JPH11297463A - Heating system and image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To restrain the temperature difference between a contacted place and a noncontacted place with a heating object material of the rotary body surface, and to improve heating efficiency by forming a rotary body as a multilayer structure. SOLUTION: A fixing roller 1 is formed as a multilayer structure having a surface separable layer 11, a conductive layer 12 heated by electromagnetic induction, a high heat conduction layer 13 having thermal conductivity higher than the conductive layer 12 and a low heat conduction layer 14 for preventing heat dissipation to the inside of a roller in order from the heating object material side (the outside). Therefore, when high heat conduction layer 13 is arranged inside the conductive layer 12 which is a heating layer, the layer function to uniformize the temperature difference in the surface of the fixing roller 1 like a heat pipe. Electric power consumption is reduced, since a heat radiation quantity into the air from the inside surface of the fixing roller 1 can be reduced by arranging the low heat conduction layer 14 inside the high heat conduction layer 13. Device start time can be shortened, without a special mechanism by these effects and an offset of an unfixed toner image 7 can be prevented.

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 eddy current is generated in a conductive layer provided on the inner surface of the fixing roller by a magnetic flux from an exciting coil, and the fixing roller is heated by Joule heat to perform a heating process. A heating method has been proposed. 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]

However, as a fixing roller of a fixing device of the electromagnetic induction heating type as in the above-mentioned conventional example, in general, when it is desired to generate heat efficiently, compared with aluminum or the like which has been conventionally used, the fixing roller has a higher heat. In many cases, metal rollers such as iron with low conductivity are used, and when fixing small-size transfer materials continuously, the transfer material on the surface of the fixing roller touches and does not touch in the direction of the rotation axis of the fixing roller. A large temperature difference may occur.

Therefore, regardless of the size of the transfer material, if the temperature of the surface of the fixing roller with which the transfer material comes into contact is always detected and the temperature is adjusted to a predetermined target temperature, the fixing of the portion where the small size transfer material does not come into contact is performed. There has been a problem that the temperature of the roller surface rises, hot offset of the toner occurs, and thermal deterioration of peripheral members proceeds.

Further, the conventional fixing device has a drawback that the heat generated is easily dissipated into the air, resulting in poor thermal efficiency.

[0007] Therefore, the present invention is to reduce the temperature difference between the place where the material to be heated on the surface of the rotating body is in contact and the place where it is not contacted and to improve the heating efficiency by appropriately setting the layer structure of the rotating body. It is an object of the present invention to provide a heating device and an image forming apparatus which enable the above.

[0008]

Means for Solving the Problems [1] A heating apparatus having a rotating body for heating a material to be heated by generating heat by the action of a magnetic field by a magnetic field generating means, wherein the rotating body has a multilayer structure. Heating equipment.

[2]: A rotating body that heats the material to be heated by generating heat by the action of the magnetic field generated by the magnetic field generating means, and a pressing member that is pressed against the rotating body with each other. A heating device for introducing and conveying a material to be heated between a pressure member and a heating member, wherein the rotating body has a multilayer structure.

[3] The heating device according to [1] or [2], wherein the rotating body has a conductive layer and a high heat conductive layer.

[4] The heating device according to [1], [2] or [3], wherein the exciting coil of the magnetic field generating means is provided outside the rotating body.

[5] The heating device according to [1], [2], [3] or [4], wherein the relative permeability of the conductive layer is 50 or more.

[6]: The conductive layer has a volume resistivity of 5.0.
The heating device according to any one of [1] to [5], wherein the heating device is at least 10 ^-8 [Ω].

[7]: Any one of [1] to [6], wherein the thickness of the conductive layer is 1 mm or less.
The heating device according to Item.

[8]: The induction depth of the induced magnetic field generated when an alternating current of 10 to 100 [kHz] is applied to the exciting coil of the magnetic field generating means into the conductive layer is 0.5 [mm].
The heating device according to any one of [1] to [7], wherein:

[0016]

[9]: The heating device according to any one of [1] to [8], wherein the high thermal conductive layer is located inside the conductive layer.

[10]: The thermal conductivity of the high thermal conductive layer is
[1] to being higher than the conductive layer

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

[11]: The thermal conductivity of the high thermal conductive layer is 2
The heating device according to any one of [1] to [10], wherein the heating temperature is at least 00 [W / m · K] (0 to 300 [° C.]).

[12]: The rotating body is provided with a thermal conductivity of 5.0 × 10 ^-2 [W / m · K] or less (0 /
The heating device according to any one of [1] to [11], wherein the heating device has a low thermal conductive layer (at a temperature of 300 to 300 ° C.).

