JP2007279672A - Fixing member, fixing device, and image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To make the heat capacity of a fixing member low while forming nip width necessary for fixing, and to prevent excessive temperature rise at both ends in a width direction without lowering temperature rise efficiency by making a fixing rotating body itself have a degaussing function for controlling the permeation of magnetic flux. <P>SOLUTION: A fixing member 20 opposed to a pressure member 30 to form a fixing nip and also heated by electromagnetic induction by a magnetic flux exciting means 24 is constituted of: the fixing rotating body 21 having a magnetic substance layer 21d whose Curie point is 100°C to 300°C; a member 22 arranged separately at a position where it is opposed to the magnetic flux exciting means while putting the fixing rotating body 21 in between and having lower resistivity than the magnetic substance layer; and a nip forming member 23 arranged inside the fixing rotating body. Since the fixing member has a self temperature control function by combining the fixing rotating body 21 and the member 22 having the lower resistivity, the raised temperature of the fixing rotating body 21 is controlled to be predetermined temperature, thereby surely preventing the excessive temperature rise at both ends in the width direction without lowering the temperature rise efficiency. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention includes a fixing member that is heated using electromagnetic induction, and a fixing member that includes the fixing member, and heats and pressurizes a recording medium carrying an unfixed image at a fixing nip to fix the unfixed image on the recording medium. The present invention relates to a fixing device and an image forming apparatus such as a copying machine, a printer, a plotter, a facsimile, or a complex machine including the fixing device.

As a fixing device used in an electrophotographic image forming apparatus, there has conventionally been widely used a fixing device using radiant heat of a halogen heater such as a roller heating method.
Among them, due to demands for energy saving and shortening of waiting time, fixing members with small heat capacity are used, as represented by belt fixing and film fixing, and it is possible to shorten the rise time of the fixing device. It has become.
In particular, in the invention described in Patent Document 1, a contact member (such as a tension roller) is pressed from the outside of the fixing belt, and a large contact length between the fixing belt and the heating roller is taken, so that a large amount of heat can be transferred from the heating roller in a short time. It is given to the fixing belt and it is possible to start up in a short time.

  Reducing the waiting time of these fixing devices is an important issue, but in order to further reduce the waiting time, in recent years, roller heating and belt heating type fixing devices that employ electromagnetic induction heating (Induction Heating) are used. Various proposals have been made. In these systems, a high-frequency magnetic field is induced from a non-contact induction coil with respect to the heat generating member, and an induced current is generated on the coil-side surface layer of the heat generating member and generates heat due to Joule heat.

  Here, as an example of a conventional electromagnetic induction heating type fixing device, for example, the fixing device described in Patent Document 2 and the like includes a support roller (heating roller) and a fixing auxiliary roller (fixing roller) as heating members. A fixing belt stretched by a support roller and a fixing auxiliary roller, a magnetic flux excitation means (induction heating means) facing the support roller via the fixing belt, a pressure roller contacting the fixing auxiliary roller via the fixing belt, Etc. The magnetic flux excitation means includes a coil portion (excitation coil) extending in the width direction (a direction orthogonal to the conveyance direction of the recording medium), a core portion (excitation coil core) facing the coil portion, and the like. .

The fixing belt is heated at a position facing the magnetic flux exciting means. The heated fixing belt heats and fixes the toner image on the recording medium conveyed to the positions of the auxiliary fixing roller and the pressure roller. Specifically, when a high-frequency alternating current is passed through the coil portion, an alternating magnetic field is formed around the coil portion, and an eddy current is generated near the surface of the support roller. When an eddy current is generated in the support roller (heat generating member), Joule heat is generated by the electrical resistance of the support roller itself. The fixing belt wound around the support roller is heated by the Joule heat.
Such an electromagnetic induction heating type fixing device has higher heat conversion efficiency than other types such as a heat roller method (heater lamp heating method) because the heat generating member is directly heated by electromagnetic induction. It is known that the surface temperature (fixing temperature) of the fixing belt can be raised to a desired temperature with a small energy consumption and a short start-up time.

On the other hand, Patent Document 3 discloses a fixing device using an electromagnetic induction heating method, and is provided in the fixing roller for the purpose of suppressing a temperature rise in a non-sheet passing region in the fixing roller (heating medium). A technique of providing a magnetic flux shielding member that shields a part of magnetic flux generated from magnetic flux excitation means (induction coil) is disclosed.
Specifically, the magnetic flux shielding member changes its position in accordance with the sheet passing area of the fixing roller made of magnetic metal, thereby changing the range of shielding the magnetic flux. This technique aims to prevent the excessive temperature rise in the non-sheet passing area by shielding the magnetic flux reaching the fixing roller in the non-sheet passing area.

Japanese Patent Application Laid-Open No. H10-228959 and the like disclose a fixing device using an electromagnetic induction heating method, and is intended to prevent the bearing from deteriorating due to the shaft core of the fixing roller (heating roller) being heated. -A technology is disclosed in which the heat generating layer of the first layer is composed of a first heat generating layer made of a magnetic material and a second heat generating layer made of a nonmagnetic material.
Specifically, the first heat generating layer is formed such that its specific resistance is higher than that of the second heat generating layer and its thickness is thicker than that of the second heat generating layer. In this technique, the second heat generating layer made of a nonmagnetic material is used as a main heat generating layer, and the first heat generating layer made of a magnetic material is provided so that the magnetic flux generated from the magnetic flux exciting means does not reach the axis of the fixing roller. To do.

In the conventional fixing device described above, it is difficult to prevent an excessive temperature increase at both ends in the width direction of the heat generating member without reducing the temperature increasing efficiency of the heat generating member. Details are as follows.
A general image forming apparatus is configured to form an image on several types of recording media having different sizes in the width direction. Here, the recording media having different sizes in the width direction include recording media of irregular sizes in addition to recording media of various regular sizes in the A and B rows of JIS dimensions. Even if the recording medium has the same size (for example, A4 size), the width when the longitudinal direction is the transport direction and when the short direction (the direction perpendicular to the longitudinal direction) is the transport direction This means that recording media with different directional sizes are handled.

  When fixing such a recording medium having a different size in the width direction with the fixing device, the temperature distribution in the width direction of the fixing member (fixing belt or fixing roller) varies according to the width direction size of the recording medium, Temperature unevenness may occur. For example, when a recording medium having a small width direction size is passed and fixed, a large amount of heat is taken away in the sheet passing area of the fixing member corresponding to the width direction size of the recording medium, and the non-continuous area. The fixing temperature is lower than that. Such a phenomenon becomes particularly prominent when a recording medium having a small size in the width direction is continuously fed. In addition, in an electromagnetic induction heating type fixing device having a quick start-up time, excessive temperature rise at both ends in the width direction is particularly remarkable.

  Therefore, when trying to control the fixing temperature in the entire width direction of the fixing member with reference to the fixing temperature in the center portion in the width direction of the fixing member, the fixing temperature in the center portion in the width direction of the fixing member can be controlled to a desired temperature. The fixing temperature at both ends in the direction will increase. In this way, when a recording medium having a large width direction is fixed in a state where the fixing temperature at both ends in the width direction of the fixing member is increased, a hot offset occurs on the recording medium corresponding to the temperature increase position. Furthermore, when the fixing temperature at both ends in the width direction exceeds the heat resistance temperature of the fixing member, it may be considered that the fixing member is thermally damaged.

  On the other hand, if it is attempted to control the fixing temperature in the entire width direction of the fixing member with reference to the fixing temperature at both ends in the width direction of the fixing member, the fixing temperature at both ends in the width direction of the fixing member can be controlled to a desired temperature. However, the fixing temperature at the center in the width direction is lowered. As described above, when the recording medium is fixed in a state where the fixing temperature in the central portion in the width direction of the fixing member is lowered, fixing failure or cold offset occurs on the recording medium corresponding to the temperature lowered position.

In order to solve such a problem, in Patent Document 3, etc., the magnetic flux in the non-sheet passing region is shielded by changing the position of the magnetic flux shielding member in accordance with the size of the recording medium. Thereby, even when a recording medium having a small width direction size is continuously operated, an effect of suppressing an excessive temperature increase in the non-rotating region can be expected to some extent.
However, the technique disclosed in Patent Document 3 cannot place the magnetic flux excitation means close to the fixing member because the magnetic flux shielding member is interposed between the magnetic flux excitation means and the fixing member (heating medium). Therefore, the temperature raising efficiency of the fixing member that is induction-heated by the magnetic flux exciting means cannot be sufficiently improved. Specifically, the startup time of the fixing member could not be shortened sufficiently.

