pressing the recording medium holding the unfixed toner image on its surface, a plurality of heat sources fixed inside the hollow fixing roll And a reflector that reflects radiant heat from each of the plurality of heat sources toward another heat source toward the inner wall surface of the hollow fixing roll.

Here, the heat source has a hollow bulb having a heating element therein, and the reflector is formed on a surface of the hollow bulb facing the other heat source. Is a preferred embodiment.

It is also a preferable embodiment that a temperature sensor is provided behind the reflector.

[0016]

Embodiments of the present invention will be described below.

FIG. 1 is a schematic diagram showing a first embodiment of the fixing device of the present invention.

The fixing device shown in FIG. 1 has a plurality of heat sources 3 therein, and rotates in a rotation direction A while forming a nip portion 2 by contacting the fixing roll 1. A pressure roll 8 rotating in the direction B,
The recording medium 7 conveyed to the nip 2 and carrying the unfixed toner image 6 on its surface is heated and pressed between the nip 2 to fix the unfixed toner image 6 on the recording medium 7. .

The fixing roll 1 is a cylindrical hollow roll having a small thickness. Inside the fixing roll 1, a plurality of (two in this case) fixed heat sources 3 are fixed along the axial direction of the fixing roll. Are arranged at symmetrical positions. Each heat source 3
It is covered with a hollow valve 4 and has a single heating element 12 inside. Since each heating element 12 has a different heat generation distribution in the axial direction of the fixing roll 1 such that, for example, the heat generation amount in one half in the axial direction of the fixing roll is higher than that in the other half, the nip portion 2 is By switching or combining the heat sources in accordance with the size of the recording medium passing through, the temperature distribution in the axial direction of the fixing roll can be kept uniform.

Each heat source 3 has a substantially semicircular reflector 5 for reflecting the radiant heat directed to another heat source out of the radiant heat radiated from the heat source 3 and directing the radiant heat toward the inner wall surface of the fixing roll 1. The central portion of the reflector 5 has a side surface for preventing the radiant heat reflected by the reflector 5 from returning to the radiating heat source 3 and directing the radiant heat toward the inner wall surface of the fixing roll 1. A reflection portion 11 having a triangular shape is provided.

Here, it is desirable that the reflector 5 be made of a material having a high reflectivity for the highest wavelength of the radiant energy determined by the color temperature of the heat source 3, but the material is not limited to this. Further, the reflectance of the reflector 5 may be changed in the axial direction of the fixing roll 1.

The pressure roll 8 may be hollow and provided with one or more heat sources inside. When a plurality of heat sources are provided, similarly to the fixing roll 1 in the present embodiment, the pressure roll 8 may be provided inside. It is preferable to include the reflector 5.

As described above, since the fixing roll 1 has the plurality of heat sources 3 having different heat generation distributions in the axial direction, even when the fixing roll 1 is a thin fixing roll and is continuously fixed on a small-size sheet, the fixing roll 1 is fixed. (1) The temperature distribution in the axial direction can be kept uniform, and the heat sources are separated from each other because of the presence of the reflectors 5 facing each other, so that one heat source heats another heat source. This prevents the heat radiation energy efficiency from deteriorating.

Therefore, the warm-up time at power-on can be shortened, and the power consumption can be reduced.

FIG. 2 is a diagram showing a change in fixing roll surface temperature depending on whether or not the reflector of the present embodiment is provided inside the fixing roll.

In FIG. 2, the vertical axis represents the surface temperature of the fixing roll 1, and the horizontal axis represents the time during which the recording medium 7 carrying the unfixed toner image 6 is continuously passed through the nip portion 2 of the fixing device. To represent.

In the graph, a circle indicates the measurement result of the surface temperature of the fixing roll 1 in the fixing device of the present embodiment having the reflector 5 inside the fixing roll 1, and a cross indicates
9 shows the results of actual measurement of the fixing roll surface temperature in a fixing device in which a reflector is removed from the inside of the fixing roll.

As is apparent from FIG. 2, when the apparatus is on standby (position 0.0 on the horizontal axis), the surface temperature of the fixing roll is the same irrespective of whether or not a reflector is provided.

However, when the recording medium is continuously passed through the nip portion, the surface temperature of the fixing roll, which has been deprived of heat by evaporation of the moisture contained in the recording medium, drops, and reaches a constant surface temperature. The drop in the surface temperature of the fixing device of the present embodiment having a body is smaller than that of the fixing device without a reflector.

This is because, in the fixing device of the present embodiment having the reflector and the fixing device having no reflector, the heat of the fixing roll taken away by the recording medium passing through the nip portion is supplemented by the heat source. In this case, there is a difference in the heat radiation energy efficiency, and the provision of the reflector means that the deterioration of the heat radiation energy efficiency caused by heating the heat sources mutually is improved.

Next, a second embodiment of the fixing device of the present invention will be described.

FIG. 3 is a schematic diagram showing a second embodiment of the fixing device of the present invention.

