JP2003131503A - Heating device, thermal fixing device, and image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To solve the problem that since the surface temperature of a thin film being in contact with a recording material can not be set high in a conventional heating device off a thin film heating system, it is difficult to ensure a heating performance due to that the quantity of heat supplied to toner becomes insufficient when the device operates at high speed. SOLUTION: In the heating device, the face of a heating body, which is in contact with the thin film, is a curved face. Also, in the area outside a nip, an insulation board and the thin film are in contact with each other. The area of the contact with the thin film, which is upstream in the nip, is wider than the area of the contact with the thin film, which is downstream in the nip.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heating element comprising a resistance heating element formed on an insulating substrate and a glass protective layer covering the resistance heating element, and a heat-resistant thin film pressed against the heating element. And a pressurizing body that forms a nip portion, and a heating device that heats the recording material by applying heat from the heating body to the recording material passing through the nip portion, and a recording material using the heating device. The present invention relates to a heat fixing device that fixes and fixes the above unfixed toner image on the recording material, and an image forming apparatus such as a copying machine or a laser beam printer to which the heat fixing device is applied.

[0002]

2. Description of the Related Art Conventionally, for example, in a heating device for heating a recording material as a material to be heated, a heating roller maintained at a predetermined temperature and a pressurizing member which presses against the heating roller via an elastic layer. A heat roller method is widely used in which a recording material is nipped and conveyed by a roller and heated. In addition to these, various methods and configurations such as a flash heating method, an open heating method, and a hot plate heating method are known and put into practical use.

In particular, recently, instead of the above-mentioned method, a heating body (heater) fixedly supported as shown in FIG.
23, a heat-resistant thin film 22 that is conveyed while being pressed against the heating body 23, and a pressurizing body that adheres the recording material P as a heated body to the heating body 23 through the thin film 22 (hereinafter , Which is referred to as a pressure roller), and applies the heat of the heating body 23 to the recording material P via the thin film 22 to thereby form the unfixed toner image T formed and carried on the recording material surface. An image heating fixing method (heating apparatus of thin film heating method) of heating and fixing on a recording material surface has been proposed. The heating body 23 is an insulating substrate 25 such as ceramic.
And a base protection glass 26.

In such a thin film heating type heating device or image heating fixing device, a low heat capacity heating member can be used as a heating member. Therefore, it is possible to save power and shorten the wait time (quick start) as compared with the above-mentioned contact heating method such as a heat roller method and a belt heating method.

FIG. 5 is a schematic diagram showing an example of a heating device of the above-mentioned thin film heating system in which the maximum sheet passing width is A3 size. This heating device is disclosed, for example, in Japanese Patent Laid-Open No. 4-4407.
JP-A-5-44083 and JP-A-4-24-2.
This is a so-called tensionless type device disclosed in JP-A-04980 to JP-A-4-204984.

In this tensionless type device, an endless belt-shaped or cylindrical one is used as the heat-resistant thin film 22, and at least a part of the circumference of the thin film 22 is always tension-free (no tension is applied). The thin film 22 is a device that is driven to rotate by the rotational driving force of the pressing body 28.

Endless heat-resistant thin film 22
Is externally fitted to the stay 21, which is a thin film guide member including the heating body 23. The inner peripheral length of the endless thin film 22 and the outer peripheral length of the stay 21 including the heating body 23 are larger than those of the thin film 22 by, for example, about 3 mm. Therefore, the thin film 22 is fitted with a sufficient peripheral length. is doing.

The stay 21 is made of a high heat resistant resin such as polyimide, polyamideimide, PEEK, PPS, liquid crystal polymer, or a composite material of these resins and ceramics, metal, glass, etc. I am using.

In order to reduce the heat capacity of the thin film 22 and improve the quick start property, the thin film thickness is 100 μm or less, preferably 50 μm or less and 20 μm or more, which are heat-resistant PTFE, PFA and FE.
It is possible to use a single-layer thin film such as P, or a composite thin film in which PTFE, PFA, FEP, etc. are coated on the outer peripheral surface of a thin film such as polyimide, polyamideimide, PFEK, PES, PPS, etc. The outer peripheral surface is coated with PTFE.

The pressure roller 28 is a thin film outer surface contact drive means for forming a pressure contact nip portion (nip portion) N1 by sandwiching the thin film 22 with the heating body 23 and driving the thin film 22 to rotate. The thin film drive roller / pressure roller 28 is composed of a cored bar 28a, an elastic layer 28b made of silicon rubber or the like, and an outermost release layer 28c, and a predetermined pressing force is applied by a bearing means and a biasing means (not shown). The thin film 22 is sandwiched in between and pressed against the surface of the heating body 23. The rotational force acts on the thin film 22 by the frictional force between the pressure roller 28 and the outer surface of the thin film, which is generated by the rotation of the pressure roller 28.

