JPS6018070B2 - Copy machine fixing device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a fixing device for a copying machine, and more particularly to an atmospheric fixing device that fixes a toner image on a sheet using heat radiation from a heat source.

In an electrophotographic copying machine, for example, a visible image transfer type electrophotographic copying machine, a static latent image corresponding to an original image formed on a photoreceptor drum is converted into a visible toner image by a developing device, This toner image is transferred to a copy sheet. The toner image transferred to this copy sheet is fixed by various fixing methods. In an atmospheric fixing device, which is one field of this fixing method, the copy sheet separated from the photoreceptor drum after transfer is conveyed by a predetermined conveying device, and the sheet is conveyed by heating elements such as nichrome wires facing each other. The toner on the copy sheet is fused by the radiant heat of the heating element.
This achieves the so-called sheet fixing function. When passing a copy sheet between such fixing devices, the conveyance function may be hindered for some reason.

For example, there is a risk that the sheet conveyance function between the fixing devices may be disrupted, resulting in a so-called jam.
If the sheet comes into contact with the above-mentioned heating element, there is a danger that it will ignite and cause a fire. Furthermore, if a sheet jams and remains for a long time between fixing devices under high temperature conditions, it may cause spontaneous combustion. Further, in this type of fixing device, since the surface of the fixing device facing the sheet is open over a wide area, thermal efficiency is poor and temperature rise characteristics are also not good. The present invention has been made to eliminate the above-mentioned drawbacks, and an object of the present invention is to provide a fixing device for a copying machine that can prevent the occurrence of fire and has excellent fixing efficiency.

The present invention will be explained below with reference to illustrated embodiments.

In FIG. 1, the heat shielding roll 1 has a cylindrical shape as shown in FIG. 2, and a heater 3 made of an electric resistance heating element such as a heat source lamp or a nichrome wire is provided inside the roll. On the other hand, a roll 2 is provided at the bottom of the shielding rotary 1 as a pair of opposing members.
On both roll days, 2 is this direction of travel a with the copy sheet S in between.
It is arranged in a direction perpendicular to the Heat shield roll 1
A part of the peripheral wall facing the sheet S side is cut out along the axis of the roll 1, as shown in FIG. The heat shield roll is made of metal, for example, and achieves heat retention and heat reflection functions for the heater 3.

On the circumference of the roll 1, ring-shaped heat dissipating fins lb are provided integrally or substantially integrally with each other at predetermined intervals, and a portion thereof is cut out equally to the notch opening la of the roll. The roll 2 is made of a material such as metal, glass, or ceramics. In this case, if one made of transparent glass is used, fin radiation heat can be used more effectively. The circumferential surface of the roll 2 is coated with resin such as Teflon, rubber, or the like. here,
In FIG. 1, the heat shielding roll 1 is normally held in the position shown in the figure, and in this state, when a print button (not shown) of a copying machine equipped with this fixing device is pressed,
Heater 3 installed in the roll is turned on.

On the other hand, the copy sheet S, on which the toner image has been transferred through the above-described copying process, is sent toward both rolls 1 and 2 by a transport device (not shown). The copy sheet S travels between these rolls in the direction of arrow a,
Furthermore, the radiant heat from the heater 3 is radiated onto the surface of the copy sheet S on the side of the toner image through the notch opening la (see FIG. 2), whereby the toner T is fused. That is, fixing is performed in this state. In this state, both rolls 2 do not rotate at all. In this case, the roll may be in a non-rotating state and the roll 2 may be rotated. Here, the copy sheet S is on both rolls 1
.

- The wheels 2 are rotated by a drive device (not shown) in the directions of the respective arrows, as shown in FIG. Then, the sheet is forcibly fed out with the jam caused by the frictional force between the circumferential parts of both rolls 1 and 2, so the sheet does not stay on both rolls for a long time, which can prevent a fire. This can be prevented from occurring. Furthermore, during fixing, the heat radiated by the heater 3 is shielded by the shield roll, and moreover, the heat reflected from the inner peripheral surface of the roll is effectively radiated onto the sheet surface through the notch opening la. Therefore, it has excellent thermal efficiency and improves temperature rise characteristics. Incidentally, after both the rolls 1 and 2 finish feeding the sheet, they stop at the positions shown in the figure in preparation for the next fixing. Incidentally, in the above embodiment, both rolls are rotated at the same time as the jam state is detected, but the heater 3 may be turned off at the same time. Further, in order to improve heat radiation efficiency, a metallic thermal radiation plate 4 may be provided on the back side of the heater 3. In this case, the heat reflecting plate 4 may be rotated together with the roll 1, or may be fixed. In this embodiment, since the heat shielding roll 1 is provided with the radiation fins lb, a cooling effect of the roll itself can be expected. In this case, by coating the circumferential surface of the radiation fin lb with a resin such as Teflon, which has excellent adhesion properties, silicone rubber, etc., cleaning can be easily performed when toner or dust adheres. .
In addition, a heater 5 may be provided inside the lower roll 2 in FIG. 1 to perform auxiliary heating. In this case, the heater 5 may be constantly energized for heat retention. Further, the roll 2 as a supporting member works together with the shielding roll 1 to achieve the sheet feeding function in the event of a jam, but in place of the roll 2, it can also achieve the above function in the same way. A flat plate made of rubber or the like may be used. Furthermore, the heat shielding roll may be arranged at a location on the roll 2 side. Incidentally, in the above embodiment, the heat shielding roll 1 is rotated by detecting the jam state, but jam detection in this case can be achieved by the following means.