On the other hand, in the technique of Patent Document 4 and the like, the heat generating layer of the fixing member is made of a first heat generating layer made of a magnetic material and a non-magnetic material in order to prevent the shaft core of the fixing member (fixing roller) from being heated. It is composed of the second heat generating layer, and an effect of preventing excessive temperature rise at both ends in the width direction of the fixing member cannot be expected.
Here, in Patent Document 4, in order to install the magnetic flux shielding member of Patent Document 3 in order to prevent excessive temperature rise at both ends in the width direction of the fixing member, the magnetic flux is fixed between the fixing member and the magnetic flux exciting means. A shielding member is interposed. Accordingly, in this case as well, similarly to Patent Document 3, the magnetic flux exciting means cannot be brought close to the heat generating member, and the temperature raising efficiency of the fixing member cannot be sufficiently improved.

In view of this, there has been proposed a fixing device configured to solve the above-described problems and to obtain an effect of improving the temperature raising efficiency of the fixing member and preventing an excessive temperature rise at both ends in the width direction of the fixing member (for example, Patent Document 5).
FIG. 6 shows an example. This fixing device includes a sleeve-like heating roller 101 as a heat generating member constituting a fixing member, and an inner core (made of a magnetic material disposed in the heating roller 101). For example, a ferrite roller 102, a magnetic flux shielding member 103, a fixing roller 106, a fixing belt 100 stretched by the heating roller 101 and the fixing roller 106, and a magnetic flux facing the heating roller 101 via the fixing belt 100. Excitation means 104, 105, a pressure roller 107 that contacts the fixing roller 106 via the fixing belt 100, an auxiliary heating halogen heater 108 provided inside the pressure roller 107, an inlet guide 109, etc. is doing. The magnetic flux exciting means is composed of a coil (induction coil) 105 extending in the width direction (direction orthogonal to the conveyance direction of the recording medium P), a core 104 (coil core), and the like. 104a and a side core 104b are provided.

  In this fixing device, since the core (ferrite roller) 102 is provided inside the heating roller 101, the heating roller 101 is efficiently heated at a position where the magnetic flux excitation means 104 and the internal core (ferrite roller) 102 face each other, and fixing. The belt 100 is heated. That is, when a high-frequency alternating current is passed through the coil 105 of the magnetic flux exciting means 104, magnetic lines of force are formed between the core of the magnetic flux exciting means 104 and the inner core 102 in the heating roller 101, and an eddy current is generated on the surface of the heating roller. Joule heat is generated by the electrical resistance of the heating roller itself, and the heating roller 101 and the fixing belt 100 wound around the heating roller are efficiently heated by the Joule heat. On the other hand, the magnetic flux shielding member 103 provided in the heating roller is configured so that the range of shielding the peripheral surface of the inner core 102 can be varied. By adjusting the shielding range of the core 102, the range in the width direction of the magnetic force lines passing through the heating roller 101 is also adjusted, and the heating range in the width direction of the heating roller and the fixing belt is varied.

  In the configuration shown in FIG. 6, the magnetic flux exciting means 104 is disposed outside the heating roller 101, and the inner core 102 for magnetizing and the magnetic flux shielding member 103 are provided inside the heating roller 101. And an effect of preventing excessive temperature rise at both ends in the width direction.

FIG. 7 shows another configuration example of the fixing device that can obtain the same effect as described above. This fixing device has a cylindrical fixing sleeve 110 made of a magnetic heat generating member and a pressure roller 115. Inside the fixing sleeve 110, a magnetic flux excitation means made up of a core 111 and an induction coil 112 is provided. The magnetic flux shielding member 113 and the outer core 114 are provided on the outside.
In this configuration, the magnetic flux excitation means including the core 111 and the induction coil 112 is arranged inside the fixing sleeve 110, and the external core is arranged outside the fixing sleeve 110, thereby confining and raising the magnetic circuit of the induced magnetic field. The temperature efficiency can be increased. Further, since the magnetic flux shielding member 113 is provided between the fixing sleeve and the outer core, it is possible to prevent excessive temperature rise at both ends in the width direction. In addition, by using the fixing sleeve 110 that can be elastically deformed, the fixing nip can be easily formed by pressing the pressure roller 115.

Further, FIG. 8 shows another configuration example of the fixing device that can obtain the same effect as described above. The fixing device includes a fixing roller 120 having a cylindrical cored bar, an elastic heat insulating layer made of a foam material, and a magnetic heating layer, and a pressure roller 125 is pressed against the fixing roller 120. A magnetic flux excitation means 123 is disposed outside the fixing roller 120. In addition, an inner core 121 made of a magnetic material and a magnetic flux shielding member 122 are provided inside the cored bar of the fixing roller 120.
In this configuration, the magnetic flux exciting means 123 is disposed outside the fixing roller 120, and the inner core 121 and the magnetic flux shielding member 122 are provided inside the cored bar of the fixing roller 120. Therefore, as in FIG. And an effect of preventing excessive temperature rise at both ends in the width direction. Further, by providing the magnetic heat generating layer on the elastic heat insulating layer and arranging the magnetic flux exciting means 123 outside the fixing roller 120, the heat generating member surface layer side generates heat, and the heat generating member has a low heat capacity for a short time. It is possible to start at.

JP-A-9-218601 JP-A-2005-70376 Japanese Patent Laid-Open No. 10-74009 Reissue WO2003 / 43379 JP 2005-241891 A

  In the fixing device having the structure as shown in FIGS. 6 to 8, ferrite or the like is placed at a position facing the magnetic flux excitation means with a fixing rotating body (sleeve, belt, roller, etc. having a heat generating member) constituting the fixing member interposed therebetween. Since the inner core or the outer core made of the high magnetic permeability material is arranged, a line of magnetic force is formed between the core of the magnetic flux exciting means and the magnetic shunt core, so that the temperature raising efficiency can be improved. . Also, a magnetic flux shielding member is variably provided between the fixing rotator and the inner core or the outer core, and by adjusting the shielding range, the width direction range of the magnetic flux passing through the fixing rotator is also adjusted. The heating range in the width direction of the rotating body can be varied.

  However, in the configuration in which the inner core and the outer core made of a high permeability material such as ferrite are provided separately from the core of the magnetic flux exciting means as described above, the number of parts of the fixing device increases and the cost increases. Further, in the configuration in which the core and the magnetic flux shielding member are provided inside the fixing rotator, since heat is taken away by the core and the magnetic flux shielding member, the heat capacity as the fixing member is increased and the rise of temperature is delayed. Further, in the configuration in which the shielding range is adjusted by moving the magnetic flux shielding member, a mechanism for moving the magnetic flux shielding member is required, which further increases the manufacturing cost of the fixing device.

  The present invention has been made in view of the above circumstances. By providing the fixing rotating body with a magnetic shunt function for controlling the transmission of magnetic flux, a low heat capacity can be realized while forming a nip width necessary for fixing. A fixing member having a simple structure and a low cost, capable of reliably preventing overheating at both ends in the width direction without lowering the temperature raising efficiency, a fixing device including the fixing member, and the fixing thereof An object of the present invention is to provide an image forming apparatus including the apparatus.

In order to achieve the above object, the present invention employs the following technical means.
The first means of the present invention is a fixing member that forms a fixing nip opposite to the pressure member and is electromagnetically heated by magnetic flux excitation means, and has a Curie point of 100 ° C. to 300 ° C. A cylindrical or belt-shaped fixing rotator, and a member having a lower resistivity than the magnetic layer disposed separately at a position facing the magnetic flux exciting means across the fixing rotator. Features.
According to a second means of the present invention, in the fixing member of the first means, the member having a low resistivity is a plate-like member (low resistance plate-like member).

According to a third means of the present invention, in the fixing member of the first or second means, the fixing rotator has an induction heating layer having a low resistance.
According to a fourth means of the present invention, in the fixing member of any one of the first to third means, the magnetic layer has a magnetic shunt function for controlling transmission of magnetic flux according to temperature. To do.
Further, according to a fifth means of the present invention, in the fixing member of any one of the first to fourth means, the cross-sectional shape of the low resistivity member (for example, a low resistance plate-like member) is the same as that of the fixing rotating body. It is characterized by an arc shape along the curvature.

Sixth means of the present invention, in the fixing member of the first to fifth any one means, the volume resistivity of the low resistivity member (for example, low-resistance plate member) is 5.0 × 10 ^{- 8} Ω · m or less.
According to a seventh means of the present invention, in the fixing member of any one of the third to sixth means, the induction heating layer of the fixing rotator has a volume resistivity of 5.0 × 10 ⁻⁸ Ω · m. It is characterized by the following.
Further, an eighth means of the present invention is characterized in that, in the fixing member of the sixth means, the low resistivity member (for example, a low resistance plate-like member) is made of a nonmagnetic metal or alloy.
The ninth means of the present invention is characterized in that, in the fixing member of the seventh means, the induction heating layer of the fixing rotating body is made of a nonmagnetic metal or alloy.

