JP2001166621A - Fixing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a fixing device having a configuration small in the number of components and capable of being easily manufactured, and capable of reducing the power consumption at a standby time by suppressing a convection caused inside the fixing device. SOLUTION: In the fixing device 11 provided with a fixing roller 1 with a built-in heater 4, a pressure roller 2 which is brought into press contact with the fixing roller 1, and a frame 3 for surrounding both rollers and used also as an outer frame for the device, projection parts 6a and 6b are arranged from the top part 8 of the frame 3 toward the vicinity of a contact point between the outer periphery of the fixing roller 1 and a vertical line, then, the air convection current is suppressed in the internal space of the frame 3. The projection parts 6a and 6b are symmetrically arranged across the fixing roller 1 one by one in the vertical direction from the top part 8 of the frame 3 toward the vicinity of the fixing roller 1. The projection parts 6a and 6b are molded from a heat insulating resin with les heat conductivity, and the parts 6a and 6b are fixed on the frame 3, or in another method, the frame 3 and the projection part 6 are integrally molded from the heat insulating resin.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fixing device which is mounted on an image forming and recording apparatus such as a copying machine, a printer, a facsimile and fixes an unfixed toner on a recording medium.

[0002]

2. Description of the Related Art In an image forming apparatus such as a copying machine, a printer, and a facsimile, an unfixed image formed by a toner made of a heat-meltable resin or the like transferred onto a sheet as a recording medium is fixed on the sheet. As a fixing device, a fixing roller having a built-in heater and a pressure roller are brought into pressure contact with each other,
2. Description of the Related Art A heat roller type fixing device is generally used in which a sheet is conveyed while being held between both rollers, and an unfixed toner image is fixed by heat and pressure.

FIG. 6 shows an example of a conventional heat roller type fixing device. In the fixing device 21 shown in FIG. 6, the fixing roller 1 provided inside the frame 3 also serving as the outer frame of the fixing device 21 is provided by bearings (not shown) provided on both side surfaces of the frame 3 of the fixing device 21. , Rotatably supported. Further, the fixing roller 1 has a built-in heater 4 using a halogen lamp or the like as a heat source, and the outer peripheral surface of the fixing roller 1 heated by the heater 4 is controlled by a temperature controller so that a predetermined fixing temperature is maintained. (Hereinafter, referred to as temperature control management). The pressure roller 2 has a shaft rotatably supported on a pressure arm (not shown) and is movable in the vertical direction. The pressure roller 2 is normally mounted in a state of being pressed against the fixing roller 1. Further, on the front and rear surfaces of the frame 3 facing the contact portion between the fixing roller 1 and the pressure roller 2, there are provided sheet passing openings 7a and 7b for passing a sheet as a recording medium. Then, paper passing guides 5 a to 5 d are provided from the paper passing openings 7 a and 7 b to between the fixing roller 1 and the pressure roller 2. The paper passing guides 5a and 5b and 5c and 5d are installed facing each other. The paper passing guides 5a to 5d are guide portions for introducing and leading out a recording medium such as a sheet between both rollers.

At the time of printing, the fixing roller 1 is fixed to a fixing device 21.
The pressurizing roller 2 is driven to rotate in the forward direction in the sheet transport direction at a peripheral speed substantially equal to the speed of the sheet introduced into the inside, and the pressure roller 2 is driven to rotate. The sheet conveyed from the transfer unit (not shown) of the image forming apparatus contacts the fixing roller 1 and passes through the nip between the fixing roller 1 and the pressure roller 2 so that the unfixed toner image is thermally fused. And is fixed on the paper surface.

During printing standby, the rotation of the fixing roller 1 and the pressure roller 2 is stopped, and the temperature of the outer peripheral surface of the fixing roller is controlled so as to maintain a predetermined standby temperature.

[0006]

In the image forming apparatus, high speed and high image quality as well as low power consumption have become major technical problems. The image forming apparatus has a warm-up mode immediately after the power is turned on, a print mode in which printing is performed, and a standby mode in which a standby state is set when a predetermined time has elapsed after printing is completed. Has been made.

For example, in the warming-up mode, the heating time of the fixing roller 1 is shortened as compared with the conventional heat fixing method, so that the heating time is shortened and the power consumption is reduced. In addition, adopting low temperature fixing toner,
Even if the heating temperature of the fixing roller 1 is lowered in the printing mode,
The power consumption is reduced by ensuring that the toner can be fixed on the paper. Further, the power consumption is reduced by changing the material and shape of the fixing device to increase the heat insulating effect in the standby mode.

