JP3317154B2 - Fixing device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fixing device used in an image forming apparatus such as an electrophotographic copying machine, a printer, and a facsimile, and more particularly, to a method in which toner held on a sheet is melted by heating. The present invention relates to an induction heating type fixing device for fixing a sheet.

[0002]

2. Description of the Related Art An electrophotographic copying machine or the like is provided with a fixing device for melting a toner image transferred onto a sheet such as recording paper or transfer material as a recording medium by heat and fixing the toner image on the sheet. ing. As the heating method of the fixing device, there are a halogen lamp heating method, an induction heating method, and the like. In recent years, the induction heating method has attracted attention because of its advantages of a high temperature rising rate and contributing to energy saving.

As a conventional fixing device employing an induction heating system, for example, as shown in JP-A-59-33787, a spirally wound coil is disposed inside a heat roller, and a magnetic flux generated by the coil is used. There is a fixing device in which a heat roller is directly induction-heated so that warm-up is accelerated.

In order to further reduce the warm-up time without increasing power consumption in an induction heating type heat roller fixing device, it is necessary to reduce the heat capacity of the heat roller, that is, to make the heat roller thinner. However, since the heat roller applies a pressing force to the sheet, the heat roller needs some strength. For this reason, there is a limit to the reduction in heat capacity due to the thinning of the heat roller, and it has been difficult to make the heat roller thinner in manufacturing.

In recent years, for example, Japanese Patent Laid-Open No.
Japanese Patent Application Laid-Open No. 4276 and Japanese Unexamined Patent Application Publication No. 8-160007 disclose a film fixing device having excellent temperature-raising characteristics. This film fixing device has a thin film that is a rotating body, an exciting coil disposed inside the film, and a pressure roller, and generates an eddy current in the film by a magnetic flux generated by the exciting coil. The film is induction heated. The pressure roller is in pressure contact with the holding member holding the excitation coil via a film, and moves the film together with the heated film while sandwiching the sheet with the heated film, thereby heating and melting the toner held on the sheet. Has been established.

[0006]

In a fixing device in which a rotating body which generates heat by induction heating is moved while being held between a holder as a holding member and a pressing roller, the holder is constituted by a pressing roller. Bending (bending deformation) is caused by receiving a pressing force from the substrate. In addition, since the holder is heated by ambient heat, the deformation of the holder is relatively large, particularly when the holder is formed of a resin material.

If the rigidity of the holder is low and the amount of deformation of the holder due to the pressure is large, a gap is formed between the bent holder and the rotating body at the nip portion, and the nip pressure becomes uneven along the longitudinal direction of the holder. As a result, there arises a problem that uniform fixability cannot be obtained. Further, there is a possibility that rotation failure or breakage of the rotating body or sheet conveyance failure may be caused.

In a fixing device used in a high-speed image forming apparatus, it is necessary to increase the nip width, and to secure a large nip width, it is necessary to increase the pressure from the pressure roller. . In order to counter the high pressure from the pressure roller, it is conceivable to increase the thickness of the holder or increase the diameter of the holder to increase the rigidity of the holder. However, when the thickness of the holder is increased, the distance between the rotating body and the coil is increased, the magnetic coupling between the two is weakened, and the efficiency of heating the rotating body (energy transfer efficiency) is reduced. I will. If the heating efficiency is poor, more power must be applied in order to obtain the required amount of heat generated by the rotating body, which is contrary to the demand for energy saving. Further, when the holder diameter is increased, there is a problem that the increase in the diameter causes an increase in the size of the entire fixing device and an increase in cost.

SUMMARY OF THE INVENTION The present invention has been made to solve the problems associated with the above-described conventional technology, and increases the rigidity of a holding member that is pressed by a pressing member via a rotating body, thereby achieving uniform fixing performance. It is another object of the present invention to provide a fixing device capable of preventing rotation failure or breakage of a rotating body, or occurrence of sheet conveyance failure.

[0010]

According to a first aspect of the present invention, there is provided a fixing device for fixing a toner held on a recording medium by heating and fusing the toner on the recording medium. A rotating body formed of a metal material; a core; and a coil formed by winding a winding around the core, and generating an induction current in the rotating body to heat the rotating body by induction heating. A magnetic flux generating means, an insulating holding member that holds the magnetic flux generating means and is fixedly installed inside the rotating body, and presses against the holding member via the rotating body, and removes unfixed toner. A pressing member that moves the held recording medium with the rotating member while sandwiching the recording medium between the rotating member and the rotating member, wherein the rigidity of the holding member is increased by supporting the pressure from the pressing member. Increase pressure support And, wherein the pressure support means, the core
A support plate disposed between the material and the coil.
That has been made is a fixing device according to claim.

