JPH10319750A - Induction heating fixing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce the power consumption in a support member and maximize the heat generation of a fixing roller by bringing a magnetic flux through member into contact with a conductive support member for partially surrounding a core to form a closed loop, and passing a part of the magnetic flux generated in the core through the support member. SOLUTION: This device has a rectangular core 8 for forming a closed magnetic path, and the core 8 is partially passed through the hollow part of a fixing roller 3. A magnetic flux through member 17 is brought into contact with a bearing 14 to pass a part of the magnetic flux generated in the core 8 through support members 11, 12, 14, 15. An AC power is applied to a coil 5 to heat the fixing roller 3 to a temperature suitable for fixation. After the roller temperature reaches the fixable temperature, the fixing roller 3 and a pressure roller are rotated in mutually reverse directions while sliding to nip a sheet having toner adhered thereto. The sheet is carried while receiving the heat of the fixing roller 3 and the pressure worked from both the rollers.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an induction heating type fixing device used in, for example, an electrophotographic copying machine, a printer, and a facsimile.

[0002]

2. Description of the Related Art A fixing device for fixing a toner image formed on a sheet such as a recording medium or a transfer material as a recording medium to an electrophotographic copying machine, a printer, a facsimile or the like is provided in the sheet. ing.

There are various types of fixing devices. For example, a general heat roller type fixing device includes a fixing roller that thermally melts toner on a sheet, and presses the fixing roller to sandwich the sheet. And a pressure roller. The fixing roller is formed in a cylindrical shape, and a heating element for heating the fixing roller is provided inside the fixing roller. The heating roller heats the fixing roller to a temperature (fixable temperature) necessary for fusing and fixing the toner.

Generally, a tubular heater such as a halogen heater lamp is used as a heating element in the heat roller fixing device. At present, the halogen heater lamp is arranged on the center axis of the fixing roller, and a halogen heater is provided. What heats a fixing roller by radiant heat of a lamp has become mainstream. However, such a fixing device using a halogen heater lamp is inexpensive in terms of cost, but has the drawback of low thermal efficiency and large energy loss due to heating by radiant heat.

Therefore, in order to solve the disadvantage of the heating by the halogen heater lamp and respond to the recent demand for energy saving, a closed magnetic circuit is formed as disclosed in, for example, Japanese Patent Publication No. 4-73155. A coil (induction coil) is wound around a part of a core (iron core), and the core wound with this coil is inserted into a conductive fixing roller, and an alternating current is passed through the coil. An induction heating type fixing device has been developed in which an induction current is generated in a fixing roller to generate heat in the fixing roller.

A fixing device using such induction heating is:
Since the fixing roller generates heat directly by electromagnetic induction, its heat conversion efficiency is higher than that of the heating method using a halogen heater lamp, and the surface of the fixing roller can be quickly heated to a fixing temperature with less power. Becomes In particular, those having a core that forms a closed magnetic circuit as described in the above publication have almost no leakage of magnetic flux, and thus can efficiently generate a secondary current in the fixing roller. And high-speed printers.

[0007]

By the way, as shown in the above-mentioned publication, in an induction heating fixing device having a fixing roller in which a core is inserted, conventionally, a fixing roller is generally rotatably supported. Metal bearings, sleeves, support frames,
Various conductive support members such as fixing rings are provided.

However, in such a roller supporting structure, since a conductive (metal) supporting member for supporting the fixing roller surrounds a part of the core to form a closed loop, not only the fixing roller but also the supporting member is formed. Is also heated by heating, the power consumption of the fixing roller is reduced by the power consumption of the supporting member, and the heat value of the fixing roller (secondary copper loss).
There is a problem that is reduced.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems associated with the prior art. Even when the supporting member of the fixing roller is made of a conductive material, the supporting member is induction-heated. An object of the present invention is to provide an induction heating fixing device capable of maximizing the amount of heat generated by induction heating only a fixing roller without using the fixing roller.

[0010]

According to the present invention, there is provided an induction heating fixing apparatus of an induction heating system for fixing a toner image formed on a recording medium to the recording medium, the apparatus comprising a conductive material. A formed cylindrical fixing roller, a pressure roller provided to be in pressure contact with the fixing roller, and a pressure roller for nipping the recording medium between the fixing roller, and a part inserted through a hollow portion of the fixing roller. A core forming a closed magnetic path, a coil wound around a part of the core, disposed in the hollow portion of the fixing roller, and inductively heating the fixing roller, and a closed loop surrounding a part of the core. Formed, a conductive support member for supporting the fixing roller,
A magnetic flux penetrating member that contacts the support member and allows a part of the magnetic flux generated in the core to penetrate the support member.

According to the structure of the present invention, the magnetic flux penetrating member is brought into contact with the conductive support member surrounding the part of the core forming the closed magnetic path and forming a closed loop, and the part of the magnetic flux generated in the core is converted into the part. Because the support member was made to penetrate,
The support member is not subjected to induction heating, that is, there is no secondary copper loss in the support member, and the energy consumed in the support member is changed to iron loss (iron loss <copper loss). Accordingly, the power consumption of the fixing member is reduced, and the power consumption of the fixing roller is increased accordingly, so that the calorific value (secondary copper loss) of the fixing roller increases.