According to a tenth means of the present invention, in the fixing member of any one of the first to ninth means, the thickness of the magnetic layer is 100 μm or less.
According to an eleventh means of the present invention, in the fixing member of any one of the third to tenth means, the thickness of the induction heating layer is 50 μm or less.
Further, a twelfth means of the present invention is the fixing member of any one of the first to eleventh means, wherein the fixing rotator is separated from an elastic layer and a release layer on the magnetic layer or the induction heating layer. It has a layer.

According to a thirteenth means of the present invention, in the fixing member of any one of the first to twelfth means, the thickness of the low-resistivity member (for example, a low-resistance plate-like member) is not less than the penetration depth of the magnetic flux and 2 mm. It is characterized as follows.
According to a fourteenth means of the present invention, in the fixing member of any one of the first to thirteenth means, the member having a low resistivity in the rotation direction of the fixing rotating body (for example, a low resistance plate-like member). The width is the heating width of the fixing rotator.
The fifteenth means of the present invention is the fixing member of any one of the first to fourteenth means, wherein the distance between the magnetic layer and the low resistivity member (for example, a low resistance plate-like member) is 5 mm. It is characterized as follows.

According to a sixteenth means of the present invention, in the fixing member of any one of the first to fifteenth means, a heat insulating member is provided between the low resistivity member (for example, a low resistance plate member) and the fixing rotating body. It is provided.
According to a seventeenth means of the present invention, in the fixing member of any one of the first to sixteenth means, the member having a low resistivity in the rotation direction of the fixing rotator (for example, a low resistance plate member). The width is changed in the axial direction.

According to an eighteenth means of the present invention, in the fixing member of any one of the first to seventeenth means, a nip forming member made of a heat insulating material capable of elastic deformation is provided in the fixing rotating body. .
According to a nineteenth means of the present invention, in the fixing member of the eighteenth means, the nip forming member is a roller-like member provided rotatably.
According to a twentieth means of the present invention, in the fixing device of the eighteenth means, the nip forming member is a pad-like member.

The twenty-first means of the present invention is characterized in that, in the fixing member of any one of the first to twentieth means, a lubricant is applied to the inner peripheral surface of the fixing rotating body.
According to a twenty-second means of the present invention, in the fixing member of any one of the eighteenth to twenty-first means, the fixing rotating body is a fixing sleeve capable of elastic deformation supported by the nip forming member. It is characterized by that.
Further, according to a twenty-third means of the present invention, in the fixing member of any one of the eighteenth to twenty-first means, the fixing rotator includes the low-resistivity member (for example, a low-resistance plate member) and the nip formation. The fixing belt is a flexible fixing belt supported by a member.

  A twenty-fourth means of the present invention comprises a magnetic flux exciting means, a fixing member that is electromagnetically heated by the magnetic flux exciting means, and a pressure member that is in pressure contact with the fixing member. In a fixing device for heating and pressurizing a recording medium carrying an unfixed image at a fixing nip between the two and fixing the unfixed image on the recording medium, any one of the first to twenty-third means is used as the fixing member The fixing member is provided.

According to a twenty-fifth means of the present invention, in the fixing device of the twenty-fourth means, the pressure member is disposed to face a nip forming member provided in a fixing rotating body of the fixing member, and the pressure member The fixing rotator is pressed against the nip forming member to form a fixing nip.
According to a twenty-sixth aspect of the present invention, in the fixing device according to the twenty-fifth aspect, the nip forming member is made of an elastic material that is softer than the pressure member, and the fixing rotator is concave on the fixing rotator side. It has a shape.

According to a twenty-seventh means of the present invention, in the fixing device according to any one of the twenty-fourth to the twenty-sixth means, the pressure member is a pressure roller.
According to a twenty-eighth means of the present invention, in the fixing device of the twenty-seventh means, the pressure roller has a driving means.

  The twenty-ninth means of the present invention comprises means for forming an image on an image carrier, means for transferring an image on the image carrier to a recording medium, and means for fixing the image transferred to the recording medium. The image forming apparatus includes a fixing device of any one of 24th to 28th means as the fixing means.

  In the present invention, a fixing member that forms a fixing nip opposite to the pressing member and that is electromagnetically heated by magnetic flux excitation means is a cylindrical or belt-like member having a magnetic layer with a Curie point of 100 ° C. to 300 ° C. And a member having a lower resistivity than the magnetic layer (for example, a low-resistance plate-like member) disposed separately at a position facing the magnetic flux exciting means across the fixing rotator. Therefore, the magnetic layer becomes a magnetic material (ferromagnetic material) at a temperature below the Curie point, and becomes a non-magnetic material (paramagnetic material or diamagnetic material) at a temperature above the Curie point. It has a magnetic shunt function that controls transmission. As a result, when the temperature of the fixing rotator is lower than the Curie point, the effect of confining the magnetic flux in the fixing rotator promotes the temperature rise due to the induced current. As a result, a member having a low resistivity (for example, a low resistance plate-like member) is reached, the generation of an induced current in the fixing rotating body is suppressed, and the temperature rise is stopped. As described above, the fixing member of the present invention has a self-temperature control function by a combination of the fixing rotator and a member having a lower resistivity than the magnetic layer (for example, a low-resistance plate-like member). Depending on the setting, the temperature rise temperature of the fixing rotator can be controlled to a predetermined temperature, and an excessive temperature rise at both ends in the width direction can be reliably prevented without lowering the temperature rise efficiency. Further, since the self-temperature control function can be obtained without providing the inner core and the magnetic flux shielding member as in the prior art, a low-cost fixing member can be realized with a simple configuration. Furthermore, in the fixing member of the present invention, in addition to the above-described configuration, by providing a low resistance induction heat generating layer on the fixing rotating body, high frequency induction by inverter control can be performed, and the heat generation efficiency is further improved and the start-up is improved. Rapid temperature rise can be performed.

The fixing device of the present invention includes a magnetic flux exciting means, a fixing member that is electromagnetically heated by the magnetic flux exciting means, and a pressure member that is in pressure contact with the fixing member. The fixing member has the above-described configuration and effects. Using a fixing member realizes a low-cost fixing device that can quickly raise the temperature and reliably prevent overheating at both ends in the width direction without lowering the heating efficiency. can do.
In addition, a nip forming member is provided in a cylindrical or belt-shaped fixing rotator of the fixing member, and a fixing nip is formed by pressurizing the fixing rotator toward the nip forming member with the pressure member, thereby providing a sufficient nip width. And fixing ability can be improved.

  The image forming apparatus of the present invention includes a low-cost fixing device that can perform a rapid temperature rise and reliably prevent an excessive temperature rise at both ends in the width direction without reducing the temperature raising efficiency. Accordingly, it is possible to realize an image forming apparatus that can obtain an energy saving effect at a low cost and has a good fixing property.

Hereinafter, the best mode for carrying out the present invention will be described in detail with reference to the drawings.
First, the basic principle of the magnetic shunt function of the fixing member according to the present invention and the self-temperature control function of the fixing device using the same will be described.

  In the electromagnetic induction heating type fixing device, a magnetic material layer is provided on a fixing rotating body (sleeve, belt, roller) serving as a heat generating member, and the magnetic material layer has a Curie point adjusted to 100 ° C. to 300 ° C. For example, an excessive temperature rise can be prevented by using a magnetic shunt alloy such as Fe—Ni or Cu—Ni. That is, the magnetic shunt alloy such as Fe-Ni and Cu-Ni can easily adjust the temperature of the Curie point by changing the composition ratio, and prevents the excessive temperature rise by setting the upper limit of the temperature rise temperature. can do. The ferromagnetic material used for the magnetic layer is not limited to the magnetic shunt alloy described above, and other magnetic shunt alloys may be used as long as the Curie point is 100 ° C. to 300 ° C.

In a magnetic shunt alloy having a Curie point adjusted to 100 ° C. to 300 ° C., a magnetic state (ferromagnetic material) when the temperature is lower than the Curie point, or a nonmagnetic state (paramagnetic or antimagnetic) when the temperature is higher than the Curie point. The self-temperature control function can be demonstrated by the transition of physical properties to (magnetic).
FIG. 9 schematically shows the magnetic shunt function when the fixing member is composed of three layers of an induction heating layer composed of a thin copper (Cu) layer, a magnetic layer composed of a magnetic shunt alloy, and a low resistance member (for example, aluminum (Al)). FIG. As shown in mode 1 of FIG. 9, when the temperature is equal to or lower than the Curie point and the magnetic shunt alloy is in a magnetic state, the magnetic flux from the coil does not pass beyond the penetration depth in the magnetic state, and the Cu thin layer Heat generation mainly occurs on the surface of the induction heating layer.
This is because when the magnetic shunt alloy is in a magnetic state, heat is generated by the eddy current load of the heat generating layer. However, as shown in mode 2 of FIG. 9, when the temperature becomes the Curie point or higher and the magnetic shunt alloy becomes a non-magnetic body. The magnetic flux from the coil passes through the magnetic layer and passes to the Al layer, and Al, which is a good conductor, enters the magnetic circuit, so that the load becomes less than the optimum value and the input power is reduced and the heat generation stops. This stops the heating of the heat generating layer. The above is the principle of the self-temperature control function.