In the fixing device having such a configuration, the pressing force acting on the holding member from the pressing member via the rotating body is supported by the pressure supporting means. Therefore, since the rigidity of the holding member is increased, even if the holding member is formed from a resin material, the amount of deformation of the holding member becomes relatively small. Accordingly, there is no gap between the holding member and the rotating body in the nip portion, and the nip pressure becomes uniform along the longitudinal direction of the holding member, and as a result, uniform and good fixability is obtained. Further, there is no possibility that rotation failure or breakage of the rotating body or recording medium conveyance failure may be caused. In addition, the thickness of the holding member itself can be reduced, and as a result, the air gap between the rotating body and the magnetic flux generating means can be narrowed, the magnetic coupling between the two becomes stronger, and the heating efficiency of the rotating body improves. Further
The pressure supporting means is disposed between the core material and the coil.
Since it is composed of a support plate, it is
Since the rigidity of the entire holding member increases, the holding member itself does not
The required rigidity is reduced, so the holding member is small
It is possible to reduce the size, diameter, and thickness. In addition,
Since the plate and the generated magnetic flux are arranged in parallel,
Loss due to heat generation of the rotor
The rate does not decrease.

Further, in the fixing device according to claim 2, wherein the support plate is characterized in that it is formed from non-magnetic material.

With such a configuration, the support plate is less likely to generate heat by induction, the loss due to the heat generation of the support plate is reduced, and the heating efficiency of the rotating body is not reduced.

According to a third aspect of the present invention, in the fixing device, the support plate is provided with an extending portion that extends substantially parallel to a direction in which the pressing member is pressed against the holding member. I do.

According to this structure, the pressing force applied to the holding member from the pressing member via the rotating body is supported by the support plate disposed along the direction in which the pressing force is applied, in particular, by the extended portion thereof. This increases the rigidity of the holding member.

[0016] In the fixing device according to claim 4, longitudinal ends of the support plate protrudes outward from an axial end portion of the holding member, the longitudinal end, strong structure It is characterized by being fixed to.

According to this structure, since the pressing force applied from the pressing member is directly supported by the support plate fixed to the strong structure, the rigidity of the holding member is further increased,
Uniform and good fixing properties can be obtained, and poor rotation of the rotating body does not occur. In addition, the holding member only needs to hold the rotating body between the pressing member and the function of smoothly sliding the rotating body, so that the thickness of the holding member can be further reduced, and The heating efficiency is further improved.

According to a fifth aspect of the present invention, in the fixing device, at least a surface layer of the support plate has an insulating property.

With this configuration, the surface layer of the support plate functions as an insulating portion for electrically insulating the core material and the coil, and electrical insulation between the two is ensured. Less occurrence and higher reliability.

According to a sixth aspect of the present invention, in the fixing device, the support plate is formed with a through hole for preventing generation of an induced current.

With this configuration, the generation of an induced current in the support plate is prevented, so that it is difficult for the support plate to generate heat, and a decrease in the heating efficiency of the rotating body is prevented.

According to a seventh aspect of the present invention, there is provided a recording medium.
The toner held on top is melted by heating and set on the recording medium.
A fixing device, which is formed of a metal material.
A rotating body, a core material, and a winding wound around the core material
And an induced current is generated in the rotating body.
Magnetic flux generating means for induction heating the rotating body,
Holds the magnetic flux generating means and fixes it inside the rotating body
An insulating holding member to be installed, and
The non-fixed toner was held while being pressed against the holding member.
While rotating the recording medium between the rotating body and the
A pressure member that moves with the body
In the above, the pressure from the pressing member is supported and the holding is performed.
A pressure support means for increasing the rigidity of the member;
The means is a portion of the holding member that contacts the rotating body.
And a magnetic metal part formed from a magnetic metal.
And a fixing device.

With this configuration, the rigidity of the entire holding member is increased by disposing the magnetic metal portion on the sliding portion between the holding member and the rotating body, so that the pressing force applied from the pressing member is reduced. Even if it is supported by itself, there is no gap between the magnetic metal portion and the rotating body, uniform and good fixing properties can be obtained, and poor rotation of the rotating body does not occur. Further, although the magnetic metal portion generates heat by the magnetic flux generated by the magnetic flux generating means, the heat energy is transmitted to the rotating body, so that the fixing device has good thermal efficiency and energy saving as a whole.

Further, in the fixing device according to claim 8, wherein the magnetic metal part, characterized in that the electrical ground have been made.

With this configuration, it is possible to reliably prevent the current flowing through the coil from being short-circuited via the rotating body.

Further, in the fixing device according to the ninth aspect , the magnetic flux generating means is configured so that the magnetic metal portion becomes a substantially maximum heat generating portion.

With this configuration, the speed of temperature rise of the rotating body is increased.

[0028]

Embodiments of the present invention will be described below with reference to the drawings.

Embodiment 1 FIG. 1 is a sectional view schematically showing a fixing device according to Embodiment 1 of the present invention.

