JP2007242635A - Heating device, and image forming device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve problems such as degradation of heating efficiency by temperature rise of an induction coil, using a structure suppressing leakage flux of an induction coil provided outside of a heating rotator (a fixing roller) by a shield member. <P>SOLUTION: An induction coil 32 is wound along an outer peripheral surface of a fixing roller 28, its side opposite to the fixing roller 28 is covered by a shield member 34 having a nearly U-shaped cross-section, and a number of holes 46 for promoting heat dissipation are uniformly formed on a whole surface of the shield member 34. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a heating device that heats a sheet-like body such as paper or film, and an image forming apparatus such as a copying machine, a printer, or a facsimile provided with the heating device as a fixing device.

  In an image forming apparatus such as a copying machine, a printer, or a facsimile, a recording material that electrostatically carries a toner image made of resin, magnetic material, coloring, or the like is passed through a fixing device to be fixed. The fixing device includes a fixing roller as a heating rotator, and a pressure roller that forms a fixing nip portion between the fixing roller, and heat and pressure while nipping and conveying the recording material at the fixing nip portion. As a result, the toner image is melted and fixed on the recording material.

As a heating method of the fixing roller in such a fixing device, an induction heating method using high-frequency induction as a heating source is known as described in Patent Document 1, for example.
In the induction heating type fixing device described in Patent Document 1, an induction coil is concentrically disposed inside a hollow fixing roller made of a metal conductor, and a high-frequency current is passed through the induction coil so that the fixing roller is driven by a high-frequency magnetic field. Inductive eddy current is generated in the fixing roller, and the fixing roller itself generates heat due to the skin resistance of the fixing roller itself.
According to this induction heating type fixing device, the electric-to-heat conversion efficiency is extremely high, and the heat generation source (the heat generating layer of the fixing roller) can be disposed very close to the toner image. Compared to the conventional heat roller system that heats from the inside of the roller, it has a feature that it can shorten the time (warm-up time) required for the temperature of the surface of the fixing roller to become an appropriate temperature when the fixing device is started. .

However, the method in which the induction coil is provided inside the fixing roller has a problem that the induction coil becomes high temperature due to the temperature rise inside the fixing roller and the heat generated by the electric resistance of the induction coil itself, thereby reducing the power efficiency. Moreover, although the induction coil is coated with resin, there is a problem in that this coating melts due to a high temperature and the insulation of the induction coil is impaired.
In addition, when it is necessary to replace the fixing roller due to an accident or life, it takes time to remove the induction coil from the inside of the fixing roller, and it takes time to replace the fixing roller. there were.
As a fixing roller, there is a type in which a thin metal sleeve having flexibility is used instead of a rigid metal pipe, but the above-mentioned problem similarly occurs.

Therefore, as disclosed in Patent Document 2, for example, in order to suppress the temperature rise of the induction coil, a proposal has been made to provide a cooling means for blowing air into the fixing roller or the like.
However, since not only the induction coil and the core that supports the induction coil but also the inner surface of the fixing roller is cooled, there is a problem that this affects the surface temperature of the fixing roller and the fixing ability is impaired.

By the way, in the heating device of the induction heating system, in addition to the problem related to the temperature rise of the induction coil, the magnetic flux leaks to the outside, and malfunctions and magnetic heat generation are caused to devices and harnesses existing around the fixing device. There was a concern to invite.
In Patent Document 3, in a type in which an induction coil is provided inside a fixing roller, a heat radiating means is provided on the core of the induction coil to suppress temperature rise, and a shield member made of a ferromagnetic material is provided to suppress magnetic flux leakage. A heating device (fixing device) is disclosed.

Patent Document 4 discloses a heating device (fixing device) in which an induction coil for generating magnetic flux is provided outside a fixing roller, and the opposite side of the induction coil to the fixing roller is covered with a magnetic material to prevent magnetic flux leakage. Yes.
If the induction coil is provided outside the fixing roller, the fixing roller can be easily replaced, and the temperature rise of the induction coil is less than that when the induction coil is provided inside the fixing roller, so that the heating efficiency is improved.

JP 59-33787 JP 54-39645 A Japanese Patent Laid-Open No. 9-16006 JP 11-297462 A

As described above, the method in which the induction coil is provided outside the heating rotator (fixing roller) has an absolute advantage in maintainability related to replacement of the fixing roller and the like, compared with the method in which the induction coil is provided inside the fixing roller.
However, in order to prevent leakage of magnetic flux to the outside, when the shield coil (magnetic material) covers the opposite side of the induction coil from the fixing roller, although there is a difference in degree, the induction coil is placed inside the fixing roller. The same problem as in the case of providing it occurs.