The temperature detecting element 27 detects the temperature of the heating element 23 and supplies it to a CPU (not shown).
The electric power supplied from the AC power supply to the heating body 23 is adjusted so that the detected temperature becomes constant based on the detected temperature.

Considering the temperature determining process of the thin film 22, the thin film 22 is supplied with heat from the heating body 23 in the nip portion N1 (heat transfer 33 in the figure) at the same time as shown in FIG. Heat is supplied to the recording material P and the unfixed image T (heat transfer 34 in the figure).

Further, the temperature of the heating body holding stay portion 21 is still low at the end of the weight-up, and the thin film 22 radiates heat to the heating body holding stay while going around the heating body holding stay portion (see FIG. Medium heat transfer 36), and the temperature in the nip portion of the thin film is determined by the above thermal balance.

As described above, in the conventional thin film heating type fixing device, the amount of heat supplied to raise the temperature of the thin film 22 is obtained only by the contact with the heating body 23 in the nip portion, and the thin film is fixed. If the temperature is to be raised, the width of the nip portion should be widened or the controlled temperature should be raised or the material of the thin film 22 should be changed to one with good thermal conductivity, which is not sufficient for speeding up the apparatus. It was

[0015]

It has been said that the fixing device of the thin film heating type is not suitable for increasing the speed of the device as compared with the heat roller type fixing device. In the heat roller method, since the temperature detecting element is provided on the roller surface, the roller surface temperature in the nip portion that is in direct contact with the recording material is not so different from the control temperature of the temperature detecting element, and is generally about 160 to 200 ° C. Has become.

On the other hand, in the thin film heating type fixing device, the temperature measuring element is provided on the insulating substrate, and the temperature of the insulating substrate rises to the temperature controlled temperature of the temperature measuring element. The temperature of the thin film that is being supplied with heat while in dynamic contact is lower than the temperature control temperature on the contact surface side with the insulating substrate, and since a resin material such as polyimide is used for the thin film, the thin film is The heat conduction in the thickness direction is poor, and the temperature of the thin film surface that is in direct contact with the recording material further decreases. When the temperature control temperature of the temperature measuring element is set to 195 ° C., for example, the temperature of the thin film surface in the nip portion which is in direct contact with the recording material is 50 to 60 as compared with the temperature control temperature.
It has decreased by about ℃.

On the other hand, since the upper limit of the temperature control temperature is determined by the heat resistance of the stay supporting the heating element and the bonding portion of the temperature measuring element installed on the heating element, the temperature of the surface which is in direct contact with the recording material is determined by the heat roller method. It will be lower than that. When the speed of the apparatus is increased, the time for which the unfixed toner image T stays in the nip portion is shortened in inverse proportion to the speed, and the unfixed image T is melted and fixed on the recording material P at a low thin film surface temperature. It becomes impossible to supply the required amount of heat in the nip.

The present invention solves the above problems in a fixing device of a thin film heating system, and supplies sufficient heat to the recording material from the thin film in the nip portion even when the speed of the device is increased, so that the recording material P is removed. A heating device for performing heat treatment, a heating fixing device that supplies sufficient heat from the heating device to a recording material to secure the fixing property of an unfixed toner image on the recording material, and a stable high precision by applying the heating fixing device It is an object of the present invention to obtain an image forming apparatus capable of printing.

[0019]

The present invention is a heating apparatus having the following constitution. A heat fixing device and an image forming device.

(1) A heating element comprising a resistance heating element formed on an insulating substrate and a glass protective layer covering the resistance heating element, and a heat-resistant thin film are pressed against the heating element to form a nip portion. In a heating device for applying heat from the heating body to the recording material passing through the nip portion to heat the recording material, the surface of the heating body on the side in contact with the thin film is A heating device having a curved surface, wherein the insulating base and the thin film are brought into contact with each other even outside the nip portion area, and a contact area with the thin film upstream of the nip portion is made wider than that downstream of the nip portion.

(2) In the heating device of (1), the heating body and the thin film are not only in the nip portion,
A heating device characterized in that it makes contact even outside the nip portion and has a contact area of 30% or more of the width of the nip portion at least upstream of the nip portion.

