JP2003316182A - Fixing device and image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To facilitate the handling of a core, to reduce the cost, to facilitate adjustment of inductance, to make a temperature distribution of a heating member proper, and to perform proper temperature control. <P>SOLUTION: A fixing device has a heat roll 41 being the heating member which generates heat by flow of an induction current, an induction coil 44 which generates a magnetic flux by supply of a coil current, a plurality of cores 48 arranged in the induction coil, and a heat roll temperature sensor 45 being a heat roll temperature detection means which detects the temperature of the heat roll, and center axes of the heat roll 41, the induction coil 44, and the cores 48 are aligned, and the induction coil 44 is like a spring of which the section in the lengthwise direction (axial direction) is circular, and the cores 48 have circular sections in the lengthwise direction, and the heat roll temperature sensor 45 is installed so as to face the cores 48. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus for forming and fixing an image on a recording material to form an image, and a fixing apparatus for performing the fixing.

[0002]

2. Description of the Related Art In an electrophotographic image forming apparatus, an image read by a scanner is read, a toner image of the read image is formed on a recording material in an image forming section, and the formed recording material is fixed. It was sent to an apparatus, where the unfixed toner image on the recording material was fixed, and a print image was obtained on the recording material.

The fixing device is provided with a heating roller (fixing roller) as a heating member having a heating source inside, and a pressure roller as a pressing member for pressing the heating roller to form a fixing nip. The roller is rotationally driven by a drive source, and the pressure roller is rotated by being driven by the heating roller.
The heating roller and the pressure roller heat and pressurize the recording material while the recording material is nipped and conveyed in the fixing nip to melt and fix the toner image on the recording material.

Conventionally, a halogen lamp has been used as a heating source, but in order to save energy, an induction heating type fixing device using an induction coil is considered as a heating source having high energy efficiency. .

The induction heating type fixing device is provided with an induction coil in the heating roller, and when an alternating current, which is a coil current, is supplied to the induction coil, a magnetic flux is generated in the induction coil, and the magnetic flux induces the heating roller. A current flows, and the heating roller generates heat due to Joule loss of the induced current.

There is also a structure in which a core for efficiently generating magnetic flux is provided inside the induction coil. Further, the temperature of the heating roller, which is the temperature on the heating roller, is detected by the heating roller temperature sensor, and the temperature of the heating roller of the recording material is controlled to determine whether the temperature is appropriate for fixing.

[0007]

However, in the case where the core is a single body and is large, it is difficult to handle, a general-purpose product cannot be used and costs are high, and it is difficult to adjust the impedance of the induction coil. There was a problem such as.

Further, when the core is divided, there is a demand to operate the heating roller by optimizing the temperature distribution of the heating roller. In addition, there is a demand for proper temperature control of the heating roller.

An object of the present invention is to install a plurality of cores on an induction coil to facilitate the handling of the cores, reduce the cost and facilitate the adjustment of the inductance.
In addition, the temperature distribution of the heating roller is made proper and proper temperature control is performed.

[0010]

In order to solve the above problems, the invention according to claim 1 is directed to an induction coil which generates a magnetic flux by energizing a coil current and a magnetic flux generated from the induction coil. In a fixing device provided with a cylindrical heating member that generates heat with an induction current and fixing the developer on the recording material by heating the heating member, the induction coil is wound inside the heating member and in a circumferential direction. It is characterized in that it comprises a plurality of cores which are drawn and arranged in the inside of the induction coil and in the axial direction.

According to the first aspect of the present invention, since a plurality of cores are arranged, the cores can be easily handled, the cost can be reduced, and the inductance can be easily adjusted.

According to a second aspect of the invention, in the first aspect of the invention, the induction coil has a circular axial section, and the center of the induction coil section is in the axial direction of the heating member. It is characterized in that it coincides with the center of the cross section.

According to the second aspect of the present invention, since the induction coil forms a uniform magnetic flux in the circumferential direction of the heating member, preliminary rotation of the heating member is unnecessary, and an appropriate temperature in the circumferential direction of the heating member is required. A distribution can be formed.

According to a third aspect of the invention, in the first or second aspect of the invention, the outer peripheral surface of the induction coil is separated from the inner peripheral surface of the heating member by 2 to 3 mm. It is characterized by

According to the third aspect of the present invention, the heating member can maintain the insulating property from the induction coil and obtain a heating temperature sufficient for fixing.