That is, the air heated by the heat generated by the induction coil itself is trapped in the shield member, and this temperature rise exceeds the natural heat dissipation action of the shield member, further raising the temperature of the induction coil. As a result, the electrical resistance of the induction coil is increased, the power consumption is increased, and the heating efficiency of the fixing roller is reduced. There is also a concern of causing dielectric breakdown of the induction coil.
Further, an eddy current is also generated in the shield member itself due to the magnetic flux generated by the induction coil, and the shield member itself also generates heat. This further promotes the problem related to the temperature rise of the induction coil.

  Accordingly, the present invention provides a heating device that can suppress an increase in the temperature of the induction coil in a method in which the induction coil is provided outside the heating rotator (fixing roller), and can sufficiently utilize the advantages of the method, and this as a fixing device. An object of the present invention is to provide an image forming apparatus.

  In order to achieve the above object, according to the first aspect of the present invention, a heating rotator that generates heat by an induced current and heats the sheet-like body, and a magnetic flux that is provided outside the heating rotator and generates an induced current are generated. In the heating device having the induction coil to be made and the shield member that suppresses the magnetic flux leakage of the induction coil, the heat radiation of the shield member is configured to be promoted.

  According to a second aspect of the present invention, in the heating apparatus according to the first aspect of the present invention, the shield member has a configuration in which an opening for ventilation is provided.

  According to a third aspect of the present invention, in the heating device according to the second aspect, the vent opening is formed in accordance with the temperature distribution of the induction coil.

  According to a fourth aspect of the present invention, in the heating apparatus according to the second or third aspect, the vent opening is a hole.

  According to a fifth aspect of the present invention, in the heating device according to the second or third aspect, the ventilation opening is a slit.

  According to a sixth aspect of the present invention, in the heating apparatus according to the fifth aspect, the slit is formed so as to block an eddy current generated in the shield member.

  According to a seventh aspect of the present invention, in the heating apparatus according to the first aspect, the shield member has a configuration in which a heat radiation area is enlarged.

  According to an eighth aspect of the present invention, in the heating apparatus according to the seventh aspect, the heat radiation area is enlarged by forming a convex portion.

  The invention according to claim 9 employs a configuration in which, in the heating device according to claim 7, the heat radiation area is enlarged by forming a recess.

  In a tenth aspect of the present invention, a heating rotator that generates heat by an induced current and heats the sheet-like body, an induction coil that is provided outside the heating rotator and generates a magnetic flux that generates an induced current, and the induction coil In the heating apparatus having a holding member that holds the magnetic flux and a shield member that suppresses magnetic flux leakage of the induction coil, the heat generation of the shield member due to the magnetic flux is configured to be suppressed.

  According to an eleventh aspect of the present invention, in the heating apparatus according to the tenth aspect, the shield member has a laminated structure of a magnetic layer and an insulator layer, and the laminated structure blocks eddy currents generated in the shield member. It has a configuration that it has directionality.

  According to a twelfth aspect of the present invention, in the heating device according to the eleventh aspect, the shield member has a structure having a ventilation opening.

  In a thirteenth aspect of the present invention, in the heating apparatus according to the twelfth aspect, the vent opening is formed in accordance with the temperature distribution of the induction coil.

  The invention according to claim 14 is the heating apparatus according to claim 12 or 13, wherein the opening for ventilation is a hole.

  The invention according to claim 15 is the heating device according to claim 12 or 13, wherein the ventilation opening is a slit.

  In a sixteenth aspect of the present invention, in the heating apparatus according to the fifteenth aspect, the slit is formed so as to block an eddy current generated in the shield member.

  In the invention described in claim 17, in the heating device described in claim 11, the shield member has a configuration in which a heat radiation area is enlarged.

  According to an eighteenth aspect of the present invention, in the heating device according to the seventeenth aspect, the heat radiation area is enlarged by forming a convex portion.

  According to a nineteenth aspect of the present invention, in the heating device according to the seventeenth aspect, the heat radiation area is enlarged by forming a recess.

  According to a twentieth aspect of the present invention, in the heating device according to the twentieth or nineteenth aspect, the heat radiation area is enlarged only in a layer having a higher thermal conductivity among the magnetic layer and the insulator layer. , Is adopted.

  The invention according to claim 21 employs a configuration in which the heating device according to claim 1 or 10 has cooling means for cooling the shield member.

  According to a twenty-second aspect of the present invention, in the heating apparatus according to the twenty-first aspect, the cooling means is an air cooling fan.

  In a twenty-third aspect of the present invention, the heating apparatus according to the twenty-second aspect employs a configuration in which the airflow generated by the air cooling fan is configured not to affect the atmosphere in the temperature detection region.

  In a twenty-fourth aspect of the present invention, the heating apparatus according to the twenty-second aspect employs a configuration in which the airflow generated by the air cooling fan is configured not to affect the temperature of the heating rotating body.