Here, the skin depth (penetration depth) δ is:
δ = k (ρ / fμ) ^1/2
(K: constant, ρ: resistivity, μ: relative permeability, f: frequency)
In the magnetic material state with high magnetic permeability, the penetration depth of the magnetic flux is shallower than that in the non-magnetic material state.
The eddy current load d is
d = volume resistivity of heating layer / δ
Defined by
However, when the thickness of the heat generating layer (= t) is less than the penetration depth of the magnetic flux, the eddy current load d is
d = volume resistivity of heat generation layer / t
Defined by

By utilizing the above self-temperature control function for the fixing rotator (fixing sleeve, fixing belt or fixing roller), the problem of the end temperature rise when the fixing rotator having a small heat capacity is used can be solved.
As described above, the problem of the temperature rise at the edge portion is that the temperature at the paper entry part is taken away by the paper when passing small size paper, but the heat quantity is not taken away from the outside of the paper. When power is applied so as to maintain the temperature, the temperature at the end portion is extremely increased as compared with the central portion. For this reason, when the end temperature becomes excessively high, it is necessary to stop the paper feeding until the temperature becomes the same as that in the center, which impairs convenience. If this is not done, a hot offset image is generated, and the image quality cannot be compensated.
However, by using a fixing member that combines a fixing rotating body using a magnetic shunt alloy and a low-resistance good conductor (for example, Al) as described above, when the end temperature is excessive, the magnetic shunt is Since the alloy changes its state at the Curie point and the load is not appropriate, power is not applied to the end portion, and the problem of the end temperature rise can be solved.

  Here, FIG. 10 is a view showing an example of a fixing device using a fixing member in which a magnetic shunt alloy and a low-resistance good conductor (for example, Al) are combined, (a) is a schematic configuration diagram of the fixing device, and (b). FIG. 4 is a diagram illustrating a layer configuration of a fixing member. The fixing member shown in FIG. 10 has a configuration in which a fixing sleeve 131 having a magnetic shunt alloy and a Cu induction heating layer is provided on the outer periphery of a fixing roller 132 made of a core metal and foamed rubber. A pressure roller 133 is provided in pressure contact. The outer periphery of the fixing sleeve 131 is provided with a magnetic flux exciting means including an induction coil 134 and a core 133 connected to the inverter control circuit 135, and the Cu induction heating layer of the fixing sleeve 131 is generated by the magnetic flux from the magnetic flux exciting means. Is induction heated. In the fixing device having such a configuration, the self-temperature control function as shown in FIG. 9 is exhibited by making the core of the fixing roller 132 aluminum (Al), which is a low resistance member.

  However, in order to use this magnetic shunt alloy as the magnetic layer of the fixing sleeve 131, it is necessary to secure a nip width necessary for image fixing by a pressure member 133 facing the so-called fixing sleeve 131. Moderate flexibility is required.

Therefore, in order to obtain efficient heat generation, the present inventors have added a metal having a volume resistivity of 5.0 × 10 ⁻⁸ Ω · m or less as a heat generation layer in addition to a magnetic layer (magnetism control alloy) (see FIG. 10, a Cu induction heating layer of the fixing sleeve 131 is used. However, since it is necessary to give the fixing sleeve 131 appropriate flexibility, a thin layer of 100 μm is used as the magnetic shunt alloy layer, and the heating layer also has a volume resistivity. A metal of 5.0 × 10 ⁻⁸ Ω · m or less is used in a thickness of 50 μm or less.

  Accordingly, since the penetration depth above the Curie point is large, the magnetic flux passes through the Al cored bar of the fixing roller 132 and the self-temperature control function is exhibited. In addition to this, it is not necessary to provide an internal core (ferrite roller or the like) as shown in the prior art which is disposed in the cored bar separately from the fixing roller 132, so that the heat capacity of the fixing member can be reduced. Plays.

  On the other hand, not only the flexibility of the fixing sleeve 131 is sufficient to give the nip width at the pressure contact portion with the pressure member 133, but also a nip forming member having an appropriate elasticity in the fixing sleeve 131 (the fixing roller in FIG. 10). 132), and the fixing sleeve 131 having the magnetic shunt alloy layer is sandwiched between the pressing member 136 and the nip width needs to be formed.

  However, in order to fully exhibit the self-temperature control function of the magnetic shunt alloy, it is desirable that the gap between the magnetic shunt alloy layer and the Al core metal be 7 mm or less so that the magnetic flux reaches the Al core metal of the fixing roller. This limits the thickness of the elastic body, making it difficult to form the fixing nip width. That is, as shown in FIG. 11, when the thickness of the foam rubber constituting the fixing roller 132 is reduced to 5 mm, the magnetic flux passes through the Al cored bar and the self-temperature control function is exhibited. Becomes thinner and it becomes difficult to form a nip width. In addition, as shown in FIG. 12, when the thickness of the foamed rubber of the fixing roller 132 is increased to 10 mm, the nip width can be easily formed, but the magnetic flux hardly reaches the Al core metal, and the self-temperature control function Cannot be fully exerted.

Here, the heat generation amount below the Curie point is W1, the heat generation amount above the Curie point is W2, and the heat generation suppression rate is
(W1-W2) / W1 × 100 [%]
If defined as, the self-temperature control function depends on the distance between the magnetic shunt alloy and the low-resistance member (Al cored bar) (magnetic shunt alloy-Al gap). The rate is required to be 45%, and as shown in the graph of FIG. 13, the distance between the heat generating layer and the low resistance member (Al cored bar) is about 7 mm. Therefore, it is difficult to secure the fixing nip width in the configuration in which the cored bar of the fixing roller 132 as shown in FIG. 10 is used as a low resistance member for obtaining a self-temperature control function.

Accordingly, in consideration of the above points, the present invention realizes a low heat capacity while forming a nip width necessary for fixing, and a fixing member having a configuration capable of sufficiently exhibiting a self-temperature control function using a magnetic shunt alloy. And a fixing device having the fixing member has been developed.
That is, in the present invention, the fixing member that forms a fixing nip opposite to the pressure member and that is electromagnetically heated by the magnetic flux exciting means is a cylindrical member having a magnetic layer with a Curie point of 100 ° C. to 300 ° C. A belt-like fixing rotator and a member having a lower resistivity than the magnetic layer disposed separately at a position facing the magnetic flux excitation means across the fixing rotator are provided. More specifically, in the present invention, a cylindrical fixing sleeve having a magnetic layer or a belt-like fixing belt is used as the fixing rotating body, and the position facing the magnetic flux excitation means with the fixing sleeve or fixing belt interposed therebetween. In addition, a member having a lower resistivity than the magnetic layer (for example, a low-resistance plate-like member (hereinafter referred to as a low-resistance plate-like member)) is disposed separately. As a result, the distance between the low-resistance plate-like member and the magnetic layer (magnetic shunt alloy) can be set to a distance (for example, 5 mm or less) at which the self-temperature control function can be reliably exhibited.
In addition to the low resistance plate-like member, if a nip forming member is provided in the fixing sleeve or fixing belt so as to face the pressure member and sandwich the fixing sleeve or fixing belt, the nip width necessary for fixing can be secured. can do.

  Hereinafter, a specific example of a fixing member according to the present invention, a fixing device using the fixing member, and an image forming apparatus including the fixing device will be described.

1A and 1B are explanatory views of the configuration of a fixing device according to an embodiment of the present invention. FIG. 1A is a sectional view showing a schematic configuration of the fixing device, and FIG. 1B is a diagram showing the fixing device shown in FIG. 3 is a schematic cross-sectional view of a main part showing a layer configuration of a portion A surrounded by a dotted line of a fixing member 20 to be configured. FIG.
As shown in FIG. 1, the fixing device 19 of this embodiment includes an induction heating unit 24 as a magnetic flux exciting unit, a fixing member 20 that is electromagnetically heated by the induction heating unit 24, and a pressure that presses the fixing member 20. A member 30 is provided.

