JPS5968766A - Heat fixation device - Google Patents

Abstract

PURPOSE:To improve the thermal efficiency of a heat fixation device and, at the same time, to use the heat fixation device for cut sheets, by heat-fixing a toner image onto a recording sheet while the recording sheet is passed through a nip section. CONSTITUTION:At the time of fixation operation, a pressure roll 23 is rotated in the direction shown by the arrow and pressure-contacted with a exothermic head 20, and thus, forms a nip section 27. When a recording sheet 26 carrying an unfixed toner image is sent into the nip section 27, the sheet receives carrying force caused by the rotation of the pressure roll 23 and, at the same time, the heating action of an exothermic body 21. Thus the fixation action is performed. Since the heat capacity of the exothermic body 21 can be minimized remarkably, the rising time required to reach a fixable temperature after the power supply is made can be reduced extremely, and the amount of the heat radiation can be reduced because of the used exothermic section being small in size, when such a device is used, the utilization efficiency of heat is improved and even cut sheets can be fixed.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a thermal fixing device for fixing a powder toner image held on a recording sheet to the sheet surface by the action of heat and pressure.

In hard copy devices such as electrophotographic copying machines, printers, and facsimile machines, thermal fixing devices that fix dry toner images formed on recording sheets such as copy paper to the sheet surface by the action of heat have been widely put into practical use. There is.

There are various operating principles and configurations of thermal fixing devices, but an example of a thermal roller fixing device, which is one of the most widely used thermal fixing devices, is shown in FIG. ] is a thermal roller, which is formed by applying a thin layer 3 of non-adhesive fluororesin, silicone rubber, etc. to the surface of a hollow metal cylinder 2, and providing a heating lamp 4 inside. Reference numeral 5 denotes a pressure roller, which is constructed by coating the outer surface of a core metal 6 with a non-adhesive elastomer 7 such as silicone rubber.

8 is a guide on the sheet entry side, 10 is a sheet peeling claw, 1
1 is cleaning grade. When fixing the recording sheet 13, the heat roller 1 and the pressure roller 5 are brought into pressure contact with each other to form a nip portion 12 with a width of 3 to 5 degrees on the pressure contact surface, and the surface temperature of the heat roller 1 is 160 to 200.
It is controlled to be C.

When the recording sheet 13 bearing a toner image is inserted into the heat roller fixing device configured as described above and passed through the nip portion 12, the toner on the sheet 13 is subjected to both heat and pressure, and is well maintained. It is fixed on the recording sheet. The pressure in such a heat roller fixing device is applied by applying pressure to the toner during fixing to improve contact between toner particles and increasing thermal conductivity, and by widening the width of the nip 2 to lengthen the fixing action time. It has two roles: In conventional heated roller fixing devices, in order to obtain the necessary nip width, 1 to 2 glands (3 cTn) are used per unit length (1 cTn).
) The nip width obtained by applying pressure and pulling is 3~
Practical fixing performance can be obtained with approximately 6
This method requires a long time of several minutes, and is a major obstacle when constructing a small and simple device.

On the other hand, on the other hand, there is a fixing device with a simple structure that has been used for a long time in facsimile machines and the like, and an example thereof is shown in FIG. In FIG. 2, 14 is a hot plate type fixing device, 15 and 18 are sheet feeding rollers, 16 is a recording sheet carrying an l.car image, and 17 is a recording sheet wound into a roll. The hot plate type fixing device 14 has a heater inside, and the surface that comes into contact with the recording sheet is made of a polished or plated metal plate to ensure good thermal conductivity and slipperiness against the sheet. . In order to ensure close contact between the surface of the hot plate type fixing device 14 and the recording sheet 6,
A driving force is applied to the front sheet feeding sheet roller 18 to pull the recording sheet 16, and a rear sheet feeding sheet roller (4) and sheet feeding roller 5 is provided with resistance by friction.
The recording sheet 16 is configured to rotate driven by the recording sheet 16. In this way, in a hot plate type fuser, the tension of the recording sheet is used to obtain close contact between the fuser and the recording sheet, so when a roll-shaped recording sheet is used, the tension is continuously applied. However, it has the disadvantage that it cannot be applied to fixing cut sheets.