  According to a twenty-fifth aspect of the present invention, in the heating apparatus according to the twenty-second aspect, the sheet-like body carries an unfixed image, and the airflow generated by the air cooling fan does not affect the unfixed image. It has been configured to be.

  In a twenty-sixth aspect of the present invention, in the heating apparatus according to any one of the twenty-first to twenty-fifth aspects, the shield member has a vent opening.

  According to a twenty-seventh aspect of the present invention, in the heating apparatus according to the twenty-sixth aspect, the vent opening is formed in accordance with the temperature distribution of the induction coil.

  The invention according to claim 28 is the heating device according to claim 26 or 27, wherein the ventilation opening is a hole.

  According to a twenty-ninth aspect of the present invention, in the heating device according to the twenty-sixth or twenty-seventh aspect, the ventilation opening is a slit.

  According to a thirty-third aspect of the present invention, in the heating device according to the twenty-ninth aspect, the slit is formed so as to block an eddy current generated in the shield member.

  According to a thirty-first aspect of the present invention, in the heating device according to one of the twenty-first to twenty-fifth aspects, the shield member has a configuration in which a heat radiation area is enlarged.

  In the invention of claim 32, in the heating device of claim 31, the heat radiation area is enlarged by forming a convex portion.

  According to a thirty-third aspect of the present invention, in the heating apparatus according to the thirty-first aspect, the heat radiation area is enlarged by forming a recess.

  According to a thirty-fourth aspect of the present invention, in the heating device according to the twenty-first aspect, the cooling means includes a refrigerant passage formed in the shield member and a refrigerant driving member that moves the refrigerant through the refrigerant passage. , Is adopted.

  According to a thirty-fifth aspect of the present invention, in the heating apparatus according to the thirty-fourth aspect, the refrigerant is air and the refrigerant driving member is an air pump.

  In a thirty-sixth aspect of the invention, in the heating apparatus according to the thirty-fourth aspect, the refrigerant is a liquid and the refrigerant driving member is a liquid pump.

  According to a thirty-seventh aspect of the present invention, in the heating device according to one of the first to thirty-sixth aspects, the induction coil is held by the shield member.

  According to a thirty-eighth aspect of the invention, in an image forming apparatus having a fixing device for fixing an unfixed image, the fixing device is one of the first to thirty-seventh aspects.

  According to invention of Claim 1, 2, 3, 4, 5 or 38, since it is comprised so that heat dissipation of a shield member can be accelerated | stimulated, the temperature rise of an induction coil can be suppressed, and a heating rotary body of Safety can be improved by improving heating efficiency, saving power, and preventing dielectric breakdown of the induction coil.

  According to the invention of claim 6 or 38, since the slit is formed so as to block the eddy current generated in the shield member, heat generation by electromagnetic induction of the shield member can be suppressed, and the temperature of the induction coil can be suppressed. The rise can be suppressed to a high level.

  According to the invention of claim 7, 8, 9 or 38, since the heat dissipation area of the shield member is enlarged, the temperature rise of the induction coil can be suppressed by promoting the heat dissipation of the shield member. It is possible to improve the heating efficiency of the rotating body, save power, and improve safety by preventing dielectric breakdown of the induction coil.

  According to the invention of claim 10, 11 or 38, since the heat generation of the shield member due to the magnetic flux can be suppressed, the temperature rise of the induction coil can be suppressed, and the heating efficiency of the heating rotator is improved. Thus, it is possible to improve safety by saving power and preventing dielectric breakdown of the induction coil.

  According to the invention of claim 12, 13, 14, 15, 16 or 38, since the shield member has a ventilation opening, the heat dissipation of the shield member in addition to the heat generation suppressing function of the shield member. The function can be obtained, and the temperature rise of the induction coil can be suppressed to a high level.

  According to the invention of claim 17, 18, 19, 20 or 38, since the heat dissipation area of the shield member is enlarged, the heat dissipation function of the shield member is obtained in addition to the heat generation suppressing function of the shield member. The temperature rise of the induction coil can be suppressed to a high level.

  According to the invention of claim 21, 22 or 38, since the cooling means for cooling the shield member is provided, the temperature rise of the induction coil can be suppressed by promoting the heat radiation of the shield member. It is possible to improve the heating efficiency of the rotating body, save power, and improve safety by preventing dielectric breakdown of the induction coil.

  According to the twenty-third or thirty-eighth aspect of the invention, since the airflow generated by the air-cooling fan is configured not to affect the atmosphere in the temperature detection area, erroneous detection by the temperature detection means can be prevented.

  According to the twenty-fourth or thirty-eighth aspect of the invention, since the airflow generated by the air cooling fan is configured not to affect the temperature of the heating rotator, it is possible to prevent the heating efficiency of the heating rotator from being reduced.

  According to the twenty-fifth or thirty-eighth aspect of the invention, since the airflow generated by the air cooling fan is configured not to affect the unfixed image, it is possible to prevent image disturbance and paper jam.