According to a fourth aspect of the present invention, in the invention according to any one of the first to third aspects, the core has a circular cross section in the axial direction, and the center of the cross section coincides with the center of the heating member. It is characterized by doing.

According to the fourth aspect of the invention, it is possible to prevent temperature unevenness due to each core and form a more appropriate temperature distribution in the circumferential direction of the heating member.

According to a fifth aspect of the present invention, an induction coil that generates a magnetic flux by passing a coil current and a heating member that generates heat by an induction current induced by the magnetic flux generated from the induction coil are provided on the recording material. In the fixing device for fixing the developer by heating the heating member, the induction coil is provided inside the heating member, and includes a plurality of cores arranged inside the induction coil and axially divided. When the length of each core is L [mm] and the core gap between the cores is g [mm], the core satisfies the conditions of L ≧ g and g <− (1/4) · L + 15. , Is characterized.

According to the invention of claim 5, it is possible to form an appropriate temperature distribution in the axial direction of the heating member.

According to a sixth aspect of the present invention, an induction coil that generates a magnetic flux by passing a coil current and a heating member that heats by an induction current induced by the magnetic flux generated from the induction coil are provided. In the fixing device for fixing the developer by heating the heating member, the induction coil is provided inside the heating member, and a plurality of cores arranged inside the induction coil and axially divided, and the core. And a heating member temperature detecting means which is installed at a position opposite to and detects the temperature of the heating member.

According to the sixth aspect of the invention, since the heating member temperature detecting means is provided at a position facing the core on the heating member, the temperature can be properly controlled.

The invention according to claim 7 is the invention according to any one of claims 1 to 6, wherein the heating member has a thickness of 3
It is characterized in that it is from 00 [μm] to 2 [mm].

According to the invention of claim 7, the strength of the heating member can be maintained and the heat capacity can be suppressed.

An eighth aspect of the present invention is an image forming apparatus comprising the fixing device according to any one of the first to seventh aspects, which forms an image of the developer on the recording material by fixing by the fixing device. It is characterized by being.

According to the invention described in claim 8,
It is possible to provide an image forming apparatus having the characteristics of the fixing device described in any one of 7 above.

[0026]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the accompanying drawings. In addition, in the present embodiment, a heating roller 41 described later is a heating member described in claims of the present invention, an induction coil 44 is an induction coil described in claims, and a core 48 is described in claims. The heating roller temperature sensor 45 functions as the core, the heating member temperature detection unit described in the claims, and the fixing device 40 functions as the fixing device described in the claims.

The present embodiment will be described with reference to FIGS. FIG. 1 is a block configuration diagram of an image forming apparatus α according to the present embodiment, and FIG. 2 is an image forming unit 20 of the image forming apparatus α.
FIG. 3 is a cross-sectional view showing the configuration of the fixing device 40, and FIG. 4 is a perspective view showing the heating roller 41 of the fixing device 40.

As shown in FIG. 1, an image forming apparatus α according to the present embodiment has a CPU (Central Pr) for centrally controlling each component.
ocessing Unit) 1 and RAM for temporarily storing information
(Random Access Unit) 2, ROM (Read Only Memory) 3 that stores various data and programs, a scanner 10 that reads image information of a print target, and an image forming unit 20 that forms an image on a paper A that is a recording material. A sheet feeding unit 30 that supplies the sheet A to the image forming unit 20, a fixing device 40 that fixes the toner that is the developer on the sheet A formed by the image forming unit 20, and a display that displays various information. Section 50.

RAM 2, ROM 3, scanner 10, image forming unit 20, paper feeding unit 30, fixing device 40A, and display unit 50 are C
It is connected to PU1. Under the control of the CPU 1, the image forming apparatus α reads the image information of the print target with the scanner 10, transmits the image information of the print target to the image forming unit 20 via the RAM 2, and is supplied from the paper feeding unit 30. An image of the formed paper A is formed on the basis of the image information of the print target, and the toner on the formed paper A is fixed by the fixing device 40.

