JPH10207276A - Fixing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve thermal efficiency, and to uniformize the temp. distribution in the shaft direction by providing a mirror reflecting heat from a heat generating source inside an end section of a heating roll. SOLUTION: In this fixing device, on the heat generating source, the current flow is allowed to flow from a power source through a leader line 10a, and the heat generating source 10 generates the heat. Most of the radiant heat from the heat generating source 10 directly reach an inner peripheral surface 1a of the heating roll 1, and the heating roll 1 is heated. Moreover, a portion of the heat generation at an end part of the heat generating source 10, reflected by a mirror section 9, reaches the inner peripheral surface 1a of the heating roll 1. At this time, the mirror section 9 becomes to the convex mirror face in the case of viewing it from the heating roll 1 inside, the heat generated on the end part of the heat generating source 10 can be efficiently fed to the end section of the heating roll 1. Moreover, since the heating roll 1 inside is hermetically closed substantially by the mirror section 9, the heat generated inside the heating roll 1 is prevented from flowing the outside through a hollow shaft 4. Therefore thermal efficiency in the fixing device can be improved.

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 image forming apparatus such as a copying machine and a printer.
In particular, it relates to a fixing device with improved thermal efficiency.

[0002]

2. Description of the Related Art Various types of fixing devices are known, one of which is a heating / pressure roll type fixing device.

[0003] The fixing device of the heating / pressing roll type comprises:
The heating roller includes a heating roller provided with a heat source therein, and a pressure roller pressed against the heating roller. The nip portion between the heating roller and the pressure roller is a sheet on which the toner image has been transferred. , Fixing is performed by heat and pressure.

In such a heating / pressing roll type fixing device, in order to improve the thermal efficiency of the fixing device, it is necessary to efficiently transfer heat supplied from a heat source to the surface of the heating roll. Also, if the fixing temperature is not uniform in the axial direction of the heating roll, fixing unevenness occurs,
It is necessary to sufficiently transfer the heat supplied from the heat source to the axial end of the heating roll. Various configurations have been proposed to improve the thermal efficiency in the above-described heating / pressure roll type fixing device.

[0005] For example, as described in Japanese Utility Model Publication No. 61-4923, the end of the roll body is held by a heat insulating member and a heat shield wheel is provided inside, so that the heat from the end is removed. Arrangements that seek to minimize escape are known. However, in the configuration described in the publication, since the center of the heat insulating member and the heat shield wheel is hollow in order to draw out the end of the heater to the end of the roll body, the heat from the heater is hollow. It is difficult to say that heat is radiated from the gap and the heat supplied from the heat source is efficiently transmitted to the heating roll. Further, since the heat from the heater escapes from the end to the outside, the surface temperature of the heating roll is significantly reduced at the end, and the axial temperature distribution becomes non-uniform. That is, the configuration described in Japanese Utility Model Publication No. 61-4923 does not sufficiently solve the problem of improving the thermal efficiency and making the temperature distribution in the axial direction uniform.

[0006] Also, Japanese Patent Application Laid-Open No. 61-147276,
As described in JP-A-1-49073,
A shutter mechanism is provided at each of the upstream and downstream openings including the recording paper passing portion of the fixing device, and each shutter is opened when the recording paper is passed, and the shutter is closed when the recording paper is not passed, thereby fixing the fixing device. In addition to keeping the heat of the heating roll warm by minimizing the heat leaking from the outside to the outside, the temperature of the cleaning unit included in the image forming unit disposed close to the upstream side of the fixing device due to the heat from the fixing device It is known to prevent the toner from blocking due to heat in the cleaning unit by preventing the toner from rising. However, when such a shutter mechanism is used on both the upstream side and the downstream side of the fixing device, a complicated drive mechanism for sequentially opening and closing both shutter mechanisms in conjunction with the passage of paper must be provided. However, there is a problem that the configuration becomes complicated. Even when such a shutter mechanism is provided, there is a problem that a large amount of heat escapes from the inside of the fixing device because both shutters are open when the sheet passes.

In any of the above publications, the surface of the sheet is hot immediately after the sheet is discharged from the fixing device, so that the sheet cannot be touched. Further, until the paper discharged from the fixing device is discharged out of the device, heat from the fixing device is transmitted to the surface of the paper and released into the image forming apparatus, so that the temperature inside the device increases. There is.

