JP2002162848A - Fixing device and image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To solve a problem of the insufficiency of temperature at the end in an induction heating type fixing device using a coil having a winding part parallel with the rotary shaft direction of a heating roller in order to reduce the loss of magnetic flux. SOLUTION: The heating roller is made to generate heat by a magnetic field generating means constituted of the coil having the winding part nearly parallel with the rotary shaft of the heating roller and a magnetic field generating means constituted of the coil having the winding part nearly parallel with a direction orthogonal to the rotary shaft of the heating roller.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fixing device for heating a toner image to fix it on a recording material, and an image forming apparatus having the fixing device.

[0002]

2. Description of the Related Art As a fixing device in an image forming apparatus for forming an image by an electrophotographic method, a fixing device that heats a toner image by using heat generated by a heating roller due to an eddy current generated by electromagnetic induction has attracted attention. A patent application has been filed.

Many of such induction heating type fixing devices include a magnetic flux generating means for generating an eddy current inside a heating roller, as shown in FIG. 4 of Japanese Patent Application Laid-Open No. 9-106207, for example. The magnetic flux generating means includes a core, and a coil having a winding portion substantially perpendicular to the rotation axis of the heating roller and winding the core.

[0004]

However, the above-mentioned conventional induction heating type fixing device has a problem that the loss of magnetic flux is large and it is difficult to design a device having high energy efficiency. In order to solve this problem, there has been proposed a fixing device in which a magnetic field generating means is constituted by a core and a coil having a winding portion substantially parallel to the rotation axis of the heating roller and winding the core (Japanese Patent Application No. 2002-214,058). FIG. 2 of JP-A-9-102207. In the fixing device according to this proposal, although the loss of magnetic flux is small and the energy efficiency is improved, there is a problem that the temperature at the axial end of the heating roller is low and insufficient fixing tends to occur at the end of the recording material. .

If the length of the magnetic field generating means is increased to solve this problem, the leakage of magnetic flux becomes remarkable, which is not desirable in terms of safety and radio wave management.

The present invention solves the above-described problems in the conventional induction heating type fixing device, and can perform uniform fixing with high energy efficiency and extremely low magnetic flux leakage. An object of the present invention is to provide a fixing device of a small induction heating system.

[0007]

The object of the present invention is achieved by the following invention.

[0008] 1. Made of conductive and ferromagnetic material,
A heating roller that performs fixing while conveying the recording material by rotation,
A pressure member pressed against the heating roller, a core made of a ferromagnetic material, and a coil wound around the core, the winding member having a winding portion substantially parallel to a direction X of a rotation axis of the heating roller; An X-winding coil for generating a Y magnetic flux passing in a roller substantially parallel to the Y-direction orthogonal to the X-direction, a Y-magnetic flux generating means including a power supply for supplying an alternating current to the X-winding coil, and the Y-magnetic flux generating means A cylindrical or cylindrical core made of a magnetic material, and a coil for winding the core, the winding being substantially parallel to the Y direction. And the inside of the heating roller is X
A Y-winding coil for generating an X magnetic flux passing substantially parallel to the direction and a power supply for supplying an alternating current to the Y-winding coil.
A fixing device comprising: a magnetic flux generating unit.

[0009] 2. 2. The fixing device according to claim 1, wherein the power source of the Y magnetic flux generating unit and the power source of the X magnetic flux generating unit are one common power source.

[0010] 3. 2. The fixing device according to claim 1, wherein the power supply of the Y magnetic flux generation unit and the power supply of the X magnetic flux generation unit are separately provided.

4. The fixing device according to any one of claims 1 to 3, wherein a distance between an inner surface of the heating roller and the core of the Y magnetic flux generating unit is set to a value within a range of 1.5 mm to 5 mm. apparatus.

5. The fixing device according to any one of claims 1 to 4, wherein the X-th winding coil and the Y-turn coil are formed of a litz wire.

6. The heating width of the heating roller can be changed by changing the length of the coil by expanding and contracting the Y-wound coil in the X direction.
The fixing device according to claim 1.

7. The fixing device according to any one of claims 1 to 6, wherein a length of the core of the Y magnetic flux generation unit in the X direction is substantially equal to a free length of the Y-turn coil.

[8] 8. An image forming apparatus comprising: the fixing device according to any one of 1 to 7; and an image forming unit that forms an unfixed toner image on a recording material and conveys the recording material to the fixing device. .

9. 9. The image forming apparatus according to claim 8, further comprising a control unit that performs control for changing a coil length of the Y-winding coil according to a size of a recording material.

[0017]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An image forming apparatus according to an embodiment of the present invention will be described with reference to FIG. FIG. 1 shows an image forming apparatus according to an embodiment of the present invention, and the image forming apparatus incorporates a fixing device according to the embodiment shown in FIG.