  The induction heating unit 24 as a magnetic flux excitation unit includes a core unit 25 (coil core) and a coil unit 26 (induction coil). The coil portion 26 is formed by winding a litz wire in which fine wires are bundled around a core portion 25 (or a coil guide (not shown)) disposed so as to cover a part of the outer periphery of the fixing member 20, in the width direction of the fixing member (FIG. 1). In the direction perpendicular to the paper surface). The core portion 25 is made of a ferromagnetic material (for example, a ferrite having a relative permeability of about 1000 to 3000), and is formed with a center core 25a and a side core in order to form an efficient magnetic flux toward the fixing rotating body 21 of the fixing member 20. 26b is provided. Moreover, the core part 25 is installed so that the coil part 25 extended in the width direction may be opposed.

  The fixing member 20 is separately disposed at a position facing the induction heating unit 24 with the fixing rotating body 21 sandwiched between the cylindrical fixing rotating body 21 having a magnetic layer 21d having a Curie point of 100 ° C. to 300 ° C. And a member (for example, a low resistance plate-like member) 22 having a lower resistivity than the magnetic layer. Further, a nip forming member 23 that is rotatable in a roller shape is provided in the fixing rotator 21 at a position facing the pressing member 30, and the nip forming member 23 and the pressing member 30 are connected to the fixing rotator. The fixing nip is formed by press-contacting 21.

  Here, the cylindrical fixing rotating body 21 is a fixing sleeve that can be elastically deformed. For example, as shown in FIG. 1B, the magnetic layer 21d, the low-resistance induction heating layer 21c, the elastic layer 21b, the separation layer, and the like. It is formed by stacking four layers of the mold layer 21a. In this embodiment, a four-layer structure is used, but a three-layer structure in which the induction heat generation layer is omitted may be used. In this case, the magnetic layer 21d also serves as the induction heat generation layer. However, by providing the low-resistance induction heating layer 21a made of a non-magnetic material, it is possible to improve the heating efficiency by using a high-frequency inverter control circuit (frequency 10 kHz to 1 MHz) for the induction heating unit 24. It is preferable to provide a resistance induction heating layer 21c.

The magnetic layer 21d of the fixing sleeve 21 is a layer made of a magnetic shunt alloy such as Fe—Ni or Cu—Ni having a Curie point of 100 ° C. to 300 ° C., for example, and has a thickness of 100 μm or less. Here, as an example, the thickness of the magnetic layer is 50 μm.
The induction heating layer 21c is made of, for example, a nonmagnetic metal or alloy having a volume resistivity of 5.0 × 10 ⁻⁸ Ω · m or less, and has a thickness of 50 μm or less. Here, as an example, an induction heating layer made of a nonmagnetic material copper (Cu) and having a thickness of 15 μm is used, but other metals and alloys may be used as long as they are good conductors.
The elastic layer 21b is made of an elastic material that also serves as the base material of the fixing sleeve 21, and as an example, is formed of silicone rubber (Si rubber) having a thickness of 200 μm.
The release layer 21a is formed of a fluorine compound such as PFA (tetrafluoroperfluoroalkyl vinyl ether resin), and has a thickness of 30 μm. The release layer 21a is for enhancing the toner release property on the surface of the fixing sleeve 21 with which the toner image (toner) T on the recording medium P is in direct contact.

As described above, the base material of the fixing sleeve 21 is composed of an elastic layer 21b such as silicone rubber (Si rubber), and an induction heating layer 21c and a magnetic layer 21d are formed on one surface thereof by plating, sputtering, vapor deposition, etc. By setting the thickness of the magnetic layer 21d to 100 μm or less and the thickness of the induction heating layer 21c to 50 μm or less, the fixing sleeve 21 can be provided with the flexibility necessary for forming the nip.
This flexibility is mainly considered by bending rigidity. When the induction heating layer 21c made of metal is used for the fixing sleeve 21, the fixing sleeve 21 is thinned so that the moment of inertia of the cross section is reduced by the cube of the thickness. By doing so, the mechanical strength (bending rigidity) is lowered and flexibility is given.
The bending stiffness is
Flexural rigidity = E x I
(E: Young's modulus, I: secondary moment of section)
Defined by

The low resistance plate-like member 22 disposed separately at a position facing the induction heating unit 24 across the fixing sleeve 21 has a longitudinal direction in the width direction of the fixing member 20 (axial direction perpendicular to the paper surface of FIG. 1). It is extended and installed. The cross-sectional shape of the low resistance plate-like member 22 is an arc shape along the curvature of the fixing sleeve 21, and the magnetic body of the fixing sleeve 21 is caused by a sudden change in the curvature at the end of the plate-like member. This prevents the metal and alloy constituting the layer 21d and the induction heating layer 21c from being broken. The volume resistivity of the low resistance plate-like member 22 is 5.0 × 10 ⁻⁸ Ω · m or less, and a nonmagnetic metal or alloy plate (for example, an aluminum (Al) plate, a copper (Cu) plate, etc.) ) 22b.

  The thickness of the plate material 21b of the low resistance plate-like member 22 is not less than the penetration depth of magnetic flux and not more than 2 mm, and is 1.5 mm in the example of FIG. In order to achieve sufficient self-temperature control by the low resistance plate-like member 22, the thickness of the plate material 22b made of metal or alloy needs to be equal to or greater than the penetration depth of the plate material. However, from the viewpoint of rigidity that satisfies the low heat capacity of the fixing member 20, the thickness is preferably 2 mm or less.

  Further, the width of the low resistance plate-like member 22 in the rotation direction of the fixing sleeve 21 is the heating width of the heat generation layer of the fixing sleeve 21 (a width obtained by combining the ranges of arrows B (heat generation range) on both sides with the center core 25a interposed). It is said. This heating width is approximately the coil width. If the low resistance plate-like member 21 is disposed within this width, the self-temperature control function is sufficiently exhibited. Moreover, it is not preferable to make it more than this from a viewpoint of low heat capacity.

  In the fixing member 20 of the present embodiment, the low resistance plate-like member 22 is arranged separately from the nip forming member 23 at a position facing the induction heating unit 24, so that it is close to the fixing sleeve 21. Thus, it is easy to dispose the low-resistance plate-like member 22, and the distance between the magnetic layer 21d of the fixing sleeve 21 and the low-resistance plate-like member 22 can be easily reduced to 10 mm or less, and the fixing member 20 can be set to a distance (gap between the magnetic layer 21d and the low resistance plate-like member 22: 5 mm or less) for reliably exhibiting the self-temperature control function.

  Further, in the fixing member 20 of the present embodiment, a heat insulating member 22 a is provided between the plate member 22 b constituting the low resistance plate-like member 22 and the fixing sleeve 21. As described above, the heat transfer from the fixing sleeve 21 to the low resistance plate-like member 22 is suppressed by restricting the low resistance plate material 22b from directly contacting the fixing sleeve 21 by the heat insulating member 22a. Thereby, a substantial reduction in heat capacity can be realized. The heat insulating member 22a is preferably a so-called foamed material or felt.

  By the way, when normal use of the fixing device 19 is considered, the sheet passing of the recording medium P is based on the center in the width direction of the fixing member 20 (axial direction perpendicular to the paper surface of FIG. 1), and thermistor, thermopile, etc. Since the temperature control point at which the temperature is detected by the temperature sensor is also based on the center in the width direction (axial direction), the temperature of the central portion of the fixing sleeve 21 does not increase excessively. For this reason, in the center of the fixing sleeve 21 in the width direction (axial direction) and in the sheet passing range of the corresponding minimum sheet width, the self-temperature control function for preventing excessive temperature rise is not so necessary. For this reason, the width of the low resistance plate-like member 22 in the rotation direction of the fixing sleeve 21 is desirably changed in cross-sectional shape in the axial direction of the fixing member in order to reduce the heat capacity. FIG. 2 is an explanatory diagram of the structure of the fixing member as an example. As shown in FIG. 2B, in the low resistance plate-like member 22 disposed on the inner peripheral side of the fixing sleeve 21 of the fixing member 20, The width of the low resistance plate material 22b in the fixing sleeve rotation direction is changed (narrowed) at the center in the width direction (axial direction) of the fixing sleeve 21. However, in order to integrally mold the low resistance plate-like member 22, it is not necessary to remove all the low resistance plate material 22b at the center in the width direction (axial direction) of the fixing sleeve 21, and the width is narrower than the coil width at the center. The low resistance plate material 22b may be left.

  In the fixing device 19 having the configuration shown in FIG. 1, a nip forming member 23 that is rotatable in a roller shape is provided in a fixing sleeve 21 of the fixing member 20 at a position facing the pressure member 30. The member 23 and the pressure member 30 are pressed against each other with the fixing sleeve 21 interposed therebetween to form a fixing nip. Further, by providing the nip forming member 23 for forming the fixing nip and the low resistance plate-like member 22 separately, a configuration for exhibiting the self-temperature control function and a configuration for forming the fixing nip. The heat capacity can be reduced while forming the nip width necessary for fixing, and it is possible to reliably prevent the excessive temperature rise at both ends in the width direction without lowering the temperature raising efficiency.

