JPH05134572A - Thermal fixing device - Google Patents

Abstract

PURPOSE:To minimize the divergence of heat from the thermal fixing roller of a thermal fixing unit. CONSTITUTION:A thermal fixing roller 6 and a pressurizing roller 7 are housed so as to rotate in a housing case 3. Further, an insulator 15 for insulating the heat radiated from the thermal fixing roller 6, is attached to the circumference of the thermal fixing roller 6 in the housing case 3, with a slight gap taken, and an air thin layer for insulating the heat 18, is formed between the inner periphery of the insulator 15 and the surface of the thermal fixing roller 6 In this constitution, the heat radiated from the thermal fixing roller 6 is insulated by the insulator 15, simultaneously, the convection of the air of the surface of a roller is cut off by the air thin layer for insulating the heat 18, and the divergence of the heat from the thermal fixing roller can be minimized.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heat fixing device, and more particularly to a heat fixing device for efficiently fixing a toner image on a medium in an electrophotographic copying machine, a printer, a facsimile or the like which uses toner for image formation.

[0002]

2. Description of the Related Art Generally, in electrophotographic copying machines, printers, facsimiles, etc. (hereinafter referred to as copying machines) which use toner for image formation, powder of toner or the like is produced by using static electricity or chemical dispersion. Is attached to a support such as paper or OHP sheet to form an image. At this time, since the powder adheres only with a weak force, it is necessary to prevent the image of the support from being changed or moved. Therefore,
In the electrophotographic process, a fixing process for fixing the powder on the support is provided. As an example of this fixing process, a fixing unit is used which melts powder such as toner on a support by a heat fixing device to cause strong fixing between the support and the support. FIG. 7 shows an example of a conventional heat fixing device. This heat fixing device includes a heat fixing roller 51 in which a heat source is included in a metal casing 50, and a paper P which is arranged to face the heat fixing roller 51. And a pressure roller 52 for pressing and fixing the heat fixing roller 51 to the heat fixing roller 51. Of these, the heat fixing roller 51 is composed of a hollow heat roller 53 and a halogen rod-shaped lamp 54 arranged inside as a heat source.
The surface of the hollow heat roller 53 is coated with Teflon resin or the like so that good heat conduction can be obtained. On the other hand, the halogen rod-shaped lamp 54 has filaments arranged so that a uniform temperature distribution can be obtained over the entire length of the roller. By the way, since the heat fixing roller 51 has a large designed heat capacity, it is difficult to warm it up rapidly, and sufficient fixing cannot be performed unless warm-up time is taken. For this reason, it may be possible to keep the power supply on all the time, but this is not economical in terms of power consumption. Therefore, energy saving is achieved by the temperature control method. A thermistor is used as the temperature control member, and the lamp is ON / OFF controlled within a predetermined temperature range. Further, even in the case where the lamp is controlled to be turned on and off, it is preferable in terms of device performance to minimize the lighting heating time of the lamp by suppressing heat radiation from the roller surface as much as possible. Therefore, in order to reduce the heat radiation from the roller surface, a thermal fixing device has been proposed in which a reflecting plate for reflecting infrared rays is provided at an outer peripheral position in the vicinity of the rotating roller (see Japanese Patent Laid-Open No. 62-150278). An example of the reflector is shown in FIG. In addition, a heat fixing device has been proposed in which a heat absorbing member having a ceramic paper having a far infrared ray radiating function is attached to the inner surface of a housing that accommodates a heat fixing roller (Japanese Patent Laid-Open No. 63-2237).
70 publication).

[0003]

By the way, in each of the above-mentioned thermal fixing devices, a heat reflection plate is arranged around the roller portion, and far infrared radiation heat from the roller portion is returned to the roller portion by reflection or radiation. It aims to increase the thermal efficiency. However, the temperature of the atmosphere in contact with the roller portion rises as the temperature of the roller portion rises due to heat transfer in the air layer. As a result, the temperature of the heat reflection plate rises to the same level as the ambient temperature, radiation and heat transfer further proceed to the outside of the heat reflection plate, and the internal heat is radiated to the outside of the housing. In particular, when the gap between the heat reflection plate around the roller portion and the housing is large and the air layer formed in that portion is thick, the air in the housing causes convection, and the heat of the heat reflection plate portion is removed, There is a problem that the thermal efficiency of the roller portion is significantly reduced. In such a case, it is possible to separately provide a large capacity cooling device for preventing the temperature rise of the entire device, but it becomes difficult to reduce the size of the device as the power consumption increases and the device size increases. There is a problem. If the inside of the device is not sufficiently cooled, the temperature of the developing section becomes high. At this time, if the temperature of the developing section becomes high, the developing performance deteriorates. Therefore, the fixing section and the developing section must be installed separately in the apparatus, which also hinders downsizing of the apparatus.

