JP2002231428A - Heating system and image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent shortening of the endurable service life, to realize energy- saving, and to prevent a system inside temperature rise while performing preliminary heating in standby, in a heating system for heating a heating object P by the heat of a rotary body 10 by carrying the heating object P holded by a nip part N formed of a pressurizing member 30 and the rotary body 10 heated by electromagnetic induction with the action of a magnetic field of magnetic field generating means 17 and 18, in which a temperature detecting means 28 is arranged in a heating area of the rotary body 10 and preliminary heating is performed by the heat of the rotary body 10 in the stopping state of the rotary body 10. SOLUTION: Multistage preliminary heating is performed in a state of stopping the rotary body 10. That s, a multistage preliminary heating temperature is provided, and a preheating state is determined on the basis of temperature information detected by the temperature detecting means 28, and the preliminary heating temperature is properly changed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to a magnetic field generating means,
It has a rotating body that generates electromagnetic induction heat by the action of the magnetic field of the magnetic field generating means, and a pressurizing member that forms a nip portion by mutual pressure contact with this rotating body, and generates an eddy current in the rotating body using electromagnetic induction. The present invention relates to a heating device of an electromagnetic induction heating type, which heats the material to be heated by the heat generated by the rotating body.

Further, this electromagnetic induction heating type heating device is
The present invention relates to an image forming apparatus, such as an electrophotographic apparatus and an electrostatic recording apparatus, provided as an image heating apparatus that heats an image formed on a recording material.

[0003]

2. Description of the Related Art In an image forming apparatus such as an electrophotographic apparatus and an electrostatic recording apparatus, a heating apparatus (an image heating and fixing apparatus) for fixing an unfixed toner image formed on a recording material will be described as an example. As a heating device for an unfixed toner image, a contact heating method such as a heat roller method or a film heating method has been widely used. In recent years, a heating device using an electromagnetic induction method as a heating source has been proposed.

In a heating device for an unfixed full-color toner image, up to four toner layers may be stacked,
If the interface between the recording material and the toner layer is not sufficiently heated, poor fixing may occur, so it is necessary to hold the toner layer firmly until the toner layer is reliably fixed.

Japanese Patent Laid-Open Publication No. Hei 10-171296 discloses a method of controlling the heating device of the electromagnetic induction type, in which the fixing film having a low heat capacity as a rotating body which generates heat by electromagnetic induction heats up locally in the device. Proposals have been made to reduce the first print time (FPOT) by performing preliminary rotation and preliminary heating of the fixing film during the process.

[0006]

However, in the control in which the fixing film is pre-rotated at the same time as the pre-heating during the standby of the apparatus, the frequency of use of the image forming apparatus is low, and when the standby state becomes long, the standby state of the image forming apparatus is reduced. The rotation of the fixing film is prolonged, and as a result, the rotation ratio of the fixing film in standby becomes large in the durable life of the heating device, and there is a problem that the number of printable sheets is reduced.

Therefore, a method of preheating with the fixing film stopped can be considered. However, when a magnetic field generating means having a large heat capacity is provided in the fixing film and the fixing film is locally heated, the fixing film is not heated. The rise time up to the fixable temperature changes depending on the temperature state. Also,
If the fixing film having a relatively small heat capacity is heated in a stopped state during standby, a large temperature gradient is generated between a heated portion and a non-heated portion at one position around the fixing film. For this reason, it is difficult to predict the preheating temperature necessary to stably raise the temperature of the fixing film to a fixing feasible temperature after the printing is started and before the leading end of the recording material reaches the fixing nip portion. there were. A method of keeping the preheating temperature high can be considered, but there is a problem that not only unnecessary energy is consumed but also the temperature rise in the image forming apparatus is adversely affected.

Accordingly, the present invention provides a heating device of the electromagnetic induction heating type, which is capable of preventing a decrease in the durable life of the device while performing preheating during standby of the device with a simple structure, as well as an appropriate preliminary heating. The purpose is to contribute to energy saving by selecting the heating temperature.

In the image forming apparatus, the first print out time (FPOT) is shortened and the life of the heating apparatus is extended, and the temperature rise in the apparatus is reduced while contributing to energy saving. With the goal.

[0010]

According to the present invention, there is provided a heating apparatus and an image forming apparatus having the following constitutions.

(1) The nip comprises a magnetic field generating means, a rotating body which generates electromagnetic induction by the action of the magnetic field of the magnetic field generating means, and a pressing member which forms a nip portion by mutually pressing the rotating body. A heating device for nipping and transporting the material to be heated by the unit and heating the material to be heated by the heat generated by the rotating body, wherein a temperature detecting means is disposed in a heating area of the rotating body, and by the heat generated by the rotating body,
In a heating device for preheating the rotating body in a stopped state, the heating device has a multistage preheating temperature, determines a preheating state based on temperature information detected by the temperature detecting means, and appropriately changes the preheating temperature. A heating device.

(2) Power control for performing variable control between a minimum non-zero power and a maximum power to maintain the rotating body at a predetermined temperature based on the temperature information detected by the temperature detecting means. (1) wherein the power control includes power control that repeats an ON state and an OFF state, and the preheating temperature is appropriately changed based on a change in the ON and OFF states. A heating device as described.

(3) Assuming that the ON time before and after the OFF is Ton (before) and Ton (after),
The heating device according to (2), wherein the on-time of (before) is compared with the on-time of Ton (after), and the preheating temperature is appropriately changed when a predetermined relationship of the on-time is satisfied. .

(4) Assuming that the ON time before and after the OFF is Ton (before) and Ton (after),
The heating device according to (2), wherein the on-time of (before) is compared with the on-time of Ton (after), and the preheating temperature is appropriately changed when a predetermined relationship of the on-time is satisfied. .

(5) In the comparison of the ON times, when Ton (before) -Ton (after) ≧ To (To is a positive value including zero), the preheating temperature is changed. The heating device according to (3) or (4).

(6) The heating device according to any one of (1) to (5), wherein the preheating temperature is changed to a low temperature.

(7) An image forming apparatus comprising: an image forming means for forming an image on a recording material; and a heating device for heating the image formed on the recording material, wherein the heating device comprises (1)
An image forming apparatus, which is the heating apparatus according to any one of (1) to (6).

