JPH11258939A - Heating device and image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce a temperature difference between a part where a material to be heated comes in contact and a part where it does not come in contact without deteriorating the durability of the surface of a rotating body by disposing a member having a high heat conductivity so that it may about on the inner peripheral surface of the rotating body. SOLUTION: A fixing roller 1 and a pressure roller 2 are rotatably supported and only the roller 1 is driven. An exciting coil 3 is wound round a core 4 and disposed inside a holder 5. A magnetic field induced by an AC current makes an eddy current flow on the inner surface of the roller 1 being a conductive layer so as to generate Joule heat. A temperature sensor 6 is disposed to about on the surface of the roller 1, and power supply to the coil 3 is increased/decreased based on a detected signal from the sensor 6 so as to automatically control the surface temperature of the roller 1 at a specified constant temperature. A solid roller 11 abuts on the inner surface of the roller 1, is rotatably arranged, and uses high heat conductive substance, which functions as a heat pipe, and acts to uniformly level the temperature differences on the surface of the roller 1.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to a heating device and an image forming apparatus provided with the heating device as image heating means.

[0002]

2. Description of the Related Art An image forming apparatus using an electrophotographic method is:
Normally, a transfer-receiving member electrostatically carrying a toner composed of a resin, a magnetic material, a colorant, and the like is nipped and conveyed by a pressing portion (nip portion) of a fixing roller and a pressing roller that are pressed and rotated with each other. There is a fixing device that fuses and fixes the toner image on the transfer material by applying heat and pressure.

As a heating method in such a fixing device, for example, an electromagnetic heating method has been proposed in which an eddy current is generated in a conductive layer provided on the inner surface of a fixing roller by a magnetic flux generated by an exciting coil, and heat is generated by Joule heat. In this method, the heat source can be placed very close to the toner, so that the temperature of the surface of the fixing roller at the time of starting the fixing device is more suitable for fixing than the heat roller method using a conventional halogen lamp. The feature is that the time required to reach the temperature can be shortened. Another feature is that the heat transfer path from the heat generation source to the toner is short and simple, so that the heat efficiency is high.

[0004]

In the fixing device of the electromagnetic heating system as in the above-mentioned conventional example, a fixing roller as a heating element generally uses a thin-walled hollow metal core in many cases. In addition, a metal such as iron, which has a higher magnetic permeability but lower thermal conductivity than aluminum and the like, which is conventionally used, is used.

When a fixing device having this configuration is used to continuously fix, for example, a small-sized transfer material, the fixing roller is made of a metal such as iron, which has a lower thermal conductivity than conventional aluminum and the like. A temperature difference occurs in the direction of the rotation axis of the fixing roller between a position where the transfer material is in contact and a position where the transfer material is not in contact. If the temperature of the portion where the transfer material contacts is always adjusted to a predetermined target temperature, the temperature of both ends of the roller where the transfer material does not contact increases, causing hot offset of toner and thermal deterioration of peripheral members. There was a problem that there is.

In order to alleviate the temperature difference generated in the direction of the rotation axis of the fixing roller, a method has been proposed in which a heat pipe made of aluminum or the like having a high thermal conductivity is brought into contact with the outer peripheral surface of the fixing roller. There is also a problem that the durability of the surface of the fixing roller is deteriorated due to deterioration due to sliding friction between the roller and the heat pipe.

Therefore, the present invention provides a structure in which a member having a high thermal conductivity is provided in contact with the inner peripheral surface of a rotating body, so that the material to be heated does not come into contact with the rotating body without deteriorating the durability of the surface of the rotating body. It is an object of the present invention to provide a heating device and an image forming apparatus capable of suppressing a temperature difference of the image forming apparatus.

[0008]

Means for Solving the Problems [1]: In a heating apparatus having a hollow rotating body for heating a material to be heated, a member having high thermal conductivity disposed so as to contact an inner peripheral surface of the rotating body. A heating device comprising:

[2]: In a heating device having a hollow rotating body for heating a material to be heated by electromagnetic induction heat generated by a magnetic field generated by a magnetic field generating means, the heating apparatus is disposed so as to contact an inner peripheral surface of the rotating body. A heating device comprising a highly thermally conductive member.