That is, for example, as shown in FIG. 1, on the entrance side of both rolls 1 and 2, the leading edge of the advancing copy sheet S is detected by a microswitch MS. If, for example, a timer is activated at the same time as the microswitch MS is turned on, and the microswitch MS2 whose leading edge of the sheet is on the exit side is activated within a predetermined set time, it is assumed that no jam occurs and the sheet S is transferred to the conveyor belt. etc., in a normal state. On the other hand, if a jam occurs between both rolls, the leading edge of the sheet will continue to advance even after a predetermined time.
2 will no longer work.

When this state is detected, that is, a jam is detected, this jam signal is output to the disturbance circuits of both rolls, and both rolls are rotated. Therefore, the jammed sheet is forcibly fed. Note that a detection roller 6 is used in place of the microswitch MS2 on the exit side, and is made to rotate freely by frictional contact force when the sheet moves. Then, if the micro switch MS on the entrance side is turned on and the timer is activated, and the detection roller 6 does not rotate even after a predetermined period of time has elapsed, this condition is detected and the jam is assumed to have occurred. roll 1
, 2. Note that a photo sensor may be used instead of the above microswitch. As other detection methods, the following means may be used.

That is, a lamp 7 and a photo sensor 8 facing each other with the copy sheet in between are provided near the exit sides of both rolls. Normally, this type of copy sheet has a fibrous vertical weave when viewed in detail, and when light passes through such a sheet and it is moved, the light that has passed through the fibrous structure is absorbed. The strength of changes over time. In other words, the intensity of the light changes like an alternating current waveform. Further, when the sheet is in a moving state and stops due to a jam or the like, the intensity of the light becomes constant over time and becomes like a DC waveform. Jam detection can be performed by detecting this difference.
By using the above-mentioned jam detection means, it is possible to control the rotation of the heat shielding roll, but the characteristic feature of this case is that only when a jam is detected,
It rotates the roll.

On the other hand, in addition to this method, the following means can also be used to achieve the intended purpose. That is, whether a jam occurs or not, the heat shielding roll 1 and roll 2
After the leading edge of the sheet has passed between both rolls and a predetermined time has elapsed, the sheet is rotated without fail. In this way, a jammed copy sheet can be forcibly sent out without the need for a jam detection means. Therefore, the intended purpose of preventing the occurrence of fire is achieved. Incidentally, when fusing is being performed, the heat shielding roll 1 is held in the position shown in FIG. There is a risk that the sheet will catch fire.

As a means to eliminate such problems, the
A heat-resistant glass or wire mesh may be attached to the portion a, that is, the portion shown by the imaginary line in FIG. In this case, for example, the circumferential surface of the glass is slightly retracted from the circumferential surface of the roller so as not to interfere with the movement of the sheet. With this configuration, it is possible to prevent the leading end of the sheet from entering the entrance portion la.
As other methods for preventing entry, the following measures may be taken. That is, as shown in FIG. 4, the tips of the plurality of guide claws 11 arranged between the radiation fins lb are made to face toward the opening la of the roll 1. The sheet is guided downward by the pawl 11 and advanced. Next, the example shown in FIG. 5 shows yet another means for preventing the sheet from entering. That is, the heat shielding roll 1 and the roll 12 are covered with covers 13 and 14. Further, the roll 12 is made of a porous material such as a stitched alloy or a self-heating ceramic, and hot air from a hot air fan 15 is circulated as shown in the figure. In this case, since hot air is blown onto the sheet S, there is no risk that the leading edge of the sheet will enter the roll 1. In addition, in this case, the cover 13
It is desirable that the nozzle portion 13a on the left side in the figure be made wider, and the nozzle portion 13b on the right side in the figure be made narrower. That is, the wind pressure is strong in one nozzle part 13b, and the other nozzle part 1
3b is weaker, which is convenient for conveying the sheet. FIG. 6 shows another embodiment of the heat shielding roll, in which the outer periphery of a notched roll 16 having heat retention and heat reflection functions is further covered with another notched roll 17.
Cover it with water.