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

[14]: 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 [13] as a heating means
An image forming apparatus provided with the heating device described in the above section.

[Operation] In other words, by appropriately setting the layer structure of the rotating body, it is possible to suppress the temperature difference between the place where the material to be heated on the surface of the rotating body is in contact and the place where it is not.

In particular, since the rotating body has the conductive layer and the high thermal conductive layer, the high thermal conductive layer is formed so as to equalize the temperature of the surface of the rotating body where the material to be heated contacts and where it does not. To prevent the temperature difference.

Further, by disposing the low thermal conductive layer inside the high thermal conductive layer, heat radiation to the air and the like inside the rotating body is reduced, and the thermal efficiency is improved.

[0025]

DETAILED 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 has an outer diameter of 40 [mm].
m] and a layer of PFA 10 to 50 [μm].

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 loaded with a force of about 30 [kg] by a mechanism (not shown) using a spring or the like in the rotation axis direction of the fixing roller 1, and in this case, the width (nip width) of the pressure contact portion is about 6 [kg]. mm]. However, the nip width may be changed by changing the load depending on circumstances.

The exciting coil 3 is disposed along the outer peripheral surface of the fixing roller 1 and is covered with a magnetic material 4. It is desirable that the magnetic material 4 has a high magnetic permeability and a low residual magnetic flux density, such as ferrite and permalloy. This exciting coil 3 has 10 to 1
An alternating current of 00 [kHz] is applied, and a 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, thereby generating Joule heat. In order to increase the heat generation, it is preferable to arrange the exciting coil 3 as close as possible without contacting the outer peripheral surface of the fixing roller as long as the mechanical accuracy allows. Further, it is preferable to increase the amplitude of the current flowing through the exciting coil 3 or increase the frequency of the alternating current.

The temperature sensor 5 is disposed 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 5, the surface temperature of the fixing roller 1 is automatically controlled so as to become a predetermined constant temperature.

The transport guide 6 is arranged at a position where the transfer material 8 transported while carrying the unfixed toner image 7 is guided to a pressure contact portion (nip portion) N between the fixing roller 1 and the pressure roller 2. .

The separation claw 9 is disposed in contact with or close to the surface of the fixing roller 1.

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 8 carrying the toner image 7 is guided by the conveyance guide 6 and introduced into the fixing nip portion N, is conveyed with the rotation of the fixing roller 1, and the toner image 7 is transferred by the heat and the nip pressure of the fixing roller 1. Is established.

The fixing device in which the exciting coil 3 is disposed outside the fixing roller 1 as in this embodiment is different from the fixing device in which the exciting coil 3 having the conventional structure is disposed inside the fixing roller. Therefore, the fixing roller 1 can be easily replaced due to an accident or life, and the heat generated by the electric resistance of the exciting coil 3 can be easily radiated.

§2. Layer Configuration of Fixing Roller 1 Next, the layer configuration of the fixing roller 1 will be described. The fixing roller 1 of this embodiment includes, in order from the heated material side (outside), a surface release layer 11 which is a heat-resistant resin having excellent release properties, a conductive layer 12 which generates heat by electromagnetic induction, and a conductive layer 12. It has a multilayer structure having a high thermal conductive layer 13 having a higher thermal conductivity and a low thermal conductive layer 14 for preventing heat radiation to the inside of the roller.

The surface release layer 11 is made of, for example, PTFE 10-5.
0 [μm], PFA 10 to 50 [μm], conductive layer 12
Has a relative magnetic permeability of 50 or more and a volume resistivity of 5.0 × 10 ^−8.
[Ω · m] or more and a thickness of 1 [mm] or less, and the exciting coil 3 provided outside the fixing roller has a thickness of 10 to 100 mm.
It is desirable that the skin penetration depth of the induced magnetic field generated when an alternating current of [kHz] flows into the conductive layer 12 be 0.5 [mm] or less. For example, when an alternating current of 60 [kHz] is applied to the exciting coil 3, iron may be formed with a thickness of about 0.1 [mm], and nickel may be made thinner.

The high thermal conductive layer 13 has a thermal conductivity of 200 [W / m].
[K] or more (at 0 to 300 [° C.]) is desirable. For example, in the case of aluminum or copper, a layer thickness of 1 [mm] or more is good. The low thermal conductive layer 14 has a thermal conductivity of 5.0 × 10 ^-2 [W
/ M · K] or less (at 0 to 300 ° C.).