In the fixing device using induction heating according to the present embodiment, an induction eddy current is induced in a metal conductor by a high-frequency magnetic field generated by applying a high-frequency current to a coil, and the metal conductor itself is formed by a skin resistance of the metal conductor itself. The Joule is designed to generate heat. In this type of induction heating fixing device, electric-heat conversion efficiency is improved by using high-frequency induction, so that energy saving (low power consumption) of the fixing device and
Improving user operability (quick print) can be achieved.

More specifically, as shown in FIG. 1, the induction heating fixing device heats and fuses the toner held on the recording medium 10 to fix it on the recording medium 10, and is formed of a metal material. A fixing sleeve 12 (corresponding to a rotating body) and a coil assembly 13 for generating an induction current in the fixing sleeve 12 and inductively heating the fixing sleeve 12.
(Corresponding to magnetic flux generating means) and the coil assembly 13
And an insulating holder 14 (corresponding to a holding member) fixedly installed inside the fixing sleeve 12, and the recording medium 10 holding the unfixed toner while being pressed against the holder 14 via the fixing sleeve 12. The fixing sleeve 12
And a pressure roller 15 (corresponding to a pressure member) which is moved together with the fixing sleeve 12 while being sandwiched between them. The pressure roller 15 is rotatably provided in the direction of arrow a in FIG. 1, and the fixing sleeve 12 having a hollow cylindrical shape is sandwiched between the pressure roller 15 and the holder 14. To rotate.

The recording medium 10 holding the unfixed toner, that is, the sheet, is conveyed from the left as indicated by an arrow b in FIG. 1 and is transferred to a nip 16 which is a contact portion between the fixing sleeve 12 and the pressure roller 15. It is sent toward. Sheet 10
The sheet is conveyed while being nipped by the nip portion 16 while the heat of the fixing sleeve 12 subjected to the induction heating and the pressure acting from the pressure roller 15 are applied. As a result, the unfixed toner is fixed on the sheet 10, and a fixed toner image is formed on the sheet 10. The toner is held on the side of the sheet 10 that contacts the fixing sleeve 12. The sheet 10 that has passed through the nip 16 is naturally separated from the fixing sleeve 12 by a curvature due to the strength of the sheet itself, and is conveyed rightward in FIG. The sheet 10 is conveyed by a discharge roller (not shown) and discharged onto a discharge tray.

The fixing sleeve 12 is a thin hollow metal conductor having flexibility, for example, nickel, iron, SU, or the like.
It is preferable to form a conductive ferromagnetic material such as S430 as the base material 17. If the fixing sleeve 12 is formed of a ferromagnetic material, a large amount of magnetic flux passes through the inside of the fixing sleeve 12, so that the heat generation efficiency is further improved. The thickness of the metal base 17 of the fixing sleeve 12 is, for example, 20 μm to 6 μm.
A thickness of about 0 μm is preferred. Fixing sleeve base material 17
In order to facilitate separation of the sheet 10,
A release layer 11 having good release properties and heat resistance with respect to the toner is formed by coating with a fluororesin.

A coil assembly 13 for generating a high-frequency magnetic field is arranged inside the fixing sleeve 12 to induce induced eddy current in the fixing sleeve 12 to generate Joule heat. This coil assembly 13 is held inside a non-rotating holder 14. Also, holder 1
Four ends (not shown) for restricting the fixing sleeve 12 from shifting in the longitudinal direction of the holder 14 are provided at both ends of the holder 4.

The coil assembly 13 includes a core 18 (corresponding to a core) made of a magnetic material and having an I shape, and an induction coil 20 formed by winding a coil around the core 18.
And

The pressure roller 15 comprises a shaft core 21 and a silicone rubber layer 22 formed around the shaft core 21. The silicon rubber layer 22 covers the sheet 1 from the surface.
0 is a rubber layer having releasability and heat resistance as well as easy release. Sliding bearings (not shown) are formed at both ends of the pressure roller 15, and are rotatably attached to a frame of a fixing unit (not shown). The pressure roller 15 is formed of a fixing member 12 by a spring material (not shown).
Is pressed in the direction toward the holder 14 with the. Further, a drive gear (not shown) is fixed to one end of the pressure roller 15, and is driven to rotate by a drive source (not shown) such as a motor connected to the drive gear.

Further, in the fixing device, a temperature sensor (not shown) including a thermistor or the like is provided so as to be in pressure contact with the surface or the inner peripheral surface of the fixing sleeve 12 in order to detect the temperature of the fixing sleeve 12. . While detecting the temperature of the fixing sleeve 12 with this temperature sensor, the fixing sleeve 1
The energization of the induction coil 20 is controlled so that the temperature of No. 2 becomes the optimum temperature.

In particular, the fixing device includes a pressure roller 15
Pressure supporting means 40 is provided to support the pressure from and increase the rigidity of the holder 14. In the first embodiment, the pressure support means 40 includes the core 18 and the induction coil 2.
0 and a pair of support plates 41 arranged between the support plates 41.