  According to the invention of claim 26, 27, 28, 29, 30 or 38, since the shield member has a ventilation opening, in addition to the cooling function of the shield member by the cooling means, the shield The heat dissipation function of the member can be obtained, and the temperature rise of the induction coil can be suppressed to a high level.

  According to the invention of claim 31, 32, 33 or 38, since the heat dissipation area of the shield member is enlarged, the heat dissipation function of the shield member is obtained in addition to the cooling function of the shield member by the cooling means. The temperature rise of the induction coil can be suppressed to a high level.

  According to the invention of claim 34, 35, 36 or 38, since the refrigerant is cooled through the shield member, a high cooling function can be obtained, and the temperature rise of the induction coil can be suppressed to a high level. Can do.

  According to the invention of claim 37 or 38, since the induction coil is held by the shield member, there is no need to separately provide a configuration for holding the induction coil, and the configuration is simplified and the cost is reduced. Can be achieved.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
First, an overview of the overall configuration of the printer 2 as an example of an image forming apparatus according to the present embodiment will be described with reference to FIG.
The printer 2 includes a paper feeding unit 4, a registration roller pair 6, a photosensitive drum 8 as an image carrier, a transfer unit 10, a fixing device 12 as an induction heating type heating device, and the like ( Claim 38).
The paper feeding means 4 feeds the paper P as a recording material stored in a stacked state and the paper P stored in the paper feeding tray 14 one by one in order from the top. It has a roller 16 and the like.
The paper P sent out by the paper supply roller 16 is temporarily stopped by the registration roller pair 6 and corrected in the posture, and then formed at the timing synchronized with the rotation of the photosensitive drum 8, that is, on the photosensitive drum 8. Then, the toner image is sent to the transfer portion N by the registration roller pair 6 at a timing when the leading end of the toner image coincides with a predetermined position at the leading end of the sheet P in the transport direction.

  Around the photosensitive drum 8, in the rotation direction indicated by the arrows, a charging roller 18 as a charging unit, a mirror 20 constituting a part of an exposure unit (not shown), a developing unit 22 including a developing roller 22a, A transfer unit 10 and a cleaning unit 24 including a cleaning blade 24a are disposed. Between the charging roller 18 and the developing means 22, exposure light Lb is irradiated to the exposure unit 26 on the photosensitive drum 8 via the mirror 20 and scanned.

The image forming operation in the printer 2 is performed in the same manner as before. That is, when the photosensitive drum 8 starts to rotate, the surface of the photosensitive drum 8 is uniformly charged by the charging roller 18, and the exposure light Lb is irradiated and scanned on the exposure unit 26 based on the image information to create an image to be created. An electrostatic latent image corresponding to is formed. The electrostatic latent image is moved to the developing means 22 by the rotation of the photosensitive drum 8, where toner is supplied to be visualized to form a toner image.
The toner image formed on the photosensitive drum 8 is transferred onto the paper P that has entered the transfer portion N at a predetermined timing by applying a transfer bias by the transfer means 10.

The paper P carrying the toner image is conveyed toward the fixing device 12, fixed by the fixing device 12, and then discharged and stacked on a paper discharge tray (not shown).
Residual toner remaining on the photosensitive drum 8 without being transferred at the transfer portion N reaches the cleaning means 24 as the photosensitive drum 8 rotates, and is scraped off by the cleaning blade 24 a while passing through the cleaning means 24. To be cleaned.
Thereafter, the residual potential on the photosensitive drum 8 is removed by a neutralizing unit (not shown), and is prepared for the next image forming process.

  As shown in FIG. 1, the fixing device 12 includes a fixing roller 28 as a heating rotator, a pressure roller 30 as a pressure member that forms a fixing nip SN between the fixing roller 28, and a fixing roller. 28, an induction coil 32 provided outside the shield 28, a shield member 34 that covers the opposite side of the induction coil 32 from the fixing roller 28 and suppresses magnetic flux leakage of the induction coil 32, and a temperature at which the surface temperature of the fixing roller 28 is detected. The thermistor 36 as a detecting means, the control means 40 for controlling the power supply to the induction coil 32 via the power source 38 based on the detection signal of the thermistor 36, and the sheet P as a sheet-like material is guided to the fixing nip portion SN. And a separation claw 44 for separating the paper P after fixing from the fixing roller 28. The separation claw 44 is disposed in contact with or close to the surface of the fixing roller 28.

The control means 40 means a microcomputer including a CPU, ROM, RAM, I / O interface and the like. In this embodiment, the main controller of the printer 2 (not shown) also serves as the control means 40.
The thermistor 36 is disposed so as to contact the surface of the fixing roller 28. By increasing or decreasing the power supply to the induction coil 32 based on the detection signal of the thermistor 36, the surface temperature of the fixing roller 28 is a predetermined constant temperature. Is automatically controlled by the control means 40.

