JPH05307333A - Fixing device - Google Patents

Abstract

PURPOSE:To provide a fixing device being advantageous to the miniaturization of a device in order to reduce power consumption. CONSTITUTION:The fixing device incorporated in an electrostatic recording device is provided with a heat roller 13 with built-in heating source. A sheet-like heater 11 (heating wire) used as the heating source is formed by covering an exothermic resistor with an insulating heat-resisting member, and the heater 11 is tightly stuck to and fixed on all over the inside surface of the heat roller 13. The heat roller 13 is formed of high strength material such as Ni etc., and the roller is made thin. Besides, the heat roller can be also formed by winding a graphite wire and sintering.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fixing device incorporated in an electrostatic recording device which uses toner as a recording medium.

[0002]

2. Description of the Related Art As is well known, the image process of an electrostatic recording apparatus includes an electrostatic latent image forming process, an electrostatic latent image developing process, a transfer process and a fixing process. In the electrostatic latent image forming process, an electrostatic latent image is formed by optically projecting an image on a photosensitive drum or a photosensitive belt or by applying an electric charge on a dielectric drum.

In the electrostatic latent image developing process, the electrostatic latent image is developed by electrostatically attaching toner as a recording medium to the electrostatic latent image thus formed. The toner used for the development is transferred to the recording paper in the transfer process, and then the transferred toner is fixed to the recording paper in the fixing process.

Pressure fixing method, flash fixing method, and heat fixing method are known as fixing methods for transfer toner, and the toner fixing mechanism differs depending on which method is adopted. Meanwhile, in office automation equipment such as printers and copiers, power saving, downsizing, and reduction in warm-up time are required, but this is the case in the case of a toner fixing mechanism adopting a pressure fixing method and a flash fixing method. I cannot answer your request.

To explain this in detail, the toner fixing mechanism adopting the pressure fixing method has the advantages that the power consumption is very small and no warm-up time is required. However, the disadvantages of fixing the powder toner by the pressure fixing method are that the size of the apparatus is increased by using three fixing rollers due to poor fixing property and high applied pressure, and the parallelism in the axial direction is reduced. It has been pointed out that a mechanism for taking it is required and that the weight of the device is increased because a roller that can withstand pressure is used.

Therefore, in order to improve the poor fixing property of the powder toner, the linear pressure between the pressure rollers is set to 20 to 40 kg / c.
A method has been proposed in which coated paper is used as the recording paper and the powder toner is pressed into the coating agent while being increased to m. However, such a method is used because wrinkles are generated on the recording paper due to high fixing pressure, fibers of the recording paper are crushed and gloss is generated, and coated paper does not meet the market needs. Can not.

Also, in the case of the toner fixing mechanism adopting the flash fixing method, warm-up time is not required, but the power consumption is extremely large, and further, smoke removing and deodorizing equipment is required, so that the size increase is inevitable. ..

On the other hand, in the case of the toner fixing mechanism adopting the heat fixing method, a heat roller having a heater is used, and it is necessary to wait for the heater to warm up, that is, warm up time. Moreover, there is a drawback that the power consumption by the heater is large. However, the heat fixing method is widely used because the apparatus can be made smaller and lighter than the above two methods and the apparatus configuration is simple.

FIG. 6 shows a conventional heat roller fixing device adopting a heat fixing method. In the figure, 1 is a heat roller, 2 is a backup roller, 3 is a heater of a halogen lamp built in the heat roller 1, 4 is a cleaner for removing toner and dust adhering to the roller, and 5 is a thermocouple (or thermistor). , 6 are sheets of paper that peel the paper from the rollers, and 7 is a spring that applies pressure between the rollers.

The operation of the fixing device having such a structure is as follows.

The recording paper 100 on which the toner image 8 is formed is conveyed from the left side in FIG. In the fixing device, the heat roller 1 is heated by the heater 3, this is detected by the thermocouple 5, and the surface temperature of the heat roller 1 is kept constant by a controller (not shown). Then, after detecting that the roller surface has reached a desired temperature, the recording paper 100 is passed between the heat roller 1 and the backup roller 2. As a result, the toner image 8 on the recording paper 100 is melted by the heat from the heat roller 1 and the pressure applied by the backup roller 2, and is fixed and solidified on the recording paper 100 due to the temperature decrease after passing between the rollers.