As shown in FIG. 2, the image forming section 20 includes a rotatable photosensitive drum 21 which is a medium for image formation, a charger 22 for charging the photosensitive drum 21, and an exposing means 23 for exposing the photosensitive drum 21. A developing unit 24 for developing the toner onto the photosensitive drum 21, a transfer unit 25 for transferring the developed toner image onto the paper A, and a cleaner 26 for removing the toner remaining in the development.

When the paper A is conveyed to the image forming section 20, the surface of the rotating photosensitive drum 21 is charged to a predetermined potential by the charger 22 and imagewise exposed by the exposing means 23 so that the surface of the photosensitive drum 21 is exposed. An electrostatic latent image is formed, and this latent image is developed by the developing device 24.
The toner image is visualized as a toner image by developing with a toner, and the obtained toner image is transferred onto the paper A conveyed to the photosensitive drum 21 by the transfer means 25. Photosensitive drum 21 after transfer
Cleans the transfer residual toner remaining on the surface of the cleaner 2
After being removed in 6, the image is prepared for the next image formation.

On the other hand, the paper A carrying the toner image as described above is sent from the photosensitive drum 21 to the fixing device 40,
Then, the unfixed toner image on the paper A is fixed, and a print image is obtained on the paper A.

As shown in FIGS. 1 and 3, the fixing device 40
Includes a heating roller 41 that is a rotatable heating member that heats the paper A, and a pressure roller 42 that is a pressing member that presses the paper A to form a fixing nip and presses the paper A.
A cylindrical bobbin 43 is fixed inside the heating roller 41 with the same central axis, an induction coil 44 wound around the bobbin 43 in a spring shape, and the heating roller 41 is contacted to detect the heating roller temperature. A fixed heating roller temperature sensor 45, a coil power supply 46 that outputs a coil current that is supplied to the induction coil 44, and a coil power supply 46 when the heating roller 41 contacts the heating roller 41 and becomes overheated. Temperature fuse 47, which is an energization / interruption means for interrupting the coil current, and a plurality of cylindrical cores 48, which have the same central axis inside the bobbin 43 and are arranged with a predetermined gap in the longitudinal direction of the bobbin. And.

The induction coil 44 also generates a magnetic flux in the longitudinal direction. In the present embodiment, the induction coil 44
The longitudinal direction of is the same as the axial direction. The heating roller 41, the induction coil 44, and the bobbin 4 are arranged in order from the outer circumference.
3, the core 48 has the same central axis. The heating roller temperature sensor 45 and the coil power supply 46 are connected to the CPU 1.

The heating roller 41 is made of a magnetic material as a heat generating portion, preferably a ferromagnetic material such as F.
e, FeOx, ferromagnetic stainless steel, nickel, nickel-cobalt or the like. Also, the heating roller 4
An elastic layer for effective pressure application and a release layer for separating the developer of the recording material may be provided on one surface.

The heating roller 41 has a thickness of 300
A configuration of [μm] to 2 [mm] is preferable. this is,
When it is thinner than 300 [μm], the heating roller lacks strength, and when it is thicker than 2 [mm], the heat capacity becomes large, so that the time and power required for warming up and maintaining the fixing temperature become large. This is because it will end up. Further, in this embodiment, the heating roller 41 having an outer diameter of 40 to 50 [mm] is used.

The bobbin 43 is, for example, PBT (polybutylene terephthalate), PI (polyimide), PPS.
(Polyphenylene sulfide), PAI (polyamide imide) or the like. The core 48 is, for example,
It is composed of materials such as ferrite and laminated steel plates. The heating roller temperature sensor 45 is a sensor such as a thermocouple, a thermistor, or an infrared radiation temperature sensor.

The CPU 1 causes the coil power supply 46 to output an alternating current, which is a coil current, and the magnetic flux that changes periodically is induced by the energization of the alternating current to the induction coil 44.
By applying a periodically changing magnetic flux to the heating roller 41, an induction current flows on the heating roller 41, and the heating roller 41 is heated by Joule loss of the induction current.
The temperature of the heating roller 41 is controlled by receiving a signal of the heating roller temperature of the heating roller 41 from the heating roller temperature sensor 45 and controlling the coil current from the coil power supply 46 so that the fixing temperature becomes appropriate.

At the same time, the CPU 1 rotationally drives the heating roller 41 by a driving source (not shown), and the pressure roller 42 is rotated by being driven by the heating roller 41. By rotating the heating roller 41 and the pressure roller 42,
The paper A inserted into the fixing nip is heated and pressed to melt and fix the toner image on the paper A.