The present invention has been made in order to eliminate the above-mentioned drawbacks of the conventional heat fixing device, and includes a heat generating head disposed in a fixed manner and a rotating pressure roller having a flexible surface that are brought into pressure contact to form a nip portion. A heating element is provided in an area corresponding to the nip portion of the head, and the recording sheet carrying the toner image is passed through the nip portion to heat and fix the toner image on the recording sheet.The structure is simple and the rising speed is fast. It is an object of the present invention to provide a heat fixing device that has good thermal efficiency and can be applied to cut sheets.

The present invention will be described in detail below based on Examples.

FIG. 3 is a diagram showing a first embodiment of the heat fixing device according to the present invention. In FIG. 3, reference numeral 20 denotes a fixed heating head, which is composed of a support 22 and a heating element 2.

A pressure roller 23 is formed of a core metal 24 and a flexible elastomer layer 25 disposed around its outer periphery. 26 is a recording sheet holding an unfixed toner image. During the fixing operation, the pressure roller 23 is rotated in the direction of the arrow and pressed against the heat generating head 20 to form a nip portion 27 . When the recording sheet 26 carrying an unfixed toner image is fed 9 into this nip portion 27, it is subjected to a conveying force due to the rotation of the pressure roller 23, and the recording sheet 26 is fixed by being heated by the heating element 21. action takes place.

The heating head 20 is constructed by forming a heating element 2 at a portion corresponding to the nip of a support 22 made of a heat-resistant member such as ceramic or metal. The heating element has a width that is approximately equal to the width of the nip portion 27, or has a width with a slight margin, and a material with good surface smoothness and wear resistance is selected, or the heating element is The surface is treated with a material that is slippery and wear-resistant. The heating element may be a ribbon made of commonly used iron-chromium alloy or nickel-chromium alloy, or a heater wire formed into a flat coil or zigzag shape. However, as an example of a more suitable heating element, a metal compound semiconductor film such as tantalum nitride (Ta, N) is used as the heating element, and the surface thereof is coated with an oxidation prevention layer such as silicon oxide (Sin) and oxidation. Tantalum Ta,
0. Some products are constructed by laminating wear-resistant layers such as. The basic configuration of such a heating element is known as a heating element configuration used in a so-called thin film type thermal head in a thermal recording head for thermal recording. Similarly, the configuration of the heating element applied to what is called a thick-film thermal head can also be applied to the heating head of the thermal fixing device according to the present invention.

Thick film heating elements are made by coating a heat-resistant insulating material such as an alumina substrate with conductive paint at a distance to form a pair of electrodes, applying a resistor between the electrodes and firing, and then Then, a wear-resistant layer is formed by applying glass or the like and firing it.

The heating element constructed by such various means has a temperature rise characteristic as fast as that applied in the recording method known as thermosensitive recording, and has a temperature rise characteristic as fast as that applied to the recording method known as thermosensitive recording, and has a temperature rise characteristic as fast as that applied to the recording method known as thermosensitive recording, and has a temperature rise characteristic as fast as that applied to the recording method known as thermosensitive recording, and has It is resistant to abrasion due to high temperatures and contact with recording sheets. In addition, it is sufficient that the heat generating element 2 provided in the heat generating head 20 having such a configuration corresponds to the nip portion 27 and has an area with some margin. Since the corresponding portions, that is, the heat generating head portions other than the fixing action portion, do not need to be heated, the heat utilization efficiency is high, and the desired fixing effect can be obtained with a small amount of supplied power.

The pressure roller 23 is formed by coating a flexible elastomer layer 25 on the outer peripheral surface of a core metal 24, and the elastomer layer 25 is heat resistant, such as silicone rubber impregnated with silicone oil. It is also preferable to be made of a non-adhesive material, and during operation, it is driven in the direction of the arrow and also plays the role of conveying the recording sheet 26. The recording sheet 26 carrying the unfixed toner image is fed into the nip portion 27 such that the surface carrying the toner image of the sheet faces the pressure roller 23 .

In addition, in the present invention, as needed, a heat roller fixing device such as that used in the conventional heat roller fixing device shown in FIG.
Cleaning device, peeling nail, silicone oil application device,
A nip release device or the like can be added.