The fixing roller 28 is formed as an iron cylinder having an outer diameter of 50 mm and a thickness of 0.8 mm. Although not shown, the outer peripheral surface of the fixing roller 28 has a thickness of 10 to 50 μm, such as PTFE or PFA. The mold release layer is formed. A layer having a low thermal conductivity such as foamed silicon rubber may be provided as an insulating layer on the inner surface of the iron cylinder.
The pressure roller 30 has an outer diameter of 40 mm, an aluminum core 30a, and an elastic layer 30b made of silicon rubber having a thickness of 2 to 3 mm provided on the outer periphery of the core 30a. . The fixing roller 28 and the pressure roller 30 are rotatably supported by a support member (not shown), and the fixing roller 28 is connected to a drive mechanism (not shown). The pressure roller 30 is pressed against the fixing roller 28 by an urging means (not shown), and the width of the fixing nip portion SN is set to about 7 mm. The pressure roller 30 is driven and rotated by the frictional force of the fixing nip SN. Depending on the conditions, the pressure load and the fixing nip width are changed.

The induction coil 32 is formed as a twisted wire (Litz wire) formed by winding a plurality of thin wires, and is wound in a plane along the outer peripheral surface of the fixing roller 28 as shown in FIG.
An alternating current of 10 k to 1 M (Hz) is applied to the induction coil 32. The magnetic flux induced by the alternating current generates an eddy current in the conductive layer (cylindrical body) of the fixing roller 28 and generates Joule heat. In order to increase the heat generation of the fixing roller 28, the induction coil 32 may be brought close to the outer peripheral surface of the fixing roller 28 as long as mechanical accuracy permits.

  As shown in FIG. 1, the shield member 34 is U-shaped in cross section and has a shape extending in the axial direction of the fixing roller 28. The induction coil 32 is housed in the recess of the shield member 34 and is held by the shield member 34 (claim 37). The induction coil 32 may be held by a holding member different from the shield member 34.

  In a state where the fixing roller 28 is driven to rotate and an alternating current is applied to the induction coil 32 and the surface of the fixing roller 28 reaches a predetermined temperature, the sheet P carrying the unfixed toner image is guided to the conveyance guide 42 and fixed. The nip portion SN is entered. The sheet P is nipped and conveyed as the fixing roller 28 rotates, and the toner image is fixed to the sheet P by the heat and pressure of the fixing roller 28.

  Due to the U-shaped cross-section of the shield member 34 that is open only on the fixing roller 28 side, the magnetic flux generated by the induction coil 32 is concentrated toward the fixing roller 28, so the outside (other than the region facing the fixing roller 28). Magnetic flux leakage to the region) is suppressed, and heat generation efficiency by electromagnetic induction in the fixing roller 28 is increased.

As the fixing roller 28 rises in temperature, the heat is radiated to the shield member 34 and the shield member 34 is heated. The induction coil 32 itself also generates heat due to its electrical resistance, and the shield member 34 itself, which is a magnetic material, also generates heat due to the magnetic flux generated by the induction coil 32. The ambient temperature of the induction coil 32 rises under these complex temperature rise conditions, and the temperature rise is promoted by the closed shape of the shield member 34 that is open only on the fixing roller 28 side.
For this reason, the temperature of the induction coil 32 rises, the electrical resistance increases, the power consumption increases, and the heating efficiency (heat generation efficiency) of the fixing roller 28 decreases. In addition, dielectric breakdown of the induction coil 32 may occur.

In order to prevent such a problem, the fixing device 12 in the present embodiment is configured to be able to promote heat dissipation of the shield member 34 (claim 1). Specifically, the shield member 34 is formed with a number of holes 46 as vent openings for promoting heat dissipation of the shield member 34 (claims 2 and 4).
The hole 46 in the present embodiment is a circular hole having a diameter of 5 mm, and is formed not only on the portion corresponding to the outer peripheral surface of the fixing roller 28 of the shield member 34 but also on the four side surfaces. It is formed according to the temperature distribution. The holes 46 are formed not only on the portion corresponding to the outer peripheral surface of the fixing roller 28 of the shield member 34 but also on the four side surfaces in order not to reduce the shielding function and to facilitate heat circulation and to dissipate heat. This is to encourage. The shape of the hole 46 may be an ellipse or a rectangle.

In the case of the litz wire form, the heat generation distribution of the induction coil 32 itself is proportional to the density of the twisted line of the induction coil 32. Therefore, if the induction coil 32 is wound evenly, the heat generation distribution of the induction coil 32 itself is uniform, but if it is wound non-uniformly, a difference occurs in the heat generation distribution.
The above "depending on the temperature distribution of the induction coil 32" means that the number of the holes 46 is determined in the portion where the induction coil 32 is closely wound when the winding method of the induction coil 32 is not uniform. It means to increase or increase the opening diameter.
In this embodiment, since the temperature distribution of the induction coil 32 is uniform, the holes 46 are formed uniformly on the entire surface of the shield member 34.