[0008] Among the above operation modes, the standby mode has the largest power consumption. The power consumption in the standby mode is about 6 times the total power consumption in each operation mode.
Heat insulation measures in standby mode,
It is most effective for reducing power consumption.

As described above, in the standby mode, the rotation of the fixing roller 1 and the pressure roller 2 is stopped, and the temperature control is performed so that the temperature of the outer peripheral surface of the fixing roller 1 is maintained at a predetermined standby temperature. ing. Then, convection as shown in FIG. 7 occurs around the fixing roller 1 in the inner space of the frame 3 in the fixing device 21. That is, the air around the fixing roller 1 heated by the heater 4 incorporated in the fixing roller 1 starts convection, and the increased airflow is
When it reaches the ceiling 8 of the frame 3, it diverges to the left and right,
One descends toward the fixing roller 1, and the other descends along the front surface or the rear surface of the frame 3, and is discharged to the outside of the fixing device 21 through the paper passage opening 7.

Therefore, conventionally, the following method has been implemented as a heat insulation measure. That is, as shown in FIG. 8, a method of installing a heat insulating cover 9 surrounding the frame 3 to prevent heat radiation to the outside, or as shown in FIG. 9, in order to prevent heat radiation from the paper passage opening 7 to the outside, A method of installing a heat insulating shutter 10 that seals the paper passage opening 7 so that it can be opened and closed has been used.

However, using these methods,
The number of parts increases. Further, since the adiabatic shutter 10 is a movable mechanism, it is necessary to provide a driving unit or the like for operating the shutter 10. Therefore, there is a problem that it is difficult to reduce the cost of parts and man-hours during manufacturing.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a fixing device which can be manufactured easily and at low cost, suppresses convection generated inside the fixing device, and can reduce power consumption during standby. I do.

[0013]

(1) A fixing roller incorporating a heat source, a pressure roller disposed in pressure contact with the fixing roller, and a frame surrounding both rollers and also serving as an outer frame of the device. A fixing device for fixing the unfixed image to the recording medium by heat and pressure by passing a recording medium carrying the unfixed image between the two rollers, in the vicinity of a contact point between the outer periphery of the fixing roller and a vertical line The surface facing the fixing roller is provided with a convex portion having a flat surface in the vertical direction.

In this configuration, in a fixing device having a frame surrounding a fixing roller having a built-in heat source and a pressure roller arranged in pressure contact with the fixing roller, a surface facing the fixing roller has a flat surface. The shape portion is provided in the vertical direction from the vicinity of a vertical contact point on the outer periphery of the fixing roller. Accordingly, the air convected around the fixing roller inside the frame of the fixing device hardly flows out of the frame, and the heat of the fixing roller is prevented from being released to the outside of the fixing device, thereby reducing power consumption of the fixing device. can do.

(2) The present invention is characterized in that one of the convex portions is provided symmetrically with respect to the fixing roller from the ceiling inside the frame to the vicinity of the fixing roller.

In this configuration, one convex portion is provided in the vertical direction from the ceiling inside the frame to the vicinity of the fixing roller, and one convex portion is provided symmetrically with respect to the fixing roller. Therefore, the convex portion functions as a flow resistor, and can prevent the rising airflow generated near the paper passage opening from being separated from the surface of the fixing roller to prevent the airflow from being accelerated. It is possible to suppress the momentum of the airflow flowing from the inside to the outside through the paper passage opening. When the force of the convection is weakened, the thermal resistance in the space between the fixing roller surface and the frame and the resistance of the heat path radiating to the outside through the paper passage opening increase, and the heat radiation is suppressed.
Power consumption due to heat generation of the heater can be reduced.

(3) The convex portion is formed integrally with a guide member for introducing and leading a recording medium between the rollers.

In this configuration, a guide member for introducing and leading the recording medium between the fixing roller and the pressure roller,
The protruding part is integrally molded. Therefore,
Since the gap between the inside of the frame and the paper passage opening can be reduced, the flow resistance of the gap increases, and the flow of air between the inside of the frame and the outside through the paper passage opening is stopped. By setting the unit, it is possible to suppress the generation of an airflow that rises along the surface of the fixing roller from the vicinity of the paper feed port, so that convection of air around the fixing roller can be suppressed, and a high heat insulating effect can be obtained. .

(4) The convex portion is formed of a heat insulating resin.