Therefore, an object of the present invention is to solve the problems of the above-mentioned conventional techniques, to minimize the heat radiation from the fixing section to the outside, and to minimize the power consumption required for heating the lamp. To provide a fixing device.

[0005]

In order to achieve the above object, the present invention relates to a thermal fixing device for pressing a copy medium onto the thermal fixing roller by a pressure roller arranged to face the thermal fixing roller and fixing and conveying the same. The heat fixing roller and the pressure roller are housed in a housing, and a heat insulating body that blocks heat radiation from the heat fixing roller is arranged around the heat fixing roller. A heat insulating air thin layer is formed between the heat fixing roller surface and the heat fixing roller surface.

[0006]

According to the present invention, the heat fixing roller and the pressure roller are housed in the housing, and the heat insulating body for blocking the heat radiation from the heat fixing roller is arranged around the roller in the housing. Since a thin layer of adiabatic air is formed between the inner peripheral surface of the heat insulator and the roller surface, heat insulation from the roller portion is blocked by the heat insulator portion, and heat insulating air formed between the roller portion and the heat insulator is formed. The layers block the convection of air on the roller surface to minimize heat dissipation from the roller section.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a heat fixing device according to the present invention will be described below with reference to the accompanying drawings. In FIG. 1, reference numeral 1 denotes a part of the equipment case of the copying machine.
The fuser housing 3 is attached to the flange 2 formed at a predetermined position of
Are fixed by screws. This housing 3 is an upper housing 4
And a lower housing 5 are connected to each other. The housing 3 has a heat fixing roller 6 including a heat source therein, and the heat fixing roller 6 is arranged so as to face the heat fixing roller 6. And a pressure roller 7 that is pressed against and fixed. Of these, the heat fixing roller 6 is composed of a hollow heat roller 8 and a halogen rod-shaped lamp 9 arranged inside as a heat source. The structure of these roller pairs 6 and 7 is the same as that of the roller pair of the conventional example, and the heat roller surface has a Teflon resin coat having heat resistance and good releasability from the toner, and the pressure roller side has Silicone rubber material is applied to provide heat resistance and a wide nip width.

The pressure roller 7 is rotated by a spring (not shown) so that a pressing force acts in the direction of the center of the rotation axis of the heat fixing roller 6 in order to have a nip portion with a predetermined width between the pressure roller 7 and the heat fixing roller 6. A lever 11 that rotates around the pin 10 urges the heat fixing roller 6 toward the center of the rotation axis of the heat fixing roller 6. Further, guide plates 12 and 13 are attached to the front and rear of the roller portion so that the paper P is surely inserted into the nip portion and discharged from the discharge port. On the other hand, a temperature sensor 14 for detecting the temperature of the heat fixing roller 6 is attached above the heat fixing roller 6. A thermistor is used as the temperature sensor 14 in this embodiment, but a temperature sensor such as a thermocouple may be used. Further, a heat insulator 15 is attached to the outer circumference of the heat fixing roller 6 in the housing 3 with screws 16 over the entire width of the roller so as to cover the surface of the heat fixing roller 6 with a slight gap t. At this time, the gap t is set to 1 mm or less. The heat insulator 15 is made of a resin or the like, and a polyimide resin or a polyether ether ketone resin material that can be molded into an arbitrary shape corresponding to the shape of the heat fixing roller 6 is suitable. In addition, foamed silicone rubber, glass wool or the like is used. You can also do it. It should be noted that if it is molded in a predetermined shape in advance, it can be fixed to the housing 3 with the screw 16 or the like as described above. In this case, a resin bush 17 or the like is attached to the shaft portion of the screw 16 and the screw 16 It is preferable to prevent heat from radiating to the outside by heat conduction from the. On the other hand, in the case where the heat insulator is formed by the filling operation, as shown in FIG. 3, it is possible to install a metal partition plate 20 having a reflection effect on the outer peripheral position of the heat fixing roller and fill the resin behind it. is there. In this case, the resin constitutes the heat insulator 15, and the radiant heat from the heat fixing roller 6 can be reflected by the metal partition plate 20, so that the heat radiation from the heat fixing roller 6 can be efficiently blocked. As a result, the temperature rise inside the entire device can be suppressed. Further, since the metal partition plate 20 is arranged so as to hold a slight gap with the heat fixing roller 6, this gap portion forms the adiabatic air thin layer 18. Due to the presence of the thin insulating air layer 18, generation of an air convection layer on the surface of the heat fixing roller 6 can be prevented.

The structure of the heat fixing device in the width direction will be described with reference to FIG. FIG. 2 is a vertical sectional view of the heat fixing device shown in FIG. Bearings 21, 21 are fitted on both side surfaces of the housing 3, and the hollow heat roller 8 of the heat fixing roller 6 is rotatably supported by the bearing 21. Furthermore, the sliding contact electrodes 2 are provided on both ends of the hollow heat roller 8.
2, 22 are connected. Bearings 23, 23 are provided inside the lower housing 4, and the pressure roller 7 is rotatably supported.

