JPH10319748A - Induction heating fixing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide sufficient heat never causing a fixing failure by Joule's heat and miniaturize a heating rotary body by providing a conductive member having an electric resistance larger than aluminum. SOLUTION: A sheet 10 holding unfixed toner 1 is carried from the left as shown by the arrow (b), and sent toward a nip part 19 which is the contact part between a fixing roller 12 and a pressure roller 13. The fixing roller 12 is formed of a conductive member consisting of a hollowed cylindrical pipe having an electric resistance larger than aluminum. The sheet 10 is held by the nip part 19 and carried while adding the heat transferred from the high- temperature fixing roller 12 and the pressure worked from the pressure roller 13. Thus, the image formed by the toner 11 is fixed onto the sheet 10. The toner 11 is held on the surface of the sheet 10 on the side contact with the fixing roller 12.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fixing device used in, for example, an electrophotographic copying machine, a printer, a facsimile, and the like. More specifically, the present invention relates to a fixing device using a low frequency induction heating to form a toner image on a recording medium. The present invention relates to a fixing device for fixing.

[0002]

2. Description of the Related Art In an electrophotographic copying machine, printer, facsimile, or the like, an image (toner image) formed by an unfixed toner is fixed on a paper sheet such as recording paper or a transfer material as a recording medium. A fixing device is provided.

A general fixing device has a fixing roller for fixing a toner image on a sheet, and a pressure roller for pressing the fixing roller to hold the sheet. The fixing roller has a hollow cylindrical shape, and a heat source for raising the temperature to a temperature required for fixing for melting the toner by heat is provided inside.

As a heat source for raising the temperature of the fixing roller, a tubular heater such as a halogen lamp is generally used. The halogen lamp is disposed on the center axis of the fixing roller, and heats the fixing roller by radiant heat. Such a halogen lamp heating method is advantageous in terms of manufacturing cost, but has low heat conversion efficiency because of heating by radiant heat,
There is a disadvantage that energy loss is large.

In order to solve these drawbacks and respond to recent demands for energy saving, an induction heating type fixing device,
For example, a fixing device has been proposed in which a coil formed by helically winding a coil is formed by penetrating a core forming a closed magnetic path inside a fixing roller formed of a conductive member. .

[0006] The heat source in the induction heating system is Joule heat based on the induced current, which is induced in the fixing roller by magnetic flux generated in the core by energizing the coil. In other words, the induction heating method is a mode in which the object to be heated is directly heated by electromagnetic induction, and therefore has a higher heat conversion efficiency than the halogen lamp heating method.

Therefore, the temperature of the fixing roller can be quickly raised to a predetermined fixing temperature with less electric power, and energy saving can be achieved. In particular, the type having a core that forms the above-described closed magnetic path has almost no leakage of magnetic flux, and the induced current is efficiently generated in the fixing roller, so that it has a high energy saving effect, and is used in a large high-speed copying machine or a high-speed printer. Are suitable.

[0008]

As the conductive member forming the fixing roller, aluminum having a small specific gravity and excellent thermal conductivity is used in consideration of the weight reduction of the apparatus and the uniformity of temperature distribution. ing.

However, since aluminum has a small electric resistance, the induced current increases and the amount of Joule heat generated increases. This far exceeds the minimum amount of heat required to secure the fixing performance. Therefore, in order to obtain an appropriate amount of heat, the number of turns of the coil is increased to reduce the induced voltage on the secondary side. In other words, the required minimum amount of heat is obtained by reducing the induced current and reducing the Joule heat loss. However, an increase in the number of windings causes a problem that the winding diameter of the coil increases.

Further, since the coil is arranged inside the fixing roller, a predetermined effect of making the temperature gradient uniform cannot be exerted unless the internal space has a sufficient margin. Therefore, when increasing the winding diameter of the coil and increasing the number of turns of the coil, in order to have a sufficient margin in the internal space,
It is necessary to increase the diameter of the fixing roller itself. as a result,
This hinders downsizing of the fixing device, causing an increase in the occupied area of the entire device and an increase in manufacturing cost.