[3]: a hollow rotating body which heats the material to be heated by electromagnetic induction heat generated by the magnetic field generated by the magnetic field generating means;
A heating device that has a pressing member that is in pressure contact with the rotating body and that introduces and conveys a material to be heated between the rotating body and the pressing member and performs a heat treatment; A heating device comprising a member having high thermal conductivity disposed so as to be in contact with a peripheral surface.

[4] The rotator according to [1], [2] or [3], wherein an eddy current is generated by an exciting coil provided inside the rotator and heat is generated. Heating equipment.

[5]: The high thermal conductive member rotates together with the rotating body [1], [2],
The heating device according to [3] or [4].

[6] The heating device according to any one of [1] to [5], wherein the member having high thermal conductivity is a solid roller.

[7]: The high thermal conductive member is disposed at a position on the downstream side in the rotation direction of a pressure contact portion between the rotating body and the pressing member [1] to [6]. The heating device according to claim 1.

[8] The heating device according to any one of [1] to [7], wherein the high heat conductive member is separated from the inner surface of the rotating body when the device is started.

[0016]

[9]: The heating device according to any one of [1] to [8], wherein the high heat conductive member is a non-magnetic substance.

[10]: The member having high thermal conductivity is a substance having a higher thermal conductivity than the rotating body.

The heating device according to any one of [9].

[11] The heating device according to any one of [1] to [10], wherein the high thermal conductive member is made of aluminum.

[12] The heating method according to any one of [1] to [11], wherein the recording material carrying the unfixed image is heated and the image is fixed on the recording material. apparatus.

[13] An image forming apparatus comprising: an image forming means for carrying a toner image on a recording material; and an image heating means for heating the recording material carrying the toner image. Any one of [1] to [12] as a heating means
An image forming apparatus provided with the heating device described in the above section.

[Action] In order to achieve the above-mentioned object, the invention according to the present application has a high thermal conductivity member disposed so as to be in contact with the inner peripheral surface of the rotating body, thereby improving the durability of the rotating body surface. The temperature difference between where the material to be heated contacts and where it does not contact is suppressed without deteriorating the properties.

Further, in the heating device of the electromagnetic induction heating system, by having a member having high heat conductivity disposed so as to be in contact with the inner peripheral surface of the rotating body, the material constituting the rotating body becomes thermally conductive. Regardless, it is possible to select a magnetic material suitable for electromagnetic induction heating, and to easily provide a device that suppresses the temperature difference between where the material to be heated is in contact and where it is not, without deteriorating the durability of the rotating body surface. ing.

In particular, the high thermal conductivity member is made of a non-magnetic material having a higher thermal conductivity than the rotating body, so that the electromagnetic induction heating apparatus can be provided more appropriately. I have.

[0024]

DESCRIPTION OF THE PREFERRED EMBODIMENTS (First Embodiment) §1. Overall Configuration of Fixing Device (Heating Device) FIG. 1 is a diagram that best illustrates the features of the present invention and is a schematic cross-sectional view of a fixing device according to an embodiment of the present invention.

The fixing roller 1 is formed of an iron core cylinder having an outer diameter of 40 [mm] and a thickness of 0.7 [mm], for example, PTFE 10 to 50 [μm] or P
A layer of FA 10 to 50 [μm] may be provided.

The pressure roller 2 is composed of an iron core and a fixing roller 1.
In order to improve the surface releasability similarly to
A layer of 0 to 50 [μm] or PFA of 10 to 50 [μm] may be provided, and the outer diameter is 30 [mm].

The fixing roller 1 and the pressure roller 2 are rotatably supported, so that only the fixing roller 1 is driven. The pressure roller 2 is in pressure contact with the surface of the fixing roller 1 and is arranged so as to be driven to rotate by a frictional force at a pressure contact portion (nip portion) N. The pressure roller 2 is pressed by a mechanism (not shown) using a spring or the like in the rotation axis direction of the fixing roller 1. The pressure roller 2 is about 30 [kg]
Weight], and in this case, the width (nip width) of the press contact portion is about 6 [mm]. However, depending on circumstances, the nip width may be changed by changing the load.