[0012]

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

FIG. 1 is a sectional view showing a schematic structure of a main part of an induction heating fixing device (hereinafter simply referred to as a "fixing device") to which the present invention is applied, and FIG. 2 is a schematic structure of a fixing roller supporting structure of the device. FIG.

This fixing device heats and melts toner 2 held on a sheet 1 as a recording medium and fixes the toner on the sheet 1. The fixing device is rotatably driven in the direction of arrow a in FIG. A fixing roller 3, a pressure roller 4 that is provided in pressure contact with the fixing roller 3, and that rotates following the rotation of the fixing roller 3, and a coil 5 that induces and heats the fixing roller 3.

The fixing roller 3 is a conductive hollow cylindrical pipe, and is formed of a conductive material such as a carbon steel pipe, a stainless alloy pipe, or an aluminum pipe (roller shell). Is formed within a range in which sufficient mechanical strength can be ensured, and with a thickness that can ensure a constant heat capacity. Also, on its outer peripheral surface,
To facilitate separation of the sheet 1, a heat-resistant release layer having good release properties and heat resistance for the toner 2 is formed by coating a fluororesin.

The pressure roller 4 is also cylindrical and has a shaft core 6.
And a silicone rubber layer 7 formed around the shaft core 6. The silicon rubber layer 7 is a rubber layer having a releasability from which the sheet 1 is easily separated from the surface and also having heat resistance. The pressure roller 4 is constantly urged in a direction toward the fixing roller 3 by a spring material (not shown).

The fixing device has a rectangular core 8 forming a closed magnetic circuit, and a part of the core 8 is
Through the hollow portion 3a. The coil 5 is formed by spirally winding a winding 9 around a core 8, and is disposed concentrically inside the fixing roller 3. The core 8 is a so-called iron core used for an ordinary transformer or the like, and preferably has a high magnetic permeability such as a silicon steel sheet laminated iron core. Of course, a columnar core may be used instead of the laminated core. Further, as the winding 9 of the coil 5, an ordinary single conductor having a fusion layer and an insulating layer on the surface is used.

As a support structure of the fixing roller 3, as shown in FIG. 2, stepped cylindrical sleeves 11 are fitted on both ends of the fixing roller 3, and this sleeve 11 is provided on a support frame (sheet metal) 12. It passes through the mounting hole 13.
The core 8 also penetrates the support frame 12. A bearing 14 is disposed between the sleeve 11 and (the mounting hole 13 of) the support frame 12. Further, the fixing roller 3
A fixing ring 15 for regulating the axial position of the fixing roller 3 is fitted in a ring groove 16 formed at an end of the fixing roller 3. The sleeve 11, the support frame 12, the bearing 14, and the fixing ring 15 are all made of conductive metal and constitute a support member. The fixing roller 3 is rotatably supported by these support members 11, 12, 14, and 15. The fixing roller 3 has a driving gear (not shown) fixed to one end thereof, and is rotatably driven by a driving source (not shown) such as a motor connected to the driving gear.

In the fixing operation, first, an AC power supply (not shown) is applied to the coil 5, and the temperature of the fixing roller 3 is adjusted to a temperature suitable for fixing (for example, 150 to 2) by induction heating.
(00 ° C). After the roller temperature reaches the feasible fixing temperature, the fixing roller 3 and the pressure roller 4 rotate in opposite directions while slidingly contacting each other, and sandwich the sheet 1 to which the toner 2 has adhered. That is, the sheet 1 holding the unfixed toner 2 is conveyed from the left as indicated by an arrow b in FIG. 1 and is fed toward a nip 10 which is a contact portion between the fixing roller 3 and the pressure roller 4. Then, the sheet is conveyed while being nipped by the nip 10 while receiving the heat of the heated fixing roller 3 and the pressure applied from the rollers 3 and 4.
In this process, the toner 2 on the sheet 1 is melted by the heat of the fixing roller 3 in the nip 10 and both the rollers 3
The sheet is fixed on the sheet 1 by the pressure applied from the sheet 4. The sheet 1 on which the toner 2 has been fixed after passing through the nip 10 is
As the fixing roller 3 and the pressure roller 4 rotate, the sheet is conveyed rightward in FIG. Then, the paper is conveyed by a paper discharge roller (not shown) and discharged onto a paper discharge tray (not shown) such as a copying machine or a printer.

However, in the support structure of the fixing roller 3 as described above, the conductive (metal) supporting members 11, 12, 14, 15 for supporting the fixing roller 3 surround a part of the core 8 to form a closed loop. In the fixing operation, not only the fixing roller 3 but also the support members 11, 12,
The heating of the fixing rollers 14 and 15 is also performed, and the calorific value (secondary copper loss) of the fixing roller is reduced as described above.