More specifically, in the coil assembly 13 of the present embodiment, the coil 20 is formed by winding a copper wire around a pair of support plates 41, 41 a plurality of times. The core 18 is inserted between the pair of support plates 41, 41 so as to be orthogonal to the copper wire of the coil 20. The coil assembly 13 is housed and held in the holder 14 made of a resin material such that the longitudinal direction of the cross section of the core 18 is orthogonal to the sheet conveying direction and is not exposed to the outside.

The core 18 is made of, for example, a ferrite core or a laminated core. Since the shape of the core 18 is a simple I-shape, the manufacturing cost of the core 18 is low, and the work of disposing the core 18 between the pair of support plates is simplified. Further, when the coil assembly 13 is held in the holder 14, the end face of the core 18 located in the cross-sectional longitudinal direction is the holder 1.
4 is close to the inner wall. By arranging the core 18 in this manner, the air gap between the fixing sleeve 12 and the fixing sleeve 12 is narrowed, and the magnetic coupling with the fixing sleeve 12 is increased, so that high power transmission efficiency can be obtained. The end surface of the core 18 may be formed, for example, in an arc shape so as to be along the inner surface of the holder 14.

Since the holder 14 is heated by heat of the induction coil 20 and heat conduction from the surroundings, the holder 14 needs to have heat resistance that can withstand at least the fixing temperature, that is, the surface temperature of the fixing sleeve 12. Further, since the fixing device of the first embodiment performs electromagnetic induction heating, the holder 14 that houses the coil assembly 13 as a magnetic flux generating unit is provided with an insulator to prevent a short circuit between the fixing sleeve 12 and the coil 20. Needs to be For this reason, a resin holder having excellent precision in molding is adopted, and the holder 14 is formed from a resin material having heat resistance and insulating properties. As the resin material, a thermosetting resin such as a phenol resin (fillerless) may be used.

As the copper wire constituting the coil 20, it is preferable to use a single or litz copper wire having a fusion layer and an insulating layer on the surface.

The support plate 41 is formed in a simple plate shape having a length substantially equal to the axial length of the holder 14, and has an extending portion 41 a extending substantially parallel to the direction in which the pressure roller 15 is pressed against the holder 14. Have. Further, the extending portion 41a is arranged so as to be parallel to the magnetic flux generated by the coil assembly 13. This is because, when the extending portion 41a is arranged so as to be orthogonal to the generated magnetic flux, the amount of heat generated in the extending portion 41a increases, the loss of the generated magnetic flux increases, and the heating efficiency of the fixing sleeve 12 decreases. That's why. In the configuration shown in FIG.
1a extends in the vertical direction in the figure, and its upper end and lower end are in contact with the inner peripheral surface of the holder 14. Support plate 41
Is made of a material having non-magnetic properties. As such a material, a material having a non-magnetic permeability of approximately 1 is suitable. Specifically, the support plate 41 is made of aluminum,
It is formed of silver, copper, SiO2, ceramic, SUS304, or the like.

Both ends of the holder 14 accommodating and holding the coil assembly 13 are fixed to a strong structure such as a frame of a fixing unit (not shown) or a frame of an image forming apparatus.

In the first embodiment having the pressure supporting means 40 having the above-described structure, the pressing force acting on the holder 14 from the pressing roller 15 via the fixing sleeve 12 is arranged along the direction in which the pressing force acts. The supporting plate 41 is supported by the extended portion 41a. Therefore, since the rigidity of the holder 14 is increased, even if the holder 14 is formed from a resin material, the amount of deformation of the holder 14 is relatively small. Accordingly, there is no gap between the holder 14 and the fixing sleeve 12 in the nip portion 16, and the nip pressure becomes uniform along the longitudinal direction of the holder, and as a result, uniform and good fixing properties can be obtained. . Further, there is no fear that the rotation failure or breakage of the fixing sleeve 12 or the conveyance failure of the sheet 10 is caused.

Further, since the rigidity of the entire resin holder 14 is increased by the support plate 41a, the rigidity that the resin holder 14 itself has to bear is reduced, so that the holder 14 can be reduced in size, diameter, or thickness. Is possible. As a result, the air gap between the fixing sleeve 12 and the coil assembly 13 can be further reduced, and the magnetic coupling between the two can be further increased, so that the heating efficiency of the fixing sleeve 12 can be improved. Further, as the diameter of the holder 14 is reduced, the cost can be reduced and the entire fixing device can be reduced in size.

Further, since the support plate 41 is made of a non-magnetic material, the support plate 41 is less likely to generate heat, and there is no possibility that the heating efficiency of the fixing sleeve 12 will be reduced. In addition, since the extending portion 41a of the support plate 41 is arranged in parallel with the generated magnetic flux, the fixing sleeve 1 is also considered from this point.
The heating efficiency of No. 2 does not decrease.