FIG. 2 shows the results of monitoring the time since starting the apparatus and the surface temperature of the fixing roller in the conventional fixing apparatus of the type in which the exciting coil is disposed inside the fixing roller, and FIG. 3 shows the present embodiment. 5 shows the results of monitoring the time from the start of the fixing device and the surface temperature of the fixing roller. The horizontal axis in FIGS. 2 and 3 represents the time from the start of the fixing device, and the vertical axis represents the surface temperature of the fixing roller.

As can be seen from the figure, the time required for the surface temperature of the fixing roller 1 to reach the predetermined target temperature Tt after starting the apparatus is shorter in the fixing device of this embodiment than in the conventional device. You can see that

This is because the heat generation layer 12 generates heat in the conductive layer 12 which is very close to the release layer 11 on the surface of the fixing roller 1, so that the apparatus startup time can be shortened.

FIG. 4 shows the result of monitoring the surface temperature of the fixing roller in the direction of the rotation axis of the fixing roller when a small-sized transfer material is continuously fixed in the fixing device having the conventional configuration, and FIG. The result of monitoring the surface temperature of the fixing roller in the direction of the roller rotation axis when the small-sized transfer material is continuously fixed in the fixing device of the present embodiment is shown. 4 and 5, the horizontal axis 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 the figure, when the transfer material 8 of a small size is continuously fixed, the surface temperature of the fixing roller at the central portion where the transfer material comes into contact is set to the target temperature Tt. Surface temperature is quite high (Tt + 2
0). The fact that the surface temperature of the both ends of the fixing roller becomes considerably high means that the toner 7 is hot-offset and the peripheral members that are close to each other, even if the transfer material 8 of a small size is continuously fixed. This is not a preferable phenomenon in consideration of the temperature rise, and the temperature should be reduced as much as possible.

Therefore, by providing the high thermal conductive layer 13 below (inside) the conductive layer 12 which is the heat generating layer as in the present embodiment,
The layer functions to equalize the temperature difference on the surface of the fixing roller like a heat pipe. As a result, the temperature of both ends of the fixing roller, which is high as shown in FIG. 4, can be reduced as shown in FIG.

Further, since the low heat conductive layer 14 is provided under the high heat conductive layer 13 as in the present embodiment, the amount of heat radiated from the inner surface of the fixing roller to the air can be reduced. Approximately 10% less power is required for fixing.

With these effects, it is possible to reduce the time required for starting the apparatus without a special mechanism and to prevent the toner image 7 from being offset.

<Second Embodiment> In this embodiment, a halogen lamp as a heat source is disposed at the position of the rotation axis of the fixing roller without providing the low heat conductive layer of the fixing device of the first embodiment. FIG. 6 shows a sectional view of the apparatus. The other configuration is substantially the same as that of the first embodiment, and the same elements are denoted by the same reference numerals and the description thereof will not be repeated.

The halogen lamp 10 is disposed at the position of the rotation axis of the fixing roller 1, and is supplied with power of 300 to 800 [W] only when the apparatus is on standby. On the other hand, in such a fixing device that does not use a halogen lamp, if the fixing roller remains stopped during standby of the device, a large temperature difference occurs due to local heat generation in the circumferential direction of the fixing roller. In order to solve the problem, the rotation of the fixing roller is indispensable even in the standby state of the apparatus, but it is desirable to stop the rotation of the roller during the standby state of the apparatus in order to avoid the rubbing wear of the surface of the fixing roller.

On the other hand, in the fixing device of the present embodiment having the above-described mechanism, the temperature of the fixing roller surface is controlled only by the halogen lamp 10 so that the surface temperature of the fixing roller becomes the predetermined target temperature Tt when the device is on standby. The temperature distribution becomes substantially uniform even when the fixing roller is stopped in the direction.

As described above, in this embodiment, the temperature is controlled only by the halogen lamp provided inside the fixing roller during the standby state of the apparatus, so that the rotation of the fixing roller is stopped during the standby state of the apparatus, and the rotation of the fixing roller is stopped. Since a substantially uniform temperature distribution can be obtained, rubbing wear of the surface of the fixing roller can be reduced to extend the service life, and noise of the fixing device during standby can be reduced.

<Third Embodiment> This embodiment uses an electromagnetic induction heating method in combination with a fixing device having the same configuration as the second embodiment when the fixing device is started or when returning from a standby state. Power is also supplied to the halogen lamp 10 to simultaneously heat the fixing roller from inside and outside.