In this configuration, the convex portion is formed of a heat insulating resin. Therefore, the heat of the air convected around the fixing roller is not radiated to the outside through the convex portion, and a higher heat insulating effect can be obtained.

(5) In the configuration of (2), the convex portion may be formed integrally with the frame by a heat insulating resin.

In this configuration, the heat insulating resin
The convex portion and the frame are integrally molded. Therefore, the thermal conductivity of the frame is reduced, the heat insulating effect is increased, and the number of parts can be reduced, so that the cost can be reduced.

[0023]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A first embodiment of the present invention will be described with reference to FIGS.

FIG. 1 is a sectional view of a fixing device according to a first embodiment of the present invention. FIG. 2 is a cross-sectional view illustrating a state of convection of air in the fixing device according to the first embodiment. FIG. 3 is a cross-sectional view illustrating an installation position of a convex portion of the fixing device according to the first embodiment. FIG. 4 is a cross-sectional view showing an embodiment in which a plurality of convex portions are provided along the rotation direction of the fixing roller in a frame of the fixing device.

The fixing device 11 is provided with a convex portion near the contact point between the outer periphery of the fixing roller 1 and the vertical line in the conventional fixing device 21. The detailed configuration will be described below.

The fixing device 11 has a substantially rectangular parallelepiped frame 3 which also serves as an outer frame of the device. Further, a fixing roller 1 and a pressure roller 2 are provided inside the frame 3. The fixing roller 1 has a built-in heater 4 using a halogen lamp or the like as a heat source, and is rotatably supported by bearings (not shown) provided on both side surfaces of the frame 3. Pressure roller 2
The shaft is rotatably supported on a pressing arm (not shown), and is movable in the vertical direction. Further, on the front surface and the rear surface of the frame 3 facing the contact portion between the fixing roller 1 and the pressure roller 2, there are provided paper passage openings 7a and 7b for passing a sheet as a recording medium. Then, the paper passing openings 7a and 7
Paper passing guides 5a to 5d are provided from b to between the fixing roller 1 and the pressure roller 2 (hereinafter, referred to as between both rollers). The paper passing guides 5a and 5b and 5c and 5d
They are installed facing each other. Paper passing guides 5a to 5d
Is a guide section for introducing and leading out a recording medium such as a sheet between the rollers.

As described above, around the fixing roller 1 in the internal space of the frame 3, the air is heated by the heat of the heater 4 built in the fixing roller 1, and convection of the air occurs. Since the convection of the air promotes heat radiation from the surface of the fixing roller 1 to the outside of the fixing device 11,
A large heat insulating effect can be obtained by suppressing the convection of air.

As a countermeasure, from the ceiling portion 8 inside the frame 3 to the vicinity of the contact point between the outer periphery of the fixing roller 1 and the vertical line, flat convex portions 6a and 6b are formed on the right and left sides of the fixing roller 1 with the fixing roller 1 interposed therebetween. It is provided one by one symmetrically. The convex portions 6a and 6b suppress generation of convection in the internal space of the frame 3. The upper surface and both side surfaces of the convex portions 6a and 6b are molded with a heat-insulating resin, and
Is fixed to the ceiling portion 8 and both side surfaces thereof with a heat-resistant adhesive. Further, if the frame 3 of the fixing device 1 is molded from a heat insulating resin and the convex portion 6 is installed by integral molding with the frame 3, in addition to the heat insulation effect by suppressing convection, the thermal conductivity of the frame itself is reduced. Also provides a heat insulating effect. Furthermore, by integrally molding the frame 3 and the convex portion 6, the number of parts can be reduced, and the cost of parts and the number of manufacturing steps can be reduced.

FIG. 2 shows the convection of air around the fixing roller 1. The convection of the air generated around the fixing roller 1 is generated along the surface of the fixing roller 1 by the paper passing openings 7a and 7b.
It is accelerated as it goes vertically upward from the vicinity, and is accelerated most at a position near the contact point between the outer periphery of the fixing roller 1 and the vertical line. The convex portion 6 functions as a flow resistor, and the paper passage opening 7
Since the ascending flow generated near a.7b is separated from the surface of the fixing roller 1 to prevent the airflow from being accelerated, the convection generated inside the frame 3 and the fixing device 11
Through the paper passage openings 7a and 7b from inside the fixing device 1
1 can suppress the momentum of the airflow toward the outside. When the force of the convection of the air is weakened, the thermal resistance between the surface of the fixing roller 1 and the frame 3 and the thermal resistance of the path discharged to the outside through the paper passage openings 7a and 7b are increased, and the fixing device is increased. The heat radiation to the outside of 11 is suppressed. Therefore, even if the heater 4 is not continuously heated, the fixing roller 1 is maintained at a predetermined temperature, so that power consumption can be reduced.