Therefore, in the present invention, the support member (for example,
In the example of FIG. 2, the magnetic flux penetrating member 17 is brought into contact with the bearing 14), and a part of the magnetic flux φ generated in the core 8 is partially supported.
1, 12, 14, and 15 are made to penetrate. For example, the magnetic flux penetrating member 17 forms a part of the core 8 and is formed to protrude from the core 8. As a result, as will be described later, the support members 11, 12, 14, and 15 are not heated by induction, and power is consumed not as secondary copper loss but as iron loss.

The basic operation principle of the induction heating fixing device configured as described above is the same as that of a transformer, and the coil 5 corresponds to a primary coil (N winding) on the input side as an induction coil. Reference numeral 3 corresponds to a secondary coil (one turn) on the output side as a roller shell. Then, an AC voltage V1 is applied to the primary coil (coil 5), and a current I1 is applied.
Flows, a magnetic flux φ is generated in the core 9 forming the closed magnetic circuit,
The change in the magnetic flux φ causes the secondary coil (fixing roller 3)
, An induced electromotive force V2 is generated, and an induced current I2 flows along the circumferential direction of the fixing roller 3. At this time, since a closed magnetic path is formed by the core 9, there is no leakage magnetic flux in principle, and therefore, the primary side (input) energy V1 × I1 and the secondary side (output) energy V2 × I2 are substantially equal.

There are three places where heat is generated in this induction heating. The first is a primary copper loss generated in the conductive wire (in copper) of the primary coil, that is, the heat generated in the coil 5, and the second is:
The secondary copper loss generated in the conductor (in the copper) of the secondary coil, that is, the heat generated by the fixing roller 3, and the third is the iron loss composed of the Joule heat loss and the hysteresis loss generated inside the iron core, that is, the core loss It is fever. In the induction heating fixing device, the first and third losses (heat generation) are energy losses. Therefore, while these losses (heat generation) are suppressed as much as possible, the second copper loss (Joule heat) is reduced by thermal energy. And heats the fixing roller 3.

In particular, in the present embodiment, the magnetic flux penetrating member 17 is brought into contact with the conductive support member (bearing 14) that forms a closed loop by surrounding a part of the core 8 that forms a closed magnetic path. Since a part of the generated magnetic flux φ is made to penetrate the support members 11, 12, 14, and 15,
The support members 11, 12, 14, 15 are no longer subjected to induction heating, that is, there is no secondary copper loss in the support members 11, 12, 14, 15, and the support members 11, 12, 14, 1, 1
All the energy consumed in 5 will change from copper loss to iron loss. Iron loss is smaller than copper loss. Therefore, the power consumption (energy loss) of the support members 11, 12, 14, and 15 is reduced, and the power consumption of the fixing roller 3 is increased accordingly. Amount (secondary copper loss) increases. That is, even if the support members 11, 12, 14, 15 are formed of a conductive material, energy is not wastefully consumed by these support members 11, 12, 14, 15, so that only the fixing roller 3 is used. Induction heating can be performed efficiently, and a higher energy saving effect can be obtained.

[0025]

As described above, according to the present invention,
By contacting the magnetic flux penetrating member with a conductive supporting member that forms a closed loop surrounding a part of the core, a part of the magnetic flux generated in the core is made to penetrate the supporting member,
The support member is not induction heated (no secondary copper loss),
All can be consumed as iron loss. Therefore, the power consumption (energy loss) of the supporting member is reduced, and the power consumption of the fixing roller is increased accordingly. Therefore, the efficiency is further increased, and the heat generation amount (secondary copper loss) of the fixing roller is maximized. It becomes possible to.

[Brief description of the drawings]

FIG. 1 is a sectional view showing a schematic configuration of a main part of an induction heating fixing device to which the present invention is applied.

FIG. 2 is a cross-sectional view illustrating a schematic configuration of a fixing roller support structure of the fixing device.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 sheet (recording medium) 2 toner 3 fixing roller 4 pressure roller 5 coil 8 core 11 sleeve (support member) 12 support frame (support member) 14 bearing (support member) 15 fixing Ring (support member) 17 ... magnetic flux penetration member

────────────────────────────────────────────────── ───

[Procedure amendment]

[Submission date] May 21, 1997

[Procedure amendment 1]

[Document name to be amended] Drawing

[Correction target item name] All figures

[Correction method] Change

[Correction contents]

FIG.

FIG. 2

Claims (1)

[Claims] 1. An induction heating fixing device of an induction heating system for fixing a toner image formed on a recording medium to the recording medium, comprising: a cylindrical fixing roller formed of a conductive material; A pressure roller that sandwiches the recording medium between the fixing roller and a core partly inserted into a hollow portion of the fixing roller to form a closed magnetic path; and a part of the core. A coil that is wound and disposed in the hollow portion of the fixing roller and that induction-heats the fixing roller; and a conductive support member that forms a closed loop surrounding a part of the core and supports the fixing roller. And a magnetic flux penetrating member that contacts the support member and allows a part of the magnetic flux generated in the core to penetrate the support member.