[0008]

SUMMARY OF THE INVENTION An object of the present invention is to improve the thermal efficiency and to make the axial temperature distribution uniform. Another object of the present invention is to improve the thermal efficiency with a simple configuration and not to raise the temperature of the sheet discharged from the fixing device more than necessary.

[0009]

According to the present invention, there is provided a fixing device including a heating roll having a heat source therein and a pressure roll pressed against the heating roll. A mirror surface for reflecting heat from the heat source is provided inside the mirror. The mirror surface is preferably convex when viewed from the inside of the heating roll for reflecting heat from the heat source and guiding the heat to the end of the heating roll.

Further, the present invention includes a heating roll having a heat source therein, a pressure roll pressed against the heating roll, and an upstream opening and a downstream opening along a sheet transport path. And a fixing device having a fixing cover surrounding the heating roll and the pressure roll, wherein at least a part of the sheet is exposed to the outside of the fixing device, and the sheet after fixing near a downstream opening of the fixing cover. A cooling and conveying unit that conveys the sheet in a sandwiched state, and a heat shielding cover that is disposed on the heating roll side of the cooling and conveying unit and that prevents heat from the heating roll from directly reaching the cooling and conveying unit. Is provided.

[0011]

FIG. 1 is a sectional view showing a main part of a first embodiment of a fixing device according to the present invention. Both ends of the cylindrical heating roll 1 in the axial direction (only one end is shown in the figure) are provided with a polyimide resin or a polyimide resin via an annular low friction member 2 made of a fluorinated resin or the like. A disc-shaped heat insulating member 3 made of silicon resin or the like is fitted. A hollow shaft 4 is attached to the heat insulating member 3. A flange 5 is integrally formed at an end of the hollow shaft 4, and the flange 5 is fixed to a frame 7 with screws 6. A flat-conical heat insulating bush 8 is provided near the inside of the heat insulating member 3 in the axial direction. This insulation bush 8
For example, the bush portion is formed of a metal such as brass, for example, and has a mirror surface portion 9 on the inner surface. When the angle formed by the apex of the mirror surface portion 9 is θ, θ ≧ 180 °. That is, the heating roll 1
Is provided with a mirror surface that is convex when viewed from the inside. Further, the outer diameter of the mirror surface portion 9 is a size that fits into the inner peripheral surface 1 a of the heating roll 1. In this embodiment, the inner peripheral surface 1 of the portion where the heat insulating member 3 at the end of the heating roll 1 is fitted.
The inner diameter of b is slightly larger than the inner diameter of the inner peripheral surface 1a. In the center axis portion of the heat insulating bush 8, there is formed a minimum small diameter hole 11 through which a lead wire 10a from an end of a heat source 10 such as a quartz heater arranged on the heating roll 1 can be drawn. The lead wire 10 a of the heat source 10 is drawn out of the heating roll 1 through the hole 11.

In the fixing device shown in FIG. 1, a heating roller 1 is rotatably supported via a low friction member 2 by a heat insulating member 3 fixed to a frame 7 side. 1 is driven to rotate.
Further, a current is supplied to the heat source 10 from a power source (not shown) via the lead wire 10a, and the heat source 10 generates heat. Most of the radiant heat from the heat source 10 directly reaches the inner peripheral surface 1a of the heating roll 1 and the heating roll 1 is heated. Some of the heat generated at the end of the heat source 10 is
And reaches the inner peripheral surface 1 a of the heating roll 1. At this time, since the mirror surface portion 9 has a convex mirror surface as viewed from the inside of the heating roll 1, the heat generated at the end of the heat source 10 can be efficiently supplied to the end of the heating roll 1. Can be. Further, since the inside of the heating roll 1 is substantially sealed by the mirror surface portion 9, the heat generated inside the heating roll 1 does not flow outside through the hollow shaft 4. Therefore, the thermal efficiency of the fixing device can be improved and the temperature distribution in the axial direction can be made uniform.

FIG. 2 is a sectional view of a main part of a fixing device according to a second embodiment of the present invention. The members corresponding to those of the first embodiment are denoted by the same reference numerals. In the second embodiment, a heat source 12 having a structure in which two lead wires 12a and 12b are drawn from one side is used. In this case, a completely sealed mirror portion 13 can be used on the side opposite to the side on which the lead wires 12a and 12b are provided, so that the heat generated inside the heating roll 1 is transferred to the outside. It can be completely prevented from flowing out.