Furthermore, it is not necessary to use a relatively expensive resin material which exhibits sufficient heat resistance at the operating temperature (fixing temperature) as the resin material for forming the holder 14, and the cost is excellent. The strength of the holder material itself can be increased by using a fiber-reinforced thermosetting resin such as a phenol resin (containing glass fiber), and the rigidity of the holder 14 can be further increased. In this case, after extruding the holder 14 from the fiber-reinforced thermosetting resin, it is preferable to perform a high-temperature quenching treatment at a temperature equal to or higher than a use temperature (fixing temperature) to accelerate the reaction of the uncrosslinked portions.

Since the support plate 41 has a simple plate shape, the configuration of the coil assembly 13 does not become complicated.

Further, as clearly shown in FIG. 1, the holder 14 is formed so as to have a continuous edge, that is, an endless cross section when viewed in a cross section orthogonal to the axis. With such a shape, the rigidity of the holder 14 can be increased. In addition, since the periphery of the coil assembly 13 is insulated endlessly by the holder 14, electrical insulation between the coil 20 and the fixing sleeve 12 is ensured, and the current flowing through the coil 20 passes through the fixing sleeve 12. Short circuit can be reliably prevented.

<Embodiment 2> FIG. 2 is a perspective view showing a main part of a pressure supporting means according to Embodiment 2, and members common to those shown in FIG. 1 are denoted by the same reference numerals. The description is omitted. The second embodiment differs from the first embodiment in that the structure for fixing the holder 14 and the support plate 41 is modified.

In the first embodiment, the support plate 41 is housed in the holder 14 such that the end of the support plate 41 does not protrude from the end of the holder 14, and both ends of the holder 14 are fixed to the strong structure.

On the other hand, in the second embodiment, the longitudinal end 41b of the support plate 41 is
And protrudes outward from the axial end 14a, and the projected longitudinal end 41b is fixed to a strong structure 42 such as a fixing unit frame. A flange portion 41c, which is fixed to the strong structure 42 by a screw or the like, is formed by bending at a longitudinal end portion 41b of the support plate 41. Only one end 41b of the support plate 41 is
, But both ends 41b are connected to the strong structures 42.
It is preferable to fix the lens to the cantilever, since it does not become cantilevered. The upper and lower ends of the extending portion 41a of the support plate 41 are in contact with the inner peripheral surface of the holder 14, as in the first embodiment.

In the second embodiment, since the pressing force applied from the pressure roller 15 is directly supported by the support plate 41 fixed to the strong structure 42, the rigidity of the holder 14 can be further increased. Uniform and good fixing properties can be obtained, and no defective rotation of the fixing sleeve 12 occurs.

The holder 14 has a structure in which the holder 14 is held by a support plate 41 disposed therein.
It is not necessary to secure the required rigidity when fixing to the strong structure 42 at the end. That is, the resin-made holder 14 of the second embodiment is provided between the fixing sleeve 1 and the pressure roller 15.
It suffices to mainly exert the function of holding the fixing sleeve 2 and sliding the fixing sleeve 12 smoothly. Therefore, the thickness of the holder 14 itself can be further reduced than in the first embodiment.
The heating efficiency of the fixing sleeve 12 can be further improved.

Third Embodiment FIG. 3 is a cross-sectional view illustrating a main part of a pressure support unit according to a third embodiment.

The support plate 41 of the third embodiment is
At least the surface layer 43 has an insulating property. Specifically, the surface of the support plate 41 is coated with PI (polyimide) or the like to form the insulating surface layer 43.

By forming the insulating surface layer 43 on the support plate 41, the support plate 41 functions as an insulating portion for electrically insulating the core 18 and the induction coil 20 from each other. Insulation is ensured. For this reason, this fixing device is less likely to cause a failure and has high reliability.

Fourth Embodiment FIG. 4 is a sectional view showing a main part of a pressure supporting means according to a fourth embodiment.

The support plate 41 of the fourth embodiment is
Through holes 44 and 45 for preventing generation of an induced current are formed. Specifically, the extension portion 41a of the support plate 41
A hole 44 shown in FIG. 3A and a slit 45 shown in FIG. 3B are opened to form the through hole.

By forming the through holes 44 and 45 in the support plate 41, generation of an induced eddy current in the support plate 41 is suppressed. For this reason, the support plate 4
No. 1 is more difficult to induce heat, and a decrease in the heating efficiency of the fixing sleeve 12 is prevented.

FIG. 5 is a graph showing the relationship between the area ratio of the through-hole portion and the loss of the applied power due to the heat generation of the support plate. The graph shows the case where a 1.0 mm-thick aluminum support plate is used. Is shown. From this graph, by setting the area ratio of the through holes 44 and 45 to an appropriate range,
It can be seen that the heat loss can be reduced while maintaining the strength of the support plate 41.