In the fixing device 19 having the configuration shown in FIG. 1, the nip forming member 23 has a two-layer configuration in which a heat insulating material 23b capable of elastic deformation in the form of a roller is provided around the core material 23a. It can be rotated around the center.
The pressure member 30 is a pressure roller having a metal core 30a and an elastic layer 30b formed of an elastic material such as silicone rubber. The pressure roller 30 is placed in the fixing sleeve 21 of the fixing member 20. It is arranged so as to face the provided nip forming member 23. Then, the fixing sleeve 21 is pressed against the nip forming member 23 by the pressure roller 30 to form a fixing nip. At this time, the heat insulating material 23b of the nip forming member 23 is made of an elastic material softer than the pressure roller 30 (for example, foamed material such as urethane rubber), and the fixing sleeve 21 side is recessed in the fixing nip portion. ing. As a result, the nip width necessary for fixing the toner image T on the recording medium P can be ensured.

  Next, a prototype experiment was conducted to evaluate the characteristics of the fixing device having the configuration of this embodiment. In this experimental example, the fixing sleeve 21 was formed by forming a Cu induction heating layer with a thickness of 10 μm in the center on a 35 μm thick magnetic layer made of Fe—Ni magnetic shunt alloy. Next, a low resistance plate member 22 having a thickness of 1.5 mm was formed using aluminum, and a heat insulating layer 22a of foam rubber having a thickness of 1 mm was disposed on the plate member 22b. Using the fixing sleeve 21 and the low-resistance plate-like member 22 manufactured as described above as the fixing member 20 of the fixing device 19 having the configuration shown in FIG. 1A, induction heating experiments were conducted to evaluate the characteristics. As a result, the heat generation suppression rate required for self-temperature control was 95% or more. Further, by arranging the roller-shaped nip forming member 23 in the fixing sleeve 21, a sufficient fixing nip width was successfully obtained.

  In the embodiment of the fixing device having the configuration shown in FIG. 1 described above, the nip forming member 23 is a two-layer roller, but may be a single-layer roller without the core 23a. Moreover, it is not limited to a roller shape, A pad-shaped member may be used for the nip forming member 23.

  Here, FIG. 3 is a schematic configuration diagram of a fixing device showing another embodiment of the present invention, in which the nip forming member 23 is configured by a pad-like member 27. The pad-like member 27 is made of a heat insulating material and is pressed toward the pressure roller 30 by a pressing member such as a spring to form a fixing nip. At this time, the pad-like member 27 of the nip forming member 23 is made of an elastic material softer than the pressure roller 30 (for example, foam material such as urethane rubber), and the fixing sleeve 21 side is recessed in the fixing nip portion. It has become. As a result, similarly to the configuration of FIG. 1, the nip width necessary for fixing the toner image T on the recording medium P can be ensured.

  By the way, in the fixing device having the configuration shown in FIG. 1, the driving means for rotating the fixing member 20 and the pressure roller 30 is provided on one of the roller-shaped nip forming member 23 and the pressure roller 30 and is driven by the driving means. One is rotated and the other is driven to rotate. At the time of fixing driving, the nip forming member 23 rotates clockwise, the pressure roller 30 rotates counterclockwise, and the fixing sleeve 21 rotates clockwise to fix the recording medium P carrying the toner image. The toner image is fixed on the recording medium P by being nipped and conveyed by the nip portion and heated by the fixing sleeve 21 heated by the induction heating portion 24 and pressure by the pressure roller 30.

  On the other hand, when the nip forming member 23 is constituted by the pad-like member 27 as in the fixing device having the configuration shown in FIG. 3, the pad-like member 27 cannot be rotated. The rotating driving means is provided only on the pressure roller 30 side, and the pressure roller 30 rotates counterclockwise. The fixing sleeve 21 is configured to rotate clockwise. During the fixing driving, the pressure roller 30 rotates counterclockwise, the fixing sleeve 21 rotates clockwise, and the recording medium P carrying the toner image is nipped and conveyed by the fixing nip portion, and the induction heating unit 24 is driven. The toner image is fixed on the recording medium P by the heating by the fixing sleeve 21 heated in step 1 and the pressure by the pressure roller 30.

  In the fixing device having the configuration shown in FIG. 1, the low resistance plate-like member 22 is separately fixed inside the fixing sleeve 21, but is brought close to the magnetic layer (magnetism alloy) of the fixing sleeve 21. Therefore, when the fixing sleeve 21 is rotated, the heat insulating member 22a provided on the low resistance plate-like member 22 and the inner peripheral surface of the fixing sleeve 21 come into contact with each other, and the fixing sleeve 21 is fatigued by friction during sliding. There is a possibility that the magnetic layer formed on the inner peripheral surface side of the rupture may break. In the fixing device having the configuration shown in FIG. 3, the nip forming member 23 is constituted by the pad-like member 27, and therefore, when the fixing sleeve 21 is rotated, the pad-like member 27 and the inner peripheral surface of the fixing sleeve 21 are in contact with each other. There is a possibility that the magnetic layer formed on the inner peripheral surface side of the fixing sleeve 21 may break due to fatigue due to friction. Therefore, in this embodiment, in order to solve such a problem, the lubricant is applied to the inner peripheral surface of the fixing sleeve 21.

  In the fixing device of the present embodiment, the sliding member is arranged in the fixing sleeve 21, and therefore fatigue due to friction occurs. However, by applying a lubricant, fatigue due to friction can be greatly reduced, and magnetic properties can be reduced. Problems such as breakage of the body layer can be reduced. As the lubricant, a lubricant typified by fluorine grease or silicone oil can be used as appropriate. In addition, the inner circumference of the fixing sleeve 21 is preliminarily soaked into the heat insulating member 22 a provided on the low resistance plate-like member 22 or the pad-like member 27 constituting the nip forming member 23. A lubricant can be easily applied to the surface.

Although one embodiment of the fixing member and the fixing device according to the present invention has been described above, the fixing rotating body constituting the fixing member 20 is not limited to the cylindrical fixing sleeve 21 as shown in FIGS. Alternatively, a fixing belt may be used.
FIG. 4 shows an embodiment of the invention, and is a schematic configuration diagram of a fixing device using a fixing belt as a fixing rotating body. In the fixing device shown in FIG. 4, the configuration of the induction heating unit 24 that is a magnetic flux exciting unit and the pressure roller 30 that is a pressure member are the same as those of the fixing device of FIG. The fixing rotator is composed of a flexible fixing belt 28 supported by a low resistance plate-like member 22 and a nip forming member 23.

The layer structure of the fixing belt 28 is the same as that shown in FIG. 1B, for example, and is formed by laminating four layers: a magnetic layer, a low-resistance induction heating layer, an elastic layer, and a release layer. The magnetic layer of the fixing belt 28 is a layer made of a magnetic shunt alloy such as Fe—Ni or Cu—Ni having a Curie point of 100 ° C. to 300 ° C., for example, and has a thickness of 100 μm or less. The induction heating layer is made of, for example, a nonmagnetic metal or alloy having a volume resistivity of 5.0 × 10 ⁻⁸ Ω · m or less, and has a thickness of 50 μm or less. Here, as an example, a thin layer of copper (Cu), which is a nonmagnetic material, is an induction heating layer formed by plating, sputtering, vapor deposition, or the like, but other metals or alloys may be used as long as they are good conductors.
The elastic layer is formed of an elastic material such as silicone rubber (Si rubber) that also serves as the base material of the fixing belt 28, and has a thickness that does not lose the function as a flexible belt.
The release layer is formed of a thin layer of a fluorine compound such as PFA (tetrafluoride-perfluoroalkyl vinyl ether resin).

  As described above, the base material of the fixing belt 28 is composed of an elastic layer such as silicone rubber (Si rubber), and an induction heating layer and a magnetic layer are formed on one surface thereof, and the thickness of the magnetic layer is 100 μm or less. By setting the thickness of the heat generating layer 21c to 50 μm or less, the fixing belt 28 can be provided with flexibility necessary for nip formation.

The fixing belt 28 includes a low resistance plate-like member 22 formed in an arc shape in cross section, which is fixedly disposed facing the coil 26 of the induction heating unit 24, and a rotatable roller-like nip forming member 23. The induction heating unit 24 performs induction heating in the same manner as the above-described fixing sleeve. The outline of the self-temperature control function at this time is the same as that in the case where the above-described fixing sleeve is used.
At the position where the fixing belt 28 is installed on the nip forming member 23, the pressure member 30 is in pressure contact to form a fixing nip. At this time, the heat insulating material 23b of the nip forming member 23 is made of an elastic material softer than the pressure roller 30 (for example, a foam material such as urethane rubber), and the fixing belt 28 side is recessed in the fixing nip portion. ing. Thus, the nip width necessary for fixing the toner image T on the recording medium P can be ensured.