Furthermore, in the embodiment shown in FIG. 3, since the heating element 21 is formed in a planar shape, the nip width of the nip portion 27 formed by the pressure roller 23 that is pressed against the heating element 21 is as shown in FIG. It is easy to widen the conventional one-type heat roller shown in FIG. Therefore, when heating the recording sheet from the back surface to fuse the toner on the surface as in the embodiment shown in FIG. In this case, high temperatures must be applied, and if the temperature of the heating element is high, if the recording sheet is paper, it will easily burn, and if the recording sheet is plastic, it will deform or fuse to the heating element. There is a risk that
In the embodiment shown in the figure, since the nip width can be easily widened, there is no need to raise the temperature of the heating element to such a high level that scorching or the like occurs even when heating is performed from the back surface of the sheet.

FIG. 4 shows a second embodiment of the present invention, in which the shape of the heating element is different from that of the embodiment shown in FIG. 3, and fixing is performed with the temperature of the heating element further lowered. It is what makes it possible. That is, the heating element 28 of the heating head 200 is configured to have a concave shape close to the curvature of the outer peripheral surface of the pressure roller 23. Therefore, by applying only a slight pressure force between the pressure roller 23 and the heat generating head 20,
A nip portion 29 having a large nip width as shown in the figure is formed. When the nip width is increased, the time for the recording sheet 26 to pass through the nip becomes longer, and the temperature difference between the front and back sides of the recording sheet becomes smaller. Therefore, fusing can be performed while the temperature of the heating element 28 is kept low, increasing the lifespan. Ru. As mentioned above, the purpose of the configuration of the embodiment shown in FIG. 4 is to increase the nip width and obtain the necessary nip width with weak pressure. If there was
In a combination of rollers like the conventional device shown in FIG. 1, the practically obtained nip width is about 6 mm even when strong nip pressure is applied, whereas in the embodiment shown in FIG. Now, using a pressure roller of the same diameter,
It is easy to obtain a nip width of 15+ am, and the nip pressure at this time can be set to an extremely small value if the curvature of the concave surface of the heating element 28 is made the same as the curvature of the outer peripheral surface of the pressure roller 23. However, even if the nip width is Furthermore, by reducing the nip pressure, it is also useful to prevent wrinkles from forming on the recording sheet.

In the embodiments shown in FIGS. 3 and 4 above, if the pressure roller, heating head, etc. are arranged so that the toner image bearing surface of the recording sheet faces the pressure roller, good fixing operation can be achieved. However, when the toner image bearing surface faces the heat generating head side, the toner image flows in a trailing manner, making it impossible to perform a good fixing operation. Therefore, this is inconvenient as a fixing device for double-sided copying.

The embodiment shown in FIG. 5 shows a configuration for eliminating this inconvenience. That is, in FIG.
30 is a heat-resistant sheet, and the sheet 30 is attached to the heating head 20.
and the recording sheet 26, the pressure roller 23
It is configured to run at the same linear velocity as the circumferential velocity of. Therefore, since the recording sheet 26 carrying the toner image passes through the nip portion while being held between the pressure roller 23 and the heat-resistant sheet 30, there is no possibility that the toner image on the recording sheet will be disturbed. In this configuration, it is convenient to feed the recording sheet 26 in such a direction that the unfixed toner image contacts the heat-resistant sheet 30. If the arrangement is reversed, the pressure roller 2
The heating element 2 is heated to a temperature that fixes the unfixed toner image on the side 3.
When the temperature of step 8 is raised, the temperature of the recording sheet surface on the heat-resistant sheet 30 side reaches a temperature that excessively melts the toner.
This is because there is a possibility that a high-temperature offset phenomenon of toner may occur in the heat-resistant sheet 30. However, if the toner image is formed on only one side of the recording sheet, it is not impossible to carry out the fixing operation so that the toner image contacts the pressure roller 23, but this is not a preferable fixing method.

The heat-resistant sheet 30 can be made of a plastic film. Examples of applicable plastic films include nylon 66 (continuous use temperature:
190C), polytetrafluoroethylene PT, FE (
Same temperature: 260C), polyvinyl alcohol (same temperature: 220C), polyimide (same temperature: 4003)
:) and so on. It is preferable that the plastic film constituting these sheets 30 be as thin as possible within a range that allows for mechanically stable running;
It is selected and used within the range of 0 to 100μ.