(3) In the heating device according to (1), the surface of the heating body which is in contact with the thin film is a cylindrical surface.

(4) In the heating device of (1), the heating element is mounted on the stay so that the downstream end of the insulating base nip portion of the heating member is inclined so as to be closer to the pressure roller side than the upstream end of the insulating base nip portion. A heating device characterized in that

(5) In the heating device of (4), the heating device has an inclination angle of 5 ° to 45 ° with respect to the horizontal.

(6) In the heating device of (1), the heating element is ceramic, aluminum nitride, or SUS.

(7) In the heating device of (3), the thin film has a diameter smaller than that of the cylindrical heating element.

(8) In the heating device of (1), the resistance heating element is divided into at least two when viewed in a vertical cross section in the longitudinal direction of the heating element, and one of the resistance heating elements is located at the center of the resistance heating element. The heating device is characterized in that the portion is arranged at a position aligned with the central portion of the nip portion, and the other portion is arranged outside the nip portion upstream of the nip portion.

(9) In the heating device of (1), a roller is provided to improve the contact state between the heating body and the thin film outside the nip portion, and the roller is attached to the thin film outside the nip portion. A heating device characterized by being configured to be pressed by.

(10) In a heat fixing device for conveying a recording material on the surface of which an unfixed toner image is formed under pressure to heat and fix the unfixed toner image on the recording material, the recording material is heated. A heating and fixing device comprising the heating device according to any one of (1) to (9) as a heating device.

(11) Image forming means for directly or indirectly forming an unfixed toner image on a recording material, and heating for fixing the unfixed toner image formed on the recording material on the recording material by heating. An image forming apparatus having a fixing unit, wherein the heating and fixing unit according to (10) is provided as the heating and fixing unit.

[0031]

BEST MODE FOR CARRYING OUT THE INVENTION An embodiment of the present invention will be described below with reference to the drawings.

(Embodiment 1) FIG. 1 is a view showing a sectional shape of a heating element according to a first embodiment of the present invention which is perpendicular to the longitudinal direction,
FIG. 2 is a detailed view showing the vicinity of the heating body. 11 in the figure
Is a heating element, and this heating element 11 protects the insulating substrate 14 and the heating element 16 from sliding between the insulating substrate 14 of ceramic, aluminum nitride, SUS or the like and the heating element 16 (16a, 16b) or the thin film. Protective glass 15,
The temperature measuring element 17 is included, and in this embodiment, the inner width W of the cross section (see FIG. 4) is set to 15 mm. Reference numeral 12 is a heat-resistant thin film that is conveyed while being pressed against the heating body 11, and 13 is a stay that holds the heating body 11. In the heating body 11, the downstream end of the insulating base nip portion is located farther from the upstream end of the insulating base nip portion. Is also attached to the stay 13 while being inclined so as to approach the pressure roller side. Reference numeral 18 denotes a pressure roller which is pressed against the heating body 11 and the thin film 12 so as to face each other, and is an elastic rubber layer
It consists of a and a cored bar 18b such as aluminum.

N1 is a nip portion where the thin film 12 comes into contact with the recording material P to supply heat, and in this embodiment, the width of the nip portion is about 7 mm. As shown in FIG. 2, the heating element 11 is disposed so as to be inclined with respect to the horizontal by an angle θ (5 ° to 15 °, but in this embodiment, it is set to 15 °), and the heating element 11 and the thin film 12 are separated from each other. The contact is made not only inside the nip portion but also outside the nip portion, and a contact area of 30% or more of the width of the nip portion is provided at least upstream of the nip portion. The surface of the heating element 11 on the side in contact with the thin film 12 is a cylindrical surface.

Further, the heating element 16 in the heating element is divided into two parts like the heating elements 16a and 16b shown in FIG. 2, and the center of the heating element 16a is aligned with the center line NC of the nip portion N1. The heating element 16b is disposed at a position protruding from the nip portion N1 to the upstream side of the sheet passage.

In this embodiment, both the heating elements 16a and 16b have a length of 3.5 mm. The temperature measuring element 17 is arranged on the center line NC of the nip portion N1 in order to easily control the temperature of the heating body near the nip portion to be constant. According to the present embodiment, the area N2 where the thin film 12 and the heating body 11 are in contact with each other upstream of the nip portion N1 is about 5 mm, and the thin film when entering the nip portion N1 due to the amount of heat supplied to the thin film 12 at this portion. Average temperature is 20
The temperature can be raised by about 0 ° C.