As shown in FIG. 4, the heating roller 41 includes:
A plurality of cores 4 inside the induction coil 44 (inside the bobbin 43)
8 are longitudinally arranged with a predetermined gap.
Since the plurality of cores 48 are arranged, it is possible to easily handle the cores, reduce costs, and easily adjust the inductance.

The temperature distribution T in the longitudinal direction of the heating roller 41 has a periodic distribution shape. In the longitudinal direction, the cycle of the temperature distribution T is the length of each core 48, and the temperature is
The temperature is highest in the center of each core 48 and lowest in the center of each gap.

The heating roller temperature sensor 45 and the temperature fuse 47 are located on the heating roller 41 so as to face the center position of the core 48A of the plurality of cores 48 which is located at the center position of the heating roller 41 in the longitudinal direction. Mounted on.
This is because the heat does not easily escape at the central position of the heating roller 41, and as described above, the center of the core 48 has the highest temperature. Therefore, the heating roller temperature sensor 45 can actually detect the highest temperature in a range where the image fixing quality does not deteriorate (within the range in which the above-described periodic temperature unevenness is allowable), and the temperature control can be performed for the highest temperature. . In particular, it is possible to effectively detect an abnormal temperature overtemperature. Similarly, the thermal fuse 47 can interrupt the power supply when the abnormal temperature of the highest temperature, that is, the overtemperature, occurs in a range where the image fixing quality is not deteriorated.

5 and 6, the length of one of the plurality of cores 48 in the longitudinal direction and the gap between the cores 48 (hereinafter referred to as core gap) and the temperature of the heating roller 41 are shown. The allowable range of distribution will be described. Figure 5
It is a diagram showing the allowable range of the temperature distribution of the heating roller,
(I) is a diagram showing the length L and the core gap g of one core, (II) is a graph showing the temperature distribution allowable range of the heating roller, and FIG. 6 is an induction coil with respect to the filling rate of the core. FIG. 3 is a graph showing the characteristics of FIG. 3, (I) is a graph showing the inductance of the induction coil with respect to the filling rate of the core, and (II) is a graph showing the reactance of the induction coil with respect to the filling rate of the core.

First, as shown in FIG. 5 (I), the length of one of the plurality of cores 48B in the longitudinal direction is L, and each core 48 is
The length of the core gap in the longitudinal direction of B is g. Therefore,
The conditions for the length L of one core and the core gap g to obtain an appropriate temperature distribution were determined. As shown in FIG. 5 (II), when the length L [mm] of one core 48B and the core gap g [mm] of each core 48B have a proper temperature distribution of the heating roller, a circle is marked. , If not appropriate ×
Is scoring.

The determination as to whether the temperature distribution of the heating roller is in the proper range is made by two points, that is, whether the temperature unevenness is within the allowable range and whether the filling rate of the core is within the allowable range. Therefore, when both of the two points were within the allowable range, a mark of O was given. First, it is determined whether the temperature unevenness is within an allowable range by determining whether the temperature gap between the highest point and the lowest point of the above-described periodic temperature unevenness of the plurality of cores is within 10 [° C.], and the image fixed on the recording material. Was judged to be good by the visual inspection of the tester, the temperature unevenness was judged to be within the allowable range.

The experimental condition is that the outer diameter of the heating roller is 40 mm.
-50 [mm], the input power from the coil power supply to the induction coil is about 1000 [W], and the target temperature (fixing temperature) is about 200 [° C]. The same applies to other experiments described in the form of
It was taken into consideration that the heating roller is used during fixing in the range close to this condition.

Next, the determination of whether the filling rate of the core is within the allowable range will be described with reference to FIG. The filling rate [%] of the core used in FIG. 6 is represented by the total volume of the core / the total area inside the induction coil. At this time, the cross-sectional area of the core in the longitudinal direction, the length L of one core, and the core gap g were changed to obtain data, and the relationship curve was drawn.

As shown in FIG. 6 (I), an appropriate region C1 exists in the inductance [μH] of the induction coil with respect to the filling rate of the core. If the inductance is larger than the proper region C1, the heat generation efficiency is increased, but the magnetic flux density becomes too large and saturated, making temperature control impossible. Further, if the inductance is smaller than that of the proper region C1, the heat generation efficiency is insufficient and the desired temperature cannot be obtained.