[Operation] In other words, in a standby state of the apparatus, by performing preheating while the rotating body that generates electromagnetic induction heat is stopped, the rotation ratio of the rotating body in the standby state of the apparatus becomes zero. It is possible to prevent a decrease in the durable life of the device while performing preheating during standby.

By having a multi-stage preheating temperature, by sequentially shifting to a lower preheating temperature, it is possible to suppress useless energy input, which is advantageous for raising the temperature in the apparatus and also contributing to energy saving. In addition, even with a heating device in which a part of the fixing film having a relatively small heat capacity generates heat and a temperature gradient is generated, the thermal state of the entire heating device is estimated only by the temperature detecting element disposed in the heating region of the fixing film. Therefore, the preheating temperature can be switched with a simple configuration.

In the image forming apparatus, the first print-out is performed by preheating during standby of the apparatus.
Since the time (FPOT) can be shortened, and even if the frequency of use of the image forming apparatus is low and the standby state is lengthened, the rotation ratio of the rotating body in the standby becomes zero among the durable life of the heating apparatus. It is possible to eliminate a decrease in the number of printable sheets due to the preliminary rotation of the rotating body during standby. In addition, since the heating device has a multi-stage pre-heating temperature, by sequentially shifting to a lower pre-heating temperature, it is possible to suppress unnecessary input of energy, which is advantageous for raising the temperature inside the device, and is also effective in energy saving. Useful.

[0021]

DESCRIPTION OF THE PREFERRED EMBODIMENTS First Embodiment (1) Example of Image Forming Apparatus FIG. 1 is a schematic configuration diagram of an example of an image forming apparatus. The image forming apparatus of this example is an electrophotographic color printer.

Reference numeral 101 denotes a photosensitive drum (image bearing member) made of an organic photosensitive member or an amorphous silicon photosensitive member, and is rotated at a predetermined process speed (peripheral speed) in a counterclockwise direction indicated by an arrow.

The photosensitive drum 101 undergoes a uniform charging process of a predetermined polarity and potential by a charging device 102 such as a charging roller during the rotation process.

Next, a laser beam 103 output from a laser optical box (laser scanner) 110 is placed on the charged surface.
, The image information is subjected to a scanning exposure process. The laser optical box 110 outputs a laser beam 103 modulated (on / off) in accordance with a time-series electric digital pixel signal of image information from an image signal generating device such as an image reading device (not shown) to output a rotating photosensitive drum. An electrostatic latent image corresponding to the image information scanned and exposed on the surface 101 is formed. Reference numeral 109 denotes a mirror that deflects the output laser light from the laser optical box 110 to the exposure position of the photosensitive drum 101.

In the case of full-color image formation, scanning exposure and latent image formation are performed on a first color-separated component image of a target full-color image, for example, a yellow component image. Is developed as a yellow toner image by the operation of the yellow developing device 104Y. The yellow toner image is transferred to the surface of the intermediate transfer drum 105 at a primary transfer portion T1 which is a contact portion (or a close portion) between the photosensitive drum 101 and the intermediate transfer drum 105.

After the transfer of the toner image to the surface of the intermediate transfer drum 105, the surface of the rotating photosensitive drum 101 is
7 removes adhered residues such as transfer residual toner and is cleaned.

The process cycle of charging, scanning exposure, development, primary transfer, and cleaning as described above performs the second color separation component image (eg, magenta component image,
The magenta developing device 104M is activated), the third color-separated component image (for example, the cyan component image, the cyan developing device 104C is activated), and the fourth color-separated component image (for example, the black component image, the black developing device 104BK is activated). Each color separation component image is sequentially executed, and four toner images of a yellow toner image, a magenta toner image, a cyan toner image, and a black toner image are sequentially superimposed and transferred onto the surface of the intermediate transfer drum 105, and a desired full-color image is transferred. Are synthesized and formed.

The intermediate transfer drum 105 has a medium-resistance elastic layer and a high-resistance surface layer on a metal drum, and has substantially the same peripheral speed as the photosensitive drum 101 in contact with or close to the photosensitive drum 101. , Is rotated clockwise as indicated by an arrow, and a bias potential is applied to the metal drum of the intermediate transfer drum 105 so that the toner image on the photosensitive drum 101 side is transferred to the intermediate transfer drum 105 by a potential difference from the photosensitive drum 101.
Transfer to the surface side.

The color toner image synthesized and formed on the surface of the rotary intermediate transfer drum 105 is transferred to the secondary transfer portion T2, which is a contact nip portion between the rotary intermediate transfer drum 105 and the transfer roller 106, by the secondary transfer portion T2. The image is transferred onto the surface of the recording material P as a material to be heated, which is fed into the transfer unit T2 from a paper supply unit (not shown) at a predetermined timing. The transfer roller 106 supplies a charge of the opposite polarity to the toner from the back surface of the recording material P, and sequentially collectively transfers the combined color toner images from the surface of the intermediate transfer drum 105 to the recording material P.

The recording material P having passed through the secondary transfer portion T2 is separated from the surface of the intermediate transfer drum 105 and
After being heated and fixed to the unfixed toner image, the unfixed toner image is discharged to a discharge tray (not shown) outside the apparatus as a color image formed product. The heating device 100 will be described in detail in the following section (2).

After the transfer of the color toner image onto the recording material P, the rotating intermediate transfer drum 105 is cleaned by the cleaner 108 by removing the adhered residue such as untransferred toner and paper dust. The cleaner 108 is normally kept in a non-contact state with the intermediate transfer drum 105, and is brought into contact with the intermediate transfer drum 105 in the process of performing the secondary transfer of the color toner image from the intermediate transfer drum 105 to the recording material P. Will be retained.

The transfer roller 106 is always kept in a non-contact state with the intermediate transfer drum 105, and during the secondary transfer of the color toner image from the intermediate transfer drum 105 to the recording material P, the intermediate transfer drum 105 is maintained. Is kept in contact with the recording material P via the recording material P.

The image forming apparatus of the present embodiment can also execute a print mode of a monocolor image such as a black and white image. Also, a double-sided image print mode or a multiple image print mode can be executed.

In the case of the double-sided image print mode, the recording material P on which the first-side image has been printed out of the heating device 100 is turned upside down via a recirculation transport mechanism (not shown), and is sent again to the secondary transfer portion T2. Then, the toner image is transferred to the two surfaces, and the toner image is again introduced into the heating device 100 and subjected to the fixing process of the toner image on the two surfaces, so that a double-sided image print is output.