As described above, according to the first embodiment, in order to raise the temperature in the nip portion of the thin film 12, heat can be supplied to the thin film 12 not only in the nip portion but also in another portion. take. That is, since the thin film 12 rotates while supplying heat to the stay, it is most effective to preheat the thin film 12 immediately before the nip portion in order to raise the temperature in the nip portion of the thin film 12. Is.

In order to achieve this with a simple structure, the surface shape of the heating body 11 on the side in contact with the thin film 12 is, for example, a cylindrical surface, and the heating body 11 is tilted so as to rise to the right in FIG. Heater 1
1 and the thin film 12 contact each other in a wide area upstream of the nip portion, and heat is supplied from the heating body 11 in the contact area with the heating body upstream of the nip portion before the thin film 12 enters the nip portion. As a result, the temperature of the thin film 12 rises, and even when the speed of the apparatus is increased, the heat treatment can be performed with a sufficient amount of heat. By using this heating apparatus as the heat source of the heat fixing apparatus, the recording material on the recording material can be processed. The formed unfixed toner image is given a sufficient amount of heat to secure the fixing property.

(Embodiment 2) FIG. 3 is a diagram schematically showing the relationship between the radius and the contact area between the heating element 51 and the thin film 52 in the second embodiment of the present invention. In the figure, 51 is a heating element,
Reference numeral 52 is a thin film, and 53 is a pressure roller.

When the radius R1 of the heating element and the radius R2 of the thin film are taken as R1 <R2, the surface of the heating element and the thin film 12 are in contact at the nip portion N1, but the N2 portion upstream of the nip portion (FIG. 3 (a)). (See), the phenomenon that it becomes difficult to contact occurs. In order to prevent this, as shown in FIG. 3B, the heating body radius R1 is set to be slightly larger than the thin film radius R2. In this embodiment, R1 is 14 mm, R
2 was 12 mm.

When the pressing force 54 is applied to this structure, the thin film 12 is pressed against the surface of the heating body at the nip portion N1 with the pressure distribution of the nip portion, but the radius R2 of the thin film 12 is larger than the radius R1 of the heating body. Since it is small, the thin film 12 is deformed along the surface of the heating body with 57 in the figure as a fulcrum, and therefore 56 in the N2 upstream of the nip.
The surface of the heating element is contacted with a relatively wide range of contact force as shown in.

With this structure, it is easy to secure contact between the heating body 51 and the thin film 52 at the nip portion upstream contact portion, and preheating of the thin film 52 can be sufficiently performed.

(Embodiment 3) FIG. 4 is a schematic view of a third embodiment of the present invention, in which 61 is a heating element, 62 is a thin film, and 63 is a pressure roller. In this embodiment, the heating body 61 and the thin film 6 upstream of the nip portion shown in FIG.
In order to ensure the contact area N2 with the thin film 2, the small size roller 64 shown in FIG. 4 is applied to the thin film 62 by the force in the direction of the arrow in the figure. In this embodiment, the small size roller 64
Had a diameter of 2 mm. Also with this configuration, the preheating of the thin film 62 can be efficiently performed, and sufficient fixing property can be secured even when the speed of the apparatus is increased.

[0043]

As described above, according to the present invention, a heating body including a resistance heating element formed on an insulating substrate and a glass protective layer covering the resistance heating element, and a heat-resistant thin film are provided. In a heating device that has a pressing body that presses the heating body to form a nip portion, and applies heat from the heating body to a recording material that passes through the nip portion to heat the recording material, The surface of the heating element that is in contact with the thin film is a curved surface, and the insulating base and the thin film are contacted even outside the nip region, and the contact area with the thin film upstream of the nip is wider than that downstream of the nip. Because I did
Even if the speed of the apparatus is increased, the surface temperature of the thin film that is in direct contact with the recording material in the nip portion can be increased by preheating, and a heating device that prevents deterioration of the heating process due to insufficient heat given to the recording material can be obtained. .

According to the present invention, since the diameter of the thin film is smaller than the diameter of the cylindrical heating element, the thin film contacts the surface of the heating element in a wide range, and the thin film before entering the nip portion. Heat is supplied from the heating body in the contact area with the nip upstream heating body, and as a result, the thin film temperature rises sufficiently.

According to the present invention, the resistance heating element is divided into at least two pieces when viewed in a vertical cross section in the longitudinal direction of the heating element, and one of the resistance heating elements has a central portion which is the central portion of the nip portion. Since the thin film is placed in the position where the thin film is in contact with the heating element upstream of the nip portion before it enters the nip portion, the heat from the heating element The temperature of the thin film is sufficiently increased as a result.