The excitation coil 3 is disposed inside the holder 5 so as to be wound around the core member 4. An alternating current of 10 to 100 [kHz] is applied to the exciting coil 3. The magnetic field induced by the alternating current causes an eddy current to flow on the inner surface of the fixing roller 1 which is a conductive layer to generate Joule heat.
In order to increase the heat generation, the number of turns of the exciting coil 3 may be increased, the core 4 may be made of ferrite or permalloy having a high magnetic permeability and a low residual magnetic flux density, or the frequency of the alternating current may be increased.

The temperature sensor 6 is arranged so as to contact the surface of the fixing roller 1. By increasing or decreasing the power supply to the exciting coil 3 based on the detection signal of the temperature sensor 6, the surface temperature of the fixing roller 1 is automatically controlled so as to become a predetermined constant temperature.

The transport guide 7 is arranged at a position where the transfer material 9 transported while carrying the unfixed toner image 8 is guided to a pressure contact portion (nip portion) N between the fixing roller 1 and the pressure roller 2. .

The separation claw 10 is disposed in contact with or close to the surface of the fixing roller 1.

The solid roller 11 is rotatably disposed so as to contact the inner surface of the fixing roller 1 and has a diameter of 5 to 5.
It is preferable to use a substance having a high thermal conductivity of 15 [mm]. The solid roller 11 is in pressure contact with the inner surface of the fixing roller 1 and is arranged so as to be driven to rotate by frictional force at a pressure contact portion (nip portion).

When the fixing roller 1 is driven to rotate by a driving unit (not shown), an alternating current is applied to the exciting coil 3 and the fixing nip N is heated to a predetermined temperature. The transfer material P carrying the toner image 8 is guided by the conveyance guide 7 and introduced into the fixing nip N, and is conveyed with the rotation of the fixing roller 1 so that the toner image 8 is transferred by the heat and the nip pressure of the fixing roller 1. Is established.

§2. FIG. 2 shows the result of monitoring the surface temperature of the fixing roller in the direction of the rotation axis of the fixing device in a standby state of the fixing device having the conventional configuration in the roller rotation axis direction, and FIG. 5 shows the result of monitoring the surface temperature of the fixing roller of the fixing device having the conventional configuration when fixing is performed in the direction of the roller rotation axis. In FIG. 2, the horizontal axis represents the position in the rotation axis direction of the fixing roller, and the vertical axis represents the surface temperature of the fixing roller. Similarly, the horizontal axis of FIG. 3 represents the position in the direction of the rotation axis of the fixing roller, and the vertical axis represents the surface temperature of the fixing roller.

As can be seen from FIG. 2, the surface temperature of the fixing roller is substantially uniform at the target temperature Tt over the direction of the roller rotation axis during standby of the apparatus. As can be seen from FIG. 3, when the small-sized transfer material 9 is continuously fixed, the surface of the both ends of the fixing roller is set in order to set the surface temperature of the fixing roller at the central portion where the transfer material 9 contacts to the target temperature Tt. It can be seen that the temperature is high (Tt + 20). The fact that the surface temperature of both ends of the fixing roller becomes high means that the small-sized transfer material 9 is fixed continuously, but the hot surface when the large-size transfer material 9 is passed immediately thereafter. Taking into account the occurrence of offset and the temperature rise of adjacent peripheral members, it cannot be said that this is a preferable phenomenon, and it should be reduced as much as possible.

When a material having a high thermal conductivity is brought into contact with the fixing roller, it functions as a heat pipe, and functions to equalize the temperature difference on the surface of the fixing roller. Therefore, in the present embodiment, by bringing the solid roller 11 having high thermal conductivity into contact with the inner surface of the fixing roller 1, the temperature of both ends of the fixing roller, which is high as shown in FIG. 3, can be reduced.

FIG. 4 shows the result of monitoring the surface temperature of the fixing roller 1 in the direction of the rotation axis of the fixing roller 1 in the fixing device of the present embodiment having the above-mentioned mechanism, and FIG. The result of monitoring the surface temperature of the fixing roller 1 of the fixing device of the present embodiment in the case of performing continuous fixing in the roller rotation axis direction is shown. The horizontal axis in FIG. 4 indicates the position of the fixing roller 1 in the rotation axis direction, and the vertical axis indicates the fixing roller 1.
Represents the surface temperature. Similarly, the horizontal axis in FIG. 5 indicates the position of the fixing roller 1 in the rotation axis direction, and the vertical axis indicates the fixing roller 1.
Represents the surface temperature.