  In the fixing device having the configuration shown in FIG. 4, the driving means for rotating the fixing member 20 and the pressure roller 30 is provided in one of the roller-shaped nip forming member 23 and the pressure roller 30, one of which is driven by the driving means. It is the structure which is rotated and the other rotates following. During fixing driving, the nip forming member 23 rotates clockwise, the pressure roller 30 rotates counterclockwise, and the fixing belt 28 rotates clockwise to fix the recording medium P carrying the toner image. The toner image is fixed on the recording medium P by being nipped and conveyed by the nip portion and heated by the fixing belt 28 heated by the induction heating portion 24 and pressure by the pressure roller 30.

  In the fixing device having the configuration shown in FIG. 4, the low-resistance plate-like member 22 is separately fixed and arranged inside the fixing belt 28. However, since the fixing belt 28 also serves as a supporting member for the fixing belt 28, the fixing belt 28. The heat insulating member 22a provided on the low resistance plate-like member 22 and the inner peripheral surface of the fixing belt 28 are in contact with each other during rotation, and formed on the inner peripheral surface side of the fixing belt 28 due to fatigue due to friction during sliding. There is a possibility that the formed magnetic layer breaks. Therefore, in this embodiment, in order to solve such a problem, the lubricant is applied to the inner peripheral surface of the fixing belt 28.

  In the fixing device of this embodiment, since the sliding member is arranged in the fixing belt 28, fatigue due to friction occurs. However, by applying a lubricant, fatigue due to friction can be greatly reduced, and magnetic properties can be reduced. Problems such as breakage of the body layer can be reduced. As described above, as described above, a lubricant represented by fluorine grease or silicone oil can be used as appropriate. Further, the lubricant can be easily applied to the inner peripheral surface of the fixing belt 28 by means of, for example, soaking the lubricant in a heat insulating member provided in the low resistance plate-like member 22 in advance.

Although the embodiments of the fixing member and the fixing device according to the present invention have been described above, the embodiments of the image forming apparatus using the fixing device of the present invention will be described next.
Needless to say, the fixing device described in the above-described embodiments can be suitably used for image forming apparatuses such as monochrome copying machines, printers, plotters, and facsimiles. Since the effect of preventing excessive temperature rise is also excellent, high-quality fixing performance can be obtained, which is suitable for use in an image forming apparatus that forms a multicolor or full-color image. Therefore, here, a configuration example of a full-color image forming apparatus will be described.

FIG. 5 is a schematic configuration diagram showing an example of the configuration of the image forming apparatus fully off.
In FIG. 5, reference numeral 1 denotes an apparatus main body of a tandem type color copier as an image forming apparatus, 2 denotes a writing unit that emits laser light based on input image information, and 3 denotes an original conveyance for conveying an original D to an original reading unit 4. , 4 is a document reading unit that reads image information of the document D, 7 is a paper feeding unit that accommodates a recording medium P such as transfer paper, 9 is a registration roller that adjusts the conveyance timing of the recording medium P, 11Y, 11M, 11C and 11BK are photosensitive drums (image carriers) on which toner images of yellow, magenta, cyan, and black are formed, 12 is a charging unit that charges the photosensitive drums 11Y, 11M, 11C, and 11BK, and 13 Is a developing unit for developing the electrostatic latent image formed on each of the photosensitive drums 11Y, 11M, 11C, and 11BK, and 14 is formed on each of the photosensitive drums 11Y, 11M, 11C, and 11BK. Transfer Paiasurora for transferring superimposed on the recording medium P the toner images, 15 denotes the photosensitive drums 11Y, 11M, 11C, cleaning unit for collecting the untransferred toner on 11BK, a.

  Reference numeral 16 denotes a transfer belt cleaning unit that cleans the transfer belt 17, reference numeral 17 denotes a transfer belt that conveys the recording medium P so that toner images of a plurality of colors are carried on the recording medium P, and reference numeral 19 denotes the recording medium P. 2 shows an electromagnetic induction heating type fixing device that fixes the upper toner image (unfixed image).

Hereinafter, an operation during normal color image formation in the image forming apparatus will be described.
First, the document D is transported from the document table in the direction of the arrow in the drawing by the transport roller of the document transport unit 3 and placed on the contact glass 5 of the document reading unit 4. Then, the document reading unit 4 optically reads the image information of the document D placed on the contact glass 5.

  Specifically, the document reading unit 4 scans the image of the document D on the contact glass 5 while irradiating light emitted from an illumination lamp. Then, the light reflected by the document D is imaged on the color sensor via the mirror group and the lens. The color image information of the document D is read for each color separation light of RGB (red, green, blue) by the color sensor, and then converted into an electrical image signal. Further, color conversion processing, color correction processing, spatial frequency correction processing, and the like are performed by the image processing unit based on the RGB color separation image signals to obtain yellow, magenta, cyan, and black color image information.

  Then, the image information of each color of yellow, magenta, cyan, and black is transmitted to the writing unit 2. The writing unit 2 emits laser light (exposure light) based on the image information of each color toward the corresponding photosensitive drums 11Y, 11M, 11C, and 11BK.

  On the other hand, the four photosensitive idle drums 11Y, 11M, 11C, and 11BK are rotated clockwise in FIG. First, the surfaces of the photosensitive drums 11Y, 11M, 11C, and 11Bk are uniformly charged at a portion facing the charging unit 12 (charging process). Thus, a charged potential is formed on the photoconductive drums 11Y, 11M, 11C, and 11Bk. Thereafter, the surfaces of the charged photosensitive drums 11Y, 11M, 11C, and 11Bk reach the irradiation positions of the respective laser beams.

  In the writing unit 2, laser light corresponding to the image signal is emitted from the four light sources corresponding to each color. Each laser beam passes through a different optical path for each color component of yellow, magenta, cyan, and black (exposure process).

  Laser light corresponding to the yellow component is irradiated on the surface of the first photosensitive drum 11Y from the left side of the drawing. At this time, the yellow component laser light is scanned in the rotation axis direction (main scanning direction) of the photosensitive drum 11Y by a polygon mirror that rotates at high speed. Thus, an electrostatic latent image corresponding to the yellow component is formed on the photosensitive drum 11Y charged by the charging unit 12.

  Similarly, the laser beam corresponding to the magenta component is irradiated onto the surface of the second photosensitive drum 11M from the left side of the paper, and an electrostatic latent image corresponding to the magenta component is formed. The cyan component laser light is applied to the surface of the third photosensitive drum 11C from the left side of the paper, and an electrostatic latent image of the cyan component is formed. The black component laser beam is applied to the surface of the fourth photosensitive rest drum 11BK from the left side of the paper to form an electrostatic latent image of the black component.

Thereafter, the surfaces of the photoconductive drums 11Y, 11M, 11C, and 11BK on which the electrostatic latent images of the respective colors are formed reach positions facing the developing unit 13, respectively. Then, each color toner is supplied from each developer 13 onto the photosensitive drums 11Y, 11M, 11C, and 11BK, and the latent images on the photosensitive drums 11Y, 11M, 11C, and 11BK are developed (developing step).
Thereafter, the surfaces of the photosensitive drums 11Y, 11M, 11C, and 11BK after the development process reach the facing portions of the transfer belt 17, respectively. Here, a transfer bias roller 14 is installed at each facing portion so as to contact the inner peripheral surface of the transfer belt 17. Then, the toner images of the respective colors formed on the photosensitive drums 11Y, 11M, 11C, and 11BK are sequentially superimposed and transferred onto the recording medium P on the transfer belt 17 at the position of the transfer bias roller 14 (transfer). Process).

Then, the surfaces of the photosensitive drums 11Y, 11M, 11C, and 11BK after the transfer process reach positions facing the cleaning unit 15, respectively. The untransferred toner remaining on the photoreceptors 11Y, 11M, 11C, and 11BK is collected by the cleaning unit 15 (cleaning process).
Thereafter, the surfaces of the photosensitive drums 11Y, 11M, 11C, and 11BK are neutralized by passing through a neutralization unit (not shown), and a series of image forming processes on the photosensitive drums 11Y, 11M, 11C, and 11BK is completed.

On the other hand, the recording medium P on which the toners of the respective colors on the photosensitive drums 11Y, 11M, 11C, and 11BK are transferred (carrying) is run in the direction of the arrow in the drawing and reaches a position facing the separation charger 18. . Then, the charge accumulated in the recording medium P is neutralized at a position facing the separation charger 18, and the recording medium P is separated from the transfer belt 17 without causing toner dust or the like.
Thereafter, the surface of the transfer belt 17 reaches the position of the transfer belt cleaner 16. Then, the deposit adhered on the transfer belt 17 is collected by the transfer belt cleaning unit 16.