According to the present invention, a roller is provided to improve the contact state between the heating body and the thin film in the contact area outside the nip portion, and the roller is pressed against the thin film in the contact area outside the nip portion. Therefore, the thin film is efficiently heated in the contact area with the nip portion upstream heating body before entering the nip portion, and sufficient heat treatment can be performed even when the apparatus speeds up.

According to the present invention, in the heat fixing device for conveying the recording material on the surface of which the unfixed toner image is formed under pressure to heat and fix the unfixed toner image on the recording material,
Since the heating device of the present invention is provided as a heating device for heating the recording material, it is possible to obtain a heating and fixing device that always performs stable heating and fixing processing.

According to the present invention, image forming means for directly or indirectly forming an unfixed toner image on a recording material,
An image forming apparatus having a heat fixing means for heat-fixing an unfixed toner image formed on the recording material on the recording material, since the above-mentioned heat fixing apparatus of the present invention is provided as the heat fixing means. It is possible to obtain an image forming apparatus having a short uptime and capable of always performing stable and highly accurate printing.

[Brief description of drawings]

FIG. 1 is a diagram showing a configuration of a heating device according to a first embodiment of the present invention.

FIG. 2 is a diagram illustrating in detail the main configuration of the heating device according to the first embodiment.

FIG. 3 is a diagram showing the relationship between the radius of the heating element and the thin film of Example 2 of the present invention and the contact pressure resulting therefrom.

FIG. 4 is a diagram showing a configuration of a third embodiment of the present invention.

FIG. 5 is a schematic view showing a conventional thin-film heating type heating device.

FIG. 6 is a diagram schematically illustrating heat supplied to and heat discharged from a thin film in a conventional configuration.

[Explanation of symbols]

11, 51, 61 Heated body 12, 52, 62 Heat-resistant thin film 13 stay 14 Insulation substrate 15 Protective glass 16 (16a, 16b) heating element 17 Temperature sensor 18, 53, 63 Pressure roller 54 Pressure N1 Nip part

Claims (11)

[Claims] 1. A heating element comprising a resistance heating element formed on an insulating substrate and a glass protective layer covering the resistance heating element, and a heat-resistant thin film is pressed against the heating element to form a nip portion. In a heating device for heating a recording material by applying heat from the heating element to a recording material passing through the nip portion, a surface of the heating element on a side in contact with the thin film is a curved surface. The heating device is characterized in that the insulating base and the thin film are brought into contact with each other even outside the nip region, so that the contact area with the thin film upstream of the nip region is wider than that downstream of the nip region. 2. The heating device according to claim 1, wherein the heating body and the thin film are in contact not only inside the nip portion but also outside the nip portion, and at least 30% or more of the width of the nip portion is upstream of the nip portion. A heating device having a contact area of. 3. The heating device according to claim 1, wherein a surface of the heating body which is in contact with the thin film is a cylindrical surface. 4. The heating device according to claim 1, wherein the heating member is mounted on the stay so that a downstream end portion of the insulating base nip portion of the heating body is tilted so as to be closer to the pressure roller side than an upstream end portion of the insulating base nip portion. A heating device characterized by the above. 5. The heating device according to claim 4, wherein the inclination angle of the heating element is 5 ° to 45 ° with respect to the horizontal. 6. The heating device according to claim 1, wherein the heating element is ceramic, aluminum nitride, or S.
A heating device, which is US. 7. The heating device according to claim 3, wherein the thin film has a diameter smaller than that of the cylindrical heating element. 8. The heating device according to claim 1, wherein the resistance heating element is divided into at least two pieces when viewed in a vertical cross section in a longitudinal direction of the heating element, and one of the resistance heating elements is provided at a central portion thereof. Is located at a position aligned with the central part of the nip part, and the other is located outside the nip part upstream of the nip part. 9. The heating device according to claim 1, wherein a roller is provided in order to improve the contact state between the heating body and the thin film outside the nip portion, and the roller is attached to the thin film outside the nip portion. A heating device configured to be pressed. 10. A heating and fixing device that heats and fixes the unfixed toner image on the recording material by conveying under pressure the recording material on which the unfixed toner image is formed. A heating and fixing device comprising the heating device according to any one of claims 1 to 9 as a device. 11. An image forming unit for directly or indirectly forming an unfixed toner image on a recording material, and a heat fixing for heating and fixing the unfixed toner image formed on the recording material on the recording material. An image forming apparatus comprising: a heat fixing device according to claim 10 as the heat fixing device.