SUMMARY OF THE INVENTION The present invention has been made to solve the problems associated with the above-mentioned conventional technology, and has as its object to provide an induction heating fixing device capable of reducing the size of a fixing roller.

[0012]

In order to achieve the above object, an induction heating fixing apparatus according to the present invention presses a hollow cylindrical heating rotator formed of a conductive member and a recording medium holding toner. A pressurizing rotator sandwiched between the heating rotator, a core partially inserted into a hollow portion of the heating rotator to form a closed magnetic path, and a heating rotator wound around the core. And a coil disposed in the hollow portion for induction heating the heating rotator, wherein the conductive member has an electric resistance greater than that of aluminum.

In the invention specified in this way, in order to obtain the necessary minimum amount of heat for securing the fixing performance, the number of turns of the coil is reduced as compared with the case where aluminum is used, and the number of turns on the secondary side is reduced. By increasing the induced voltage to increase the induced current, the Joule heat loss (power consumption) is made the same. That is, even if the number of turns of the coil is reduced as compared with the case where aluminum is used, a sufficient amount of heat that does not cause fixing failure can be obtained by Joule heat, and the heating rotator can be downsized. .

[0014]

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

FIG. 1 is a schematic configuration diagram showing an induction heating fixing device according to an embodiment of the present invention, and FIG. 2 is a sectional view of the fixing roller shown in FIG.

As shown in FIGS. 1 and 2, the induction heating fixing device according to the embodiment of the present invention heats and fuses a toner 11 held on a paper sheet (recording medium) 10 for copying. , Is fixed on the sheet 10. In addition, the induction heating fixing device includes a pressure roller (pressure rotation) that presses the fixing roller (heated rotating body) 12 to be heated by induction and the fixing roller 12 by pressing the sheet 10 holding the toner 11. And a coil 14 for inductively heating the fixing roller 12.

The fixing roller 12 is formed of a hollow cylindrical pipe, and is formed of a conductive member having an electric resistance higher than that of aluminum. The thickness of the fixing roller 12 ensures a sufficient mechanical strength against the pressing force from the pressure roller 13 and a sufficient heat capacity, for example, does not cause a fixing failure even when a large number of copies are performed. It is set to have a heat capacity. Further, a fluororesin coating layer is formed on the outer peripheral surface of the fixing roller 12. The fluororesin coating layer has good releasability from the sheet 10 and the toner 11 and also has heat resistance.

At both ends of the fixing roller 12, sliding bearings (not shown) are formed, and are rotatably attached to a frame of the fixing unit (not shown). Further, a driving gear connected to a driving source such as a motor is fixed to one end of the fixing roller 12 (not shown). The driving gear is for rotating the fixing roller 12 in the direction of arrow a in FIG.

The pressure roller 13 comprises a shaft core 15 and a silicon rubber layer 16 formed around the shaft core 15. The silicone rubber layer 16 has releasability from the sheet 10 and has heat resistance. Further, the pressing roller 13 is formed by a spring material (not shown) using the fixing roller 1.
2. The pressure roller 1
Reference numeral 3 rotates following the rotation of the fixing roller 12.

The coil 14 is formed by spirally winding a winding 18, is inserted into a rectangular core 17 forming a closed magnetic circuit, and is disposed concentrically inside the fixing roller 12. That is, a part of the core 17 passes through the hollow portion of the fixing roller 12. The core 17 is a so-called iron core used for an ordinary transformer or the like. For example, a core having a high magnetic permeability such as a silicon steel sheet laminated iron core is preferable. Of course, a columnar core may be used regardless of the laminated core. As the winding 18 of the coil 14, an ordinary single conductor having a fusion layer and an insulating layer on the surface is used.

Next, the fixing operation of the induction heating fixing device will be described.