The heat-resistant sheet 30 can be fed in various ways, but in the embodiment shown in FIG.
2 shows an example in which the heat-resistant sheet 30 is gripped and at the same time the same roller is rotated at a predetermined speed to send out the heat-resistant sheet 30 in the direction of the arrow.

Note that the roller 33 is a driven roller for applying appropriate tension to the heat-resistant sheet 30. The tension of the sheet 30 is applied by the pressure roller 23 to the sheet 30 and the recording sheet 26.
must not be strong enough to impair the effect of pressing against the heating element 28. Also in this example, the heat-resistant sheet) 30
A cleaning blade, a silicone oil application device, a recording sheet peeling device, etc. can be appropriately arranged around the periphery of the recording sheet.

As described above in detail based on the embodiments, the present invention provides a heat fixing device in which a fixedly arranged heat generating head and a rotary pressure roller having a flexible surface are brought into pressure contact to form a nip portion, and A heating element is provided in the area corresponding to the nip portion of the head, and the recording sheet carrying the toner image is passed through the nip portion to heat and fix the toner image on the recording sheet. The heat capacity of the heating element is significantly smaller than that of a roller, making it possible to significantly shorten the start-up time from the start of energization until it reaches the temperature that allows fixing, and because the heat generating part is small, less heat is lost through heat radiation. Therefore, it is possible to obtain a heat fixing device that has good heat utilization efficiency, is small in size and has a simple configuration, and is capable of fixing cut sheets.

In addition, by making the surface of the heating element provided on the heating head surface a curved surface that is approximately equal to the curvature of the outer peripheral surface of the pressure roller, the nip width can be easily widened and the nip pressure can be weakened. Increased durability of component parts,
Moreover, the occurrence of wrinkles on the recording sheet can be reduced.

Furthermore, the heating head and the pressure roller are brought into pressure contact with each other through a heat-resistant sheet that is fed at the circumferential speed of the pressure roller, and the recording sheet is conveyed and fixed by the pressure roller and the heat-resistant sheet. Effects such as making it possible to fix a recording sheet having a toner image can be obtained.

[Brief explanation of the drawing]

FIG. 1 is a schematic sectional view showing an example of a conventional heat roller fixing device, FIG. 2 is a schematic sectional view showing an example of the same conventional hot plate fixing device, and FIG. 3 is a schematic sectional view showing an example of a conventional hot plate fixing device. FIGS. 4 and 5 are schematic cross-sectional views showing one embodiment of the heat fixing device, and FIGS. 4 and 5 are schematic cross-sectional views showing still other embodiments of the present invention, respectively. In the figure, ] is a heat roller, 5 is a pressure roller, ]
3 is a recording sheet, 14 is a hot plate type fixing device, 16 is a long recording sheet, 20 is a heating head, 2] is a heating element, 22 is a support, 23 is a pressure roller, 24 is a core metal, 25 is flexible One layer of elastomer, 26 is a recording sheet, 27 is a nip part, 2
8 is a heating element, 29 is a nip portion, and 30 is a heat-resistant sheet. Patent applicant: Olympus Optical Industry Co., Ltd. East 1 Figure 3 Figure 4

Claims (3)

[Claims] (1) A heat fixing device for heating and fixing a powder toner image carried on a recording sheet includes a heat-generating head fixedly arranged and a flexible surface that comes into pressure contact with the heat-generating head to form a nip. and a heating element provided in a region corresponding to the nip portion of the heat generating head, and configured to heat and fix the toner image on the recording sheet by passing the recording sheet through the nip portion. A heat fixing device characterized by: (2) The heat fixing device according to claim 1, wherein the heating element provided in the heating head has a curved surface with a curvature approximately equal to the curvature of the outer peripheral surface of the pressure roller. (3) The heat generating head and the pressure roller are pressed together via a heat-resistant sheet that is fed at the same peripheral speed as the pressure roller, and the recording sheet is fixed between the heat-resistant sheet and the pressure roller. A heat fixing device according to claim 1, characterized in that: