JPH1154242A - Heating device and image-forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce the temperature difference between a center part and an end part of a pressurizing roller so as to prevent the generation of creases on heated material by arranging a pressurizing roller cover for making heat of the roller escape more at the center part than the end part of the roller in the axial direction of the roller, near the pressurizing roller. SOLUTION: When printing action is stated, a ceramic heater 4 is heated to specified temperature by a temperature control means, and the temperature of a pressurizing roller 2 rises due to heat transmitted from the ceramic heater 4. When paper is passed continuously, the pressurizing roller 2 is hated, so that the temperature of the ceramic heater 4 is lowered stepwise. The end part temperature of the pressurizing roller 2 is reserved by a pressurizing roller cover 211 so as to become higher than the center part. The end part is therefore enlarged, and the pressurizing roller 2 is formed in an inverted crown shape. When paper is feed in this state, force of extending the paper toward the end part works. As a result, the generation of creases on paper is suppressed, and fixing capability at the end part is improved.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heating device for introducing and conveying a material to be heated into a nip portion between a heating element and a pressure roller and heating the material to be heated, and using the heating device as an image heating means. The present invention relates to an image forming apparatus having the same.

In particular, a printer for obtaining an image recorded matter by heating and fixing an unfixed image formed and carried on a recording material by an appropriate image forming means such as an electrophotographic system, an electrostatic recording system, a magnetic recording system, etc. The present invention relates to an image forming apparatus such as an image forming machine and a facsimile, and a heating apparatus for the image forming apparatus.

[0003]

2. Description of the Related Art Conventionally, an image forming apparatus such as a printer or a copying machine of an electrostatographic system or the like forms an unfixed toner image on a recording material in an image forming section and heats the recording material in a heat fixing section. Then, the toner image is fixed on the recording material by applying pressure to form an image.

As a heat fixing unit (fixing device) of such an image forming apparatus, a heat roller type heating device has been widely used. As shown in FIG. 8, a heat source H such as a halogen heater is provided in the inside, and a metal heat roller 21 as a heating body which is controlled at a predetermined fixing temperature and an elastic pressure roller which presses against the metal heat roller 21 are pressed. The heat roller 21 and the pressure roller 2 are rotated by rotating the pair of heat rollers 21 and the pressure roller 2 as a body, and the unfixed image forming portion (not shown) is formed on a pressure contact portion (hereinafter, a fixing nip portion) N of the roller pair. By supplying the recording material P on which the toner image T is formed and carried and passing the fixing nip N through the nip, the unfixed toner is transferred to the recording material P by the heat of the heat roller 21 and the pressing force of the fixing nip N. Fix it.

In this heat roller method, since the heat roller 21 has a large heat capacity, it takes a long time to raise the surface of the heat roller 21 to a predetermined temperature. Therefore, when the printer receives an output signal from the host computer, the heat roller 21 must be constantly heated so that the printer can be operated immediately, and there is a problem that power consumption is increased.

To solve such a problem, Japanese Patent Laid-Open Publication No.
JP-A-4-44075-44083 and JP-A-4-204980-204984 disclose a film heating apparatus using a heat-resistant thin film. FIG. 7 shows a schematic diagram of an example of this apparatus. In FIG. 7, reference numeral 1 denotes a cylindrical fixing film having a heat-resistant polyimide film whose outer surface is coated with fluorine. 3 is a heater stay made of a heat-resistant resin, 4 is a heater made of ceramic,
Ag / Si formed by screen printing in the form of a narrow band on the surface in contact with the film 1 side on a substrate made of alumina having good thermal conductivity.
It consists of a Pd resistance heating element, an electrode screen printed with Ag on both ends, and a heat-resistant, pressure-resistant glass coat for protecting the surface of Ag / Pd, and a thermistor element 5 for detecting the temperature of the alumina substrate adhered to the back surface The resistance heating element is energized and controlled to a predetermined temperature. The center of the lower surface of the heater stay 3 is cut in the longitudinal direction (perpendicular to the paper surface), and the ceramic heater 4 is bonded thereto. A film guide 6 reinforces the heater stay 3 and guides the inner surface of the fixing film 6.

The fixing film 1 generally has a total pressure of 100 μm.
The film is loosely fitted to a stay formed by the heater stay 3 and the film guide 6 with a film having a thickness of not more than m, preferably not more than 60 μm. The pressure roller 2 is pressed against the ceramic heater 4 with a predetermined pressure through the film 1 to form a nip N.

In this fixing device, the pressure roller 2 is used as a drive roller, and the pressure roller 2 is driven to rotate by a drive unit (not shown), and a cylindrical film is formed by the frictional force between the surface of the pressure roller and the outer surface of the film. 1 is driven to rotate along the heater stay 3 and the film guide 6, and the recording material P is introduced and conveyed between the film 1 and the pressure roller 2, so that the unfixed toner image T is fixed on the recording material P. Let me.

[0009]

In the above-mentioned heat roller fixing device and film fixing device, the pressure roller is rotated by driving means (not shown) to transport the recording material P. Configuration.

In such a configuration, for example, in the film fixing device shown in FIG. 7, the pressure roller 2 is driven to move and convey the film 1 and the recording material P. When the outer diameter changes due to the expansion, the conveyance speed of the recording material P changes.

The temperature of the pressure roller 2 gradually rises while the recording material P is continuously conveyed, but heat is more radiated at the ends in the longitudinal direction of the pressure roller than at the center. Therefore, when a large amount of the recording material P is conveyed, the temperature at the center finally becomes higher by 5 to 10 deg than at the ends, and the center expands more thermally. 0
It is a so-called crown shape which is about 5 mm larger.

When the recording material P is conveyed in such a state, the paper feed speed is faster in the central portion, so that the paper end portion is shifted toward the center of the paper, and paper wrinkles may occur. This paper wrinkle is more remarkable in thin paper having a lower rigidity. Such paper wrinkles also occur in the heat roller fixing device.

Accordingly, an object of the present invention is to reduce the temperature difference between the center and the end of the pressure roller when the material to be heated is conveyed continuously, or to reduce the temperature at the end to the center. It is an object of the present invention to provide a heating apparatus and an image forming apparatus which can suppress generation of wrinkles of a material to be heated by making the pressure roller straight or inverted crown by increasing the height.

[0014]

According to the present invention, there is provided a heating apparatus and an image forming apparatus having the following constitutions.

[1]: A heating element and a pressure roller which presses against the heating element to form a heating nip portion are provided, and a member to be heated is introduced into the heating nip portion, conveyed, and heated. In the heating device, a heating roller cover is disposed in the vicinity of the pressure roller, wherein a pressure roller cover through which heat of the roller escapes more in a central portion of the roller than in an end portion of the roller with respect to an axial direction of the pressure roller. .

[2] The heating device according to [1], wherein the pressure roller cover has a heat radiation opening at a position corresponding to the axial center of the pressure roller.

[3]: has a heating element and a pressure roller which presses against the heating element to form a heating nip portion, and introduces a member to be heated into the heating nip portion, conveys and heats the member. In the heating device, a fan for cooling a central portion in the axial direction of the pressure roller is provided.

[4] The heating device according to [3], wherein the driving of the fan is controlled based on a temperature difference between an axial end portion of the pressure roller and a central portion in the axial direction.

[5] The heating device according to [3], wherein the drive of the fan is controlled based on the pressure roller surface temperature, the integrated number of sheets passed, or the sheet passing mode.

[6]: It has a heating element and a pressure roller which presses against the heating element to form a heating nip portion, and introduces a member to be heated into the heating nip portion, conveys it, and performs heat treatment. In the heating device, a heat transfer member that absorbs heat in a central portion in an axial direction of the pressure roller is provided.

[7] The heating device according to [6], wherein the heat transfer member is a driven roller that is driven to rotate by contacting the axial center portion of the pressure roller.

[8] The heating device according to any one of [1] to [7], wherein the pressure roller conveys the material to be heated by rotation.

[0023]

[9]: The material to be heated is a recording medium carrying an unfixed image, and the unfixed image is heat-fixed to the recording medium by heat treatment in the heating nip [1] to [8]. ] The heating device according to any one of the above.

[10]: An image forming means for forming a developer image on a recording medium, and an image heating means for heating the developer image, the image heating means being provided in the above [1] to [1]

[9] An image forming apparatus, which is the heating apparatus according to any one of [9].

<Operation> That is, in the first invention according to the present application, the provision of the pressure roller cover suppresses heat radiation at the roller end with respect to the axial direction of the pressure roller, thereby preventing the end of the roller from coming into contact with the end. Reduce the temperature difference from the central part, or make the roller end part higher in temperature than the roller central part, make the pressure roller straight or inverted crown shape, and generate wrinkles when conveying the material to be heated by the pressure roller. Has been prevented.

According to a second aspect of the present invention, a cooling fan is provided, and the center of the pressure roller 2 is cooled such that the temperature at the center in the axial direction does not become higher than that at the ends. Thereby, the pressure roller is formed in a straight or inverted crown shape, thereby preventing wrinkles when the material to be heated is conveyed by the pressure roller.

Also, by performing cooling based on information such as the temperature of the pressure roller, the temperature difference between the central portion and the end portion of the pressure roller, and the total number of sheets passed, wrinkles can be accurately prevented.

According to a third aspect of the present invention, a heat transfer member is provided, and the heat transfer member comes into contact with the center of the pressure roller to remove heat, so that the temperature at the end of the pressure roller rises. The pressure roller is formed in a straight or inverted crown shape to prevent wrinkles when the material to be heated is conveyed by the pressure roller.

[0029]

BEST MODE FOR CARRYING OUT THE INVENTION

[First Embodiment] A first embodiment of the present invention will be described with reference to FIGS. FIG. 1 shows the first embodiment of the present invention.
FIG. 2 is an exploded perspective view of a pressure roller and a pressure roller cover of the heating device according to the embodiment, and FIG. 3 is a longitudinal sectional model diagram of the device. This heating device is used as a fixing device of a laser beam printer.

Reference numeral 1 denotes a fixing film which is formed by coating a cylindrical polyimide film having a length of 226 mm, an inner diameter of 24 mm and a thickness of 45 μm on the outer surface with 10 μm of PTFE. 2 is a pressure roller which has a core diameter of 11 mm and an outer diameter of 17 m.
Fluorine rubber latex is fired on a surface layer of silicone rubber having a thickness of 3 mm and a thickness of 3 mm and baked at 30 μm.

Reference numeral 3 denotes a tub-shaped film guide having a substantially semicircular cross section, and reference numeral 4 denotes a ceramic heater which is a heating element, which is 6.5 mm wide, 236 mm long and 0.635 mm thick.
Is obtained by screen printing silver palladium as a resistance heating element on an alumina substrate. The ceramic heater 4 is fitted in the center of the lower surface of the film guide 3 along its length. The fixing film 1 is loosely fitted to the film guide 3 including the ceramic heater 4, and the pressing roller 2 is pressed against the ceramic heater 4 via the fixing film 1.

Reference numeral 5 denotes a temperature detecting element (thermistor) for detecting the temperature of the ceramic heater 4, which is adhered to the substrate surface opposite to the heating element, detects the temperature on the back side of the heater, and sends a signal to a control device (not shown). It is used to control the energization of the ceramic heater 4 so that the nip N reaches a predetermined temperature.

Reference numeral 6 denotes a film stay which guides the fixing film 1 at the upper portion, and cooperates with the film guide 3 to hold the film 1 so that the film 1 can be smoothly rotated.

Reference numeral 7 denotes a pressure spring, and 8 denotes a spring receiver which receives the force of the pressure spring 7 and applies pressure to the film stay 6, applying pressure to both ends of the film stay 6, and applying a pressure via the film guide 3 and the film 1. The ceramic heater 4 is pressed against the pressure roller 2.

Reference numeral 9 denotes a gear attached to the end of the shaft of the pressure roller. The driving force of a drive unit (not shown) is transmitted to rotate the pressure roller 2 to rotate the fixing film 1 and convey the recording material P. Do.

Reference numeral 10b denotes a connector connected to the terminal of the thermistor 5 on the ceramic heater 4, and reference numeral 10c denotes a connector for supplying AC to the resistance heating element of the ceramic heater 4. A pressure roller cover 11 also serves as a paper guide for guiding the recording material P to the nip portion N. The cover 11 covers the lower side of the nip portion of the pressure roller 2 and has a gap of about 1 to 2 mm with the roller. The heat is kept so that the heat of the heated pressure roller 2 does not escape. Reference numeral 12 denotes a heat-dissipating window (opening) having a width of about 100 mm at the center of the pressure roller cover 11 so that the heat of the pressure roller 2 can easily escape.

The heat-resistant film 1 is rotated by the rotation of the pressure roller 2, and the ceramic heater 4 is rotated.
When the heater 4 is heated to a predetermined temperature by applying power to the recording material P, the recording material P carrying the unfixed toner image T, which is the material to be heated, is located between the fixing film 1 and the pressure roller 2 in the nip portion N. Then, the heat from the ceramic heater 4 is applied to the recording material P via the fixing film 1, and the unfixed toner image T is thermally fixed on the surface of the recording material P. The recording material P that has passed through the fixing nip N is conveyed after being separated from the surface of the heat-resistant film 15 by a curvature.

Next, the case where this fixing device is incorporated in a printer and A4 or letter size paper is used as a recording material will be specifically described.

When the printing operation is started, the ceramic heater 4 is heated to a predetermined temperature by the temperature control means. The pressure roller 2 is also heated by the heat from the ceramic heater 4 being transmitted. Heater temperature 20 at the beginning of paper passing
The temperature of the pressure roller 2 is 0 ° C., and the temperature of the pressure roller is 80 ° C. The temperature of the ceramic heater 4 is reduced stepwise because the pressure roller 2 is heated when continuous paper feeding is performed. Specifically, from the 5th sheet passing through 19
0 ° C, 180 ° C from the 11th sheet, 170 ° C from the 20th sheet,
At this time, the temperature of the pressure roller 2 is 90 ° C.
° C and 110 ° C. On the other hand, since the temperature at the end of the pressure roller 2 is maintained by the pressure roller cover 11,
The temperature becomes higher than the center at 0 ° C, 100 ° C, and 115 ° C.

When printing is continued as it is, the temperature of the pressure roller finally becomes 115 ° C. at the center and 120 ° C. at the end.

At this time, the outer diameter of the pressure roller 2 is such that the silicone rubber has a volume thermal expansion coefficient of 1.05 × 10 ⁻³ / deg.
mm, the center outer diameter D0 is room temperature 20 ° C.
Π {(D0 / 2) ² -8.5 ² } = 1.05 × 10 ⁻³ × 9
5 × π (8.5 ² −5.5 ² ) D0 = φ17.48 The outer diameter D1 at the end is π ｛(D1 / 2) ² -8.5 ² ｝ = 1.05 × 10 ⁻³ × 9
5 × π (8.5 ² −5.5 ² ) D1 = φ17.51, and the end is larger than the center by about 0.03 mm to form an inverted crown shape. For this reason, when the paper is fed in this state, a force to extend the paper toward the end works as shown in FIG. 4, and as a result, the occurrence of wrinkling of the paper is suppressed.

Further, in the related art, the amount of heat radiation at the end of the pressure roller tends to be large and the temperature of the pressure roller tends to be low. However, in the present embodiment, the pressure roller is provided with a cover for keeping the end of the pressure roller warm. Since the temperature at the end of the roller is increased, the fixing property at the end is improved.

[Second Embodiment] Next, a second embodiment will be described. FIG. 5 is an explanatory diagram of a configuration of a main part of the embodiment. In the figure, reference numeral 13 denotes a fan for cooling the central longitudinal portion of the pressure roller 2, reference numerals 14a and 14b denote temperature detecting elements for measuring the temperature of the longitudinal center and longitudinal end portions of the surface of the pressure roller, respectively, and reference numeral 15 denotes the temperature detecting element. Control means for controlling the drive of the fan 13 based on the temperature information from

When the printing operation is started, the control means 15 compares the detected temperatures of the temperature detecting elements 14a and 14b, and makes the temperature at the center part a predetermined value higher than the end part so that the pressure roller 2 does not have a crown shape. When the height is higher than the above, the fan 13 is turned on to cool the central part of the pressure roller 2. When the temperature at the center is equal to or lower than a predetermined value as compared with the temperature at the end, the fan is turned off. As a result, the temperature of the central portion of the pressure roller is equal to or slightly lower than that of the end portion, and as a result, the pressure roller 2 has a straight or inverted crown shape, thereby preventing the occurrence of wrinkles.

In this embodiment, the temperature detecting elements 14a, 1
Although the control of the fan 13 is performed based on the detected temperature of 4b, the present invention is not limited to this, and the control is performed by estimating the temperature rise of the pressure roller 2 from the time from the start of printing and the accumulated number of sheets passed. Is also good. For example, as described in the first embodiment, since the fixing temperature changes depending on the number of sheets passed, the fan 13 is turned on based on the fixing temperature adjustment information without using the temperature detecting elements 14a and 14b. , May be turned off. Specifically, the fan 13 is turned on from the tenth sheet after the start of continuous printing at which the fixing temperature reaches 170 ° C.

Regardless of the configuration, the condition under which the fan 13 is turned on may be appropriately set based on the fixing temperature control method or the pressure roller diameter.

In this embodiment, whether or not to cool the pressure roller 2 can be arbitrarily selected, so that the roller 2 can be cooled in accordance with the paper passing mode. For example, it is possible to prevent wrinkles more effectively by selecting to rotate the fan during double-sided printing where wrinkles are likely to appear.

[Third Embodiment] Next, a third embodiment will be described. FIG. 6 is an explanatory diagram of a configuration of a main part of the present embodiment. In the figure, reference numeral 16 denotes a heat transfer roller as a heat transfer member which comes into contact with the roller near the center of the pressure roller 2 and follows the roller together, and is made of aluminum having good heat conductivity. Therefore, since the heat is transferred to the center of the pressure roller 2 by the heat transfer roller 15, the temperature of the center and the end of the pressure roller 2 is almost the same or the temperature of the end is higher. The shape of No. 2 is a straight or inverted crown, and the generation of wrinkles can be prevented.

According to this embodiment, the heat at the center of the pressure roller can be stably removed with a simple configuration.

The heat transfer member is not limited to a driven roller, but may be a sliding member fixed and supported in a state of being in contact with the center of the pressure roller so that the pressure roller can slide. May be.

[Others] In the above embodiment, the description has been made with the film fixing device.
The same effect can be obtained by applying the present invention to a heat roller fixing device.

[0052] The heating device of the present invention is not limited to the fixing device described in the above embodiment, but also includes, for example, a device for heating a recording material carrying an image to improve the surface properties (glossy or the like), a device for temporarily attaching, and the like. It can be widely used as a so-called image heating device or a device for feeding a sheet-like material and performing a drying process and a laminating process.

[0053] In the present invention, the heating element is not limited to a resistance heating element, and may be an electromagnetic induction heating element that generates heat by applying a magnetic force to a conductive magnetic substance.

[0054]

As described above, according to the present invention,
Reduce the temperature difference between the central part and the end part of the pressure roller when conveying the heated material continuously, or raise the temperature at the end part higher than the center so that the pressure roller is straight or inverted crown. By making the shape, it is possible to provide a heating device and an image forming apparatus capable of suppressing generation of wrinkles of the material to be heated.

[Brief description of the drawings]

FIG. 1 is a perspective model diagram according to a first embodiment of the present invention.

FIG. 2 is an explanatory perspective view of a pressure roller and a roller cover according to the first embodiment of the present invention.

FIG. 3 is a schematic longitudinal sectional view of the fixing device according to the first embodiment of the present invention.

FIG. 4 is an explanatory view showing the effect of preventing the occurrence of wrinkles.

FIG. 5 is an explanatory view of a main part of the second embodiment.

FIG. 6 is an explanatory view of a main part of a third embodiment.

FIG. 7 is an explanatory view of a conventional heat fixing device.

FIG. 8 is an explanatory view of a conventional heat fixing device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Fixing film 2 Pressure roller 3 Film guide 4 Ceramic heater 11 Pressure roller cover 12 Heat dissipation window

Claims (10)

[Claims] 1. A heating device having a heating element and a pressure roller for pressing the heating element to form a heating nip, introducing a member to be heated into the heating nip, transporting the heated element, and performing a heat treatment. 3. The heating device according to claim 1, wherein a pressure roller cover is disposed in the vicinity of the pressure roller, in which the heat of the roller in the axial direction of the pressure roller escapes more in the center of the roller than in the end of the roller. 2. The heating device according to claim 1, wherein the pressure roller cover has a heat radiation opening at a position corresponding to an axial center of the pressure roller. 3. A heating device having a heating element and a pressure roller which presses against the heating element to form a heating nip portion, and introduces a member to be heated into the heating nip portion, conveys the heated member, and performs a heating process. 3. The heating device according to claim 1, further comprising a fan for cooling a central portion of the pressure roller in the axial direction. 4. The heating device according to claim 3, wherein the drive of the fan is controlled based on a temperature difference between an axial end portion of the pressure roller and a central portion in the axial direction. 5. The heating apparatus according to claim 3, wherein the drive of the fan is controlled based on a pressure roller surface temperature, an integrated number of sheets passed, or a sheet passing mode. 6. A heating device having a heating element and a pressure roller for pressing against the heating element to form a heating nip, introducing a member to be heated into the heating nip, transporting the heated element, and performing a heat treatment. 2. The heating device according to claim 1, further comprising a heat transfer member that absorbs heat in a central portion of the pressure roller in the axial direction. 7. The heating device according to claim 6, wherein the heat transfer member is a driven roller that is driven to rotate in contact with a central portion of the pressure roller in the axial direction. 8. The apparatus according to claim 1, wherein the pressure roller carries the material to be heated by rotation.
The heating device according to any one of the above. 9. The recording medium according to claim 1, wherein the material to be heated is a recording medium carrying an unfixed image, and the unfixed image is heat-fixed to the recording medium by heat treatment in the heating nip. The heating device according to any one of the above. 10. An image forming means for forming a developer image on a recording medium, and an image heating means for heating the developer image, wherein the image heating means is provided. An image forming apparatus, which is the heating apparatus according to claim 1.