[0012]

In the conventional structure described above, the light emitted from the halogen lamp heater as a heat source is applied to the inner wall of the heat roller, and the absorbed heat is consumed as heat. However, reflection of light occurs on the inner wall of the heat roller,
Only about 60% of the electric power applied to the halogen lamp heater is used for fixing heat.

The voltage application portion (terminal portion) of the halogen lamp is made of copper in consideration of conductivity, and is formed about 40 mm apart from the heat generation effective portion in order to prevent damage due to heat. For this reason, it is necessary to use a heater whose length is 80 mm (40 mm on one side) or more longer than that of the recording paper to be fixed, and accordingly, the width of the fixing device (dimension in the axial direction of the heat roller) is also widened.

An object of the present invention is to provide a fixing device which can reduce power consumption and which is advantageous for miniaturization.

[0015]

In order to achieve the above object, according to the present invention, a fixing device incorporated in an electrostatic recording device using a toner as a recording medium is provided with a heat roller having a built-in heating source. As a configuration (first configuration), a sheet-shaped heater that is in close contact with and fixed to the inner wall of the heat roller is used.

In the fixing device having the first structure, the sheet heater is formed by covering the heating resistor with an insulating heat-resistant member (second structure).

In the fixing device of the second structure, the sheet heater is wound and inserted into the heat roller (third structure).

Further, a heat roller having a built-in heat source is provided,
In a fixing device incorporated in an electrostatic recording device using toner as a recording medium, the heat roller is made of graphite (fourth structure).

Further, in the fixing device having the above-mentioned fourth structure, as the heat source, the inner wall of the heat roller is closely contacted over the entire circumference,
A configuration (fifth configuration) is characterized in that a fixed sheet heater is used.

In the fixing device of the fifth structure, the sheet-shaped heater is formed by covering the heating resistor with an insulating heat-resistant member (sixth structure).

In the fixing device of the sixth structure, the sheet heater is wound and inserted into the heat roller (seventh structure).

[0022]

When a sheet-shaped heater that adheres closely to the inner wall of the heat roller is used, the heat generated by the heater can be directly added to the heat roller, reducing heat loss and waiting for the desired heat roller temperature. It is possible to shorten the time. Also, when graphite is used for the heat roller, by reducing the thickness of the roller, it is possible to improve the thermal conductivity and simultaneously reduce the heat capacity, and the same effect can be obtained. Further, when graphite is used for the heat roller and a sheet heater is used as the heating source, the above effect is further improved.

[0023]

Embodiments of the present invention will be described below with reference to FIGS.

A first embodiment is shown in FIGS. 1 to 3.

FIG. 1 is an exploded perspective view showing the main structure of the fixing device of this embodiment. In the figure, 11 is a sheet heater used as a heating source, and 12 is a lead for applying a voltage to the sheet heater 11. Wire, 13 is a Ni tube heat roller, 1
Reference numeral 4 is a coating portion made of a material having a high releasability from toner for preventing offset, 15 is a support member made of a heat-resistant resin that supports the heat roller 13, and 16 is a ring shape for applying a voltage to the sheet-shaped heater 11. , 17 is a terminal for supplying a voltage from the apparatus side, 18 is a side plate of the fixing apparatus, and 19 is a backup roller which is in pressure contact with the heat roller 13.

The Ni tube of the heat roller 13 has a thickness of 150.
The outer diameter is 20 mm in μm. The sheet heater 11 is
It has a shape shown in FIG. 2 (A), and is spirally wound and inserted into the heat roller 13 as shown in FIG. 2 (B). The sheet heater 11 is made of molybdenum alloy, nickel alloy,
A heating resistor 20 as shown in FIG. 3 is formed of a stainless alloy or the like, and the heating resistor 20 is sandwiched between insulating heat resistant materials such as silicone rubber, fluororesin, and heat resistant nonflammable cloth to form a heater having a thickness of 1 to 3 mm. In this example, an NR-fluorine resin plate heater manufactured by Nippon Steel Co., Ltd. is used and its thickness is 1.5 mm.

In order to wind and insert as described above,
The shape of the sheet-shaped heater 11 is such that the length of the short side 11a is the inner diameter of the heat roller 13 and the long side 11b is matched with the winding angle, and has a fixing width in a spirally wound state. In this example, the parallelogram is formed by 60 ° and 120 °. A repulsive force for returning to the flat plate state acts on the sheet-shaped heater 11 inserted by being wound, and the sheet-shaped heater 11 is in close contact with the inner wall of the heat roller 13 over the entire circumference. Therefore, the heat generated by the heater can be directly added to the heat roller 13.