In the fixing device of this embodiment, as can be seen from FIGS. 4 and 5, a conventional fixing device is used (FIGS. 2 and 3).
), The temperature difference in the rotation axis direction of the fixing roller 1 could be reduced.

§3. According to the present embodiment, the following effects can be obtained.

1) The solid roller 11 disposed so as to be in contact with the inner surface of the fixing roller 1 serves as a heat pipe, and the surface of both ends of the fixing roller is used when a small-sized transfer material is continuously fixed. By reducing the rise in temperature, it is possible to prevent thermal deterioration of the apparatus, increase durability, and also prevent toner hot offset and the like.

2) Since the solid roller 11 serving as a heat pipe can be disposed on the inner peripheral surface of the fixing roller 1 instead of the outer peripheral surface, the surface of the fixing roller 1 is not slid and the durability is not deteriorated.

3) The solid roller 11 is disposed inside the fixing roller 1 at a position where the temperature difference is greatest in the direction of the roller rotation axis immediately downstream of the pressure contact portion between the fixing roller 1 and the pressure roller. Thus, the temperature difference can be reduced more effectively.

4) By using aluminum which is a non-magnetic material having a high thermal conductivity for the solid roller 11, the temperature difference generated in the rotation axis direction of the fixing roller can be effectively reduced at a relatively low cost. it can.

(Second Embodiment) FIG. 6 shows a second embodiment of the present invention.
It is a schematic structure figure of an example of an embodiment. In the present embodiment, the solid roller 11 is operated to move away from the inner peripheral surface of the fixing roller 1 (retreat to the position shown by the two-dot chain line in the figure) when the fixing device is started up. This is the same as the embodiment.

Specifically, the fixing roller is kept apart from the start of the image forming (printing) operation until the surface temperature of the fixing roller reaches a predetermined target temperature. The solid roller 11 is moved toward and away by a driving mechanism (not shown) such as a solenoid.

According to this embodiment, the fixing roller 1 is substantially
The heat capacity of the fixing device is reduced, so that the time required for starting and returning the fixing device can be reduced.

(Third Embodiment) In this embodiment, the outer diameter of the fixing roller 1 is made larger than that of the first embodiment.

In this embodiment, the outer diameter of the fixing roller 1 is set to, for example, 50 mm, and the curvature of the transfer material path in the nip portion between the fixing roller 1 and the pressure roller 2 is reduced. Thereby, curling of the transfer material after fixing can be reduced.

(Example of Image Forming Apparatus) FIG. 7 is a schematic configuration diagram of an example of the image forming apparatus. The image forming apparatus of this embodiment is a copying machine or a printer using a transfer type electrophotographic process.

Reference numeral 31 denotes a rotating drum type electrophotographic photosensitive member, which is rotated at a predetermined process speed (peripheral speed) in a clockwise direction indicated by an arrow.

Reference numeral 32 denotes a contact charging roller as a photosensitive member charging means. A predetermined charging bias is applied to the contact charging roller. The surface of the rotating photosensitive member 31 is uniformly charged to a predetermined polarity and potential by the charging roller 32. You.

Exposure 33 of the target image information is performed on the charged processing surface of the rotating photoreceptor 31 by an image information exposure unit (not shown) such as a slit image exposure unit of a document image and a laser beam scanning exposure unit. Thus, an electrostatic latent image corresponding to the target image information is formed on the surface of the rotating photoconductor 31.

The latent image is developed by the toner developing device 34 as a toner image.

The toner image is transferred from a paper feed unit (not shown) to a transfer unit, which is a press nip between the rotary photoreceptor 31 and the transfer roller 35 in contact with the photoreceptor and to which a predetermined transfer bias is applied. The image is transferred onto the transfer material 9 as the recording material conveyed at the timing.

The transfer material 9 having received the transfer of the toner image after passing through the transfer section is separated from the surface of the rotating photoreceptor 31, and is conveyed to, for example, a heating device R as a fixing device shown in the first to third embodiments. After being introduced, the unfixed toner image undergoes heat fixing processing, and is output as a copy or a print.

After the transfer of the toner image onto the transfer material 9, the surface of the rotary photoreceptor 31 is cleaned by the cleaning device 36 to remove the remaining deposits such as untransferred toner, and is repeatedly used for image formation.