First, when an AC voltage of a low frequency (50 to 60 Hz) is applied to the coil 14 from a power supply circuit (not shown), a magnetic flux is generated in the core 17, an induced voltage is generated in the fixing roller 12, and an induced current is generated. Flows. As a result, Joule heat (induction heating) based on the induction current causes the fixing roller 1
2 directly generates heat and has a predetermined temperature suitable for fixing, for example, 15
Raise the temperature to 0-200 ° C.

Sheet 10 holding unfixed toner 11
Is transported from the left as shown by the arrow b in FIG.
The paper is fed toward a nip 19 which is a contact part between the fixing roller 12 and the pressure roller 13.

The sheet 10 is conveyed while being nipped by the nip 19 while the heat transmitted from the high-temperature fixing roller 12 and the pressure applied from the pressure roller 13 are applied. As a result, an image composed of the toner 11 is fixed on the sheet 10. The toner 11
Is on the surface of the sheet 10 that is in contact with the fixing roller 12,
Is held.

The sheet 10 that has passed through the nip 19 is naturally separated from the fixing roller 12 by a curvature due to the strength of the sheet itself, and is conveyed rightward in FIG. The sheet 10 is conveyed by a discharge roller (not shown) and discharged onto a discharge tray.

Next, the operation principle of the induction heating fixing device will be described.

The operation principle of the induction heating fixing device is basically the same as that of the transformer. That is, the coil 14 corresponds to the primary coil (the number of turns N1) on the input side, and the fixing roller 1
Reference numeral 2 corresponds to an output-side secondary coil (number of turns N2) (see FIG. 2).

Therefore, the primary side coil (coil 14)
When a low-frequency (50-60 Hz) AC voltage V1 is applied to the first coil, a current I1 flows through the primary coil. The magnetic flux φ generated thereby flows through the core (17) forming a closed magnetic path, and the induced electromotive force V is applied to the secondary coil (fixing roller 12).
Yields 2. As a result, the current I2 flows along the circumferential direction of the fixing roller 12. Since the closed magnetic path is formed by the core (17), there is no leakage magnetic flux in principle, and the primary energy [V1 × I1] and the secondary energy [V2 × I2] are substantially equal. Become.

Therefore, in this system, (1) heat generation due to copper loss in the copper wire of the primary coil (coil 14), (2)
There is heat generation due to copper loss in the copper wire of the secondary coil (fixing roller 12), and (3) heat generation due to Joule heat loss and hysteresis loss generated inside the core (17). In other words, the induction heating fixing device suppresses the heat generation of (1) and (3), which cause energy loss, as much as possible, while causing the fixing roller 12 to generate heat using the copper loss of (2).

In particular, in the present invention, the fixing roller is made of a conductive member having an electric resistance higher than that of aluminum. Further, in order to make the heat quantity the same, the number of turns of the coil is reduced, the electromotive voltage induced in the secondary coil (fixing roller 12) is increased, the induced current is increased, and the Joule heat loss (power consumption) is reduced. It is the same. That is, as compared with the case where aluminum is used, even if the number of turns of the coil is reduced, a sufficient amount of heat that does not cause defective fixing can be obtained by Joule heat. Therefore, the winding diameter of the coil can be reduced and the size can be reduced.

That is, by reducing the size of the coil,
Since a sufficient margin can be secured in the internal space, even if the fixing roller is downsized, it does not adversely affect the uniformity of the temperature gradient. Therefore, it is possible to reduce the size of the fixing roller as compared with the case where aluminum is used. As a result, it is possible to reduce the occupied area of the entire apparatus and the manufacturing cost.

Next, a more specific configuration of the induction heating fixing device according to the embodiment of the present invention will be described by taking, as an example, iron which is a conductive member having an electric resistance higher than aluminum.

FIG. 3 is a chart showing physical property values related to aluminum and iron, and FIG. 4 is a chart showing a specific configuration of the induction heating fixing device.