As shown in FIG. 6 (II), similarly, the reactance [Ω] of the induction coil with respect to the filling rate of the core has an appropriate region C2. If the reactance is larger than the proper region C2, the heat generation efficiency is increased, but the magnetic flux density becomes too large and saturated, making temperature control impossible. Further, if the reactance becomes smaller than that in the proper region C2, the heat generation efficiency becomes insufficient and the desired temperature cannot be obtained.

Therefore, one core which is within the permissible range of the proper filling rate in the proper regions C1 and C2 in FIGS. 6 (I) and (II) and within the permissible range of the temperature distribution described above is used. The conditions for the length L and the core gap g are expressed by the following equations. When one length L [mm] of the core 48B and a core gap g [mm] of each core 48B are satisfied, it is necessary that L ≧ g and g <− (1/4) · L + 15 are satisfied. Core 1 that meets this condition
By providing the fixing device 40 with the core 48 having the length L and the core gap g, an appropriate temperature distribution can be obtained in the longitudinal direction.

In this case, the length of one core L = 5 to 60
[Mm], and the core gap g is preferably 1 to 12 [mm]. If L is short, the degree of freedom of core installation is high. However, if L is shorter than 5 [mm], the number will increase and the cost will increase. Conversely, L will be 60 [m].
If it is longer than m], the temperature unevenness in the core gap g becomes remarkable, and it becomes necessary to shorten the core gap g to a certain allowable range. Also, the core gap g is 1 [m
When it is shorter than m], it becomes difficult to control the impedance of the induction coil. On the contrary, when g is longer than 12 [mm],
The temperature unevenness in the longitudinal direction of the heating roller becomes large.

Next, the cross-sectional shape of the core in the longitudinal direction will be described with reference to FIG. FIG. 7 is a diagram showing the temperature distribution according to the cross-sectional shape of the core, and (I) shows the heating roller 4
It is a schematic sectional drawing which shows the shape of 1A and 41B, (II)
[Fig. 4] is a graph of temperature distribution in the circumferential direction.

As shown in FIG. 7 (I), a heating roller 41A provided with a core 48C having a central cross-sectional shape and a square cross-sectional shape in the longitudinal direction and a heating roller 41A having a central axis aligned with a circular cross-sectional shape in the longitudinal direction. The heating roller 41B provided with the core 48D was prepared, and the heating roller temperature in the circumferential direction was measured. The measurement result is shown in FIG. 7 (II). FIG. 7 (II) is a graph of the temperature distribution (relative value) showing the relative value of the temperature with respect to the angle [°] in the circumferential direction.

The temperature distribution on the heating roller 41A becomes a periodic temperature distribution T1 having four highest points, and the temperature distribution on the heating roller 41B becomes a flat temperature distribution T2. It is desirable that the temperature distribution has no temperature unevenness. Since the core 47 of the present embodiment has a circular cross section, there is no bias of the magnetic flux due to the cross-sectional shape, pre-rotation due to the bias of the cross-sectional shape is unnecessary, and temperature unevenness in the circumferential direction can be prevented.

Further, since the central axis of the induction coil 44 coincides with that of the heating roller 41, it is possible to prevent temperature unevenness in the circumferential direction regardless of the rotation of the heating roller 41, and the core 47 can be prevented.
Since the central axis is aligned with the coil 41, the temperature unevenness in the circumferential direction can be further prevented, and the fixing device 40 can perform fixing with uniform image quality.

Next, the gap between the heating roller and the induction coil (referred to as coil gap) will be described with reference to FIG. FIG. 8 is a diagram showing the efficiency according to the coil gap, and (I) shows the heating roller 41C and the induction coil 4
It is a schematic sectional drawing which shows the positional relationship of 4A, (II) is a graph of the efficiency with respect to a coil gap.

As shown in FIG. 8 (I), the heating roller 41
The distance between the inner circumference of A and the outer circumference of the induction coil 44 is shown as a coil gap G [mm]. FIG. 8 (II) shows a graph of efficiency (relative value) with respect to the coil gap G. Efficiency is the ratio of the heating temperature of the heating roller to the input power of the coil current.