Since heat that is trapped inside the shield member 34 (accommodating space of the induction coil 32) escapes to the outside of the shield member 34 through the hole 46, the heat storage of the shield member 34 is suppressed, and the induction coil 32 Temperature rise is suppressed.
Forming the ventilation opening in the shield member 34 leads to a reduction in the shielding function, but the frequency used is 10 k to 1 M (Hz), and 30 to 0.3 (km), which is a long wavelength, Even if a ventilation opening of about 10 mm or less is provided, the shielding function is sufficient.
Further, even if the hole 46 is formed in the shield member 34, the remaining area of the shield member 34 becomes a bypass of magnetic field lines with respect to the magnetic flux that leaks from the hole 46 to the outside. Hard to happen.
The size of the ventilation opening and the thickness of the shield member 34 are determined by the frequency and material used.

[Example 1]
As a result of uniformly forming a hole 46 having a diameter of 5 mm in the shield member 34 made of ferrite, applying an alternating current of 30 kHz to the induction coil 32, and heating the fixing roller 28 having a PTFE release layer having a thickness of 30 μm, The leakage magnetic flux was at a level with no problem, and the heating efficiency of the fixing roller 28 was also good.
[Comparative Example 1]
Except that the hole 46 was not formed in the shield member 34, the heating efficiency of the fixing roller 28 deteriorated under the same conditions as in Example 1.
[Comparative Example 2]
Except that the hole 46 was formed in only half of the shield member 34, the same conditions as in Example 1 were performed. As a result, temperature unevenness occurred on the surface of the fixing roller 28.

  The method of winding the induction coil 32 is not limited to that shown in FIGS. 1 and 2. If the induction coil 32 is provided outside the fixing roller 28, the heating function of the fixing roller 28 similar to the above is provided. Obtainable.

Next, another embodiment will be described based on FIG.
In the present embodiment, a large number of slits 48 are formed in the shield member 34 as openings for ventilation (Claim 5). Other configurations are the same as those in the above embodiment (the same applies to the following embodiments). The size of the slit 48 is such that the long side 48a is 50 mm, the short side 48b is 2 mm, and the gap w between the slits 48 is 1 mm.
Similarly to the above-described embodiment, the heat that tends to be trapped inward of the shield member 34 escapes to the outside of the shield member 34 through the slit 48, so that the heat storage of the shield member 34 is suppressed, and the temperature of the induction coil 32 is reduced. The rise is suppressed.
The slit 48 is formed so as to block the eddy current generated in the shield member 34. That is, the long side 48a is formed so that the direction of the long side 48a is substantially perpendicular to the direction of the current flowing through the induction coil 32.
By setting the direction of the slit 48 in this way, the slit 48 functions as an insulating layer, an eddy current generated in the shield member 34 is hindered, and heat generation of the shield member 34 itself due to electromagnetic induction is suppressed. Therefore, the ventilation function by the slit 48 and the heat generation suppression function of the shield member 34 are combined, and the temperature rise suppression function of the induction coil 32 is improved.

In the above-described embodiment, a ventilation opening is formed in the shield member 34 to promote heat dissipation of the shield member 34. However, the temperature rise of the induction coil 32 can be similarly suppressed by expanding the heat dissipation area of the shield member 34. A function can be obtained (claim 7).
For example, as shown in FIG. 5, a large number of heat radiation fins 50 as convex portions may be formed on the outer surface of the shield member 34 (claim 8). Moreover, as shown in FIG. 6, you may form many hollows 52 in the outer surface of the shield member 34 (Claim 9).

Next, another embodiment will be described based on FIG.
Each of the above embodiments is characterized in that the heat dissipation of the shield member 34 is promoted. However, in this embodiment, the heat generation of the shield member 34 due to electromagnetic induction is suppressed. In other words, it is not an approach based on the shape improvement of the shield member 34 but an approach based on material and functional improvements.
The shield member 34 in the present embodiment has a laminated structure of a magnetic layer 54 and an insulator layer 56 and has a direction to block eddy currents generated in the shield member 34 (claims). 10, 11). As the magnetic layer 54, ferrite, iron, cobalt, nickel, or the like can be used. As the insulator layer 56, ceramics, a DLC (diamond-like carbon) film, or the like can be used.