Reference numeral 1 denotes a photoreceptor as an image carrier, which is a photoreceptor having an organic photoconductive layer formed on a drum-shaped conductive substrate made of aluminum. The photoconductor 1 is an OPC photoconductor on which a negative electrostatic latent image is formed. Reference numeral 2 denotes a charging device including a scorotron charger having a corona discharge electrode and a control electrode. As the charging device 2, a known arbitrary device such as a contact charging device such as a roller charging device can be used. Reference numeral 3 denotes an exposure apparatus having a laser diode and a scanning optical system. As the exposure device 3, any known device such as an LED array and a liquid crystal can be used. Reference numeral 4 denotes a developing device that contains a two-component developer and performs reversal development in which toner is attached to an exposed portion of the photoconductor 1 by a developing sleeve to which a bias having the same polarity as that of the electrostatic latent image on the photoconductor 1 is applied. is there. As the developer used for development, a one-component developer containing no carrier can be used. Reference numeral 5 denotes a transfer device that electrostatically transfers the toner image on the photoconductor 1 to the recording material P, 6 denotes a fixing device that heats and fixes the toner image on the recording material P, and 7 denotes the recording material P that is discharged and separated. A separation device 8 is a cleaning device that removes, from the photoconductor 1, deposits such as toner and paper powder remaining on the photoconductor 1 after transfer. The recording material P is supplied from a paper feed cassette 9 to a transfer position between the photoconductor 1 and the transfer device 5.

FIG. 2 shows the fixing device 6. From the above-described image forming unit, that is, an image forming unit that forms a toner image on the photoconductor 1 by charging, exposing, and developing, forms an unfixed toner image on the recording material P by the transfer device 5, and conveys the toner image, The recording material P carrying the deposited toner image is conveyed to the fixing device 6. In the frame 10 of the fixing device 6, a heating roller 11 and a pressing roller 12 as a pressing member that is in pressure contact with the heating roller 11 are arranged. As the heating roller 11, a roller composed of a drum-shaped base made of a conductive and ferromagnetic material and a release surface layer made of a fluororesin is used. As the pressure roller 12, a roller composed of a surface layer made of an aluminum base and silicon rubber is used. In addition to the pressure roller 12, a belt or a plate-shaped non-rotational pressure member can be used as the pressure member.

The recording material P includes a heating roller 11 and a pressing roller 1
When passing through the nip between the two, the unfixed toner image T1 on the recording material P is heated and melted to become a fixed toner image T2. The recording material P carrying the fixed toner image T2 is a fixing discharge roller 1
The sheet is guided and discharged by 7 and 18. Reference numerals 13 and 14 denote recording material guides, and reference numerals 15 and 16 denote separation claws.

FIG. 3 shows a heating section of the fixing device 6. Inside the heating roller 11, a flat core 20 having a long side parallel to the rotation axis direction of the heating roller 11 and a coil 21 that winds the core 20 are arranged. Inside the heating roller 11, there is also a columnar or cylindrical core 22, a coil 23 for winding the core 22, and a columnar or cylindrical core 24.
And a coil 25 for winding the core 24.

In this specification, the direction of the rotation axis of the heating roller 11 is called an X direction, and a direction orthogonal to the X direction is a Y direction.
Say direction.

The coil 21 as an X-winding coil has a winding portion 21A substantially parallel to the X direction. The coils 23 and 25 as Y-wound coils have winding portions 23A and 25A substantially parallel to Y, respectively. Cores 20, 22 and 24
And the coils 21, 23 and 25 constitute a magnetic field generating means, and generate a magnetic flux as shown in FIG. 4 by passing a current through the coils 21, 23 and 25. As for the coils 21, 23 and 25, it is desirable to configure them with a litz wire composed of 20 or more single wires.

FIG. 4A shows a magnetic flux distribution on a surface of the heating roller 11 parallel to the X direction, and FIG. 4B shows a magnetic flux distribution by the coil 21 on a surface of the heating roller 11 orthogonal to the X direction. FIG. 4C shows the X of the heating roller 11.
7 shows a distribution of magnetic flux by a coil 23 or 25 on a plane orthogonal to the direction.

As shown in FIG. 4A, the heating roller 11
The magnetic flux M1 generated by the current flowing through the coil 21 passes through the central portion L0, and both ends L1, L2
, Magnetic fluxes M2 and M3 generated by currents flowing through the coils 23 and 25 pass. Magnetic fluxes M1, M2, M formed by alternating current supplied to the coils 21, 23, 25
Due to 3, eddy current is generated in the heating roller 11, and Joule heat is generated.

The magnetic flux M1 generated by the current flowing through the coil 21 is, as shown in FIGS.
1 passes through the inside of the central portion L0 in the X direction substantially parallel to the Y direction. Thus, the core 20 and the coil 21 constitute a Y magnetic flux generating means. In addition, the magnetic flux M2 generated by the current flowing through the coil 23 passes through the inside of the end L1 of the heating roller 11 substantially parallel to the X direction as shown in FIG. Thus, the core 22 and the coil 23 constitute X magnetic flux generating means. Further, the magnetic flux M3 generated by the current flowing through the coil 25 passes through the inside of the end portion L2 of the heating roller 11 substantially parallel to the X direction as shown in FIG. in this way,
The core 24 and the coil 25 constitute X magnetic flux generating means.

The magnetic flux M1 generates Joule heat at the center of the heating roller 11 in the X direction, and the magnetic fluxes M2 and M3 generate Joule heat at both ends of the heating roller 11. As a result, the surface of the heating roller 11 has a uniform temperature distribution over its entire length.

The material of the heating roller 11 is as follows.
A ferromagnetic material having conductivity and high magnetic permeability is used, and iron or an alloy of iron with nickel or cobalt is preferable.

As a material for forming the cores 20, 22, and 24, a ferromagnetic material having a high magnetic permeability is used, and iron, an alloy of iron and nickel, cobalt (eg, permalloy),
Ferrite or the like is used. The cores 20, 22, 2
As 4, a laminated core having high magnetic permeability and low eddy current loss can also be used.

In particular, META manufactured by Koyo Materialika Co., Ltd.
Magnetic amorphous alloys such as GLAS and Finemet manufactured by Hitachi Metals, Ltd. are preferred because they have excellent magnetic properties such as high saturation magnetic flux density, high magnetic permeability, and low magnetic loss.

FIG. 5 shows a drive circuit for the coils 21, 23 and 25. As shown in FIG. 5A, by driving the coils 21, 23, and 25 connected in series to one power supply 26, the heating roller 11 can be uniformly heated over its entire length. Further, as shown in FIG. 5B, a power supply 27 for the coil 21 and a power supply 28 for the coils 23 and 25 can be provided separately. In this way, by separately providing the temperature, it is possible to individually control the temperature of the central portion and both ends of the heating roller 11, and it is possible to perform finer control for making the temperature of the heating roller 11 uniform. Become.

As the power supplies 26, 27, 28, 5 kHz
It is desirable to output an alternating current having the above frequency, and it is particularly desirable to use a power supply that outputs an alternating current having a frequency of 10 to 200 kHz.

A magnetic flux M1 substantially parallel to the Y direction is formed by the core 20, the coil 21, and the power supply 26 or 27,
These constitute Y magnetic flux generating means. The heating roller 11 can be heated with high efficiency by the Y magnetic flux generating means. Open end face 20 on which coil 21 of core 20 is not wound
A, 20B and the interval between the inner peripheral surface of the heating roller 11 are set to 1.5
It is desirable that the thickness be in the range of mm to 5 mm in order to further reduce the loss of magnetic flux.

The cores 22, 24, the coils 23, 25,
Magnetic flux M2 substantially parallel to the X direction by the power source 26 or 28
Are formed, and these constitute X magnetic flux generating means. The low temperature at the end of the heating roller 11 is corrected by the X magnetic flux generating means.

Further, the coil 2 is changed according to the size of the recording material P.
On / off control of 3, 25 is also possible.

In this embodiment, the heating position of the heating roller 11 is controlled according to the size of the recording material P. The change in the heat generation position of the heating roller 11 will be described with reference to FIG.

The left end of the coil 23 and the right end of the coil 25 are fixed. Then, the coils 23 and 25 are extended by displacing the right end of the coil 23 and the left end of the coil 25 according to the size of the recording paper P, and the coil length D1 in FIG. 6A is changed to the coil length D2 in FIG. Change to As a result, the lengths of the magnetic fluxes M2 and M3 passing through the heating roller 11 change, the eddy current generation position in the heating roller 11 changes, and the heat generation position of the heating roller 11 changes. Thereby, the recording material P
Is generated in a range corresponding to the size of the recording paper P, and uniform fixing is performed on the recording paper P of various sizes. The cores 22 and 24 are fixed, and the free length D1 in the state where the coils 23 and 25 do not extend, that is, the state shown in FIG.
Is substantially equal to the length D0 of the cores 22 and 24 in the X direction, so that the fixing device 6 can be heated with the highest energy efficiency in the steady operation state.

Further, it is also possible to extend and compress the coils 23 and 25 from the free length L3 so that heating according to the size of the recording material P is performed.

Based on the recording material size information from the paper feed cassette 9 shown in FIG. 1, control means (not shown) shown in FIG.
Alternatively, by performing control to change the coil lengths of the coils 23 and 25 as shown in FIG. 6B, the heating position of the heating roller 11 is controlled in accordance with the size of the recording material P, so that recording materials P of various sizes can be formed. On the other hand, uniform fixing is performed.