Here, the recording medium P transported onto the transfer belt 17 is transported from the picture paper section 7 via the registration roller 9 and the like.
Specifically, the recording medium P fed by the paper feeding roller 8 from the paper feeding unit 7 that stores the recording medium P passes through a conveyance guide (not shown) and is guided to the registration roller 9. The recording medium P that has reached the registration roller 9 is conveyed toward the position of the transfer belt 17 in time.

The recording medium P on which the full-color image has been transferred through the transfer process is separated from the transfer belt 17 and then guided to the fixing device 19.
The fixing device 19 is an electromagnetic induction heating type fixing device having the configuration described in the above embodiment. In this fixing device 19, unfixing is performed at the nip between the fixing member 20 heated by electromagnetic induction and the pressure roller 30. The recording medium P carrying the color toner image is heated and pressurized, and the color image (toner) is fixed on the recording medium P (fixing step).
The recording medium P after the fixing step is discharged as an output image to a discharge tray (not shown) outside the apparatus main body 1 by a discharge roller (not shown), and a series of image forming processes is completed.

  In the image forming apparatus shown in FIG. 5, as described in the above-described embodiment of the fixing device (any one of the configurations shown in FIGS. 1 to 4), the temperature can be raised quickly and the temperature raising efficiency is lowered. By providing the low-cost fixing device 19 with excellent safety, which can reliably prevent overheating at both ends in the width direction without causing a low cost, an energy-saving effect can be obtained at a low cost, and the fixing property is good and safe. Also excellent in properties.

  The embodiments of the present invention have been described above. However, the present invention is not limited to the configurations shown in the above embodiments, and within the scope of the technical idea of the present invention, other than suggested in the above embodiments. However, it is obvious that the embodiment can be modified as appropriate. In addition, the number, arrangement, shape, and the like of the constituent members of the above-described embodiment are not limited to the above-described embodiment, and can be set to a suitable number, arrangement, shape, and the like in practicing the present invention.

1 is a diagram illustrating a configuration of a fixing device according to an embodiment of the present invention. FIG. 6 is a configuration explanatory diagram of a fixing device showing another embodiment of the present invention. FIG. 6 is a configuration explanatory diagram of a fixing device showing another embodiment of the present invention. FIG. 6 is a configuration explanatory diagram of a fixing device showing another embodiment of the present invention. FIG. 5 is an explanatory diagram illustrating a configuration of an image forming apparatus according to another embodiment of the present invention. It is a schematic block diagram of the fixing device which shows an example of a prior art. It is a schematic block diagram of the fixing device which shows another example of a prior art. It is a schematic block diagram of the fixing device which shows another example of a prior art. It is explanatory drawing of the principle of the self-temperature control function of the fixing member based on this invention. FIG. 3 is an explanatory diagram of a basic configuration of a fixing device having a self-temperature control function. It is explanatory drawing of the subject of the fixing device of a structure shown in FIG. It is explanatory drawing of another subject of the fixing device of a structure shown in FIG. It is a graph which shows the relationship between the magnetic coupling rate and the heat_generation | fever suppression rate with respect to the gap of a magnetic shunt alloy and a low resistance member (Al).

Explanation of symbols

1. Image forming device body (device body)
19 Fixing Device 20 Fixing Member 21 Fixing Sleeve (Fixing Rotator)
21a Release layer 21b Elastic layer 21c Induction heating layer 21d Magnetic layer (magnetic shunt alloy)
22 Low resistance plate member (member with lower resistivity than magnetic layer)
22a Heat insulation member 22b Low resistance plate material 23 Nip forming member 24 Induction heating part (magnetic flux excitation means)
25 Core part (coil core)
26 Coil part (induction coil)
27 Pad-shaped member 28 Fixing belt (fixing rotating body)
30 Pressure roller (Pressure member)
P Recording medium T Toner image

Claims (29)

A fixing member that forms a fixing nip opposite to the pressure member and is electromagnetically heated by magnetic flux excitation means,
A cylindrical or belt-shaped fixing rotator having a magnetic material layer with a Curie point of 100 ° C. to 300 ° C., and the magnetic material separately disposed at a position facing the magnetic flux exciting means across the fixing rotator. And a member having a lower resistivity than the layer. The fixing member according to claim 1,
The fixing member having a low resistivity is a plate-like member. The fixing member according to claim 1 or 2,
The fixing rotator has a low resistance induction heat generating layer. The fixing member according to any one of claims 1 to 3,
The fixing member according to claim 1, wherein the magnetic layer has a magnetic shunt function that controls transmission of magnetic flux according to temperature. In the fixing member according to any one of claims 1 to 4,
The fixing member according to claim 1, wherein a cross-sectional shape of the low resistivity member is an arc shape along a curvature of the fixing rotating body. The fixing member according to any one of claims 1 to 5,
The fixing member, wherein the low resistivity member has a volume resistivity of 5.0 × 10 ⁻⁸ Ω · m or less. The fixing member according to any one of claims 3 to 6,
The fixing member according to claim 1, wherein the induction heating layer of the fixing rotator has a volume resistivity of 5.0 × 10 ⁻⁸ Ω · m or less. The fixing member according to claim 6,
The fixing member having a low resistivity is made of a nonmagnetic metal or alloy. The fixing member according to claim 7,
The fixing member according to claim 1, wherein the induction heating layer of the fixing rotator is made of a nonmagnetic metal or alloy. The fixing member according to any one of claims 1 to 9,
The fixing member, wherein the magnetic layer has a thickness of 100 μm or less. The fixing member according to any one of claims 3 to 10,
The fixing member according to claim 1, wherein the thickness of the induction heating layer is 50 μm or less. The fixing member according to any one of claims 1 to 11,
The fixing rotator has an elastic layer and a release layer on the magnetic layer or the induction heat generation layer. The fixing member according to any one of claims 1 to 12,
The fixing member characterized in that the thickness of the low resistivity member is not less than the penetration depth of magnetic flux and not more than 2 mm. The fixing member according to claim 1,
The fixing member according to claim 1, wherein a width of the low-resistivity member in a rotation direction of the fixing rotator is a heating width of the fixing rotator. The fixing member according to any one of claims 1 to 14,
A fixing member, wherein a distance between the magnetic layer and the low resistivity member is 5 mm or less. The fixing member according to any one of claims 1 to 15,
A fixing member, wherein a heat insulating member is provided between the low resistivity member and the fixing rotator. The fixing member according to any one of claims 1 to 16,
A fixing member, wherein a width of the low resistivity member in the rotation direction of the fixing rotator is changed in an axial direction. The fixing member according to any one of claims 1 to 17,
A fixing member comprising a nip forming member made of a heat insulating material capable of elastic deformation in the fixing rotating body. The fixing member according to claim 18, wherein
The fixing member according to claim 1, wherein the nip forming member is a roller-like member provided rotatably. The fixing device according to claim 18.
The fixing member, wherein the nip forming member is a pad-like member. The fixing member according to any one of claims 1 to 20,
A fixing member, wherein a lubricant is applied to an inner peripheral surface of the fixing rotating body. The fixing member according to any one of claims 18 to 21,
The fixing member, wherein the fixing rotator is a fixing sleeve capable of elastic deformation supported by the nip forming member. The fixing member according to any one of claims 18 to 21,
The fixing rotating member is a fixing belt having flexibility, which is supported by the low resistivity member and the nip forming member. A magnetic flux exciting means; a fixing member that is electromagnetically heated by the magnetic flux exciting means; and a pressure member that presses against the fixing member. An unfixed image is formed at a fixing nip between the fixing member and the pressure member. In a fixing device that heats and presses a supported recording medium and fixes the unfixed image on the recording medium,
24. A fixing device comprising the fixing member according to claim 1 as the fixing member. The fixing device according to claim 24, wherein
The pressure member is disposed to face a nip forming member provided in the fixing rotator of the fixing member, and the fixing rotator is pressed against the nip forming member by the pressure member to form a fixing nip. A fixing device. The fixing device according to claim 25.
The fixing device is characterized in that the nip forming member is made of an elastic material softer than the pressure member, and the fixing rotator side has a concave shape in the fixing nip portion. The fixing device according to any one of claims 24 to 26, wherein:
The fixing device, wherein the pressure member is a pressure roller. 28. The fixing device according to claim 27.
A fixing device having a driving unit in the pressure roller. An image forming apparatus comprising: means for forming an image on an image carrier; means for transferring an image on the image carrier to a recording medium; and means for fixing the image transferred to the recording medium.
29. An image forming apparatus comprising the fixing device according to claim 24 as the fixing unit.

Images