The support member 15 made of heat-resistant resin is used for the heat roller 1
Not only is the roller 3 driven to rotate with the sheet-shaped heater 11, but also functions to prevent the sheet-shaped heater 11 from coming out of the heat roller 13. Therefore, the end surface of the portion that enters the inside of the heat roller 13 is in contact with the end surface of the sheet-shaped heater 11.
The support member 15 also functions as the shaft of the heat roller 13, and the side plate 18 is provided on the side opposite to the side inserted into the heat roller 13.
It has a shaft portion 15a fitted into the hole 21 (bearing portion of the heat roller 13).

The gear portion 15b and the shaft portion 15a of the support member 15
In between, a groove 15c for fitting the electrode 16 for applying a voltage to the sheet-shaped heater 11 is formed. The electrode 16 is fitted in the groove 15c, and the projection 16a formed integrally with the electrode 16 and connected to the lead wire 12 is fitted in the hole 21 formed in the shaft portion 15a. A support member (not shown) that supports the opposite side of the heat roller 13 is the support member 15 of FIG. 1 from which the gear portion 15b is removed.

Each support member is provided with a key 22 as shown in FIG. 1 for the support member 15, and the key 22 is engaged with a key groove 23 provided in the heat roller 13. Therefore, the heat roller 13 is rotated together with the sheet-shaped heater 11 by driving the gear portion 15b by a drive system (not shown).

While the electrode 16 also rotates when the heat roller 13 rotates, the voltage supply to the electrode 16 is performed through the voltage supply terminal 17 attached to the side plate 18 via an insulating member. The contact portion 17a of the terminal 17 is adapted to be in pressure contact with the electrode 16 and slide relative to each other.
A voltage is applied to the seat plate heater 11 via the lead wire 12.

The backup roller 19 is a heat roller 13.
Has a length corresponding to the coating portion 14 and is in pressure contact with the coating portion 14.

The fixing device having the above-mentioned structure was mounted in the electrostatic recording device to print out. Since the base range of the toner used is of the polyester type, the coating portion 14 is used.
The coating agent was PFA resin, the power consumption of the sheet-shaped heater 11 was about 1.5 w / cm ² , and the fixing width was 220 mm (A4 vertical feed; paper width 210 mm). The power consumption is about 200w. When 100 V is applied to the voltage supply terminal 17, the time required to reach the fixing temperature of 170 ° C. is 9.
It was 8 seconds. The results are as follows when compared with various comparative examples.

(Comparative Example 1) A structure similar to that of the above-mentioned first embodiment was adopted, and a heat roller was used instead of an aluminum tube having a thickness of 1.5 mm.
It takes 19.2 seconds to reach (0 ° C.), which is more than twice as long as when a Ni tube is used.

(Comparative Example 2) A fixing device was constructed by replacing the sheet-shaped heater 11 with a halogen lamp as the heating source with the same construction as the first embodiment (A4 vertical feed fixing; paper width 210 mm). The lamp length is 308 mm, and the terminal for voltage application to the halogen lamp is 7 mm on one side, so the total length of the fixing device is 322 mm.
Became. This is a total length 264 using a sheet heater.
It is about 60 mm longer than the fixing device of mm.

In the above description, an example in which a parallelogram sheet heater is spirally wound and brought into close contact with the inner wall of the heat roller has been described. However, a rectangular sheet heater is used and wound in a cylindrical shape to form the heat roller. You may insert it in. In this case, the temperature is low at one location along the circumference of the heat roller along the axis (the portion corresponding to the joint of the cylinder of the sheet-like heater), and if fixing is performed as it is, there will be partial fixing failure on the recording paper. Occur.

In order to solve this problem, the heat generation of the heating resistor near the seam of the sheet-shaped heater may be made larger than that of other portions. In this example, the heat generation near the seam is increased by 20% with respect to the heat generation at the central portion of the sheet-shaped heater, so that it is possible to prevent a partial temperature decrease on the surface of the heat roller and perform good fixing.