When the coil lengths of the coils 23 and 25 are controlled as described above, for example, when forming an image of the most frequently used size such as A4 size,
It is desirable that the fixing is performed on the third and the 25th without applying any extension or compression force. That is, the coil 2
It is desirable that the free length of 3, 25 be the coil length in the normal operation state of the fixing device 6. And
The length D0 of the cores 22 and 24 in the X direction is determined by the coils 23 and 25.
Are almost equal to the free length D1 of the fixing device in the normal operation of the fixing device in that the highest heat generation efficiency can be obtained.

[0041]

According to the first, second, third, fourth or eighth aspect of the present invention, the temperature of the heating roller in the direction of the rotation axis, that is, the end in the direction perpendicular to the recording material conveyance direction is prevented from dropping. The loss of magnetic flux is small and uniform fixing can be performed. In addition, it is possible to prevent leakage of an electromagnetic wave generated to make the temperature on the heating roller uniform.

According to the fifth aspect of the present invention, it is possible to perform heating with high energy efficiency. According to the sixth or ninth aspect of the invention, the heating roller can generate heat in a range corresponding to the size of the recording material, and a uniform fixing effect can be obtained for recording materials of various sizes.

According to the seventh aspect of the present invention, no stress is applied to the coil of the magnetic field generating means in a normal operation state, so that the life of the coil can be prevented from being shortened to cope with the size of the recording material.

[Brief description of the drawings]

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

FIG. 2 is a diagram illustrating a fixing device according to an embodiment of the present invention.

FIG. 3 is a diagram illustrating a heating unit of the fixing device.

FIG. 4 is a diagram showing a magnetic flux distribution.

FIG. 5 is a diagram showing a coil drive circuit of the fixing device according to the embodiment of the present invention.

FIG. 6 is a diagram for explaining a change in a heat generation position of a heating roller.

[Explanation of symbols]

 6 Fixing device 11 Heating roller 12 Pressure roller 20, 22, 24 Core 21, 23, 25 Coil 26, 27, 28 Power supply

Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat II (reference) H05B 6/40 H05B 6/40 6/44 6/44 F term (reference) 2H033 AA03 BA25 BB18 BE06 CA17 CA27 CA30 3J103 AA02 BA04 FA18 FA20 GA57 GA58 GA60 HA03 HA32 3K059 AA08 AB08 AB19 AB20 AB22 AB28 AC07 AC10 AC73 AD03 AD05 AD27 AD34 BD17 BD23 CD14 CD44 CD53 CD66 CD73 CD77

Claims (9)

[Claims] 1. A heating roller which is made of a conductive and ferromagnetic material and performs fixing while conveying a recording material by rotation, a pressing member which presses against the heating roller, a core made of a ferromagnetic material, and a core made of a ferromagnetic material. A coil that is wound and has a winding portion that is substantially parallel to the direction X of the rotation axis of the heating roller, and generates a Y magnetic flux that passes through the heating roller substantially parallel to a Y direction orthogonal to the X direction. A Y magnetic flux generating means provided with a power supply for supplying an alternating current to the X winding coil, and a Y magnetic flux generating means which is disposed adjacent to both ends in the X direction of the Y magnetic flux generating means and is made of a magnetic material; A columnar or cylindrical core, a coil wound around the core, having a winding portion substantially parallel to the Y direction, and generating an X magnetic flux passing through the heating roller substantially parallel to the X direction; Y winding coil and the Y winding coil X magnetic flux generating means provided with a power supply for supplying an alternating current. 2. The power supply of said Y magnetic flux generating means and said X power supply.
2. The fixing device according to claim 1, wherein the power supply of the magnetic flux generating unit includes one common power supply. 3. The power supply of said Y magnetic flux generating means and said X power supply.
The fixing device according to claim 1, wherein the power source of the magnetic flux generating unit is provided separately. 4. The apparatus according to claim 1, wherein an interval between an inner surface of said heating roller and said core of said Y magnetic flux generating means is set to a value within a range of 1.5 mm to 5 mm. 2. The fixing device according to claim 1. 5. The fixing device according to claim 1, wherein the X-th coil and the Y-coil are made of a litz wire. 6. The heating width of the heating roller can be changed by changing the coil length by expanding and contracting the Y-wound coil in the X direction.
The fixing device according to claim 1. 7. The fixing device according to claim 1, wherein a length of the core of the Y magnetic flux generating unit in the X direction is substantially equal to a free length of the Y winding coil. . 8. The fixing device according to claim 1, further comprising: an image forming unit that forms an unfixed toner image on the recording material and conveys the recording material to the fixing device. Characteristic image forming apparatus. 9. The image forming apparatus according to claim 8, further comprising control means for performing control for changing a coil length of the Y-winding coil according to a size of a recording material.