<Others> 1) The heating device of the present invention is not limited to the fixing device of the embodiment, but may be any other device, for example, a device for heating a transfer material carrying an image to improve its surface properties (such as gloss). Of course, it can be widely used as a heating device such as a device for assuming attachment, a device for feeding and drying / laminating a sheet-like material.

2) The high heat conductive member of the present invention is not limited to a solid roller, but may be a member that slides on the inner surface of a rotating body or a heat pipe.

[0059]

As described above, according to the present invention, the member to be heated can be provided without deteriorating the durability of the surface of the rotating body by arranging the member having high thermal conductivity in contact with the inner peripheral surface of the rotating body. A heating device and an image forming apparatus capable of suppressing a temperature difference between a portion where the contact is made and a portion where the contact is not made.

[Brief description of the drawings]

FIG. 1 is a schematic cross-sectional view of a fixing device according to a first embodiment of the present invention.

FIG. 2 is a graph showing a relationship between a position in a roller rotation axis direction and a surface temperature of a fixing roller in a standby state of the fixing device when a conventional fixing device is used.

FIG. 3 is a graph showing a relationship between a position in a roller rotation axis direction and a surface temperature of a fixing roller when a small-sized transfer material is continuously fixed when a conventional fixing device is used.

FIG. 4 is a graph showing the relationship between the position of the fixing device in the standby direction and the surface temperature of the fixing roller when the fixing device of the present invention is used.

FIG. 5 is a graph showing the relationship between the position in the roller rotation axis direction and the surface temperature of the fixing roller during continuous fixing of the small-size transfer material when the fixing device of the present invention is used.

FIG. 6 is a schematic configuration diagram of a fixing device according to a second embodiment of the present invention.

FIG. 7 is a schematic configuration diagram of an image forming apparatus according to the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Fixing roller 2 Pressure roller 3 Excitation coil 4 Core material 5 Holder 6 Temperature sensor 7 Transport guide 8 Unfixed toner image 9 Transfer material 10 Separation claw 11 Solid roller

Claims (13)

[Claims] 1. A heating apparatus having a hollow rotating body for heating a material to be heated, comprising a highly thermally conductive member disposed so as to contact an inner peripheral surface of the rotating body. apparatus. 2. A heating apparatus having a hollow rotating body for heating a material to be heated by electromagnetic induction heat generated by a magnetic field generated by a magnetic field generating means, wherein a high heat disposed to contact an inner peripheral surface of the rotating body. A heating device comprising a conductive member. 3. A hollow rotating body for heating a material to be heated by electromagnetic induction heat generated by a magnetic field generated by a magnetic field generating means, and a pressing member pressed against the rotating body with each other. A heating device that introduces and conveys a material to be heated between a pressurizing member and heats the material, comprising a member having high thermal conductivity disposed so as to contact an inner peripheral surface of the rotating body. And a heating device. 4. The heating device according to claim 1, wherein the rotator generates heat by generating an eddy current by an excitation coil provided inside the rotator. 5. The high thermal conductive member rotates together with the rotating body.
A heating device as described. 6. The heating apparatus according to claim 1, wherein the member having high thermal conductivity is a solid roller. 7. The device according to claim 1, wherein the member having high thermal conductivity is disposed at a position downstream of the press-contact portion between the rotating body and the pressing member in the rotation direction. The heating device according to Item. 8. The apparatus according to claim 1, wherein the high thermal conductive member is separated from the inner surface of the rotating body when the apparatus is started.
The heating device according to any one of claims 1 to 7. 9. The heating device according to claim 1, wherein the high thermal conductive member is a non-magnetic substance. 10. The high thermal conductivity member is a substance having a higher thermal conductivity than a rotating body.
The heating device according to any one of claims 9 to 9. 11. The heating device according to claim 1, wherein the high thermal conductive member is made of aluminum. 12. The heating apparatus according to claim 1, wherein the recording material carrying the unfixed image is heated to fix the image on the recording material. 13. An image forming apparatus, comprising: an image forming unit that carries a toner image on a recording material; and an image heating unit that heats the recording material carrying the toner image. An image forming apparatus comprising the heating device according to claim 1.