Fifth Embodiment FIG. 6 is a sectional view showing a fixing device according to a fifth embodiment. Members common to those shown in FIG. 1 are denoted by the same reference numerals, and description thereof is omitted. I do. In the fifth embodiment, the rigidity of the holder 58 made of a resin material is
Embodiment 1 differs from Embodiment 1 in that the height is increased without using Embodiment 1.

The coil assembly 13 in the fixing device according to the fifth embodiment has a bobbin 19 having a through hole in the center.
The coil 20 is formed by winding a copper wire around the bobbin 19 a plurality of times. The core 18 is inserted into the through hole of the bobbin 19 so as to be orthogonal to the copper wire of the coil 20.
Is inserted. The coil assembly 13 includes the bobbin 1
The core 18 is provided in the holder 14 formed separately from the core 18.
Are parallel to the sheet conveying direction and are stored and held so as not to be exposed to the outside. Since the bobbin 19 is heated by heat of the induction coil 20 and heat conduction from the surroundings, the bobbin 19 needs to have heat resistance that can withstand at least the fixing temperature, that is, the surface temperature of the fixing sleeve 12. For this reason, the bobbin 19 is made of, for example, ceramic or engineering plastic having heat resistance and insulating properties. Since the coil assembly 13 includes the bobbin 19 around which the copper wire is wound, the coil winding manufacturing process is facilitated and stable winding is enabled. In addition, the bobbin 19 functions as an insulating portion for electrically insulating the core 18 and the induction coil 20, and the electrical insulation between the two 18 and 20 is ensured. Less and more reliable.

The holder 58 of the fifth embodiment is made of the resin material shown in the first embodiment, and has a groove 59 facing the portion in contact with the fixing sleeve 12 when viewed in a cross section orthogonal to the axis. It has a cylindrical shape.

The pressure support means 40 for supporting the pressure from the pressure roller 15 and increasing the rigidity of the resin holder 58
Is arranged at a position in contact with the fixing sleeve 12 in the resin holder 58, and is constituted by a magnetic metal part 60 formed of a magnetic metal. A magnetic metal generally refers to a material having a relative magnetic permeability of about 100 or more. The higher the relative magnetic permeability, the higher the magnetic flux density and the easier it is to generate heat. Magnetic metal part 60
Specifically, SUS430, cobalt, nickel,
It is made of iron, nickel-iron alloy (permalloy), or the like. The magnetic metal part 60 is formed in an arc-shaped cross section, and is fitted in the concave groove 59 of the resin holder 58. The magnetic metal part 60 is electrically grounded.

FIG. 7 is an explanatory diagram for explaining the principle of heating the fixing sleeve 12 in the induction heating fixing device. When a high-frequency current (several kHz to several tens of kHz) is applied to the coil 20, a magnetic flux perpendicular to the longitudinal direction of the fixing sleeve 12 from the core 18 as shown in FIG. 25a occurs. This magnetic flux 25a
Are also high-frequency magnetic fluxes.

The magnetic flux 25b arriving at the conductive fixing sleeve 12 turns along the fixing sleeve 12 and becomes a magnetic flux 25c passing through the circumferential surface of the fixing sleeve 12 at a ratio depending on the relative magnetic permeability of the conductor. The magnetic flux 25 c concentrated on the peripheral surface of the fixing sleeve 12 has the maximum density at a portion facing the coil 20.

Due to the action of the concentrated magnetic flux 25c, a vortex-like induced current is generated in the fixing sleeve 12 in the fixing sleeve 12 according to "Lenz's law" so as to generate a magnetic flux in the opposite direction to the magnetic flux 25c. I do. This induced eddy current is converted into Joule heat by the skin resistance of the fixing sleeve 12. Thereby, the fixing sleeve 12 generates heat.

In this configuration, the magnetic flux density in the circumferential surface becomes maximum at points P and R of the fixing sleeve 12, and conversely,
It becomes minimum at points Q and S. Therefore, since the induced current density has the same tendency, the heat generation of the fixing sleeve 12 is not uniform in the circumferential surface, and the points P and R become the heat generation maximum points, and the portions 26a surrounded by the two-dot chain line 26b locally generates heat. The locally heated portions 26a and 26b
6 corresponds to the upper region and the lower region of the fixing sleeve 12. Therefore, the nip portion 16 and one of the heat generating portions (areas) overlap at least partially. In the illustrated embodiment, the core 18 around which the coil 20 is formed is arranged in parallel to the conveying direction of the sheet 10, so that one of the heat generating area of the fixing sleeve 12 and the nip 16 And the heat of the fixing sleeve 12 is sufficiently and efficiently transmitted to the toner.

As described above, the coil assembly 13 as the magnetic flux generating means is configured such that the magnetic metal portion 60 becomes a substantially maximum heat generating portion.