As is clear from the above description, in the fixing device of this embodiment, the sheet heater is used as the heating source and is brought into close contact with the inner wall of the heat roller, so that the thermal conductivity is improved and the heat loss is lost. It is possible to reduce the waiting time until the temperature rises to the required temperature. Further, the length of the device can be made shorter than that of the halogen lamp used conventionally. Furthermore, when a high-strength material such as Ni is used for the heat roller, the thickness of the roller can be reduced, which is more effective.

A second embodiment is shown in FIGS. 4 and 5.

An aluminum tube is mainly used for the conventional heat roller, and a halogen lamp heater as a heating source is arranged in the tube. Then, of the light emitted from the halogen lamp heater, it is contributed to the fixing as heat as much as it is absorbed by the tube wall without being reflected. However, when aluminum is used as the heat roller, the roller must be thickened so that the roller does not bend due to the pressure applied to the backup roller.

When the thickness of the roller is increased as described above, energy required for raising the temperature of the roller is required, so that the warm-up time becomes long. To solve this problem, Japanese Patent Laid-Open No. 59-4
In 389, a heat roller made of Ni electroforming is used,
Further, in JP-A-54-21739, by making the roller thin, the heat capacity is reduced, the warm-up time is shortened, and the rigidity and mass productivity of the roller are provided.

Among them, the former heat roller using the Ni electroformed product is effective in reducing the power consumption since the thickness of the roller is thinned and the heat capacity is reduced accordingly. However, under the present circumstances in which the heat roller itself needs to have a smaller diameter due to the downsizing of the fixing device accompanying the downsizing and thinning of the device, the electroformed roller is formed on the mold corresponding to the inner diameter with Ni. After being laminated, it is easily deformed when molded by the step of peeling from the mold.

In the latter case where a thin roller is made of another metal, a sheet metal is wound in conformity with a mold and a seam is welded to form a pipe, so that the diameter is 15 mm or less. In the case of a roller having a small diameter, not only manufacturing difficulties but also roundness becomes a problem.

This example solves the above problem. By forming the heat roller from graphite, a heat roller having strength can be obtained even when the diameter of the heat roller is reduced, and power saving is realized. can do. Next, the structure and operation of the fixing device of this embodiment will be described with reference to FIGS.

FIG. 4 is an exploded perspective view showing the structure of the main part of the fixing device of this embodiment, in which 31 is a graphite heat roller and 3 is a graphite heat roller.
2 is a coating part made of a material having a high releasability from toner for preventing offset, 33 is a support member made of heat-resistant resin, 34 is a halogen lamp inserted in the heat roller 31 as a heating source, 35 is a side plate, 36 is a fixing member for fixing the halogen lamp 34, and 37 is a backup roller. The fixing member 36 is fixed to the side plate 35, and the halogen lamp 34
Is applied with a voltage by an electrode portion (not shown) attached to the fixing member 36.

As shown in FIG. 5, the heat roller 31 is formed by winding a graphite wire 40 in a mold corresponding to the inner diameter of the roller to form a roller, and sintering it in the range of 1000 to 3000 ° C. to form a roller. Thickness 100 μm, outer diameter 1
It is 5 mm. If it is left as it is, not only the graphite wire has irregularities on the surface of the roller, but also the releasing property from the toner is low, so that an offset occurs in the toner image. For this reason, a releasable material such as a fluororesin is applied to form the coat portion 32 to smooth the roller surface and improve the toner releasability.

The heat roller 31 has sufficient strength in spite of being thin-walled (tensile strength is 5.0 × 10 ⁸ Pa for nickel and 6.2 for graphite).
× 10 is ⁸ Pa), yet thermal conductivity of the graphite 80 According to Kaye & Laby, 1973
It is 230 w · m ⁻¹ · k ⁻¹ , which can be said to be good in consideration of the roller thickness even when compared with 94 of nickel and 236 of aluminum.

That is, the heat roller 31 made of graphite
Has a sufficient strength, so that the wall thickness can be reduced. In addition, the roller thickness can be reduced to improve the thermal conductivity, and at the same time, the heat capacity can be reduced to reduce the heat loss, and the waiting time to reach the required temperature can be shortened. Become.

The support member 33 is obtained by omitting the electrode 16 fitting portion from the support member 15 of the previous example, and is fitted to the side plate 35.
The shaft portion 33a supported, the gear portion 33b, and the heat roller 3
1 is provided with a support portion 33c.
A key 38 is provided on 3c. The key 38 engages with a key groove 39 provided in the heat roller 31 to lock the heat roller 31 in the rotational direction when the support portion 33c is fitted and fixed to the heat roller 31. Although only one support member 33 is shown in FIG. 4, the other one of the heat rollers 31 is fixed to a similar support member (without a gear portion), and the heat roller 31 is supported by both side plates in this state.