Then, one of the rolls 16 and 17 is rotated, and the other is rotated. Now, suppose that the copy sheet S is sent in the direction of the arrow and enters the gap between the rolls 16 and 17 as shown in the figure.If this gap is kept small, even if it ignites, it will be extinguished immediately. It is possible to do so, and if one sheet is rolled into this gap, it is safe even if it ignites. In this case, radiation fins lb as shown in FIG. 2 may be provided around the inner roll 16.
By the way, if the temperature of the above-mentioned heat shielding roll or the like exceeds 400 C, there is a risk of a fire occurring in the event of a jam.

To deal with this, for example, the heat shield roll itself may be cooled with cooling fins, or a temperature sensor such as a bimetal or thermocouple may be installed on the roll surface to prevent dangerous temperatures. It may also be possible to turn off the power to the heater when the In this case, there is a risk that the fixing function cannot be achieved substantially, so as shown in FIG. 7, two roll pairs are provided in parallel, and normally,
Fixing is performed using one pair of rolls, and when the temperature reaches a dangerous temperature, the power to the heater for this pair of rolls is turned off, and at the same time, the power to the heater for the other pair of rolls is turned on. In this way, by alternately using each pair of rolls, the occurrence of a fire can be prevented and the fusing function can still be achieved. In addition, a heat shielding roll may be configured as shown in FIG. 8 as a fire prevention means.

That is, the heat shield roll 18 is formed into a tubular shape, and a heat medium 19 such as water is sealed in the lower part of the roll. In addition, as this kind of hot soot,
In addition, hot soot oils such as SK oil and KSK oil (trade name) may be used. If you do this, roll 1
The inside of the void portion 18a of No. 8 becomes a steam atmosphere, and a further cooling effect can be expected. Moreover, it is possible to prevent the cut portion of the roll 18 from being overheated due to radiant heat from the heater 3, and the temperature distribution is also relatively uniform. Note that this hot soot cooling method is applied to the outer notch roll 1 shown in FIG.
7 may be applied. Further, an impregnating porous material such as Akatsuki alloy or steel wool may be placed in the heat medium enclosure portion of the roll 18 in FIG. 8. In this way, even if only a part of the outer surface of the roll 18 corresponding to the heating medium sealed part is cooled by a cooling fan or the like, the hot soot liquid permeates through the entire roll due to capillary action. are cooled almost evenly. In addition, as a means to prevent the occurrence of a fire, the cylindrical curved portion of the heat shielding roll 1 shown in FIG. 2 and the peripheral surface of the outer notch roll 17 or the inner notch roll 16 shown in FIG. 6 may be covered with an appropriate heat insulating material. Cornering may also be performed by As described above, according to the present invention, when a jam occurs in a copy sheet, the heat shield roll and the counterbalance member in contact therewith forcefully send out the copy sheet, so that the sheet does not stay in the fixing device section for a long time. Therefore, it is possible to prevent the occurrence of a fire, and at the time of fixing, the radiant heat from the heat source through the roll notch is effectively projected onto the sheet surface, resulting in excellent thermal efficiency and The temperature rise characteristics are also improved.

[Brief explanation of the drawing]

FIG. 1 is a front view showing an embodiment of the apparatus of the present invention, FIG. 2 is a perspective view of the heat shield roll in the above embodiment, and FIG. FIG. 4 is a front view showing an example of means for preventing copy sheets from entering the heat shielding roll; FIG. 5 is a front view showing another example of the above means. 6 is a front sectional view showing an example of a heat shielding roll configured with an outer cylindrical part and an inner cylindrical part. FIG. FIG. 8 is a front sectional view showing an example of a configuration in which a thermal butterfly is enclosed within a heat shielding roll. DESCRIPTION OF SYMBOLS 1...Heat shield o-ru, 2,1 2...Twill member, 3...Heat source, S...Copy sheet. Travel 1 figure Rare 2 figure Bridle figure 4 figure Rare figure 5 figure Bell 6 figure Rare figure 6 figure

Claims (1)

[Claims] 1. A contact member and a cylindrical heat shielding roll are arranged to face each other with a copy sheet in between, and a part of the peripheral wall of the heat shielding roll facing the sheet side is arranged along the axial direction. A heat source for heat fixing is arranged in the notch and inside the roll, and radiant heat from this source is applied to the sheet surface through the notch to fix the toner image formed on the sheet. A copying apparatus characterized in that the sheet feeding function is achieved by imparting a rotating action to the roll and sandwiching the sheet between the peripheral surface of the roll and the contact member. Fixing device of the machine.