In the case of the multiple image print mode, the recording material P on which the first image has been printed out of the heating device 100 is sent again to the secondary transfer portion T2 without being turned over via a recirculation transport mechanism (not shown). Receiving the second transfer of the toner image to the surface on which the first image has been printed,
Then, a multi-image print is output by receiving the second fixing process of the toner image.

(2) Heating device 100 In this example, the heating device 100 is an electromagnetic induction heating type device. FIG. 2 is a cross-sectional side view of a main part of the heating device 100 of the present embodiment, FIG. 3 is a frontal view of the main part, and FIG. 4 is a longitudinal front view of the main part.

The magnetic field generating means includes magnetic cores 17a, 17b,
17c and the exciting coil 18.

The magnetic cores 17a, 17b, and 17c are members having a high magnetic permeability, and are preferably made of a material used for a transformer core such as ferrite or permalloy, and more preferably, ferrite having a small loss even at 100 kHz or more.

The exciting coil 18 has power feeding portions 18a and 18b.
The excitation circuit 27 is connected to (FIG. 5). The excitation circuit 27 can generate a high frequency of 20 kHz to 500 kHz by a switching power supply.

The exciting coil 18 generates an alternating magnetic flux by an alternating current (high-frequency current) supplied from the exciting circuit 27.

Reference numerals 16a and 16b denote film guide members having a substantially semi-arc-shaped trough shape in cross section. The film guide members have substantially cylindrical bodies with their opening sides facing each other, and have a fixing film which is a cylindrical electromagnetically inductive heating film on the outside. 10 is loosely fitted.

The film guide member 16a holds magnetic cores 17a, 17b, and 17c as magnetic field generating means and an exciting coil 18 inside.

A sliding member 40 is provided in the film guide member 16a on the side of the nip portion N facing the pressure roller 30 and inside the fixing film 10.

Reference numeral 22 denotes a horizontally long pressing rigid stay disposed in contact with the flat surface of the inner surface of the film guide member 16b.

Reference numeral 19 denotes an insulating member for insulating the magnetic cores 17a, 17b, 17c and the exciting coil 18 from the rigid pressurizing stay 22.

The flange members 23a and 23b are externally fitted to the left and right ends of the assembly of the film guide members 16a and 16b, and are rotatably mounted while fixing the left and right positions.
When the fixing film 10 rotates, the fixing film 10 receives the end of the fixing film 10 and serves to regulate the shifting of the fixing film along the length of the film guide member.

The pressure roller 30 as a pressure member is made of a heat-resistant and elastic material such as silicone rubber, fluoro rubber, fluoro resin, etc., which is formed by concentrically forming a roller around the core metal 30a. And a layer 30b. further,
A fluororesin can be provided as a release layer (not shown) on the outermost layer. Both ends of the metal core 30a are rotatably supported by bearings between a metal plate (not shown) of the apparatus.

Pressing springs 25a and 25b are respectively contracted between both ends of the pressing rigid stay 22 and spring receiving members 29a and 29b on the apparatus chassis side, so that a pressing force is applied to the pressing rigid stay 22. ing. As a result, the sliding member 40 on the lower surface of the film guide member 16a and the pressure roller 30 are pressed against each other with the fixing film 10 interposed therebetween to form a fixing nip portion N having a predetermined width.

The pressing roller 30 is driven to rotate in the counterclockwise direction indicated by the arrow by the driving means M. A rotational force acts on the fixing film 10 by a frictional force between the pressure roller 30 and the outer surface of the fixing film 10 due to the rotational driving of the pressure roller 30,
The fixing film 10 has a film guide member having a peripheral speed substantially corresponding to the rotational peripheral speed of the pressure roller 30 in the clockwise direction indicated by the arrow while the inner surface of the fixing film 10 slides in the fixing nip N in close contact with the lower surface of the sliding member 40. The outer circumference of 16a and 16b is rotated.

In this case, in order to reduce the mutual sliding frictional force between the lower surface of the sliding member 40 and the inner surface of the fixing film 10 in the fixing nip portion N, the sliding member 4 of the fixing nip portion N is reduced.
A lubricant such as heat-resistant grease can be interposed between the lower surface of the fixing film 10 and the inner surface of the fixing film 10.

As shown in FIG. 5, a convex rib portion 16e is formed on the peripheral surface of the film guide member 16a at a predetermined interval along the length thereof, so that the peripheral surface of the film guide member 16a is fixed to the fixing film. The rotational load of the fixing film 10 is reduced by reducing the contact sliding resistance with the inner surface of the fixing film 10. Such a convex rib portion is formed by the film guide member 16.
b can be similarly formed and provided.

FIG. 6 schematically shows how the alternating magnetic flux is generated. The magnetic flux C represents a part of the generated alternating magnetic flux.

The alternating magnetic flux C guided to the magnetic cores 17a, 17b and 17c is applied between the magnetic cores 17a and 17b and between the magnetic cores 17a and 17c. 1 to generate an eddy current. This eddy current generates Joule heat (eddy current loss) in the electromagnetic induction heating layer 1 due to the specific resistance of the electromagnetic induction heating layer 1. The heat value Q here is determined by the density of the magnetic flux passing through the electromagnetic induction heating layer 1 and has a distribution as shown in the graph of FIG. In the graph of FIG. 6, the vertical axis represents the center of the magnetic core 17a as 0.
Indicates the position in the circumferential direction of the fixing film 10 represented by the angle θ, and the horizontal axis indicates the amount of heat Q generated in the electromagnetic induction heating layer 1 of the fixing film 10. Here, the heating area H is defined as an area where the heating value is Q / e or more, where Q is the maximum heating value. This is an area where a heat value required for fixing can be obtained.

The temperature of the fixing film 10, that is, the temperature of the fixing nip portion N is controlled so that a predetermined temperature is maintained by controlling the current supply to the exciting coil 18 by a temperature control system including a temperature detecting means. You. That is, reference numeral 28 denotes a temperature sensor such as a thermistor for detecting the temperature of the fixing film 10, and in this embodiment, the temperature sensor 28 is attached to the heat generating area H on the inner surface of the fixing film.
It is arranged to be exposed on the outside. This temperature sensor 28
Comes into contact with the inner surface of the fixing film 10
Detect the temperature of Temperature information of the fixing film 10 measured by the temperature sensor 28 is input to the control circuit CPU (FIG. 5). The control circuit CPU controls the excitation circuit 27 based on the input temperature information to control the current supply to the excitation coil 18 and regulates the temperature of the fixing film 10, that is, the temperature of the fixing nip N to a predetermined temperature.