In this way, the heat roller 31 is supported by both supporting members.
The rotation of the rotary shaft can be suppressed by fixing the heat roller. However, in order to prevent cracks from occurring at the connection portion between the heat roller 31 and the support member 33 due to the pressure from the backup roller 37, the heat roller that is the connection portion is connected. The thickness of the end portion of 31 may be increased. In this case, if the outer diameter is made uniform throughout and the inner diameter is changed, the fixing performance will not be affected.

The fixing device having such a structure was put in an electrostatic recording device to print out. Since the base resin of the toner used was a polyester-based resin, the offset preventing coat portion 32 was made of a fluorine-based PFA resin.
The halogen lamp 34 used had a power consumption of 100 w. When electricity was applied to this and fixing was performed, the temperature changed abruptly, so the temperature was adjusted by adjusting the power applied to the halogen lamp 34.

According to this, about 20 w is sufficient for stabilization at the fixing temperature of 170 ° C., and power of 50 w or less may be applied even during fixing.

As is clear from the above description, in the fixing device of the present embodiment, the heat roller made of graphite is used, and the roller thickness is reduced to improve the thermal conductivity and at the same time reduce the heat capacity. The heat loss can be reduced, and the waiting time until the temperature rises to the required temperature can be shortened.

In the above-mentioned first embodiment, a sheet-like heater that adheres closely to the inner wall of the heat roller is used as the heating source.
In the second embodiment, the heat roller is made of graphite to have a thin wall. However, by combining these, that is, by using a graphite roller as the heat roller and a sheet heater as the heating source, it is more excellent. You can get the effect.

[0055]

As described above, according to the present invention, it is possible to reduce heat loss and power consumption, and to shorten the waiting time until the temperature rises to the required temperature. Further, when the sheet-shaped heater is used as the heating source, the length of the heat roller can be shortened, and the device can be downsized.

[Brief description of drawings]

FIG. 1 is an exploded perspective view showing a main structure of a fixing device according to a first exemplary embodiment of the present invention.

2A and 2B are shape explanatory views of the sheet-shaped heater of the first embodiment of the present invention, FIG. 2A is a perspective view of the sheet-shaped heater, and FIG.
(B) is a perspective view showing a wound state of the sheet-shaped heater.

FIG. 3 is a shape explanatory view of a heating resistor of the sheet-shaped heater according to the first embodiment of the present invention.

FIG. 4 is an exploded perspective view showing a main part structure of a fixing device according to a second embodiment of the present invention.

FIG. 5 is a perspective view showing the shape of a graphite heat roller according to a second embodiment of the present invention.

FIG. 6 is a side view showing the structure of a conventional heat roller fixing device.

[Explanation of symbols]

 11 Sheet Heater (Heating Source) 13,31 Heat Roller (Heating Source) 15,33 Supporting Member 20 Heating Resistor 34 Halogen Lamp (Heating Source) 40 Graphite Wire

Claims (7)

[Claims] 1. A fixing device incorporated in an electrostatic recording apparatus using a toner as a recording medium, the fixing device including a heat roller having a built-in heat source and supported at both ends by support members. A fixing device characterized by using a sheet-shaped heater that is adhered and fixed to the inner wall over the entire circumference. 2. The fixing device according to claim 1, wherein the sheet-shaped heater is formed by covering the heating resistor with an insulating heat-resistant member. 3. The fixing device according to claim 2, wherein the sheet-shaped heater is wound and inserted into the heat roller. 4. A fixing device incorporated in an electrostatic recording device using a toner as a recording medium, the heating roller having a heat source built-in, both ends being supported by supporting members, wherein the heat roller is made of graphite. A fixing device. 5. The fixing device according to claim 4, wherein a sheet-shaped heater is used as a heating source, which is in close contact with and fixed to the inner wall of the heat roller over the entire circumference. 6. The fixing device according to claim 5, wherein the sheet-shaped heater is formed by covering the heating resistor with an insulating heat-resistant member. 7. The fixing device according to claim 6, wherein the sheet-shaped heater is wound and inserted into the heat roller.