According to the present embodiment, the time required for starting the fixing device and returning from the standby state can be reduced.

<Example of Image Forming Apparatus> FIG. 7 is a schematic configuration diagram of an example of an 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 driven to rotate 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 charging roller 32. 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 surface of the rotating photoreceptor 31 by an image information exposure unit (not shown) such as a slit image exposure unit of the original 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 at a predetermined timing from a paper supply unit (not shown) to a transfer unit, which is a press-contact nip portion between the rotary photoreceptor 31 and a transfer roller 35 in contact with the transfer roller 35 to which a predetermined transfer bias is applied. The image is transferred onto the transferred transfer material 8 as the recording material.

The transfer material 8 having passed the transfer section and having received the toner image is separated from the surface of the rotating photoreceptor 31, and is, for example, a heating device R as a fixing device shown in the first to third embodiments.
And is subjected to a heat fixing process for the unfixed toner image, and is output as a copy or a print.

After the transfer of the toner image onto the transfer material 8, the surface of the rotating photoreceptor 31 is cleaned by the cleaning device 36 to remove residual deposits such as untransferred toner, and is repeatedly used for image formation.

<Others> It is assumed that the heating device of the present invention is not only a fixing device of the embodiment but also a device for improving the surface properties (such as gloss) by heating a transfer material carrying an image. It can be widely used as a heating device such as a device for attaching, a device for feeding and drying and laminating a sheet.

[0060]

As described above, according to the present invention,
Providing a heating apparatus and an image forming apparatus capable of suppressing a temperature difference between a place where a material to be heated comes into contact with and a place not to be heated and improving a heating efficiency by appropriately setting a layer configuration of a rotating body. it can.

[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 the relationship between the time from the start of the fixing device and the surface temperature of the fixing roller when a conventional fixing device is used.

FIG. 3 is a graph showing the relationship between the time from the start of the fixing device and the surface temperature of the fixing roller when the fixing device of the present invention is used.

FIG. 4 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. 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 cross-sectional view of a fixing device according to a second or third 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 Exciting coil 4 Magnetic material 5 Temperature sensor 6 Transport guide 7 Unfixed toner image 8 Transfer material 9 Separation claw 10 Halogen lamp

Claims (14)

[Claims] 1. A heating device having a rotating body for heating a material to be heated by generating heat by the action of a magnetic field generated by a magnetic field, wherein the rotating body has a multilayer structure. 2. A rotating body for heating a material to be heated by generating heat by the action of a magnetic field generated by a magnetic field generating means, and a pressing member pressed against the rotating body with each other, wherein the rotating body and the pressing member A heating device for introducing, transporting, and performing heat treatment between the rotating member and the heating member, wherein the rotating body has a multilayer structure. 3. The heating device according to claim 1, wherein the rotating body has a conductive layer and a high heat conductive layer. 4. An apparatus according to claim 1, wherein said exciting coil of said magnetic field generating means is provided outside the rotating body.
4. The heating device according to 2 or 3. 5. The heating device according to claim 1, wherein the relative permeability of the conductive layer is 50 or more. 6. The conductive layer having a volume resistivity of 5.0 × 10.
The heating device according to any one of claims 1 to 5, wherein the heating device is at least ^-8 [Ω]. 7. The heating device according to claim 1, wherein the thickness of the conductive layer is 1 [mm] or less. 8. The magnetic field generating means according to claim 1, wherein
8. The skin according to claim 1, wherein a skin penetration depth of an induced magnetic field generated when an alternating current of 100 [kHz] is passed into the conductive layer is 0.5 [mm] or less. A heating device as described. 9. The heating device according to claim 1, wherein the high heat conductive layer is located inside the conductive layer. 10. The heat conductive layer according to claim 1, wherein the heat conductive layer has a higher thermal conductivity than the conductive layer.
The heating device according to Item. 11. The thermal conductivity of the high thermal conductive layer is 200
The heating device according to any one of claims 1 to 10, wherein the heating temperature is [W / m · K] or more (when the temperature is 0 to 300 [° C]). 12. The rotating body has a thermal conductivity of 5.0 × 10 ^-2 [W / m · K] or less (0 to 300) inside the high thermal conductive layer.
The heating device according to any one of claims 1 to 11, further comprising a low thermal conductive layer (at [° C]). 13. The heating apparatus according to claim 1, wherein the recording material carrying the unfixed image is heated, and the image is fixed on the recording material. 14. 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. An image forming apparatus comprising the heating device according to any one of claims 1 to 13.