In this embodiment, the lamination direction of the shield member 34 is the axial direction of the fixing roller 28, and the magnetic layer 54 and the insulator layer 56 block the eddy current generated in the shield member 34, that is, the induction coil 32. It extends in a direction substantially orthogonal to the direction of the flowing current. Such a laminated structure has the same function as the eddy current loss suppressing function in the laminated iron core.
[Example 2]
Using a shield member 34 in which nickel magnetic layers 54 and ceramic insulator layers 56 are alternately stacked, an AC current of 20 kHz is applied to the induction coil 32, and a fixing roller 28 having a PTFE release layer having a thickness of 30 μm. As a result of the heating, the leakage magnetic flux was at a level with no problem, and the heating efficiency of the fixing roller 28 was also good.

The shield member 34 shown in FIG. 7 may further include a ventilation opening (claim 12). In this case, as in the above embodiment, the hole 46 may be formed (claim 14), or the slit 48 may be formed (claim 15).
Moreover, you may form these ventilation openings according to the temperature distribution of the induction coil 32 (Claim 13). Further, the slit 48 may be formed so as to block the eddy current generated in the shield member 34 (claim 16).
[Example 3]
Except that the holes 46 were uniformly formed on the entire surface of the shield member 34, the same procedure as in Example 2 was performed. As a result, the leakage magnetic flux was at a satisfactory level, and the heating efficiency of the fixing roller 28 was better than that in Example 2. .

In the shield member 34 shown in FIG. 7, the heat dissipation area of the shield member 34 may be enlarged (claim 17). Further, the heat radiation area may be enlarged by forming a convex portion (for example, the heat radiation fin 50 shown in FIG. 5) (claim 18), or a recess (for example, the recess 52 shown in FIG. 6). It is good also as a structure made | formed by forming (Claim 19).
Further, the heat radiation area such as the protrusions and depressions may be enlarged only in the magnetic layer 54 and the insulator layer 56 having the higher thermal conductivity (claim 20). .

Next, another embodiment will be described based on FIG.
In the present embodiment, a simple shield member 34 that does not have an opening for ventilation and does not have a structure for suppressing heat generation by electromagnetic induction, and an air cooling fan 60 as a cooling means for cooling the shield member 34 (claim 21). 22), an airflow guide plate 62 for preventing the airflow from the air cooling fan 60 from affecting the atmosphere in the temperature detection region of the thermistor 36 (Claim 23), and the airflow from the air cooling fan 60 is undetermined on the paper P. An airflow guide plate 64 is provided for preventing the influence of the landing image (claim 25).
The airflow guide plates 62 and 64 also function to prevent the airflow from the air cooling fan 60 from affecting the temperature of the fixing roller 28 (claim 24).

When the airflow from the air cooling fan 60 strikes the shield member 34, heat dissipation of the shield member 34 is promoted. The airflow hitting the shield member 34 is guided by the airflow guide plates 62 and 64 and flows so as not to hinder.
When the airflow from the air cooling fan 60 directly hits the paper P carrying the unfixed image, the unfixed image is scattered or the paper P fluctuates with the airflow, so that the paper sheet does not stably enter the fixing nip portion SN. Although this may occur, according to the present embodiment, such a concern can be resolved.

The shield member 34 according to the present embodiment may further include a ventilation opening (claim 26). In this case, the hole 46 may be formed (Claim 28) or the slit 48 may be formed (Claim 29), as in the above embodiment. Moreover, you may form these ventilation openings according to the temperature distribution of the induction coil 32 (Claim 27). Furthermore, the slit 48 may be formed so as to block the eddy current generated in the shield member 34 (claim 30).
Further, the shield member 34 in the present embodiment may have a configuration in which the heat dissipation area is enlarged (claim 31). Further, the heat radiation area may be enlarged by forming convex portions (for example, heat radiation fins 50 shown in FIG. 5) (claim 32), or recesses (for example, the recess 52 shown in FIG. 6). It is good also as a structure made | formed by forming (Claim 33).

[Example 4]
In the configuration having the air cooling fan 60, the fixing roller 28 is a steel cylinder having an outer diameter of 40 mm and a thickness of 0.7 mm provided with a release layer of PTFE having a thickness of 20 μm and is not shown. 5 is formed by alternately laminating ferrite magnetic layers 54 and anodized insulator layers 56, and on the outer surface of the anodized insulator layer 56, which has a higher thermal conductivity, Fixing is performed by applying a 30 kHz alternating current to the induction coil 32 using a shield member 34 that has the same convex portion and has a ventilation opening similar to the hole 46 shown in FIG. As a result of heating the roller 28, the leakage magnetic flux was at a level with no problem, and the heating efficiency of the fixing roller 28 was also good.

Next, another embodiment will be described based on FIG.
In the present embodiment, a permalloy shield member 34 having a refrigerant passage 66 therein, and a small air pump 68 (concept of a blower fan and a suction fan) as a refrigerant driving member that moves air as refrigerant in the refrigerant passage 66. (Claims 34 and 35). The air discharged from the air pump 68 enters from the inlet 66a of the refrigerant passage 66 and blows out from the outlet 66b. The shield member 34 is cooled by the outside air moving in the refrigerant passage 66.
Water may be used as the refrigerant, and a small liquid pump (including the concept of a suction pump) may be used as the refrigerant driving member. Moreover, you may use gas as a refrigerant | coolant.