The smaller the distance between the convex portions 6a and 6b and the fixing roller, the greater the flow resistance and the higher the convection suppressing effect. Therefore, it is preferable that the convex portion 6 is as close as possible to the surface of the fixing roller 1. As shown in FIG. 3, the minimum distance x from the convex portion 6 to the outer peripheral surface of the fixing roller 1 is determined in consideration of manufacturing / assembly accuracy. About 3 mm is desirable. If the accuracy can be improved without increasing the manufacturing cost, the interval x may be further reduced.

Here, convection of air occurs around the pressure roller 2 as in the fixing roller 1, but the pressure of the heater 4 is limited to the pressure roller 2 only at the contact portion with the fixing roller 1.
, The surface temperature of the pressure roller 2 is lower by at least 50 ° C. than that of the fixing roller 1. Therefore, the air convection around the pressure roller 2 is smaller than the air convection around the fixing roller 1.
Therefore, even if a convex portion for the purpose of suppressing convection is provided in the vicinity of the pressure roller, the effect obtained is small, and since heat flows out to the outside by heat conduction through the convex portion, the effect is opposite. I will. Therefore, the countermeasures against convection by installing the convex portion are performed only on the fixing roller 1.

In addition to the flat-shaped convex portions 6a and 6b installed in the vertical direction shown in FIG.
As shown in (1), a method is conceivable in which a plurality of flat plates are provided in the vicinity of the fixing roller 1 inside the frame along the rotation direction of the fixing roller 1 like convex portions 6c and 6d. In the convex portions 6c and 6d, the convex portions 6a and 6
In order to obtain the same effect as in the case where b is provided, it is necessary to provide a convex portion in which at least two or more flat plates are close to each other. However, the convex portions 6c and 6d
4 has a convection suppressing effect, but on the other hand, since a path for radiating heat through the convex portions 6c and 6d is newly formed, the fixing device 1 is thermally conductive.
2, the amount of heat radiated to the outside increases, so that the effect of suppressing heat radiation due to convection suppression is offset. Therefore, in order to suppress heat radiation, it is preferable that the number of protrusions is as small as possible. Therefore, convection can be effectively suppressed by arranging the convex portions 6a and 6b one by one at symmetrical positions with respect to the fixing roller 1 as shown in FIG.

According to an experiment, the frame 3 of the fixing device 11
The effect of providing the protruding portion 6 on the inner side of the sheet through the paper passage opening 7 is larger than the heat dissipation path between the fixing roller 1 and the frame 3. The thermal resistance value of the conventional fixing device 21 shown in FIG.
About 8% increase.

The convex portion 6 does not necessarily have to be provided symmetrically with respect to the fixing roller 1 and the space for installing the convex portion is narrow due to the arrangement of other components and the like. Even when only books can be installed, the same convection suppressing effect can be obtained. This is because the air convection region is small even when only one convex portion is arranged because the space where the air convection flows is small when the space in the frame is narrow due to other components installed in the frame. This is because it is possible to further suppress the heat radiation.

Next, a fixing device according to a second embodiment of the present invention will be described with reference to FIG. Fixing device 13 shown in FIG.
The fixing device 11 differs from the fixing device 11 in the shapes of the paper passing guides 5a and 5c and the convex portions 6a and 6b, and the other portions have the same shape. Therefore, different parts will be described.

In the fixing device 13, the integrated paper passage guide 1 is opposed to the paper passage guide 5b at the paper passage opening 7a.
1a is arranged. In addition, an integrated paper passage guide 11b is disposed opposite the paper passage guide 5d at the paper passage opening 7b. The integrated paper passing guides 11a and 11b
A convex portion provided vertically below the vicinity of a contact point between the outer periphery of the fixing roller 1 and the vertical line, and a paper passing guide portion for introducing and leading a sheet between the rollers are integrally formed of a heat insulating resin. It is. The cross section of the integrated paper passing guides 11a and 11b is formed in an L-shape by a convex portion and a paper passing guide portion.