When the fixing film 10 rotates, the power is supplied from the excitation circuit 27 to the excitation coil 18 so that the fixing film 10 generates electromagnetic induction as described above, and the fixing nip N rises to a predetermined temperature. In the temperature-controlled state, the recording material P on which the unfixed toner image t conveyed from the image forming unit is formed has an image surface facing upward between the fixing film 10 and the pressure roller 30 in the fixing nip N, That is, the fixing nip portion N is introduced to face the fixing film surface, and the image surface is closely attached to the outer surface of the fixing film 10 in the fixing nip portion N, and the fixing nip portion N is conveyed together with the fixing film 10. In the process of nipping and transporting the recording material P together with the fixing film 10 through the fixing nip N, the unfixed toner image t on the recording material P is heated and fixed by heating by the electromagnetic induction heat of the fixing film 10. After passing through the fixing nip N, the recording material P is separated from the outer surface of the fixing film 10 and is discharged and conveyed. After passing through the fixing nip, the heat-fixed toner image on the recording material is cooled to become a permanent fixed image.

In this embodiment, as shown in FIG. 2, a thermo-detecting element, which is a temperature detecting element, is provided at a position of the fixing film 10 opposite to the heat generating area H (FIG. 6) in order to cut off power supply to the exciting coil 18 during runaway. A switch 50 is provided.

FIG. 7 is a circuit diagram of the safety circuit used in this example. Thermo switch 50 which is a temperature detecting element is +24
The VDC power supply and the relay switch 51 are connected in series.
1 is cut off, the relay switch 51 operates,
When the power supply to the excitation circuit 27 is cut off, the power supply to the excitation coil 18 is cut off. The thermoswitch 50 set the OFF operation temperature to 220 ° C.

The thermoswitch 50 is disposed in a non-contact manner on the outer surface of the fixing film 10 so as to face the heat generating area H of the fixing film 10. Thermoswitch 50 and fixing film 1
The distance between 0 and 2 was approximately 2 mm. Accordingly, the fixing film 10 is not damaged by the contact of the thermoswitch 50, and the deterioration of the fixed image due to durability can be prevented.

According to this embodiment, even when the heating device is stopped in a state where the paper is sandwiched in the fixing nip portion N, the power supply to the exciting coil 18 is continued and the fixing film 10 continues to generate heat, the paper is still sandwiched. Since no heat is generated in the fixing nip N, the paper is not directly heated. Further, since the thermoswitch 50 is disposed in the heat generation region H where the amount of heat generation is large, the thermoswitch 50 detects 220 ° C., and when the thermoswitch is turned off, the relay switch 51 connects the excitation coil 18 to the excitation coil 18. Is cut off.

According to this example, the ignition temperature of the paper is about 400 ° C.
Since it is near, heat generation of the fixing film can be stopped without firing the paper.

A temperature fuse can be used as a temperature detecting element in addition to the thermoswitch.

A) Excitation Coil 18 As the excitation coil 18, a bundle (bundled wire) of a plurality of copper thin wires, each of which is individually insulated and coated, is used as a conductive wire (electric wire) constituting a coil (wire loop). Are wound several times to form the exciting coil. In this example, the exciting coil 18 is formed by winding 10 turns.

As the insulating coating, a coating having heat resistance is preferably used in consideration of heat conduction due to heat generation of the fixing film 10. For example, a coating of polyamideimide or polyimide may be used.

The density of the exciting coil 18 may be improved by applying an external pressure.

The shape of the exciting coil 18 conforms to the curved surface of the heat generating layer as shown in FIGS. In this embodiment, the distance between the heating layer 1 of the fixing film 10 and the exciting coil 18 is set to be approximately 2 mm.

The material of the film guide member 16a, which also serves as the exciting coil holding member, preferably has excellent insulation and good heat resistance. For example, phenol resin, fluorine resin (PFA resin, PTFE resin, FEP resin), polyimide resin, polyamide resin, polyamideimide resin, PE
It is preferable to select EK resin, PES resin, LCP resin, or the like.

The shorter the distance between the magnetic cores 17a, 17b, 17c and the exciting coil 18 and the heat generating layer of the fixing film is, the higher the magnetic flux absorption efficiency is.
If the distance exceeds 5 mm, the efficiency is significantly reduced. If the distance is within 5 mm, the distance between the heating layer of the fixing film 10 and the exciting coil 18 does not need to be constant.

Exciting coil lead wires 18 a and 18 from the film guide member 16 a holding the exciting coil 18
As for b (FIG. 5), an insulating coating is applied to the portion outside the member 16a outside the bundle.

B) Fixing Film 10 FIG. 8 is a schematic diagram of the layer structure of the fixing film 10 in this embodiment. The fixing film 10 of the present embodiment includes a heat generating layer 1 made of a metal film or the like serving as a base layer of the electromagnetic induction heat generating fixing film 10, an elastic layer 2 laminated on its outer surface, and a release layer 3 laminated on its outer surface. With a composite layer structure of Heating layer 1
For adhesion between the elastic layer 2 and the elastic layer 2 and between the elastic layer 2 and the release layer 3, a primer layer (not shown) may be provided between the respective layers. In the fixing film 10 having a substantially cylindrical shape, the heat generating layer 1 is on the inner surface side, and the release layer 3 is on the outer surface side. As described above, when the alternating magnetic flux acts on the heat generating layer 1, an eddy current is generated in the heat generating layer 1, and the heat generating layer 1 generates heat.
The heat is transferred to the fixing film 10 via the elastic layer 2 and the release layer 3.
Is heated to heat the recording material P as the material to be heated, which is passed through the fixing nip N, so that the toner image is heated and fixed.

A. Heating Layer 1 The heating layer 1 is preferably made of a ferromagnetic metal such as nickel, iron, ferromagnetic SUS, and nickel-cobalt alloy.