In the fifth embodiment having the pressure support means 40 having the above-described structure, the rigidity of the entire resin holder 58 is reduced by disposing the magnetic metal portion 60 at the sliding portion between the resin holder 58 and the fixing sleeve 12. Since the resin holder 58 itself supports the pressing force applied from the pressure roller 15, there is no gap between the magnetic metal portion 60 and the fixing sleeve 12, and uniform and good fixing is achieved. And the fixing sleeve 12 does not have poor rotation.

In this case, the magnetic metal portion 60 generates heat due to the magnetic flux generated in the coil assembly 13, but the heat energy is transmitted to the fixing sleeve 12, so that as a whole, the heat efficiency is good and energy saving is achieved. Fixed device can be provided.

Further, since the magnetic metal portion 60 is electrically grounded, it is possible to reliably prevent the current flowing through the coil 20 from being short-circuited via the fixing sleeve 12.

FIG. 8 is a graph showing the temperature rise characteristics of the fixing device according to the fifth embodiment together with a comparative example. FIG. 8A is a graph showing a temperature rise characteristic of Comparative Example 1 using a resin holder having no magnetic metal portion 60. (B) shows the temperature rising characteristic of the fifth embodiment, and (C) shows the comparative example 2 in which the coil assembly of the fifth embodiment is arranged such that the longitudinal direction of the cross section of the core is orthogonal to the sheet conveying direction. (D) is the temperature rising characteristic of the fifth embodiment.
3 shows a temperature rising characteristic of Comparative Example 3 in which a metal part made of a non-magnetic metal is arranged in place of the magnetic metal part 60 of FIG.

In general, the time called “quick fixing” in the fixing device is preferably within 10 seconds from the start of power supply in consideration of operability. It is required to raise the temperature of the fixing sleeve to a fixing temperature range (for example, 150 to 200 ° C.).

In Comparative Example 1 (A in the figure), the temperature of the fixing sleeve could be raised to the fixing temperature within the allowable time limit, but the rigidity of the holder was insufficient due to the lack of the pressure supporting means 40.
Stable fixability could not be realized.

In Comparative Example 2 (C in the figure), the magnetic metal part 60
Provided, the rigidity of the holder could be secured, but the temperature rise rate was slow because the magnetic metal portion 60 did not become the maximum heat generating portion, and the fixing sleeve did not rise to the predetermined fixing temperature even after the allowable time limit. .

In Comparative Example 3 (D in the figure), the rigidity of the holder could be secured because the metal portion made of a non-magnetic metal was provided.
Since the heat of the fixing sleeve was taken away by the metal part, the temperature rising rate was slow, and the fixing sleeve did not rise to the predetermined fixing temperature even after the allowable time had passed.

On the other hand, in the fifth embodiment, since the magnetic metal portion 60 is provided, the rigidity of the holder can be ensured.
Since the magnetic metal portion 60 coincides with the maximum heat generating portion and the heat induced by the magnetic metal portion 60 is transmitted to the fixing sleeve 12, the temperature rising speed is high, and the temperature of the fixing sleeve is raised to the fixing temperature within the allowable limit time. did it.

[0081]

As described above, according to the fixing device of the first aspect, the rigidity of the holding member against which the pressing member is pressed via the rotating body is increased by the pressure supporting means, so that a uniform fixing is achieved. The rotation of the rotating body and damage,
Alternatively, it was possible to provide a fixing device capable of preventing occurrence of recording medium conveyance failure. Further, as a result of the thickness of the holding member itself being reduced, the heating efficiency of the rotating body is improved. Furthermore, the holding part
Since the rigidity that the material itself has to bear is reduced,
By reducing the size, diameter and thickness of the holding member,
Excellent fixing, high thermal efficiency and energy saving
Device. In addition, support play to increase the rigidity of the holding member
The heat source is arranged in parallel with the generated magnetic flux,
The rate does not decrease.

Further, according to the fixing device of the second aspect , the support plate is less likely to generate induced heat, and the heating efficiency of the rotating body does not decrease.

According to the fixing device of the third aspect , the pressing force acting on the holding member from the pressing member via the rotating body is a supporting plate disposed along the direction in which the pressing force acts. In particular, the rigidity of the holding member is increased by being supported by the extending portion, and the same effect as that of the first aspect is obtained.

According to the fixing device of the fourth aspect , since the pressing force applied from the pressing member is directly supported by the support plate fixed to the strong structure, the rigidity of the holding member is further increased. . Further, the thickness of the holding member can be further reduced, and the heating efficiency of the rotating body is further improved.

According to the fixing device of the fifth aspect , the surface layer functions as an insulating portion for electrically insulating the core from the coil, and the fixing device is less likely to fail and has high reliability. Get higher.

[0086] Further, according to the fixing device according to claim 6, the support plate is less likely to induction heating generator of the induced current is blocked, decrease in the heating efficiency of the rotating body is prevented.