  In each of the above embodiments, the heating device as the fixing device has been exemplified. However, the heating device according to the present invention is a device that heats transfer paper (paper) carrying an image and modifies its surface properties (such as gloss). As an apparatus for performing hypothetical dressing, or an apparatus for supplying a sheet-like body and drying / laminating it.

1 is a schematic front view of a fixing device as a heating device according to an embodiment of the present invention. FIG. 2 is a schematic exploded perspective view of a fixing device. 1 is a schematic front view of a printer as an image forming apparatus including a fixing device. It is a perspective view of the shield member in other embodiments. It is a general | schematic sectional drawing of the shield member in other embodiment. It is a general | schematic sectional drawing of the shield member in other embodiment. It is a perspective view of the shield member in other embodiments. It is a general | schematic front view of the fixing device in other embodiment. It is a perspective view of the shield member in other embodiments.

Explanation of symbols

P Sheet-like paper 28 Fixing roller 32 as heating rotator 32 Inductive coil 34 Shield member 46 Hole as vent opening 48 Slit as vent opening 50 Radiating fin as convex 52 Depression 54 Magnetic layer 56 Insulator Layer 60 Air Cooling Fan 66 Refrigerant Passage 68 Air Pump as Refrigerant Drive Member

Claims (26)

A heating rotator that generates heat by induction current and heats the sheet-like body, an induction coil that is provided outside the heating rotator to generate magnetic flux that generates induction current, a holding member that holds the induction coil, and In the heating apparatus having a shield member for suppressing magnetic flux leakage of the induction coil,
A heating device configured to be capable of suppressing heat generation of the shield member due to the magnetic flux. The heating device according to claim 1, wherein
The heating device, wherein the shield member has a laminated structure of a magnetic layer and an insulator layer, and the laminated structure has a direction to block an eddy current generated in the shield member. The heating device according to claim 2, wherein
The heating device, wherein the shield member has an opening for ventilation. The heating device according to claim 3, wherein
The heating device, wherein the ventilation opening is formed according to a temperature distribution of the induction coil. The heating device according to claim 3 or 4,
The heating device, wherein the ventilation opening is a hole. The heating device according to claim 3 or 4,
The heating device, wherein the ventilation opening is a slit. The heating device according to claim 6, wherein
The heating device, wherein the slit is formed so as to block an eddy current generated in the shield member. The heating device according to claim 2, wherein
The heating device, wherein the shield member has an enlarged heat radiation area. The heating device according to claim 8, wherein
The heating device, wherein the heat radiation area is enlarged by forming a convex portion. The heating device according to claim 8, wherein
The heating device is characterized in that the heat radiation area is enlarged by forming a recess. The heating device according to claim 9 or 10,
The heating device according to claim 1, wherein the heat radiation area is enlarged only in a layer having a higher thermal conductivity among the magnetic layer and the insulator layer. The heating device according to claim 1, wherein
A heating device comprising cooling means for cooling the shield member. The heating device according to claim 12, wherein
The heating device, wherein the cooling means is an air cooling fan. The heating device according to claim 13,
A heating device, characterized in that the airflow generated by the air cooling fan is configured not to affect the atmosphere in the temperature detection region. The heating device according to claim 13,
A heating apparatus, characterized in that the airflow generated by the air cooling fan is configured not to affect the temperature of the heating rotator. The heating device according to claim 13,
A heating apparatus, wherein the sheet-like body carries an unfixed image, and is configured so that an airflow generated by the air cooling fan does not affect the unfixed image. The heating device according to one of claims 12 to 16,
The heating device, wherein the shield member has an opening for ventilation. The heating device according to claim 17,
The heating device, wherein the ventilation opening is formed according to a temperature distribution of the induction coil. The heating device according to claim 17 or 18,
The heating device, wherein the ventilation opening is a hole. The heating device according to claim 17 or 18,
The heating device, wherein the ventilation opening is a slit. The heating device according to claim 20,
The heating device, wherein the slit is formed so as to block an eddy current generated in the shield member. The heating device according to one of claims 12 to 16,
The heating device, wherein the shield member has an enlarged heat radiation area. The heating device according to claim 22,
The heating device, wherein the heat radiation area is enlarged by forming a convex portion. The heating device according to claim 22,
The heating device is characterized in that the heat radiation area is enlarged by forming a recess. 25. A heating device as claimed in one of claims 1 to 24,
The heating device, wherein the induction coil is held by the shield member. In an image forming apparatus having a fixing device for fixing an unfixed image,
An image forming apparatus, wherein the fixing device is a heating device according to any one of claims 1 to 25.

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