FIG. 3 is a sectional view of an essential part showing an example of a mounting structure of the heat insulating bush 8. In the example shown in FIG. 3, an annular groove 1 is provided near the end of the inner peripheral surface 1a of the heating roll 1.
4 and a claw portion 16 that engages with the groove 14 is provided on the outer peripheral surface of the heat insulating bush 8. Further, a knob 17 is provided integrally with the heat-insulating bush 8, and when the heat-insulating bush 8 is pressed into the inside of the heating roll 1 with the knob 17, the claw portion 16 of the heat-insulating bush 8 becomes a groove of the heating roll 1. 14 and the heat insulating bush 8 is
3 and attached to the heating roll 1.

FIG. 4 is a sectional view of a main part showing another example of the mounting structure of the heat insulating bush 8. As shown in FIG. In the example shown in FIG. 4, a female screw 18 is provided near the end of the inner peripheral surface 1a of the heating roll 1.
And a male screw 19 screwed with the female screw 18 is provided on the outer peripheral surface of the heat insulating bush 8. By holding the knob 17 integrally formed with the heat insulating bush 8 and screwing the heat insulating bush 8 into the inside of the heating roll 1, the male screw 19 of the heat insulating bush 8 becomes the female screw 18 of the heating roll 1.
And the heat insulating bush 8 is attached to the heating roll 1 together with the mirror surface portion 13.

FIG. 5 is a schematic sectional view showing still another embodiment of the fixing device of the present invention. A heating roll 21 having a heat source therein and a pressure roll 22 pressed against the heating roll 21 are arranged inside a fixing cover 23. The fixing cover 23 includes an upper cover 23 a and a lower cover 2.
3b, and an upstream opening 24 is provided in the sheet transport path portion between the upper cover 23a and the lower cover 23b.
And a downstream opening 25.

A shutter 26 is provided on the upstream side of the upper cover 23a so as to open and close the upstream opening 24. In the vicinity of the downstream opening 25, a pair of cooling rolls 27a and 27b are provided with the sheet conveyance path interposed therebetween. As a material of the cooling roll pair 27a, 27b,
It is desirable to select aluminum or the like having high thermal conductivity. Further, on the downstream side of the upper cover 23a and the lower cover 23b, heat shield covers 28a and 28b that cover the inside of the fixing device of the pair of cooling rolls 27a and 27b are formed integrally with the upper cover 23a and the lower cover 23b. I have. The gap between the heat shield cover 28a and the heat shield cover 28b forms a downstream opening 25, and the downstream opening 25 has a minimum interval through which a sheet can pass.

In the fixing device shown in FIG. 5, since the upstream opening 24 is covered with the shutter 26 in the standby state, the heat inside the fixing cover 23 is radiated from the upstream opening 24 to the upstream side. Never be. Therefore,
The cleaning unit included in the image forming unit disposed on the upstream side of the fixing device does not become overheated, and there is no inconvenience that the toner causes blocking due to heat in the cleaning unit. Also, the downstream opening 25 is very narrow, and the downstream opening 25
A pair of cooling rolls 27 pressed together
Since a and 27b are present, the heat inside the fixing cover 23 is not radiated to the outside from the downstream side.

Next, a toner image is transferred onto a sheet in an image forming section (not shown), and the sheet P on which the toner image has been transferred is conveyed to a fixing device. As shown in FIG. 5, the shutter 26 is opened, the paper P is fed into the nip between the heating roll 21 and the pressure roll 22, and the toner image is fixed on the paper P by heat and pressure. The sheet P after fixing is placed in the downstream opening 2.
5 and further pass through the nip portion between the cooling rolls 27a and 27b to be transported outside the fixing device. Cooling roll 27
a, 27b, a heat shield cover 28
a, 28b, the cooling rolls 27a,
27b is maintained at a relatively low temperature. When the sheet P passes through the nip portion between the cooling rolls 27a and 27b, the heat of the sheet is taken by the cooling rolls 27a and 27b, and the surface temperature of the sheet P decreases.