A non-magnetic metal may be used, but a metal such as nickel, iron, magnetic stainless steel, and a cobalt-nickel alloy, which can absorb magnetic flux, is more preferable.

It is preferable that the thickness is larger than the skin depth represented by the following formula and 200 μm or less. The skin depth σ [m] is determined by the frequency f [Hz] of the excitation circuit and the magnetic permeability μ.
Is expressed as σ = 503 × (ρ / fμ) ^1/2 with the specific resistance ρ [Ωm].

This indicates the depth of absorption of electromagnetic waves used in electromagnetic induction. At a depth deeper than this, the intensity of the electromagnetic waves is 1 / e or less. (FIG. 9).

The thickness of the heat generating layer 1 is preferably 1 to 100 μm.
m is good. If the thickness of the heat generating layer 1 is smaller than 1 μm, most of the electromagnetic energy cannot be absorbed, so that the efficiency is deteriorated. On the other hand, if the heat generating layer exceeds 100 μm, the rigidity becomes too high, and the flexibility deteriorates, which is not practical for use as a rotating body. Therefore, the thickness of the heating layer 1 is 1 to 1
00 μm is preferred.

B. Elastic Layer 2 The elastic layer 2 is made of silicone rubber, fluorine rubber, fluorosilicone rubber, or the like, and has good heat resistance and good thermal conductivity.

The thickness of the elastic layer 2 is preferably from 10 to 500 μm. The elastic layer 2 has a thickness necessary to guarantee the quality of a fixed image. When a color image is printed, a solid image is formed over a large area on the recording material P, especially for a photographic image. In this case, if the heating surface (the release layer 3) cannot follow the unevenness of the recording material or the unevenness of the toner layer, uneven heating occurs, and uneven gloss occurs in the image in portions where the amount of heat transfer is large and small. Areas with a large amount of heat transfer have high gloss,
The glossiness is low in portions where the amount of heat transfer is small. When the thickness of the elastic layer 2 is 10 μm or less, the elastic layer 2 cannot follow the irregularities of the recording material or the toner layer, resulting in uneven image gloss. When the thickness of the elastic layer 2 is 1000 μm or more, the thermal resistance of the elastic layer becomes large, and the temperature response decreases. More preferably, the thickness of the elastic layer 2 is preferably 50 to 500 μm.

If the hardness of the elastic layer 2 is too high, the unevenness of the recording material or the toner layer cannot be completely followed, and image gloss unevenness occurs. Therefore, the hardness of the elastic layer 2 is 6
0 ° or less (JIS-A: using a JIS KA type measuring device), more preferably 45 ° or less.

The thermal conductivity λ of the elastic layer 2 is 0.2
5 to 0.84 [W / m · ° C.] is preferable. Thermal conductivity λ is 0.
If it is less than 25 [W / m · ° C.], the thermal resistance is large, and the temperature rise in the surface layer (release layer 3) of the fixing film becomes slow. When the thermal conductivity λ is larger than 0.84 [W / m · ° C.], the hardness becomes too high or the compression set becomes worse. Therefore, the thermal conductivity λ is 0.25
0.84 [W / m · ° C.] is preferable. More preferably 0.
It is preferably from 33 to 0.63 [W / m · ° C.].

C. Release Layer 3 The release layer 3 is made of a fluororesin (PFA, PTFE, FEP),
A material having good releasability and heat resistance, such as silicone resin, fluorosilicone rubber, fluorine rubber, and silicone rubber, can be selected.

The thickness of the release layer 3 is preferably 1 to 100 μm. If the thickness of the release layer 3 is less than 1 μm, there arises a problem that uneven coating of the coating film causes a part having poor releasability or insufficient durability. In addition, when the release layer exceeds 100 μm, there is a problem that heat conduction is deteriorated. In particular, in the case of a resin release layer, the hardness becomes too high, and the effect of the elastic layer 2 is lost.

As shown in FIG. 10, a heat insulating layer 4 may be provided on the film guide surface side of the heat generating layer 1 (on the side of the heat generating layer 1 opposite to the elastic layer 2).

As the heat insulating layer 4, a fluororesin (PFA resin, PTFE resin, FEP resin), a polyimide resin, a polyamide resin, a polyamideimide resin, a PEEK resin,
A heat-resistant resin such as PES resin and PPS resin is preferable.

The thickness of the heat insulating layer 4 is 10 to 10
00 μm is preferred. When the thickness of the heat insulating layer 4 is smaller than 10 μm, the heat insulating effect cannot be obtained, and the durability is insufficient. On the other hand, if it exceeds 1000 μm, the magnetic core 17a
The distance of the heat generating layer 1 from the coils 17b and 17c and the exciting coil 18 increases, and the magnetic flux is not sufficiently absorbed by the heat generating layer 1.

Since the heat insulating layer 4 can insulate the heat generated in the heat generating layer 1 so as not to go to the inside of the fixing film, the heat supply efficiency to the recording material P side is higher than when the heat insulating layer 4 is not provided. Become. Therefore, power consumption can be suppressed.

C) Temperature Control of Apparatus Next, the heat generation area H of the fixing film 10 which is a feature of the present invention.
A method for judging a preheating state based on a temperature result measured by the temperature detecting element 28 disposed in the apparatus and performing temperature control will be described in detail with reference to FIGS.

FIG. 11 shows that the power of the image forming apparatus main body is turned on.
FIG. 9 is a flowchart showing a state in which a transition is made in the order of>, <warm-up>, <ready>, <standby>, <print>, or <sleep>.

The horizontal axis in FIG. 12 indicates the time axis, and from the left side, <power ON>, <warm up>,
It shows a state of transition in the order of <ready> and <standby>.

FIG. 13 shows a state where the image forming apparatus main body transitions from the left in the order of <power ON>, <warm up>, <ready>, <standby>, <print>, and <standby>.

In both FIGS. 12 and 13, the vertical axis indicates the rotational state of the fixing film, the fixing film temperature, and the ON width of the power control from the top.

The curve of the fixing film temperature in the figure shows the heat generation position temperature (FIG. 6, the position of the heat generation area H) and the discharge side temperature (not shown,
7 shows a temperature change at a position (θ = π in FIG. 6).

Hereinafter, referring to FIGS. 11 and 12, an example of a method for judging a preheating state based on a temperature result measured by the temperature detecting element 28 disposed in the heat generating area H of the fixing film 10 and performing temperature control will be described. The switching of the preheating temperature during standby will be described.