In the coil gap G [mm], the efficiency increases as the coil gap G becomes smaller, but when the coil gap G becomes smaller than 2 [mm],
The inductance of the induction coil exceeds the permissible range, temperature control becomes impossible, and the rotating heating roller may come into contact with the fixed induction coil, resulting in a gap between the induction coil and the heating roller. Insulation may not be maintained. On the contrary, the coil gap G is 3 [mm]
If it becomes larger than this, a desired temperature cannot be obtained, and self-heating of the induction coil is caused.

Therefore, it is preferable that the coil gap G [mm] has a relationship of 2 [mm] <G <3 [mm].

Therefore, according to the present embodiment, in the fixing device using the plurality of cores 48, since the plurality of cores 48 are arranged in the induction coil 44, the handling of the cores is facilitated, the cost is reduced and the inductance is adjusted. Can be facilitated. The circular spring-shaped induction coil 44 has a circular cross section in the longitudinal direction, and the heating roller 41
No preliminary rotation is required, and an appropriate temperature distribution can be formed in the circumferential direction of the heating roller 41. Further, since the induction coil 44 has the same central axis as the heating roller 44, even if the heating roller 41 is rotated, an appropriate temperature distribution can be formed in the circumferential direction of the heating roller 41.

When the coil gap G satisfies the condition of 2 [mm] <G <3 [mm], the heating roller 41 maintains the insulating property with the induction coil 44 and has a heating temperature sufficient for fixing. Obtainable. Further, the core 48 has a circular cross section in the longitudinal direction and its central axis is aligned with the heating roller 41 to prevent temperature unevenness due to each core 48, and to form a more appropriate temperature distribution in the circumferential direction of the heating roller 41. can do.

Further, one length L [mm] of the core 48,
Regarding the core gap g [mm] of each core 48, L ≧
Since g and g <− (1/4) · L + 15 are satisfied, an appropriate temperature distribution can be formed in the longitudinal direction of the heating roller 41. In addition, the thickness of the heating roller 41 is set to 3
Since it is set to 00 [μm] to 2 [mm], the heating roller 41
The strength can be maintained and the heat capacity can be suppressed.

Further, since the heating roller temperature sensor 45 is provided at a position facing the center of the core 48B on the heating roller 41, the temperature can be properly controlled. Further, since the temperature fuse 47 is provided at a position facing the center of the core 48B on the heating roller 41, the energization can be properly cut off when the temperature is abnormal.

The heating roller temperature sensor 45 and the thermal fuse 47 are not limited to one each. Further, it may be arranged so as to face the center of the core 48 other than the central core 48B.

Although the embodiments of the present invention have been described above, the present invention is not necessarily limited to only the above-described means and methods, and achieves the object of the present invention and brings about the effects of the present invention. Modifications can be appropriately made within the range.

[0066]

According to the invention described in claim 1, since a plurality of cores are arranged, the cores can be easily handled, the cost can be reduced, and the inductance can be easily adjusted.

According to the second aspect of the present invention, since the induction coil forms a uniform magnetic flux in the circumferential direction of the heating member, preliminary rotation of the heating member is unnecessary, and an appropriate temperature is set in the circumferential direction of the heating member. A distribution can be formed.

According to the third aspect of the present invention, the heating member can maintain the insulating property with the induction coil and can obtain the heating temperature sufficient for fixing.

According to the fourth aspect of the present invention, it is possible to prevent temperature unevenness due to each core and form a more appropriate temperature distribution in the circumferential direction of the heating member.

According to the invention of claim 5, it is possible to form an appropriate temperature distribution in the axial direction of the heating member.

According to the sixth aspect of the present invention, since the heating member temperature detecting means is provided at a position facing the core on the heating member, the temperature can be properly controlled.

According to the seventh aspect of the invention, the strength of the heating member can be maintained and the heat capacity can be suppressed.

According to the invention described in claim 8,
It is possible to provide an image forming apparatus having the characteristics of the fixing device described in any one of 7 above.

[Brief description of drawings]

FIG. 1 is a block configuration diagram of an image forming apparatus α according to an embodiment of the present invention.

FIG. 2 is an image forming unit 20 and a fixing device 40 of the image forming apparatus α.
It is a figure which shows the structure of.