The fixing device shown in FIG. 3 has a plurality of heat sources 3 therein and moves while forming a nip portion 2 by contacting the fixing roll 1 rotating in the rotation direction A. Endless belt 13, and the endless belt 13 is pressed against the fixing roll 1 to rotate in the rotation direction B.
The recording medium 7 carrying the unfixed toner image 6 on its surface, which has been conveyed to the nip portion 2, is heated and pressed while being sandwiched between the nip portion 2, so as to be unfixed. The toner image 6 is fixed on the recording medium 7.

The fixing roll 1 has the same configuration as the fixing roll in the first embodiment shown in FIG. 1, and the same components are denoted by the same reference numerals, and redundant description will be omitted.

As in the first embodiment, the fixing device of the second embodiment includes a plurality of heat sources 3 so that the temperature distribution in the axial direction of the fixing roll 1 can be improved and the reflection can be improved. Since the heat radiation energy efficiency is prevented from being deteriorated by the body 5, the warm-up time at the time of turning on the power is shortened, and the power consumption is also reduced.

Next, a third embodiment of the fixing device of the present invention will be described.

FIG. 4 is a schematic diagram showing a fixing device according to a third embodiment of the present invention.

The same components as those of the first embodiment shown in FIG. 1 are denoted by the same reference numerals, and the features will be described.

In this embodiment, the reflector 9 is formed on a part of the surface of the hollow bulb 4 of the heat source 3 instead of the reflector 5 shown in FIG.

By forming the reflector 9 directly on the hollow bulb 4 in this manner, the same operation and effect as in the first embodiment can be maintained, the number of components can be further reduced, and the size can be reduced. is there.

Although the embodiment having two rolls is shown here, in the configuration having the belt shown in FIG. 3, the reflector 5 is connected to the hollow valve 4 similarly to the embodiment shown in FIG. May be formed directly.

Next, a fourth embodiment of the fixing device of the present invention will be described.

FIG. 5 is a schematic configuration diagram showing a fourth embodiment of the fixing device of the present invention.

The same components as those in the first embodiment shown in FIG. 1 are denoted by the same reference numerals, and duplicate description will be omitted.

In this embodiment, in addition to the components of the first embodiment shown in FIG. 1, a temperature sensor 10 for detecting the internal temperature of the fixing roll 1 behind the reflector 5 is provided.
It has.

The temperature sensor 10 allows the fixing roll 1
Since the internal temperature of the fixing roll 1 can be detected, the power can be saved by using the power for the heat source power supply and the overheating prevention mechanism of the fixing roll 1.

In the configuration having the belt shown in FIG. 3, a temperature sensor 10 may be provided behind the reflector 5, and the same effect can be obtained in that case.

[0048]

As described above, according to the fixing device of the present invention, even if a plurality of heat sources are provided inside the fixing roll, the fixing roll can be efficiently heated. And power consumption can be reduced.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram showing a first embodiment of a fixing device of the present invention.

FIG. 2 is a diagram showing a change in the surface temperature of a fixing roll caused by providing the reflector of the present embodiment inside the fixing roll.

FIG. 3 is a schematic configuration diagram illustrating a fixing device according to a second exemplary embodiment of the present invention.

FIG. 4 is a schematic configuration diagram illustrating a fixing device according to a third embodiment of the present invention.

FIG. 5 is a schematic configuration diagram illustrating a fourth embodiment of the fixing device of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Fixing roll 2 Nip part 3 Heat source 4 Hollow valve 5, 9 Reflector 6 Toner image 7 Recording medium 8, 14 Pressure roll 10 Temperature sensor 11 Reflection part 12 Heating element 13 Endless belt

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Ryuichi Inamiya 2274 Hongo, Ebina-shi, Ebina-shi, Kanagawa Prefecture Inside Fuji Xerox Co., Ltd. In-house (72) Inventor Keitaro Sonoguchi 2274 Hongo, Ebina-shi, Kanagawa Prefecture Fuji Xerox Co., Ltd.Ebina Office F-term (reference)

Claims (4)

[Claims] A pair of rolls having a heat source inside at least one of them and rotating while forming a nip portion by contacting each other, and being conveyed to the nip portion;
In a fixing device in which a recording medium carrying an unfixed toner image on its surface is heated and pressed to fix the unfixed toner image on the recording medium, at least one of the pair of rolls is a hollow roll. There, inside the at least one hollow roll, a plurality of fixed heat sources, and a reflector that reflects radiant heat from each of the plurality of heat sources toward another heat source toward the inner wall surface of the hollow roll. A fixing device comprising: 2. A fixing device comprising: a hollow fixing roll having a heat source therein and rotating in a predetermined direction; and a belt moving with the rotation of the fixing roll while forming a predetermined nip portion between the fixing roll and the fixing roller. A fixing device for fixing the unfixed toner image to the recording medium by heating and pressing the recording medium conveyed to the nip portion and holding the unfixed toner image on the surface, wherein the hollow fixing roll A plurality of heat sources fixed inside the fixing device, and a reflector that reflects radiant heat from each of the plurality of heat sources toward another heat source toward an inner wall surface of the hollow fixing roll. . 3. The heat source has a hollow bulb having a heating element therein, and the reflector is formed on a surface of the hollow bulb facing the other heat source. The fixing device according to claim 1, wherein: 4. A fixing device according to claim 1, further comprising a temperature detection sensor behind said reflector.