<Warm-up> is started by <power ON> of the image forming apparatus. At this time, the rotation of the fixing film 10 is started, and the heating is turned on. Once fixing film 1
When the temperature of 0 was raised to 180 ° C <Ready>
And shift to <standby>.

In the standby state, the rotation of the fixing film 10 is stopped, and a temperature control is performed to maintain the heat generation area H of the fixing film 10 at a predetermined preheating temperature. The temperature is controlled by the thermistor 28 in contact with the heating area H on the inner surface of the fixing film 10.
Is controlled by the control circuit CPU and the excitation circuit 27 based on the temperature detected by the control circuit CPU. Excitation coil 1 for temperature control
8 by changing the frequency of the high-frequency current applied and adjusting the supplied power.

In this example, voltage resonance type switching is performed, and as shown in FIG.
可 変 25 [μsec] (4-100% when 25 μsec is 100%), OFF width is 15 [μsec]
c], and the power is controlled by controlling the ON width. When converted to frequency, 62.5-25 [kHz] =
1 / (1 + 15) to 1 / (25 + 15) [μsec ⁻¹ ]
Becomes

In FIG. 12, the power control variably controls the ON width between a minimum of 4% and a maximum of 100%, and supplies power required to maintain the temperature of the heat generation region at the first preheating temperature (region A). ). When the ON width becomes the minimum value (4%), the temperature of the heat generation region gradually rises (region B), and the power is detected to be + 5 ° C. higher than the first preheating temperature, the power is turned off. Electric power O
The period during which the FF is performed is set to be until the temperature of the heat generating region is detected to be lower than the first preheating temperature (region C). After the detection, the ON width variable control is restarted (area D). That is, 0
Between% and 4%, the ON width variable control is not performed. Thereafter, ON
The variable width control and the power OFF control are repeated. The power O
The temperature for FF is set to {preheating temperature + 5 ° C.}, but this temperature can be set arbitrarily within a positive range.

Here, members such as magnetic field generating means 17a, 17b, 17c, 18 and film guides 16a, 16b which constitute the inside of the fixing film 10 are referred to as a fixing internal unit.

A plurality of preheating temperatures are switched according to the thermal state of the fixing internal unit. In this example, two stages of preheating temperatures are set, and switching is performed when the temperature of the fixing internal unit is low and high.

The preheating temperatures in the two stages are a first preheating temperature (170 ° C.) and a second preheating temperature (120 ° C.), respectively.

The heating ON time during standby is Ton,
The OFF time is Toff, and the heating ON time before and after the Toff is Ton (before) and Ton (after).
By comparing the times of Ton (before) and Ton (after), the thermal state of the fixing internal unit is determined. When the fixing internal unit is cold, heat flow from the fixing film to the fixing internal unit is generated, and Ton (front) -Ton
(After) <0 continues. When the fixing internal unit is warmed by the preheating, the heat flow from the fixing film to the internal unit decreases, and the state of Ton (before) -Ton (after) ≧ 0 is established. When this condition is satisfied, the control circuit C
Change to the second preheating temperature lower by one step at PU. Since the control method of the second preheating temperature performs the same control as that of the first preheating temperature, the description is omitted.

When a print signal is received thereafter, normal <print> is performed, and after printing, the process proceeds to the second preheating temperature of standby. This is because the fixing internal unit has been sufficiently warmed up for printing once after shifting to the second preheating temperature.

It should be noted that there is no problem even if the temperature shifts to the first preheating temperature after printing. This is because Ton (front)-Ton (back) in a short time because the fixing internal unit is sufficiently warmed.
This is because the state becomes ≧ 0, and immediately shifts to the second preheating temperature.

If the print signal does not come in after the elapse of a predetermined time, the process shifts to <sleep> and the heating is stopped. Recovery from the sleep state is performed from <warm-up>.

Note that a print signal is always accepted after <Ready>, and the operation can shift to <Print> operation from any state.

Next, a case where a print signal is input from the state of (1) to (5) in FIG. 11, that is, a case where a print signal is input during standby at the first preheating temperature will be described with reference to FIG.

In FIG. 13, five continuous prints were made during the standby at the first preheating temperature. Until a print signal is input, the description is omitted because it is the same as described above. After the printing is completed, the process proceeds to the first preheating temperature of <standby>. This is because, since the printing was performed before the transition to the second preheating temperature, it is not possible to determine whether the fixing internal unit may transition to the second preheating temperature. FIG. 13 shows a case where the operation is shifted to the standby state in a state where the fixing internal unit is not sufficiently heated. Heating ON immediately after standby
Time gradually increases, and Ton (1) <Ton (2) <
Ton (3), that is, Ton (before)-Ton (after) <
The state of 0 continues. And the heating ON time is Ton (3)
> Ton (4), and Ton (front) −Ton (rear) ≧
0, and the process proceeds to the second preheating temperature. Ton (before) <
The time that the state of Ton (after) lasts, that is, Ton
(N), (n = 1, 2, 3,...) Change according to the degree of warming of the fixing internal unit, and are automatically adjusted so as to be long when the unit is cold and short when the unit is warm.

It should be noted that Ton (before) −Ton (after) ≧ To
By setting the condition of To ≧ 0, To = 0
Variations in the switching timing of the preheating temperature due to fluctuations in the control calculation that occur in the vicinity can be prevented. For example, by setting To = 0.1 sec, To
The comparison result before and after n is stable, and a switching timing in which the preheating temperature is stable can be obtained.

When the standby is performed with the fixing film 10 stopped, since the fixing film 10 has a low heat capacity, the temperature of the fixing internal unit has an influence on the heating speed of the fixing film. This is because if the temperature of the fixing internal unit is low, part of the heat of the fixing film is used for raising the temperature of the fixing internal unit. Also,
When a part of the fixing film having a relatively small heat capacity is heated in the stopped state, a temperature gradient is generated depending on the position of one round of the fixing film. 12 and 13 show the heat generation position temperature and the discharge side temperature of the fixing film during the preliminary heating in the standby state after the warm-up, and the discharge side temperature is 65 degrees.
In the case where the preheating is performed at 170 ° C., the temperature difference may be 100 ° C. or more.