[0087] Further, according to the fixing device according to claim 7, rigidity of the entire holding member by disposing the magnetic metal part to the sliding portion between the holding member and the rotary member is increased, according to claim 1
It has the same effect as. Further, since the heat of the magnetic metal portion that has generated is transmitted to the rotating body, the fixing device has good thermal efficiency and energy saving as a whole.

[0088] According to the fixing device according to claim 8, the current flowing through the coil is reliably prevented from short-circuiting through the rotating body, the fixing device has less occurrence of a failure,
Increases reliability.

Further, according to the fixing device of the ninth aspect , the magnetic metal portion is suitably induction-heated, and the speed of heating the rotating body is increased.

[Brief description of the drawings]

FIG. 1 is a sectional view schematically showing a fixing device according to a first embodiment.

FIG. 2 is a perspective view illustrating a main part of a pressure support unit according to a second embodiment.

FIG. 3 is a cross-sectional view illustrating a main part of a pressure support unit according to a third embodiment.

FIG. 4 is a cross-sectional view illustrating a main part of a pressure support unit according to a fourth embodiment.

FIG. 5 is a graph showing a relationship between an area ratio of a through hole and a loss of applied power due to heat generation of a support plate.

FIG. 6 is a cross-sectional view illustrating a fixing device according to a fifth embodiment .

FIG. 7 shows the application of a fixing sleeve in an induction heating fixing device.
It is explanatory drawing explaining a heat principle .

FIG. 8 shows a temperature rise characteristic of the fixing device according to the fifth embodiment .
It is a graph shown with a comparative example .

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 10 ... Sheet (recording medium) 12 ... Fixing sleeve (rotary body) 13 ... Coil assembly (magnetic flux generation means) 14 , 58 ... Holder (holding member) 14a ... Axial end of the holder 15 ... Pressurizing roller (Pressurizing) 16) Nip portion (contact portion between rotating body and pressing member) 18 ... Core (core material) 20 ... Induction coil 40 ... Pressure support means 41 ... Support plate 41a ... Extension portion 41b ... Longitudinal end of support plate Part 42 ... Strong structure 43 ... Surface layer 44,45 ... Hole, slit (hole part ) 60 ... Magnetic metal part

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-8-137308 (JP, A) JP-A-7-114276 (JP, A) JP-A-8-44227 (JP, A) 22207 (JP, A) (58) Field surveyed (Int. Cl. ⁷ , DB name) G03G 13/20 G03G 15/20

Claims (9)

(57) [Claims] 1. A fixing device for heating and melting toner held on a recording medium to fix the toner on the recording medium, comprising: a rotating body formed of a metal material; a core; A coil formed by winding a winding, a magnetic flux generating means for generating an induction current in the rotating body and inductively heating the rotating body, and holding the magnetic flux generating means and inward of the rotating body. An insulating holding member fixedly installed on the rotating member, while being pressed against the holding member via the rotating member, and holding the recording medium holding unfixed toner between the rotating member and the rotating member. a movement allowed to the pressure member, the fixing device having, in favor of pressure from the pressure member have a pressure support means to increase the rigidity of the holding member, the pressure support means, the said core coil Between
A fixing device comprising a support plate placed thereon . 2. The support plate is formed from a non-magnetic material.
The fixing device according to claim 1, characterized in that it is. 3. The support plate, wherein the pressing member is located in front of the support plate.
Stretching extending almost parallel to the direction of pressing against the holding member
The fixing device according to claim 1, characterized in that parts are provided. 4. The support plate according to claim 1, wherein said support plate has a longitudinal end.
The fixing device according to claim 1, characterized in that than the axial end portions of the serial holding member protrudes outward, the longitudinal end portion, and fixed to the intensity structure. 5. The support plate has at least a surface layer.
2. The fixing device according to claim 1 , wherein the fixing device has an insulating property . 6. The support plate is configured to generate an induced current.
The fixing device according to claim 1, hole portions for blocking is characterized in that it is made form. 7. A method for heating and melting the toner held on a recording medium.
A fixing device for melting and fixing the recording medium, comprising: a rotating body made of a metal material; a core ; and a core formed by winding a winding around the core.
And an induced current is generated in the rotating body,
Magnetic flux generating means for induction heating the rotating body, and holding the magnetic flux generating means and inside the rotating body
While being in pressure contact with the insulating holding member fixedly installed and the holding member via the rotating body,
Between the recording medium holding the fixing toner and the rotating body.
Pressurizing member that moves with the rotating body while being held between
And the rigidity of the holding member by supporting the pressure from the pressing member.
Pressure supporting means, and the pressure supporting means comprises the rotating body in the holding member.
Placed in contact with
A fixing device comprising a metal part . 8. The magnetic metal part is electrically grounded.
The fixing device according to claim 7, characterized in that is. 9. The magnetic flux generating means, wherein the magnetic metal portion is
The fixing device according to claim 7 , wherein the fixing device is configured to be a substantially maximum heat generating portion .