If the integrated paper passage guides 11a and 11b are formed by integrally molding the paper passage guide portion and the convex portion, the gap between the inside of the frame 3 and the paper passage openings 7a and 7b becomes small. The flow resistance of the gap increases, and the paper passage opening 7a
-There is no air flow between the inside and outside of the frame 3 through 7b. In addition, the convex portions of the integrated sheet passing guides 11a and 11b can suppress the generation of an airflow that rises from the vicinity of the sheet passing openings 7a and 7b along the surface of the fixing roller 1. Therefore, the fixing device 1 of the first embodiment
1, the paper passage openings 7a and 7b
The amount of heat flowing out through the heat exchanger can be further reduced.

[0038]

According to the present invention, the following effects can be obtained.

(1) In a fixing device having a structure in which a fixing roller having a built-in heat source and a pressure roller arranged in pressure contact with the fixing roller are surrounded by a frame, a surface facing the fixing roller has a flat convex portion. However, since the fixing roller is provided in the vertical direction from the vicinity of the vertical contact point on the outer periphery of the fixing roller, air convection around the fixing roller inside the frame of the fixing device hardly flows out of the frame, and the heat of the fixing roller Can be prevented from being released to the outside of the fixing device, and the power consumption of the fixing device can be reduced.

(2) The convex portions function as flow resistors by providing one convex portion in the vertical direction from the ceiling portion inside the frame to the vicinity of the fixing roller, symmetrically with respect to the fixing roller. Since the rising airflow generated near the paper passage opening is separated from the surface of the fixing roller to prevent the airflow from being accelerated, the convection generated inside the frame and the inside from the inside to the outside through the paper passage opening. The momentum of the airflow heading for can be suppressed. When the force of the convection is weakened, the thermal resistance in the space between the fixing roller surface and the frame and the resistance of the heat path radiating to the outside through the paper passage opening increase, the heat radiation is suppressed, and the heat generated by the heater is reduced. Power consumption can be reduced.

(3) Since the guide member for guiding the recording medium into and out of the fixing roller and the pressure roller and the convex portion are integrally formed, the inside of the frame and the paper passage opening are formed. Can be reduced, the flow resistance of the gap increases, and the flow of air between the inside and the outside of the frame through the paper passage opening can be eliminated. In addition, since the generation of the airflow rising along the surface of the fixing roller from the vicinity of the paper feed port can be suppressed by providing the convex portion, the convection of air around the fixing roller can be suppressed, and a high heat insulating effect can be obtained. Obtainable.

(4) By molding the convex portion with the heat insulating resin, the heat of the air convected around the fixing roller is not radiated to the outside through the convex portion, and a higher heat insulating effect is obtained. Obtainable.

[Brief description of the drawings]

FIG. 1 is a sectional view showing a fixing device according to a first embodiment of the present invention.

FIG. 2 is a cross-sectional view illustrating a state of convection generated inside a frame of the fixing device according to the first exemplary embodiment of the present invention.

FIG. 3 is a diagram showing an installation position of a convex portion in the first embodiment.

FIG. 4 is a diagram illustrating an embodiment in which a plurality of convex portions are provided inside a frame of a fixing device along a rotation direction of a roller.

FIG. 5 is a sectional view showing a fixing device according to a second embodiment of the present invention.

FIG. 6 is a sectional view showing a conventional heat roller type fixing device.

FIG. 7 is a diagram showing convection generated inside a conventional fixing device frame.

FIG. 8 is a diagram illustrating a state in which a heat insulating cover is installed in a conventional fixing device.

FIG. 9 is a diagram illustrating a state in which a heat insulating shutter is installed in a conventional fixing device.

[Explanation of symbols]

 1-Fixing Roller 2-Pressure Roller 3-Frame 4-Heater 6a / 6b-Protrusion 8-Ceiling 11-Fixing Device

Claims (4)

[Claims] An image forming apparatus comprising: a fixing roller having a built-in heat source; a pressure roller disposed in pressure contact with the fixing roller; and a frame surrounding both rollers and also serving as an outer frame of a device. A fixing medium for fixing the unfixed image to the recording medium by heat and pressure by passing the recording medium carrying the unfixed image to the fixing medium in a vertical direction from near the contact point between the outer periphery of the fixing roller and a vertical line. A fixing device comprising a convex portion having a flat surface facing a roller. 2. The fixing device according to claim 1, wherein one of the convex portions is provided at a position symmetrical with respect to the fixing roller from the ceiling inside the frame to the vicinity of the fixing roller. A fixing device according to item 1. 3. The fixing device according to claim 1, wherein the convex portion is formed integrally with a guide member for introducing and leading a recording medium between the two rollers. 4. The fixing device according to claim 1, wherein the convex portion is formed of a heat insulating resin.