FIG. 3 is a cross-sectional view showing a configuration of a fixing device 40.

4 is a perspective view showing a heating roller 41 of the fixing device 40. FIG.

FIG. 5 is a diagram showing an allowable range of temperature distribution of the heating roller, (I) is a diagram showing a length L and a core gap g of one core, and (II) is a temperature distribution allowable range of the heating roller. It is a graph which shows a range.

FIG. 6 is a diagram showing characteristics of the induction coil with respect to the filling rate of the core, (I) is a graph showing the inductance of the induction coil with respect to the filling rate of the core, and (II) is an induction with respect to the filling rate of the core. It is a graph which shows the reactance of a coil.

FIG. 7 is a diagram showing a temperature distribution according to the cross-sectional shape of the core, (I) is a schematic cross-sectional view showing the shapes of the heating rollers 41A and 41B, and (II) is a temperature distribution in the circumferential direction. Is a graph of.

FIG. 8 is a diagram showing efficiency according to a coil gap,
(I) is a schematic cross-sectional view showing the positional relationship between the heating roller 41C and the induction coil 44A, and (II) is a graph of efficiency with respect to the coil gap.

[Explanation of symbols]

α ... Image forming device 1 ... CPU 2 ... RAM 3 ... ROM 10 ... Scanner 20 ... Imaging department 21 ... Photosensitive drum 22 ... Charger 23 ... Exposure means 24 ... Developer 25 ... Transferring means 26 ... Cleaner 30 ... Paper feeder 40 ... Fixing device 41, 41A, 41B, 41C ... Heating roller 42 ... Pressure roller 43 ... Bobbin 44, 44A ... Induction coil 45 ... Heating roller temperature sensor 46 ... Power supply for coil 47 ... Thermal fuse 48, 48A, 48B, 48C, 48D ... Core 50 ... Display A ... paper

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Miho Toyoda             2970 Ishikawa-cho, Hachioji-shi, Tokyo Konica stock             Inside the company F term (reference) 2H033 AA18 AA31 BA25 BA26 BA32                       BB03 BB13 BB18 BB21 BB22                       BE06                 3K059 AA03 AB19 AC33 AD05 AD12                       CD02 CD72 CD77

Claims (8)

[Claims] 1. A developer on a recording material, comprising: an induction coil that generates a magnetic flux by passing a coil current; and a cylindrical heating member that generates heat by an induction current induced by the magnetic flux generated from the induction coil. In the fixing device for fixing by heating the heating member, the induction coil is wound in the heating member in the circumferential direction, and a plurality of cores are arranged in the induction coil in the axial direction. A fixing device comprising: 2. The induction coil has a circular cross section in the axial direction, and the center of the cross section of the induction coil coincides with the center of the cross section of the heating member in the axial direction. 1
The fixing device described. 3. The fixing device according to claim 1, wherein the outer peripheral surface of the induction coil is spaced apart from the inner peripheral surface of the heating member by 2 to 3 mm. 4. The fixing device according to claim 1, wherein the core has a circular cross section in the axial direction, and the center of the cross section coincides with the center of the heating member. 5. An induction coil for generating a magnetic flux by energizing a coil current and a heating member for generating heat by an induction current induced by the magnetic flux generated by the induction coil are provided to heat the developer on the recording material. In a fixing device for fixing by heating a member, the induction coil includes a plurality of cores provided inside the heating member and divided in the axial direction of the induction coil. When the length of the core is L [mm] and the core gap between the cores is g [mm], the conditions of L ≧ g and g <− (1/4) · L + 15 are satisfied. Fixing device. 6. An induction coil for generating a magnetic flux by energizing a coil current and a heating member for generating heat by an induced current induced by the magnetic flux generated by the induction coil are provided to heat the developer on the recording material. In a fixing device for fixing by heating a member, the induction coil is provided inside the heating member, and a plurality of cores arranged inside the induction coil and axially divided, and installed at positions facing the core. And a heating member temperature detecting means for detecting the temperature of the heating member. 7. The heating member has a thickness of 300 [μm].
The fixing device according to any one of claims 1 to 6, wherein the fixing device has a size of 2 to 2 mm. 8. An image forming apparatus comprising the fixing device according to claim 1, wherein an image of the developer is formed on the recording material by fixing by the fixing device.