First, regarding the number of turns of the coil, Joule heat loss (power consumption) used for heating (heating) the fixing roller.
Are the same, iron and aluminum are compared.

As described above (see FIG. 2), the operation principle of the induction heating fixing device is basically the same as that of the transformer.
Therefore, the number of turns of the primary coil is N1, the number of turns of the secondary coil is N2, and the AC voltage applied to the primary coil is V.
When the induced electromotive force of the primary and secondary coils is represented by V2, the following equation (1) is established, and (N1 / N2) = (V1 / V2). When represented by R, it can be represented by the following equation (2): N1 ² = V1 ² / (R × P)

Therefore, as shown in FIG. 4, the specific dimensions of the AC voltage V1 applied to the primary coil are 100 [V], the power consumption P is 750 [W],
When the number of turns N1 of the primary coil is 451T, the number of turns of the secondary coil is iron, and the number of turns N2 of the secondary coil is 1T, and the resistance of the secondary coil is RFe, the equations (1) and (2) are used.
Equation (3), (451) ² = (100) ² / (RFe × 750) holds.

On the other hand, the AC voltage V1 applied to the primary coil is 100 [V], the power consumption P is 750 [W], the number of turns N1 of the primary coil is XT, and the secondary coil is made of aluminum. When the number of turns N2 of the secondary side coil is 1T and the resistance of the secondary side coil is RAl, as in the case of the equation (3), the equations (1) and (2) are used to calculate the equation (4), X ² = (100) ² / (RAl × 750) holds.

As shown in FIG. 3, the electrical resistance [μΩcm ³ ] of aluminum is “2.655”, that of iron is “9.71”, and the equation (5): RAl = 0.27RFe Holds.

Therefore, when the equation (3) is divided by the equation (4), the following equation is obtained: (451) ² / X ² = RAl / RFe. From the relation of the equation (5), X ² = (451) ² × (RFe / RAl) = (451) ² /0.27=(868) ² That is, the number of turns of the coil is “868”.

As described above, heating (heating) of the fixing roller
When the same Joule heat loss (power consumption) is used, an iron fixing roller having 451 T of coil turns corresponds to an aluminum fixing roller having 868 T of turns. That is, as described above, by forming the fixing roller from a conductive member having electric resistance higher than that of aluminum, the winding diameter of the coil can be reduced as compared with the case where aluminum is used.

Next, regarding the outer diameter size of the fixing roller,
When the heat capacities are the same, iron and aluminum are further compared.

The iron core cross-sectional area SAl when the secondary coil is made of aluminum is given by the following equation (6), where V is the power supply voltage, f is the power supply frequency, N is the number of turns of the coil, and Bm is the magnetic flux density. V / (4.44 × f × N × S) is satisfied.

On the other hand, an iron-made fixing roller having a coil number of 451 T corresponds to an aluminum-made fixing roller having a coil number of 868 T, and as shown in FIG. [V], the power supply frequency f is 60 [Hz], and the iron core cross-sectional area SFe when the fixing roller is made of iron is 6.25 [cm ² ].
Formula (7), 100 / (4.44 × 60 × 451 × 6.25) = 10
The relationship of 0 / (4.44 × 60 × 868 × SAl), that is, the relationship of 1 / (451 × 6.25) = 1 / (868 × SAl) is satisfied.

Accordingly, from the equation (7), the iron core cross-sectional area SAl in the case of aluminum is given by SAl = (451 × 6.25) /868=3.25 (1.
8 × 1.8 [cm ^□ ]). That is, the diagonal distance L of the iron core is: L = 18 × (2) ^1/2 = 25.5 [mm] = 2.55 [c
m]. Further, as shown in FIG. 4, specific dimensions around the iron core are 2.3 [mmφ] (0.23 mm).
[Cmφ]) with 7 layers of wire, with a clearance of 4
[Mm] (0.4 [cm]), the inner diameter Din of the aluminum roller uses the diagonal distance L, and is expressed by the following equation (8): Din = ((L / 2) + (2.3 × 7) ) +4) × 2 = 65.7 [mm] = 6.57 [cm].