The temperature of the cooling rolls 27a and 27b rises because the cooling rolls 27a and 27b take away the heat of the paper P.
Is exposed to the outside of the fixing device, during the waiting period of the fixing device, the heat of the cooling rolls 27a and 27b is released to the outside and decreases to a temperature sufficient to perform the cooling function.

FIG. 6 is a schematic sectional view showing still another embodiment of the fixing device of the present invention. The members corresponding to those in the embodiment shown in FIG. 5 are denoted by the same reference numerals. In the embodiment shown in FIG. 6, further cooling rolls 29a and 29b are disposed downstream of the cooling rolls 27a and 27b.
Upstream cooling roll 27a and downstream cooling roll 29a
The upper cooling belt 30a is wound between the upper cooling belt 27a and the lower cooling belt 30b is wound between the upstream cooling roll 27b and the downstream cooling roll 29b. In the embodiment shown in FIG. 6, since the sheet is cooled while being conveyed while being sandwiched by the cooling belts 30a and 30b having a certain length in the sheet conveying direction, the cooling effect on the sheet is further improved. Be certain.

FIG. 7 is a schematic sectional view showing still another embodiment of the fixing device of the present invention. The members corresponding to those in the embodiment shown in FIG. 5 are denoted by the same reference numerals. In the embodiment shown in FIG. 7, a plurality of pairs of cooling rolls 3 are provided between the heating roll 21, the pressure roll 22 and the cooling rolls 27a, 27b.
1a, 31b, 32a and 32b are arranged. In the embodiment shown in FIG. 7, since the sheet after fixing contacts the cooling roll a plurality of times, the cooling effect is improved as compared with the embodiment shown in FIG.

[0023]

【The invention's effect】

(1) Since the heat from the heat source at the end of the pressure roll can be effectively used, the thermal efficiency can be improved and the temperature distribution in the axial direction can be made uniform.

(2) The thermal efficiency can be improved with a simple structure, and the temperature of the sheet discharged from the fixing device can be reduced.

(3) There is no need to provide a shutter mechanism downstream of the fixing device, so that the configuration is simplified.

[Brief description of the drawings]

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

FIG. 2 is a sectional view of a main part of a fixing device according to a second embodiment of the present invention.

FIG. 3 is a sectional view of a main part showing an example of a mounting structure of a heat insulating bush 8;

FIG. 4 is a sectional view of a main part showing another example of the mounting structure of the heat insulating bush 8;

FIG. 5 is a schematic sectional view showing still another embodiment of the fixing device of the present invention.

FIG. 6 is a schematic sectional view showing still another embodiment of the fixing device of the present invention.

FIG. 7 is a schematic sectional view showing still another embodiment of the fixing device of the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Heating roll, 2 ... Low friction member, 3 ... Heat insulation member, 4 ...
Hollow shaft, 5 ... flange, 6 ... screw, 7 ... frame, 8 ...
Insulated bush, 9: mirror surface, 10: heat source, 11: hole,
12: heat generation source, 13: mirror surface portion, 14: groove, 16: claw portion,
17: knob, 18: female screw, 19: male screw, 21: heating roll, 22: pressure roll, 23: fixing cover, 24 ...
Upstream opening, 25 ... Downstream opening, 26 ... Shutter,
27a, 27b: cooling roll, 28a, 28b: heat shield cover, 29a, 29b: cooling roll, 30a, 30b ...
Cooling belt, 31a, 31b, 32a, 32b ... cooling roll

Claims (3)

[Claims] 1. A fixing device comprising: a heating roll having a heat source therein; and a pressure roll pressed against the heating roll, wherein a heat source is provided inside an end of the heating roll. A mirror surface for reflecting the heat of the fixing device. 2. The fixing device according to claim 1, wherein the mirror surface is convex when viewed from the inside of the heating roll for reflecting heat from the heat source and guiding the heat to an end of the heating roll. 3. A heating roll having a heat source therein, a pressure roll pressed against the heating roll, and an upstream opening and a downstream opening along a paper transport path. In a fixing device including a roll and a fixing cover surrounding the pressure roll, at least a part of the fixing device is exposed to the outside of the fixing device, and the sheet after fixing is held near a downstream opening of the fixing cover. A cooling / conveying means for conveying in a state, and a heat shielding cover arranged on the heating roll side of the cooling / conveying means for preventing heat from the heating roll from directly reaching the cooling / conveying means. A fixing device characterized by the above-mentioned.