However, even if the above-mentioned temperature difference occurs, the first preheating temperature can be raised to a temperature at which the recording material P can be sufficiently fixed until the recording material P reaches the fixing nip N after receiving the print signal. By setting the temperature,
A good-quality fixed image can be obtained without causing fixing failure. Further, when the fixing internal unit is warmed up, even at a lower preheating temperature, it is possible to raise the temperature sufficiently to a fixing-possible temperature before the recording material P reaches the fixing nip N after receiving the print signal.

As an experimental example, the effect of the preheating was controlled under the following three conditions to confirm the effect. In any of the conditions, the first printout time (FPOT) is shorter than the time (warm-up time) in which the heating device is heated from the sufficiently cooled state to the fixing temperature (the warm-up time).

[0110]

[Table 1]

The heating device (fixing device) 100 includes a fixing film 10 having an inner diameter of 35 mm and a length of 37 mm.
0 mm (heating layer 1: nickel electroformed 50 μm, elastic layer 2:
Silicone rubber 300 μm (JIS-A hardness 5 °), release layer 3: PFA 30 μm), pressure roller 30: outer diameter φ2
5 mm × 360 mm (core 30 a: iron φ19 mm, elastic layer 30 a: silicone rubber 3 mm, release layer: PFA50
μm), a nip width of 6.5 to 7.0 mm, and a pressure of 25 N.

In Experimental Examples 1 to 3, under all conditions,
The recording material P is fixed to the fixing nip N after receiving the print signal.
The fixing film was able to be heated to a temperature at which fixation was possible before the temperature reached.

The preheating temperature of the present invention can be appropriately set in accordance with the fixing conditions of the heating device and the conditions set by the image forming apparatus in addition to the conditions used in the experimental examples.

According to the present invention, during standby, heating is performed with a part of the fixing film 10 having a relatively small heat capacity stopped, and printing is started even when a large temperature gradient occurs due to the position of one round of the fixing film 10. Then, before the leading end of the recording material P reaches the fixing nip portion N, the temperature of the fixing film 10 can be stably raised to a fixing-possible temperature.

When the temperature of the fixing internal unit is low, the temperature of the fixing film 10 is raised, and when the temperature of the fixing internal unit is high, even if the temperature of the fixing film 10 is lowered, after the printing is started, Before the leading end of the recording material P reaches the fixing nip portion N, the temperature of the fixing film 10 can be stably increased to a fixing-possible temperature.

The preheating temperature can be set at three or more stages as necessary.

As the power control method, in addition to the ON width variable / OFF width fixed control of the high frequency switching, the ON width fixed / OFF width variable control and the frequency fixed ON
Controls such as / OFF width duty control and ON / OFF ratio fixed frequency control can be used.

Further, the switching control of the preheating temperature according to the present invention is also effective for power fluctuation due to the input voltage. If the input voltage is high and the input power is high, Ton (before)
<From the state of Ton (after) Ton (before) ≧ Ton (after)
However, the warm-up time for starting up from the standby state to the fixing temperature is shortened due to the large input power. Startup is possible. Therefore, it was also confirmed that the temperature was changed to a lower preheating temperature without consuming unnecessary power.

The pre-heating temperature of the fixing film 10 is set by heating the unfixed toner image t on the recording material P by overheating.
It is preferable to set the temperature to be lower than the temperature at which it adheres to zero, that is, the temperature at which hot offset occurs. This is because a high-quality image cannot be obtained when printing is started at a temperature higher than the hot offset temperature.

Further, the temperature of the fixing film 10 must be lower than the heat resistant temperature of the members constituting the fixing film.

Further, in this embodiment, the temperature detecting element 28 is disposed at the center in the longitudinal direction. However, in order to grasp the temperature state of the portion where the recording material is passed, the temperature detecting element is disposed in the paper passing area. Is desirable.

By performing the above control, as shown in FIG. 11, when the leading end of the recording material P reaches the heating device 100, the surface temperature of the fixing film 10 has reached the fixing-possible temperature. In the case of a color image, fixing failure did not occur and the first print out time (FPOT) was shortened.

As in the control of the present embodiment, by stopping the fixing film 10 which is a rotating body that generates electromagnetic induction during standby, the frequency of use of the image forming apparatus is low and the standby state is prolonged. But heating device 1
Since the rotation ratio of the fixing film 10 in the standby in the durability life of 00 is zero, the decrease in the number of printable sheets due to the standby can be prevented.

In addition, since the useless energy input can be suppressed, it is advantageous for raising the temperature inside the apparatus, and also useful for energy saving.

[Second Embodiment] In this embodiment, the description of the same parts as those in the first embodiment will be omitted, and the features of this embodiment will be described below. The parts will be described.

FIGS. 14 and 15 correspond to FIGS. 12 and 13, respectively, in the first embodiment.
The operation is the same as in the first embodiment shown in FIG.
According to the flowchart.

In this embodiment, the power control of the preheating during the standby is performed at a fixed value. 8% as the ON width of the first preheating temperature, 4% as the ON width of the second preheating temperature
And

The reason why the ON width of the first preheating temperature is set to 8% is as follows.
In the region of Ton (front) in FIG.
% If the ON width is assumed to be 4% in this area, the power is insufficient and the first temperature of the heat generation position temperature is reduced.
This is because the preheating temperature (170 ° C.) cannot be maintained.
For this reason, an ON width that can sufficiently maintain the preheating temperature was set. The second preheating temperature (120 ° C.) was set to 4% as the ON width in consideration of the same conditions.

In the present invention, the same effects as in the first embodiment can be obtained.

The value of the fixed ON width can be appropriately set according to the fixing conditions of the heating device and the conditions set by the image forming apparatus.

[Other Embodiments] In the above-described embodiment, since the toner containing a low softening substance is used, the heating device 100 is not provided with an oil application mechanism for preventing offset. When a toner containing no substance is used, an oil application mechanism may be provided.

Further, a cooling section may be provided after the fixing nip to perform cooling separation. Also, when a toner containing a low softening substance is used, oil application or cooling separation may be performed. Also, when a toner containing a low softening substance is used, oil application or cooling separation may be performed.

Although the image forming apparatus has been described as a one-photoconductor four-color image forming apparatus, it may be a four-photoconductor four-color image forming apparatus.