Further, the thickness is 0.5 [cm] and the outer diameter is 6.
When the heat capacity QFe of an iron roller having an inner diameter of 04 [cmφ] (that is, the inner diameter is 5.04 [cmφ]) is equal to the heat capacity QFe of an aluminum roller, the outer diameter of the aluminum roller is represented by Dex. As shown in FIG. 3, iron is
Specific gravity is 7.87 [g / cm ³ ] and specific heat is 0.11 [cal /
g · ° C.], and aluminum has a specific gravity of 2.669.
[G / cm ³ ] and the specific heat are 0.215 [cal / g · ° C.], therefore, Equation (9): QFe = QAl = π ((6.04 / 2) ² − (5.04 / 2) ² ) × 7.87 × 0.11 = π ((Dex / 2) ² − (6.57 / 2) ² ) × 2.699 × 0.215

Therefore, equation (9) is given by: QFe = QAl = 3.89 = 0.58 ((Dex / 2) ² −1
0.8), and (Dex / 2) ² = 17.51 = (8.4) ² . That is, the outer diameter Dex of the aluminum roller
Is 8.4 [cm].

Therefore, when the heat capacity is the same,
The fact that the fixing roller 12 is made of iron and has an outer diameter of 6.04 [cmφ] corresponds to 8.4 [cmφ] of aluminum. That is, as described above, by forming the fixing roller from a conductive member having an electrical resistance higher than that of aluminum, it is possible to reduce the size of the fixing roller as compared with the case where aluminum is used.

[0048]

As described above, according to the present invention, even if the heating rotator (fixing roller) is formed of a conductive member having an electric resistance higher than that of aluminum, the heat quantity is the same. That is, as compared with the case where aluminum is used, the number of turns of the coil is reduced, the induced voltage of the secondary coil (fixing roller) is increased, and the induced current is increased, so that the Joule heat loss (power consumption) is the same. I have. Therefore, compared to the case where aluminum is used, even if the number of turns of the coil is reduced, a sufficient amount of heat that does not cause a fixing failure can be obtained by Joule heat, and the coil diameter is reduced to reduce the coil diameter. Can be

Further, by reducing the size of the coil,
Since a sufficient margin can be ensured in the internal space, even if the fixing roller (heating rotator) is downsized, it does not adversely affect the uniformity of the temperature gradient. Therefore, it is possible to reduce the size of the heating rotator (fixing roller) as compared with the case where aluminum is used. As a result, it is possible to reduce the occupied area of the entire apparatus and the manufacturing cost.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram showing an induction heating fixing device according to an embodiment of the present invention.

FIG. 2 is a cross-sectional view of the fixing roller shown in FIG.

FIG. 3 is a table showing physical property values related to aluminum and iron.

FIG. 4 is a table showing a specific configuration of the induction heating fixing device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 ... Paper sheet (recording medium), 11 ... Toner, 12 ... Fixing roller (heating rotating body), 13 ... Pressure roller (pressure rotating body), 14 ... Coil, 17 ... Core, 18 ... Winding.

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Ryo Takasu, Inventor Ryo Takasu 2-3-3, Azuchicho, Chuo-ku, Osaka City Osaka International Building Minolta Co., Ltd. Tokuden Corporation

Claims (1)

[Claims] 1. A heating rotator having a hollow cylindrical shape formed of a conductive member, a pressing rotator pressing a recording medium holding a toner in contact with the heating rotator, and a heating rotator. Induction heating comprising: a core partially inserted into a hollow portion of a body to form a closed magnetic path; and a coil wound around the core and arranged in the hollow portion of the heating rotator to induction-heat the heating rotator. In the fixing device, the conductive member has an electric resistance higher than that of aluminum.