As is clear from the figure, the heat insulator 15 is arranged in the entire width direction of the roller inside the housing.
The heat radiation from the hollow heat roller 8 is minimized.

FIG. 4 shows an example in which a plurality of arc-shaped stainless steel heat shield plates 24 are arranged with a slight gap t as a modification of the heat insulator 15 used in the heat fixing device.

In FIG. 4, each heat shield plate 24 is fixed at a predetermined position by a screw 25, but a resin bush 26 is fitted as a spacer between the heat shield plates to increase the temperature of the heat shield plate. Heat is not taken from the plate 24 via the screws 25. The gap t between each heat shield plate 24 is set to about 1 mm so that an air convection layer does not occur between the surface of the heat fixing roller 6 and each heat shield plate 24 as in the above-described embodiment. ..

FIG. 5 shows a modified example in which the heat insulator 15 is also attached to the pressure roller 7 side. By thus providing the heat insulating body 15 also on the pressure roller 7 side, it is possible to prevent heat radiation from the pressure roller portion 7 whose temperature has risen due to the heat transmitted from the heat fixing roller 6, and to improve the thermal efficiency of the heat fixing device as a whole. Can be improved. In this case as well, the pressure roller 7
It is preferable to maintain the gap t between the surface of and the heat insulator 15 at 1 mm or less.

FIG. 6 shows an embodiment in which a heat exhaust path W is formed inside the equipment case of a copying machine so that the heat generated in the developing and transferring process is separated from the heat fixing device portion and discharged to the outside of the equipment case. It is shown. In FIG. 6, reference numeral 30 indicates a device case of the copying machine, and a paper discharge port 31 is formed on the side surface of the device case 30. The housing 3 of the heat fixing device is attached adjacent to the paper discharge port 31. This heat fixing device has the same structure as the heat fixing device shown in FIG. 1, and is provided with a heat insulator 15 on the heat fixing roller 6 side. Further, the heat insulator 32 is arranged and fixed so that the surface of the housing 3 of the heat fixing device is one side of the path. A substantially inverted L-shaped exhaust heat path W is formed in a portion defined by the heat insulator 32 and the surface of the housing 3. Further, a large number of holes 33, 33 ... Are provided on the surface of the device case 31 above the position where the heat fixing device is arranged, so that the heat generated in the developing and transferring process is transferred from the heat fixing device through the exhaust heat path W. It can be separated from the radiated heat and discharged to the outside of the device case 30. At this time, since the exhaust heat convects the surface of the housing 3 of the heat fixing device, the heat of the housing surface whose temperature has risen is taken away, and the temperature rise of the entire device can be suppressed.

[0015]

As is apparent from the above description, according to the present invention, the heat fixing roller and the pressure roller are housed in the housing, and the heat insulating body for blocking the heat radiation from the heat fixing roller is housed in the housing. Since it was placed around the roller inside the body, and a thin layer of heat-insulating air was formed between the inner peripheral surface of this heat insulating body and the roller surface, radiation from the heat source and heat radiation due to heat conduction were suppressed, and The heat dissipation can be reduced, the thermal efficiency can be improved, the process inside the device can be designed compactly, and the device can be downsized.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing an embodiment of a heat fixing device according to the present invention.

FIG. 2 is a vertical sectional view taken along line II-II of the thermal fixing device shown in FIG.

FIG. 3 is a partial cross-sectional view showing an embodiment of a heat insulator used in the heat fixing device according to the present invention.

FIG. 4 is a cross-sectional view showing an embodiment of a heat fixing device according to the present invention.

FIG. 5 is a cross-sectional view showing an embodiment of a heat fixing device according to the present invention.

FIG. 6 is a cross-sectional view showing an embodiment of the heat fixing device according to the present invention.

FIG. 7 is a cross-sectional view showing an example of a conventional heat fixing device.

[Explanation of symbols]

 3 Case 6 Heat Fixing Roller 7 Pressure Roller 8 Hollow Heat Roller 9 Halogen Rod Lamp 15, 32 Heat Insulator 20 Metal Partition Plate 24 Heat Shield Plate

Claims (1)

[Claims] 1. In a thermal fixing device for pressing a copy medium against the thermal fixing roller by a pressure roller arranged to face the thermal fixing roller and fixing and conveying the same, the thermal fixing roller and the pressure roller are housed in a housing. In addition, a heat insulating body that blocks heat radiation from the heat fixing roller is arranged around the heat fixing roller, and a heat insulating air thin layer is formed between the inner peripheral surface of the heat insulating body and the surface of the heat fixing roller. A heat fixing device characterized in that