Further, the four-color image forming apparatus has been described. When the present invention is applied to a monochrome and one-pass multi-color image forming apparatus, the fixing film 10 does not include the elastic layer 2 and the heating layer 1 and the release layer. It is also possible to configure only three.

The heating device of the present invention is not limited to the image heating and fixing device of the embodiment, but may be any other device such as an image heating device for heating a recording material carrying an image to improve the surface properties such as gloss, An image heating device that heats the carried recording material to presume an image, feeds a sheet-like material, and performs a drying process.
It can be widely used as a heating device for laminating, hot pressing and removing wrinkles.

[0136]

As described above, according to the present invention, a magnetic field generating means, a rotating body which generates electromagnetic induction by the action of the magnetic field of the magnetic field generating means, and a nip portion formed by mutual pressure contact with the rotating body. A heating member of an electromagnetic induction heating type, comprising a heating member that generates an eddy current in a rotating body using electromagnetic induction and heats the material to be heated by the heat generated by the rotating body. An image forming apparatus, such as an electrophotographic apparatus or an electrostatic recording apparatus, provided with a heating type heating apparatus as an image heating apparatus for heating an image formed on a recording material, generates electromagnetically induced heat in a standby state of the apparatus. By performing preheating while the rotating body is stopped, the rotation ratio of the rotating body at the time of standby of the apparatus becomes zero, thereby preventing a decrease in the durability life of the apparatus while performing preheating during the standby of the apparatus. Door can be.

By having a multi-stage preheating temperature, by sequentially shifting to a lower preheating temperature, it is possible to suppress useless energy input, which is advantageous for raising the temperature in the apparatus, and also useful for energy saving. In addition, even with a heating device in which a part of the fixing film having a relatively small heat capacity generates heat and a temperature gradient is generated, the thermal state of the entire heating device is estimated only by the temperature detecting element disposed in the heating region of the fixing film. Therefore, the preheating temperature can be switched with a simple configuration.

In the image forming apparatus, the first print-out operation is performed by preheating during standby of the apparatus.
Since the time (FPOT) can be shortened, and even if the frequency of use of the image forming apparatus is low and the standby state is lengthened, the rotation ratio of the rotating body in the standby becomes zero among the durable life of the heating apparatus. It is possible to eliminate a decrease in the number of printable sheets due to the preliminary rotation of the rotating body during standby. In addition, since the heating device has a multi-stage pre-heating temperature, by sequentially shifting to a lower pre-heating temperature, it is possible to suppress unnecessary input of energy, which is advantageous for raising the temperature inside the device, and is also effective in energy saving. Useful.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of an image forming apparatus used in an embodiment.

FIG. 2 is a cross-sectional side view of a main part of the heating device.

FIG. 3 is a front view of the same main part.

FIG. 4 is a longitudinal sectional front view of the same main part.

FIG. 5 is a diagram showing a relationship between a magnetic field generating means and an excitation circuit.

FIG. 6 is a diagram showing a relationship between a magnetic field generating means and a heating value Q;

FIG. 7 is a diagram schematically showing a safety circuit.

FIG. 8 is a schematic diagram of a layer structure of a fixing film of electromagnetic induction heat generation (part 1).

FIG. 9 is a graph showing a relationship between a heating layer depth and an electromagnetic wave intensity.

FIG. 10 is a schematic diagram of a layer structure of an electromagnetically induced heating fixing film (part 2).

FIG. 11 is a flowchart illustrating control according to the embodiment;

FIG. 12 is a diagram showing control according to the first embodiment (part 1);

FIG. 13 is a view showing control according to the first embodiment (part 2);

FIG. 14 is a diagram showing control according to the second embodiment (part 1);

FIG. 15 is a diagram showing control according to the second embodiment (part 2);

FIG. 16 is an explanatory diagram of power control.

[Explanation of symbols]

1. Heat generation layer, 2. Elastic layer, 3. Release layer, 4. Thermal insulation layer, 10 Fixing film, 16 Film guide member, 17 Magnetic core, 18 Excitation coil, 28 ・
・ Temperature detecting element (thermistor), 50 ・ ・ Temperature detecting element for safety

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Tomoyuki Shida 3-30-2 Shimomaruko, Ota-ku, Tokyo F-term in Canon Inc. (reference) 2H033 AA23 AA32 BA30 BE06 CA02 CA05 CA28 CA32 CA45 3K059 AA08 AB04 AC33 AD28 AD34 CD09 CD10

Claims (7)

[Claims] 1. A nip portion comprising: a magnetic field generating means; a rotating body that generates electromagnetic induction by the action of a magnetic field of the magnetic field generating means; and a pressing member that forms a nip by mutually pressing the rotating body. A heating device that clamps and conveys the material to be heated and heats the material to be heated by the heat generated by the rotating body, wherein a temperature detecting unit is disposed in a heating area of the rotating body, and the heat generated by the rotating body causes the rotating body In a heating device for preheating in a stopped state, having a multistage preheating temperature, judging a preheating state based on temperature information detected by the temperature detecting means, and appropriately changing the preheating temperature. Characteristic heating device. 2. A power control for performing variable control between a non-zero minimum power and a maximum power to maintain the rotating body at a predetermined temperature based on temperature information detected by the temperature detecting means. The power control is ON and the
It has power control to repeat the state of F, and the ON and OFF
The heating device according to claim 1, wherein the preheating temperature is appropriately changed based on a change in the state of the heating device. 3. The ON time before and after the OFF is set to To.
Assuming n (before) and Ton (after), the ON times of the Ton (before) and Ton (after) are compared, and when a predetermined ON time relationship is satisfied, the preheating temperature is appropriately changed. The heating device according to claim 2, wherein the heating is performed. 4. The ON time before and after the OFF is set to To.
Assuming n (before) and Ton (after), the ON times of the Ton (before) and Ton (after) are compared, and when a predetermined ON time relationship is satisfied, the preheating temperature is appropriately changed. The heating device according to claim 2, wherein the heating is performed. 5. The preheating temperature is changed when the comparison of ON time satisfies Ton (before) -Ton (after) ≧ To (To is a positive value including zero). The heating device according to claim 3. 6. The heating device according to claim 1, wherein the preheating temperature is changed to a low temperature. 7. An image forming means for forming an image on a recording material,
An image forming apparatus comprising a heating device for heating an image formed on a recording material, wherein the heating device is the heating device according to any one of claims 1 to 6. .